41 |
Testování lokátoru poruch na nesymetrickém vedení / Earth fault locator testing on the model of unsymmetrical linesKohůt, Miroslav January 2016 (has links)
This master’s thesis is about earth fault locator testing on the model of unsymmetrical lines. The introductory part of thesis describes the function of the selected locator, mainly for the used calculation algorithm of fault location, options setting of fault locator and connection of the locator to the network. Master’s thesis in its practical part deals, with the setting fault locator for a particular test system on the model of the MV line and implementation of selected testing on the model unsymmetrical lines. The first part of the testing is focusing on verify the accuracy locator on an unsymmetrical line. The second test is then designed for obtaining the most accurate information on the distance of the fault, which fault locator can give. The final part is focused on verification algorithm for more accurate calculation of the fault location.
|
42 |
Transverse Spin and Classical Gluon Fields: Combining Two Perspectives on Hadronic StructureSievert, Matthew D. 10 October 2014 (has links)
No description available.
|
43 |
Cross-Country Faults in Resonant-Earthed Networks / Dubbla Enfasiga Jordfel i Spoljordade NätGomes Guerreiro, Gabriel Miguel January 2020 (has links)
Reliability requirements for power systems have been constantly increasing, as customers of electric power desire high power availability. In order to improve continuity of supply in medium voltage (MV) networks, utilities in many countries in Europe, North/South America and Oceania use resonant earthing and allow the operation of the network during a single phasetoearth fault for periods from several seconds up to several hours, since the earthfault current at the fault point in such systems is considerably reduced and is unlikely to damage equipment or create hazardous voltages for people or livestock. Due to the neutral potential displacement during the phasetoearth fault, the healthy phases can rise up to 1.73 times the nominal values in the entire network, overstressing insulation and increasing the probability of a second fault from another phasetoearth fault somewhere in the network. The situation of two simultaneously active phasetoearth faults on different phases at different locations in a network is commonly called a crosscountry or doubleearth fault. The current through the earth then becomes many times higher than in case of a single phasetoearth fault in a resonantearthed network. Few studies about CrossCountry faults in MV systems have been done so far, particularly with real fault data and simulations. This thesis has as main objectives to: improve understanding of how crosscountry faults behave in resonantearthed systems; show how the double fault situation can be analytically calculated; and study what difficulties these faults can pose to traditional distance protection. This is done by: analyzing recordings of real faults, obtained from utilities in Scandinavia; modelling the fault situations analytically; simulating such systems with real system data; and examining in particular how faultedphase selection and distance protection behave during these faults. The developed mathematical model was compared with a simple simulated system. The results showed that the modelling produces accurate results. Analysis of the real faults showed that crosscountry faults cannot be equated directly to more traditional singlephase or doublephase faults on particular feeders, since voltages and currents can behave in atypical manners. Finally, during the comprehensive simulations of such network, limitations of traditional distance protection were identified. Phasetophase loops can face difficulties in properly detecting crosscountry faults even when one of the two simultaneous faults is relatively close to the measuring point. Phasetoearth loops can only be reliable when faults are solid or with very low resistance and in conditions where zero sequence current is present, while for multiple infeeds can also face difficulties. / Kraven på elkraftsystemets pålitlighet ökar hela tiden, då kundernas krav på tillgänglighet hela tiden stiger. Som ett led i att förbättra leveranssäkerheten på mellanspänningsnivån har ett flertal elnätsbolag i Europa, Nord och Sydamerika samt Oceanien börjat använda spoljordning. Genom detta kan jordfel under drift tillåtas, på allt ifrån sekundbasis till timmar. På detta sätt undviks driftavbrott vid jordfel. Spoljordning gör att jordfelsströmmen reduceras vilket minimerar risken för person, djur och egendomsskador. Under ett enfasigt jordfel höjs spänningen i de två opåverkade faserna till maximalt 1.73 gånger den nominella spänningen, detta i hela det aktuella nätet. Spänningshöjningen riskerar att ge skador på isolaringen, vilket gör att risken för uppkomsten av ett andra jordfel någonstans i samma nätavsnitt ökar. Att två enfasiga jordfel på olika platser inträffar samtidigt i samma nät, kallas dubbelt jordfel, på engelska crosscountry fault. Strömmen genom jord i ett spoljordat nät blir i detta fallet mycket högre än för ett enfasigt jordfel. Än så länge har bara ett fåtal studier med verkliga data och simuleringar gällande dubbla jordfel på mellanspänningsnivå utförts. Detta examensarbete syftar till att: förbättra förståelsen för hur dubbla jordfel uppkommer i spoljordade nät; beskriva hur dubbla jordfel kan beräknas analytiskt; och visa på vilka svårigheter dubbla jordfel kan ge för distansskydd. Detta görs genom: att analysera verkliga fel uppkomna i Skandinavien; analytisk modellering av dessa situationer; simulering med data från verkliga elnät; undersökning av hur felbehäftade delar och dess distansskydd beter sig vid fel. Den utvecklade matematiska modelleringsmetoden är jämförd med ett enkelt system som var simulerat, och resultaten av jämförelsen visar att modellen ger ett överensstämmande och noggrant resultat. Analysen av verkliga fel visar att dubbla jordfel inte direkt kan likställas med traditionella enfas- eller tvåfasfel för ett och samma utgående fack, då spänning och strömmar kan ha olika beteende. Avslutningsvis kunde begränsningar hos traditionella distansskydd upptäckas, tack var en omfattande simulering av nyss nämnda elnät. Fas- fas slingan kan se svårigheter att detektera dubbla fel även när ett av dessa två är nära till mätpunkten. Fas- jord slingan är endast pålitlig när felresistansen är försumbar, eller i fall där felresistansen är låg, samt i fall när nollföljdsströmmen är närvarande. Flera felströmsinmatningar kan likaså ställa till svårigheter.
|
44 |
Re-embodying jurisprudence: using theatre and multimedia arts-based methods to support critical thinking, feeling and transformation in lawDhaliwal, Manpreet (Preeti) Kaur 01 May 2017 (has links)
This thesis offers theoretical and practical explorations of how multimedia arts-based methods and embodied storytelling support critical and transformative understandings of law. Using theatre as both subject and method, the author demonstrates how laws live in bodies, with a focus on race, whiteness, migration and the Komagata Maru. Drawing on various theatre practices as well as critical race, feminist and performance scholarship, the author calls for a new way of interacting with law: jurisprudential theatre. Jurisprudential theatre is a method that employs autobiography, utopian visioning, legal research and audience involvement to create plays that examine existing law while filling affective spaces that existing law neglects. This method builds an alternate archive that supplements existing laws but can also be used to study them. The author explains the method through a performance art piece titled Re-embodying. She then uses jurisprudential theatre to examine the legal history of the Komagata Maru through case law and two play texts, all of which lay the groundwork for the method’s application in the first draft of a play titled Eustitia.
“Rather than laying my life and research out in a chronological, linear fashion with smooth transitions, this thesis blends scholarly, autobiographical, episodic and creative writing – sometimes abrupt, sometimes guided. This framework takes you on a journey to the Komagata Maru through my experiences and understandings of race, whiteness, law and trauma. This thesis asks you to bear witness while offering you life stories, performance art, the draft of a play, images and academic prose. I invite you to join me in a creative and performative process that will move you beyond the confines of the page to online worlds and internal realms. Why? To study and experience (as best we can in a text-based relationship) the internal and embodied consequences of law alongside its external, material and relational impacts.” / Graduate / 0465 / 0398 / 0631 / dhaliwal.preeti@gmail.com
|
45 |
Les effets politiques des spectacles médiatiques d’immigration : une analyse critique des discours de la presse écrite canadienne sur l’arrivée du MV Sun SeaBlondin-Gravel, Raphaëlle 01 1900 (has links)
Ce mémoire de maîtrise porte sur les effets politiques des discours médiatiques sur la gouvernance et la régulation des demandeurs d’asile au Canada. À travers une analyse critique des discours de la presse écrite canadienne au sujet de l’arrivée en août 2010 de 492 requérants du statut de réfugié à bord du bateau MV Sun Sea en Colombie-Britannique, l’auteure identifie les principales interprétations de cet évènement ainsi que leurs relations avec la mise en place subséquente de mesures visant à restreindre les possibilités d’accès non autorisés au Canada, notamment par la création d’une nouvelle catégorisation discriminatoire des demandeurs d’asile.
L’analyse révèle l’articulation de ces discours autour de deux thématiques distinctes, mais interreliées. Tandis que les discours sécuritaires associent l’arrivée non autorisée des demandeurs d’asile à une menace à la sécurité de la nation, les discours humanitaires interprètent cet évènement comme une demande d’aide de la part d’un groupe de personnes menacées par leur propre pays. Ce mémoire propose une analyse multidimensionnelle de ces deux cadrages et de leurs effets politiques qui considère leurs dimensions discursives, contextuelles et affectives. L’analyse démontre comment ces deux discours en apparence conflictuels partagent en fait un même sous-texte racial qui fait de ce type de spectacle médiatique un dispositif clé de « gouvernementalité racialisée de l’immigration » (Bilge, 2012, 2013). / This master’s thesis addresses the political effects of media discourses on the governance and regulation of asylum seekers in Canada. Through a critical analysis of the Canadian press discourses around the arrival on august 2010 of 492 asylum seekers on the ship MV Sun Sea in British Columbia, the author identify the main interpretations of this event, along with their relations with the subsequent establishment of restrictive measures designed to prevent the possibilities of unauthorised arrivals to Canada, especially through the creation of a new discriminatory categorisation for asylum seekers.
Analysis reveals the articulation of these discourses around two distinctive but interconnected themes. While security discourses associate the unauthorised arrival of the asylum seekers as a threat to national security, humanitarian discourses interpret this event as a request for help from a group of persons threatened by their own country. This thesis proposes a multidimensional analysis of these framings and of their political effects that considers their discursive, contextual and affective dimensions. The analysis reveals that these two apparently opposed discourses actually share the same racial subtext making this kind of media spectacle a key device of the “racialised governementality of immigration” (Bilge, 2012, 2013).
|
46 |
Power line communications for the electrical utility: physical layer design and channel modelingAquilué de Pedro, Ricardo 16 July 2008 (has links)
El món de les comunicacions per la xarxa elèctrica (CXE) pot ser dividit en tres grans tipus: CXE en baix voltatge (CXE-BV), en mig voltatge (CXE-MV) i en alt voltatge (CXE-AV). En aquests últims anys, les CXE-BV han atret una gran expectació, ja que les seves capacitats han fet d'aquesta tecnologia una bona opció com alternativa pel bucle local d'accés i pel desplegament de xarxes d'àrea local, focalitzades aquestes últimes en l'entorn domèstic. A més, les CXE-BV inclouen un conjunt d'aplicacions de baixa velocitat orientades a l'operador, com la lectura automàtica de comptadors (LAC), distribució de càrrega, facturació dinàmica, etc. Per altra banda, les CXE-MV i CXE-AV, històricament lligades a tasques de telecontrol i teleprotecció, s'estan començant a considerar com un canal de comunicacions eficient i fiable. El desenvolupament de sistemes digitals i els esforços d'estandardització estan fent d'aquests canals un medi atractiu per a que els operadors elèctrics ofereixin serveis de comunicacions, ja que no necessiten invertir en infraestructura perquè la xarxa elèctrica ja està desplegada.En aquesta Tesi s'introduiran i es comentaran les particularitats de les tres xarxes elèctriques, després, es mostraran al lector les solucions tecnològiques existents pels canals de BV basats en la norma Europea CENELEC així com pels canals d'AV, mostrant que els sistemes actuals de LAC ofereixen una diversitat freqüencial molt baixa i que els mòdems CXE-AV estan ancorats en estendards antiquats.Aquest treball es mou per les tres topologies de la xarxa, particularment, en aplicacions orientades a la banda CENELEC, en mesura i modelat de canal, i en mesura i disseny del nivell físic per sistemes CXE-BV, CXE-MV i CXE-AV respectivament. Els sistemes actuals que exploten la banda CENELEC ofereixen mecanismes d'explotació de la diversitat freqüencial del canal molt limitats o nuls, donant lloc a una baixa robustesa en front a interferències i soroll de fons acolorit. Aquest treball proposa un esquema de modulació multiportadora que, mantenint una complexitat baixa, ofereix unes altes prestacions permetent un bon nivell d'explotació de la selectivitat freqüencial. Per al que a CXE-MV respecta, aquesta Tesi desenvolupa un model de canal determinístic-estadístic pels anells urbans de distribució de potència i, finalment, en sistemes CXE-AV, aquest treball proposa, basat en mesures de canal i proves de camp, un nivell físic de banda ampla capaç de incrementar la velocitat de comunicació mentre manté una baixa densitat espectral de potència limitant així la interferència a altres sistemes.PARAULES CLAU: Power line communications (PLC), low voltage (LV), medium voltage (MV), high voltage (HV), automatic meter reading (AMR), orthogonal frequency division multiplexing (OFDM), multicarrier spread spectrum (MC-SS), communication system design, channel measurements, channel modeling, scattering parameters. / El mundo de las comunicaciones por la red eléctrica (CRE) puede ser dividido en tres grandes tipos: CRE en bajo voltaje (CRE-BV), en medio voltaje (CRE-MV) y en alto voltaje (CRE-AV). En estos últimos años, las CRE-BV han atraído una gran expectación, ya que sus capacidades han hecho de esta tecnología una buena opción como alternativa para el bucle local de acceso y para el despliegue de redes de área local, focalizadas estas últimas en el entorno doméstico. Además, las CRE-BV incluyen un conjunto de aplicaciones de baja velocidad orientadas al operador como la lectura automática de contadores (LAC), distribución de carga, facturación dinámica, etc. Por otro lado, las CRE-MV y CRE-AV, históricamente ligadas a tareas de telecontrol y teleprotección, se están empezando a considerar como un canal de comunicaciones eficiente y fiable. El desarrollo de sistemas digitales y los esfuerzos de estandarización están haciendo de estos canales un medio atractivo para que los operadores eléctricos ofrezcan servicios de comunicaciones, ya que no necesitan invertir en infraestructura porque la red eléctrica ya está desplegada.En esta Tesis se introducirán y se comentarán las particularidades de las tres redes eléctricas, luego, se mostrarán al lector las soluciones tecnológicas existentes para los canales de BV basados en la norma Europea CENELEC así como para los canales de AV, mostrando que los sistemas actuales de LAC ofrecen una diversidad frecuencial muy baja y que los módems CRE-AV están anclados en estándares anticuados.Este trabajo se mueve por las tres topologías de red, particularmente, en aplicaciones orientadas a la banda CENELEC, en medida y modelado de canal, y en medida y diseño del nivel físico para sistemas CRE-BV, CRE-MV y CRE-AV respectivamente. Los sistemas actuales que explotan la banda CENELEC ofrecen mecanismos de explotación de la diversidad frecuencial del canal muy limitados o nulos, dando lugar a una escasa robustez frente a interferencias y ruido de fondo coloreado. Este trabajo propone un esquema de modulación multiportadora que, manteniendo una complejidad baja, ofrece unas altas prestaciones permitiendo un buen nivel de explotación de la selectividad frecuencial. Por lo que a CRE-MV respecta, esta Tesis desarrolla un modelo de canal determinístico-estadístico para los anillos urbanos de distribución de potencia y, finalmente, en sistemas de CRE-AV, este trabajo propone, basado en medidas de canal y pruebas de campo, un nivel físico de banda ancha capaz de incrementar la velocidad de comunicación mientras mantiene una baja densidad espectral de potencia limitando así la interferencia a otros sistemas.PALABRAS CLAVE: Power line communications (PLC), low voltage (LV), medium voltage (MV), high voltage (HV), automatic meter reading (AMR), orthogonal frequency division multiplexing (OFDM), multicarrier spread spectrum (MC-SS), communication system design, channel measurements, channel modeling, scattering parameters. / The world of Power line communications (PLC) can be divided into three main types: low voltage PLC (LV-PLC), medium voltage PLC (MV-PLC) and high voltage PLC (HV-PLC). These last years, LV-PLC has attracted a great expectation since its wideband capabilities has made this technology a suitable choice for last-mile access and in-home communications. Moreover, LV-PLC also includes a utility oriented low frequency and low speed applications, such as automatic meter reading (AMR), load distribution, dynamic billing and so on. On the other hand, MV-PLC and HV-PLC, historically oriented to teleprotection and telecontrol tasks, are being considered as a reliable communication channel. The development of digital equipment and the standardization efforts are making those channels an attractive medium for electrical utilities telecommunications services, since the network, as well as in LV-PLC, is already deployed. In this PhD dissertation, the three different PLC topologies are reviewed and the different communications techniques in such channels exposed. Then, a deep technological review of existing AMR solutions for the European CENELEC band, as well as HV-PLC systems is given, showing that existing AMR systems deliver low frequency diversity and HV-PLC systems are anchored in old fashioned standards.This work walks around the three topologies, specifically, CENELEC band utility oriented applications, channel measurement and modeling and channel measurement and physical layer design, regarding LV-PLC, MV-PLC and HV-PLC respectively. Existing CENELEC compliant systems deliver low or none frequency diversity mechanisms, yielding in a low robustness against colored noise and interference. This work propose a multicarrier based physical layer approach that, while keeping the complexity low, delivers high performance allowing a great level of frequency diversity. Focusing on MV-PLC, a hybrid deterministic-statistical channel model for urban underground rings is developed and, finally, in HV-PLC systems, this work proposes, based on measurements and field tests, a wideband physical layer in order to increase data rate while keeping low both the power spectral density and possible interference to other systems.KEYWORDS: Power line communications (PLC), low voltage (LV), medium voltage (MV), high voltage (HV), automatic meter reading (AMR), orthogonal frequency division multiplexing (OFDM), multicarrier spread spectrum (MC-SS), communication system design, channel measurements, channel modeling, scattering parameters.
|
47 |
Stanovení zóny havarijního plánování dle zákona č. 59/2006 Sb., o prevenci závažných havárií pro objekt ČEPRO, a.s. {--} sklad Včelná. / The sector determination of emergency plan for ČEPRO, Corp. - store Včelná, by act No. 59/2006 Sb., about the prevention of hard accidents.PAULŮ, Zuzana January 2010 (has links)
ABSTRACT For my diploma thesis I have chosen a topic focusing on the setting of the zone of emergency planning in accordance with Act No. 59/2006 on prevention of major accidents, for the facility of ČEPRO Inc., the storage area of Včelná. The topic has been chosen for several reasons {--} I consider it interesting, and I am convinced that it is absolutely essential to create a zone of emergency planning for the above mentioned complex. A major accident is defined under Act 59/2006 of Collection, on prevention of major accidents, as an extraordinary, partly or completely unmanageable, terminable and spatially limited event, for example a major leakage, fire or explosion, which has already appeared or whose occurrence is imminent in connection with using the venue or facility in which a dangerous substance is produced, processed, prepared or stored, and which leads to a major jeopardy or to a major impact upon life and health of people, livestock and environment or financial damage. The first part of the diploma thesis presents the legislation concerning the setting the zone of emergency planning. Furthermore, the legislation concerning the issue in selected countries of the European Union is mentioned. The description of the storage facility belonging to the company ČEPRO Inc. in Včelná in the town of České Budějovice follows. The second part of the thesis focuses on the setting of the zone of emergency planning for the ČEPRO company in Včelná, and the evaluation of the questionnaires submitted to residents living in the surroundings of this storage facility. The discussion of the issues given above is presented in the third part of the diploma thesis. The following hypotheses were set and analysed {--} whether the emergency plan for the ČEPRO Inc. in Včelná is sufficiently elaborated and whether the residents living in the surroundings of ČEPRO have become sufficiently familiar with a potential danger.
|
48 |
Contribution des technologies CPL et sans fil à la supervision des réseaux de distribution d'électricité / Contribution of PLC and wireless technologies to supervision of electric distribution networksLefort, Romain 03 February 2015 (has links)
Le déploiement d'une infrastructure de supervision permet une gestion plus intelligente des réseaux de distribution d'électricité comparé à un renforcement traditionnel pour répondre aux nouveaux enjeux de la maitrise de l'énergie (Consommations, EnR, VE, ...). Pour acheminer les données, les Courants Porteurs en Ligne (CPL) possèdent un atout majeur. En effet, cette technologie permet de superposer un signal de plus haute fréquence au signal électrique 50/60 Hz. Toutefois, le support de transmission est difficile et non maîtrisable. Ces travaux de recherche ont pour objectif d'apporter une contribution à cette problématique par l'élaboration d'une plateforme de simulation des réseaux pour des fréquences allant jusqu'à 1 MHz dans un but de transmission de données. Des éléments clés des réseaux sont traités de façon séparés puis assemblés pour estimer les performances des CPL « Outdoor » actuels. La variation du comportement des réseaux en fonction du temps et de la fréquence, en particulier des perturbations en tête d'installation clients sur 24h est étudiée. Les transformateurs entre les réseaux HTA et BT sont modélisés sous la forme d'un « modèle à constantes localisées » et d'un « modèle boite noire ». Les deux modèles sont appliqués sur un transformateur H61 100 kVA. Par la suite, une modélisation des câbles de distribution est proposée sous forme d'un « modèle cascadé ». Celle-ci est appliquée sur un câble souterrain BT. Chaque modèle est obtenu à l'aide de mesures d'impédances, et validé par des mesures de transmissions. Pour compléter, une étude préliminaire sur les communications radio mobile est réalisée pour la supervision des réseaux de distribution. / Establishing a supervisory infrastructure allows a better smart management than an expensive strengthening of distribution network to respond to new constraints at the energies control (Consumption, REN, EV ...). To transmit data, Power Line Communication (PLC) technologies present an advantage in this context. In fact, it enables a superposition of High Frequency (HF) signals on electrical signal 50/60 Hz. However, electric networks have not been developed to this application because of difficult propagation conditions. This research work makes a contribution to develop a simulation platform in objective to transmit data to 1 MHz. In first time, each network element is studied singly and in second time, together, to estimate "Outdoor PLC" transmission performance. The first element studied is the networks variation in function of frequency and time. Several 24h disturbance measurements on LV customers are presented. The second element is the transformers which established connection between Medium Voltage (MV) and Low Voltage (LV). The proposed modeling method is based on a "lumped model" and a "black box model". These models are applied to a 100 kVA H61 transformer most commonly used by French distribution system operator in rural and suburban networks. The third element is the power line used in MV and LV networks. The proposed modeling method is based on a "cascaded model" from the theory of transmission line. This model is applied to one power line used in LV underground network. Each model is obtained from various impedance measurements. To complete, an introductory study on mobile radio communication is performed to remote network distribution.
|
49 |
Kontejnerové NN/VN rozvodny / Containerized Low-Voltage/ Middle-Voltage SubstationsMarcol, Michal January 2013 (has links)
As it is already apparent from a title of my work, I will be engaged in proposal of container VN/NN distributor using components from company ABB. This work will be after final making also used by company ABB to simplify procedure of proposal of any kind of container distributor. In my labor I will be generally deal with individual products, which will after that be used in distributor. Next I will be engaged in particular making of distributor, which should be made. The distributor will be designed for a separate part of the transformer and for a transformer as a unit, which is not separated from substation.
|
50 |
Caractérisation des limites fondamentales de l'erreur quadratique moyenne pour l'estimation de signaux comportant des points de rupture / Characterization of mean squared error fundamental limitations in parameter estimation of signals with change-pointsBacharach, Lucien 28 September 2018 (has links)
Cette thèse porte sur l'étude des performances d'estimateurs en traitement du signal, et s'attache en particulier à étudier les bornes inférieures de l'erreur quadratique moyenne (EQM) pour l'estimation de points de rupture, afin de caractériser le comportement d'estimateurs, tels que celui du maximum de vraisemblance (dans le contexte fréquentiste), mais surtout du maximum a posteriori ou de la moyenne conditionnelle (dans le contexte bayésien). La difficulté majeure provient du fait que, pour un signal échantillonné, les paramètres d'intérêt (à savoir les points de rupture) appartiennent à un espace discret. En conséquence, les résultats asymptotiques classiques (comme la normalité asymptotique du maximum de vraisemblance) ou la borne de Cramér-Rao ne s'appliquent plus. Quelques résultats sur la distribution asymptotique du maximum de vraisemblance provenant de la communauté mathématique sont actuellement disponibles, mais leur applicabilité à des problèmes pratiques de traitement du signal n'est pas immédiate. Si l'on décide de concentrer nos efforts sur l'EQM des estimateurs comme indicateur de performance, un travail important autour des bornes inférieures de l'EQM a été réalisé ces dernières années. Plusieurs études ont ainsi permis de proposer des inégalités plus précises que la borne de Cramér-Rao. Ces dernières jouissent en outre de conditions de régularité plus faibles, et ce, même en régime non asymptotique, permettant ainsi de délimiter la plage de fonctionnement optimal des estimateurs. Le but de cette thèse est, d'une part, de compléter la caractérisation de la zone asymptotique (en particulier lorsque le rapport signal sur bruit est élevé et/ou pour un nombre d'observations infini) dans un contexte d'estimation de points de rupture. D'autre part, le but est de donner les limites fondamentales de l'EQM d'un estimateur dans la plage non asymptotique. Les outils utilisés ici sont les bornes inférieures de l’EQM de la famille Weiss-Weinstein qui est déjà connue pour être plus précise que la borne de Cramér-Rao dans les contextes, entre autres, de l’analyse spectrale et du traitement d’antenne. Nous fournissons une forme compacte de cette famille dans le cas d’un seul et de plusieurs points de ruptures puis, nous étendons notre analyse aux cas où les paramètres des distributions sont inconnus. Nous fournissons également une analyse de la robustesse de cette famille vis-à-vis des lois a priori utilisées dans nos modèles. Enfin, nous appliquons ces bornes à plusieurs problèmes pratiques : données gaussiennes, poissonniennes et processus exponentiels. / This thesis deals with the study of estimators' performance in signal processing. The focus is the analysis of the lower bounds on the Mean Square Error (MSE) for abrupt change-point estimation. Such tools will help to characterize performance of maximum likelihood estimator in the frequentist context but also maximum a posteriori and conditional mean estimators in the Bayesian context. The main difficulty comes from the fact that, when dealing with sampled signals, the parameters of interest (i.e., the change points) lie on a discrete space. Consequently, the classical large sample theory results (e.g., asymptotic normality of the maximum likelihood estimator) or the Cramér-Rao bound do not apply. Some results concerning the asymptotic distribution of the maximum likelihood only are available in the mathematics literature but are currently of limited interest for practical signal processing problems. When the MSE of estimators is chosen as performance criterion, an important amount of work has been provided concerning lower bounds on the MSE in the last years. Then, several studies have proposed new inequalities leading to tighter lower bounds in comparison with the Cramér-Rao bound. These new lower bounds have less regularity conditions and are able to handle estimators’ MSE behavior in both asymptotic and non-asymptotic areas. The goal of this thesis is to complete previous results on lower bounds in the asymptotic area (i.e. when the number of samples and/or the signal-to-noise ratio is high) for change-point estimation but, also, to provide an analysis in the non-asymptotic region. The tools used here will be the lower bounds of the Weiss-Weinstein family which are already known in signal processing to outperform the Cramér-Rao bound for applications such as spectral analysis or array processing. A closed-form expression of this family is provided for a single and multiple change points and some extensions are given when the parameters of the distributions on each segment are unknown. An analysis in terms of robustness with respect to the prior influence on our models is also provided. Finally, we apply our results to specific problems such as: Gaussian data, Poisson data and exponentially distributed data.
|
Page generated in 0.0844 seconds