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Search results for: MOLECULAR MECHANICS
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Simulation and discretization of random field in the slip line method.
PublicationW pracy rozpatrywany jest problem nośności granicznej podłoża o własnościach stochastycznych przy obciążeniu spoczywającym na nim ciężkim sztywnym bloku.Opisano sposób generacji wielowymiarowego pola losowego oparty na diagonalizacji macierzy kowariancji przy wykorzystaniu macierzy dolnotrójkątnej .Szczególną uwagę zwrócono na wpływ dyskretyzacji ośrodka na rozwiązanie oraz jego zbieżność.
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Large rotations in first-order shear deformation FE analysis of laminated shells
PublicationAbstrakt: Teoria powłok o skończonych obrotach w ramach modelu ścinania pierwszego rzędu stanowi podstawę zaprezentowanego w pracy algorytmu MES statycznej, geometrycznie nieliniowej analizy konstrukcji warstwowych. Szczególną uwagę zwrócono na właściwy opis skończonych obrotów przy zastosowaniu kątów Eulera oraz procedurę uaktualniania parametrów obrotowych. Przedstawiono sformułowanie przyrostowe w stacjonarnym opisie Lagrange´a....
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Application of potential theory in calculating wave-induced vertical forces on horizontal cylinders near a plane boundary
PublicationHydrodynamiczne obciażenia wywołane falowaniem morskim działajace na poziomo ułożoną przy dnie rurę, rozpatrywane są w ujęciu dyfrakcyjnym przy założeniu istnienia funkcji potencjału. Potencjał zdefiniowano jako superpozycję potencjału fali inicjującej oraz potencjału perturbacji spowodowanej istnieniem obiektu przy dnie. Wyniki rozwiązań teoretycznych porównano z wynikami doswiadczeń przeprowadzonych w Wielkim Kanale falowym w...
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Soft soil overconsolidation and CPTU dissipation test
PublicationOkreślenie stanu naprężeń oraz historii naprężeń w słabym podłożu pod wałem przeciwpowodziowym na podstawie badań CPTU i DMT. Przeprowadzono badania dysypacji nadwyżki ciśnienia wody w porach w podłożu pod wałem oraz po stronie odpowietrznej i odwodnej. Kształt krzywej dysypacji zależy od prekonsolidacji gruntu słabego. Przedstawiono sposoby określania współczynnika konsolidacji oraz współczynnika filtracji w gruntach słabych w...
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Comparison of volume-and surface-detention-time distributions
PublicationCzas zatrzymania ścieków w reaktorze jest bardzo ważnym parametrem projektowym. Jego wyznaczenie jest trudne i kłopotliwe. Z tego względu zbadano możliwość zastąpienia wartości tego parametru, wyznaczonej tylko dla swobodnej powierzchni ścieków. W wyniku stwierdzono dopuszczalność takiej zamiany.
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Reverse flow routing problem solved by the Space-Time Conservation Method
PublicationW artykule rozpatruje się zagadnienie odwrotnej transformacji przepływów dla przypadku przepływu nieustalonego wolno zmiennego w kanałach otwartych, opisanego układem równań de Saint Venanta. Przedstawiono specyficzne dla rozpatrywanego przypadku problemy powstające na etapie jego rozwiązywania oraz zaproponowano efektywny algorytm obliczeniowy, wykorzystujący nową, atrakcyjną metodę czasoprzestrzennych objętości skończonych. Do...
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Calculation of flatness errors formed on the tool during finishing machining by lapping. Second International Tribology Conference, SITC 2002.
PublicationPłaskość przedmiotów obrabianych zależy głównie od płaskości narzędzia stosowanego w docieraniu. Orientacja przedmiotu na docieraku musi być wyznaczona w celu określenia korelacji pomiędzy błędami płaskości obu powierzchni. Metoda wyznaczania błędów niepłaskości narzędzia przedstawiona została w referacie. Pokazane zostały przykładowe położenia przedmiotów o różnych kształtach na czynnej powierzchni docieraka z błędem wklęsłości.
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Approximated boundary conditions of the equation of difussion
PublicationProblem podejmowany w pracy dotyczy warunku brzegowego w równaniach fizyki matematycznej, opisujących procesy migracji zanieczyszczeń. W szczególności skoncentrowano się na badaniu wpływu na rozwiązanie przyjmowanych w rozwiązaniach numerycznych aproksymacji ''odpływowego'' warunku brzegowego w jednowymiarowym równaniu adwekcji - dyspersji. Rozważania teoretyczne przeprowadzono w oparciu o rozwiązania analityczne oraz numeryczne...
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A selectively reduced degree basis for efficient mixed nonlinear isogeometric beam formulations with extensible directors
PublicationThe effect of higher order continuity in the solution field by using NURBS basis function in isogeometric analysis (IGA) is investigated for an efficient mixed finite element formulation for elastostatic beams. It is based on the Hu–Washizu variational principle considering geometrical and material nonlinearities. Here we present a reduced degree of basis functions for the additional fields of the stress resultants and strains...
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Flood Routing by the Non-Linear Muskingum Model: Conservation of Mass and Momentum
PublicationIn this paper, the conservative properties of the Muskingum equation, commonly applied to solve river flood routing, are analysed. The aim of this analysis is to explain the causes ofthe mass balance error, which is observed in the numerical solutions of its non-linear form. The linear Muskingum model has been considered as a semi-discrete form of the kinematic wave equation and therefore it was possible to derive its two non-linear...
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COMPARATIVE NUMERICAL ANALYSIS OF DIFFERENT STRENGTHENING SYSTEMS OF HISTORICAL BRICK ARCHES
PublicationThe article presents a comparative numerical analysis of various ways to strengthen historical brick arches. Five ways of strengthening brick arches with steel tie-rods have been proposed. Two of these involve the use of braces wrapped around pillars supporting the arch connected with a tie-rod; another two ways involve the use of the tie-rods with welded metal sheets of different sizes; the last way involves the use of the tie-rod...
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Vibration of the bridge under moving singular loads - theoretical formulation and numerical solution
PublicationThe paper presents the results of the numerical analysis of a simple vehicle passing over a simply supported bridge span. The bridge is modelled by a Euler-Bernoulli beam. The vehicle is modelled as a linear, visco-elastic oscillator, moving at a constant speed. The system is described by a set of differential equations of motion and solved numerically using the Runge-Kutta algorithm. The results are compared with the solution...
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Impact of Energy Slope Averaging Methods on Numerical Solution of 1D Steady Gradually Varied Flow
PublicationIn this paper, energy slope averaging in the one-dimensional steady gradually varied flow model is considered. For this purpose, different methods of averaging the energy slope between cross-sections are used. The most popular are arithmetic, geometric, harmonic and hydraulic means. However, from the formal viewpoint, the application of different averaging formulas results in different numerical integration formulas. This study...
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Effect of power frequency on the stress state of disc actuator
PublicationThis paper presents the concept of determining the optimum frequency of coil supply in inductive-dynamic drive. As a criterion to obtain the sought frequency, the smallest value of reduced stress in the disc was assumed while maintaining the desired dynamics. The disc stress is determined on the basis of solution of vibrating thin plate equation. Magnetic pressure acting on the disc is obtained from a hybrid circumferentially-field...
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Lax-Wendroff and McCormack Schemes for Numerical Simulation of Unsteady Gradually and Rapidly Varied Open Channel Flow
PublicationTwo explicit schemes of the finite difference method are presented and analyzed in the paper. The applicability of the Lax-Wendroff and McCormack schemes for modeling unsteady rapidly and gradually varied open channel flow is investigated. For simulation of the transcritical flow the original and improved McCormack scheme is used. The schemes are used for numerical solution of one dimensional Saint-Venant equations describing free...
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Estimation of Stresses in a Dry Sand Layer Tested on Shaking Table
PublicationTheoretical analysis of shaking table experiments, simulating earthquake response of a dry sand layer, is presented. The aim of such experiments is to study seismic-induced compaction of soil and resulting settlements. In order to determine the soil compaction, the cyclic stresses and strains should be calculated first. These stresses are caused by the cyclic horizontal acceleration at the base of soil layer, so it is important...
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Whirling system of water exchangein breeding pools
PublicationTo secure the proper conditions of life for sea mammals existing in closed systems one has to maintain the character of the breeding basins (i.e. shape, dimensions, facing of walls and bottom, quality and motion of water) as natural as possible. An appropriate system of water exchange plays a very important role here. A full renewal of water is time-consuming, expensive and troublesome, so can be made only periodically, and should...
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Buckling of thin-walled columns accounting for initial geometrical imperfections
PublicationThe paper is devoted to the effect of some geometrical imperfections on the critical buckling load of axially compressed thin-walled I-columns. The analytical formulas for the critical torsional and flexural buckling loads accounting for the initial curvature of the column axis or the twist angle respectively are derived. The classical assumptions of theory of thin-walled beams with non-deformable cross-sections are adopted. The...
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Elastic wave propagation for condition assessment of steel bar embedded in mortar
PublicationThis study deals with experimental and numerical investigations of elastic wave propagation in steel bars partially embedded in mortar. The bars with different bonding lengths were tested. Two types of damage were considered: damage of the steel bar and damage of the mortar. Longitudinal waves were excited by a piezoelectric actuator and a vibrometer was used to non-contact measurements of velocity signals. Numerical calculations...
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Suitability study of hybrid model of electrodynamic actuator
PublicationThe paper presents the proposal of the hybrid circumferential model of an electrodynamic actuator. The field model uses the inductor current as the input data which is obtained from the circumferential model or experimentally.
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Effect of power frequency on the stress state of disc actuator
PublicationThe paper presents the concept of determinig the optimum frequency of coil supply in inductive-dynamic drive. As a criterion to obtain the sought frequency, the smallest value of reduced stress in the disc was assumed while maintaining the desired dynamics.
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Simplified probabilistic analysis of settlement of cyclically loaded soil stratum using point estimate method
PublicationThe paper deals with the probabilistic analysis of settlement of a non-cohesive soil layer subjected to cyclic loading. Originally, the settlement assessment is based on deterministic compaction model which requires integration of a set of differential equations. However, making use of the Bessel functions the settlement of the soil stratum can be calculated by means of simplified algorithm. The compaction model parameters were...
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DYNAMIC ANALYSIS OF HISTORIC RAILWAY BRIDGES IN POLAND IN THE CONTEXT OF ADJUSTING THEM TO PENDOLINO TRAINS
PublicationThe article presents the dynamic analysis of the historic railway bridge in Tczew as an example of the usefulness of such type of bridge for high-speed trains. The model of the bridge and the simulation of rolling stock passage was performed in SOFISTIK program. The scope of work includes experimental studies, the solution of the problem concerning the correct solution features dynamic model takes into account the dependencies...
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COMPUTER-AIDED CONSTRUCTION AT DESIGNING REINFORCED CONCRETE COLUMNS AS PER EC
PublicationThe article presents the author’s computer program for designing and dimensioning columns in reinforced concrete structures taking into account phenomena affecting their behaviour and information referring to design as per EC. The computer program was developed with the use of C++ programming language. The program guides the user through particular dimensioning stages: from introducing basic data such as dimensions, concrete...
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A COMPARISON OF THE WIND SPECTRUM ACCORDING TO DIFFERENT METHODS - AN ORIGINAL PROJECT OF A BUILDING ON A CLIFF IN GDYNIA
PublicationThe article presents numerical simulations of the dynamic wind loads on the structure of a building designed on a cliff in Gdynia. The results obtained from the two methods: Davenport’s and Karman’s are compared. The results allowed a comparison of the two methods, and they provided an answer to the question how a construction, designed in such an unusual condition of a cliff behaves under the influence of the gusting wind. The...
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Stress anisotropy characterisation with the help of Barkhausen effect detector with adjustable magnetic field direction
PublicationIn the paper we describe a novel apparatus for the measurement of the Barkhausen noise (BN) angular dependence, which in turn may be indicative of the stress induced anisotropy of magnetic properties. Such dependence can be further used for the stress distribution evaluation. The change of magnetization direction in the material is obtained by varying the magnetic flux density in two perpendicular yokes of the apparatus. We present...
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Evaluation of the impact of geometry and plastic deformation on the stray magnetic field around the bone shaped sample
PublicationInfluence of two factors: the variable cross-section and the localized plastic deformation, which affect the stray magnetic field profile of a ferromagnetic sample have been studied. Evaluation of an effect size is based on the analysis of the stray magnetic field component which is tangential to the longest dimension of a sample. However, in order to describe the nature of the stray magnetic field, the normal component (perpendicular...
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Analysis of the selection of low-temperature medium for a turbine power plant using ocean thermal energy (OTEC)
PublicationThe paper presents the results and conclusions of numerical calculations modelled in the EES program of a closed OTEC cycle. The following mediums were analysed: ammonia, R32, R41, R404a, R407c, R410a, R423a, R500, R502, R507a and R114, R152a, R234fa, R600, R1234yf, R1234ze. Analogous assumptions were adopted as in the ORC cycle with heat regeneration for dry refrigerants without regeneration for wet refrigerants. Each of them...
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Locating and Identifying Ferromagnetic Objects
PublicationThe new non-iterative method of determining the dipole moment and location is presented in this paper. The algorithm of an object's localization and identification was achieved by using numerical calculations and approximation method. The arbitrary shapes of an object were assumed in the identification algorithm - axially symmetric spheroid (a prolate and an oblate). Several examples of localization and identification of an object's...
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Multidipoles model of ship's magnetic field
PublicationShips made of ferromagnetic metals interfere with Earth's magnetic field in their surrounding. The disturbance of the magnetic field makes possible localization and even identification of the ship, which could determine a threat to the ship. The measurement of the magnetic field around the ship enables to determine its magnetic signature. The paper presents a multidipoles model of the ship magnetic field, which allows to determine...
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Simulations of fracture in concrete elements using continuous and discontinuous models
PublicationArtykuł przedstawia wyniki symulacji MES w elementach betonowych przy zastosowaniu modeli ciągłych i nieciągłych. Stosując modele ciągłe symulowano proces lokalizacji odkształceń. Stosując modele nieciągłe symulowano proces zarysowania. Obliczenia wykonano dla różnych typów obciążeń.
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Analysis of aircraft magnetic interference
PublicationThe magnetometric method is used among other things on mobile platforms (planes, helicopters) in military systems and in geological research. Optically-pumped and SQUID magnetometers are used in magnetic systems on airplanes. To be able to attain the sensitivity of modern magnetometers in flight, it is important that maneuver-related magnetic interference effects be minimized. The mathematical model of an aircraft as a source of...
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Reduction of Inrush Current by Demagnetization of Magnetic Core
PublicationW artykule przedstawiono demagnetyzację rdzenia transformatora jako metodę ograniczania prądu załączeniowego. W zaproponowanej metodzie źródłem energii wykorzystywanej do rozmagnesowania jest kondensator. W przeprowadzonych obliczeniach symulacyjnych rozważono różne wartości pojemności kondensatora i wartości napięcia w celu określenia optymalnych wartości tych parametrów. Następnie obliczono strumienie szczątkowe, jakie ustalają...
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Experimental Verification of Storm Sewer Transient Flow Simulation
PublicationThe paper focuses mainly on laboratory investigations of transient and transcritical flow in a single pipe of a sewer system. The aim of this paper is to present a comparison between pressure values calculated by an improved McCormack scheme and those measured at the hydraulic laboratory of the Gdansk University of Technology, which were observed inside a pipe in an experiment for water flow with pressurization. The analysis proves...
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ANALYSIS OF BRACE STIFFNESS INFLUENCE ON STABILITY OF THE TRUSS
PublicationThe paper is devoted to the numerical and experimental research of stability of a truss with side elastic supports at the top chord. The structure is a model of a real roof truss scaled by factor ¼. The linear buckling analysis and non-linear static analysis were carried out. The buckling length factor for the compressed top chord was calculated and the limit load for the imperfect truss shell model with respect to brace stiffness...
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Impact of Urbanization on Stormwater Runoff from a Small Urban Catchment: Gdańsk Małomiejska Basin Case Study
PublicationThis paper deals with the impact of different forms of urbanization on the basin outflow. The influence of changes in land cover/use, drainage system development, reservoirs, and alternative ways of stormwater management (green roofs, permeable pavements) on basin runoff was presented in the case of a small urban basin in Gdańsk (Poland. Seven variants of area development (in the period of 2000-2012) – three historical and four...
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Comparison of Average Energy Slope Estimation Formulas for One-dimensional Steady Gradually Varied Flow
PublicationTo find the steady flow water surface profile, it is possible to use Bernoulli’s equation, which is a discrete form of the differential energy equation. Such an approach requires the average energy slope between cross-sections to be estimated. In the literature, many methods are proposed for estimating the average energy slope in this case, such as the arithmetic mean, resulting in the standard step method, the harmonic mean and...
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Experimental Determination of Limit Adhesive Shear Strtess between Solid Wall and Liquid
PublicationTheoretically slip of a fluid with respect to the solid wall should occur even at a very low velocity of motion. However theoretical analysisand some empirical data suggest that there must be a limit value of shear stress, below which the slip does not appear. A simple metyhod of this stress determination was proposed in the paper.
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Modelling of FloodWave Propagation with Wet-dry Front by One-dimensional Diffusive Wave Equation
PublicationA full dynamic model in the form of the shallow water equations (SWE) is often useful for reproducing the unsteady flow in open channels, as well as over a floodplain. However, most of the numerical algorithms applied to the solution of the SWE fail when flood wave propagation over an initially dry area is simulated. The main problems are related to the very small or negative values of water depths occurring in the vicinity of...
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Problem of Clogging in Drainage Systems in the Examples of the Zur and Podgaje Dams
PublicationDrainage plays an extremely important role in hydraulic structures, such as earth dams. Observations of drainage in hydraulic structures under various soil conditions indicate that the phenomenon of clogging can lead to a radical reduction in the efficiency of drainage, making it non-functional within a few years after construction. This article describes the problems of drainage clogging by iron oxide in the examples of the Zur...
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Numerical Simulations and Tracer Studies as a Tool to Support Water Circulation Modeling in Breeding Reservoirs
PublicationThe article presents a proposal of a method for computer-aided design and analysis of breeding reservoirs in zoos and aquariums. The method applied involves the use of computer simulations of water circulation in breeding pools. A mathematical model of a pool was developed, and a tracer study was carried out. A simplified model of two-dimensional flow in the form of a biharmonic equation for the stream function (converted into...
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Application of the Boundary Element Method for the Simulation of Two-dimensional Viscous Incompressible Flow
PublicationThe paper presents the application of an indirect variant of the boundary element method (BEM) to solve the two-dimensional steady flow of a Stokes liquid. In the BEM, a system of differential equations is transformed into integral equations. Thi smakes it possible to limit discretization to the border of the solution. Numerical discretization of the computational domain was performed with linear boundary elements, for which a...
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Outlet Flow Velocity In Circular Culvert
PublicationThe outlet flow velocity in the end section of the culvert barrel depends in most cases on the culvert geometry, including the barrel slope, as well as on upstream and downstream channel parameters. Flowing water can create pressure flow or free surface flow in the culvert barrel. In the case of an unsubmerged barrel outlet, the free-surface flow is more frequent than the full flow. Increased velocities can cause channel bed scour...
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Velocity Field Characteristics at the Inlet to a Pipe Culvert
PublicationA poorly designed culvert inlet structure causes scouring, which can lead to the collapse of the culvert and significant damage to the neighboring land. A set of laboratory tests was evaluated to examine velocity distribution at the culvert inlet. A three-dimensional acoustic Doppler velocimeterwas used to measure instantaneous flowvelocity upstream of the culvert. The analysis of mean velocities, turbulence strength, and Reynolds...
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Effect of Pendolino high-speed rail on the structure of buildings located the proximity of the railway tracks
PublicationThe following research focuses on the dynamic analysis of the impact of the high-speed train inducted vibrations on the structures located near railway tracks. The office complex chosen as the subject of calculations is located in the northern part of Poland, in Gdańsk, in the proximity of Pendolino, the high speed train route. The high speed trains are the response for the growing needs for more efficient railway system. However...
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Cable-stayed cantilever structures as an expat of unique application in the construction of a building located in seismic area – an author’s project of multifunctional building in Lisbon, Portugal
PublicationThe article presents numerical simulations for the modelling of seismic impact on the structure of unique cantilever cablestayed structure with application of two methods. The Response Spectrum method, in which a spectrum of the structure's responses to an earthquake's impact is generated and the Accelerogram method, in which we generate dynamic load in the form of a diagram of the connection between acceleration and time for...
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Shell with random geometric imperfections simulation-based approach
PublicationPrzedstawiono analizę powłok z losowymi imperfekcjami. Zastosowano nieliniowe geometrycznie i materiałowo modele. Geometryczne imperfekcje opisano za pomocą pojedynczych zmiennych oraz pól losowych. Wykorzystano metodę Monte Carlo i metodę elementów skończonych. Zbadano wpływ różnych rozkładów prawdopodobieństwa imperfekcji geometrycznych na probabilistyczny rozkład nośności granicznej powłok. Zastosowane rozkłady ekstremalne imperfekcji...
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Simplified modelling of heat transfer in groundwater
PublicationPrzenoszenie ciepła w wodach podziemnych jest skomplikowanym, przestrzennym procesem. Z tego względu do rozwiązywania zadań praktycznych celowe jest konstruowanie modeli uproszczonych. W pracy zaproponowano sposób formułowania modelu dwuwymiarowego. Został on pozytywnie zweryfikowany na przykładzie badania przyczyn strat energii cieplnej w elektrowni Kozienice.
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The protocol for using elastic wall model in modeling blood flow within human artery
PublicationMedical diagnostic tools will play a major role in the future for an effective patient treatment and reduction their mortality, related to the cardiovascular system diseases (CVDs). There is an urgent need for developing diagnostic procedure to be robust, reliable, accurate and efficient, in the framework of a paradigm shift. Application of numerical techniques is seen as a perspective tool for such purpose. Nevertheless, existing...
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Numerical Analysis of Turbulent Flow over a Backward-facing Step in an Open Channel
PublicationComputational examinations of the flow field in an open channel having a single Backward--Facing Step (BFS) with a constant water depth of 1.5 m were performed. The effects of the expansion ratio, and the flow velocity along the reattachment length, were investigated by employing two different expansion ratios of 1.5 and 2, and eight various flow velocities of 0.5, 1, 2, 3, 4, 5, 7.5 and 10 m/sec in the Computational Fluid Dynamic...