Готові списки джерел за темами / Time domain spectral element

Добірка наукової літератури з теми "Time domain spectral element"

Автор: Grafiati

Опубліковано: 6 вересня 2023

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Статті в журналах з теми "Time domain spectral element"

Mukherjee, Shuvajit, S. Gopalakrishnan, and Ranjan Ganguli. "Stochastic time domain spectral element analysis of beam structures." Acta Mechanica 230, no. 5 (November 12, 2018): 1487–512. http://dx.doi.org/10.1007/s00707-018-2272-6.

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Liu, Yaxing, Joon-Ho Lee, Tian Xiao, and Qing H. Liu. "A spectral-element time-domain solution of Maxwell's equations." Microwave and Optical Technology Letters 48, no. 4 (2006): 673–80. http://dx.doi.org/10.1002/mop.21440.

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Mukherjee, Shuvajit, S. Gopalakrishnan, and Ranjan Ganguli. "Time domain spectral element-based wave finite element method for periodic structures." Acta Mechanica 232, no. 6 (March 15, 2021): 2269–96. http://dx.doi.org/10.1007/s00707-020-02917-y.

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Fiborek, Piotr, Paweł H. Malinowski, Paweł Kudela, Tomasz Wandowski, and Wiesław M. Ostachowicz. "Time-domain spectral element method for modelling of the electromechanical impedance of disbonded composites." Journal of Intelligent Material Systems and Structures 29, no. 16 (February 27, 2018): 3214–21. http://dx.doi.org/10.1177/1045389x18758193.

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The research focuses on the electromechanical impedance method. The electromechanical impedance method can be treated as non-destructive testing or structural health monitoring approach. It is important to have a reliable tool that allows verifying the integrity of the investigated objects. The electromechanical impedance method was applied here to assess the carbon fibre–reinforced polymer samples. The single and adhesively bonded samples were investigated. In the reported research, the electromechanical impedance spectra up to 5 MHz were considered. The investigation comprised of modelling using spectral element method and experimental measurements. Numerical and experimental spectra were analysed. Differences in spectra caused by differences in considered samples were observed.

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Pind, Finnur, Allan P. Engsig-Karup, Cheol-Ho Jeong, Jan S. Hesthaven, Mikael S. Mejling, and Jakob Strømann-Andersen. "Time domain room acoustic simulations using the spectral element method." Journal of the Acoustical Society of America 145, no. 6 (June 2019): 3299–310. http://dx.doi.org/10.1121/1.5109396.

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Pranowo, Pranowo, and Djoko Budiyanto Setyohadi. "Numerical simulation of electromagnetic radiation using high-order discontinuous galerkin time domain method." International Journal of Electrical and Computer Engineering (IJECE) 9, no. 2 (April 1, 2019): 1267. http://dx.doi.org/10.11591/ijece.v9i2.pp1267-1274.

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<span>In this paper, we propose the simulation of 2-dimensional electromagnetic wave radiation using high-order discontinuous Galerkin time domain method to solve Maxwell's equations. The domains are discretized into unstructured straight-sided triangle elements that allow enhanced flexibility when dealing with complex geometries. The electric and magnetic fields are expanded into a high-order polynomial spectral approximation over each triangle element. The field conservation between the elements is enforced using central difference flux calculation at element interfaces. Perfectly matched layer (PML) boundary condition is used to absorb the waves that leave the domain. The comparison of numerical calculations is performed by the graphical displays and numerical data of radiation phenomenon and presented particularly with the results of the FDTD method. Finally, our simulations show that the proposed method can handle simulation of electromagnetic radiation with complex geometries easily.</span>

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Lee, Joon-Ho, and Qing Huo Liu. "A 3-D Spectral-Element Time-Domain Method for Electromagnetic Simulation." IEEE Transactions on Microwave Theory and Techniques 55, no. 5 (May 2007): 983–91. http://dx.doi.org/10.1109/tmtt.2007.895398.

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Sheng, YiJun, XiaoDong Ye, Gui Wang, and TianYu Lu. "Stability-Improved Spectral-Element Time-Domain Method Based on Newmark-$\beta$." IEEE Microwave and Wireless Components Letters 29, no. 4 (April 2019): 243–45. http://dx.doi.org/10.1109/lmwc.2019.2900842.

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Yin, Changchun, Zonghui Gao, Yang Su, Yunhe Liu, Xin Huang, Xiuyan Ren, and Bin Xiong. "3D Airborne EM Forward Modeling Based on Time-Domain Spectral Element Method." Remote Sensing 13, no. 4 (February 8, 2021): 601. http://dx.doi.org/10.3390/rs13040601.

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Airborne electromagnetic (AEM) method uses aircraft as a carrier to tow EM instruments for geophysical survey. Because of its huge amount of data, the traditional AEM data inversions take one-dimensional (1D) models. However, the underground earth is very complicated, the inversions based on 1D models can frequently deliver wrong results, so that the modeling and inversion for three-dimensional (3D) models are more practical. In order to obtain precise underground electrical structures, it is important to have a highly effective and efficient 3D forward modeling algorithm as it is the basis for EM inversions. In this paper, we use time-domain spectral element (SETD) method based on Gauss-Lobatto-Chebyshev (GLC) polynomials to develop a 3D forward algorithm for modeling the time-domain AEM responses. The spectral element method combines the flexibility of finite-element method in model discretization and the high accuracy of spectral method. Starting from the Maxwell's equations in time-domain, we derive the vector Helmholtz equation for the secondary electric field. We use the high-order GLC vector interpolation functions to perform spectral expansion of the EM field and use the Galerkin weighted residual method and the backward Euler scheme to do the space- and time-discretization to the controlling equations. After integrating the equations for all elements into a large linear equations system, we solve it by the multifrontal massively parallel solver (MUMPS) direct solver and calculate the magnetic field responses by the Faraday's law. By comparing with 1D semi-analytical solutions for a layered earth model, we validate our SETD method and analyze the influence of the mesh size and the order of interpolation functions on the accuracy of our 3D forward modeling. The numerical experiments for typical models show that applying SETD method to 3D time-domain AEM forward modeling we can achieve high accuracy by either refining the mesh or increasing the order of interpolation functions.

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Waszkowiak, Wiktor, Marek Krawczuk, and Magdalena Palacz. "Finite Element Approaches to Model Electromechanical, Periodic Beams." Applied Sciences 10, no. 6 (March 14, 2020): 1992. http://dx.doi.org/10.3390/app10061992.

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Periodic structures have some interesting properties, of which the most evident is the presence of band gaps in their frequency spectra. Nowadays, modern technology allows to design dedicated structures of specific features. From the literature arises that it is possible to construct active periodic structures of desired dynamic properties. It can be considered that this may extend the scope of application of such structures. Therefore, numerical research on a beam element built of periodically arranged elementary cells, with active piezoelectric elements, has been performed. The control of parameters of this structure enables one for active damping of vibrations in a specific band in the beam spectrum. For this analysis the authors propose numerical models based on the finite element method (FEM) and the spectral finite element methods defined in the frequency domain (FDSFEM) and the time domain (TDSFEM).

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Дисертації з теми "Time domain spectral element"

Davies, Richard Wyn. "A hybrid spectral element method for the time domain solution of wave scattering problems." Thesis, Swansea University, 2007. https://cronfa.swan.ac.uk/Record/cronfa42272.

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This thesis considers the development and analysis of a hybrid spectral element method for the solution of two-dimensional wave scattering problems in the time domain. The components, namely a quadrilateral formulation of the diagonal mass matrix spectral element method and a triangular formulation of the spectral discontinuous Galerkin finite element method, are introduced and tested separately before being coupled to form the final hybrid procedure. Subsequently, a simple circular scattering problem is analysed to validate the computational model and various methods of curved boundary representation are tested to assess their impact on solution accuracy. Finally, a range of two-dimensional wave scattering problems are modelled, showing the computational efficiency of the higher order approximation in comparison with low order linear models.

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Bottero, Alexis. "Simulation numérique en forme d'onde complète d'ondes T et de sources acoustiques en mouvement." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0325/document.

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Cette thèse mêle observations, simulations et développement d'outils numériques haute performance dans le domaine de l’acoustique sous-marine, et notamment pour l’étude des ondes T. Après une revue de la littérature sur les ondes T, nous avons analysé des données réelles enregistrées en Italie. Afin de modéliser le phénomène nous avons développé un solveur éléments spectraux axisymétriques dans le domaine temporel, que nous présentons et validons. Nous présentons également une étude paramétrique de l'influence de la pente du plancher océanique dans un scénario typique de génération/conversion d'une onde T. L'énergie et la durée de ces ondes s’avère être particulièrement sensible à l'environnement. En particulier nous avons vu que les pentes et les caractéristiques du fond marin jouaient un rôle capital. Nos études confirment qu’aux distances régionales le profil de vitesse dans l'océan s'avère n'être qu'un paramètre de deuxième ordre. Pour en évaluer l’impact nous avons développé une procédure pour le calcul de cartes de perte de transmission et de dispersion à partir de simulations numériques en forme d'onde complète dans le domaine temporel. Dans un second temps nous montrons qu'un bateau commercial de taille moyenne peut créer par diffraction des ondes T d'une d'amplitude conséquente et de faible dispersion. Ce mode de génération d'onde T, encore non documenté, doit être particulièrement fréquent dans les zones où le trafic maritime est important et pourrait expliquer certaines ondes T abyssales encore incomprises. Pour finir, nous présentons des outils numériques pour calculer le champ acoustique créé par une source en mouvement
This thesis combines observations, simulations and development of high performance numerical tools in the field of underwater acoustics, and in particular for the study of T-waves. After a literature review on T-waves, we analysed real data recorded in Italy. In order to model the phenomenon we have developed an axisymmetric spectral element solver in the time domain, which we present and validate. We also present a parametric study of the influence of seafloor slope in a typical scenario of generation / conversion of a T-wave. The energy and duration of these waves is particularly sensitive to the environment. In particular, we have seen that the slopes and characteristics of the seabed are of crucial importance. Our studies confirm that at regional distances the ocean speed profile is only a second order parameter. To evaluate its impact we have developed a procedure for the calculation of transmission and dispersion loss maps from full waveform numerical simulations in the time domain. In a second step we show that a medium-sized commercial boat can create T-waves of a significant amplitude and of low dispersion by diffraction. This T-wave generation mode, still undocumented, must be particularly frequent in areas where maritime traffic is dense and could explain some abyssal T-waves still misunderstood. Finally, we present numerical tools for calculating the acoustic field created by a moving source

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朱展強 and Chin-keung Chu. "Parallel computation for time domain boundary element method." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31220678.

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雷哲翔 and Zhexiang Lei. "Time domain boundary element method & its applications." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1993. http://hub.hku.hk/bib/B31233703.

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Hargreaves, J. A. "Time domain boundary element method for room acoustics." Thesis, University of Salford, 2007. http://usir.salford.ac.uk/16604/.

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This thesis is about improving the suitability of the time domain Boundary Element Method (BEM) for predicting the scattering from surface treatments used to improve the acoustics of rooms. The discretised integral equations are typically solved by marching on in time from initial silence; however, this being iterative has potential for divergence. Such instability and high computational cost have prohibited the time domain BEM from widespread use. The underlying integral equation is known to not possess unique solutions at certain frequencies, physically interpreted as cavity resonances, and these manifest as resonant poles, all excited and potentially divergent due to numerical error. This has been addressed by others using the combined field integral equation; an approach built upon in this thesis. Accuracy and stability may also be compromised by poor discretisation and integration accuracy. The latter is investigated on real-world surfaces, demonstrating that the popular Gaussian integration schemes are not suitable in some circumstances. Instead a contour integration scheme capable of resolving the integrands‟ singular nature is developed. Schroeder diffusers are Room Acoustic treatments which comprise wells separated by thin fins. The algorithm is extended to model such surfaces, applying the combined field integral equation to the body and an open surface model to the fins. It is shown that this improves stability over an all open surface model. A new model for compliant surfaces is developed, comparable to the surface impedance model used in the frequency domain. This is implemented for surfaces with welled and absorbing sections, permitting modelling of a Schroeder diffuser as a box with surface impedances that simulate the delayed reflections caused by the wells. A Binary Amplitude Diffuser - a partially absorbing diffuser - is also modelled. These new models achieve good accuracy but not universal stability and avenues of future research are proposed to address the latter issue.

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Chu, Chin-keung. "Parallel computation for time domain boundary element method /." Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B20565574.

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Lei, Zhexiang. "Time domain boundary element method & its applications /." [Hong Kong : University of Hong Kong], 1993. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13570365.

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Ali, Hassan O. "Finite-element time-domain analysis of axisymmetrical radiating structures." Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/7897.

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A method of computation based on the finite element method was used to solve axisymmetrical electromagnetic wave propagation problems directly in the time-domain. The finite element method, employing first order triangular elements, was used to generate a system of second order linear differential equations. The system of differential equations was solved for the magnetic field using a suitable differential equation solving algorithm written in the course of this work. The method was used to model several situations involving axisymmetrical radiating structures directly in the time domain and the results compared well with the published data. Situations involving pulses, which are of particular interest to EMI/EMC field, were successfully studied. Conclusions were drawn on the suitability of the method in modeling radiated emissions from printed circuit board configurations, under the influence of transient exciting fields.

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Allgaier, Markus [Verfasser]. "Ultrafast nonlinear optics: from spectral to time domain applications / Markus Allgaier." Paderborn : Universitätsbibliothek, 2019. http://d-nb.info/1177138034/34.

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Hissen, Huzifa Zain Alabdeen Abdarahman. "Spectral characterization of materials using terahertz time domain spectroscopy (THz-TDS)." Thesis, Stellenbosch : Stellenbosch University, 2014. http://hdl.handle.net/10019.1/96030.

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Thesis (MSc)--Stellenbosch University, 2014.
ENGLISH ABSTRACT: Terahertz (THz) radiation is often used in many promising applications such as information and communication technology and airport security. Optimized and adapted terahertz fields hold huge promise for leading this technology further. This study is focused on terahertz time domain spectroscopy (THz-TDS). In THz-TDS the electric field is measured, therefore both amplitude and phase information of the THz pulse can be obtained. We used the pump-probe technique in order to measure a THz pulse from the photoconductive antenna. A pulsed fiber laser with FWHM of ' 100 fs was used for this. The frequency spectrum of the measured THz pulse was obtained via a fast Fourier transform. We studied the principles of the THz pulse generation as well as detection, with a photoconductive antenna as emitter and detector. In this study terahertz spectroscopy has been used to investigate the refractive index and absorption coefficient of different types of materials in the terahertz region. The last part of this study deals with a simple process for material parameter extraction of a polymer sample using commercial software called Teramat1.0. It uses the sample thickness, the reference THz pulse and the transmitted THz pulse to retrieve the complex refractive index of the sample.
AFRIKAANSE OPSOMMING: Terahertz (THz) straling word gereeld gebruik vir belowende toepassings soos inligting en kommunikasie tegnologie en lughawe sekuriteit. Geoptimeerde en aangepaste terahertz velde dra by tot die bevordering van die tegnologie. Hierdie studie fokus op terahertz tyd domein spektroskopie (THz-TDS). In THz-TDS word die elektriese veld gemeet en dus word beide amplitude en fase inligting van die THz puls verkry. Ons gebruik ’n pomp en toets tegniek om die THz puls deur ’n fotogeleidende antenna te bepaal. ’n Gepulseerde vesel laser met FWHM van 100 fs word hiervoor benut. Die frekwensie spektrum van die gemete THz puls word bereken deur ’n vinnige Fourier transvorm te bereken. Die beginsels van die generering en deteksie van THz pulse is bestudeer met ’n fotogeleidende antenna as sender en ontvanger. In die studie is terahertz spektroskopie gebruik om die brekingsindekse en die absorpsie koeffisiënte van verskillende materiale in die terahertz gebied te bepaal. Die laaste gedeelte van die studie handel oor ’n eenvoudige proses om die materiaal parameters van ’n polimeer te bepaal deur gebruik te maak van kommersiële sagteware Teramat 1.0. Die monster dikte, die THz verwysingspuls en die deurgelate puls word gebruik om die komplekse brekingsindeks van die materiaal te bereken.

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Книги з теми "Time domain spectral element"

Ostachowicz, W. M. Guided waves in structures for SHM: The time-domain spectral element method. Chichester, West Sussex: Wiley, 2012.

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Farahani, Ali Reza Vashghani. 3D finite element time domain methods. Ottawa: National Library of Canada, 2003.

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Lo, Jonathan O. Y. Time domain finite element analysis of microwave planar networks. Ottawa: National Library of Canada = Bibliothèque nationale du Canada, 1992.

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Li, Jichun, and Yunqing Huang. Time-Domain Finite Element Methods for Maxwell's Equations in Metamaterials. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-33789-5.

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Golla, David Frank. Dynamics of viscoelastic structures: a time-domain finite element formulation. [Downsview, Ont.]: [Institute for Aerospace Studies], 1985.

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Golla, David Frank. Dynamics of viscoelastic structures: A time-domain finite element formulation. [Downsview, Ont.]: Institute for Aerospace Studies, 1986.

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Golla, D. F. Dynamics of viscoelastic structures - a time-domain, finite element formulation. [S.l.]: [s.n.], 1985.

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Li, Jichun. Time-Domain Finite Element Methods for Maxwell's Equations in Metamaterials. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013.

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United States. National Aeronautics and Space Administration. Scientific and Technical Information Division., ed. Time-domain finite elements in optimal control with application to launch-vehicle guidance. [Washington, D.C.]: National Aeronautics and Space Administration, Office of Management, Scientific and Technical Information Division, 1991.

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Частини книг з теми "Time domain spectral element"

Jain, Mayank, and Santosh Kapuria. "Efficient Layerwise Time-Domain Spectral Finite Element for Guided Wave Propagation Analysis of Multi-layered Panels." In Lecture Notes in Civil Engineering, 128–38. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-07322-9_14.

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Yeung, Carman, and Ching Tai Ng. "Analysis of Scattering and Mode Conversion of Torsional Guided Waves by Cracks in Pipes Using Time-Domain Spectral Element Method." In Lecture Notes in Civil Engineering, 1123–30. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-8079-6_105.

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Sarkar, Avirup, and Ashutosh Bagchi. "Stress Analysis of Concrete Gravity Dams Using Time Domain Spectral Finite Element Method Under the Action of Seismic Ground Motion." In Lecture Notes in Civil Engineering, 623–31. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-39117-0_63.

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Datta, Asoke Kumar. "Spectral Domain." In Time Domain Representation of Speech Sounds, 13–22. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-13-2303-4_2.

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Schanz, Martin. "Time domain boundary element formulation." In Wave Propagation in Viscoelastic and Poroelastic Continua, 39–56. Berlin, Heidelberg: Springer Berlin Heidelberg, 2001. http://dx.doi.org/10.1007/978-3-540-44575-3_4.

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Li, Jichun, and Yunqing Huang. "Time-Domain Finite Element Methods for Metamaterials." In Time-Domain Finite Element Methods for Maxwell's Equations in Metamaterials, 53–125. Berlin, Heidelberg: Springer Berlin Heidelberg, 2012. http://dx.doi.org/10.1007/978-3-642-33789-5_3.

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Raiyan Kabir, S. M., B. M. A. Rahman, and A. Agrawal. "Finite Element Time Domain Method for Photonics." In Recent Trends in Computational Photonics, 1–37. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-55438-9_1.

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Schanz, M., L. Gaul, W. Wenzel, and B. Zastrau. "A Boundary Element Formulation for Generalized Viscoelastic Solids in Time Domain." In Boundary Element Topics, 31–50. Berlin, Heidelberg: Springer Berlin Heidelberg, 1997. http://dx.doi.org/10.1007/978-3-642-60791-2_3.

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Fukui, T., and K. Tani. "Stability of Time Domain Boundary Element Method in Wave Propagation Problems." In Boundary Element Methods, 82–91. Berlin, Heidelberg: Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-662-06153-4_10.

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Lambers, James V. "A Spectral Time-Domain Method for Computational Electrodynamics." In Numerical Mathematics and Advanced Applications 2009, 561–69. Berlin, Heidelberg: Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-11795-4_60.

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Тези доповідей конференцій з теми "Time domain spectral element"

Xue, Yilun, Qiang Ren, and Yuanguo Zhou. "Transient Thermal Analysis Based on Spectral Element Time Domain Method." In 2019 Cross Strait Quad-Regional Radio Science and Wireless Technology Conference (CSQRWC). IEEE, 2019. http://dx.doi.org/10.1109/csqrwc.2019.8799354.

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Sheng, YiJun, Kan Xu, Feng Zhang, and RuShan Chen. "Application of curved parametric hexahedron in spectral-element time-domain." In 2010 International Symposium on Signals, Systems and Electronics (ISSSE). IEEE, 2010. http://dx.doi.org/10.1109/issse.2010.5607123.

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Ren, Qiang, Qiwei Zhan, and Qing Huo Liu. "Discontinuous Galerkin spectral elemen/finite element time domain (DGSE/FETD) method for anisotropic medium." In 2015 USNC-URSI Radio Science Meeting (Joint with AP-S Symposium). IEEE, 2015. http://dx.doi.org/10.1109/usnc-ursi.2015.7303365.

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Xu, H., Q. S. Yan, Y. H. Wu, Z. B. Ye, and R. S. Chen. "Analysis of transient electromagnetic scattering using spectral-element time-domain method." In 2012 International Conference on Microwave and Millimeter Wave Technology (ICMMT). IEEE, 2012. http://dx.doi.org/10.1109/icmmt.2012.6230067.

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Kan Xu, Rushan Chen, Yijun Sheng, Ping Fu, Chuan Chen, Qingshang Yan, and Yan Yan Yu. "Spectral-element analysis of microwave Gunn oscillator in the time domain." In 2011 IEEE Electrical Design of Advanced Packaging and Systems Symposium (EDAPS). IEEE, 2011. http://dx.doi.org/10.1109/edaps.2011.6213721.

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Kong, Lingrong, and Shitao Chen. "Spectral element time-domain method simulation of the Maxwell-Schrödinger system." In 2017 IEEE Electrical Design of Advanced Packaging and Systems Symposium (EDAPS). IEEE, 2017. http://dx.doi.org/10.1109/edaps.2017.8277006.

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Xu, H., D. Z. Ding, and R. S. Chen. "Analysis of PIN diode limiter circuit using spectral-element time-domain method." In 2015 Asia-Pacific Microwave Conference (APMC). IEEE, 2015. http://dx.doi.org/10.1109/apmc.2015.7413550.

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Xu, H., Z. He, D. Z. Ding, and R. S. Chen. "Scattering analysis of magnetized plasma objects with spectral-element time-domain method." In 2016 IEEE International Conference on Computational Electromagnetics (ICCEM). IEEE, 2016. http://dx.doi.org/10.1109/compem.2016.7588570.

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Sheng, Y. J., R. S. Chen, and Z. B. Ye. "Transient analysis of IMPATT oscillator with extended spectral-element time-domain method." In 2012 International Conference on Microwave and Millimeter Wave Technology (ICMMT). IEEE, 2012. http://dx.doi.org/10.1109/icmmt.2012.6230145.

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Yujie Yan, Aiqiang Cheng, Dazhi Ding, and Rushan Chen. "Simulation of a submicron ballistic diode with spectral-element time-domain method." In 2016 Progress in Electromagnetic Research Symposium (PIERS). IEEE, 2016. http://dx.doi.org/10.1109/piers.2016.7735846.

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Звіти організацій з теми "Time domain spectral element"

White, D., M. Stowell, J. Koning, R. Rieben, A. Fisher, N. Champagne, and N. Madsen. Higher-Order Mixed Finite Element Methods for Time Domain Electromagnetics. Office of Scientific and Technical Information (OSTI), February 2004. http://dx.doi.org/10.2172/15014733.

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T.F. Eibert, J.L. Volakis, and Y.E. Erdemli. Hybrid Finite Element-Fast Spectral Domain Multilayer Boundary Integral Modeling of Doubly Periodic Structures. Office of Scientific and Technical Information (OSTI), March 2002. http://dx.doi.org/10.2172/821699.

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Pingenot, J., and V. Jandhyala. Final Report for Time Domain Boundary Element and Hybrid Finite Element Simulation for Maxwell's Equations. Office of Scientific and Technical Information (OSTI), March 2007. http://dx.doi.org/10.2172/902353.

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Rieben, Robert N. A Novel High Order Time Domain Vector Finite Element Method for the Simulation of Electromagnetic Devices. Office of Scientific and Technical Information (OSTI), January 2004. http://dx.doi.org/10.2172/15014486.

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Yan, Su, and Jian-Ming Jin. Time-Domain Finite Element Analysis of Nonlinear Breakdown Problems in High-Power-Microwave Devices and Systems. Fort Belvoir, VA: Defense Technical Information Center, December 2015. http://dx.doi.org/10.21236/ad1006412.

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Anderson, Gerald L., and Kalman Peleg. Precision Cropping by Remotely Sensed Prorotype Plots and Calibration in the Complex Domain. United States Department of Agriculture, December 2002. http://dx.doi.org/10.32747/2002.7585193.bard.

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This research report describes a methodology whereby multi-spectral and hyperspectral imagery from remote sensing, is used for deriving predicted field maps of selected plant growth attributes which are required for precision cropping. A major task in precision cropping is to establish areas of the field that differ from the rest of the field and share a common characteristic. Yield distribution f maps can be prepared by yield monitors, which are available for some harvester types. Other field attributes of interest in precision cropping, e.g. soil properties, leaf Nitrate, biomass etc. are obtained by manual sampling of the filed in a grid pattern. Maps of various field attributes are then prepared from these samples by the "Inverse Distance" interpolation method or by Kriging. An improved interpolation method was developed which is based on minimizing the overall curvature of the resulting map. Such maps are the ground truth reference, used for training the algorithm that generates the predicted field maps from remote sensing imagery. Both the reference and the predicted maps are stratified into "Prototype Plots", e.g. 15xl5 blocks of 2m pixels whereby the block size is 30x30m. This averaging reduces the datasets to manageable size and significantly improves the typically poor repeatability of remote sensing imaging systems. In the first two years of the project we used the Normalized Difference Vegetation Index (NDVI), for generating predicted yield maps of sugar beets and com. The NDVI was computed from image cubes of three spectral bands, generated by an optically filtered three camera video imaging system. A two dimensional FFT based regression model Y=f(X), was used wherein Y was the reference map and X=NDVI was the predictor. The FFT regression method applies the "Wavelet Based", "Pixel Block" and "Image Rotation" transforms to the reference and remote images, prior to the Fast - Fourier Transform (FFT) Regression method with the "Phase Lock" option. A complex domain based map Yfft is derived by least squares minimization between the amplitude matrices of X and Y, via the 2D FFT. For one time predictions, the phase matrix of Y is combined with the amplitude matrix ofYfft, whereby an improved predicted map Yplock is formed. Usually, the residuals of Y plock versus Y are about half of the values of Yfft versus Y. For long term predictions, the phase matrix of a "field mask" is combined with the amplitude matrices of the reference image Y and the predicted image Yfft. The field mask is a binary image of a pre-selected region of interest in X and Y. The resultant maps Ypref and Ypred aremodified versions of Y and Yfft respectively. The residuals of Ypred versus Ypref are even lower than the residuals of Yplock versus Y. The maps, Ypref and Ypred represent a close consensus of two independent imaging methods which "view" the same target. In the last two years of the project our remote sensing capability was expanded by addition of a CASI II airborne hyperspectral imaging system and an ASD hyperspectral radiometer. Unfortunately, the cross-noice and poor repeatability problem we had in multi-spectral imaging was exasperated in hyperspectral imaging. We have been able to overcome this problem by over-flying each field twice in rapid succession and developing the Repeatability Index (RI). The RI quantifies the repeatability of each spectral band in the hyperspectral image cube. Thereby, it is possible to select the bands of higher repeatability for inclusion in the prediction model while bands of low repeatability are excluded. Further segregation of high and low repeatability bands takes place in the prediction model algorithm, which is based on a combination of a "Genetic Algorithm" and Partial Least Squares", (PLS-GA). In summary, modus operandi was developed, for deriving important plant growth attribute maps (yield, leaf nitrate, biomass and sugar percent in beets), from remote sensing imagery, with sufficient accuracy for precision cropping applications. This achievement is remarkable, given the inherently high cross-noice between the reference and remote imagery as well as the highly non-repeatable nature of remote sensing systems. The above methodologies may be readily adopted by commercial companies, which specialize in proving remotely sensed data to farmers.

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Yan, Yujie, and Jerome F. Hajjar. Automated Damage Assessment and Structural Modeling of Bridges with Visual Sensing Technology. Northeastern University, May 2021. http://dx.doi.org/10.17760/d20410114.

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Recent advances in visual sensing technology have gained much attention in the field of bridge inspection and management. Coupled with advanced robotic systems, state-of-the-art visual sensors can be used to obtain accurate documentation of bridges without the need for any special equipment or traffic closure. The captured visual sensor data can be post-processed to gather meaningful information for the bridge structures and hence to support bridge inspection and management. However, state-of-the-practice data postprocessing approaches require substantial manual operations, which can be time-consuming and expensive. The main objective of this study is to develop methods and algorithms to automate the post-processing of the visual sensor data towards the extraction of three main categories of information: 1) object information such as object identity, shapes, and spatial relationships - a novel heuristic-based method is proposed to automate the detection and recognition of main structural elements of steel girder bridges in both terrestrial and unmanned aerial vehicle (UAV)-based laser scanning data. Domain knowledge on the geometric and topological constraints of the structural elements is modeled and utilized as heuristics to guide the search as well as to reject erroneous detection results. 2) structural damage information, such as damage locations and quantities - to support the assessment of damage associated with small deformations, an advanced crack assessment method is proposed to enable automated detection and quantification of concrete cracks in critical structural elements based on UAV-based visual sensor data. In terms of damage associated with large deformations, based on the surface normal-based method proposed in Guldur et al. (2014), a new algorithm is developed to enhance the robustness of damage assessment for structural elements with curved surfaces. 3) three-dimensional volumetric models - the object information extracted from the laser scanning data is exploited to create a complete geometric representation for each structural element. In addition, mesh generation algorithms are developed to automatically convert the geometric representations into conformal all-hexahedron finite element meshes, which can be finally assembled to create a finite element model of the entire bridge. To validate the effectiveness of the developed methods and algorithms, several field data collections have been conducted to collect both the visual sensor data and the physical measurements from experimental specimens and in-service bridges. The data were collected using both terrestrial laser scanners combined with images, and laser scanners and cameras mounted to unmanned aerial vehicles.

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Knight, R. D., and B. A. Kjarsgaard. Comparative pXRF and Lab ICP-ES/MS methods for mineral resource assessment, Northwest Territories. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/331239.

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The Geological Survey of Canada undertook a mineral resource assessment for a proposed national park in northern Canada (~ 33,500 km2) spanning the transition from boreal forest to barren lands tundra. Bedrock geology of this region is complex and includes the Archean Slave Craton, the Archean and Paleoproterozoic Rae domain of the Churchill Province, the Paleoproterozoic Thelon and Taltson magmatic-tectonic zones, and the Paleoproterozoic East Arm sedimentary basin. The area has variable mineral potential for lode gold, kimberlite-hosted diamonds, VMS, vein uranium and copper, SEDEX, as well as other deposit types. A comparison of analytical methods was carried out after processing the field collected samples to acquire both the &lt; 2 mm and for the &lt; 0.063 mm size fractions for 241 surficial sediment (till) samples, collected using a 10 x 10 km grid. Analytical methods comprised: 1) aqua regia followed by ICP-MS analysis, 2) 4-acid hot dissolution followed by ICP-ES/MS analysis, 3) lithium metaborate/tetraborate fusion methods followed by ICP-ES for major elements and ICP-MS for trace elements and, 4) portable XRF on dried, non-sieved sediment samples subjected to a granular segregation processing technique (to produce a clay-silt proxy) for seventeen elements (Ba, Ca, Cr, Cu, Fe, K, Mn, Ni, Pb, Rb, Sr, Th, Ti, U, V, Zn, and Zr) Results indicate that pXRF data do not replicate exactly the laboratory 4-acid and fusion data (in terms of precision and accuracy), but the relationship between the datasets is systematic as displayed in x-y scattergrams. Interpolated single element plots indicate that till samples with anomalies of high and low pXRF concentration levels are synonymous with high and low laboratory-based analytical concentration levels, respectively. The pXRF interpolations thus illustrate the regional geochemical trends, and most importantly, the significant geochemical anomalies in the surficial samples. These results indicate that pXRF spectrometry for a subset of elements is comparable to traditional laboratory methods. pXRF spectrometry also provides the benefit of rapid analysis and data acquisition that has a direct influence on real time sampling designs. This information facilitates efficient and cost-effective field projects (i.e. where used to identify regions of interest for high density sampling), and to prioritize samples to be analyzed using traditional geochemical methods. These tactics should increase the efficiency and success of a mineral exploration and/or environmental sampling programs.

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Taylor. L51755 Development and Testing of an Advanced Technology Vibration Transmission. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), July 1996. http://dx.doi.org/10.55274/r0010124.

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Fiber optic sensors have been under development in industrial and government laboratories around the world for over a decade. The commercial market for fiber sensors for measuring parameters such as temperature, displacement, and liquid level is now estimated to exceed $100 M/year. Aside from the commercial interest, the U. S. Department of Defense has vigorously pursued the development of fiber gyroscopes and hydrophones. In spite of the high level of research and development activity, however, until recently fiber sensors had not been successfully applied in high-temperature engine environments. The goal of this effort is to develop and test high-temperature fiber optic sensors and show that they are suitable for monitoring vibration and other instabilities in gas turbine engines. The underlying technology developed during the course of PRCI projects PR- 219-9120 and PR-219-9225 during 1991-94 serves as the foundation for PR-240-9416. Transducers with the fiber optic Fabry-Perot interferometer (FFPI) configuration have been adapted for use in the turbomachinery environment.To ensure the survival of the FFPI sensors at high temperatures, two techniques for coating the fibers with metal have been developed: electroplating and vacuum deposition. Coated sensors have subsequently been embedded in aluminum and brass alloys. Experiments on a small Sargent Welch turbine engine have shown the high sensitivity of embedded FFPI strain sensors to vibration in rolling bearings. Data have been collected in both the time and frequency domain. A new accelerometer design in which a metal-coated fiber containing the FFPI element is soldered directly to a diaphragm in a stainless steel housing shows response similar to a piezoelectric accelerometer in shaker table tests. The high sensitivity of the FFPI accelerometer has been demonstrated in field tests in a Solar Centaur turbine engine, and the design has survived temperatures greater than 500�C in a test oven. A magnetometer with a physical configuration similar to that of the accelerometer has been used to measure the distance from the sensor head to a rotating shaft made of ferromagnetic material. This device, which functions as a proximity probe, has been used to monitor shaft rotation rate (keyphasor application) and as a shaft thrust position sensor. These results indicate the potential for performing critical measurements in turbine engines with FFPI sensors. They can measure acceleration, distance (proximity), strain (as it relates to bearing defect diagnosis), and gas pressure, and can operate at higher temperatures than conventional transducers.

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Tan, Peng, and Nicholas Sitar. Parallel Level-Set DEM (LS-DEM) Development and Application to the Study of Deformation and Flow of Granular Media. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, March 2023. http://dx.doi.org/10.55461/kmiz5819.

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We present a systematic investigation of computational approaches to the modeling of granular materials. Granular materials are ubiquitous in everyday life and in a variety of engineering and industrial applications. Despite the apparent simplicity of the laws governing particle-scale interactions, predicting the continuum mechanical response of granular materials still poses extraordinary challenges. This is largely due to the complex history dependence resulting from continuous rearrangement of the microstructure of granular material, as well as the mechanical interlocking due to grain morphology and surface roughness. X-Ray Computed Tomography (XRCT) is used to characterize the grain morphology and the fabric of the granular media, naturally deposited sand in this study. The Level-Set based Discrete Element Method (LS-DEM) is then used to bridge the granular behavior gap between the micro and macro scale. The LS-DEM establishes a one-to-one correspondence between granular objects and numerical avatars and captures the details of grain morphology and surface roughness. However, the high-fidelity representation significantly increases the demands on computational resources. To this end a parallel version of LS-DEM is introduced to significantly decrease the computational demands. The code employs a binning algorithm, which reduces the search complexity of contact detection from O(n2) to O(n), and a domain decomposition strategy is used to elicit parallel computing in a memory- and communication-efficient manner. The parallel implementation shows good scalability and efficiency. High fidelity LS avatars obtained from XRCT images of naturally deposited sand are then used to replicate the results of triaxial tests using the new, parallel LS-DEM code. The result show that both micro- and macro-mechanical behavior of natural material is well captured and is consistent with experimental data, confirming experimental observation that the primary source of peak strength of sand is the mechanical interlocking between irregularly shaped grains. Specifically, triaxial test simulations with a flexible membrane produce a very good match to experimentally observed relationships between deviatoric stress and mobilized friction angle for naturally deposited sand. We then explore the viability of modeling dynamic problems with a new formulation of an impulse based LS-DEM. The new formulation is stable, fast, and energy conservative. However, it can be numerically stiff when the assembly has substantial mass differences between particles. We also demonstrate the feasibility of modeling deformable structures in the rigid body framework and propose several enhancements to improve the convergence of collision resolution, including a hybrid time integration scheme to separately handle at rest contacts and dynamic collisions. Finally, we extend the impulse-based LS-DEM to include arbitrarily shaped topographic surfaces and exploit its algorithmic advantages to demonstrate the feasibility of modeling realistic behavior of granular flows. The novel formulation significantly improves performance of dynamic simulations by allowing larger time steps, which is advantageous for observing the full development of physical phenomena such as rock avalanches, which we present as an illustrative example.

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