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Using design theory to characterize various forms of breakthrough R&D projects and their management: revisiting Manhattan & Polaris.
No full textIn this paper we propose to revisit two emblematic projects, Manhattan and Polaris, with the models developed by design theory. In particular we demonstrate, relying on recent advances in design theory, how these major projects, traditionally presented as radical innovations, are in fact quite different. We show that this explains the different managerial strategies of this two cases : whereas Polaris focuses on the control of the design process, Manhattan exhibit a very original strategy, characterized by the simultaneous exploration of different solutions, to manage unforeseeable uncertainties. We therefore hope to demonstrate the fruitfulness of the dialogue between design theory and project management
Tomographic incoherent phase imaging, a diffraction tomography alternative
No full textInternational audienc
Abella: A System for Reasoning about Relational Specifications
No full textInternational audienceThe Abella interactive theorem prover is based on an intuitionistic logic that allows for inductive and co-inductive reasoning over relations. Abella supports the λ-tree approach to treating syntax containing binders: it allows simply typed λ-terms to be used to represent such syntax and it provides higher-order (pattern) unification, the ∇ quantifier, and nominal constants for reasoning about these representations. As such, it is a suitable vehicle for formalizing the meta-theory of formal systems such as logics and programming languages. This tutorial exposes Abella incrementally, starting with its capabilities at a first-order logic level and gradually presenting more sophisticated features, ending with the support it offers to the two-level logic approach to meta-theoretic reasoning. Along the way, we show how Abella can be used prove theorems involving natural numbers, lists, and automata, as well as involving typed and untyped λ-calculi and the π-calculus
OPTIMAL INSURANCE FOR CATASTROPHIC RISK: THEORY AND APPLICATION TO NUCLEAR CORPORATE LIABILITY
No full textWe analyze the optimal insurance coverage for high severity-low probability accidents, both from theoretical and applied standpoints. Such accidents qualify as catastrophic when their risk premium is a non-negligible proportion of the victims’ wealth, although the probability of occurrence is very small. We show that this may be the case when the individual’s absolute risk aversion is very large in the accident case. We characterize the optimal insurance contract firstly for an individual, and secondly for a firm that may be at the origin of an accident that affects the whole population. The optimal indemnity schedule converges to a limit when the probability of the accident tends to zero. In the case of corporate civil liability, this limit schedule is a straight deductible contract that corresponds to an indemnification of victims ranked in order of priority according to the severity of their losses. We also show that the size of the deductible depends on the individuals’ risk aversion and also on the cost of contingent risk capital that is required to sustain the indemnity payment, should an accident occur. The empirical part of the paper is an application of these general principles to the case of nuclear accidents. Large scale nuclear accidents are typical examples of high severity-low probability risks. We calibrate a model on French data in order to estimate the optimal liability ceiling of an electricity producer in the nuclear energy sector. We use data drawn from the cat-bond markets to estimate the cost of contingent capital for low probability events, and we show that the minimal corporate liability adopted in 2004 through the revision of the Paris Convention is probably lower than the level that would correspond to an optimal risk coverage of the population
Combinatorial Simplex Algorithms Can Solve Mean Payoff Games
No full textInternational audienceA combinatorial simplex algorithm is an instance of the simplex method in which the pivoting depends on combinatorial data only. We show that any algorithm of this kind admits a tropical analogue which can be used to solve mean payoff games. Moreover, any combinatorial simplex algorithm with a strongly polynomial complexity (the existence of such an algorithm is open) would provide in this way a strongly polynomial algorithm solving mean payoff games (all the arithmetic operations being performed on data polynomially bounded in the size of the input, in particular). Mean payoff games are known to be in NP and co-NP; whether they can be solved in polynomial time is an open problem. Our algorithm relies on a tropical implementation of the simplex method over a real closed field of Hahn series. One of the key ingredients is a new scheme for symbolic perturbation which allows us to lift an arbitrary mean payoff game instance into a non-degenerate linear program over Hahn series
Decaying Turbulence in the Generalised Burgers Equation
No full textInternational audienceWe consider the generalised Burgers equationwhere is strongly convex and is small and positive. We obtain sharp estimates for Sobolev norms of u (upper and lower bounds differ only by a multiplicative constant). Then, we obtain sharp estimates for the dissipation length scale and the small-scale quantities which characterise the decaying Burgers turbulence, i.e. the structure functions and the energy spectrum. The proof uses a quantitative version of an argument by Aurell, Frisch, Lutsko and Vergassola [1]. Note that we are dealing with decaying, as opposed to stationary turbulence. Thus, our estimates are not uniform in time. However, they hold on a time interval , where and depend only on and the initial condition, and do not depend on the viscosity. These results allow us to obtain a rigorous theory of the one-dimensional Burgers turbulence in the spirit of Kolmogorov's 1941 theory. In particular, we obtain two results which hold in the inertial range. On one hand, we explain the bifractal behaviour of the moments of increments, or structure functions. On the other hand, we obtain an energy spectrum of the form . These results remain valid in the inviscid limit
Label-free Modular Systems for Classical and Intuitionistic Modal Logics
No full textInternational audienceIn this paper we show for each of the modal axioms d, t, b, 4, and 5 an equivalent set of inference rules in a nested sequent system, such that, when added to the basic system for the modal logic K, the resulting system admits cut elimination. Then we show the same result also for intuitionistic modal logic. We achieve this by combining structural and logical rules
Contribution aux risques d’information asymétrique,de longévité et d’externalisation
No full textCe mémoire est une synthèse de mes travaux de recherche depuis ma thèse doctorale. Ces travaux s’articulent selon trois thèmes: Risque de défaut et information asymétrique, Risque de longévité et règle de Ramsey avec utilité progressive, Contrat Partenariat-Public-Privé et Externalisation de la dette. Ces sujets sont issus de motivations rattachéesaux domaines de la finance, de l’assurance ou de l’ ́économie. L’étude de cesproblèmes fait intervenir des outils mathématiques et probabilistes variés,comme par exemple des outils de grossissements de filtrations, des techniquesd’optimisation reposant sur des méthodes de dualité , du contrôle stochastique,des méthodes de programmation dynamique et de la théorie des jeux
The response of superpressure balloons to gravity wave motions
No full textInternational audienceSuperpressure balloons (SPB), which float on constant density (isopycnic) surfaces, provide a unique way of measuring the properties of atmospheric gravity waves (GW) as a function of wave intrinsic frequency. Here we devise a quasi-analytic method of investigating the SPB response to GW motions. It is shown that the results agree well with more rigorous numerical simulations of balloon motions and provide a better understanding of the response of SPB to GW, especially at high frequencies. The methodology is applied to ascertain the accuracy of GW studies using 12 m diameter SPB deployed in the 2010 Concordiasi campaign in the Antarctic. In comparison with the situation in earlier campaigns, the vertical displacements of the SPB were measured directly using GPS. It is shown using a large number of Monte Carlo-type simulations with realistic instrumental noise that important wave parameters, such as momentum flux, phase speed and wavelengths, can be retrieved with good accuracy from SPB observations for intrinsic wave periods greater than ca. 10 min. The noise floor for momentum flux is estimated to be ca. 10-4 mPa. © Author(s) 2014