46 research outputs found
MODÉLISATION NUMÉRIQUE DE L’EFFET DES VIEILLISSEMENTS DE POUTRE EN BÉTON ARMÉ SOUS CHARGE MÉCANIQUE
No full textL’objectif de la présente thèse est d’analyser les poutres en matériaux composites gradués
fonctionnellement (FGM) sous la flexion statique, en utilisant la théorie HSDT
(la déformation par cisaillement d'ordre supérieur), est considéré. Un modèle mathématique est
établi, pour ces poutres composites des différentes conditions aux limites, libres, simplement
appuyés et encastrés, sous chargement. Nouvelle fonction polynomiale de cisaillement est
utilisée. Les conditions aux bords de contraintes nulles dans cette étude. Pas de facteur de
correction et prise en compte. Les propriétés des matériaux sont considérés graduées à travers
l'épaisseur, une simple loi est prise en compte. Cas illustratifs de poutres à appuis simples et
extrémités encastrés soumises à une force concentrée au centre de la poutre, et à une charge
uniformément répartie pour les poutres à appuis simples, respectivement. Ensuite, les poutres
en porte à faux sont soumises à une force de cisaillement concentrée à l'extrémité libre, et
également les poutres en porte à faux portent une charge uniformément répartie. Les cas
illustratifs présentés précédemment démontrent l'originalité de ce travail dans cette
investigation. Le modèle mathématique est établi par des équations différentielles dérivées du
principe de travail virtuel. Les équations d'équilibre et les conditions aux limites sont
présentées. Basée sur la forme de différentiation pour prédire le champ de déplacement.
La solution du modèle analytique est présentée. Le champ de déplacement incluant la rotation,
contrainte, déformation prédites à partir du modèle proposé, sont présentés. Enfin,
la comparaison entre le modèle actuel et les modèles de solutions existants dans la littérature a
montré une meilleure similitude et convergence
GPU-accelerated CFD Simulations for Turbomachinery Design Optimization
No full textDesign optimization relies heavily on time-consuming simulations, especially when using gradient-free optimization methods. These methods require a large number of simulations in order to get a remarkable improvement over reference designs, which are nowadays based on the accumulated engineering knowledge already quite optimal.High-Performance Computing (HPC) is essential to reduce the execution timeof the simulations. While parallel programming using the CPU is established since more than two decades, the use of accelerators, such as the Graphics Processing Unit (GPU), is relatively recent in design optimization. The GPU has actually a huge computational power comparable to a many-core cluster but concentrated in one device. This raw power is not easy to utilize as entire code parts have to be rewritten using a GPU programming language. Even though high-level standards (e.g. openACC) are able to bring a basic acceleration with a low development effort, it is not simple to get large speedups with these methods. Low-level programming languages are more efficient but different speedups are reported and there is a need fora deep analysis to make the GPU potential more transparent to scientists especially non-experts in HPC.In order to study the GPU acceleration for CFD steady simulations, two in-house CFD solvers have been ported to the GPU; one with explicit and the second with implicit time-stepping. After the porting and the validation of the GPU solvers, the GPU code optimization leads to the identification of a set of key parameters affecting the GPU efficiency. At the same time, both methods have been compared resulting into a performance model and a classification of the GPU acceleration of some CFD operations. The purpose is to enable scientists to take an educated decision concerning the GPU porting of their CPU applications by providing an expected GPU speedup.In addition to the two GPU CFD solvers that are now integrated into the in-house design optimization software package, this research provided key elements to reduce the ambiguity about the GPU potential, namely a qualitative analysis and a classification. These tools can help selecting the best candidate for a breakthrough in CFD acceleration. At the same time, this work identified serious limitations in the preconditioning of a linear system of equations and the limit of today iterative matrix factorization methods in terms of stability and convergence. There is a need for a paradigm shift toward inherently parallel preconditioners. The developed tools have been used for the optimization of a compressor and a turbine cascade resultinginto a faster optimization process on the GPU
Concrete Strength Variation Effect on Numerical Thermal Deformations of FRP Bars-Reinforced Concrete Beams in Hot Regions
No full textUsability of Rich Internet Applications
No full textThis thesis reports the outcome of a study that is performed for Info Support. Info Support is a software house that is interested in new technologies. Unit finance and insurance is interested in the usability of Rich Internet Applications. Rich Internet Applications are new kind of web applications that offer more possibilities to design user friendly and attractive graphical user interface (GUI) that is comparable to the GUI of desktop applications. To investigate if the usability of the Rich Internet Application is indeed better then the traditional web application, two car insurance web applications are built as a proof of concept. These web applications are built with the same usability principles and have the same content and functionalities. The only difference is the technology that is used for building the web applications. The RIA is built with JavaFX and the traditional web application with PHP/HTML. These two applications are tested in an experiment where 26 participants with different ages and sex have tested two web applications in a lab. The results of this experiment is statistically analyzed to find dependency. From the analysis we have found that the satisfaction is significant for the tested web applications and therefore we can conclude that the usability of the Rich Internet Applications is indeed more usable than the traditional web application. This finding can be useful for finance and insurance companies to convert their web applications into RIA to attract more clients to buy their products.Media knowledge engineeringElectrical Engineering, Mathematics and Computer Scienc
Well-posedness and energy decay for Timoshenko systems with discrete time delay under frictional damping and/or infinite memory in the displacement
No full textInternational audienceIn this paper, we consider a vibrating system of Timoshenko-type in a bounded one-dimensional domain with discrete time delay and complementary frictional damping and infinite memory controls all acting on the transversal displacement. We show that the system is well-posed in the sens of semigroup and that, under appropriate assumptions on the weights of the delay and the history data, the stability of the system holds in case of the equal-speed propagation as well as in the opposite case in spite of the presence of a discrete time delay, where the decay rate of solutions is given in terms of the smoothness of the initial data and the growth of the relaxation kernel at infinity. The results of this paper extend the ones obtained by the present author and Messaoudi in (Acta Math Sci 36:1–33, 2016) to the case of presence of discrete delay
Analysis of some Gastronomic Culturemes in the Extremely Contemporary Beur Novel Symbolic Images and Evoked Stories
No full textWhat subtle links between gastronomic culturemes and matrimonial customs can be revealed in the course of an extremely contemporary novel that invites us to taste the flavors of culinary art and those of an art of writing? The ineffable and unexpected answer is undoubtedly to be found in the refined intuition of an author who knows how to combine and cleverly merge community traditions of origin and Westernity in a test of the fleeting signs of interculturality. However, at the end of the road, the characters rebel, eager for freedom, still undecided between the desire to become Westernized and the need to preserve their Maghrebines
Use of modern GPUs in Design Optimisation
No full textGraphics Processing Units (GPUs) are a promising alternative hardware to CentralProcessing Units (CPU) for accelerating applications with a high computational power demand. In many fields researchers are taking advantage of the high computational power present in GPUs to speed up their applications. These applications span from data mining to machine learning and life sciences. The field of design optimization in particular benefits from this alternative hardware. The automated search on the design space has been delegated to GPUs or to a system of CPUs assisted by GPUs. This paper is among the firsts to review the use of GPUs especially for design optimization. The focus is on topology optimization, shape optimization and multidisciplinary design optimization (MDO). The target is to provide an overview not only on the progress madein design optimization using GPUs but also to highlights limitations that researchers have to cope with and the areas that require more research.Numerical Analysi
Women and politics in Algeria: essays on political representation
No full textGender and politics scholars have sought to determine whether there is a link between women’s descriptive representation, operationalized as the proportion of seats held by women in a national legislature, and women’s substantive representation, usually operationalized as laws that advance women’s rights. But, except for a few studies, the Arab world has not received significant attention which is surprising because the region has experienced a significant increase in women’s presence in politics. Further, most of this work has focused on democratic contexts, obscuring whether hypothesized links between women’s descriptive and substantive representation work in the same way in authoritarian contexts. To fill these gaps in the literature, I focus on the case of Algeria, where women’s presence in parliament increased from 8% to 31.6% after the adoption of a gender quota in 2012.
Drawing on in-depth interviews with a wide range of stakeholders, my research examines the backgrounds of women elected, constituency service priorities, legislative dynamics, and women’s agency. I argue that the “authoritarian toolkit,” i.e., the resources available to authoritarian governments to manage and control political outcomes, shapes women’s descriptive, substantive, and symbolic representation in ways that are distinct from how these dynamics operate in more democratic contexts.
While women parliamentarians reject the notion that they have an obligation to introduce and pass women’s rights laws, they invest time in helping their male and female constituents solve their everyday problems to challenge the notion that women do not belong in politics. Therefore, there may not be strong links between women's descriptive and substantive representation. However, the efforts of elected women on behalf of their male constituents may advance women’s symbolic representation by demonstrating women's abilities in the political realm.Ph.D.Includes bibliographical reference
Semi-supervised Statistical Approach for Network Anomaly Detection
No full textAbstractIntrusion Detection Systems (IDS) have become a very important defense measure against security threats. In recent years, computer networks are widely deployed for critical and complex systems, which make them more vulnerable to network attacks. In this paper, we propose a two-stage Semi-supervised Statistical approach for Anomaly Detection (SSAD). The first stage of SSAD aims to build a probabilistic model of normal instances and measures any deviation that exceeds an established threshold. This threshold is deduced from a regularized discriminant function of Maximum Likelihood (ML). The purpose of the second stage is to reduce False Alarm Rate (FAR) through an iterative process that reclassifies anomaly cluster, from the first stage, using a similarity distance and anomaly's cluster dispersion rate. We evaluate the proposed approach on the well-known intrusion detection dataset NSL-KDD and Kyoto 2006+. The experimental results show that SSAD outperforms the Naïve Bayes methods in terms of Detection Rate and False Positive Rate
Toward a GPU-aware comparison of explicit and implicit CFD simulations on structured meshes
No full textA computational Fluid Dynamics (CFD) code for steady simulations solves a set of non-linear partial differential equations using an iterative time stepping process, which could follow an explicit or an implicit scheme. On the CPU, the difference between both time stepping methods with respect to stability and performance has been well covered inthe literature. However, it has not been extended to consider modern high-performance computing systems such as GraphicsProcessingUnits(GPU). In this work, we first presentan implementation of the two time-stepping methods on the GPU, highlighting the different challenges on the programming approach. Then we introduce a classificationof basic CFD operations, found on the degree of parallelism they expose, and study the potential of GPU acceleration for every class. The classification provides local speedupsof basic operations, which are finally used to compare the performance of both methods on the GPU. The target of this work is to enable an informed-decision on the mostefficient combination of hardware and method when facing a new application. Our findings prove,that the choice between explicit and implicit time integration relies mainly on theconvergence of explicit solvers and the efficiency of preconditioners on the GPU
