Complex Eigenvalue Analysis for Structures with Viscoelastic Behavior

This document deals with a method for eigenvalue extraction for the analysis of structures with viscoelastic materials. A generalized Maxwell model is used to model linear viscoelasticity. Such kind of model necessitates a state-space formulation to perform eigenvalue analysis with standard solvers. This formulation is very close to ADF formulation. The use of several materials on the same structure and during the same analysis may lead to a large number of internal states. This article purpose is to identify simultaneously all the viscoelastic materials and to constrain them to have the same time-constants. As it is usually possible, the size of the state-space problem is therefore widely reduced. Moreover, an accurate method for reducing mass and stiffness operators is proposed; The enhancement of the modal basis allows to obtain good results with large reduction. As the length of the paper is limited, only theoretical development are presented in the present paper while numerical results will be presented in the conference.Comment: ASME 2011 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference (IDETC/CIE2011), Washington : France (2011

The Minimal Controllability Problem for structured systems

This paper considers the Minimal Controllability Problem (MCP), {\em i.e.} the problem of controlling a linear system with an input vector having as few non-zero entries as possible. We focus on structured systems which represent an interesting class of parameter dependent linear systems and look for structural controllability properties based on the sparsity pattern of the input vector. We show first that the MCP is solvable when a rank condition is satisfied and show that generically one non-zero entry in the input vector is sufficient to achieve controllability when there is no specific system structure. We give, according to the fixed zero/non-zero pattern of the state matrix entries, the minimum number and the possible location of non-zero entries in the input vector to ensure generic controllability. The analysis based on graph tools provides with a simple polynomial MCP solution and highlights the structural mechanisms that make it useful to act on some variables to ensure controllability

Vers un modèle du développement vocationnel de l'adulte

The first part of this article places in its proper context previous research work conducted in vocational development during adult life; this brief overview serves as a yardstick to appraise the lack of importance and general directions given in the literature to this period of life. The authors argue that continuing education curricula would benefit immensely from greater interest and knowledge derived from the vocational aspects of adults. The second part of this paper presents a model of adulthood vocational development. The model assumes that career development is a life-span process that goes through various structural periods which are either preceded or followed by transition cycles. As vocational development unfolds throughout nine identified stages, adults are usually action-oriented during their structural periods and question-oriented during their transition periods. This constant vocational self-evaluation is the determining force that will give rise to drastic career changes, retrogradation, etc. As each of the nine vocational development periods has distinct characteristics, it becomes possible not only to anticipate them but also to relate them to a particular adult individual's development stage.Cet article pre´sente tout d'abord l'importance et les objectifs de l'e´tude du de´veloppement vocationnel de l'adulte ainsi que son rapport avec les recherches de´ja` faites et la docu- mentation existante. Les auteurs pre´tendent que la pe´riode adulte (adulthood) a e´te´, a` quelques exceptions pre`s, ignore´e dans son aspect vocationnel alors que pre´cise´ment cette connaissance pourrait s'ave´rer essentielle dans l'e´laboration des curricula pour l'e´ducation permanente. Par la suite, les auteurs pre´sentent le mode`le lui-me^me. Ce mode`le postule que le de´veloppement vocationnel de l'adulte se poursuit jusqu 'a` la mort et se re´alise par pe´riodes de structuration suivies ou pre´ce´de´es de pe´riodes de transition. Tout en poursuivant son de´veloppement vocationnel tout le long de ces pe´riodes, l'adulte vit des pe´riodes de structuration, davantage marque´es par une action plus intense, alors que les pe´riodes de transition sont surtout characte´ristiques de "questionnement"; ces dernie`res peuvent conduire a` une varie´te´ de phe´nome`nes vocationnels incluant, par exemple, des changements radicaux de carrie`re, des re´trogradations, etc. Chacune des neuf pe´riodes de transition et de structuration ont des contenus bien spe´cifiques qui les distinquent les unes des autres. Ces diverses pe´riodes (ou stades) sont des passages pre´visibles de l'adulte dans sa vie vocationnelle qui donnent un sens, une direction a` son e´volution ou a` son de´veloppement vocationnel

Quasi-Likelihood Estimation for Ornstein-Uhlenbeck Diffusion Observed at Random Time Points

2000 Mathematics Subject Classification: 60J60, 62M99.In this paper, we study the quasi-likelihood estimator of the drift parameter θ in the Ornstein-Uhlenbeck diffusion process, when the process is observed at random time points, which are assumed to be unobservable. These time points are arrival times of a Poisson process with known rate. The asymptotic properties of the quasi-likelihood estimator (QLE) of θ, as well as those of its approximations are also elucidated. An extensive simulation study of these estimators is also performed. As a corollary to this work, we obtain the quasi-likelihood estimator iteratively in the deterministic framework with non-equidistant time points.The first and third authors greatly appreciate the support of the Naturel Sciences and Engineering Research Council of Canada for this research

Viscous photons in relativistic heavy ion collisions

Theoretical studies of the production of real thermal photons in relativistic heavy ion collisions at the Relativistic Heavy Ion Collider (RHIC) are performed. The space-time evolution of the colliding system is modelled using MUSIC, a 3+1D relativistic hydrodynamic simulation, using both its ideal and viscous versions. The inclusive spectrum and its azimuthal angular anisotropy are studied separately, and the relative contributions of the different photon sources are highlighted. It is shown that the photon v2 coefficient is especially sensitive to the details of the microscopic dynamics like the equation of state, the ratio of shear viscosity over entropy density, eta/s, and to the morphology of the initial state.Comment: 15 pages, 12 figures. References updated and discussion adde