Diffusion Monte Carlo method: numerical analysis in a simple case

The Diffusion Monte Carlo method is devoted to the computation of electronic ground-state energies of molecules. In this paper, we focus on implementations of this method which consist in exploring the configuration space with a {\bf fixed} number of random walkers evolving according to a Stochastic Differential Equation discretized in time. We allow stochastic reconfigurations of the walkers to reduce the discrepancy between the weights that they carry. On a simple one-dimensional example, we prove the convergence of the method for a fixed number of reconfigurations when the number of walkers tends to $+\infty$ while the timestep tends to 0. We confirm our theoretical rates of convergence by numerical experiments. Various resampling algorithms are investigated, both theoretically and numericall

On The Role Of Management Commitment In Export Performance: A Meta-Analysis

Research on exporting frequently points the role of management commitment in the export performance of the firm. This article reviews the conceptual, methodological, and empirical insights gained from a systematic analysis of 65 studies conducted on this subject. Undoubtedly, this stream of research has enhanced understanding of the importance of management commitment in affecting exporting activities. However, conceptually, there is still a lack of integral theoretical framework. Methodologically, limitations are identified concerning sampling designs, fieldwork procedures, and analytical methods. Empirically, hypothesized associations between export commitment and export performance lead to conflicting findings. After a presentation of meta-analysis techniques used and articles compiled, our paper provides an original investigation of this issue by implementing three meta-analyses to examine the relationship between commitment to export and export performance. The meta-analysis, more relevant than simple literature surveys, generally leads to the conclusion that there is a significant positive relationship between export commitment and export performance. Moreover, our findings suggest directions for future research in the field

On The Role Of Management Commitment In Export Performance: A Meta-Analysis

Research on exporting frequently points the role of management commitment in the export performance of the firm. This article reviews the conceptual, methodological, and empirical insights gained from a systematic analysis of 65 studies conducted on this subject. Undoubtedly, this stream of research has enhanced understanding of the importance of management commitment in affecting exporting activities. However, conceptually, there is still a lack of integral theoretical framework. Methodologically, limitations are identified concerning sampling designs, fieldwork procedures, and analytical methods. Empirically, hypothesized associations between export commitment and export performance lead to conflicting findings. After a presentation of meta-analysis techniques used and articles compiled, our paper provides an original investigation of this issue by implementing three meta-analyses to examine the relationship between commitment to export and export performance. The meta-analysis, more relevant than simple literature surveys, generally leads to the conclusion that there is a significant positive relationship between export commitment and export performance. Moreover, our findings suggest directions for future research in the field

Bullose diabétique

Bullosis diabeticorum is a rare skin complication of diabetes, it is un an usual bullous dermatosis, particular by its exclusive occurrence in diabetics. We report a case of a 59 years old patient with a history of diabetes mellitus treated by insulin for 30 years and pulmonary pleurisy treated 3 years ago and who consulted for recent and spontaneous bullae, localized in hands (A) and feet (B). Their contents was serous as well as hemorragic. Clinically, peripheral neuropathy was also noticed. The evolution under symptomatic treatment was favorable. Bullosis diabeticorum is a rare condition that occurs in 0.5% of diabetics and could be secondary to vascular alterations which can be the cause of skin fragility and cleavage of the skin. The frequent presence of peripheral neuropathy may also explain the preferential distal localization of lesions. Therapeutically, no particular treatment seems necessary except local antiseptic care after the recess bubbles. Bullosis diabeticorum is a characteristic skin complication of diabetes. Its etiology is still unknown. Its evolution is benign and its management is essentially preventive.Pan African Medical Journal 2016; 2

LVRT control srategy of DFIG based wind turbines combining passive and active protection

Due to its advantages, Doubly Fed Induction Generator (DFIG) is the most used generator in the wind power area. However, the DFIG provides electrical power at a constant frequency even if the rotor speed varies; also, it allows a better capture of wind energy. Although the DFIG has a high sensitivity regarding the electrical faults, which brings up many challenges in terms of compliance: Power provider and electrical operator (in terms of production continuity and quality of energy). Actually, the grid connection requirements impose strict rules to respect for Low Voltage Ride Through (LVRT) and grid support capabilities following the Grid Code (GC). Therefore, it’s crucial for wind turbines (WT) to propose an advanced control. In fact, when detecting voltage dips, WTs must stay connected to the grid to provide the required reactive power in order to have a safe and reliable operation. The objective of this article is to propose a new LVRT strategy able to keep WTs connected to the grid despite severe voltage dips. The principle of this strategy is to make a connection between the level of dips and the optimal solution to overcome the fault. For this reason, the proposed strategy is based on the combination of two solutions (an active and a passive method): The first aims to improve the control strategy to mitigate the over-current at low voltage dips. The second is applied for severe voltage dips using protection circuits: Series Dynamic Braking Resistor (SDBR) and DC-Chopper

Análisis de lineamientos en las rocas que afloran en el sinclinal de Ouaouizaght, Alto Atlas Central

In this work, we perform a lineament analysis of the Ouaouizaght syncline area (Central High Atlas, Morocco) in terms of their structural and tectonic significance. The methodology consists of satellite image (Lansat 8 OLI) processing by means of principal component analysis (PCA). The maximum of lineament orientation in the study area shows a NE-SW direction and two relative maxima oriented N0 and N90. The higher density areas of lineaments are located along the four borders of the Ouaouizaght syncline probably highlighting the importance of major faults characterized by diapiric processes ( e.g., movement of salt towards the anticline cores delimiting the Ouaouizaght syncline) during the extensional stageand importance of these previous discontinuities in the subsequent tectonic inversionEn este trabajo realizamos un análisis de lineamientos en el área del sinclinal de Ouaouizaght (Atlas Alto Central, Marruecos) para entender su significado estructural y tectónico. La metodología consiste en el procesamiento de la imagen de satélite Lansat 8 OLI por medio de un análisis de componentes principales. La orientación principal de los lineamientos obtenidos que se deduce en el área de estudio es NE-SO y además se observan dos máximos relativos orientados N0 y N90. Las áreas que presentan una mayor densidad de lineamientos se localizan a lo largo de los cuatros márgenes del sinclinal de Ouaouizaght. Esto probablemente refleja la importancia de las fallas principales caracterizadas por procesos diapíricos ( e.g. , movimiento de sal hacia los núcleos de los anticlinales que bordean el sinclinal de Ouaouizaght) durante la etapa extensional y la importancia de estas discontinuidades previas en la posterior inversión tectónic

Vertical Electrical Sounding (VES) Technique to Map Potential Aquifers of the Guigou Plain (Middle Atlas, Morocco): Hydrogeological Implications

peer reviewedVertical electrical sounding (VES) as a geoelectrical method has proven its effectiveness throughout the history of groundwater geophysical investigation. In this sense, VES was carried out 47 in the study area with the aim of determining the geometry and limits of Quaternary basaltic aquifer formations and, above all, the location of electrical discontinuities in the area located in the north of Morocco, between the center of Almis Guigou and the city of Timahdite. This area is experiencing an overexploitation of the groundwater due to excessive pumping and the development of intensive agriculture activities, resulting in a continuous decrease in piezometric levels. The processing of the diagrams by WINSEV software showed the presence of an electrically resistant surface level, attributed to basaltic formations, of the Quaternary age, whose thicknesses reach at least 150 m to the SW of the area. This level is superimposed on a moderately conductive horizon which, according to local geology, corresponds to Pliocene marl and limestone alternations. The correlation of VES interpretation models allowed us to elaborate thematic maps and geoelectrical sections which illustrate the vertical and lateral extension of the basaltic reservoir as well as its thickness, which decreases in general from the south-west to the north-east; however, the main electrical discontinuities also correspond to faults and fractures, and they show a NE–SW direction sub-parallel to the major accidents of the Middle Atlas. A prospectivity map of the local aquifer was generated, coinciding with regional fault lines and confirmed by the alignment of very good flowing water boreholes. This geophysical study by electrical sounding shed light on the geometry and extension of the aquifer and opened avenues to draw further conclusions on its physical and hydrodynamic characteristics, as well as to optimize the future siting of groundwater exploitation boreholes through the elaboration of the local aquifer prospectivity map

Le Genre et la santé des enfants : possibilités d'analyse à partir de l'EDS'95 de l'Egypte

L'objectif de ce papier est d'examiner la possibilité de réalisation d'une approche de genre à partir des données d'une enquête démographique. Il s'agit de tester la compatibilité d'un cadre conceptuel lié à cette approche de genre avec les données de l'EDS (Enquête Démographique et de Santé) de 1995 de l'Egypte. Pour ce faire, nous présenterons en premier lieu la signification de l'approche de genre en démographie, en mettant l'accent sur les problèmes liés à la conceptualisation et à l'opérationnalisation et en présentant l'apport de cette approche dans le cadre de l'analyse de la santé des enfants. Ensuite, nous essayerons d'élaborer un cadre conceptuel convenable et pertinent pour l'étude de la santé des enfants, à partir d'une approche de genre. Enfin, nous examinerons la possibilité d'une analyse des données de l'EDS95 de l'Egypte par rapport au cadre conceptuel élaboré précédemment, à travers une exploration de l'enquête et des variables qui permettent la mesure des différents concepts. Rappelons dans cette introduction que l'élaboration de ce papier s'inscrit dans le cadre d'un projet de thèse qui porte sur l'étude de la relation genre/santé des enfants dans le cas du Maroc et de l'Egypte. Les objectifs de cette étude se résument dans les points suivants: 1) Analyser au niveau individuel la relation genre/santé des enfants au Maroc et en Egypte à travers une approche comparative et à travers la recherche des mécanismes d'action dans le but d'approfondir l'approche explicative ; 2) Identifier parmi les variables explicatives, celles qui ont le plus d'impact sur la santé des enfants ; 3) Explorer l'apport des enquêtes de type EDS à propos de la mesure des rapports de genre et de leur relation avec la santé des enfants et examiner leurs limites. Le présent papier constitue ainsi un préliminaire nécessaire pour la définition des concepts et l'exploration de la nature des données, avant d'entamer une analyse statistique détaillée pour la vérification des hypothèses de recherche. Cette dernière étape fera l'objet de nos prochains papiers

Improving productivity and worker conditions in assembly : part 2 : rapid deployment of learnable robot skills

Collaborative robots (cobots) have a strong potential to improve both productivity as well as the working conditions of assembly operators by assisting in their tasks and by decreasing their physical and cognitive stress. The use of cobots in factories however introduces multiple challenges: how should the overall assembly architecture look like? How to allocate specific (sub)tasks to the operator or the cobot? How to program and deploy the cobot? How to make changes to the robot program? In this paper dilogy, we briefly highlight our recent contributions to this field. In part I we presented our collaborative architecture for human-robot assembly tasks and discussed the working principles of our task allocation framework, based upon agent capabilities and ergonomic measurements. In this second part we focus on our programming by demonstration approach targeted at expediting the deployment of learnable robot skills