Wyniki wyszukiwania dla: PROPAGATION
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Damage-Involved Structural Pounding in Bridges under Seismic Excitation
PublikacjaDuring severe earthquakes, pounding between adjacent superstructure segments of highway elevated bridges was often observed. It is usually caused by the seismic wave propagation effect and may lead to significant damage. The aim of the present paper is to show the results of the numerical analysis focused on damage-involved pounding between neighbouring decks of an elevated bridge under seismic excitation. The analysis was carried...
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Data Compression in Ultrasonic Network Communication via Sparse Signal Processing
PublikacjaThis document presents the approach of using compressed sensing in signal encoding and information transferring within a guided wave sensor network, comprised of specially designed frequency steerable acoustic transducers (FSATs). Wave propagation in a damaged plate was simulated using commercial FEM-based software COMSOL. Guided waves were excited by means of FSATs, characterized by the special shape of its electrodes, and modeled...
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Filter-Hilbert Method for Automatic Correction of Non-Anechoic Antenna Measurements with Embedded Self-Calibration Mechanism
PublikacjaOne of the most important steps in the process of antenna development involves measurements of its prototype. Far-field performance of radiators is normally characterized in strictly controlled environments such as anechoic chambers which can ensure certification-grade accuracy. Unfortunately, they are also characterized by high construction costs which might not be justified for low-budget research and/or teaching-related activities....
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SPECTRAL RESPONSE OF STATIONARY JACK-UP PLATFORMS LOADED BY SEA WAVES AND WIND USING PERTURBATION METHOD
PublikacjaThe paper addresses non-linear vibrations of offshore jack-up drilling platforms loaded by sea waves and wind in their stationary condition using the perturbation method. Non-linearity of dynamic equations of motion for fixed offshore platforms yields from two factors. The first is load excitation generating non-linear velocity coupling in a dynamic system. This coupling is inherent in the modified Morison equation, involving the...
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Generalization of Kramers-Krönig relations for evaluation of causality in power-law media
PublikacjaClassical Kramers-Krönig (K–K) relations connect real and imaginary parts of the frequency-domain response of a system. The K–K relations also hold between the logarithm of modulus and the argument of the response, e.g. between the attenuation and the phase shift of a solution to a wave-propagation problem. For square-integrable functions of frequency, the satisfaction of classical K–K relations implies causality in the time domain....
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Assessment of Wide-Sense Stationarity of an Underwater Acoustic Channel Based on a Pseudo-Random Binary Sequence Probe Signal
PublikacjaThe performances of Underwater Acoustic Communication (UAC) systems are strongly related to the specific propagation conditions of the underwater channel. Designing the physical layer of a reliable data transmission system requires a knowledge of channel characteristics in terms of the specific parameters of the stochastic model. The Wide-Sense Stationary Uncorrelated Scattering (WSSUS) assumption simplifies the stochastic description...
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Person Tracking in Ultra-Wide Band Hybrid Localization System Using Reduced Number of Reference Nodes
PublikacjaIn this article a novel method of positional data integration in an indoor hybrid localization system combining inertial navigation with radio distance measurements is presented. A point of interest is the situation when the positional data and the radio distance measurements are obtained from less than thee reference nodes and it is impossible to unambiguously localize the moving person due to undetermined set of positional equations....
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Hydraulic analysis of causes of washout of Gdynia-Orłowo seashore during the flood in the Kacza river estuary
PublikacjaIn July 2016 in the Three-city agglomeration a rainfall episode of over a day duration and 150 mm summary rainfall height, occurred. This situation, extreme as for Polish conditions, caused significant freshets in rivers and streams running into Gdansk Bay, the Baltic Sea, and serving as collectors of rainfall waters for the sea-coast towns. In many areas of the Three-city flood phenomena and overflows took place. The flood also...
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Structure, luminescent properties and FDTD simulation of TeO2-BaO-Bi2O3-Ag:Ln3+ glass-ceramics system
PublikacjaTeO2-BaO-Bi2O3-Ag glass systems (TBB) co-doped with terbium and europium ions have been successfully synthesized through conventional melt-quenching technique. Heat treatment procedure at 350 °C has been conducted in order to synthesize silver nanoparticles embedded in TBB glass matrix. Structural measurements involved XRD studies that revealed no crystallization of glass structure after heat treatment at elevated temperatures....
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Memetic approach for multi-objective overtime planning in software engineering projects
PublikacjaSoftware projects often suffer from unplanned overtime due to uncertainty and risk incurred due to changing requirement and attempt to meet up with time-to-market of the software product. This causes stress to developers and can result in poor quality. This paper presents a memetic algorithmic approach for solving the overtime-planning problem in software development projects. The problem is formulated as a three-objective optimization...
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Pounding Between Superstructure Segments in Multi-Supported Elevated Bridge with Three-Span Continuous Deck Under 3D Non-Uniform Earthquake Excitation
PublikacjaReports after severe ground motions show that the earthquake-induced structural pounding may lead to significant damage in elevated bridges. The aim of this paper is to analyse pounding between superstructure segments of a highway elevated bridge with three-span continuous deck under 3D non-uniform earthquake excitation, which is induced by spatial seismic effects related to the propagation of seismic wave. The conditional stochastic...
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Natural convective heat transfer from isothermal cuboids
PublikacjaThe paper presents results of theoretical and experimental investigations of the convective heat transfer from isothermal cuboid. The analytical solution was performed taking into account complete boundary layer length and the manner of its propagation around isothermal cuboid. It arises at horizontal bottom surface and grows on vertical lateral surface of the block. After changing its direction, the boundary layer occurs above...
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Broadband communication solutions for maritime ITSs: Wider and faster deployment of new e-navigation services
Publikacjan its initial part, the paper presents an overview of popular technologies and systems currently developed or employed in maritime communication. These solutions are used to provide both ship-to-ship and ship-to-shore communication for the purpose of supporting specific services, often dedicated to maritime safety and e-navigation. Utility of such communication systems have been thoroughly verified over the years and their strengths...
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GPS-derived height changes in diurnal and sub-diurnal timescales
PublikacjaThis paper describes the research concerning precise short-time GPS solutions conducted in the Centre of Applied Geomatics, Military University of Technology, Warsaw, Poland. The data from ASG-EUPOS (Polish Active Geodetic Network) was processed using Bernese 5.0 software and EPN (EUREF Permanent Network) standards and models. In this study, the adapted 3-hour observation window is shifted every hour for obtaining hourly geocentric...
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Radio Channel Measurements in Off-Body Communications in a Ferry Passenger Cabin
PublikacjaThis paper presents an off-body radio channel measurements in a ferry passenger cabin at 2.45 GHz band, for static sleeping scenarios with different body orientation and on-body antennas placements, and also for upper and lower sleeping berths. The measurements have been performed with two types of on-body wearable receiving antennas: FlexPIFA (flexible planar inverted F antenna), and FlexNotch (flexible adhesive-backed notch antenna)...
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Non-ergodic fragmentation upon collision-induced activation of cysteine–water cluster cations
PublikacjaCysteine–water cluster cations Cys(H2O)3,6 + and Cys(H2O)3,6H+ are assembled in He droplets and probed by tandem mass spectrometry with collision-induced activation. Benchmark experimental data for this biologically important system are complemented with theory to elucidate the details of the collisioninduced activation process. Experimental energy thresholds for successive release of water are compared to water dissociation energies...
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Investigation of the Efficiency of a Dual-Fuel Gas Turbine Combustion Chamber with a Plasma‒Chemical Element
PublikacjaThe study is devoted to the possibility of increasing the efficiency of the working process in dual-fuel combustion chambers of gas turbine engines for FPSO vessels. For the first time, it is proposed to use the advantages of plasma‒chemical intensification of the combustion of hydrocarbon fuels in the dual-fuel combustion chambers, which can simultaneously operate on gaseous and liquid fuels. A design scheme of a combustion chamber...
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Finite element models used in diagnostics of transverse cracks in bridge approach pavement
Dane BadawczeTransverse cracks in the asphalt pavement were observed on bridge structures next to single-module expansion joints with a 5 meter approach slab set at the depth of 1 m. The finite element (FE) models of the approach pavement were created to investigate the reasons of premature cracking and crack initiation mechanism over the back edge of the abutment...
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A spline-based FE approach to modelling of high frequency dynamics of 1-D structures
PublikacjaIn this paper a computational methodology leading to the development of a new class of FEs, based on the application of continuous and smooth approximation polynomials, being splines, has been presented. Application of the splines as appropriately defined piecewise elemental shape functions led the authors to the formulation of a new approach for FEM, named as spFEM, where contrary to the well-known NURBS approach, the boundaries...
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Implementation of Non-Probabilistic Methods for Stability Analysis of Nonlocal Beam with Structural Uncertainties
PublikacjaIn this study, a non-probabilistic approach based Navier’s Method (NM) and Galerkin Weighted Residual Method (GWRM) in term of double parametric form has been proposed to investigate the buckling behavior of Euler-Bernoulli nonlocal beam under the framework of the Eringen's nonlocal elasticity theory, considering the structural parameters as imprecise or uncertain. The uncertainties in Young’s modulus and diameter of the beam are...