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1دورية أكاديمية
المؤلفون: Nickelson, Liudmila, Plonis, Darius
المصدر: Romanian reports in physics, Bucuresti : Publishing House of the Romanian Academy, 2021, vol. 73, no. 4, art. no. 804, p. 1-18 ; ISSN 1221-1451 ; eISSN 1841-8759
مصطلحات موضوعية: EM wave propagation, plane wave, light, microwaves, dispersion characteristic, Maxwell’s equations, wave equation, Helmholtz equation, signs of solutions, units of frequency, electromagnetics, plasmonics, optics
الوصف: Proposed article analyzes the various traditions that are applied in EM field theory by experts from different branches of physics, the same results of the study may look different. Here is compared the style of presentation of dispersion characteristics and also the frequency measurement units may not match entirely in microwave and optical ranges. There is explained the causes and logic of such discrepancies. Timedependent and position-dependent solutions of the Helmholtz equation are often with opposite signs found in literature on microwave electrodynamics and optics including plasmonics. As a result, intermediate and final expressions may contain opposite signs. A detailed solution to the wave equation and the reasons for the appearance of opposite signs has been made here.
وصف الملف: application/pdf
العلاقة: http://vgtu.oai.elaba.lt/documents/107877897.pdfTest; http://vgtu.lvb.lt/VGTU:ELABAPDB107877897&prefLang=en_USTest
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2دورية أكاديمية
المؤلفون: Japertas, Saulius, Grimaila, Vitas
المصدر: Radioengineering, Brno : Brno University of Technology, 2017, vol. 26, iss. 1, p. 191-197 ; ISSN 1210-2512 ; eISSN 1805-9600
مصطلحات موضوعية: cellular networks, radio wave propagation, mobile communications
الوصف: The paper presents measurement results of the GSM (900 MHz band), UMTS (2100 MHz band), and LTE (1800 MHz band) propagation path loss (PL) in the urban area behind the buildings of ten different heights. The results were compared with the 7 most popular models. It was found that the existing models approximate the experimental results with relatively large errors. The new model, which evaluates the path loss variation nature behind the buildings, is proposed. This new model shows good agreement with measurements for all three mobile technologies. The average relative error is less than 6.5 %.
وصف الملف: application/pdf
العلاقة: http://ktu.oai.elaba.lt/documents/21798873.pdfTest; http://ktu.lvb.lt/KTU:ELABAPDB21798873&prefLang=en_USTest
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3دورية أكاديمية
المؤلفون: Čalnerytė, Dalia, Kriščiūnas, Andrius, Barauskas, Rimantas
المصدر: Wave motion, Amsterdam : Elsevier, 2020, vol. 94, art. no. 102515, p. 1-13 ; ISSN 0165-2125 ; eISSN 1878-433X
مصطلحات موضوعية: finite element model, modal synthesis, short wave propagation
الوصف: New higher-order finite elements of enhanced convergence properties for acoustic wave simulation are presented in the paper. The element matrices are obtained by combining modal synthesis and optimization techniques in order to achieve minimum errors of higher modes of the computational domain. As a result, simulation models of propagating wave pulses require a smaller number of finite element divisions per wavelength compared to the conventional element model thus significantly reducing computational costs. Though finite element matrices are obtained in optimization, the resulting patterns of the matrices are versatile and further can be used in any wave propagation model. The mass matrices of the elements are diagonal, so explicit time integration schemes are applicable. The usage of new elements is especially efficient in situations where wavelengths of the simulated signal are much shorter than the dimensions of the computational domain. This is referred to as short wave propagation analysis. The results of wave propagation simulation for ultrasonic measurements are presented as application examples. The B-scans and computed dispersion curves are provided for visual interpretation of the results.
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4دورية أكاديمية
المؤلفون: Bansevičius, R., Kargaudas, V.
المصدر: Ultragarsas = Ultrasound, Kaunas : Technologija, 2005, Nr. 3(56), p. 11-16 ; ISSN 1392-2114
مصطلحات موضوعية: wave propagation, elastic tube, viscous fluid, heat conduction
الوصف: The Kirchhoff theory of wave propagation in a viscous heat-conducting fluid is valid when a circular tube is rigid. In this study approximate solution for viscous, heat-conducting fluid in elastic tubes is developed. This solution coincides identically with some published approximations if elasticity of the tube is neglected and presents influence and interaction of viscosity, heat conductivity in fluid and damping in the tube material. A close examination of the obtained solution and published investigations of elastic shells with ideal fluid inside is also carried out.
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5دورية أكاديمية
المؤلفون: Gailevičius, Darius, Hayran, Zeki, Turduev, Mirbek, Kurt, Hamza, Juodkazis, Saulius, Malinauskas, Mangirdas, Mizeikis, Vygantas, Staliunas, Kestutis
المصدر: Advanced fabrication technologies for micro/nano optics and photonics X / eds.: Georg von Freymann, Winston V. Schoenfeld, Raymond C. Rumpf, Bellingham : SPIE, 2017, art. no. 101150Z, [9 p.] ; ISBN 9781510606715 ; eISBN 9781510606722
مصطلحات موضوعية: Photodetectors, Nanostructures, Infrared detection, Photonic crystals, Absorption, Photonic microstructures, Wave propagation, Infrared radiation, Nanolithography
الوصف: We propose a high sensitivity photodetection tool at near-infrared frequencies, based on a principle of slowed- and stopped-light in chirped photonic micro/nano-structures. The main goal is to substantially increase the efficiency of photodetection and provide chromatic resolution in infrared photodetection. In particular we concentrate on the design of the chirped photonic micro/nano-structures providing a maximum field enhancement, and frequency dependence of stopped light distribution.
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6دورية أكاديمية
المصدر: Information and software technologies : proceedings of the 22nd international conference, ICIST 2016, Druskininkai, Lithuania, October 13-15, 2016 / Giedre Dregvaite, Robertas Damasevicius, eds, Cham : Springer, 2016, p. 745-752 ; ISBN 9783319462530 ; eISBN 9783319462547
مصطلحات موضوعية: finite elements, wave propagation, numerical dispersion, modal synthesis
الوصف: Numerical dispersion errors are inherent for simulations based on wave propagation models with discrete meshes. The paper presents approach applied to reduce errors of this type in finite element models. High order 2D synthesized finite elements with enhanced convergence properties are obtained by modal synthesis technique. Obtained elements have diagonal mass matrix which enables to employ explicit integration schemes for wave simulation. Waves of more than two times wider frequency can be simulated using model of synthesized elements compared to models assembled of conventional elements. Furthermore, such elements could be used as a template of higher-order element to construct finite element models for all simulation problems of this kind.
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7دورية أكاديمية
المؤلفون: Kriščiūnas, Andrius, Barauskas, Rimantas
المصدر: Informacinės technologijos ir valdymas = Information technology and control, Kaunas : KTU, 2016, vol. 45, iss. 3, p. 308-320 ; ISSN 1392-124X ; eISSN 2335-884X
مصطلحات موضوعية: wave propagation, finite elements, modal synthesis, phase velocity error
الوصف: The modal-synthesis based approach is employed for obtaining the higher-order dynamic 1D finite elements with enhanced convergence properties. The obtained dynamic models are used for modelling short transient waves and wave pulses propagating in elastic or acoustic environments by using rough space steps. Only few nodal points per pulse length are enough for obtaining reasonable simulation results. The main advantage of the created elements compared with earlier similar approach is the diagonal mass matrix of the element. The elements are compatible with conventional finite elements, may be used in branchy non-homogenous structures, as well as enable to implement non-reflecting boundary conditions. The saving of computational resource was estimated.
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8دورية أكاديمية
المؤلفون: Gric, Tatjana, Eldlio, M., Cada, Michael, Pistora, J.
المصدر: Journal of electromagnetic waves and applications, 2015, Vol. 29, iss. 8, p. 1068-1081 ; ISSN 0920-5071
مصطلحات موضوعية: Inhomogeneous optical media, Wave propagation, Inhomogeneous waveguide, Electric field
الوصف: We present a novel theoretical approach for analytically solving wave propagation through two-dimensional (2D) inhomogeneous slab waveguides. The validity and reliability of our analytical approach is verified by its application to electrical field distribution in 2D waveguides, when compared with numerically exact solution. The main advantage of this theoretical treatment is that the obtained solution is global and can be presented in an analytical form. The effects of the refractive index profile on the guided modes are analyzed by introducing the field distributions of the guided modes. Our analytical calculations show significant potential for use in various applications.
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9دورية أكاديمية
المؤلفون: Gric, Tatjana, Cada, Michael
المصدر: Journal of electromagnetic waves and applications, Oxon : Taylor & Francis, 2015, Vol. 29, no. 1, p. 124-131 ; ISSN 0920-5071 ; eISSN 1569-3937
مصطلحات موضوعية: Inhomogeneous optical media, Wave propagation, Diffused channel waveguide, Electric field
الوصف: A novel analytic solution to field distribution is used to calculate the intensity distribution for channel waveguides with a two-dimensional diffusion-type refractive index profile. Composition profiles for the waveguides are obtained by applying the two-dimensional diffusion theory to treat the case of isotropic sideways diffusion. The dependence of the field distributions on the width/depth ratio is studied as an aid to the design of modulators and switches for integrated optics.
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10دورية أكاديمية
المؤلفون: Gric, Tatjana, Eldlio, Mohamed, Cada, Michael
المصدر: Photonics North 2014 : proceedings of SPIE, Montreal, Canada, May 28-30, 2014 / Editor(s): Steve MacLean; David V. Plant, Bellingham : SPIE, 2014, Vol. 9288, p. 1-5 ; ISSN 0277-786X ; ISBN 9781628413632
مصطلحات موضوعية: Inhomogeneous optical media, Wave propagation
الوصف: Optical waveguides have been a subject of an intensive theo retical research, resulting in applications in several fields, and stimulated research in integrated optics. Homogeneous dielectric waveguides and their properties are covered in detail in many articles and textbooks. However, in wave guides loaded with arbitrary inhomogeneous dielectrics, analytical solutions are possible only for a limited number of permittivity profiles in simple geometries. The analysis of longitudinally inhomogeneous waveguides has been already proposed, but the main drawback of this approach is that it requires cumbersome and time-consuming integration. We therefore suggest to take this a step further by applying our new original analytical approach that does not require integration. The aim of this work is to establish a different method that is generally applicable to any vectorial time-dependent, anisotropic, non-linear, inhomogeneous, dissipative and dispersive media to analyze the field distribution of inhomogeneous 1-D and 2-D waveguides with symmetric and asymmetric permittivity profiles. Our initial consideration of slab problems with arbitrary profiles by means of analytical method shows a great deal of potential for use in applications in fields such as physics, and engineering.
