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Wyniki wyszukiwania dla: body of revolution (bor), cylindrical waveguides, finite-element method (fem), generalized impedance matrix (gim), periodic structures, scattering, waveguide discontinuities.
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Minimization of vibrations during milling of flexible structures using mechatronic design techniques
PublikacjaThe paper presents an innovative effective method of minimizing vibrations during milling of flexible structures, using a new vibration suppression method based on a workpiece holder with adjustable support stiffness. The proposed method is rooted in mechatronic design techniques, which can become a standard procedure for optimizing the milling process.
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Role of methylation in electron scattering on X(CH3)4 (X= C, Si, Ge) molecules (2)
PublikacjaTo investigate how replacement of H atom with methyl group (CH3) – in tetrahedral compounds of carbon, silicon and germanium – affects electron scattering process, total cross sections (TCS) for electron scattering from C(CH3)4, Si(CH3)4 and Ge(CH3)4 molecules have been compared with data for CH4, SiH4 and GeH4 molecules. All examined data have been obtained with the same experimental setup. The shape of all discussed TCS energy...
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Application of Analytic Signal and Smooth Interpolation in Pulse Width Modulation for Conventional Matrix Converters
PublikacjaThe paper proposes an alternative and novel approach to the PWM duty cycles computation for Conventional Matrix Converters (CMC) fed by balanced, unbalanced or non–sinusoidal AC voltage sources. The presented solution simplifies the prototyping of direct modulation algorithms. PWM duty cycles are calculated faster by the smooth interpolation technique, using only vector coordinates, without trigonometric functions and angles. Both...
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Model Order Reduction for Problems With Dispersive Surface Boundary Conditions
PublikacjaThis letter proposes a new scheme for reduced-order finite-element modeling of electromagnetic structures with nonlinear, dispersive surface boundary conditions, which optimally exploits the numerically stable and efficient MOR framework for second-order systems provided by SAPOR method. The presented results of numerical experiments for an example of a waveguide filter demonstrate the superior accuracy of the resulting reduced models...
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Design of dimensionally stable composites using efficient global optimization method
PublikacjaDimensionally stable material design is an important issue for space structures such as space laser communication systems, telescopes, and satellites. Suitably designed composite materials for this purpose can meet the functional and structural requirements. In this paper, it is aimed to design the dimensionally stable laminated composites by using efficient global optimization method. For this purpose, the composite plate optimization...
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Process control of air stream deodorization from vapors of VOCs using a gas sensor matrix conducted in the biotrickling filter (BTF)
PublikacjaThis article presents the validity, advisability and purposefulness of using a gas sensor matrix to monitor air deodorization processes carried out in a peat-perlite-polyurethane foam-packed biotrickling filter. The aim of the conducted research was to control the effectiveness of air stream purification from vapors of hydrophobic compounds, i.e., n-hexane and cyclohexane. The effectiveness of hydrophobic n-hexane and cyclohexane...
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Impedance monitoring of corrosion degradation of plasma electrolytic oxidation coatings (PEO) on magnesium alloy
PublikacjaImpedance technique based on continuous multisinusoidal current perturbation was used to explain degradation process of plasma electrolytic oxidation coatings (PEO) on magnesium alloy. An obtained impedance spectrum was fitted by electrical equivalent circuit to describe properties of conversion layer on magnesium alloy. Additionally, galvanostatic mode maintained during experiment, with DC current equal to zero, allowed to achieve...
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A Compact Basis for Reliable Fast Frequency Sweep via the Reduced-Basis Method
PublikacjaA reliable reduced-order model (ROM) for fast frequency sweep in time-harmonic Maxwell’s equations by means of the reduced-basis method is detailed. Taking frequency as a parameter, the electromagnetic field in microwave circuits does not arbitrarily vary as frequency changes, but evolves on a very low-dimensional manifold. Approximating this low-dimensional manifold by a low dimension subspace, namely, reduced-basis space, gives...
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The Conceptual Research over Low-Switching Modulation Strategy for Matrix Converters with the Coupled Reactors
PublikacjaIn this paper, different Pulse Width Modulation (PWM) strategies for operating with a low-switching frequency, a topology that combines Conventional Matrix Converters (CMCs), and Coupled Reactors (CRs) are presented and discussed. The principles of the proposed strategies are first discussed by a conceptual analysis and later validated by simulation. The paper shows how the combination of CMCs and CRs could be of special interest...
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Systems of differential equations with a singular matrix
PublikacjaPraca dotyczy układów równań różniczkowych z macierzą osobliwą. Szczególnymi przypadkami takich układów są równania różniczkowo-algebraiczne. Korzystając z odpowiedniej nierówności różniczkowej dla układów równań i metody quasi linearyzacji pokazano, iż odpowiednie monotoniczne ciągi są zbieżne do rozwiązania naszego problemu i jest to zbieżność kwadratowa. O funkcji f występującej po prawej stronie zagadnienia zakładano...
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A polynomial algorithm for finding T-span of generalized cacti
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Generalized adaptive notch filter with a self-optimization capability
PublikacjaW pracy przedstawiono samonastrajalny wariant tzw. uogólnionego adaptacyjnego filtru wycinającego. Automatycznym strojeniem objęte są dwa współczynniki wzmocnienia adaptacji, odpowiedzialne za śledzenie amplitud i częstotliwości parametrów identyfikowanego obiektu.
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Generalized quazilinearization for systems of degenerate singular perturbation problem
PublikacjaPraca dotyczy ogólnej metody kwazilinearyzacji dla układów równań różniczkowych z parametrami.
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Extended generalized blockmodeling for compound communities and external actors
PublikacjaWiększość sieci społecznych charakteryzuje się swoją wewnętrzną, unikatową strukturą. W artykule poddano analizie sieci społeczne złożone z wielu mniejszych grup społecznościowych, które określamy mianem złożonych sieci społecznych. Dla tego typu sieci zaproponowano rozszerzenie metody ogólnego modelowania blokowego biorąc pod uwagę specyficzną strukturę złożonych sieci społecznych oraz ich relacje z zewnętrznymi aktorami. W oparciu...
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Extended generalized blockmodeling for compound communities and external actors
PublikacjaNiektóre sieci społeczne wykazują się specyficzną strukturą wewnętrzną. W artykule rozpatrujemy społeczności, które składają się z mniejszych wspólnot. Takie społeczności nazywamy społecznościami złożonymi. Dla takich struktur zastosowalismy metodę ogólnego modelowania blokowego proponując odpowiednie rozrzerzenia dla tej metody. Wzięliśmy pod uwagę specyfikę złożonych struktur społecznych oraz ich relacje z aktorami zewnętrznymi...
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Approximation Strategies for Generalized Binary Search in Weighted Trees
PublikacjaWe consider the following generalization of the binary search problem. A search strategy is required to locate an unknown target node t in a given tree T. Upon querying a node v of the tree, the strategy receives as a reply an indication of the connected component of T\{v} containing the target t. The cost of querying each node is given by a known non-negative weight function, and the considered objective is to minimize the total...
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A polynomial algorithm for finding T-span of generalized cacti.
PublikacjaW pracy opisano wielomianowy algorytm wyznaczający optymalne T-pokolorowania dla uogólnionych kaktusów.
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Modelling of in-plane wave propagation in a plate using spectral element method and Kane–Mindlin theory with application to damage detection
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Meso-mechanical modelling of damage in concrete using discrete element method with porous ITZs of defined width around aggregates.
PublikacjaArtykuł omawia wyniki obliczeń numerycznych pękania dla betonu stosując metodę elementów dyskretnych. Beton był opisany jako materiał 4-fazowy i był poddany zginaniu. W obliczeniach uwzględniono strefy ITZ o skończonej szerokości dookoła wszystkich ziaren kruszywa. Nacisk położono na przebieg mikropęknięć przy kruszywie. Wyniki porównano bezpośrednio z doświadczeniami. Obliczenia wykonano także dla szorstkich ziaren kruszywa....
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Chemical Derivatization Processes Applied to Amine Determination in Samples of Different Matrix Composition
PublikacjaAmines are important biological compounds, and so their analysis and monitoring in various matrices is worthy of investigation and development.Due to the polar nature of amines, chromatographic analysis of free amines is generally unsatisfactory owing to adsorption and decomposition of the solute on the column, resulting in peak tailing and losses. Therefore, many derivatization reactions are employed to reduce the polarity, improve...
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Measurements of Spectral Spatial Distribution of Scattering Materials for Rear Projection Screens used in Virtual Reality Systems
PublikacjaRapid development of computing and visualisation systems has resulted in an unprecedented capability to display, in real time, realistic computer-generated worlds. Advanced techniques, including three-dimensional (3D) projection, supplemented by multi-channel surround sound, create immersive environments whose applications range from entertainment to military to scientific. One of the most advanced virtual reality systems are CAVE-type...
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A New Approach to the PWM Modulation for the Multiphase Matrix Converters Supplying Loads with Open-End Winding.
PublikacjaThis article presents three variants of the Pulse Width Modulation (PWM) for the Double Square Multiphase type Conventional Matrix Converters (DSM-CMC) supplying loads with the open-end winding. The first variant of PWM offers the ability to obtain zero value of the common-mode voltage at the load's terminals and applies only six switches within the modulation period. The second proposal archives for less Total Harmonic Distortion...
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Uwarunkowania propagacyjne w ultraszerokopasmowej komunikacji typu off-body w środowisku trudnym
PublikacjaW niniejszym referacie przedstawiono analizę uwarunkowań propagacyjnych w ultraszerokopasmowej komunikacji typu off-body w środowisku trudnym pod względem propagacji fal radiowych. Badania przeprowadzono z użyciem mobilnego stanowiska pomiarowego zawierającego węzły sieci WBAN wyposażone w ultraszerokopasmowe moduły radiowe DWM1000 firmy DecaWave. Uzyskane wartości tłumienia systemowego przeanalizowano dla dwóch dynamicznych scenariuszy...
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Remote Monitoring System for Impedance Spectroscopy using Wireless Sensor Network
PublikacjaThe architecture of a miniaturized impedanceanalyser with wireless communication module for remoteImpedance Spectroscopy (IS) of anticorrosion coatings ondifficult-to-reach objects (e.g. on the steel construction ofthe bridge) is described in this paper. Some practical aspectsof implementation of a Wireless Sensor Network (WSN) arealso discussed. A low scale, middle range, WSN networkcomposed of a Base Station (BS) with a Personal...
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3D buckling analysis of a cylindrical metal bin composed of corrugated sheets strengthened by vertical stiffeners
PublikacjaW artykule pokazano obszerne wyniki analizy wyboczeniowej 3D przy zastosowaniu metody elementów skończonych dla silosu złożonego z blachy falistej i słupów rozmieszczonych równomiernie wokół obwodu. Obliczenia wykonano dla silosu bez i z imperfekcjami geometrycznymi i obciążeniowymi. Wyniki obliczeń porównano z Eurokodem.
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Critical assessment of Eurocode approach to stability of metal cylindrical silos with corrugated walls and vertical stiffeners.
PublikacjaPrzedmiotem artykułu było krytyczne oszacowanie podejścia w Eurokodzie odnośnie stateczności metalowych cylindrycznych silosów z blachy falistej i słupów. Obliczenia 3D wykonane stosując MES. Symulowano blachę gładką ze słupami belkowymi o zastępczej sztywności. W obliczeniach uwzględniono falistość blachy. Pokazano, że wzory normowe znacznie odbiegają od wyników MES.
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Recent steel structures in Poland - the selected projects
PublikacjaThe paper presents selected examples of recently completed steel structures in Poland. These are roofs over sport stadiums, construction of public buildings and bridges. Described examples do not exhaust the acquis in the field of steel constructions in Poland. The authors, however, may hope that the presented con-structions represents current achievements in Poland in the field of steel structures.
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Low-cost multi-objective design of compact microwave structures using domain patching
PublikacjaA good compromise between size and electrical performance is an important design consideration for compact microwave structures. Comprehensive information about size/performance trade-offs can be obtained through multi-objective optimization. Due to considerable electromagnetic (EM) cross-couplings in highly compressed layouts, the design process has to be conducted at the level of high-fidelity EM analysis which is computationally...
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Special Issue: “Non-Destructive Testing of Structures”
PublikacjaThe Special Issue “Non-Destructive Testing of Structures” has been proposed to present recent developments in the field of diagnostics of structural materials and components in civil and mechanical engineering. The papers highlighted in this editorial concern various aspects of non-invasive diagnostics, including such topics as condition assessments of civil and mechanical structures and connections of structural elements, the...
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Optimization of the Relative Humidity of Reactant Gases in Hydrogen Fuel Cells Using Dynamic Impedance Measurements
PublikacjaWater management is a key factor affecting the efficiency of proton exchange membrane fuel cells (PEMFCs). The currently used monitoring methods of PEMFCs provide limited information about which processes or components that humidity has a significant impact upon. Herein, we propose the use of a novel approach of impedance measurements using a multi-sinusoidal perturbation signal, which enables impedance measurements under dynamic...
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Finite-state lexical tools
PublikacjaArtykuł przedstawia trzy pakiety oprogramowania zawierające narzędzia poziomu leksykalnego wykorzystujące automaty skończone: dwa zbiory samodzielnych programów i skryptów pomocniczych - jeden używający prostych automatów skończonych, drugi używający automatów Mealy`ego oraz bibliotekę funkcji. Wszystkie przedstawione pakiety posiadają podobne funkcje. Zamiast opisywać poszczególne pakiety, opis skupiony jest na dostarczanych przez...
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Shaping the spatial structures of post-socialist cities
PublikacjaThis paper deals with issues and problems associated with transformation of spatial structures of post-socialist cities. The special attention is paid to the cases of Polish cities and towns and the analysis of their evolution – from the “post-communist structures” to the “cities in the age of globalization”. In the light of this the factors influencing the spatial transformation of these are analyzed. The paper is concluded with...
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Non-linear FEM analysis of earthquake-induced pounding between the main building and the stairway tower of the Olive View Hospital
PublikacjaCelem artykułu jest dokładna, trójwymiarowa analiza MES dotycząca zderzeń pomiędzy budynkiem głównym a konstrukcją wolnostojącej klatki schodowej szpitala Olive View podczas trzęsienia ziemi San Fernando w roku 1971. Wyniki analizy pokazują, iż kolizje mogą prowadzić do znacznego wzrostu odpowiedzi lżejszej konstrukcji klatki schodowej, powodować uszkodzenia w miejscach kontaktu oraz potęgować uszkodzenia u podstawy tej budowli....
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Curve Curvature Analysis of a Grain Trajectories in Variable Honing of Cylindrical Holes of Thin Wall Cylinder Liners as a Honing Process Optimization Strategy
PublikacjaThe main problem of honing of thin wall cylinder liners is a thermal distortion of honed holes. The higher the value of the temperature of the honed workpiece, the greater its holes deformation. The paper presents a method of reducing the temperature occurring in the honing process as a result of the application of a variable honing kinematics conditions with particular emphasis on the analysis of the effect of the value of the...
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New matrix-free reference material for ethene in the form of optical fibres
PublikacjaReference materials are indispensable in the qualitycontrol and quality assurance of analytical measurements. Onenovel approach to the generation of standard gaseous mixturesof toxic, reactive, volatile, labile, and malodorous substancesinvolves thermal decomposition or rearrangement, under definedtemperature conditions, of compounds immobilized, bychemical bonding, on the surface of an appropriate carrier torelease specific amounts...
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A Quantitative Investigation of Dislocation Density in an Al Matrix Composite Produced by a Combination of Micro-/Macro-Rolling
PublikacjaAn aluminum matrix composite with dispersed carbon nanotubes (CNTs) was produced via flake powder metallurgy using a micro-rolling process and vacuum hot pressing (VHP), followed by conventional rolling using a macro-rolling process. The microstructure and mechanical properties of the produced composites were studied. In addition, a new quantitative model was introduced to study the dislocation density based on the microstructural...
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Application of quartz crystal microbalance and dynamic impedance spectroscopy to the study of copper corrosion inhibitors
PublikacjaThe study investigates the application of Dynamic Electrochemical Impedance Spectroscopy (DEIS) and Electrochemical Quartz Crystal Microbalance (EQCM) techniques to examine the corrosion inhibition of copper by Benzotriazole and Sodium Folate in a 0.1 M NaCl solution. DEIS, an advanced version of Electrochemical Impedance Spectroscopy (EIS), allows for real-time monitoring of non-stationary electrochemical systems,...
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Probabilistic sensitivity of limit states of structures : The Monte Carlo simulation
PublikacjaThe main issue of the paper is the probabilistic sensitivity of the limit states of structures with respect to selected input design variables. Attempt to the problem is done by the dedicated Monte Carlo simulation procedure. Basic design variables are random variables of given probability distributions, presented in the form of random numbers. Uni-parametrical increment of the dominant basic variable (basic variables) is done,...
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Computational modelling of historic masonry railroad arch bridges
PublikacjaThe problems encountered during the analyzes of structural response of historic masonry railroad arch bridges are described in this paper. The attention is mainly focused on the stiffness of the masonry arches, their strengths and appropriate estimation of railroad load intensity. Issues related to computational modelling of two, existing, almost 130 years old masonry arch railroad bridges are presented in this context. The main...
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Evaluation of Temperature Influence on Electrochemical Processes Occurring in a Lithium-Ion Supercapacitor with the Use of Dynamic Electrochemical Impedance Spectroscopy
PublikacjaIn order to obtain the full impedance characteristics of a lithium-ion capacitor as a function of temperature, the authors proposed the use of dynamic electrochemical impedance spectroscopy. Impedance tests were carried out under wide range of dynamic temperature changes for lithium-ion supercapacitors. Significant differences in electrochemical processes were observed as a result of working temperature. Moreover, the quality of...
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Two-Rate Based Low-Complexity Variable Fractional-Delay FIR Filter Structures
PublikacjaThis paper considers two-rate based structures for variable fractional-delay (VFD) finite-length impulse response (FIR) filters. They are single-rate structures but derived through a two-rate approach. The basic structure considered hitherto utilizes a regular half-band (HB) linear-phase filter and the Farrow structure with linear-phase subfilters. Especially for wide-band specifications, this structure is computationally efficient...
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Cyclic behaviour modelling of additively manufactured Ti-6Al-4V lattice structures
PublikacjaThe present work is concerned with the numerical modelling of the cyclic behaviour of Ti-6Al-4V lattice structures. In the study, diamond structures of titanium alloy produced by the additive laser powder bed fusion (LPBF) method with different degrees of relative density were used. Realistic geometric models of the studied mesostructures were generated using computed microtomography, taking into account the imperfections of the...
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Joint experimental and theoretical study on low-energy elastic electron scattering by gaseous alkynes: Differential cross sections, shape resonances, and methylation effects
PublikacjaA detailed comparison of experimental and theoretical elastic cross sections for low-energy electron scattering by ethyne, taken earlier in our group by Gauf et al. [Phys. Rev. A 87, 012710 (2013)], and some of its methylated derivatives, propyne, and the isomers 1-butyne and 2-butyne, taken here, are presented. The present differential cross sections were measured at incident electron energies ranging from 1 eV to 30 eV and...
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Low-energy positron scattering from gas-phase pyrimidine: A quantum treatment of the dynamics and a comparison with experiments
PublikacjaWe are reporting detailed quantum scattering calculations that describe the diffusion of a beam of low-energy positrons interacting with the pyrimidine target as a gas-phase partner. The calculations have employed an essentially ab initio model for the short-range correlation interaction and for the electrostatic interaction of an impinging positron and the electron+nuclear structure of the target molecule at its equilibrium geometry.
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Rubrene Thin Films with Viably Enhanced Charge Transport Fabricated by Cryo-Matrix-Assisted Laser Evaporation
PublikacjaAmong organic semiconductors, rubrene (RB; C42H28) is of rapidly growing interest for the development of organic and hybrid electronics due to exceptionally long spin diffusion length and carrier mobility up to 20 cm2V−1s−1 in single crystals. However, the fabrication of RB thin films resembling properties of the bulk remains challenging, mainly because of the RB molecule’s twisted conformation. This hinders the formation of orthorhombic...
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Electrical and mechanical characterization of two-phase alloys by means of scanning probe microscopy in dynamic impedance spectroscopy mode
PublikacjaDynamic impedance spectroscopy, evaluated for measuring non-stationary systems, was used in combination with scanning probe microscope. Using this approach, localized impedance measurements in the AFM contact mode could be carried out. Additionally, impedance–force curves were made at each phase of investigated materials to illustrate the relation between impedance and the force applied to a probe. Therefore, correlation of electrical...
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Torsional Stability Assessment of Columns Using Photometry and FEM
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Geometrically nonlinear FEM analysis of 6-parameter resultant shell theory based on 2-D Cosserat constitutive model
PublikacjaWe develop the elastic constitutive law for the resultant statically and kinematically exact, nonlinear, 6-parameter shell theory. The Cosserat plane stress equations are integrated through-the- thickness under assumption of the Reissner-Mindlin kinematics. The resulting constitutive equations for stress resultant and couple resultants are expressed in terms of two micropolar constants: the micropolar modulus Gc and the micropolar...
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Design and experimental investigations of a cylindrical microjet heat exchanger for waste heat recovery systems
PublikacjaCompact heat exchangers have more and more applications in many areas, including the HVAC, food and petrochemical industry. This paper describes the development of heat exchanger technology for waste heat recovery (WHR) from a range of processes. Case-study testing shows that the proposed heat exchanger can successfully enhance heat transfer and recover waste heat in a range of applications making them economically, environmentally and...
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The Conley Index and Rigorous Numerics for Attracting Periodic Orbits
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