Path Relinking in Pareto Multi-objective Genetic Algorithms

Path relinking algorithms have proved their efficiency in single objective optimization. Here we propose to adapt this concept to Pareto optimization. We combine this original approach to a genetic algorithm. By applying this hybrid approach to a bi-objective permutation flow-shop problem, we show the interest of this approach. In this paper, we present first an Adaptive Genetic Algorithm dedicated to obtain a first well diversified approximation of the Pareto set. Then, we present an original hybridization with Path Relinking algorithm, in order to intensify the search between solutions obtained by the first approach. Results obtained are promising and show that cooperation between these optimization methods could be efficient for Pareto optimization

Theoretical modeling of a new structure of III-V tandem solar cells by using parabolic trough concentrator

In this study, potential efficiency of GaInP/GaAs mechanically stacked two-junction solar cell is theoretically investigated by optimizing the thickness of GaAs and GaInPandusing a new optical model to separate the junction between the two solar cell in order to solve problems of tunnel junction and difficulties of fabrication. The principal of this new model is inspired from that of parabolic trough concentrator. Results show that the optimum conversion efficiency is 43 % under AM1.5 spectral illuminations. The obtained results from computation and Matlab simulation of three fundamental parameters which are Reflectance R, external quantum efficiency QE and current density J, would be helpful in designing and fabricating high efficiency GaInP/GaAs mechanically stacked solar cell in experiment.Keywords: GaInP/GaAs; parabolic trough concentrator; optical model; AM1, 5 illuminatio

Etat Environnemental Des Sols De La Region De Casablanca

La pollution chimique, dans la région de Casablanca impacte la qualité des sols agricoles. Cinq sites de la région de Casablanca sont étudiés : les sites d’Oued Hassar, Oued Merzeg, Bouskoura, Benslimane-Mohammedia et Bouznika. L’objectif est l’analyse comparative de cinq éléments traces métalliques(Cadmium, Plomb, Cuivre, Zinc et Nickel) des sols afin d’évaluer l’état environnemental et de préserver les potentialités et l’innocuité des sites de la région de Casablanca . Un suivi des variations des paramètres physico-chimiques du sol (pH, carbonates de calcium et matières organiques) est réalisé, suite à la dégradation de l’eau d’irrigation par l’utilisation d’eaux usées, et de l’impact de la pollution chimique. L’étude statistique par le test d’Anova montre des différences significatives concernant les paramètres physico-chimiques entre tous les sites. L’analyse des éléments traces métalliques montre que les sols des sites irrigués par Oued Hassar présentent des teneurs en Cadmium de 2,91 ppm et en Plomb de 137,61ppm qui dépassent les normes préconisées par l’Organisation Mondiale de la Santé (O.M.S.), respectivement de 2 ppm et 100 ppm. Les teneurs en Cuivre dans les sols des sites irrigués par l’Oued Merzeg restent les plus élevées et sont de 896,62 ppm. Les teneurs en Zinc dans les sols proches de la cimenterie de Bouskoura sont prédominantes par rapport aux autres éléments et sont de 537,22 ppm. Dans les sols de MohammediaBenslimane, les teneurs de Cadmium sont de 2 ,36 ppm . Les teneurs en Plomb dépassent rarement 100 ppm.L’étude statistique par le test d’Anova montre des différences significatives entre tous les sites pour tous les éléments traces métalliques sauf pour le Nickel. Chemical pollution in the peri-urban area of Casablanca impacts the quality of agricultural soils.Five sites from the region of Casablanca have been studied: Oued Hassar, Oued Merzeg, Bouskoura, Benslimane-Mohammedia, and Bouznika.The objective is the comparative analysis of five trace metal elements in soils in order to assess the environmental state and to preserve the potential and harmlessness of sites in the Casablanca region.The environmental state of these sites requires knowledge of the physico-chemical parameters of the soil (PH, Calcium carbonates, organic matter), following the degradation of irrigation water by the use of wastewater or the impact of chemical pollution.The environmental state studied through metallic trace elements shows that the soils of sites irrigated by Oued Hassar have cadmium and lead contents which exceed the standards recommended by the World health organisation (WHO), respectively 2 ppm and 100 ppm.The contents are respectively 2,91 ppm and 137,61ppm.The copper contents in the soils irrigated by the Merzeg wadi remain the highest.The contents are 896,62 ppm. The zinc contents in soils near the Bouskoura cement plant are predominant compared to the other elements.The contents are 537,22 ppm. In Mohammedia-Benslimane soils, the cadmium contents are very variable, moderate and can exceed 2 ppm. Lead levels rarely exceed 100 ppm.The statistical study by the Anova test shows significant differences in the contents of metallic trace elements except for nickel

Impact of Tube Voltage on Radiation Dose (CTDI) and Image Quality at Chest CT Examination

During Computed Tomography (CT) scan examinations, it is important to ensure a good diagnosis by providing the maximum information to detect pathologies and this can be done with a reduced dose. In this respect, several methods of dose reduction have been studied and evaluated. This work investigates the effect of tube voltage while varying the tube current on image quality and radiation dose at Chest CT examination. This study was conducted on HITACHI CT 16 slice Scanner using two phantoms for evaluating the dose and image quality; a PMMA phantom and a CATPHAN 500. Two tube voltages of 120 KVp and 100 KVp have been used for some variation of the tube currents (mAs) and recording the values of the measured quantities (CTDIv, spatial resolution, contrast to noise ratio CNR and noise). The scanning with 100 KVp at Chest CT examination led to a reduction in CTDIv until 45 %, an increase of noise from 17 % to 45 %, and the Spatial Resolution fell slightly (6 and 7 pl/cm) compared to the 120 KVp. The CNR shows a slight regression from 11 to 22 % for the 120 KVp and 100 KVp. This study has shown that despite the increase in the image noise at low tube voltage 100 KVp, it is possible to reduce the radiation dose by up to 45 % without degradation of image quality at Chest CT examination. Further works will evaluate the effect of acquisition parameters in other CT examinations