363 research outputs found
Quantitative analysis of multi-periodic supply chain contracts with options via stochastic programming
We propose a stochastic programming approach for quantitative analysis of supply contracts, involving flexibility, between a buyer and a supplier, in a supply chain framework. Specifically, we consider the case of multi-periodic contracts in the face of correlated demands. To design such contracts, one has to estimate the savings or costs induced for both parties, as well as the optimal orders and commitments. We show how to model the stochastic process of the demand and the decision problem for both parties using the algebraic modeling language AMPL. The resulting linear programs are solved with a commercial linear programming solver; we compute the economic performance of these contracts, giving evidence that this methodology allows to gain insight into realistic problems.stochastic programming; supply contract; linear programming; modeling software; decision tree
Design and operations of gas transmission networks
Problems dealing with the design and the operations of gas transmission networks are challenging. The difficulty mainly arises from the simultaneous modeling of gas transmission laws and of the investment costs. The combination of the two yields a non- linear non-convex optimization problem. To obviate this shortcoming, we propose a new formulation as a multi-objective problem, with two objectives. The first one is the investment cost function or a suitable approximation of it; the second is the cost of energy that is required to transmit the gas. This energy cost is approximated by the total energy dissipated into the network. This bi-criterion problem turns out to be convex and easily solvable by convex optimization solvers. Our continuous optimization formulation can be used as an efficient continuous relaxation for problems with non-divisible restrictions such as a limited number of available commercial pipe dimensions.gas transmission networks, reinforcement, convex optimization
La genĂšse du poste de chef dâĂ©tat-major des armĂ©es
Lâhistoire de lâĂ©mergence du poste de chef d'Ă©tat-major des armĂ©es reste Ă Ă©crire, plus encore si lâon sâintĂ©resse Ă lâavant-1962. Elle est pourtant au cĆur de lâĂ©volution du systĂšme politico-militaire français et, au-delĂ , du modĂšle rĂ©publicain. Cet article en pose les premiers jalons en sâappuyant sur les rares Ă©tudes existant et sur les rĂ©sultats de recherches inĂ©dites. Lâensemble illustre lâintĂ©rĂȘt de lâapproche politico-administrative pour ouvrir de nouvelles perspectives dans lâhistoire de la dĂ©fense française depuis 1870.The origins of the post of French chief of staff of the armed forces. The history of the emergence of the office of chief of staff of the armed forces remains to be written, especially if one is interested in what occurred before 1962. The post does, however, lie at the heart of the evolution of the French system of civil-military relations and, going beyond that, it lies at the heart of the âRepublican modelâ. This article points the way towards a full history, drawing upon the rare studies that already exist as well as on unpublished research. The matter illustrates the interest in adopting a politico-administrative approach to the study of the topic, by means of which one can open up new perspectives into the history of French defence since 1870
Colonel PĂ©tain, Cours dâinfanterie enseignĂ© Ă lâĂcole supĂ©rieure de guerre (1911).
Ă la diffĂ©rence de Foch, PĂ©tain nâa jamais beaucoup Ă©crit et encore moins publiĂ©. DâoĂč lâintĂ©rĂȘt du cours dâinfanterie dactylographiĂ© retrouvĂ© par Jean Delmas dans les archives de lâĂcole supĂ©rieure de guerre Ă la fin des annĂ©es 1960, quand il y Ă©tait professeur dâhistoire. VersĂ© aux collections des bibliothĂšques de lâĂcole militaire et de Vincennes, ce texte Ă©tait depuis connu des historiens mais nâavait jamais Ă©tĂ© mis Ă la disposition des lecteurs. Ă la veille du centenaire de la Grande gue..
Ăric SchĂ©rer, Les uniformes des officiers de la marine, 1830-1940
Cet ouvrage constitue une rĂ©ussite Ă©vidente, sur le fond comme dans la forme. PubliĂ© dans un format Ă lâitalienne, il se prĂ©sente comme un « beau livre », Ă la prĂ©sentation Ă©lĂ©gante, aussi agrĂ©able Ă feuilleter pour le plaisir quâĂ consulter pour les besoins dâune recherche. Un rĂ©sultat obtenu en particulier grĂące Ă un Ă©quilibre tenu entre le texte, savant sans ĂȘtre jamais obscur, et les nombreuses illustrations qui le soutiennent, issues en premier lieu de la collection de lâauteur. Car Ăric..
Denis Lefebvre, Les secrets de lâexpĂ©dition de Suez, 1956
En dĂ©pit de son importance, la crise de Suez nâa pas fait lâobjet, en France, de nombreux travaux de synthĂšse. Quand, en 1996, Ă lâoccasion du quarantiĂšme anniversaire de la crise, Denis Lefebvre se lança dans lâaventure, le petit ouvrage quâil publia alors contribua Ă combler ce vide de maniĂšre bienvenue. On ne peut donc que se fĂ©liciter de le voir aujourdâhui republiĂ© sous une forme nettement enrichie. Lâouvrage a en effet pratiquement doublĂ© et son titre annonce des rĂ©vĂ©lations, dans un cl..
Co-design of the Medical Assistive and Transactional Technologies system
National audienceThis paper could argue that the co-design method is strongly needed to design acceptable and usable assistive technologies. It describes the co-design of the Medical Assistive and Transactional Technologies (MATT) system. This method was implemented for Matthieu a quadriplegic and a non verbal person. The paper reports how the collaborative design was running between Matthieu, his occupational therapists, his family and the designer team
Decomposition and parallel processing techniques for two-time scale controlled Markov chains
This paper deals with a class of ergodic control problems
for systems described by Markov chains with
strong and weak interactions. These systems are composed
of a set of m subchains that are weakly coupled.
Using results recently established by Abbad et
al. one formulates a limit control problem the solution
of which can be obtained via an associated non-differentiable
convex programming (NDCP) problem. The
technique used to solve the NDCP problem is the Analytic
Center Cutting Plane Method (ACCPM) which
implements a dialogue between, on one hand, a master
program computing the analytical center of a localization
set containing the solution and, on the other hand,
an oracle proposing cutting planes that reduce the size
of the localization set at each main iteration. The interesting
aspect of this implementation comes from two
characteristics: (i) the oracle proposes cutting planes
by solving reduced sized Markov Decision Problems
(MDP) via a linear program (LP) or a policy iteration
method; (ii) several cutting planes can be proposed simultaneously
through a parallel implementation on m
processors. The paper concentrates on these two aspects
and shows, on a large scale MDP obtained from
the numerical approximation "a la Kushner-Dupuisâ of
a singularly perturbed hybrid stochastic control problem,
the important computational speed-up obtained
An oracle based method to compute a coupled equilibrium in a model of international climate policy
This paper proposes a computational game-theoretic model for the international negotiations that should take place at the end of the period covered by the Kyoto protocol. These negotiations could lead to a self-enforcing agreement on a burden sharing scheme given the necessary global emissions limit that will be imposed when the real extent of climate change is known. The model assumes a non-cooperative behavior of the parties except for the fact that they will be collectively committed to reach a target on total cumulative emissions by the year 2050. The concept of normalized equilibrium, introduced by J.B. Rosen for concave games with coupled constraints, is used to characterize a family of dynamic equilibrium solutions in an m-player game where the agents are (groups of) countries and the payoffs are the welfare gains obtained from a Computable General Equilibrium (CGE) model. The model deals with the uncertainty about climate sensitivity by computing an S-adapted equilibrium. These equilibria are computed using an oracle-based method permitting an implicit definition of the payoffs to the different players, obtained through simulations performed with the global CGE model GEMINI-E
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