Publications reported by three months

1.Węglewski W., Pitchai P., Bochenek K., Bolzon G., Konetschnik R., Sartory B., Ebner R., Kiener D., Basista M., Experimental and numerical investigation of the deformation and fracture mode of microcantilever beams made of Cr(Re)/Al2O3 metal–matrix composite, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, ISSN: 1073-5623, DOI: 10.1007/s11661-020-05687-3, Vol.51, No.5, pp.2377-2390, 2020
Węglewski W., Pitchai P., Bochenek K., Bolzon G., Konetschnik R., Sartory B., Ebner R., Kiener D., Basista M., Experimental and numerical investigation of the deformation and fracture mode of microcantilever beams made of Cr(Re)/Al2O3 metal–matrix composite, METALLURGICAL AND MATERIALS TRANSACTIONS A-PHYSICAL METALLURGY AND MATERIALS SCIENCE, ISSN: 1073-5623, DOI: 10.1007/s11661-020-05687-3, Vol.51, No.5, pp.2377-2390, 2020

Abstract:
This work presents a combined experimental and computational study of the deformation and fracture of microcantilever specimens made of chromium(rhenium)-alumina metal–matrix composite (MMC), with a particular focus on the failure properties of the metal–ceramic interfaces. The obtained experimental results show that the bending strength of microcantilevers containing alumina particles in critical cross-sections near specimen's fixed end is considerably higher than that of unreinforced chromium(rhenium) samples. Brittle cracking along chromium–alumina interfaces is the dominant fracture mode of the composite microcantilevers. The interface characteristics are determined in an indirect way by numerical simulations of the experiment with account of the actual specimen microstructure from the scanning electron microscope (SEM) images. A parametric study demonstrates that the overall material response may be reproduced by different sets of model parameters, whereas the actual failure mode permits to discriminate among the possible alternatives. Using this approach, the in situ values of the chromium–alumina interface cohesive strength and the fracture energy are estimated.

2.Majewski M., Hołobut P., Kursa M., Kowalczyk-Gajewska K., Packing and size effects in elastic-plastic particulate composites: micromechanical modelling and numerical verification, International Journal of Engineering Science, ISSN: 0020-7225, DOI: 10.1016/j.ijengsci.2020.103271, Vol.151, pp.103271-1-18, 2020
Majewski M., Hołobut P., Kursa M., Kowalczyk-Gajewska K., Packing and size effects in elastic-plastic particulate composites: micromechanical modelling and numerical verification, International Journal of Engineering Science, ISSN: 0020-7225, DOI: 10.1016/j.ijengsci.2020.103271, Vol.151, pp.103271-1-18, 2020

Abstract:
The issue of applicability of the Morphologically Representative Pattern (MRP) approach to elastic-plastic composites is addressed. The extension to the regime of non-linear material behaviour is performed by employing the concept of incremental linearization of the material response in two basic variants: tangent and secant. The obtained predictions are evaluated through comparison with the outcomes of numerical analyses. Finite Element simulations are carried out using periodic unit cells with cubic arrangements of spherical particles and representative volume elements (RVE) with 50 randomly placed inclusions. In addition to the analysis of the packing effect in two-phase composites, the size effect is also studied by assuming an interphase between the matrix and inclusions. It is concluded that the MRP approach can be used as an effective predictive alternative to computational homogenization, not only in the case of linear elasticity but also in the case of elastic-plastic composites.

Keywords:
particulate composites, elastoplasticity, micromechanics, size effect, packing effect, morphologically representative pattern

3.Szewczyk P.K., Gradys A., Kyun Kim S., Persano L., Marzec M., Kryshtal A., Busolo T., Toncelli A., Pisignano D., Bernasik A., Kar-Narayan S., Sajkiewicz P., Stachewicz U., Enhanced piezoelectricity of electrospun polyvinylidene fluoride fibers for energy harvesting, ACS Applied Materials and Interfaces, ISSN: 1944-8244, DOI: 10.1021/acsami.0c02578, Vol.12, No.11, pp.13575-13583, 2020
Szewczyk P.K., Gradys A., Kyun Kim S., Persano L., Marzec M., Kryshtal A., Busolo T., Toncelli A., Pisignano D., Bernasik A., Kar-Narayan S., Sajkiewicz P., Stachewicz U., Enhanced piezoelectricity of electrospun polyvinylidene fluoride fibers for energy harvesting, ACS Applied Materials and Interfaces, ISSN: 1944-8244, DOI: 10.1021/acsami.0c02578, Vol.12, No.11, pp.13575-13583, 2020

Abstract:
Piezoelectric polymers are promising energy materials for wearable and implantable applications for replacing bulky batteries in small and flexible electronics. Therefore, many research studies are focused on understanding the behavior of polymers at a molecular level and designing new polymer-based generators using polyvinylidene fluoride (PVDF). In this work, we investigated the influence of voltage polarity and ambient relative humidity in electrospinning of PVDF for energy-harvesting applications. A multitechnique approach combining microscopy and spectroscopy was used to study the content of the β-phase and piezoelectric properties of PVDF fibers. We shed new light on β-phase crystallization in electrospun PVDF and showed the enhanced piezoelectric response of the PVDF fiber-based generator produced with the negative voltage polarity at a relative humidity of 60%. Above all, we proved that not only crystallinity but also surface chemistry is crucial for improving piezoelectric performance in PVDF fibers. Controlling relative humidity and voltage polarity increased the d33 piezoelectric coefficient for PVDF fibers by more than three times and allowed us to generate a power density of 0.6 μW·cm^–2 from PVDF membranes. This study showed that the electrospinning technique can be used as a single-step process for obtaining a vast spectrum of PVDF fibers exhibiting different physicochemical properties with β-phase crystallinity reaching up to 74%. The humidity and voltage polarity are critical factors in respect of chemistry of the material on piezoelectricity of PVDF fibers, which establishes a novel route to engineer materials for energy-harvesting and sensing applications.

Keywords:
PVDF, polymer crystallinity, electrospinning, piezoelectricity, voltage polarity

4.Alvi S., Jarząbek D.M., Kohan M.G., Hedman D., Jenczyk P., Natile M.M., Vomiero A., Akhtar F., Synthesis and mechanical characterization of a CuMoTaWV high-entropy film by magnetron sputtering, ACS Applied Materials and Interfaces, ISSN: 1944-8244, DOI: 10.1021/acsami.0c02156, Vol.12, No.18, pp.21070-21079, 2020
Alvi S., Jarząbek D.M., Kohan M.G., Hedman D., Jenczyk P., Natile M.M., Vomiero A., Akhtar F., Synthesis and mechanical characterization of a CuMoTaWV high-entropy film by magnetron sputtering, ACS Applied Materials and Interfaces, ISSN: 1944-8244, DOI: 10.1021/acsami.0c02156, Vol.12, No.18, pp.21070-21079, 2020

Abstract:
Development of high-entropy alloy (HEA) films is a promising and cost-effective way to incorporate these materials of superior properties in harsh environments. In this work, a refractory high-entropy alloy (RHEA) film of equimolar CuMoTaWV was deposited on silicon and 304 stainless-steel substrates using DC-magnetron sputtering. A sputtering target was developed by partial sintering of an equimolar powder mixture of Cu, Mo, Ta, W, and V using spark plasma sintering. The target was used to sputter a nanocrystalline RHEA film with a thickness of ~900 nm and an average grain size of 18 nm. X-ray diffraction of the film revealed a body-centered cubic solid solution with preferred orientation in the (110) directional plane. The nanocrystalline nature of the RHEA film resulted in a hardness of 19 ± 2.3 GPa and an elastic modulus of 259 ± 19.2 GPa. A high compressive strength of 10 ± 0.8 GPa was obtained in nanopillar compression due to solid solution hardening and grain boundary strengthening. The adhesion between the RHEA film and 304 stainless-steel substrates was increased on annealing. For the wear test against the E52100 alloy steel (Grade 25, 700-880 HV) at 1 N load, the RHEA film showed an average coefficient of friction (COF) and wear rate of 0.25 (RT) and 1.5 (300 °C), and 6.4 × 10^–6 mm^3/N m (RT) and 2.5 × 10^–5 mm^3/N m (300 °C), respectively. The COF was found to be 2 times lower at RT and wear rate 10^2 times lower at RT and 300 °C than those of 304 stainless steel. This study may lead to the processing of high-entropy alloy films for large-scale industrial applications.

Keywords:
high-entropy alloys, magnetron sputtering, spark plasma sintering, mechanical properties, wear

5.Ryś M., Forest S., Petryk H., A micromorphic crystal plasticity model with the gradient-enhanced incremental hardening law, International Journal of Plasticity, ISSN: 0749-6419, DOI: 10.1016/j.ijplas.2019.102655, Vol.128, pp.102655-1-21, 2020
Ryś M., Forest S., Petryk H., A micromorphic crystal plasticity model with the gradient-enhanced incremental hardening law, International Journal of Plasticity, ISSN: 0749-6419, DOI: 10.1016/j.ijplas.2019.102655, Vol.128, pp.102655-1-21, 2020

Abstract:
A model of crystal plasticity is developed in which the effects of plastic flow non-uniformity are described through the full dislocation density tensor. The micromorphic approach is used in which the dislocation density tensor is represented by the curl of an independent constitutive variable called microdeformation. The microdeformation tensor is enforced by an energetic penalty term to be close to the actual plastic distortion tensor. The curl of microdeformation tensor enters the constitutive model in two independent but complementary ways. First, it is an argument of the free energy density function, which describes the kinematic-type hardening in cyclic non-uniform deformation. Second, its rate influences the rates of critical resolved shear stresses, which corresponds to additional isotropic hardening caused by incompatibility of the plastic flow rate. The latter effect, missing in the standard slip-system hardening rule, is described in a simple manner that does not require any extra parameter in comparison to the non-gradient theory. In the proposed model there are two independent internal length scales whose interplay is examined by means of 1D and 2D numerical examples of plastic shearing of a single crystal.

Keywords:
gradient theory, crystal plasticity, dissipation, length scale, cyclic deformation, numerical regularization

6.Postek E., Sadowski T., Thermomechanical effects during impact testing of WC/Co composite material, COMPOSITE STRUCTURES, ISSN: 0263-8223, DOI: 10.1016/j.compstruct.2020.112054, Vol.241, pp.112054-1-25, 2020
Postek E., Sadowski T., Thermomechanical effects during impact testing of WC/Co composite material, COMPOSITE STRUCTURES, ISSN: 0263-8223, DOI: 10.1016/j.compstruct.2020.112054, Vol.241, pp.112054-1-25, 2020

Abstract:
WC/Co metal-matrix ceramic composites (MMCs) are used for manufacturing cutting and drilling tools, surgical tools, mill inserts, jet engines, and other high-responsibility structures. The combination of a phase of hard wolfram carbide (WC) grains with a metallic ductile interface of cobalt (Co) yields a complex microstructure with significantly different mechanical properties of the phases. The aim of this study is to investigate the thermomechanical behavior of the MMC polycrystalline material with ductile binders under impact conditions. An adiabatic and coupled thermomechanical analysis of the WC/Co composite under impact loading is performed using FEM. The heat conduction is considered in the analysis in order to capture heat transfer in the polycrystalline structure, i.e. between the grains and the grain boundaries (GBs). The Johnson-Cook yield function is used in the constitutive model of the ductile Co interface, while the WC phase is linear elastic. The motivation comes from the observation that the heat conductivity effect is often omitted, even in recent papers **[75]. Significant differences between temperatures and plastic strains in the adiabatic and coupled solutions are observed, which leads to the main conclusion that the adiabatic solution should not be used for assessing the impact response of the composite material.

Keywords:
metal-ceramic composite, impact, coupled problem, thermomechanics, ductile interface

7.Liu X., Kopeć M., Fakir O., Qu H., Wang Y., Wang L., Li Z., Characterisation of the interfacial heat transfer coefficient in hot stamping of titanium alloys, International Communications in Heat and Mass Transfer, ISSN: 0735-1933, DOI: 10.1016/j.icheatmasstransfer.2020.104535, Vol.113, pp.104535-1-14, 2020
Liu X., Kopeć M., Fakir O., Qu H., Wang Y., Wang L., Li Z., Characterisation of the interfacial heat transfer coefficient in hot stamping of titanium alloys, International Communications in Heat and Mass Transfer, ISSN: 0735-1933, DOI: 10.1016/j.icheatmasstransfer.2020.104535, Vol.113, pp.104535-1-14, 2020

Abstract:
The interfacial heat transfer coefficient (IHTC) for titanium alloys is an important parameter in non-isothermal hot stamping processes to determine the temperature field as well as temperature-dependent material behaviours that consequently affect the post-form properties of the formed components. However, the IHTC for titanium alloys in hot stamping processes has seldom been studied before. In the present research, the effects of contact pressure, lubricant, surface roughness, tooling material and initial blank temperature on the IHTC for the titanium alloy Ti-6Al-4V were studied and modelled to characterise the IHTC values under various hot stamping conditions as well as identify the functional mechanisms affecting the IHTC. Furthermore, the results of hot stamping of Ti-6Al4V wing stiffener components were used to verify the simulation results of the temperature field of the formed component with an error of less than 5%.

Keywords:
interfacial heat transfer coefficient (IHTC), Ti-6Al-4V, hot stamping, experimental validation

8.Błachowski B., Świercz A., Ostrowski M., Tauzowski P., Olaszek P., Jankowski Ł., Convex relaxation for efficient sensor layout optimization in large‐scale structures subjected to moving loads, Computer-Aided Civil and Infrastructure Engineering, ISSN: 1093-9687, DOI: 10.1111/mice.12553, pp.1-16, 2020
Błachowski B., Świercz A., Ostrowski M., Tauzowski P., Olaszek P., Jankowski Ł., Convex relaxation for efficient sensor layout optimization in large‐scale structures subjected to moving loads, Computer-Aided Civil and Infrastructure Engineering, ISSN: 1093-9687, DOI: 10.1111/mice.12553, pp.1-16, 2020

Abstract:
This paper proposes a computationally effective framework for load‐dependent optimal sensor placement in large‐scale civil engineering structures subjected to moving loads. Two common problems are addressed: selection of modes to be monitored and computational effectiveness. Typical sensor placement methods assume that the set of modes to be monitored is known. In practice, determination of such modes of interest is not straightforward. A practical approach is proposed that facilitates the selection of modes in a quasi‐automatic way based on the structural response at the candidate sensor locations to typical operational loads. The criterion used to assess sensor placement is based on Kammer's Effective Independence (EFI). However, in contrast to typical implementations of EFI, which treat the problem as a computationally demanding discrete problem and use greedy optimization, an approach based on convex relaxation is proposed. A notion of sensor density is applied, which converts the original combinatorial problem into a computationally tractable continuous optimization problem. The proposed framework is tested in application to a real tied‐arch railway bridge located in central Poland.

Keywords:
optimal sensor placement, effective independence method, Fisher information matrix

9.Jankowski Ł., Quality over quantity: the case of a model journal, Computer-Aided Civil and Infrastructure Engineering, ISSN: 1093-9687, DOI: 10.1111/mice.12560, pp.1-1, 2020
10.Pierini F., Guglielmelli A., Urbanek O., Nakielski P., Pezzi L., Buda R., Lanzi M., Kowalewski T.A., De Sio L., Thermoplasmonic‐activated hydrogel based dynamic light attenuator, Advanced Optical Materials, ISSN: 2195-1071, DOI: 10.1002/adom.202000324, pp.2000324-1-7, 2020
Pierini F., Guglielmelli A., Urbanek O., Nakielski P., Pezzi L., Buda R., Lanzi M., Kowalewski T.A., De Sio L., Thermoplasmonic‐activated hydrogel based dynamic light attenuator, Advanced Optical Materials, ISSN: 2195-1071, DOI: 10.1002/adom.202000324, pp.2000324-1-7, 2020

Abstract:
This work describes the morphological, optical, and thermo‐optical properties of a temperature‐sensitive hydrogel poly(N‐isopropylacrylamide‐co‐N‐isopropylmethacrylamide) [P(NIPAm‐co‐NIPMAm]) film containing a specific amount of gold nanorods (GNRs). The light‐induced thermoplasmonic heating of GNRs is used to control the optical scattering of an initially transparent hydrogel film. A hydrated P(NIPAm‐co‐NIPMAm) film is optically clear at room temperature. When heated to temperatures over 37 °C via light irradiation with a resonant source (λ = 810 nm) to the GNRs, a reversible phase transition from a swollen hydrated state to a shrunken dehydrated state occurs. This phenomenon causes a drastic and reversible change in the optical transparency from a clear to an opaque state. A significant red shift (≈30 nm) of the longitudinal band can also be seen due to an increased average refractive index surrounding the GNRs. This change is in agreement with an ad hoc theoretical model which uses a modified Gans theory for ellipsoidal nanoparticles. Morphological analysis of the composite film shows the presence of well‐isolated and randomly dispersed GNRs. Thermo‐optical experiments demonstrate an all‐optically controlled light attenuator (65% contrast ratio) which can be easily integrated in several modern optical applications such as smart windows and light‐responsive optical attenuators.

Keywords:
active plasmonics, gold nanorods, hydrogels, optical attenuators, optical transparency, plasmonic nanoparticles, polymers

11.Szymczyk M., Nowak M., Sumelka W., Plastic strain localization in an extreme dynamic tension test of steel sheet in the framework of fractional viscoplasticity, Thin-Walled Structures, ISSN: 0263-8231, DOI: 10.1016/j.tws.2019.106522, Vol.149, pp.106522-1-11, 2020
Szymczyk M., Nowak M., Sumelka W., Plastic strain localization in an extreme dynamic tension test of steel sheet in the framework of fractional viscoplasticity, Thin-Walled Structures, ISSN: 0263-8231, DOI: 10.1016/j.tws.2019.106522, Vol.149, pp.106522-1-11, 2020

Abstract:
The paper considers the plastic strain localization phenomenon in the framework of the fractional viscoplasticity. As an illustrative example, full spatial modelling of a tension test under extreme dynamic conditions is presented. The modelling assumes adiabatic conditions including isotropic work hardening-softening effects induced by plastic strains, temperature and damage (scalar). Special attention is paid to additional, compared to the classical Perzyna viscoplasticity, model parameters resulting from application of fractional calculus in the evolution law for plastic strains. It is shown that the proposed formulation allows for high flexibility of modelling of the localization zone with a limited number of model parameters.

Keywords:
fractional viscoplasticity, strain localization, extreme dynamics

12.Golasiński K., Pieczyska E., Maj M., Staszczak M., Świec P., Furuta T., Kuramoto S., Investigation of strain rate sensitivity of gum metal under tension using digital image correlation, ARCHIVES OF CIVIL AND MECHANICAL ENGINEERING, ISSN: 1644-9665, DOI: 10.1007/s43452-020-00055-9, Vol.20, No.2, pp.53-1-14, 2020
Golasiński K., Pieczyska E., Maj M., Staszczak M., Świec P., Furuta T., Kuramoto S., Investigation of strain rate sensitivity of gum metal under tension using digital image correlation, ARCHIVES OF CIVIL AND MECHANICAL ENGINEERING, ISSN: 1644-9665, DOI: 10.1007/s43452-020-00055-9, Vol.20, No.2, pp.53-1-14, 2020

Abstract:
Mechanical behavior of a multifunctional titanium alloy Gum Metal was investigated by conducting tensile tests at various strain rates and applying digital image correlation (DIC) technique. Stress–strain curves confirmed low Young's modulus and high strength of the alloy. The determined values of yield strength had a tendency to increase, whereas the elongation to the specimen rupture tended to decrease with increasing strain rate. True stress versus strain curves were analyzed using selected lengths of virtual extensometer (VE) placed in the strain localization area. When the initial length of the VE was the same as the gauge length, work hardening was observed macroscopically at lower strain rates, and a softening was seen at higher strain rates. However, the softening effect was not observed at the shorter VE lengths. Evolution of the Hencky strain and rate of deformation tensor component fields were analyzed for various strain rates at selected stages of Gum Metal loading. The DIC analysis demonstrated that for lower strain rates the deformation is macroscopically uniform up to the higher average Hencky strains, whereas for higher strain rates the strain localization occurs at the lower average Hencky strains of the deformation process and takes place in the smaller area. It was also found that for all strain rates applied, the maximal values of Hencky strain immediately before rupture of Gum Metal samples were similar for each of the applied strain rates, and the maximal local values of deformation rate were two orders higher when compared to applied average strain rate values.

Keywords:
titanium alloy, gum metal, strain rate sensitivity, strain localization, digital image correlation, full-field deformation analysis

13.Ranachowski Z., Ranachowski P., Dębowski T., Brodecki A., Kopeć M., Roskosz M., Fryczowski K., Szymków M., Krawczyk E., Schabowicz K., Mechanical and non-destructive testing of plasterboards subjected to a hydration process, Materials, ISSN: 1996-1944, DOI: 10.3390/ma13102405, Vol.13, No.10, pp.2405-1-18, 2020
Ranachowski Z., Ranachowski P., Dębowski T., Brodecki A., Kopeć M., Roskosz M., Fryczowski K., Szymków M., Krawczyk E., Schabowicz K., Mechanical and non-destructive testing of plasterboards subjected to a hydration process, Materials, ISSN: 1996-1944, DOI: 10.3390/ma13102405, Vol.13, No.10, pp.2405-1-18, 2020

Abstract:
The aim of this study was to investigate the effect of plasterboards' humidity absorption on their performance. Specimens' hydration procedure consisted of consecutive immersing in water and subsequent drying at room temperature. Such a procedure was performed to increase the content of moisture within the material volume. The microstructural observations of five different plasterboard types were performed through optical and scanning electron microscopy. The deterioration of their properties was evaluated by using a three-point bending test and a subsequent ultrasonic (ultrasound testing (UT)) longitudinal wave velocity measurement. Depending on the material porosity, a loss of UT wave velocity from 6% to 35% and a considerable decrease in material strength from 70% to 80% were observed. Four types of approximated formulae were proposed to describe the dependence of UT wave velocity on board moisture content. It was found that the proposed UT method could be successfully used for the on-site monitoring of plasterboards' hydration processes.

Keywords:
plasterboards, moisture content, hydration processes, mechanical properties, ultrasound measurements

14.Knap L., Graczykowski C., Holnicki-Szulc J., Wołejsza Z., Strategies for reduction of energy consumption during ascending and descending process of modern telescopic HAPS aerostats, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/bpasts.2020.131833, Vol.68, No.1, pp.155-168, 2020
Knap L., Graczykowski C., Holnicki-Szulc J., Wołejsza Z., Strategies for reduction of energy consumption during ascending and descending process of modern telescopic HAPS aerostats, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/bpasts.2020.131833, Vol.68, No.1, pp.155-168, 2020

Abstract:
In this article, the authors propose and investigate a new concept of HAPS aerostat design in a modular form, which allows for sequential increasing or decreasing of the total volume, up to the desired size. In its initial form, the aerostat has relatively small dimensions but its central cylindrical part is multi-segmented and can be easily extended. The application of controllable construction couplings enables precise control of the aerostat expansion process and significantly improves its vertical mobility. The paper describes details of telescopic aerostat construction, presents a mathematical model of its vertical motion and investigates numerically two volume control strategies aimed at maximization of operation efficiency and minimization of operation cost. The results obtained reveal the main problems that have to be addressed and the factors that play a key role in design of such telescopic aerostats and control of their vertical mobility.

Keywords:
helium airship, control of vertical mobility, reduced energy consumption, optimum ascending and descending path

15.Kołbuk D., Heljak M., Choińska E., Urbanek O., Novel 3D hybrid nanofiber scaffolds for bone regeneration, Polymers, ISSN: 2073-4360, DOI: 10.3390/polym12030544, Vol.12, No.3, pp.544-1-18, 2020
Kołbuk D., Heljak M., Choińska E., Urbanek O., Novel 3D hybrid nanofiber scaffolds for bone regeneration, Polymers, ISSN: 2073-4360, DOI: 10.3390/polym12030544, Vol.12, No.3, pp.544-1-18, 2020

Abstract:
Development of hybrid scaffolds and their formation methods occupies an important place in tissue engineering. In this paper, a novel method of 3D hybrid scaffold formation is presented as well as an explanation of the differences in scaffold properties, which were a consequence of different crosslinking mechanisms. Scaffolds were formed from 3D freeze-dried gelatin and electrospun poly(lactide-co-glicolide) (PLGA) fibers in a ratio of 1:1 w/w. In order to enhance osteoblast proliferation, the fibers were coated with hydroxyapatite nanoparticles (HAp) using sonochemical processing. All scaffolds were crosslinked using an EDC/NHS solution. The scaffolds' morphology was imaged using scanning electron microscopy (SEM). The chemical composition of the scaffolds was analyzed using several methods. Water absorption and mass loss investigations proved a higher crosslinking degree of the hybrid scaffolds than a pure gelatin scaffold, caused by additional interactions between gelatin, PLGA, and HAp. Additionally, mechanical properties of the 3D hybrid scaffolds were higher than traditional hydrogels. In vitro studies revealed that fibroblasts and osteoblasts proliferated and migrated well on the 3D hybrid scaffolds, and also penetrated their structure during the seven days of the experiment.

Keywords:
hybrid scaffolds, electrospinning, freeze-drying, gelatin, hydroxyapatite, sonochemical covering/grafting

16.Magliulo M., Lengiewicz J., Zilian A., Beex L.A.A., Non-localised contact between beams with circular and elliptical cross-sections, COMPUTATIONAL MECHANICS, ISSN: 0178-7675, DOI: 10.1007/s00466-020-01817-1, Vol.65, No.5, pp.1247-1266, 2020
Magliulo M., Lengiewicz J., Zilian A., Beex L.A.A., Non-localised contact between beams with circular and elliptical cross-sections, COMPUTATIONAL MECHANICS, ISSN: 0178-7675, DOI: 10.1007/s00466-020-01817-1, Vol.65, No.5, pp.1247-1266, 2020

Abstract:
The key novelty of this contribution is a dedicated technique to efficiently determine the distance (gap) function between parallel or almost parallel beams with circular and elliptical cross-sections. The technique consists of parametrizing the surfaces of the two beams in contact, fixing a point on the centroid line of one of the beams and searching for a constrained minimum distance between the surfaces (two variants are investigated). The resulting unilateral (frictionless) contact condition is then enforced with the Penalty method, which introduces compliance to the, otherwise rigid, beams' cross-sections. Two contact integration schemes are considered: the conventional slave-master approach (which is biased as the contact virtual work is only integrated over the slave surface) and the so-called two-half-pass approach (which is unbiased as the contact virtual work is integrated over the two contacting surfaces). Details of the finite element formulation, which is suitably implemented using Automatic Differentiation techniques, are presented. A set of numerical experiments shows the overall performance of the framework and allows a quantitative comparison of the investigated variants.

Keywords:
beams, contact, circular and elliptical cross-sections, rigid cross-sections, single-pass algorithm, two-half-pass algorithm

17.Mościcki T., Psiuk R., Słomińska H., Levintant-Zayonts N., Garbiec D., Pisarek M., Bazarnik P., Nosewicz S., Chrzanowska-Giżyńska J., Influence of overstoichiometric boron and titanium addition on the properties of RF magnetron sputtered tungsten borides, SURFACE AND COATINGS TECHNOLOGY, ISSN: 0257-8972, DOI: 10.1016/j.surfcoat.2020.125689, Vol.390, pp.125689-1-12, 2020
Mościcki T., Psiuk R., Słomińska H., Levintant-Zayonts N., Garbiec D., Pisarek M., Bazarnik P., Nosewicz S., Chrzanowska-Giżyńska J., Influence of overstoichiometric boron and titanium addition on the properties of RF magnetron sputtered tungsten borides, SURFACE AND COATINGS TECHNOLOGY, ISSN: 0257-8972, DOI: 10.1016/j.surfcoat.2020.125689, Vol.390, pp.125689-1-12, 2020

Abstract:
In this work, (W,Ti)B2 films with different stoichiometric ratio Ti/W deposited on silicon and 304 stainless steel by radio frequency magnetron sputtering are presented. The coatings were deposited from plasma spark sintered targets obtained from the mixture of pure boron, tungsten and titanium powders. It is shown that during plasma spark sintering process using overstoichiometric boron and a low content of titanium change the WB2 to WB4 phase with almost no secondary phases. Subsequently, the impact of titanium content on the films properties is investigated systematically, including the chemical and phase composition, crystalline structure, surface and cross-section morphology. Simultaneously, nano-indentation test and ball-on-disk tribometery are performed to analyse the hardness and tribological properties of the films. It is shown that deposited films with titanium content of 3.6 and 5.5 at.% are formed in the zone T of the Thornton's Structural Zone Model. In opposite to α-WB2 magnetron sputtered coatings they are more flexible and hard nanocomposite coatings. The results show that the addition of titanium is apparently changing the film structure from nanocrystalline columnar to amorphous, very dense and compact structure with the addition of TiB2 phase. That films are simultaneously hard (H > 37.5 GPa), have high hardness to effective Young's modulus ratio values (H/E* > 0.1) and elastic recovery (We > 60%) appropriate for tough and resistant to cracking materials. The presented (W,Ti)B2 films exhibit also tribological and corrosion properties better than unalloyed coatings.

Keywords:
superhard films, ternary tungsten borides, RF magnetron sputtering, wear resistance, corrosion

18.Paprocki B., Pręgowska A., Szczepański J., Optimizing information processing in brain-inspired neural networks, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/bpasts.2020.131844, Vol.68, No.2, pp.225-233, 2020
Paprocki B., Pręgowska A., Szczepański J., Optimizing information processing in brain-inspired neural networks, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.24425/bpasts.2020.131844, Vol.68, No.2, pp.225-233, 2020

Abstract:
The way brain networks maintain high transmission efficiency is believed to be fundamental in understanding brain activity. Brains consisting of more cells render information transmission more reliable and robust to noise. On the other hand, processing information in larger networks requires additional energy. Recent studies suggest that it is complexity, connectivity, and function diversity, rather than just size and the number of neurons, that could favour the evolution of memory, learning, and higher cognition. In this paper, we use Shannon information theory to address transmission efficiency quantitatively. We describe neural networks as communication channels, and then we measure information as mutual information between stimuli and network responses. We employ a probabilistic neuron model based on the approach proposed by Levy and Baxter, which comprises essential qualitative information transfer mechanisms. In this paper, we overview and discuss our previous quantitative results regarding brain-inspired networks, addressing their qualitative consequences in the context of broader literature. It is shown that mutual information is often maximized in a very noisy environment e.g., where only one-third of all input spikes are allowed to pass through noisy synapses and farther into the network. Moreover, we show that inhibitory connections as well as properly displaced long-range connections often significantly improve transmission efficiency. A deep understanding of brain processes in terms of advanced mathematical science plays an important role in the explanation of the nature of brain efficiency. Our results confirm that basic brain components that appear during the evolution process arise to optimise transmission performance.

Keywords:
neural network, entropy, mutual information, noise, inhibitory neuron

19.Pawłowska S., Rinoldi C., Nakielski P., Ziai Y., Urbanek O., Li X., Kowalewski T.A., Ding B., Pierini F., Ultraviolet light‐assisted electrospinning of core–shell fully cross‐linked P(NIPAAm‐co‐NIPMAAm) hydrogel‐based nanofibers for thermally induced drug delivery self‐regulation, Advanced Materials Interfaces, ISSN: 2196-7350, DOI: 10.1002/admi.202000247, pp.2000247-1-13, 2020
Pawłowska S., Rinoldi C., Nakielski P., Ziai Y., Urbanek O., Li X., Kowalewski T.A., Ding B., Pierini F., Ultraviolet light‐assisted electrospinning of core–shell fully cross‐linked P(NIPAAm‐co‐NIPMAAm) hydrogel‐based nanofibers for thermally induced drug delivery self‐regulation, Advanced Materials Interfaces, ISSN: 2196-7350, DOI: 10.1002/admi.202000247, pp.2000247-1-13, 2020

Abstract:
Body tissues and organs have complex functions which undergo intrinsic changes during medical treatments. For the development of ideal drug delivery systems, understanding the biological tissue activities is necessary to be able to design materials capable of changing their properties over time, on the basis of the patient's tissue needs. In this study, a nanofibrous thermal‐responsive drug delivery system is developed. The thermo‐responsivity of the system makes it possible to self‐regulate the release of bioactive molecules, while reducing the drug delivery at early stages, thus avoiding high concentrations of drugs which may be toxic for healthy cells. A co‐axial electrospinning technique is used to fabricate core–shell cross‐linked copolymer poly(N‐isopropylacrylamide‐co‐N‐isopropylmethacrylamide) (P(NIPAAm‐co‐NIPMAAm)) hydrogel‐based nanofibers. The obtained nanofibers are made of a core of thermo‐responsive hydrogel containing a drug model, while the outer shell is made of poly‐l‐lactide‐co‐caprolactone (PLCL). The custom‐made electrospinning apparatus enables the in situ cross‐linking of P(NIPAAm‐co‐NIPMAAm) hydrogel into a nanoscale confined space, which improves the electrospun nanofiber drug dosing process, by reducing its provision and allowing a self‐regulated release control. The mechanism of the temperature‐induced release control is studied in depth, and it is shown that the system is a promising candidate as a "smart" drug delivery platform.

Keywords:
biomimetic nanomaterials, electrospun core–shell nanofibers, hierarchical nanostructures, smart drug delivery, thermo‐responsive hydrogels

20.Jarząbek D.M., Harvey C., Levintant-Zayonts N., Wojciechowski T., Gniadek M., Krajewski M., Pathak S., Enhancement of mechanical properties of vertically aligned carbon nanotube arrays due to N+ ion irradiation, NANOTECHNOLOGY, ISSN: 0957-4484, DOI: 10.1088/1361-6528/ab8665, Vol.31, No.28, pp.285703-1-9, 2020
Jarząbek D.M., Harvey C., Levintant-Zayonts N., Wojciechowski T., Gniadek M., Krajewski M., Pathak S., Enhancement of mechanical properties of vertically aligned carbon nanotube arrays due to N+ ion irradiation, NANOTECHNOLOGY, ISSN: 0957-4484, DOI: 10.1088/1361-6528/ab8665, Vol.31, No.28, pp.285703-1-9, 2020

Abstract:
In this work we apply N+ ion irradiation on vertically aligned carbon nanotube (VACNT) arrays in order to increase the number of connections and joints in the CNT network. The ions energy was 50 keV and fluence 5 × 10^17 ions cm^−2. The film was 160 μm thick. SEM images revealed the ion irradiation altered the carbon bonding and created a sponge-like, brittle structure at the surface of the film, with the ion irradiation damage region extending ~4 μm in depth. TEM images showed the brittle structure consists of amorphous carbon forming between nanotubes. The significant enhancement of mechanical properties of the irradiated sample studied by the cyclic nanoindentation with a flat punch indenter was observed. Irradiation on the VACNT film made the structure stiffer, resulted in a higher percentage recovery, and reduced the energy dissipation under compression. The results are encouraging for further studies which will lead to create a class of materials - ion-irradiated VACNT films - which after further research may find application in storage or harvesting energy at the micro/nanoscale.

Keywords:
vertically aligned carbon nanotubes, ion irradiation, nanoindentation

21.Krajewski M., Liou S.C., Chiou W.A., Tokarczyk M., Małolepszy A., Płocińska M., Witecka A., Lewińska S., Ślawska-Waniewska A., Amorphous FexCo1–x wire-like nanostructures manufactured through surfactant-free magnetic-field-induced synthesis, Crystal Growth and Design, ISSN: 1528-7483, DOI: 10.1021/acs.cgd.0c00070, Vol.20, No.5, pp.3208-3216, 2020
Krajewski M., Liou S.C., Chiou W.A., Tokarczyk M., Małolepszy A., Płocińska M., Witecka A., Lewińska S., Ślawska-Waniewska A., Amorphous FexCo1–x wire-like nanostructures manufactured through surfactant-free magnetic-field-induced synthesis, Crystal Growth and Design, ISSN: 1528-7483, DOI: 10.1021/acs.cgd.0c00070, Vol.20, No.5, pp.3208-3216, 2020

Abstract:
So far, it has been proven that the magnetic-field-induced (MFI) synthesis is a process which mainly leads to the formation of magnetic metallic one-dimensional nanostructures. Taking advantage of this method, the new procedures which allow manufacture of the magnetic bimetallic iron–cobalt wire-like nanochains with Fe0.75 Co0.25, Fe0.50 Co0.50, and Fe0.25 Co0.75 compositions are demonstrated in this work. They were produced through a simple one-step magnetic-field-induced (MFI) chemical co-reduction of three different mixtures containing a proper amount of Fe2+ and Co2+ ions with aqueous sodium borohydride solution as the reducing agent. The synthesis process was carried out at room temperature without the use of templates, surfactants, complexing agents, and organic solvents. The morphological and structural studies indicated that all as-prepared materials were amorphous, and they were composed of nanoparticles aligned in almost straight chains. Moreover, they revealed the core–shell structures with bimetallic alloy cores containing desired iron-to-cobalt ratios and very thin oxide shells. Furthermore, the obtained nanostructures behaved as ferromagnetic materials. Their magnetic properties were correlated with their structural properties and chemical compositions. It was observed that their saturation magnetization decreased significantly with increasing content of cobalt in the chains, whereas the variation of their coercivity was less pronounced.

22.Kowalczyk T., Functional micro- and nanofibers obtained by nonwoven post-modification, Polymers, ISSN: 2073-4360, DOI: 10.3390/polym12051087, Vol.12, No.5, pp.1087-1-20, 2020
Kowalczyk T., Functional micro- and nanofibers obtained by nonwoven post-modification, Polymers, ISSN: 2073-4360, DOI: 10.3390/polym12051087, Vol.12, No.5, pp.1087-1-20, 2020

Abstract:
Micro- and nanofibers are historically-known materials that are continuously reinvented due to their valuable properties. They display promise for applications in many fields, from tissue engineering to catalysis or sensors. In the first application, micro- and nanofibers are mainly produced from a limited library of biomaterials with properties that need alteration before use. Post-modification is a very effective method for attaining on-demand features and functions of nonwovens. This review summarizes and presents methods of functionalization of nonwovens produced by electrostatic means. The reviewed modifications are grouped into physical methods, chemical modification, and mixed methods.

Keywords:
nanofiber post-modification, functional nanofibers, tissue engineering

23.Olaszek P., Wyczałek I., Sala D., Kokot M., Świercz A., Monitoring of the static and dynamic displacements of railway bridges with the use of inertial sensors, SENSORS, ISSN: 1424-8220, DOI: 10.3390/s20102767, Vol.20, No.10, pp.2767-1-24, 2020
Olaszek P., Wyczałek I., Sala D., Kokot M., Świercz A., Monitoring of the static and dynamic displacements of railway bridges with the use of inertial sensors, SENSORS, ISSN: 1424-8220, DOI: 10.3390/s20102767, Vol.20, No.10, pp.2767-1-24, 2020

Abstract:
In the case of the monitoring of bridges, the determination of vertical displacements is one of the most important issues. A new measuring system has been developed and implemented for assessment of railway bridges based on measurements of the structural response to passing trains. The system uses inertial sensors: Inclinometers and accelerometers that do not need any referential points. The system records signals related to the passage of a train over a monitored bridge. The signals from inclinometers before the train's entry are used to determine the static movement. Integrated signals from inclinometers and accelerometers are used to determine dynamic displacements when the train goes through the bridge. Signals from inclinometers are used to determine the so-called "quasi-static" component of the displacement and signal from the accelerometer to determine the dynamic component. Field tests have been carried out on a viaduct along a high-speed railway line. Periodic comparative measurements are carried out using a Total Station to verify static measurements and using inductive sensors to verify dynamic measurements. Tests of the system carried out so far have proven its usefulness for monitoring bridges in a high-speed railway (up to 200 km/h) with high accuracy while determining dynamic displacements.

Keywords:
bridge monitoring, dynamic and static displacements, inertial sensors, total station, indirect measurement

24.Colabella L., Cisilino A., Fachinotti V., Capiel C., Kowalczyk P., Multiscale design of artificial bones with biomimetic elastic microstructures, Journal of the Mechanical Behavior of Biomedical Materials, ISSN: 1751-6161, DOI: 10.1016/j.jmbbm.2020.103748, Vol.108, pp.103748-1-9, 2020
Colabella L., Cisilino A., Fachinotti V., Capiel C., Kowalczyk P., Multiscale design of artificial bones with biomimetic elastic microstructures, Journal of the Mechanical Behavior of Biomedical Materials, ISSN: 1751-6161, DOI: 10.1016/j.jmbbm.2020.103748, Vol.108, pp.103748-1-9, 2020

Abstract:
Cancellous bone is a highly porous, heterogeneous, and anisotropic material which can be found at the epiphyses of long bones and in the vertebral bodies. The hierarchical architecture makes cancellous bone a prime example of a lightweight natural material that combines strength with toughness. Better understanding the mechanics of cancellous bone is of interest for the diagnosis of bone diseases, the evaluation of the risk of fracture, and for the design of artificial bones and bone scaffolds for tissue engineering. A multiscale optimization method to maximize the stiffness of artificial bones using biomimetic cellular microstructures described by a finite set of geometrical micro-parameters is presented here. The most outstanding characteristics of its implementation are the use of: an interior point optimization algorithm, a precalculated response surface methodology for the evaluation of the elastic tensor of the microstructure as an analytical function of the micro-parameters, and the adjoint method for the computation of the sensitivity of the macroscopic mechanical response to the variation of the micro-parameters. The performance and effectiveness of the tool are evaluated by solving a problem that consists in finding the optimal distribution of the microstructures for a proximal end of a femur subjected to physiological loads. Two strategies for the specification of the solid volume fraction constraints are assessed. The results are compared with data of a computed tomography study of an actual human bone. The model successfully predicts the main features of the spatial arrangement of the trabecular and cortical microstructures of the natural bone.

Keywords:
multiscale optimization, cancellous bone, bone scaffolds, parameterized microstructures

25.Hou J., Wang H., Xu D., Jankowski Ł., Wang P., Damage identification based on adding mass for liquid-solid coupling structures, Applied Sciences, ISSN: 2076-3417, DOI: 10.3390/app10072312, Vol.10, No.7, pp.2312-1-20, 2020
Hou J., Wang H., Xu D., Jankowski Ł., Wang P., Damage identification based on adding mass for liquid-solid coupling structures, Applied Sciences, ISSN: 2076-3417, DOI: 10.3390/app10072312, Vol.10, No.7, pp.2312-1-20, 2020

Abstract:
Damage identification for liquid–solid coupling structures remains a challenging topic due to the influence of liquid and the limitation of experimental conditions. Therefore, the adding mass method for damage identification is employed in this study. Adding mass to structures is an effective method for damage identification, as it can increase not only the experimental data but also the sensitivity of experimental modes to local damage. First, the fundamental theory of the adding mass method for damage identification is introduced. After that, the method of equating the liquid to the attached mass is proposed by considering the liquid–solid coupling. Finally, the effectiveness and reliability of damage identification, based on adding mass for liquid–solid coupling structures, are verified through experiments of a submerged cantilever beam and liquid storage tank.

Keywords:
structural health monitoring, damage identification, liquid-solid coupling, adding mass, sensitivity

26.Boopathi S., Poma Bernaola A., Kolandaivel P., Novel 2019 coronavirus structure, mechanism of action, antiviral drug promises and rule out against its treatment, Journal of Biomolecular Structure and Dynamics, ISSN: 0739-1102, DOI: 10.1080/07391102.2020.1758788, pp.1-17, 2020
Boopathi S., Poma Bernaola A., Kolandaivel P., Novel 2019 coronavirus structure, mechanism of action, antiviral drug promises and rule out against its treatment, Journal of Biomolecular Structure and Dynamics, ISSN: 0739-1102, DOI: 10.1080/07391102.2020.1758788, pp.1-17, 2020

Abstract:
In the past two decades, the world has faced several infectious disease outbreaks. Ebola, Influenza A (H1N1), SARS, MERS, and Zika virus have had a massive global impact in terms of economic disruption, the strain on local and global public health. Most recently, the global outbreak of novel coronavirus 2019 (SARS-CoV-2) that causes COVID-19 is a newly discovered virus from the coronavirus family in Wuhan city, China, known to be a great threat to the public health systems. As of 15 April 2020, The Johns Hopkins University estimated that the COVID-19 affected more than two million people, resulting in a death toll above 130,000 around the world. Infected people in Europe and America correspond about 40% and 30% of the total reported cases respectively. At this moment only few Asian countries have controlled the disease, but a second wave of new infections is expected. Predicting inhibitor and target to the COVID-19 is an urgent need to protect human from the disease. Therefore, a protocol to identify anti-COVID-19 candidate based on computer-aided drug design is urgently needed. Thousands of compounds including approved drugs and drugs in the clinical trial are available in the literature. In practice, experimental techniques can measure the time and space average properties but they cannot be captured the structural variation of the COVID-19 during the interaction of inhibitor. Computer simulation is particularly suitable to complement experiments to elucidate conformational changes at the molecular level which are related to inhibition process of the COVID-19. Therefore, computational simulation is essential tool to elucidate the phenomenon. The structure-based virtual screening computational approach will be used to filter the best drugs from the literature, the investigate the structural variation of COVID-19 with the interaction of the best inhibitor is a fundamental step to design new drugs and vaccines which can combat the coronavirus. This mini-review will address novel coronavirus structure, mechanism of action, and trial test of antiviral drugs in the lab and patients with COVID-19.

Keywords:
coronavirus, computational simulation, coronavirus spike, ACE2 receptor, antiviral drugs, COVID-19

27.Papliński P., Wańkowicz J., Śmietanka H., Ranachowski P., Ranachowski Z., Kúdela Jr S., Aleksiejuk M., Comparative studies on degradation of varistors subjected to operation in surge arresters and surge arrester counters, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.24425/amm.2020.131739, Vol.65, No.1, pp.367-374, 2020
Papliński P., Wańkowicz J., Śmietanka H., Ranachowski P., Ranachowski Z., Kúdela Jr S., Aleksiejuk M., Comparative studies on degradation of varistors subjected to operation in surge arresters and surge arrester counters, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.24425/amm.2020.131739, Vol.65, No.1, pp.367-374, 2020

Abstract:
The paper presents results of investigation of microstructure and micro-hardness for material of ZnO varistors applied to 110 kV surge arrester and surge arrester counter. The research combined two pairs of varistors, each consisted of one varistor subjected before to operation, while the other one was brand new unit and constituted a reference. All varistors were made of the same material by the reputable manufacture. The tests revealed a different degree of the material degradation for varistors subjected before to operation. This also refers to different degradation mechanism observed for the material of these varistors, if typical effects of degradation of aged ZnO varistors were considered as a reference. Physical state of spinel in the microstructure had a significant impact on the material degradation, however a considerable loosening of the microstructure associated with bismuth oxide was observed too. It was surprising, since the precipitates of the bismuth oxide phase most often showed very good binding to the ZnO matrix and high resistance to associated electrical, thermal and mechanical effects. The degradation effects in the ZnO matrix proved to be limited only.

Keywords:
surge arrester, surge arrester counter, MO varistors, microstructure of ceramics, ceramic material degradation

28.Pęcherski R.B., Rusinek A., Frąś T., Nowak M., Nowak Z., Energy-based yield condition for orthotropic materials exhibiting asymmetry of elastic range, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.24425/amm.2020.132819, Vol.65, No.2, pp.771-778, 2020
Pęcherski R.B., Rusinek A., Frąś T., Nowak M., Nowak Z., Energy-based yield condition for orthotropic materials exhibiting asymmetry of elastic range, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.24425/amm.2020.132819, Vol.65, No.2, pp.771-778, 2020

Abstract:
The aim of the paper is to formulate physically well founded yield condition for initially anisotropic solids revealing the asymmetry of elastic range. The initial anisotropy occurs in material primarily due to thermo-mechanical pre-processing and plastic deformation during the manufacturing processes. Therefore, materials in the "as-received" state become usually anisotropic. After short account of the known limit criteria for anisotropic solids and discussion of mathematical preliminaries the energy-based criterion for orthotropic materials was formulated and confronted with experimental data and numerical predictions of other theories. Finally, possible simplifications are discussed and certain model of isotropic material with yield condition accounting for a correction of shear strength due to initial anisotropy is presented. The experimental verification is provided and the comparison with existing approach based on the transformed-tensor method is discussed.

Keywords:
energy-based yield condition, orthotropic solids, initial anisotropy, strength differential effect, numerical simulation

29.Proniewska K., Pręgowska A., Malinowski P., Identification of human vital functions directly relevant to the respiratory system based on the cardiac and acoustic parameters and random forest, IRBM, ISSN: 1959-0318, DOI: 10.1016/j.irbm.2020.02.006, pp.1-6, 2020
Proniewska K., Pręgowska A., Malinowski P., Identification of human vital functions directly relevant to the respiratory system based on the cardiac and acoustic parameters and random forest, IRBM, ISSN: 1959-0318, DOI: 10.1016/j.irbm.2020.02.006, pp.1-6, 2020

Abstract:
Regarding sleep research, polysomnography (PSG) also called a sleep study, is a gold standard. It incorporates brain waves, the oxygen level in the blood, heart rate and breathing, and leg movement recordings. PSG is a complicated and expensive laboratory-based procedure, usually done in hospitals or special sleep center. In this study, an alternative technique for Sleep-Related Breathing Disorders (SRBD) based on selected cardiac and acoustic parameters and the Random Forest (RF) has been studied. A system dedicated to the detection of simultaneously acquired ECG and acoustic signals, which are collected during sleep at home environment is proposed. Results obtained indicate that classification and regression tree models such as RF are appropriate for the evaluation of sleep disorders like SRBD. The best identification of sleep irregularities at level 89.00 percent for the raw database was obtained. Thus, statistical predictive models allow identification of breathing events with high levels of sensitivity and specificity, providing an inexpensive and accurate diagnosis.

Keywords:
patient monitoring, random forest, disorders, biomarkers

30.Ranachowski Z., Ranachowski P., Brodecki A., Kopeć M., Kúdela Jr S., Quasi-static and dynamic testing of carbon fiber reinforced magnesium composites, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.24425/amm.2020.132836, Vol.65, No.2, pp.893-899, 2020
Ranachowski Z., Ranachowski P., Brodecki A., Kopeć M., Kúdela Jr S., Quasi-static and dynamic testing of carbon fiber reinforced magnesium composites, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.24425/amm.2020.132836, Vol.65, No.2, pp.893-899, 2020

Abstract:
Two types of composites, consisting of pure magnesium matrix reinforced with two commercially used carbon fibers, were systematically studied in this paper. The composites fabricated by the pressure infiltration method, were subjected to quasistatic and dynamic compression tests. Morphology of fiber strands was observed using scanning electron microscope (SEM). The application of carbon fibre reinforcement led to the stiffening of tested materials, resulting in the limitation of the possible compression to approx. 2.5%. The performed tests revealed the remarkable difference in compression strength of investigated compositions. The cause of that effect was that GRANOC fiber reinforced composite exhibited insufficient bond quality between the brittle fibers and the ductile matrix. T300 reinforced composite presented good connection between reinforcement and matrix resulting in increased mechanical properties. Investigated composites demonstrated higher mechanical strength during deformation at high strain rates. Microscopic observations also proved that the latter fibers with regular shape and dense packaging within the filaments are proper reinforcement when designing the lightweight composite material.

Keywords:
Mg matrix composite, compressive properties, carbon fiber, Split-Hopkinson pressure bar

31.Konowrocki R., Modelling of Dynamic Aspects of Operation In Railway Vehicle Traction Drive System Including the Electromechanical Coupling, Rail Vehicles 2018, XXIII Scientific Conference 'Rail Vehicles 2018', 2018-05-22/05-25, Katowice, Chorzow (Poland) (PL), DOI: 10.20858/sjsutst.2019.105.9, No.105, pp.101-111, 2019
Konowrocki R., Modelling of Dynamic Aspects of Operation In Railway Vehicle Traction Drive System Including the Electromechanical Coupling, Rail Vehicles 2018, XXIII Scientific Conference 'Rail Vehicles 2018', 2018-05-22/05-25, Katowice, Chorzow (Poland) (PL), DOI: 10.20858/sjsutst.2019.105.9, No.105, pp.101-111, 2019

Abstract:
In this paper, the influence of electromechanical interaction in an electric motor on the railway vehicle driving system dynamics was investigated. This is the train driven by DC. In particular, there is considered influence of electromagnetic field between a rotor and stator on excitation of resonant torsional vibrations of the drive system. Conclusions drawn from the computational results can be very useful during the design phase of these devices as well as helpful for their users during regular maintenance.

Keywords:
railway drive system, electromechanical coupling, numerical analysis, electric motor, torsion vibration, railway vehicle operation

32.Dobrosielski W.T., Zarzycki H., Czerniak J.M., Szczepański J., New fuzzy numbers comparison operators in energy effectiveness simulation and modeling systems, ECMS 2018, 32nd EUROPEAN Conference on Modelling and Simulation, 2018-05-22/05-25, Wilhelmshaven (DE), DOI: 10.7148/2018-0454, pp.1-6, 2018
Dobrosielski W.T., Zarzycki H., Czerniak J.M., Szczepański J., New fuzzy numbers comparison operators in energy effectiveness simulation and modeling systems, ECMS 2018, 32nd EUROPEAN Conference on Modelling and Simulation, 2018-05-22/05-25, Wilhelmshaven (DE), DOI: 10.7148/2018-0454, pp.1-6, 2018

Abstract:
Energy efficiency is often a key optimization problem. Many control systems use fuzzy logic and as a result applying compare operators to fuzzy numbers. The article deals with the issue of comparing fuzzy numbers. The similarity relation is most probably the most frequently used and the most difficult to precisely determine the convergence measure. Analysis of the similarity of two objects is a basic assessment tool and constitutes the basis for reasoning by analogy. It also directly affects the energy effectiveness of the universe that it controls. This article presents the methods for determining the similarity used in fuzzy logic. Many of these methods were dedicated only to fuzzy triangular or trapezoidal numbers (Dobrosielski et al. 2017, Chi-Tsuen Yeh 2017, Abbasbandy and Hajjar 2009). This was a computational inconvenience and posed a question about the axiological basis of this type of comparison. The authors proposed two new approaches for comparing fuzzy numbers using one of the known extensions of fuzzy numbers (Kacprzyk and Wilbik 2009, 2005). This allowed to simplify the operation and eliminate the duality (Zadrożny, 2004).

Keywords:
fuzzy logic, comparison, OFN, GR, ML, TR

33.Balevicius R., Kacianauskas R., Mróz Z., Sielamowicz I., Comparison of wall pressures measured in the model silo with DEM simulation, Prace IPPT - IFTR Reports, ISSN: 2299-3657, pp.220-221, 2008
34.Ziętek G., Mróz Z., Description of cyclic hardening of material with plasticity induced martensitic transformation, Prace IPPT - IFTR Reports, ISSN: 2299-3657, pp.430-431, 2008
35.Paczelt I., Mróz Z., Numerical analysis of some steady state wear problems, Prace IPPT - IFTR Reports, ISSN: 2299-3657, pp.74-75, 2008
36.Szczepański J., On a problem of Nirenberg concerning expanding maps in Hilbert space, Proceedings of the American Mathematical Society, ISSN: 1088-6826, DOI: 10.2307/2159486, Vol.116, No.4, pp.1041-1044, 1992
Szczepański J., On a problem of Nirenberg concerning expanding maps in Hilbert space, Proceedings of the American Mathematical Society, ISSN: 1088-6826, DOI: 10.2307/2159486, Vol.116, No.4, pp.1041-1044, 1992

Abstract:
Let H be a Hubert space and f: H —» H a continuous map which is expanding (i.e., ||f(x) — f(y)|| >= ||x - y|| for all x, y ε H) and such that f(H) has nonempty interior. Are these conditions sufficient to ensure that f is onto? This question was stated by Nirenberg in 1974. In this paper we give a partial negative answer to this problem; namely, we present an example of a map F: H —» H which is not onto, continuous, F(H) has nonempty interior, and for every x, y ε H there is no ε N (depending on x and y) such that for every n > no ||F^n(x)-F^n(y)||>=c^(n-m)||x-y|| where F^n is the nth iterate of the map F , c is a constant greater than 2, and m is an integer depending on x and y. Our example satisfies ||F(x)|| = c||x|| for all x ε H . We show that no map with the above properties exists in the finite-dimensional case.

37.Nasalski W., Tamir T., Lin L., Displacement of the intensity peak in narrow beams reflected at a dielectric interface, Journal of the Optical Society of America A, ISSN: 1084-7529, DOI: 10.1364/JOSAA.5.000132, Vol.5, No.1, pp.132-140, 1988
Nasalski W., Tamir T., Lin L., Displacement of the intensity peak in narrow beams reflected at a dielectric interface, Journal of the Optical Society of America A, ISSN: 1084-7529, DOI: 10.1364/JOSAA.5.000132, Vol.5, No.1, pp.132-140, 1988

Abstract:
The net displacement of the intensity peak in relatively narrow Gaussian beams reflected at a dielectric interface is shown to be produced by a combination of four distinct nonspecular effects, namely, lateral, focal, and angular shifts and a modification of the beam-waist magnitude. We also find that these effects cause the axis of the reflected beam to follow a trajectory that depends on the beam width and on the distance from the waist of the geometric-optical reflected beams. To determine all the details of this nonspecular behavior, we derive a new expression for the reflected field; in contrast to previously reported results, this expression also holds for small beam widths and for incidence angles equal or close to the critical angle of total reflection. Our derivation yields accurate results for the four distinct nonspecular effects and provides a consistent explanation of the available experimental data on the net displacement of the beam peak.