Filtry
wszystkich: 3837
wybranych: 3226
-
Katalog
Filtry wybranego katalogu
wyświetlamy 1000 najlepszych wyników Pomoc
Wyniki wyszukiwania dla: FORCED WAVES
-
A Bayesian regularization-backpropagation neural network model for peeling computations
PublikacjaA Bayesian regularization-backpropagation neural network (BRBPNN) model is employed to predict some aspects of the gecko spatula peeling, viz. the variation of the maximum normal and tangential pull-off forces and the resultant force angle at detachment with the peeling angle. K-fold cross validation is used to improve the effectiveness of the model. The input data is taken from finite element (FE) peeling results. The neural network...
-
Acoustic streaming caused by some types of aperiodic sound. Buildup of acoustic streaming
PublikacjaThe analysis of streaming caused by aperiodic sound of different types (switched on at transducer sound or sound determined by initial conditions) is undertaken. The analysis bases on analytical governing equation for streaming Eulerian velocity, which is a result of decomposition of the hydrodynamic equations into acoustic and non-acoustic parts. Its driving force (of acoustic nature) represents a sum of two terms; one is the...
-
A Numerical Study on Baseline-Free Damage Detection Using Frequency Steerable Acoustic Transducers
PublikacjaIn structural health monitoring (SHM) a considerable amount of damage detection algorithms based on guided waves (GW) have been developed. Most of them rely on extensive transducer networks, besides preliminary reference measurements of the structures. This originated a growing demand for hardware simplification and cost reduction of the wave-based SHM methods, driving the conception of new solutions enabling both: the reduction...
-
Underwater Acoustic Imaging of the Sea
PublikacjaAcoustic waves are a carrier of information mainly in environments where the use of other types of waves, for example electromagnetic waves, is limited. The term acoustical imaging is widely used in the ultrasonic engineering to imaging areas in which the acoustic waves propagate. In particular, ultrasound is widely used in the visualization of human organs - ultrasonography (Nowicki, 2010). Expanding the concept, acoustical imaging...
-
A gap waveguide-based mechanically reconfigurable phase shifter for high-power Ku-band applications
PublikacjaThis paper presents a novel design of a low-loss, reconfgurable broadband phase shifter based on groove gap waveguide (GGW) technology. The proposed phase shifter consists of a folded GGW and three bends with a few pins forming the GGW and one bend attached to a movable plate. This movable plate allows for adjustments to the folded waveguide length, consequently altering the phase of electromagnetic waves. The advantage of GGW...
-
Towards an Understanding of the Stability Assessment of Floating Buildings
PublikacjaOne of the most important aspects of the design of floating facilities such as ships, floating offshore structures or floating houses is stability. Its impact on both general safety and operational aspects renders it a fundamental consideration already in preliminary design stages. Usually, the concept of sufficient stability of floating buildings is associated with the ability to keep an allowed heel angle and residual freeboard,...
-
Multistatyczny, Dopplerowski System określania położenia i prędkości ruchomych celów w wodzie
PublikacjaW omawianym w pracy multistatycznym, dopplerowskim systemie określania położenia i prędkości ruchomych celów w wodzie źródłem sygnału są dwa nadajniki emitujące sinusoidalne, akustyczne fale ciągłe o różnych częstotliwościach, które po odbiciu od ruchomego celu są obierane przez cztery hydrofony. W artykule przedstawiono analize teoretyczna efektu Dopplera, na którym oparte jest działanie systemu oraz metodę rozwiązania głównych...
-
Magnetoacoustic Heating in Nonisentropic Plasma Caused by Different Kinds of Heating-Cooling Function
PublikacjaThe nonlinear phenomena which associate with magnetoacoustic waves in a plasma are analytically studied. A plasma is an open system with external inflow of energy and radiation losses. A plasma’s flow may be isentropically stable or unstable. The nonlinear phenomena occur differently in dependence on stability or instability of a plasma’s flow. The nonlinear instantaneous equation which describes dynamics of nonwave entropy mode...
-
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...
-
Analytical approach for membrane action in laterally-restrained reinforced concrete square slabs under uniformly distributed loads
PublikacjaLaterally-restrained reinforced concrete slabs can mobilise compressive membrane action and subsequent tensile membrane action under extreme loading conditions, thereby enhancing the load resistance under uniformly distributed loads. Previous analytical study focuses primarily on tensile membrane action in simply-supported slabs. This paper describes an analytical approach for membrane action in laterally-restrained square slabs....
-
Numeryczna analiza wpływu kierunku rozchodzenia się fali wybuchu na krzywiznę asymetrycznie walcowanego pasma Al-Cu. Numerical analysis the influence of the direction of explosion wave at the curvature of asymmetrical rolling of bimetallic plate.
PublikacjaW artykule przedstawiono numeryczną analizę wpływu kierunku rozchodzenia się fali wybuchu na krzywiznę asymetrycznie walcowanego pasma Al-Cu. Przeprowadzono symulacje dla procesu walcowania w temperaturze 20 C. Proces walcowania prowadzono w walcarce duo D 150 mm, o prędkości obwodowej 18,5 obr/min. Badania przeprowadzono dla dwóch stosunków grubości warstw 2/10 i 4/8. Symulację procesu przeprowadzono dla trzech gniotów 10%, 20%,...
-
Experimental research on a hydrodynamic thrust bearing with hydrostatic lift pockets: Influence of lubrication modes on bearing performance
PublikacjaThe aim of the study is to investigate the performance of a thrust bearing equipped with hydrostatic lift pockets under different lubrication modes. Three types of flat land bearing lubrication modes are studied experimentally: hydrostatic lubrication (HS; forced oil injection to the pockets), hybrid lubrication (HS + HD; hydrostatic lubrication combined with the external forced bearing oil supply) and hydrodynamic lubrication...
-
Alternative convolution approach to friction in unsteady pipe flow
PublikacjaIn the paper some aspects of the unsteady friction in pipe flow expressed by the convolution are analyzed. This additional term introduced into the motion equation involves the accelerations of fluid occurring in the past and a weighting function. The essence of such approach is to assume the appropriate form of weighting function. However, until now no fully reliable formula for this function has been found. To avoid some inconveniences...
-
Relative Productivity, Country Size and Export Diversification
PublikacjaThis paper analyses the effects of productivity and country size on the extent of trade structure diversification. Using a testable version of the Ricardian model, we show that relative export variety is an outcome of two forces: a relative productivity change (technological progress) and a relative country size change (labour force growth). The model predictions are validated empirically using product-level trade data for a sample...
-
Engineering method of tire rolling resistance evaluation
PublikacjaTire rolling resistance is one of the most difficult tire parameters to measure. The reason is that for modern tires the force of rolling resistance corresponds to 0.5–1% of tire load, thus measurements of very small forces must be performed in a heavily loaded system. This constitutes great problems, especially in road conditions. Laboratory measurements are easier to perform, as the environment may be better controlled, but roadwheel...
-
Comparison of the fracture toughness of pine wood determined on the basis of orthogonal linear cutting and frame sawing
PublikacjaIn this paper, the values of the fracture toughness of Scots pine determined by cutting tests are presented. The cutting tests were carried out using the samples of Scotch pine (Pinus sylvestris L.) from Pomeranian Region, Poland. These experiments were carried out on two research stands: orthogonal linear cutting tests were conducted using the microtome instrument and the frame saw PRW-15M was used for sawing tests. The values...
-
Dependence of Power Characteristics on Savonius Rotor Segmentation
PublikacjaSavonius rotors are large and heavy because they use drag force for propulsion. This leads to a larger investment in comparison to horizontal axis wind turbine (HAWT) rotors using lift forces. A simple construction of the Savonius rotor is preferred to reduce the production effort. Therefore, it is proposed here to use single-segment rotors of high elongation. Nevertheless, this rotor type must be compared with a multi-segment...
-
Impact resistance of plain and twill fabric in GFRP measured by active thermography
PublikacjaThis paper discusses the impact resistance of glass-fibre reinforced polymer (GFRP) composites depending on the type of reinforcement – plain or twill weave. The values of impact energy were: 3J, 10J and 15J. Specimens featuring twill weave transferred higher force during the impact as compared with plain weave specimens. It was observed that an increase of impact energy was accompanied by an increase of the disproportion in...
-
Scattering by parallel cylindrical posts with conducting strips. W: Pro- gress in electromagnetics research. Ed. J.A. Kong. Cambridge, Massachusett/ USA/: EMW Publ.**2003 s. 305-333, 18 rys. 5 tabl. bibliogr. 14 poz. Electromagnetic Waves. PIER [nr] 43. Rozpraszanie na równoległych metalizowanych obiektach cylindrycznych.
PublikacjaRozwinięto teorię rozpraszania fali elektromagnetycznej w obszarach otwar-tych i zamkniętych na metalizowanych obiektach cylindrycznych przy użyciuzmodyfikowanej procedury iteracyjnej i metody dopasowania rodzajów. W wynikuanalizy uzyskano pole rozproszone w przypadku struktur otwartych oraz odpo-wiedzi częstotliwościowe współczynników odbicia i transmisji w prostokąt-nych złączach falowodowych. Obrót i przemieszczenie...
-
Ultrawideband transmission in physical channels: a broadband interference view
PublikacjaThe superposition of multipath components (MPC) of an emitted wave, formed by reflections from limiting surfaces and obstacles in the propagation area, strongly affects communication signals. In the case of modern wideband systems, the effect should be seen as a broadband counterpart of classical interference which is the cause of fading in narrowband systems. This paper shows that in wideband communications, the time- and frequency-domain...
-
Biomechanics of Lumbar Spine Injury in Road Barrier Collision–Finite Element Study
PublikacjaLiterature and field data from CIREN database have shown that lumbar spine injuries occur during car crashes. There are multiple hypotheses regarding how they occur; however, there is no biomechanical explanation for these injuries during collisions with road safety barriers (RSBs). Therefore, the objective of this study was to investigate the mechanics of vertebral fractures during car collisions with concrete RSBs. The finite...
-
Mathematical Modeling of Ice Thrusting on the Shore of the Vistula Lagoon (Baltic Sea) and the Proposed Artificial Island
PublikacjaCoastal lagoons are inland and shallow water bodies, separated from the ocean by a barrier. In cold regions, ice phenomena in shallow water coastal lagoons occur every winter season. Ice is predominantly formed on the surface due to density stratification and surface cooling. The ice dynamics in such areas are dominantly affected by winds. Water dynamics also cause ice movement, but due to the large areal scale of lagoons, the...
-
The early failure of the gamma nail and the dynamic hip screw in femurs with a wide medullary canal. A biomechanical study of intertrochanteric fractures
PublikacjaBackground: Intertrochanteric fractures may occur in a bone with a wide medullary canal that may lead to significant mobility of a intramedullary nail, contrary to an extramedullary device. This study evaluates the Dynamic Hip Screw and the gamma nail in AO 31.A2.1 fractures in these circumstances. Methods: Synthetic femora with canals drilled to 18 mm were used. Five fixation types were examined: a 2 - hole and a 4 – hole Dynamic...
-
Mitigating the seismic pounding of multi-story buildings in series using linear and nonlinear fluid viscous dampers
PublikacjaSeismic-induced pounding between adjacent buildings may have serious consequences, ranging from minor damage up to total collapse. Therefore, researchers try to mitigate the pounding problem using different methods, such as coupling the adjacent buildings with stiff beams, connecting them by using viscoelastic links, and installing damping devices in each building individually. In the current paper, the effect of using linear and...
-
Acoustical images of the Gulf of Gdansk
PublikacjaAcoustic images of seabed are of interest to specialists in the field of marine engineering, marine navigation, marine archeology, hydrogeology, etc. New technolo gies based on use of elastic waves, predominantly acoustic waves that allow detecting complexity of geometric forms of seabed, ensure progress in studying the bathymetric structure of seafloor. Use of parametric sources of waves generated...
-
International cooperation between Department of Structural Mechanics of Civil Engineering Department of Gdansk University of Technology and Département Mécanique Ecole Polytechnique Universitaire de Lille (former EUDIL) Université des Sciences et Technologies de Lille.
PublikacjaW pracy przestawiono historię współpracy naukowej miedzy Wydz. Inż. Lad. Politechniki Gdańskiej i Wydziałem Mechanicznym Uniwersytetu w Lille (Francja). Podano najważniejsze publikacje, tytuły wspólnych prac dyplomowych i doktoratów realizowanych we współpracy. Przedstawiono na tym tle kierunki badań naukowych.
-
Improvement of ships seakeeping performance by application of the full-scale cfd simulations
PublikacjaThe ship’s fuel economy is increasingly important. The paper presents the effect of redesigning a case study ship for increasing seakeeping performance. Selected wave parameters reflect very difficult operational conditions existing on the North Sea and the Baltic Sea. The analyzed variants of a case study ship represent the latest developments of modern hull forms. The concepts similar to V-shaped bulbous bow, X-bow, X-aft, B-bow...
-
Design and Performance Evaluation of the Energy Subsystem of a Hybrid Light andWave Energy Harvester
PublikacjaThe paper presents the design and performance of an energy subsystem (ES) dedicated to hybrid energy harvesters (HEHs): wave energy converters (WECs) combined with photovoltaic panels (PVPs). The considered ES is intended for compact HEHs powering autonomous end-node devices in distributed IoT networks. The designed ES was tested experimentally and evaluated in relation to the mobile and wireless distributed communication use case....
-
Posttraumatic Orbital Emphysema: A Numerical Model
PublikacjaOrbital emphysema is a common symptom accompanying orbital fracture. The pathomechanism is still not recognized and the usually assumed cause, elevated pressure in the upper airways connected with sneezing or coughing, does not always contribute to the occurrence of this type of fracture. Observations based on the finite model (simulating blowout type fracture) of the deformations of the inferior orbital wall after a strike in...
-
Are Pair Trading Strategies Profitable During COVID-19 Period?
PublikacjaPair trading strategy is a well-known profitable strategy in stock, forex, and commodity markets. As most of the world stock markets declined during COVID-19 period, therefore this study is going to observe whether this strategy is still profitable after COVID-19 pandemic. One of the powerful algorithms of DBSCAN under the umbrella of unsupervised machine learning is applied and three clusters were formed by using market and accounting...
-
Truss imperfections in the design of bar and diaphragm bracing systems
PublikacjaIn the article three variants of roof bracing were considered: bar bracing, diaphragm bracing and the combination of bar and diaphragm bracing. Different analytical and numerical ways of taking into account the imperfections of the truss girder were compared. The entire 3D model of the roof (shell and beam elements with the eccentricities taken into account) was analysed numerically. Selected stressed-skin aspects were considered....
-
Estimation of fracture toughness and shear yield stress of orthotropic materials in cutting with rotating tools
PublikacjaThe cutting force is an energetic effect of splitting material, and might be considered from a point of view of modern fracture mechanics. Forecasting of the shear plane angle in cutting broaden possibilities for modelling of the cutting process even for thin uncut chips. Such mathematical model has been developed here for description of the orthotropic materials’ cutting on the base of fracture theory, and includes work of separation...
-
A System for Cooling Electronic Elements with EHD Coolant Flow
PublikacjaA system for cooling electronic components where the liquid coolant flow is forced with ion-drag type EHD micropumps was tested.
-
Time-Domain Description of Point-Source Acoustic Wavefields as a Useful Approach in Ultrasonic Techniques
PublikacjaIn traditional acoustics, field problems are usually treated in the frequency domain, broadband fields being reduced to superposition of harmonic spectrum components. However, this approach is inherently acausal and it is known that in case of arbitrary signals, the distribution-based, time-domain description can be more effective. The present paper is an attempt to expand the time-domain linear systems formalism onto space problems...
-
Time-domain description of point-source acoustic wavefields as a useful approach in ultrasonic techniques
PublikacjaIn traditional acoustics, field problems are usually treated in the frequency domain, broadband fields being reduced to superposition of harmonic spectrum components. However, this approach is inherently acausal and it is known that in case of arbitrary signals, the distribution-based, time-domain description can be more effective. The present paper is an attempt to expand the time-domain linear systems formalism onto space problems...
-
Mechanics of mesh implanted into abdominal wall under repetitive load. Experimental and numerical study
PublikacjaThere are a number of papers discussing medical and mechanical aspects of ventral hernia management. Despite intensive work on the problem understanding, recurrences of the sickness still happen too often. For that reason new aspects of the problem must be considered. In this paper, a change in the abdominal implant’s stiffness is discussed, which is caused by cyclic loading. Such loading influence abdominal implant e.g. while...
-
Zespół wypalenia zawodowego i zmęczenie w kontekście pracy zmianowej i stresu zawodowego wśród pielęgniarek chirurgicznych
PublikacjaTwo aspects of work-related consequences among surgery nurses are discussed: burnout syndrome and fatigue, having an impact on the quality of medical care and safety of patients. Siegrist's effort-reward imbalance model has been adopted as a concept of occupational stress. The organization of working time, i.e. the length of shifts and their rotation, was considered. Nurses on twelve-hour shifts worked much harder, were more tired...
-
5-Bromo-2′-deoxycytidine—a potential DNA photosensitizer
PublikacjaA double-stranded oligonucleotide, 80 base pairs in length, was multiply labeled with 5-bromo-2′-deoxycytidine (BrdC) using polymerase chain reaction (PCR). The modified oligonucleotide was irradiated with 300 nm photons and its damage was assayed by employing DHPLC, LC-MS and denaturing polyacrylamide gel electrophoresis (PAGE). Two types of damage were demonstrated, namely, single strand breaks (SSBs) and intrastrand cross-links...
-
Study of Icosahedral Clusters in Close-packed Simple Liquids
PublikacjaThe local structure of liquid copper was determined using Steinhardt order parameters, with particular attention paid to icosahedral clusters. The positions of atoms were obtained from three sets of molecular dynamics simulations, with the forces obtained from: the Sutton-Chen (SC) potential, the Naval Research Laboratory total energy tight-binding (NRL-TB) method and the divide-and-conquer learn-on-the-fly (DCLOTF) method, respectively....
-
Analysis of allophones based on audio signal recordings and parameterization
PublikacjaThe aim of this study is to develop an allophonic description of English plosive consonants based on recordings of 600 specially selected words. Allophonic variations addressed in the study may have two sources: positional and contextual. The former one depends on the syllabic or prosodic position in which a particular phoneme occurs. Contextual allophony is conditioned by the local phonetic environment. Co-articulation overlapping...
-
Characterization of Arctic Driftwood as Naturally Modified Material. Part 1: Machinability
PublikacjaArctic driftwood has reached the coast of Iceland for centuries. This material was used by the inhabitants of the island as a building material for houses, boats, churches and pasture fences. Nowadays, the driftwood is used in the furniture industry, for the finishing of internal and external walls of buildings and also by artists. The properties of driftwood differ to that of original resource due the long-term effects of exposure...
-
Proximal fibular osteotomy as a treatment for degenerative meniscal extrusion
PublikacjaMeniscal extrusion treatment is a key focus area for research and clinical study of degenerative knee pathology. The contact forces between the meniscus and the bones cause external displacements of the meniscus that are resisted by the circumferential fibres. The main risk factors for the excessive deformation of the meniscus are meniscal root tears, disruption of the circumferential fibres, knee malalignment and high body mass...
-
Earthquake-induced pounding between equal height multi-storey buildings considering soil-structure interaction
PublikacjaThe present paper investigates the coupled effect of the supporting soil flexibility and pounding between neighbouring, insufficiently separated equal height buildings under earthquake excitation. Two adjacent three-storey structures, modelled as inelastic lumped mass systems with different structural characteristics, have been considered in the study. The models have been excited using a suit of ground motions with different peak...
-
Magnetoacoustic heating in a quasi-isentropic magnetic gas
PublikacjaThe nonlinear heating of a plasma which associates with the transfer of energy of magnetoacoustic waves into that of the entropy mode, is analytically studied. A plasma is uniform and motionless at equilibrium. Perturbations in a plasma are described by a system of ideal magnetohydrodynamic equations. The equilibrium straight magnetic strength and the wave vector form a constant angle which varies from 0 to π/2. There exist four...
-
Rough Set Based Modeling and Visualization of the Acoustic Field Around the Human Head
PublikacjaThe presented research aims at modeling acoustical wave propagation phenomena by applying rough set theory in a novel manner. In a typical listening environment sound intensity is determined by numerous factors: a distance from a sound source, signal levels and frequencies, obstacles’ locations and sizes. Contrarily, a free-field is characterized by direct, unimpeded propagation of the acoustical waves. The proposed approach is...
-
Improvement of ships seakeeping performance by application of the Full-scale CFD simulations – case study
PublikacjaThe ship’s fuel economy is increasingly important. The paper presents the effect of redesigning a case study ship for increasing seakeeping performance. Selected wave parameters reflects very difficult operational con-ditions existing on the North Sea and the Baltic Sea. The analyzed variants of a case study ship represent the latest developments of modern hull forms. The concepts similar to V-shaped bulbous bow, X-bow, X-aft,...
-
Mechanical response of human thoracic spine ligaments under quasi-static loading: An experimental study
PublikacjaPurpose This study aimed to investigate the geometrical and mechanical properties of human thoracic spine ligaments subjected to uniaxial quasi-static tensile test. Methods Four human thoracic spines, obtained through a body donation program, were utilized for the study. The anterior longitudinal ligament (ALL), posterior longitudinal ligament (PLL), capsular ligament (CL), ligamenta flava (LF), and the interspinous ligament and...
-
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...
-
Sawing Processes as a Way of Determining Fracture Toughness and Shear Yield Stresses of Wood
PublikacjaA new computational model, based on fracture mechanics, was used to determine cutting forces. Unlike traditional computing methods, which depend on many coefficients reflecting the machining of solid wood, the new model uses two main parameters: fracture toughness and shear yield stresses. The aim of this study was to apply this new method to determine these parameters for the tooth cutting edge principal positions and longitudinal...
-
Experimental and analytical analysis of punching shear in flat slabs supported on column topped with concrete head
PublikacjaAn experimental laboraatory test of the two series of slab-column elements topped with drop panels of varying sizes is described in this paper. The scope of the paper is to investigate the influence of the drop panel size and stiffness on the behaviour of the connection between the flat slab and the column topped by the concrete head. The impact of the head size and stiffness is analysed analytically and experimentally. The experimental...