1. | 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. | |
2. | 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 | |
3. | Czerkies M., Korwek Z., Prus W., Kochańczyk M., Jaruszewicz-Błońska J., Tudelska K., Błoński S., Kimmel M., Brasier A.R., Lipniacki T., Cell fate in antiviral response arises in the crosstalk of IRF, NF-κB and JAK/STAT pathways, Nature Communications, ISSN: 2041-1723, DOI: 10.1038/s41467-017-02640-8, Vol.9, pp.493, 2018Czerkies M., Korwek Z., Prus W., Kochańczyk M., Jaruszewicz-Błońska J., Tudelska K., Błoński S., Kimmel M., Brasier A.R., Lipniacki T., Cell fate in antiviral response arises in the crosstalk of IRF, NF-κB and JAK/STAT pathways, Nature Communications, ISSN: 2041-1723, DOI: 10.1038/s41467-017-02640-8, Vol.9, pp.493, 2018Abstract: The innate immune system processes pathogen-induced signals into cell fate decisions. How information is turned to decision remains unknown. By combining stochastic mathematical modelling and experimentation, we demonstrate that feedback interactions between the IRF3, NF-κB and STAT pathways lead to switch-like responses to a viral analogue, poly(I:C), in contrast to pulse-like responses to bacterial LPS. Poly(I:C) activates both IRF3 and NF-κB, a requirement for induction of IFNβ expression. Autocrine IFNβ initiates a JAK/STAT-mediated positive-feedback stabilising nuclear IRF3 and NF-κB in first responder cells. Paracrine IFNβ, in turn, sensitises second responder cells through a JAK/STAT-mediated positive feedforward pathway that upregulates the positive-feedback components: RIG-I, PKR and OAS1A. In these sensitised cells, the ‘live-or-die’ decision phase following poly(I:C) exposure is shorter—they rapidly produce antiviral responses and commit to apoptosis. The interlinked positive feedback and feedforward signalling is key for coordinating cell fate decisions in cellular populations restricting pathogen spread. Keywords: cellular signalling networks, innate immunity, regulatory networks, stochastic modelling | |
4. | 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. | |
5. | 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 | |
6. | Glinicki M.A., Antolik A., Gawlicki M., Evaluation of compatibility of neutron-shielding boron aggregates with Portland cement in mortar, CONSTRUCTION AND BUILDING MATERIALS, ISSN: 0950-0618, DOI: 10.1016/j.conbuildmat.2017.12.228, Vol.164, pp.731-738, 2018Glinicki M.A., Antolik A., Gawlicki M., Evaluation of compatibility of neutron-shielding boron aggregates with Portland cement in mortar, CONSTRUCTION AND BUILDING MATERIALS, ISSN: 0950-0618, DOI: 10.1016/j.conbuildmat.2017.12.228, Vol.164, pp.731-738, 2018Abstract: Enhanced neutron radiation shielding capacity of protective structures can be achieved using cement-based composites with boron-containing aggregates. Experimental tests were performed to evaluate the effect of boron aggregates (colemanite, ulexite, borax, boron carbide) and nanosilica on the setting time and hydration heat of cement in mortars using isothermal calorimetry. Boron leaching test from mineral aggregates were performed in water and saturated Ca(OH)2 solution. Cement setting retardation effects were found qualitatively correlated with boron leaching from mineral aggregates. A linear dependence of compressive strength of borated mortars and heat released after 72 h of cement hydration was found. A maximum content of boron compounds in mortar, allowing for a systematical control of setting time, was evaluated Keywords: Boron minerals, Cement setting, Colemanite, Early strength, Heat of hydration, Isothermal calorimetry, Leaching, Nanosilica, Neutron shielding, Retardation, Ulexite | |
7. | Kowalczyk-Gajewska K., Maździarz M., Atomistic and mean-field estimates of effective stiffness tensor of nanocrystalline copper, International Journal of Engineering Science, ISSN: 0020-7225, DOI: 10.1016/j.ijengsci.2018.04.004, Vol.129, pp.47-62, 2018Kowalczyk-Gajewska K., Maździarz M., Atomistic and mean-field estimates of effective stiffness tensor of nanocrystalline copper, International Journal of Engineering Science, ISSN: 0020-7225, DOI: 10.1016/j.ijengsci.2018.04.004, Vol.129, pp.47-62, 2018Abstract: The full elasticity tensor for nano-crystalline copper is derived in molecular simulations by performing numerical tests for a set of generated samples of the polycrystalline material. The results are analysed with respect to the anisotropy degree of the overall stiffness tensor resulting from the limited number of grain orientations and their spatial distribution. The dependence of the overall bulk and shear moduli of an isotropized polycrystal on the average grain diameter is analysed. It is found that while the shear modulus decreases with grain size, the bulk modulus shows negligible dependence on the grain diameter and is close to the bulk modulus of a single crystal. A closed-form mean-field model of effective elastic properties for a bulk nano-grained polycrystal with cubic grains, i.e. made of a material with cubic symmetry, is formulated. In the model all parameters are based on the data for a single crystal and on the averaged grain size without any need for additional fitting. It is shown that the proposed model provides predictions of satisfactory qualitative and quantitative agreement with atomistic simulations. Keywords: Molecular statics, Elasticity, Polycrystal, Effective medium, Nano-crystalline copper | |
8. | Rydzek G., Pakdel A., Witecka A., Shri D.N.A., Gaudière F., Nicolosi V., Mokarian-Tabari P., Schaaf P., Boulmedais F., Ariga K., pH-Responsive Saloplastics Based on Weak Polyelectrolytes: From Molecular Processes to Material Scale Properties, Macromolecules, ISSN: 0024-9297, DOI: 10.1021/acs.macromol.8b00609, Vol.51, No.12, pp.4424-4434, 2018Rydzek G., Pakdel A., Witecka A., Shri D.N.A., Gaudière F., Nicolosi V., Mokarian-Tabari P., Schaaf P., Boulmedais F., Ariga K., pH-Responsive Saloplastics Based on Weak Polyelectrolytes: From Molecular Processes to Material Scale Properties, Macromolecules, ISSN: 0024-9297, DOI: 10.1021/acs.macromol.8b00609, Vol.51, No.12, pp.4424-4434, 2018Abstract: Compact polyelectrolyte complexes (COPECs), also named saloplastics, represent a new class of material with high fracture strain and self-healing properties. Here, COPECs based on poly(methacrylic acid) (PMAA) and poly(allylamine hydrochloride) (PAH) were prepared by centrifugation at pH 7. The influence of postassembly pH changes was monitored chemically by ATR-FTIR, ICP, DSC, and TGA, morphologically by SEM, and mechanically by strain to break measurements. Postassembly pH stimuli misbalanced the charge ratio in COPECs, impacting their concentration in counterions, cross-link density, and polymer chain mobility. At the material level, changes were observed in the porosity, composition, water content, and mechanical properties of COPECs. The cross-link density was a prominent factor governing the saloplastic’s composition and water content. However, the porosity and mechanical properties were driven by several factors including salt-induced plasticization and conformational changes of polyelectrolytes. This work illustrates how multiple-scale consequences arise from a single change in the environment of COPECs, providing insights for future design of stimuli-responsive materials. | |
9. | Rojek J., Zubelewicz A., Madan N., Nosewicz S., The discrete element method with deformable particles, INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, ISSN: 0029-5981, DOI: 10.1002/nme.5767, Vol.114, No.8, pp.828-860, 2018Rojek J., Zubelewicz A., Madan N., Nosewicz S., The discrete element method with deformable particles, INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, ISSN: 0029-5981, DOI: 10.1002/nme.5767, Vol.114, No.8, pp.828-860, 2018Abstract: This work presents a new original formulation of the discrete element method (DEM) with deformable cylindrical particles. Uniform stress and strain fields are assumed to be induced in the particles under the action of contact forces. Particle deformation obtained by strain integration is taken into account in the evaluation of interparticle contact forces. The deformability of a particle yields a nonlocal contact model, it leads to the formation of new contacts, it changes the distribution of contact forces in the particle assembly, and it affects the macroscopic response of the particulate material. A numerical algorithm for the deformable DEM (DDEM) has been developed and implemented in the DEM program DEMPack. The new formulation implies only small modifications of the standard DEM algorithm. The DDEM algorithm has been verified on simple examples of an unconfined uniaxial compression of a rectangular specimen discretized with regularly spaced equal bonded particles and a square specimen represented with an irregular configuration of nonuniform-sized bonded particles. The numerical results have been verified by a comparison with equivalent finite elementmethod results and available analytical solutions. The micro-macro relationships for elastic parameters have been obtained. The results have proved to have enhanced the modeling capabilities of the DDEM with respect to the standard DEM. Keywords: average stress, deformable particles, discrete element method, elastic constants, micro-macro
relationships, nonlocal contact model | |
10. | Zawidzki M., Szklarski J., Effective Multi-objective Discrete Optimization of Truss-Z Layouts Using a GPU, APPLIED SOFT COMPUTING, ISSN: 1568-4946, DOI: 10.1016/j.asoc.2018.05.042, pp.1-22, 2018Zawidzki M., Szklarski J., Effective Multi-objective Discrete Optimization of Truss-Z Layouts Using a GPU, APPLIED SOFT COMPUTING, ISSN: 1568-4946, DOI: 10.1016/j.asoc.2018.05.042, pp.1-22, 2018Abstract: Truss-Z (TZ) is an Extremely Modular System for creating skeletal free-form ramps and ramp networks. The TZ structures are comprised of four variations of two types of basic unit subjected to rotation. The two types of units are: R and L being a mirror reflection of each other. This paper presents a novel method based on image processing, evolutionary algorithm and intensive parallelization of multi-objective optimization of TZ layouts.
The algorithm returns a sequence of modules. The result guarantees a TZ connection between two given points (regions) and minimizes the fitness function representing certain costs associated with setting up the TZ structure.
The fitness function depends on the cost of TZ structure as well as the variety of costs related to the environment where the it is to be placed. E.g.: the earthworks, vegetation removal, obstacles avoidance, etc. There are no restrictions on the fitness function definition. It can depend on any variable which can be represented by a two-dimensional map of any property of the environment.
The formulation of the presented method is suited for application of well-established image processing methods which efficiently evaluate candidate solutions on a GPU. As a result, the employed genetic algorithm efficiently probes the search space. The practical applicability of this approach is demonstrated with three case-studies:
1) simultaneous paving of a path with congruent units in a hilly environment with trees & bushes and finding the best location for a pier over an existing river;
2) constructing of a TZ connector spanning over a mountain valley with lakes (where supports can not be placed);
3) retrofitting of an existing railway station with a large wheelchair TZ ramp of over 10 m elevation while preserving trees and minimizing the earthworks. Keywords: Truss-Z, Extremely Modular System, Retrofitting, accessibility, multi-objective, discrete, combinatorial, optimization, genetic algorithm, parallel computing, GPU, GPGPU | |
11. | 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 | |
12. | Tůma K., Stupkiewicz S., Petryk H., Rate-independent dissipation in phase-field modelling of displacive transformations, JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, ISSN: 0022-5096, DOI: 10.1016/j.jmps.2018.02.007, Vol.114, pp.117-142, 2018Tůma K., Stupkiewicz S., Petryk H., Rate-independent dissipation in phase-field modelling of displacive transformations, JOURNAL OF THE MECHANICS AND PHYSICS OF SOLIDS, ISSN: 0022-5096, DOI: 10.1016/j.jmps.2018.02.007, Vol.114, pp.117-142, 2018Abstract: In this paper, rate-independent dissipation is introduced into the phase-field framework for modelling of displacive transformations, such as martensitic phase transformation and twinning. The finite-strain phase-field model developed recently by the present authors is here extended beyond the limitations of purely viscous dissipation. The variational formulation, in which the evolution problem is formulated as a constrained minimization problem for a global rate-potential, is enhanced by including a mixed-type dissipation potential that combines viscous and rate-independent contributions. Effective computational treatment of the resulting incremental problem of non-smooth optimization is developed by employing the augmented Lagrangian method. It is demonstrated that a single Lagrange multiplier field suffices to handle the dissipation potential vertex and simultaneously to enforce physical constraints on the order parameter. In this way, the initially non-smooth problem of evolution is converted into a smooth stationarity problem. The model is implemented in a finite-element code and applied to solve two- and three-dimensional boundary value problems representative for shape memory alloys Keywords: Phase-field method, Microstructure, Martensite, Twinning, Non-smooth optimization | |
13. | 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 | |
14. | 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 | |
15. | 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 | |
16. | 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. | |
17. | Maździarz M., Mrozek A., Kuś W., Burczyński T., Anisotropic-Cyclicgraphene: A New Two-Dimensional Semiconducting Carbon Allotrope, Materials, ISSN: 1996-1944, DOI: 10.3390/ma11030432, Vol.11, No.3, pp.432, 2018Maździarz M., Mrozek A., Kuś W., Burczyński T., Anisotropic-Cyclicgraphene: A New Two-Dimensional Semiconducting Carbon Allotrope, Materials, ISSN: 1996-1944, DOI: 10.3390/ma11030432, Vol.11, No.3, pp.432, 2018Abstract: A potentially new, single-atom thick semiconducting 2D-graphene-like material, called
Anisotropic-cyclicgraphene , has been generated by the two stage searching strategy linking molecular
and ab initio approach. The candidate was derived from the evolutionary-based algorithm and
molecular simulations was then profoundly analysed using first-principles density functional theory
from the structural, mechanical, phonon, and electronic properties point of view. The proposed
polymorph of graphene (rP16-P1m1) is mechanically, dynamically, and thermally stable and can
achieve semiconducting with a direct band gap of 0.829 eV. Keywords: carbon; graphene; graphyne; ab initio calculations; Semiconductors | |
18. | Pieczyska E.A., Maj M., Golasiński K., Staszczak M., Furuta T., Kuramoto S., Thermomechanical Studies of Yielding and Strain Localization Phenomena of Gum Metal under Tension, Materials, ISSN: 1996-1944, DOI: 10.3390/ma11040567, Vol.11, No.567, pp.1-13, 2018Pieczyska E.A., Maj M., Golasiński K., Staszczak M., Furuta T., Kuramoto S., Thermomechanical Studies of Yielding and Strain Localization Phenomena of Gum Metal under Tension, Materials, ISSN: 1996-1944, DOI: 10.3390/ma11040567, Vol.11, No.567, pp.1-13, 2018Abstract: This paper presents results of investigation of multifunctional -Ti alloy Gum Metal subjected to tension at various strain rates. Digital image correlation was used to determine strain distributions and stress-strain curves, while infrared camera allowed for us to obtain the related temperature characteristics of the specimen during deformation. The mechanical curves completed by the temperature changes were applied to analyze the subsequent stages of the alloy loading. Elastic limit, recoverable strain, and development of the strain localization were studied. It was found that the maximal drop in temperature, which corresponds to the yield limit of solid materials, was referred to a significantly lower strain value in the case of Gum Metal in contrast to its large recoverable strain. The temperature increase proves a dissipative character of the process and is related to presence of w and a” phases induced during the alloy fabrication and their exothermic phase transformations activated under loading. During plastic deformation, both the strain and temperature distributions demonstrate that strain localization for higher strain rates starts nucleating just after the yield limit leading to specimen necking and rupture. Macroscopically, it is exhibited as softening of the stress-strain curve in contrast to the strain hardening observed at lower strain rates. Keywords: gum metal, yield limit, thermomechanical coupling, infrared thermography, digital image correlation, strain localization | |
19. | 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 | |
20. | Postek E., Sadowski T., Distributed microcracking process of WC/Co cermet under dynamic impulse compressive loading , COMPOSITE STRUCTURES, ISSN: 0263-8223, DOI: 10.1016/j.compstruct.2018.04.014, Vol.194, pp.494-508, 2018Postek E., Sadowski T., Distributed microcracking process of WC/Co cermet under dynamic impulse compressive loading , COMPOSITE STRUCTURES, ISSN: 0263-8223, DOI: 10.1016/j.compstruct.2018.04.014, Vol.194, pp.494-508, 2018Abstract: Cermet Materials (CM), for example, WC/Co, have very good mechanical, thermal and wear properties. They are used for manufacturing of cutting tools. However, their behavior under dynamic loads is still not properly understood.
Experiments, e.g. Siegl and Fischmester (1988) and Ravichandran (1994), indicate that the fracture energy of
WC/Co is expended through ductile failure of the Co: (1) close to the binder/tungsten carbide interface (Liu et al., 2017) [64] or by (2) dimple rupture across the interphase (Sigl and Exner, 1987) [22]. Stress concentrations around grain boundaries lead to initiation of microcracks which are dispersed by dynamic loading.
The main goal of the paper is to investigate the previously formulated models of the two-phase composite (Sadowski et al., 2005, 2006, 2007; Dębski and Sadowski, 2014, 2017) [47–51] in the case of dynamic compressive
pulses that are common in the case of cutting tools. 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 obtained results show that microcracking process and stress distributions are different for quasi-static and dynamic loadings. Early development of microcracks distribution revealed by damage parameter was observed. Keywords: Cermet, Dynamic compressive impulse, Interface elements, Distributed microcracking process | |
21. | Jarząbek D.M., The impact of weak interfacial bonding strength on mechanical properties of metal matrix - ceramic reinforced composites, COMPOSITE STRUCTURES, ISSN: 0263-8223, DOI: 10.1016/j.compstruct.2018.06.071, Vol.201, pp.352-362, 2018Jarząbek D.M., The impact of weak interfacial bonding strength on mechanical properties of metal matrix - ceramic reinforced composites, COMPOSITE STRUCTURES, ISSN: 0263-8223, DOI: 10.1016/j.compstruct.2018.06.071, Vol.201, pp.352-362, 2018Abstract: In this work the influence of weak interface between particles and matrix on mechanical properties of metal matrix – ceramic reinforced composites is studied. Firstly, the samples made of coelectrodeposited Ni-SiC composites with 10% of SiC with poor interface bonding have been prepared. Furthermore, the tensile tests of samples have been performed. The determined Young’s modulus was equal to 67 ± 8 GPa and the ultimate tensile strength to 230 ± 15 MPa. It is assumed that the very weak interface is the reason for the poor mechanical properties of the created material. In order to confirm the assumption and get the necessary parameters for the numerical model, the measurements of the normal and shear interfacial bonding strength of the interface have been performed. The measured normal interfacial bonding strength is equal to 0.1 ± 0.03 MPa and the interfacial shear strength is equal to 4.9 ± 0.2 MPa. The experimental results have been confirmed qualitatively by the computer simulations. Representative Volume Element has been created and modelled by the Finite Element Method with cohesive zone elements. The computer simulations result in the Young’s modulus values from 119 GPa up to 126 GPa. Keywords: Interfacial bonding strength, Metal matrix composites, Tensile strength, Silicon carbide, Electrodeposited nickel, Cohesive elements | |
22. | Postek E., Sadowski T., Dynamic pulse sensitivity of WC/Co composite, COMPOSITE STRUCTURES, ISSN: 0263-8223, DOI: 10.1016/j.compstruct.2017.10.092, No.203, pp.498-512, 2018Postek E., Sadowski T., Dynamic pulse sensitivity of WC/Co composite, COMPOSITE STRUCTURES, ISSN: 0263-8223, DOI: 10.1016/j.compstruct.2017.10.092, No.203, pp.498-512, 2018Abstract: Cutting tools are manufactured among others from cermet (e.g. WC/Co) having excellent mechanical properties. Geometry of the internal microstructure is complex and mechanical response due to quasi-static or dynamic loading is difficult to be described. Particularly, the dynamic loading is not investigated enough precise up till now.
Experimental evidences, e.g. Siegl and Fischmester (1988), Ravichandran (1994), indicate that the fracture energy of WC/Co is expended through ductile failure of the Co: (1) near the binder/tungsten carbide interface or by (2) dimple rupture across the interphase. Concentrations of stresses around grain boundaries lead to initiation of microcrack system, which is dispersed for dynamic loading.
The aim of the paper is to extend the previously formulated models (Sadowski et al., 2005, 2006, 2007, Dębski and Sadowski, 2014, 2017) of the polycrystalline composite towards more advanced finite element formulation, applicable for description of the cermet behavior under dynamic pulses. The model takes into account: (1) spatial distribution of the cermet constituents, (2) system of grain boundaries/binder interfaces modeled by interface elements, (3) rotation of brittle grains.
The obtained results show that stress distributions and gradual microcracking processes are quite different for quasi-static and dynamic loadings. It was revealed by damage parameter indicating concentration of microcracks. Keywords: Metal-ceramic composite, Interface elements, Crack propagation, Dynamic loading, | |
23. | Suchorzewski J., Korol E., Tejchman J., Mróz Z., Experimental study of shear strength and failure mechanisms in RC beams scaled along height or length, ENGINEERING STRUCTURES, ISSN: 0141-0296, DOI: 10.1016/j.engstruct.2017.12.003, Vol.157, pp.203-223, 2018Suchorzewski J., Korol E., Tejchman J., Mróz Z., Experimental study of shear strength and failure mechanisms in RC beams scaled along height or length, ENGINEERING STRUCTURES, ISSN: 0141-0296, DOI: 10.1016/j.engstruct.2017.12.003, Vol.157, pp.203-223, 2018Abstract: The paper presents results of laboratory experiments carried out on longitudinally reinforced concrete beams subjected to four-point bending. Beams of separately varying height and length were analyzed to investigate the size effect on nominal strength and post-critical brittleness. Beams were scaled in the height direction in the first test series and in the length direction in the second series. Due to lack of geometrical similarity, different failure mechanisms were exhibited. Load-deflection diagrams and crack paths were registered during experiments. The digital image correlation technique was applied to visualize strain localization on the concrete surface. The crack opening and crack slip displacements were also measured. The beam response was characterized by two non-dimensional parameters ηa = a/D and ηb = b/D defined as the ratios of shear and bending spans to the beam depth D assumed as the size parameter and the reinforcement position parameter ηc = c′/D. Two major failure mechanisms were observed: flexural failure in the central beam zone combined with plastic yielding of the reinforcement and the diagonal shear crack failure in external shear zones. Two distinct modes of shear failure can be specified depending on the dominance of crack opening or crack closure contact zones. Two different effective stresses associated with failure mechanisms were defined to specify the beam strength’s dependence on ηa, ηb, ηc and D. Some analytical formulae specifying the critical shear stress dependence on ηa, ηc and strengths ratio of reinforcement and concrete were presented at the end of paper and compared with experimental data. Keywords: Concrete beams, Longitudinal reinforcement, Four-point bending, Failure modes, Height or length variation, Size effect | |
24. | Dulnik J., Kołbuk D., Denis P., Sajkiewicz P., The effect of a solvent on cellular response to PCL/gelatin and PCL/collagen electrospun nanofibres, EUROPEAN POLYMER JOURNAL, ISSN: 0014-3057, DOI: 10.1016/j.eurpolymj.2018.05.010, Vol.104, pp.147-156, 2018Dulnik J., Kołbuk D., Denis P., Sajkiewicz P., The effect of a solvent on cellular response to PCL/gelatin and PCL/collagen electrospun nanofibres, EUROPEAN POLYMER JOURNAL, ISSN: 0014-3057, DOI: 10.1016/j.eurpolymj.2018.05.010, Vol.104, pp.147-156, 2018Abstract: Bicomponent polycaprolactone/gelatin and polycaprolactone/collagen fibres were formed by electrospinning using two kinds of solvents: a representative of commonly used solvents with this polymer composition, highly toxic hexafluoroisopropanol (HFIP) and alternative, less harmful one, the mixture of acetic (AA) and formic (FA) acids. Both material types were subjected to investigations of structure and in-vitro cellular activity. Viscosity and Fourier transform infrared spectroscopy (FTIR) measurements shown that the type of solvent used influences the structure of solution and conformation of polymer molecules. In-vitro quantitative tests as well as cell culture morphology observations proved that materials electrospun with the use of ‘green’ solvents can yield similar results to those obtained by made with toxic ones. Slightly better cellular response to materials electrospun from HFIP can be explained by relatively well dispersed components within the fibre and more expanded conformation of molecules, resulting in better exposition of RGD (Arg-Gly-Asp) binding sites to cells’ integrin receptors. Keywords: Cellular tests, Electrospinning, Biopolymers, Viscosity, Solvents | |
25. | 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. | |
26. | Bigoni D., Bordignon N., Piccolroaz A., Stupkiewicz S., Bifurcation of elastic solids with sliding interfaces, PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, ISSN: 1364-5021, DOI: 10.1098/rspa.2017.0681, Vol.474, pp.20170681-1-21, 2018Bigoni D., Bordignon N., Piccolroaz A., Stupkiewicz S., Bifurcation of elastic solids with sliding interfaces, PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES, ISSN: 1364-5021, DOI: 10.1098/rspa.2017.0681, Vol.474, pp.20170681-1-21, 2018Abstract: Lubricated sliding contact between soft solids is an interesting topic in biomechanics and for the design of small-scale engineering devices. As a model of this mechanical set-up, two elastic nonlinear solids are considered jointed through a frictionless and bilateral surface, so that continuity of the normal component of the Cauchy traction holds across the surface, but the tangential component is null. Moreover, the displacement can develop only in a way that the bodies in contact do neither detach, nor overlap. Surprisingly, this finite strain problem has not been correctly formulated until now, so this formulation is the objective of the present paper. The incremental equations are shown to be non-trivial and different from previously (and erroneously) employed conditions. In particular, an exclusion condition for bifurcation is derived to show that previous formulations based on frictionless contact or ‘spring-type’ interfacial conditions are not able to predict bifurcations in tension, while experiments—one of which, ad hoc designed, is reported—show that these bifurcations are a reality and become possible when the correct sliding interface model is used. The presented results introduce a methodology for the determination of bifurcations and instabilities occurring during lubricated sliding between soft bodies in contact Keywords: frictionless contact, large strains, nonlinear elasticity | |
27. | Enayati M.S., Behzad T., Sajkiewicz P., Rafienia M., Bagheri R., Ghasemi-Mobarakeh L., Kołbuk D., Pahlevanneshan Z., Bonakdar S.H., Development of electrospun poly (vinyl alcohol)-based bionanocomposite scaffolds for bone tissue engineering, Journal of Biomedical Materials Research Part A, ISSN: 1549-3296, DOI: 10.1002/jbm.a.36309, Vol.106, No.4, pp.1111-1120, 2018Enayati M.S., Behzad T., Sajkiewicz P., Rafienia M., Bagheri R., Ghasemi-Mobarakeh L., Kołbuk D., Pahlevanneshan Z., Bonakdar S.H., Development of electrospun poly (vinyl alcohol)-based bionanocomposite scaffolds for bone tissue engineering, Journal of Biomedical Materials Research Part A, ISSN: 1549-3296, DOI: 10.1002/jbm.a.36309, Vol.106, No.4, pp.1111-1120, 2018Abstract: The article is focused on the role of nanohydroxy apatite (nHAp) and cellulose nanofibers (CNFs) as fillers in the electrospun poly (vinyl alcohol) (ES-PVA) nanofibers for bone tissue engineering (TE). Fibrous scaffolds of PVA, PVA/nHAp (10 wt.%), and PVA/nHAp(10 wt.%)/CNF(3 wt.%) were successfully fabricated and characterized. Tensile test on electrospun PVA/nHAp10 and PVA/nHAp10/CNF3 revealed a three-fold and seven-fold increase in modulus compared with pure ES-PVA (45.45 ± 4.77). Although, nanofiller loading slightly reduced the porosity percentage, all scaffolds had porosity higher than 70%. In addition, contact angle test proved the great hydrophilicity of scaffolds. The presence of fillers reduced in vitro biodegradation rate in PBS while accelerates biomineralization in simulated body fluid (SBF). Furthermore, cell viability, cell attachment, and functional activity of osteoblast MG-63 cells were studied on scaffolds showing higher cellular activity for scaffolds with nanofillers. Generally, the obtained results confirm that the 3-componemnt fibrous scaffold of PVA/nHAp/CNF has promising potential in hard TE. Keywords: electrospinning, PVA bionanocomposites, scaffolds, bone tissue engineering, cell culture | |
28. | Jeznach O., Kołbuk D., Sajkiewicz P., Injectable hydrogels and nanocomposite hydrogels for cartilage regeneration, Journal of Biomedical Materials Research Part A, ISSN: 1549-3296, DOI: 10.1002/jbm.a.36449, pp.1-51, 2018Jeznach O., Kołbuk D., Sajkiewicz P., Injectable hydrogels and nanocomposite hydrogels for cartilage regeneration, Journal of Biomedical Materials Research Part A, ISSN: 1549-3296, DOI: 10.1002/jbm.a.36449, pp.1-51, 2018Abstract: Cartilage loss due to age‐related degeneration and mechanical trauma is a significant and challenging problem in the field of surgical medicine. Unfortunately, cartilage tissue can be characterized by the lack of regenerative ability. Limitations of conventional treatment strategies, such as auto‐, allo‐ and xenografts or implants stimulate an increasing interest in the tissue engineering approach to cartilage repair. This review discusses the application of polymer‐based scaffolds, with an emphasis on hydrogels in cartilage tissue engineering. We highlight injectable hydrogels with various micro‐ and nanoparticles, as they constitute a novel and attractive type of scaffolds. We discuss advantages, limitations and future perspectives of injectable nanocomposite hydrogels for cartilage tissue regeneration. Keywords: polymers, hydrogels, injectable hydrogels, injectable nanocomposite hydrogels, cartilage repair, cartilage tissue engineering | |
29. | Jarecki L., Pecherski R.B., Kinetics of oriented crystallization of polymers in the linear stress-orientation range in the series expansion approach , Express Polymer Letters, ISSN: 1788-618X, DOI: 10.3144/expresspolymlett/2018.29, Vol.12, No.4, pp.330-348, 2018Jarecki L., Pecherski R.B., Kinetics of oriented crystallization of polymers in the linear stress-orientation range in the series expansion approach , Express Polymer Letters, ISSN: 1788-618X, DOI: 10.3144/expresspolymlett/2018.29, Vol.12, No.4, pp.330-348, 2018Abstract: An analytical formula is derived for the oriented crystallization coefficient governing kinetics of oriented crystallization under uniaxial amorphous orientation in the entire temperature range. A series expansion approach is applied to the free energy of crystallization in the Hoffman-Lauritzen kinetic model of crystallization at accounting for the entropy of orientation of the amorphous chains. The series expansion coefficients are calculated for systems of Gaussian chains in linear stress-orientation range. Oriented crystallization rate functions are determined basing on the ‘proportional expansion’ approach proposed by Ziabicki in the steady-state limit. Crystallization kinetics controlled by separate predetermined and sporadic primary nucleation is considered, as well as the kinetics involving both nucleation mechanisms potentially present in oriented systems. The involvement of sporadic nucleation in the transformation kinetics is predicted to increase with increasing amorphous orientation. Example computations illustrate the dependence of the calculated functions on temperature and amorphous orientation, as well as qualitative agreement of the calculations with experimental results.
Keywords: modeling and simulation, kinetics of oriented crystallization, amorphous orientation, sporadic nucleation, predetermined nucleation
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30. | 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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31. | Pisarski D., Konowrocki R., Szmidt T., Dynamics and optimal control of an electromagnetically actuated cantilever pipe conveying fluid, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2018.06.045, Vol.432, pp.420-436, 2018Pisarski D., Konowrocki R., Szmidt T., Dynamics and optimal control of an electromagnetically actuated cantilever pipe conveying fluid, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2018.06.045, Vol.432, pp.420-436, 2018Abstract: This paper deals with the problem of applying electromagnetic devices of the motional type to improve the dynamic stability of a pipe conveying air. When the flow velocity reaches a critical value, the steady equilibrium position becomes unstable, and self-excited lateral vibrations arise. In contrast, electromagnetic devices of the transformer type have been demonstrated to be highly effective in the passive stabilization of such a system, as well as the active stabilization of similar non-conservative systems with a follower force. In the present paper, we apply a pair of motional devices made of a conducting plate which is attached to the pipe and moves together with it within the perpendicular magnetic field generated by the controlled electromagnets. This motion generates eddy currents in the plates and a drag force of a viscous character. In this setting, we first investigate the possibility of designing a stabilizing control within the region of the magnetic field where every passive solution results in an unstable or conservative state. For that purpose, we determine a practical condition justifying the existence of a stabilizing control for a given set of system parameters. Later we pose and solve an optimal control problem aiming at stabilizing the system with the optimal rate of decrease of the system’s energy. The solution is examined by means of numerical simulations performed within the three regions of the flow velocity: low subcritical, where the Coriolis acceleration of the conveyed fluid generates the predominate damping force; high subcritical, where the inertia of the fluid begins to dominate the dynamics of the system; and low supercritical,where unstable flutter vibrations start to arise. The effectiveness of the designed optimal controller is validated by comparisons with the corresponding passive solutions. Keywords: fluid–structure interaction, electromagnetic device, optimal control, stabilization, smart structure | |
32. | Kubissa W., Glinicki M.A., Dąbrowski M., Permeability testing of radiation shielding concrete manufactured at industrial scale, MATERIALS AND STRUCTURES, ISSN: 1359-5997, DOI: 10.1617/s11527-018-1213-0, Vol.51, No.83, pp.1-15, 2018Kubissa W., Glinicki M.A., Dąbrowski M., Permeability testing of radiation shielding concrete manufactured at industrial scale, MATERIALS AND STRUCTURES, ISSN: 1359-5997, DOI: 10.1617/s11527-018-1213-0, Vol.51, No.83, pp.1-15, 2018Abstract: The effect of the composition of industrial concrete designed for radiation shielding structures on the air permeability and the diffusion of moisture was studied. The mix design for heavyweight concrete of bulk density 3168–3317 kg/m3 was developed using barite and magnetite aggregate and cements blended with fly ash and blastfurnace slag. Structural elements, like columns of a height of 4 m and massive blocks made of mixtures with different cements were manufactured using ready mixed concrete pumped into the formwork. Core specimens were taken from the elements at different locations. The air permeability index was tested using Autoclam device. Evaluation of the quality of concrete on the basis of API results varied from “very good” to “good”. The moisture distribution inside concrete specimens was equilibrated to RH = 60 ± 5%. Observation of RH changes allowed to determine the moisture diffusion coefficient. Significant differences of the permeability and moisture diffusion coefficient depending on the location of the core specimens drilling and mix design of concrete were found. The D coefficient provided a good reflection of the different quality of heavyweight concrete in structural elements. Keywords: Air permeability, Autoclam, Barite, Blended cement, Cracking, Heavyweight aggregate, Magnetite, Moisture diffusion, Radiation shielding concrete, Relative humidity | |
33. | Maj J., Basista M., Węglewski W., Bochenek K., Strojny-Nędza A., Naplocha K., Panzner T., Tatarkova M., Fiori F., Effect of microstructure on mechanical properties and residual stresses in interpenetrating aluminum-alumina composites fabricated by squeeze casting, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2017.12.091, Vol.715, pp.154-162, 2018Maj J., Basista M., Węglewski W., Bochenek K., Strojny-Nędza A., Naplocha K., Panzner T., Tatarkova M., Fiori F., Effect of microstructure on mechanical properties and residual stresses in interpenetrating aluminum-alumina composites fabricated by squeeze casting, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2017.12.091, Vol.715, pp.154-162, 2018Abstract: Aluminum-alumina composites with interpenetrating network structure are interesting structural materials due to their high resistance to elevated temperature and frictional wear, good heat conductivity, enhanced mechanical strength and fracture toughness. In this paper aluminum-alumina bulk composites and FGMs are manufactured by pressure infiltration of porous alumina preforms with molten aluminium alloy (EN AC-44200). Influence of the interpenetrating microstructure on the macroscopic bending strength, fracture toughness, hardness and heat conduction is examined. Special focus is on processing-induced thermal residual stresses in aluminium-alumina composites due to their potentially detrimental effects on material performance in structural elements under in-service conditions. The residual stresses are measured experimentally in the ceramic phase by neutron diffraction and simulated numerically using a micro-CT based Finite Element model, which takes into account the actual interpenetrating microstructure of the composite. The model predictions for two different volume fractions of alumina agree fairly well with the neutron diffraction measurements Keywords: A. stress measurements, X-ray analysis, finite element analysis, B. composites, C. casting methods | |
34. | Kopeć M., Wang K., Politis D.J., Wang Y., Wang L., Lin J., Formability and microstructure evolution mechanisms of Ti6Al4V alloy during a novel hot stamping process, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2018.02.038, pp.1-20, 2018Kopeć M., Wang K., Politis D.J., Wang Y., Wang L., Lin J., Formability and microstructure evolution mechanisms of Ti6Al4V alloy during a novel hot stamping process, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2018.02.038, pp.1-20, 2018Abstract: A novel hot stamping process for Ti6Al4V alloy using cold forming tools and a hot blank was presented in this paper. The formability of the material was studied through uniaxial tensile tests at temperatures ranging from 600 to 900 °C and strain rates ranging from 0.1 to 5 s-1. An elongation ranging from 30% to 60% could be achieved at temperatures ranging from 750 to 900°C respectively. The main microstructure evolution mechanisms varied with the deformation temperature, including recovery, phase transformation and recrystallization. The hardness of the material after deformation first decreased with the temperature due to recovery, and subsequently increased mainly due to the phase transformation. During the hot stamping tests, qualified parts could be formed successfully at heating temperatures ranging from 750 to 850°C. The forming failed at lower temperatures due to the limited ductility of the material. At temperatures higher than 900°C, extensive phase transformation of α to β occurred during the heating. During the transfer and forming, the temperature dropped significantly which led to the formation of transformed β, reduction of the formability and subsequent failure. The post-form hardness distribution demonstrated the same tendency as that after uniaxial tensile tests. Keywords: titanium alloys, Ti6Al4V, hot stamping, microstructure | |
35. | Pakdel A., Witecka A., Rydzek G., Shri D.N.A., Nicolosi V., A comprehensive analysis of extrusion behavior, microstructural evolution, and mechanical properties of 6063 Al–B4C composites produced by semisolid stir casting, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2018.02.080, Vol.721, pp.28-37, 2018Pakdel A., Witecka A., Rydzek G., Shri D.N.A., Nicolosi V., A comprehensive analysis of extrusion behavior, microstructural evolution, and mechanical properties of 6063 Al–B4C composites produced by semisolid stir casting, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2018.02.080, Vol.721, pp.28-37, 2018Abstract: In this study, composites of aluminum alloy 6063 reinforced with 10 wt% boron carbide microparticles were successfully fabricated by a combination of spark plasma sintering and stir casting methods, followed by hot extrusion. A systematic study on the relationship between extrusion process variables (i.e. extrusion ratio, temperature, and punch speed) and porosity, particle refinement, particle distribution and consequently tensile properties and fracture behavior of the composites was performed. Extensive electron microscopy analysis and tensile testing of the composites revealed a multifactoral interdependency of microstructural evolution and mechanical properties on the extrusion process variables. For example, while increasing the extrusion ratio at higher temperatures led to moderate particle refinement, better densification of the composites, and improvement in mechanical properties, concurrent particle fragmentation and microvoid formation around the particles at lower temperatures had opposing effects on the mechanical behavior. We show that the dependency of mechanical properties on all such microstructural factors makes it difficult to predict optimum extrusion conditions in aluminum matrix composites. That is, unlike the common approach, extruding the composites at higher temperatures and achieving more reduction in area may not necessarily lead to the most favorable mechanical properties. Keywords: Aluminum matrix composite, Hot extrusion, Mechanical behavior, Microstructure, Spark plasma sintering, Stir casting | |
36. | 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 | |
37. | 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 | |
38. | 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. | |
39. | 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 | |
40. | Chrzanowska-Giżyńska J., Denis P., Hoffman J., Giżyński M., Mościcki T., Garbiec D., Szymański Z., Tungsten borides layers deposited by a nanosecond laser pulse, SURFACE AND COATINGS TECHNOLOGY, ISSN: 0257-8972, DOI: 10.1016/j.surfcoat.2017.12.040, Vol.335, pp.181-187, 2018Chrzanowska-Giżyńska J., Denis P., Hoffman J., Giżyński M., Mościcki T., Garbiec D., Szymański Z., Tungsten borides layers deposited by a nanosecond laser pulse, SURFACE AND COATINGS TECHNOLOGY, ISSN: 0257-8972, DOI: 10.1016/j.surfcoat.2017.12.040, Vol.335, pp.181-187, 2018Abstract: Tungsten borides belong to the group of potentially superhard materials which hardness could be compared to cubic boron nitride and diamond. However, difficulty in fabrication of single phase material using conventional methods is the main drawback of this group of ceramics. In order to overcome this problem material can be deposited as a thin layer e.g. in the pulsed laser deposition process. In this paper, the effect of laser wavelength and energy density of nanosecond Nd:YAG laser on the WBx-type layers were analyzed using wavelengths 355 and 1064 nm with the energy density of laser beam from 1.7 to 5 J/cm2 and from 1.7 to 9.3 J/cm2, respectively. The WB2.5 and WB4.5 targets synthesized in Spark Plasma Sintering process were used and the layers were deposited onto Si (100) substrate heated to a temperature of 570 °C. Layers' microstructure were analyzed using X-ray Diffraction and scanning electron microscope equipped with energy dispersive X-ray spectrometer. Change of laser wavelength and energy density resulted in variations of the chemical composition and morphology of deposited layers. Finally, W2B-βWB, αWB-WB-WB3 and WB3, and boron layers were deposited wherein WB3 structure is formed in a wide range of laser fluences and at both investigated wavelength. Next, WB3 layers were investigated in the indentation test at a load of 5–30 mN and its hardness was up to 50 ± 10 GPa Keywords: Pulsed laser deposition, Super-hard materials, Tungsten borides, Tungsten triboride | |
41. | Vakis A.I., Yastrebov V.A., Scheibert J., Nicola L., Dini D., Minfray C., Almqvist A., Paggi M., Lee S., Limbert G., Molinari J.F., Anciaux G., Aghababaei R., Echeverri Restrepo S., Papangelo A., Cammarata A., Nicolini P., Putignano C., Carbone G., Stupkiewicz S., Lengiewicz J., Costagliola G., Bosia F., Guarino R., Pugno N.M., Müser M.H., Ciavarella M., Modeling and simulation in tribology across scales: An overview, TRIBOLOGY INTERNATIONAL, ISSN: 0301-679X, DOI: 10.1016/j.triboint.2018.02.005, Vol.125, pp.169-199, 2018Vakis A.I., Yastrebov V.A., Scheibert J., Nicola L., Dini D., Minfray C., Almqvist A., Paggi M., Lee S., Limbert G., Molinari J.F., Anciaux G., Aghababaei R., Echeverri Restrepo S., Papangelo A., Cammarata A., Nicolini P., Putignano C., Carbone G., Stupkiewicz S., Lengiewicz J., Costagliola G., Bosia F., Guarino R., Pugno N.M., Müser M.H., Ciavarella M., Modeling and simulation in tribology across scales: An overview, TRIBOLOGY INTERNATIONAL, ISSN: 0301-679X, DOI: 10.1016/j.triboint.2018.02.005, Vol.125, pp.169-199, 2018Abstract: This review summarizes recent advances in the area of tribology based on the outcome of a Lorentz Center workshop surveying various physical, chemical and mechanical phenomena across scales. Among the main themes discussed were those of rough surface representations, the breakdown of continuum theories at the nano- and microscales, as well as multiscale and multiphysics aspects for analytical and computational models relevant to applications spanning a variety of sectors, from automotive to biotribology and nanotechnology. Significant effort is still required to account for complementary nonlinear effects of plasticity, adhesion, friction, wear, lubrication and surface chemistry in tribological models. For each topic, we propose some research directions. Keywords: Tribology, Multiscale modeling, Multiphysics modeling, Roughness, Contact, Friction, Adhesion, Wear, Lubrication, Tribochemistry | |
42. | Nowicki A., Trawiński Z., Gambin B., Secomski W., Szubielski M., Parol M., Olszewski R., 20-MHZ ultrasound for measurements offlow-mediated dilation and shear rate in the radialartery
, ULTRASOUND IN MEDICINE AND BIOLOGY, ISSN: 0301-5629, DOI: 10.1016/j.ultrasmedbio.2018.02.011, Vol.44, No.6, pp.1187-1197, 2018Nowicki A., Trawiński Z., Gambin B., Secomski W., Szubielski M., Parol M., Olszewski R., 20-MHZ ultrasound for measurements offlow-mediated dilation and shear rate in the radialartery
, ULTRASOUND IN MEDICINE AND BIOLOGY, ISSN: 0301-5629, DOI: 10.1016/j.ultrasmedbio.2018.02.011, Vol.44, No.6, pp.1187-1197, 2018Abstract: A high-frequency scanning system consisting of a 20-MHz linear array transducer combined with a 20-MHz pulsed Dopplerprobe was introduced to evaluate the degree of radial artery ﬂow-mediated dilation (FMD [%]) in two groups of patients after5 min of controlled forearm ischemia followed by reactive hyperemia. In group I, comprising 27 healthy volunteers, FMD (mean ± standard deviation) was 15.26 ± 4.90% (95% conﬁdence interval [CI]: 13.32%–17.20%); in group II, comprising 17 patients with chronic coronary artery disease, FMD was signiﬁcantly less at 4.53 ± 4.11% (95% CI: 2.42%–6.64%). Speciﬁcally, the ratio FMD/SR (mean ± standard deviation),wasequalto5.36×10−4±4.64×10−4 (95%CI:3.54×10−4 to7.18×10−4)ingroupIand1.38×10−4±0.89×10−4 (95% CI: 0.70 × 10−4 to 2.06 × 10−4) in group II. Statistically signiﬁcant differences between the two groups were conﬁrmed by a Wilcoxon–Mann–Whitney test for both FMD and FMD/SR (p < 0.01). Areas under receiver operating characteristic curves for FMD and FMD/SR were greater than 0.9. The results conﬁrm the usefulness of the proposed measurements of radial artery FMD and SR in differentiation of normal patients from those with chronic coronary artery disease. (E-mail: anowicki@ippt.gov.pl) © 2018 World Federation for Ultrasound in Medicine & Biology. All rights reserved. Keywords: Flow-mediated vasodilation, Radial artery, Shear rate, Reactive hyperemia, Endothelium, Pulsed doppler, Ultrasonography
| |
43. | 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 | |
44. | Zawidzki M., Jankowski Ł., Optimization of modular Truss-Z by minimum-mass design under equivalent stress constraint, SMART STRUCTURES AND SYSTEMS, ISSN: 1738-1584, DOI: 10.12989/sss.2018.21.6.715, Vol.21, No.6, pp.715-725, 2018Zawidzki M., Jankowski Ł., Optimization of modular Truss-Z by minimum-mass design under equivalent stress constraint, SMART STRUCTURES AND SYSTEMS, ISSN: 1738-1584, DOI: 10.12989/sss.2018.21.6.715, Vol.21, No.6, pp.715-725, 2018Abstract: Truss-Z (TZ) is an Extremely Modular System (EMS). Such systems allow for creation of structurally sound free-form structures, are comprised of as few types of modules as possible, and are not constrained by a regular tessellation of space. Their objective is to create spatial structures in given environments connecting given terminals without self-intersections and obstacle-intersections. TZ is a skeletal modular system for creating free-form pedestrian ramps and ramp networks. The previous research on TZ focused on global discrete geometric optimization of the spatial configuration of modules. This paper reports on the first attempts at structural optimization of the module for a single-branch TZ. The internal topology and the sizing of module beams are subject to optimization. An important challenge is that the module is to be universal: it must be designed for the worst case scenario, as defined by the module position within a TZ branch and the geometric configuration of the branch itself. There are four variations of each module, and the number of unique TZ configurations grows exponentially with the branch length. The aim is to obtain minimum-mass modules with the von Mises equivalent stress constrained under certain design load. The resulting modules are further evaluated also in terms of the typical structural criterion of compliance. Keywords: Extremely Modular System, Truss-Z, structural optimization, modular structures, minimum mass design, frame structures | |
45. | Balevičius R., Mróz Z., Modeling of combined slip and finite sliding at spherical grain contacts, GRANULAR MATTER, ISSN: 1434-5021, DOI: 10.1007/s10035-017-0778-6, Vol.10, pp.1-27, 2018Balevičius R., Mróz Z., Modeling of combined slip and finite sliding at spherical grain contacts, GRANULAR MATTER, ISSN: 1434-5021, DOI: 10.1007/s10035-017-0778-6, Vol.10, pp.1-27, 2018Abstract: The present paper is aimed at developing the analytical description of the interaction of two contacting spheres for several classes of slip and sliding trajectories, typical in the experimental testing. The analysis accounts for memory effects in the slip regime and configurational effects in the sliding regime, expressed in terms of an active loading surface and memory surfaces within the space of contact forces. Analytical relations for contact response are derived for linear and piecewise-linear motion trajectories of the sphere. The problem of multiple contact interaction of the sphere moving over the regularly packed granular bed is also considered analytically. It is demonstrated that the dual contact activation-separation processes occur within the combined slip–sliding modes, essentially affecting the distribution of contact tractions. The results obtained are relevant for the class of contact problems requiring analysis of interaction of slip and sliding displacements, in particular in testing grain contact interaction aimed at specification of elastic, frictional and wear parameters. Keywords: Sphere–sphere contact, Memory rules, Slip and sliding, Displacement and force control, Monotonic and reciprocal sliding, Friction, Granular bed | |
46. | Krajewski M., Brzozka K., Tokarczyk M., Kowalski G., Lewinska S., Slawska-Waniewska A., Lin W.S., Lin H.M., Impact of thermal oxidation on chemical composition and magnetic properties of iron nanoparticles, Journal of Magnetism and Magnetic Materials, ISSN: 0304-8853, DOI: 10.1016/j.jmmm.2018.03.047, Vol.458, pp.346-354, 2018Krajewski M., Brzozka K., Tokarczyk M., Kowalski G., Lewinska S., Slawska-Waniewska A., Lin W.S., Lin H.M., Impact of thermal oxidation on chemical composition and magnetic properties of iron nanoparticles, Journal of Magnetism and Magnetic Materials, ISSN: 0304-8853, DOI: 10.1016/j.jmmm.2018.03.047, Vol.458, pp.346-354, 2018Abstract: The main objective of this work is to study the influence of thermal oxidation on the chemical composition and magnetic properties of iron nanoparticles which were manufactured in a simple chemical reduction of Fe3+ ions coming from iron salt with sodium borohydride. The annealing processing was performed in an argon atmosphere containing the traces of oxygen to avoid spontaneous oxidation of iron at temperatures ranging from 200 °C to 800 °C. The chemical composition and magnetic properties of as-prepared and thermally-treated nanoparticles were determined by means of X-ray diffractometry, Raman spectroscopy, Mössbauer spectroscopy and vibrating sample magnetometry. Due to the magnetic interactions, the investigated iron nanoparticles tended to create the dense aggregates which were difficult to split even at low temperatures. This caused that there was no empty space between them, which led to their partial sintering at elevated temperatures. These features hindered their precise morphological observations using the electron microscopy techniques. The obtained results show that the annealing process up to 800 °C resulted in a progressive change in the chemical composition of as-prepared iron nanoparticles which was associated with their oxidation. As a consequence, their magnetic properties also depended on the annealing temperature. For instance, considering the values of saturation magnetization, its highest value was recorded for the as-prepared nanoparticles at 1 T and it equals 149 emu/g, while the saturation point for nanoparticles treated at 600 °C and higher temperatures was not reached even at the magnetic field of about 5 T. Moreover, a significant enhancement of coercivity was observed for the iron nanoparticles annealed over 600 °C. Keywords: Chemical composition, Chemical reduction, Iron nanoparticle, Magnetic properties, Oxidation | |
47. | Skłodowska K., Dębski P.R., Michalski J.A., Korczyk P.M., Dolata M., Zając M., Jakiela S., Simultaneous Measurement of Viscosity and Optical Density of Bacterial Growth and Death in a Microdroplet, Micromachines, ISSN: 2072-666X, DOI: 10.3390/mi9050251, Vol.9, No.5, pp.1-13, 2018Skłodowska K., Dębski P.R., Michalski J.A., Korczyk P.M., Dolata M., Zając M., Jakiela S., Simultaneous Measurement of Viscosity and Optical Density of Bacterial Growth and Death in a Microdroplet, Micromachines, ISSN: 2072-666X, DOI: 10.3390/mi9050251, Vol.9, No.5, pp.1-13, 2018Abstract: Herein, we describe a novel method for the assessment of droplet viscosity moving inside microfluidic channels. The method allows for the monitoring of the rate of the continuous growth of bacterial culture. It is based on the analysis of the hydrodynamic resistance of a droplet that is present in a microfluidic channel, which affects its motion. As a result, we were able to observe and quantify the change in the viscosity of the dispersed phase that is caused by the increasing population of interacting bacteria inside a size-limited system. The technique allows for finding the correlation between the viscosity of the medium with a bacterial culture and its optical density. These features, together with the high precision of the measurement, make our viscometer a promising tool for various experiments in the field of analytical chemistry and microbiology, where the rigorous control of the conditions of the reaction and the monitoring of the size of bacterial culture are vital. Keywords: droplet microfluidics, cell growth, viscosity, rheology, Escherichia coli | |
48. | 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 | |
49. | Maździarz M., Rojek J., Nosewicz S., Molecular dynamics study of self-diffusion in stoichiometric B2-NiAl crystals, Philosophical Magazine, ISSN: 1478-6435, DOI: 10.1080/14786435.2018.1480838, Vol.98, No.24, pp.2257-2274, 2018Maździarz M., Rojek J., Nosewicz S., Molecular dynamics study of self-diffusion in stoichiometric B2-NiAl crystals, Philosophical Magazine, ISSN: 1478-6435, DOI: 10.1080/14786435.2018.1480838, Vol.98, No.24, pp.2257-2274, 2018Abstract: Self-diffusion parameters in stoichiometric B2-NiAl solid state crystals were estimated by molecular statics/dynamics simulations with the study of required simulation time to stabilise diffusivity results. An extrapolation procedure to improve the diffusion simulation results was proposed. Calculations of volume diffusivity for the B2 type NiAl in the 1224–1699 K temperature range were performed using the embedded-atom-model potential. The results obtained here are in much better agreement with the experimental results than the theoretical estimates obtained with other methods. Keywords: NiAl; nickel–aluminium;
diffusivity; molecular
dynamics; molecular statics;
embedded-atom method;
sintering | |
50. | 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 | |
51. | Mościcki T., Hoffman J., Szymański Z., Laser ablation in an ambient gas: Modelling and experiment, JOURNAL OF APPLIED PHYSICS, ISSN: 0021-8979, DOI: 10.1063/1.5010413, Vol.123, pp.083305-1-8, 2018Mościcki T., Hoffman J., Szymański Z., Laser ablation in an ambient gas: Modelling and experiment, JOURNAL OF APPLIED PHYSICS, ISSN: 0021-8979, DOI: 10.1063/1.5010413, Vol.123, pp.083305-1-8, 2018Abstract: The laser ablation of graphite in ambient argon is studied both experimentally and theoretically in conditions corresponding to the initial conditions of carbon nanotube synthesis by the laser vaporization method. The results of the experiment show that the maximum plasma temperature of 24 000 K is reached 25 ns after the beginning of the laser pulse and decreases to about 4000–4500 K after 10 μs. The maximum electron density of 8 × 1025 m−3 is reached 15 ns from the beginning of the laser pulse. The hydrodynamic model applied shows comparable plasma temperatures and electron densities. The model also replicates well a shock wave and plume confinement—intrinsic features of supersonic flow of the ablated plume in an ambient gas. The results show that the theoretical model can be used to simulate nanosecond laser ablation in an ambient gas from the beginning of the process up to several microseconds. | |
52. | 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 | |
53. | 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 | |
54. | 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 | |
55. | 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 | |
56. | 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 | |
57. | 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 | |
58. | 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 | |
59. | Schabowicz K., Jóźwiak-Niedźwiedzka D., Ranachowski Z., Kudela Jr. S., Dvorak T., Microstructural characterization of cellulose fibres in reinforced cement boards, ARCHIVES OF CIVIL AND MECHANICAL ENGINEERING, ISSN: 1644-9665, DOI: 10.1016/j.acme.2018.01.018, Vol.18, No.4, pp.1068-1078, 2018Schabowicz K., Jóźwiak-Niedźwiedzka D., Ranachowski Z., Kudela Jr. S., Dvorak T., Microstructural characterization of cellulose fibres in reinforced cement boards, ARCHIVES OF CIVIL AND MECHANICAL ENGINEERING, ISSN: 1644-9665, DOI: 10.1016/j.acme.2018.01.018, Vol.18, No.4, pp.1068-1078, 2018Abstract: The microscopic analysis of the different cellulose fibre cement composites is presented. The observations of the fibres in optical microscope in transmitted light and in scanning electron microscope are described. The micro computed tomography (micro-CT) and SEM were used to determine the distribution of the fibres in the matrix. The investigated fibre cement boards were produced by extrusion process and panels were cured in natural conditions. The main goal of the research was application of different microscopic methods to analyze the fibres distribution as a result of a different methods of their production. Micro-CT was used for 3D visualization of fibres distribution in three different fibre cement boards. It was possible to determine the average diameter of the fibres and their concentration using the high-resolution mode of micro-CT scanning procedure. Finally, a procedure which can be applied as a useful tool for analysis of the different procedures used in production of fibre cement boards is described. This procedure can be successfully used in the quality control system of cellulose fibre distribution in cement composites Keywords: Cellulose fibre reinforced cement boards, Microstructure, Fibre distribution, X-ray microtomography, SEM-EDS analysis | |
60. | Mucha M., Wcisło B., Pamin J., Kowalczyk-Gajewska K., Instabilities in membrane tension: Parametric study for large strain thermoplasticity, ARCHIVES OF CIVIL AND MECHANICAL ENGINEERING, ISSN: 1644-9665, DOI: 10.1016/j.acme.2018.01.008, Vol.18, No.4, pp.1055-1067, 2018Mucha M., Wcisło B., Pamin J., Kowalczyk-Gajewska K., Instabilities in membrane tension: Parametric study for large strain thermoplasticity, ARCHIVES OF CIVIL AND MECHANICAL ENGINEERING, ISSN: 1644-9665, DOI: 10.1016/j.acme.2018.01.008, Vol.18, No.4, pp.1055-1067, 2018Abstract: This paper deals with the numerical analysis of localized deformation for a rectangular plate in membrane tension, modelled with large strain thermoplasticity. The aim is to determine the influence of selected factors on the localization phenomena, which can result from geometrical, material, and thermal softening. Two types of boundary conditions are considered: plane stress and plane strain, as well as two yield functions, Huber–Mises–Hencky and Burzyński–Drucker–Prager, with selected values of friction angle. First, isothermal conditions are considered and next, a conductive case with thermal softening is studied. Moreover, three types of plastic behaviour are analysed: strain hardening (with different values of hardening modulus), ideal plasticity, and strain softening. Numerical tests, performed using AceGen/FEM packages, are carried out for the rectangular plate under tension with an imperfection, using three finite element discretizations. The results for plane strain in the isothermal model show that with the decrease of linear hardening modulus, we can observe stronger mesh sensitivity, while for plane stress, mesh sensitivity is visible for all cases. Furthermore, for the thermomechanical model the results also depend on the mesh density due to insufficient heat conduction regularization Keywords: Thermoplasticity, Large strains, Strain localization, Parametric study | |
61. | Lumelskyj D., Rojek J., Tkocz M., Detection of strain localization in numerical simulation of sheet metal forming, ARCHIVES OF CIVIL AND MECHANICAL ENGINEERING, ISSN: 1644-9665, DOI: 10.1016/j.acme.2017.08.004, Vol.18, No.2, pp.490-499, 2018Lumelskyj D., Rojek J., Tkocz M., Detection of strain localization in numerical simulation of sheet metal forming, ARCHIVES OF CIVIL AND MECHANICAL ENGINEERING, ISSN: 1644-9665, DOI: 10.1016/j.acme.2017.08.004, Vol.18, No.2, pp.490-499, 2018Abstract: This paper presents an investigation on the detection of strain localization in numerical simulation of sheet metal forming. Two methods to determine the onset of localized necking have been compared. The first criterion, newly implemented in this work, is based on the analysis of the through-thickness thinning (through-thickness strain) and its first time derivative in the most strained zone. The limit strain in the second method, studied in the authors’ earlier works, is determined by the maximum of the strain acceleration. The limit strains have been determined for different specimens undergoing deformation at different strain paths covering the whole range of the strain paths typical for sheet forming processes. This has allowed to construct numerical forming limit curves (FLCs). The numerical FLCs have been compared with the experimental one. Mesh sensitivity analysis for these criteria has been performed for the selected specimens. It has been shown that the numerical FLC obtained with the new criterion predicts formability limits close to the experimental results so this method can be used as a potential alternative tool to determine formability in standard finite element simulations of sheet forming processes. Keywords: Sheet forming, Formability, Forming limit diagram, Strain localization, Numerical simulation | |
62. | Radziejewska J.^{♦}, Sarzyński A., Strzelec M., Diduszko R., Hoffman J., Evaluation of residual stress and adhesion of Ti and TiN PVD films by laser spallation technique, OPTICS & LASER TECHNOLOGY, ISSN: 0030-3992, DOI: 10.1016/j.optlastec.2018.02.014, Vol.104, pp.140-147, 2018Radziejewska J.^{♦}, Sarzyński A., Strzelec M., Diduszko R., Hoffman J., Evaluation of residual stress and adhesion of Ti and TiN PVD films by laser spallation technique, OPTICS & LASER TECHNOLOGY, ISSN: 0030-3992, DOI: 10.1016/j.optlastec.2018.02.014, Vol.104, pp.140-147, 2018Abstract: The laser spallation technique was applied for measurement of residual stress and adhesion of thin films. Two films of different properties, ductile and soft Ti, and hard and brittle TiN, were studied. The films were produced on 304 steel substrate by PVD method. The residual stress value obtained by laser spallation technique LST were compared with stress value from X-ray diffraction method. Good agreement of stress values measured by both methods was attained. Additionally, the interface strength of the films was tested by laser adhesion spallation technique LASAT with use of VISAR system. It was shown that shock wave induced by a nanosecond laser pulse adequately determines properties of PVD thin films on metal substrate Keywords: Laser spallation technique, Residual stress, Adhesion, Thin layer, PVD, VISAR system | |
63. | 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 | |
64. | Sławianowski J.J., Kovalchuk V., Gołubowska B., Martens A., Rożko E.E., Space‐time as a structured relativistic continuum, MATHEMATICAL METHODS IN THE APPLIED SCIENCES, ISSN: 0170-4214, DOI: 10.1002/mma.5087, Vol.41, pp.5404-5422, 2018Sławianowski J.J., Kovalchuk V., Gołubowska B., Martens A., Rożko E.E., Space‐time as a structured relativistic continuum, MATHEMATICAL METHODS IN THE APPLIED SCIENCES, ISSN: 0170-4214, DOI: 10.1002/mma.5087, Vol.41, pp.5404-5422, 2018Abstract: There are various models of gravitation: the metrical Hilbert‐Einstein theory, a wide class of intrinsically Lorentz‐invariant tetrad theories (generally covariant in the space‐time sense), and many gauge models based on various internal symmetry groups (Lorentz, Poincare, GL(n,R), SU(2,2), GL(4,C), etc). The gauge models are usually preferred but nevertheless it is an interesting idea to develop the class of GL(4,R)‐invariant (or rather GL(n,R)‐invariant) tetrad (n‐leg) generally covariant models. This is done below and motivated by our idea of bringing back to life the Thales of Miletus concept of affine symmetry. Formally, the obtained scheme is a generally covariant tetrad (n‐leg) model, but it turns out that generally covariant and intrinsically affinely invariant models must have a kind of nonaccidental Born‐Infeld‐like structure. Let us also mention that they, being based on tetrads (n‐legs), have many features common with continuous defect theories. It is interesting that they possess some group‐theoretical solutions and more general spherically symmetric solutions, discussion of which is the main new result presented in this paper, including the applications of the 't Hooft‐Polyakov monopoles in the generally covariant theories, which enables us to find some rigorous solutions of our strongly nonlinear equations. It is also interesting that within such a framework, the normal‐hyperbolic signature of the space‐time metric is not introduced by hand but appears as a kind of solution, rather integration constants, of differential equations. Let us mention that our Born‐Infeld scheme is more general than alternative tetrad models. It may be also used within more general schemes, including also the gauge ones. Keywords: micromorphic medium, modified gravity, relativistic continuum, spherically symmetric solutions, theory of fundamental interactions. | |
65. | Małolepszy A., Błoński S., Chrzanowska-Giżyńska J., Wojasiński M., Płociński T., Stobiński L., Szymański Z., Fluorescent carbon and graphene oxide nanoparticles synthesized by the laser ablation in liquid, APPLIED PHYSICS A-MATERIALS SCIENCE AND PROCESSING, ISSN: 0947-8396, DOI: 10.1007/s00339-018-1711-5, pp.124-282, 2018Małolepszy A., Błoński S., Chrzanowska-Giżyńska J., Wojasiński M., Płociński T., Stobiński L., Szymański Z., Fluorescent carbon and graphene oxide nanoparticles synthesized by the laser ablation in liquid, APPLIED PHYSICS A-MATERIALS SCIENCE AND PROCESSING, ISSN: 0947-8396, DOI: 10.1007/s00339-018-1711-5, pp.124-282, 2018Abstract: The results of synthesis of the fluorescent carbon dots (CDots) from graphite target and reduced graphene oxide (rGO) nanoparticles performed by the nanosecond laser ablation in polyethylene glycol 200 (PEG200) are shown. Two-step laser irradiation (first graphite target, next achieved suspension) revealed a very effective production of CDots. However, the ablation in PEG appeared to be effective with 1064 nm laser pulse in contrast to the ablation with 355 nm laser pulse. In the case of rGO nanoparticles similar laser irradiation procedure was less efficient. In both cases, received nanoparticles exhibited strong, broadband photoluminescence with a maximum dependent on the excitation wavelength. The size distribution for obtained CDots was evaluated using the DLS technique and HRTEM images. The results from both methods show quite good agreement in nanoparticle size estimation although the DLS method slightly overestimates nanoparticle’s diameter | |
66. | 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. | |
67. | Zaremba D., Błoński S., Jachimek M., Marijnissen M.J., Jakieła S., Korczyk P.M., Investigations of modular microfluidic geometries for passive manipulations on droplets, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/119068, Vol.66, No.2, pp.139-149, 2018Zaremba D., Błoński S., Jachimek M., Marijnissen M.J., Jakieła S., Korczyk P.M., Investigations of modular microfluidic geometries for passive manipulations on droplets, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/119068, Vol.66, No.2, pp.139-149, 2018Abstract: Multiple pipetting is a standard laboratory procedure resulting in the compartmentalisation of a liquid sample. Microfluidics offers techniques which can replace this process by the use of tiny droplets. Passive manipulation on droplets is an interesting and promising approach for the design of microfluidic devices which on one hand are easy-to-use and on the other, execute complex laboratory procedures. We present a comprehensive study of the geometry of microfluidic components which encode different operations on droplets into the structure of the device. The understanding of hydrodynamic interactions between the continuous flow and a droplet travelling through confined space of nontrivial microfluidic geometries is crucial for a rational and efficient design of new generation of modular microfluidic processors with embedded instructions. Keywords: microfluidics, two-phase flows, droplets | |
68. | 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 | |
69. | Wojnar R., Kinetic equation for the dilute Boltzmann gas in an external field, ACTA PHYSICA POLONICA B, ISSN: 0587-4254, DOI: 10.5506/APhysPolB.49.905, Vol.49, No.5, pp.905-920, 2018Wojnar R., Kinetic equation for the dilute Boltzmann gas in an external field, ACTA PHYSICA POLONICA B, ISSN: 0587-4254, DOI: 10.5506/APhysPolB.49.905, Vol.49, No.5, pp.905-920, 2018Abstract: We report a kinetic equation for an auxiliary distribution function f(k,v1,t) which yields the intermediate scattering function Is(k,t). To this end, the projection operator proposed by Stecki was applied. The scattering operator was given in explicit form in the limit of low density gas. The general kinetic equation was next specialized for the case of Lorentz gas. | |
70. | Jóźwik I., Strojny-Nędza A., Chmielewski M., Pietrzak K.^{♦}, Kurpaska Ł., Nosewicz S., High resolution SEM characterization of nano-precipitates in ODS steels, MICROSCOPY RESEARCH AND TECHNIQUE, ISSN: 1059-910X, DOI: 10.1002/jemt.23004, Vol.81, No.5, pp.502-508, 2018Jóźwik I., Strojny-Nędza A., Chmielewski M., Pietrzak K.^{♦}, Kurpaska Ł., Nosewicz S., High resolution SEM characterization of nano-precipitates in ODS steels, MICROSCOPY RESEARCH AND TECHNIQUE, ISSN: 1059-910X, DOI: 10.1002/jemt.23004, Vol.81, No.5, pp.502-508, 2018Abstract: The performance of the present-day scanning electron microscopy (SEM) extends far beyond delivering electronic images of the surface topography. Oxide dispersion strengthened (ODS) steel is on of the most promising materials for the future nuclear fusion reactor because of its good radiation resistance, and higher operation temperature up to 750°C. The microstructure of ODS should not exceed tens of nm, therefore there is a strong need in a fast and reliable technique for their characterization. In this work, the results of low-kV SEM characterization of nanoprecipitates formed in the ODS matrix are presented. Application of highly sensitive photo-diode BSE detector in SEM imaging allowed for the registration of single nm-sized precipitates in the vicinity of the ODS alloys. The composition of the precipitates has been confirmed by TEM-EDS. Keywords: ODS steels, scanning electron microscopy, spark plasma sintering | |
71. | Urbanek O., Kołbuk D., Wróbel M., Articular cartilage: New directions and barriers of scaffolds development– review, International Journal of Polymeric Materials and Polymeric Biomaterials, ISSN: 0091-4037, DOI: 10.1080/00914037.2018.1452224, pp.1-16, 2018Urbanek O., Kołbuk D., Wróbel M., Articular cartilage: New directions and barriers of scaffolds development– review, International Journal of Polymeric Materials and Polymeric Biomaterials, ISSN: 0091-4037, DOI: 10.1080/00914037.2018.1452224, pp.1-16, 2018Abstract: Despite progress which has been made in recent years in the field of cell-based therapies or cell scaffolds for cartilage regeneration, a lot of work still needs to be done. Scaffolds remain a great base for tissue regeneration. However, proper implantation procedures or post-treatment still await development.
In this review we summarize paths of cartilage treatment, especially focusing on cell scaffold design and manufacture. As well as the advantages and disadvantages of available or investigated methods and materials, especially focusing on cartilage scaffold design. We show the most promising directions and barriers in the creation of healthy tissue. Keywords: Cartilage regeneration, medical devices, scaffold development, tissue engineering | |
72. | 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. | |
73. | Błachowski B., Pnevmatikos N., Neural network based vibration control of seismically excited civil structures, Periodica Polytechnica Civil Engineering, ISSN: 0553-6626, DOI: 10.3311/PPci.11601, Vol.62, No.3, pp.620-628, 2018Błachowski B., Pnevmatikos N., Neural network based vibration control of seismically excited civil structures, Periodica Polytechnica Civil Engineering, ISSN: 0553-6626, DOI: 10.3311/PPci.11601, Vol.62, No.3, pp.620-628, 2018Abstract: This study proposes a neural network based vibration control system designed to attenuate structural vibrations induced by an earthquake. Classical feedback control algorithms are susceptible to parameter changes. For structures with uncertain parameters they can even cause instability problems. The proposed neural network based control system can identify the structural properties of the system and avoids the above mentioned problems. In the present study it is assumed that a full state of the structure is known, which means the at each floor horizontal displacements and rotations about the vertical axis are measured. Additionally, it is assumed the acceleration signal coming from the earthquake is also available. The proposed neural control strategy is compared with the classical linear quadratic regulator (LQR) not only in terms of displacement responses, but also required control forces. Moreover, the influence of different weighting matrices on performance of the proposed control strategy has been presented.
The effectiveness of the neuro-controller has been demonstrated on two numerical examples: a simple single degree of freedom (DOF) structure and a multi-DOF structure representing a twelve story building. Both structures under consideration have been excited with El Centro acceleration signal. The results of numerical simulations on the SDOF system indicate that using neuro-controller it would be possible to obtain smaller amplitudes as compared with the LQ regulator, but it would require higher control effort. Keywords: vibration control, artificial neural networks, seismic excitation | |
74. | Rokicki G., Kowalczyk T., Kaczorowski M., Sześcioczłonowe węglany cykliczne jako modyfikatory żywic epoksydowych, POLIMERY, ISSN: 0032-2725, DOI: 10.14314/polimery.2018.2.2, Vol.63, No.2, pp.90-101, 2018Rokicki G., Kowalczyk T., Kaczorowski M., Sześcioczłonowe węglany cykliczne jako modyfikatory żywic epoksydowych, POLIMERY, ISSN: 0032-2725, DOI: 10.14314/polimery.2018.2.2, Vol.63, No.2, pp.90-101, 2018Abstract: Przedstawiono metodę modyfikacji żywic epoksydowych biscyklicznymi węglanami sześcioczłonowymi. Wykazano, że katalizowana kwasami Lewisa reakcja oksiranów z sześcioczłonowymi węglanami cyklicznymi przebiega głównie z wytworzeniem spiroortowęglanu pięcio-sześcioczłonowego. W jej wyniku powstają poli(etero-węglany), polietery i pięcioczłonowe węglany cykliczne. W niskiej temperaturze reakcja może ulec zahamowaniu na etapie spiroortowęglanu. Wykazano, że żywice epoksydowe zmodyfikowane dodatkiem 10 % mas. oligomeru uretanowego, zakończonego sześcioczłonowymi cyklicznymi węglanami lub biscyklicznym węglanem zawierającym resztę glikolu tri(oksyetylenowego), charakteryzują się udarnością o 66–83 % większą niż żywica niemodyfikowana, przy zachowanym poziomie wartości pozostałych cech wytrzymałościowych. Keywords: biscykliczne węglany sześcioczłonowe, modyfikacja żywicy epoksydowej, cykliczny węglan jako aktywny rozcieńczalnik, kationowa kopolimeryzacja oksiranów z sześcioczłonowymi cyklicznymi węglanami, polimeryzacja z otwarciem pierścienia | |
75. | Kruk A., Gadomska-Gajadhur A., Dulnik J., Rykaczewska I., Ruśkowski P., Sebai A., Synoradzki L., Ocena właściwości użytkowych rusztowań komórkowych o strukturze gąbczastej oraz wzrostu na nich fibroblastów, POLIMERY, ISSN: 0032-2725, DOI: 10.14314/polimery.2018.4.3, Vol.63, No.4, pp.18-22, 2018Kruk A., Gadomska-Gajadhur A., Dulnik J., Rykaczewska I., Ruśkowski P., Sebai A., Synoradzki L., Ocena właściwości użytkowych rusztowań komórkowych o strukturze gąbczastej oraz wzrostu na nich fibroblastów, POLIMERY, ISSN: 0032-2725, DOI: 10.14314/polimery.2018.4.3, Vol.63, No.4, pp.18-22, 2018Abstract: Zbadano wpływ dodatku ciekłych prekursorów porów na morfologię, porowatość i właściwości mechaniczne polilaktydowych rusztowań komórkowych. Rusztowania otrzymano metodą mokrej inwersji faz w wariancie freeze extraction. Oceniono cytotoksyczność wybranych rusztowań w stosunku do fibroblastów mysich oraz ich przydatność do hodowli komórkowych. Wykazano, że dodatek prekursora porów dopolilaktydu korzystnie zmienia morfologię wytworzonych rusztowań, jednocześnie pogarszając ich wytrzymałość mechaniczną. Stwierdzono, że polilaktydowe rusztowania komórkowe z powodzeniem mogą być wykorzystywane do hodowli komórkowych. Keywords: usztowania komórkowe, polilaktyd, hodowle komórkowe, fibroblasty | |
76. | Meissner M., A Novel Method for Determining Optimum Dimension Ratios for Small Rectangular Rooms, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, DOI: 10.24425/122369, Vol.43, No.2, pp.217-225, 2018Meissner M., A Novel Method for Determining Optimum Dimension Ratios for Small Rectangular Rooms, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, DOI: 10.24425/122369, Vol.43, No.2, pp.217-225, 2018Abstract: A new method for determining optimum dimension ratios for small rectangular rooms has been presented. In a theoretical model, an exact description of the room impulse response was used. Based on the impulse response, a frequency response of a room was calculated to find changes in the sound pressure level over the frequency range 20-200 Hz. These changes depend on the source and receiver positions, thus, a new metric equivalent to an average frequency response was introduced to quantify the overall sound pressure variation within the room for a selected source position. A numerical procedure was employed to seek a minimum value of the deviation of the sound pressure level response from a smooth fitted response determined by the quadratic polynomial regression. The most smooth frequency responses were obtained when the source was located at one of the eight corners of a room. Thus, to find the best possible dimension ratios, in the numerical procedure the optimal source position was assumed. Calculation results have shown that optimum dimension ratios depend on the room volume and the sound damping inside a room, and for small and medium volumes these ratios are roughly 1:1.48:2.12, 1:1.4:1.89 and 1:1.2:1.45. When the room volume was suitably large, the ratio 1:1.2:1.44 was found to be the best one. Keywords: room acoustics, small rooms, optimum dimension ratios, room impulse response, frequency room response | |
77. | 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 | |
78. | 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 | |
79. | Ustrzycka A., Szuwalski K., Annular rotating disks optimal with respect to mixed creep rupture, JOURNAL OF THEORETICAL AND APPLIED MECHANICS, ISSN: 1429-2955, DOI: 10.15632/jtam-pl.56.1.57, Vol.56, No.1, pp.57-69, 2018Ustrzycka A., Szuwalski K., Annular rotating disks optimal with respect to mixed creep rupture, JOURNAL OF THEORETICAL AND APPLIED MECHANICS, ISSN: 1429-2955, DOI: 10.15632/jtam-pl.56.1.57, Vol.56, No.1, pp.57-69, 2018Abstract: Optimal shapes in the class of polynomial functions for rotating annular disks with respect to the mixed creep rupture time are found. Two effects leading to damage: diminishing of transversal dimensions and growth of micro-cracks are simultaneously taken into account. The first of them requires the finite strain analysis, the latter is described by Kachanov’s evolution equation. Behaviour of the material is described by nonlinear Norton’s law, generalized for true stresses and logarithmic strains, and the shape change law in form of similarity of true stresses and logarithmic strains deviators. For optimal shapes of the disk, changes of geometry and a continuity function are presented. The theoretical considerations based on the perception of the structural components as some highlighted objects with defined properties is presented Keywords: annular disk, mixed creep rupture, optimal design | |
80. | Frąś L.J., Pęcherski R.B., Modified split hopkinson pressure bar for investigations of dynamic behaviour of magnetorheological materials, JOURNAL OF THEORETICAL AND APPLIED MECHANICS, ISSN: 1429-2955, DOI: 10.15632/jtam-pl.56.1.323, Vol.56, No.1, pp.323-328, 2018Frąś L.J., Pęcherski R.B., Modified split hopkinson pressure bar for investigations of dynamic behaviour of magnetorheological materials, JOURNAL OF THEORETICAL AND APPLIED MECHANICS, ISSN: 1429-2955, DOI: 10.15632/jtam-pl.56.1.323, Vol.56, No.1, pp.323-328, 2018Abstract: The magnetorheological fluid is a functional material that is changing its rheological properties and finally solidifies in a magnetic field. The dynamic behaviour, tested with the use of the Split Hopkinson Pressure Bar is an important issue for description of this material, which is commonly used in different kinds of shock absorbers. This note presents a new idea how to modify the known SHPB set up in order to investigate dynamic properties of magnetorheological materials. Keywords: Split Hopkinson Pressure Bar (SHPB), Magnetorheological Fluid (MRF), dynamic behaviour, solidification in magnetic field, ferroelements | |
81. | Matsui R., Takeda K., Tobushi H., Pieczyska E.A., Mechanical properties and advanced subjects in shape memory alloys and polymers, JOURNAL OF THEORETICAL AND APPLIED MECHANICS, ISSN: 1429-2955, DOI: 10.15632/jtam-pl.56.2.447, Vol.56, No.2, pp.447-456, 2018Matsui R., Takeda K., Tobushi H., Pieczyska E.A., Mechanical properties and advanced subjects in shape memory alloys and polymers, JOURNAL OF THEORETICAL AND APPLIED MECHANICS, ISSN: 1429-2955, DOI: 10.15632/jtam-pl.56.2.447, Vol.56, No.2, pp.447-456, 2018Abstract: Advanced subjects in mechanical properties of shape memory alloys and polymers are discussed. In the subloop loading under a stress-controlled condition of the shape memory alloy, the transformation-induced stress relaxation appears due to variation in temperature. The enhancement of corrosion and corrosion fatigue life of the shape memory alloy is discussed. The development of a functionally-graded shape memory alloy and polymer is expected to obtain better performance. Three-way motion appears in the shape memory composite with the shape memory alloy and polymer. Keywords: shape memory alloy, shape memory polymer, functionally-graded shape memory material, shape memory composite | |
82. | 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 | |