Global optimization in inverse problem of scatterometry

International audienceIn the current work, we consider the inverse problem in scatterometry which consists in determining the feature shape from an experimental ellipsometric signature. The reformulation of the given nonlinear identification problem was considered as a parametric optimization problem using the Least Square criterion. In this work, a design procedure for global robust optimization is developed using Kriging and global optimization approaches. Robustness is determined by Kriging model to reduce the number of real functional calculations of Least Square criterion. The technical of the global optimization methods is adopted to determine the global robust optimum of a surrogate model

INSECTICIDAL AND ANTIOXIDANT ACTIVITIES OF AQUEOUS EXTRACTS OF TWO ALGERIAN MEDICINAL PLANTS

In this work, we determined the insecticidal activity and antioxidant activity of aqueous extracts of Nerium oleander (Apocynaceae) leaves and Peganum harmala (Zygophyllaceae) seeds, two well-known Algerian medicinal plants. Four concentrations of each extract were applied in total randomization by spraying directly on the eggs and larvae of Ectomyelois ceratoniae (Zeller, 1879) (Lepidoptera: Pyralidae) under laboratory conditions. Our findings revealed that eggs hatching after four days were not affected by the aqueous extract, with a rate of 54% of hatching eggs in both control and treated eggs. Additionally, toxicity by contact on larvae was not evident and the mortality percentage did not exceed 8%, regardless of the extract plant and concentration. Phytochemical screening showed a slight presence of terpenes and saponins and an absence of alkaloids. However, polyphenols were present in medium concentrations in the aqueous extracts of both plants. The antioxidant activities of N. oleander and P. harmala extracts were found to be 71.80 and 72.94%, respectively. Total phenolic content (TPC) and total flavonoid content (TFC) of the studied extracts were 50.69 mg gallic acid equivalent (GAE)/100 g dry weight (DW) and 3.55 in terms of quercetin equivalent (QE)/100 g DW, respectively, in N. oleander. In P. harmala, the TPC and TFC were 52.30 mg GAE/100 g DW and 3.49 mg QE/100 g DW, respectively. Our study clearly shows the limited insecticidal effect of the aqueous extracts, although they showed an interesting antioxidant potential, which could help to decrease the incidence of oxidative stress-induced damage

Optimal control for a two-sidedly degenerate aggregation equation

In this paper, we are concerned with the study of the mathematical analysis for an optimal control of a nonlocal degenerate aggregation model. This model describes the aggregation of organisms such as pedestrian movements, chemotaxis, animal swarming. We establish the wellposedness (existence and uniqueness) for the weak solution of the direct problem by means of an auxiliary nondegenerate aggregation equation, the Faedo–Galerkin method (for the existence result) and duality method (for the uniqueness). Moreover, for the adjoint problem, we prove the existence result of minimizers and first-order necessary conditions. The main novelty of this work concerns the presence of a control to our nonlocal degenerate aggregation model. Our results are complemented with some numerical simulations

Improved energy conversion performance of a novel design of concentrated photovoltaic system combined with thermoelectric generator with advance cooling system

Most of the incident solar energy on a PV panel is converted into waste heat. This consequently reduces the efficiency of PV system. Therefore, if certain portion of this waste heat can be utilized adding a thermoelectric generator (TEG) in the PV panel endowed by an efficient cooling system, the output performance of the system can be improved significantly. In this study, a new configuration of nanofluid-based PV/T-TEG hybrid system with cooling channel is proposed to convert certain portion of waste heat to electrical energy in order to improve the overall efficiency of hybrid system. Thus, the nanofluid acts as a coolant and absorbs the heat from the back side of TEG module raising its gradient of temperature, as well as the overall performance of the system. Through a numerical modelling approach, performance of the proposed innovative design has been investigated and compared with the conventional solar-harvesting technology systems. At the optimum value of solar concentration C, and maximum operating temperature of 35°C, the obtained results reveal that the electrical energy in NCPV/T-TEG configuration has been found higher by 10%, 47.7% and 49.5% against NCPV/T, CPV and CPV/TEG-HS systems, respectively. Overall, the proposed design of NCPV/T-TEG hybrid system has potential for further development in high-concentration solar systems. © 2018 Elsevier Lt

Energy performance investigation of nanofluid‐based concentrated photovoltaic / <scp>thermal‐thermoelectric</scp> generator hybrid system

Nanofluid can be used in a CPV/T solar collector to boost electrical and thermal performances as this technology has drawn great attention from researchers over the last decades. In a CPV/T system, the amount of collected heat could be significantly higher than the amount of electrical power. Combining thermoelectric generator (TEG) and nanofluid-based CPV/T system may result in better electrical performance than CPV/T system alone. In the present work, a nanofluid-based CPV/T-TEG hybrid system with a cooling channel was designed and tested, and the obtained performance was compared with conventional cooling methods [ie, natural cooling (CPV/TEG) and water cooling (WCPV/T-TEG) methods]. At the optimum value of solar concentration, C = 14.6, the electrical performance of the nanofluid-based concentrated photovoltaic/thermal-thermoelectric generator (NCPV/T-TEG) configuration was found to be ~89% higher than the standard PV modules. For the same concentration, the electrical performance of the above configuration was found to be ~13.9% and ~8.4% higher than CPV/TEG and WCPV/T-TEG configurations, respectively. In addition, the overall thermal energy of the NCPV/T-TEG was found to be higher by 4.98% compared to WCPV/T-TEG hybrid system. The NCPV/T-TEG configuration was found to produce 92.47%, 41.06%, and 8.8% higher daily exergy compared to standard PV cell, CPV/TEG, and WCPV/T-TEG, respectively. Overall, the proposed design of the NCPV/T-TEG hybrid system has the potential for further development in high-concentration solar systems

Effect of plastic strain of nickel single crystal on the equilibrium state of hydrogen in surface and subsurface

Le présent travail a pour objectif d’étudier la synergie entre la déformation plastique et les processus d’adsorption et d’absorption de l’hydrogène en surface et en subsurface du nickel monocristallin. La Réaction d’Evolution de l’Hydrogène (REH) et l’absorption de l’hydrogène en subsurface (RAH)partagent le plus souvent l’intermédiaire commun : l’hydrogène adsorbé (Hads). Le chemin réactionnel de la REH sur des surfaces de nickel (100) en milieu acide sulfurique peut être présenté par un mécanisme de Volmer-Heyrovsky. Les paramètres cinétiques élémentaires correspondants comme les coefficients de symétrie, les enthalpies d'activation, le nombre de sites actifs, ont été simulés via un modèle thermocinétique en utilisant les données expérimentales. Ces paramètres peuvent être affectés par la déformation plastique. Cette dernière modifie la densité et la distribution des dislocations stockées affectant la rugosité de surface à l'échelle atomique et engendrant des sites actifs supplémentaires d'adsorption. En revanche, l’émergence de ligne de glissement à la surface conduit à un phénomène de désactivation associé la formation de plan plus compact (111). L’entrée d’atomes d’hydrogène associée à l’étape de transfert surface-Subsurface peut être mesurée à l’aide d’une méthode potentiostatique de type pulsé. Cette dernière a permis de caractériser la diffusion et le piégeage de l'hydrogène en subsurface. Deux zones peuvent être distinguées, l’une proche de la surface (subsurface) et l’autre au coeur de l'échantillon. Dans ce cas, le coefficient de diffusion associé à la subsurface semble être beaucoup plus élevé que celui obtenu au coeur du métal. En revanche,l’application d’une contrainte mécanique conduit à une augmentation de la densité de pièges. Cette dernière, développée au voisinage de la surface : « subsurface », est plus faible que celle à coeur du matériau, ce qui suggère un effet adoucissant en subsurface.The present work has for objective to study the synergy between the plastic strain and the processes of adsorption and absorption of hydrogen on the surface and the subsurface of nickel single crystal.Hydrogen Evolution Reaction (HER) and Hydrogen Absorption in subsurface (HAR) share mostly the common intermediate: the adsorbed hydrogen (Hads). The HER pathway on nickel (100) single crystal surfaces in sulphuric acid medium can be related by a Volmer-Heyrovsky mechanism. The corresponding elementary kinetic parameters as symmetry coefficients, activation enthalpies, number of active sites, have been identified via a thermokinetic model using experimental data. These parameters can be affected by defects associted with plastic strain. Irreversible plastic strain modifies the density and the distribution of storage dislocations affecting the surface roughness at atomic scale and generating additional active adsorption sites. Further more, surface emergence of mobile dislocations induces the formation of slip bands, which modify the surface roughness and the electronic state of the surface and increases the (111) surface density. The entry of hydrogen atoms associated to the transfer step surface-Subsurface can be measured using a potentiostatic double-Steptechnique (pulse method). This last allowed to characterizing the diffusion and trapping of hydrogen in the subsurface. Two domains can be distinguished, that of the subsurface and that of the bulk of the sample. In this case, the diffusion coefficient near the surface (subsurface) seems to be much higher than that obtained in the bulk of the metal. On the other hand, the application of mechanical stressleads to an increase of traps density. This last, developed near the surface: « subsurface », is lower than that at the bulk of material, which suggest a softening effect in the subsurface

Apports des TIC dans l'enseignement et l’apprentissage des mathématiques : Scénarisation pédagogique et pratiques de l'enseignement à distance

L’intégration des TICE (technologie d’information et de communication dans l’enseignement) nécessite une réflexion profonde sur l’évolution des pratiques de classe. Elle nécessite surtout l’innovation dans le choix et dans la conception des situations des apprentissages qui utilisent d’une façon progressive et rationnelle les ressources numériques. Le choix adéquat des approches pédagogiques et didactiques de l'enseignant et des ressources numériques à utiliser ont un impact direct sur l’amélioration de la qualité des apprentissages mathématiques. Dans notre contribution nous réservons une place pour l’impact de la scénarisation et le film éducatif notamment dans l’apprentissage et l’enseignement à distance pour assurer la continuité pédagogique. Nous nous concentrons aussi sur la classe inversée et le e-learning pour leurs rôles dans l’auto-apprentissage des apprenants. Toutefois, il faut signaler que la conception de nouvelles ressources éducatives numériques et leur mise en oeuvre présentent un défi majeur pour les enseignants ; pour produire une nouvelle ressource numérique, il faut combiner les fonctionnalités de plusieurs logiciels. On parle alors des concepts liés à la genèse et l’orchestration instrumentale [1, 12]