Marge de stabilité des systèmes linéaires : une extension du critère de Routh-Hurwitz

Nous exposons une condition nécessaire et suffisante, portant sur les coefficients d'un polynôme, qui permet de localiser les racines de celui-ci relativement à un secteur angulaire du plan complexe, ce qui généralise le champ de validité du théorème de Routh-Hürwitz qui est limité au cas du demi-plan gauche. Ce résultat théorique permet d'étendre le critère de stabilité absolue de Routh-Hürwitz, utilisé notamment pour le réglage du gain des systèmes asservis linéaires, au cas où l'on souhaite préserver une marge de stabilité réglable, les pôles de la fonction de transfert étant alors situés à l'intérieur du secteur angulaire qui définit la zone de stabilité

Performance of Small Cluster Surveys and the Clustered LQAS Design to estimate Local-level Vaccination Coverage in Mali

<p>Abstract</p> <p>Background</p> <p>Estimation of vaccination coverage at the local level is essential to identify communities that may require additional support. Cluster surveys can be used in resource-poor settings, when population figures are inaccurate. To be feasible, cluster samples need to be small, without losing robustness of results. The clustered LQAS (CLQAS) approach has been proposed as an alternative, as smaller sample sizes are required.</p> <p>Methods</p> <p>We explored (i) the efficiency of cluster surveys of decreasing sample size through bootstrapping analysis and (ii) the performance of CLQAS under three alternative sampling plans to classify local VC, using data from a survey carried out in Mali after mass vaccination against meningococcal meningitis group A.</p> <p>Results</p> <p>VC estimates provided by a 10 × 15 cluster survey design were reasonably robust. We used them to classify health areas in three categories and guide mop-up activities: i) health areas not requiring supplemental activities; ii) health areas requiring additional vaccination; iii) health areas requiring further evaluation. As sample size decreased (from 10 × 15 to 10 × 3), standard error of VC and ICC estimates were increasingly unstable. Results of CLQAS simulations were not accurate for most health areas, with an overall risk of misclassification greater than 0.25 in one health area out of three. It was greater than 0.50 in one health area out of two under two of the three sampling plans.</p> <p>Conclusions</p> <p>Small sample cluster surveys (10 × 15) are acceptably robust for classification of VC at local level. We do not recommend the CLQAS method as currently formulated for evaluating vaccination programmes.</p

A novel system for spatial and temporal imaging of intrinsic plant water use efficiency

Instrumentation and methods for rapid screening and selection of plants with improved water use efficiency are essential to address current issues of global food and fuel security. A new imaging system that combines chlorophyll fluorescence and thermal imaging has been developed to generate images of assimilation rate (A), stomatal conductance (gs), and intrinsic water use efficiency (WUEi) from whole plants or leaves under controlled environmental conditions. This is the first demonstration of the production of images of WUEi and the first to determine images of gs from themography at the whole-plant scale. Data are presented illustrating the use of this system for rapidly and non-destructively screening plants for alterations in WUEi by comparing Arabidopsis thaliana mutants (OST1-1) that have altered WUEi driven by open stomata, with wild-type plants. This novel instrument not only provides the potential to monitor multiple plants simultaneously, but enables intra- and interspecies variation to be taken into account both spatially and temporally. The ability to measure A, gs, and WUEi progressively was developed to facilitate and encourage the development of new dynamic protocols. Images illustrating the instrument's dynamic capabilities are demonstrated by analysing plant responses to changing photosynthetic photon flux density (PPFD). Applications of this system will augment the research community's need for novel screening methods to identify rapidly novel lines, cultivars, or species with improved A and WUEi in order to meet the current demands on modern agriculture and food production. © The Author 2013. Published by Oxford University Press on behalf of the Society for Experimental Biology

Collateral damage? Small-scale fisheries in the global fight against IUU fishing

© 2020 The Authors. Fish and Fisheries published by John Wiley & Sons Ltd Concern over illegal, unreported and unregulated (IUU) fishing has led to a number of policy, trade and surveillance measures. While much attention has been given to the impact of IUU regulation on industrial fleets, recognition of the distinct impacts on small-scale fisheries is conspicuously lacking from the policy and research debate. In this paper, we outline three ways in which the application of IUU discourse and regulation undermines small-scale fisheries. First, the mainstream construction of “illegal,” “unreported” and “unregulated” fishing, and also the categorical use of “IUU” in an all-inclusive sense, disregards the diversity, legitimacy and sustainability of small-scale fisheries practices and their governing systems. Second, we explore how the recent trade-related measures to counter IUU fishing mask and reinforce existing inequalities between different sectors and countries, creating an unfair burden on small-scale fisheries and countries who depend on them. Third, as IUU fishing is increasingly approached as “organized crime,” there is a risk of inappropriately targeting small-scale fisheries, at times violently. Reflecting on these three trends, we propose three strategies by which a more sensitive and ultimately more equitable incorporation of small-scale fisheries can be supported in the global fight against IUU fishing

Investigating the capability of C-band radar to monitor wheat characteristics

International audienc

Characterisation of the soil structure and microwave backscattering based on numerical three dimensional surface representation

International audienc

Backscattering on soil structure described by plane facets

International audienceIn this paper, a new approach for soil roughness description is proposed. It is based on numerical three-dimensional soil surface images obtained by a stereoscopic device with a very fine resolution. The collected database contains four soils with different roughness (from smooth to ploughed). Each three-dimensional (3D) image is first approximated by juxtaposition of small plane facets. Statistics are then retrieved from sizes and slopes of facets in the segmented image. Analytical formulations are proposed for statistical laws showing a clear discrimination between the different soils of our database. In order to study numerically backscattering behaviour over soil, we generate profiles with respect to the retrieved statistics by applying Monte Carlo method. The Moment Method is used to compute the backscattered field over perfect conductor generated profiles. Finally, the results of numerical electromagnetic simulation are compared with the analytical Integral Equation Model (IEM) solution. Excellent agreement is obtained for soils belonging to the validity domain of IEM. For rougher soils, our model shows a realistic behaviour with incidence angle

Estimation of Watershed Soil Moisture Index from ERS/SAR Data

International audienceThe aim of this article is to show that a watershed hydrological index could be derived from ERS/SAR measurements. Indeed, it is well known that, over bare soil, the SAR signal is a function of the geometric and dielectric surface properties. The problem to estimate soil moisture is to free from the effects of the space and time fluctuations of soil roughness and from the vegetation cover attenuation and scattering. The methodology presented here is based on the selection of land cover types or “targets,” for which the SAR signal is mainly sensitive to soil water content variations, and for which the vegetation and the roughness effects (in SAR signal) can be estimated and removed if needed. This method has been validated over an agricultural watershed in France. We show that the accuracy of the retrieved soil moisture is ±0.04–0.05 cm3/cm3, except during May and June, when vegetation cover is too dense to get reliable soil information

Combining fog architectures and distributed event-based systems for mobile sensor location certification

International audienceEvent filtering is of paramount importance in large-scale urban sensing, where an enormous quantity of data is generated. Multiple criteria can be considered for filtering, location being one of the most valuable ones. Obtaining high-quality (trustworthy, accurate) location information helps to contextualize the event content and provides trust both on the source producer and on the publication itself. However, IoT-based urban services rely often on cloud architectures, which have no means to support location certification. To meet the need for location certification support in urban distributed event-based systems (DEBS), we propose three different fog architectures targeted at scenarios with mobile event producer

Putting all the pieces together : integrating current knowledge of the biology, ecology, fisheries status, stock structure and management of yellowfin tuna (Thunnus albacares)

Yellowfin tuna (Thunnus albacares; YFT) is an apex marine predator inhabiting tropical and sub-tropical pelagic waters. It supports the second largest tuna fishery in the world. Here, we review the available literature on YFT to provide a detailed overview of the current knowledge of its biology, ecology, fisheries status, stock structure and management, at global scale. YFT are characterized by several peculiar anatomical and physiological traits that allow them to survive in the oligotrophic waters of the pelagic realm. They are opportunistic feeders, which allows fast growth and high reproductive outputs. Globally, YFT fisheries have expanded over the last century, progressively moving from coastal areas into the majority of sub-tropical and tropical waters. This expansion has led to a rapid increase in global commercial landings, which are predominantly harvested by industrial longline and purse seine fleets. For management purposes, YFT is divided into four stocks, each of which is currently managed by a separate tuna Regional Fisheries Management Organization. Our current understanding of YFT stock structure is, however, still uncertain, with conflicting evidence arising from genetic and tagging studies. There is, moreover, little information about their complex life-history traits or the interactions of YFT populations with spatio-temporally variable oceanographic conditions currently considered in stock assessments. What information is available, is often conflicting at the global scale. Finally, we suggest future research directions to manage this valuable resource with more biological realism and more sustainable procedures