Are neighbors welcome ? e-buyer search, price competition and coalition strategy in the Internet retailing

On étudie les forces qui régissent l'agrégation des sites Web marchands (B-to-C) en concurrence sur un marché électronique différencié, où le coût de recherche pour les consommateurs est indépendant du coût d'adaptation/transport supporté lorsque le bien trouvé ne correspond pas à leur préférence. On s'intéresse à la possibilité pour les sites Internet de se coaliser, ce qui se traduit par une réduction du coût de recherche pour trouver d'autres sites à l'intérieur de la coalition. On effectue la statique comparative des structures de coalitions (en fonction du degré de différenciation de ses partenaires) lorsque les sites se font une concurrence en prix. On montre qu'un site préfère se coaliser avec un partenaire fortement différencié et fixe dans ce cas un prix unique plus bas.En vendant au détail;Coûts de recherche;Coalition

Stability of the Structure of the Technical Coefficients: Hybrid Estimator Approach

Les comptes nationaux ont été, pendant longtemps, l’une des préoccupations majeures dans la production de statistiques économiques au sein de l’administration publique sénégalaise. Les travaux de la comptabilité nationale s’intéressent beaucoup à la production statistique des comptes et d’autres tableaux synthétiques comme le Tableau Economique d’Ensemble et le Tableau des Entrées Intermédiaires (TEI). Le TEI, conçu grâce à la détermination des coefficients techniques, met en exergue les interrelations entre les différentes branches d’activités. La présente étude s’inspire des travaux de Leontief [1927] sur les modèles input-output et propose une démarche synthétique permettant de calculer des coefficients techniques robustes, ainsi que leurs intervalles de confiance. Les données utilisées proviennent d’une compilation des Tableaux Entrées Sorties (TES) de 1980 à 2004. Pour assurer la robustesse des résultats, un estimateur hybride, combinaison optimale de la moyenne et de la médiane a été privilégié. Les résultats obtenus mettent en évidence, une bonne adéquation entre les intervalles estimés et les données réelles observées. Les simulations faites dans le cas d’une flambée du prix du baril en 2005, répliquent assez bien la réalité observée dans la structure économique au Sénégal.Estimateur hybride; coefficients techniques; modèle input output

Estimation of the Equilibrium Interest Rate: Case of CFA zone

Problem Statement The framework of this study is consisted of the countries of zone CFA and in fact the two central banks (BCEAO and BEAC) in charge of the monetary policy implementation. There was a great resurgence of interest these last years on the question in the way of leading the monetary policy. One of the indicators of this phenomenon is the enormous volume of recent papers and the conferences prepared on this subject. In addition, much of macro economists proposed specific rules of policy or ruled on the way in which the monetary policy should be led. The principal objective of this study is the evaluation of the macroeconomic gold rule in the CFA countries which stipulates that in an economy with equilibrium growth and under simplifying macroeconomic assumptions: the neutral interest rate is equal to the potential growth rate of the economy. Research Method To achieve this objective we try to determine the weight of the goals of monetary and fiscal policies attaches with a quadratic reaction function which takes into account a target of inflation, public expenditure and interest rate. And then the methodology of determination of the neutral interest rate is derived from a generalized Taylor rule. The estimation of the parameters is based on panel data econometrics, the generalized method of moments and the Kalman filter. These different methods are used to emphasize the robustness of the results of our analysis. Results and conclusion The estimates carried out on the panel data emphasize a neutral interest rate in the interval of 1.4% to 1.6%. It is generally noticed that the estimates made on the panel data are compatible with those carried out by using the Kalman filter. In addition, it is observed that, overall the level of the natural interest rate in UEMOA zone (1.51) is lower than CEMAC zone (1.65). The most important neutral rate is observed in the Malian economy and the lowest in the Burkina economy. But we notice a larger homogeneity in CEMAC zone (standard deviation of 0.12) than UEMOA zone ( standard deviation of 0.29).Taylor Rule; equilibrium interest rate; Kalman filter

Consumers' Search Cost and Emerging Structure of Web Sites Coalitions : a multi-agent based simulation of an electronic market

On développe un modèle multi-agent, extension d'un modèle analytique qui étudie la structure des coalitions de sites B-to-C, lorsque les consommateurs-internautes ont un coût de recherche pour trouver le bien qui correspond à leur préférence, et lorsque les coalitions de sites permettent de réduire ces coûts de recherche via des moteurs de recherche spécialisés. Ce modèle multi-agent comporte des agents hétérogènes à rationnalité limitée: sites et internautes, dont on défini l'état et les règles de comportement. Notre objectif est de faire des simultations qui mettent en jeu ces deux types d'agents (une populations de sites marchands et une population de consommateurs), de les faire intéragir à travers une procédure de recherche des consommateurs et un processus de formation des coalitions des sites, et d'observer la dynamique du système, en particulier en ce qui concerne la structure de coalition émergente. Le modèle multi-agent étends ainsi les résultats obtenus dans le modèle analytique, avec des hypothèses moins restrictives. En plus du processus de formation des coalitions, le modèle théorique se voit aussi enrichi par d'autres règles de comportement pour les sites (entrée sur le marché, faillite), ce qui apporte des enseignements sur la dynamique de la concurrence lorsque la formation des coalition permet d'accroître la demande au détriment des sites peu ou non coalisées.Commerce électronique;Multi-agents;formation de coalitions

Irreversibility and Uncertainty in Multifunctional Forest Management Allocation

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Overview of the mean of production used for FSW

The Friction Stir welding process is now introduced in production plants. More and more applications are developed and the most part of the work is now centered on the mean of production to be used. Institut de Soudure and Arts et Métiers ParisTech are working on this subject since mid of 2005. The results of this work is a recognize knowledge on the methodology for qualifying a Friction Stir Welding Equipment [1]. In the same time, and based on this work, Institut de Soudure has bought a new kind of Friction Stir Welding machine based on a KUKA Robot

Empirical Models for Predicting Soil-Climate and Related Pasture Grass Preformance in Maui, Hawaii (An Evaluation of Soil-Climate Criteria of Soil Taxonomy)

Soil Taxonomy requires soil-climate for soil classification and the interpretation of the relationships between soil, climate, and plant. The depth at which soil temperature and soil moisture regimes are currently measured or estimated have been, however, given without presenting any evidence of any particular importance of soil-climate at these depths to soil genesis and/or plant growth. The objectives of this study were to develop mathematical models that can provide first approximations of soil temperatures at different depths and evaluate the depth at which soil temperature and/or soil moisture correlate most to herbage production. Such a knowledge can be used as a criterion for better identification of soil-climate and serve as a basis for the evaluation of the current soil-climate criteria of Soil Taxonomy. Located on the island of Maui, Hawaii, the area of the study extended along a climosequence with a wide range of ecological zones. The altitudes vary from 36 to 1620 m, the soils from Inceptisols (Andepts) to Mollisols and Oxisols, mean annual air temperatures from 13 to 24 °c, and total mean annual precipitation from 100 to 872 mm. Computerized automatic weather stations were installed to monitor air and soil-climate environment at 11 sites and pasture grass growth was observed at four of the sites. The measurements included air temperature, soil temperatures at 0.1- and 0.5- m depths, soil moisture at 0.1- and 0.5-m depths, relative humidity, rainfall, and solar radiation. The dominant grass species were buffel grass, kikuyu grass, and an admixture of fescue, sweet vernal, rattail, Yorkshire fog, and white clover. Simple linear, multiple, and quadratic regression models were developed to estimate the soil temperatures at 0.1- and 0.5-m depths from air temperature and other environmental factors. All of the models showed a satisfactory coefficient of determination, but the quadratic models were judged to have a greater predictive ability than the others because of their slightly higher R2 and smaller residual mean squares. In addition, the quadratic models depicted better the curvilinear relationship between the air and soil temperatures. Soil temperatures predicted by the quadratic models were in better agreement with the measured temperatures than those predicted by the model currently used in Soil Taxonomy. A modification of the Soil Taxonomy model is proposed for soil temperature, that is, to add 2 °c to the air temperature if the air temperature is less than 22 °c or to add 4 °c if the air temperature is equal to or greater than 22 °c. Such a modification gives a close approximation of the measured soil temperature at 0.5-m depth. Seasonal fluctuations of herbage production were more correlated to soil-climate at 0.5-m depth than to atmospheric weather or soil-climate at 0.1-m depth. The-use of soil-climate properties in Soil Taxonomy is, therefore, justified. The greater impact of soil moisture at 0.5-rn depth suggests the location of the soil moisture control section at or below that depth, regardless of soil texture. It is concluded that if Soil Taxonomy is to be a basis of prognosis of plant response to soil, soil-climate, and other crop production parameters, the diagnostic criteria of soil-climate at 0.5-m depth best serve the purpose

Experimental investigation of the influence of the FSW plunge processing parameters on the maximum generated force and torque

The paper presents the results of an experimental investigation, done on the friction stir welding (FSW) plunging stage. Previous research works showed that the axial force and torque generated during this stage were characteristic for a static qualification of a FSW machine. Therefore, the investigation objectives are to better understand the relation between the processing parameters and the forces and torque generated. One of the goals is to find a way to reduce the maximum axial force and torque occurring at the end of the plunging stage in order to allow the use of a flexible FSW machine. Thus, the influence of the main plunge processing parameters on the maximum axial force and torque are analysed. In fact, forces and torque responses can be influenced by the processing parameter. At the end, a diagram presenting the maximum axial force and torque according to the processing parameters is presented. It is an interesting way to present the experimental results. This kind of representation can be useful for the processing parameters choice. They can be chosen according to the force and torque responses and consequently to the FSW machine capacities

Her Story told Her Way: A Narrative Inquiry into Black Women’s Perception of the Strong Black Woman.

The narrative surrounding the meaning of being a Black woman has historically been dominated by stereotypes such as the mammy, jezebel, sapphire, and angry Black woman. Black women have attempted to control their own narrative through the internalization of these stereotypes, leading to the creation of the Strong Black Woman (SBW) construct. While the SBW is comprised of a sense of caretaker, independence, and emotional restraint, Black women’s attempts at embodying this construct in the face of societal oppression and familial responsibilities can and often does have negative effects on their mental health. Although the behaviors associated with the SBW have the potential to be empowering, they also have the potential of marginalizing, isolating, and allowing the Black woman to be overworked and misused. This dissertation is a study intended to provide insight into how Black women who are members of Black Greek letter sororities perceive the self-identified status of SBW, and to see if they perceive it as having an impact on their help seeking behavior. To date, there are no studies that specifically narrate the mental health of Black women in sororities and their identity as a SBW. Too often, the story of the Black woman is controlled by others, which allows stereotypes and misconceptions to become the norm. This study will empower Black women to control their own narratives and tell their stories the way they see fit