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Search results for: ACTIVE DYNAMIC THERMOGRAPHY
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A low-voltage CMOS negative impedance converter for analogue filtering applications
PublicationLow-voltage high-frequency continuous-time filters are still required in many applications and are the subject of continuing research. There are many techniques to realize integrated filters, including OTA C, Opamp RC and MOSFET-C-Opamp. The latter two show high dynamic range at low supply voltage, but their frequency operating range is usually limited to several megahertz. Transconductance filters are dedicated to higher frequencies....
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Boundary value problems with advanced arguments involving upper and lower solutions in reverse order
PublicationPraca dotyczy problemów brzegowych dla równań różniczkowo-całkowych pierwszego rzędu z argumentami wyprzedzonymi. Podano wystarczające warunki, dla których problemy dotyczące takich równań mają rozwiązania minimalne i maksymalne w odpowiadającym obszarze ograniczonym przez rozwiązania górne i dolne. W celu uzyskania wyników zastosowano nową metodę opartą na twierdzeniu Heikkila-Lakshmikantham'a. Wyniki zilustrowano na przykładzie.
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Differential-algebraic systems with initial time difference
PublicationO funkcjach występujących w zagadnieniu zakładano m.in. warunek typu Perrona uzyskując pewne wyniki porównawcze dla zagadnień różniczkowo-algebraicznych startujących z różnych punktów początkowych. Wyniki porównawcze uzyskano również wykorzystując odpowiednią funkcję typu Lapunova. Sformułowane zostały warunki dostateczne na to aby rozwiązanie było stabilne.
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On delay differential equations with boundary conditions
PublicationPodano warunki na istnienie rozwiązania zagadnienia brzegowego typu opóźnionego, zakładając pewne warunki monotoniczności funkcji występującej po prawej stronie naszego zagadnienia. Pokazano, że dwa ciągi monotoniczne są zbieżne do rozwiązania dokładnego.
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Fractional differential equations with deviating arguments
PublicationDla równań różniczkowych typu ułamkowego, zostały podane warunki dostateczne na istnienie jednego rozwiązania lub rozwiazań ekstremalnych. Nierówności różniczkowe są też doskutowane.
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Multiple solutions for a class of boundary-value problems with deviating arguments and integral boundary conditions
PublicationPraca dotyczy istnienia dodatnich rozwiązań dla równań różniczkowych rzędu drugiego z całkowymi warunkami brzegowymi i z odchylonymi argumentami typu wyprzedzonego. Korzystając z tw. Avery-Petersona dla stożków, podano warunki dostateczne na istnienie trzech dodatnich rozwiazań w/w problemów. Podano przykład pokazujący iż przyjęte załozenia są spełnione.
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Method of lines for Hamilton-Jacobi functional differential equations.
PublicationInitial boundary value problems for nonlinear first order partial functional differential equations are transformed by discretization in space variables into systems of ordinary functional differential equations. A method of quasi linearization is adopted. Suffcient conditions for the convergence of the method of lines and error estimates for approximate solutions are presented. The proof of the stability of the diffrential difference...
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Positive solutions to third-order impulsive Sturm-Liouville boundary value problems with deviated arguments and one-dimensional p-Laplacian
PublicationBadane są równania różniczkowe z impulsami trzeciego rzędu z odchylonymi argumentami przy zadanych warunkach brzegowych typu Sturma-Liouvilla. Podano warunki dostateczne na istnienie dodatnich rozwiązań takich problemów stosując twierdzienie o punkcie stałym dla stożków.
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On neutral differential equations and the monotone iterative method
PublicationThe application of the monotone iterative method to neutral differential equations with deviating arguments is considered in this paper. We formulate existence results giving sufficient conditions which guarantee that such problems have solutions. This approach is new and to the Authors' knowledge, this is the first paper when the monotone iterative method is applied to neutral first-order differential equations with deviating...
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First-order differential equations with nonlocal boundary conditions
PublicationWe study a first-order boundary value problem subject to some boundary conditions given by Riemann-Stieltjes integrals. Using a monotone iterative method, we formulate sufficient conditions which guarantee the existence of extremal or quasi-solutions in the corresponding region bounded by upper and lower solutions of our problems. The case when a unique solution exists is also investigated. Some examples are given to illustrate...
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Systems of boundary value problems of advanced differential equations
PublicationThis paper considers the existence of extremal solutions to systems of advanced differential equations with corresponding nonlinear boundary conditions. The monotone iterative method is applied to obtain the existence results. An example is provided for illustration.
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Monotone iterative method to second order differential equations with deviating arguments involving Stieltjes integral boundary conditions
PublicationWe use a monotone iterative method for second order differential equations with deviating arguments and boundary conditions involving Stieltjes integrals. We establish sufficient conditions which guarantee that such problems have extremal solutions in the corresponding region bounded by lower and upper solutions. We also discuss the situation when problems have coupled quasi-solutions. We illustrate our results by three examples.
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Polymeric Bearings – A New Base Isolation System to Reduce Structural Damage during Earthquakes
PublicationBase isolators, like lead rubber bearings, high damping rubber bearings or friction pendulum systems are extensively used in practice in many seismically active regions to protect structures against earthquake forces. The present paper reports the results obtained from the experimental study aimed to determine the effectiveness of the Polymeric Bearings in suppressing structural vibrations during dynamic excitations and therefore...
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Building damage due to structural pounding during earthquakes
PublicationEarthquake-induced pounding between adjacent buildings has been identified as one of the reasons for substantial damage or even total collapse of colliding structures. A major reason leading to interactions in buildings results from the differences in their dynamic parameters and also from insufficient distance between the structures. Although the research on structural pounding has been much advanced, the studies have mainly been...
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Voltage and frequency regulation of a standalone induction generator by reduced-rating power electronic compensators - comparative evaluation
PublicationIn this paper are considered two fundamental topologies of power electronic compensators for voltage and frequency control of a standalone self-excited induction generator (IG) system. These are voltage and current source inverter based shunt compensators with energy storage. The aim of this study is to assess main features of both topologies in dynamic and steady-state IG operation. The whole system is modelled with the aid of...
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Analysis and bioanalysis: an effective tool for data collection of environmental conditions and processes
PublicationReliable information that allows us to estimate the state of the environment and to forecast changes in the ecosystem are constantly required. Increasing environmental consciousness and dynamic development of analytical techniques are the main reasons for determining the wide range of pollutants occurring at very low concentrations in complex matrix samples. The presence and concentration of many of those pollutants in the environment...
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Experiments on compression ignition engine powered by nano-fuels
PublicationThe use of nanoparticles in fuels provides new opportunities for modification of fuel properties, which may affect the operational parameters of engines, in particular the efficiency and fuel consumption. The paper presents comparison of compression ignition engine performance fuelled with neat diesel and nano-diesel. Alumina (Al2O3) was used as nanoparticles. Surface-active substances, including Span 80 surfactant, as well as...
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Investigating lubricants behaviour in microgravity for vibration damping purposes
PublicationVibration 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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Wielopoziomowy przekształtnik trakcyjny SiC z izolacją od sieci 3kV DC realizowaną za pomocą transformatorów 30kHz do napędów EZT
PublicationW referacie przedstawiono wielopoziomowy izolowany kaskadowy przekształtnik DC-AC z tranzystorami SiC MOSFET 1,2kV, przeznaczony do napędów elektrycznych zespołów trakcyjnych (EZT). Zaproponowana konstrukcja przekształtnika, przeznaczonego do pracy przy zasilaniu z sieci trakcyjnej 3kV DC, spełnia założenia energoelektronicznego transformatora trakcyjnego (z ang. Power Electronic Traction Transformer). Budowa modułowa z niskonapięciowych...
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Feedback Control of Doubly-Fed Generator Connected to Current Source Converter
PublicationDoubly-fed induction generator (DFIG) system supplied by current source converter (CSC) is considered in this article. The DFIG can work in two independent modes: AC grid connection and stand-alone mode. The DFIG is connected to the ac grid directly through its stator and the CSC links the rotor side. In this mode, the active and reactive powers of the DFIG must be controlled. This article proposes two control system structures...
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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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Nonlinear Control of a Doubly Fed Generator Supplied by a Current Source Inverter
PublicationNowadays, wind turbines based on a doubly fed induction generator (DFIG) are a commonly used solution in the wind industry. The standard converter topology used in these systems is the voltage source inverter (VSI). The use of reverse-blocking insulated gate bipolar transistor (RB-IGBT) in the current source inverter topology (CSI), which is an alternative topology, opens new possibilities of control methods. This paper presents...
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Symulacja pracy przesuwnika fazowego w sieci elektroenergetycznej przy połączeniu transformatora szeregowego w gwiazdę
PublicationPoniższy artykuł prezentuje sposób regulacji mocy czynnej i biernej za pomocą przesuwnika fazowego, którego uzwojenie transformatora dodawczego (szeregowego) jest połączone w gwiazdę. W artykule pokazano regulację mocy czynnej i biernej na przykładzie wybranego systemu elektroenergetycznego. Omawiany przesuwnik fazowy reguluje jednocześnie przepływem mocy czynnej i biernej w danym systemie elektroenergetycznym.
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YADE - An extensible framework for the interactive simulation of multiscale, multiphase, and multiphysics particulate systems
PublicationThis contribution presents the key elements of YADE, an extensible open-source framework for dynamic simulations. During the past 19 years, YADE has evolved from "Yet Another Dynamic Engine"' to a versatile multiscale and multiphysics solver, counting a large, active, and growing community of users and developers. The computationally intense parts of the source code are written in C++, using flexible object models that allow for...
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Magnetic and capacitive couplings influence on power losses in double circuit high voltage overhead transmission line
PublicationPurpose – The paper aims to discuss problems of power and energy losses in a double-circuit overhead transmission line. It was observed from energymeters’ readings, that in such a line, active power losses can be measured as “negative”. The “negative” active power losses appear when the active power injected to the circuit is lower than the active power received at the circuit end. The purpose of this paper is to explain this phenomenon. Theoretical...
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Arch footbridge over Warta river in Wronki - design and construction
PublicationThe paper presents the concept of dynamic redesign of lively footbridge. The goal was to reduce probable dynamic excitation and change detailed structural concept. After the complex study the new design was created. In effect completely new static and dynamic properties were reached. Static and dynamic assumptions are explainde. General information, photos and drawings are presented. The final price of the project amounted to 1.25...
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Optimized Space Vector Modulation strategy for five phase voltage source inverter with third harmonic injection
PublicationThis paper presents a simple and an effective SVM algorithm for five-phase Voltage-Source Inverters with the possibility to control independently the voltage vectors for fundamental and auxiliary orthogonal subspaces. The essential benefit is that output voltage is generated using only four active voltage vectors with limited numbers of switching. In the proposed solution, four active vectors are arbitrary chosen, independent of...
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Behaviour of Asymmetric Structure with Base Isolation Made of Polymeric Bearings
PublicationEarthquake-induced ground motions are the most severe and unpredictable threats to the structures all around the world. Seismic excitations cause a lot of damage in a wide variety of ways, leaving thousands of casualties in their wake. Due to randomness of earthquake occurrence, lack of visible causes and their power of destructiveness, structural engineers need to develop new technical solutions and protection systems against...
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Analysis and Comparison of Safety of Children and Adult Passenger in Car Based on Crash Tests Results
PublicationMost important features of the child seat were presented. There was made analysis of selected dynamic loads acting on mannequins heads during a collision. Comparison of loads acting on the kid in a child seat and the other passengers in a car is presented. In analysis of the results particular attention has been paid on the children's secure in a car. The phenomena of collision child's occipital bone with seat backrest was described....
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Kontrolki ActiveX - Osadzanie kontrolek ActiveX w dokumentach WWW
PublicationW artykule opisano cechy i zasady funkcjonowania kontrolek ActiveX. Przedstawiono rozwój technologii Active na przestrzeni ostatnich lat. Na zasadzie lekcji omówiono metody edycji dokumentów WWW wykorzystujących technologię Active i sposób konfigurowania kontrolek w języku HTML.
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Dynamics analysis of footbridge mode shapes the s8 expressway on the basis of the results of in situ tests
PublicationNon-destructive diagnostics for structure may use dynamic measurements realized during vibrations of a facility induced by dynamic environmental impact, enforced by the use of inductors or impulse impact. Dynamic tests and the analysis were undertaken for a footbridge situated over the expressway S8. The studies in situ allowed for dynamic characteristics to be determined: frequency, shape modes and damping for respective frequency...
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Antimicrobial molecular nanocarrier–drug conjugates
PublicationMany antimicrobial drugs are poorly active against pathogenic microbes causing intracellular infections, such as Mycobacterium tuberculosis or Plasmodium falciparum. On the other hand, several known antimicrobial agents are not effective enough because of their limited cellular penetration. A common feature of both challenges is the inability of an active agent to cross the biological membrane(s). One of the possible approaches...
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VSC converters control for offshore wind farms HVDC grid connection
PublicationThe paper proposes a voltage sourced converter (VSC) new control method. A well-known in the electric power systems correlation between voltage angle and active power and correlation between voltage and reactive power is used instead of feedforward control. This allows for a fast and almost independent control of active and reactive power flow.
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Structural Dynamics and Stability of Composite Structures
PublicationThis an editorial for a special Issue devoted to the application of dynamic and stability analysis of composite structures. In structural applications, past few decades have seen outstanding advances in the use of composite materials including Functionally Graded Materials (FGM). Most structures, whether they are used in civil, marine, or aerospace engineering, are subjected to dynamic loads during their operation.Therefore, dynamic...
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Deep slot effect in the squirrel-cage induction motors with scalar (V/F) control
PublicationQualitative characteristics of the electrical drive considerably depend on identification accuracy of math model parameters. In particular, it is depend on detection accuracy of stator active resistance r1 that is used in calculation of flux linkages, rotary speed in sensorless control systems. Paper provides analysis of influence of stator deep slot effect to stator active resistance value
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Numerical analysis of open channel steady gradually varied flow using the simplified saint-venant equations
PublicationFor one-dimensional open-channel flow modeling, the energy equation is usually used. There exist numerous approaches using the energy equation for open-channel flow computations, which resulted in the development of several very efficient methods for solving this problem applied to channel networks. However, the dynamic equation can be used for this purpose as well. This paper introduces a method for solving a system of non-linear...
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Transport of paracetamol in swellable and relaxing polyurethane nanocomposite hydrogels
PublicationPolyurethane hydrogels are potentially attractive materials for biomedical applications. They are able to absorb large amount of water, biological fluids or active substances, and thus, they have potential to be used as absorbents or wound-healing dressings. They are also used for the controlled release of therapeutics because of their capacity to embed biologically active agents in their water-swollen network. The presence of...
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Wear of Electroplated Tools Used for Flat Grinding of Ceramics
PublicationTwo methods for the abrasive properties evaluation, based on the image processing, are presented in the paper. Image processing analysis was developed to evaluate quickly the abrasive properties as the tool wears down. The coefficient based on the image brightness was calculated and additional analysis was based on the number of grains located on the active surface of the tool before and after machining. The active surfaces of...
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Development of an Advanced Control Algorithm for DAB DC/DC Converters: Inrush Current Limitation and Enhanced Operation in Transient States.
PublicationThe publication addresses the dynamic state challenges encountered during development of a dual active bridge (DAB) converter within DC microgrid systems. The conventional startup method is identified as instigating a cascade of unfavorable outcomes, encompassing elevated starting current, transformer current asymmetry, DC voltage distortions, EMI and heightened thermal stress on semiconductor components. Additionally, it necessitates...
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Volumetric incorporation of NV diamond emitters in nanostructured F2 glass magneto-optical fiber probes
PublicationIntegration of optically-active diamond particles with glass fibers is a powerful method of scaling diamond's magnetic sensing functionality. We propose a novel approach for the integration of diamond particles containing nitrogen-vacancy centers directly into the fiber core. The core is fabricated by stacking the preform from 790 soft glass canes, drawn from a single rod dip-coated with submicron diamond particles suspended in...
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Understanding the origin of high corrosion inhibition efficiency of bee products towards aluminium alloys in alkaline environments
PublicationVarious bee products were found to be efficient corrosion inhibitors of aluminium in different environments. In particular, bee pollen was found to be highly effective in alkaline electrolytes, yet its highly complex composition and possible synergistic interactions hinder determination of the compounds acting as active corrosion inhibitors. The main purpose of the following work is to investigate the effect of solvents used for...
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Lagrangian model of an isolated dc-dc converter with a 3-phase medium frequency transformer accounting magnetic cross saturation
PublicationThis article presents a nonlinear equivalent circuit model of an isolated dc-dc converter with a 3-phase medium frequency transformer. The model takes into account the magnetic cross saturation of the 3-phase core-type magnetic circuit. The model is suitable in detailed electromagnetic transient simulations of power systems involving isolated dc-dc converters. The model is developed using the Lagrange energy method. It involves...
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Identyfikacja parametrów dynamicznych want mostu Rędzińskiego we Wrocławiu
Publicationthe paper presents results of dynamic analysis conducted on stay-cables of rędziński bridge in wrocław. identified in situ dynamic parameters (natural frequency and logarithmic decrement damping ratio) of selected stays were and compared to the values featured in the project.
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Dynamic load balancing with data partitioning for efficient paralel compu-ting.**2003, 227 s. 214 rys. 9 tab. bibliogr. 160 poz. maszyn. Rozprawa doktorska /14.01.2003/ Wydz. ETI Promotor: prof. dr hab. inż. H. Krawczyk. Dynamiczne równoważenie obciążenia z podziałem danych dla efektywnego prze-twarzania równoległego.
Publication...
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The Impact of Sloshing Liquids on Ship Stability for Various Dimensions of Partly Filled Tanks
PublicationLiquid sloshing phenomenon taking place in partly filled ships' tanks directly affects the stability of a vessel. However, only static calculations are carried out onboard ships nowadays and static transfer of liquid weight is taken into account in the course of routine stability calculation. The paper is focused on a dynamic heeling moment due to liquid sloshing in tanks onboard ships. A number of numerical simulations of liquid...
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A Method of Assessment of the Liquid Sloshing Impact on Ship Transverse Stability
PublicationLiquid sloshing phenomenon taking place in partly filled ships? tanks directly affects the stability of a vessel. However, only static calculations are carried out onboard ships nowadays and static transfer of liquid weight is taken into account in the course of routine stability calculation. The paper is focused on a dynamic heeling moment due to liquid sloshing in tanks onboard ships. The set of numerical simulations of liquid...
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Porównanie działania transformatora symetryzującego (zygzak) z aktywnym energoelektronicznym symetryzatorem prądów fazowych linii niskiego napięcia
PublicationNa potrzeby planowania sieci niskiego napięcia operatorzy systemów dystrybucyjnych (OSD) zakładają symetryczne warunki obciążenia linii. Z roku na rok, rośnie liczba rozproszonych systemów fotowoltaicznych (PV) zainstalowanych w sieciach niskiego napięcia, których większość to małe jednofazowe systemy dachowe. Dodatkowo, do niesymetrii obciążenia przyczyniają się instalowane masowo pompy ciepła i ładowane jednofazowo samochody...
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Simulation Studies of Control Systems for Doubly Fed Induction Generator Supplied by the Current Source Converter
PublicationThe control system for a Doubly Fed Induction Generator (DFIG) supplied by a grid-connected Current Source Converter (CSC) is presented in this paper. Nonlinear transformation of DFIG model to the multi-scalar form is proposed. The nonlinear control strategy of active and reactive power of DFIG is realized by feedback linearization. In the proposed control scheme, the DFIG model and CSI parameters are included. Two Proportional-Integral...
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Analysis of the Possibilities of Applying 3D Print Methods for the Needs of Ship-Building Industry
PublicationArticle presents the analysis of applying additive and hybrid manufacturing methods and its impact on dynamic stiffness of prepared samples. Dynamic analysis of the handle bracket specimens consisted in plotting the resonance curves and using these curves to estimate the dynamic stiffness of elements produced with additive manufacturing technology. Authors focused especially on 3D print in Fused Deposiotion Modeling/Fused Filament...
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A comparative analysis of numerically simulated and experimentally measured static responses of a floating dock
PublicationTwo numerical methods, dynamic and static analyses, are proposed to calculate the static responses of a floating dock under different ballast water distributions. Model-scale experimental tests were conducted to compare with these numerical methods. The dynamic analysis includes a 6-degree-of-freedom (6-DOF) model, a hydrostatic force model and a hydrodynamic force model to simulate the dock's freely floating processes. The dock's...