Entropy optimisation for distributed detection systems

In the general framework of data fusion, detection theory allows to distinguish a finite set of situations from observations . Bayes and Neyman-Pearson criteria are generally used in order to develop optimal detection rules . Nevertheless, in some applications (in particular when the a priori probabilities Pjj = 0, 1 of the hypotheses are uncertain or when one of them is near zero), it could be interesting to consider the optimisation of the quantity of information which is relevant for the detection problem . This approach could be used in digital communication problems where the information quantity sent is more interesting than the information itself . For such systems, an entropy based criterion seems to be of interest . Using such a criterion, we recall the entropy optimisation results for centralised detection networks . Within the framework of parallel distributed detection, we suggest to optimise the local detectors without taking into account the fusion problem, that we optimize separately. The main interest of this approach is that its implementation is simple . We recall then the results of the simultaneous optimisation of the local detectors and of the fusion operator. We also use an informational criterion for the optimisation of serial distributed networks . Finally, the different optimisation results are compared on an illustrative example . This allows to underline the very interesting robustness properties with respect to rare events of the informational approach, as opposed to the classical one .Dans le contexte général de la fusion de données, la théorie de la détection permet de discriminer de façon optimale, à partir d'observations, un nombre fini de situations. Classiquement, les critères de Bayes et de Neyman-Pearson sont utilisés dans la littérature. Pourtant, dans certaines applications (en particulier lorsque les probabilités a priori Pj j = 0.1 des hypothèses sont mal connues, ou si l'une d'entre elles est proche de zéro), il pourrait s'avérer intéressant de baser le problème d'optimisation sur la quantité d'information pertinente pour le problème de détection. Cette approche pourrait notamment s'adapter aux problèmes de communication numérique où l'on s'intéresse davantage à la quantité d'information transmise, plutôt qu'à l'information elle-même. Pour de tels systèmes, un critère entropique peut être intéressant. En utilisant un tel critère, nous rappelons les résultats de l'optimisation entropique des architectures de détection centralisée. Dans le cadre de la détection décentralisée parallèle, nous proposons d'optimiser les détecteurs locaux sans prendre en compte le problème de la fusion, que nous optimisons séparément. L'intérêt principal de cette approche est qu'elle offre une solution simple à mettre en œuvre. Nous rappelons alors les résultats de l'optimisation simultanée des détecteurs locaux et de l'opérateur de fusion. Nous proposons également d'utiliser le critère informationnel dans le cadre de l'optimisation d'une architecture décentralisée série. Enfin, une comparaison des résultats de l'optimisation de toutes ces architectures sur un exemple illustratif nous permet de mettre en évidence des propriétés très intéressantes de robustesse vis-à-vis d'événements rares de l'approche informationnelle, contrairement à l'approche classique

ECORISK2050: An Innovative Training Network for predicting the effects of global change on the emission, fate, effects, and risks of chemicals in aquatic ecosystems

By 2050, the global population is predicted to reach nine billion, with almost three quarters living in cities. The road to 2050 will be marked by changes in land use, climate, and the management of water and food across the world. These global changes (GCs) will likely affect the emissions, transport, and fate of chemicals, and thus the exposure of the natural environment to chemicals. ECORISK2050 is a Marie Skłodowska-Curie Innovative Training Network that brings together an interdisciplinary consortium of academic, industry and governmental partners to deliver a new generation of scientists, with the skills required to study and manage the effects of GCs on chemical risks to the aquatic environment. The research and training goals are to: (1) assess how inputs and behaviour of chemicals from agriculture and urban environments are affected by different environmental conditions, and how different GC scenarios will drive changes in chemical risks to human and ecosystem health; (2) identify short-to-medium term adaptation and mitigation strategies, to abate unacceptable increases to risks, and (3) develop tools for use by industry and policymakers for the assessment and management of the impacts of GC-related drivers on chemical risks. This project will deliver the next generation of scientists, consultants, and industry and governmental decision-makers who have the knowledge and skillsets required to address the changing pressures associated with chemicals emitted by agricultural and urban activities, on aquatic systems on the path to 2050 and beyond

Compact ECL gate design for double mesa HBT process

Emitter Coupled Logic (ECL) gate is a good candidate for gigabit logic when one uses GaAs/GaAlAs Heterojunction Bipolar Transistor (HBT). With the double mesa process, intercon­nections between the 5 transistors of the elemental gate have to climb the emitter and base mesas, leading to lack of density. A more compact design of the ECL gate has been achieved, in which the transistors are directly connected on the top of the base mesa. The DC characteristics of this gate are similar to these obtained with conventional gate design and the surface is reduced by a factor 1.6

Non-LTE modelling of the HC2NC and HNC3 abundance in astrophysical environments

International audienceThe isomers of HC3N, namely HC2NC and HNC3, are widely observed in the interstellar medium and in circumstellar envelopes. Their abundance has been determined under the assumption of local thermodynamic equilibrium (LTE) conditions or non-LTE radiative transfer models, but in considering the collisional excitation of HC3N as the same for all isomers. Chemical models for the prototypical cold cores, TMC-1 and L1544, reproduced the abundance of HC3N fairly well, but they tend to overestimate the abundances of HC2NC and HNC3 with respect to the observations. It is therefore worth revisiting the interpretation of the observational spectra of these isomers using a rigorous non-LTE modelling. The abundance of HC2NC and HNC3 were then determined using non-LTE radiative transfer calculations based on the proper rate coefficients for the first time in this work. Modelling the brightness temperature of HC2NC and HNC3 when using their proper collision rate coefficients shows that models based on LTE or non-LTE with approximate collision data may lead to deviations of up to a factor of similar to 1.5. Reinterpreting the observational spectra led us to significant differences relative to the observed abundances previously determined. Our findings suggest quite similar abundance ratios for the TMC-1 and L1544 cold cores as well as the L483 protostar. This work will encourage further modelling with more robust non-LTE radiative transfer calculations and future studies to revisit the chemistry of HC3N and its isomers in cold molecular clouds

Design of new fluorinated bridged push-pull stilbenes and preparation of LB films for second harmonic generation in the blue domain

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