Developed nonlinear model based on bootstrap aggregated neural networks for predicting global hourly scale horizontal irradiance

This research study examines the use of two models of artificial intelligence based on a single neural network (SNN) and bootstrap aggregated neural networks (BANN) for the prediction value of hourly global horizontal irradiance (GHI) received over one year in Tamanrasset City (Southern Algeria). The SNN and BANN were created using overall data points. To improve the accuracy and durability of neural network models generated with a limited amount of training data, stacked neural networks are developed. To create many subsets of training data, the training dataset is re-sampled using bootstrap re-sampling with replacement. A neural network model is created for each set of training datasets. A stacked neural network is created by combining multiple individual neural networks (INN). For the testing phase, higher correlation coefficients (R = 0.9580) were discovered when experimental global horizontal irradiance (GHI) was compared to predicted global horizontal irradiance (GHI). The performance of the models (INN, BANN, and SNN) demonstrates that models generated with BANN are more accurate and robust than models built with individual neural networks (INN) and (SNN)

Effect of the turbulence model on the aerodynamic structure around a Savonius wind rotor

Ce travail vise à étudier l'effet du modèle de turbulence sur les caractéristiques aérodynamiques de l'écoulement autour d'un rotor Savonius. Pour faire, nous avons développé une simulation numérique à l'aide du code commercial CFD Fluent. Le modèle numérique est basé sur la résolution des équations de Navier -Stokes. Ces équations sont résolues par une discrétisation volumes finis. Deux modèles de turbulence sont considérés : le modèle k-ԑ et le modèle k-ԑ RNG. Particulièrement, nous sommes intéressés à visualiser le champ de vitesse, la vitesse moyenne et la pression statique. L'accord entre nos résultats numériques et les résultats antérieurs confirme la validité de la méthode d'analyse adoptée

Caractérisation hydrodynamique des turbines de Rushton dans une cuve agitée en régime turbulent

L’étude numérique de l’influence du nombre des pales d’une turbine de Rushton sur la structure hydrodynamique d’une cuve agitée a été entamée. Les équations de Naviers-Stokes régissant le phénomène sont résolues par une méthode de discrétisation aux volumes finis. Le modèle de turbulence utilisé est du type k–epsilon standard. Les résultats numériques issus de l’application de notre code de calcul sont présentés dans différents plans de la cuve

The Effects of Curved Blade Turbine on the Hydrodynamic Structure of a Stirred Tank

This work is aimed at studying the hydrodynamic structure in a cylindrical stirred vessel equipped with an eight-curved blade turbine. Flow fields were measured by two-dimensional particle image velocimetry (PIV) to evaluate the effect of the curved blade turbine. Velocity field, axial and radial velocity distribution, root mean square (rms) of the velocity fluctuations, vorticity, and turbulent kinetic energy were presented. Therefore, two recirculation loops were formed close to the free surface and in the bottom of the tank. Moreover, the highest value area of the vorticity is localized in the upper region of the tank which follows the same direction of the first circulation loop. The turbulent kinetic energy is maximum at the blade tip following the trailing vortices

Studies on Arabic Dialectology and Sociolinguistics

This volume contains over fifty articles related to various fields of modern Arabic dialectology. All the articles are revised and enhanced versions of papers read on the 12th Conference of the Association Internationale de Dialectologie Arabe (AIDA) held in Marseille in June 2017. Since its first conference in Paris in 1993, AIDA members gather every two years in different country. The collection of the AIDA proceedings offer an updated insight of the development of the field. During the past few decadesthe the study of Arabic dialects has become an important branch of research covering a wide range of subjects from phonological analyses, morphosyntax, semantics to pragmatics, sociolinguistics, folk linguistics, studies on literacy and writings, cultural and artistic practices, etc. As many articles of this volume illustrate, the study of Arabic dialects explores different aspects of the languages and cultures of the contemporary Arab world. A remarkable feature is the growing and constant participation of young scholars from all around the globe

The evolving SARS-CoV-2 epidemic in Africa: Insights from rapidly expanding genomic surveillance

INTRODUCTION Investment in Africa over the past year with regard to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) sequencing has led to a massive increase in the number of sequences, which, to date, exceeds 100,000 sequences generated to track the pandemic on the continent. These sequences have profoundly affected how public health officials in Africa have navigated the COVID-19 pandemic. RATIONALE We demonstrate how the first 100,000 SARS-CoV-2 sequences from Africa have helped monitor the epidemic on the continent, how genomic surveillance expanded over the course of the pandemic, and how we adapted our sequencing methods to deal with an evolving virus. Finally, we also examine how viral lineages have spread across the continent in a phylogeographic framework to gain insights into the underlying temporal and spatial transmission dynamics for several variants of concern (VOCs). RESULTS Our results indicate that the number of countries in Africa that can sequence the virus within their own borders is growing and that this is coupled with a shorter turnaround time from the time of sampling to sequence submission. Ongoing evolution necessitated the continual updating of primer sets, and, as a result, eight primer sets were designed in tandem with viral evolution and used to ensure effective sequencing of the virus. The pandemic unfolded through multiple waves of infection that were each driven by distinct genetic lineages, with B.1-like ancestral strains associated with the first pandemic wave of infections in 2020. Successive waves on the continent were fueled by different VOCs, with Alpha and Beta cocirculating in distinct spatial patterns during the second wave and Delta and Omicron affecting the whole continent during the third and fourth waves, respectively. Phylogeographic reconstruction points toward distinct differences in viral importation and exportation patterns associated with the Alpha, Beta, Delta, and Omicron variants and subvariants, when considering both Africa versus the rest of the world and viral dissemination within the continent. Our epidemiological and phylogenetic inferences therefore underscore the heterogeneous nature of the pandemic on the continent and highlight key insights and challenges, for instance, recognizing the limitations of low testing proportions. We also highlight the early warning capacity that genomic surveillance in Africa has had for the rest of the world with the detection of new lineages and variants, the most recent being the characterization of various Omicron subvariants. CONCLUSION Sustained investment for diagnostics and genomic surveillance in Africa is needed as the virus continues to evolve. This is important not only to help combat SARS-CoV-2 on the continent but also because it can be used as a platform to help address the many emerging and reemerging infectious disease threats in Africa. In particular, capacity building for local sequencing within countries or within the continent should be prioritized because this is generally associated with shorter turnaround times, providing the most benefit to local public health authorities tasked with pandemic response and mitigation and allowing for the fastest reaction to localized outbreaks. These investments are crucial for pandemic preparedness and response and will serve the health of the continent well into the 21st century

Stabilisation par retour d'état d'une classe de systèmes dynamiques à temps discret et à retards multiples variant dans le temps

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Contribution à la commande robuste d'une classe de systèmes dynamiques à retard

Ce mémoire de thèse est consacré au développement des outils d'analyse et des techniques de calcul de lois de commande par retour d'état ou de sortie pour une classe de systèmes dynamiques à états retardés. Les modèles utilisés pour décrire les comportements des systèmes à retard sont des représentations d'états linéaires invariantes dans le temps et de dimension infinie. Les modèles considérés sont sujets à des incertitudes résultant d'approximations lors de la modélisation. Les techniques d'analyse et de commande proposées dans ce mémoire tiennent compte des incertitudes et sont dites alors robustes. L'analyse envisagée dans cette thèse a pour objectif de fournir des conditions sous forme d'inégalités linéaires matricielles dépendantes de la taille du retard afin de tester la stabilité de cette classe de systèmes avec ou sans incertitudes. Les techniques de calcul de lois de commande visent quant à elle à déterminer les correcteurs de type retour d'état ou de sortie pour assurer la stabilité de l'ensemble pour toutes les incertitudes admissibles. Les techniques d'analyse et de commande proposées dans cette thèse reposent sur la théorie de Lyapunov (le théorème de Lyapunov-Krasovskii ou le théorème de Lyapunov- Razumikhin), et sur la résolution de problèmes numériques souvent de type LMI.This PhD thesis is dedicated to the development of the tools for the computation of state or output feedback control law for a class of dynamical time-delay systems. The considered models are linear time invariant state space models of infinite dimension. They are subject to uncertainties that can result from approximations while building the model. Techniques relevant to analysis and control have to take those uncertainties into account. The analysis tools considered in this thesis have to provide dependent-delay conditions to check the stability for the considered class of time delay systems. Some criteria are given to this end. The tools dedicated to the computation of control laws enable to design a state feedback or static or dynamical output feedback as well as observer-based controller to guarantee the stability of the closed-loop system whatever the nature of uncertainty is. All those tools, for both analysis and control, rely upon Lyapunov theory (Lyapunov-Krasovskii theorem and Lyapunov-Razumikhin theorem), as well as upon numerical solutions to problems expressed in terms of LMI.POITIERS-BU Sciences (861942102) / SudocSudocFranceF