1. | Sadowski P., Stupkiewicz S., Friction in lubricated soft-on-hard, hard-on-soft and soft-on-soft sliding contacts, TRIBOLOGY INTERNATIONAL, ISSN: 0301-679X, DOI: 10.1016/j.triboint.2018.08.025, Vol.129, pp.246-256, 2019Sadowski P., Stupkiewicz S., Friction in lubricated soft-on-hard, hard-on-soft and soft-on-soft sliding contacts, TRIBOLOGY INTERNATIONAL, ISSN: 0301-679X, DOI: 10.1016/j.triboint.2018.08.025, Vol.129, pp.246-256, 2019Abstract: Friction in lubricated soft contacts is examined using a ball-on-disc tribometer with the focus on the effect of configuration. In the soft-on-hard and hard-on-soft configurations, one of the contact-pair members is soft while the other one is hard. In the soft-on-soft configuration, both members are soft. For a soft disc, time-dependent viscoelastic deformations contribute to friction. Upon correction for the hysteretic losses, estimated using a theoretical model, the friction coefficient in the full-film regime does not depend on configuration. This holds also for high loads, when the deformations are finite. The combined effect of configuration and surface roughness on the transition from the full-film to the mixed lubrication regime is also examined. Keywords: Soft-EHL, Mixed lubrication, Surface roughness, Finite deformation | |
2. | Nosewicz S., Rojek J., Wawrzyk K., Kowalczyk P., Maciejewski G.^{♦}, Maździarz M., Multiscale modeling of pressure-assisted sintering, COMPUTATIONAL MATERIALS SCIENCE, ISSN: 0927-0256, DOI: 10.1016/j.commatsci.2018.10.001, Vol.156, pp.385-395, 2019Nosewicz S., Rojek J., Wawrzyk K., Kowalczyk P., Maciejewski G.^{♦}, Maździarz M., Multiscale modeling of pressure-assisted sintering, COMPUTATIONAL MATERIALS SCIENCE, ISSN: 0927-0256, DOI: 10.1016/j.commatsci.2018.10.001, Vol.156, pp.385-395, 2019Abstract: This report presents the modeling of pressure-assisted sintering within the framework of a multiscale approach. Three individual numerical methods have been collectively applied to predict the behavior of a sintering body at three different scales. The appropriate solutions to connect each model/scale have been proposed. Molecular dynamics have been employed to evaluate the grain boundary diffusion coefficient at the atomistic scale. The obtained results of diffusive parameters have been transferred to the micromechanical model of sintering. Here, the discrete element method was used to represent the sintered material properties at the microscopic scale. Micromechanical based results have been validated by own experimental data of material density evolution, indicating the required coincidence. The transfer from micro- to the macroscopic model has been realized by determining the macroscopic viscous moduli from discrete element simulations and subsequently applying them to the continuum model of sintering. The numerical results from finite element simulations at the macroscopic scale have been compared with discrete element ones. Keywords: Sintering; Multiscale modeling; Discrete element method; Molecular dynamics; Finite element method | |
3. | Lewandowski M.J., Stupkiewicz S., Size effects in wedge indentation predicted by a gradient-enhanced crystal-plasticity model, International Journal of Plasticity, ISSN: 0749-6419, DOI: 10.1016/j.ijplas.2018.05.008, Vol.109, pp.54-78, 2018Lewandowski M.J., Stupkiewicz S., Size effects in wedge indentation predicted by a gradient-enhanced crystal-plasticity model, International Journal of Plasticity, ISSN: 0749-6419, DOI: 10.1016/j.ijplas.2018.05.008, Vol.109, pp.54-78, 2018Abstract: A recently developed gradient-enhanced crystal-plasticity model is applied to predict the size effects in wedge indentation. In the model, the internal length scale is defined through standard quantities that appear in the underlying non-gradient hardening law. A careful calibration of the non-gradient hardening law is thus performed, and the model is validated against published experimental results. To this end, a comprehensive computational study of wedge indentation into a nickel single crystal is performed, and the obtained results show a good agreement with the experiment in terms of the load–penetration depth curves for three wedge angles, as well as in terms of the distributions of lattice rotation, GND density, and net Burgers vector. For the indentation depth of about 200 μm, as employed in the experiment, the predicted size effects are insignificant. Accordingly, the size effects are next studied for the indentation depth varied between 200 μm and 1 μm. As an intermediate result, apparently not published to date, the general 3D crystal plasticity model with anisotropic hardening is consistently reduced to a 2D plane-strain model in which plastic deformation is realized by three effective in-plane slip systems, each representing two crystallographic slip systems. Keywords: Indentation size effect, Geometrically necessary dislocations, Crystal plasticity, Gradient plasticity, Finite-element method | |
4. | Pierini F., Nakielski P., Urbanek O., Pawłowska S., Lanzi M., De Sio L., Kowalewski T.A., Polymer-Based Nanomaterials for Photothermal Therapy: From Light-Responsive to Multifunctional Nanoplatforms for Synergistically Combined Technologies, BIOMACROMOLECULES, ISSN: 1525-7797, DOI: 10.1021/acs.biomac.8b01138, Vol.0, pp.1-21, 2018Pierini F., Nakielski P., Urbanek O., Pawłowska S., Lanzi M., De Sio L., Kowalewski T.A., Polymer-Based Nanomaterials for Photothermal Therapy: From Light-Responsive to Multifunctional Nanoplatforms for Synergistically Combined Technologies, BIOMACROMOLECULES, ISSN: 1525-7797, DOI: 10.1021/acs.biomac.8b01138, Vol.0, pp.1-21, 2018Abstract: Materials for the treatment of cancer have been studied comprehensively over the past few decades. Among the various kinds of biomaterials, polymer-based nanomaterials represent one of the most interesting research directions in nanomedicine because their controlled synthesis and tailored designs make it possible to obtain nanostructures with biomimetic features and outstanding biocompatibility. Understanding the chemical and physical mechanisms behind the cascading stimuli-responsiveness of smart polymers is fundamental for the design of multifunctional nanomaterials to be used as photothermal agents for targeted polytherapy. In this review, we offer an in-depth overview of the recent advances in polymer nanomaterials for photothermal therapy, describing the features of three different types of polymer-based nanomaterials. In each case, we systematically show the relevant benefits, highlighting the strategies for developing light-controlled multifunctional nanoplatforms that are responsive in a cascade manner and addressing the open issues by means of an inclusive state-of-the-art review. Moreover, we face further challenges and provide new perspectives for future strategies for developing novel polymeric nanomaterials for photothermally assisted therapies. | |
5. | Gruziel M., Thyagarajan K., Dietler G., Stasiak A., Ekiel-Jeżewska M.L., Szymczak P., Periodic Motion of Sedimenting Flexible Knots, PHYSICAL REVIEW LETTERS, ISSN: 0031-9007, DOI: 10.1103/PhysRevLett.121.127801, Vol.121, No.12, pp.127801-1-6, 2018Gruziel M., Thyagarajan K., Dietler G., Stasiak A., Ekiel-Jeżewska M.L., Szymczak P., Periodic Motion of Sedimenting Flexible Knots, PHYSICAL REVIEW LETTERS, ISSN: 0031-9007, DOI: 10.1103/PhysRevLett.121.127801, Vol.121, No.12, pp.127801-1-6, 2018Abstract: We study the dynamics of knotted deformable closed chains sedimenting in a viscous fluid. We show experimentally that trefoil and other torus knots often attain a remarkably regular horizontal toroidal structure while sedimenting, with a number of intertwined loops, oscillating periodically around each other. We then recover this motion numerically and find out that it is accompanied by a very slow rotation around the vertical symmetry axis. We analyze the dependence of the characteristic timescales on the chain flexibility and aspect ratio. It is observed in the experiments that this oscillating mode of the dynamics can spontaneously form even when starting from a qualitatively different initial configuration. In numerical simulations, the oscillating modes are usually present as transients or final stages of the evolution, depending on chain aspect ratio and flexibility, and the number of loops. | |
6. | Lanzi M., Salatelli E., Giorgini L., Marinelli M., Pierini F., Effect of the incorporation of an Ag nanoparticle interlayer on the photovoltaic performance of green bulk heterojunction water-soluble polythiophene solar cells, POLYMER, ISSN: 0032-3861, DOI: 10.1016/j.polymer.2018.07.012, Vol.149, pp.273-285, 2018Lanzi M., Salatelli E., Giorgini L., Marinelli M., Pierini F., Effect of the incorporation of an Ag nanoparticle interlayer on the photovoltaic performance of green bulk heterojunction water-soluble polythiophene solar cells, POLYMER, ISSN: 0032-3861, DOI: 10.1016/j.polymer.2018.07.012, Vol.149, pp.273-285, 2018Abstract: Two water-soluble regioregular poly(3-alkylthiophene)s, incorporating aminic groups at the end of the side chains, have been synthesized using a post-polymerization functionalization procedure on a ω-bromine substituted polyalkylthiophene. The high solubility of the obtained polymers in water allowed for the preparation of “green” bulk heterojunction solar cells which reached a power conversion efficiency of 4.85% when PC61BM was used as electron-acceptor material. Improved optical absorption and photocurrent have been obtained by interposing a layer of Ag nanoparticles between the buffer and the photoactive layer, leading to a final power conversion efficiency of 5.51%. Keywords: Water-soluble polythiophene, Bulk heterojunction solar cell, Organic photovoltaic | |
7. | Bukowicki M., Ekiel-Jeżewska M.L., Different bending models predict different dynamics of sedimenting elastic trumbbells, SOFT MATTER, ISSN: 1744-683X, DOI: 10.1039/C8SM00604K, Vol.14, pp.5786-5799, 2018Bukowicki M., Ekiel-Jeżewska M.L., Different bending models predict different dynamics of sedimenting elastic trumbbells, SOFT MATTER, ISSN: 1744-683X, DOI: 10.1039/C8SM00604K, Vol.14, pp.5786-5799, 2018Abstract: The main goal of this paper is to examine theoretically and numerically the impact of a chosen bending model on the dynamics of elastic filaments settling in a viscous fluid under gravity at low-Reynolds-number. We use the bead-spring approximation of a filament and the Rotne–Prager mobility matrix to describe hydrodynamic interactions between the beads. We analyze the dynamics of trumbbells, for which bending angles are typically larger than for thin and long filaments. Each trumbbell is made of three beads connected by springs and it exhibits a bending resistance, described by the harmonic or – alternatively – by the ‘cosine’ (also called the Kratky–Porod) bending models, both often used in the literature. Using the harmonic bending potential, and coupling it to the spring potential by the Young's modulus, we find simple benchmark solutions: stable stationary configurations of a single elastic trumbbell and attraction of two elastic trumbbells towards a periodic long-lasting orbit. As the most significant result of this paper, we show that for very elastic trumbbells at the same initial conditions, the Kratky–Porod bending potential can lead to qualitatively and quantitatively different spurious dynamics, with artificially large bending angles and unrealistic shapes. We point out that for the bead models of an elastic filament, the range of applicability of the Kratky–Porod model might not go beyond bending angles smaller than π/2 for touching beads and beyond an even much lower value for beads well-separated from each other. The existence of stable stationary configurations of elastic trumbbells and a family of periodic oscillations of two elastic trumbbells are very important findings on their own. | |
8. | Chrzanowska-Giżyńska J., Denis P., Woźniacka S., Kurpaska Ł., Mechanical properties and thermal stability of tungsten boride films deposited by radio frequency magnetron sputtering, CERAMICS INTERNATIONAL, ISSN: 0272-8842, DOI: 10.1016/j.ceramint.2018.07.208, Vol.44, No.16, pp.19603-19611, 2018Chrzanowska-Giżyńska J., Denis P., Woźniacka S., Kurpaska Ł., Mechanical properties and thermal stability of tungsten boride films deposited by radio frequency magnetron sputtering, CERAMICS INTERNATIONAL, ISSN: 0272-8842, DOI: 10.1016/j.ceramint.2018.07.208, Vol.44, No.16, pp.19603-19611, 2018Abstract: Tungsten and boron compounds belong to the group of superhard materials since their hardness could exceed 40 GPa. In this study, the properties of the tungsten boride WBx coatings deposited by radio frequency magnetron sputtering were investigated. The sputtering was performed from specially prepared targets that were composed of boron and tungsten mixed in a molar ratio of 2.5 and sintered in Spark Plasma Sintering (SPS) process. WB films were deposited on silicon (100) and stainless steel 304 substrates at temperatures of 23 ÷ 770 °C. Microstructure, chemical and phase composition were investigated by using Scanning Electron Microscope (SEM), X-Ray Photoelectron Spectroscopy (XPS) and X-Ray Diffraction (XRD), respectively. The mechanical properties like Vickers hardness and Young's modulus were obtained by using nanoindentation test at a load of 5 ÷ 100 mN. The friction coefficient and wear resistance of αWB coatings were investigated in scratch test and reciprocal sliding wear instrumentation. Moreover, in order to investigate thermal properties, the αWB films were annealed at 1000 °C in argon/air for 1 h and at 250 °C for 2 h in air atmosphere. Results of our research confirm that αWB coatings can be considered as an alternative to superhard materials in the production of wear resistant, long-lasting tools. Keywords: Hard coatings, Hard materials, Magnetron sputtering, Mechanical properties, Thermal properties, Tungsten boride | |
9. | Malińska D., Szymański J., Patalas-Krawczyk P., Michalska B., Wojtala A., Prill M., Partyka M., Drabik K., Walczak J.^{♦}, Sewer A., Johne S., Luettich K., Peitsch M.C., Hoeng J., Duszyński J., Szczepanowska J., van der Toorn M., Więckowski M.R., Assessment of mitochondrial function following short- and long-term exposure of human bronchial epithelial cells to total particulate matter from a candidate modified-risk tobacco product and reference cigarettes, Food and Chemical Toxicology, ISSN: 0278-6915, DOI: 10.1016/j.fct.2018.02.013, Vol.115, pp.1-12, 2018Malińska D., Szymański J., Patalas-Krawczyk P., Michalska B., Wojtala A., Prill M., Partyka M., Drabik K., Walczak J.^{♦}, Sewer A., Johne S., Luettich K., Peitsch M.C., Hoeng J., Duszyński J., Szczepanowska J., van der Toorn M., Więckowski M.R., Assessment of mitochondrial function following short- and long-term exposure of human bronchial epithelial cells to total particulate matter from a candidate modified-risk tobacco product and reference cigarettes, Food and Chemical Toxicology, ISSN: 0278-6915, DOI: 10.1016/j.fct.2018.02.013, Vol.115, pp.1-12, 2018Abstract: Mitochondrial dysfunction caused by cigarette smoke is involved in the oxidative stress-induced pathology of airway diseases. Reducing the levels of harmful and potentially harmful constituents by heating rather than combusting tobacco may reduce mitochondrial changes that contribute to oxidative stress and cell damage. We evaluated mitochondrial function and oxidative stress in human bronchial epithelial cells (BEAS 2B) following 1- and 12-week exposures to total particulate matter (TPM) from the aerosol of a candidate modified-risk tobacco product, the Tobacco Heating System 2.2 (THS2.2), in comparison with TPM from the 3R4F reference cigarette. After 1-week exposure, 3R4F TPM had a strong inhibitory effect on mitochondrial basal and maximal oxygen consumption rates compared to TPM from THS2.2. Alterations in oxidative phosphorylation were accompanied by increased mitochondrial superoxide levels and increased levels of oxidatively damaged proteins in cells exposed to 7.5 μg/mL of 3R4F TPM or 150 μg/mL of THS2.2 TPM, while cytosolic levels of reactive oxygen species were not affected. In contrast, the 12-week exposure indicated adaptation of BEAS-2B cells to long-term stress. Together, the findings indicate that 3R4F TPM had a stronger effect on oxidative phosphorylation, gene expression and proteins involved in oxidative stress than TPM from the candidate modified-risk tobacco product THS2.2. Keywords: Mitochondria, Mitochondrial respiratory chain, Oxidative stress, BEAS-2B cells, Cigarette, Tobacco heating system | |
10. | Jarząbek D.M., Dziekoński C., Dera W., Chrzanowska J., Wojciechowski T., Influence of Cu coating of SiC particles on mechanical properties of Ni/SiC co-electrodeposited composites, CERAMICS INTERNATIONAL, ISSN: 0272-8842, DOI: 10.1016/j.ceramint.2018.08.271, Vol.44, pp.21750-21758, 2018Jarząbek D.M., Dziekoński C., Dera W., Chrzanowska J., Wojciechowski T., Influence of Cu coating of SiC particles on mechanical properties of Ni/SiC co-electrodeposited composites, CERAMICS INTERNATIONAL, ISSN: 0272-8842, DOI: 10.1016/j.ceramint.2018.08.271, Vol.44, pp.21750-21758, 2018Abstract: In this paper, the study of the mechanical properties of composites consisting of electrodeposited Ni and co-electrodeposited SiC particles coated with a thin Cu layer was presented. It was demonstrated that the coating allowed to increase the concentration of ceramic particles in the composite. Although the plating parameters were the same for both types of composites, the concentration of SiC was 15% for the composite containing coated particles (Ni/SiC-Cu) and 10% for the composite containing uncoated particles (Ni/SiC). Furthermore, tensile tests showed that the Ni/SiC-Cu samples exhibited higher Young's modulus than the pure electrodeposited Ni samples or Ni/SiC samples. The measured Young's modulus of the Ni/SiC-Cu composite was 250 ± 10 GPa. However, the ultimate tensile strength of the Ni/SiC-Cu composite was lower than that of pure Ni. To explain the mechanical behaviour of the Ni/SiC-Cu composite, the microstructure of the interface of this composite and its bonding strength were studied. Microstructure studies conducted using a scanning electron microscope (SEM) revealed that the SiC/Cu interface was smooth and of good quality whereas the Cu/Ni interface was rough but also of good quality. The measured bonding, normal, and shear strength values demonstrated that the SiC/Cu interface was weak, and that was the main reason for the low ultimate tensile strength of the composite. The shear strength of the SiC/Cu interface was measured using a novel method: micropillars shearing including atomic force microscopy (AFM). Finally, a simple finite element model of the Ni/SiC-Cu composite, based on cohesive elements, was developed. Keywords: Interfacial bonding strength, Metal matrix composites, Tensile strength, Silicon carbide, Electrodeposited nickel | |
11. | Poma A.B.^{♦}, Li M.S., Theodorakis P.E., Generalization of the elastic network model for the study of large conformational changes in biomolecules, Physical Chemistry Chemical Physics, ISSN: 1463-9076, DOI: 10.1039/C8CP03086C, Vol.20, pp.17020-17028, 2018Poma A.B.^{♦}, Li M.S., Theodorakis P.E., Generalization of the elastic network model for the study of large conformational changes in biomolecules, Physical Chemistry Chemical Physics, ISSN: 1463-9076, DOI: 10.1039/C8CP03086C, Vol.20, pp.17020-17028, 2018Abstract: The elastic network (EN) is a prime model that describes the long-time dynamics of biomolecules. However, the use of harmonic potentials renders this model insufficient for studying large conformational changes of proteins (e.g. stretching of proteins, folding and thermal unfolding). Here, we extend the capabilities of the EN model by using a harmonic approximation described by Lennard-Jones (LJ) interactions for far contacts and native contacts obtained from the standard overlap criterion as in the case of Gō-like models. While our model is validated against the EN model by reproducing the equilibrium properties for a number of proteins, we also show that the model is suitable for the study of large conformation changes by providing various examples. In particular, this is illustrated on the basis of pulling simulations that predict with high accuracy the experimental data on the rupture force of the studied proteins. Furthermore, in the case of DDFLN4 protein, our pulling simulations highlight the advantages of our model with respect to Gō-like approaches, where the latter fail to reproduce previous results obtained by all-atom simulations that predict an additional characteristic peak for this protein. In addition, folding simulations of small peptides yield different folding times for α-helix and β-hairpin, in agreement with experiment, in this way providing further opportunities for the application of our model in studying large conformational changes of proteins. In contrast to the EN model, our model is suitable for both normal mode analysis and molecular dynamics simulation. We anticipate that the proposed model will find applications in a broad range of problems in biology, including, among others, protein folding and thermal unfolding. Keywords: Free Energy, protein, elastic network, molecular dynamics, normal mode analysis | |
12. | Frydrych K., Kowalczyk-Gajewska K., Microstructure Evolution in Cold-Rolled Pure Titanium: Modeling by the Three-Scale Crystal Plasticity Approach Accounting for Twinning, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, ISSN: 1073-5623, DOI: 10.1007/s11661-018-4676-2, Vol.49, No.8, pp.3610-3623, 2018Frydrych K., Kowalczyk-Gajewska K., Microstructure Evolution in Cold-Rolled Pure Titanium: Modeling by the Three-Scale Crystal Plasticity Approach Accounting for Twinning, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, ISSN: 1073-5623, DOI: 10.1007/s11661-018-4676-2, Vol.49, No.8, pp.3610-3623, 2018Abstract: A three-scale crystal plasticity model is applied to simulate microstructure evolution in hcp titanium subjected to cold rolling. Crystallographic texture and misorientation angle development, as an indicator of grain refinement, are studied. The impact of twinning activity on both phenomena is accounted for by combining the original three-scale formulation with the probabilistic twin-volume consistent (PTVC) reorientation scheme. The modeling results are compared with available experimental data. It is shown that the simulated textures are in accordance with the experimental measurements. The basic components of misorientation angle distribution, especially in the range of high angle boundaries, are also well reproduced. | |
13. | Niemczyk B., Sajkiewicz P.Ł., Kołbuk D., Injectable hydrogels as novel materials for central nervous system regeneration, Journal of neural engineering, ISSN: 1741-2560, DOI: 10.1088/1741-2552/aacbab, Vol.15, No.5, pp.051002-1-15, 2018Niemczyk B., Sajkiewicz P.Ł., Kołbuk D., Injectable hydrogels as novel materials for central nervous system regeneration, Journal of neural engineering, ISSN: 1741-2560, DOI: 10.1088/1741-2552/aacbab, Vol.15, No.5, pp.051002-1-15, 2018Abstract: Approach. Injuries of the central nervous system (CNS) can cause serious and permanent disability due to limited regeneration ability of the CNS. Presently available therapies are focused on lesion spreading inhibition rather than on tissue regeneration. Recent investigations in the field of neural tissue engineering indicate extremely promising properties of novel injectable and non-injectable hydrogels which are tailored to serve as biodegradable scaffolds for CNS regeneration. Objective. This review discusses the state-of-the-art and barriers in application of novel polymer-based hydrogels without and with nanoparticles for CNS regeneration. Main results. Pure hydrogels suffer from lack of similarities to natural neural tissue. Many of the biological studies indicated nano-additives in hydrogels may improve their topography, mechanical properties, electroconductivity and biological functions. The most promising biomaterials which meet the requirements of CNS tissue engineering seem to be injectable thermosensitive hydrogels loaded with specific micro-and nanoparticles. Significance. We highlight injectable hydrogels with various micro-and nanoparticles, because of novelty and attractiveness of this type of materials for CNS regeneration and future development perspectives. Keywords: hydrogels, nanoparticles, injectable, microparticles, nanoﬁbers, central nervous system
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14. | Żuk P.J., Kochańczyk M., Lipniacki T., Sampling rare events in stochastic reaction-diffusion systems within trajectory looping, PHYSICAL REVIEW E, ISSN: 1539-3755, DOI: 10.1103/PhysRevE.98.022401, Vol.98, pp.022401-1-10, 2018Żuk P.J., Kochańczyk M., Lipniacki T., Sampling rare events in stochastic reaction-diffusion systems within trajectory looping, PHYSICAL REVIEW E, ISSN: 1539-3755, DOI: 10.1103/PhysRevE.98.022401, Vol.98, pp.022401-1-10, 2018Abstract: In bistable reaction–diffusion systems, transitions between stable states typically occur on timescales orders of magnitude longer than the chemical equilibration time. Estimation of transition rates within explicit Brownian dynamics simulations is computationally prohibitively costly. We present a method that exploits a single trajectory, generated by a prior simulation of diffusive motions of molecules, to sample chemical kinetic processes on timescales several orders of magnitude longer than the duration of the diffusive trajectory. In this approach, we “loop” the diffusive trajectory by transferring chemical states of the molecules from the last to the first time step of the trajectory. Trajectory looping can be applied to enhance sampling of rare events in biochemical systems in which the number of reacting molecules is constant, as in cellular signal transduction pathways. As an example, we consider a bistable system of autophosphorylating kinases, for which we calculate state-to-state transition rates and traveling wave velocities. We provide an open-source implementation of the method. | |
15. | Postek E., Sadowski T., Qualitative comparison of dynamic compressive pressure load and impact of WC/Co composite, International Journal of Refractory Metals and Hard Materials, ISSN: 0263-4368, DOI: 10.1016/j.ijrmhm.2018.07.009, Vol.77, pp.68-81, 2018Postek E., Sadowski T., Qualitative comparison of dynamic compressive pressure load and impact of WC/Co composite, International Journal of Refractory Metals and Hard Materials, ISSN: 0263-4368, DOI: 10.1016/j.ijrmhm.2018.07.009, Vol.77, pp.68-81, 2018Abstract: Degradation of Cermet Materials (CM) under impact and pulse pressure is not thoroughly investigated. In this
study, we qualitatively compare the behaviour of WC/Co samples under these types of loading.
The new models of impact and dynamic compressive load of a WC/Co plate were investigated. We developed two models of the composite plate, namely, a continuous model and a model with crack appearance possibility in the interfaces/binders.
We noted a qualitative difference of the shapes of the deformed structure due to different models and kind of loading. The differences also concern the Mises stress, equivalent plastic strains and damage parameter.
The proposed models are suitable for both impact and pressure load. The possibility of cracks appearance should not be neglected. In case of the model with discontinuities, for both kinds of loads, the grains rotation and sliding is more distinct than in case of the continuous model. Keywords: Cermet, Impact, Pressure load, Interface elements, Distributed microcracking process, Numerical models | |
16. | Frydrych K., Kowalczyk-Gajewska K., Grain refinement in the equal channel angular pressing process: simulations using the crystal plasticity finite element method, MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING, ISSN: 0965-0393, DOI: 10.1088/1361-651X/aad46d, Vol.26, No.6, pp.065015-1-32, 2018Frydrych K., Kowalczyk-Gajewska K., Grain refinement in the equal channel angular pressing process: simulations using the crystal plasticity finite element method, MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING, ISSN: 0965-0393, DOI: 10.1088/1361-651X/aad46d, Vol.26, No.6, pp.065015-1-32, 2018Abstract: Grain refinement due to severe plastic deformation is simulated using the crystal plasticity finite element method in the total Lagrangian setting. A rate-independent model with the regularized Schmid law is applied. As an example, a single pass of the equal channel angular pressing process is considered. Texture evolution, misorientation angle distributions and maps of new grains are presented. A special algorithm for tracking the creation of new grains in finite element simulations is developed. The results are analysed with respect to experimental data available in the literature. The possible mechanisms leading to the fragmentation of grains in a face centred cubic material are discussed. The influence of the quality of the microstructure representation on the simulation results is assessed Keywords: crystal plasticity, severe plastic deformation, grain refinement, finite element method | |
17. | Bochenek K., Węglewski W., Morgiel J., Basista M., Influence of rhenium addition on microstructure, mechanical properties and oxidation resistance of NiAl obtained by powder metallurgy, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2018.08.032, Vol.735, pp.121-130, 2018Bochenek K., Węglewski W., Morgiel J., Basista M., Influence of rhenium addition on microstructure, mechanical properties and oxidation resistance of NiAl obtained by powder metallurgy, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2018.08.032, Vol.735, pp.121-130, 2018Abstract: The search for new materials capable of replacing nickel-based superalloys in aerospace applications has increased rapidly in the recent years. One of the candidates for this purpose is nickel aluminide NiAl provided that its main drawback, namely the inferior fracture toughness at room temperature is overcome. We propose rhenium as an addition to NiAl to improve its mechanical properties without compromising on the oxidation resistance. Two powder metallurgy techniques (HP and SPS) were used to obtain NiAl/Re sinters. Small amounts of rhenium (0.6 at.%; 1.25at.%; 1.5 at.%) almost doubled the flexural strength of NiAl and improved its fracture toughness by 60%. Microscopic investigations revealed rhenium particles at the boundaries of NiAl grains resulting in an enhanced fracture toughness. Mass changes during oxidation at 900 oC, 1100 oC and 1300 oC were relatively low. Plausible mechanisms of the fracture toughness enhancement and the oxidation behavior are discussed. Keywords: nickel aluminide, rhenium, fracture toughness, oxidation resistance, powder metallurgy, grain boundary strengthening | |
18. | Sajkiewicz P., Heljak M.K., Gradys A., Choińska E., Rumiński S., Jaroszewicz T., Bissenik I., Święszkowski W.^{♦}, Degradation and related changes in supermolecular structure of poly(caprolactone) in vivo conditions, Polymer Degradation and Stability, ISSN: 0141-3910, DOI: 10.1016/j.polymdegradstab.2018.09.023, Vol.157, pp.70-79, 2018Sajkiewicz P., Heljak M.K., Gradys A., Choińska E., Rumiński S., Jaroszewicz T., Bissenik I., Święszkowski W.^{♦}, Degradation and related changes in supermolecular structure of poly(caprolactone) in vivo conditions, Polymer Degradation and Stability, ISSN: 0141-3910, DOI: 10.1016/j.polymdegradstab.2018.09.023, Vol.157, pp.70-79, 2018Abstract: The degradation in vivo and its effect on the supermolecular structure of poly(caprolactone) was examined. Poly(caprolactone) (PCL) samples were prepared in the form of porous scaffolds implanted into rat calvarial defects. The degradation was investigated by means of gel permeation chromatography, wide angle X-ray scattering (WAXS), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The study showed that the observed decrease of PCL crystallinity during degradation is accompanied by reduction of crystal size and/or perfection. The observed phenomenon could be explained by the presence of the high content of the low mobile fraction of investigated polymer, consisting not only almost 50% of crystal fraction but also most probably relatively high fraction of s.c. rigid amorphous fraction (RAF). Considering the type of structure characterized by the dominance of low mobile fraction, it is expected that the degradation will mainly concern these fractions, which in turn will lead to a decrease in the degree of crystallinity as well as crystal size and/or perfection. Keywords: PCL degradation, In-vivo conditions, Crystallinity, Rigid amorphous fraction | |
19. | Hou J., An Y., Wang S., Wang Z., Jankowski Ł., Ou J., Structural Damage Localization and Quantification Based on Additional Virtual Masses and Bayesian Theory, JOURNAL OF ENGINEERING MECHANICS-ASCE, ISSN: 0733-9399, DOI: 10.1061/(ASCE)EM.1943-7889.0001523, Vol.144, No.10, pp.04018097-1-9, 2018Hou J., An Y., Wang S., Wang Z., Jankowski Ł., Ou J., Structural Damage Localization and Quantification Based on Additional Virtual Masses and Bayesian Theory, JOURNAL OF ENGINEERING MECHANICS-ASCE, ISSN: 0733-9399, DOI: 10.1061/(ASCE)EM.1943-7889.0001523, Vol.144, No.10, pp.04018097-1-9, 2018Abstract: In vibration-based damage identification, a common problem is that modal information is not enough and insensitive to local damage. To solve this problem, an effective method is to increase the amount of modal information and enhance the sensitivity of the experimental data to the local damage. In this paper, a damage identification method based on additional virtual masses and Bayesian theory is proposed. First, the virtual structure with optimal additional mass and high sensitivity to local damage is determined through sensitivity analysis, and then a large number of virtual structures can be obtained by adding virtual masses; thus, a lot of modal and statistical information of virtual structures can be obtained. Second, the Bayesian theory is used to obtain the posterior probability distribution of the damage factor when structural a priori information is considered. Third, by finding the extreme value of the probability density function, the damage factor is derived based on the a priori information and the statistical information of virtual structures. Finally, the effectiveness of the proposed method is verified by numerical simulations and experiments of a 3-story frame structure. Experimental and numerical results show that the proposed method can be used to identify the damage severity of each substructure and thus damaged substructures can be localized and quantified; the error in damage factor is basically within 5%, which shows the accuracy of the proposed method. The proposed method can not only provide the structural damage localization and quantification result (i.e., the damage factor), but also the probability distribution of the damage factor; moreover, it has high sensitivity to damage and high accuracy and efficiency. Keywords: Structural health monitoring, Damage identification, Bayesian theory, Virtual distortion method (VDM), Virtual mass | |
20. | Ashraf W., Glinicki M.A., Olek J., Statistical Analysis and Probabilistic Design Approach for Freeze–Thaw Performance of Ordinary Portland Cement Concrete, JOURNAL OF MATERIALS IN CIVIL ENGINEERING, ISSN: 0899-1561, DOI: 10.1061/(ASCE)MT.1943-5533.0002494, Vol.30, No.11, pp.04018294-1-10, 2018Ashraf W., Glinicki M.A., Olek J., Statistical Analysis and Probabilistic Design Approach for Freeze–Thaw Performance of Ordinary Portland Cement Concrete, JOURNAL OF MATERIALS IN CIVIL ENGINEERING, ISSN: 0899-1561, DOI: 10.1061/(ASCE)MT.1943-5533.0002494, Vol.30, No.11, pp.04018294-1-10, 2018Abstract: This paper features the development of a probabilistic model linking freeze–thaw (F-T) performance of concrete mixtures to their composition. A sensitivity analysis was performed on several concrete mixture parameters to identify the factors that have strong correlations with F-T resistance of concrete. The F-T performance level was defined as a discrete measure of the frost resistance of concrete. Finally, a new model to predict F-T damage incorporating the variability in concrete mix parameters (as selected from sensitivity analysis) was developed. This model was developed using only those data sets that contained the results of the relative dynamic modulus of elasticity (RDME) testing performed according to ASTM and AASHTO specifications. Concrete mixtures containing only ordinary portland cement (OPC) as the sole binder (i.e., mixtures that did not contain any supplementary cementitious materials) were considered. The reliability of the model was demonstrated using several examples of concrete mixtures of various compositions. Accordingly, this model provides the opportunity to optimize the concrete mix proportion for the required performance level of concrete under F-T exposure condition. Keywords: Freeze–thaw, Durability, Concrete, Pavement, Sensitivity analysis, Probabilistic design | |
21. | Jurczak G., Variation of second-order piezoelectric coefficients with respect to a finite strain measure, Acta Crystallographica Section A
FOUNDATIONS AND ADVANCES, ISSN: 2053-2733, DOI: 10.1107/S2053273318008628, Vol.A74, pp.518-523, 2018Jurczak G., Variation of second-order piezoelectric coefficients with respect to a finite strain measure, Acta Crystallographica Section A
FOUNDATIONS AND ADVANCES, ISSN: 2053-2733, DOI: 10.1107/S2053273318008628, Vol.A74, pp.518-523, 2018Abstract: In this article the consequence of a change of finite strain measure is theoretically considered for nonlinear piezoelectric crystals. Analytical predictions show that second-order piezoelectric coefficients are finite strain measure dependent. Therefore, the use of any finite strain measure in constitutive modelling of piezoelectric materials requires an adequate choice of higher-order piezoelectric coefficients. This allows one to avoid unwanted corrections to the elastic and electric fields in the case of nonlinear modelling of piezoelectric materials, e.g. for piezoelectric heterostructures such as quantum wells or dots. A general transformation formula for second-order piezoelectric coefficients (elastostriction) is derived. As an example, specific transformation formulae for two common crystallographic classes, namely 43m and 6mm, are presented. The piezoelectric coefficients for GaN and GaAs crystals, as representative cases of these crystal classes, are recalculated and their dependence on the strain measure is demonstrated. A further implication of that effect is that a complete set of second-order piezoelectric coefficients should contain additional information about the strain measure applied during calculations or measurements. Keywords: piezoelectricity, nonlinear piezoelectricity, elastostriction, finite strain measure | |
22. | Kruk A., Gadomska-Gajadhur A., Rykaczewska I., Dulnik J., Ruśkowski P., Synoradzki L., Influence of liquid pore precursors on morphology and mechanical properties of 3D scaffolds obtained by dry inversion phase method, Journal of Biomedical Materials Research Part B: Applied Biomaterials, ISSN: 1552-4973, DOI: 10.1002/jbm.b.34200, 2018Kruk A., Gadomska-Gajadhur A., Rykaczewska I., Dulnik J., Ruśkowski P., Synoradzki L., Influence of liquid pore precursors on morphology and mechanical properties of 3D scaffolds obtained by dry inversion phase method, Journal of Biomedical Materials Research Part B: Applied Biomaterials, ISSN: 1552-4973, DOI: 10.1002/jbm.b.34200, 2018Abstract: Polyester 3D scaffolds were obtained by dry inversion phase method. The influence of a polymer and liquid pore precursor type on the 3D scaffolds morphology, porosity and mechanical properties was tested. Polymers and precursors forming a porous structure were identified. It was found that 3D scaffolds having the most preferable structure for cell cultures were obtained from polylactide with the addition of n‐butanol as the liquid pore precursor. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res B Part B, 2018. Keywords: liquid pore precursors, mechanical properties, dry inversion phase method, 3D scaffolds | |
23. | Faraj R., Graczykowski C., Holnicki-Szulc J., Adaptable pneumatic shock absorber, JOURNAL OF VIBRATION AND CONTROL, ISSN: 1077-5463, DOI: 10.1177/1077546318795532, 2018Faraj R., Graczykowski C., Holnicki-Szulc J., Adaptable pneumatic shock absorber, JOURNAL OF VIBRATION AND CONTROL, ISSN: 1077-5463, DOI: 10.1177/1077546318795532, 2018Abstract: Recent progress in the field of sensors, actuators, and smart materials allows the construction of more and more efficient controllable pneumatic dampers for shock absorption. Typically, such devices apply online semi-active control techniques, which utilize electromagnetic, piezoelectric, or magnetostrictive valves. As a result, they are characterized by a high efficiency of impact absorption, but simultaneously by a complicated construction and a specialized electronic system. The alternative solutions are semi-passive absorbers that ensure a similar performance by using a much simpler, low-cost construction and a less complicated adaptation mechanism. This paper introduces an adaptable semi-passive single-chamber pneumatic shock absorber, SOFT-DROP, which provides the optimal impact absorption and energy dissipation after a single reconfiguration performed at the beginning of the process. The high effectiveness of the proposed concept is proved in numerical and experimental investigations of the device. Moreover, the proposed semi-passive damper is also compared against already known pneumatic absorbers that utilize semi-active control methods. Ultimately, the device might be used in an airdrop system for delivery of light packages. Keywords: adaptable, semi-passive, impact absorption, optimal design, pneumatic shock absorber | |
24. | Tasinkiewicz J., Falińska K., Lewin P., Litniewski J., Improving broadband ultrasound attenuation assessment in cancellous bone by mitigating the influence of cortical bone: Phantom and in-vitro study, Ultrasonics, ISSN: 0041-624X, DOI: 10.1016/j.ultras.2018.06.018, Vol.92, pp.1-7, 2018Tasinkiewicz J., Falińska K., Lewin P., Litniewski J., Improving broadband ultrasound attenuation assessment in cancellous bone by mitigating the influence of cortical bone: Phantom and in-vitro study, Ultrasonics, ISSN: 0041-624X, DOI: 10.1016/j.ultras.2018.06.018, Vol.92, pp.1-7, 2018Abstract: The purpose of this work was to present a new approach that allows the influence of cortical bone on noninvasive measurement of broadband ultrasound attenuation (BUA) to be corrected. The method, mplemented here at 1 MHz makes use of backscattered signal and once refined and clinically confirmed, it would offer an alternative to ionizing radiation based methods, such as DEXA (Dual-nergy X-ray absorptiometry), quantitative computed tomography (QCT), radiographic absorptiometry (RA) or single X-ray absorptiometry (SXA), which are clinically approved for assessment of progress of osteoporosis. In addition, as the method employs reflected waves, it might substantially enhance the applicability of BUA - from being suitable to peripheral bones only it would extend this applicability to include such embedded bones as hip and femoral neck. The proposed approach allows the cortical layer parameters used for correction and the corrected value and parameter of the ancellous bone (BUA) to be determined simultaneously from the single (pulse-echo) bone backscattered wave; to the best of the authors’ knowledge such approach was not previously reported. The validity of the method was tested using acoustic data obtained from a custom- esigned bone-mimicking phantom and a calf femur. The relative error of the attenuation coefficient assessment was determined to be 3.9% and 4.7% for the bone phantom and calf bone specimens, respectively. When the cortical shell influence was not taken into account the corresponding errors were considerably higher 8.3% (artificial bone) and 9.2% (calf femur). As indicated above, once clinically proven, the use of this BUA measurement technique in reflection mode would augment diagnostic power of the attending physician by permitting to include bones, which are not accessible for transmission mode evaluation, e.g. hip, spine, humerus and femoral neck. Keywords: Broadband ultrasound attenuation, Correction of influence of cortical bone, Trabecular bone | |
25. | Nasalski W., Elegant Laguerre–Gaussian beams — formulation of exact vector solution
, Journal of Optics, ISSN: 2040-8978, DOI: 10.1088/2040-8986/aadc8a, Vol.20, No.105601, pp.1-11, 2018Nasalski W., Elegant Laguerre–Gaussian beams — formulation of exact vector solution
, Journal of Optics, ISSN: 2040-8978, DOI: 10.1088/2040-8986/aadc8a, Vol.20, No.105601, pp.1-11, 2018Abstract: In photonic applications of optical beams, their transverse cross-section should be often narrow, with a diameter in their waist of the order of one wavelength or even less. Within this range, the paraxial approximation of beam fields is not valid and standard corrections by field expansions with respect to a small parameter are not efficient as well. Thus, still there is a need for more accurate beam field description. In this report, an exact vector solution for free-space propagation is given in terms of elegant Laguerre–Gaussian beams. The analysis starts from the known paraxial field approximation and next, through bidirectional field transformation and application of a Hertz potential leads to an exact vector solution. The role of the paraxial solution in construction of the exact solution is elucidated. The method works well not only in cases of free-space propagation but also in description of beam interactions with planar interfaces and multilayers. Keywords: elegant Laguerre–Gaussian beams, paraxial and nonparaxial solutions, bidirectional transformation, Hertz potentials | |
26. | Szymczyk M., Nowak M., Sumelka W., Numerical Study of Dynamic Properties of Fractional Viscoplasticity Model, SYMMETRY, ISSN: 2073-8994, DOI: 10.3390/sym10070282, Vol.10, No.282, pp.1-17, 2018Szymczyk M., Nowak M., Sumelka W., Numerical Study of Dynamic Properties of Fractional Viscoplasticity Model, SYMMETRY, ISSN: 2073-8994, DOI: 10.3390/sym10070282, Vol.10, No.282, pp.1-17, 2018Abstract: The fractional viscoplasticity (FV) concept combines the Perzyna type viscoplastic model and fractional calculus. This formulation includes: (i) rate-dependence; (ii) plastic anisotropy; (iii) non-normality; (iv) directional viscosity; (v) implicit/time non-locality; and (vi) explicit/stress-fractional non-locality. This paper presents a comprehensive analysis of the above mentioned FV properties, together with a detailed discussion on a general 3D numerical implementation for the explicit time integration scheme. Keywords: fractional viscoplasticity, rate dependence, plastic anisotropy, non-normality, directional viscosity, explicit/implicit non-locality | |
27. | Zawidzki M., Szklarski J., Transformations of Arm-Z modular manipulator with Particle Swarm Optimization, Advances in Engineering Software, ISSN: 0965-9978, DOI: 10.1016/j.advengsoft.2018.05.003, pp.1-14, 2018Zawidzki M., Szklarski J., Transformations of Arm-Z modular manipulator with Particle Swarm Optimization, Advances in Engineering Software, ISSN: 0965-9978, DOI: 10.1016/j.advengsoft.2018.05.003, pp.1-14, 2018Abstract: A novel concept of hyper-redundant, snake-like manipulator is presented. It is based on the reconfigurable modular construction system–Arm-Z (AZ). AZ is comprised of linearly joined congruent modules with possibility of relative twist. AZ is an Extremely Modular System, i.e. it is composed of a single basic unit and allows for creating free-form shapes. Required level of usefulness and efficiency are among the most challenging design aspects of such reconfigurable systems. Here AZ is considered in the context of kinematics of robotic arms. In general, due to its highly non-linear nature, it is very difficult to find transitions between given states (configurations), especially under realistic environmental and structural constraints. As a way to control the manipulator, an implementation of Particle Swarm Optimization (PSO) for finding transitions between AZ states in realistic scenarios is proposed. Four practical examples are presented which are variations of two distinct problems: bending of a hexagonal AZ in a narrow slot (strong environmental constraints), and reaching a given point in 3D space by the tip of dodecagonal AZ (acting as a robotic arm). The problem of AZ transformation has been defined as a multi-objective optimization. The methodology is general with no restrictions to the objective function. Since the problem is strongly non-linear, in order to cover large space of potential solutions, the algorithm runs for a relatively large number of random initial swarms. This task was distributed on a computer cluster. Although the nature of AZ reconfiguration is discrete, the optimization algorithm is continuous. Keywords: Extremely modular system, Arm-Z, Pipe-Z, Discrete optimization, Dihedral rotation, Reconfiguration, Particle Swarm Optimization, Redundant robot, Hyper-redundant manipulator | |
28. | Dębski P.R., Skłodowska K., Michalski J.A., Korczyk P.M., Dolata M., Jakiela S., Continuous Recirculation of Microdroplets in a Closed Loop Tailored for Screening of Bacteria Cultures, Micromachines, ISSN: 2072-666X, DOI: 10.3390/mi9090469, Vol.9, pp.1-11, 2018Dębski P.R., Skłodowska K., Michalski J.A., Korczyk P.M., Dolata M., Jakiela S., Continuous Recirculation of Microdroplets in a Closed Loop Tailored for Screening of Bacteria Cultures, Micromachines, ISSN: 2072-666X, DOI: 10.3390/mi9090469, Vol.9, pp.1-11, 2018Abstract: Emerging microfluidic technology has introduced new precision controls over reaction conditions. Owing to the small amount of reagents, microfluidics significantly lowers the cost of carrying a single reaction. Moreover, in two-phase systems, each part of a dispersed fluid can be treated as an independent chemical reactor with a volume from femtoliters to microliters, increasing the throughput. In this work, we propose a microfluidic device that provides continuous recirculation of droplets in a closed loop, maintaining low consumption of oil phase, no cross-contamination, stabilized temperature, a constant condition of gas exchange, dynamic feedback control on droplet volume, and a real-time optical characterization of bacterial growth in a droplet. The channels (tubing) and junction cubes are made of Teflon fluorinated ethylene propylene (FEP) to ensure non-wetting conditions and to prevent the formation of biofilm, which is particularly crucial for biological experiments. We show the design and operation of a novel microfluidic loop with the circular motion of microdroplet reactors monitored with optical sensors and precision temperature controls. We have employed the proposed system for long term monitoring of bacterial growth during the antibiotic chloramphenicol treatment. The proposed system can find applications in a broad field of biomedical diagnostics and therapy. Keywords: microfluidic loop, bacteria cultures, screening, antibiotic treatment, Escherichia coli | |
29. | Nowak Ł.J., Nowak K.M., Sound differences between electronic and acoustic stethoscopes, BioMedical Engineering OnLine, ISSN: 1475-925X, DOI: 10.1186/s12938-018-0540-2, Vol.17, pp.104-1-11, 2018Nowak Ł.J., Nowak K.M., Sound differences between electronic and acoustic stethoscopes, BioMedical Engineering OnLine, ISSN: 1475-925X, DOI: 10.1186/s12938-018-0540-2, Vol.17, pp.104-1-11, 2018Abstract: Background: The area of application of electronic stethoscopes in medical diagnostics covers the scope of usability of the acoustic stethoscopes, from which they have evolved and which they could potentially replace. However, the principle of operation of these two groups of diagnostic devices is substantially different. Thus, an important question arises, regarding the differences in parameters of the transmitted sound and their potential diagnostic consequences in clinical practice.
Methods: In order to answer this question, heart auscultation signals are recorded using various stethoscopes and divided into short fragments based on the analysis of the synchronized recordings of electrocardiogram signals. Next, a dedicated algorithm is used to extract representative datasets for each case, which are then analyzed for their acoustic parameters. Four different electronic stethoscopes were investigated, together with an acoustic stethoscope as a reference point.
Results: The determined acoustic characteristics of the considered stethoscopes differ significantly between each other.
Conclusions: The differences in sound transmitted by various stethoscope models may translate into significant differences in quality of the obtained diagnosis. It is also pointed out, that the terminology and application guidelines regarding the electronic stethoscopes are misleading and should be changed. Keywords: Stethoscope, Auscultation, Electronic stethoscope, Acoustic diagnostics | |
30. | Strojny-Nędza A., Pietrzak K.^{♦}, Gładki A., Nosewicz S., Jarząbek D.M., Chmielewski M., The effect of ceramic type reinforcement on structure and properties of Cu-Al2O3 composites, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/124271, Vol.66, No.4, pp.553-560, 2018Strojny-Nędza A., Pietrzak K.^{♦}, Gładki A., Nosewicz S., Jarząbek D.M., Chmielewski M., The effect of ceramic type reinforcement on structure and properties of Cu-Al2O3 composites, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/124271, Vol.66, No.4, pp.553-560, 2018Abstract: The purpose of this paper is to elaborate on mechanical alloy
ing conditions for a composite powder consisting of copper a
nd brittle aluminium oxides. Detailed analysis of the Cu-Al2O3
powder mixture structure obtained in the mechanical alloyi
ng process allows for the
study of the homogenization phenomena and for obtaining gra
ins (in composite form) with a high degree of uniformity. The
Cu-5 vol.%Al2O3
composites were obtained by means of the spark plasma sinter
ing technique. The results presented herein were studied an
d discussed in
terms of the impact of using a different form of aluminium oxid
e powder and a different shape of copper powder on composite pr
operties.
Research methodology included microstructure analysis as
well as its relation to the strength of Cu-Al2O3
interfaces. It transpires from the
results presented below that the application of electrocor
undum as a reinforcement phase in composites decreases poro
sity in the ceramic
phase, thus improving thermal properties and interfacial s
trength. Keywords: metal matrix composites, spark plasma sintering, thermal conductivity, interfacial strength | |
31. | Frąś L.J., Dziekoński C., Dera W., Jarząbek D.M., Piezoelectric bimorph as a high-sensitivity viscosity resonant sensor to test the anisotropy of magnetorheological fluid, REVIEW OF SCIENTIFIC INSTRUMENTS, ISSN: 0034-6748, DOI: 10.1063/1.5025123, Vol.89, No.10, pp.105111-1-7, 2018Frąś L.J., Dziekoński C., Dera W., Jarząbek D.M., Piezoelectric bimorph as a high-sensitivity viscosity resonant sensor to test the anisotropy of magnetorheological fluid, REVIEW OF SCIENTIFIC INSTRUMENTS, ISSN: 0034-6748, DOI: 10.1063/1.5025123, Vol.89, No.10, pp.105111-1-7, 2018Abstract: In this paper, we present a device which is very sensitive for small changes in the viscosity of the investigated fluid. The main part of the device is a piezo-electric bimorph which consists of the brass shim with two piezo-ceramic layers on the opposite sides. One of them is responsible for generating vibrations, whereas the second one is meant to measure system response which is produced by the damping properties of the surrounding fluid. During the experiment, the cylindrical bar is forced to move by the series of sinusoidal waves with different frequencies and at constant amplitudes. The probe is immersed in the fluid and then the amplitude vs frequency and phase vs frequency curves are obtained. Next, one can determine the viscosity according to a proper mathematical model. The resonant frequency is related to the damping coefficient which depends on the viscosity of the surrender fluid and immersion depth of the probe. The coefficients necessary for calculating viscosity are obtained by fitting the resonance curve to the amplitude vs frequency data obtained from the experiment. The device has been applied to study the anisotropy of magnetorheological fluids. The weak anisotropy of viscosity has been observed. The highest value of viscosity was observed in the case of viscosity measurement in the direction orthogonal to the magnetic field and the lowest in the direction parallel to the magnetic field. | |
32. | Żurek Z.H., Kukla D., LDC1000 converter for NDT material diagnostics and characterisation, INSIGHT, ISSN: 1354-2575, DOI: 10.1784/insi.2018.60.7.375, Vol.60, No.7, pp.375-379, 2018Żurek Z.H., Kukla D., LDC1000 converter for NDT material diagnostics and characterisation, INSIGHT, ISSN: 1354-2575, DOI: 10.1784/insi.2018.60.7.375, Vol.60, No.7, pp.375-379, 2018Abstract: The LDC1000 module[1,2] measurement tool is a commercial inductive converter made by Texas Instruments (TI). It has been designed to measure the distance to a surface from a given point above the surface of conducting materials. However, its design and software make it possible to use the device in many other innovative applications, such as in machine diagnostics (the measurement of shaft torsions and the detection and measurement of unbalance in rotating masses) and in the non-destructive testing (NDT) of continuity, shape and structural flaws. Examples of the application of this converter to flaw crack detection, to the measurement of electrical and magnetic parameters and to distance determination from a point above the surface to the surface of conducting materials, as well as to the estimation of the thickness of a non-conductive layer on a conductive surface, are described in this paper. The LDC1000 converter has been available commercially for a few years and its basic scope of application is expanding all of the time[4,5]. It has also been the subject matter for some PhD theses[6]. The principles for measuring the components of the normalised impedance are explained in the initial part of this paper, which is necessary in order to gain a full understanding of the converter operation. The LDC1000 converter operates in the current resonance region (resonance takes place between the inductive coil and the tested material). From the manifold diagnostic possibilities of the converter, its application in flaw detection will be presented in this paper. Crack detection and conductivity and distance measurements have been carried out and the local circuit inductance has been recorded. Measurements have been conducted with the standard flaw detection probe and the time required for performing repeatability measurements has also been investigated. | |
33. | Szolc T., Konowrocki R., Pisarski D., Pochanke A., Influence of Various Control Strategies on Transient Torsional Vibrations of Rotor-Machines Driven by Asynchronous Motors
, IFToMM, The 10th IFToMM International Conference on Rotor Dynamics, 2018-01-23/01-27, Rio de Janeiro (BR), DOI: 10.1007/978-3-319-99272-3_15, No.4, pp.205-230, 2018Szolc T., Konowrocki R., Pisarski D., Pochanke A., Influence of Various Control Strategies on Transient Torsional Vibrations of Rotor-Machines Driven by Asynchronous Motors
, IFToMM, The 10th IFToMM International Conference on Rotor Dynamics, 2018-01-23/01-27, Rio de Janeiro (BR), DOI: 10.1007/978-3-319-99272-3_15, No.4, pp.205-230, 2018Abstract: In the paper, a dynamic electromechanical interaction between the selected kind of rotating machines and their driving electric motors is investigated. These are the high-speed beater mills and crushers as well as blowers, pumps and compressors, all driven by the asynchronous motors through elastic couplings with linear and non-linear characteristics. In particular, there is considered an influence of negative electromagnetic damping generated by the motor on a possibility of excitation of resonant torsional vibrations. Moreover, for the asynchronous motor in transient and steady-state operating conditions, there are tested several control strategies which are based on the closed-loop vector and scalar principles. The theoretical calculations have been performed by means of the advanced structural mechanical models. Conclusions drawn from the computational results can be very useful during a design phase of these devices as well as helpful for their users during a regular maintenance. Keywords: Rotor-machine, Asynchronous motor, Electromechanical interaction, Torsional vibrations, Control strategies | |
34. | Makowska K., Brodecki A.^{♦}, Mackiewicz S., Kowalewski Z.L., Damage development of inconel 718 due to laboratory simulated creep
, JOURNAL OF THEORETICAL AND APPLIED MECHANICS, ISSN: 1429-2955, DOI: 10.15632/jtam-pl.56.3.893, Vol.56, No.3, pp.893-896, 2018Makowska K., Brodecki A.^{♦}, Mackiewicz S., Kowalewski Z.L., Damage development of inconel 718 due to laboratory simulated creep
, JOURNAL OF THEORETICAL AND APPLIED MECHANICS, ISSN: 1429-2955, DOI: 10.15632/jtam-pl.56.3.893, Vol.56, No.3, pp.893-896, 2018Abstract: The paper presents an attempt of application of the acoustic birefringence coefficient for early stage degradation assessment of Inconel 718 nickel superalloy after short-term creep. It is shown that it can serve as a good damage sensitive parameter and, moreover, it can be well correlated with hardness variation. Keywords: creep, nickel superalloy, microstructure, pre-deformation, hardness, acoustic birefringence | |
35. | Tasinkiewicz J., Lewandowski M., Klimonda Z., Walczak M., Synthetic Aperture Cardiac Imaging with Reduced Number of Acquisition Channels. A Feasibility Study, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, DOI: 10.24425/123915, Vol.43, No.3, pp.437-446, 2018Tasinkiewicz J., Lewandowski M., Klimonda Z., Walczak M., Synthetic Aperture Cardiac Imaging with Reduced Number of Acquisition Channels. A Feasibility Study, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, DOI: 10.24425/123915, Vol.43, No.3, pp.437-446, 2018Abstract: Commercially available cardiac scanners use 64–128 elements phased-array (PA) probes and classical delay-and-sum beamforming to reconstruct a sector B-mode image. For portable and hand-held scanners, which are the fastest growing market, channel count reduction can greatly decrease the total power and cost of devices. The introduction of ultra-fast imaging methods based on plane waves and diverging waves provides new insight into heart’s moving structures and enables the implementation of new myocardial assessment and advanced flow estimation methods, thanks to much higher frame rates. The goal of this study was to show the feasibility of reducing the channel count in the diverging wave synthetic aperture image reconstruction method for phased-arrays. The application of ultra-fast 32-channel subaperture imaging combined with spatial compounding allowed the frame rate of approximately 400 fps for 120 mm visualization to be achieved with image quality obtained on par with the classical 64-channel beamformer. Specifically, it was shown that the proposed method resulted in image quality metrics (lateral resolution, contrast and contrast-to-noise ratio), for a visualization depth not exceeding 50 mm, that were comparable with the classical PA beamforming. For larger visualization depths (80–100 mm) a slight degradation of the above parameters was observed. In conclusion, diverging wave phased-array imaging with reduced number of channels is a promising technology for low-cost, energy efficient hand-held cardiac scanners. Keywords: phased-array, ultrasound imaging, diverging wave, synthetic transmit aperture | |
36. | Byra M., Wójcik J., Nowicki A., Using Empirical Mode Decomposition of Backscattered Ultrasound Signal Power Spectrum for Assessment of Tissue Compression, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, DOI: 10.24425/123916, Vol.43, No.3, pp.447-453, 2018Byra M., Wójcik J., Nowicki A., Using Empirical Mode Decomposition of Backscattered Ultrasound Signal Power Spectrum for Assessment of Tissue Compression, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, DOI: 10.24425/123916, Vol.43, No.3, pp.447-453, 2018Abstract: Quantitative ultrasound has been widely used for tissue characterization. In this paper we propose a new approach for tissue compression assessment. The proposed method employs the relation between the tissue scatterers’ local spatial distribution and the resulting frequency power spectrum of the backscat- tered ultrasonic signal. We show that due to spatial distribution of the scatterers, the power spectrum exhibits characteristic variations. These variations can be extracted using the empirical mode decomposition and analyzed. Validation of our approach is performed by simulations and in-vitro experiments using a tissue sample under compression. The scatterers in the compressed tissue sample approach each other and consequently, the power spectrum of the backscattered signal is modified. We present how to assess this phenomenon with our method. The proposed in this paper approach is general and may provide useful information on tissue scattering properties. Keywords: tissue characterization, tissue compression, quantitative ultrasound, empirical mode decomposition, signal anaysis | |
37. | Brodecki A., Szymczak T., Kowalewski Z., Digital image correlation technique as a tool for kinematics assessment of structural components, ACTA MECHANICA ET AUTOMATICA, ISSN: 1898-4088, DOI: 10.2478/ama-2018-0016, Vol.12, No.2, pp.101-104, 2018Brodecki A., Szymczak T., Kowalewski Z., Digital image correlation technique as a tool for kinematics assessment of structural components, ACTA MECHANICA ET AUTOMATICA, ISSN: 1898-4088, DOI: 10.2478/ama-2018-0016, Vol.12, No.2, pp.101-104, 2018Abstract: The paper reports the results of tests carried out for kinematic properties determination of components under cyclic loading. DIC system called 5M PONTOS was employed to follow variations of displacement versus time. It was conducted by the use of markers stuck on selected sections of components tested. The results are presented in 2D and 3D coordinate systems expressing behaviour of such elements as: mechanical coupling device, boat frame and car engine. These data enabled to capture weak and strong sections of the component examined at various loading conditions. Keywords: Digital Image Correlation System, Cyclic Loading, PONTOS, Motion, Displacement, 3D Coordinate System | |
38. | Papliński P., Wańkowicz J., Ranachowski P., Ranachowski Z., Doświadczenia z eksploatacji wysokonapięciowych liczników zadziałań oraz badania degradacji mikrostruktury pochodzących z nich warystorów ZnO, PRZEGLĄD ELEKTROTECHNICZNY, ISSN: 0033-2097, DOI: 10.15199/48.2018.10.01, Vol.94, No.10, pp.1-7, 2018Papliński P., Wańkowicz J., Ranachowski P., Ranachowski Z., Doświadczenia z eksploatacji wysokonapięciowych liczników zadziałań oraz badania degradacji mikrostruktury pochodzących z nich warystorów ZnO, PRZEGLĄD ELEKTROTECHNICZNY, ISSN: 0033-2097, DOI: 10.15199/48.2018.10.01, Vol.94, No.10, pp.1-7, 2018Abstract: W pracy przedstawione zostały doświadczenia z eksploatacji liczników zadziałań, które stanowiły inspirację do badań pochodzących z nich warystorów ZnO. Badana była mikrostruktura elementów pochodzących z uszkodzonych liczników zadziałań. Odniesienie stanowił analogiczny warystor, z licznika który nie był w eksploatacji. Badania wykazały nietypowy skład fazowy tworzywa badanych warystorów oraz niską jednorodność i spoistość ich czerepu. Opisano i udokumentowano procesy degradacji tworzywa o zróżnicowanym nasileniu. Wykazano szkodliwy wpływ wilgoci we wnętrzu rozszczelnionego licznika zadziałań na jego funkcjonowanie, w tym na umieszczone w nim warystory ZnO. Przedstawiono ponadto wnioski dotyczące kontroli eksploatacyjnej liczników zadziałań. Keywords: licznik zadziałań, warystory ZnO, mikrostruktura ceramiki ZnO, degradacja materiału ceramicznego | |
39. | Niemczyk B., Sajkiewicz P., Gradys A., The Effect of Chemical Composition on Crosslinking Kinetics of Methylcellulose/Agarose Hydrogel, ISBPPB 2018, 4th International Conference on Biomedical Polymers and Polymeric Biomaterials, 2018-07-15/07-18, Kraków (PL), pp.174, 2018 | |
40. | Pisarski D., On optimal distributed semi-active control of vibrating structures, WCSCM, 7th World Conference on Structural Control and Monitoring, 2018-07-23/07-26, Qingdao (CN), pp.3148-3149, 2018Pisarski D., On optimal distributed semi-active control of vibrating structures, WCSCM, 7th World Conference on Structural Control and Monitoring, 2018-07-23/07-26, Qingdao (CN), pp.3148-3149, 2018Abstract: A novel semi-active control method for mitigation of structural vibration is studied. The method relies on distributed state information patterns and solutions to optimal control problem that aims at replicating the structures of the optimal open-loop switched stabilizing controls. The performance of the designed method is validated by means of numerical experiments performed for a double cantilever system equipped with a set of semi-active elastomers with controlled viscoelastic properties. | |
41. | Walenta Z.A., Słowicka A.M., Detonation Waves in Narrow Channels of Various Shapes
, ISIS23, 23rd International Shock Interaction Symposium, 2018-07-09/07-13, Kruger National Park (ZA), pp.135-140, 2018Walenta Z.A., Słowicka A.M., Detonation Waves in Narrow Channels of Various Shapes
, ISIS23, 23rd International Shock Interaction Symposium, 2018-07-09/07-13, Kruger National Park (ZA), pp.135-140, 2018Abstract: One of the important contemporary technological problems is connected with necessity of extinguishing detonation, which may occur in pipelines transporting gaseous fuels. To achieve this goal usually a matrix of very narrow channels is placed inside the pipeline, perpendicularly to its axis. In our recent paper (Walenta and Slowicka (2016)) we have shown, that channels with sharp changes of cross-section should be more eﬃcient in this respect than traditionally used straight channels with constant cross-section area. In this paper we demonstrate how detonation behaves in the channels, in which gas ﬂows under realistic conditions – when friction and heat exchange are present. We take into account the fact, that gas ﬂowing through such channels accelerates and its density decreases considerably. Keywords: detonation waves, detonation damping, narrow channels | |
42. | Jóźwiak-Niedźwiedzka D., Dąbrowski M., Brandt A.M., Burakowska A., Baran T., The results of the concrete shield of the EWA nuclear reactor/Wyniki badania betonu z obudowy reaktora jądrowego EWA, CEMENT, WAPNO, BETON, ISSN: 1425-8129, Vol.3, pp.226-238, 2018Jóźwiak-Niedźwiedzka D., Dąbrowski M., Brandt A.M., Burakowska A., Baran T., The results of the concrete shield of the EWA nuclear reactor/Wyniki badania betonu z obudowy reaktora jądrowego EWA, CEMENT, WAPNO, BETON, ISSN: 1425-8129, Vol.3, pp.226-238, 2018Keywords: nuclear reactor, concrete shield, radiation influence | |
43. | Jóźwiak-Niedźwiedzka D., Antolik A., Glinicki M.A., Investigation of potential for alkali-silica reaction in granitic aggregates, SLD4, 4th International Conference on Service Life Design for Infrastructures, 2018-08-27/08-30, Delft (NO), pp.131-134, 2018Jóźwiak-Niedźwiedzka D., Antolik A., Glinicki M.A., Investigation of potential for alkali-silica reaction in granitic aggregates, SLD4, 4th International Conference on Service Life Design for Infrastructures, 2018-08-27/08-30, Delft (NO), pp.131-134, 2018Abstract: Crushed granite aggregates due to good physical and mechanical properties are widely
accepted for production of durable concrete. This kind of aggregates are considered as not
alkali-silica reactive (ASR). However, all of them contain silica. In some of them SiO2 occurs
in a strained form or the crystals are small enough to be treated as microcrystalline, so they
can be prone to ASR.
Various granite aggregates taken from largest exploited Polish quarries were tested.
Petrographic analysis on thin sections and accelerated mortar-bar test were carried out to
assess potential of the alkali-silica reactivity.
The petrographic analysis revealed differences in mineral composition of the tested
granites. The strained quartz and microcrystalline quartz were the main potentially deleterious
mineral in analyzed granite aggregates. Also the myrmekites were particularly visible in the
granitic rocks. The results of the mortar-bar tests confirmed such predictions. The mortar
beams showed expansion more than 0.1% after 28 days of exposition in 1M NaOH and 80°C.
The bars made with RILEM cement showed fast and large elongation. In all cases the increase
in mortar beam elongation was linear. The SEM-EDS analysis confirmed the presence of the
ASR gel both, in the aggregate and in the matrix. | |
44. | Dąbrowski M., Glinicki M.A., Gibas K., Antolik A., Dziedzic K., Influence of Surface Retarders on Texture Profile And Durability of Upper Layer of Exposed Aggregate Concrete Pavement, ICDCS-6, Sixth International Conference on Durability of Concrete Structures, 2018-07-18/07-20, University of Leeds, Leeds, West Yorkshire (GB), No.PSE17, pp.451-456, 2018Dąbrowski M., Glinicki M.A., Gibas K., Antolik A., Dziedzic K., Influence of Surface Retarders on Texture Profile And Durability of Upper Layer of Exposed Aggregate Concrete Pavement, ICDCS-6, Sixth International Conference on Durability of Concrete Structures, 2018-07-18/07-20, University of Leeds, Leeds, West Yorkshire (GB), No.PSE17, pp.451-456, 2018Abstract: Exposed aggregate concrete (EAC) pavement technology is used in Poland for construction of major highways and expressways. When properly executed, it is an efficient technique to provide desired friction for skid resistance without compromising the noise limitations. Concrete mix uniformity, proper dosing of retarding agent and optimal time to brush with a mechanical broom are supposed to have a major impact on the properties of the upper pavement layer. An experimental investigation was performed on exposed aggregate concrete specimens manufactured in the laboratory in a way to simulate the industrial production of two-layer concrete slab with exposed aggregate. The texture depth was determined using a laser profiler. The compressive strength of concrete, the water absorption rate, and permeability of chloride ions through concrete were also determined. The freeze-thaw resistance and surface scaling resistance were tested and analyzed with respect to air void characteristics. Results revealed an increase in surface scaling for EAC slabs with higher w/c ratio and slabs simulating local bleeding. The most efficient method to determine indirectly the durability of EAC slabs was the set of permeability tests comprised of measurements of chloride migration and rate of water absorption. The change of macrotexture depth with increase of w/c ratio and retarding admixture type was found. Keywords: highway pavement, exposed aggregate concrete, surface retarder, durability, concrete preparation parameter, water absorption, chloride migration, surface scaling, macrotexture | |
45. | Jóźwiak-Niedźwiedzka D., Gibas K., Glinicki M.A., Petrographic evaluation of reactive minerals in selected crushed aggregates in Poland, 13th International Symposium on Concrete Roads, 2018-06-19/06-22, Berlin (DE), pp.1-4, 2018Jóźwiak-Niedźwiedzka D., Gibas K., Glinicki M.A., Petrographic evaluation of reactive minerals in selected crushed aggregates in Poland, 13th International Symposium on Concrete Roads, 2018-06-19/06-22, Berlin (DE), pp.1-4, 2018Abstract: The long term performance of concrete pavements can be reduced due to improper selection of
aggregates, thus prevention of damage due to alkali-silica reaction (ASR) requires a detailed
examination of minerals in aggregates. The amount of reactive silica in the aggregate is an
important factor governing the severity of ASR, which depends critically on the nature of the
reactive aggregate.
In the present study the potential for ASR in selected rocks in Poland was evaluated using
petrographic methods. The tests were performed on crushed aggregates from different regions,
covering a variety of rock origin and their geological structure. The optical microscopy in
transparent light on thin sections was used as a principal tool to assess the mineral composition of
aggregates. The content of reactive siliceous minerals was assessed. The petrographic
examination concerned different forms of silica. Quartz grains were classified according to their
mean diameter so as to identify the reactive range.
The application of the petrographic method allowed for classification of aggregate for ASR
potential using RILEM recommendation. The results of the study allow to make a quick and
responsible decision to direct the aggregates to further detailed tests, reject or accept them as
concrete components for concrete pavements. Keywords: alkali-silica reaction, polymineral grains, petrographic analysis | |
46. | Dąbrowski M., Jóźwiak-Niedźwiedzka D., Antolik A., Glinicki M.A., Effects of cyclic wet-dry- external alkali exposure on microstructure and water permeability of air-entrained pavement concrete, 13th International Symposium on Concrete Roads, 2018-06-19/06-22, Berlin (DE), pp.1-4, 2018Dąbrowski M., Jóźwiak-Niedźwiedzka D., Antolik A., Glinicki M.A., Effects of cyclic wet-dry- external alkali exposure on microstructure and water permeability of air-entrained pavement concrete, 13th International Symposium on Concrete Roads, 2018-06-19/06-22, Berlin (DE), pp.1-4, 2018Abstract: Penetration of external alkalis from deicing salts into concrete pavement can promote deleterious alkali-silica reaction (ASR) and therefore reduce its long-term performance. In severe exposure
conditions (wet and heavy traffic load) the susceptibility of aggregates to ASR may be aggravated. To study this phenomenon on concrete specimens the combined cyclic exposure method was
developed at VDZ Düsseldorf. Such a cyclic wet-dry-external alkali exposure was used on air entrained concrete specimens to investigate its influence on the microstructure and the
permeability of concrete. Air voids characteristics, mercury intrusion porosimetry, porosity accessible to water and water absorption of concrete was tested. Concrete microstructure was
observed in scanning electron microscope to reveal the specific features. The applied cyclic wetdry-external alkali exposure induced a marked decrease of total porosity of concrete and the
appearance of ASR gel in cement matrix. An increase of the rate of water absorption of concrete was also found. Keywords: alkali-silica reaction, VDZ test, microstructure, permeability, water absorption | |
47. | Jurczak G., Maździarz M., Dłużewski P., Dimitrakopulos G., Komninou Ph., Karakostas T., On the Applicability of the Theory of Elasticity to Very Thin Layers, EDS2018, 19th International Conference on Extended Defects in Semiconductors, 2018-06-24/06-29, Thessaloniki (GR), pp.1, 2018Jurczak G., Maździarz M., Dłużewski P., Dimitrakopulos G., Komninou Ph., Karakostas T., On the Applicability of the Theory of Elasticity to Very Thin Layers, EDS2018, 19th International Conference on Extended Defects in Semiconductors, 2018-06-24/06-29, Thessaloniki (GR), pp.1, 2018Abstract: Theory of elasticity, a continuum model of a macroscopic material is commonly used to model a relaxation of a crystalline heterostructures. There are many reports on the successful application of theory of elasticity to nanometer crystalline heterostructures, even if the continuum condition for these structures is hardly fulfilled. On the other hand progress in epitaxial growth techniques allows to prepare the stable ultra thin layers with the thickness about a single monolayer. For such extremely thin layers the theory of elasticity seems to fail in describing the relaxation process. The results provided by theory of elasticity and experimental measurements or molecular statics/dynamics become diverging. The key problem in that case seems to be located at the interface between layers and related to composition change, which is problematic in classic, elastic approach. By applying a “substitutive” composition of the interface layers which is just an interpolation, it is possible to obtain a good agreement with molecular statics, even for 1 monolayer heterostructure. Instead of classic approach to the composition within the theory of elasticity, we propose another approach which takes into account the composition as an extra degree of freedom along with classical displacement. Such approach creates a chemo-elastic coupling with composition interpolated by use of the Vegard’s law. This allows to take into account a composition changes at the interface and avoid mesh refining necessary at the classic approach. Keywords: theory of elasticity, semiconductor, monolayer, relaxation | |
48. | Pieczyska E., Golasiński K., Maj M., Staszczak M., Mackiewicz S., Zubko M., Takesue N., Gum metal in compression – investigation of mechanical anisotropy caused by texture, ICEM 2018, 18TH INTERNATIONAL CONFERENCE ON EXPERIMENTAL MECHANICS, 2018-07-01/07-05, BRUKSELA (BE), No.454, pp.1-2, 2018 | |
49. | Staszczak M., Pieczyska E.A., Odriozola I., Martin R., Investigation of functional properties of new shape memory polymer, ICEM 2018, 18TH INTERNATIONAL CONFERENCE ON EXPERIMENTAL MECHANICS, 2018-07-01/07-05, BRUKSELA (BE), No.199, pp.1-2, 2018 | |
50. | Dulnik J., Sajkiewicz P., The Comparison of Crosslinking Methods of Bicomponent PCL/gelatin Electrospun Nanofibres, ISBPPB 2018, 4th International Conference on Biomedical Polymers and Polymeric Biomaterials, 2018-07-15/07-18, Kraków (PL), pp.109, 2018 | |
51. | Cristea M., Ionita D., Oprea S., Pieczyska E.A., How loading type affects viscoelastic response in polyurethane structures, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.342-343, 2018 | |
52. | Staszczak M., Pieczyska E.A., Matsui R., Takeda K., Estimation of energy storage and dissipation in Shape Memory Polymer during its deformation, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.338-339, 2018 | |
53. | Pieczyska E.A., Dunić V., Slavkovic R., Kowalewski Z., Stress relaxation effects in TiNi SMA, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.350-351, 2018 | |
54. | Pieczyska E., Golasiński K., Maj M., Mackiewicz S., Staszczak M., Zubko M., Takesue N., Mechanical anisotropy of Gum Metal analyzed by ultrasonic measurements and digital image correlation, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.352-353, 2018Pieczyska E., Golasiński K., Maj M., Mackiewicz S., Staszczak M., Zubko M., Takesue N., Mechanical anisotropy of Gum Metal analyzed by ultrasonic measurements and digital image correlation, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.352-353, 2018Abstract: Experimental investigation of mechanical anisotropy in a multifunctional beta titanium alloy Gum Metal under compression is reported. Non-destructive and destructive techniques were used to analyze unique mechanical behavior of the alloy. Structural characterization showed a strong <110> texture of Gum Metal, which is a result of cold-swaging applied during its fabrication [1]. Due to this kind of texture Gum Metal can be treated as transversally isotropic solid. Ultrasonic measurements determined elastic constants with high accuracy. A significant difference between Young’s moduli of the alloy calculated for parallel and perpendicular directions to the alloy swaging direction was demonstrated. Compression of Gum Metal cube samples with two orientations was conducted on a testing machine. Two perpendicular walls of each sample were monitored by two visible range cameras during the deformation process for further 2-dimensional digital image correlation (DIC) analysis. Strong mechanical anisotropy of Gum Metal was confirmed by a detailed analysis of the stress vs. strain curves and strain distributions. | |
55. | Ustrzycka A., Mróz Z., Kowalewski Z.L., Characterization of Damage Evolution Supported by ESPI Analysis, ICEM 2018, 18TH INTERNATIONAL CONFERENCE ON EXPERIMENTAL MECHANICS, 2018-07-01/07-05, BRUKSELA (BE), No.082, pp.1, 2018 | |
56. | Ustrzycka A., Irradiation creep damage in nuclear reactor components
, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.116-117, 2018 | |
57. | Ustrzycka A., Mróz Z., Kucharski S., Kowalewski Z.L., Analysis of fatigue crack initiation caused by cyclic microplasticity
, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.272-273, 2018 | |
58. | Golasiński K., Pieczyska E.A., Mackiewicz S., Staszczak M., Zubko M., Takesue N., Analysis Gum Metal crystallographic texture and misorientation in correlation to its mechanical behavior, CAC, XXIV CONFERENCE ON APPLIED CRYSTALLOGRAPHY, 2018-09-02/09-06, Arłamów (PL), No.OY1-5, pp.37-38, 2018Golasiński K., Pieczyska E.A., Mackiewicz S., Staszczak M., Zubko M., Takesue N., Analysis Gum Metal crystallographic texture and misorientation in correlation to its mechanical behavior, CAC, XXIV CONFERENCE ON APPLIED CRYSTALLOGRAPHY, 2018-09-02/09-06, Arłamów (PL), No.OY1-5, pp.37-38, 2018Keywords: Gum Metal, EBSD, ultrasonic measurement | |
59. | Golasiński K., Pieczyska E., Maj M., Staszczak M., Takesue N., Superelastic-like behavior of Gum Metal under compression inspected by infrared thermography, ESOMAT 2018, 11th European Symposium on Martensitic Transformations, 2018-08-27/08-31, Metz (FR), pp.84, 2018 | |
60. | Golasiński K.M., Pieczyska E., Maj M., Staszczak M., Kuramoto S., Gum Metal under cyclic tension inspected by a fast and sensitive infrared camera, QIRT 2018, 14th Quantitative InfraRed Thermography Conference, 2018-06-25/06-29, Berlin (DE), pp.1-6, 2018Golasiński K.M., Pieczyska E., Maj M., Staszczak M., Kuramoto S., Gum Metal under cyclic tension inspected by a fast and sensitive infrared camera, QIRT 2018, 14th Quantitative InfraRed Thermography Conference, 2018-06-25/06-29, Berlin (DE), pp.1-6, 2018Abstract: This work presents results of experimental investigation of recoverable deformation of a β-Ti alloy Gum Metal inspected by infrared (IR) thermography. To this end, a flat specimen of Gum Metal was subjected to cyclic tension with an increasing strain on a testing machine and was simultaneously monitored by a fast and sensitive IR camera. The IR measurements determined an average temperature accompanying the alloy deformation process for subsequent tension cycles and allowed to estimate thermoelastic effect, which is related to the alloy yield point. Thermomechanical couplings accompanying the loading-unloading cycles were analyzed for estimating the range of reversible deformation from mechanical and thermal perspectives as well as discussed in the view of Lord Kelvin’s formula. | |
61. | Blachowski B., Tauzowski P., Lógó J., Elasto-Plastic Topology Optimization Under Stochastic Loading Conditions, EngOpt, 6th International Conference on Engineering Optimization, 2018-09-17/09-19, Lizbona (PT), DOI: 10.1007/978-3-319-97773-7_7, pp.70-79, 2018Blachowski B., Tauzowski P., Lógó J., Elasto-Plastic Topology Optimization Under Stochastic Loading Conditions, EngOpt, 6th International Conference on Engineering Optimization, 2018-09-17/09-19, Lizbona (PT), DOI: 10.1007/978-3-319-97773-7_7, pp.70-79, 2018Abstract: Optimal topologies obtained for structures subjected to deterministic loading can be sensitive to loading variations in terms of both magnitude and direction. Therefore, in this study we consider problem of topology optimization for structures subjected to probabilistic loading. The proposed method applies basic findings from probability theory, which allow to transform the original problem of topology optimization under single probabilistic loading into analogous problem of topology optimization under multiple deterministic loading cases. After recalling the theoretical background of the method,’ its effectiveness is demonstrated on an examples of cantilever structure subjected to horizontally oriented load with randomly varying angle of action. Keywords: Topology optimization, Stochastic load, Elastoplastic FE analysis | |
62. | Postek E., Sadowski T., Temperature effects during impact of WC/Co composites, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.1, 2018Postek E., Sadowski T., Temperature effects during impact of WC/Co composites, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.1, 2018Abstract: Generally, the papers on dynamic loading of composites more focus on the layered composites, for example [1]. High attention is paid to blast load. However, in our opinion, the process of impact a gap for analysis of WC/Co composite during impact conditions. During impact of WC/Co composite objects and the other composites with metallic binder heat of plastic work is generated. If the process is fast enough the problem can be treated as adiabatic. However, more common situation is slower process when the heat is generated in metallic interfaces and the neighbouring grains are heated due to conduction. The process should be rather considered as coupled [2]. We developed our model of WC/Co composite towards impact load, [3]. Keywords: thermomechanics, coupled problems, composites | |
63. | Postek E., Nowak Z., Pęcherski R., Impact resistance of crushable foam skeleton, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.1-2, 2018Postek E., Nowak Z., Pęcherski R., Impact resistance of crushable foam skeleton, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.1-2, 2018Abstract: The analyses of the modern cellular materials due to complexity of their internal structure require efficient computer methods and codes. The new method that has been developed mostly in the last 10 years is peridynamics [1, 2]. The developments resulted in highly parallelized code [3] that we use in our analysis.
The subject of the study are alumina foams produced by gelcasting method. The results of microtomography of alumina foams are used to create the numerical model reconstructing the structure of foam skeleton. The numerical simulations of failure strength under compression for alumina foams are performed. The calculations with use of the numerical model are time consuming. Therefore, the simplified method of the assessment of failure strength is proposed. The 3D model of the foam structure is created. The detailed description of the model generation is presented in Nowak et al. [5].
The numerical models of real Al2O3 foam with porosity 96 %, and discussion of theirs mechanical properties have been presented. The method of the assessment of failure strength of real alumina foam produced by the gelcasting is proposed.
We attempt to present the mechanism of damaging of a crushable foam under impact. Keywords: foams, damage, impact, peridynamics | |
64. | Pawłowska S., Pierini F., Kowalewski T.A., Highly flexible filaments in an oscillatory microchannel flow, EFMC12, 12th European Fluid Mechanics Conference, 2018-09-09/09-13, Wiedeń (AT), pp.1, 2018 | |
65. | Postek E., Sadowski T., Temperature effect in 2 phase ceramic based composite during impact conditions, ICCS21, 21st International Conference on Composite Materials, 2018-09-04/09-07, University of Bologna, Bologna (IT), DOI: 10.15651/978-88-938-5079-7, pp.100, 2018Postek E., Sadowski T., Temperature effect in 2 phase ceramic based composite during impact conditions, ICCS21, 21st International Conference on Composite Materials, 2018-09-04/09-07, University of Bologna, Bologna (IT), DOI: 10.15651/978-88-938-5079-7, pp.100, 2018Abstract: Cermet Materials (CM) are often used for manufacturing of different cutting tools. They have very good mechanical, wear and thermal properties. In our opinion, the dynamic load is still not enough thoroughly analysed, and the impact load as well. The tools are subjected to different dynamic effects.We have taken into account complex spatial distribution of cermet phases, grain/binder interfaces modeled by interface elements, possibility of cracks appearance within binders using interface elements as well, and rotation of brittle grains.
The main goal of the presentation is to develop further previously formulated models of two-phase composite [1-4] to capture effects of temperature due to impact. The source of the thermal loading is the conversion of plastic work into heat [5, 6]. The increase of temperature takes place in the Co interfaces. We investigate adiabatic and fully coupled solutions.
We note differences in the behaviour of the samples when the thermal loading is not considered. We have found that the thermal softening effect in the interface material is important as well. We enhance the description of the damage mechanism in the presence of temperature increase.
Acknowledgements
This work was financially supported by Ministry of Science and Higher Education (Poland) within the statutory research (IPPT PAN) and National Science Centre (Poland) project No 2016/21/B/ST8/01027 (Lublin University of Technology). The calculations were done at the Interdisciplinary Centre for Mathematical and Computational Modelling, University of Warsaw, Poland. The licenses for the MSC Patran and Abaqus programs were provided by Academic Computer Centre in Gdańsk, Poland.
References:
[1] Sadowski T, Hardy S, Postek E. Prediction of the mechanical response of polycrystalline ceramics containing metallic intergranular layers under uniaxial tension. Comput Mat Sci 2005;34:46-63.
[2] Sadowski T, Hardy S, Postek E. A new model for the time-dependent of polycrystalline ceramic materials with metallic inter-granular layers under tension. Mat. Sci. Eng. A 2006;424:230-238.
[3] Sadowski T, Postek E, Denis C. Stress distribution due to discontinuities in polycrystalline ceramics containing metallic inter-granular layers. Comput Mat Sci 2007;39: 230-236.
[4] Postek E, Sadowski T. Dynamic pulse sensitivity of WC/Co composite, (accepted in Composite Structures).
[5] Wriggers P, Miehe C, Kleiber M, Simo JC. On the coupled thermomechanical treatment of necking problems via finite element methods. Int. J. Num. Meth. Eng. 1992; 33:869–883.
[6] Rojek J, Onate E, Postek E. Application of explicit FE codes to simulation of sheet and bulk metal forming processes. J. Mat. Proc. Tech. 1998; 80–81: 620–627.
Keywords: cermet composites, coupled solutions, thermomechanics | |
66. | Urbanek O., Kołbuk D., Sonochemical modification of electrospun fibres with hydroxyapatite nanoparticles, ESB2018, 29th European Conference on Biomaterials, 2018-09-09/09-13, Maastricht (NL), pp.523-524, 2018 | |
67. | Kopeć M., Wang K., Wang Y., Wang L., Lin J., Feasibility study of a novel hot stamping process for Ti6Al4V alloy, MATEC Web of Conferences, ISSN: 2261-236X, DOI: 10.1051/matecconf/201819008001, Vol.190, pp.1-5, 2018Kopeć M., Wang K., Wang Y., Wang L., Lin J., Feasibility study of a novel hot stamping process for Ti6Al4V alloy, MATEC Web of Conferences, ISSN: 2261-236X, DOI: 10.1051/matecconf/201819008001, Vol.190, pp.1-5, 2018Abstract: To investigate the feasibility of a novel hot stamping process for the Ti6Al4V titanium alloy using low temperature forming tools, mechanical properties of the material were studied using hot tensile tests at a temperature range of 600 - 900°C with a constant strain rate of 1s-1. Hot stamping tests were carried out to verify the feasibility of this technology and identify the forming window for the material. Results show that when the deformation temperature was lower than 700°C, the amount of elongation was less than 20%, and it also had little change with the temperature. However, when the temperature was higher than 700°C, a good ductility of the material can be achieved. During the forming tests, parts failed at lower temperatures (600°C) due to the limited formability and also failed at higher temperatures (950°C) due to the phase transformation. The post-form hardness firstly decreased with the temperature increasing due to recovery and then increased due to the phase transformation. Qualified parts were formed successfully between temperatures of 750 - 850°C, which indicates that this new technology has a great potential in forming titanium alloys sheet components. Keywords: titanium, hot stamping, metal forming | |
68. | Wang K., Kopeć M., Qu H., Wang Y., Wang L., Lin J., Li Z., A unified constitutive model for two-phase titanium alloys under hot stamping condition, ICNFT 2018, 5th International Conference on New Forming Technology, 2018-08-18/08-21, Bremen (DE), pp.1-1, 2018 | |
69. | Tauzowski P., Blachowski B., Lógó J., Functor-Oriented Finite Element Programming with Application to Structural Topology Optimization, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), No.P076, pp.490-491, 2018Tauzowski P., Blachowski B., Lógó J., Functor-Oriented Finite Element Programming with Application to Structural Topology Optimization, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), No.P076, pp.490-491, 2018Abstract: The subject of this study is an efficient approach to the development of a finite element framework, which is intended to be used for solving a variety of problems in computational solid mechanics. One of such problems, recently becoming an active field of research, is topology optimization of structures made of elastic-plastic materials. For finding the optimal topology of real, practical and complex structures the knowledge of a number of numerical algorithms is required, to mention a few: modification of finite element meshes, aggregation of tangent stiffness matrices, or direct and iterative solvers. The classical computer implementation of the original Classical Optimality Criteria method (COC) of the topology optimization problem given by Bendsoe and Sigmund is relatively simple and contains 99 lines of code in the MATLAB language. However, it assumes that there exists only a single loading case, single displacement (compliance) constraint, the material is linearly elastic and the optimal topology can be found using the so-called Solid Isotropic Material with Penalization (SIMP) algorithm, which is based on the original COC method. In reality, engineers face a slightly different problem. They need to find the topology of a minimum weight structure subjected to multiple loading cases, made of an elasto-plastic material, and with a limit on stresses. The above mentioned SIMP approach may not lead to an optimal solution. Keywords: functor-oriented programming, topology optimization, elastoplastic FE analysis | |
70. | Ostrowski M., Blachowski B., Jankowski L., Pisarski D., Semi-Active Control of Mechanical Energy Transport Between Vibrational Modes , SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), No.P136, pp.408-409, 2018Ostrowski M., Blachowski B., Jankowski L., Pisarski D., Semi-Active Control of Mechanical Energy Transport Between Vibrational Modes , SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), No.P136, pp.408-409, 2018Abstract: The vibration attenuation problem has been solved using many different methods, some of which involve the use of advanced control algorithms. The topic of harvesting the energy of structural vibrations is less explored. For that reason, this contribution studies the problem of conversion of mechanical energy of vibrations. The paper presents a method of semi-active control, which is applied to dynamically transfer the vibration energy into a selected vibration mode. The target mode is selected in such a way that the amount of energy that can be recovered during the vibration process is maximized. In other words, switching between two modes is not intended to dissipate the energy of vibrations, but rather to maximize the energy-harvesting potential of the overall system. The concept will be illustrated using an example of a simple frame structure, in which semi-actively controlled lockable joints modify the modal properties of the structure. Keywords: semi-active control, lockable joints, energy-harvesting | |
71. | Kecik K., Zaszczyńska A.^{♦}, Mitura A., Experimental Investigations of Energy Recovery from an Electromagnetic Pendulum Vibration Absorber, Journal of Vibration Testing and System Dynamics, ISSN: 2475-4811, DOI: 10.5890/JVTSD.2018.09.002, Vol.2, No.3, pp.209-219, 2018Kecik K., Zaszczyńska A.^{♦}, Mitura A., Experimental Investigations of Energy Recovery from an Electromagnetic Pendulum Vibration Absorber, Journal of Vibration Testing and System Dynamics, ISSN: 2475-4811, DOI: 10.5890/JVTSD.2018.09.002, Vol.2, No.3, pp.209-219, 2018Abstract: The paper presents an experimental study of a special non−linear low frequency system dedicated to vibration mitigation and energy recovery. The dual−function design was based on an autoparametric vibration system, which consists of an oscillator with an added pendulum vibration absorber. Its structure includes an energy harvesting device: a levitating magnet in a coil. The pendulum motion shows simultaneously the effects of vibration reduction and energy recovery. The influences of the magnet−coil configurations, and load resistances on vibration reduction and energy harvesting were studied in detail. Keywords: Experiment, Energy recovery, Pendulum, Vibration mitigation | |
72. | Blachowski B., Tauzowski P., Logo J., Topology optimization of elastoplastic structures: Stress intensity driven formulation and functor-oriented implementation, CST2018, The Thirteenth International Conference on Computational Structures Technology 2018, 2018-09-04/09-06, Sitges, Barcelona (ES), No.0090, pp.1-3, 2018Blachowski B., Tauzowski P., Logo J., Topology optimization of elastoplastic structures: Stress intensity driven formulation and functor-oriented implementation, CST2018, The Thirteenth International Conference on Computational Structures Technology 2018, 2018-09-04/09-06, Sitges, Barcelona (ES), No.0090, pp.1-3, 2018Abstract: This study is devoted to a practical method for topology optimization of elastoplastic structures subjected to stress constraints. Instead of the classical compliance minimization problem the aim of this work is to find a minimum weight structure, which is able to carry given load and the corresponding stresses do not exceed an allowable limit. The general form of the problem is based on the classical limit design formulations of plasticity. The proposed method finds optimal structure in an iterative way using only stress intensity distribution and doesn’t require computing of any gradients or sensitivities.
Our method starts with determining representative stresses in every quadrilateral finite element. At first an elastoplastic analysis is performed to obtain stress values in four Gaussian points, then by the use of von Misses criterion and these stress values the resultant stress is calculated. Next, having obtained stress intensity distribution within the structure we apply penalization to avoid stress concentration issues. Finally, the material is removed proportionally to the stress intensities of individual finite elements. The above mentioned procedure is repeated until limit load capacity is achieved for a given loading vector. The checkerboard problem is solved by means of design filter. Two benchmark problems have been selected as illustrative examples. They are: cantilever and simply supported beam. For these examples parametric studies on different length to height ratios and support patterns are conducted. Additionally, the results of topology optimization for different values of filter radius and penalty parameter are presented.
Finally, efficient computer implementation based on functor-oriented programming is discussed. It is demonstrated how Functor and Template-based programming can be utilized to create versatile Finite Element environment. Within this environment computation of all element matrices and loading vectors can be called in the same way, this in turn allows for implementation of effective aggregation procedure. Keywords: topology optimization, minimum-weight design, functor-oriented programming, stress constraints | |
73. | Dlugosz A., Pokorska I., Glinicki M.A., Jaskulski R.^{♦}, Application of evolutionary algorithms in identification of thermal properties of hardening concerte, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.1-2, 2018 | |
74. | Kowalewski Z.L., Szymczak T., Badania wytrzymałościowe połączeń spawanych w elementach wybranych konstrukcji, XXIV Seminarium NIENISZCZĄCE BADANIA MATERIAŁÓW, 2018-03-14/03-16, Zakopane (PL), pp.21-50, 2018 | |
75. | Kowalewski Z.L., Advances in fatigue investigations of materials – state of the art and new challenges, 12th INTERNATIONAL ARMAMENT CONFERENCE, 2018-09-17/09-20, Jachranka (PL), pp.161-162, 2018 | |
76. | Szymczak T., Brodecki A.^{♦}, Makowska K., Kowalewski Z.L., Tow truck frame made of high strength steel under cyclic loading, 35 DANUBIA-ADRIA, 35th Danubia-Adria Symposium on Advances in Experimental Mechanics, 2018-09-25/09-28, Sinaia (RO), pp.145-146, 2018 | |
77. | Szymczak T., Kowalewski Z.L., Visco-plastic effects due to deformation along circular loading path
, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.42-43, 2018 | |
78. | Makowska K., Kowalewski Z., Dudda W., Ziółkowski P., Badur J., Damage assessment of exploited turbine blades using barkhausen noise parameters
, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.270-271, 2018 | |
79. | Szymczak T., Kowalewski Z.L., Brodecki A.^{♦}, Mini-compact tension specimens for fracture toughness evaluation
, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), pp.274-275, 2018 | |
80. | Mackiewicz S., Badania ultradźwiękowe w sprzężeniu powietrznym, XXIV Seminarium NIENISZCZĄCE BADANIA MATERIAŁÓW, 2018-03-14/03-16, Zakopane (PL), pp.135-153, 2018 | |
81. | Mackiewicz S., Istota, znaczenie oraz metodyka wyznaczania parametru SNR w radiografii cyfrowej, STARY MŁYN, KRAJOWA KONFERENCJA BADAŃ RADIOGRAFICZNYCH - „STARY MŁYN 2018”, 2018-09-10/09-12, Bolesławiec (PL), pp.1-13, 2018 | |
82. | Popławski B., Mikułowski G., Suwała G., Jankowski Ł., Optimization of actuator placement for vibration damping in the Prestress-Accumulation release control approach, WCSCM, 7th World Conference on Structural Control and Monitoring, 2018-07-22/07-25, Qingdao (CN), pp.818-827, 2018Popławski B., Mikułowski G., Suwała G., Jankowski Ł., Optimization of actuator placement for vibration damping in the Prestress-Accumulation release control approach, WCSCM, 7th World Conference on Structural Control and Monitoring, 2018-07-22/07-25, Qingdao (CN), pp.818-827, 2018Abstract: This contribution proposes a quantitative criterion for optimization of actuator placement for the Prestress–Accumulation Release (PAR) strategy of mitigation of vibrations. The PAR strategy is a semi-active control approach that relies on controlled redistribution of modal energy into high-frequency high-order modes, where it is effectively dissipated by means of the natural mechanisms of material damping. The energy transfer is achieved by a controlled temporary removal of selected structural constraints. An example is a short-time decoupling of rotational degrees of freedom in a frame node, so that the bending moments are no longer transferred between the involved beams. If it such a decoupling is performed at the maximum of the shear/bending strain energy of adjacent beams, it results in an almost instantaneous energy release into high-frequency local vibrations and quick dissipation of energy. We propose and test a quantitative criterion for placement of such actuators. The criterion is based on local modal strain energy that can be released into high-order modes. The numerical time complexity is linear with respect to the number of actuators, which facilitates quick selection of placements in large structures. Keywords: semi-active control, damping of vibrations, actuator placement, smart structures, Prestress-Accumulation Release (PAR) | |
83. | Popławski B., Mikułowski G., Mróz A.^{♦}, Jankowski Ł., Decentralized algorithm for semi-active damping of forced vibrations using controllable truss-frame nodes, WCSCM, 7th World Conference on Structural Control and Monitoring, 2018-07-22/07-25, Qingdao (CN), pp.582-590, 2018Popławski B., Mikułowski G., Mróz A.^{♦}, Jankowski Ł., Decentralized algorithm for semi-active damping of forced vibrations using controllable truss-frame nodes, WCSCM, 7th World Conference on Structural Control and Monitoring, 2018-07-22/07-25, Qingdao (CN), pp.582-590, 2018Abstract: Semi-active systems for mitigation of vibrations proved to be effective in many applications. Their prominent advantage is that they combine strong points of passive and active damping systems. Proper design can ensure their reliability, which is what passive systems are praised for. A high effectiveness in vibration damping links them with active systems. At the same time they do not have many deficiencies of active systems. They are adaptive, so they can stay effective in different environmental conditions, which is the factor that eliminates passive systems from many implementations. Their mass and energy consumption is very low, and the controlled structure can stay in the safe configuration even in case of power supply failure, which puts them in contrast to many active systems. The mentioned attributes make them a good choice for many structures subjected to vibrations, especially when there is a strong emphasis on maximization of the efficiency/mass ratio of the damping system.
This contribution presents a decentralized closed-loop control strategy and applies it in a frame structure equipped with controllable truss-frame nodes. Such nodes can be switched between frame-like and truss-like states in a controllable manner. In the frame-like state the node transmits all forces and moments, while in the truss-like state only axial and shearing forces are transmitted. These nodes allow for structural reconfiguration, which can be utilized by semi-active control strategies for the purpose of vibration damping. The implemented control algorithm applies the Prestress-Accumulation Release (PAR) strategy based on the transmission of the accumulated potential energy to high modes of vibration, which are highly dissipative. Strain measurements are conducted locally on selected elements. A similar strategy proved its effectiveness in mitigation of free structural vibrations. This research studies the concept of its application to mitigation of forced structural vibrations, caused by variable external conditions. Keywords: Semi-active damping, Truss-frame nodes, Prestress-Accumulation Release (PAR), Decentralized control | |
84. | Hou J., Wang S., Jankowski Ł., Structure damage localization of the slab track by adding virtual masses, WCSCM, 7th World Conference on Structural Control and Monitoring, 2018-07-22/07-25, Qingdao (CN), pp.1368-1373, 2018Hou J., Wang S., Jankowski Ł., Structure damage localization of the slab track by adding virtual masses, WCSCM, 7th World Conference on Structural Control and Monitoring, 2018-07-22/07-25, Qingdao (CN), pp.1368-1373, 2018Abstract: In this paper, a damage localization method based on additional virtual mass and dynamic test of simple harmonic excitation is proposed. Firstly, when additional masses are added to the structure, a large number of virtual structures can be constructed; then the virtual construction formula is derived in order to obtain the dynamic response of virtual structures without adding real mass. After dynamic test of simple harmonic excitation, the dynamic response of virtual structures can be obtained using the acceleration response and virtual construction formula. Furthermore, when the applied harmonic excitation frequency is close to the natural frequency of the structure, the structural response can reach a maximum by adding advisable mass and the mass value can be calculated. When the local structure is damaged, the extreme value and the corresponding position of the additional mass are found by adding mass at different positions in the structure. Thus, the approximate location of the damage is determined according to the results. Finally, the numerical simulation of the elastic foundation beam model simplified by track structure is carried out, and the results show that the damage can be localized. Keywords: structural health monitoring, damage identification, slab track, virtual mass | |
85. | Błachowski B., Świercz A., Jankowski Ł., Virtual Distortion Method based optimal sensor placement for damage identification, ISMA 2018, The Leuven Conference on Noise and Vibration Engineering, 2018-09-17/09-19, Leuven (BE), pp.3689-3698, 2018Błachowski B., Świercz A., Jankowski Ł., Virtual Distortion Method based optimal sensor placement for damage identification, ISMA 2018, The Leuven Conference on Noise and Vibration Engineering, 2018-09-17/09-19, Leuven (BE), pp.3689-3698, 2018Abstract: The paper presents a novel method for sensor placement optimized towards effective identification of structural damages. The derivation of the method is based on the concept of virtual distortions together with information provided by a set of strain gauges. Then, a gradient oriented optimization is applied to identify sensor locations, which are the most sensitive to potential damage scenarios. Steepest descent method is utilized to determine the optimal values of the objective function. Additionally, dependence of the method on the applied excitation signal is discussed. Finally, effectiveness of the proposed methodology is demonstrated on an example of optimal search for sensor placement on a 6-bay planar truss structure. | |
86. | Mikułowski G., Semi-active damping of forced vibrations by means of pneumatic supports, ISMA 2018, The Leuven Conference on Noise and Vibration Engineering, 2018-09-17/09-19, Leuven (BE), pp.1051-1061, 2018Mikułowski G., Semi-active damping of forced vibrations by means of pneumatic supports, ISMA 2018, The Leuven Conference on Noise and Vibration Engineering, 2018-09-17/09-19, Leuven (BE), pp.1051-1061, 2018Abstract: Vibration mitigation and vibration isolation are problems existing in a variety of industry branches. Pneumatic suspensions and isolators are a widely utilized technology, and in many applications they need to adapt their properties to a varying mass of the supported object, e.g., loaded or unloaded lorries. However, the pneumatic solutions posses limitations in the field of adequate damping. The change in mass results in a change in the required level of damping. This contribution presents and verifies a concept of an enhanced damping pneumatic device using an example of a Pneumatic Adaptive Absorber (PAA) adapted to the task of mitigation of forced vibrations. The investigation presents a concise introduction to the concept, as well as analytical and numerical modelling of the conceptual device. The contribution proposes a control algorithm based on performed analysis of mechanical energy dissipation process. The concept is verified experimentally in a laboratory. The proposed modelling seems to be in agreement with the demonstrator response. | |
87. | Mikułowski G., Popławski B., Wiszowaty R., Mróz A.^{♦}, Jankowski Ł., An investigation on a semi-active damping of forced structural vibrations by means of controllable structural nodes, ISMA 2018, The Leuven Conference on Noise and Vibration Engineering, 2018-09-17/09-19, Leuven (BE), pp.189-201, 2018Mikułowski G., Popławski B., Wiszowaty R., Mróz A.^{♦}, Jankowski Ł., An investigation on a semi-active damping of forced structural vibrations by means of controllable structural nodes, ISMA 2018, The Leuven Conference on Noise and Vibration Engineering, 2018-09-17/09-19, Leuven (BE), pp.189-201, 2018Abstract: Vibration mitigation in space structures creates a unique class of a technical problem where resistant for outgassing and non-fluidic solutions are preferable. Additionaly, a vibration induced by time-varying excitations needs to be effectively reduced. The vibration mitigation task is speciffically difficult in the case of light, slender and inherently flexible structures of various types, such as supporting structures, deployable structures, modular structures or wide-span skeletal roofing structures. This study presents a concept of a vibration attenuation method based on semi-active joints and dedicated to frame structures under forced vibration excitation. The presented investigation contains an analysis of the problem of the optimal control of a structure fitted with semi-active structural members. Furthermore, an adequate model of the semi-active joints is developed and a numerical example is presented. Finally, the research provides an experimental verification of the developed control algorithms, which is conducted on a test stand in a laboratory environment. | |
88. | Popławski B., Mikułowski G., Wiszowaty R., Jankowski Ł., Semi-active mitigation of externally induced vibrations, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), No.P197, pp.1-2, 2018Popławski B., Mikułowski G., Wiszowaty R., Jankowski Ł., Semi-active mitigation of externally induced vibrations, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), No.P197, pp.1-2, 2018Abstract: Almost all man-made structures are exposed to vibration. Regardless of whether these are large structures such as bridges or skyscrapers, machines with rotating parts such as engine shafts, frame structures or vehicle suspensions, excessive vibrations can be very harmful. From the perspective of their effects they can be seen as very spectacular (e.g., a collapse of a bridge) or not worth much attention (e.g., a failure of a motor shaft), but in each of these cases, the effect is the destruction of the structure and a negative impact on the users of these devices.
Several approaches can be used by the designers to overcome this phenomenon. The most basic, but often sufficient, method is to introduce changes in the mechanical parameters of the system affecting the severity of vibration in operational conditions, i.e., its mass or stiffness. If such design changes cannot be realized, or if vibration problems are detected after the system is manufactured, or if a vibration suppression system must be used for other reasons, one of the three basic types of such systems can be used.
The primary choice is usually a passive vibration damping system. These are relatively simple systems whose mode of operation is the passive dissipation of the energy of structural vibrations. Their design and simple functionality ensures that they are highly reliable, but their simplicity is reflected, unfortunately, in their limited efficiency. Their flexibility may be also considered as insufficient: once configured, even a small change in the specific operating conditions can result in a drastic loss of performance. This indicates a rather narrow spectrum (frequency range) of correct system operation.
Active systems constitute a much more effective damping approach. In this case, vibration attenuation is achieved not by means of dampers, but by actuators integrated into the structure. This approach allows to achieve very good results of vibration mitigation over a wide range of excitation frequencies. High efficiency, however, is burdened with a much higher degree of complexity of such a system as compared to the passive systems. In order to develop such a system, it is necessary to design the controller and install actuators that implement the control algorithm. During the vibration suppression, the actuators themselves require a large energy supply, which can be troublesome in some cases.
The compromise between these damping systems are semi-active systems, where the actuators are used to affect structural properties instead of exerting large external forces. In terms of reliability, semi-active systems can be compared with passive systems, while in terms of the efficiency of damping with active ones. They also do not require large amounts of electric energy to implement the control algorithm. Despite being a relatively new research area with less established design and development procedures, their advantages seem to be large enough to attract a growing number of scientists and engineers.
This contribution presents a strategy for semi-active reduction of forced vibrations in frame structures. Analogous damping technique proved to be effective in damping of free vibrations. The control strategy is based on the Prestress Accumulation–Release (PAR) concept and uses specially designed semi-active rotational nodes. Successive decentralization of the damping system demonstrates that apart from the global mechanism of the energy dissipation based on the PAR, it is also possible to disperse it locally to individual beams that are separate elements of the damping system. | |
89. | Gawlicki M., Jankowski Ł., Identification of a load moving on a plate using the l1 norm minimization, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), No.P226, pp.1-2, 2018Gawlicki M., Jankowski Ł., Identification of a load moving on a plate using the l1 norm minimization, SolMech 2018, 41st SOLID MECHANICS CONFERENCE, 2018-08-27/08-31, Warszawa (PL), No.P226, pp.1-2, 2018Abstract: There are two fundamental inverse problems in the field of structural health monitoring (SHM): identification of damages and identification of loads. Effectiveness of the related computational methods is crucial for maintaining integrity of the monitored structures. This contribution considers identification of unknown loads based on measurements of structural response. It is a relatively extensively researched problem: reviews of techniques used for off-line load identification can be found in [1,2], while techniques for online identification are reviewed in [3].
If the aim is to identify independent force histories in each of the excited degrees of freedom (Dofs), the uniqueness of the solution can be possible only if there are at least as many sensors (equations) as the excited Dofs (unknowns). Such a requirement can be satisfied in case of a few unknown stationary loads, but it becomes problematic if the unknown load is (even single but) moving in an unknown way across the structure. In such a case, a very large number of Dofs can be potentially excited and a limited number of sensors are available to measure the response. As a result, the naïve direct formulation of the inverse problem is underdetermined, and the solution is not unique.
This contribution is devoted to indirect identification of a single moving load that excites a 2D structure (plate). To attain the uniqueness, the solution space needs to be significantly constrained. However, instead of assuming a known trajectory of the load and identifying its value, the aim is to identify the trajectory only. Such a problem is important, e.g., in traffic monitoring and control [4,5]. Effectively, the approach is based on the assumption of sparsity of the excitation, which seems to suit the practice: even if the location of the load is unknown, at each time instant only a single (or a limited number of) Dofs is excited. Such an approach follows the methodology of compressed sensing [6], which includes such SHM-related applications as identification of impact load position [7]. The assumption of sparsity is usually expressed as a requirement of a bounded l1 norm of the solution [8].
The approach has already been verified numerically and experimentally using a flexible 1D structure (a beam) excited with a moving mass [9]. The cases considered there included single or multiple passes of the mass across the beam. The assumption of sparsity allowed the space-time trajectory of the load to be identified. Here, the goal is to test the approach in a much more complex problem that involves a 2D structure, e.g., a plate, subjected to a single moving load. In the fully dynamic case the task is computationally very demanding, thus we focus here on the quasi-static case. This abstract describes briefly the method and the experimental stand. Detailed results will be presented during the conference. | |
90. | Faraj R., Graczykowski C., Mikułowski G., Wiszowaty R., Holnicki-Szulc J., Control techniques for adaptive absorbers, WCSCM, 7th World Conference on Structural Control and Monitoring, 2018-07-22/07-25, Qingdao (CN), pp.1-9, 2018Faraj R., Graczykowski C., Mikułowski G., Wiszowaty R., Holnicki-Szulc J., Control techniques for adaptive absorbers, WCSCM, 7th World Conference on Structural Control and Monitoring, 2018-07-22/07-25, Qingdao (CN), pp.1-9, 2018Abstract: The paper is aimed at discussion of various control techniques developed for adaptive impact-absorbers protecting structures and machines. Different approaches to the problem of optimal damper design are presented and systems comparison is provided with the example of pneu-matic shock-absorber. The influences of selected control strategy on the absorber characteris-tics, its efficiency and adaptation capabilities are shown. The contribution includes both numerical and experimental examples. The authors highlight the fact that the final design of the device should be elaborated simultaneously with the development of dedicated control system. In some cases properly assumed architecture of the control system enables significant simplifi-cation of the absorber. The paper covers analyses of semi-passive devices with single reconfig-uration to identified excitation conditions and semi-active absorbers capable of adaptation to unknown impact loading. Adaptation mechanisms of such devices and their robustness are com-pared in reference to volatility of system parameters and variety of loading conditions. Limita-tions of smart devices (e.g. piezo-electric valve in pneumatic absorbers) used in practice for absorbers’ control are described in relevant mathematical models. Technological challenges in the design and manufacturing of absorbers are identified and methods of their overcoming are proposed. Keywords: Adaptive Impact Absorption, adaptive control, adaptable system, damper | |
91. | Faraj R., High Performance Pneumatic Shock-absorbers for aeronautical applications, ICAS2018, 31st Congress of the International Council of the Aeronautical Sciences, 2018-09-09/09-14, Belo Horizonte (BR), pp.1-10, 2018Faraj R., High Performance Pneumatic Shock-absorbers for aeronautical applications, ICAS2018, 31st Congress of the International Council of the Aeronautical Sciences, 2018-09-09/09-14, Belo Horizonte (BR), pp.1-10, 2018Abstract: The paper is aimed at development of high performance shock-absorbers for aeronautical applications. This contribution concerns pneumatic dampers because of their lightweight, technical simplicity and low manufacturing costs. The concept of semi-passive devices is introduced and single reconfiguration technique is discussed for both single- and double-chamber shock-absorber. Presented general approach to optimal design of the semi-passive devices can be applied for design of different types of fluid-based absorbers, e.g. hydraulic or oleo-pneumatic dampers. The absorbers can be used as a suspension of light airdrop system as well as a part of landing gear of small UAV. | |
92. | Pieczyska E.A., Golasiński K., Maj M., Staszczak M., Kowalewski Z.L., Furuta T., Kuramoto S., Yielding and strain localization effects in gum metal - a unique ti alloy -investigated by digital image correlation and infrared thermography
, 35 DANUBIA-ADRIA, 35th Danubia-Adria Symposium on Advances in Experimental Mechanics, 2018-09-25/09-28, Sinaia (RO), pp.57-58, 2018 | |
93. | Denis P., Sajkiewicz P., Electrospun nonwovens with poly(glycerol sebacate), BiPoCo 2018, 4th International Conference on Bio-based Polymers and Composites, 2018-09-02/09-06, Balatonfured (HU), pp.1-2, 2018 | |
94. | Dobkowska-Chudon W., Wrobel M., Karłowicz P., Dabrowski A., Krupienicz A., Targowski T., Nowicki A., Olszewski R., Detecting cerebrovascular changes in the brain caused by hypertension in atrial fibrillation group using acoustocerebrography, PLOS ONE, ISSN: 1932-6203, DOI: 10.1371/journal.pone.0199999, pp.1-10, 2018Dobkowska-Chudon W., Wrobel M., Karłowicz P., Dabrowski A., Krupienicz A., Targowski T., Nowicki A., Olszewski R., Detecting cerebrovascular changes in the brain caused by hypertension in atrial fibrillation group using acoustocerebrography, PLOS ONE, ISSN: 1932-6203, DOI: 10.1371/journal.pone.0199999, pp.1-10, 2018Abstract: Acoustocerebrography is a novel, non-invasive, transcranial ultrasonic diagnostic method
based on the transmission of multispectral ultrasound signals propagating through the brain
tissue. Dedicated signal processing enables the estimation of absorption coefficient, frequency-
dependent attenuation, speed of sound and tissue elasticity. Hypertension and atrial
fibrillation are well known factors correlated with white matter lesions, intracerebral hemorrhage
and cryptogenic stroke numbers. The aim of this study was to compare the acoustocerebrography
signal in the brains of asymptomatic atrial fibrillation patients with and
without hypertension. The study included 97 asymptomatic patients (40 female and 57
male, age 66.26 ± 6.54 years) who were clinically monitored for atrial fibrillation. The
patients were divided into two groups: group I (patients with hypertension) n = 75, and group
II (patients without hypertension) n = 22. Phase and amplitude of all spectral components
for the received signals from the brain path were extracted and compared to the phase and
amplitude of the transmitted pulse. Next, the time of flight and the attenuation of each frequency
component were calculated. Additionally, a fast Fourier transformation was performed
and its features were extracted. After introducing a machine learning technique, the
ROC plot of differentiations between group I and group II with an AUC of 0.958 (sensitivity
0.99 and specificity 0.968) was obtained. It can be assumed that the significant difference in
the acoustocerebrography signals in patients with hypertension is due to changes in the
brain tissue, and it allows for the differentiating of high-risk patients with asymptomatic atrial
fibrillation and hypertension. Keywords: changes in the brain, hypertension in atrial, acoustocerebrography | |
95. | Papliński P., Wańkowicz J., Ranachowski P., Ranachowski Z., Microstructure and degree of degradation of ZnO varistors in surge arresters due to operation
, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.24425/123800, Vol.63, No.3, pp.1267-1273, 2018Papliński P., Wańkowicz J., Ranachowski P., Ranachowski Z., Microstructure and degree of degradation of ZnO varistors in surge arresters due to operation
, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.24425/123800, Vol.63, No.3, pp.1267-1273, 2018Abstract: The paper presents the test results for the microstructure of ZnO varistors comprising high voltage gapless surge arresters. The tests were performed on varistors produced in different periods and by various manufacturers. The research was inspired by different characteristics of changes in values of current flowing through surge arresters as a function of changes in values of system voltage in a 220 kV substation, and the temperature in a multi-year cycle. Furthermore, the effects of varistor microstructure degradation following a failure of an unsealed surge arrester were investigated. The results provided the grounds for assessment of ZnO varistor microstructure parameters in terms of their durability and resistance to degradation processes. Keywords: surge arrester, MO varistor, microstructure of ceramics, ceramic material degradation | |
96. | Lewandowski M., Walczak M., Witek B., Rozbicki J., Steifer T., Demonstrator przenosnego systemu Phased-Array z funkcją Full-Matrix Capture, BADANIA NIENISZCZĄCE I DIAGNOSTYKA, ISSN: 2451-4462, Vol.3, pp.70-71, 2018Lewandowski M., Walczak M., Witek B., Rozbicki J., Steifer T., Demonstrator przenosnego systemu Phased-Array z funkcją Full-Matrix Capture, BADANIA NIENISZCZĄCE I DIAGNOSTYKA, ISSN: 2451-4462, Vol.3, pp.70-71, 2018Abstract: Ultradźwiękowe systemy Phased-Array (PA) umożliwiają detekcję i ocenę wad za pomocą wieloelementowych głowic ze skanowaniem elektronicznym. Zaawansowane metody kierowania wiązki oraz wizualizacji znacznie ułatwiają badania obiektów o skomplikowanej geometrii. Należy jednak pamiętać, ze klasyczna metoda PA bazuje na tych samych zasadach fizycznych, co skanowanie standardowymi głowicami jednoelementowymi i posiada te same ograniczenia. W naszym laboratorium pracujemy nad implementacją nowej klasy metod obrazowania UT, które wykorzystują technikę Full-Matrix Capture (FMC) oraz Total Focusing Method (TFM). Metody te dają zupełnie nowe możliwości rekonstrukcji obrazów wad i pozwalają na uzyskanie jednorodnej rozdzielczości poprzecznej w całej głębokości badania. W tym celu zbudowaliśmy demonstrator przenośnego systemu PA wyposażony w funkcje FMC i TFM. Akwizycja pełnej macierzy ech oraz przetwarzanie softwarowe na wbudowanym procesorze GPU (Nvidia Tegra) zapewniają duże możliwości przetwarzania i analizy sygnałów. Demonstrator jest wyposażony w 32-kanały akwizycji w konfiguracji 32:128 i współpracuje ze standardowymi głowicami PA firmy Olympus. Keywords: UT, Phased-Array, akwizycja pełnej macierzy, GPU | |
97. | Walczak J.^{♦}, Partyka M., Duszyński J., Szczepanowska J., Implications of mitochondrial network organization in mitochondrial stress signalling in NARP cybrid and Rho0 cells, Scientific Reports, ISSN: 2045-2322, DOI: 10.1038/s41598-017-14964-y, Vol.7, No.14864, pp.1-14, 2017Walczak J.^{♦}, Partyka M., Duszyński J., Szczepanowska J., Implications of mitochondrial network organization in mitochondrial stress signalling in NARP cybrid and Rho0 cells, Scientific Reports, ISSN: 2045-2322, DOI: 10.1038/s41598-017-14964-y, Vol.7, No.14864, pp.1-14, 2017Abstract: Mitochondrial dysfunctions lead to the generation of signalling mediators that influence the fate of that organelle. Mitochondrial dynamics and their positioning within the cell are important elements of mitochondria-nucleus communication. The aim of this project was to examine whether mitochondrial shape, distribution and fusion/fission proteins are involved in the mitochondrial stress response in a cellular model subjected to specifically designed chronic mitochondrial stress: WT human osteosarcoma cells as controls, NARP cybrid cells as mild chronic stress and Rho0 as severe chronic stress. We characterized mitochondrial distribution in these cells using confocal microscopy and evaluated the level of proteins directly involved in the mitochondrial dynamics and their regulation. We found that the organization of mitochondria within the cell is correlated with changes in the levels of proteins involved in mitochondrial dynamics and proteins responsible for regulation of this process. Induction of the autophagy/mitophagy process, which is crucial for cellular homeostasis under stress conditions was also shown. It seems that mitochondrial shape and organization within the cell are implicated in retrograde signalling in chronic mitochondrial stress. | |
98. | Poma A.B.^{♦}, Cieplak M., Theodorakis P.E., Combining the MARTINI and Structure-Based Coarse-Grained Approaches for the Molecular Dynamics Studies of Conformational Transitions in Proteins, Journal of Chemical Theory and Computation, ISSN: 1549-9618, DOI: 10.1021/acs.jctc.6b00986, Vol.13, pp.1366-1374, 2017Poma A.B.^{♦}, Cieplak M., Theodorakis P.E., Combining the MARTINI and Structure-Based Coarse-Grained Approaches for the Molecular Dynamics Studies of Conformational Transitions in Proteins, Journal of Chemical Theory and Computation, ISSN: 1549-9618, DOI: 10.1021/acs.jctc.6b00986, Vol.13, pp.1366-1374, 2017Abstract: The application of coarse-grained (CG) models in biology is essential to access large length and time scales required for the description of many biological processes. The ELNEDIN protein model is based on the well-known MARTINI CG force-field and incorporates additionally harmonic bonds of a certain spring constant within a defined cutoff distance between pairs of residues, in order to preserve the native structure of the protein. In this case, the use of unbreakable harmonic bonds hinders the study of unfolding and folding processes. To overcome this barrier we have replaced the harmonic bonds with Lennard–Jones interactions based on the contact map of the native protein structure as is done in Go̅-like models. This model exhibits very good agreement with all-atom simulations and the ELNEDIN. Moreover, it can capture the structural motion linked to particular catalytic activity in the Man5B protein, in agreement with all-atom simulations. In addition, our model is based on the van der Waals radii, instead of a cutoff distance, which results in a smaller contact map. In conclusion, we anticipate that our model will provide further possibilities for studying biological systems based on the MARTINI CG force-field by using advanced-sampling methods, such as parallel tempering and metadynamics. Keywords: Martini force field, protein, molecular simulation, stretching AFM, large conformational changes | |
99. | Poma A.B.^{♦}, Chwastyk M., Cieplak M., Elastic moduli of biological fibers in a coarse-grained model: crystalline cellulose and β-amyloids, Physical Chemistry Chemical Physics, ISSN: 1463-9076, DOI: 10.1039/C7CP05269C, Vol.19, pp.28195-28206, 2017Poma A.B.^{♦}, Chwastyk M., Cieplak M., Elastic moduli of biological fibers in a coarse-grained model: crystalline cellulose and β-amyloids, Physical Chemistry Chemical Physics, ISSN: 1463-9076, DOI: 10.1039/C7CP05269C, Vol.19, pp.28195-28206, 2017Abstract: We study the mechanical response of cellulose and β-amyloid microfibrils to three types of deformation: tensile, indentational, and shear. The cellulose microfibrils correspond to the allomorphs Iα or Iβ whereas the β-amyloid microfibrils correspond to the polymorphs of either two- or three-fold symmetry. This response can be characterized by three elastic moduli, namely, YL, YT, and S. We use a structure-based coarse-grained model to analyze the deformations in a unified manner. We find that each of the moduli is almost the same for the two allomorphs of cellulose but YL is about 20 times larger than YT (140 GPa vs. 7 GPa), indicating the existence of significant anisotropy. For cellulose we note that the anisotropy results from the involvement of covalent bonds in stretching. For β-amyloid, the sense of anisotropy is opposite to that of cellulose. In the three-fold symmetry case, YL is about half of YT (3 vs. 7) whereas for two-fold symmetry the anisotropy is much larger (1.6 vs. 21 GPa). The S modulus is derived to be 1.2 GPa for three-fold symmetry and one half of it for the other symmetry and 3.0 GPa for cellulose. The values of the moduli reflect deformations in the hydrogen-bond network. Unlike in our theoretical approach, no experiment can measure all three elastic moduli with the same apparatus. However, our theoretical results are consistent with various measured values: typical YL for cellulose Iβ ranges from 133 to 155 GPa, YT from 2 to 25 GPa, and S from 1.8 to 3.8 GPa. For β-amyloid, the experimental values of S and YT are about 0.3 GPa and 3.3 GPa respectively, while the value of YL has not been reported. Keywords: Tensile, shear, indentation, Atomic Force Microscopy, amyloid, cellulose | |
100. | Pałka K., Zaszczyńska A.^{♦}, Kleczewska J., Polymerization shrinkage of dental composites, ENGINEERING OF BIOMATERIALS / INŻYNIERIA BIOMATERIAŁÓW, ISSN: 1429-7248, Vol.20, No.143, pp.62, 2017Pałka K., Zaszczyńska A.^{♦}, Kleczewska J., Polymerization shrinkage of dental composites, ENGINEERING OF BIOMATERIALS / INŻYNIERIA BIOMATERIAŁÓW, ISSN: 1429-7248, Vol.20, No.143, pp.62, 2017Abstract: Dental composites are based on polymer resin matrix which diminishes its volume during polymerization process due to joining of monomer chains [1]. It is the reason of polymerization shrinkage of each polymer material. Serious consequence of the shrinkage in dentistry is marginal leakage and secondary caries
resulting from this [2]. Therefore, the develop a low shrinkage material is a big challenge in the manufacturing of dental composites. There are many methods of diminishing polymerization shrinkage. One group is focused on resin matrix composition, the second on filler selection [3] and the
others on applying technique [4]. Literature presents a lot of methods of shrinkage measurements [1]. In previous study the Authors used the method based on microCT measurements [5]. In this paper a new approach has been presented. In this study, the new method of polymerization shrinkage was applied to evaluate the polymerization shrinkage of selected dental composites showing differences in composition. | |
101. | Niemczyk B., Sajkiewicz P., The effect of chemical composition on viscoelastic properties of methylcellulose/agarose hydrogel, 7th KMM-VIN Industrial Workshop “Biomaterials: Key Technologies for Better Healthcare”, 2017-09-27/09-28, Erlangen (DE), pp.44, 2017Niemczyk B., Sajkiewicz P., The effect of chemical composition on viscoelastic properties of methylcellulose/agarose hydrogel, 7th KMM-VIN Industrial Workshop “Biomaterials: Key Technologies for Better Healthcare”, 2017-09-27/09-28, Erlangen (DE), pp.44, 2017Keywords: methylcellulose, agarose, hydrogel, cross-linking kinetics, DMA, modulus | |
102. | Pałka K., Zaszczyńska A., Kleczewska J., Polymerization shrinkage of dental composites, 26th Annual Conference Biomaterials in Medicine and Veterinary Medicine, 2017-10-12/10-15, Rytro (PL), pp.1, 2017 | |
103. | Poma A.B.^{♦}, Chwastyk M., Cieplak M., Coarse-grained model of the native cellulose and the transformation pathways to the allomorph, CELLULOSE, ISSN: 0969-0239, DOI: 10.1007/s10570-016-0903-4, Vol.23, pp.1573-1591, 2016Poma A.B.^{♦}, Chwastyk M., Cieplak M., Coarse-grained model of the native cellulose and the transformation pathways to the allomorph, CELLULOSE, ISSN: 0969-0239, DOI: 10.1007/s10570-016-0903-4, Vol.23, pp.1573-1591, 2016Abstract: All-atom simulations are used to derive effective parameters for a coarse-grained description of the crystalline cellulose I Keywords: Cellulose, microfibril, allomorphs, structural transition, molecular dynamics, free energy | |
104. | Oparka M., Walczak J.^{♦}, Malińska D., van Oppen L.M.P.E., Szczepanowska J., Koopman W.J.H., Więckowski M.R., Quantifying ROS levels using CM-H2DCFDA and HyPer, Methods, ISSN: 1046-2023, DOI: 10.1016/j.ymeth.2016.06.008, Vol.109, pp.3-11, 2016Oparka M., Walczak J.^{♦}, Malińska D., van Oppen L.M.P.E., Szczepanowska J., Koopman W.J.H., Więckowski M.R., Quantifying ROS levels using CM-H2DCFDA and HyPer, Methods, ISSN: 1046-2023, DOI: 10.1016/j.ymeth.2016.06.008, Vol.109, pp.3-11, 2016Abstract: At low levels, reactive oxygen species (ROS) can act as signaling molecules within cells. When ROS production greatly exceeds the capacity of endogenous antioxidant systems, or antioxidant levels are reduced, ROS levels increase further. The latter is associated with induction of oxidative stress and associated signal transduction and characterized by ROS-induced changes in cellular redox homeostasis and/or damaging effects on biomolecules (e.g. DNA, proteins and lipids). Given the complex mechanisms involved in ROS production and removal, in combination with the lack of reporter molecules that are truly specific for a particular type of ROS, quantification of (sub)cellular ROS levels is a challenging task. In this chapter we describe two strategies to measure ROS: one approach to assess general oxidant levels using the chemical reporter CM-H2DCFDA (5-(and-6)-chloromethyl-2′,7′-dichlorodihydrofluorescein diacetate), and a second approach allowing more specific analysis of cytosolic hydrogen peroxide (H2O2) levels using protein-based sensors (HyPer and SypHer). Keywords: Reactive oxygen species, Hydrogen peroxide, CM-H2DCFDA, HyPer, SypHer | |
105. | Pałka K., Zaszczyńska A.^{♦}, Kleczewska J., Polymerization shrinkage of new flow-type dental composite using micro-ct, ENGINEERING OF BIOMATERIALS / INŻYNIERIA BIOMATERIAŁÓW, ISSN: 1429-7248, Vol.19, No.138, pp.75, 2016Pałka K., Zaszczyńska A.^{♦}, Kleczewska J., Polymerization shrinkage of new flow-type dental composite using micro-ct, ENGINEERING OF BIOMATERIALS / INŻYNIERIA BIOMATERIAŁÓW, ISSN: 1429-7248, Vol.19, No.138, pp.75, 2016Abstract: Polymerization shrinkage of the resin-based dental composites constitutes a risk of the failure of the interfacial bonds as a result of shrinkage stresses. It may result in marginal leakage, premature failure of the restoration, and even micro-cracking of the tooth [1,2]. Therefore, the research for develop a low shrinkage material has been a goal in the manufacture of dental composites. The color restorative materials are very interesting and market demand for these products was increased recently. They are used especially in milk tooth as fissure sealing, for marking root canal openings or as decoration (tooth tattoo) [3]. In this study, the research of polymerization shrinkage of flow-type dental composites was conducted. | |
106. | Pałka K., Zaszczyńska A.^{♦}, Kleczewska J., Polymerization shrinkage of new flow-type dental composite using micro-CT, 25th Annual Conference Biomaterials in Medicine and Veterinary Medicine, 2016-10-13/10-16, Rytro (PL), pp.1, 2016 | |
107. | Wojewoda M., Walczak J.^{♦}, Duszyński J., Szczepanowska J., Selenite activates the ATM kinase-dependent DNA repair pathway in human osteosarcoma cells with mitochondrial dysfunction, Biochemical Pharmacology, ISSN: 0006-2952, DOI: 10.1016/j.bcp.2015.03.016, Vol.95, No.3, pp.170-176, 2015Wojewoda M., Walczak J.^{♦}, Duszyński J., Szczepanowska J., Selenite activates the ATM kinase-dependent DNA repair pathway in human osteosarcoma cells with mitochondrial dysfunction, Biochemical Pharmacology, ISSN: 0006-2952, DOI: 10.1016/j.bcp.2015.03.016, Vol.95, No.3, pp.170-176, 2015Abstract: Mitochondrial dysfunction and reactive oxygen species (ROS) induced oxidative damage are implicated in the pathogenesis of several human diseases. Based on our previous findings that ROS level was higher in human osteosarcoma cybrids—Neuropathy, Ataxia and Retinitis Pigmentosa (NARP) and was reduced by selenite treatment, this study was designed to elucidate the effects of selenite administration on oxidative and nitrosative damage to lipids, proteins and DNA.
Oxidative and nitrosative damage to lipids and proteins was not increased in NARP cybrids or mitochondrial DNA-lacking Rho0 cells (displaying mitochondrial dysfunction) when compared with control WT cells. However, we found the enhanced formation of DNA double-strand breaks based on the level of histone γH2AX (phosphorylated at Ser 139), which is known to be phosphorylated by ATM (Ataxia Telangiectasia Mutated) kinase in response to DNA damage. Selenite increased the activity of ATM kinase in NARP cybrids and Rho0 cells without concomitant increase in levels of histone γH2AX.
Activation of the ATM kinase-dependent DNA repair pathway triggered by selenite could not be associated with enhanced DNA damage but might rather result from selenite-induced activation of ATM-dependent DNA repair mechanisms which could account for protective effects of this agent. Keywords: Mitochondrial dysfunction, Selenite, DNA repair, ATM kinase, Oxidative damage | |
108. | Poma A.B.^{♦}, Chwastyk M., Cieplak M., Polysaccharide–protein complexes in a Coarse-Grained Model, JOURNAL OF PHYSICAL CHEMISTRY B, ISSN: 1520-6106, DOI: 10.1021/acs.jpcb.5b06141, Vol.119, pp.12028-12041, 2015Poma A.B.^{♦}, Chwastyk M., Cieplak M., Polysaccharide–protein complexes in a Coarse-Grained Model, JOURNAL OF PHYSICAL CHEMISTRY B, ISSN: 1520-6106, DOI: 10.1021/acs.jpcb.5b06141, Vol.119, pp.12028-12041, 2015Abstract: We construct two variants of coarse-grained models of three hexaoses: one based on the centers of mass of the monomers and the other associated with the C4 atoms. The latter is found to be better defined and more suitable for studying interactions with proteins described within α-C based models. We determine the corresponding effective stiffness constants through all-atom simulations and two statistical methods. One method is the Boltzmann inversion (BI) and the other, named energy-based (EB), involves direct monitoring of energies as a function of the variables that define the stiffness potentials. The two methods are generally consistent in their account of the stiffness. We find that the elastic constants differ between the hexaoses and are noticeably different from those determined for the crystalline cellulose Iβ. The nonbonded couplings through hydrogen bonds between different sugar molecules are modeled by the Lennard-Jones potentials and are found to be stronger than the hydrogen bonds in proteins. We observe that the EB method agrees with other theoretical and experimental determinations of the nonbonded parameters much better than BI. We then consider the hexaose-Man5B catalytic complexes and determine the contact energies between their the C4−α-C atoms. These interactions are found to be stronger than the proteinic hydrogen bonds: about four times as strong for cellohexaose and two times for mannohexaose. The fluctuational dynamics of the coarse-grained complexes are found to be compatible with previous all-atom studies by Bernardi et al. Keywords: Polysaccharide, protein, principal component analysis, coarse graining, molecular simulation | |
109. | Chwastyk M., Poma A.B.^{♦}, Cieplak M., Statistical radii associated with amino acids to determine the contact map: fixing the structure of a type I cohesin domain in the Clostridium thermocellum cellulosome, PHYSICAL BIOLOGY, ISSN: 1478-3967, DOI: 10.1088/1478-3975/12/4/046002, Vol.12, No.046002, pp.1-11, 2015Chwastyk M., Poma A.B.^{♦}, Cieplak M., Statistical radii associated with amino acids to determine the contact map: fixing the structure of a type I cohesin domain in the Clostridium thermocellum cellulosome, PHYSICAL BIOLOGY, ISSN: 1478-3967, DOI: 10.1088/1478-3975/12/4/046002, Vol.12, No.046002, pp.1-11, 2015Abstract: We propose to improve and simplify protein refinement procedures through consideration of which pairs of amino acid residues should form native contacts. We first consider 11 330 proteins from the CATH database to determine statistical distributions of contacts associated with a given type of amino acid. The distributions are set across the distances between the α-C atoms that are in contact. Based on this data, we determine typical radii of effective spheres that can be placed on the α-C atoms in order to reconstruct the distribution of the contact lengths. This is done by checking for overlaps with enlarged van der Waals spheres associated with heavy atoms on other amino acids.The resulting contacts can be used to identify non-native contacts that may arise during the time evolution of structure-based models. Here, the radii are used to guide reconstruction of nine missing side chains in a type I cohesin domain with the Protein Data Bank code 1AOH. We first identify the likely missing contacts and then sculpt the corresponding side chains by standard refinement tools to achieve consistency with the expected contact map. One ambiguity in refinement is resolved by determining all-atom conformational energies. Keywords: Cohesin, Go-like model, protein prediction, proteins, AFM, stretching | |
110. | Walczak J.^{♦}, Szczepanowska J., Zaburzenia dynamiki i dystrybucji mitochondriów w komórkach w stwardnieniu zanikowym bocznym (ALS), Postępy Biochemii, ISSN: 0032-5422, Vol.61, No.2, pp.183-190, 2015Walczak J.^{♦}, Szczepanowska J., Zaburzenia dynamiki i dystrybucji mitochondriów w komórkach w stwardnieniu zanikowym bocznym (ALS), Postępy Biochemii, ISSN: 0032-5422, Vol.61, No.2, pp.183-190, 2015Abstract: Stwardnienie zanikowe boczne (ALS) jest chorobą o złożonej etiologii, prowadzącą do degradacji neuronów ruchowych. Jednym z pierwszych objawów w rozwoju wielu chorób neurodegeneracyjnych, m. in. w ALS, są zaburzenia funkcjonowania mitochondriów. Już kilka dekad temu obserwowano zmiany morfologii mitochondriów w tkankach pacjentów cierpiących na to schorzenie. Mitochondria są organellami dynamicznymi, ulegają ciągłym procesom fuzji i fragmentacji oraz przemieszczania się w komórce. Prawidłowy przebieg procesów związanych z dynamiką i dystrybucją mitochondriów jest kluczowy dla funkcjonowania komórek, a w szczególności komórek nerwowych o silnie wydłużonych aksonach. Praca ta stanowi podsumowanie istniejącej wiedzy na temat roli dynamiki i dystrybucji mitochondriów w patofizjologii ALS, formy rodzinnej i sporadycznej. Keywords: ALS, dynamika mitochondriów, transport mitochondriów, neurodegeneracja | |
111. | Jain A.^{♦}, Tripathi S.K., Nano-porous activated carbon from sugarcane waste for supercapacitor application, Journal of Energy Storage, ISSN: 2352-152X, DOI: 10.1016/j.est.2015.09.010, Vol.4, pp.121-127, 2015Jain A.^{♦}, Tripathi S.K., Nano-porous activated carbon from sugarcane waste for supercapacitor application, Journal of Energy Storage, ISSN: 2352-152X, DOI: 10.1016/j.est.2015.09.010, Vol.4, pp.121-127, 2015Abstract: Low cost with high specific capacitance and energy density is the critical and main requirement for practical supercapacitors. In the present work, nano porous activated carbon having specific surface area of 400 m2 g-1 from sugarcane waste (bagasse) has been synthesized and characterized as an electrode material for supercapacitor applications using ionic liquid based polymer gel electrolytes. The fabricated cell shows the overall specific capacitance of 372 mF cm-2 which is equivalent to single electrode specific capacitance of 248 F g-1 . The corresponding energy and power density of 16.3Wh kg-1 and 1.66 kWkg-1 were achieved for EDLCs. | |
112. | Poma A.^{♦}, Monteferrante M., Bonella S., Ciccotti G., The quantum free energy barrier for hydrogen vacancy diffusion in Na3AlH6, Physical Chemistry Chemical Physics, ISSN: 1463-9076, DOI: 10.1039/C2CP42536J , Vol.14, pp.15458-15463, 2012Poma A.^{♦}, Monteferrante M., Bonella S., Ciccotti G., The quantum free energy barrier for hydrogen vacancy diffusion in Na3AlH6, Physical Chemistry Chemical Physics, ISSN: 1463-9076, DOI: 10.1039/C2CP42536J , Vol.14, pp.15458-15463, 2012Abstract: The path integral single sweep method is used to assess quantum effects on the free energy barrier for hydrogen vacancy diffusion in a defective Na3AlH6 crystal. This process has been investigated via experiments and simulations due to its potential relevance in the H release mechanism in sodium alanates, prototypical materials for solid state hydrogen storage. Previous computational studies, which used density functional methods for the electronic structure, were restricted to a classical treatment of the nuclear degrees of freedom. We show that, although they do not change the qualitative picture of the process, nuclear quantum effects reduce the free energy barrier height by about 18% with respect to the classical calculation improving agreement with available neutron scattering data. Keywords: Alanate, proton transfer, electron hopping, Car-Parrinello MD, molecular dynamics, Free Energy, Path Integral | |
113. | Lewandowski M., Metody rekonstrukcji obrazu z głowic phased array, XVIII Seminarium Nieniszczące Badania Materiałów, 2012-03-13/03-16, Zakopane (PL), pp.1-7, 2012 | |
114. | Poma A.B.^{♦}, Site L.D., Classical to Path-Integral Adaptive Resolution in Molecular Simulation: Towards a Smooth Quantum-Classical Coupling, PHYSICAL REVIEW LETTERS, ISSN: 0031-9007, DOI: 10.1103/PhysRevLett.104.250201, Vol.104, pp.250201-1-4, 2011Poma A.B.^{♦}, Site L.D., Classical to Path-Integral Adaptive Resolution in Molecular Simulation: Towards a Smooth Quantum-Classical Coupling, PHYSICAL REVIEW LETTERS, ISSN: 0031-9007, DOI: 10.1103/PhysRevLett.104.250201, Vol.104, pp.250201-1-4, 2011Abstract: Simulations that couple different molecular models in an adaptive way by changing resolution on the fly allow us to identify the relevant degrees of freedom of a system. This, in turn, leads to a detailed understanding of the essential physics which characterizes a system. While the delicate process of transition from one model to another is well understood for the adaptivity between classical molecular models the same cannot be said for the quantum-classical adaptivity. The main reason for this is the difficulty in describing a continuous transition between two different kinds of physical principles: probabilistic for the quantum and deterministic for the classical. Here we report the basic principles of an algorithm that allows for a continuous and smooth transition by employing the path integral description of atoms. Keywords: path integral, classical-quantum coupling, adaptive resolution scheme, polymer ring, quantum structure | |
115. | Poma A.B.^{♦}, Site L.D., Adaptive resolution simulation of liquid para-hydrogen: Testing the robustness of the quantum-classical adaptive coupling, Physical Chemistry Chemical Physics, ISSN: 1463-9076, DOI: 10.1039/C0CP02865G , Vol.13, pp.10510-10519, 2011Poma A.B.^{♦}, Site L.D., Adaptive resolution simulation of liquid para-hydrogen: Testing the robustness of the quantum-classical adaptive coupling, Physical Chemistry Chemical Physics, ISSN: 1463-9076, DOI: 10.1039/C0CP02865G , Vol.13, pp.10510-10519, 2011Abstract: Adaptive resolution simulations for classical systems are currently made within a reasonably consistent theoretical framework. Recently we have extended this approach to the quantum-classical coupling by mapping the quantum nature of an atom onto a classical polymer ring representation within the path integral approach [Poma & Delle Site, Phys. Rev. Lett., 2010, 104, 250201]. In this way the process of interfacing adaptively a quantum representation to a classical one corresponds to the problem of interfacing two regions with a different number of effective “classical” degrees of freedom; thus the classical formulation of the adaptive algorithm applies straightforwardly to the quantum-classical problem. In this work we show the robustness of such an approach for a liquid of para-hydrogen at low temperature. This system represents a highly challenging conceptual and technical test for the adaptive approach due to the extreme thermodynamical conditions where quantum effects play a central role. Keywords: Adaptive resolution Scheme, parahydrogen, path integral, polymer ring, quantum fluid | |
116. | Kowalewski Z., Szymczak T., Makowska K., Augustyniak B., A role of destructive and non-destructive tests in creep damage identification, KEY ENGINEERING MATERIALS, ISSN: 1662-9795, DOI: 10.4028/www.scientific.net/KEM.233-236.269, Vol.488-489, pp.315-318, 2011Kowalewski Z., Szymczak T., Makowska K., Augustyniak B., A role of destructive and non-destructive tests in creep damage identification, KEY ENGINEERING MATERIALS, ISSN: 1662-9795, DOI: 10.4028/www.scientific.net/KEM.233-236.269, Vol.488-489, pp.315-318, 2011Abstract: The paper presents relationships between strain level generated by creep process and two parameters determined form non-destructive tests, i.e. acoustic birefringence and amplitude of magnetoacoustic emission for three kinds of steel: 40HNMA, P91 and 13HMF. Moreover, the relationships between prior deformation level and selected mechanical parameters resulting from the standard tensile tests subsequently carried out at room temperature were established. As a consequence, this enabled to formulate mutual relationships between these mechanical parameters and parameters obtained from the ultrasonic/magnetic investigations. Keywords: creep, damage, yield point, ultimate tensile stress, Young’s modulus, acoustic
birefringence, magnetoacoustic emission. | |
117. | Lewandowski M., Systemy głowic wieloprzetwornikowych - podstawy fizyczne, XVII Seminarium Nieniszczące Badania Materiałów, 2011-03-08/03-11, Zakopane (PL), pp.1-10, 2011 | |
118. | Holnicki-Szulc J., Pawłowski P., Mikułowski M., Graczykowski C., Adaptive impact absorption and applications to landing devices, Advances in Science and Technology, ISSN: 1662-0356, DOI: 10.4028/www.scientific.net/AST.56.609, Vol.56, pp.609-613, 2008Holnicki-Szulc J., Pawłowski P., Mikułowski M., Graczykowski C., Adaptive impact absorption and applications to landing devices, Advances in Science and Technology, ISSN: 1662-0356, DOI: 10.4028/www.scientific.net/AST.56.609, Vol.56, pp.609-613, 2008Abstract: This paper demonstrates progress in Adaptive Impact Absorption (AIA) research field obtained recently in our research group and is based on previously published conference communicates. The monograph (Ref.[1]), under preparation, will present soon more detailed discussion of the considered problems. In contrast to the standard passive systems the proposed AIA approach focuses on active adaptation of energy absorbing structures (equipped with sensor system detecting and identifying impact in real time and controllable semi-active dissipaters, so called structural fuses) with high ability of adaptation to extreme overloading. A semi-active or fully-active solutions can be applied, which depend on constant or time-dependent modifications realized via controllable dissipative devices. Feasible, adaptive dissipative devices under considerations can be based on MR fluids or (hydraulic or pneumatic) piezo-valves. The presentation will be devoted to the following applications of AIA concept: Adaptive Landing Gears (ALG) for mitigation of exploitative aircraft loads and adaptive flow control based airbags for emergency landing of the helicopter. Keywords: Adaptive Impact Absorption, Controlled Shock-absorbers, Adaptive Landing
Gear, Inflatable Structures | |
119. | Poma A.B.^{♦}, Site L.D., Separation of variables in molecular-dynamics simulations: A criterion to estimate the quality of the approximation, PHYSICAL REVIEW E, ISSN: 1539-3755, DOI: 10.1103/PhysRevE.78.056703, Vol.78, pp.056703-1-11, 2008Poma A.B.^{♦}, Site L.D., Separation of variables in molecular-dynamics simulations: A criterion to estimate the quality of the approximation, PHYSICAL REVIEW E, ISSN: 1539-3755, DOI: 10.1103/PhysRevE.78.056703, Vol.78, pp.056703-1-11, 2008Abstract: We propose a simple method to evaluate the approximation of separation of variables in molecular dynamics (MD) and related fields. It is based on a point-by-point evaluation of the difference between the true potential and the corresponding potential where the separation of variables is applied. The major advantage of such an approach is the fact that it requires only the analytical form of the potential as provided in most of the MD codes. We provide two examples of application, namely, a diatomic molecule adsorbing on a flat surface and an alkane (aliphatic) chain. Keywords: Quality control, independent DOF, coarse graining, aliphatic chain, intramolecular | |
120. | Wikło M., Holnicki-Szulc J., Impact Load Identification Based on Local Measurements, KEY ENGINEERING MATERIALS, ISSN: 1662-9795, DOI: 10.4028/www.scientific.net/KEM.293-294.159, Vol.293-294, pp.159-166, 2005Wikło M., Holnicki-Szulc J., Impact Load Identification Based on Local Measurements, KEY ENGINEERING MATERIALS, ISSN: 1662-9795, DOI: 10.4028/www.scientific.net/KEM.293-294.159, Vol.293-294, pp.159-166, 2005Abstract: A new methodology for load identification is proposed. The global dynamic structural response is modeled using only pre-computed, time dependent, dynamic influence matrix, describing structural response to locally generated unit impulses. Then, the impact load identification procedure is based on distance minimization between the modeled and measured local dynamic responses in sensor locations. The theoretical background as well as numerical examples is presented. Keywords: structural health monitoring, impact detection, inverse dynamics | |
121. | Kowalewski Z., Creep of Metals Subjected to Prior Plastic Deformation, KEY ENGINEERING MATERIALS, ISSN: 1662-9795, DOI: 10.4028/www.scientific.net/KEM.274-276.913, Vol.274-276, pp.913-918, 2004Kowalewski Z., Creep of Metals Subjected to Prior Plastic Deformation, KEY ENGINEERING MATERIALS, ISSN: 1662-9795, DOI: 10.4028/www.scientific.net/KEM.274-276.913, Vol.274-276, pp.913-918, 2004Abstract: An influence of prior tensile plastic deformation on the basic creep parameters such as minimum creep rate, time to rupture, duration of creep stages and ductility is studied for copper and aluminium alloy. The materials were tested at two different temperatures; copper at 523 K and 573 K; aluminium alloy at 423 K and 473 K. It is shown for both materials, that depending on the deformation history the basic creep parameters may attain values which are more beneficial from engineering point of view than those for the nonprestrained material determined. It is also shown that in some cases prior plastic deformation may lead to the detrimental effects expressed by the lifetime reduction. The experimental data achieved are discussed in detail and used to verify the basic assumptions of the recovery creep theory. Keywords: Creep, Plastic Deformation, Creep Rupture, Lifetime, Minimum Creep Rate | |
122. | Nasalski W., Amplitude-polarization representation of three-dimensional beams at a dielectric interface, JOURNAL OF OPTICS A-PURE AND APPLIED OPTICS, ISSN: 1464-4258, DOI: 10.1088/1464-1258/5/2/309, Vol.5, No.2, pp.128-136, 2003Nasalski W., Amplitude-polarization representation of three-dimensional beams at a dielectric interface, JOURNAL OF OPTICS A-PURE AND APPLIED OPTICS, ISSN: 1464-4258, DOI: 10.1088/1464-1258/5/2/309, Vol.5, No.2, pp.128-136, 2003Abstract: Three-dimensional optical beams incident on a dielectric interface undergo deformations upon reflection and refraction. Within first-order optics these deformations may be interpreted as longitudinal and transverse displacements and deflections of beam axes. In general, these effects are different for TE and TM components of the beam field. The problem of beam reflection and refraction at the interface is formulated and solved in such a manner that the beams are obtained with uniquely defined uniform displacements of their axes in a spatial domain and their spectrum centres in a spectral domain. Additional modifications of the beam polarization state remain generally small and non-uniform throughout the entire beam spectrum. In this context, a special role of polarization states diagonal in the interface plane is indicated. Keywords: Beam optics, polarization optics, reflection, refraction, Lorentz group | |
123. | Kowalewski Z., Turski K., Multiaxial Proportional and Non-Proportional Cyclic Behaviour of 40H Steel and PA6 Aluminium Alloy, KEY ENGINEERING MATERIALS, ISSN: 1662-9795, DOI: 10.4028/www.scientific.net/KEM.233-236.269, Vol.233-236, pp.269-274, 2003Kowalewski Z., Turski K., Multiaxial Proportional and Non-Proportional Cyclic Behaviour of 40H Steel and PA6 Aluminium Alloy, KEY ENGINEERING MATERIALS, ISSN: 1662-9795, DOI: 10.4028/www.scientific.net/KEM.233-236.269, Vol.233-236, pp.269-274, 2003Abstract: The phenomena arising during proportional and non-proportional cyclic loadings are experimentally investigated for 40H steel and PA6 aluminium alloy. Variations of the mechanical properties due to different two types of cyclic loading are assessed on the basis of the yield surface evolution. Effects of strain rate and magnitude of cyclic loading amplitude are also considered. Analysis of the stress and strain signals during non-proportional cyclic loading along circular path has shown significant effect of a phase shift of the maximum stress with respect to the corresponding maximum strain, which was not observed during tests carried out along proportional loading paths Keywords: Additional Hardening, Non-Proportional Cyclic Loading, Phase Shift, Yield Surfaces | |
124. | Dłużewski P., Jurczak G., Maciejewski G., Kret S., Ruterana P., Nouet G., Finite Element Simulation of Residual Stresses in Epitaxial Layers, Materials Science Forum (MSF), ISSN: 1662-9752, DOI: 10.4028/www.scientific.net/MSF.404-407.141, Vol.404-407, pp.141-146, 2002Dłużewski P., Jurczak G., Maciejewski G., Kret S., Ruterana P., Nouet G., Finite Element Simulation of Residual Stresses in Epitaxial Layers, Materials Science Forum (MSF), ISSN: 1662-9752, DOI: 10.4028/www.scientific.net/MSF.404-407.141, Vol.404-407, pp.141-146, 2002Abstract: A nonlinear finite element approach presented here is based on the constitutive equations for anisotropic hyperelatic materials. By digital image processing the elastic incompatibilities (lattice mismatch) are extracted from the HRTEM image of GaN epilayer. Such obtained tensorial field of dislocation distribution is used next as the input data to the FE code. This approach is developed to study the stress distribution associated with lattice defects in highly mismatched heterostructures applied as buffer layers for the optically active structures. Keywords: Dislocations, Anisotropic Hyperelasticity, Residual Stresses | |
125. | Nasalski W., Three-dimensional beam reflection at dielectric interfaces, Optics Communications
, ISSN: 0030-4018, DOI: 10.1016/S0030-4018(01)01420-1, Vol.197, pp.217-233, 2001Nasalski W., Three-dimensional beam reflection at dielectric interfaces, Optics Communications
, ISSN: 0030-4018, DOI: 10.1016/S0030-4018(01)01420-1, Vol.197, pp.217-233, 2001Abstract: Polarisation, amplitude and beam shape aspects of the three-dimensional optical beam reflection at dielectric interfaces are analysed within a framework of the aberrationless approach. Roles of the paraxial approximation, the cross-dimensional coupling and the nonparaxial cross-polarisation coupling in the beam description are discussed. It is shown that the substantial first-order transverse beam modifications exist for both – linear and circular – beam polarisation states. Characteristic features of the single beam bistable switch at nonlinear interfaces are also discussed and numerical examples of the reflected beam field reshaping are presented.
Keywords: Total internal reflection, Effects of nonspecular reflection, Beam shaping, Nonlinear interfaces, Optical bistability | |
126. | Nasalski W., Beam switching at planar photonic structures, OPTO-ELECTRONICS REVIEW, ISSN: 1230-3402, Vol.9, No.3, pp.280-286, 2001Nasalski W., Beam switching at planar photonic structures, OPTO-ELECTRONICS REVIEW, ISSN: 1230-3402, Vol.9, No.3, pp.280-286, 2001Abstract: Beam reflection at a focusing nonlinear-linear interface near critical incidence of total internal reflection is analysed.
Basics of the three-dimensional formulation of the problem are outlined. Numerical simulations of the beam reflection are presented.
It is shown that owing to cross focusing and deformations of incident and reflected beams, a bistable switch is possible to achieve.
Characteristic features of this switch are discussed.
Keywords: nonspecular reflection, nonlinear interfaces, beam switching, optical bistability | |
127. | Nasalski W., Modelling of beam reflection at a nonlinear–linear interface, JOURNAL OF OPTICS A-PURE AND APPLIED OPTICS, ISSN: 1464-4258, DOI: 10.1088/1464-4258/2/5/314, Vol.2, No.5, pp.433-441, 2000Nasalski W., Modelling of beam reflection at a nonlinear–linear interface, JOURNAL OF OPTICS A-PURE AND APPLIED OPTICS, ISSN: 1464-4258, DOI: 10.1088/1464-4258/2/5/314, Vol.2, No.5, pp.433-441, 2000Abstract: An analytic model of beam reflection at a nonlinear–linear interface is presented.
An incident field approaches a nonlinear side of the interface at an angle close to a critical
angle of total internal reflection. A nonlinearity of the plain Kerr focusing type is considered.
A beam field at the interface is described by changes of the beam parameters during
propagation and reflection, that is, by aberrationless effects of nonlinear propagation and
nonspecular effects of reflection. Numerical iteration of the analytic solution indicates that,
for certain sets of incident beam and interface parameters, a bistable switch of the reflected
beam can be obtained. Characteristic features of this switch appear to be different from those
of a plane wave reflection. Keywords: nonlinear interfaces, optical bistability, nonspecular reflection | |
128. | Nasalski W., Scale formulation of first-order nonlinear optics , Optics Communications
, ISSN: 0030-4018, DOI: 10.1016/S0030-4018(96)00769-9, Vol.137, pp.107-112, 1997Nasalski W., Scale formulation of first-order nonlinear optics , Optics Communications
, ISSN: 0030-4018, DOI: 10.1016/S0030-4018(96)00769-9, Vol.137, pp.107-112, 1997Abstract: Multidimensional propagation of a light pulse or beam in a nonlinear sample of a Kerr type is described within the first-order optics formalism. A scale transformation that relates the nonlinear and linear propagation processes is defined by use of the nonlinear aberrationless effects. The nonlinear ray transfer matrix and Wigner distribution function are explicitly given in a factored form for the propagation of a symmetric Gaussian optical signal. An on-axis phase correction to the nonlinear first-order formalism is also specified. | |
129. | Nasalski W., Aberrationless effects of nonlinear propagation,
Journal of the Optical Society of America B, ISSN: 0740-3224, DOI: 10.1364/JOSAB.13.001736, Vol.13, No.8, pp.1736-1747, 1996Nasalski W., Aberrationless effects of nonlinear propagation,
Journal of the Optical Society of America B, ISSN: 0740-3224, DOI: 10.1364/JOSAB.13.001736, Vol.13, No.8, pp.1736-1747, 1996Abstract: For nonlinear propagation, scaled complex ray tracing [Opt. Commun. 119, 218 (1995)] in samples of Kerr media is accomplished in terms of four independent aberrationless effects: optical self-shortening, beam waist shift, waist width modification, and on-axis phase shift. A complex amplitude nonlinear modification is also introduced, and a symplectic nonlinear ABCDmatrix is determined. All the aberrationless effects are self-consistently defined, and their dynamics are shown for focusing and defocusing nonlinearities, beam powers up to the self-trapped soliton or critical levels, and propagation ranges including those that contain a self-collapse point. The multidimensional nature of the analysis is indicated, and its relevance to pulse compression, Z-scan measurements, and higher-order mode propagation is outlined. | |
130. | Nasalski W., Longitudinal and transverse effects of nonspecular reflection, Journal of the Optical Society of America A, ISSN: 1084-7529, DOI: 10.1364/JOSAA.13.000172, Vol.13, No.1, pp.172-181, 1996Nasalski W., Longitudinal and transverse effects of nonspecular reflection, Journal of the Optical Society of America A, ISSN: 1084-7529, DOI: 10.1364/JOSAA.13.000172, Vol.13, No.1, pp.172-181, 1996Abstract: A rigorous spectral analysis is given for the nonspecular reflection of a three-dimensional Gaussian beam at a dielectric isotropic planar structure. For the first time all independent nonspecular effects are derived in a self-consistent manner for the three-dimensional case. It is shown that the longitudinal nonspecular effects in the incidence plane, that is, the lateral and focal shifts of the beam waist position, the angular rotation of the reflected-beam axis, and the modifications of the beam waist width and complex amplitude, have their direct analogies in the plane transverse to the incidence and interface planes that gives transverse nonspecular effects. Moreover, the existence of the other, not yet reported, effect of nonspecular modification of the beam polarization is also proved. A role for TM and TE polarizations in reflected-beam formation is indicated. The results show that, up to the symmetric second-order terms in approximation of Fresnel coefficients, each of the longitudinal and transverse beam factors independently preserves its shape under reflection at the expense of changes of the beam reference frame, width, amplitude, and polarization parameters | |
131. | Nasalski W., Complex ray tracing of nonlinear propagation, Optics Communications
, ISSN: 0030-4018, DOI: 10.1016/0030-4018(95)00186-C, Vol.119, pp.218-226, 1995Nasalski W., Complex ray tracing of nonlinear propagation, Optics Communications
, ISSN: 0030-4018, DOI: 10.1016/0030-4018(95)00186-C, Vol.119, pp.218-226, 1995Abstract: A new scale transformation of complex ray parameters is introduced in an unified manner to treat the nonlinear propagation in Kerr media. It is shown that the nonlinear propagation, including soliton propagation, can be consistently traced by complex rays specific to the linear propagation with the imposed scale effects of self-shortening, self-focusing and phase self-modification. The solution obtained is explicitly described as the propagation in a free-space modified by three propagation effects, namely, the nonlinear changes of the beam or pulse waist position, waist width and on-axis phase. A field of cylindrical symmetry and arbitrary transverse dimension is analyzed for power levels ranging from the linear propagation to the soliton self-trapping. It is shown that the method can be formulated within a frame of the nonlinear ABCD matrix formalism and specified to comply with the variational analysis of the problem. | |
132. | Dłużewski P., Continuum Theory of Dislocations in Angular Coordinates, Solid State Phenomena, ISSN: 1662-9779, DOI: 10.4028/www.scientific.net/SSP.35-36.539, Vol.35-36, pp.539-544, 1993Dłużewski P., Continuum Theory of Dislocations in Angular Coordinates, Solid State Phenomena, ISSN: 1662-9779, DOI: 10.4028/www.scientific.net/SSP.35-36.539, Vol.35-36, pp.539-544, 1993Abstract: The dislocation density tensor is considered as a measure of angular inelastic deformation of crystal lattice. The modelling of plastic deformation of dislocated crystal is done by means of the vector constitutive relation imposed on the force-velocity dependence for dislocations. The force exerted on a dislocation is treated here as a direct reason of the dislocation movement. This force is induced by the elastic deformation of crystal lattice and by the osmotic stress due to the unbalanced concentration of vacancies. Keywords: Activation Energy of Dislocation Motion, Constitutive Equations of Dislocation Movement, Continuum Theory of Dislocations, Curvature Tensor, Dislocation Balance Law, Dislocation Density Tensor, Force on Dislocation, Internal Stress, Osmotic Pressure, Peach-Koehler Formula, Residual Stress, Thermodynamic Restrictions, Vacancy Concentration | |