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    Wyświetlanie 1-26 z 26
    Tytuł:
    Numerical analysis of the finite amplitude plane wave propagation problem
    Autorzy:
    Baranowska, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/332213.pdf
    Data publikacji:
    2006
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Opis:
    The paper presents the results of the theoretical investigations of the finite amplitude plane wave propagation problem. The case of harmonic plane pressure wave of megahertz frequency propagating in water is discussed. Mathematical model and some results of numerical calculations are shown. The nonlinear acoustics equation was considered to build the mathematical model. To solve the problem numerically the finite-difference method was applied. The influence of discrete model parameters on the numerical calculations accuracy was studied. The results of computer calculations for different values of physical parameters were also analyzed.
    Źródło:
    Hydroacoustics; 2006, 9; 1-8
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electromagnetic Scattering of Inhomogeneous Plane Wave by Ensemble of Cylinders
    Autorzy:
    Dinia, Lorenzo
    Mangini, Fabio
    Frezza, Fabrizio
    Powiązania:
    https://bibliotekanauki.pl/articles/309062.pdf
    Data publikacji:
    2020
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    electromagnetic scattering
    inhomogeneous wave dispersion
    lossy media
    multi-cylinders scattering
    vectorial cylindrical-harmonics
    Opis:
    The interaction between an ensemble of cylinders and an inhomogeneous plane wave is introduced and is determined, in the present paper, through a rigorous theoretical approach. Scattered electromagnetic field generated by an indefinite number of infinite circular cylinders is analyzed by the application of the generalized vector cylinder harmonics (VCH) expansion. The exact mathematical model relied upon to represent this scenario considers the so-called complex-angle formalism reaching a superposition of vectorial cylindrical-harmonics and Foldy-Lax Multiple scattering equations (FLMSE) to account for the multiscattering process between the cylinders. The method was validated by comparing the numerical results obtained with the use of the finite element method and a homemade Matlab code.
    Źródło:
    Journal of Telecommunications and Information Technology; 2020, 3; 86-92
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Modeling of the finite amplitude plane wave propagation in non-dissipative medium
    Autorzy:
    Baranowska, A.
    Powiązania:
    https://bibliotekanauki.pl/articles/331517.pdf
    Data publikacji:
    2008
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Tematy:
    amplitude plane wave
    Burgers equation
    mathematical model
    Opis:
    The paper presents results of theoretical analysis of the finite amplitude plane wave propagation problem. The case of harmonic plane wave propagation in non-dissipative medium was considered. The mathematical model and some results of numerical investigations are presented. The mathematical model was built on the basis of one-dimensional continuity equation, equation of motion in differential form and state equation. The finite difference method was applied to solve the problem numerically. The pressure changes and harmonic pressure amplitude changes were analysed. The results of computer calculations were compared with solution of the Burgers equation.
    Źródło:
    Hydroacoustics; 2008, 11; 11-18
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Uniqueness, reciprocity theorems and plane wave propagation in different theories of thermoelasticy
    Autorzy:
    Kumar, R.
    Gupta, V.
    Powiązania:
    https://bibliotekanauki.pl/articles/955280.pdf
    Data publikacji:
    2013
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    termoelastyczność
    fala płaska
    termosprężystość
    isotropic
    thermoelasticity
    uniqueness theorem
    reciprocity theorem
    plane wave
    Opis:
    In this work, a compact form of different theories of thermoelasticity is considered. The governing equations for particle motion in a homogeneous isotropic thermoelastic medium are presented. Uniqueness and reciprocity theorems are proved. The plane wave propagation in a homogeneous isotropic thermoelastic medium is studied. For a three dimensional problem there exist four waves, namely a P-wave, two transverse waves (S1, S2) and a thermal wave (T). From the obtained results the different characteristics of waves such as the phase velocity and attenuation coefficient are computed numerically and presented graphically. Some special cases are also discussed.
    Źródło:
    International Journal of Applied Mechanics and Engineering; 2013, 18, 4; 1067-1086
    1734-4492
    2353-9003
    Pojawia się w:
    International Journal of Applied Mechanics and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Effects of Loss Factor on Plane Wave Propagation through a Left-Handed Material Slab
    Autorzy:
    Sabah, C.
    Powiązania:
    https://bibliotekanauki.pl/articles/1812347.pdf
    Data publikacji:
    2008-06
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    04.30.Nk
    41.20.Jb
    78.20.Ci
    Opis:
    This article presents a theoretical and numerical discussion of the reflection and transmission analysis through a lossy left-handed material slab embedded between two semi-infinite dielectric media. The properties of the lossy left-handed material are given in detail and the required equations for the electromagnetic plane wave propagation are derived to solve the problem. The main important contribution of this article is the characterization of left-handed material that is different from its counterpart known in the literature. After introducing the left-handed material slab, the analytical solution is found for the powers carried by an electromagnetic wave. Then, the reflected, the transmitted, and the loss power are computed in terms of the incidence angle, the frequency, and the slab thickness in the numerical results with the emphasis on the loss factor.
    Źródło:
    Acta Physica Polonica A; 2008, 113, 6; 1589-1597
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Interference Fringes in the Plane Wave Topographic Images of Growth Bands in Si:Ge
    Autorzy:
    Wieteska, K.
    Wierzchowski, W.
    Graeff, W.
    Lefeld-Sosnowska, M.
    Regulska, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/2030662.pdf
    Data publikacji:
    2002-05
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    61.72.Ff
    Opis:
    An Si:Ge crystal with approximately 3% of germanium was studied with strongly collimated short-wavelength monochromatic synchrotron beam (beamline E2 at HASYLAB). The topographs obtained in the asymmetric 224 reflection revealed the presence of interference fringes related to growth bands caused by segregation of germanium. The fringes, observed for the first time, were strongly dependent on the angular setting and it was possible to distinguish at least three systems of fringes. A number of features of the existing strain field, which may be important for the formation of the fringes, was determined using other topographic methods, especially the Bragg-case section topography.
    Źródło:
    Acta Physica Polonica A; 2002, 101, 5; 729-734
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    A resonance approach for the plane-wave reflection loss model including sediment and basement rigidity
    Autorzy:
    Fokina, M.
    Fokin, V.
    Powiązania:
    https://bibliotekanauki.pl/articles/332711.pdf
    Data publikacji:
    1999
    Wydawca:
    Polskie Towarzystwo Akustyczne
    Opis:
    The exact expression for reflection coefficient has been obtained with the Thomson-Haskell technique for the bottom model consisting of an elastic homogeneous layer overlying elastic half-space. The behaviour of the frequency-angular dependence for exact values of the reflection coefficient was studied. Inspection of exact expression for reflection coefficient shows that resonance behaviour will exhibit when the real part of denominator vanishes. The characteristic equations were obtained and roofs of equations were found. Resonance positions for compressional and shear wave velocities were determined. Frequency-angular resonance positions were obtained bofh using resonance theory and exact computations. Comparison of obtained resonance positions was performed. The changes in the position for the resonance peaks for frequency- angular resonances as a function of the bottom model parameters were analysed. This work was supported by the Russian Foundation for Basic Research (No.97-05-64712).
    Źródło:
    Hydroacoustics; 1999, 2; 101-106
    1642-1817
    Pojawia się w:
    Hydroacoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Electromagnetic Scattering by a Cylinder in a Lossy Medium of an Inhomogeneous Elliptically Polarized Plane Wave
    Autorzy:
    Mangini, Fabio
    Dinia, Lorenzo
    Frezza, Fabrizio
    Powiązania:
    https://bibliotekanauki.pl/articles/309521.pdf
    Data publikacji:
    2019
    Wydawca:
    Instytut Łączności - Państwowy Instytut Badawczy
    Tematy:
    electromagnetic scattering
    inhomogeneous wave dispersion
    vectorial cylindrical-harmonics
    Opis:
    In this paper, a rigorous theoretical approach, adopted in order to generalize the Vectorial CylindricalHarmonics (VCH) expansion of an inhomogeneous elliptically polarized plane wave, is presented. An application of the VCH expansion to analyze electromagnetic field scattered by an infinite circular cylinder is presented. The results are obtained using the so-called complex-angle formalism reaching a superposition of Vectorial Cylindrical-Harmonics. To validate the method, a Matlab code was implemented. Also, the validity of the methodology was confirmed through some comparisons between the proposed method and the numerical results obtained based on the Finite Element Method (FEM) in the canonical scenario with a single cylinder.
    Źródło:
    Journal of Telecommunications and Information Technology; 2019, 4; 36-42
    1509-4553
    1899-8852
    Pojawia się w:
    Journal of Telecommunications and Information Technology
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Reflection and Transmission of Plane Wave at an Interface Between Two Rotating Micropolar Piezoelectric Solid Half-Spaces
    Autorzy:
    Singh, Baljeet
    Sangwan, Asha
    Singh, Jagdish
    Powiązania:
    https://bibliotekanauki.pl/articles/2141703.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    plane wave
    micropolar piezoelectricity
    reflection and transmission
    amplitude ratios
    energy ratios
    rotation
    Opis:
    In this paper, we investigate a problem on reflection and transmission of plane-waves at an interface between two dissimilar half-spaces of a transversely isotropic micropolar piezoelectric material. The entire model is assumed to rotate with a uniform angular velocity. The governing equations of rotating and transversely isotropic micropolar piezoelectric medium are specialized in a plane. Plane-wave solutions of two-dimensional coupled governing equations show the possible propagation of three coupled plane-waves. For an incident plane-wave at an interface between two dissimilar half-spaces, three reflected and three transmitted waves propagate with distinct speeds. The connections between the amplitude ratios of reflected and transmitted waves are obtained. The expressions for the energy ratios of reflected and transmitted waves are also obtained. A numerical example of the present model is considered to illustrate the effects of rotation on the speeds and energy ratios graphically.
    Źródło:
    Archives of Acoustics; 2021, 46, 4; 623-635
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Influence of diffusion and impedence parameters on wave propagation in thermoelastic medium
    Autorzy:
    Kaushal, Sachin
    Kumar, Rajneesh
    Parmar, Kulwinder
    Powiązania:
    https://bibliotekanauki.pl/articles/2174177.pdf
    Data publikacji:
    2021
    Wydawca:
    Uniwersytet Zielonogórski. Oficyna Wydawnicza
    Tematy:
    fala płaska
    dyfuzja
    impedancja
    plane wave
    amplitude ratios
    diffusion
    impedance parameters
    Opis:
    The aim of the present paper is to study the impact of diffusion and impedance parameters on the propagation of plane waves in a thermoelastic medium for Green and Lindsay theory (G-L) and the Coupled theory (C-T) of thermoelasticity. Results are demonstrated for impedance boundary conditions and the amplitude ratios of various reflected waves against the angle of incidence are calculated numerically. The characteristics of diffusion, relaxation time and impedence parameter on amplitude ratios have been depicted graphically. Some cases of interest are also derived from the present investigation.
    Źródło:
    International Journal of Applied Mechanics and Engineering; 2021, 26, 4; 99--112
    1734-4492
    2353-9003
    Pojawia się w:
    International Journal of Applied Mechanics and Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    An Investigation on Acoustic Wave Focalization by a Square Lattice Flat Lens
    Autorzy:
    Alagoz, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/177219.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    square lattice sonic crystal
    wave focusing
    plane-wave expansion method
    FDTD simulation
    Opis:
    A sonic crystal consists of a finite-size periodic array of scatters embedded in a background material. One of the fascinating properties of sonic crystals is the focusing phenomenon. In this study, the near field focusing effect of a solid-air 2D sonic crystal lens with a square lattice configuration is investigated in the second frequency band. The band structure and equifrequency contour of the crystal are analyzed to reveal the dispersion of an acoustic wave on the crystal structure. The frequency dependence of the acoustic wave focalization by the sonic crystal flat lens is demonstrated via Finite Difference Time Domain simulation results and experimental measurements.
    Źródło:
    Archives of Acoustics; 2012, 37, 1; 81-87
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Using PWE/FE Method to Calculate the Band Structures of the Semi-Infinite PCs : Periodic in x-y Plane and Finite in z–direction
    Autorzy:
    Qian, D.
    Shi, Z.
    Powiązania:
    https://bibliotekanauki.pl/articles/176974.pdf
    Data publikacji:
    2017
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    semi-infinite phononic crystal
    coupled plane wave expansion
    finite element method
    band structure
    Opis:
    This paper introduces the concept of semi-infinite phononic crystal (PC) on account of the Infinite periodicity in x-y plane and finiteness in z-direction. The plane wave expansion and finite element methods are coupled and formulized to calculate the band structures of the proposed periodic elastic composite structures based on the typical geometric properties. First, the coupled plane wave expansion and finite element (PWE/FE) method is applied to calculate the band structures of the Pb/rubber, steel/epoxy and steel/aluminum semi-infinite PCs with cylindrical scatters. Then, it is used to calculate the band structure of the Pb/rubber semi-infinite PC with cubic scatter. Last, the band structure of the rubbercoated Pb/epoxy three-component semi-infinite PC is calculated by the proposed method. Besides, all the results are compared with those calculated by the finite element (FE) method implemented by adopting COMSOL Multiphysics. Numerical results and further analysis demonstrate that the proposed PWE/FE method has strong applicability and high accuracy.
    Źródło:
    Archives of Acoustics; 2017, 42, 4; 735-742
    0137-5075
    Pojawia się w:
    Archives of Acoustics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Basic Logic Gates in Two Dimensional Photonic Crystals for All Optical Device Design
    Autorzy:
    Sonth, Mahesh V
    Srikanth, Gimmadi
    Agrawal, Pankaj
    Premalatha, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/1844637.pdf
    Data publikacji:
    2021
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    basic gates
    photonic crystals
    finite difference time domain
    plane wave expansion
    photonic band gap
    Opis:
    The research carried out in the field of optics and photonics with an idea to design and develop the all optical logic devices in the fascinating material known as photonic crystals (PhCs). The structural investigation reveals that the two dimensional (2-D) PhCs is more suitable for fabrication of optoelectronic components. In this article we have designed basic logic gates in 2-D PhCs as they are the building blocks for the construction of optical devices and in these, refractive index is periodically modulated with the wavelength. The understanding of light behaviour in complex PhCs helps in creating photonic band gap (PBG) that can prevent light of certain wavelength propagating in crystal lattice structure. For the selected geometry structure, three PBG bands will exists out of which two of them are transverse electric (TE) and one is transverse magnetic (TM) mode. The PBG bands in the TE mode ranges from 0.31( α λ ) to 0.46( α λ ), 0.61( α λ ) to 0.63( α λ ) and TM mode ranges from 0.86( α λ ) to 0.93( α λ ). The free space wavelength of 1550 nm is set for the finite difference time domain (FDTD) simulation of the structure. The response time and computational overhead required for the proposed OR gate is 0.128ps and 4.4MB is obtained. Also we calculated the extinction ratio for AND gate and NOT gate as 6.19 dB and 10.21 dB respectively.
    Źródło:
    International Journal of Electronics and Telecommunications; 2021, 67, 2; 247-261
    2300-1933
    Pojawia się w:
    International Journal of Electronics and Telecommunications
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Three dimensional photonic crystals
    Autorzy:
    Dissanayake, S. E.
    Wijewardena Gamalath, K. A. I. L.
    Powiązania:
    https://bibliotekanauki.pl/articles/1194049.pdf
    Data publikacji:
    2015
    Wydawca:
    Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
    Tematy:
    Fcc lattice and diamond lattice
    GaAs
    Photonic crystal
    dielectric contrast
    filling fraction
    plane wave expansion
    Opis:
    The plane wave expansion method was implemented in modelling and simulating the band structures of three dimensional photonic crystals with FCC lattice formed from air spheres drilled in GaAs and diamond lattice formed by GaAs spheres drilled in air. Both these structures lead to a complete band gap not allowing EM waves with the frequency of the band gap to propagate through the crystal in any direction. Diamond lattice photonic crystal has a complete band gap for a wider range of filling fraction than FCC photonic crystal and also it has a wider band gap width.
    Źródło:
    World Scientific News; 2015, 12; 12-23
    2392-2192
    Pojawia się w:
    World Scientific News
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Non-plane wave scattering from a single eccentric circular inclusion - Part I: SH waves
    Niepłaskie rozpraszanie fal od kołowego mimośrodowo osadzonego wtrącenia w materiale – część I: fale SH
    Autorzy:
    Weber, W.
    Zastrau, B. W.
    Powiązania:
    https://bibliotekanauki.pl/articles/281878.pdf
    Data publikacji:
    2011
    Wydawca:
    Polskie Towarzystwo Mechaniki Teoretycznej i Stosowanej
    Tematy:
    non-plane waves
    eccentric scatterer
    scattering
    SH wave
    elastic wave
    TRC
    Opis:
    In this contribution, an analytical formalism for investigating the scattering behaviour of a single multi-layered inclusion in a homogeneous isotropic matrix under the influence of non-plane elastic SH waves is derived. Herein, the inclusion is assumed to have a circular shape with its layers being eccentrically arranged. Numerical examples are performed with Textile Reinforced Concrete, a new building material in civil engineering. Within these investigations both shielding and amplification of SH waves is shown.
    W pracy przedstawiono analityczny formalizm zagadnienia rozpraszania fal na pojedynczym, wielowarstwowymwtrąceniu materiałowym w izotropowej, jednorodnej strukturze osnowy poddanej działaniu niepłaskich fal spolaryzowanych w płaszczyźnie poziomej (fale typu SH). Założono, że wtrącenie ma kołowy kształt, a jego warstwy są rozmieszczone mimośrodowo. Zamieszczono rezultaty symulacji numerycznych na przykładzie nowego materiału budowlanego, jakim jest beton wzmacniany tekstyliami. Pokazano efekt ekranowania i wzmacniania fal SH w takiej strukturze.
    Źródło:
    Journal of Theoretical and Applied Mechanics; 2011, 49, 4; 1183-1201
    1429-2955
    Pojawia się w:
    Journal of Theoretical and Applied Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Implant Safety Tool Application to Assist the Assessment of Radio-Frequency Radiation Exposure
    Autorzy:
    Gas, Piotr
    Miaskowski, Arkadiusz
    Powiązania:
    https://bibliotekanauki.pl/articles/124187.pdf
    Data publikacji:
    2019
    Wydawca:
    Polskie Towarzystwo Inżynierii Ekologicznej
    Tematy:
    Implant Safety Tool
    pectus excavatum
    metal implants
    Nuss procedure
    MRI devices
    plane wave
    FDTD method
    RF exposure standards
    Opis:
    This paper discusses a new Implant Safety Tool, used to assess the safety of patients with metal implants exposed to radio-frequency (RF) fields. This specialist tool is discussed on the example of pectus patients with titanium bar-implant inserted during the minimally invasive Nuss procedure. The authors created a 3D realistic model of a 34-year-old male patient with a Nuss bar-implant. A numerical analysis based on the finite-difference time-domain (FDTD) method was performed for a far field source in the form of a plane wave with the frequency of 64 MHz, which corresponds to the RF exposure generated by MRI devices at 1.5 T. The obtained results allow concluding that the concave Nuss bar-implant poses no risk during environmental and occupational RF field exposures.
    Źródło:
    Journal of Ecological Engineering; 2019, 20, 10; 24-33
    2299-8993
    Pojawia się w:
    Journal of Ecological Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Simulation of two dimensional photonic band gaps
    Autorzy:
    Dissanayake, S. E.
    Wijewardena Gamalath, K. A. I. L.
    Powiązania:
    https://bibliotekanauki.pl/articles/411904.pdf
    Data publikacji:
    2014
    Wydawca:
    Przedsiębiorstwo Wydawnictw Naukowych Darwin / Scientific Publishing House DARWIN
    Tematy:
    Photonic crystal
    square lattice
    triangular lattice
    honeycomb lattice
    plane wave expansion
    mode field distribution
    GaAs
    dielectric kontrast
    filling fraction
    gap maps
    Opis:
    The plane wave expansion method was implemented in modelling and simulating the band structures of two dimensional photonic crystals with square, triangular and honeycomb lattices with circular, square and hexagonal dielectric rods and air holes. Complete band gaps were obtained for square lattice of square GaAs rods and honeycomb lattice of circular and hexagonal GaAs rods as well as triangular lattice of circular and hexagonal air holes in GaAs whereas square lattice of square or circular air holes in a dielectric medium ε = 18 gave complete band gaps. The variation of these band gaps with dielectric contrast and filling factor gave the largest gaps for all configurations for a filling fraction around 0.1.The gap maps presented indicated that TM gaps are more favoured by dielectric rods while TE gaps are favoured by air holes. The geometrical gap maps operating at telecommunication wavelength λ = 1.55 m showed that a complete band gap can be achieved for triangular lattice with circular and hexagonal air holes in GaAs and for honeycomb lattice of circular GaAs rods.
    Źródło:
    International Letters of Chemistry, Physics and Astronomy; 2014, 5; 58-88
    2299-3843
    Pojawia się w:
    International Letters of Chemistry, Physics and Astronomy
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Analiza falowa tarczy w płaskim stanie naprężenia metodą ruchomych, najmniejszych kwadratów
    Analysis of a plane stress wave by the moving least squares method
    Autorzy:
    Dornowski, W.
    Powiązania:
    https://bibliotekanauki.pl/articles/210263.pdf
    Data publikacji:
    2014
    Wydawca:
    Wojskowa Akademia Techniczna im. Jarosława Dąbrowskiego
    Tematy:
    mechanika konstrukcji
    metody bezsiatkowe
    metoda ruchomych najmniejszych kwadratów
    fale sprężyste
    civil engineering
    meshless method
    moving least squares method
    elastic waves
    Opis:
    W pracy rozwiązano zadanie początkowo-brzegowe propagacji płaskiej fali naprężenia w tarczy stalowej metodą ruchomych najmniejszych kwadratów. Stosowano różne siatki węzłów. W przypadku siatek z węzłami generowanymi losowo istotne znaczenie ma wybór węzłów sąsiedztwa aproksymacyjnego. Przyjęto kryterium topologiczne wynikające z triangulacji zbioru węzłów, która minimalizuje łączną długość krawędzi triangulacji. Stwierdzono, że triangulacyjny sposób wyboru otoczenia aproksymacyjnego i wygładzanie siatki nieregularnej metodą Laplace’a znacznie poprawia dokładność rozwiązania. Efekt odbicia fali naprężenia od brzegu swobodnego modelowano przez wprowadzenie węzłów fikcyjnych (poza obszarem tarczy). Otrzymane rezultaty porównano z wynikami obliczeń metodą różnicową, stwierdzając ich zgodność jakościową i ilościową.
    A meshless method based on the moving least squares approximation is applied to stress wave propagation analysis. Two kinds of node meshes, the randomly generated mesh and the regular mesh are used. The nearest neighbours’ problem is developed from a triangulation that satisfies minimum edges length conditions. It is found that this method of neighbours’ choice significantly improves the solution accuracy. The reflection of stress waves from the free edge is modelled using fictitious nodes (outside the plate). The comparison with the finite difference results also demonstrated the accuracy of the proposed approach.
    Źródło:
    Biuletyn Wojskowej Akademii Technicznej; 2014, 63, 3; 189-206
    1234-5865
    Pojawia się w:
    Biuletyn Wojskowej Akademii Technicznej
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Excitation of Bulk Spin Waves by Acoustic Wave at the Plane Defect of a Ferromagnet
    Autorzy:
    Gusieva, Y.
    Graczyk, P.
    Gorobets, O.
    Krawczyk, M.
    Powiązania:
    https://bibliotekanauki.pl/articles/1030772.pdf
    Data publikacji:
    2018-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.30.Ds
    75.78.-n
    75.80.+q
    Opis:
    Excitation of bulk spin waves by acoustic wave localized on the elastic planar defect in the bulk ferromagnet was analytically and numerically investigated. We showed that besides magnetic oscillations forced by acoustic wave strain the resonance between Kosevich wave and bulk spin wave can occurs. For the frequency of the Kosevich wave far below the resonance frequency the amplitude of dynamic magnetization is negligible. For the frequency above the resonance the acoustic wave excites bulk spin wave of the same frequency but different absolute value of the wave vector.
    Źródło:
    Acta Physica Polonica A; 2018, 133, 3; 489-491
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Damage detection of a T-shaped panel by wave propagation analysis in the plane stress
    Wykrywanie uszkodzeń w tarczy typu T z użyciem analizy propagacji fal w płaskim stanie naprężenia
    Autorzy:
    Rucka, M.
    Witkowski, W.
    Chróścielewski, J.
    Wilde, K.
    Powiązania:
    https://bibliotekanauki.pl/articles/231134.pdf
    Data publikacji:
    2012
    Wydawca:
    Polska Akademia Nauk. Czytelnia Czasopism PAN
    Tematy:
    wykrywanie uszkodzeń
    tarcza stalowa
    tarcza typu T
    propagacja fal
    stan naprężenia płaskiego
    damage detection
    steel panel
    T-shaped panel
    wave propagation
    spectral element method
    Opis:
    A computational approach to analysis of wave propagation in plane stress problems is presented. The initial-boundary value problem is spatially approximated by the multi-node C0 displacement-based isoparametric quadrilateral finite elements. To integrate the element matrices the multi-node Gauss-Legendre-Lobatto quadrature rule is employed. The temporal discretization is carried out by the Newmark type algorithm reformulated to accommodate the structure of local element matrices. Numerical simulations are conducted for a T-shaped steel panel for different cases of initial excitation. For diagnostic purposes, the uniformly distributed loads subjected to an edge of the T-joint are found to be the most appropriate for design of ultrasonic devices for monitoring the structural element integrity.
    W pracy zaprezentowano podejście obliczeniowe do analizy propagacji fal w płaskim stanie naprężenia. Problem brzegowo-początkowy podlega przestrzennej aproksymacji z użyciem wielowęzłowych, izoparametrycznych, czworobocznych elementów klasy C0. Macierze elementowe są całkowane numerycznie za pomocą kwadratury Gauss-Legendre-Lobatto. Aproksymacje w dziedzinie czasu wykonano za pomocą algorytmu Newmarka. Symulacje numeryczne przeprowadzono dla tarczy w kształcie litery T dla różnych przypadków wzbudzania fali. W pracy wykazano, że dla celów diagnostyki najlepszym rodzajem obciążenia jest obciążenie liniowe równomiernie przyłożone do krawędzi tarczy.
    Źródło:
    Archives of Civil Engineering; 2012, 58, 1; 3-24
    1230-2945
    Pojawia się w:
    Archives of Civil Engineering
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Spin Wave Excitations of the Interacting Two-Dimensional In-Plane Nano-Vortices
    Autorzy:
    Mamica, S.
    Powiązania:
    https://bibliotekanauki.pl/articles/1030500.pdf
    Data publikacji:
    2018-03
    Wydawca:
    Polska Akademia Nauk. Instytut Fizyki PAN
    Tematy:
    75.30.Ds
    75.70.Kw
    75.75.Jn
    Opis:
    The aim of this work is to study spin-wave excitations in the row of interacting two-dimensional nanodots in the vortex state. We use a discrete dipole model taking into account the nearest-neighbour exchange and dipolar interactions. Magnetic configuration of each dot is assumed to form an in-plane vortex (circular magnetization). We examine the dependence of frequencies and profiles of spin-wave modes vs. the dipolar-to-exchange interaction ratio and the dot separation. Special attention is paid to some particular modes: lowest-frequency azimuthal modes and the fundamental mode, an analogue of the uniform excitation. Some conclusions regarding the influence of the size of dots the row consists of as well as the chirality of neighbouring vortices are provided too.
    Źródło:
    Acta Physica Polonica A; 2018, 133, 3; 505-507
    0587-4246
    1898-794X
    Pojawia się w:
    Acta Physica Polonica A
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Sensor performance and cut-off wavelength tradeoffs of III-V focal plane arrays
    Autorzy:
    James, Jonathan Ch.
    Haran, Terence L.
    Lane, Sarah E.
    Powiązania:
    https://bibliotekanauki.pl/articles/2204205.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
    Tematy:
    infrared focal plane arrays
    III-V semiconductor infrared detector technologies
    infrared sensor performance modelling
    infrared sensor design
    mid-wave and longwave infrared sensors
    Opis:
    Infrared detector technologies engineered from III-V semiconductors such as strained-layer superlattice, quantum well infrared photodetectors, and quantum dot infrared photodetectors provide additional flexibility to engineer bandgap or spectral response cut-offs compared to the historical high-performance detector technology of mercury/cadmium/telluride. The choice of detector cut-off depends upon the sensing application for which the system engineer is attempting to maximize performance within an expected ensemble of operational scenarios that define objects or targets to be detected against specific environmental backgrounds and atmospheric conditions. Sensor performance is typically characterised via one or more metrics that can be modelled or measured experimentally. In this paper, the authors will explore the impact of detector cut-off wavelength with respect to different performance metrics such as noise equivalent temperature difference and expected target detection or identification ranges using analytical models developed for several representative sensing applications encompassing a variety of terrestrial atmospheric conditions in the mid-wave and long-wave infrared wavelength bands. The authors will also report on their review of recently published literature concerning the relationships between cut-off wavelength and the other detector performance characteristics such as quantum efficiency or dark current for a variety of detector technologies.
    Źródło:
    Opto-Electronics Review; 2023, 31, Special Issue; art. no. e144570
    1230-3402
    Pojawia się w:
    Opto-Electronics Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Application of potential theory in calculating wave-induced vertical forces on horizontal cylinders near a plane boundary
    Autorzy:
    Marcinkowski, T.
    Wilde, P.
    Powiązania:
    https://bibliotekanauki.pl/articles/241390.pdf
    Data publikacji:
    2006
    Wydawca:
    Polska Akademia Nauk. Instytut Budownictwa Wodnego PAN
    Tematy:
    hydrodynamic forces
    underwater pipeline
    potential theory
    diffraction theory
    curvilinear coordinates
    Opis:
    Hydrodynamic forces acting on a horizontal cylinder located in the vicinity of the bottom are analyzed by a diffraction theory which solves the problem in terms of a velocity potential. The cylinder is assumed to be rigidly anchored to the bottom at a sufficient depth, so that it has no influence on the surface profile. The potential function φ is defined as the sum of the incident wave velocity potential φ w and the scattered wave velocity potential φa. The results of measurements of wave-induced pressures and forces on a horizontal cylinder located close to the bottom are compared with the theoretical solution based on the potential theory for incompressible, perfect fluid and ideal boundary conditions at the bottom and the surface of the cylinder. The experiments were carried out in the Large Wave Channel in Hannover with a cylinder of 0.8 m diameter. Thus the results are in a scale which corresponds to real pipelines. The analysis shows that the potential theory explains the components with double frequency of the wave in pressures and vertical forces as far as the amplitudes are concerned. In the experiments, the Keulegan-Carpenter number is rather low and the inertia hydrodynamic forces on the cylinder are dominant. It seems that the observed phase shift between the force component and the wave results from the energy dissipation which is not considered in the theoretical solution.
    Źródło:
    Archives of Hydro-Engineering and Environmental Mechanics; 2006, 53, 1; 49-69
    1231-3726
    Pojawia się w:
    Archives of Hydro-Engineering and Environmental Mechanics
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Recent development in all-optical ultrasonic shear wave inspection
    Niedawne odkrycie w całkowicie optycznej ultradźwiękowej inspekcji fal poprzecznych
    Autorzy:
    Messaoudi, M.
    Pouet, B.
    Powiązania:
    https://bibliotekanauki.pl/articles/107939.pdf
    Data publikacji:
    2018
    Wydawca:
    Stowarzyszenie Inżynierów i Techników Mechaników Polskich
    Tematy:
    laser ultrasound
    in-plane displacement
    three dimensional
    directivity pattern
    shear waves
    ultradźwięki wzbudzane laserowo
    przesunięcie w płaszczyźnie
    trójwymiarowy
    wzorzec kierunkowy
    fale poprzeczne
    Opis:
    A laser-based technique for efficiently generating and detection ultrasonic shear-wave is described. For the detection, a new laser interferometric scheme was recently developed in order to measure the three components of the ultrasonic field. This scheme takes advantage of the large étendue achieved with interferometer based on two-wave mixing in photorefractive crystal. Detection of the out-of-plane component as well as the two orthogonal in-plane components of the surface displacement is achieved using a single laser probe beam and a single, large aperture, collecting optic combined with detector arrays. With this interferometer, all wave types can be detected. The detection of the in-plane component allows efficient detection of shear waves, particularly when the direction of ultrasounds propagation is normal to the surface of inspection. However, for remote shear wave inspection, one must also be able to efficiently generate normal incidence shear waves. With laser-based generation, shear waves are mainly generated off the normal incidence. In this paper, in addition to presenting the tri-component interferometer, an improved method for normal-incidence shear wave generation is described. The combination of shear-wave LU generation with a multi-component laser receiver makes LU pulse-echo shear-wave inspection possible. Results from characterization of the receiver and of the generation are shown.
    Opisano technikę laserową do wydajnego generowania i wykrywania ultradźwiękowych fal poprzecznych. W celu detekcji opracowano nowy laserowy układ interferometryczny do pomiaru trzech składników pola ultradźwiękowego. Schemat ten wykorzystuje dużą wartość uzyskaną przy pomocy interferometru opartego na mieszaniu dwóch fal w fotorefrakcyjnym krysztale. Wykrywanie elementu poza płaszczyzną, jak również dwóch ortogonalnych elementów w płaszczyźnie przemieszczenia powierzchni, uzyskuje się za pomocą pojedynczej wiązki sondy laserowej i pojedynczej, dużej apertury, zbierającej układ optyczny połączonej z układami detektorów. Za pomocą tego interferometru można wykryć wszystkie typy fal. Wykrywanie elementu w płaszczyźnie umożliwia skuteczne wykrywanie fal poprzecznych, szczególnie gdy kierunek propagacji ultradźwięków jest normalny do powierzchni kontroli. Jednak w przypadku zdalnej inspekcji fali poprzecznej ważne jest również by móc wydajnie generować padające fale poprzeczne. W przypadku generowania laserowego fale poprzeczne są wzbudzane głównie poza normalną . W niniejszej pracy, oprócz prezentacji interferometru trójskładnikowego, opisano ulepszoną metodę generowania padających fal normalnych. Połączenie generatora LU fali padającej z wieloskładnikowym odbiornikiem laserowym umożliwia inspekcję falą poprzeczną z wykorzystaniem trybu LU pulse-echo. Przedstawiono wyniki charakteryzacji odbiornika i generatora.
    Źródło:
    Badania Nieniszczące i Diagnostyka; 2018, 3; 31-34
    2451-4462
    2543-7755
    Pojawia się w:
    Badania Nieniszczące i Diagnostyka
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
    Tytuł:
    Discussion around IR material and structure issues to go toward high performance small pixel pitch IR HOT FPAs
    Autorzy:
    Gravrand, Olivier
    Baier, Nicolas
    Ferron, Alexandre
    Rochette, Florent
    Lobre, Clément
    Bertoz, Jocelyn
    Rubaldo, Laurent
    Powiązania:
    https://bibliotekanauki.pl/articles/2204207.pdf
    Data publikacji:
    2023
    Wydawca:
    Polska Akademia Nauk. Stowarzyszenie Elektryków Polskich
    Tematy:
    mid-wave infrared
    focal plane array
    high operating temperature
    small pitch
    modulation transfer function
    finite element method
    Opis:
    In the last decade, infrared imaging detectors trend has gone for smaller pixels and larger formats. Most of the time, this scaling is carried out at a given total sensitive area for a single focal plane array. As an example, QVGA 30 μm pitch and VGA 15 μm pitch exhibit exactly the same sensitive area. SXGA 10 μm pitch tends to be very similar, as well. This increase in format is beneficial to image resolution. However, this scaling to even smaller pixels raises questions because the pixel size becomes similar to the IR wavelength, but also to the typical transport dimensions in the absorbing material. Hence, maintaining resolution for such small pixel pitches requires a good control of the modulation transfer function and quantum efficiency of the array, while reducing the pixel size. This might not be obtained just by scaling the pixel dimensions. As an example, bulk planar structures suffer from excessive lateral diffusion length inducing pixel-to-pixel cross talk and thus degrading the modulation transfer function. Transport anisotropy in some type II superlattice structures might also be an issue for the diffusion modulation transfer function. On the other side, mesa structures might minimize cross talk by physically separating pixels, but also tend to degrade the quantum efficiency due to a non-negligible pixel fill factor shrinking down the pixel size. This paper discusses those issues, taking into account different material systems and structures, in the perspective of the expected future pixel pitch infrared focal plane arrays.
    Źródło:
    Opto-Electronics Review; 2023, 31, Special Issue; art. no. e144561
    1230-3402
    Pojawia się w:
    Opto-Electronics Review
    Dostawca treści:
    Biblioteka Nauki
    Artykuł
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