Optimal linear stability condition for scalar differential equations with distributed delay

Linear scalar differential equations with distributed delays appear in the study of the local stability of nonlinear differential equations with feedback, which are common in biology and physics. Negative feedback loops tend to promote oscillations around steady states, and their stability depends on the particular shape of the delay distribution. Since in applications the mean delay is often the only reliable information available about the distribution, it is desirable to find conditions for stability that are independent from the shape of the distribution. We show here that for a given mean delay, the linear equation with distributed delay is asymptotically stable if the associated differential equation with a discrete delay is asymptotically stable. We illustrate this criterion on a compartment model of hematopoietic cell dynamics to obtain sufficient conditions for stability

Introducing "2.0" functionalities in an ERP

Companies and ERP editors show an increasing interest for the Web 2.0 technologies, aiming at involving the user of a web site in the creation of content. We summarize in this communication what these tools are and give an overview of recent examples of their use in companies. We show on the example of the most recent ERP of SAP, Business By Design, that if "2.0 tools" are now available in some ERPs, their integration in the business processes is not yet fully done. We suggest in that purpose the first draft of a methodology aiming at developing "2.0 business processes" using an ERP 2.0

Participatory Design Project Management : Addressing Production Effectiveness for WMSD Prevention. The Case of the Carving Line of a Duck Slaughterhouse

International audienceResearch has highlighted the multifactorial origin of work-related musculoskeletal disorders (WMSD), and the weight of psychosocial factors. Less research work has been devoted to the design of ergonomic interventions aiming at WMSD prevention. Yet, analysing and assessing such interventions may yield two types of results : * ergonomic interventions put to the test the models of the pathology that are produced by researchers, and the successes and failures of the former bring information on the operational value of the latter ; * formalising the effective components of prevention interventions may help to foster capitalisation and spreading of methods among the practitioners. Based on an intervention carried out in a duck slaughterhouse, the research aimed at testing following hypotheses regarding the design of a WMSD : * importance of setting up a real project management, combining health issues and economic stakes, and involving the top management, the middle management and the workers ; * worker participation is a way to design better technical solutions ; but it is also an opportunity for them to develop a new relation to their own work, that is a necessary component of prevention

Conception et organisation du travail dans les abattoirs en France : la polyvalence est-elle une solution aux TMS ?

International audienceLa polyvalence des opérateurs semble aujourd'hui être, pour certains, le traitement organisationnel miracle tant attendu au problème des TMS dans les abattoirs. Il est indiscutable que la rotation qu'elle permet dans les ateliers va dans le sens, sous certaines conditions, de la prévention des maladies professionnelles, de l'enrichissement du travail et de l'élargissement des compétences. Au-delà de ces aspects de santé, la polyvalence crée une souplesse dans la gestion des ressources humaines qui permet tout un ensemble de régulations qui ne pouvaient se faire jusque là. Construire la polyvalence est intéressant tant du point de vue de la santé que de celui de la productivité. Il convient de rappeler deux choses : - la rotation entre les différents postes n'est qu'une des formes de la polyvalence, même si c'est celle qui est le plus fréquemment envisagée, - la rotation n'est pas automatiquement synonyme de pluri-compétences ; elle peut avoir comme seul objectif de rompre la monotonie du travail ou d'alléger les contraintes par rapport à la tenue de certains postes, sans qu'il y ait un enrichissement significatif de l'activité. Les entreprises dans lesquelles nous sommes intervenus étaient toutes, comme c'est généralement le cas dans les abattoirs, organisées sous la forme de chaîne de production selon une très forte division du travail. C'est bien parce que les tâches sont extrêmement découpées que la question de la polyvalence se pose avec autant d'acuité et de complexité. Nous tenterons ici, sur la base d'un ensemble d'interventions, de témoigner d'un certain nombre de constats qui encadrent la polyvalence. L'idée générale que nous allons défendre est la suivante : si la polyvalence est une réponse organisationnelle aux TMS, c'est aussi une réponse qui se construit, sans quoi, la rotation sur les postes devient alors un phénomène amplificateur dans les processus d'apparition des TMS. Nous allons donc présenter un certain nombre de réflexions permettant de construire efficacement la polyvalence. Dans un souci de clarté, le texte distinguera des conditions matérielles, organisationnelles, stratégiques, humaines et pédagogiques, en reprenant le lien étroit qui existe entre la polyvalence et l'apprentissage : parce que la polyvalence sous-entend un apprentissage, les conditions de l'apprentissage sont aussi celles de la polyvalence

Hydrodynamic modeling of partial dikes

International audienceDue to lack of space, the city of Monaco has extended over the sea, by land reclaiming. The bordering waterdepths are now so deep that the city has been considering building housings set on jacket types of struc tures. These constructions would have to be protected from sea waves, by so-called "partial dikes". An example of such partial dikes is the BYBOP caisson that was installed recently at the mouth of Port Hercule. Its shape was optimized through systematic model tests. Quite noticeable are the slanted parts that protrude both on the up-wave and down-wave sides. The appendix on the lee-side was found to have quite a strong effect on the reduction of the transmission coeffcient

Semirelativistic Hamiltonians and the auxiliary field method

Approximate analytical closed energy formulas for semirelativistic Hamiltonians of the form $\sigma\sqrt{\bm p^{2}+m^2}+V(r)$ are obtained within the framework of the auxiliary field method. This method, which is equivalent to the envelope theory, has been recently proposed as a powerful tool to get approximate analytical solutions of the Schr\"odinger equation. Various shapes for the potential $V(r)$ are investigated: power-law, funnel, square root, and Yukawa. A comparison with the exact results is discussed in detail

Mining association rules for the quality improvement of the production process

Academics and practitioners have a common interest in the continuing development of methods and computer applications that support or perform knowledge-intensive engineering tasks. Operations management dysfunctions and lost production time are problems of enormous magnitude that impact the performance and quality of industrial systems as well as their cost of production. Association rule mining is a data mining technique used to find out useful and invaluable information from huge databases. This work develops a better conceptual base for improving the application of association rule mining methods to extract knowledge on operations and information management. The emphasis of the paper is on the improvement of the operations processes. The application example details an industrial experiment in which association rule mining is used to analyze the manufacturing process of a fully integrated provider of drilling products. The study reports some new interesting results with data mining and knowledge discovery techniques applied to a drill production process. Experiment’s results on real-life data sets show that the proposed approach is useful in finding effective knowledge associated to dysfunctions causes