Teses / dissertações sobre o tema "Time reversal of diffusion"
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Roelly, Sylvie, e Michèle Thieullen. "Duality formula for the bridges of a Brownian diffusion : application to gradient drifts". Universität Potsdam, 2005. http://opus.kobv.de/ubp/volltexte/2006/671/.
Texto completo da fonteBlondel, Thibaud. "Approche Matricielle de l'Imagerie Sismique". Thesis, Paris Sciences et Lettres (ComUE), 2019. https://pastel.archives-ouvertes.fr/tel-03174491.
Texto completo da fonteThe project aims at extending to geophysical and seismic imaging a matrix approach of wave propagation in heterogeneous media. The method aims at separating single-scattering from multiple-scatterings contribution in a data set, thus allowing us to improve imaging in heterogeneous media, as if we could see through thick fog. The idea was successfully developed in the ultrasound imaging context at the Langevin Institute, restricted so far to 1-D linear arrays of ultrasonic sources/receivers. It consists in exploiting the set of inter-element impulse responses associated to an array of sensors. This response matrix contains all the information available on the scattering medium under investigation. A set of matrix operations can then be applied whether it be for detection, imaging, characterization or monitoring purposes. The method was tested on actual coarse-grain materials like steel, and was found to improve defect detection very significantly. The adaptability of the method in geophysics (with 2-D unevenly distributed passive sensors as opposed to controllable and periodic 1-D ultrasonic arrays) is to be investigated in this project. On the one hand, iterative time reversal and related techniques can be taken advantage of to overcome aberration effects associated to long-scale inhomogeneities of the superficial layer, leading to a better constrast and resolution of the subsoil image [1-4]. On the other hand, a more sophisticated random matrix approach can be used in areas where short-scale inhomogeneities are strongly scattering and/or concentrated [5-7]. In this regime, conventional imaging methods suffer from the multiple scattering of waves that results in a speckle image, with no direct connection with the medium's reflectivity. In the case of purely passive sensors such as classical geophones, the response matrix will be obtained passively from cross-correlation of ambient noise, as was thoroughly established by pioneer works at ISTERRE [8]. The main objective is to get rid of multiple scattering and push back the imaging-depth limit of existing imaging techniques. In addition, the study of the multiple scattering contribution can also be useful for characterization purposes. Transport parameters such as the scattering or transport mean free paths can actually yield key information about the concentration and the size of the inhomogeneities. References: [1] C. Prada and M. Fink, Wave Motion 20, 151 (1994). [2] C. Prada, S. Manneville, D. Spoliansky, and M. Fink, J. Acoust. Soc. Am. 99, 2067 (1996). [3] J-L. Robert, PhD dissertation on “Evaluation of Green's functions in complex media by decomposition of the Time Reversal Operator: Application to Medical Imaging and aberration correction “, Université Paris VII, 2008. [4] G. Montaldo, M. Tanter, and M. Fink, Phys. Rev. Lett. 106, 054301, 2011. [5] A. Aubry, A. Derode, Phys. Rev. Lett. 102, 084301, 2009. [6] A. Aubry, A. Derode, J. Appl. Phys. 106, 044903, 2009. [7] S. Shahjahan, A. Aubry, F. Rupin, B. Chassignole, and A. Derode, Appl. Phys. Lett. 104, 234105, 2014. [8] Campillo, M., P. Roux, and N.M. Shapiro (2011), Using seismic noise to image and to monitor the Solid Earth, in Encyclopedia of Solid Earth Geophysics, Gupta, Harsh K. (Ed.), 1230-1235, Springer, 2011
Yang, Yougu. "Propagation des ondes acoustiques dans les milieux granulaires confinés". Phd thesis, Université Paris-Est, 2013. http://tel.archives-ouvertes.fr/tel-01037954.
Texto completo da fonteStephens, Edmund. "Time reversal violation in atoms". Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334916.
Texto completo da fonteLopez-Castellanos, Victor. "Ultrawideband Time Domain Radar for Time Reversal Applications". The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1301040987.
Texto completo da fonteNaguleswaran, Siva. "Time reversal symmetry in nonlinear optics". Thesis, University of Canterbury. Physics, 1998. http://hdl.handle.net/10092/8166.
Texto completo da fonteO'Donoughue, Nicholas A. "Stochastic Time Reversal for Radar Detection". Research Showcase @ CMU, 2011. http://repository.cmu.edu/dissertations/178.
Texto completo da fonteEdelmann, Geoffrey F. "Underwater acoustic communications using time reversal /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2003. http://wwwlib.umi.com/cr/ucsd/fullcit?p3099539.
Texto completo da fonteJohnsson, Mattias Torbjörn. "Time reversal symmetry and the geometric phase". Thesis, University of Canterbury. Physics, 1998. http://hdl.handle.net/10092/8171.
Texto completo da fonteLiddy, David W. Holmes John F. "Acoustic room de-reverberation using time-reversal acoustics /". Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA374579.
Texto completo da fonte"September 1999". Thesis advisor(s):, Andrés Larraza, Bruce C. Denardo. Includes bibliographical references (p. 49). Also available online.
AHMAD, FAHEEM, e PRAMOD KAKKERLA. "FOCUSING OF UWB RADAR SIGNALS USING TIME REVERSAL". Thesis, Högskolan i Gävle, Avdelningen för elektronik, matematik och naturvetenskap, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-15500.
Texto completo da fonteLiddy, David W., e John F. Holmes. "Acoustic room de-reverberation using time-reversal acoustics". Thesis, Monterey, California: Naval Postgraduate School, 1999. http://hdl.handle.net/10945/13698.
Texto completo da fonteRaghukumar, Kaustubha. "Pressure sensitivity kernels applied to time-reversal acoustics". Diss., [La Jolla] : University of California, San Diego, 2009. http://wwwlib.umi.com/cr/ucsd/fullcit?p3359854.
Texto completo da fonteTitle from first page of PDF file (viewed July 23, 2009). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
Hockings, William Hill. "Time Reversal Violation in Nuclear Effective Field Theory". Diss., The University of Arizona, 2006. http://hdl.handle.net/10150/196076.
Texto completo da fonteVallon, Henri. "Focusing high-power electromagnetic waves using time-reversal". Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLC006/document.
Texto completo da fonteA main aspect of this work has been to develop analytical and statistical models of the power efficiency of a time-reversal amplification system (TRAS).It is also important to evaluate the efficiency of a reverberation chamber. This allows quantifying the power received by one or more antenna when the reverberation chamber is excited. This factor is important when considering construction of the most efficient chamber for time-reversal amplification.Measurements assessing the loading effect of antennas in reverberation chambers when the field can be considered diffused were also undertaken. The study focuses on the evaluation of the varying quality factor when adding loaded antennas in the chamber.Another focus of this work is to evaluate the ratios between signals during calibration and focusing phase. An important aspect of the studies presented in this work thus concerns evaluation of the maximum value of the impulse response in a complex propagation system.We also present the power gain of time-reversal techniques and its statistical advantages compared to a classic use of a reverberation chamber.The development of a prototype required the design and implementation of each of the branches of the complete systems.The first measurement campaigns allowed the complete validation of the models
Rane, Swati. "Diffusion tensor imaging at long diffusion time". Diss., Atlanta, Ga. : Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/29708.
Texto completo da fonteCommittee Chair: Hu, Xiaoping; Committee Member: Brummer, Marijn; Committee Member: Duong, Tim; Committee Member: Keilholz, Shella; Committee Member: Schumacher, Eric. Part of the SMARTech Electronic Thesis and Dissertation Collection.
Wang, Daniel Y. "Spatiotemporal processing and time-reversal for underwater acoustic communications". Thesis, Massachusetts Institute of Technology, 2005. http://handle.dtic.mil/100.2/ADA455115.
Texto completo da fonteNorville, Pelham D. "Time-Reversal Techniques in Seismic Detection of Buried Objects". Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/14475.
Texto completo da fonteGlotov, Petr. "Time Reversal of Electromagnetic Waves in Randomly Layered Media". NCSU, 2006. http://www.lib.ncsu.edu/theses/available/etd-02272006-183752/.
Texto completo da fonteHofer, Stephen. "Time reversal symmetry breaking in 4f-doped Topological Insulators". OpenSIUC, 2018. https://opensiuc.lib.siu.edu/theses/2400.
Texto completo da fonteBrevis, Vergara Rodrigo Ignacio. "Source time reversal methods for acoustic and elastic waves". Tesis, Universidad de Chile, 2018. http://repositorio.uchile.cl/handle/2250/152342.
Texto completo da fonteEsta tesis estudia la detección y reconstrucción del término espacial de una fuente de variables separables en problemas de onda acústica y elástica. Para esto, estudiamos el método time-reversal mirror, el cual explota una invariancia intrínseca de la física a nivel microscópico que se observa también a nivel macroscópico en las ecuaciones de ondas. Esto significa que es posible recuperar la condición inicial de una ecuación de ondas homogénea revirtiendo la onda a través del tiempo. Para localizar y reconstruir el término espacial de la fuente, desarrollamos un método llamado source time reversal. La aplicación subyacente aquí es la detección de fuentes sísmicas en la minería. Es sabido que la actividad minera induce temblores dentro de las minas [50]. Esto se vuelve bastante peligroso si no se toman las precauciones adecuadas. Conocer sobre el origen de las actividades sísmicas puede ser utilizado para reducir el peligro de derrumbes y mejorar la seguridad dentro de las minas. Este trabajo se divide en tres capítulos; cada uno de ellos constituye un documento autocontenido para ser presentado como artículo. El primer capítulo aborda el problema de reconstrucción de fuente para ondas acústicas. Para esto introducimos el método source time reversal, la cual reconstruye el término espacial de una fuente de la forma f(x)g(t), donde f(x) entrega la forma y g(t) representa la distribución en tiempo de la fuente. Además, presentamos una estimación del error de la reconstrucción para el caso cuando f es una función de cuadrado integrable. Aquí, proponemos un método de regularización para implementar la reconstrucción de la fuente numéricamente. Adicionalmente, analizamos las principales características y limitaciones del método propuesto cuando se aplica a ondas acústicas. El capítulo dos estudia el problema de reconstrucción de fuente para ondas elásticas. Extendemos el método source time reversal para problemas elásticos. Además, introducimos un nuevo método de regularización para implementar la reconstrucción del término espacial de la fuente numéricamente para grandes volúmenes de datos. El nuevo método de regularización elimina las altas frecuencias presentes en la señal procesada, lo que permite utilizar mallas numéricas más gruesas y reduce el costo computacional. Finalmente, este capítulo presenta diversos experimentos numéricos para probar que el método es válido en el caso elástico. El último capítulo analiza un problema de reconstrucción de fuente diferente. Aquí consideramos una fuente compuesta por una suma finita de funciones de variable separable, donde cada término temporal de la fuente es una función delta de Dirac actuando a un tiempo diferente. Basado en una propiedad de tiempo reverso, la fuente puede ser localizada observando el desplazamiento y la velocidad de desplazamiento en el problema reverso [31]. Nosotros extendemos esta idea a sistemas de ondas elásticas. Adicionalmente, proponemos un algoritmo para la implementación numérica.
CONICYT, CMM - Conicyt PIA AFB170001 y el proyecto GEAGAM
Oborn, Jeremy Michael. "Time Reversed Smoke Simulation". BYU ScholarsArchive, 2017. https://scholarsarchive.byu.edu/etd/7218.
Texto completo da fonteSchlegel, Marc. "Time reversal odd effects in semi-inclusive deep inelastic scattering". [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981070086.
Texto completo da fonteRavaine, Boris. "Violation of parity and time-reversal in atoms and molecules". abstract and full text PDF (free order & download UNR users only), 2007. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3258941.
Texto completo da fonteRoot, Joseph Andrew. "Capabilities of an underwater acoustic volumetric array using time-reversal". Thesis, Georgia Institute of Technology, 2000. http://hdl.handle.net/1853/18944.
Texto completo da fonteMellars, Ehren Axel. "Time-reversal symmetry and topology in one-dimensional Josephson junctions". Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8739/.
Texto completo da fonteHe, Jiaze. "Time-reversal Based Array Damage Imaging in Structural Health Monitoring". Thesis, North Carolina State University, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10110540.
Texto completo da fonteComposite materials are receiving increasing attention and broadly used in aerospace industry due to their superior strength-to-weight ratio, corrosion resistance and design flexibility. The need for rapid nondestructive evaluation (NDE) techniques for composites is growing rapidly as the complexity and dimensions of the structures are increasing significantly. Structural health monitoring (SHM) has been attracting much attention as a means of providing in-service and in-situ monitoring of various critical structures. Due to their capability of long-range and through-the-thickness interrogation of the structures for small defects, guided waves have been studied extensively in damage detection for plate-like structures.
However, a few challenges exist when Lamb wave-based SHM/NDE techniques are employed. For example, the dispersion effect decreases the accuracy of many damage imaging algorithms; damage severity quantification is always a difficult problem. To provide possible solutions to above challenges, two damage imaging algorithms were developed and utilized for Lamb-wave based damage imaging.
The first algorithm is reverse-time migration (RTM), which was first used in geophysics to provide proper solutions to complex wave phenomena. The traditional imaging condition utilized in SHM is called excitation-time imaging condition, which used ray tracing and group velocity corresponding to the center frequency of the input signal. Due to the dispersion effect, the time-of-flight (ToF) estimation cannot always be accurate, especially for the situations that the Lamb waves propagate for a long distance. In this thesis, new imaging conditions are proposed to form enhanced zero-lag cross-correlation reverse-time migration (E-CCRTM) techniques. The proposed damage imaging technique takes into account the amplitude, phase, and all the frequency content of the Lamb waves propagating in the plate; thus, the severity of multiple sites of damage can be non-biasedly imaged regardless of the damage locations in comparison with using existing imaging conditions. The other imaging algorithm is called ‘DORT-MUSIC’. A Lamb wave-based, subwavelength imaging algorithm is developed for damage imaging in large-scale, plate-like structures based on a decomposition of the time-reversal operator (DORT) method combined with the multiple signal classification (MUSIC) algorithm in the space-frequency domain. The physics of wave propagation, reflection, and scattering that underlies the response matrix in the DORT method is mathematically formulated in the context of guided waves. Singular value decomposition (SVD) is then employed to decompose the experimentally measured response matrix into three matrices, detailing the incident wave propagation from the linear actuator array, reflection from the damage, and followed by scattering waves toward the linear sensing array for each small damage. The SVD and MUSIC-based imaging condition enable quantifying the damage severity by a ‘reflectivity’ parameter and super-resolution imaging.
The two algorithms were also integrated with a hybrid system mainly comprised piezoelectric actuators mounted onto the structure and a laser Doppler vibrometer (LDV) for reception. The flexibility of the proposed system was used for inspection of various plate-like structures. The experimental results show that the 2-D E-CCRTM has robust performance to image and quantify multiple sites of damage in large area of the plate using a single PZT actuator with a nearby areal scan using LDV, and the DORT-MUSIC (TR-MUSIC) imaging technique can provide rapid, highly accurate imaging results as well as damage quantification with unknown material properties.
Mumm, Hans Pieter. "A test of time reversal violation in neutron beta decay /". Thesis, Connect to this title online; UW restricted, 2004. http://hdl.handle.net/1773/9802.
Texto completo da fonteDenison, Michael Hunter. "Image Source Modeling of Time Reversal for Room Acoustics Applications". BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7449.
Texto completo da fontePhung, Huong Thi Hoai. "Imaging of seismic and hum sources by time reversal method". Paris 7, 2010. http://www.theses.fr/2010PA077169.
Texto completo da fonteStudies of earthquake sources is one of purpose of many scientists. Today, with the development of FDSN (Federation of Digital Seismometers Networks), the seismograms are continuously recorded. They provide information on seismic source and on propagation (related to earth structure) effect. We can easily locate an earthquake by applying the classical methods on seismograms. However, to have a more accurate result on seismic source (seismic moment tensor, source time function), we need to solve an inverse problem. Time-reversal (hereafter referred to as TR) method has been successfully applied for acoustic waves in many fields such as imaging, underwater acoustics, non destructive testing, and for seismic waves in seismic earthquake location, and glacial earthquake imaging. In this thesis , we present the application of TR method to synthetic seismograms due to virtual earthquakes. We show the focusing of January 12th 2010 Haiti earthquake in space and time and the reconstructed focal mechanism by applying the TR method to complete and one-bit seismograms. The level of oscillation of seismic "hum" is well observed. However, the spatial and temporal origin of "hum" is still uncertain, and the idea is to use the advantage focusing source of the TR method to locate it. We assume that this source may be located in space, not in time. We show that hum source is not local but might be distributed in a very large region
Ilg, Matthias. "An investigation of spatially bounded, time independent quantum systems". Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/28046.
Texto completo da fonteDumont, Elisabeth M. M. "Unconventional vortex dynamics in superconducting states with broken time reversal symmetry /". [S.l.] : [s.n.], 2000. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=13938.
Texto completo da fonteGraziani, Filippo. "Modulazioni "Time-reversal" con codifiche a bassa profondità per comunicazioni ultrasoniche". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22625/.
Texto completo da fonteTrung, Kien-Nguyen [Verfasser]. "Time reversal transmission approach for ultra wideband communications / Trung Kien Nguyen". Hannover : Technische Informationsbibliothek und Universitätsbibliothek Hannover (TIB), 2011. http://d-nb.info/1017987165/34.
Texto completo da fonteOgawa, Kazuhisa. "Optical Interferometric Measurements Inspired by Time-Reversal Symmetry of Quantum Mechanics". 京都大学 (Kyoto University), 2015. http://hdl.handle.net/2433/202718.
Texto completo da fonteTwengström, Mikael. "Time-reversal symmetry breaking and mixed coherence lengths in multicomponent superconductors". Thesis, KTH, Fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-138163.
Texto completo da fonteReis, Itamar. "Axion term in topological insulators with broken time reversal and parity". Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/46360.
Texto completo da fonteNguyen, Linh V., e Leonid A. Kunyansky. "A Dissipative Time Reversal Technique for Photoacoustic Tomography in a Cavity". SIAM PUBLICATIONS, 2016. http://hdl.handle.net/10150/622000.
Texto completo da fonteOdedo, Victor. "High resolution time reversal (TR) imaging based on spatio-temporal windows". Thesis, University of Manchester, 2017. https://www.research.manchester.ac.uk/portal/en/theses/high-resolution-time-reversal-tr-imaging-based-on-spatiotemporal-windows(f0589f73-901f-4de2-9886-7045b7f6cfd4).html.
Texto completo da fonteAsh, Jason Travis. "Time Reversal and Applications in Solid-State NMR of Quadrupolar Nuclei". The Ohio State University, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=osu1213361614.
Texto completo da fonteWinter, Thomas A. "Examination of time-reversal acoustic application to shallow water active sonar systems". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/ADA378874.
Texto completo da fonteXia, Jing. "Optical studies of broken time-reversal symmetry in solids using Sagnac interferometry /". May be available electronically:, 2008. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
Texto completo da fonteKandler, Anne, e James Steele. "Innovation diffusion in time and space". Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-188644.
Texto completo da fonteTraytak, Sergey D. "Time-dependent competition effects in diffusion-limited crystal growth: Time-dependent competition effects in diffusion-limitedcrystal growth". Diffusion fundamentals 6 (2007) 47, S. 1-2, 2007. https://ul.qucosa.de/id/qucosa%3A14226.
Texto completo da fonteFalcetelli, Francesco. "Modelling of Pencil-Lead Break Acoustic Emission Sources using the Time Reversal Technique". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16554/.
Texto completo da fonteAbrantes, António Adolfo Mendes. "Examination of time-reversal acoustics in shallow water and applications to underwater communications /". Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1999. http://handle.dtic.mil/100.2/ADA368422.
Texto completo da fonte"June 1999". Thesis advisor(s): Kevin B. Smith, Andrés Larraza, Monique P. Fargues. Includes bibliographical references (p. 75-77). Also available online.
Heinemann, Michael Gerhard. "Experimental studies of applications of time-reversal acoustics to non-coherent underwater communications". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2000. http://handle.dtic.mil/100.2/.
Texto completo da fonteThesis advisor(s): Larraza, Andrès ; Smith, Kevin B. "March 2000." Includes bibliographical references (p. 59-60). Also available online.
Stokely, John P. "Experimental studies of two-way single element time reversal in a noisy waveguide". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2001. http://handle.dtic.mil/100.2/ADA393134.
Texto completo da fonteYavuz, Mehmet Emre. "Time reversal based signal processing techniques for ultrawideband electromagnetic sensing in random media". Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1198770526.
Texto completo da fonteAbboud, Layane. "Time Reversal techniques applied to wire fault detection and location in wire networks". Phd thesis, Supélec, 2012. http://tel.archives-ouvertes.fr/tel-00771964.
Texto completo da fonte