1. | Konowrocki R., Szolc T., An Analysis of Electromechanical Interactions in the Railway Vehicle Traction Drive Systems Driven by AC Motors, Proceedings of the International Scientific Conference Transport of the 21st Century,Research Methods and Solutions to Current Transport Problems. ISCT21 2019. Advances in Intelligent Systems and Computing, 2019-06-09/06-12, Ryn, Poland (PL), DOI: 10.1007/978-3-030-27687-4_23, Vol.1032, pp.236-245, 2020Konowrocki R., Szolc T., An Analysis of Electromechanical Interactions in the Railway Vehicle Traction Drive Systems Driven by AC Motors, Proceedings of the International Scientific Conference Transport of the 21st Century,Research Methods and Solutions to Current Transport Problems. ISCT21 2019. Advances in Intelligent Systems and Computing, 2019-06-09/06-12, Ryn, Poland (PL), DOI: 10.1007/978-3-030-27687-4_23, Vol.1032, pp.236-245, 2020Abstract: In the paper dynamic electromechanical interactions between the rail-way drive systems and their driving electric motors are investigated. These are drive systems of high-speed trains (HST) and locomotives driven by AC motors. In particular, there is considered an influence of negative electromagnetic damp-ing generated by the asynchronous motor on a possibility of excitation of reso-nant torsional vibrations. The theoretical calculations have been performed by means of the advanced structural mechanical models. Conclusions drawn from the computational results can be very useful during a design phase of these ob-jects as well as helpful for their users during a regular maintenance Keywords: railway drive, electromechanical interactions, AC Motors, railway dynamic, numerical investigation | |
2. | Kalinowski D., Konowrocki R., Szolc T., An influence of design features of tramway vehicles on kinematic extortion from geometry of a track, Proceedings of the International Scientific Conference Transport of the 21st Century,Research Methods and Solutions to Current Transport Problems. ISCT21 2019. Advances in Intelligent Systems and Computing, 2019-06-09/06-12, Ryn, Poland (PL), DOI: 10.1007/978-3-030-27687-4_21, Vol.1032, pp.204-214, 2020Kalinowski D., Konowrocki R., Szolc T., An influence of design features of tramway vehicles on kinematic extortion from geometry of a track, Proceedings of the International Scientific Conference Transport of the 21st Century,Research Methods and Solutions to Current Transport Problems. ISCT21 2019. Advances in Intelligent Systems and Computing, 2019-06-09/06-12, Ryn, Poland (PL), DOI: 10.1007/978-3-030-27687-4_21, Vol.1032, pp.204-214, 2020Abstract: In the paper, simulation results of safety against derailment for a tramway vehicles with an arbitrary configuration of wagons and bogies is presented. The existing European standard EN 14363 covers all necessary tests for different railway vehicles, but it is inadequate for tramway vehicles, especially in safety against a derailment examination. Its operational conditions are much different. The described observations suggest that the methodology of safety against derailment testing described in the EN 14363 standard cannot be used without any modifications in the case of testing of tramway vehicles. On the basis of the computational results, a significant influence of different configurations of urban tramway vehicles on the wheel-rail contact forces was discussed, in particular on the Y/Q derailment factor Keywords: tramway dynamics, safety against derailment, simpack, numerical study | |
3. | Frydrych K., Simulations of Grain Refinement in Various Steels Using the Three-Scale Crystal Plasticity Model, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, ISSN: 1073-5623, DOI: 10.1007/s11661-019-05373-z, Vol.50, No.10, pp.4913-4919, 2019Frydrych K., Simulations of Grain Refinement in Various Steels Using the Three-Scale Crystal Plasticity Model, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, ISSN: 1073-5623, DOI: 10.1007/s11661-019-05373-z, Vol.50, No.10, pp.4913-4919, 2019Abstract: In this paper, the recently developed three-scale crystal plasticity model is applied to simulate microstructural evolution of austenitic and ferritic stainless steels subjected to large plastic strains. It is shown that the model is able to correctly predict both texture and misorientation angle distributions in the materials studied. Moreover, it can correctly capture the grain-refinement kinetics and the influence of the stacking fault energy. Finally, it is confirmed that the 3SCP model is a computationally attractive alternative for reliable modeling of microstructural evolutions in metals and alloys. | | (200p.) |
4. | Dąbrowski M., Glinicki M.A., Dziedzic K., Antolik A., Validation of sequential pressure method for evaluation of the content of microvoids in air entrained concrete, CONSTRUCTION AND BUILDING MATERIALS, ISSN: 0950-0618, DOI: 10.1016/j.conbuildmat.2019.08.014, Vol.227, No.116633, pp.1-12, 2019Dąbrowski M., Glinicki M.A., Dziedzic K., Antolik A., Validation of sequential pressure method for evaluation of the content of microvoids in air entrained concrete, CONSTRUCTION AND BUILDING MATERIALS, ISSN: 0950-0618, DOI: 10.1016/j.conbuildmat.2019.08.014, Vol.227, No.116633, pp.1-12, 2019Abstract: The suitability of the sequential air pressure method (SAM) to evaluate the quality of air entrainment in concrete mix to support prediction of durability of hardened concrete was studied. The experiments included both laboratory-produced mixes and on-site trials on mixes delivered for highway pavement construction. The fresh air content and the air void distribution was tested using the SAM apparatus. The air content and the air void characteristics in hardened concrete was tested using the microscopic analysis on polished sections. Standard fresh mix properties were also tested and the compressive strength and salt-scaling resistance of concrete was determined. Effects of type and proportion of admixtures, type of crushed aggregate, timing of SAM measurements and the method of mix consolidation were analyzed. The relationship between the SAM number and the air void characteristics in hardened concrete was critically evaluated. The relationship between SAM number and the content of microvoids (A300) is found for the laboratory mixes and confirmed with few field test results. The criterion of SAM number ≤ 0.4 is proposed for the target microvoids content A300 ≥ 1.5% and the enhanced salt scaling resistance of concrete. Keywords: Air entrainment, Air void distribution, Concrete durability, Fresh concrete, Frost-salt scaling, Microvoids content, Mix design, Sequential pressure method, Spacing factor, Test methods | | (140p.) |
5. | Bazarnik P., Nosewicz S., Romelczyk-Baishya B., Chmielewski M., Strojny-Nędza A., Maj J., Huang Y., Lewandowska M., Langdon T.G., Effect of spark plasma sintering and high-pressure torsion on the microstructural and mechanical properties of a Cu–SiC composite, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2019.138350, Vol.766, pp.138350- , 2019Bazarnik P., Nosewicz S., Romelczyk-Baishya B., Chmielewski M., Strojny-Nędza A., Maj J., Huang Y., Lewandowska M., Langdon T.G., Effect of spark plasma sintering and high-pressure torsion on the microstructural and mechanical properties of a Cu–SiC composite, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2019.138350, Vol.766, pp.138350- , 2019Abstract: This investigation examines the problem of homogenization in metal matrix composites (MMCs) and the methods of increasing their strength using severe plastic deformation (SPD). In this research MMCs of pure copper and silicon carbide were synthesized by spark plasma sintering (SPS) and then further processed via high-pressure torsion (HPT). The microstructures in the sintered and in the deformed materials were investigated using Scanning Electron Microscopy (SEM) and Scanning Transmission Electron Microscopy (STEM). The mechanical properties were evaluated in microhardness tests and in tensile testing. The thermal conductivity of the composites was measured with the use of a laser pulse technique. Microstructural analysis revealed that HPT processing leads to an improved densification of the SPS-produced composites with significant grain refinement in the copper matrix and with fragmentation of the SiC particles and their homogeneous distribution in the copper matrix. The HPT processing of Cu and the Cu–SiC samples enhanced their mechanical properties at the expense of limiting their plasticity. Processing by HPT also had a major influence on the thermal conductivity of materials. It is demonstrated that the deformed samples exhibit higher thermal conductivity than the initial coarse-grained samples. Keywords: Copper, Silicon carbide, High-pressure torsion, Spark plasma sintering, Thermal conductivity | | (140p.) |
6. | Maździarz M., Comment on ‘The Computational 2D Materials Database: high-throughput modeling and discovery of atomically thin crystals’, 2D Materials, ISSN: 2053-1583, DOI: 10.1088/2053-1583/ab2ef3, Vol.6, No.4, pp.048001-1-3, 2019Maździarz M., Comment on ‘The Computational 2D Materials Database: high-throughput modeling and discovery of atomically thin crystals’, 2D Materials, ISSN: 2053-1583, DOI: 10.1088/2053-1583/ab2ef3, Vol.6, No.4, pp.048001-1-3, 2019Abstract: Recently Haastrup et al 2018 (2D Mater. 5 042002) introduced the Computational 2D Materials Database (C2DB), which organises a variety of structural, thermodynamic, elastic, electronic, magnetic, and optical properties of around 1500 two-dimensional materials distributed over more than 30 different crystal structures. Unfortunately, the work contains serious and fundamental flaws in the field of elasticity and mechanical stability tests that make it unreliable. Keywords: ab initio calculations; elastic stability; 2D materials; materials discovery | | (140p.) |
7. | Kucharski S., Starzyński G., Contact of rough surfaces under normal and tangential loading, WEAR, ISSN: 0043-1648, DOI: 10.1016/j.wear.2019.203075, Vol.440-441, No.203075, pp.1-14, 2019Kucharski S., Starzyński G., Contact of rough surfaces under normal and tangential loading, WEAR, ISSN: 0043-1648, DOI: 10.1016/j.wear.2019.203075, Vol.440-441, No.203075, pp.1-14, 2019Abstract: Contact between a deformable, random rough surface and a rigid flat counterpart was investigated experimentally and theoretically. In the experimental setup, two modes of rough surface flattening were performed, namely normal compression and sliding (tangential load) in presence of normal compression. The load-approach relationship and friction coefficient were measured. After unloading the surface, the topography was measured using scanning profilometry. The deformation of roughness zone, i.e. evolution of the real contact area (RCA), and roughness parameters were analysed. A model based on statistical analysis and a finite element solution was applied to predict the load–approach relationship. The numerical and experimental results were compared. The effect of friction coefficient was discussed. Keywords: Contact mechanics, Roughness, Normal load, Tangential load | | (140p.) |
8. | Bobrowski A., Lipniacki T., Robin-type boundary conditions in transition from reaction-diffusion equations in 3D domains to equations in 2D domains, Journal of Differential Equations, ISSN: 0022-0396, DOI: 10.1016/j.jde.2019.08.022, Vol.268, No.1, pp.239-271, 2019Bobrowski A., Lipniacki T., Robin-type boundary conditions in transition from reaction-diffusion equations in 3D domains to equations in 2D domains, Journal of Differential Equations, ISSN: 0022-0396, DOI: 10.1016/j.jde.2019.08.022, Vol.268, No.1, pp.239-271, 2019Abstract: We consider a singular limit of diffusion equations in 3D domains of thickness converging to zero. In the 2D limit the resulting reaction-diffusion equation has a source term resulting from the Robin-type boundary conditions imposed on boundaries of the original 3D domain. The proposed approach can be applied to constructing approximate solutions of diffusion problems in thin planar, cylindrical, or spherical layers between two membranes. As an example we refer to the problem of activation of B lymphocytes, which typically have large nuclei and a thin cytoplasmic layer which can be considered as a spherical shell. For this example, assuming additionally axial symmetry we provide a rigorous convergence theorem in the language of semigroups of operators. Keywords: Semigroups of operators, Degenerate convergence, Singular perturbation, Boundary conditions, Thin layers, Signaling pathways, Phosphorylation–dephosphorylation cycle | | (140p.) |
9. | Ustrzycka A., Mróz Z., Kowalewski Z.L., Kucharski S., Analysis of fatigue crack initiation in cyclic microplasticity regime, INTERNATIONAL JOURNAL OF FATIGUE, ISSN: 0142-1123, DOI: 10.1016/j.ijfatigue.2019.105342, pp.1-15, 2019Ustrzycka A., Mróz Z., Kowalewski Z.L., Kucharski S., Analysis of fatigue crack initiation in cyclic microplasticity regime, INTERNATIONAL JOURNAL OF FATIGUE, ISSN: 0142-1123, DOI: 10.1016/j.ijfatigue.2019.105342, pp.1-15, 2019Abstract: The present work provides description of fatigue crack initiation in metals subjected to cyclic loading within the nominal elastic or initial elastic-plastic regimes next passing to elastic response during cyclic deformation and shake down process. It is assumed that damage growth proceeds due to action of local stress, specified as the sum of mean stress and its fluctuations induced by material inhomogeneities such as grain boundaries, inclusions, cavities, boundary asperities, also due to design notches or holes introduced into the element. The damage growth model is proposed, based on the critical plane concept. The macrocrack initiation then corresponds to a critical value of accumulated damage. The modelling of damage growth is supported by Electronic Speckle Pattern Interferometry (ESPI) apparatus using the coherent laser light. The damage growth effect is analysed by microindentation tests. The fatigue tests are performed for high strength steel specimens with central hole. Keywords: Fatigue crack initiation, Micro-plasticity, Damage evolution, Optical ESPI method, Micro indentation | | (140p.) |
10. | Chlanda A., Oberbek P., Heljak M., Górecka Ż., Czarnecka K., Chen K.-S., Woźniak M.J., Nanohydroxyapatite adhesion to low temperature plasma modified surface of 3D-printed bone tissue engineering scaffolds - qualitative and quantitative study, SURFACE AND COATINGS TECHNOLOGY, ISSN: 0257-8972, DOI: 10.1016/j.surfcoat.2019.07.070, Vol.375, pp.637-644, 2019Chlanda A., Oberbek P., Heljak M., Górecka Ż., Czarnecka K., Chen K.-S., Woźniak M.J., Nanohydroxyapatite adhesion to low temperature plasma modified surface of 3D-printed bone tissue engineering scaffolds - qualitative and quantitative study, SURFACE AND COATINGS TECHNOLOGY, ISSN: 0257-8972, DOI: 10.1016/j.surfcoat.2019.07.070, Vol.375, pp.637-644, 2019Abstract: Biodegradable 3D-printed polycaprolactone scaffolds for bone tissue engineering applications have been extensively studied as they can provide an attractive porous architecture mimicking natural bone, with tunable physical and mechanical properties enhancing positive cellular response. The main drawbacks of polycaprolactone-based scaffolds, limiting their applications in tissue engineering are: their hydrophobic nature, low bioactivity and poor mechanical properties compared to native bone tissue. To overcome these issues, the surface of scaffolds is usually modified and covered with a ceramic layer. However, a detailed description of the adhesion forces of ceramic particles to the polymer surface of the scaffolds is still lacking. Our present work is focused on obtaining PCL-based composite scaffolds to strengthen the architecture of the final product. In this manuscript, we report qualitative and quantitative evaluation of low temperature plasma modification followed by detailed studies of the adhesion forces between chemically attached ceramic layer and the surface of polycaprolactone-nanohydroxyapatite composite 3D-printed scaffolds. The results suggest modification-dependent alteration of the internal structure and morphology, as well as mechanical and physical scaffold properties recorded with atomic force microscopy. Moreover, changes in the material surface were followed by enhanced adhesion forces binding the ceramic layer to polymer-based scaffolds. Keywords: Surface modification, Low temperature plasma, Atomic force microscopy, Bone tissue engineering | | (100p.) |
11. | Byra M., Galperin M., Ojeda-Fournier H., Olson L., O Boyle M., Comstock C., Andre M., Breast mass classiﬁcation in sonography with transfer learning using a deep convolutional neural network and color conversion, Medical Physics, ISSN: 0094-2405, DOI: 10.1002/mp.13361, Vol.46, No.2, pp.746-755, 2019Byra M., Galperin M., Ojeda-Fournier H., Olson L., O Boyle M., Comstock C., Andre M., Breast mass classiﬁcation in sonography with transfer learning using a deep convolutional neural network and color conversion, Medical Physics, ISSN: 0094-2405, DOI: 10.1002/mp.13361, Vol.46, No.2, pp.746-755, 2019Abstract: Purpose: We propose a deep learning-based approach to breast mass classification in sonography and compare it with the assessment of four experienced radiologists employing breast imaging reporting and data system 4th edition lexicon and assessment protocol. Methods: Several transfer learning techniques are employed to develop classifiers based on a set of 882 ultrasound images of breast masses. Additionally, we introduce the concept of a matching layer. The aim of this layer is to rescale pixel intensities of the grayscale ultrasound images and convert those images to red, green, blue (RGB) to more efficiently utilize the discriminative power of the convolutional neural network pretrained on the ImageNet dataset. We present how this conversion can be determined during fine-tuning using back-propagation. Next, we compare the performance of the transfer learning techniques with and without the color conversion. To show the usefulness of our approach, we additionallyevaluate it using two publiclyavailable datasets. Results: Color conversion increased the areas under the receiver operating curve for each transfer learning method. For the better-performing approach utilizing the fine-tuning and the matching layer, the area under the curve was equal to 0.936 on a test set of 150 cases. The areas under the curves for the radiologists reading the same set of cases ranged from 0.806 to 0.882. In the case of the two separate datasets, utilizing the proposed approach we achieved areas under the curve of around 0.890. Conclusions: The concept of the matching layer is generalizable and can be used to improve the overall performance of the transfer learning techniques using deep convolutional neural networks. When fully developed as a clinical tool, the methods proposed in this paper have the potential to help radiologists with breast mass classification in ultrasound. © 2018 American Association of Physicists in Medicine [https://doi.org/10.1002/mp.13361] Keywords: BI-RADS, breast mass classification, convolutional neural networks, transfer learning, ultrasound imaging
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12. | Kalociński D., Steifer T., On unstable and unoptimal prediction, MATHEMATICAL LOGIC QUARTERLY, ISSN: 1521-3870, DOI: 10.1002/malq.201800085, pp.1-10, 2019Kalociński D., Steifer T., On unstable and unoptimal prediction, MATHEMATICAL LOGIC QUARTERLY, ISSN: 1521-3870, DOI: 10.1002/malq.201800085, pp.1-10, 2019Abstract: We consider the notion of prediction functions (or predictors) studied before in the context of randomness and stochasticity by Ko, and later by Ambos‐Spies and others. Predictor is a total computable function which tries to predict bits of some infinite binary sequence. The prediction error is defined as the limit of the number of incorrect answers divided by the number of answers given so far. We discuss indefiniteness of prediction errors for weak 1‐generics and show that this phenomenon affects certain c.e. sequences as well. On the other hand, a notion of optimal predictor is considered. It is shown that there is a sequence for which increasingly better predictors exist but for which no predictor is optimal. | | (100p.) |
13. | Pręgowska A., Proniewska K., van Dam P., Szczepański J., Using Lempel-Ziv complexity as effective classification tool of the sleep-related breathing disorders, Computer Methods and Programs in Biomedicine, ISSN: 0169-2607, DOI: 10.1016/j.cmpb.2019.105052, Vol.182, pp.105052-1-7, 2019Pręgowska A., Proniewska K., van Dam P., Szczepański J., Using Lempel-Ziv complexity as effective classification tool of the sleep-related breathing disorders, Computer Methods and Programs in Biomedicine, ISSN: 0169-2607, DOI: 10.1016/j.cmpb.2019.105052, Vol.182, pp.105052-1-7, 2019Abstract: Background and objective
People suffer from sleep disorders caused by work-related stress, irregular lifestyle or mental health problems. Therefore, development of effective tools to diagnose sleep disorders is important. Recently, to analyze biomedical signals Information Theory is exploited. We propose efficient classification method of sleep anomalies by applying entropy estimating algorithms to encoded ECGs signals coming from patients suffering from Sleep-Related Breathing Disorders (SRBD).
Methods
First, ECGs were discretized using the encoding method which captures the biosignals variability. It takes into account oscillations of ECG measurements around signals averages. Next, to estimate entropy of encoded signals Lempel–Ziv complexity algorithm (LZ) which measures patterns generation rate was applied. Then, optimal encoding parameters, which allow distinguishing normal versus abnormal events during sleep with high sensitivity and specificity were determined numerically. Simultaneously, subjects’ states were identified using acoustic signal of breathing recorded in the same period during sleep.
Results
Random sequences show normalized LZ close to 1 while for more regular sequences it is closer to 0. Our calculations show that SRBDs have normalized LZ around 0.32 (on average), while control group has complexity around 0.85. The results obtained to public database are similar, i.e. LZ for SRBDs around 0.48 and for control group 0.7. These show that signals within the control group are more random whereas for the SRBD group ECGs are more deterministic. This finding remained valid for both signals acquired during the whole duration of experiment, and when shorter time intervals were considered. Proposed classifier provided sleep disorders diagnostics with a sensitivity of 93.75 and specificity of 73.00%. To validate our method we have considered also different variants as a training and as testing sets. In all cases, the optimal encoding parameter, sensitivity and specificity values were similar to our results above.
Conclusions
Our pilot study suggests that LZ based algorithm could be used as a clinical tool to classify sleep disorders since the LZ complexities for SRBD positives versus healthy individuals show a significant difference. Moreover, normalized LZ complexity changes are related to the snoring level. This study also indicates that LZ technique is able to detect sleep abnormalities in early disorders stage. Keywords: Information theory, Lempel-Ziv complexity, Entropy, ECG, Sleep-related breathing disorders, Randomness | | (100p.) |
14. | Glinicki M.A., Jóźwiak-Niedźwiedzka D., Dąbrowski M., The Influence of Fluidized Bed Combustion Fly Ash on the Phase Composition and Microstructure of Cement Paste, Materials, ISSN: 1996-1944, DOI: 10.3390/ma12172838, Vol.12, No.2838, pp.1-14, 2019Glinicki M.A., Jóźwiak-Niedźwiedzka D., Dąbrowski M., The Influence of Fluidized Bed Combustion Fly Ash on the Phase Composition and Microstructure of Cement Paste, Materials, ISSN: 1996-1944, DOI: 10.3390/ma12172838, Vol.12, No.2838, pp.1-14, 2019Abstract: Fly ashes from coal combustion in circulating fluidized bed boilers in three power plants were tested as a potential additive to cement binder in concrete. The phase composition and microstructure of cement pastes containing fluidized bed fly ash was studied. The fractions of cement substitution with fluidized bed fly ash were 20% and 30% by weight. X-ray di#raction (XRD) tests and thermal analyses (derivative thermogravimetry (DTG), di#erential thermal analysis (DTA) and thermogravimetry (TG)) were performed on ash specimens and on hardened cement paste specimens matured in water for up to 400 days. Quantitative evaluation of the phase composition as a function of fluidized bed fly ash content revealed significant changes in portlandite content and only moderate changes in the content of ettringite. Keywords: clean coal combustion, fluidized bed fly ash, microstructure, phase composition, portlandite, unburned carbon | | (100p.) |
15. | Colabella L., Cisilino A.P., Fachinotti V., Kowalczyk P., Multiscale design of elastic solids with biomimetic cancellous bone cellular microstructures, STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION, ISSN: 1615-147X, DOI: 10.1007/s00158-019-02229-3, Vol.60, No.2, pp.639-661, 2019Colabella L., Cisilino A.P., Fachinotti V., Kowalczyk P., Multiscale design of elastic solids with biomimetic cancellous bone cellular microstructures, STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION, ISSN: 1615-147X, DOI: 10.1007/s00158-019-02229-3, Vol.60, No.2, pp.639-661, 2019Abstract: Natural (or biological) materials usually achieve outstanding mechanical performances. In particular, cancellous bone presents a high stiffness/strength toweight ratio, so its structure inspires the development of novel ultra-light cellularmaterials.Amultiscale method for the design of elastic solids with a cancellous bone parameterized biomimetic microstructure is introduced in this work. The method combines a finite element model to evaluate the stiffness of the body at the macroscale with a gradient-based nonlinear constrained optimization solver to obtain the optimal values of themicroparameters andmicrostructure orientation over the body domain. The most salient features of the implementation are an offline response surface methodology for the evaluation of the microstructure elastic tensor in terms of the microparameters, an adjoint method for the computation of the sensitivity of the macroscopic stiffness to the microparameters, a quasi-Newton approximation for the evaluation of the Hessian matrix of the nonlinear optimizer, and a distanceweighted filter of the microparameters to remediate checkerboard effects. The settings of the above features, the optimizer termination options, and the initial values of the microparameters are investigated for the best performance of the method. The effectiveness of the method is demonstrated for several examples, whose results are compared with the reference solutions calculated using a SIMP method. The method shows to be effective; it attains results coherent with SIMP approaches in terms of stiffness and spatial material distribution. The good performance of themultiscalemethod is attributed to the capability of the parameterized mimeticmicrostructure to attain bulk and shear moduli that are close to the Hashin-Shtrikman upper bounds over the complete solid volume fraction range. Keywords: Multiscale optimization, Cancellous bone, Parameterized microstructure, Interior-point optimizer, Biomimetic materials | | (100p.) |
16. | Gambin B., Kruglenko E., Tymkiewicz R., Litniewski J., Ultrasound assessment of the conversion of sound energy into heat in tissue phantoms enriched with magnetic micro- and nanoparticles, Medical Physics, ISSN: 0094-2405, DOI: 10.1002/mp.13742, Vol.46, No.10, pp.4361-4370, 2019Gambin B., Kruglenko E., Tymkiewicz R., Litniewski J., Ultrasound assessment of the conversion of sound energy into heat in tissue phantoms enriched with magnetic micro- and nanoparticles, Medical Physics, ISSN: 0094-2405, DOI: 10.1002/mp.13742, Vol.46, No.10, pp.4361-4370, 2019Abstract: Purpose: Nowadays, the improvement of ultrasonic hyperthermia therapy is often achieved by adding hard particles to the sonicated medium in order to increase the heating efficiency. The explanation of the phenomenon of ultrasonic heating still requires testing on tissue mimicking materials (TMMs), enriched with particles of different sizes and physical properties. Our goal was to determine, by comparing their quantitative acoustic properties, which TMMs, with magnetic micro- or nanoparticles, convert more ultrasonic energy into heat or which of the particles embedded in the agar gel act as more effective thermal sonosensitizers. Methods: We manufactured a pure agar gel and an agar gel with the addition of magnetic micro- or nanoparticles in two proportions of 8 and 16 mg/ml. Ultrasound quantitative techniques, the broadband reflection substitution technique and backscattered spectrum analysis were used to characterize the samples by speed of sound (SOS), frequency-dependent attenuation, and backscattering coefficients. The integrated backscattering coefficients were also calculated. The quantitative parameters, scattering, and attenuation coefficients of ultrasound in phantoms with micro- and nanoparticles were estimated. Based on the attenuation and scattering of ultrasound in the samples, the ultrasonic energy absorption, which determines the heating efficiency, was evaluated. Additionally, the temperature increase during sonication of the phantoms by an ultrasonic beam was directly measured using thermocouples. Results: The density of the materials with nanoparticles was higher than for the materials with microparticles with the same fractions of particles. The SOS for all materials ranged from 1489 to 1499 m/s. The attenuation in the whole frequency range (3–8 MHz) was higher for the materials with nanoparticles than for the materials with microparticles. For the materials with the lower content (8 mg/ml) of particles, the attenuation coefficient was 0.2 dB/(MHz cm). For the 16 mg/ml concentration of nanoparticles and microparticles, the attenuation coefficients were 0.66 and 0.45 dB/(MHz cm), resectively. The value of backscattering coefficient in the whole frequency range was greater for the materials with microparticles than for the materials with nanoparticles. The values of the integrated backscattering coefficient were 0.05 and 0.08 1/m for the materials with nanoparticles and 0.46 and 0.82 1/m for the materials with microparticles and concentrations of 8 and 16 mg/ml, respectively. The rates of temperature increase in the first 3 s due to ultrasonic heating were higher for the materials with nanoparticles than for the materials with microparticles. Conclusions: Based on acoustical measurements, we confirmed that all materials can be used as tissue phantoms in the study of ultrasonic hyperthermia, as their properties were in the range of soft tissue properties. We found that the nanoparticle-doped materials had greater attenuation and smaller scattering of ultrasound than the materials with microparticles, so absorption in these materials is greater. Thus, the TMMs with nanoparticles convert more acoustic energy into heat and we conclude that magnetic nanoparticles are more effective thermal sonosensitizers than microparticles. This conclusion is confirmed by direct measurement of the temperature increase in the samples subjected to sonification. Keywords: backscattering coefficient, frequency-dependent attenuation, hyperthermia TMM, magnetic particles, ultrasound absorption | | (100p.) |
17. | Gruziel-Słomka M., Kondratiuk P., Szymczak P., Ekiel-Jeżewska M.L., Stokesian dynamics of sedimenting elastic rings, SOFT MATTER, ISSN: 1744-683X, DOI: 10.1039/c9sm00598f, Vol.15, pp.7262-7274, 2019Gruziel-Słomka M., Kondratiuk P., Szymczak P., Ekiel-Jeżewska M.L., Stokesian dynamics of sedimenting elastic rings, SOFT MATTER, ISSN: 1744-683X, DOI: 10.1039/c9sm00598f, Vol.15, pp.7262-7274, 2019Abstract: We consider elastic microfilaments which form closed loops. We investigate how the loops change shape and orientation while settling under gravity in a viscous fluid. Loops are circular at the equilibrium. Their dynamics are investigated numerically based on the Stokes equations for the fluid motion and the bead–spring model of the microfilament. The Rotne–Prager approximation for the bead mobility is used. We demonstrate that the relevant dimensionless parameter is the ratio of the bending resistance of the filament to the gravitation force corrected for buoyancy. The inverse of this ratio, called the elasto-gravitation number [scr B, script letter B], is widely used in the literature for sedimenting elastic linear filaments. We assume that [scr B, script letter B] is of the order of 104–106, which corresponds to easily deformable loops. We find out that initially tilted circles evolve towards different sedimentation modes, depending on [scr B, script letter B]. Very stiff or stiff rings attain almost planar, oval shapes, which are vertical or tilted, respectively. More flexible loops deform significantly and converge towards one of several characteristic periodic motions. These sedimentation modes are also detected when starting from various shapes, and for different loop lengths. In general, multi-stability is observed: an elastic ring converges to one of several sedimentation modes, depending on the initial conditions. This effect is pronounced for very elastic loops. The surprising diversity of long-lasting periodic motions and shapes of elastic rings found in this work gives a new perspective for the dynamics of more complex deformable objects at micrometer and nanometer scales, sedimenting under gravity or rotating in a centrifuge, such as red blood cells, ring polymers or circular DNA. | | (100p.) |
18. | Minafò G., Rezaee-Hajidehi M., Giambanco G., A Mechanical Approach for Evaluating the Distribution of Confinement Pressure in FRP-Wrapped Rectangular Columns, JOURNAL OF ENGINEERING MECHANICS-ASCE, ISSN: 0733-9399, DOI: 10.1061/(ASCE)EM.1943-7889.0001673, Vol.145, No.12, pp.04019092-1-9, 2019Minafò G., Rezaee-Hajidehi M., Giambanco G., A Mechanical Approach for Evaluating the Distribution of Confinement Pressure in FRP-Wrapped Rectangular Columns, JOURNAL OF ENGINEERING MECHANICS-ASCE, ISSN: 0733-9399, DOI: 10.1061/(ASCE)EM.1943-7889.0001673, Vol.145, No.12, pp.04019092-1-9, 2019Abstract: In recent decades, fiber reinforced polymer (FRP) wrapping has become a common technique to retrofit reinforced concrete (RC) columns. Numerous research works have sought to verify analytically and experimentally its effectiveness in terms of enhancement of axial load bearing capacity and ductility. These studies highlighted that in the case of sharp-cornered sections, the maximum allowable confinement pressure is limited by premature failure at corners and, consequently, stress in the FRP, as well as the distribution of the confinement pressure, is not uniform. The prediction of this phenomenon is not straightforward, and existing theoretical studies propose complex numerical simulations, whereas technical codes provide simplified or empirical relationships for its assessment. This paper presents an analytical model for the evaluation of the effective distribution of confinement pressure in FRP confined concrete members with rounded corners. The model allows considering the interaction with the concrete core and different brittle failure modes, including FRP rupture and debonding. It leads to determining the distribution of the confinement pressure along the section. Results are compared with those achieved by finite-element (FE) analyses and with numerical and experimental data available in the literature. Good agreement is obtained in all cases, showing the reliability of the proposed model. Keywords: Fiber reinforced polymer (FRP) wrapping, Corner radius, Confinement pressure, Brittle failure | | (100p.) |
19. | Nowak Ł.J., Nowak K.M., Perceptual audio processing stethoscope, JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, ISSN: 0001-4966, DOI: 10.1121/1.5126226, Vol.146, No.3, pp.1769-1773, 2019Nowak Ł.J., Nowak K.M., Perceptual audio processing stethoscope, JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, ISSN: 0001-4966, DOI: 10.1121/1.5126226, Vol.146, No.3, pp.1769-1773, 2019Abstract: Stethoscopes are used to transmit body sounds related to various physiological processes to ears of a physician, providing basic or supportive information for eventual diagnosis. Unfavorably, the dominant frequency components of most of the auscultation signals are localized close to the lower frequency limits of the human auditory system, restricting the achievable selectivity and specificity. The present study introduces an approach that aims at overcoming the existing limitations. A signal processing scheme utilizing knock rejection, dynamic compressor, and pseudo-stereo synthesizer blocks is described, along with hardware implementation and results of the initial subjective evaluation. | | (100p.) |
20. | Byra M., Wu M., Zhang X., Jang H., Ma Y-J., Chang E.Y., Shah S., Du J., Knee menisci segmentation and relaxometry of 3D ultrashort echo time cones MR imaging using attention U‐Net with transfer learning, Magnetic Resonance in Medicine, ISSN: 1522-2594, DOI: 10.1002/mrm.27969, pp.1-14, 2019Byra M., Wu M., Zhang X., Jang H., Ma Y-J., Chang E.Y., Shah S., Du J., Knee menisci segmentation and relaxometry of 3D ultrashort echo time cones MR imaging using attention U‐Net with transfer learning, Magnetic Resonance in Medicine, ISSN: 1522-2594, DOI: 10.1002/mrm.27969, pp.1-14, 2019Abstract: Jiang Du, Department of Radiology, University of California, San Diego, CA 92103‐8226. Email: jiangdu@ucsd.edu Funding information The authors acknowledge grant support from GE Healthcare, NIH (1R01 AR062581, 1R01 AR068987 and 1R01 NS092650), and the VA Clinical Science Research & Development Service (1I01CX001388, I21RX002367). Purpose: To develop a deep learning‐based method for knee menisci segmentation in 3D ultrashort echo time (UTE) cones MR imaging, and to automatically determine MR relaxation times, namely the T1, T1ρ, and T∗ 2 parameters, which can be used to assess knee osteoarthritis (OA). Methods: Whole knee joint imaging was performed using 3D UTE cones sequences to collect data from 61 human subjects. Regions of interest (ROIs) were outlined by 2 experienced radiologists based on subtracted T1ρ‐weighted MR images. Transfer learning was applied to develop 2D attention U‐Net convolutional neural networks for the menisci segmentation based on each radiologist’s ROIs separately. Dice scores were calculated to assess segmentation performance. Next, the T1, T1ρ, T∗ 2 relaxations, and ROI areas were determined for the manual and automatic segmentations, then compared. Results: The models developed using ROIs provided by 2 radiologists achieved high Dice scores of 0.860 and 0.833, while the radiologists’ manual segmentations achieved a Dice score of 0.820. Linear correlation coefficients for the T1, T1ρ, and T∗ 2 relaxations calculated using the automatic and manual segmentations ranged between 0.90 and 0.97, and there were no associated differences between the estimated average meniscal relaxation parameters. The deep learning models achieved segmentation performance equivalent to the inter‐observer variability of 2 radiologists. Conclusion: The proposed deep learning‐based approach can be used to efficiently generate automatic segmentations and determine meniscal relaxations times. The method has the potential to help radiologists with the assessment of meniscal diseases, such as OA.
Keywords: deep learning, menisci, osteoarthritis, quantitative MR, segmentation | | (100p.) |
21. | Jeznach O., Kołbuk D., Sajkiewicz P., Aminolysis of Various Aliphatic Polyesters in a Form of Nanofibers and Films, Polymers, ISSN: 2073-4360, DOI: 10.3390/polym11101669, Vol.11, No.1669, pp.1-16, 2019Jeznach O., Kołbuk D., Sajkiewicz P., Aminolysis of Various Aliphatic Polyesters in a Form of Nanofibers and Films, Polymers, ISSN: 2073-4360, DOI: 10.3390/polym11101669, Vol.11, No.1669, pp.1-16, 2019Abstract: Surface functionalization of polymer scaffolds is a method used to improve interactions of materials with cells. A frequently used method for polyesters is aminolysis reaction, which introduces free amine groups on the surface. In this study, nanofibrous scaffolds and films of three different polyesters–polycaprolactone (PCL), poly(lactide-co-caprolactone) (PLCL), and poly(l-lactide) (PLLA) were subjected to this type of surface modification under the same conditions. Efficiency of aminolysis was evaluated on the basis of ninhydrin tests and ATR–FTIR spectroscopy. Also, impact of this treatment on the mechanical properties, crystallinity, and wettability of polyesters was compared and discussed from the perspective of aminolysis efficiency. It was shown that aminolysis is less efficient in the case of nanofibers, particularly for PCL nanofibers. Our hypothesis based on the fundamentals of classical high speed spinning process is that the lower efficiency of aminolysis in the case of nanofibers is associated with the radial distribution of crystallinity of electrospun fiber with more crystalline skin, strongly inhibiting the reaction. Moreover, the water contact angle results demonstrate that the effect of free amino groups on wettability is very different depending on the type and the form of polymer. The results of this study can help to understand fundamentals of aminolysis-based surface modification. Keywords: aminolysis, polyester, electrospinning, nanoﬁbers, ﬁlm, surface chemical modiﬁcation | | (100p.) |
22. | Krajewski M., Liao P.Y., Michalska M., Tokarczyk M., Lin J.Y., Hybrid electrode composed of multiwall carbon nanotubes decorated with magnetite nanoparticles for aqueous supercapacitors, Journal of Energy Storage, ISSN: 2352-152X, DOI: 10.1016/j.est.2019.101020, Vol.26, pp.101020-101020, 2019Krajewski M., Liao P.Y., Michalska M., Tokarczyk M., Lin J.Y., Hybrid electrode composed of multiwall carbon nanotubes decorated with magnetite nanoparticles for aqueous supercapacitors, Journal of Energy Storage, ISSN: 2352-152X, DOI: 10.1016/j.est.2019.101020, Vol.26, pp.101020-101020, 2019Abstract: This work describes a use of a composite nanomaterial which consists of multiwall carbon nanotubes covered by iron oxide nanoparticles as a hybrid electrode in aqueous supercapacitor. The investigated nanomaterial was manufactured in a two-step simple chemical synthesis in which the first step was a functionalization of carbon nanotubes whereas the second one was the deposition of iron oxide. According the morphological and structural characterization, the carbon nanotubes with diameters of 10–40 nm were successfully covered by randomlydispersed magnetite nanoparticles with average diameter of 10 nm. Moreover, the thermogravimetric analysis results indicated that the mass ratio between carbon nanotubes and iron oxide nanoparticles was about 65–35%. The electrochemical performance of studied hybrid electrode was tested in 1M aqueous KCl electrolyte. The highest specific capacitance of 143 F g‒1 was recorded at a discharge current density of 1 A g‒1. The investigated nanomaterial also exhibited excellent cycling stability i.e. 81% retention of the initial capacitance after 3000 cycles. Keywords: Hybrid electrode, Magnetite, Multiwall carbon nanotube, Nanocomposite, Supercapacitor | | (100p.) |
23. | Cegielska O., Sajkiewicz P., Targeted Drug Delivery Systems for the Treatment of Glaucoma: Most Advanced Systems Review, Polymers, ISSN: 2073-4360, DOI:
10.3390/polym11111742, Vol.11, No.1742, pp.1-18, 2019Cegielska O., Sajkiewicz P., Targeted Drug Delivery Systems for the Treatment of Glaucoma: Most Advanced Systems Review, Polymers, ISSN: 2073-4360, DOI:
10.3390/polym11111742, Vol.11, No.1742, pp.1-18, 2019Abstract: Each year, new glaucoma drug delivery systems are developed. Due to the chronic nature of the disease, it requires the inconvenient daily administration of medications. As a result of their elution from the eye surface and penetration to the bloodstream through undesired permeation routes, the bioavailability of active compounds is low, and systemic side effects occur. Despite numerous publications on glaucoma drug carriers of controlled drug release kinetics, only part of them consider drug permeation routes and, thus, carriers’ location, as an important factor affecting drug delivery. In this paper, we try to demonstrate the importance of the delivery proximal to glaucoma drug targets. The targeted delivery can significantly improve drug bioavailability, reduce side effects, and increase patients’ compliance compared to both commercial and scientifically developed formulations that can spread over the eye surface or stay in contact with conjunctival sac. We present a selection of glaucoma drug carriers intended to be placed on cornea or injected into the aqueous humor and that have been made by advanced materials using hi-tech forming methods, allowing for effective and convenient sustained antiglaucoma drug delivery. Keywords: hydrogels, nanofibers, electrospinning, glaucoma, ophthalmology | | (100p.) |
24. | Niemczyk-Soczyńska B., Gradys A., Kołbuk D., Krzton-Maziopa A., Sajkiewicz P., Crosslinking Kinetics of Methylcellulose Aqueous Solution and Its Potential as a Scaffold for Tissue Engineering, Polymers, ISSN: 2073-4360, DOI: 10.3390/polym11111772, Vol.11, No.1772, pp.1-17, 2019Niemczyk-Soczyńska B., Gradys A., Kołbuk D., Krzton-Maziopa A., Sajkiewicz P., Crosslinking Kinetics of Methylcellulose Aqueous Solution and Its Potential as a Scaffold for Tissue Engineering, Polymers, ISSN: 2073-4360, DOI: 10.3390/polym11111772, Vol.11, No.1772, pp.1-17, 2019Abstract: Thermosensitive, physically crosslinked injectable hydrogels are in the area of interests of various scientific fields. One of the representatives of this materials group is an aqueous solution of methylcellulose. At ambient conditions, methylcellulose (MC) is a sol while on heating up to 37 °C, MC undergoes physical crosslinking and transforms into a gel. Injectability at room temperature, and crosslinkability during subsequent heating to physiological temperature raises hopes, especially for tissue engineering applications. This research work aimed at studying crosslinking kinetics, thermal, viscoelastic, and biological properties of MC aqueous solution in a broad range of MC concentrations. It was evidenced by Differential Scanning Calorimetry (DSC) that crosslinking of MC is a reversible two-stage process, manifested by the appearance of two endothermic effects, related to the destruction of water cages around methoxy groups, followed by crosslinking via the formation of hydrophobic interactions between methoxy groups in the polymeric chains. The DSC results also allowed the determination of MC crosslinking kinetics. Complementary measurements of MC crosslinking kinetics performed by dynamic mechanical analysis (DMA) provided information on the final storage modulus, which was important from the perspective of tissue engineering applications. Cytotoxicity tests were performed using mouse fibroblasts and showed that MC at low concentration did not cause cytotoxicity. All these efforts allowed to assess MC hydrogel relevance for tissue engineering applications. Keywords: methylcellulose, thermosensitive hydrogel, crosslinking kinetics, DSC, DMA, cellular tests | | (100p.) |
25. | Guo T., Ma Y-J., High R.A., Tang Q., Wong J.H., Byra M., Searleman A.C., To S.C., Wan L., Le N., Du J., Chang E., Assessment of an in vitro model of rotator cuff degeneration using quantitative magnetic resonance and ultrasound imaging with biochemical and histological correlation, European Journal of Radiology, ISSN: 0720-048X, DOI: 10.1016/j.ejrad.2019.108706, Vol.121, pp.1-10, 2019Guo T., Ma Y-J., High R.A., Tang Q., Wong J.H., Byra M., Searleman A.C., To S.C., Wan L., Le N., Du J., Chang E., Assessment of an in vitro model of rotator cuff degeneration using quantitative magnetic resonance and ultrasound imaging with biochemical and histological correlation, European Journal of Radiology, ISSN: 0720-048X, DOI: 10.1016/j.ejrad.2019.108706, Vol.121, pp.1-10, 2019Abstract: Purpose Quantitative imaging methods could improve diagnosis of rotator cuff degeneration, but the capability of quantitative MR and US imaging parameters to detect alterations in collagen is unknown. The goal of this study was to assess quantitative MR and US imaging measures for detecting abnormalities in collagen using an in vitro model of tendinosis with biochemical and histological correlation. Method 36 pieces of supraspinatus tendons from 6 cadaveric donors were equally distributed into 3 groups (2 subjected to different concentrations of collagenase and a control group). Ultrashort echo time MR and US imaging measures were performed to assess changes at baseline and after 24 h of enzymatic digestion. Biochemical and histological measures, including brightfield, fluorescence, and polarized microscopy, were used to verify the validity of the model and were compared with quantitative imaging parameters. Correlations between the imaging parameters and biochemically measured digestion were analyzed. Results Among the imaging parameters, macromolecular fraction (MMF), adiabatic T1ρ, T2*, and backscatter coefficient (BSC) were useful in differentiating between the extent of degeneration among the 3 groups. MMF strongly correlated with collagen loss (r=-0.81; 95% confidence interval [CI]: -0.90,-0.66), while the adiabatic T1ρ (r = 0.66; CI: 0.42,0.81), T2* (r = 0.58; CI: 0.31,0.76), and BSC (r = 0.51; CI: 0.22,0.72) moderately correlated with collagen loss. Conclusions MMF, adiabatic T1ρ, and T2* measured and US BSC can detect alterations in collagen. Of the quantitative MR and US imaging measures evaluated, MMF showed the highest correlation with collagen loss and can be used to assess rotator cuff degeneration.
Keywords: Rotator cuff tendon, Tendinopathy, Quantitative MRI, UTE, Quantitative ultrasound | | (100p.) |
26. | Błoński S., Pręgowska A., Michalek T., Szczepański J., The use of Lempel-Ziv complexity to analyze turbulence and flow randomness based on velocity fluctuations, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/bpasts.2019.130876, Vol.67, No.5, pp.957-962, 2019Błoński S., Pręgowska A., Michalek T., Szczepański J., The use of Lempel-Ziv complexity to analyze turbulence and flow randomness based on velocity fluctuations, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/bpasts.2019.130876, Vol.67, No.5, pp.957-962, 2019Abstract: One of the mathematical tools to measure the generation rate of new patterns along a sequence of symbols is the Lempel-Ziv complexity (LZ). Under additional assumptions, LZ is an estimator of entropy in the Shannon sense. Since entropy is considered as a measure of randomness, this means that LZ can be treated also as a randomness indicator. In this paper, we used LZ concept to the analysis of different flow regimes in cold flow combustor models. Experimental data for two combustor’s configurations motivated by efficient mixing need were considered. Extensive computer analysis was applied to develop a complexity approach to the analysis of velocity fluctuations recorded with hot-wire anemometry and PIV technique. A natural encoding method to address these velocity fluctuations was proposed. It turned out, that with this encoding the complexity values of the sequences are well correlated with the values obtained by means of RMS method (larger/smaller complexity larger/smaller RMS). However, our calculations pointed out the interesting result that most complex, this means most random, behavior does not overlap with the “most turbulent” point determined by the RMS method, but it is located in the point with maximal average velocity. It seems that complexity method can be particularly useful to analyze turbulent and unsteady flow regimes. Moreover, the complexity can also be used to establish other flow characteristics like its ergodicity or mixing. Keywords: turbulence, complexity, entropy, randomness | | (100p.) |
27. | Byra M., Wan L., Wong J.H., Du J., Shah SB., Andre M.P., Chang E.Y., Quantitative ultrasound and b-mode image texture featurescorrelate with collagen and myelin content in human ulnarnerve fascicles, ULTRASOUND IN MEDICINE AND BIOLOGY, ISSN: 0301-5629, DOI: 10.1016/j.ultrasmedbio.2019.02.019, Vol.45, No.7, pp.1830-1840, 2019Byra M., Wan L., Wong J.H., Du J., Shah SB., Andre M.P., Chang E.Y., Quantitative ultrasound and b-mode image texture featurescorrelate with collagen and myelin content in human ulnarnerve fascicles, ULTRASOUND IN MEDICINE AND BIOLOGY, ISSN: 0301-5629, DOI: 10.1016/j.ultrasmedbio.2019.02.019, Vol.45, No.7, pp.1830-1840, 2019Abstract: We investigate the usefulness of quantitative ultrasound and B-mode texture features for characterization of ulnar nerve fascicles. Ultrasound data were acquired from cadaveric specimens using a nominal 30-MHz probe. Next, the nerves were extracted to prepare histology sections. Eighty-five fascicles were matched between the B-mode images and the histology sections. For each fascicle image, we selected an intra-fascicular region of interest. We used histology sections to determine features related to the concentration of collagen and myelin and ultrasound data to calculate the backscatter coefficient (–24.89 ± 8.31 dB), attenuation coefficient (0.92 ± 0.04 db/cm-MHz), Nakagami parameter (1.01 ± 0.18) and entropy (6.92 ± 0.83), as well as B-mode texture features obtained via the gray-level co-occurrence matrix algorithm. Significant Spearman rank correlations between the combined collagen and myelin concentrations were obtained for the backscatter coefficient (R = –0.68), entropy (R = –0.51) and several texture features. Our study indicates that quantitative ultrasound may potentially provide information on structural components of nerve fascicles. Keywords: NerveQuantitative ultrasoundHigh frequencyHistologyPattern recognitionTexture analysis | | (70p.) |
28. | Roszkiewicz A., Jain A., Teodorczyk M., Nasalski W., Formation and Characterization of Hole Nanopattern on Photoresist Layer by Scanning Near-Field Optical Microscope
, Nanomaterials, ISSN: 2079-4991, DOI: 10.3390/nano9101452, Vol.9, No.1452, pp.1-11, 2019Roszkiewicz A., Jain A., Teodorczyk M., Nasalski W., Formation and Characterization of Hole Nanopattern on Photoresist Layer by Scanning Near-Field Optical Microscope
, Nanomaterials, ISSN: 2079-4991, DOI: 10.3390/nano9101452, Vol.9, No.1452, pp.1-11, 2019Abstract: PatterningoflinesofholesonalayerofpositivephotoresistSXAR-P3500/6(AllresistGmbH, Strausberg, Germany) spin-coated on a quartz substrate is carried out by using scanning near-ﬁeld optical lithography. A green 532 nm-wavelength laser, focused on a backside of a nanoprobe of 90 nm diameter, is used as a light source. As a result, after optimization of parameters like laser power, exposuretime,orsleeptime,itisconﬁrmedthatitispossibletoobtainauniformnanopattern structure in the photoresist layer. In addition, the lines of holes are characterized by a uniform depth (71–87nm)andrelativelyhighaspectratiorangingfrom0.22to0.26. Numericalmodellingperformed with a rigorous method shows that such a structure can be potentially used as a phase zone plate. Keywords: optical lithography; photoresist; quartz; hole nanopatterning
| | (70p.) |
29. | Oberbek P., Kozikowski P., Czarnecka K., Sobiech P., Jakubiak S., Jankowski T., Inhalation exposure to various nanoparticles in work environment—contextual information and results of measurements, Journal of Nanoparticle Research, ISSN: 1388-0764, DOI: 10.1007/s11051-019-4651-x, Vol.21, No.222, pp.1-24, 2019Oberbek P., Kozikowski P., Czarnecka K., Sobiech P., Jakubiak S., Jankowski T., Inhalation exposure to various nanoparticles in work environment—contextual information and results of measurements, Journal of Nanoparticle Research, ISSN: 1388-0764, DOI: 10.1007/s11051-019-4651-x, Vol.21, No.222, pp.1-24, 2019Abstract: Outside the wide range of potential benefits, the use of nanomaterials can endanger human health, mostly through skin contact and the risk of inhalation. This article presents the results of harmonized measurements with contextual information on the emission of nanoparticles during the manufacturing and application of nanotechnology products. The purpose of the research was to investigate the actual levels of exposure to nano-objects in real working conditions in chosen Polish companies. Measurements were carried out in various workplaces: during silver nanoparticle synthesis, production of thin nanocarbon layers, 3D-printing with the use of a nanohydroxyapatite-polymer composite and the production of special seals from thin glass foils. Research was conducted on the basis of task-based measurements and offline microscopic analysis. Real-time particle DiSCmini counters were used to determine the nano-object concentration during different processes and events: samplers for collecting air dust, and a scanning electron microscope to confirm the presence of nanoparticles emitted from selected sources. Average particle sizes obtained with analysis of microscopic images were as follows: 46.7 ± 13.4 nm, 19.8 ± 4.8 nm, 22.4 ± 7.6 nm, 49.2 ± 26.3 nm respectively for workplaces. The concentration during significant events was referred to the background particle level. During one of the repeated processes, an unexpected and extremely high nanoparticle emission was recorded, which, in the long run, could cause a health hazard to workers. The studies have shown the importance of collective protective measures, revealed unexpected sources of accidentally generated nanoparticles and allowed to obtain knowledge about levels of exposure to nanoparticles during the various processes. Keywords: Nanoparticles, Ultrafine particles, Occupational exposure, Field monitoring, Occupational health, Real-time measurement | | (70p.) |
30. | Lanzi M., Pierini F., Effect of Electron-Acceptor Content on the Efficiency of Regioregular Double-Cable Thiophene Copolymers in Single-Material Organic Solar Cells, ACS Omega, ISSN: 2470-1343, DOI: 10.1021/acsomega.9b02790, pp.A-L, 2019Lanzi M., Pierini F., Effect of Electron-Acceptor Content on the Efficiency of Regioregular Double-Cable Thiophene Copolymers in Single-Material Organic Solar Cells, ACS Omega, ISSN: 2470-1343, DOI: 10.1021/acsomega.9b02790, pp.A-L, 2019Abstract: Three regioregular thiophenic copolymers, characterized by a bromine atom or a C60-fullerene group at different molar ratios at the end of a decamethylenic plastifying side chain, have been successfully synthesized using a straightforward postpolymerization functionalization procedure based on a Grignard coupling reaction. Owing to their good solubility in common organic solvents, the products were fully characterized using chromatographic, spectroscopic, thermal, and morphological techniques and used as single materials in the photoactive layers of organic solar cells. The photoconversion efficiencies obtained with copolymers were compared with those of a reference cell prepared using a physical blend of the precursor homopolymer and [6,6]-phenyl-C61-butyric acid methyl ester. The best results were obtained with COP2, the copolymer with a 21% molar content of C60-functionalized side chains. The use of the double-cable polymer made possible an enhanced control on the nanomorphology of the active blend, thus reducing phase-segregation phenomena as well as the macroscale separation between the electron-acceptor and -donor components, yielding a power conversion efficiency higher than that of the reference cell (4.05 vs 3.68%). Moreover, the presence of the halogen group was exploited for the photo-cross-linking of the active layer immediately after the thermal annealing procedure. The cross-linked samples showed an increased stability over time, leading to good efficiencies even after 120 h of accelerated aging: this was a key feature for the widespread practical applicability of the prepared devices. | | (70p.) |
31. | Nowak Z., Nowak M., Pęcherski R.B., Wiśniewski K., Widłaszewski J., Kurp P., Computational modeling of thermoplastic behavior of inconel 718 in application to laser-assisted bending of thin-walled tubes, INTERNATIONAL JOURNAL FOR MULTISCALE COMPUTATIONAL ENGINEERING, ISSN: 1543-1649, Vol.17, No.3, pp.317-338, 2019Nowak Z., Nowak M., Pęcherski R.B., Wiśniewski K., Widłaszewski J., Kurp P., Computational modeling of thermoplastic behavior of inconel 718 in application to laser-assisted bending of thin-walled tubes, INTERNATIONAL JOURNAL FOR MULTISCALE COMPUTATIONAL ENGINEERING, ISSN: 1543-1649, Vol.17, No.3, pp.317-338, 2019Abstract: Laser-assisted tube bending is a promising manufacturing process which enables production of forms and shapes that cannot be obtained by purely mechanical bending. It is particularly suitable for high hardness and brittle materials, such as nickel alloys, ceramics and cast iron. In the current paper, mechanical loading and simultaneous heating by a moving laser beam are used in a controlled manner to obtain the required deformation. Experimental investigation of the Inconel 718 (IN718) alloy provides the basis for identification of parameters of two constitutive models, which encompass softening phenomena and the coupling of temperature and strains. Numerical simulations are conducted to provide more insight into the laser-assisted bending process of the IN718 thin-walled tubes. Temperature, stress and deformation fields are determined in sequentially coupled thermomechanical analyses using the FE code ABAQUS. Laser beam is modeled as a surface heat flux using the dedicated DFLUX procedure. The temperature field is used as a thermal load in the static general step, together with an external mechanical load. The process of tube bending is controlled by the displacement of the piston rod of the actuator, while the thrust force is the resulting value. Keywords: laser-assisted bending of tubes, identification of material parameters, numerical simulations | | (40p.) |
32. | Sugak D., Syvorotka I., Yakhnevych U., Buryy O., Levintant-Zayonts N., Savytskyy H., Bonchyk O., Ubizskii S., Comparative Investigations of Nanohardness and Impurity Distribution Profiles of Lithium Niobate Single Crystals Diffusion Doped by Copper Ions, Crystal Research and Technology, ISSN: 1521-4079, DOI: 10.1002/crat.201900117, pp.1900117-1-1900117-7, 2019Sugak D., Syvorotka I., Yakhnevych U., Buryy O., Levintant-Zayonts N., Savytskyy H., Bonchyk O., Ubizskii S., Comparative Investigations of Nanohardness and Impurity Distribution Profiles of Lithium Niobate Single Crystals Diffusion Doped by Copper Ions, Crystal Research and Technology, ISSN: 1521-4079, DOI: 10.1002/crat.201900117, pp.1900117-1-1900117-7, 2019Abstract: Spatial changes of optical and mechanical properties of doped lithium niobate (LN, LiNbO3) single crystals are investigated. The crystals are doped with copper ions by thermal diffusion at elevated temperatures. LiNbO3 crystal absorption spectra are recorded in a direction perpendicular to the direction of diffusion. The concentrations of copper ions are calculated using the Smakula–Dexter formula. To determine a relation between changes of optical and mechanical properties, the hardness profiles of the doped crystals are investigated by the nanoindentation technique. Young’s modulus and hardness are specified in accordance with the Oliver–Pharr method. | | (40p.) |
33. | Dobruch-Sobczak K., Piotrzkowska-Wróblewska H., Klimoda Z., Secomski W., Karwat P., Markiewicz-Grodzicka E., Kolasińska-Ćwikła A., Roszkowska-Purska K., Litniewski J., Monitoring the response to neoadjuvant chemotherapy in patients with breast cancer using ultrasound scattering coefficient: A preliminary report
, Journal of Ultrasonography, ISSN: 2084-8404, DOI: 10.15557/JoU.2019.0013, Vol.19, No.77, pp.89-97, 2019Dobruch-Sobczak K., Piotrzkowska-Wróblewska H., Klimoda Z., Secomski W., Karwat P., Markiewicz-Grodzicka E., Kolasińska-Ćwikła A., Roszkowska-Purska K., Litniewski J., Monitoring the response to neoadjuvant chemotherapy in patients with breast cancer using ultrasound scattering coefficient: A preliminary report
, Journal of Ultrasonography, ISSN: 2084-8404, DOI: 10.15557/JoU.2019.0013, Vol.19, No.77, pp.89-97, 2019Abstract: Objective: Neoadjuvant chemotherapy was initially used in locally advanced breast cancer, and currently it is recommended for patients with Stage 3 and with early-stage disease with human epidermal growth factor receptors positive or triple-negative breast cancer. Ultrasound imaging in combination with a quantitative ultrasound method is a novel diagnostic approach. Aim of study: The aim of this study was to analyze the variability of the integrated backscatter coefficient, and to evaluate their use to predict the effectiveness of treatment and compare to ultrasound examination results. Material and method: Ten patients (mean age 52.9) with 13 breast tumors (mean dimension 41 mm) were selected for neoadjuvant chemotherapy. Ultrasound was performed before the treatment and one week after each course of neoadjuvant chemotherapy. The dimensions were assessed adopting the RECIST criteria. Tissue responses were classified as pathological response into the following categories: not responded to the treatment (G1, cell reduction by ≤9%) and responded to the treatment partially: G2, G3, G4, cell reduction by 10–29% (G2), 30–90% (G3), >90% (G4), respectively, and completely. Results: In B-mode examination partial response was observed in 9/13 cases (completely, G1, G3, G4), and stable disease was demonstrated in 3/13 cases (completely, G1, G4). Complete response was found in 1/13 cases. As for backscatter coefficient, 10/13 tumors (completely, and G2, G3, and G4) were characterized by an increased mean value of 153%. Three tumors 3/13 (G1) displayed a decreased mean value of 31%. Conclusion: The variability of backscatter coefficient, could be associated with alterations in the structure of the tumor tissue during neoadjuvant chemotherapy. There were unequivocal differences between responded and non-responded patients. The backscatter coefficient analysis correlated better with the results of histopathological verification than with the B-mode RECIST criteria. Keywords: integrated backscatter coefficient (IBSCs), neoadjuvant chemotherapy (NAC), breast cancer, ultrasound | | (20p.) |
34. | Zaszczyńska A., Sajkiewicz P., Gradys A., Kołbuk D., Urbanek O., Cellular studies on piezoelectric polyvinylidene fluoride nanofibers subjected to ultrasounds stimulations, ENGINEERING OF BIOMATERIALS / INŻYNIERIA BIOMATERIAŁÓW, ISSN: 1429-7248, Vol.XXII, No.153, pp.25-25, 2019 | | (20p.) |
35. | Bajerski P., Pęcherski R.^{♦}, Chudy D., Jarecki L., Crystallization Kinetics of Polyamide 2200 in the Modelling of Additive Manufacturing Processes by FE Analyses
, ENGINEERING TRANSACTIONS (ROZPRAWY INŻYNIERSKIE), ISSN: 0867-888X, DOI: 10.24423/EngTrans.1013.20190729 , Vol.67, No.3, pp.301-309, 2019Bajerski P., Pęcherski R.^{♦}, Chudy D., Jarecki L., Crystallization Kinetics of Polyamide 2200 in the Modelling of Additive Manufacturing Processes by FE Analyses
, ENGINEERING TRANSACTIONS (ROZPRAWY INŻYNIERSKIE), ISSN: 0867-888X, DOI: 10.24423/EngTrans.1013.20190729 , Vol.67, No.3, pp.301-309, 2019Abstract: The thermoplastic polymers present amorphous or semi-crystalline structures which are very important factors in describing volumetric shrinkage. The thermoplastic materials are commonly used for production of daily life products, industrial or as the prototypes. Different techniques of manufacturing polymer structures are considered like: injection molding, extrusion, milling, additive manufacturing (AM). AM is a very fast developing ﬁeld in the manufacturing and research. Unfortunately, components or prototypes made using the thermoplastic semi-crystalline materials in 3D techniques have quite low mechanical strength compared to the parts made by injection molding processes. It is caused by porosity obtained during the processing, as well as by fraction of crystallinity in the volume of the components. Additionally, the volumetric shrinkage is hard to predict without knowledge of its origin. Therefore, it is necessary to consider crystallization kinetics and the melting of the analysed materials. The investigations presented in this work concern the crystallization and melting model to be implemented in the ﬁnite element (FE) analyses. With use of the model, one can predict development of the structure during the real processes and, in the future, to control the warpage of the manufactured components. Keywords: additive manufacturing; Avrami model; crystallization; Diﬀerential Scanning Calorimetry (DSC); glass transition temperature; Hoﬀman-Lauritzen theory; melting; PA2200; van Krevelen empirical model. | | (20p.) |
36. | Byra M.^{♦}, Wu M., Zhang X., Jang H., Ma Y., Chang E., Shah S., Du J., Assessing the performance of knee meniscus segmentation with deep convolutional neural networks in 3D ultrashort echo time (UTE) Cones MR imaging, 27th ISMRM Annual Meeting & Exhibition, 2019-05-11/05-16, Montreal (CA), pp.1-5, 2019 | |
37. | Kaczmarek A., Małolepszy A., Hoffman J., Chrzanowska-Giżyńska J., Błoński S., Szymański Z., Mościcki T., Functionalization of carbon nanodots in liquids using laser ablation method, CNM 2019, 6th CONFERENCE ON NANO- AND MICROMECHANICS, 2019-07-03/07-05, Rzeszów (PL), pp.1-3, 2019Kaczmarek A., Małolepszy A., Hoffman J., Chrzanowska-Giżyńska J., Błoński S., Szymański Z., Mościcki T., Functionalization of carbon nanodots in liquids using laser ablation method, CNM 2019, 6th CONFERENCE ON NANO- AND MICROMECHANICS, 2019-07-03/07-05, Rzeszów (PL), pp.1-3, 2019Keywords: carbon nanoparticles, C-dots, laser ablation in liquid, photoluminescence | |
38. | Katz T., Oprogramowanie do modelowania propagacji fal ultradźwiękowych metodą ray tracing, XXV Seminarium Nieniszczące Badania Materiałów, 2019-03-20/03-22, Zakopane (PL), pp.131-140, 2019 | |
39. | Postek E., Pęcherski R., Nowak Z., Viscoplasticity effect during impact of metallic foams, CCAM & 3D-Printing, Collaborative Conference on Advanced Materials, 2019-08-26/08-30, St. Julian's (MT), pp.16-17, 2019Postek E., Pęcherski R., Nowak Z., Viscoplasticity effect during impact of metallic foams, CCAM & 3D-Printing, Collaborative Conference on Advanced Materials, 2019-08-26/08-30, St. Julian's (MT), pp.16-17, 2019Abstract: In the last 20 years, a new rapidly developing method is applied to calculations of solid mechanics problems, [1]. It is a non-local method. The predecessors of the method that have been applied to crystals were developed in [2] and [3]. In the presentation, we show an application of the method for the evaluation of the viscoplasticity effects [4, 5] in the copper foams. The oxygen free high conductivity copper (OHFC) can be applied to produce the open-cell multifunctional structures, for example, heat exchangers, heat capacitors, using additive manufacturing [6]. We use the highly parallelized program Peridigm for the analysis, [7].
Figure 1(a) shows an exemplary impacting foam sample attacking with a velocity of 20 m/s an elastic block. The highest plastic strains are in the case of ideally elastic-plastic case (b). The equivalent plastic strains are higher when neglecting the strain rate hardening effects (d) than including both strain hardening and strain rate hardening effects (c). We provide dependences of the equivalent plastic strains on impact velocities and strain rate hardening exponents.
Literature;
1. S.A. Silling, Journal of Mechanics and Physics of Solids, 48, 175 (2000).
2. D. Rogula, Nonlocal theory of material media (Springer), 123 (1982).
3. A. Kunin, Elastic media with microstructure, one dimensional models (Springer), (1982).
4. J.A. Mitchell, A Nonlocal, Ordinary, State-Based Plasticity Model for Peridynamics (SANDIA ), (2011).
5. J.T. Foster, S.A. Silling, W.W. Chen, International Journal for Numerical Mechods in Engineering, 81,1242 (2010).
6. R.B. Pęcherski, M. Nowak, Z. Nowak, International Journal for Multiscale Computational Engineering, 15, 431 (2017).
7. M.L. Parks, D.J. Littlewood, J.A. Mitchell, S.A. Silling, Peridigm Users’ Guide (SANDIA), (2012).
Keywords: metallic foams, composites, impact loading, peridynamics, parallel computing | |
40. | Golasiński K., Pieczyska E., Maj M., Mackiewicz S., Staszczak M., Zubko M., Takesue N., Elastic and plastic anisotropy of gum metal investigated by ultrasound measurements and digital image correlation, ISMMS, 10th International Symposium on Mechanics of Materials and Structures, 2019-06-02/06-06, Augustów (PL), pp.43-44, 2019Golasiński K., Pieczyska E., Maj M., Mackiewicz S., Staszczak M., Zubko M., Takesue N., Elastic and plastic anisotropy of gum metal investigated by ultrasound measurements and digital image correlation, ISMMS, 10th International Symposium on Mechanics of Materials and Structures, 2019-06-02/06-06, Augustów (PL), pp.43-44, 2019Keywords: Mechanical Anisotropy, Ti alloy, Gum Metal, Ultrasound Measurement, Digital Image Correlation | |
41. | Makowska K., Szymczak T., Kowalewski Z.L., Evaluation of microstructure and mechanical properties of ferromagnetic structural materials using barkhausen noise, ISMMS, 10th International Symposium on Mechanics of Materials and Structures, 2019-06-02/06-06, Augustów (PL), pp.74-75, 2019Makowska K., Szymczak T., Kowalewski Z.L., Evaluation of microstructure and mechanical properties of ferromagnetic structural materials using barkhausen noise, ISMMS, 10th International Symposium on Mechanics of Materials and Structures, 2019-06-02/06-06, Augustów (PL), pp.74-75, 2019Keywords: Barkhausen noise, microstructure, hardness, ultimate tensile strength, structural steels | |
42. | Pieczyska E.A., Golasiński K., Maj M., Staszczak M., Kuramoto S., Furuta T., Gum metal - a unique Ti alloy - investigated by digital image correlation and infrared thermography, ISMMS, 10th International Symposium on Mechanics of Materials and Structures, 2019-06-02/06-06, Augustów (PL), pp.86-87, 2019Pieczyska E.A., Golasiński K., Maj M., Staszczak M., Kuramoto S., Furuta T., Gum metal - a unique Ti alloy - investigated by digital image correlation and infrared thermography, ISMMS, 10th International Symposium on Mechanics of Materials and Structures, 2019-06-02/06-06, Augustów (PL), pp.86-87, 2019Keywords: Advanced material, Titanium alloy, Gum Metal, Superelasticity, High Strength, Tension, Infrared Camera, DIC | |
43. | Staszczak M., Pieczyska E., Urbański L., Odriozola I., Martin R., Shape memory polymer subjected to thermomechanical loading - investigation of application parameter, ISMMS, 10th International Symposium on Mechanics of Materials and Structures, 2019-06-02/06-06, Augustów (PL), pp.105-106, 2019Staszczak M., Pieczyska E., Urbański L., Odriozola I., Martin R., Shape memory polymer subjected to thermomechanical loading - investigation of application parameter, ISMMS, 10th International Symposium on Mechanics of Materials and Structures, 2019-06-02/06-06, Augustów (PL), pp.105-106, 2019Keywords: shape memory polymer, shape fixity, shape recovery, thermomechanical loading program | |
44. | Szymczak T., Brodecki A., Rudnik D., Kowalewski Z., Digital image correlation technique for analysis of structural components of different stiffness under static loading, ISMMS, 10th International Symposium on Mechanics of Materials and Structures, 2019-06-02/06-06, Augustów (PL), pp.121-122, 2019Szymczak T., Brodecki A., Rudnik D., Kowalewski Z., Digital image correlation technique for analysis of structural components of different stiffness under static loading, ISMMS, 10th International Symposium on Mechanics of Materials and Structures, 2019-06-02/06-06, Augustów (PL), pp.121-122, 2019Keywords: structural components, static loading, markers, displacement, deflection, DIC | |
45. | Szymczak T., Brodecki A., Kowalewski Z.L., Non-standard specimens for fracture toughness testing of welds, ISMMS, 10th International Symposium on Mechanics of Materials and Structures, 2019-06-02/06-06, Augustów (PL), pp.119-120, 2019Szymczak T., Brodecki A., Kowalewski Z.L., Non-standard specimens for fracture toughness testing of welds, ISMMS, 10th International Symposium on Mechanics of Materials and Structures, 2019-06-02/06-06, Augustów (PL), pp.119-120, 2019Keywords: mini-specimen CT, fracture toughness, CTOD, fatigue pre-cracking, notch, fracture, parent material, weld, HAZ | |
46. | Sadowski T., Postek E., Pietras D., Boniecki M., Szutkowska M., Modelling of Quasi-static and Dynamic Damage Process in Ceramic Matrix
Composites, MECHCOMP 2019, 5th International Conference on Mechanics of Composites, 2019-07-01/07-04, Lizbona (PT), pp.80-81, 2019Sadowski T., Postek E., Pietras D., Boniecki M., Szutkowska M., Modelling of Quasi-static and Dynamic Damage Process in Ceramic Matrix
Composites, MECHCOMP 2019, 5th International Conference on Mechanics of Composites, 2019-07-01/07-04, Lizbona (PT), pp.80-81, 2019Abstract: Quasi-static degradation of brittle composites exhibits different mechanical response under uniaxial
tension and uniaxial compression. In this paper we analysed cracking processes and failure under
quasi-static loading of 2 phase ceramic material made of alumina and zirconia mixture, subjected to
tension and compression. Constitutive modelling of two phase ceramic composites obeys description
of: (1) elastic deformations of initially porous material, (2) limited plasticity and (3) cracks initiation
and propagation. Modelling of polycrystalline ceramics at mesoscopic level under mechanical loading is
related to analysis of a set of grains, which create so called Representative Volume Element (RVE). The
basic elements of the defect structure inside polycrystal are: micro- and meso-cracks, kinked and wing
cracks. To get macroscopic response of the material one can calculate averaged values of stress and strain over the RSE with application of analytical approach. Dynamic degradation process was illustrated
for 2 phase ceramic matix composite and cermet, which was subjected to short compressive impulse.
The pulse duration was 10-7s and the applied pressure level - 480 MPa. In the proposed more advanced
nite elements formulation of the cermet behaviour is was necessary to take into account the following
data and phenomena revealing inside of the RVE: (1) spatial distribution of the cermet constituents,
(2) system of grain boundaries/binder interfaces modelled by interface elemnets, (3) rotation of brittle
grains. The cermet response due to pulse loading is signifcantly different in comparison to the quasistatic
behaviour, i.e. the stress distributions and microcracking processes are quite different. Keywords: brittle composites, damage, quasi-static behaviour, dynamics, RVE | |
47. | Jeznach O., Kolbuk D., Sajkiewicz P., Surface functionalization of polyesters nanofibers via aminolysis and gelatin immobilization, TERMIS EU 2019, TERMIS European Chapter Meeting 2019, Tissue Engineering Therapies: From Concept to Clinical Translation & Commercialisation, 2019-05-27/05-31, Rodos (GR), pp.1606, 2019 | |
48. | Ura D.P., Gradys A., Zaszczyńska A., Sajkiewicz P., Stachewicz U., Controlling of mechanical properties of electrospun PMMA fibers via voltage polarity, 8th International PhD Meeting, 2019-08-28/08-29, Dresden (DE), pp.1, 2019 | |
49. | Ura D.P., Gradys A., Zaszczyńska A., Sajkiewicz P., Stachewicz U., Controlling of mechanical properties of electrospun PMMA fibers via voltage polarity, 7th Dresden Nanoanalysis Symposium: Nano-scale characterization for cutting-edge materials research and sustainable materials development, 2019-08-30/08-30, Dresden (DE), pp.1-2, 2019 | |
50. | Pieczyska E.A., Golasiński K., Maj M., Staszczak M., Kuramoto S., Furuta T., Gum Metal mechanical properties investigated by infrared camera and digital image correlation, SMST, Shape Memory and Superelastic Technologies, 2019-05-13/05-17, Konstanz (DE), pp.1-2, 2019 | |
51. | Kruglenko E., Krajewski M., Tymkiewicz R., Litniewski J., Gambin B., Magnetic and ultrasonic thermal effects of magnetic nanoparticles in a tissue phantom, Applications of Electromagnetics in Modern Techniques and Medicine (PTZE), XXIX Sympozjum PTZE, Zastosowania elektromagnetyzmu we współczesnej inżynierii i medycynie, 2019-06-09/06-12, Janów Podlaski, Polska (PL), DOI: 10.23919/PTZE.2019.8781747, pp.89-92, 2019Kruglenko E., Krajewski M., Tymkiewicz R., Litniewski J., Gambin B., Magnetic and ultrasonic thermal effects of magnetic nanoparticles in a tissue phantom, Applications of Electromagnetics in Modern Techniques and Medicine (PTZE), XXIX Sympozjum PTZE, Zastosowania elektromagnetyzmu we współczesnej inżynierii i medycynie, 2019-06-09/06-12, Janów Podlaski, Polska (PL), DOI: 10.23919/PTZE.2019.8781747, pp.89-92, 2019Abstract: The aim of the paper was a preliminary comparison of heating efficiency by the two physically different modalities, namely ultrasound sonication and alternating magnetic field, of magnetic nanoparticles added to an agar-gel. Special agar-based tissue mimicking material (TMM) were manufactured from agar with the addition of produced by us iron oxide magnetic nanoparticles of order c/a 11 nanometers. To perform comparison of heating by the measured temperature rise curves caused by the two physical fields differently acting on the material sample, in the case of ultrasonic radiation we did not locate the sensor of thermometer in the ultrasonic beam focus, as it was usually studied, but we put it in the place where distribution of ultrasound intensity was more homogeneous. It was motivated by the fact that the “homogeneous heating” by the magnetic iron oxide nanoparticles which are spatially homogeneously distributed should be compared with the ultrasonic heating effects caused by the spatially homogeneous ultrasonic sources. The obtained results confirm that for both fields, ultrasound and magnetic, the temperature increase was caused by the presence of nanoparticles. In the case of heating by magnetic field pure agar-gel was not heated at all, and during sonication the pure agar-gel exhibited very small thermal effect, due only to the structure of the agar-gel crosslinking. We concluded that the ultrasonic absorption was in our experiment greater than magnetic, but the temperature rise after 180 s of magnetic field action was greater than of sonication. Keywords: Heating systems, Ultrasonic imaging, Temperature measurement, Acoustics, Magnetic fields, Nanoparticles, Ultrasonic variables measurement
| |
52. | Rustighi E., Jankowski Ł., Prediction of acoustic emission of a rigid electrodes DEAP loudspeaker, RASD, 13th International Conference on Recent Advances in Structural Dynamics, 2019-04-15/04-17, Lyon, France (FR), pp.1-4, 2019Rustighi E., Jankowski Ł., Prediction of acoustic emission of a rigid electrodes DEAP loudspeaker, RASD, 13th International Conference on Recent Advances in Structural Dynamics, 2019-04-15/04-17, Lyon, France (FR), pp.1-4, 2019Abstract: Dielectric Electro-Active Polymers (DEAPs) are lightweight materials whose dimensions change significantly when subjected to electric stimulation. One form of DEAP construction consists of a thin layer of dielectric sandwiched between two perforated rigid electrodes. They can be used as an actuator or a sensor and have the potential to be an effective replacement for many conventional transducers. This paper refers to their use as loudspeakers. To date, at DEAP loudspeakers have been prototyped and tested but no numerical prediction of their acoustic perfomances has been presented. In this paper an elemental model is presented, where the electrodes are modelled as bending plates, the dielectric as a Winkler bedding and the acoustic impedance calculated assuming baffled conditions. The impedances of the elements are stacked together and preliminary results are shown. | |
53. | Błachowski B., Tauzowski P., Świercz A., Jankowski Ł., Sensor placement for structural damage identification by means of topology optimization, PCM-CMM, 4th Polish Congress of Mechanics, 23rd International Conference on Computer Methods in Mechanics, 2019-09-08/09-12, Kraków (PL), pp.1, 2019Błachowski B., Tauzowski P., Świercz A., Jankowski Ł., Sensor placement for structural damage identification by means of topology optimization, PCM-CMM, 4th Polish Congress of Mechanics, 23rd International Conference on Computer Methods in Mechanics, 2019-09-08/09-12, Kraków (PL), pp.1, 2019Abstract: Damage identification attracted a lot of attention during the last three decades. The reason for that is the fact that large number of existing civil infrastructures reached their service life and growing number of structures is equipped with Structural Health Monitoring (SHM) systems. A successful structural damage identification is determined by three inseparably coupled factors: sensor placement, damage location and its extend, and finally location and time-frequency characteristics of the applied excitation. The purpose of this study is to address the first of the mentioned aspects, namely optimal sensor placement. A vast literature has been devoted to optimal sensor placement methods among which Effective Independence (EI) method proposed by Kammer and Tinker is one of the most successfully applied in practice. However, EI method is dedicated rather to test-analysis correlation and therefore more specific methods for damage identification are still needed. Additionally, in the case of large civil structures, which are intended to be equipped with large amount of sensors of different type, other sensor placement methods can be more efficient. Recently, a promising idea of utilizing a topology optimization approach for the purpose of sensor placement has been proposed by Bruggi and Mariani. The goal of this study is to extend their method, which has been verified on a plate structure, to the case of a FE model of a real arch bridge structure consisting a few thousands degrees of freedom. The main purpose of this work is to find the optimal arrangement of sensors on the structure to detect defects most accurately. The objective function for the problem formulated in this way is the total, weighted difference between the deformation of a damaged and undamaged state. This problem is very similar to the topological optimization, where we search for the optimal material distribution minimizing the mass of the structure while meeting the conditions related to some mechanical properties such as the maximum displacement of the structure, stress intensity or load capacity. This similarity led us to apply topological optimization to the problem of optimal placement of damage sensors. Several numerical examples prove the applicability of topological optimization for optimal sensor placement problem. Keywords: Sensor Placement, Damage Identification, Topology Optimization | |
54. | Piechocka I.K., Wolska N., Luzak B., The role of shear flow in glycosylated fibrin clot response, 3rd Interdisciplinary FNP Conference, 2019-04-11/04-12, Warszawa (PL), pp.39, 2019 | |
55. | Piechocka I.K., Wolska N., Luzak B., Glycation of fibrinogen affects FXIII-induced crosslinking and shear flow response of fibrin networks, The 44th FEBS Congress, 2019-07-06/07-11, Kraków (PL), pp.132, 2019 | |
56. | Piechocka I.K., Wolska N., Luzak B., Shear flow promotes isotropic redistribution of fibrin fibers inside glycosylated fibrin networks, Joint 12th EBSA congress and 10th ICBT-IUPAP congress, 2019-07-20/07-24, Madryt (ES), pp.100, 2019 | |
57. | Liou S.C., Krajewski M., Chiou W.A., Tokarczyk M., Kowalski G., TEM Studies of Fe1-xNix Nanowires by Magnetic-Field-Induced Synthesis, M&M 2019, Microscopy & Microanalysis 2019, 2019-08-04/08-08, Portland (US), DOI: 10.1017/S143192761901170X, No.25, pp.2194-2195, 2019 | |
58. | Krajewski M., Tokarczyk M., Witecka A., Lewińska S., Ślawska-Waniewska A., Liou S.C., Chiou W.A., Płocińska M., Towards magnetic 1D nanostructures - magnetic field as a growth parameter, LIV Zakopane School of Physics
Breaking Frontiers: Submicron Structures in Physics and Biology, 2019-05-21/05-25, Zakopane (PL), pp.42-42, 2019 | |
59. | Krajewski M., Tokarczyk M., Witecka A., Lewińska S., Ślawska-Waniewska A., Małolepszy A., Liou S.C., Chiou W.A., Manufacturing and magnetic properties of FexCo1‒x wire-like nanoalloys, CNM 2019, 6th CONFERENCE ON NANO- AND MICROMECHANICS, 2019-07-03/07-05, Rzeszów (PL), pp.103-104, 2019Krajewski M., Tokarczyk M., Witecka A., Lewińska S., Ślawska-Waniewska A., Małolepszy A., Liou S.C., Chiou W.A., Manufacturing and magnetic properties of FexCo1‒x wire-like nanoalloys, CNM 2019, 6th CONFERENCE ON NANO- AND MICROMECHANICS, 2019-07-03/07-05, Rzeszów (PL), pp.103-104, 2019Keywords: magnetic-field-induced process, magnetic material, nanoalloy, wire-like nanostructure | |
60. | Krajewski M., Magnetic-field-assisted synthesis of iron-based wire-like nanostructures, IMSNC-2019, 2nd International Conference on Material Science and Nanotechnology, 2019-07-15/07-17, London (GB), pp.48-48, 2019 | |
61. | Krajewski M., Tokarczyk M., Stefaniuk T., Kowalski G., Lewińska S., Ślawska-Waniewska A., High temperature treatment of nanochains composed of Fe1‒xCox nanoparticles, IBCM 2019, III International Baltic Conference on Magnetism: focus on nanobiomedicine and smart materials, 2019-08-18/08-22, Svetlogorsk (RU), pp.52-52, 2019 | |
62. | Kalociński D., Steifer T., An Almost Perfectly Predictable Process with No Optimal Predictor, IEEE-ISIT, IEEE International Symposium on Information Theory, 2019-07-07/07-12, Paryż (FR), DOI: 10.1109/ISIT.2019.8849587, pp.2504-2508, 2019Kalociński D., Steifer T., An Almost Perfectly Predictable Process with No Optimal Predictor, IEEE-ISIT, IEEE International Symposium on Information Theory, 2019-07-07/07-12, Paryż (FR), DOI: 10.1109/ISIT.2019.8849587, pp.2504-2508, 2019Abstract: A novel kind of a negative result is presented for the problem of computable prediction. A non-stationary binary stochastic process is constructed for which almost surely no effective method of prediction achieves the infimum of prediction errors defined as the normalized Hamming distance between the sequence of predictions and the realization of the process. Yet it is shown that this process may be effectively predicted almost surely up to an arbitrarily small error since the infimum of prediction errors is zero. | |
63. | Byra M., Sznajder T., Korzinek D., Piotrzkowska-Wróblewska H., Dobruch-Sobczak K., Nowicki A., Marasek K., Impact of Ultrasound Image Reconstruction Method on Breast Lesion Classification with Deep Learning. Pattern Recognition and Image Analysis, IbPRIA 2019, 9th Iberian Conference on Pattern Recognition and Image Analysi, 2019-07-01/07-04, Madryt (ES), pp.41-52, 2019Byra M., Sznajder T., Korzinek D., Piotrzkowska-Wróblewska H., Dobruch-Sobczak K., Nowicki A., Marasek K., Impact of Ultrasound Image Reconstruction Method on Breast Lesion Classification with Deep Learning. Pattern Recognition and Image Analysis, IbPRIA 2019, 9th Iberian Conference on Pattern Recognition and Image Analysi, 2019-07-01/07-04, Madryt (ES), pp.41-52, 2019Abstract: In this work we investigate the usefulness and robustness of transfer learning with deep convolutional neural networks (CNNs) for breast lesion classification in ultrasound (US). Deep learning models can be vulnerable to adversarial examples, engineered input image pixel intensities perturbations that force models to make classification errors. In US imaging, distribution of US image pixel intensities relies on applied US image reconstruction algorithm. We explore the possibility of fooling deep learning models for breast mass classification by modifying US image reconstruction method. Raw radio-frequency US signals acquired from malignant and benign breast masses were used to reconstruct US images, and develop classifiers using transfer learning with the VGG19, InceptionV3 and InceptionResNetV2 CNNs. The areas under the receiver operating characteristic curve (AUCs) obtained for each deep learning model developed and evaluated using US images reconstructed in the same way were equal to approximately 0.85, and there were no associated differences in AUC values between the models (DeLong test p-values > 0.15). However, due to small modifications of the US image reconstruction method the AUC values for the models utilizing the VGG19, InceptionV3 and InceptionResNetV2 CNNs significantly decreased to 0.592, 0.584 and 0.687, respectively. Our study shows that the modification of US image reconstruction algorithm can have significant negative impact on classification performance of deep models. Taking into account medical image reconstruction algorithms may help develop more robust deep learning computer aided diagnosis systems. Keywords: Adversarial attacks, Breast lesion classification, Computer aided diagnosis, Deep learning, Robustness, Ultrasound imaging, Transfer learning | |
64. | Nowicki A., Bezpieczeństwo badań ultrasonograficznych – wskaźniki termiczny i mechaniczny, Inżynier i Fizyk Medyczny, ISSN: 2300-1410, Vol.8, No.4, pp.325-330, 2019Nowicki A., Bezpieczeństwo badań ultrasonograficznych – wskaźniki termiczny i mechaniczny, Inżynier i Fizyk Medyczny, ISSN: 2300-1410, Vol.8, No.4, pp.325-330, 2019Abstract: W ciągu ostatnich kilku dziesięcioleci ultradźwięki znalazły szerokie zastosowanie w diagnostyce obrazowej. Ten artykuł przeglądowy omawia potencjalne efekty biologiczne związane z propagacją ultradźwięków w tkankach i podaje fizyczne podstawy wprowadzonych indeksów mechanicznego MI i ter micznego TI zgodnych z Output Display Standard (ODS). W praktyce klinicznej otrzymywane wyniki są kompromisem pomiędzy jakością obrazu a możliwością systemu uzyskiwania zadowalających obrazów głęboko leżących struktur tkankowych – wyboru dokonuje się, biorąc pod uwagę minimalizację bioefektów. Moce wyjściowe ultrasonografów są regulowane i ograniczane do określonych poziomów. Bezpieczne dawki ultradźwiękowe wyznacza się według określonych zasad, a na ekranie wyświetlane są związane z nimi wielkości. Wielkości te określają możliwości wystąpienia zmian mechanicznych i termicznych w tkankach i dlatego mają znaczenia kliniczne. Wprowadzone wskaźniki – mechaniczny MI i termiczny TI uwzględniają fizyczny mechanizm oddziaływania między ultradźwiękami i biologiczną tkanką, który zależy od czasowych i przestrzennych parametrów pola akustycznego generowanego przez głowice ultradźwiękowe. Przewidywany wzrost temperatury określa się, stosując trzy różne modele tkankowe: homogeniczny, warstwowy i układ kość/tkanka Keywords: ultrasonografia, wskaźnik termiczny TI, wskaźnik mechaniczny MI, kawitacja, standardy IEC
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65. | Mościcki T., Psiuk R., Słomińska H., Influence of titanium addition on the phase composition and properties of tungsten borides thin films, PLATHINIUM, Plasma Thin film International Union Meeting, 2019-09-23/09-27, Antibes (FR), pp.1-2, 2019 | |
66. | Szmidt T., Konowrocki R., Pisarski D., Stabilization of a cantilever pipe conveying fluid using electromagnetic actuators of the transformer type, PCM-CMM, 4th Polish Congress of Mechanics, 23rd International Conference on Computer Methods in Mechanics, 2019-09-08/09-12, Kraków (PL), pp.1, 2019Szmidt T., Konowrocki R., Pisarski D., Stabilization of a cantilever pipe conveying fluid using electromagnetic actuators of the transformer type, PCM-CMM, 4th Polish Congress of Mechanics, 23rd International Conference on Computer Methods in Mechanics, 2019-09-08/09-12, Kraków (PL), pp.1, 2019Keywords: Pipe Conveying Fluid, Electromagnetic Actuator, Stability, Flutter Experiment | |
67. | Mackiewicz S., Modelowanie propagacji fal ultradźwiękowych w badaniach nieniszczących, XXV Seminarium Nieniszczące Badania Materiałów, 2019-03-20/03-22, Zakopane (PL), pp.111-130, 2019 | |
68. | Mackiewicz S., Badania eksploatacyjne korozji rurociągów technikami radiografii cyfrowej, KKBR Stary Młyn, KRAJOWA KONFERENCJA BADAŃ RADIOGRAFICZNYCH STARY MŁYN, 2019-09-09/09-11, Bolesławiec k/Wieruszowa (PL), pp.7-23, 2019 | |
69. | Pieczyska E., Kowalewski Z., Dunic V., Slavkovic R., Matsui R., Investigation of mechanical and thermomechanical effects in shape memory alloy during transformationinduced creep phenomena, DAS 2019, 36th DANUBIA-ADRIA Symposium on Advances in Experimental Mechanics, 2019-09-24/09-27, Pilzno (CZ), pp.91-92, 2019 | |
70. | Glinicki M.A., Problem reaktywności kruszywa – cz. 1 rozpoznanie, Budownictwo, Technologie, Architektura, ISSN: 1644-745X, Vol.1, pp.58-60, 2019Glinicki M.A., Problem reaktywności kruszywa – cz. 1 rozpoznanie, Budownictwo, Technologie, Architektura, ISSN: 1644-745X, Vol.1, pp.58-60, 2019Abstract: Przemysł cementowy uznaje, że problem reaktywności to problem jakości kruszywa. Producenci kruszyw mineralnych uważają, że reaktywność jest problemem jakości cementu. A Komisja Europejska uważa, że najważniejszy jest wolny handel. Tak w skrócie można scharakteryzować stan normalizacji betonu i jego składników według Europejskiego Komitetu Normalizacyjnego CEN w zakresie bardzo istotnym dla zarządców i użytkowników obiektów betonowych, zwłaszcza nawierzchni kluczowych autostrad i mostów, projektowanych co najmniej na 50-100 lat użytkowania. | |
71. | Glinicki M.A., Problem reaktywności kruszywa – cz. 2 kategoryzacja i przeciwdziałanie, Budownictwo, Technologie, Architektura, ISSN: 1644-745X, Vol.3, pp.62-65, 2019 | |
72. | Glinicki M.A., Właściwości betonu nawierzchniowego z kruszywem odkrytym – wpływ rodzaju cementu i pielęgnacji, DROGOWNICTWO, ISSN: 0012-6357, Vol.4, pp.99-104, 2019Glinicki M.A., Właściwości betonu nawierzchniowego z kruszywem odkrytym – wpływ rodzaju cementu i pielęgnacji, DROGOWNICTWO, ISSN: 0012-6357, Vol.4, pp.99-104, 2019Abstract: Przestawiono analizę zagadnień projektowania składu betonu nawierzchniowego z kruszywem odkrytym, przeznaczonego na nawierzchnie drogowe o kategorii ruchu KR5-KR7. Omówiono wyniki badań betonu wykonanego w laboratorium w sposób imitujący wykonanie warstwy z kruszywem odkrytym. Wyznaczono wytrzymałość betonu, charakterystykę porów, szybkość absorpcji powierzchniowej wody i mrozoodporność powierzchniową w obecności roztworu chlorku sodu. Wyniki badań przeanalizowano w odniesieniu do zróżnicowania rodzaju cementu (CEM I, CEM III/A) i rodzaju pielęgnacji. Stwierdzono znaczący wzrost złuszczeń powierzchniowych i szybkości penetracji wody skorelowany z niedostatkiem pielęgnacji. Keywords: beton napowietrzony, charakterystyka porów, mrozoodporność, nawierzchnia drogowa dwuwarstwowa, pielęgnacja, przepuszczalność, warstwa z kruszywem odkrytym | |
73. | Pieczyska E.A., Golasiński K., Maj M., Staszczak M., Furuta T., Kuramoto S., Gum metal subjected to tension at various strain rates - experimental results analysed by dic, PCM-CMM, 4th Polish Congress of Mechanics, 23rd International Conference on Computer Methods in Mechanics, 2019-09-08/09-12, Kraków (PL), pp.1, 2019Pieczyska E.A., Golasiński K., Maj M., Staszczak M., Furuta T., Kuramoto S., Gum metal subjected to tension at various strain rates - experimental results analysed by dic, PCM-CMM, 4th Polish Congress of Mechanics, 23rd International Conference on Computer Methods in Mechanics, 2019-09-08/09-12, Kraków (PL), pp.1, 2019Keywords: Gum metal, Titanium alloy, Tensile loading, Digital Image Correlation | |
74. | Golasiński K., Pieczyska E.A., Maj M., Staszczak M., Takesue N., Thermomechanical behavior of gum metal under cyclic compression, PCM-CMM, 4th Polish Congress of Mechanics, 23rd International Conference on Computer Methods in Mechanics, 2019-09-08/09-12, Kraków (PL), pp.1, 2019Golasiński K., Pieczyska E.A., Maj M., Staszczak M., Takesue N., Thermomechanical behavior of gum metal under cyclic compression, PCM-CMM, 4th Polish Congress of Mechanics, 23rd International Conference on Computer Methods in Mechanics, 2019-09-08/09-12, Kraków (PL), pp.1, 2019Keywords: Gum Metal, Multifunctional Ti-based Alloy, Cyclic Compression, Infrared Thermography | |
75. | Pieczyska E., Golasiński K., Maj M., Furuta T., Kuramoto S., Development of strain localization in a beta-titanium alloy Gum Metal analyzed by infrared camera and digital image correlation for various strain rates, AITA 2019, 15th International Workshop on Advanced Infrared Technology and Applications, 2019-09-16/09-19, Florencja (IT), pp.1-4, 2019Pieczyska E., Golasiński K., Maj M., Furuta T., Kuramoto S., Development of strain localization in a beta-titanium alloy Gum Metal analyzed by infrared camera and digital image correlation for various strain rates, AITA 2019, 15th International Workshop on Advanced Infrared Technology and Applications, 2019-09-16/09-19, Florencja (IT), pp.1-4, 2019Abstract: Effects of thermomechanical couplings were studied in a new beta Ti alloy by IR and DIC techniques. The obtained stress-strain curves confirmed low Young’s modulus and high strength of the alloy. The determined values of yield strength increases and values of elongation till rupture decreases with increasing strain rate. It was found, by using fast and sensitive infrared camera, that the large limit of the Gum Metal reversible nonlinear deformation originates from mechanisms of dissipative nature, probably exothermic stress-induced transition of alpha" nanodomains. Keywords: Titanium alloy, Gum Metal, strain rate, infrared camera, temperature change, DIC | |
76. | Dulnik J., Sajkiewicz P., Characterization of bicomponent polycaprolactone/gelatin electrospun nanofibres crosslinked with edc/nhs, 28th Annual Conference of the Polish Society for Biomaterials 'Biomaterials in Medicine and Veterinary Medicine, 2019-10-10/10-13, Rytro (PL), pp.26-26, 2019 | |
77. | Zaszczyńska A., Sajkiewicz P., Gradys A., Kołbuk D., Urbanek O., Cellular studies of piezoelectric nanofibers with ultrasound stimulations, Aerogels Processing, Modelling and Environmental-Driven Applications, 2019-10-21/10-23, Coimbra (PT), No.P04, pp.36, 2019 | |
78. | Sajkiewicz P., Jeznach O., Kołbuk-Konieczny D., Functionalization of Aliphatic Polyester Fibers Formed by Electrospinning - The Effect of Crystallinity on Aminolysis, BIOMATSEN, 4th International Congress on Biomaterials and Biosensors, 2019-05-12/05-18, Fethiye (TR), No.Id-289, pp.96-97, 2019Sajkiewicz P., Jeznach O., Kołbuk-Konieczny D., Functionalization of Aliphatic Polyester Fibers Formed by Electrospinning - The Effect of Crystallinity on Aminolysis, BIOMATSEN, 4th International Congress on Biomaterials and Biosensors, 2019-05-12/05-18, Fethiye (TR), No.Id-289, pp.96-97, 2019Keywords: Nanofibers, polyesters, surface functionalization, aminolysis, structure | |
79. | Psiuk R., Garbiec D., Wiśniewska M., Denis P., Mościcki T., Mikrostruktura i właściwości borków wolframu domieszkowanych cyrkonem wytwarzanych metodą spiekania iskrowo-plazmowego SPS, OSSPS, II Ogólnopolskie Seminarium Spark Plasma Sintering, 2019-10-24/10-24, Warszawa (PL), pp.20-20, 2019 | |
80. | Jurczak G., Dłużewski P., The effect of finite strain measure change on second-order piezoelectricity, EUROMAT 2019, European Congress and Exhibition on Advanced Materials and Processes 2019, 2019-09-01/09-05, Stockholm (SE), pp.1, 2019Jurczak G., Dłużewski P., The effect of finite strain measure change on second-order piezoelectricity, EUROMAT 2019, European Congress and Exhibition on Advanced Materials and Processes 2019, 2019-09-01/09-05, Stockholm (SE), pp.1, 2019Abstract: Very rapid technological development in the electronic branch of the industry observed during last decades, together with the progressive miniaturisation of electronic devices induce increasing interest in the subject of piezoelectric semiconducting heterostructures. In some cases, the linearity of the piezoelectric effect under extreme strain and electric field conditions is challenged for these heterostructures. There are many experimental reports in the literature dealing with nonlinear piezoelectricity as well as theoretical calculations which predict the nonlinear behaviour of such crystalline heterostructures.
If, as stated above, the nonlinearity appears under extreme load conditions, therefore from the point of view of mechanics a finite deformation approach shoud be applied to properly describe the kinematics of the deformed crystal. Thus, problem of the choice of a proper strain measure appears as far as many different finite strain measures can be used to describe deformation of the body. Furthermore, higher order piezoelectric coefficients which are derivatives of the heterostructure energy (deformation in the vicinity of the natural state of the body) over the strain depends on the choice of the strain measure [1,2].
Theoretical prediction shows that second-order piezoelectric coefficients are finite strain measure dependent. Therefore, the use of any finite strain measure in constitutive modelling of nonlinear piezoelectric materials requires an adequate choice of higher-order piezoelectric coefficients. Otherwise, erroneous elastic and electric fields may appear in the case of modelling of nonlinear piezoelectric phenomena, e.g. for quantum heterostructures such as wells or dots. 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.
General transformation formula for second-order piezoelectric coefficients (elastostriction) is derived as well as individual transformation formulae for common crystallographic classes (e.g. cubic, hexagonal).
References:
1. Dłużewski, P. (2000). J. Elast. 60, 119–129.
2. Jurczak, G. (2018) Acta Cryst. A74, 518–523. Keywords: piezoelectricity; second order piezoelectric coefficients; | |
81. | Ignaczak J., Stress-heat flux characterization of linear dynamic coupled thermoelasticity for an inhomogeneous isotropic infinite cylinder under plane strain conditions and zero heat flux normal to the plane, COMPOSITE INTERFACES, ISSN: 0927-6440, DOI: 10.1080/01495739.2018.1492358, Vol.41, pp.1201-1211, 2018Ignaczak J., Stress-heat flux characterization of linear dynamic coupled thermoelasticity for an inhomogeneous isotropic infinite cylinder under plane strain conditions and zero heat flux normal to the plane, COMPOSITE INTERFACES, ISSN: 0927-6440, DOI: 10.1080/01495739.2018.1492358, Vol.41, pp.1201-1211, 2018Abstract: Stress-heat flux characterization of linear dynamic coupled thermoelasticityfor an inhomogeneous isotropic infinite cylinder under plane strain conditions and zero heat-flux normal to the plane is presented. It is shown that for a bounded cross-section of the cylinder, a 3D stress-heat flux process is generated by a 2D one, and a uniqueness theorem for the associated 2D initial-boundary value problem is established. In addition, an asymptotic approach to the 2D stress-heat flux initial-boundary value problem, in the form of a power series with respect to a small thermoelastic coupling field, is proposed. Also, Green' s formulas for time-periodic complex-valued solutions to 2D stress-heat flux field equations are obtained; and the existence of a globally constrained real-valued periodic and attenuated on the timeaxis stress-heat flux mode satisfying homogeneous natural boundary conditions is proved. The stress-heat flux characterization covers a large class of FGM's with physical properties smoothly distributed over the cross-section of the infinite cylinder. The results obtained are complementary to those of linear dynamic coupled thermoelasticity published up to date and should prove useful for a number of researchers in the field. Keywords: Existence of a stress-heat flux mode, Green's formulas, isotropic inhomogeneous media, linear dynamic coupled thermoelasticity, stressheat flux characterization, stress-heat flux field equations of linear thermo-elastodynamics, uniqueness theorem | | (25p.) |
82. | Pieczyska E.A., Golasiński K.M., Staszczak M., Maj M., Furuta T., Kuramoto S., INFRARED THERMOGRAPHY AND DIC USED TO INVESTIGATE GUM METAL LOCALIZATION EFFECTS, IRF2018, 6th International Conference Integrity-Reliability-Failure, 2018-07-22/07-26, Lizbona (PT), No.7199, pp.825-826, 2018Pieczyska E.A., Golasiński K.M., Staszczak M., Maj M., Furuta T., Kuramoto S., INFRARED THERMOGRAPHY AND DIC USED TO INVESTIGATE GUM METAL LOCALIZATION EFFECTS, IRF2018, 6th International Conference Integrity-Reliability-Failure, 2018-07-22/07-26, Lizbona (PT), No.7199, pp.825-826, 2018Abstract: This paper presents an investigation of strain localization phenomena during tension of a β-Ti alloy Gum Metal that can deform reversibly to large strains (around 2%). Digital image correlation (DIC), with the especially developed PAN algorithm at IPPT, and infrared thermography were used to determine strain and the related temperature distributions with high accuracy. The analysis of strain and temperature distributions showed that the increase in the strain rate affects both the onset and development of the strain localization process. Keywords: infrared thermography, thermomechanical behavior, gum metal | |
83. | Blinowski A., Jan Rychlewski: 23 V 1934 -- 05 VIII 2011, Journals of the Polish Mathematical Society, ISSN: 1730-2668, Vol.41, No.2, pp.199-207, 2013Blinowski A., Jan Rychlewski: 23 V 1934 -- 05 VIII 2011, Journals of the Polish Mathematical Society, ISSN: 1730-2668, Vol.41, No.2, pp.199-207, 2013Abstract: Zamiarem autora niniejszej noty wspomnieniowej było napisanie jej wspólnie z innymi współpracownikami i uczniami profesora Rychlewskiego. Zamiar okazał się niemożliwy do spełnienia. Doktorantów prof. Rychlewskiego z Polski i z Chin należy szukać co najmniej na trzech kontynentach od Montrealu poprzez Europę Zachodnią i Środkową po Singapore. Profesor przeżył 77 lat, dziś ---- niecałe dwa lata po Jego śmierci --- co najmniej troje spośród jego uczniów już ten wiek osiągnęło lub osiągnie w najbliższych miesiącach. Swoją działalność naukową w Instytucie Podstawowych Problemów Techniki PAN rozpoczął on bowiem na początku lat 60. w niemal rówieśniczej grupie. Został on wkrótce w naturalny sposób nieformalnym jej przewodnikiem, zanim jeszcze uzyskał sam jakiekolwiek stopnie naukowe. Ze względów formalnych kilku z jego ówczesnych współpracowników broniło opracowanych w znacznej mierze pod jego kierownictwem prac doktorskich u innego promotora. Sam on uważał się za ucznia profesorów Witolda Nowackiego i Wacława Olszaka. Asystentem tego ostatniego na Politechnice Warszawskiej był jeszcze przed formalnym ukończeniem uczelni. Wpływ na Jego działalność naukową wywarł również wcześnie zmarły prof. W. Urbanowski. | |
84. | Lewis R.W., Postek E.W., Gethin D.T., Yang X.S., Pao W.K.S., Chao L., Numerical methods in simulation of industrial processes, AET2006, First International Conference on Advances in Engineering and Technology, 2006-07-16/07-19, Entebbe (UG), No. , pp.764-795, 2006Lewis R.W., Postek E.W., Gethin D.T., Yang X.S., Pao W.K.S., Chao L., Numerical methods in simulation of industrial processes, AET2006, First International Conference on Advances in Engineering and Technology, 2006-07-16/07-19, Entebbe (UG), No. , pp.764-795, 2006Abstract: The paper deals with an overview of some industrial applications leading to a formulation for advanced numerical techniques. The applications comprise squeeze casting processes, forming of tablets and petroleum reservoir modelling. All of the problems lead to solutions of highly nonlinear, coupled sets of multiphysics equations. Keywords: squeeze forming, powder compaction, oil fields, coupled problems, thermomechanics, porous media, fluid flow, nonlinear solid mechanics, phase transformations, microstructural solidification models, numerical methods, contact problems, discrete elements, finite elements. | |
85. | Pieczyska E.A., Gadaj S.P., Nowacki W.K., Tobushi H., Thermomechanical investigations of martensitic and reverse transformations in TiNi shape memory alloy, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, Vol.52, No.3, pp.165-171, 2004Pieczyska E.A., Gadaj S.P., Nowacki W.K., Tobushi H., Thermomechanical investigations of martensitic and reverse transformations in TiNi shape memory alloy, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, Vol.52, No.3, pp.165-171, 2004Abstract: Shape memory alloys are characterised by interesting properties, i.e. shape memory effect and pseudoelasticity, which enable their
increasing application. Thermomechanical aspects of martensitic and reverse transformations in TiNi shape memory alloy subjected to tension
tests were investigated. The stress-strain characteristics obtained during the tests were completed by the temperature characteristics. The temperature
changes were calculated on the basis of thermograms determined by an infrared camera. Taking advantages from the infrared technique,
the temperature distributions on the specimen’s surface were found. Heterogeneous temperature distributions, related to the nucleation and
development of the new martensite phase, were registered and analysed. A significant temperature increase, up to 30 K, was registered during
the martensitic transformation. The similar effects of the heterogeneous temperature distribution were observed during unloading, while the
reverse transformation, martensite into austenite took place, accompanied by significant temperature decrease. Keywords: shape memory alloy, pseudoelasticity, transformation front, thermomechanical, investigations | |
86. | Sadowski T., Hardy S., Postek E., Modelowanie polikrystalicznej ceramiki z warstwami międzyziarnowymi w stanach jednoosiowego rozciągania, Eksploatacja i niezawodność, ISSN: 1507-2711, No.4, pp.79-82, 2004Sadowski T., Hardy S., Postek E., Modelowanie polikrystalicznej ceramiki z warstwami międzyziarnowymi w stanach jednoosiowego rozciągania, Eksploatacja i niezawodność, ISSN: 1507-2711, No.4, pp.79-82, 2004Abstract: W pracy przedstawiono model polikrystalicznego materiału ceramicznego, w którym ziarna połączone są poprzez cienkie warstwy o innych własnościach mechanicznych. Powoduje to powstanie niejednorodnych rozkładów deformacji oraz koncentracje naprężeń inicjujące mikrouszkodzenia. Keywords: ceramika, mikrouszkodzenia, polikryształy, modele numeryczne | |
87. | Ignaczak J., Plane harmonic waves in a microperiodic layered thermoelastic solid revisited
, COMPOSITE INTERFACES, ISSN: 0927-6440, DOI: 10.1080/01495730390425080, Vol.27, No.9, pp.779-793, 2004Ignaczak J., Plane harmonic waves in a microperiodic layered thermoelastic solid revisited
, COMPOSITE INTERFACES, ISSN: 0927-6440, DOI: 10.1080/01495730390425080, Vol.27, No.9, pp.779-793, 2004Keywords: harmonic thermoelastic waves, microperiodic composites | |
88. | Klisiński M., Luo Ch., Postek E., Discussion on application of piece-wise linear weight functions in 2D contact problems, Computer Assisted Mechanics and Engineering Sciences, ISSN: 1232-308X, No.10, pp.265-281, 2003Klisiński M., Luo Ch., Postek E., Discussion on application of piece-wise linear weight functions in 2D contact problems, Computer Assisted Mechanics and Engineering Sciences, ISSN: 1232-308X, No.10, pp.265-281, 2003Abstract: Standard higher order finite elements often perform unsatisfactory in contact problems. The major difficulties are caused by uneven distribution of nodal forces resulting in oscillating contact pressure. The paper presents a new approach that eliminates this drawback. The weight functions are chosen in such a way that even distributions of nodal forces are obtained. It is achieved by applying piece-wise linear weighting functions. Two new 3D isoparametric quadratic elements are derived: 6-node triangle and 8-node quadrilateral, and tested in many examples. The new elements have unsymmetric stiffness matrices, but the provided examples show their good performance in contact problems. Keywords: coontact problems, weighting functions, quadratic finite elements | |
89. | Giżejowski M.A., Karczewski J.A., Postek E., Sotomski W., Wierzbicki S., Witkowski J., Behaviour and modelling of semi-rigid structural frame systems, Botswana Journal of Technology, ISSN: 1019-1593, pp.51-61, 2003Giżejowski M.A., Karczewski J.A., Postek E., Sotomski W., Wierzbicki S., Witkowski J., Behaviour and modelling of semi-rigid structural frame systems, Botswana Journal of Technology, ISSN: 1019-1593, pp.51-61, 2003Abstract: A computational finite element model is developed to predict the load-deflection characteristic of portal frames with semi-rigid welded and bolted joints. Plate components of frame members and joints are modelled by thin shell finite elements while bolt connectors by springs with the force-deformation characteristic evaluated from test results. The computer software ABAQUS is used. Experimental investigations were designed in order to evaluate frame load deflection characteristics, joint local rotations, failure modes, and the contribution of end-plates and bolt connectors to the joint rotations. Theoretical results of frame load-deflection characteristics predicted with use of ABAQUS program are compared with the experimental results. The modelling of friction effect between the contact surfaces of bolted joints is verified to be the most important factor. The comparative analysis leads to the conclusion that the proposed advanced shell model can be very useful in the verification of simplified models being developed for practical applications. Keywords: semi-rigid connections, limit states analysis, experiments, variable load, finite element method | |
90. | Ignaczak J., Plane harmonic waves in a microperiodic layered infinite thermoelastic solid
, COMPOSITE INTERFACES, ISSN: 0927-6440, DOI: 10.1080/714050871, Vol.26, No.11, pp.1033-1054, 2003 | |
91. | Postek E., Siemaszko A., Kleiber M., Reliability Study of a Containment Shell, JOURNAL OF THEORETICAL AND APPLIED MECHANICS, ISSN: 1429-2955, Vol.40, No.1, pp.179-203, 2002Postek E., Siemaszko A., Kleiber M., Reliability Study of a Containment Shell, JOURNAL OF THEORETICAL AND APPLIED MECHANICS, ISSN: 1429-2955, Vol.40, No.1, pp.179-203, 2002Abstract: Computational time needed for reliability abalysis of realistic structural problems as a rule is very high. Improvements in efficiency are critical to allow solution of large realistic problems. The realiability analysis is usually performed using approximate First Order Reliability Method (FORM). Iterative solution procedures of FORM require extensive design sensitivity computations of high accuracy. The design of realistic structures requires computer-based numerical procedures, such as finite element analysis. The design sensitivity gradients are not explicitly available in terms of design variables. The most intensive computational task of design sensitivity computation should be carried out by highly efficient and accurate methods such as discrete design sensitivity analysis, This paper describes requirements for design sensitivity information for reliability analysis. The way of coupling reliability computationa with discrete AVM and DDM methods of design sensitivity analysis is pointed out. A computational program developed for layered concrete shells allows one to solve large realistic reliability problems. The reliability study of an RC nuclear containment shell is carried out. Reliability studies show which pf mthe parameters have the highest impact on the reliability of the vessel. Keywords: Nuclear engineering, reliability, design sensitivity, FEM | |
92. | Janas M., Sokół-Supel J., Postek E., Arching action in slackened structures, FOUNDATIONS OF CIVIL AND ENVIRONMENTAL ENGINEERING, ISSN: 1642-9303, No.2, pp.97-109, 2002Janas M., Sokół-Supel J., Postek E., Arching action in slackened structures, FOUNDATIONS OF CIVIL AND ENVIRONMENTAL ENGINEERING, ISSN: 1642-9303, No.2, pp.97-109, 2002Abstract: Elastic-plastic composite slabs with no-tension matrix are considered, with unilateral in-plane restraints at supports. In such conditions important compressive membrane forces (arching action) are generated by transversal loads. Because of unstable character of such flexural response it is very sensitive to slackening due to clearances at supports. An approximate method based on the post-yield approach (PYA) was adopted and permits to determine easily the ultimate supportable load for slackened structures. The method was calibrated and verified by the FEM incremental analysis. | |
93. | Postek E., Kleiber M., Niezawodność dużych nieliniowych układów konstrukcyjnych – wybrane studium, PRZEGLĄD MECHANICZNY, ISSN: 0033-2259, No.5, pp.33-37, 2002Postek E., Kleiber M., Niezawodność dużych nieliniowych układów konstrukcyjnych – wybrane studium, PRZEGLĄD MECHANICZNY, ISSN: 0033-2259, No.5, pp.33-37, 2002Abstract: W artykule przedstawiono sposób postępowania podczas szacowania niezawodnoÊci dużych nieliniowych układów konstrukcyjnych. Nacisk położono na zastosowanie metody różniczkowania bezpośredniego (DDM). Jako przykład wybrano żelbetową konstrukcję budynku osłonowego reaktora nuklearnego. Keywords: inżynieria nuklearna, niezawodność, analiza wrażliwości, konstrukcje żelbetowe | |
94. | Ignaczak J., Saint-venant's principle for a microperiodic composite thermoelastic semispace: the dynamical refined average theory, COMPOSITE INTERFACES, ISSN: 0927-6440, DOI: 10.1080/01495730290074649, Vol.25, No.11, pp.1065-1079, 2002 | |
95. | Rojek J., Zienkiewicz OC., Onate E., Postek E., Advances in FE explicit formulation for simulation of metalforming processes, JOURNAL OF MATERIALS PROCESSING TECHNOLOGY, ISSN: 0924-0136, DOI: 10.1016/S0924-0136(01)00894-9, No.119, pp.41-47, 2001Rojek J., Zienkiewicz OC., Onate E., Postek E., Advances in FE explicit formulation for simulation of metalforming processes, JOURNAL OF MATERIALS PROCESSING TECHNOLOGY, ISSN: 0924-0136, DOI: 10.1016/S0924-0136(01)00894-9, No.119, pp.41-47, 2001Abstract: This paper presents some advances of finite element explicit formulation for simulation of metal forming processes. Because of their computational efficiency, finite element programs based on the explicit dynamic formulation proved to be a very attractive tool for the simulation of metal forming processes. The use of explicit programs in the sheet forming simulation is quite common, the possibilities of these codes in bulk forming simulation in our opinion are still not exploited sufficiently. In our paper, we will consider aspects of bulk forming simulation. We will present new formulations and algorithms developed for bulk metal forming within the explicit formulation. An extension of a finite element code for the thermomechanical coupled analysis is discussed. A new thermomechanical constitutive model developed by the authors and implemented in the program is presented. A new formulation based on the so-called split algorithm allows us to use linear triangular and tetrahedral elements in the analysis of large plastic deformations characteristic to forming processes. Linear triangles and tetrahedra have many advantages over quadrilateral and hexahedral elements. Linear triangles and tetrahedra based on the standard formulations exhibit volumetric locking and are not suitable for large plastic strain simulation. The new formulation allows to overcome this difficulty. New formulations and algorithms have been implemented in the finite element code Stampack developed at the International Centre for Numerical Methods in Engineering in Barcelona. Numerical examples illustrate some of the possibilities of the finite element code developed and validate new algorithms. Keywords: Explicit formulation, Forming simulation, Split algorithm | |
96. | Giżejowski M., Karczewski J., Postek E., Badania ram z węzłami podatnymi – weryfikacja doświadczalna modeli, INŻYNIERIA I BUDOWNICTWO, ISSN: 0021-0315, No.8, pp.433-439, 2000Giżejowski M., Karczewski J., Postek E., Badania ram z węzłami podatnymi – weryfikacja doświadczalna modeli, INŻYNIERIA I BUDOWNICTWO, ISSN: 0021-0315, No.8, pp.433-439, 2000Abstract: W artykule przedstawione zostały badania ram stalowych o węzłach podatnych. Dokonana została weryfikacja doświadczalna modeli teoretycznych. Analiza numeryczna została wykonana dla trójwymiarowych modeli powłokowych ram z uwzględnieniem podatności węzłów łączonyc na śruby oraz dla porównania z węzłami spawanymi. W modelowaniu komputerowym uwzględniono nielinową geometrię, sp®ężyto-plastyczne własności materiału, kontakt-tarcie moędzy płytami doczołowymi. Śruby zostały zastąpione sprężynami o charakterytyce M-Fi. Sprawdzana była nośność graniczna ram. Keywords: analiza nieliniowa, węzły podatne, ramy, konstrukcje stalowe, połączenia, nośność graniczna | |
97. | Ignaczak J., A spatial decay estimate for transient thermoelastic process in a composite semispace, COMPOSITE INTERFACES, ISSN: 0927-6440, DOI: 10.1080/014957300280533, Vol.23, No.1, pp.1-14, 2000 | |
98. | Giżejowski M., Postek E., Modelowanie zachowania się ram stalowych z węzłami podatnymi, INŻYNIERIA I BUDOWNICTWO, ISSN: 0021-0315, No.11, pp.645-651, 1999Giżejowski M., Postek E., Modelowanie zachowania się ram stalowych z węzłami podatnymi, INŻYNIERIA I BUDOWNICTWO, ISSN: 0021-0315, No.11, pp.645-651, 1999Abstract: Opracowane modele numeryczne konstrukcji ram stalowych o węzłach podatnych. Ramy byly konstrukcjami o węzłach spawanych oraz łączonych na śruby. Konstrukcje modelowane byly metodą elementów skończonych przy zastosowaniu elementów powłokowych. W modelach numerycznych uwzględniane byly połączenia śrubowe o nieliniowych charakterystykach oraz powierzchnie kontaktu plyt czołowych w węzłach. Badane bylo zachowanie ram pod obciążeniem rosnącym monotonicznie oraz zmiennym. Opracowany rowniez zostal model numeryczny służący obliczaniu statecznosci ram poslugując sie analogia pręta Roordy. Zostalo to zrealizowane drogą obliczenia obciążenia krytycznego, wartości i postaci własnych dla ukladu idealnego, następnie narzucenia imperfekcji zgodnych z postaciami wlasnymi na konstrukcję idealną i w końcu wykonaniu analizy przyrostowej.
Keywords: analiza nieliniowa, stateczność, imperfekcje, postacie własne, węzły podatne, ramy, konstrukcje stalowe | |
99. | Karczewski J.A., Postek E., Wierzbicki S., Experimental shakedown analysis of double butt, prestressed, bolted connections, 6th International Conference, Modern Building Materials Structures and Techniques, 1999-05-19/05-22, Wilno (LT), pp.196-201, 1999Karczewski J.A., Postek E., Wierzbicki S., Experimental shakedown analysis of double butt, prestressed, bolted connections, 6th International Conference, Modern Building Materials Structures and Techniques, 1999-05-19/05-22, Wilno (LT), pp.196-201, 1999Abstract: This paper deals with the experiment on double butt prestressed bolted connections. The goal of the experiment is to verify a 3D computational model of the connection. The connections are loaded cyclically according to a load program based on load variability observed in engineering practice
Keywords: prestressing, deformability, ultimate load, elastooptic layer | |
100. | Rojek J., Onate E., Postek E., Application of explicit FE codes to simulation of sheet and bulk metal forming processes, JOURNAL OF MATERIALS PROCESSING TECHNOLOGY, ISSN: 0924-0136, DOI: 10.1016/S0924-0136(98)00169-1, No.80-81, pp.620-627, 1998Rojek J., Onate E., Postek E., Application of explicit FE codes to simulation of sheet and bulk metal forming processes, JOURNAL OF MATERIALS PROCESSING TECHNOLOGY, ISSN: 0924-0136, DOI: 10.1016/S0924-0136(98)00169-1, No.80-81, pp.620-627, 1998Abstract: This paper presents the application of an explicit dynamic finite element code for simulation of metal forming processes, of both sheet and bulk forming. The experiences reported here have been gained during the development and use of our own explicit program Stampack. An original formulation of a triangular shell element without rotational degrees of freedom is reviewed combining the explicit sheet forming simulation with the implicit springback analysis as well as the parallelization of the explicit program described. An extension of a finite element code for coupled thermomechanical analysis is discussed. A new thermomechanical constitutive model developed by the authors and implemented in the program is presented. Numerical examples illustrate some of the possibilities of the finite element code developed. Keywords: Metal forming, Sheet stamping, Finite element simulation, Explicit dynamic analysis, Thermomechanical analysis | |
101. | Karczewski J., Postek E., Wierzbicki S., Modelowanie zachowania się nakładkowego sprężonego połączenia śrubowego, Badania nośności granicznej konstrucji metalowych, 1998-10-23/10-25, Wrocław Szklarska Poręba (PL), pp.169-176, 1998Karczewski J., Postek E., Wierzbicki S., Modelowanie zachowania się nakładkowego sprężonego połączenia śrubowego, Badania nośności granicznej konstrucji metalowych, 1998-10-23/10-25, Wrocław Szklarska Poręba (PL), pp.169-176, 1998Abstract: Odkształcalność stalowej konstrukcji nośnej budynków, wynikająca z odkształceń jej elmentow i połączeń, w zasadniczej części przypadków, jest ograniczona czynnikami eksploatacyjnymi. W przypadku potaczeń śrubowych wysętpujące luzy między trzpieniami i otworami są przyczyną zwiększonej podatnosci konstrukcji. Wstępne spreżenie tego typu połączenia powoduje znaczną redukcję odksztacałnosci samego połączenia a co za tym idzie także konstrukcji. Zjawisko to wykorzystano w szeroko obecnie stosowanych połączeniach ciernych. Wadą tych połączeń jest przyjęcie założeenia, w ktorym pojawienie się stanu granicznego nosności utożsamia się z pierwszym poślizgiem. W rzeczywistosci sprężone pola.czenie srubowe nadal jest zdolne do przyjecia dodatkowego przyrostu obci^zenia. Wyniki szeregu prac, głównie doswiadczalnych [2], [3], potwierdzaja. to spostrzeżenie. Zgodnie z nimi, przy mozliwosci dalszego przyjmowania obciążenia, odkształcalnosc połączenia po pierwszym poślizgu byla nadal znacznie mniejsza od odksztalceń analogicznych połączeń śrubowych niesprężonych. W pracy przedstawiono model nakładkowego połączenia srubowego, wstępnie sprężonego. Zastosowano w nim jedną rubę (wstępne ujęcie). Miało to na celu uzyskanie dobrych warunkow poznania zachowania się takich połączeń. Keywords: sprężenie, płączenia nakładkowe, rozciąganie, modele numeryczne, experyment | |
102. | Ignaczak J., Saint-venant type decay estimates for transient heat conduction in a composite rigid semispace, COMPOSITE INTERFACES, ISSN: 0927-6440, DOI: 10.1080/01495739808956144, Vol.21, No.3, pp.185-204, 1998 | |
103. | Ignaczak J., Baczyński Z.F., On a refined heat conduction theory for microperiodic layered solids, COMPOSITE INTERFACES, ISSN: 0927-6440, DOI: 10.1080/01495739708956127, Vol.20, pp.749-771, 1997Ignaczak J., Baczyński Z.F., On a refined heat conduction theory for microperiodic layered solids, COMPOSITE INTERFACES, ISSN: 0927-6440, DOI: 10.1080/01495739708956127, Vol.20, pp.749-771, 1997Abstract: A refined averaged theory of a rigid heat conductor with a microperiodic structure is used to solve a one-dimensional initial boundary value problem ofheat conduction in a periodically layeredplate with a largenumber of homogeneous isotropic layers. A uniqueness theorem for the averaged problem is proved, and two closed-form solutions for a periodically
layered semispace are obtained. One of the two solutions represents the temperature
field in the layered semispace due to a sudden heating of the boundary plane, while the
other stands for the temperaturefield in the layeredsemispace produced by laser surface
heating. Numerical examples are included. | |
104. | Ignaczak J., Hetnarski R., On solition-like thermoelastic waves, COMPOSITE INTERFACES, ISSN: 0927-6440, DOI: 10.1080/00036819708840557, Vol.65, No.1, pp.183-204, 1997 | |
105. | Blinowski A., Ostrowska-Maciejewska J., On the elastic orthotropy, ARCHIVES OF MECHANICS, ISSN: 0373-2029, Vol.48, No.1, pp.129-141, 1996 | |
106. | Postek E., Kleiber M., Design sensitivity of reinforced concrete plate/shell structures, CMM1995, XII Polish Conference on Computer Methods in Mechanics, 1995-05-09/05-13, Warszawa Zegrze (PL), No. , pp.279-280, 1995Postek E., Kleiber M., Design sensitivity of reinforced concrete plate/shell structures, CMM1995, XII Polish Conference on Computer Methods in Mechanics, 1995-05-09/05-13, Warszawa Zegrze (PL), No. , pp.279-280, 1995Abstract: Design sensitivity gradients are believed to have great significance in realistic asscsment of structural response. Sensitivity techniques form a tool to follow changes in structural behaviour caused by variations of design parameters. The sensitivity gradients make it also possible to investigate the influence of different type of material or geometrical imperfections on the structural response. One of the first papers considering the design sensitivity analysis (DSA) was presented by Zienkiewicz and Campbell |lj. Recently, efforts of the investigators are mostly focused on the r.onlinear performance of structures. The total Lagrangian formulation with the computer Implementation in Adina was presented in ]2]. A formulation considering path-dependent problems was given in [3] and the updated Lagrangian formulation of the design sensitivity problems for arbitrary nonlinearities was given in [4]. Applications of the DSA to the slate estimation of complex structures were presented in |5). The response of reinforced concrete structures should always be considered nonlinear and thus it may be used as an example illustrating the theory of design sensitivity for nonlinear systems. This paper deals with the design sensitivity of reinforced plate and shell structures. References 1. 0. C. Zicnkiowicz, J.S. Campbell, Shape optimization and sequential linear programmiri R. II. Gallagher and O.C. Xienkicwicz, eds Optimum Structural Design, Wiley, 1973. 2. M. Ilaririan, J.B. Cardoso, J.S. Arora, Use of ADINA for design optimization of nonlinear structures, C'omput. Struct., 26 (1987), pp. 123-133. 3. C.A. Vidal, R.I3. Ilaber, Design sensitivity analysis for rate independent elasl.opla.stjr Comp. Mcth. Appl. Mcch. Eng., 107 (1993), pp. 393-431. 4. M. Kleiber, Shape and nonshapc structural design sensitivity analysis for problems w;; any material .and kinematic nonlincarity, Comp. Mclh. Appl. Eng., 108 (1993), pp. 73-97 5. M. Kleiber, T.D. Hien, E. Postek, Incremental finite eleirint sensitivity analysis for non-linear mechanics applications, Int. .!. Num. Me/It. Eng., 37 (1994), pp. 3291-3308. Keywords: parameter sensitivity, plate-shell structures, nonlinear analysis | |
107. | Plaut R.H., Mróz Z., Upheaval Buckling of a Mechanism under External Pressure and Compressive Loading, International Journal of Mechanical Engineering Education, ISSN: 0306-4190, DOI: 10.1177/030641909402200201, Vol.22, No.2, pp.79-82, 1994Plaut R.H., Mróz Z., Upheaval Buckling of a Mechanism under External Pressure and Compressive Loading, International Journal of Mechanical Engineering Education, ISSN: 0306-4190, DOI: 10.1177/030641909402200201, Vol.22, No.2, pp.79-82, 1994Abstract: A mechanical or structural element often buckles when it is compressed beyond a certain amount. Constraints may raise the value of the critical compressive load. In some cases a constraint may completely prevent the occurrence of buckling. This situation is demonstrated here by a simple two-bar model that rests on a rigid foundation and is subjected to pressure and compressive loading. If the system is ‘perfect’, buckling is not possible. However, if the foundation is not flat, or if the load is applied eccentrically, a sudden jump in deflection may occur as the load is increased. | |
108. | Kleiber M., Hien T.D., Postek E., Incremental finite element sensitivity analysis for nonlinear applications, INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, ISSN: 0029-5981, DOI: 10.1002/nme.1620371906, Vol.37, pp.3291-3308, 1994Kleiber M., Hien T.D., Postek E., Incremental finite element sensitivity analysis for nonlinear applications, INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, ISSN: 0029-5981, DOI: 10.1002/nme.1620371906, Vol.37, pp.3291-3308, 1994Abstract: Finite element formulations for structural sensitivity analysis of non‐linear systems with fixed overall shape are discussed. Both the direct differentiation and adjoint variable methods are employed. The resulting sensitivity algorithms are consistent with time integration scheme adopted for solving equilibrium problem. Effectiveness and computational aspects of the procedures are discussed and compared. Numerical algorithms are shown to be readily implemented in existing finite element codes. Large‐scale examples illustrate the paper. Keywords: sensitivity analysis, nonlinear systems, incremental approach, finite element method | |
109. | Postek E., Rojek J., Antúnez H., Nonlinear static analysis of a guyed mast with finite element method, CMM1993, XI Polish Conference on Computer Methods in Mechanics
, 1993-05-11/05-14, Kielce-Cedzyna (PL), No. , pp.743-750, 1993Postek E., Rojek J., Antúnez H., Nonlinear static analysis of a guyed mast with finite element method, CMM1993, XI Polish Conference on Computer Methods in Mechanics
, 1993-05-11/05-14, Kielce-Cedzyna (PL), No. , pp.743-750, 1993Abstract: This paper deals with numerical aspects of nonlinear static analysis of a guyed mast of 649 m height. A concept of a new structure constructed of solid bars instead of tubes is analyzed. Due to decrease of member diameters the wind load declines, thus the horizontal displacements are smaller. A few structural variants of the proposed mast are calculated. Keywords: guyed mast, nonlinear analysis, tendons | |
110. | Kacprzyk Z., Postek E., Biblioteka izoparametrycznych elementów skończonych systemu FEAS, Metody Komputerowe w Inżynierii Lądowej, ISSN: 0867-5007, Vol.2, No.3, pp.89-108, 1993Kacprzyk Z., Postek E., Biblioteka izoparametrycznych elementów skończonych systemu FEAS, Metody Komputerowe w Inżynierii Lądowej, ISSN: 0867-5007, Vol.2, No.3, pp.89-108, 1993Abstract: W artykule przedstawiona została biblioteka izoparametrycznych elementów skończonych opartych o paraboliczinee funkcje ksztaltu. W bibliotece zawarte zostały elementy tarczowe o liczbie węzłów od 4 do 8, bryłowe o liczbie węzłów od 8 do 20, 4 i 8 węzłowe elementy płyyty Mindlina, 3 węzłowy element powtoki osiowo-symetrycznej oraz 8 węzłowy element typu Ahmada. Przedstawiona biblioteka implementowana jest w systemie analizy konstrukcji inżynierskich FEAS i znajdzie sie ona w nowej wersji systemu. Konstrukcje mogq być modelowane przy użyciu elementów znajdujqcych się w tzw. bibliotece inżynierskiej skladającej się z elementów, których macierze sztywności obliczone zostaly analitycznie oraz w bibliotece , parabolicznej. W tym wypadku jednak za poprawność modelu odpowiada calkowicie użytkownik. Nowa biblioteka systemu wykorzystywana będzie zarówno w obliczeniach inżynierskich jak i w procesie nauczania mechaniki na Wydziale Inżynierii Lądowej. Keywords: elementy paraboliczne, metoda elementĂłw skończonych, dydaktyka | |
111. | Postek E., Hien T.D., On the applications of the sensitivity analysis to the design of spatial bar structures, ARCHIVES OF CIVIL ENGINEERING, ISSN: 1230-2945, Vol.38, No.1-2, pp.17-33, 1992Postek E., Hien T.D., On the applications of the sensitivity analysis to the design of spatial bar structures, ARCHIVES OF CIVIL ENGINEERING, ISSN: 1230-2945, Vol.38, No.1-2, pp.17-33, 1992Abstract: The paper deals with structural sensitivity analysis and its application in the engineering practice. The considerations are illustrated by numerical results concerning an industrial steel room as 3D structure. Keywords: sensitivity analysis, adjoint variable method, direct differentiation method, design codes, steel structures | |
112. | Kleiber M., Hien T.D., Postek E., Structural Design Sensitivity Analysis by Incremental Procedures, CMM10, X Polish Conference Computer Methods in Mechanics, 1991-05-14/05-17, Swinoujscie (PL), DOI: , pp.357-364, 1991Kleiber M., Hien T.D., Postek E., Structural Design Sensitivity Analysis by Incremental Procedures, CMM10, X Polish Conference Computer Methods in Mechanics, 1991-05-14/05-17, Swinoujscie (PL), DOI: , pp.357-364, 1991Abstract: An incremental formulation based on the Taylor's expansion for nonlinear design sensitivity problems is developed. Computational aspects are discussed. A few numerical benchmark problems illustrate the paper. Keywords: design sensitivity, nonlinear geometry, incremental procedure | |