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De Boisboissel G.,Ecoles de Saint-Cyr Coetquidan
ICMT 2015 - International Conference on Military Technologies 2015 | Year: 2015

This paper is a prospective view on how Lethal Autonomous Weapon Systems (LAWS) could be used by Armed Forces. It addresses the operational benefits and ethical issues in the use of such systems. Several scenarios are also presented on the future deployment of such systems on a battlefield. © 2015 University of Defence.

Brezillon A.,University of Southern Brittany | Girault G.,Ecoles de Saint-Cyr Coetquidan | Cadou J.M.,University of Southern Brittany
Computers and Fluids | Year: 2010

This paper deals with the computation of Hopf bifurcation points in fluid mechanics. This computation is done by coupling a bifurcation indicator proposed recently (Cadou et al., 2006) [1] and a direct method (Jackson, 1987; Jepson, 1981) [2,3] which consists in solving an augmented system whose solutions are Hopf bifurcation points. The bifurcation indicator gives initial critical values (Reynolds number, Strouhal frequency) for the direct method iterations. Some classical numerical examples from fluid mechanics, in two dimensions, are studied to demonstrate the efficiency and the reliability of such an algorithm. © 2010 Elsevier Ltd.

Cadou J.M.,University of Southern Brittany | Guevel Y.,University of Southern Brittany | Girault G.,University of Southern Brittany | Girault G.,Ecoles de Saint-Cyr Coetquidan
Fluid Dynamics Research | Year: 2012

This paper deals with the numerical study of bifurcations in the two-dimensional (2D) lid-driven cavity (LDC). Two specific geometries are considered. The first geometry is the two-sided non-facing (2SNF) cavity: the velocity is imposed on the upper and the left side of the cavity. The second geometry is the four-sided (4S) cavity where all the sides have a prescribed motion. For the first time, the linear stability analysis is performed by coupling two specific algorithms. The first one is dedicated to the computation of the stationary bifurcations and the bifurcated branches. Then, a second algorithm is dedicated to the computation of Hopf bifurcations. In this study, for both problems, it is shown that the flow becomes asymmetric via a stationary bifurcation. The critical Reynolds numbers are close to 1070 and 130, respectively, for the 2SNF and the 4S cavity. Following the stationary bifurcated branches, supplementary results concerning the stability are found. Firstly, for both examples, a second stationary bifurcation appears on the unstable solution, for a Reynolds number equal to 1890 and 360, respectively, for the 2NSF and the 4S cavity. Secondly, a second stationary bifurcation is found on the stable solutions of the 4S LDC for a critical Reynolds number close to 860. Nevertheless, no Hopf bifurcation has been found on this stable bifurcated branch for Reynolds numbers between 130 and 1000. Concerning the 2SNF LDC, Hopf bifurcation points have been determined on these stable bifurcated solutions. The first bifurcation occurs for a Reynolds number close to 3000 and a Strouhal number equal to 0.47. © 2012 The Japan Society of Fluid Mechanics and IOP Publishing Ltd.

Bartheye O.,Ecoles de Saint-Cyr Coetquidan
2nd International Conference on Communications Computing and Control Applications, CCCA 2012 | Year: 2012

In this paper, we try to precise what should be relevant algebraic, topological and axiomatic properties of self-orientation systems. Thanks to a formal apparatus one expects to measure the complexity of self-orientation computation process, to gain accuracy and ultimately to find new algorithms as corollaries of this modeling attempt. The main issue can be depicted as follows : assume that candidate self-orientations form a set S or a vector space V or more generally an algebraic structure A (e.g. a partially ordered set P, a monoid M, a semi-group S,...); if the computation of a self-orientation refers to a motivated choice among possible orientations inside an algebraic structure, one should be able in this structure to separate 'good' and 'bad' self-orientations. That is, consistency is required and as such needs to be defined. Take a cognitive entity e; a 'good' valuation is called a e-model and is noted e and a 'bad' valuation is called e-counter-model and is noted e. Therefore, consistent self-orientations can be called formal actions provided that the algebraic structure must agree with the separable property which in terms of polynomial algebra corresponds to the reducible property. This paper try to connect algebraic and geometrical representations of actions and axiomatic consistent representations using deductive systems and Hopf Algebras. © 2012 IEEE.

Guevel Y.,University of Southern Brittany | Girault G.,Ecoles de Saint-Cyr Coetquidan | Cadou J.M.,University of Southern Brittany
Computers and Fluids | Year: 2014

This work deals with the computation of steady bifurcation points in 2D incompressible Newtonian fluid flows. The problem is modeled with the Navier-Stokes equations with an evolving geometric parameter. The aim of the present study is to propose a reliable and efficient numerical method for parametric steady bifurcation calculations. The numerical algorithm is based on the coupling of a continuation method with a homotopy technique. The continuation method lies on the asymptotic numerical method with Padé approximants for an initial linear stability analysis with an initial geometric configuration. The homotopy technique completes the calculation with the computation of critical Reynolds numbers for different discrete values of the geometric parameter. Two classical numerical problems are approached. The first one is the flow in sudden expansion. The geometric parameter is the height of the expansion inlet. The second problem is the flow in a divergent/convergent channel. In this case, the geometric parameter is the length of the channel. Comparisons of results with those obtained from the literature are performed, showing the efficiency of the proposed algorithm. The aim of this study is to determine the critical Reynolds numbers of the flow using few computations for each geometric parameter. © 2014 Elsevier Ltd.

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