Uniqueness and existence of an outgoing solution of Helmholtz problem using Green's formula

In this article,  first we present a new approach based on Green's formula, to describe the uniqueness and existence of the solution of the Helmholtz equation. By imposing at infinity the outgoing wave condition or also called Sommerfeld radiation condition, we show how it is possible to define in a natural way an outgoing solution of the Helmholtz equation based on physical arguments. Then, we resolve the exterior problem, given by the scattering of time-harmonic acoustic wave by sound-soft obstacle, which leads to find a radiating solution  to the Helmholtz equation

Controlling access to personal data through Accredited Symmetrically Private Information Retrieval

With the digitization of society and the continuous migration of services to the electronic world, individuals have lost significant control over their data. In this paper, we consider the problem of protecting personal information according to privacy policies defined by the data subjects. More specifically, we propose a new primitive allowing a data subject to decide when, how, and by whom his data can be accessed, without the database manager learning anything about his identity, at the time the data is retrieved. The proposed solution, which we call Accredited SPIR, combines symmetrically private information retrieval and privacy-preserving digital credentials. We present three constructions based on the discrete logarithm and RSA problems. Despite the added privacy safeguards, the extra cost incurred by our constructions is negligeable compared to that of the underlying building blocks

Use of mobile agents in a federated identity structure

ABSTRAC

Etude d'une méthode de volumes finis pour la résolution des équations de Maxwell en deux dimensions d'espace sur des maillages quelconques et couplage avec l'équation de Vlasov

Nous développons et étudions une méthode de volumes finis pour résoudre le système de Maxwell instationnaire bidimensionnel sur des maillages presque quelconques (non-conformes, non-convexes, aplatis..). Nous commençons par la construction du schéma, qui est basé sur l'utilisation des opérateurs discrets de la méthode DDFV et sur un choix pertinent pour la discrétisation des conditions initiales et des conditions aux limites. Ensuite, nous prouvons que ce schéma préserve localement la condition de divergence, que l'énergie électromagnétique discrète est conservée ou décroissante (selon les conditions aux limites) et qu'elle est positive sous condition CFL. Nous montrons aussi la stabilité du schéma sous condition CFL et sa convergence dans les cas de champs réguliers et non réguliers. Ces résultats sont ensuite validés, numériquement avec quelques cas tests sur différents types de maillages. Nous vérifions aussi que l'utilisation des maillages non conformes n'amplifie pas les réflexions parasites. Enfin nous couplons ce schéma avec une méthode PIC pour résoudre le système de Maxwell-Vlasov. Nous calculons la densité de courant avec une généralisation de la méthode de Buneman à des maillages quelconques et nous montrons la conservation des équations de charge discrètes, ce qui permet de conserver la loi de Gauss. Le problème couplé est validé numériquement et la simulation de l'amortissement Landau confirme la décroissance de l'énergie, portée par le champ électrique, avec une précision dépendant du nombre de particules par mailleWe develop and study a finite volume method to solve the bidimensional nonstationary Maxwell equations on arbitrary (non-conforming, non-convex, flat...) meshes. We start by the construction of the scheme, which is based on the use of the DDFV discrete operators and a pertinent choice to discretize initial and boundary conditions. Then, we prove that the scheme locally preserves the divergence condition, that a discrete electromagnetic energy is conserved or decreasing (depending on boundary conditions) and that it is positive under a CFL condition. We also show the stability of the scheme under a CFL condition and its convergence for regular and non-regular fields. Then, these results are numerically validated with some tests using different types of meshes. We verify, also, that the use of non-conforming meshes doesn't amplify parasitic reflections. Finally, we coupled the scheme with a PIC method to solve the Maxwell-Vlasov system. We calculate the current density using a generalization of Buneman's method to arbitrary meshes and we prove that discrete charge equations, and thus Gauss' law, are conserved. The coupled problem is numerically validated and the simulation of Landau damping confirms the electric energy decrease with a precision depending on the number of particles per cel

Conflict Detection in Call Control using First-Order Logic Model Checking

Feature interaction detection methods, whether online or offline, depend on previous knowledge of conflicts between the actions executed by the features. This knowledge is usually assumed to be given in the application domain. A method is proposed for identifying potential conflicts in call control actions, based on analysis of their pre/post-conditions. First of all, pre/postconditions for call processing actions are defined. Then, conflicts among the pre/post-conditions are defined. Finally, action conflicts are identified as a result of these conflicts. These cover several possibilities where the actions could be simultaneous or sequential. A first-order logic model-checking tool is used for automated conflict detection. As a case study, the APPEL call control language is used to illustrate the approach, with the Alloy tool serving as the model checker for automated conflict detection. This case study focuses on pre/post-conditions describing call control state and media state. The results of the method are evaluated by a domain expert with pragmatic understanding of the system’s behavior. The method, although computationally expensive, is fairly general and can be used to study conflicts in other domains

Terminaison des codes convolutionnels récursifs doublement-orthogonaux

RÉSUMÉ Le travail de recherche présenté dans ce mémoire est un prolongement des travaux précédemment entamés sur les codes convolutionnels récursifs doublement orthogonaux (RCDO). Ces codes correcteurs d’erreur ont pour objectif de corriger les erreurs se produisant lors de la transmission, dans un canal bruité, de l’information entre une source et un destinataire. À ce jour, ces codes RCDO ont été seulement utilisés dans le contexte d’une transmission en continu et sont uniquement appliqués à des trames de longueurs indéfinies. Cependant, il devient indispensable de considérer le problème lié à la terminaison des codes convolutionnels RCDO lorsque nous envisageons de les utiliser au sein des systèmes de communication basés sur une transmission par paquets tels que WiMax, Ethernet, LTE, etc. Le problème de la terminaison est un problème ouvert en général pour tous les codes convolutionnels récursifs et consiste à ajouter une séquence de bits spécifique à la fin de la trame de sorte que le codeur RCDO reconverge vers l’état initial. Typiquement, cela implique que tous les éléments de délai composant les registres à décalage du codeur possèdent la valeur zéro à la fin de la transmission. Bien que la terminaison des codes RCDO entraîne une légère perte du taux de codage, des améliorations de protection contre les erreurs à la fin de la trame sont effectuées. Les objectifs de ce mémoire sont multiples. Dans un premier temps, ce travail permet d’étudier et de résoudre le problème de terminaison des codeurs RCDO. Nous avons proposé une nouvelle technique de terminaison capable de trouver les bits de terminaison qui permettent de reconduire le codeur RCDO vers l’état initial toute en assurant une complexité raisonnable associée à la génération de la séquence de terminaison. Cette technique nous a permis de réduire le plus possible la longueur de la séquence de terminaison à environ celle de la mémoire du codeur. À partir de la technique de terminaison proposée, il devient possible de définir les conditions de la terminaison qu’on doit imposer aux connexions du codeur dans le but de générer des codes RCDO terminables. En tenant compte des conditions de terminaison ainsi que des conditions de double orthogonalité, nous avons aussi proposé un nouvel algorithme de recherche capable de construire une architecture efficace des codeurs RCDO multi-registres terminables.----------Abstract This thesis presents an extension of a previous work started on Recursive Convolutional Doubly-Orthogonal (RCDO) codes. These error correcting codes are designed to detect and/or to correct errors caused by the corruptive channel noise during the transmission of data from a source to a destination. So far, RCDO codes were only decoded in a streaming fashion and were only applied to frames of indefinite lengths. However, it is essential to consider the termination for convolutional RCDO codes when used in packet-based communication systems such as WiMax, Ethernet and LTE. The termination problem remains an open and complex problem for all recursive convolutioanl codes and consists of adding a well-defined sequence of tail bits at the end of the frame so that the RCDO encoder can converge to the initial state, usually the all-zero state, which denotes that all the next information and parity bits are zero. Although the termination of RCDO codes causes a small loss of the coding rate, this can facilitate a good error performance over the last bits of a frame. This thesis has several objectives. First of all, this work studies and solves the RCDO encoder termination problem. In fact, for convolutional codes, the feedforward encoders can be terminated by simply injecting a sequence of zeros to their inputs. However, this is not a trivial problem for RCDO encoders due to their particular recursive structure. A termination sequence, whose component depends on the encoder state, can be determined by solving a system of linear equations over GF(2). For that purpose, we propose a novel termination algorithm for generating, with a reasonable complexity, the tail bits that takes the encoder back to a known state. Moreover, this algorithm allows to minimize the length of the termination sequence to approximately the code memory. From the proposed termination algorithm, it becomes possible to define a number of additional conditions, called termination conditions, which must be imposed on the encoder’s connexions in order to make the RCDO encoder terminable. Taking into consideration the terminations conditions, along with the code doubly orthogonal conditions, we also propose a new searching algorithm capable of building an efficient architecture of multi shift registers terminable RCDO encoders

BRD2 and TAP-1 genes and juvenile myoclonic epilepsy

Juvenile myoclonic epilepsy (JME) is a genetically determined common subtype of idiopathic generalized epilepsy. Linkage of JME to the chromosomal region 6p21.3 has been reported. An association has been previously observed between JME and the positional candidate, 6p21.3 linked, BRD2. Another candidate in this region is the TAP-1 gene encoding the Transporter Associated with Antigen Processing. The aim of the present study is to determine whether these two genes modulate the vulnerability to JME. While no difference was observed in the allele and genotype frequencies of BRD2 between JME and controls, an association was found between a TAP-1 haplotype and JME, suggesting that this gene may be another 6p21.3 linked vulnerability factor to JM