Unconventional strong pinning in the low temperature phase of U_.9725Th_.0275Be_13

We investigated low field vortex dynamics in a single crystal of U_.9725Th_.0275Be_13. We found a sharp transition in the vortex creep rate at the lower transition temperature T_c2, coincident with the second jump in the specific heat. In the high-temperature phase, rather strong creep rates are observed. In the low temperature phase, the rates drop to undetectabely low levels. This behaviour indicates that a very strong pinning mechanism is present in the low temperature phase of U_.9725Th_.0275Be_13, which could be explained by the existence of domain walls, separating discreetly degenerate states of a superconductor, that can sustain fractional vortices and thus act as very strong pinning centers.Comment: 2 pages, 2 figures, accepted in PhysicaB, LT2

Contributions à la localisation intra-muros. De la modélisation à la calibration théorique et pratique d'estimateurs

Préfigurant la prochaine grande étape dans le domaine de la navigation, la géolocalisation intra-muros est un domaine de recherche très actif depuis quelques années. Alors que la géolocalisation est entrée dans le quotidien de nombreux professionnels et particuliers avec, notamment, le guidage routier assisté, les besoins d'étendre les applications à l'intérieur se font de plus en plus pressants. Cependant, les systèmes existants se heurtent à des contraintes techniques bien supérieures à celles rencontrées à l'extérieur, la faute, notamment, à la propagation chaotique des ondes électromagnétiques dans les environnements confinés et inhomogènes. Nous proposons dans ce manuscrit une approche statistique du problème de géolocalisation d'un mobile à l'intérieur d'un bâtiment utilisant les ondes WiFi environnantes. Ce manuscrit s'articule autour de deux questions centrales : celle de la détermination des cartes de propagation des ondes WiFi dans un bâtiment donné et celle de la construction d'estimateurs des positions du mobile à l'aide de ces cartes de propagation. Le cadre statistique utilisé dans cette thèse afin de répondre à ces questions est celui des modèles de Markov cachés. Nous proposons notamment, dans un cadre paramétrique, une méthode d'inférence permettant l'estimation en ligne des cartes de propagation, sur la base des informations relevées par le mobile. Dans un cadre non-paramétrique, nous avons étudié la possibilité d'estimer les cartes de propagation considérées comme simple fonction régulière sur l'environnement à géolocaliser. Nos résultats sur l'estimation non paramétrique dans les modèles de Markov cachés permettent d'exhiber un estimateur des fonctions de propagation dont la consistance est établie dans un cadre général. La dernière partie du manuscrit porte sur l'estimation de l'arbre de contextes dans les modèles de Markov cachés à longueur variable.Foreshadowing the next big step in the field of navigation, indoor geolocation has been a very active field of research in the last few years. While geolocation entered the life of many individuals and professionals, particularly through assisted navigation systems on roads, needs to extend the applications inside the buildings are more and more present. However, existing systems face many more technical constraints than those encountered outside, including the chaotic propagation of electromagnetic waves in confined and inhomogeneous environments. In this manuscript, we propose a statistical approach to the problem of geolocation of a mobile device inside a building, using the WiFi surrounding waves. This manuscript focuses on two central issues: the determination of WiFi wave propagation maps inside a building and the construction of estimators of the mobile's positions using these propagation maps. The statistical framework used in this thesis to answer these questions is that of hidden Markov models. We propose, in a parametric framework, an inference method for the online estimation of the propagation maps, on the basis of the informations reported by the mobile. In a nonparametric framework, we investigated the possibility of estimating the propagation maps considered as a single regular function on the environment that we wish to geolocate. Our results on the nonparametric estimation in hidden Markov models make it possible to produce estimators of the propagation functions whose consistency is established in a general framework. The last part of the manuscript deals with the estimation of the context tree in variable length hidden Markov models.PARIS11-SCD-Bib. électronique (914719901) / SudocSudocFranceF

The Use of Deferred Dispositions in Domestic Violence and Sexual Assault Cases in Maine

This report summarizes the findings from an examination of how deferred disposition is used in Maine. This option typically involves the accused pleading guilty to a charge and agreeing to meet certain conditions over a period of time, commonly one year. If conditions are met, the case is either dismissed or the defendant is found guilty of a lesser crime than the one with which he/she was originally charged. A deferred disposition can also include a more favorable outcome for the defendant (eg., a fine instead of jail). If the terms are not met, the defendant is convicted of the charge to which he/she pled guilty. There are a number of reasons for using deferred dispositions, including the desire to hold offenders accountable while sparing more stringent sanctions that have deleterious effects on recidivism. Deferral may also be used when victims are reluctant to cooperate with the prosecution, and it may be used as a solution to overcrowding. This study was conducted by the Maine Statistical Analysis Center (Maine SAC) with the cooperation of the Maine Coalition Sexual Against Assault (MECASA) and the Maine Coalition to End Domestic Violence (MCEDV) to ascertain the impact of deferred disposition on future criminal activity, specifically among offenders who are given deferred dispositions for domestic violence and sexual assault offenses. Data for this study were obtained from the Maine District Attorneys Technical Services (MEDATS), the electronic repository for Maine district attorney data, and include variables related to deferral as well as prior and recidivating events. Because the database is specific to Maine, any prior or recidivating cases that occurred elsewhere are not captured in this study. Analysis was limited to cases deferred between 2014 and 2019, cases that were closed, and cases involving defendants 18 years of age and older at time of deferral. Because individuals can be deferred more than once, some defendants appear in the dataset more than onc