Tesi sul tema "Propagation spatial"
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Mahmood, Attiya. "Impact of Antenna Mutual Coupling, Propagation, and Nonreciprocity on Propagation-Based Key Establishment". BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/6831.
Dunn, Adam. "A model of wildfire propagation using the interacting spatial automata formalism". University of Western Australia. School of Computer Science and Software Engineering, 2007. http://theses.library.uwa.edu.au/adt-WU2007.0071.
Hahn, Philip James. "Origination and Propagation of Reaction Diffusion Waves in Three Spatial Dimensions". Cleveland, Ohio : Case Western Reserve University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=case1091809306.
Title from PDF (viewed on 2009-11-23) Department of Mathematics Includes abstract Includes bibliographical references and appendices Available online via the OhioLINK ETD Center
Hahn, Philip James. "Origination and propagation of reaction diffusion waves in three spatial dimensions". online version, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=case1091809306.
Agerskov, Niels. "Adaptable Semi-Automated 3D Segmentation Using Deep Learning with Spatial Slice Propagation". Thesis, KTH, Skolan för kemi, bioteknologi och hälsa (CBH), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-241542.
Trots att framstegen inom djupinlärning banar vägen för medicinsk bildanalys snabbare än någonsin så finns det ett stort problem, mängden annoterad bilddata. Det har bland annat att göra med att medicinsk bilddata tar väldigt lång tid att annotera manuellt. I detta projektet har en semi-automatisk algoritm utvecklats som tar sig an 3D-segmentering från ett 2D-perspektiv. En bildvolym segmenteras genom att en initialiseringbild annoteras manuellt och används som hjälp för att annotera närliggande bilder i volymen. Detta upprepas sedan för resterande bilder men istället för att manuellt annotera används föregående segmentering av närverket som hjälp. Detta tillåter att algoritmen både kan generalisera till helt nya fall som ej är representerade av träningsdatan, och gör även att felaktigt segmenterade bilder kan korrigeras i efterhand. Korrigeringar kommer då att propageras genom volymen genom att varje segmentering används som hjälp för nästkommande bild. Resultaten är i nivå med motsvarande helautomatiska algoritmer inom träningsdomänen. Den största fördelen gentemot dessa är möjligheten att segmentera helt nya fall. Metoden som används för att träna nätverket att förlita sig på hjälpbilder bygger på kraftig bilddistortion av bilden som ska segmenteras. Detta tvingar nätverket att ta vara på informationen i segmenteringen av föregående bild.
Moustafa, Mahmoud. "Fabrication of Micropatterns for the Spatial Control of Cell Propagation and DIfferentiation". VCU Scholars Compass, 2014. http://scholarscompass.vcu.edu/etd/3555.
De, Rybel Tom. "Temporal-spatial discretization and fractional latency techniques for wave propagation in heterogeneous media". Thesis, University of British Columbia, 2010. http://hdl.handle.net/2429/20573.
DIAS, MAURICIO HENRIQUE COSTA. "ACTUAL MOBILE RADIO PROPAGATION CHANNEL RESPONSES ESTIMATES IN THE SPATIAL AND TEMPORAL DOMAINS". PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2003. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=3502@1.
No cenário atual das telecomunicações móveis, os arranjos de antenas voltaram a receber grande atenção dos pesquisadores, especialmente quando esquemas adaptativos de modificação de seus diagramas de radiação são utilizados. Uma das aplicações que exploram o potencial dos arranjos de antenas é o seu uso como forma de aumentar consideravelmente a eficiência espectral dos sistemas móveis atuais e da próxima geração. A outra aplicação em evidência está voltada para sistemas de localização de posição, pois algumas das técnicas conhecidas envolvem a estimação de ângulos-de-chegada usando arranjos de antenas. Diante destas possibilidades, cresce em importância o estudo das variações do canal de propagação rádio móvel no domínio em que o uso dos arranjos de antenas atua: o espacial. O presente trabalho procura contribuir para o contexto em questão, com uma investigação experimental do canal real rádio-móvel nos domínios temporal (retardos) e espacial (ângulos-de-chegada). No que se refere ao contexto nacional, contribuições similares baseadas em simulações já são encontradas; baseadas em medidas não. Em particular, sondagens na faixa de 1,8 GHz em ambientes internos típicos foram realizadas. Duas técnicas distintas de sondagem temporalespacial foram implementadas, tomando por base uma sonda de canal faixa-larga montada e testada com sucesso, como contribuição principal de uma dissertação de mestrado recentemente apresentada por um integrante do mesmo grupo de pesquisa ao qual esta tese está vinculada. Uma das técnicas sintetiza o arranjo realizando as sondagens com uma única antena que é sucessivamente deslocada para ocupar as posições correspondentes às dos elementos do arranjo. A outra técnica emprega um arranjo real. Em ambas, a configuração mais simples para um arranjo foi utilizada: a linear uniforme. As sondagens não forneciam diretamente os espectros espaciais-temporais. As estimativas dos espectros foram processadas posteriormente, aplicando técnicas como o correlograma para o domínio do retardo, e quatro técnicas distintas para o domínio espacial, que foi o foco principal deste trabalho: duas convencionais; e duas paramétricas, com potencial de aumentar a resolução das estimativas, assumindo hipóteses razoáveis sobre as respostas esperadas. De posse das respostas espectrais estimadas, comparações com estimativas teóricas permitiram uma análise de desempenho das técnicas utilizadas. Adicionalmente à investigação experimental do canal espacial, procurou-se verificar o potencial da aplicação da teoria de wavelets ao estudo do canal rádiomóvel. Em especial, uma das principais aplicações daquela teoria foi testada como técnica de pós-processamento das respostas espectrais no domínio do retardo. A supressão de ruído por decomposição wavelet foi aplicada a um vasto conjunto de medidas de canal disponíveis, fruto de trabalhos anteriores do grupo de pesquisa ao qual esta tese está vinculada, com resultados expressivos.
In the present mobile communications scenario, researchers have turned once again special attention to antennae arrays, particularly when adaptive schemes are employed to modify its radiation patterns. One of its main applications results in considerable increases to the spectral efficiency of present and next generation mobile systems. The other major application is headed towards position location systems, since some of the known techniques comprise angle-of-arrival estimation using antennae arrays. Under such possibilities, mobile radio propagation channel variations studies grow in relevance, specially regarding the antennae arrays main domain of action: the spatial domain. The present work tries to contribute to the overstated context, experimentally investigating the actual mobile radio channel over the temporal (delays) and spatial (angles of arrival) domains. Regionally speaking, similar contributions based on simulations are already found, but none based on measurements. In special, 1.8 GHz indoor soundings have been carried out. Two different temporal spatial sounding techniques have been deployed, based on na available wideband channel sounder successfully assembled and tested as the major contribution of a MSc. dissertation recently presented by a member of the same research team to which this thesis belongs. One of such techniques sinthesyzes the array carrying the sounding out with a single antenna, which is successively moved to occupy the spots corresponding to the array elements. The other method employs an actual array. For both cases, the simplest array configuration has been used: the uniform linear one. Space-time spectra were not directly available in real time during the soundings. Its estimates have been processed later, applying techniques such as the correlogram over the delay domain, and four distinct methods over the spatial domain, the main focus of the present work. Two conventional methods have been used, as well as two parametric ones, potentially capable to increase the estimates resolution, assuming reasonable hypotheses regarding the expected responses. With the estimated spectral responses in hands, comparisons with theoretical estimates allowed a performance assessment of the employed methods. In addition to the spatial channel experimental investigation, the wavelets theory potential of application to the mobile-radio channel study has been checked out. Notably, one of the wavelets theory major applications has been tested as a post-processing technique to improve delay-domain spectral responses. Wavelet decomposition based de-noising has been applied to a huge measurements ensemble, available as the product of previous works of the research group to which this thesis is attached, leading to remarkable results.
Kim, Hyunki. "Spatial variability in soils stiffness and strength /". Diss., Available online, Georgia Institute of Technology, 2005, 2005. http://etd.gatech.edu/theses/available/etd-07132005-194445/.
Mayne, Paul, Committee Member ; Frost, David, Committee Member ; Santamarina, Carlos, Committee Chair ; Rix, Glenn, Committee Member ; Ruppel, Carolyn, Committee Member.
Wiles, Andrew Donald. "Modelling Framework for Radio Frequency Spatial Measurement". Thesis, University of Waterloo, 2006. http://hdl.handle.net/10012/771.
In this thesis, a modelling framework for the investigation of spatial measurement based on radio frequency signals was developed. The simulation framework was designed for the purpose of investigating different position determination algorithms and sensor geomatries. A finite element model using the FEMLAB partial differential equation modelling tool was created for a time-domain model of electromagnetic wave propagation in order to simulate the radio frequency signals travelling from a transmitting source antenna to a set of receiving antenna sensors. Electronic line signals were obtained using a simple receiving infinitesimal dipole model and input into a time difference of arrival localization algorithm. The finite element model results were validated against a set of analytical solutions for the free space case. The accuracy of the localization algorithm was measured against a set of possible applications for a potential radio frequency spatial measurement system design.
It was concluded that the simulation framework was successful should one significant deficiency be corrected in future research endeavours. A phase error was observed in the signals extracted at the receiving antenna locations. This phase error, which can be up to 40°, was attributed to the zeroth order finite elements implemented in the finite element model. This phase error can be corrected in the future if higher order vector elements are introduced into future versions of FEMLAB or via the development of custom finite element analysis software but were not implemented in this thesis due to time constraints. Other improvements were also suggested for future work.
Sabbatini, Chiara. "Efficacité et durabilité des restrictions à grande échelle contre la pandémie de COVID-19 en France en 2020-2021". Electronic Thesis or Diss., Sorbonne université, 2023. http://www.theses.fr/2023SORUS533.
After one year of COVID-19 mitigation, in the spring of 2021, European countries faced sustained viral circulation of the Alpha variant. As vaccination campaigns advanced, the challenge persisted: finding a balance between the effectiveness of long-lasting interventions and their impact on quality of life. This thesis combines insights drawn from two studies conducted in France, with the aim of evaluating the efficacy and sustainability of the interventions employed between 2020 and 2021, while also proposing more sustainable alternatives preserving their effectiveness. We first employed an age-structured compartmental model to assess the real-time epidemic situation and conducted scenario analyses. Optimal scenarios were identified by the integration of intervention efficacy and a data-driven index accounting for the intensity and duration of social distancing measures. Our findings indicate that shorter and strict lockdowns tend to be considerably more effective than prolonged and moderate ones, all while maintaining a similar level of public discomfort and individual freedoms. Subsequently, we employed a regionally-based metapopulation model to retrospec- tively evaluate the effectiveness of the implemented strategies and potential alternatives, taking into account the interconnectivity between regions in France. The results re- vealed that the spatial interplay between regions significantly influenced the outcomes of nationwide interventions, particularly in regions characterized by high mobility rates. Moreover, our analysis showed that implementing stop-and-go lockdowns early enough, instead of a prolonged curfew period, could have substantially reduced both the healthcare and societal burdens. Our results contribute to characterize the success and failures of implemented strate- gies, highlighting the complexity of balancing effectivness and sustainability. These findings also highlights the importance of considering geographical connectivity in the implementation and evaluation of public health policies. Results can inform poli- cymakers and health authorities in designing targeted interventions, thus enhancing the overall effectiveness of management strategies
Pfeil, Erin. "Spatial and Temporal Dependent Shifts in Grassland Invasibility". Youngstown State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1289941507.
Purz, Anneke K. Verfasser], Helmut [Akademischer Betreuer] Hillebrand e Ulrike [Akademischer Betreuer] [Feudel. "Propagation of extreme events: the effect of nutrients on the bloom dynamics and spatial propagation of harmful dinoflagellates / Anneke K. Purz ; Helmut Hillebrand, Ulrike Feudel". Oldenburg : BIS der Universität Oldenburg, 2019. http://d-nb.info/1211724506/34.
Marinelli, Marco Antonio. "Modelling and communicating the effects of spatial data uncertainty on spatially based decision-making". Thesis, Curtin University, 2011. http://hdl.handle.net/20.500.11937/1842.
Nemati, Navid. "Macroscopic theory of sound propagation in rigid-framed porous materials allowing for spatial dispersion : principle and validation". Phd thesis, Université du Maine, 2012. http://tel.archives-ouvertes.fr/tel-00976907.
Crépey, Pascal. "Modélisation des dynamiques spatiotemporelles des épidémies et réseaux stochastiques multi-échelles". Paris 6, 2008. http://www.theses.fr/2008PA066570.
Soltani, Mariem. "Partitionnement des images hyperspectrales de grande dimension spatiale par propagation d'affinité". Thesis, Rennes 1, 2014. http://www.theses.fr/2014REN1S099/document.
The interest in hyperspectral image data has been constantly increasing during the last years. Indeed, hyperspectral images provide more detailed information about the spectral properties of a scene and allow a more precise discrimination of objects than traditional color images or even multispectral images. High spatial and spectral resolutions of hyperspectral images enable to precisely characterize the information pixel content. Though the potentialities of hyperspectral technology appear to be relatively wide, the analysis and the treatment of these data remain complex. In fact, exploiting such large data sets presents a great challenge. In this thesis, we are mainly interested in the reduction and partitioning of hyperspectral images of high spatial dimension. The proposed approach consists essentially of two steps: features extraction and classification of pixels of an image. A new approach for features extraction based on spatial and spectral tri-occurrences matrices defined on cubic neighborhoods is proposed. A comparative study shows the discrimination power of these new features over conventional ones as well as spectral signatures. Concerning the classification step, we are mainly interested in this thesis to the unsupervised and non-parametric classification approach because it has several advantages: no a priori knowledge, image partitioning for any application domain, and adaptability to the image information content. A comparative study of the most well-known semi-supervised (knowledge of number of classes) and unsupervised non-parametric methods (K-means, FCM, ISODATA, AP) showed the superiority of affinity propagation (AP). Despite its high correct classification rate, affinity propagation has two major drawbacks. Firstly, the number of classes is over-estimated when the preference parameter p value is initialized as the median value of the similarity matrix. Secondly, the partitioning of large size hyperspectral images is hampered by its quadratic computational complexity. Therefore, its application to this data type remains impossible. To overcome these two drawbacks, we propose an approach which consists of reducing the number of pixels to be classified before the application of AP by automatically grouping data points with high similarity. We also introduce a step to optimize the preference parameter value by maximizing a criterion related to the interclass variance, in order to correctly estimate the number of classes. The proposed approach was successfully applied on synthetic images, mono-component and multi-component and showed a consistent discrimination of obtained classes. It was also successfully applied and compared on hyperspectral images of high spatial dimension (1000 × 1000 pixels × 62 bands) in the context of a real application for the detection of invasive and non-invasive vegetation species
El, Arja Hajar. "Sondeur de canal de propagation multi-capteurs appliqué à la mesure de canal de propagation pour l'Ultra Large Bande (6 GHz - 8.5 GHz) à l'intérieur des bâtiments". Phd thesis, Télécom ParisTech, 2010. http://pastel.archives-ouvertes.fr/pastel-00575964.
López, Rafael Arcángel Cepeda. "Spatial uncertainty and path loss in UWB propagation channels, and frequency dependent path loss in multi-band OFDM". Thesis, University of Bristol, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.503865.
Tovar, Anthony Alan. "Off-axis multimode light beam propagation in tapered lenslike media including those with spatial gain or loss variation". PDXScholar, 1988. https://pdxscholar.library.pdx.edu/open_access_etds/3839.
Boucher, Pauline. "Spatial mode multiplexing : from fundamental concepts to applications". Thesis, Sorbonne université, 2018. http://www.theses.fr/2018SORUS483.
This thesis is dedicated to spatial mode multiplexing, from its fundamental concepts to its applications. The work is associated with the multi-plane light converter (MPLC) technology developed by CAILabs. This study is divided into two main parts. First, we investigate the use of independent spatial mode shaping to measure or modify spatial parameters of the electromagnetic field. We make the theoretical demonstration that the best sensitivity for the measurement of small displacements of a beam – or of the distance between two incoherent beams – is reached when an intensity measurement is made on the Hermite-Gaussian mode basis. By building the adequate MPLC system, we make the experimental validation of this result. We also make the demonstration that a MPLC system can be designed and used to transfer the control of one spatial parameter of a beam onto another. We built an experimental setup which allows to control the position of the focal point of a beam using transverse displacement and tilt. The second project we conducted was a theoretical and numerical study of the statistical transport properties of the MPLC using tools from random matrix theory. We aim at identifying the underlying physical processes which make up for the efficiency of this transformation technique
Rodríguez, Amor Daniel. "Population and evolutionary dynamics in spatial systems". Doctoral thesis, Universitat de Girona, 2013. http://hdl.handle.net/10803/128501.
Els models físics i matemàtics són de gran utilitat a l'hora d'entendre processos clau en la dinàmica poblacional i evolutiva. Aquests models permeten l'estudi de característiques molt diverses dels sistemes espacials, com són la propagació de fronts, l'evolució de la densitat de població, les interaccions entre espècies (o individus), l'evolució d'estratègies, etc. Aquesta tesi presenta diversos models físics que descriuen sistemes espacials. El primer model estudia els efectes de l'estructura de la població en fronts invasius bidimensionals. Una expressió per la velocitat del front és derivada de les equacions per a poblacions estructurades. El segon model es consagra a l’estudi d’infeccions del Vesicular Stomatitis Virus. En aquest cas, s’utilitzen equacions de reacció-difusió per descriure les interaccions entre les poblacions de cèl·lules no infectades, cèl·lules infectades i virus. A l’últim model, el joc del Dilema del Presoner s'utilitza per estudiar l'evolució d'estratègies de cooperació i deserció
Mazine, Alexandre. "La caractérisation de front d'onde dans un système de propagation à multi-illumination gérée par un modulateur spatial de lumière". Phd thesis, Télécom ParisTech, 2006. http://pastel.archives-ouvertes.fr/pastel-00001748.
Castiñeiras, Carina. "Modeling and characterization of mode coupling in next generation of few mode optical fibers". Thesis, Lille, 2018. http://www.theses.fr/2018LIL1R030.
Few multimode fiber (FMF) is a class of multimode fiber. Each mode of a FMF is considered as an independent transmission channel in telecommunication field. Thus, much higher rates than conventional optical fibers could be achieved. However, this fiber can present the mode coupling and mode dispersion that can degrade the transmission performance. The mode coupling over different fiber profiles is studied in this thesis. This work is divided into two parts: i) the modeling of the mode coupling considering the fiber as a concatenation of several curved segments, and each piece is associated with a random bending radius R. ii) The measurement of localized coupling which is based on the experimental method A-S2. Using this model and these measurements, we can demonstrate the absence or the presence of coupling of a fiber exposed to micro-curvatures or a random perturbation
Soares, Moser Carlos Anissem. "Calcul direct du son rayonné par une couche de mélange en développement spatial : étude des effets du nombre de Mach et de l'anisothermie". Poitiers, 2006. http://www.theses.fr/2006POIT2359.
In the present work has been developed a numerical methodology to accurately perform the direct computation of the sound radiated by spatially evolving two-dimensional compressible mixing layers. An improved representation of the flow noise mechanisms is provided by the use ofhigh-order-accurate compact finite difference schemes for the spatial discretization and the fourth-order Runge-Kutta scheme for the time integration. A characteristic-based formulation is used to solve by direct numerical simulation (DNS) the fully compressible Navier-Stokes equations and a conceptual model based on the characteristic analysis is used to prescribe initial and boundary conditions along with buffer zone treatments. The main focus is the analysis of Mach number and thermal effects on the mechanisms of sound generation and propagation by harmonically excited isothermal and non-isothermal mixing layers, at Reynolds number 400 and Mach number ranging from 0. 200 to 0. 400. The low Mach numbers allow us to keep almost the same flow dynamics features (sound sources). However, considerable changes are observed in the acoustic field patterns. The superdirective character on sound radiation is recognized at the higher speed mixing layers. The reciprocal influence of Mach number and thermal effects on the flow noise mechanisms is identified in non-isothermal mixing layers
Molto, Quentin. "Estimation de la biomasse en forêt tropicale humide : propagation des incertitudes dans la modélisation de la distribution spatiale de la biomasse en Guyane Française". Thesis, Antilles-Guyane, 2012. http://www.theses.fr/2012AGUY0567/document.
Tropical forest yield and important part of the aerial vegetation carbon stock on earth. Measuring and understanding this stock distribution is crucial for the management of the tropical forests facing the actual environmental challenges (REDD+, carbon market).Aerial Biomass estimation of forest census plots requires few models depending on the precision of the inventory: diameter models, height models, wood density models. Spatial extrapolation between census plots relies on aerial data (satellite measurements, images) or ground-based data (geology, altitude).The uncertainty of the estimation of a region’s biomass is the result of the uncertainty brought by all these models. The aim of the thesis is to develop models and methods to estimate the biomass of a region while propagating the uncertainties. This is applied to the neo-tropical forest of French Guiana (South America, Guianas Plateau)
Archer, Akibi A. A. "Spatial characterization of the natural mechanical vibrations occurring in-vivo during isometric contractions of the biceps brachii muscle: towards passive elastography of skeletal muscles". Diss., Georgia Institute of Technology, 2012. http://hdl.handle.net/1853/50139.
Stewart, Kelley Christine. "Quantitative Hydrodynamics Analysis of Left Ventricular Diastolic Dysfunction using Color M-Mode Echocardiography". Thesis, Virginia Tech, 2008. http://hdl.handle.net/10919/35466.
Master of Science
Ding, Weiwei. "Propagation phenomena of integro-difference equations and bistable reaction-diffusion equations in periodic habitats". Thesis, Aix-Marseille, 2014. http://www.theses.fr/2014AIXM4737.
This dissertation is concerned with propagation phenomena of some evolution equations in periodic habitats. The main results consist of the following two parts. In the first part, we investigate the spatial spreading phenomena of some spatially periodic integro-difference equations. Firstly, we establish a general theory on the existence of spreading speeds for noncompact evolution systems, under the hypothesis that the linearized systems have principal eigenvalues. Secondly, we introduce the notion of uniform irreducibility for finite Radon measures on the circle. It is shown that, any generalized convolution operator generated by such a measure admits a principal eigenvalue. Finally, applying the above general theories, we prove the existence of spreading speeds for some integro-difference equations with uniformly irreducible dispersal kernels. In the second part, we study the front propagation phenomena of spatially periodic reaction-diffusion equations with bistable nonlinearities. Firstly, we focus on the propagation solutions in the class of pulsating fronts. It is proved that, under various assumptions on the reaction terms, pulsating fronts exist when the spatial period is small or large. We also characterize the sign of the front speeds and we show the global exponential stability of the pulsating fronts with nonzero speed. Secondly, we investigate the propagation solutions in the larger class of transition fronts. It is shown that, under suitable assumptions, transition fronts are reduced to pulsating fronts with nonzero speed. But we also prove the existence of new types of transition fronts which are not pulsating fronts
Guazzelli, Elisabeth. "Deux études expérimentales du désordre en hydrodynamique physique désordre spatial de structures convectives, effet du désordre sur la propagation d'ondes de gravité". Grenoble 2 : ANRT, 1986. http://catalogue.bnf.fr/ark:/12148/cb37598023n.
Cheng, Jiqi. "A Study of Wave Propagation and Limited-Diffraction Beams for Medical Imaging". University of Toledo / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1133820434.
Farzbod, Farhad. "Analysis of Bloch formalism in undamped and damped periodic structures". Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/42885.
Ludwig, Bruno. "Etude de quelques problèmes directs et inverses en propagation d'ondes acoustiques transitoires. Méthode d'éléments finis de frontière". Compiègne, 2000. http://www.theses.fr/2000COMP1293.
COSQUER, Ronan. "Conception d'un sondeur de canal MIMO - Caractérisation du canal de propagation d'un point de vue directionnel et doublement directionnel". Phd thesis, INSA de Rennes, 2004. http://tel.archives-ouvertes.fr/tel-00007560.
Groters, Douglas J. "The temporal and spatial variability of the marine atmospheric boundary layer and its effect on electromagnetic propagation in and around the Greenland Sea marginal ice zone". Thesis, Monterey, California. Naval Postgraduate School, 1988. http://hdl.handle.net/10945/23422.
Variability of the MABL and its effect on the electromagnetic (EM) refractive structure around the Greenland Sea marginal ice zone were examined. Rawinsonde profiles and surface observations collected from 3 ships during MIZEX-87(20 March-11 April) served as the data set. A program, developed to calculate the refractivity at each vertical level of the rawinsonde profiles, also identified the levels at which trapping, superrefraction and subrefraction occurred. Temporal studies showed that a higher incidence of anomalous refractive layers occurred during periods when the region was under the influence of high pressure. More than 50% of the time, trapping and super-refractive layers were attributed to development of a capping inversion just above the MABL during these periods. Spatial studies showed that the refractive structure varied relative to distance from the ice edge as did the depth of the MABL. An upward slope in refractive layer heights was observed from the ice toward the open water. Significant spatial inhomogeneity was observed over horizontal ranges of less than 100 km. This was attributed to both the large-scale synoptic forcing affecting the region and to variations in the surface fluxes of heat and moisture over the ice and over the water. A range-dependent ray trace model developed at the Naval Ocean Systems Center was used to show how the ray paths of EM waves vary with a changing refractive structures. Keywords: Air water interactions, Greenland Sea, Atmospheric refraction, Electromagnetic wave propagation, Heat flux, Sea ice. Theses. (EDC)
http://archive.org/details/temporalspatialv00grot
Lieutenant, United States Navy
Serre, Denis. "L'imageur Interférométrique de Fresnel : un instrument spatial pour l'observation à haute résolution angulaire". Phd thesis, Université Paul Sabatier - Toulouse III, 2007. http://tel.archives-ouvertes.fr/tel-00242674.
Dans un télescope classique, la focalisation s'obtient par l'utilisation d'un miroir; dans le cas de l'Imageur Interférométrique de Fresnel, elle s'obtient par l'utilisation d'un masque diffractant comportant des dizaines ou des centaines de milliers d'ouvertures individuelles, réparties sur un support plan selon une loi se rapprochant de la disposition des anneaux d'une lentille zonée de Soret. Les contraintes de masse et de précision de fabrication de l'optique focalisatrice sont ainsi considérablement relâchées, ouvrant une voie pour concevoir un observatoire possédant une pupille d'entrée de très grande dimension. En revanche, de par la nature dispersive de cette optique, un module focal placé à grande distance est nécessaire pour achromatiser et mettre en forme l'image.
La première partie de cette thèse est consacrée à la détermination des caractéristiques des éléments constitutifs de ce type d'imageur, et à l'étude des performances et limitations associées. La deuxième partie est elle dévolue à la description et à la présentation des performances d'un prototype sol montrant expérimentalement la validité du concept. Enfin, la troisième partie étudie les objectifs astrophysiques possibles d'un Imageur de Fresnel opérationnel.
Dia'meh, Yousef Ali. "The optimization of multiple antenna broadband wireless communications : a study of propagation, space-time coding and spatial envelope correlation in Multiple Input, Multiple Output radio systems". Thesis, University of Bradford, 2013. http://hdl.handle.net/10454/6361.
Diameh, Yousef A. "The optimization of multiple antenna broadband wireless communications. A study of propagation, space-time coding and spatial envelope correlation in Multiple Input, Multiple Output radio systems". Thesis, University of Bradford, 2013. http://hdl.handle.net/10454/6361.
Fakhfakh, Nizar. "Détection et localisation tridimensionnelle par stéréovision d’objets en mouvement dans des environnements complexes : application aux passages à niveau". Thesis, Ecole centrale de Lille, 2011. http://www.theses.fr/2011ECLI0005/document.
Within the past years, railways undertakings became interested in the assessment of Level Crossings (LC) safety. We propose in this thesis an Automatic Video-Surveillance system (AVS) at LC for an automatic detection of specific events. The system allows automatically detecting and 3D localizing the presence of one or more obstacles which are motionless at the level crossing. Our research aims at developing an AVS using the passive stereo vision principles. The proposed imaging system uses two cameras to detect and localize any kind of object lying on a railway level crossing. The cameras are placed so that the dangerous zones are well (fully) monitored. The system supervises and estimates automatically the critical situations by detecting objects in the hazardous zone defined as the crossing zone of a railway line by a road or path. The AVS system is used to monitor dynamic scenes where interactions take place among objects of interest (people or vehicles). After a classical image grabbing and digitizing step, the processing is composed of the two following modules: moving and stationary objects detection and 3-D localization. The developed stereo matching algorithm stems from an inference principle based on belief propagation and energy minimization. It takes into account the advantages of local methods for reducing the complexity of the inference step achieved by the belief propagation technique which leads to an improvement in the quality of results. The motion detection module is considered as a constraint which allows improving and speeding up the 3D localization algorithm
Nemati, Navid. "Theorie macroscopique de propagation du son dans les milieux poreux 'à structure rigide permettant la dispersion spatiale: principe et validation". Phd thesis, Université du Maine, 2012. http://tel.archives-ouvertes.fr/tel-00848603.
Massé, Pierre. "Analysis, Treatment, and Manipulation Methods for Spatial Room Impulse Responses Measured with Spherical Microphone Arrays". Electronic Thesis or Diss., Sorbonne université, 2022. http://www.theses.fr/2022SORUS079.
The use of spatial room impulse responses (SRIR) for the reproduction of three-dimensional reverberation effects through multi-channel convolution over immersive surround-sound loudspeaker systems has become commonplace within the last few years, thanks in large part to the commercial availability of various spherical microphone arrays (SMA) as well as a constant increase in computing power. This use has in turn created a demand for analysis and treatment techniques not only capable of ensuring the faithful reproduction of the measured reverberation effect, but which could also be used to control various modifications of the SRIR in a more "creative" approach, as is often encountered in the production of immersive musical performances and installations. Within this context, the principal objective of the current thesis is the definition of a complete space-time-frequency framework for the analysis, treatment, and manipulation of SRIRs. The analysis tools should lead to an in-depth model allowing for measurements to first be treated with respect to their inherent limitations (measurement conditions, background noise, etc.), as well as offering the ability to modify different characteristics of the final reverberation effect described by the SRIR. These characteristics can be either completely objective, even physical, or otherwise informed by knowledge of human auditory perception with regard to room acoustics. The theoretical work in this research project is therefore presented in two main parts. First, the underlying SRIR signal model is described, heavily inspired by the historical approaches from the fields of artificial reverberation synthesis and SMA signal processing, while at the same time (incrementally) extending both. The signal model is then used to define the analysis methods that form the core of the final framework; these focus particularly on (a) identifying the "mixing time" that defines the moment of transition between the early reflection and late reverberation regimes, (b) obtaining a space-time cartography of the early reflections, and (c) estimating the frequency- and direction-dependent properties of the late reverberation's exponential energy decay envelope. In order to account for the directional dependence of these properties, a procedure for generating directional SRIR representations (i.e. directional room impulse responses, DRIR) that guarantee the preservation of certain fundamental reverberation properties must also be defined. In the second part, the model parameters made explicit by the analysis methods are exploited in order to either treat (i.e. attempt to correct some of the inevitable limitations inherent to the SMA measurement process) or more creatively manipulate and modify the SRIR. Two treatment methods in particular are developed in this thesis: (1) a pre-analysis procedure acting directly on repeated exponential sweep method (ESM) SMA measurement signals in an attempt to simultaneously increase the resulting SRIR's signal-to-noise ratio (SNR) while reducing its vulnerability to non-stationary noise events, and (2) a post-analysis denoising technique based on replacing the SRIR's background noise floor with a resynthesized extrapolation of the late reverberation tail. The theoretical descriptions thus complete, the main analysis methods as well as the DRIR generation and the denoising treatment procedures are then subjected to a series of validation tests, wherein simulated SRIRs (or parts thereof) are used to evaluate the performance, discuss the limitations, and parameterize the implementation of the different techniques. These sub-studies allow each method to be individually verified, resulting in a comprehensive investigation into the inner workings of the analysis toolbox (as well as the denoising process). Finally, to provide a concluding overview of the complete analysis-treatment-manipulation framework, similar studies are carried out using examples of real-world [...]
Okhulkova, Tatiana. "Integration of uncertainty and definition of critical thresholds for CO2 storage risk assessment". Thesis, Université Paris-Saclay (ComUE), 2015. http://www.theses.fr/2015SACLC021/document.
The main goal of the thesis is to define how the uncertainty can be accounted for in the process of riskassessment for CO2 storage and to quantify by means of numerical models the scenarii of leakage by lateralmigration and through the caprock. The chosen scenarii are quantified using the system modeling approachfor which ad-hoc predictive numerical models are developed. A probabilistic parametric uncertaintypropagation study using polynomial chaos expansion is performed. Matters of spatial variability are alsodiscussed and a comparison between homogeneous and heterogeneous representations of permeability isprovided
Castiñeiras, Carina. "Modeling and characterization of mode coupling in next generation of few mode optical fibers". Electronic Thesis or Diss., Université de Lille (2018-2021), 2018. http://www.theses.fr/2018LILUR030.
Few multimode fiber (FMF) is a class of multimode fiber. Each mode of a FMF is considered as an independent transmission channel in telecommunication field. Thus, much higher rates than conventional optical fibers could be achieved. However, this fiber can present the mode coupling and mode dispersion that can degrade the transmission performance. The mode coupling over different fiber profiles is studied in this thesis. This work is divided into two parts: i) the modeling of the mode coupling considering the fiber as a concatenation of several curved segments, and each piece is associated with a random bending radius R. ii) The measurement of localized coupling which is based on the experimental method A-S2. Using this model and these measurements, we can demonstrate the absence or the presence of coupling of a fiber exposed to micro-curvatures or a random perturbation
Fall, Bouna. "Evaluation des performances d'un système de localisation de véhicules de transports guidés fondé sur l'association d'une technique radio ULB et d'une technique de retournement temporel". Thesis, Valenciennes, 2013. http://www.theses.fr/2013VALE0028/document.
In guided transport, the precise location of trains is vital for nominal operation of the transport system. In a propagation environment such as a railway line, an effective location sensor is complex to design and validate since it must operate in the presence of many fixed and mobile obstacles constituted by the infrastructure and the trains. In this thesis, to design such a sensor, we propose the use of so-called spectral diversity techniques also found under the name of Ultra Wideband radio (UWB). In this work, the latter is also associated with the Time Reversal (TR) technique to take advantage of the complex propagation environment. The objective is to obtain a reliable and robust location of rail vehicles by focusing UWB signals to antennas or ground trains. Theoretical studies combined with simulations were performed on the properties of energy focusing of TR technique taking into account several parameters related to antennal configurations, propagation channels and the railway environment. The contribution of TR on the accuracy of the positioning system was quantified by comparing the conventional UWB positioning system alone and then, combining it with TR. The theoretical results and simulations of the proposed solution have been validated by experiments carried out in an anechoic chamber and in indoor environment
Marotta, Giuliano Sant'anna. "Análise de diferentes modelos para a correção geométrica de imagens orbitais de altíssima resolução". Universidade Federal de Viçosa, 2008. http://locus.ufv.br/handle/123456789/3707.
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Very high resolution orbital sensor images are becoming more and more frequently used for any number of applications: in the construction of databases for use in Geographic Information Systems (GIS); in the creation and revision of regional scale mapping; as support for area planning and organization in regional, municipal and urban capacities; etc. The high spatial resolution of these sensors allows for the identification of many well-defined features, and facilitates point collection for performing geometric correction on these images. However, due to this high resolution, and with the possibility of obtaining more accurate geometric corrections, great care should be taken to obtain more accurate terrestrial reference coordinates and in choosing transformation models between coordinate systems. Otherwise, the quality of the generated products may be compromised, seeing as the errors committed in reference coordinates will propagate throughout the derivative products. Consequently, to evaluate the geometric quality of these images, techniques that determine their properly assessed positional uncertainty spatially are required. The objective of the present work is to evaluate geometric corrections in the coordinates of a very high resolution orbital image, applying the following planar and spatial transformation models: affine projection, projective and modified projective. To determine parameters that correlate the image and terrestrial systems, the Method of Least Squares was employed, using the parametric model, with the purpose of adjusting image coordinates, relating these directly with homologous reference coordinates using control points that are found distributed through the image. With good precision estimates available for the reference coordinates, the quality of screen (image) coordinates and transformation parameters can be evaluated. Inverse transformations were subsequently made to obtain surface coordinates and their standard deviations. From this, using propagation of variance, an image containing the root mean square (RMS) error value in meters for each pixel was generated. With the obtained results and the spatial positional accuracy analysis, it was concluded that the three-dimensional space projective model is the most accurate of the various models presented.
Imagens provenientes de sensores orbitais de altíssima resolução vêm sendo cada vez mais utilizadas em diversos trabalhos, tais como: confecção de base de dados para uso em Sistema de Informações Geográficas (SIG); atualização e ou confecção de mapas em escalas regionais; auxílio no planejamento e organização do espaço em âmbito regional, municipal e ou urbano; etc. A alta resolução espacial desses sensores permite a identificação de muitas feições com boa definição, e proporcionam maior facilidade na coleta de pontos para a realização da correção geométrica dessas imagens. Porém, devido à alta resolução e a possibilidade de se obter resultados mais precisos na correção geométrica, deve-se ter cuidado elevado na obtenção de coordenadas terrestres de referência mais precisas e na escolha dos modelos de transformação entre sistemas de coordenadas, pois, caso contrário, a qualidade dos produtos gerados pode ser comprometida, uma vez que os erros cometidos nas coordenadas de referência se propagam para os produtos derivados. Conseqüentemente, para avaliar a qualidade geométrica dessas imagens, há a necessidade de envolver técnicas que evidenciem a incerteza posicional - devidamente avaliada - de forma espacializada. O presente trabalho tem por objetivo, avaliar a correção geométrica nas coordenadas de uma imagem orbital de altíssima resolução, aplicando os seguintes modelos planos e espaciais de transformações: modelo de projeção afim, modelo projetivo e modelo projetivo modificado. Para determinar os parâmetros que relacionam o sistema de imagem e o sistema terrestre é empregado o Método dos Mínimos Quadrados – MMQ, através do método paramétrico, com a finalidade de ajustar as coordenadas de imagem, relacionando-as diretamente com as coordenadas homólogas de referência, utilizando pontos de controle que se encontram distribuídos em toda imagem. Com a disposição de uma boa estimativa da precisão das coordenadas de referência, a qualidade das coordenadas de tela (imagem) e dos parâmetros de transformação pode ser avaliada. Posteriormente, realizam-se transformações inversas para obter as coordenadas de superfície e seus desvios padrão. Daí, através da propagação de variâncias, gera-se uma imagem contendo o valor do erro médio quadrático (RMS), em metros, para cada pixel da imagem. Consequentemente, de posse dos resultados obtidos e da análise da precisão posicional espacializada, conclui-se que o modelo projetivo utilizando o espaço tridimensional é o mais preciso quando comparado com outros modelos apresentados.
Ågren, Ola. "Finding, extracting and exploiting structure in text and hypertext". Doctoral thesis, Umeå universitet, Institutionen för datavetenskap, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-22352.
Informationsutvinning (som ofta kallas data mining även på svenska) är ett forskningsområde som hela tiden utvecklas. Det handlar om att använda datorer för att hitta mönster i stora mängder data, alternativt förutsäga framtida data utifrån redan tillgänglig data. Eftersom det samtidigt produceras mer och mer data varje år ställer detta högre och högre krav på effektiviteten hos de algoritmer som används för att hitta eller använda informationen inom rimlig tid. Denna avhandling handlar om att extrahera information från semi-strukturerad data, att hitta strukturer i stora diskreta datamängder och att på ett effektivt sätt rangordna webbsidor utifrån ett ämnesbaserat perspektiv. Den informationsextraktion som beskrivs handlar om stöd för att hålla både dokumentationen och källkoden uppdaterad samtidigt. Vår lösning på detta problem är att låta delar av dokumentationen (främst algoritmbeskrivningen) ligga som blockkommentarer i källkoden och extrahera dessa automatiskt med ett verktyg. De strukturer som hittas av våra algoritmer för strukturextraktion är i form av underordnanden, exempelvis att ett visst nyckelord är mer generellt än ett annat. Dessa samband kan utnyttjas för att skapa större strukturer i form av hierarkier eller riktade grafer, eftersom underordnandena är transitiva. Det verktyg som vi har tagit fram har främst använts för att skapa indata till ett informationsutvinningssystem samt för att kunna visualisera indatan. Huvuddelen av den forskning som beskrivs i denna avhandling har dock handlat om att kunna rangordna webbsidor utifrån både deras innehåll och länkarna som finns mellan dem. Vi har skapat ett antal algoritmer och visat hur de beter sig i jämförelse med andra algoritmer som används idag. Dessa jämförelser har huvudsakligen handlat om konvergenshastighet, algoritmernas stabilitet givet osäker data och slutligen hur relevant algoritmernas svarsmängder har ansetts vara utifrån användarnas perspektiv. Forskningen har varit inriktad på effektiva algoritmer för att hämta in och hantera stora datamängder med diskreta eller textbaserade data. I avhandlingen presenterar vi även ett förslag till ett system av verktyg som arbetar tillsammans på en databas bestående av “fingeravtryck” och annan meta-data om de saker som indexerats i databasen. Denna data kan sedan användas av diverse algoritmer för att utöka värdet hos det som finns i databasen eller för att effektivt kunna hitta rätt information.
AlgExt, CHiC, ProT
Poh, Seng Cheong Telly. "Simulations of diversity techniques for urban UAV data links". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Dec%5FPoh.pdf.
Collier, Joanne Ruth. "Spatial and propagating patterns in embyrology". Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389214.
Cheron, Elie. "Guides d'ondes et transport dans les milieux désordonnés : effets de la symétrie et de la localisation". Thesis, Le Mans, 2019. http://www.theses.fr/2019LEMA1017.
This thesis focuses on the wave propagation in disordered waveguides. First, we introduce the basic tools and concepts in order to present the different transport regimes and phenomena related to coherent effects (such as universal conductance fluctuations, enhanced backscattering or Anderson's localization). Beside the remarkable phenomena associated to diffuse transport, the coherent effects are also noticeable when the spatial distribution of the scatterers displays symmetries. The second part is dedicated to the observation of a significant and broadband enhancement in transmission through opaque barriers. The sensitivity of this phenomenon to symmetry defects is discussed in Chapter 4. Limitations due to absorption, which are always present in an experimental context, and localization are also inspected. The fourth chapter focuses on one of the signatures of the localization regime: the propagation within these insulating media is insensitive to the source. We present some special cases in which this property is broken. Finally, several preliminary studies related to other propagation phenomena in complex media are discussed as perspectives for this work
Cao, Qian. "Propagation Dynamics of Spatio-Temporal Wave Packets". University of Dayton / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1405693684.