Time Allocation of a Set of Radars in a Multitarget Environment

International audienceThe question tackled here is the time allocation of radars in a multitarget environment. At a given time radars can only observe a limited part of the space; it is therefore necessary to move their axis with respect to time, in order to be able to explore the overall space facing them. Such sensors are used to detect, to locate and to identify targets which are in their surrounding aerial space. In this paper we focus on the detection schema when several targets need to be detected by a set of delocalized radars. This work is based on the modelling of the radar detection performances in terms of probability of detection and on the optimization of a criterion based on detection probabilities. This optimization leads to the derivation of allocation strategies and is made for several contexts and several hypotheses about the targets locations

Radar Optimal Times Detection Allocation in Multitarget Environment

International audienceThis paper deals with the problem of the management of Electronically Steered Antenna (ESA) in multitarget environments. Radars are used to detect, locate and identify targets. In this paper we focus on the detection of several aerial targets in a fixed given time. The difficulty of such detection lies in the fact that targets may be located anywhere in the space, but radars can only observe a limited part of it at a time. As a result, it is necessary to change their axis position over time. This paper describes the main steps to derive an optimal radar management in this context: the modeling of the radar, the determination of a criterion based on the target detection probability and the temporal optimization process leading to sensor management strategy. An optimization solution is presented for several contexts and several hypotheses about prior knowledge concerning the targets' locations. First, we propose a method for the optimization of the radar detection probability in a single target environment. It consists in the decomposition of the detection step into an optimal number of independent elementary detections. Then, in a multitarget context with deterministic prior knowledge, we present an optimal time allocation method which is based on the results of non linear programming. Finally, in a multitarget context with probabilistic prior knowledge, results in Search Theory are used to determine an optimal temporal allocation

Si–C interactions during degradation of the diatom Skeletonema marinoi

International audienceWhile a relationship between ballast and carbon in sedimenting particles has been well-documented, the mechanistic basis of this interaction is still under debate. One hypothesis is that mineral ballast protects sinking organic matter from degradation. To test this idea, we undertook a laboratory experiment using the diatom Skeletonema marinoi to study in parallel the dissolution of one of the most common mineral ballasts, biogenic silica (bSiO2), and the associated degradation of organic matter. Three different models were applied to our results to help elucidate the mechanisms driving bSiO2 dissolution and organic compound degradation. Results of this modeling exercise suggest that the diatom frustule is made up of two bSiO2 phases that dissolve simultaneously, but at different rates. In our experiments, the first phase was more soluble (View the MathML source) and made up 31% of the total bSiO2. In this phase, bSiO2 was mainly associated with membrane lipids and the amino acids glutamic acid, tyrosine, and leucine. The second phase was more refractory (View the MathML source), and contained more neutral lipid alcohols and glycine. Until it dissolved, the first bSiO2 phase effectively protected much of the organic matter from degradation: particulate organic carbon (POC) degradation rate constants increased from 0.025 to 0.082 d−1 after the total dissolution of this phase, and particulate organic nitrogen (PON) degradation rate constants increased from 0.030 to 0.094 d−1. Similar to POC and PON, the total hydrolyzable amino acids (THAA) degradation rate constant increased from 0.054 to 0.139 d−1 after dissolution of the first bSiO2 phase. The higher THAA degradation rate constant is attributed to a pool of amino acids that was produced during silicification and enclosed between the two silica phases. This pool of amino acids might come from the incorporation of silica deposition vesicles into the diatom wall and might not be directly associated with bSiO2. In contrast, most lipid degradation was not prevented by association with the more soluble bSiO2 phase, as the average lipid degradation rate constant decreased from 0.048 to 0.010 d−1 after 17 d of degradation. This suggests that most lipids were associated with rather than protected by silica, except pigments that appeared resistant to degradation, independently from silica dissolution. When the only organic compounds remaining were associated with the second bSiO2 phase, degradation rate constants decreased greatly; concentrations changed only slightly after day 25

Biogeochemistry of lipids in a marine coastal anthropized environment : bay of Marseille - Mediterranean sea

Le cycle biogéochimique des lipides a été étudié en milieu marin côtier anthropisé. Ce travail est basé sur l’analyse chimique des stocks de lipides par CCM/DIF et la mesure de leur hydrolyse par les communautés bactériennes associées à ces stocks. Un développement méthodologique a eu pour objectif d’identifier les bactéries marines possédant l’activité lipase. Le substrat testé (ELF-palmitate), vendu comme marqueur potentiel des lipases, n’est pas hydrolysé spécifiquement par ces dernières. Par conséquent, il ne constitue pas un outil adéquat pour l’identification des bactéries lipases en milieu marin. L’étude temporelle réalisée en baie de Marseille a permis de déterminer les caractéristiques côtières propres à la baie, et de les comparer à des mesures obtenues antérieurement en milieu hauturier (site DYFAMED, Mer Ligure). Alors qu’ils représentent 1 à 7 % du carbone organique dissous (COD) en milieu hauturier, les lipides peuvent représenter jusqu’à 16% du COD en baie de Marseille en période de forte productivité, soulignant une forte accumulation de ces composés dans la matière organique dissoute (MOD). L’influence des apports côtiers dans la distribution des lipides biogéniques n’apparaît pas de manière aussi flagrante qu’on pouvait s’y attendre. Leur distribution est clairement contrôlée par les alternances saisonnières, comme dans le milieu hauturier. Ainsi, leur temps de résidence varie de 0.8-8 jours en fonction de l’activité bactérienne et de la saison. Les apports lipidiques d’origine anthropique (hydrocarbures) sont détectés à des concentrations parfois très élevées en 2007 en baie de Marseille. Entre 2007 et 2008, une forte diminution des concentrations en lipides et hydrocarbures dissous pourrait être liée à la mise en place d’un étage biologique dans le traitement des eaux usées de la ville de Marseille. Ce traitement supplémentaire aurait en effet pour principale conséquence de diminuer les apports en MOD dans les eaux usées rejetées par l’émissaire de Cortiou. Cette hypothèse implique que l’influence du panache de Cortiou soit visible jusqu’à la station Sofcom, située au milieu de la rade sud de la baie de MarseilleThe biogeochemical cycle of lipids has been studied in a marine coastal anthropized environment. This work is based on chemical analysis of lipids by TLC/FID and the measurement of their hydrolysis rates by the associated bacterial communities. A methodological development aimed to identify lipase marine bacteria. The tested substrate (ELF-palmitate), sold as a potential marker of lipases, was not specifically hydrolyzed by the latter. Therefore, it is not an appropriate tool for the identification of marine lipase bacteria. The time series conducted in the Bay of Marseille (April 2007 – December 2008) allowed the determination of coastal characteristics of the bay and their comparison with previous measurements, obtained in the open Mediterranean Sea (DYFAMED, Ligurian sea). While they represent 1 to 7% of de dissolved organic carbon (DOC) at the offshore station, lipids may represent up to 16% of DOC in the Bay of Marseille, during periods of high productivity, underlining a strong accumulation of these compounds in the dissolved organic matter (DOM). The coastal inputs did not influence the distribution of biogenic lipids as was expected. Their distribution was clearly controlled by season, as in the offshore site. Accordingly, their residence time ranged from 0.8-8 days depending on bacterial enzyme activity and season. Lipidic anthropogenic inputs (hydrocarbons) were occasionally detected at very high concentrations in the Bay of Marseille during the year 2007. Between 2007 and 2008, a significant decrease in dissolved biogenic lipid and hydrocarbon concentrations could be related to the establishment of a biological treatment of wastewaters from Marseille. Indeed, this additional processing was expected to lead to the decrease of DOM inputs in wastewaters. This hypothesis implies that the plume of the wastewaters from Cortiou could influence the quality of OM at the Sofcom station, located in the centre of the Bay of Marseille

Margaret Steward & Leslie Hunteh, The needle is threaded. The history of an industry, 1964

Duflos Marie-Thérèse. Margaret Steward & Leslie Hunteh, The needle is threaded. The history of an industry, 1964. In: Sociologie du travail, 10ᵉ année n°3, Juillet-septembre 1968. Les cadres dans l'entreprise et dans le mouvement syndical, sous la direction de Jacques Lautman et Marc Maurice. p. 345

Chombart de Lauwe M.-J., Un Monde autre : l'enfance. De ses représentations à son mythe.

Duflos Marie-Thérèse. Chombart de Lauwe M.-J., Un Monde autre : l'enfance. De ses représentations à son mythe.. In: Revue française de sociologie, 1972, 13-1. pp. 140-141

Organizational choice. Capabilities of groups at the coal face under changing technologies. By E. L. Trist et alii.

Duflos M.-T. Organizational choice. Capabilities of groups at the coal face under changing technologies. By E. L. Trist et alii.. In: Revue française de sociologie, 1964, 5-4. p. 482

Rice Albert K., The enterprise and its environment.

Duflos M.-T. Rice Albert K., The enterprise and its environment.. In: Revue française de sociologie, 1964, 5-4. pp. 482-483

Bairoch Paul, Révolution industrielle et sous-développement.

Duflos M.-T. Bairoch Paul, Révolution industrielle et sous-développement.. In: Revue française de sociologie, 1964, 5-4. pp. 476-477

Chombart de Lauwe M.-J., Un Monde autre : l'enfance. De ses représentations à son mythe.

Duflos Marie-Thérèse. Chombart de Lauwe M.-J., Un Monde autre : l'enfance. De ses représentations à son mythe.. In: Revue française de sociologie, 1972, 13-1. pp. 140-141