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Wyniki wyszukiwania dla: SENSITIVITY ANALYSIS, FREE TORSIONAL VIBRATION FREQUENCIES, THIN-WALLED BEAMS, ANALYTICAL SOLUTION, FEM
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Debonding Size Estimation in Reinforced Concrete Beams Using Guided Wave-Based Method
PublikacjaThe following paper presents the results of the theoretical and experimental analysis of the influence of debonding size on guided wave propagation in reinforced concrete beams. The main aim of the paper is a development of a novel, baseline-free method for determining the total area of debonding between steel rebar embedded in a concrete cover on the basis of the average wave velocity or the time of flight. The correctness of...
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Green analytical chemistry metrics: A review
PublikacjaGreen analytical chemistry encourages reducing the use of toxic chemicals/reagents, using energy-efficient equipment, and generating minimal waste. The recent trends in analytical method development focus on the miniaturization of the sample preparation devices, the development of solventless or solvent-minimized extraction techniques, and the utilization of less toxic solvents. The twelve principles of GAC serve as a basic guideline...
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Behavior of residual current devices at frequencies up to 50 kHz
PublikacjaThe use of residual current devices (RCDs) is obligatory in many types of low-voltage circuits. They are devices that ensure protection against electric shock in the case of indirect contact and may ensure additional protection in the case of direct contact. For the latter purpose of protection, only RCDs of a rated residual operating current not exceeding 30 mA are suitable. Unfortunately, modem current-using equipment supplied...
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Technique to improve CMRR at high frequencies in CMOS OTA-C filters
PublikacjaIn this paper a technique to improve the common-mode rejection ratio (CMRR) at high frequencies in the OTA-C filters is proposed. The technique is applicable to most OTA-C filters using CMOS operational transconductance amplifiers (OTA) based on differential pairs. The presented analysis shows that a significant broadening of CMRR bandwidth can be achieved by using a differential pair with the bodies of transistors connected to...
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Selected problems of sensitivity and reliability of a jack-up platform
PublikacjaThe paper deals with sensitivity and reliability applications to numerical studies of an off-shore platform model. Structural parameters and sea conditions are referred to the Baltic jack-up drilling platform. The study aims at the influence of particular basic variables on static and dynamic response as well as the probability of failure due to water waves and wind loads. The paper presents the sensitivity approach to a generalized...
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Materials for Mediator-free Electron Transfer in the Enzymatic Electrodes of Biobatteries and Biofuel Cells
PublikacjaWe present functionalization of single-walled carbon nanotubes (SWCNTs) and their application in the enzymatic fuel cells construction. SWCNTs were covalently modified with different types of aromatic moieties. Free radical reaction was employed to create direct carbon-carbon bond between moiety and SWCNTs. In second approach functionalization takes place through amide bonding. Functionalized SWCNTs were characterized by spectroscopy...
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A GPU Solver for Sparse Generalized Eigenvalue Problems with Symmetric Complex-Valued Matrices Obtained Using Higher-Order FEM
PublikacjaThe paper discusses a fast implementation of the stabilized locally optimal block preconditioned conjugate gradient (sLOBPCG) method, using a hierarchical multilevel preconditioner to solve nonHermitian sparse generalized eigenvalue problems with large symmetric complex-valued matrices obtained using the higher-order finite-element method (FEM), applied to the analysis of a microwave resonator. The resonant frequencies of the low-order...
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Experimental tests of reinforced concrete deep-beams
PublikacjaThe paper presents results of experimental research of the reinforced concrete deep beam with a spatial arrangement. Tested structural elements consist of the cantilever deep beam loaded on the height and transverse deep beam with hanging on it another one. The analysis includes crack morphology, effort of steel and load distribution. The article verified effectiveness of two different kind of reinforcement in both tested deep...
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Modelling methods in design (CAD, FEM)
Kursy Online -
Local buckling of compressed flange of cold-formed channel members made of aluminum alloy
PublikacjaThe paper deals with local buckling of a compressed single flange of thin-walled channel cold- formed columns and beams made of aluminum alloy. Material is described by means of the Ramberg-Osgood constitutive equation. Axial compression of the columns and beams undergoing bending is taken into consid- eration. A simple model of the member flange in the form a long beam elastically connected to the web is used to find the critical...
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Unusual divergence of magnetoacoustic beams
PublikacjaTwo-dimensional magnetosonic beams directed along a line forming a constant angle h with the equilibrium straight magnetic field are considered. Perturbations in a plasma are described by the system of ideal magnetohydrodynamic equations. The dynamics of perturbations in a beam are different in the cases of fast and slow modes, and it is determined by h and equilibrium parameters of a plasma. In particular, a beam divergence may...
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Quantum corrections to quasi-periodic solution of Sine-Gordon model and periodic solution of phi^4 model
PublikacjaAnalytical form of quantum corrections to quasi-periodic solution of Sine-Gordon model and periodic solution of phi^4 model is obtained through zeta function regularisation with account of all rest variables of a d-dimensional theory. Qualitative dependence of quantum corrections on parameters of the classical systems is also evaluated for a much broader class of potentials u(x) = b^2 f(bx) + C with b and C as arbitrary real constants
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Probabilistic sensitivity of the limit states of structures using Monte Carlom simulation
PublikacjaThe paper presents the concept of probabilistic sensitivity of structural limit states with respect to given design variables. A general idea is presented, illustrated by a simple case solved in an analytical way. More general approach is presented for the engineering structures, in this case a dedicated Monte Carlo simulation procedure is involved as part of the methodology. Illustration of the engineering case is done, by means...
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Local and global response of sandwich beams made of GFRP facings and PET foam core in three point bending test
PublikacjaIn the paper behaviour of laminated sandwich beams (FRP face sheet – PET foam core – FRP face sheet) subjected to three point bending is studied. The paper aim is to find practical descriptions enabling effective and accurate estimation of the elastic response, damage and failure of the beams, basing on experiments and static calculations. Therefore a number of tests are described, that were done on laminated coupons and foam specimens...
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Preparation of samples for analysis: the key to analytical success
PublikacjaW rozdziale przedstawiono informacje literaturowe o nowych rozwiązaniach metodycznych w zakresie:-izolacji i/lub wzbogacania śladowych składników z próbek środowiskowych-mineralizacji próbek.Szczególna uwagę zwrócono na wykorzystanie w procesie przygotowania próbek nowych typów rozpuszczalników i mediów reakcyjnych spełniających wymogi związane z koncepcją zrównoważonego rozwoju.
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Probabilistic sensitivity of limit states of structures. The Monte Carlo simulation
PublikacjaDesign sensitivity deals with the variation of structural response, implicitly dependent on the design variables of the problem. An attempt is made to implement probabilistic notation in engineering sensitivity analysis. The procedure to implement the sensitivity of a structural limit state to a given basic variable is described in the paper - its main idea, depicted by a flowchart and numerical examples of engineering analysis....
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Functional fluorine-doped tin oxide coating for opto-electrochemical label-free biosensors
PublikacjaSensors operating in multiple domains, such as optical and electrochemical, offer properties making biosensing more effective than those working in a single domain. To combine such domains in one sensing device, materials offering a certain set of properties are required. Fluorine-doped tin oxide (FTO) thin film is discussed in this work as functional optically for guiding lossy modes and simultaneously electrochemically, i.e....
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Assessment of dynamic characteristics of thin cylindrical sandwich panels with magnetorheological core
PublikacjaBased on the equivalent single-layer linear theory for laminated shells, free and forced vibrations of thin cylindrical sandwich panels with magnetorheological core are studied. Five variants of available magnetorheological elastomers differing in their composition and physical properties are considered for smart viscoelastic core. Coupled differential equations in terms of displacements based on the generalized kinematic hypotheses...
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Thermo-elastic non-linear analysis of multilayered plates and shells
PublikacjaGeometrically nonlinear FEM analysis of multilayered composite plates and shells is performed in order to resolve the stability problem of the structures being under the influence of temperature field. The Riks-Wempner-Ramm algorithm with a specially modified multi-choice unloading condition has been implemented in authors’ numerical code. As the representation of multilayered medium the Equivalent Single Layer approach with the...
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Thermal Instability of Gold Thin Films
PublikacjaThe disintegration of a continuous metallic thin film leads to the formation of isolated islands, which can be used for the preparation of plasmonic structures. The transformation mechanism is driven by a thermally accelerated diffusion that leads to the minimalization of surface free energy in the system. In this paper, we report the results of our study on the disintegration of gold thin film and the formation of nanoislands...
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Green analytical chemistry: Social dimension and teaching
PublikacjaGreen Analytical Chemistry (GAC) is the idea which every analytical chemist should be familiar of. Due to continuous improvement in the subject both from the aspects of theory and experimentation, the dynamic way analytical chemistry studies are evolving in the frame of chemistry degrees should not be surprising. Recently, many efforts have been made in order to include Green Chemistry principles to Education, also in the field...
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A review on analytical models of brushless permanent magnet machines
PublikacjaThis study provides an in-depth investigation of the use of analytical and numerical methods in analyzing electrical machines. Although numerical models such as the finite-element method (FEM) can handle complex geometries and saturation effects, they have significant computational burdens, are time-consuming, and are inflexible when it comes to changing machine geometries or input values. Analytical models based on magnetic equivalent...
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Waste-free synthesis of silica nanospheres and silica nanocoatings from recycled ethanol–ammonium solution
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Theoretical consideration of free convective heat transfer from a round isothermal plate slightly inclined from the vertical
PublikacjaA semi-analytical solution of simplified Navier-Stokes and Fourier-Kirchhoff equations describing free convective heat transfer from a round isothermal surface slightly inclined from the vertical is presented. The solution is based on the assumption, typical for natural convection, that the velocity component normal to the surface is negligibly small in comparison to the tangential one. Next we neglect the nonlinear inertia force...
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SHORT REVIEW AND 3-D FEM ANALYSIS OF BASIC TYPES OF FOUNDATION FOR OFFSHORE WIND TURBINES
PublikacjaSome problems of the foundations of offshore wind turbines are considered in this paper. A short review is presented on the two basic types of foundations, i.e. monopiles and gravity foundations, including their basic features and applications as well as general design considerations. Also, some issues regarding analysis are discussed, including geotechnical problems and modelling techniques. A numerical model of offshores turbine...
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RMS-based damage detection in reinforced concrete beams: numerical simulations
PublikacjaImage-based damage detection methods using guided waves are well known and widely applied approaches in structural diagnostics. They are usually utilized in detection of surface damages or defects of plate-like structures. The article presents results of the study of applicability of imaging wave-based methods in detection in miniscule internal damage in the form of debonding. The investigations were carried out on numerical models...
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FE analysis of a coupled energetic-statistical size effect in plain concrete beams with varying material properties.
PublikacjaThe numerical FE investigations of a coupled energetic-statistical size effect in unnotched concrete beams of similar geometry under quasi-static three point bending were performed within elasto-plasticity with non-local softening. The stochastic FE analyses were carried out with three different beam sizes. Deterministic calculations were performed with the uniform distribution of a uniaxial tensile strength. In statistical calculations...
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Torsional buckling paradox - extended studies.
PublikacjaAnalizowano wyboczenie skrętne pręta cienkościennego o dwuteowym przekroju poprzecznym ze zmienną szerokością półek. Wykazano, że siła krytyczna wyboczenia skrętnego może przekraczać granice wyznaczone przez siły odpowiadające prętom o stałych ekstremalnych szerokościach półek. Ten paradoksalny wynik uzyskano w ramach teorii prętów cienkościennych o przekroju nieodkształcalnym. Przeanalizowano siłę krytyczną wyboczenia skrętnego...
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Acoustic emission signals in concrete beams under 3-point bending (beams #1, #2, #3)
Dane BadawczeThe DataSet contains the results of the mechanical behaviour of concrete beams with dimensions 40 x 40 x 160 cm3under the 3-point bending. The beams were made of concrete with the following ingredients: cement CEM I 42.5R (330 kg/m3), aggregate 0/2 mm (710 kg/m3), aggregate 2/8 mm (664 kg/m3), aggregate 8/16 mm (500 kg/m3), water (165 kg/m3) and super-plasticizer...
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Ultrasonic Tomography of Brick Columns Based on FEM Calculations
PublikacjaUltrasonic tomography is one of the most developed method of non-destructive testing. Despite being used mainly in medicine, it is becoming more and more popular as a method for monitoring of structural elements. It allows to examine the internal structure and technical condition of the tested element. This paper investigates the influence of crosssectional geometry on an obtained tomographic image. Wave propagation signals were...
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Estimation of Failure Initiation in Laminated Composites by means of Nonlinear Six-Field Shell Theory and FEM
PublikacjaThe monography deals with the problem of failure initiation in thin laminated composites. Known techniques of laminate structures modelling are briefly characterised. Eventually, shell based approach is chosen for the purpose of the description of the composite structures behaviour, as it predicts their deformation and states of stress effectively in a global sense. The nonlinear six parameter shell theory (6p theory) with asymmetric...
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Fem analysis of cosserat plates and shells based on some constitutive relations
PublikacjaPrzeprowadzono studium doboru mikropolarnych współczynników konstytutywnych w pewnym modelu płyty Cosseratów. Wyznaczono ograniczenia na ich wartości i przeprowadzono parametryczną analizę wpływu tych współczynników na geometrycznie nieliniowe deformacje powłok z ortogonalnymi przecięciami płatów.
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Failure of cylindrical steel silos composed of corrugated sheets and columns and repair methods using a sensitivity analysis
PublikacjaW artykule omówiono przypadek awarii metalowego silosu z blachy walcowej i pionowych słupów. Wykonano analizę wyboczeniową MES z uwzględnieniem imperfekcji geometrycznych. Omówiono metody naprawcze i ich optymalizację w oparciu o analizę wrażliwości.
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Influence of Added Water Mass on Ship Structure Vibration Parameters in Virtual and Real Conditions
PublikacjaModelling of ship structures in a virtual environment is now standard practice. Unfortunately, many engineers forget to consideri the influence of added water on the frequency values and the amplitude of natural vibrations. The article presents the effect of water damping on the frequency values of the individual natural vibration modes. The tests were carried out in two stages. First, the mentioned values were determined using...
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Green analytical chemistry : theory and practice
PublikacjaThis tutorial review summarises the current state of green analytical chemistry with special emphasis on environmentally friendly sample preparation techniques. Green analytical chemistry is a part of the sustainable development concept; its history and origins are described. Miniaturisation of analytical devices and shortening the time elapsing between performing analysis and obtaining reliable analytical results are important...
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Novel Complementary Multiple Concentric Split Ring Resonator for Reliable Characterization of Dielectric Substrates with High Sensitivity
PublikacjaAccurate characterization of dielectric substrates with high sensitivity remains an important challenge in a variety of industrial applications. This paper proposes an innovative strategy to address this challenge by developing and optimizing a unique Complementary Multiple Concentric Split Ring Resonator (CMC-SRR). The major goal is to propose a sensor design with increased sensitivity and reliability for dielectric characterization....
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Experimental investigations on concrete beams reinforced with CFRP lamellas
PublikacjaPaper presents experimental investigation made on two concrete beams reinforced with internal Carbon Fibre Reinforced Polymer (CFRP) lamellas (i.e. strips, bands). The reinforcement geometrical arrangement was similar as in normal concrete beams reinforced with steel bars and stirrups. The beams were destroyed by the shear forces, as intended. Obtained load-carrying capacities were lower as expected: below 40% of a calculated value....
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The role of analytical chemistry in the study of the Anthropocene
PublikacjaThe term “Anthropocene” refers to not yet formalized epoch of geologic time during which geologic processes have been dominated by the human impact. This impact takes on many forms. Biological, physical and chemical changes to the Earth System caused by anthropogenic activity are recorded in natural archives either as new fossil assemblages (neobiota), anthropogenic deposits or a wide variety of pollutants emitted to the environment....
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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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Investigating lubricants behaviour in microgravity for vibration damping purposes
PublikacjaVibration is one of the harshest environments an object is exposed to during and after launch into space on a launch vehicle. Such vibrations should be damped to avoid destruction of the spacecraft or its elements. Currently, active and material damping is used. A possibility of using lubrication as the damping factor is suggested by some research. MoS2 is a typical solid lubricant used in space applications. Its properties vary...
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On modelling and non-linear elasto-plastic analysis of thin shells with deformable junctions
PublikacjaThe undeformed base surface of the irregular thin shell is modelled by the union of a finite number of regular smooth surface elements joined together along spatial curvilinear surface edges. The equilibrium conditions are formulated by postulating an appropriate form of the principle of virtual work, where also deformability of shell junctions is taken into account. The PVW is then discretised by C1 finite elements and the incremental-iterative...
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Application of twin-plane ECT sensor for identification of the internal imperfections inside concrete beams
PublikacjaThe main purpose of this paper is to investigate application of special construction of Electrical Capacitance Tomography (ECT) sensor to concrete beams internal homogeneity tests. Identification of internal imperfection inside the concrete beams is one of the main problems related to analysis of the construction structure bearing capacity. Therefore, this paper shows attempts to study the measurement prospects for this non-invasive,...
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Comparison of the impact test and the harmonic test in measurements of natural resonant frequencies of circular saw blades
PublikacjaIn this paper results of measurements of natural resonant frequencies of circular saw blades with the impact test and the harmonic test are presented. Comparison of these two methods revealed that during testing of circular saw blades, in which bodies the open and closed notches (cuts) for cleaning of knives are present, with the harmonic test method it has been observed appearing of quasi-twin resonant frequencies, whereas the...
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Electromagnetic Simulations with 3D FEM and Intel Optane Persistent Memory
PublikacjaAbstract—Intel Optane persistent memory has the potential to induce a change in how high-performance calculations requiring a large system memory capacity are conducted. This article presents what this change may look like in the case of factorization of large sparse matrices describing electromagnetic problems arising in the 3D FEM analysis of passive highfrequency components. In numerical tests, the Intel oneAPI MKL PARDISO was...
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Impact of Geometrical Imperfections on Estimation of Buckling and Limit Loads in a Silo Segment Using the Vibration Correlation Technique
PublikacjaThe paper examines effectiveness of the vibration correlation technique which allows determining the buckling or limit loads by means of measured natural frequencies of structures. A steel silo segment with a corrugated wall, stiffened with cold-formed channel section columns was analysed. The investigations included numerical analyses of: linear buckling, dynamic eigenvalue and geometrically static non-linear problems. Both perfect...
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Comprehensive dimension scaling of multi-band antennas for operating frequencies and substrate parameters
PublikacjaIn this paper, low-cost and comprehensive redesign of multi-band antennas with respect to the operating frequencies and material parameters of the substrate is presented. Our approach exploits an inverse surrogate model identified based on a set of reference designs optimized at the level of coarse-discretization EM simulations of the antenna at hand. An iterative correction procedure is also implemented to account for the initial...
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Debonding Detection in Reinforced Concrete Beams with the Use of Guided Wave Propagation
PublikacjaOne of the most frequent damage of the reinforced concrete structures is debonding between steel bar and concrete cover. In the case of debonding occurrence not only the strength of the structure decreases, but also it is more vulnerable to corrosion damages. For this reason fast and effective methods of debonding detection in an early stage of its development need a significant boost. The paper presents analytical and experimental...
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Macromodels for efficient FEM simulations of waveguides and resonators
PublikacjaThis paper introduces a novel technique for enhancing the efficiency of the finite element method (FEM) by incorporating special modules, called macromodels, into the standard eigenvalue formulation. The number of unknowns in the separated macromodel subdomain can be significantly reduced by orthogonal projection, using the efficient nodal order reduction algorithm. The idea of macromodels implementation is demonstrated on a simple...
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Błażej Prusak dr hab.
OsobyBłażej Prusak jest kierownikiem Katedry Finansów na Wydziale Zarządzania i Ekonomii Politechniki Gdańskiej oraz redaktorem naczelnym czasopisma Research on Enterprise in Modern Economy - theory and practice (REME)/Przedsiębiorstwo we współczesnej gospodarce - teoria i praktyka, a także członkiem komitetów redakcyjnych takich czasopism jak: Intellectual Economics; Przestrzeń. Ekonomia. Społeczeństwo; Akademia Zarządzania. Jest autorem...
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The effect of numerical 2D and 3D FEM element modelling on strain and stress distributions at laser weld notches in steel sandwich type panels
PublikacjaLike other means of transport, merchant ships face the problem of increasing requirements concerning the environment protection, which, among other issues, implies the reduction of fuel consumption by the ship. Here, the conventional approach which consists in making use of higher strength steels to decrease the mass of the ship hull can be complemented by the use of new steel structures of sandwich panel type. However, the lack...