An hybrid system approach to nonlinear optimal control problems

We consider a nonlinear ordinary differential equation and want to control its behavior so that it reaches a target by minimizing a cost function. Our approach is to use hybrid systems to solve this problem: the complex dynamic is replaced by piecewise affine approximations which allow an analytical resolution. The sequence of affine models then forms a sequence of states of a hybrid automaton. Given a sequence of states, we introduce an hybrid approximation of the nonlinear controllable domain and propose a new algorithm computing a controllable, piecewise convex approximation. The same way the nonlinear optimal control problem is replaced by an hybrid piecewise affine one. Stating a hybrid maximum principle suitable to our hybrid model, we deduce the global structure of the hybrid optimal control steering the system to the target

PERFORMANCE MANAGEMENT IN THE PUBLIC SECTOR:

Education supply in universities of most European countries has for the last ten years become a strategic matter. At present, French universities consider education supply as an investment. But they do not utilize all incentive mechanisms in order to drive their strategies. At the beginning of the year 2006, the public sector reform will tend to impose performance measurements of research and educational activities, in order to improve organizational efficiency. The aim of this reform in the French context is to provide driving elements to increase internal efficiency, social and economic impact of higher education system and to reinforce international attractiveness of public education institutions. The substitution of resources management by result management involves an agent's performance responsibility measurement. Evaluation becomes a central factor and is articulated with incentives system. The weakening of the property right system drives project bearers to maximize their utility instead of their incomes. In such a context, the understanding of individual strategies permits to understand constraints of management within universities, and to take into account the impact of stakeholders who take part in the value generation process. The major risk is to constraint the utility function of projects bearers by increasing their burden and their motivation. The result could be the limitation of the number of projects, and as well, the decreasing of university investments.performance, public sector, universities, efficiency, value generation

PERFORMANCE MANAGEMENT IN THE PUBLIC SECTOR:: Development and implementation of process-oriented performance measurement system in French universities

18 pagesEducation supply in universities of most European countries has for the last ten years become a strategic matter. At present, French universities consider education supply as an investment. But they do not utilize all incentive mechanisms in order to drive their strategies. At the beginning of the year 2006, the public sector reform will tend to impose performance measurements of research and educational activities, in order to improve organizational efficiency. The aim of this reform in the French context is to provide driving elements to increase internal efficiency, social and economic impact of higher education system and to reinforce international attractiveness of public education institutions. The substitution of resources management by result management involves an agent's performance responsibility measurement. Evaluation becomes a central factor and is articulated with incentives system. The weakening of the property right system drives project bearers to maximize their utility instead of their incomes. In such a context, the understanding of individual strategies permits to understand constraints of management within universities, and to take into account the impact of stakeholders who take part in the value generation process. The major risk is to constraint the utility function of projects bearers by increasing their burden and their motivation. The result could be the limitation of the number of projects, and as well, the decreasing of university investments

Constant contact stiffness indentation relaxation test

Nanoindentation test is of great interest to characterize small scale mechanical behavior, thus a large literature exists on the field. Nevertheless, measurements of time dependent mechanical properties by this technique is still to be improved 1. It is proposed to investigate the indentation relaxation from a different point of view. Indentation relaxation tests are usually performed keeping a constant displacement over a prescribed time duration 2. This experimental procedure is consequently very sensitive to the system drift. Hence, determination of relaxation behavior is limited to few hundreds of seconds in the best cases. Weihs and Pethica 3 and Maier et al. 4, proposed to use the continuous contact stiffness measurement as a robust measure of the contact area. Based on these studies, a novel experimental procedure has been developed. Contact stiffness is kept constant after loading to a prescribed depth, for a define period, while displacement and load are monitored. As the contact stiffness measurement is not sensitive to drift, this method allowed to perform relaxation experiments with very long hold segment. Experiments on fused silica and polymers - i.e. PMMA, PC and PS - at room temperature have been performed with a constant contact stiffness maintained up to 10 hours. It has been shown that the dispersion on the force, F, was greatly reduced (see Figure 1). This could be understood as constant contact stiffness experiments were much less affected by the system drift than constant displacement ones. This new method opens the way to time dependent mechanical characterization in a wider range of conditions, especially long time experiments and high temperature indentation tests. Please click Additional Files below to see the full abstract

Ordre et désordre dans l'échange international:Une revue de littérature

Il en est du commerce international comme du progrès technique : de faibles performances en matière de croissance et d’emploi, quand elles surviennent, lui sont facilement attribuées. Cet article rappelle que l’ouverture au commerce international, comme le progrès technique, crée l’opportunité de mieux allouer les ressources et de créer des richesses supplémentaires. La réalisation de cette opportunité dépend néanmoins largement des conditions qui président à la transition ainsi engagée. Ce serait une erreur de considérer que les avantages de l’ouverture au commerce international peuvent automatiquement être obtenus sans heurts ni conflits. La théorie du commerce international enseigne qu’il peut exister un conflit de répartition qui fait que les gains à l’échange ne profitent pas à tous dans un même pays. Des inégalités se forment et des catégories sociales entières enregistrent des pertes qu’il est difficile de compenser. Par ailleurs, des conflits peuvent aussi se produire entre nations. Si un progrès technique différencié met en cause l’avantage comparatif précédemment détenu par l’un des partenaires, ce que gagne l’un, l’autre le perd, alors même que le revenu mondial augmente. Toutefois, les écarts de performance évoluent sans cesse. Les spécialisations induites par des hétérogénéités en termes de coût de production ou de transport et d’externalités créent inévitablement des différentiels de croissance qui font que certains pays progressent plus vite que d’autres. Ces différentiels entretiennent un rapport ambigu avec le degré d’ouverture à l’échange international. La raison en est claire. Les conditions de l’ouverture comptent davantage que l’ouverture elle-même. Aussi est-il essentiel de connaître les conditions dans lesquelles nations et firmes s’adaptent à un changement intervenu dans le degré d’ouverture au commerce international

CCCP: A CCD Controller for Counting Photons

CCCP, a CCD Controller for Counting Photons, is presented. This new controller uses a totally new clocking architecture and allows to drive the CCD in a novel way. Its design is optimized for the driving of EMCCDs at up to 20MHz of pixel rate and fast vertical transfer. Using this controller, the dominant source of noise of EMCCDs at low flux level and high frame rate, the Clock Induced Charges, were reduced to 0.001 - 0.0018 electron/pixel/frame (depending of the electron multiplying gain), making efficient photon counting possible. CCCP will be deployed in 2009 on the ESO NTT through the 3D-NTT1 project and on the SOAR through the BTFI project.Comment: 10 pages, 10 figures, to appear in "Ground-based and Airborne Instrumentation for Astronomy II" SPIE conference, Marseille, 23-28 June 200

Ordre et désordre dans l'échange international : une revue de littérature.

Cette publication n'a pas de résumé

Intervertebral disc characterization by shear wave elastography: an in-vitro preliminary study

Patient-specific numerical simulation of the spine is a useful tool both in clinic and research. While geometrical personalization of the spine is no more an issue, thanks to recent technological advances, non-invasive personalization of soft tissue’s mechanical properties remains a challenge. Ultrasound elastography is a relatively recent measurement technique allowing the evaluation of soft tissue’s elastic modulus through the measurement of shear wave speed (SWS). The aim of this study was to determine the feasibility of elastographic measurements in intervertebral disc (IVD). An in-vitro approach was chosen to test the hypothesis that SWS can be used to evaluate IVD mechanical properties and to assess measurement repeatability. Eleven oxtail IVDs were tested in compression to determine their stiffness and apparent elastic modulus at rest and at 400 N. Elastographic measurements were performed in these two conditions and compared to these mechanical parameters. The protocol was repeated six times to determine elastographic measurement repeatability. Average SWS over all samples was 5.3 ± 1.0 m/s, with a repeatability of 7 % at rest and 4.6 % at 400 N; stiffness and apparent elastic modulus were 266.3 ± 70.5 N/mm and 5.4 ± 1.1 MPa at rest, respectively, while at 400 N they were 781.0 ± 153.8 N/mm and 13.2 ± 2.4 MPa. Correlations were found between elastographic measurements and IVD mechanical properties; these preliminary results are promising for further in-vivo application.The authors are grateful to the ParisTech BiomecAM chair program on subject-specific musculoskeletal modelling for funding (with the support of Proteor, ParisTech and Yves Cotrel Foundations)

An Architecture Description Language for Embedded Hardware Platforms

Embedded software development relies on various tools - compilers, simulators, execution time estimators - that encapsulate a more-or-less detailed knowledge of the target hardware platform. These tools can be costly to develop and maintain:significant benefits could be expected if they were automatically generated from models expressed in a dedicated modeling language.In contrast with Hardware Description Languages (HDLs), that focus on the internal structure and behavior of an electronic board of chip, Hardware Architecture Description Languages consider hardware as a platform for software execution. Such a platform will be described in terms of low-level programming interface (processor instruction set),resources (processing elements, memory and peripheral devices) and elementary services (arithmetic and logic operations, bus transactions).This paper gives an overview of HARMLESS (Hardware ARchitecture Modeling Language for Embedded Software Simulation), a new domain-specific language for modeling embedded hardware platforms. HARMLESS and its associated tools follow the Model-Driven Engineering philosophy: metamodeling and model transformations have been successfully applied to the automatic generation of processor simulators

Understanding Melatonin Receptor Pharmacology: Latest Insights from Mouse Models, and Their Relevance To Human Disease

Melatonin, the neuro-hormone synthesized during the night, has recently seen an unexpected extension of its functional implications toward type 2 diabetes development, visual functions, sleep disturbances, and depression. Transgenic mouse models were instrumental for the establishment of the link between melatonin and these major human diseases. Most of the actions of melatonin are mediated by two types of G protein-coupled receptors, named MT1 and MT2, which are expressed in many different organs and tissues. Understanding the pharmacology and function of mouse MT1 and MT2 receptors, including MT1/MT2 heteromers, will be of crucial importance to evaluate the relevance of these mouse models for future therapeutic developments. This review will critically discuss these aspects, and give some perspectives including the generation of new mouse models