Publications reported by three months

1.Adimy M., Chekroun A., Kaźmierczak B., Traveling waves in a coupled reaction–diffusion and difference model of hematopoiesis, Journal of Differential Equations, ISSN: 0022-0396, DOI: 10.1016/j.jde.2016.12.009, Vol.262, No.7, pp.4085-4128, 2017
Adimy M., Chekroun A., Kaźmierczak B., Traveling waves in a coupled reaction–diffusion and difference model of hematopoiesis, Journal of Differential Equations, ISSN: 0022-0396, DOI: 10.1016/j.jde.2016.12.009, Vol.262, No.7, pp.4085-4128, 2017

Abstract:
The formation and development of blood cells is a very complex process, called hematopoiesis. This process involves a small population of cells called hematopoietic stem cells (HSCs). The HSCs are undifferentiated cells, located in the bone marrow before they become mature blood cells and enter the blood stream. They have a unique ability to produce either similar cells (self-renewal), or cells engaged in one of different lineages of blood cells: red blood cells, white cells and platelets (differentiation). The HSCs can be either in a proliferating or in a quiescent phase. In this paper, we distinguish between dividing cells that enter directly to the quiescent phase and dividing cells that return to the proliferating phase to divide again. We propose a mathematical model describing the dynamics of HSC population, taking into account their spatial distribution. The resulting model is a coupled reaction–diffusion equation and difference equation with delay. We study the existence of monotone traveling wave fronts and the asymptotic speed of spread.

Keywords:
Hematopoiesis, Age-structured population, Reaction–diffusion system with delay, Difference equation, Traveling wave front, Asymptotic speed of spread

2.Bobrowski A., Kaźmierczak B., Kunze M., An averaging principle for fast diffusions in domains separated by semi-permeable membranes, MATHEMATICAL MODELS AND METHODS IN APPLIED SCIENCES, ISSN: 0218-2025, DOI: 10.1142/S0218202517500130, Vol.27, No.4, pp.663-706, 2017
Bobrowski A., Kaźmierczak B., Kunze M., An averaging principle for fast diffusions in domains separated by semi-permeable membranes, MATHEMATICAL MODELS AND METHODS IN APPLIED SCIENCES, ISSN: 0218-2025, DOI: 10.1142/S0218202517500130, Vol.27, No.4, pp.663-706, 2017

Abstract:
We prove an averaging principle which asserts convergence of diffusion processes on domains separated by semi-permeable membranes, when diffusion coefficients tend to infinity while the flux through the membranes remains constant. In the limit, points in each domain are lumped into a single state of a limit Markov chain. The limit chain’s intensities are proportional to the membranes’ permeability and inversely proportional to the domains’ sizes. Analytically, the limit is an example of a singular perturbation in which boundary and transmission conditions play a crucial role. This averaging principle is strongly motivated by recent signaling pathways models of mathematical biology, which are discussed toward the end of the paper.

Keywords:
Convergence of sectorial forms and of semigroups of operators, diffusion processes, boundary and transmission conditions, Freidlin–Wentzell averaging principle, singular perturbations, signaling pathways, kinase activity, intracellular calcium dynamics, neurotransmitters

3.Varga A., Ehrenreiter K., Aschenbrenner B., Kocieniewski P., Kochańczyk M., Lipniacki T., Baccarini M., RAF1/BRAF dimerization integrates the signal from RAS to ERK and ROKα, Science Signaling, ISSN: 1945-0877, DOI: 10.1126/scisignal.aai8482, Vol.10, No.469, pp.eaai8482-1-11, 2017
Varga A., Ehrenreiter K., Aschenbrenner B., Kocieniewski P., Kochańczyk M., Lipniacki T., Baccarini M., RAF1/BRAF dimerization integrates the signal from RAS to ERK and ROKα, Science Signaling, ISSN: 1945-0877, DOI: 10.1126/scisignal.aai8482, Vol.10, No.469, pp.eaai8482-1-11, 2017

Abstract:
Downstream of growth factor receptors and of the guanine triphosphatase (GTPase) RAS, heterodimers of the serine/threonine kinases BRAF and RAF1 are critical upstream kinases and activators of the mitogen-activated protein kinase (MAPK) module containing the mitogen-activated and extracellular signal–regulated kinase kinase (MEK) and their targets, the extracellular signal–regulated kinase (ERK) family. Either direct or scaffold protein–mediated interactions among the components of the ERK module (the MAPKKKs BRAF and RAF1, MEK, and ERK) facilitate signal transmission. RAF1 also has essential functions in the control of tumorigenesis and migration that are mediated through its interaction with the kinase ROKα, an effector of the GTPase RHO and regulator of cytoskeletal rearrangements. We combined mutational and kinetic analysis with mathematical modeling to show that the interaction of RAF1 with ROKα is coordinated with the role of RAF1 in the ERK pathway. We found that the phosphorylated form of RAF1 that interacted with and inhibited ROKα was generated during the interaction of RAF1 with the ERK module. This mechanism adds plasticity to the ERK pathway, enabling signal diversification at the level of both ERK and RAF. Furthermore, by connecting ERK activation with the regulation of ROKα and cytoskeletal rearrangements by RAF1, this mechanism has the potential to precisely coordinate the proper timing of proliferation with changes in cell shape, adhesion, or motility.

Keywords:
MAPK pathway, kinase RAF, protein isoform, phosphorylation, mathematical modeling

4.Labra C., Rojek J., Oñate E., Discrete/Finite Element Modelling of Rock Cutting with a TBM Disc Cutter, Rock Mechanics and Rock Engineering, ISSN: 0723-2632, DOI: 10.1007/s00603-016-1133-7, Vol.50, pp.621-635, 2017
Labra C., Rojek J., Oñate E., Discrete/Finite Element Modelling of Rock Cutting with a TBM Disc Cutter, Rock Mechanics and Rock Engineering, ISSN: 0723-2632, DOI: 10.1007/s00603-016-1133-7, Vol.50, pp.621-635, 2017

Abstract:
This paper presents advanced computer simulation of rock cutting process typical for excavation works in civil engineering. Theoretical formulation of the hybrid discrete/finite element model has been presented. The discrete and finite element methods have been used in different subdomains of a rock sample according to expected material behaviour, the part which is fractured and damaged during cutting is discretized with the discrete elements while the other part is treated as a continuous body and it is modelled using the finite element method. In this way, an optimum model is created, enabling a proper representation of the physical phenomena during cutting and efficient numerical computation. The model has been applied to simulation of the laboratory test of rock cutting with a single TBM (tunnel boring machine) disc cutter. The micromechanical parameters have been determined using the dimensionless relationships between micro- and macroscopic parameters. A number of numerical simulations of the LCM test in the unrelieved and relieved cutting modes have been performed. Numerical results have been compared with available data from in-situ measurements in a real TBM as well as with the theoretical predictions showing quite a good agreement. The numerical model has provided a new insight into the cutting mechanism enabling us to investigate the stress and pressure distribution at the tool–rock interaction. Sensitivity analysis of rock cutting performed for different parameters including disc geometry, cutting velocity, disc penetration and spacing has shown that the presented numerical model is a suitable tool for the design and optimization of rock cutting process.

Keywords:
Rock cutting, Disc cutters, TBM, Numerical model, Discrete/finite element method, Simulation

5.Banach Z., Larecki W., Entropy-based mixed three-moment description of fermionic radiation transport in slab and spherical geometries, Kinetic and Related Models, ISSN: 1937-5093, DOI: 10.3934/krm.2017035, Vol.10, No.4, pp.879-900, 2017
Banach Z., Larecki W., Entropy-based mixed three-moment description of fermionic radiation transport in slab and spherical geometries, Kinetic and Related Models, ISSN: 1937-5093, DOI: 10.3934/krm.2017035, Vol.10, No.4, pp.879-900, 2017

Abstract:
The mixed three-moment hydrodynamic description of fermionic radiation transport based on the Boltzmann entropy optimization procedure is considered for the case of one-dimensional flows. The conditions for realizability of the mixed three moments chosen as the energy density and two partial heat fluxes are established. The domain of admissible values of those moments is determined and the existence of the solution to the optimization problem is proved. Here, the standard approaches related to either the truncated Hausdorff or Markov moment problems do not apply because the non-negative fermionic distribution function, denoted f, must satisfy the inequality f _ 1 and, at the same time, there are three different intervals of integration in the integral formulae defining the mixed moments. The hydrodynamic equations are obtained in the form of the symmetric hyperbolic system for the Lagrange multipliers of the optimization problem with constraints. The potentials generating this system are explicitly determined as dilogarithm and trilogarithm functions of the Lagrange multipliers. The invertibility of the relation between moments and Lagrange multipliers is proved. However, the inverse relations cannot be determined in a closed analytic form. Using the H-theorem for the radiative transfer equation, it is shown that the derived system of hydrodynamic radiation equations has as a consequence an additional balance law with a non-negative source term.

Keywords:
Fermionic radiation, mixed moments, moment realizability domain, entropy optimization problem, symmetric hyperbolicity

6.Moallemi S., Pietruszczak S., Mróz Z., Deterministic size effect in concrete structures with account for chemo-mechanical loading, COMPUTERS AND STRUCTURES, ISSN: 0045-7949, DOI: 10.1016/j.compstruc.2016.10.003, Vol.182, pp.74-86, 2017
Moallemi S., Pietruszczak S., Mróz Z., Deterministic size effect in concrete structures with account for chemo-mechanical loading, COMPUTERS AND STRUCTURES, ISSN: 0045-7949, DOI: 10.1016/j.compstruc.2016.10.003, Vol.182, pp.74-86, 2017

Abstract:
The work presented here is focused on examining the size effect in concrete structures subjected to different loading conditions, which include a chemo-mechanical interaction. The study involves extensive three dimensional finite element simulations, which incorporate a constitutive law with embedded discontinuity for tracing the propagation of damage pattern. The analysis deals with various mechanical scenarios that incorporate both a cohesive and frictional damage mechanism, as well as the effects of degradation of concrete triggered by continuing alkali-silica reaction (ASR). In the latter case, a chemo-plasticity framework is employed. The first set of simulations provides a deterministic assessment of the size effect in a series of three-point bending tests as well as compression tests. For continuing ASR, it is demonstrated that, by increasing the size of the structure, a spontaneous failure may occur under a sustained load. The numerical examples given here clearly show that the size effect is associated with propagation of localized damage whose rate is controlled by a suitably defined ‘characteristic length’.

Keywords:
Size effect, Alkali-silica reaction, 3D crack propagation, Embedded discontinuity model, Bifurcation analysis

7.Bollero A., Rial J., Villanueva M., Golasiński K.M., Seoane A., Almunia J., Altimira R., Recycling of Strontium Ferrite Waste in a Permanent Magnet Manufacturing Plant, ACS Sustainable Chemistry & Engineering, ISSN: 2168-0485, DOI: 10.1021/acssuschemeng.6b03053, Vol.5, No.4, pp.3243-3249, 2017
Bollero A., Rial J., Villanueva M., Golasiński K.M., Seoane A., Almunia J., Altimira R., Recycling of Strontium Ferrite Waste in a Permanent Magnet Manufacturing Plant, ACS Sustainable Chemistry & Engineering, ISSN: 2168-0485, DOI: 10.1021/acssuschemeng.6b03053, Vol.5, No.4, pp.3243-3249, 2017

Abstract:
Residues resulting from the manufacture of strontium ferrite magnets have been recycled for further use in magnet fabrication instead of disposal as waste. The quality of the recycled ferrite powder has been tested and compared to that of the new starting ferrite material. The magnetic properties of the recycled powder not only match those of the starting material acquired by the company for the production of magnets but exceed them. A coercivity value 3.5 times larger than that of the new starting ferrite powder, accompanied by a 25% increase in remanence, makes this material a new and improved ferrite product to re-enter the production chain in the factory with an extended applications range. This improvement is proven to be due to tuning of the morphology and microstructure through processing and subsequent heat treatment. The use of processing conditions in the same range as those typically used in the preparation of ferrite powders and magnets, in combination with the superior magnetic quality of the resulting powders, makes this method a suitable path to guarantee sustainability and an efficient use of resources in permanent magnet companies.

Keywords:
Ferrites, Permanent magnets; Recovery; Recycling; Sustainability

8.Hoffman J., Chrzanowska J., Mościcki T., Radziejewska J., Stobinski L., Szymański Z., Plasma generated during underwater pulsed laser processing, APPLIED SURFACE SCIENCE, ISSN: 0169-4332, DOI: 10.1016/j.apsusc.2017.01.185, pp.1-6, 2017
Hoffman J., Chrzanowska J., Mościcki T., Radziejewska J., Stobinski L., Szymański Z., Plasma generated during underwater pulsed laser processing, APPLIED SURFACE SCIENCE, ISSN: 0169-4332, DOI: 10.1016/j.apsusc.2017.01.185, pp.1-6, 2017

Abstract:
The plasma induced during underwater pulsed laser ablation of graphite is studied both experimentally and theoretically. The results of the experiment show that the maximum plasma temperature of 25000 K is reached 20 ns from the beginning of the laser pulse and decreases to 6500 K after 1000 ns. The observed OH absorption band shows that the plasma plume is surrounded by the thin layer of dissociated water vapour at a temperature around 5500 K. The hydrodynamic model applied shows similar maximum plasma temperature at delay times between 14 ns and 30 ns. The calculations show also that already at 14th ns, the plasma electron density reaches 0.97·1027 m−3, which is the critical density for 1064 nm radiation. At the same time the plasma pressure is 2 GPa, which is consisted with earlier measurements of the peak pressure exerted on a target in similar conditions.

Keywords:
Underwater laser processing, Pulsed laser ablation in liquid, Laser induced plasma, Numerical modelling

9.Pakdel A., Witecka A., Rydzek G., Shri D.N.A., A comprehensive microstructural analysis of Al–WC micro- and nano-composites prepared by spark plasma sintering, MATERIALS AND DESIGN, ISSN: 0261-3069, DOI: 10.1016/j.matdes.2017.01.064, Vol.119, pp.225-234, 2017
Pakdel A., Witecka A., Rydzek G., Shri D.N.A., A comprehensive microstructural analysis of Al–WC micro- and nano-composites prepared by spark plasma sintering, MATERIALS AND DESIGN, ISSN: 0261-3069, DOI: 10.1016/j.matdes.2017.01.064, Vol.119, pp.225-234, 2017

Abstract:
There have been many investigations on metal matrix microcomposites produced by conventional casting routes; however, in the past decade, the focus has shifted more toward nanocomposites produced via solid state routes. To have a realistic view of performance prediction and optimum design of such composites, in this work Al matrix composites (AMCs) reinforced with WC microparticles, nanoparticles, and bimodal micro-/nano-particles were prepared by spark plasma sintering. The effects of particle size and concentration, and process variables (i.e. sintering temperature, duration, and pressure) on the evolution of microstructure, density and hardness of the composites were studied comprehensively. Full densification of AMCs with high particle concentration was problematic because of ceramic cluster formations in the microstructure. This effect was more emphasized in AMCs containing nanoparticles. AMCs with microparticles were more easily densified, but their hardness benefits were inferior. On the other hand, the mixture of micro- and nano-particles in Al-WC bimodal composites led to better matrix reinforcement integrity and an overall improvement in the microstructural properties. Finally, increasing the sintering temperature improved the microstructural features and hardness of the composites (more enhanced in high wt.% samples), but sintering duration and pressure did not have a big impact on the composite properties.

Keywords:
Composite, Nanoparticle, Microparticle, Powder metallurgy, SPS, Microstructure

10.Bajer C.I., Pisarski D., Szmidt T., Dyniewicz B., Intelligent damping layer under a plate subjected to a pair of masses moving in opposite directions, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2017.01.046, pp.1-15, 2017
Bajer C.I., Pisarski D., Szmidt T., Dyniewicz B., Intelligent damping layer under a plate subjected to a pair of masses moving in opposite directions, JOURNAL OF SOUND AND VIBRATION, ISSN: 0022-460X, DOI: 10.1016/j.jsv.2017.01.046, pp.1-15, 2017

Abstract:
Reducing displacements of a plate vibrating under a pair of masses traveling in opposite directions can be improved by adding a smart subsoil instead of a classical damping layer. We propose a material that acts according to the instantaneous state of the plate, i.e., its displacements and velocity. Such an intelligent damping layer reduces vertical displacements even by 40%–60%, depending on the type of load and the assumed objective function. Existing materials enable the application of the proposed layer in a semi-active mode. The passive mode can be applied with materials exhibiting direction-dependent viscosity.

Keywords:
Plate vibration, Moving load, Intelligent damping layer, Semi-active damping

11.Petryk H., Stupkiewicz S., Kucharski S., On direct estimation of hardening exponent in crystal plasticity from the spherical indentation test, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, ISSN: 0020-7683, DOI: 10.1016/j.ijsolstr.2016.09.025, Vol.112, pp.209-221, 2017
Petryk H., Stupkiewicz S., Kucharski S., On direct estimation of hardening exponent in crystal plasticity from the spherical indentation test, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, ISSN: 0020-7683, DOI: 10.1016/j.ijsolstr.2016.09.025, Vol.112, pp.209-221, 2017

Abstract:
A novel methodology is proposed for estimating the strain hardening exponent of a metal single crystal directly from the spherical indentation test, without the need of solving the relevant inverse problem. The attention is focused on anisotropic piling-up and sinking-in that occur simultaneously in different directions, in contrast to the standard case of axial symmetry for isotropic materials. To correlate surface topography parameters with the value of material hardening exponent, a finite-element study of spherical indentation has been performed within a selected penetration depth range using a finite-strain crystal plasticity model. It is shown how the power-law hardening exponent can be estimated from the measured pile-up/sink-in pattern around the residual impression after indentation in a (001)-oriented fcc single crystal of a small initial yield stress. For this purpose, a new parameter of surface topography is defined as the normalized material volume displaced around the nominal contact zone, calculated by integration of the local residual height (positive or negative) over a centered circular ring. That indicator can be easily determined from an experimental topography map available in a digital form. Comparison is made with the estimates based on measurements of the contact area and the slope of the load–penetration depth curve in logarithmic coordinates. The proposed methodology is extended to estimation of the hardening exponent simultaneously with the initial yield stress when the latter is not negligible. Experimental verification for a Cu single crystal leads to promising conclusions.

Keywords:
Metal crystal, Elastoplasticity, Finite deformation, Strain hardening, Experimental identification

12.Průša V., Řehoř M., Tůma K., Colombeau algebra as a mathematical tool for investigating step load and step deformation of systems of nonlinear springs and dashpots, ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND PHYSIK, ISSN: 0044-2275, DOI: 10.1007/s00033-017-0768-x, Vol.68, No.24, pp.1-13, 2017
Průša V., Řehoř M., Tůma K., Colombeau algebra as a mathematical tool for investigating step load and step deformation of systems of nonlinear springs and dashpots, ZEITSCHRIFT FUR ANGEWANDTE MATHEMATIK UND PHYSIK, ISSN: 0044-2275, DOI: 10.1007/s00033-017-0768-x, Vol.68, No.24, pp.1-13, 2017

Abstract:
The response of mechanical systems composed of springs and dashpots to a step input is of eminent interest in the applications. If the system is formed by linear elements, then its response is governed by a system of linear ordinary differential equations. In the linear case, the mathematical method of choice for the analysis of the response is the classical theory of distributions. However, if the system contains nonlinear elements, then the classical theory of distributions is of no use, since it is strictly limited to the linear setting. Consequently, a question arises whether it is even possible or reasonable to study the response of nonlinear systems to step inputs. The answer is positive. A mathematical theory that can handle the challenge is the so-called Colombeau algebra. Building on the abstract result by Průša and Rajagopal (Int J Non-Linear Mech 81:207–221, 2016), we show how to use the theory in the analysis of response of nonlinear spring–dashpot and spring–dashpot–mass systems.

Keywords:
Mechanical systems, Nonlinear ordinary differential equations, Jump discontinuities, Colombeau algebra

13.Korol E., Tejchman J., Mróz Z., Experimental and numerical assessment of size effect in geometrically similar slender concrete beams with basalt reinforcement, ENGINEERING STRUCTURES, ISSN: 0141-0296, DOI: 10.1016/j.engstruct.2017.03.011, Vol.141, pp.272-291, 2017
Korol E., Tejchman J., Mróz Z., Experimental and numerical assessment of size effect in geometrically similar slender concrete beams with basalt reinforcement, ENGINEERING STRUCTURES, ISSN: 0141-0296, DOI: 10.1016/j.engstruct.2017.03.011, Vol.141, pp.272-291, 2017

Abstract:
The paper presents a comprehensive experimental and numerical analysis of slender rectangular reinforced concrete beams with longitudinal BFRP bars without shear reinforcement subjected to 3-point bending. The experiments included 4 different beams which were similar in two directions. The main research objective was to investigate the size effect on the nominal shear strength of beams. The detailed experimental analysis of beam strength, failure mode and cracking evolution was presented and compared with previous test results on beams reinforced by ordinary steel bears. The experiments with BFRP bars were numerically reproduced using the 2D finite element method based on a coupled elastic-plastic-damage formulation. In order to describe strain localization in concrete, a non-local constitutive model was applied with account for a characteristic length of micro-structure developing in the softening regime. The numerical results were in satisfactory agreement with the experimental data. Advantages and disadvantages of BFRP reinforcement in concrete beams were next outlined.

Keywords:
BFRP bars, Concrete, Elastic-plastic-damage, Non-local softening, Shear, Size effect, Strain localization

14.Urbanek O., Sajkiewicz P., Pierini F., Czerkies M., Kołbuk D., Structure and properties of polycaprolactone/chitosan nonwovens tailored by solvent systems, Biomedical Materials, ISSN: 1748-6041, DOI: 10.1088/1748-605X/aa5647, Vol.12, No.1, pp.015020-1-12, 2017
Urbanek O., Sajkiewicz P., Pierini F., Czerkies M., Kołbuk D., Structure and properties of polycaprolactone/chitosan nonwovens tailored by solvent systems, Biomedical Materials, ISSN: 1748-6041, DOI: 10.1088/1748-605X/aa5647, Vol.12, No.1, pp.015020-1-12, 2017

Abstract:
Electrospinning of chitosan blends is a reasonable idea to prepare fibre mats for biomedical applications. Synthetic and natural components provide, for example, appropriate mechanical strength and biocompatibility, respectively. However, solvent characteristics and the polyelectrolyte nature of chitosan influence the spinnability of these blends. In order to compare the effect of solvent on polycaprolactone/chitosan fibres, two types of the most commonly used solvent systems were chosen, namely 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) and acetic acid (AA)/formic acid (FA). Results obtained by various experimental methods clearly indicated the effect of the solvent system on the structure and properties of electrospun polycaprolactone/chitosan fibres. Viscosity measurements confirmed different polymer–solvent interactions. Various molecular interactions resulting in different macromolecular conformations of chitosan influenced its spinnability and properties. HFIP enabled fibres to be obtained whose average diameter was less than 250 nm while maintaining the brittle and hydrophilic character of the nonwoven, typical for the chitosan component. Spectroscopy studies revealed the formation of chitosan salts in the case of the AA/FA solvent system. Chitosan salts visibly influenced the structure and properties of the prepared fibre mats. The use of AA/FA caused a reduction of Young's modulus and wettability of the proposed blends. It was confirmed that wettability, mechanical properties and the antibacterial effect of polycaprolactone/chitosan fibres may be tailored by selecting an appropriate solvent system. The MTT cell proliferation assay revealed an increase of cytotoxicity to mouse fibroblasts in the case of 25% w/w of chitosan in electrospun nonwovens.

Keywords:
chitosan, electrospinning, PCL/chitosan fibres, solvent system, chitosan salts

15.Meissner M., Acoustics of small rectangular rooms: Analytical and numerical determination of reverberation parameters, APPLIED ACOUSTICS, ISSN: 0003-682X, DOI: 10.1016/j.apacoust.2017.01.020, Vol.120, pp.111-119, 2017
Meissner M., Acoustics of small rectangular rooms: Analytical and numerical determination of reverberation parameters, APPLIED ACOUSTICS, ISSN: 0003-682X, DOI: 10.1016/j.apacoust.2017.01.020, Vol.120, pp.111-119, 2017

Abstract:
A small rectangular room with hard walls has a number of acoustic flaws and the most serious drawback is a long reverberation time. A technique commonly used for improving room acoustics consists in increasing a sound absorption on a ceiling. In this study, the impact of acoustical treatment of a ceiling on reverberant properties of a small rectangular room was examined. Changes in the modal reverberation time due to this treatment were investigated by the analytical method. As was evidenced by calculations, the initial increase in a sound absorption on a ceiling causes a substantial decrease in the modal reverberation time and a treatment efficiency decreases with a further absorption increase. It was found also that for a room with hard walls statistical and wave theories give the same result as the modal reverberation time for oblique modes and the Sabine’s reverberation time are identical. A more detailed information about reverberant properties of a room was provided by the numerical method employing a backward integration of the squared room impulse response. Using this method, global and local reverberation parameters were determined. Numerical simulations discovered a quite good agreement between global and local reverberation time and high differences between global and local early decay time resulting from a nonlinear shape of a decay curve. Therefore, one can conclude that the global decay times characterize reasonably well a reverberation process in a late stage of sound decay but they are not correctly describe this process in an initial stage.

Keywords:
Small room acoustics, Modal expansion method, Room impulse response, Reverberation time, Early decay time

16.Jarząbek D.M., Gwiazda M., Dera W., The Influence of Alkali Metal Chloride Treatments on the Wear Resistance of Silicon Surfaces for Possible Use in MEMS, TRIBOLOGY TRANSACTIONS, ISSN: 1040-2004, DOI: 10.1080/10402004.2017.1296211, pp.1-7, 2017
Jarząbek D.M., Gwiazda M., Dera W., The Influence of Alkali Metal Chloride Treatments on the Wear Resistance of Silicon Surfaces for Possible Use in MEMS, TRIBOLOGY TRANSACTIONS, ISSN: 1040-2004, DOI: 10.1080/10402004.2017.1296211, pp.1-7, 2017

Abstract:
The wear of contacting silicon surfaces in microelectromechanical systems (MEMS) has been a longstanding concern. To address this issue, the effects of immersing silicon surfaces into alkali metal chloride solutions (LiCl, NaCl, CsCl) on their sliding friction and wear were investigated. A custom-built reciprocating tribometer was used with a sapphire ball as the counterbody. Results indicated that the friction coefficient between the silicon surface (p-doped, orientation (100)) and a sapphire ball can be reduced by up to 30% by treating the silicon surfaces in aqueous salt solutions (concentration 1 mol/L, exposure for 24 h). These modified surfaces also have higher wear resistance and a significant change in wettability. After immersion, the contact angle between the silicon surface and water was reduced by approximately 50%. These results may lead to new, simple, and inexpensive methods to increase the wear resistance of silicon surfaces for use in MEMs devices.

Keywords:
silicon surface, wear, friction, alkali metal chlorides

17.Pisarski D., Myśliński A., Online adaptive algorithm for optimal control of structures subjected to travelling loads, OPTIMAL CONTROL APPLICATIONS & METHODS, ISSN: 0143-2087, DOI: 10.1002/oca.2321, pp.1-19, 2017
Pisarski D., Myśliński A., Online adaptive algorithm for optimal control of structures subjected to travelling loads, OPTIMAL CONTROL APPLICATIONS & METHODS, ISSN: 0143-2087, DOI: 10.1002/oca.2321, pp.1-19, 2017

Abstract:
The problem of adaptive optimal semiactive control of a structure subjected to a moving load is studied. The control is realised by a change of damping of the structure’s supports. The results presented in the previous works of the authors demonstrate that switched optimal controls can be very efficient at reducing the vibration levels of the structure. On the other hand, these controls exhibit a high sensitivity to changes of the speed of the travelling load. The aim of this paper is to develop an algorithm that enables real-time adaptation of the optimal controls according to
both the measured speed of the travelling load and the estimated state of the structure. The control objective is to provide smooth passage for the vehicles and reduce the material stresses on the carrying structures. The designed adaptive algorithm uses reference optimal controls computed for constant speeds and a set of functions describing the sensitivity of the system dynamics to the measured parameters. The convergence of the algorithm, as well as aspects of its implementation, is studied. The performance of the proposed method is validated by means of numerical simulations conducted for different travelling speed scenarios. In the assumed objective
functional, the proposed adaptive controller can outperform the reference optimal solutions by over 50%. The practicality of the proposed method should attract the attention of practising engineers.

Keywords:
Adaptive control, Moving load, Online optimal control, Sensitivity analysis, Structural vibration control

18.Secomski W., Bilmin K., Kujawska T., Nowicki A., Grieb P., Lewin P.A., In vitro ultrasound experiments: Standing wave and multiple reflections influence on the outcome, Ultrasonics, ISSN: 0041-624X, DOI: 10.1016/j.ultras.2017.02.008, Vol.77, pp.203-213, 2017
Secomski W., Bilmin K., Kujawska T., Nowicki A., Grieb P., Lewin P.A., In vitro ultrasound experiments: Standing wave and multiple reflections influence on the outcome, Ultrasonics, ISSN: 0041-624X, DOI: 10.1016/j.ultras.2017.02.008, Vol.77, pp.203-213, 2017

Abstract:
The purpose of this work was to determine the influence of standing waves and possible multiple reflections under the conditions often encountered in examining the effects of ultrasound exposure on the cell cultures in vitro. More specifically, the goal was to quantitatively ascertain the influence of ultrasound exposure under free field (FF) and standing waves (SW) and multiple reflections (MR) conditions (SWMR) on the biological endpoint (50% cell necrosis). Such information would help in designing the experiments, in which the geometry of the container with biological tissue may prevent FF conditions to be established and in which the ultrasound generated temperature elevation is undesirable. This goal was accomplished by performing systematic, side-by-side experiments in vitro with C6 rat glioma cancer cells using 12 well and 96 well plates. It was determined that to obtain 50% of cell viability using the 12 well plates, the spatial average, temporal average (ISATA) intensities of 0.32 W/cm2 and 5.89 W/cm2 were needed under SWMR and FF conditions, respectively. For 96 well plates the results were 0.80 W/cm2 and 2.86 W/cm2 respectively. The corresponding, hydrophone measured pRMS maximum pressure amplitude values, were 0.71 MPa, 0.75 MPa, 0.75 MPa and 0.73 MPa, respectively. These results suggest that pRMS pressure amplitude was independent of the measurement set-up geometry and hence could be used to predict the cells’ mortality threshold under any in vitro experimental conditions or even as a starting point for (pre-clinical) in vivo tests. The described procedure of the hydrophone measurements of the pRMS maximum pressure amplitude at the k/2 distance (here 0.75 mm) from the cell’s level at the bottom of the dish or plate provides the guideline allowing the difference between the FF and SWMR conditions to be determined in any experimental setup. The outcome of the measurements also indicates that SWMR exposure might be useful at any ultrasound assisted therapy experiments as it permits to reduce thermal effects. Although the results presented are valid for the experimental conditions used in this study they can be generalized. The analysis developed provides methodology facilitating independent laboratories to determine their specific ultrasound exposure parameters for a given biological end-point under standing waves and multiple reflections conditions. The analysis also permits verification of the outcome of the experiments mimicking pre- and clinical environment between different, unaffiliated teams of researchers.

Keywords:
Standing wave, Ultrasound pressure, Ultrasound intensity, C6 glioma, Anticancer therapy, Sonodynamic therapy, Ultrasound bio-effects

19.Martincuks A., Andryka K., Küster A., Schmitz-Van de Leur H., Komorowski M., Müller-Newen G., Nuclear translocation of STAT3 and NF-κB are independent of each other but NF-κB supports expression and activation of STAT3, Cellular Signalling, ISSN: 0898-6568, DOI: 10.1016/j.cellsig.2017.01.006, Vol.32, pp.36-47, 2017
Martincuks A., Andryka K., Küster A., Schmitz-Van de Leur H., Komorowski M., Müller-Newen G., Nuclear translocation of STAT3 and NF-κB are independent of each other but NF-κB supports expression and activation of STAT3, Cellular Signalling, ISSN: 0898-6568, DOI: 10.1016/j.cellsig.2017.01.006, Vol.32, pp.36-47, 2017

Abstract:
NF-κB and STAT3 are essential transcription factors in immunity and act at the interface of the transition from chronic inflammation to cancer. Different functional crosstalks between NF-κB and STAT3 have been recently described arguing for a direct interaction of both proteins. During a systematic analysis of NF-κB/STAT3 crosstalk we observed that appearance of the subcellular distribution of NF-κB and STAT3 in immunofluorescence heavily depends on the fixation procedure. Therefore, we established an optimized fixation protocol for the reliable simultaneous analysis of the subcellular distributions of both transcription factors. Using this protocol we found that cytokine-induced nuclear accumulation of NF-κB or STAT3 did not alter the subcellular distribution of the other transcription factor. Both knockout and overexpression of STAT3 does not have any major effect on canonical TNFα-NF-κB signalling in MEF or HeLa cells. Similarly, knockout of p65 did not alter nuclear accumulation of STAT3 in response to IL-6. However, p65 expression correlates with elevated total cellular levels of STAT3 and STAT1 and supports activation of these transcription factors. Our findings in MEF cells argue against a direct physical interaction of free cellular NF-κB and STAT3 but point to more intricate functional interactions.

Keywords:
STAT3, NF-κB, Signal transduction, Nuclear translocation, Crosstalk

20.Golasiński K.M., Pieczyska E.A., Staszczak M., Maj M., Furuta T., Kuramoto S., Infrared thermography applied for experimental investigation of thermomechanical couplings in Gum Metal, Quantitative InfraRed Thermography Journal, ISSN: 1768-6733, DOI: 10.1080/17686733.2017.1284295, pp.1-8, 2017
Golasiński K.M., Pieczyska E.A., Staszczak M., Maj M., Furuta T., Kuramoto S., Infrared thermography applied for experimental investigation of thermomechanical couplings in Gum Metal, Quantitative InfraRed Thermography Journal, ISSN: 1768-6733, DOI: 10.1080/17686733.2017.1284295, pp.1-8, 2017

Abstract:
Results of initial investigation of thermomechanical couplings in innovative β-Ti alloy called Gum Metal subjected to tension are presented. The experimental set-up, consisting of testing machine and infrared camera, enabled to obtain stress–strain curves with high accuracy and correlate them to estimated temperature changes of the specimen during the deformation process. Both ultra-low elastic modulus and high strength of Gum Metal were confirmed. The infrared measurements determined average and maximal temperature changes accompanying the alloy deformation process, allowed to estimate thermoelastic effect, which is related to the alloy yield point. The temperature distributions on the specimen surface served to analyse strain localization effects leading to the necking and rupture.

Keywords:
Gum Metal, thermomechanical coupling, nonlinear elasticity, yield point, infrared camera

21.Ignaczak J., Domański W., An asymptotic approach to one-dimensional model of nonlinear thermoelasticity at low temperatures and small strains, JOURNAL OF THERMAL STRESSES, ISSN: 0149-5739, DOI: 10.1080/01495739.2016.1276872, pp.1-10, 2017
Ignaczak J., Domański W., An asymptotic approach to one-dimensional model of nonlinear thermoelasticity at low temperatures and small strains, JOURNAL OF THERMAL STRESSES, ISSN: 0149-5739, DOI: 10.1080/01495739.2016.1276872, pp.1-10, 2017

Abstract:
A one-dimensional nonlinear homogeneous isotropic thermoelastic model with an elastic heat flow at low temperatures and small strains is analyzed using the method of weakly nonlinear asymptotics. For such a model, both the free energy and the heat flux vector depend not only on the absolute temperature and strain tensor but also on an elastic heat flow that satisfies an evolution equation. The governing equations are reduced to a matrix partial differential equations, and the associated Cauchy problem with a weakly perturbed initial condition is solved. The solution is given in the form of a power series with respect to a small parameter, the coefficients of which are functions of a slow variable that satisfy a system of nonlinear second-order ordinary differential transport equations. A family of closed-form solutions to the transport equations is obtained. For a particular Cauchy problem in which the initial data are generated by a closed-form solution to the transport equations, the asymptotic solution in the form of a sum of four traveling thermoelastic waves admitting blow-up amplitudes is presented.

Keywords:
Low temperatures, nonlinear thermoelasticity, small strains, weakly nonlinear asymptotics

22.Sadowski P., Kowalczyk-Gajewska K., Stupkiewicz S., Response discontinuities in the solution of the incremental Mori–Tanaka scheme for elasto-plastic composites, ARCHIVES OF MECHANICS, ISSN: 0373-2029, Vol.69, No.1, pp.3-27, 2017
Sadowski P., Kowalczyk-Gajewska K., Stupkiewicz S., Response discontinuities in the solution of the incremental Mori–Tanaka scheme for elasto-plastic composites, ARCHIVES OF MECHANICS, ISSN: 0373-2029, Vol.69, No.1, pp.3-27, 2017

Abstract:
The incremental Mori–Tanaka model of elasto-plastic composites is discussed, and the corresponding finite-step formulation is shown to lead to discontinuities in the overall response at the instant of elastic-to-plastic transition in the matrix. Specifically, two situations may be encountered: the incremental equations may have two solutions or no solution. In the former situation, switching between the two solutions is associated with a jump in the overall stress. Response discontinuities are studied in detail for a special case of proportional deviatoric loading. The discontinuities constitute an undesirable feature of the incremental Mori–Tanaka scheme that apparently has not been discussed in the literature so far. Remedies to the related problems are briefly discussed.

Keywords:
mean-field homogenization, Mori–Tanaka method, incremental scheme, composite materials, elasto-plasticity

23.Chmielewski M., Pietrzak K., Strojny-Nedza A., Kaszyca K., Zybala R., Bazarnik P., Lewandowska M., Nosewicz S., Microstructure and thermal properties of Cu-SiC composite materials depending on the sintering technique, SCIENCE OF SINTERING, ISSN: 0350-820X, DOI: 10.2298/SOS1701011C, Vol.49, pp.11-22, 2017
Chmielewski M., Pietrzak K., Strojny-Nedza A., Kaszyca K., Zybala R., Bazarnik P., Lewandowska M., Nosewicz S., Microstructure and thermal properties of Cu-SiC composite materials depending on the sintering technique, SCIENCE OF SINTERING, ISSN: 0350-820X, DOI: 10.2298/SOS1701011C, Vol.49, pp.11-22, 2017

Abstract:
The presented paper investigates the relationship between the microstructure and thermal properties of copper–silicon carbide composites obtained through hot pressing (HP) and spark plasma sintering (SPS) techniques. The microstructural analysis showed a better densification in the case of composites sintered in the SPS process. TEM investigations revealed the presence of silicon in the area of metallic matrix in the region close to metal ceramic boundary. It is the product of silicon dissolving process in copper occurring at an
elevated temperature. The Cu-SiC interface is significantly defected in composites obtained through the hot pressing method, which has a major influence on the thermal conductivity of materials.

Keywords:
Metal matrix composites; Silicon carbide; Interface; Spark plasma sintering; Thermal conductivity.

24.Nowak Ł., Nowak K.M., Acoustic characterization of stethoscopes using auscultation sounds as test signals, JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, ISSN: 0001-4966, DOI: 10.1121/1.4978524, Vol.141, No.3, pp.1940-1946, 2017
Nowak Ł., Nowak K.M., Acoustic characterization of stethoscopes using auscultation sounds as test signals, JOURNAL OF THE ACOUSTICAL SOCIETY OF AMERICA, ISSN: 0001-4966, DOI: 10.1121/1.4978524, Vol.141, No.3, pp.1940-1946, 2017

Abstract:
The present study introduces a detailed methodology which can be applied for objective evaluation and comparison of the acoustic parameters of medical stethoscopes using auscultation sounds as test signals. The described approach allows taking into account the acoustic coupling between the body of an auscultated patient and the chest piece of a stethoscope. Information obtained from additional, synchronized electrocardiography measurements is used to extract short, specific fragments of recordings, defined as acoustic events. Analysis of the spectral characteristics of many acoustic events allows us to compare the acoustic properties of various stethoscopes and to estimate the measurement uncertainty. The exemplary results of the comparative evaluation of acoustic properties of bell and diaphragm-type chest pieces of a single stethoscope are presented. The results show that the frequency characteristics of the signals obtained using both examined chest pieces under the conditions of the performed examinations are very similar.

25.Chwojnowski A., Kruk A., Wojciechowski C., Łukowska E., Dulnik J., Sajkiewicz P., The dependence of the membrane structure on the non-woven forming the macropores in the 3D scaffolds preparation, Desalination and Water Treatment, ISSN: 1944-3994, DOI: 10.5004/dwt.2017.11394, Vol.64, pp.324-331, 2017
Chwojnowski A., Kruk A., Wojciechowski C., Łukowska E., Dulnik J., Sajkiewicz P., The dependence of the membrane structure on the non-woven forming the macropores in the 3D scaffolds preparation, Desalination and Water Treatment, ISSN: 1944-3994, DOI: 10.5004/dwt.2017.11394, Vol.64, pp.324-331, 2017

Abstract:
Three types of membrane structures with wide pores were compared in this study. One of the membranes was obtained from polyethersulfone using cellulose fibers as the macropore precursors. Two of the fibers were obtained from poly(L-lactide). As the macropore precursors olyvinylpyrrolidone (1.2 MDa) and pork gelatin non-woven were used, the influence of non-woven fibers on the structure of membranes was shown. Necessity of specific membrane structure application was explained. The hoice of polymers and co-polymers with a range of biodegradation times can determine the scaffold type suitable for the age of a patient.

Keywords:
Polysulfone membrane, Polyester membranes, Membrane structures, Biodegradable membranes, 3D scaffold

26.Kruka A., Gadomska-Gajadhur A., Ruśkowski P., Chwojnowski A., Dulnik J., Synoradzki L., Preparation of biodegradable semi-permeable membranes as 3D scaffolds for cell cultures, Desalination and Water Treatment, ISSN: 1944-3994, DOI: 10.5004/dwt.2017.11415, Vol.64, pp.317-323, 2017
Kruka A., Gadomska-Gajadhur A., Ruśkowski P., Chwojnowski A., Dulnik J., Synoradzki L., Preparation of biodegradable semi-permeable membranes as 3D scaffolds for cell cultures, Desalination and Water Treatment, ISSN: 1944-3994, DOI: 10.5004/dwt.2017.11415, Vol.64, pp.317-323, 2017

Abstract:
Results of the preparation of semi-permeable membranes made of biodegradable polymers membranes were presented. Among known polyesters, polylactide was selected for research. The membranes were obtained using wet phase inversion method. The influence of polyvinylpyrrolidone and polymeric nano-non-wovens as pores precursors on the structure of obtained membranes was analysed. It was shown, that utilisation of polymeric nano-non-wovens enabled preparation of semi-permeable membranes, which could be used as wide-pore 3D-type cellular scaffolds.

Keywords:
Biodegradable polymers membranes, Biodegradable polyesters, Porous three-dimensional scaffolds, Inversion phase method

27.Johansen K., Kimmel E., Postema M., Theory of Red Blood Cell Oscillations in an Ultrasound Field, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, DOI: 10.1515/aoa-2017-0013, Vol.42, No.1, pp.121-126, 2017
Johansen K., Kimmel E., Postema M., Theory of Red Blood Cell Oscillations in an Ultrasound Field, ARCHIVES OF ACOUSTICS, ISSN: 0137-5075, DOI: 10.1515/aoa-2017-0013, Vol.42, No.1, pp.121-126, 2017

Abstract:
Manipulating particles in the blood pool with noninvasive methods has been of great interest in therapeutic delivery. Recently, it was demonstrated experimentally that red blood cells can be forced to translate and accumulate in an ultrasound field. This acoustic response of the red blood cells has been attributed to sonophores, gas pockets that are formed under the influence of a sound field in the inner-membrane leaflets of biological cells. In this paper, we propose a simpler model: that of the compressible membrane. We derive the spatio-temporal cel dynamics for a spherically symmetric single cell, whilst regarding the cell bilayer membrane as two monolayer Newtonian viscous liquids, separated by a thin gas void.
When applying the newly-derived equations to a red blood cell, it is observed that the void inside the bilayer expands to multiples of its original thickness, even at clinically safe acoustic pressure amplitudes. For causing permanent cell rupture during expansion, however, the acoustic pressure amplitudes needed would have to surpass the inertial cavitation threshold by a factor 10. Given the incompressibility of the inner monolayer, the radial oscillations of a cell are governed by the same set of equations as those of a forced antibubble. Evidently, these equations must hold for liposomes under sonication, as well.

Keywords:
Spatio-temporal cell dynamics, Rayleigh-Plesset equation, spherical cell, red blood cell, erythrocyte

28.Jundziłł A., Pokrywczyńska M., Adamowicz J., Kowalczyk T., Nowacki M., Bodnar M., Marszałek A., Frontczak-Baniewicz M., Mikułowski G., Kloskowski T., Gatherwright J., Drewa T., Vascularization Potential of Electrospun Poly(L-Lactide-co-Caprolactone) Scaffold: The Impact for Tissue Engineering, Medical Science Monitor, ISSN: 1643-3750, DOI: 10.12659/MSM.899659, Vol.23, pp.1540-1551, 2017
Jundziłł A., Pokrywczyńska M., Adamowicz J., Kowalczyk T., Nowacki M., Bodnar M., Marszałek A., Frontczak-Baniewicz M., Mikułowski G., Kloskowski T., Gatherwright J., Drewa T., Vascularization Potential of Electrospun Poly(L-Lactide-co-Caprolactone) Scaffold: The Impact for Tissue Engineering, Medical Science Monitor, ISSN: 1643-3750, DOI: 10.12659/MSM.899659, Vol.23, pp.1540-1551, 2017

Abstract:
BACKGROUND:
Electrospun nanofibers have widespread putative applications in the field of regenerative medicine and tissue engineering. When compared to naturally occurring collagen matrices, electrospun nanofiber scaffolds have two distinct advantages: they do not induce a foreign body reaction and they are not at risk for biological contamination. However, the exact substrate, structure, and production methods have yet to be defined.
MATERIAL AND METHODS:
In the current study, tubular-shaped poly(L-lactide-co-caprolactone) (PLCL) constructs produced using electrospinning technology were evaluated for their potential application in the field of tissue regeneration in two separate anatomic locations: the skin and the abdomen. The constructs were designed to have an internal diameter of 3 mm and thickness of 200 μm. Using a rodent model, 20 PLCL tubular constructs were surgically implanted in the abdominal cavity and subcutaneously. The constructs were then evaluated histologically using electron microscopy at 6 weeks post-implantation.
RESULTS:
Histological evaluation and analysis using scanning electron microscopy showed that pure scaffolds by themselves were able to induce angiogenesis after implantation in the rat model. Vascularization was observed in both tested groups; however, better results were obtained after intraperitoneal implantation. Formation of more and larger vessels that migrated inside the scaffold was observed after implantation into the peritoneum. In this group no evidence of inflammation and better integration of scaffold with host tissue were noticed. Subcutaneous implantation resulted in more fibrotic reaction, and differences in cell morphology were also observed between the two tested groups.
CONCLUSIONS:
This study provides a standardized evaluation of a PLCL conduit structure in two different anatomic locations, demonstrating the excellent ability of the structure to achieve vascularization. Functional, histological, and mechanical data clearly indicate prospective clinical utilization of PLCL in critical size defect regeneration.

Keywords:
Polymers, Regenerative medicine, Tissue Engineering, Tissue Scaffolds, Urinary Diversion

29.Stapelmann K., Fiebrand M., Raguse M., Lackmann J.W., Postema M., Moeller R., Awakowicz P., A combined low-pressure hydrogen peroxide evaporation plus hydrogen plasma treatment method for sterilization – Part 1: Characterization of the condensation process and proof-of-concept, Plasma Process Polymers, ISSN: 1612-8869, DOI: 10.1002/ppap.201600198, Vol.14, pp.1-10, 2017
Stapelmann K., Fiebrand M., Raguse M., Lackmann J.W., Postema M., Moeller R., Awakowicz P., A combined low-pressure hydrogen peroxide evaporation plus hydrogen plasma treatment method for sterilization – Part 1: Characterization of the condensation process and proof-of-concept, Plasma Process Polymers, ISSN: 1612-8869, DOI: 10.1002/ppap.201600198, Vol.14, pp.1-10, 2017

Abstract:
A combined hydrogen peroxide evaporation and hydrogen low-pressure plasma treatment process for sterilization is introduced and investigated. The combination of hydrogen peroxide evaporation followed by hydrogen plasma treatment offers an advantage regarding sterilization in complex metal geometries or in sealed sterile bags, where plasma treatment alone faces challenges. Within this contribution, the droplet size and film homogeneity after condensation is investigated by optical diagnostics. Sterilization tests with common challenge organisms show the sterilization capabilities of the combined proces in a process challenge device mimicking the worst-casescenario for plasma treatment in a small metal box. Furthermore, sterilization in sealed sterile bags clearly demonstrates the advantage of the combined process, showing full spore inactivation solely for the combined process

Keywords:
bacterial spores, capacitively coupled, low-pressure discharges, sterilization

30.Rojek J., Nosewicz S., Maździarz M., Kowalczyk P., Wawrzyk K., Lumelskyj D., Modeling of a Sintering Process at Various Scales, Procedia Engineering, ISSN: 1877-7058, DOI: 10.1016/j.proeng.2017.02.210, Vol.177, pp.263-270, 2017
Rojek J., Nosewicz S., Maździarz M., Kowalczyk P., Wawrzyk K., Lumelskyj D., Modeling of a Sintering Process at Various Scales, Procedia Engineering, ISSN: 1877-7058, DOI: 10.1016/j.proeng.2017.02.210, Vol.177, pp.263-270, 2017

Abstract:
This paper presents modeling of a sintering process at various scales. Sintering is a powder metallurgy process consisting in consolidation of powder materials at elevated temperature but below the melting point. Sintering models at the atomistic, microscopic and macroscopic scales have been presented. Sintering is a process governed by diffusion therefore the atomistic modeling using the molecular dynamics has been focused on investigation of the diffusion process. The micromechanical model has been developed within the framework of the discrete element method. It allows us to consider microstructure and its changes during sintering. The macroscopic model is based on the continuum phenomenological approach. It combines elastic, thermal and viscous creep deformation. The methodology to determine macroscopic quantities: stress, strains and constitutive viscous properties from the discrete element simulations has been presented. Possibilities of the developed models have been demonstrated by applying them to simulation of sintering of the intermetallic NiAl powder. Own experimental results have been used to calibrate and validate numerical models.

Keywords:
sintering, modeling, discrete element method, diffusion, molecular dynamics, macroscopic model

31.Balevičius R., Mróz Z., Analytical Modelling of Combined Slip and Sliding Modes in Contact Interaction of Two Spherical Grains, Procedia Engineering, ISSN: 1877-7058, DOI: 10.1016/j.proeng.2017.02.020, Vol.172, pp.75-82, 2017
Balevičius R., Mróz Z., Analytical Modelling of Combined Slip and Sliding Modes in Contact Interaction of Two Spherical Grains, Procedia Engineering, ISSN: 1877-7058, DOI: 10.1016/j.proeng.2017.02.020, Vol.172, pp.75-82, 2017

Abstract:
The analytical modelling of coupled slip and sliding contact response of two elastic spheres is presented for the kinematically imposed sphere centre relative motion trajectories. One sphere is assumed as a fixed, the other translating along a specified trajectory and remaining in contact condition. Two cases are considered, the first is corresponding to a linear trajectory with the contact engagement in the combined slip-sliding mode, the other is related to the contact initiation by normal loading and subsequent motion along an inclined linear trajectory. The formulae and diagrams of the evolution of driving force along the sliding path in terms of main contact geometry parameters were analytically specified. Further extensions and applications of the analysis can be envisaged in the creation of the translation controlled apparatus for the measurements of friction and restitution coefficients for the pair of spherical grains.

Keywords:
soil, spherical grains contact interaction, slip and finite sliding modes, monotonic or reciprocal sliding, coefficients of friction and restitution

32.Nowak K.M., Nowak L.J., Experimental validation of the tuneable diaphragm effect in modern acoustic stethoscopes, Postgraduate Medical Journal, ISSN: 0032-5473, DOI: 10.1136/postgradmedj-2017-134810, pp.1-5, 2017
Nowak K.M., Nowak L.J., Experimental validation of the tuneable diaphragm effect in modern acoustic stethoscopes, Postgraduate Medical Journal, ISSN: 0032-5473, DOI: 10.1136/postgradmedj-2017-134810, pp.1-5, 2017

Abstract:
Purpose The force with which the diaphragm chestpiece of a stethoscope is pressed against the body of a patient during an auscultation examination introduces the initial stress and deformation to the diaphragm and the underlying tissues, thus altering the acoustic parameters of the sound transmission path. If the examination is performed by an experienced physician, he will intuitively adjust the amount of the force in order to achieve the optimal sound quality. However, in case of becoming increasingly popular autodiagnosis and telemedicine auscultation devices with no such feedback mechanisms, the question arises regarding the influence of the possible force mismatch on the parameters of the recorded signal. Design The present study describes the results of the experimental investigations on the relation between pressure applied to the chestpiece of a stethoscope and parameters of the transmitted bioacoustic signals. The experiments were carried out using various stethoscopes connected to a force measurement system, which allowed to maintain fixed pressure during auscultation examinations. The signals were recorded during examinations of different volunteers, at various auscultation sites. Results The obtained results reveal strong individual and auscultation-site variability. Conclusions It is concluded that the underlying tissue deformation is the primary factor that alters the parameters of the recorded signals.

33.Zawidzki M., Deployable Pipe-Z, Acta Astronautica, ISSN: 0094-5765, DOI: 10.1016/j.actaastro.2016.05.023, Vol.127, pp.20-30, 2016
Zawidzki M., Deployable Pipe-Z, Acta Astronautica, ISSN: 0094-5765, DOI: 10.1016/j.actaastro.2016.05.023, Vol.127, pp.20-30, 2016

Abstract:
This paper presents a concept of deployable Pipe-Z (dPZ): a modular structural system which takes advantage of the robustness of rigid-panel mechanism and allows to create free-form links which are also reconfigurable and deployable. The concept presented can be applied for building habitats and infrastructures for human exploration of oceans and outer space. dPZ structures can adapt to changing requirements e.g. mission objectives, crew condition and technological developments. Furthermore, such lightweight and adaptable structural concept can assist in sustainable exploration development. After brief introduction, the concept of Pipe-Z (PZ) is presented. Next, the reconfigurability of PZ is explained and illustrated with continuous and collision-free transition from a PZ forming a Trefoil knot to a Figure-eight knot. The following sections introduce, explain and illustrate the folding mechanism of a single foldable Pipe-Z module (fPZM) and entire dPZ structure. The latter is illustrated with asynchronous (delayed) unfolding of a relatively complex Unknot. Several applications of PZ are suggested, namely for underwater and deep-space and surface habitats, for permanent, but in particular, temporary or emergency passages. As an example, a scenario of a failure of one of the modules of the International Space Station is presented where a rigid structure of 40 fPZMs bypasses the “dead link”. A low-fidelity prototype of a 6-module octagonal dPZ is presented; several folding schemes including concentric toric rings are demonstrated. Practical issues of pressurization and packing are briefly discussed.

Keywords:
Ocean and space outpost; Banana-split; Deployable structure; Rigid-panel folding; Free-form

34.Zawidzki M., Optimization of Multi-branch Truss-Z based on Evolution Strategy, Advances in Engineering Software, ISSN: 0965-9978, DOI: 10.1016/j.advengsoft.2016.07.015, Vol.100, pp.113-125, 2016
Zawidzki M., Optimization of Multi-branch Truss-Z based on Evolution Strategy, Advances in Engineering Software, ISSN: 0965-9978, DOI: 10.1016/j.advengsoft.2016.07.015, Vol.100, pp.113-125, 2016

Abstract:
This paper concerns multi-branch Truss-Z networks (MTZ). A possible scenario for creating a “multi-branch bridge” linking 6 terminals of pedestrian and cycling communication is presented. This process is formulated as a constrained minimization problem. New, biology-inspired nomenclature for MTZ and encoding for MTZ are introduced. Several operations for MTZs are introduced and illustrated. The functionality of these operations is illustrated with transformation from a random MTZ to a “proper” 6-branch MTZ network. A population-based heuristic experiment is presented to demonstrate that the introduced operators allow us to create any desirable MTZ. A cost function for the considered scenario is introduced. The genetic operations are interpreted and visualized. A number of feasible MTZ layouts produced by an evolution strategy-based algorithm are presented. One of these layouts is used for creation of the spatial 6-terminal MTZ, which is also visualized.

Keywords:
Extremely modular system, Modular ramp system, Multi-branch network, Modular structure encoding, Evolution strategy, Discrete layout optimization

35.Zawidzki M., Automated geometrical evaluation of a plaza (town square), Advances in Engineering Software, ISSN: 0965-9978, DOI: 10.1016/j.advengsoft.2016.01.018, Vol.96, pp.58-69, 2016
Zawidzki M., Automated geometrical evaluation of a plaza (town square), Advances in Engineering Software, ISSN: 0965-9978, DOI: 10.1016/j.advengsoft.2016.01.018, Vol.96, pp.58-69, 2016

Abstract:
This paper presents a method for an automated geometrical evaluation (AGE) intended as a design support tool for urban design of a plaza (P). AGE is based on three normalized properties derived from a plan of P, namely: smallness, enclosure, and regularity. 19 worldwide plazas have been evaluated by 20 respondents in, what is called here, human subjective evaluation (HSE). A brief analysis of HSE including the identification of redundant categories is presented. Two P evaluation methods based on all four (S,C,E,R) and selected three (S,E,R) properties are discussed. Good agreement of AGE based on S,E, and R (NPSER) with HSE is shown. P quality rating (excellent, good, fair) based on NPSER is introduced. Exceptional cases are briefly discussed

Keywords:
Urban composition; Public square; Plaza; Layout evaluation; Design support tool; Normalized accumulated quality

36.Brandt A.M., O wpływie promieniowania jonizującego na beton, przegląd stanu wiedzy, CEMENT, WAPNO, BETON, ISSN: 1425-8129, Vol.6, pp.423-438, 2016
Brandt A.M., O wpływie promieniowania jonizującego na beton, przegląd stanu wiedzy, CEMENT, WAPNO, BETON, ISSN: 1425-8129, Vol.6, pp.423-438, 2016

Abstract:
Zagadnienie wpływu promieniowania jonizującego na osłony betonowe było rozpatrywane już przez badaczy parędziesiąt lat temu, na przykład Hilsdorf i in. w 1978 r., co jednak wobec przewidywanej wówczas eksploatacji reaktorów przez 30-40 lat mogło nie mieć istotnego znaczenia. Obecnie działające i budowane elektrownie jądrowe będą zapewne działać przez 60-80 lat, więc wpływ promieniowania na mikrostrukturę i właściwości betonu w osłonach wymaga starannego zbadania. Prace takie podjęte w okresie ostatnich dziesięciu lat w laboratoriach w USA, Japonii i innych krajów wskazują na niebezpieczeństwo degradacji betonu po przyjęciu określonej dawki promieniowania, a zmiany mikrostruktury i pęcznienie betonu mogą w znacznym stopniu zmniejszyć szczelność i wytrzymałość osłon w okresie przewidzianej eksploatacji reaktorów. Podobne zjawisko może dotyczyć, choć po dłuższym okresie, także składowisk odpadów radioaktywnych. W artykule przedstawione obecną wiedzę w tej tematyce oraz zagadnienia wymagające nadal intensywnych badań.

37.Wasilewski M., Pisarski D., Bajer C.I., Adaptive stabilization of partially damaged vibrating structures, Machine Dynamics Research, ISSN: 2080-9948, Vol.40, No.1, pp.65-82, 2016
Wasilewski M., Pisarski D., Bajer C.I., Adaptive stabilization of partially damaged vibrating structures, Machine Dynamics Research, ISSN: 2080-9948, Vol.40, No.1, pp.65-82, 2016

Abstract:
In this paper, an online adaptive continuous-time control algorithm will be studied in the vibration control problem. The examined algorithm is a Reinforcement Learning based scheme able to adapt to the changing system’s dynamics and providing control converging to the optimal control. Firstly, a brief description of the algorithm is provided. Then, the algorithm is studied by the numeric simulation. The controlled model is a simple conjugate oscillator with a sudden change of its rigidity. The effectiveness of the adaptation of the algorithm is compared to the simulation results of controlling the same object by the traditional Linear Quadratic Regulator. Because of the lack of constraints for a system size or its linearity, this algorithm is suitable for optimal stabilization of more complex vibrating structures.

Keywords:
Vibration control, Adaptive control, Optimal control, Policy iterations, Hamilton-Jacobi-Bellman equation

38.Zawidzki M., Retrofitting of pedestrian overpass by Truss-Z modular systems using graph-theory approach, Advances in Engineering Software, ISSN: 0965-9978, DOI: 10.1016/j.advengsoft.2014.11.004, Vol.81, pp.41-49, 2015
Zawidzki M., Retrofitting of pedestrian overpass by Truss-Z modular systems using graph-theory approach, Advances in Engineering Software, ISSN: 0965-9978, DOI: 10.1016/j.advengsoft.2014.11.004, Vol.81, pp.41-49, 2015

Abstract:
Installing pedestrian ramps is a common improvement towards a barrier-free environment. This paper introduces a graph-theoretical method of retrofitting of a single-branch Truss-Z (TZ) ramp in a constrained environment. The results produced by this exhaustive search method are usually ideal and better than those produced previously with meta-heuristic methods. A large case study of linking two sections of the Hongo Campus of Tokyo University using an overpass in an extremely constrained environment is presented. TZ modules with 1:12 (8.3%) slope are used, which is allowable in most countries for ramps for self-powered wheelchairs. The results presented here are highly satisfactory both in terms of structural optimization and aesthetics. Visualizations of the TZ ramp system, composed of 124 units, are presented.

Keywords:
Truss-Z, Modular lightweight system, Organic design, Discrete structural optimization, Retrofitting, Pedestrian ramp, Breadth-first search, Wavefront algorithm, Unknown graph exploration

39.Bogacz R., Kurnik W., On some rotor-dynamical phenomena of high-speed trains, ARCHIVE OF APPLIED MECHANICS, ISSN: 0939-1533, DOI: 10.1007/s00419-014-0966-3, Vol.85, No.9, pp.1343-1352, 2015
Bogacz R., Kurnik W., On some rotor-dynamical phenomena of high-speed trains, ARCHIVE OF APPLIED MECHANICS, ISSN: 0939-1533, DOI: 10.1007/s00419-014-0966-3, Vol.85, No.9, pp.1343-1352, 2015

Abstract:
The paper is devoted to radial and out-of-plane vibration of railway wheels and to wheelset stability as key elements affecting high-speed vehicle dynamics, noise emission, and safety. In the present study, railway wheel tire is treated as a curved beam with various beam models, and the wheel plates are modeled as Winkler’s elastic foundation. New results are presented concerning the influence of the residual stresses on the corrugation and poligonalization of wheels as well as wave propagation in the wheel tire

Keywords:
Elastic wheel, Wheel–rail interaction, Traveling waves, Wheel poligonalization, Corrugation

40.Ramalli A., Byra M., Dallai A., Palombo C., Aizawa K., Sbragi S., Shore S., Portoli P., A Multiparametric Approach Integrating Vessel Diameter, Wall Shear Rate and Physiologic Signals for Optimized Flow Mediated Dilation Studies, IUS 2015, IEEE International Ultrasonics Symposium, 2015-10-21/10-24, Taipei (TW), DOI: 10.1109/ULTSYM.2015.0326, pp.1-4, 2015
Ramalli A., Byra M., Dallai A., Palombo C., Aizawa K., Sbragi S., Shore S., Portoli P., A Multiparametric Approach Integrating Vessel Diameter, Wall Shear Rate and Physiologic Signals for Optimized Flow Mediated Dilation Studies, IUS 2015, IEEE International Ultrasonics Symposium, 2015-10-21/10-24, Taipei (TW), DOI: 10.1109/ULTSYM.2015.0326, pp.1-4, 2015

Abstract:
Flow Mediated Dilation (FMD) is a technique widely used to assess the endothelial function by ultrasound. Ideally, both the brachial artery wall shear stress (stimulus) and the diameter change (effect) shall be estimated and monitored for up to 10 minutes, while blood flow is restricted by a cuff and then suddenly released. An inherent method's difficulty is maintaining the linear array probe aligned with the artery for such a long time. The problem is here faced by an integrated hardware/software approach that displays in real-time both the spatial velocity profiles and the diameter changes, and acquires raw data all over the exam.

Keywords:
component, Flow mediated dilation, FMD, wall shear stress, wall shear rate, diameter distension, ULA-OP

41.Zawidzki M., Chraibi M., Nishinari K., Crowd-Z: The user-friendly framework for crowd simulation on an architectural floor plan, Pattern Recognition Letters, ISSN: 0167-8655, DOI: 10.1016/j.patrec.2013.10.025, Vol.44, pp.88-97, 2014
Zawidzki M., Chraibi M., Nishinari K., Crowd-Z: The user-friendly framework for crowd simulation on an architectural floor plan, Pattern Recognition Letters, ISSN: 0167-8655, DOI: 10.1016/j.patrec.2013.10.025, Vol.44, pp.88-97, 2014

Abstract:
This paper introduces Crowd-Z (CZ): a framework that provides a user-friendly platform where architects can perform simple crowd simulations on floor plans. A simple but robust and flexible agent-based system is used for modeling of the crowd dynamics. Such simulations can be performed at any stage of design – from rough sketches to the final blueprints. CZ allows acquiring the layouts for the simulations in a number of ways: freehand sketches, importing already prepared images and appropriating preprocessed images from commercially available Computer Aided Design programs. These three methods are illustrated with practical examples, followed by a number of simulations compared with the literature or other commercially available programs.

Keywords:
Pedestrian dynamics; Agent based modeling; Design support; Digitized floor plan

42.Zawidzki M., Nishinari K., Application of evolutionary algorithms for optimum layout of Truss-Z linkage in an environment with obstacle, Advances in Engineering Software, ISSN: 0965-9978, DOI: 10.1016/j.advengsoft.2013.04.022, Vol.65, pp.43-59, 2013
Zawidzki M., Nishinari K., Application of evolutionary algorithms for optimum layout of Truss-Z linkage in an environment with obstacle, Advances in Engineering Software, ISSN: 0965-9978, DOI: 10.1016/j.advengsoft.2013.04.022, Vol.65, pp.43-59, 2013

Abstract:
Truss-Z (TZ) is a concept of a modular system for creating free-form links and ramp networks. It is intended as a universal transportation system for cyclists and pedestrians, especially ones with strollers or carts, and in particular – by persons on wheelchairs, the elders, etc. In other words, TZ is for people who have difficulties using regular stairs or escalators. With only two types of modules, TZ can be designed for nearly any situation and therefore is particularity suited for retrofitting to improve the mobility, comfort and safety of the users. This paper presents an application of evolution strategy (ES) and genetic algorithm (GA) for optimization of the planar layout of a TZ linkage connecting two terminals in a given environment. The elements of the environment, called obstacles, constrain the possible locations of the TZ modules. Criteria of this multi-objective optimization are: the number of modules to be the smallest, which can be regarded as quantitative economical optimization, and the condition that none of the modules collides with any other objects, which can be regarded as qualitative satisfaction of the geometrical constraints. Since TZ is modular, the optimization of its layout is discrete and therefore has combinatorial characteristic. Encoding of a planar TZ path, selection method, objective (cost) function and genetic operations are introduced. A number of trials have been performed; the results generated by ES and GA are compared and evaluated against backtracking-based algorithm and random search. The convergence of solutions is discussed and interpreted. A visualization of a realistic implementation of the best solution is presented. Further evaluation of the method on three other representative layouts is presented and the results are briefly discussed.

Keywords:
Truss-Z, Modular skeletal system, Organic design, Meta-heuristic discrete optimization, Retrofitting, Pedestrian ramp

43.Piechór K., Calcium Waves in Thin Visco-Elastic Cells, MATHEMATICAL MODELLING OF NATURAL PHENOMENA, ISSN: 0973-5348, DOI: 10.1051/mmnp/20138313, Vol.8, No.3, pp.206-226, 2013
Piechór K., Calcium Waves in Thin Visco-Elastic Cells, MATHEMATICAL MODELLING OF NATURAL PHENOMENA, ISSN: 0973-5348, DOI: 10.1051/mmnp/20138313, Vol.8, No.3, pp.206-226, 2013

Abstract:
The model we consider treats the cell as a viscoelastic medium lling one of two kinds of thin domains (\shapes" of cells): the thin slab being a caricature of a tissue and the thin circular cylinder mimicking a long cell. This enables us to simplify the system of mechano-chemical equations. We construct abundant classes of explicit, but approximate, formulae for heteroclinic solutions to these equations.

Keywords:
calcium waves, mechano-chemical coupling, thin domains

44.Zawidzki M., Bator M., Application of Evolutionary Algorithm for Optimization of the Sequence of Initial Conditions for the Cellular Automaton-Based Shading, Journal of Cellular Automata, ISSN: 1557-5969, Vol.7, pp.363-384, 2013
Zawidzki M., Bator M., Application of Evolutionary Algorithm for Optimization of the Sequence of Initial Conditions for the Cellular Automaton-Based Shading, Journal of Cellular Automata, ISSN: 1557-5969, Vol.7, pp.363-384, 2013

Abstract:
This paper presents an application of evolutionary algorithm (EA) for multi-objective optimization of the sequence of initial conditions (SIC) for a cellular automaton (CA) used for a potential implementation in the field of architecture. In the proposed application, a modular shading system for building facade is driven by a two color, one dimensional, range 2 CA rule {3818817080,2,2}. The SIC optimization criteria are: visual attractiveness, gradual and intuitive transition from one density level to another and even distribution of the pattern over the entire array. The ideal solutions for 10 square arrays of 7×7, 8×8,..., 16×16 cells are found by an exhaustive search method – the backtracking. The encoding of SICs using the order-based representation is introduced. A cost function evaluating both monotonicity of the average density transition, and the distribution of shading pattern is introduced. For a 100×100 cell array EA is implemented with three setups: without crossover but with intensive mutation, with crossover and without mutation, and with both crossover and mutation. Two types of crossover operations are used: uniform (UX) and one-point (OPX). A number of experiments with various combinations of parameters were performed. The results are compared and the recommended strategy is briefly discussed. The best result was produced by EA with OPX and mutation rate 0.4.

Keywords:
Modular shading system, initial conditions, multi-objective optimization, discrete optimization, backtracking, order-based representation, evolutionary algorithm

45.Zhang Q., Hou J., Duan Z., Jankowski Ł., Substructural virtual distortion method for damage identification, Engineering Mechanics, ISSN: 1000-4750, DOI: 10.6052/j.issn.1000-4750.2012.08.0613, Vol.30, No.12, pp.176-182, 2013
Zhang Q., Hou J., Duan Z., Jankowski Ł., Substructural virtual distortion method for damage identification, Engineering Mechanics, ISSN: 1000-4750, DOI: 10.6052/j.issn.1000-4750.2012.08.0613, Vol.30, No.12, pp.176-182, 2013

Abstract:
针对大型土木结构损伤识别优化效率低的问题,提出了子结构虚拟变形方法。虚拟变形方法是一种结构
快速重分析的方法,该方法利用单元的虚拟变形模拟结构的损伤,可以在不重新建立有限元模型的情况下,快速
计算出结构参数改变后的结构响应。该文基于虚拟变形法的基本思想,对子结构的刚度矩阵进行分解和对损伤后
结构运动方程进行整理,推导出利用子结构的虚拟变形刻画损伤的方法,扩展了虚拟变形方法的适用范围;并且
给出了虚拟变形和结构响应的相关性计算公式,通过相关性分析提取主要的虚拟变形,减少参与计算的子结构虚
拟变形的数目,提高计算效率;最后利用一个五十层框架的数值仿真验证方法的有效性

46.Zawidzki M., Nishinari K., Modular Truss-Z system for self-supporting skeletal free-form pedestrian networks, Advances in Engineering Software, ISSN: 0965-9978, DOI: 10.1016/j.advengsoft.2011.12.012, Vol.47, No.1, pp.147-159, 2012
Zawidzki M., Nishinari K., Modular Truss-Z system for self-supporting skeletal free-form pedestrian networks, Advances in Engineering Software, ISSN: 0965-9978, DOI: 10.1016/j.advengsoft.2011.12.012, Vol.47, No.1, pp.147-159, 2012

Abstract:
This paper presents the concept of Truss-Z (TZ) – a skeletal system for pedestrian traffic which is composed of only two modules and allows the creation of complex three-dimensional self-supporting networks connecting any number of terminals in a given environment. TZ is intended as a universal, feasible and practical system for newly designed situations and most importantly, for retrofitting, especially where the use of heavy equipment is impossible or uneconomic.
TZ allows automated creation of optimal spatial links where the only required inputs are the coordinates of the terminals and the geometry of the obstacles. As an example a six-terminal network created with a backtracking based algorithm is shown. An alternative method of aligning consecutive modules to a given 3D path is also presented.
A preliminary static analysis of the TZ module is carried out – the topological qualities of rigidity and independence are demonstrated.

Keywords:
Truss-Z, Modular skeletal system, Self-supporting structure, Organic design, Discrete structural optimization, Retrofit pedestrian link, Pathfinding with backtracking

47.Bogacz R., Czyczuła W., Pawlak-Burakowska A., Wpływ tłumienia na stateczność strumienia oscylatorów oddziałującego z belką. Stateczność przepływu cieczy, Symulacja w Badaniach i Rozwoju, ISSN: 2081-6154, Vol.3, No.2, pp.71-77, 2012
Bogacz R., Czyczuła W., Pawlak-Burakowska A., Wpływ tłumienia na stateczność strumienia oscylatorów oddziałującego z belką. Stateczność przepływu cieczy, Symulacja w Badaniach i Rozwoju, ISSN: 2081-6154, Vol.3, No.2, pp.71-77, 2012

Abstract:
W niniejszej pracy rozważana jest stateczność ruchu układu złożonego ze strumienia gęsto rozłożonej masy (oscylatorów) oddziałującego sprężyście lub lepko-sprężyście z belką na podłożu Winkera (np. modelującej rurę). Układ taki może być uproszczonym modelem układu pociąg - tor lub modelem rurociągu, przez który przepływa ciecz (dla uproszczenia nieściśliwa).

Keywords:
stateczność przepływu, ruch względny, tłumienie

48.Lewandowska B., Teoria informacji i jej zastosowania w biologii i w medycynie, XI Krajowe Forum Informacji Naukowej i Technicznej: Człowiek w przestrzeni informacyjnej, 2011-09-20/09-23, Zakopane (PL), pp.1, 2011
Lewandowska B., Teoria informacji i jej zastosowania w biologii i w medycynie, XI Krajowe Forum Informacji Naukowej i Technicznej: Człowiek w przestrzeni informacyjnej, 2011-09-20/09-23, Zakopane (PL), pp.1, 2011

Abstract:
Information theory and its application to the biology and medicine (Abstract). Information theory was founded by Claude E. Shannon in 1948. According to the C. Shannon theory, the information about an event is measured as the probability of the occurrence of the event. The cognitive possibilities which are related to the processes of knowing, understanding and learning something about the phenomenon under study, are employed also in the scientific researches into biology and medicine. A fair stock of information is contained in a living cell of an organism. The structure of an albumen is defined by the information contained in genes. The four-letter DNA language determines the laws governing the twenty-letter language of each albumen. Therefore, a genetitic information may be saved in the form of an one-dimensional instruction. C. Shannon defined mathematically the concept of the decisive information which is the measure of the decision taken on the classification of a sent out sign. In medicine making an exact diagnosis seems to be of key meaning. Proposing a suitable algorithm for generating the diagnosis process we arrive at the objectivity of the process since each illness may be regarded as a message obtained statistically. That is justified by the fact that the defined factors predispose us to some illnesses. In this way it is possible on the base of the theory of information to formalize the process of medical diagnosis.

49.Páczelt I., Mróz Z., On the analysis of steady-state sliding wear processes, TRIBOLOGY INTERNATIONAL, ISSN: 0301-679X, DOI: 10.1016/j.triboint.2008.06.007, Vol.42, No.2, pp.275-283, 2009
Páczelt I., Mróz Z., On the analysis of steady-state sliding wear processes, TRIBOLOGY INTERNATIONAL, ISSN: 0301-679X, DOI: 10.1016/j.triboint.2008.06.007, Vol.42, No.2, pp.275-283, 2009

Abstract:
The transient wear process on the frictional interface of two elastic bodies in relative steady sliding motion induces shape evolution of the contact interface and tends to a steady state in which the wear develops at constant contact stress and strain distribution. Such a steady state may be attained experimentally or in numerical analysis by integrating the wear rate in the transient wear period. An alternative method of analysis was proposed in previous papers [Páczelt I, Mróz Z. On optimal contact shapes generated by wear. Int J Numer Methods Eng 2005;63:1310–47; Páczelt I, Mróz Z. Optimal shapes of contact interfaces due to sliding wear in the steady relative motion. Int J Solids Struct 2007;44:895–925] by applying a variational procedure and minimizing a response functional corresponding to the wear-dissipation power. The present paper provides an extension of this approach and new applications to the analysis of steady states in disk and drum brakes. The wear rule is assumed as a non-linear relation of wear rate to shear stress and relative sliding velocity. The specification of steady wear states is of engineering importance as it allows for optimal shape design of contacting interfaces in order to avoid the transient run-in periods. The extension to cyclic translation cases can be generated by considering steady cyclic states of wear processes.

Keywords:
Contact problems, Sliding wear, Steady-state, Variational principle, Optimal contact surface

50.Mróz Z., Janusz Klepaczko remembered, INTERNATIONAL JOURNAL OF IMPACT ENGINEERING, ISSN: 0734-743X, DOI: 10.1016/j.ijimpeng.2009.02.003, Vol.36, No.8, pp.994-994, 2009
51.Fenga Z.-Q., Hjiaj M., de Saxcé G., Mróz Z., Influence of frictional anisotropy on contacting surfaces during loading/unloading cycles, INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS, ISSN: 0020-7462, DOI: 10.1016/j.ijnonlinmec.2006.08.002, Vol.41, No.8, pp.936-948, 2006
Fenga Z.-Q., Hjiaj M., de Saxcé G., Mróz Z., Influence of frictional anisotropy on contacting surfaces during loading/unloading cycles, INTERNATIONAL JOURNAL OF NON-LINEAR MECHANICS, ISSN: 0020-7462, DOI: 10.1016/j.ijnonlinmec.2006.08.002, Vol.41, No.8, pp.936-948, 2006

Abstract:
This paper presents numerical investigations on the loading and unloading of a three-dimensional body in frictional contact with a rigid foundation. The evolution of the sliding process during loading/unloading cycles is analyzed. The important case of anisotropy is examined along with the effect of the sliding rule. The solution algorithm is based on a variational inequality which combine the contact problem and the frictional problem. The numerical results of the punch problem show the hysteretic and irreversible behavior occurring when friction is anisotropic.

Keywords:
Elliptic friction criterion, non-associated slip rile, Uzawa algorithm, Cyclic loading

52.Trzęsowski A., Tensility and compressibility of axially symmetric nanoclusters II; cylindrical nanoclusters, JOURNAL OF TECHNICAL PHYSICS, ISSN: 0324-8313, Vol.46, No.1, pp.9-22, 2005
53.Kucharski S., Mróz Z., Identification of material parameters by means of compliance moduli in spherical indentation test, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2004.03.030, Vol.379, No.1-2, pp.448-456, 2004
Kucharski S., Mróz Z., Identification of material parameters by means of compliance moduli in spherical indentation test, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/j.msea.2004.03.030, Vol.379, No.1-2, pp.448-456, 2004

Abstract:
An identification method of elastic and plastic hardening parameters is proposed by measuring compliance moduli in loading and unloading in the spherical indentation test. The loading program is composed of consecutive loading and unloading steps from which the compliance moduli are determined from the load–penetration (P–h) curve. The hardening parameters k and m occurring in the plastic hardening curve Full-size image (<1 K) are then specified. Identification of materials described by a more complex three parameters constitutive law εp=((σ−σy)/k)′1/m′, where σy denotes the yield stress, is also analysed. The identification of Young’s modulus from the indentation test is also presented.

Keywords:
Spherical indentation test, Identification, Elasto-plastic material properties, Indentation compliance moduli

54.Seweryn A., Tomczyk A., Mróz Z., A non-local fatigue crack growth model and its experimental verification, JOURNAL OF THEORETICAL AND APPLIED MECHANICS, ISSN: 1429-2955, Vol.42, No.1, pp.69-82, 2004
Seweryn A., Tomczyk A., Mróz Z., A non-local fatigue crack growth model and its experimental verification, JOURNAL OF THEORETICAL AND APPLIED MECHANICS, ISSN: 1429-2955, Vol.42, No.1, pp.69-82, 2004

Abstract:
The present paper is concerned with the modelling of fatigue crack initiation and propagation by applying the non-local critical plane model, proposed by Seweryn and Mróz (1996, 1998). Using the linear elastic stress field at the front of a crack or sharp notch, the damage growth on a physical plane is specified in terms of mean values of the stress and strength function. The model is applied to study crack propagation under cyclically varying tension-compression conditions. The predictions are compared with experimental data.

Keywords:
fatigue, damage accumulation, crack propagation

55.Trzęsowski A., Tensility and compressibility of axially symmetric nanoclusters part I: simplified modelling, JOURNAL OF TECHNICAL PHYSICS, ISSN: 0324-8313, Vol.45, No.2, pp.141-153, 2004
56.Boukpeti N., Mróz Z., Drescher A., Modeling rate effects in undrained loading of sands, Canadian Geotechnical Journal, ISSN: 0008-3674, DOI: 10.1139/t03-077, Vol.41, No.2, pp.342-350, 2004
Boukpeti N., Mróz Z., Drescher A., Modeling rate effects in undrained loading of sands, Canadian Geotechnical Journal, ISSN: 0008-3674, DOI: 10.1139/t03-077, Vol.41, No.2, pp.342-350, 2004

Abstract:
The present technical note extends the previous work by the authors concerned with formulation of a constitutive model of elastoplastic response of sands (Superior sand model) and its application to the analyses of static liquefaction and instability states in triaxial compression and extension occurring in the undrained deformation of saturated granular materials. To account for time-dependent behavior and strain rate effects, an elastic, viscoplastic extension of the model to triaxial compression is proposed. The constitutive equations derived are used to predict the model response in different loading histories. In particular, strain rate and stress rate effects and undrained creep deformation for specified stress components are discussed in detail. Comparison of model predictions with available experimental data also is provided.Key words: saturated sand, constitutive model, elastic–viscoplastic behavior.

57.Hjiaj M., Feng Z.Q., de Saxcé G., Mróz Z., On the modelling of complex anisotropic frictional contact laws, International Journal of Engineering Science, ISSN: 0020-7225, DOI: 10.1016/j.ijengsci.2003.10.004, Vol.42, No.10, pp.1013-1034, 2004
Hjiaj M., Feng Z.Q., de Saxcé G., Mróz Z., On the modelling of complex anisotropic frictional contact laws, International Journal of Engineering Science, ISSN: 0020-7225, DOI: 10.1016/j.ijengsci.2003.10.004, Vol.42, No.10, pp.1013-1034, 2004

Abstract:
In this paper, the formulation of complex anisotropic frictional models with orthotropic friction condition and non-associated sliding rule is discussed. The friction law is described by a superellipse, which allow to consider a wide range of convex friction condition by simply varying the roundness factor affecting the shape of the limit surface. The sliding potential is also a superellipse but with a different semi-axis ratio, which lead to a non-associated sliding rule. For bodies in contact, the Signorini conditions can be formulated in terms of velocities and combined with the sliding rule to give the frictional contact law describing interfacial interactions. Its is shown that the frictional contact law as well as its inverse can be derived from the same scalar valued function called bi-potential. Due to the non-associated nature of the law, this relation is implicit. The advantage of the present formulation lies in the existence of stationary points of a functional, called bi-functional, that depends on both the displacements and the stresses.

Keywords:
Superelliptic friction criterion, Non-associated sliding rule, Bi-potential, Variational formulation

58.Mróz Z., Bojczuk D., Finite topology variations in optimal design of structures, STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION, ISSN: 1615-147X, DOI: 10.1007/s00158-003-0289-4, Vol.25, No.3, pp.153-173, 2003
Mróz Z., Bojczuk D., Finite topology variations in optimal design of structures, STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION, ISSN: 1615-147X, DOI: 10.1007/s00158-003-0289-4, Vol.25, No.3, pp.153-173, 2003

Abstract:
The method of optimal design of structures by finite topology modification is presented in the paper. This approach is similar to growth models of biological structures, but in the present case, topology modification is described by the finite variation of a topological parameter. The conditions for introducing topology modification and the method for determining finite values of topological parameters characterizing the modified structure are specified. The present approach is applied to the optimal design of truss, beam, and frame structures. For trusses, the heuristic algorithm of bar exchange is proposed for minimizing the global compliance subject to a material volume constraint and it is extended to volume minimization with stress and buckling constraints. The optimal design problem for beam and frame structures with elastic or rigid supports, aimed at minimizing the structure cost for a specified global compliance, is also considered.

Keywords:
optimal topology, finite topology modifications, structure evolution, truss and frame structures

59.Trzęsowski A., Self-Balance Equations and Bianchi-Type Distortions in the Theory of Dislocations, INTERNATIONAL JOURNAL OF THEORETICAL PHYSICS, ISSN: 0020-7748, DOI: 10.1023/A:1024494112624, Vol.42, No.4, pp.711-723, 2003
Trzęsowski A., Self-Balance Equations and Bianchi-Type Distortions in the Theory of Dislocations, INTERNATIONAL JOURNAL OF THEORETICAL PHYSICS, ISSN: 0020-7748, DOI: 10.1023/A:1024494112624, Vol.42, No.4, pp.711-723, 2003

Abstract:
We deals with two aspects of the geometric description of continuized Bravais monocrystals with many dislocations. First, a triad of vector fields is distinguished constituting a basis for the C∞-module of smooth vector fields tangent to the body. This moving frame defines its object of anholonomity as well as an intrinsic (“material”) Riemannian metric of the body. Second, these geometric objects are used to define both the notions of principal congruence of Volterra-type effective dislocations and principal local Burgers vector associated with these congruences. The main topics discussed are (i) self-balance equations of dislocations and secondary point defects generated by distributions of these dislocations; (ii) a linkage of the Bianchi classification of three-dimensional real Lie algebras with the physical classification of principal local Burgers vectors.

Keywords:
self-balance equations, Bianchi-type distortions, dislocations

60.Trzęsowski A., On the quasi-solid state of solid nanoclusters, JOURNAL OF TECHNICAL PHYSICS, ISSN: 0324-8313, Vol.44, No.4, pp.385-396, 2003
61.Stupkiewicz S., Mróz Z., Phenomenological model of real contact area evolution with account for bulk plastic deformation in metal forming, International Journal of Plasticity, ISSN: 0749-6419, DOI: 10.1016/S0749-6419(01)00037-7, Vol.19, No.3, pp.323-344, 2003
Stupkiewicz S., Mróz Z., Phenomenological model of real contact area evolution with account for bulk plastic deformation in metal forming, International Journal of Plasticity, ISSN: 0749-6419, DOI: 10.1016/S0749-6419(01)00037-7, Vol.19, No.3, pp.323-344, 2003

Abstract:
A phenomenological description of the evolution of real contact area in metal forming processes is presented with account for the effect of bulk plastic flow. A thin surface layer is considered and assumed to be weakened by the localized plastic deformation around surface asperities. The yield condition of this layer is expressed in terms of contact stresses, plastic strain rate of the bulk and real contact area fraction and its rate. The model applicability is illustrated by comparing its predictions of real contact area variation, depending on bulk strain, with predictions of micro-mechanical models and with experimental data.

Keywords:
Cutting and forming, Constitutive behaviour, Ideally plastic material, Frictional contact

62.Kowalewski T.A., Mosyak A., Hetsroni G., Tracking of coherent thermal structures on a heated wall. 2. DNS simulation, Experiments in Fluids, ISSN: 0723-4864, DOI: 10.1007/s00348-002-0574-9, Vol.34, No.3, pp.390-396, 2003
Kowalewski T.A., Mosyak A., Hetsroni G., Tracking of coherent thermal structures on a heated wall. 2. DNS simulation, Experiments in Fluids, ISSN: 0723-4864, DOI: 10.1007/s00348-002-0574-9, Vol.34, No.3, pp.390-396, 2003

Abstract:
The temporal evolution of a thermal pattern observed on a heated wall by infrared camera is correlated with the propagation velocity of the thermal perturbations calculated by DNS. In the experiment the propagation velocity was measured by using PIV-based analysis of infrared images of the thermal pattern on the wall. To verify the experimental technique of image analysis, a sequence of synthetic images, simulating thermal patterns on the wall, was generated from the DNS solution, and the convective velocity was evaluated. It was found that the convective velocity of thermal structures obtained by PIV-based analysis of the experimental and synthetic images was in relatively good agreement with that calculated from the DNS solution. The present study confirmed that for a high Prandtl number fluid (water) the propagation velocity of the thermal perturbations is only about half of the convective velocity of the velocity perturbations. It was also found that the convection velocity observed for hot spots is distinctly lower than that for the cold spots.

63.Hjiaj M., de Saxcé G., Mróz Z., A variational inequality-based formulation of the frictional contact law with a non-associated sliding rule, EUROPEAN JOURNAL OF MECHANICS A-SOLIDS, ISSN: 0997-7538, DOI: 10.1016/S0997-7538(01)01183-4, Vol.21, No.1, pp.49-59, 2002
Hjiaj M., de Saxcé G., Mróz Z., A variational inequality-based formulation of the frictional contact law with a non-associated sliding rule, EUROPEAN JOURNAL OF MECHANICS A-SOLIDS, ISSN: 0997-7538, DOI: 10.1016/S0997-7538(01)01183-4, Vol.21, No.1, pp.49-59, 2002

Abstract:
We present a variational formulation of a complex frictional contact law with anisotropic friction condition and a non-associated sliding rule. The distinguishing characteristic of the proposed formulation is that the interface law, as well as its inverse, derive from a single scalar-valued function called bi-potential. This function, which depends on both the velocities and the associated forces, is split into the sum of two dual pseudo-potentials for standard multivalued laws. The main advantages of the formalism are the compact form taken by the present complex law and convexity property of the bi-potential that can be exploited for numerical purposes.

64.Mróz Z., Oliferuk W., Energy balance and identification of hardening moduli in plastic deformation processes, International Journal of Plasticity, ISSN: 0749-6419, DOI: 10.1016/S0749-6419(00)00103-0, Vol.18, No.3, pp.379-397, 2002
Mróz Z., Oliferuk W., Energy balance and identification of hardening moduli in plastic deformation processes, International Journal of Plasticity, ISSN: 0749-6419, DOI: 10.1016/S0749-6419(00)00103-0, Vol.18, No.3, pp.379-397, 2002

Abstract:
The hardening moduli Hr and Hd of plastic deformation associated with the free energy and dissipation function in a representative material element are defined analytically and specified experimentally for three materials. Besides the stress–strain curve and work expended during the deformation process, variation of the hardening moduli with plastic deformation is also determined for austenitic steel, austenitic-ferritic steel and Fe–Si alloy.

Keywords:
Thermomechanical processes, Hardening modulus, Polycrystalline material, Energy methods, Mechanical testing

65.Monti P., Fernando H.J., Princevac M., Chan W.C., Kowalewski T.A., Padyjak E.R., Observations of Flow and Turbulence in the Nocturnal Boundary Layer over a Slope, Journal of the Atmospheric Sciences, ISSN: 0022-4928, DOI: 10.1175/1520-0469(2002)059<2513:OOFATI>2.0.CO;2, Vol.59, No.17, pp.2513-2534, 2002
Monti P., Fernando H.J., Princevac M., Chan W.C., Kowalewski T.A., Padyjak E.R., Observations of Flow and Turbulence in the Nocturnal Boundary Layer over a Slope, Journal of the Atmospheric Sciences, ISSN: 0022-4928, DOI: 10.1175/1520-0469(2002)059<2513:OOFATI>2.0.CO;2, Vol.59, No.17, pp.2513-2534, 2002

Abstract:
Measurements were conducted on an eastern slope of the Salt Lake Basin (SLB) as a part of the Vertical Transport and Mixing Experiment (VTMX) conducted in October 2000. Of interest was the nocturnal boundary layer on a slope (in particular, katabatic flows) in the absence of significant synoptic influence. Extensive measurements of mean flow, turbulence, temperature, and solar radiation were made, from which circulation patterns on the slope and the nature of stratified turbulence in katabatic winds were inferred. The results show that near the surface (<25–50 m) the nocturnal flow is highly stratified and directed downslope, but at higher levels winds strongly vary in magnitude and direction with height and time, implying the domination of upper levels by air intrusions. These intrusions may peel off from different slopes surrounding the SLB, have different densities, and flow at their equilibrium density levels. The turbulence was generally weak and continuous, but sudden increases of turbulence levels were detected as the mean gradient Richardson number () dropped to about unity. With a short timescale fluctuated on the order of a few tens of seconds while modulating with a longer (along-slope internal waves sloshing) timescale of about half an hour. The mixing efficiency (or the flux Richardson number) of the flow was found to be a strong function of , similar to that found in laboratory experiments with inhomogeneous stratified shear flows. The eddy diffusivities of momentum and heat were evaluated, and they showed a systematic variation with when scaled with the shear length scale and the rms vertical velocity of turbulence.

66.Kucharski S., Mróz Z., Identification of plastic hardening parameters of metals from spherical indentation tests, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/S0921-5093(01)01334-X, Vol.318, No.1-2, pp.65-76, 2001
Kucharski S., Mróz Z., Identification of plastic hardening parameters of metals from spherical indentation tests, MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING, ISSN: 0921-5093, DOI: 10.1016/S0921-5093(01)01334-X, Vol.318, No.1-2, pp.65-76, 2001

Abstract:
Using the two-parameter power hardening rule σ=kεpm, the parameters k and m are identified from spherical indentation loading–unloading tests which account for the variation of the indentation profile during elastic unloading and sphere deformation. The predicted and measured stress–strain curves are compared for several materials. Both experimental and actual data for 18G2A low-alloy steel are used to assess the accuracy of the identification procedure. Finally, identification of the stress–strain curve of an aluminium alloy is demonstrated.

Keywords:
Spherical indentation tests, Plastic, Low-alloy steel, Metals

67.Giambanco G., Mróz Z., The Interphase Model for the Analysis of Joints in Rock Masses and Masonry Structures, MECCANICA, ISSN: 0025-6455, DOI: 10.1023/A:1011957217840, Vol.36, No.1, pp.111-130, 2001
Giambanco G., Mróz Z., The Interphase Model for the Analysis of Joints in Rock Masses and Masonry Structures, MECCANICA, ISSN: 0025-6455, DOI: 10.1023/A:1011957217840, Vol.36, No.1, pp.111-130, 2001

Abstract:
To study the response of cementitious joints in rock masses or masonry structures, the model of interphase is considered for which the contact stresses and strains interact with the internal stresses or strains within the joint. The frictional slip and sliding effects are then combined with the inelastic deformations of the joint. The constitutive model of the joint is analysed by assuming two interfaces separating the joint from the adjacent material. The case of a cementitious layer interposed between two rigid bodies is treated in detail.

Keywords:
Softening, Contact, Interfaces, Cohesive joint

68.Hetsroni G., Kowalewski T.A., Hu B., Mosyak A., Tracking of coherent thermal structures on a heated wall by means of IR thermography, Experiments in Fluids, ISSN: 0723-4864, DOI: 10.1007/s003480000175, Vol.30, No.3, pp.286-294, 2001
Hetsroni G., Kowalewski T.A., Hu B., Mosyak A., Tracking of coherent thermal structures on a heated wall by means of IR thermography, Experiments in Fluids, ISSN: 0723-4864, DOI: 10.1007/s003480000175, Vol.30, No.3, pp.286-294, 2001

Abstract:
This paper deals with measurements of convective velocity of large-scale thermal structures, using the thin foil technique and infrared thermography to visualize the thermal pattern on the wall. An image correlation method is proposed to track the displacement of the observed thermal pattern. The idea of the method is similar to that of particle image velocimetry, but the thermal patterns on the heated wall are used, rather than tracing particles. On this basis, the thermal patterns created by the coherent structures of turbulent channel flow are examined. Particular attention is paid to the determination of the optimal parameters of image acquisition, including spatial and temporal separation. An attempt is made to relate momentum and scalar transport analyses by considering the propagation velocity of large-scale temperature structures. The proposed technique appears to be an attractive alternative for non-intrusive analysis of turbulent flow, especially, where opaqueness of channel walls excludes the use of optical methods.

69.Sergeyev O., Mróz Z., Sensitivity analysis and optimal design of 3D frame structures for stress and frequency constraints, COMPUTERS AND STRUCTURES, ISSN: 0045-7949, DOI: 10.1016/S0045-7949(99)00088-7, Vol.75, No.2, pp.167-185, 2000
Sergeyev O., Mróz Z., Sensitivity analysis and optimal design of 3D frame structures for stress and frequency constraints, COMPUTERS AND STRUCTURES, ISSN: 0045-7949, DOI: 10.1016/S0045-7949(99)00088-7, Vol.75, No.2, pp.167-185, 2000

Abstract:
The present paper deals with the problem of determining the optimal joint positions and cross-sectional parameters of linearly elastic space frames with imposed stress and free frequency constraints. The frame is assumed to be acted on by different load systems, including temperature and self-weight loads. The stress state analysis includes tension, bending, shear, and torsion of beam elements. By a sequence of quadratic programming problems, the optimal design is attained. The sensitivity analysis of distinct as well as multiple frequencies is performed through analytic differentiation with respect to design parameters. Illustrative examples of optimal design of simple and medium complexity frames are presented, and the particular case of bimodal optimal solution is considered in detail.

70.Pietruszczak S., Mróz Z., Formulation of anisotropic failure criteria incorporating a microstructure tensor, COMPUTERS AND GEOTECHNICS, ISSN: 0266-352X, DOI: 10.1016/S0266-352X(99)00034-8, Vol.26, No.2, pp.105-112, 2000
Pietruszczak S., Mróz Z., Formulation of anisotropic failure criteria incorporating a microstructure tensor, COMPUTERS AND GEOTECHNICS, ISSN: 0266-352X, DOI: 10.1016/S0266-352X(99)00034-8, Vol.26, No.2, pp.105-112, 2000

Abstract:
Anisotropy is inherently related to microstructural arrangement within a representative volume of material. The microstructure can be represented by a second order tensor whose eigenvectors specify the orientation of the axes of material symmetry. In this paper, failure criteria for geomaterials are formulated in terms of the stress state and a microstructure tensor. The classical criteria for isotropic materials are generalized for the case of orthotropy as well as transverse isotropy. The proposed approach is illustrated by a simple example demonstrating the sensitivity of the uniaxial strength of the material to the orientation of the sample relative to the loading direction.

71.Stupkiewicz S., Mróz Z., A model of third body abrasive friction and wear in hot metal forming, WEAR, ISSN: 0043-1648, DOI: 10.1016/S0043-1648(99)00124-6, Vol.231, No.1, pp.124-138, 1999
Stupkiewicz S., Mróz Z., A model of third body abrasive friction and wear in hot metal forming, WEAR, ISSN: 0043-1648, DOI: 10.1016/S0043-1648(99)00124-6, Vol.231, No.1, pp.124-138, 1999

Abstract:
A model of friction accounting for third body particles at the contact interface is derived from a simple micro-mechanical model of a particle interacting with a hard tool surface and a soft workpiece surface. Also a wear law coupled with this friction model is proposed. When wear of the tool surface is considered, the abrasive contribution of hard particles is only accounted for. The rate of wear is associated with frictional dissipation rate rather than with the product of normal pressure and slip velocity as in the classical Archard wear law. Numerical examples illustrate applicability and properties of the proposed friction and wear model.

Keywords:
Contact friction, Wear, Hot metal forming, Third body abrasion

72.Nawrocki P., Mróz Z., A constitutive model for rock accounting for viscosity and yield stress degradation, COMPUTERS AND GEOTECHNICS, ISSN: 0266-352X, DOI: 10.1016/S0266-352X(99)00020-8, Vol.25, No.4, pp.247-280, 1999
Nawrocki P., Mróz Z., A constitutive model for rock accounting for viscosity and yield stress degradation, COMPUTERS AND GEOTECHNICS, ISSN: 0266-352X, DOI: 10.1016/S0266-352X(99)00020-8, Vol.25, No.4, pp.247-280, 1999

Abstract:
A viscoplastic constitutive model of rock is proposed for which both yield stress and viscosity undergo variation during the deformation process. The model is initially formulated for a uniaxial stress state; its extension for a general stress state is also provided. Model parameters are determined from compression tests at different values of strain rate, and its application to simulate results of such tests is given. The examples of stress redistribution in a coal seam due to progressing longwall exploitation are presented by applying the developed degradation model. The model provides good simulation of material response in both stable and post-critical stages.

73.Giangi M., Stella F., Kowalewski T.A., Phase change problems with free convection: fixed grid numerical simulation, Computing and Visualization in Science, ISSN: 1432-9360, DOI: 10.1007/s007910050034, Vol.2, No.2, pp.123-130, 1999
Giangi M., Stella F., Kowalewski T.A., Phase change problems with free convection: fixed grid numerical simulation, Computing and Visualization in Science, ISSN: 1432-9360, DOI: 10.1007/s007910050034, Vol.2, No.2, pp.123-130, 1999

Abstract:
A numerical and experimental study of unsteady natural convection during freezing of water is presented. The mathematical model for the numerical simulations is based on the enthalpy-porosity method in vorticity-velocity formulation, equations are discretised on a fixed grid by means of a finite volume technique. A fully implicit method has been adopted for the mass and momentum equations. Experiments are performed for water in a differentially heated cube surrounded by air. The experimental data for natural convection with freezing in the cavity are collected to create a reference for comparison with numerical results. The method of simultaneous measurement of the flow and temperature fields using liquid crystal tracers is used. It allows us to collect transient data on the interface position, and the temperature and velocity fields. In order to improve the capability of the numerical method to predict experimental results, a conjugate heat transfer problem was solved, with finite thickness and internal heat conductivity of the non-isothermal walls. These results have been compared with the simulations obtained for the idealised case of perfectly adiabatic side walls, and with our experimental findings. Results obtained for the improved numerical model shown a very good agreement with the experimental data only for pure convection and initial time of freezing process. As time passes the discrepancies between numerical predictions and the experiment became more significant, suggesting a necessity for further improvements of the physical model used for freezing water.

74.Mróz Z., Stupkiewicz S., Constitutive model of adhesive and ploughing friction in metal-forming processes, INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES, ISSN: 0020-7403, DOI: 10.1016/S0020-7403(97)00055-6, Vol.40, No.2-3, pp.281-303, 1998
Mróz Z., Stupkiewicz S., Constitutive model of adhesive and ploughing friction in metal-forming processes, INTERNATIONAL JOURNAL OF MECHANICAL SCIENCES, ISSN: 0020-7403, DOI: 10.1016/S0020-7403(97)00055-6, Vol.40, No.2-3, pp.281-303, 1998

Abstract:
In metal-forming processes the tool-workpiece interaction is associated with friction forces due to cohesive bonds and ploughing of hard particles or asperities through the interface layer and also with irreversible asperity flattening. In the present work, the combined effect of adhesive and ploughing friction is accounted for by assuming two different length scales of interacting asperities of workpiece and tool. The constitutive model of friction slip is formulated by introducing the representative contact state variables and providing their evolution rules together with friction condition and the non-associated slip rule. The model parameters can be identified from micro-mechanical solutions of asperity flattening and ploughing problems. Also a purely phenomenological model is proposed. The dual asperity model is next applied to predict contact slip and friction response and in numerical analysis of two boundary value problems.

Keywords:
contact friction, metal forming, asperity flattening, ploughing

75.Seweryn A., Mróz Z., On the criterion of damage evolution for variable multiaxial stress states, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, ISSN: 0020-7683, DOI: 10.1016/S0020-7683(97)00121-2, Vol.35, No.14, pp.1589-1616, 1998
Seweryn A., Mróz Z., On the criterion of damage evolution for variable multiaxial stress states, INTERNATIONAL JOURNAL OF SOLIDS AND STRUCTURES, ISSN: 0020-7683, DOI: 10.1016/S0020-7683(97)00121-2, Vol.35, No.14, pp.1589-1616, 1998

Abstract:
The damage accumulation condition expressed in terms of traction components on a physical plane is discussed for both monotonic and cyclic loading conditions. The crack initiation is assumed to correspond to a critical value of damage reached on the physical plane. For singular stress distribution in the front of sharp notch or crack the non-local condition is formulated. The proposed condition is applied to predict damage distribution within the representative element for cyclic loading conditions. The rosette diagrams are constructed for visualization of damage distribution. The prediction of crack initiation for multiaxial fatigue loading is provided. The second- and fourth-order damage tensors in order to describe damage distribution within the element, and the associated compliance variation are introduced.

76.Nawrocki P., Mróz Z., A viscoplastic degradation model for rocks, INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, ISSN: 1365-1609, DOI: 10.1016/S0148-9062(98)00012-6, Vol.35, No.7, pp.991-1000, 1998
Nawrocki P., Mróz Z., A viscoplastic degradation model for rocks, INTERNATIONAL JOURNAL OF ROCK MECHANICS AND MINING SCIENCES, ISSN: 1365-1609, DOI: 10.1016/S0148-9062(98)00012-6, Vol.35, No.7, pp.991-1000, 1998

Abstract:
In this paper a viscoplastic constitutive model for rocks is proposed in which both yield stress and viscosity undergo variation during the deformation process. The model is initially formulated for a uniaxial stress state; its extension to a general stress state has been also presented. Our model is capable to sufficiently well predict both the pre-peak hardening and post-peak softening response of rock material in compression providing good simulation of material response in both stable and post-critical stages of deformation. Such behaviour can be obtained for both low and high strain rates. In our examples, model parameters are determined from uniaxial compression tests performed on sandstone at different strain rates.

77.Seweryn A., Mróz Z., A non-local stress failure condition for structural elements under multiaxial loading, ENGINEERING FRACTURE MECHANICS, ISSN: 0013-7944, DOI: 10.1016/0013-7944(94)00335-F, Vol.51, No.6, pp.955-973, 1995
Seweryn A., Mróz Z., A non-local stress failure condition for structural elements under multiaxial loading, ENGINEERING FRACTURE MECHANICS, ISSN: 0013-7944, DOI: 10.1016/0013-7944(94)00335-F, Vol.51, No.6, pp.955-973, 1995

Abstract:
A non-local stress condition for crack initiation and propagation is proposed and applied to several particular cases, such as plate with wedge-shaped notch, elliptical hole and hyperbolic notch. Brittle failure initiation for notched elements under complex loading (Modes I and II) is studied in detail. A value of critical load and crack orientation is predicted from the non-local condition, which is applicable to both regular and singular stress concentrations.

78.Mróz Z., Rodzik P., On the control of deformation process by plastic strain, International Journal of Plasticity, ISSN: 0749-6419, DOI: 10.1016/S0749-6419(95)00031-3, Vol.11, No.7, pp.827-842, 1995
Mróz Z., Rodzik P., On the control of deformation process by plastic strain, International Journal of Plasticity, ISSN: 0749-6419, DOI: 10.1016/S0749-6419(95)00031-3, Vol.11, No.7, pp.827-842, 1995

Abstract:
The incremental relations are derived between stress rate and the second order plastic strain rate (or plastic strain path curvature). Such relations could be used in setting control of the deformation process by plastic strain either in an experimental test or in numerical procedure, especially when critical and post-critical states occur for stress or strain control.

79.Mróz Z., Jarzębowski A., Phenomenological model of contact slip, ACTA MECHANICA, ISSN: 0001-5970, DOI: 10.1007/BF01178518, Vol.102, No.1, pp.59-72, 1994
Mróz Z., Jarzębowski A., Phenomenological model of contact slip, ACTA MECHANICA, ISSN: 0001-5970, DOI: 10.1007/BF01178518, Vol.102, No.1, pp.59-72, 1994

Abstract:
A constitutive model of the contact zone is proposed, accounting for dilatancy, elastic compliance, hardening and softening phenomena, and also hysteresis effects. Some model predictions are discussed in view of available experimental data.

80.Siemaszko A., Mróz Z., Sensitivity of plastic optimal structures to imperfections and non-linear geometrical effects, STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION, ISSN: 1615-147X, DOI: 10.1007/BF01743278, Vol.3, No.2, pp.99-105, 1991
Siemaszko A., Mróz Z., Sensitivity of plastic optimal structures to imperfections and non-linear geometrical effects, STRUCTURAL AND MULTIDISCIPLINARY OPTIMIZATION, ISSN: 1615-147X, DOI: 10.1007/BF01743278, Vol.3, No.2, pp.99-105, 1991

Abstract:
The sensitivity of optimal plastic design with respect to geometric imperfections and post-critical deformations is discussed. It is shown that the concept of optimal plastic design should be modified in order to provide a proper safety factor against collapse for a specified range of imperfections and configuration changes. The optimal design of two-story frames is analysed in detail.

81.Mróz Z., Goss Cz., O złożonych modelach wzmocnienia plastycznego, Mechanika Teoretyczna i Stosowana, ISSN: 0079-3701, Vol.2, No.10, pp.259-279, 1972