Maneuvering target tracking: overview and the role of imaging sensors

While solutions hased on Kalman filtering have matured, Cracking applications are faced with the emergence of enhanced maneuverahility mobiles and the generalization of multisensor architectures . This paper presents a state of the art survey including recent progress motivated hy these evolutions, with emphasis on the vole of imaging sensors . The presentation is illustrated with simulations from an air defense scenario .Alors que les solutions basées sur le filtrage de Kalman ont atteint leur maturité, les applications pistage sont confrontées à l'apparition de mobiles plus manœuvrants et à la généralisation des architectures multicapteurs. Cet article propose une synthèse de l'état de l'art incorporant les réponses récentes à ces évolutions et insistant sur le rôle des capteurs imageurs. La présentation est illustrée par des simulations d'un scénario de défense aérienn

Approximate solutions of stochastic differential delay equations with Markovian switching

Our main aim is to develop the existence theory for the solutions to stochastic differential delay equations with Markovian switching (SDDEwMSs) and to establish the convergence theory for the Euler-Maruyama approximate solutions under the local Lipschitz condition. As an application, our results are used to discuss a stochastic delay population system with Markovian switching

Systems with jumps : theory and applications

Introduced in the eigthies, the systems with jumps, also called at the beginning hybrid systems, can efficiently modelize a grea t number of physical systems subject to random jumps in their dynamics . A manoeuvering fighting aircraft, widely studied in th e litterature, is a good illustration of this type of systems . Stability, optimal control and stochastic filtering were the major areas o f study for these models . In fact this modelization results from a combination of three ingredients : diffusion, jumps and deterministi c processes . When restricting ourselves to the first two kinds of processes, we consider models with stochastic diffusions . So, after having introduced the general mathematical representation for such processes, we consider in this article a typica l application in aerospace, the target tracking, to show the significant improvements in performance brought by this approach . When then conclude, after having recalled the various contributions brought by our group on the stochastic diffusions during the last fifteen years .Introduits dans les années quatre vingt, les systèmes à sauts, plus connus à l'origine sous le nom de systèmes hybrides, offrent un cadre mathématique idéal pour l'étude de systèmes physiques caractérisés par des modifications (sauts), brutales et aléatoires de leur dynamique. Un des exemples les plus couramment rencontrés dans la littérature est celui d'un avion de chasse effectuant diverses manoeuvres. La stabilité, la commande optimale et le filtrage stachastique ont été les trois principaux domaines d'études de ces modèles. Cette modélisation résulte en fait d'un mélange de trois constituants élémentaires que sont les processus de diffusion, les processus à sauts et les processus déterministes. En se restreignant aux deux premiers ingrédients, nous parlerons de modèles à diffusions aléatoires. Après avoir introduit la modélisation mathématique de tels processus, nous nous intéressons dans cet article à une application type, la poursuite de trajectoire, afin de montrer les améliorations significatives qu'apporte cette approche. Enfin nous conclurons, non sans avoir rappelé les différents travaux accomplis sur les diffusions aléatoires dans notre groupe, au cours de ces quinze dernières années

Dendritic Hold and Read: A Gated Mechanism for Short Term Information Storage and Retrieval

Two contrasting theories have been proposed to explain the mechanistic basis of short term memory. One theory posits that short term memory is represented by persistent neural activity supported by reverberating feedback networks. An alternate, more recent theory posits that short term memory can be supported by feedforward networks. While feedback driven memory can be implemented by well described mechanisms of synaptic plasticity, little is known of possible molecular and cellular mechanisms that can implement feedforward driven memory. Here we report such a mechanism in which the memory trace exists in the form of glutamate-bound but Mg2+-blocked NMDA receptors on the thin terminal dendrites of CA1 pyramidal neurons. Because glutamate dissociates from subsets of NMDA receptors very slowly, excitatory synaptic transmission can leave a silent residual trace that outlasts the electrical activity by hundreds of milliseconds. Read-out of the memory trace is possible if a critical level of these bound-but-blocked receptors accumulates on a dendritic branch that will allow these quasi-stable receptors to sustain a regenerative depolarization when triggered by an independent gating signal. This process is referred to here as dendritic hold and read (DHR). Because the read-out of the input is not dependent on repetition of the input and information flows in a single-pass manner, DHR can potentially support a feedforward memory architecture

Generalised criteria on delay dependent stability of highly nonlinear hybrid stochastic systems

Our recent paper [2] is the first to establish delay dependent criteria for highly nonlinear hybrid stochastic differential delay equations (SDDEs) (by highly nonlinear we mean the coefficients of the SDDEs do not have to satisfy the linear growth condition). This is an important breakthrough in the stability study as all existing delay stability criteria before could only be applied to delay equations where their coefficients are either linear or nonlin- ear but bounded by linear functions (namely, satisfy the linear growth condition). In this continuation, we will point out one restrictive condition imposed in our earlier paper [2]. We will then develop our ideas and methods there in order to remove this restrictive condition so that our improved results cover a much wider class of hybrid SDDEs