A "DESIGN FOR AVAILABILITY" METHODOLOGY FOR SYSTEMS DESIGN AND SUPPORT

Prognostics and Health Management (PHM) methods are incorporated into systems for the purpose of avoiding unanticipated failures that can impact system safety, result in additional life cycle cost, and/or adversely affect the availability of a system. Availability is the probability that a system will be able to function when called upon to do so. Availability depends on the system's reliability (how often it fails) and its maintainability (how efficiently and frequently it is pro-actively maintained, and how quickly it can be repaired and restored to operation when it does fail). Availability is directly impacted by the success of PHM. Increasingly, customers of critical systems are entering into "availability contracts" in which the customer either buys the availability of the system (rather than actually purchasing the system itself) or the amount that the system developer/manufacturer is paid is a function of the availability achieved by the customer. Predicting availability based on known or predicted system reliability, operational parameters, logistics, etc., is relatively straightforward and can be accomplished using several methods and many existing tools. Unfortunately in these approaches availability is an output of the analysis. The prediction of system's parameters (i.e., reliability, operational parameters, and/or logistics management) to meet an availability requirement is difficult and cannot be generally done using today's existing methods. While determining the availability that results from a set of events is straightforward, determining the events that result in a desired availability is not. This dissertation presents a "design for availability" methodology that starts with an availability requirement and uses it to predict the required design, logistics and operations parameters. The method is general and can be applied when the inputs to the problem are uncertain (even the availability requirement can be represented as a probability distribution). The method has been demonstrated on several examples with and without PHM

Biais de confiance dans la commande publique et ses implications en termes de retards de paiement

Cet article aborde la problématique des délais de paiement de la commande publique et ses implications pour les entreprises titulaires. Dans ce sillage, une fois les travaux réalisés le processus de paiement doit être déclenché donnant lieu une libération de la dette de l’administration publique. Cependant, ce processus dans certains cas est entravé par des contraintes dont la nature différent. Le présent papier de recherche introduit la notion de « biais de confiance » comme pièce maitresse dans l’imputation de la responsabilité des retards de paiement inhérents à la commande publique. En effet, cette confiance qui se développe entre le maitre d’ouvrage et l’entreprise titulaire d’un marché public fait en sorte que ce dernier, dans l’optique de décrocher une autre commande ou pour ne pas offenser le maitre d’ouvrage ou son représentant, que la délivrance des pièces de paiement après l’exécution des travaux soit effectuée sans solliciter un accusé de réception. Ainsi, ces entreprises perdent le droit au moins de réclamer le règlement des intérêts moratoires suite au retard de paiement. Ce faisant, cet article démontre que la dimension procédurale et le biais de confiance dans la commande publique constituent une double contrainte pour les entreprises titulaires

Les facteurs d’Attractivité des Investissements Directs Etrangers par les Pays en Développement et l’effet modérateur de la qualité des institutions

   L’attractivité des investissements directs étrangers (IDE) a fait l’objet de plusieurs recherches empiriques. Beaucoup d’auteurs se sont intéressés aux facteurs qui expliquent l’afflux de ces investissements sur les pays d’accueil. L’effet d’un facteur d’attractivité des IDE change en effet d’un pays à l’autre. Cette recherche examinera l’effet modérateur de la qualité des institutions légales et gouvernementales du pays d’accueil des IDE de la relation entre ces investissements et les facteurs de leur attraction. Les principaux résultats montrent que plus les politiques gouvernementales sont efficaces, que plus la corruption est réprimée, que plus les lois protègent les investisseurs, l’attractivité des IDE est assurée par le marché financier et par la stabilité politique que l’ouverture commerciale s’améliore. Il n’en reste pas moins que les pays qui ont des institutions de qualité supérieure se trouve plus pénalisés en termes d’attractivité des IDE lorsque le poids fiscal sur les entreprises qui y opèrent s’alourdit et lorsque leur taux de change devient plus flexible

Evaluation of machine learning algorithms for forest species mapping based on Sentinel 2 data: a case study of Ait Bouzid forest (Central High Atlas, Morocco)

In arid and semi-arid environments, producing accurate maps of forest tree cover using optical remote sensing data is essential to understand their spatial distributions and dynamics. In this respect, the current study aimed to explore the effectiveness of support vector machine (SVM), K nearest neighbors (KNN), and random forest (RF)machine learning (ML) models to map the forest tree species of Ait Bouzid region (Central High Atlas, Morocco) by using Sentinel-2A data. The results from all models showed that about 19-28%, 21-27%, 16-24%, 15-18%, and 0,3-0,32% of the area was covered by euphorbia, red juniper, cedar, holm oak, bare ground, and water body, respectively. According to the overall accuracy (OA) and kappa coefficient, the SVM classifier showed the highest OA (73%) and kappa (0.66) values, followed by KNN (OA=70%, kappa=0.62) and RF (OA=67%, kappa=0.59). Regarding LC classes, water, bare soil, and holm oak could be identified with the producer's accuracy attaining 100%, while red juniper and cedar were the most challenging classes to determine for all ML classifiers, with the producer's accuracy of 40-50% and 40-67%. This study revealed the potential of ML approaches coupled with multispectral Sentinel-2A data for forest species cartography in arid areas with high accuracy. Furthermore, it provides crucial information about forest tree species distribution for developing forest management plans

Application of time–stress superposition to viscoelastic behavior of polyamide 6,6 fiber and its “true” elastic modulus

The viscoelastic behavior of semi-crystalline polyamide 6,6 fiber is exploited in viscoelastically prestressed polymeric matrix composites. To understand better the underlying prestress mechanisms, strain–time performance of the fiber material is investigated in this work, under high creep stress values (330–665 MPa). A latch-based Weibull model enables prediction of the “true” elastic modulus through instantaneous deformation from the creep-recovery data, giving 4.6 ± 0.4 GPa. The fiber shows approximate linear viscoelastic characteristics, so that the time–stress superposition principle (TSSP) can be implemented, with a linear relationship between the stress shift factor and applied stress. The resulting master creep curve enables creep behavior at 330 MPa to be predicted over a large timescale, thus creep at 590 MPa for 24 h would be equivalent to a 330 MPa creep stress for ∼5200 years. Similarly, the TSSP is applied to the resulting recovery data, to obtain a master recovery curve. This is equivalent to load removal in the master creep curve, in which the yarns would have been subjected to 330 MPa creep stress for ∼4.56 × 107 h. Since our work involves high stress values, the findings may be of interest to those involved with long-term load-bearing applications using polyamide materials

Modeling of Integrated Production Tomato under Multispan Greenhouse in Souss Massa region

Abstract: The renewal of greenhouse in Souss Massa region is a priority to improve the production of protected vegetable crops. The greenhouse structure is a complex system; it is the place of multiple interacting factors continuously in time and space. Aimed at controlling the integrated production under Multispan greenhouse, we need to consider all factors influencing volume and quality of commercial production. Among these factors, microclimate of structure mainly due to its architecture, its coverage material, its ventilation area and weather outside. In parallel with this study other factors will be studied, management of pests, diseases and management of production cost flow, aims to model the integrated production under greenhouse and to provide a convenient way of greenhouses decision making in protected production. This study was conducted in three separate unichapelle compartments 270m ² each. Inputs of fertilizer and water line were managed and controlled by a fertigation compact programmer. As climate data were collected through two weather stations installed in the greenhouse. The results of the first year showed the significant effect of the Multispan greenhouse microclimate on improving the production volume, the management of pests and diseases and economic inputs in comparison with the Canary greenhouse

Two Decades of French Urban Policy: From Social Development of Neighbourhoods to the Republican Penal State

International audienceThis paper provides an overview of French national urban policy for the period 1981–2002, organized around three themes: spatial conceptualizations of intervention areas and changing scales of intervention, discursive articulations of intervention areas, and legitimation of state intervention. By relating the transformations of this policy to the contemporary restructuring of the French state, the paper argues that although there are elements of convergence, the contemporary restructuring of the French state differs remarkably from a US or UK-style neoliberalization, partly because of the republican tradition emphasizing the active role of the state for the well-being of its citizens. This restructuring carries the signs of the strong state tradition in France, and is best understood as an articulation of neoliberalism with established political traditions, an articulation that I try to capture with the notion of a ''republican penal state''

Time-aging time-stress superposition in soft glass under tensile deformation field

We have studied the tensile deformation behaviour of thin films of aging aqueous suspension of Laponite, a model soft glassy material, when subjected to a creep flow field generated by a constant engineering normal stress. Aqueous suspension of Laponite demonstrates aging behaviour wherein it undergoes time dependent enhancement of its elastic modulus as well as its characteristic relaxation time. However, under application of the normal stress, the rate of aging decreases and in the limit of high stress, the aging stops with the suspension now undergoing a plastic deformation. Overall, it is observed that the aging that occurs over short creep times at small normal stresses is same as the aging that occurs over long creep times at large normal stresses. This observation allows us to suggest an aging time - process time - normal stress superposition principle, which can predict rheological behaviour at longer times by carrying out short time tests.Comment: 26 pages, 7 figures, To appear in Rheologica Act

Temps et espaces jeunes

Jazouli Adil. Temps et espaces jeunes. In: Agora débats/jeunesses, 1, 1995. Lieux de jeunes. pp. 9-10