The Gauss map of minimal surfaces in the Heisenberg group

We study the Gauss map of minimal surfaces in the Heisenberg group $\mathrm{Nil}_3$ endowed with a left-invariant Riemannian metric. We prove that the Gauss map of a nowhere vertical minimal surface is harmonic into the hyperbolic plane $\mathbb{H}^2$. Conversely, any nowhere antiholomorphic harmonic map into $\mathbb{H}^2$ is the Gauss map of a nowhere vertical minimal surface. Finally, we study the image of the Gauss map of complete nowhere vertical minimal surfaces.Comment: 17 pages, redaction improved

DMT Optimal On-Demand Relaying for Mesh Networks

This paper presents a new cooperative MAC (Medium Access Control) protocol called BRIAF (Best Relay based Incremental Amplify-and-Forward). The proposed protocol presents two features: on-demand relaying and selection of the best relay terminal. “On-demand relaying” means that a cooperative transmission is implemented between a source terminal and a destination terminal only when the destination terminal fails in decoding the data transmitted by the source terminal. This feature maximizes the spatial multiplexing gain r of the transmission. “Selection of the best relay terminal” means that a selection of the best relay among a set of (m-1) relay candidates is implemented when a cooperative transmission is needed. This feature maximizes the diversity order d(r) of the transmission. Hence, an optimal DMT (Diversity Multiplexing Tradeoff) curve is achieved with a diversity order d(r) = m(1-r) for 0 ≤ r ≤ 1

Unstationnary control of a launcher using observer-based structures

This paper deals with the design of a gain-scheduled controller for the attitude control of a launcher during atmospheric flight. The design is characterized by classical requirements such as phase/gain margins and flexible mode attenuations as well as time-domain constraints on the response of angle of attack to a worstcase wind profile. Moreover, these requirements must be fulfilled over the full atmospheric flight envelope and must be robust against parametric uncertainties. In order to achieve this goal, we propose a method based on minimal observer-based realizations of arbitrary stabilizing compensators. An original technique to assign the closed-loop dynamics between the state-feedback dynamics and the state-estimation dynamics is presented for the H∞ compensators case. The structure is used to mix various specifications through the Cross Standard Form(CSF) and to perform a smooth gain scheduling interpolation through an Euler-Newton algorithm of continuation

De l'utilisation de la structure estimation/commande pour le pilotage instationnaire d'un lanceur spatial

Dans cet article, nous nous intéressons au développement de techniques ayant trait à la mise sous forme LQG équivalente de correcteurs stabilisants. Dans un premier temps nous nous concentrerons plus particulièrement sur la transformation de correcteurs issus d'une synthèse Hinfinty. Nous proposons une méthode originale pour effectuer le choix des dynamiques d'estimation et de commande du correcteur équivalent en s'appuyant sur les résultats d'une synthèse H2. Puis nous proposerons une définition en temps discret de la Forme Standard de Passage (CSF) qui s'appuie également sur la paramétrisation de Youla sur la structure estimation /commande. Nous la présenterons en tant qu'outil méthodologique pour la mise en forme d'un problème multi-objectif. Nous mettrons en application la CSF sur le problème de pilotage d'un lanceur et nous montrerons l'intérêt de l'utilisation de la structure estimation/commande dans le cadre de l'inter-polation de correcteur pour le pilotage instationnaire

Turbo receivers for interleave-division multiple-access systems

In this paper several turbo receivers for Interleave-Division Multiple-Access (IDMA) systems will be discussed. The multiple access system model is presented first. The optimal, Maximum A Posteriori (MAP) algorithm, is then presented. It will be shown that the use of a precoding technique at the emitter side is applicable to IDMA systems. Several low complexity Multi-User Detector (MUD), based on the Gaussian approximation, will be next discussed. It will be shown that the MUD with Probabilistic Data Association (PDA) algorithm provides faster convergence of the turbo receiver. The discussed turbo receivers will be evaluated by means of Bit Error Rate (BER) simulations and EXtrinsic Information Transfer (EXIT) charts

Launcher attitude control: some additional design and optimization tools

This paper deals with the launcher attitude control during atmospheric flight. A two step approach combining an H1 control design and an optimization procedure is proposed. The first step is multi-objective stationary H1 design based on the Cross Standard Form. It provides easily a first rough solution from a few physical tuning parameters. The second step is a fine tuning using an multi-constraint satisfaction algorithm. This algorithm enables the certification criteria computed on the validation model to be met and is also used to propagate the nominal tuning to the full flight envelope

The State of Utah v. C. W. Brady, Jr. : Appellant\u27s Brief

Benoît Jean-Daniel. Cecil Woodham-Smith. Florence Nightingale. Paris, Albin Michel, 1953. In: Revue d'histoire et de philosophie religieuses, 36e année n°3,1956. Hommage au Professeur Jean-Daniel Benoît à l'occasion de son 70e anniversaire. p. 266

Launcher attitude control: discrete-time robust design and gain-scheduling

In this paper, a robust multi-objective design for the control of a launcher during atmospheric flight is investigated. This approach is based on the Cross Standard Form formulation which allows to incorporate the various specifications of the launcher problem in a streamlined manner. An important feature of this approach is that a non-conventional LQG/LTR approach, required to satisfy time-domain specifications, can be embedded into a more general standard problem in order to account for frequency-domain robustness constraints. The specific form of this standard problem is also very interesting for gain scheduling