Nous proposons et commençons ici l'étude des cobordismes lagrangiens reliant deux noeuds legendriens dans la symplectisation d'une variété de contact (M,ξ). En étudiant l'homomorphisme naturel du groupe des contactomorphismes de (M, ξ) vers les symplectomorphsimes de sa symplectisation, nous démontrons que l'existence d'un tel cobordisme ne dépend que de la classe d'isotopie des noeuds legendriens en question. Nous étudions ensuite le comportement des invariants classiques sous la relation de cobordisme lagrangien. A l'aide de l'inégalité de Bennequin et de ses généralisations, nous étudions les liens existants entre cette relation et la topologie des noeuds, notamment nous obtenons un critère pour calculer le 4-genre d'un noeud dans certaines situations. Nous en concluons notamment une nouvelle preuve de la conjecture locale de Thom. Parmi les applications nous donnons le lien entre les cobordismes lagrangiens et les cobordismes symplectiques via les chirurgies legendriennes. Nous démontrons aussi l'existence d'un homomorphisme induit en homologie de contact incluant cette relation dans le tableau global de la théorie symplectique des champs. ______________________________________________________________________________ MOTS-CLÉS DE L’AUTEUR : Géométrie de contact et symplectique, Lagrangien, Legendrien, Conjecture locale de Thom, Homologie de contact.

A volumetric contact dynamics model has been proposed by Gonthier et al. [1, 2, 3] for the purpose of rapidly generating reliable simulations of space-based manipulator contact dynamics. By assuming materials behave as a Winkler elastic foundation model, forces and moments between two bodies in contact can be expressed in terms of the volume of interference between the undeformed geometries of the bodies. Friction between bodies is modelled by a dwell-time dependent bristle model for both tangential friction, and spinning friction torque. This volumetric model has a number of advantages. Unlike point-contact models, it allows for the modelling of contact between complex geometries and scenarios where the contact surface is relatively large, while being less computationally expensive than finite element methods. Rolling resistance is included in the model through damping effects across the volume of interference. The friction model accounts for dwell-time dependent slip-stick effects, spinning friction torque, and the Contensou effect. In this thesis, an experimental validation of the volumetric contact model is presented for the first time. Models for simple geometries in contact (e.g. cylinder-on-plane, sphere-on-plane) have been developed for stationary contact and for contact with motion normal and tangential to the contact surface. Tangential motion is modelled with pure translation, pure rotation about the normal axis, and combined motion, in order to separately consider friction forces, spinning friction torque, and the Contensou effect, respectively. An apparatus has been developed to experimentally validate these models for metal-on-metal contact. The apparatus has two configurations, one for validating the normal contact models and the other for the friction models. Experimental measurements of forces and displacements are used to identify model parameters (e.g. volumetric stiffness, friction coefficients, etc.). For normal force experiments, modelling the contact forces as proportional to volume of interference was found to be a reasonable approximation. A Hertzian model was compared with the volumetric model for spherical payloads loaded quasi-statically. Using stiffnesses estimated from spherical experiments, small misalignments of the cylindrical payloads were estimated that corresponded well with measured results. Dynamic experiments suggest an inverse relationship between impact velocity and the hysteretic damping coefficient. The high normal forces applied in the friction experiments were found to create significant wear on the contact surfaces. Coefficients of friction between titanium and aluminum were found to be consistent translationally and rotationally. Friction forces from combined translation and rotation demonstrate that the Contensou effect is accurately described by the volumetric contact model.

Some scholars argue that organized sport is a viable context for different ethnic and racial groups to learn about one another and experience positive intergroup contact. Other scholars insist that hierarchical arrangements and competitive natures may actually exacerbate existing tensions among ethnic and racial groups. Less is known about whether or not recreational sport settings can facilitate positive intergroup contact. These contexts are often free of hierarchical arrangement and competition among participants, which potentially secure the equality of participants and facilitate positive interracial contact. The purpose of this study was to gain richer insights into the phenomenon of interracial contact that Korean Americans experience in recreational sport settings. This study was guided by three research questions: (1) Do Korean Americans perceive the presence of contact hypothesis' optimal conditions in recreational sport settings? (2) What factors influence Korean Americans' perception toward the presence or absence of optimal conditions? (3) Can participating in serious leisure activity with different racial groups contribute to interracial harmony? This study adopted qualitative research methods with a phenomenological approach. Face-to-face, in-depth, and semi-structured interviews were conducted with 15 Korean American males who participated or have been participating in recreational sports with racially mixed teams. The interviews were conducted in August and September, 2008, in two southern cities. Four findings are articulated. First, informants held variable perceptions toward the presence of contact hypothesis' optimal conditions. Second, informants supported the existence of friendship opportunities. This study identified six key factors that play a critical role in formulation of informants' perceptions toward the existence of each optimal condition. They were: (1) skill level, (2) racial stereotypes, (3) physical attributes of recreational sport participants, (4) language proficiency, (5) atmosphere or culture within different recreational sport contexts, and (6) longevity of contact. Finally, informants felt that participating in recreational sports with different racial groups contributes to harmonious interracial relations. The findings showed that it is problematic to a priori assume that recreational sports satisfy the optimal conditions of contact situations. Moreover, findings suggest that satisfaction of optimal conditions in recreational sport contexts may not be necessary for positive interracial contact to occur.

In examining the racism in sport literature, two general trends emerge: (a) a focus on Western sport organizations and the prejudice expressed by Whites in these entities; and (b) the tendency to document the occurrence of prejudice without examining key antecedent conditions. The purpose of this study was to address these gaps in the literature. Specifically, I compare the racial prejudice of White Americans with Asians and also examine the degree to which intergroup contact impacts this level of prejudice. Data were collected from Asian (n = 104) and White American (n = 100) college students. They completed a questionnaire that assessed their contact with African Americans as both team mates and exercise partners, their intergroup anxiety, and racial prejudice. Results indicate that all of the study variables were significantly correlated with one another. As expected, a multivariate analysis of variance further illustrated that Asians, relative to Whites, expressed more anxiety and prejudice, while also having less contact with African Americans. Finally, results from a moderated regression indicated that the relationship between nationality and intergroup anxiety was moderated by contact with African Americans as team mates and as exercise partners. In both cases, the lack of contact resulted in greater anxiety for Asians than it did for Whites. This study contributes to the literature by explicitly examining racial bias across cultures. In addition, the findings point to the importance of diversity in exercise and team settings as a way of reducing racial prejudice. That is, since in being contact with African Americans as team mates and exercise partners helped to reduce intergroup anxiety, efforts should be made to increase racial diversity in exercise and sport team settings.

Reproduction de : Thèse de doctorat : Génie mécanique, productique et transports : Poitiers : 2008. / Titre provenant de l'écran-titre. Bibliogr. 69 réf.

As digital microfluidics has continued to mature since its advent in the early 1980's, an increase in new and novel applications of this technology have been developed. However, even as this technology has become more common place, a consensus on the physics and force models of the motion of the contact line between the fluid, substrate, and ambient has not been reached. This uncertainty along with the dependence of the droplet geometry on the force to cause its motion has directed much of the research at specific geometries and droplet actuation methods. The goal of this thesis is to help characterize the components of the friction force which opposes droplet motion as a one dimensional system model based upon simple system parameters independent from the actuation method. To this end, the force opposing the motion of a droplet under a thin rectangular glass cover slip was measured for varying cover slip dimensions (widths, length), gap height between the cover slip and substrate, and bulk droplet velocity. The stiffness of the droplet before droplet motion began, the force at which the motion initiated, and the steady-state force opposing the droplet motion were measured. The data was then correlated to hypothesized equations and compared to simple models accounting for the forces due to the contact angle hysteresis, contact line friction, and viscous losses. It was found that the stiffness, breakaway force, and steady-state force of the droplet could be correlated to with an error standard deviation of 8 %, 14%, and 10 % respectively. Much of the error was due to an unexpected height dependence for the breakaway and steady-state forces and testing error associated with the velocity. The models for the stiffness and breakaway force over predicted the results by 36% and 16% respectively. During testing, viii stability issues with the cover slip were observed and simple dye testing was conducted to visualize the droplet flow field.

A prospective, exploratory study examined the relationships between birth family contact factors and long-term placement outcomes for children who are in foster or kinship care in New South Wales. The present study utilized data which was collected for 338 children in the Children in Care study; which was conducted between 1999 and 2009. This included data that was collected from a baseline survey and a review of case files from the State Child Welfare database. The participants of the Children in Care study were between four and eleven years of age. The present study involved a series of statistical analyses including: correlations, chi-square tests, t-tests, ANOVAS, multiple linear regressions, and binary logistic regressions. Some linear associations were identified between frequency of contact and reported issues, frequency of contact and restoration, and children’s reactions to contact and reported issues. However; these associations were found to be insignificant when controlling for other significant predictors in regression models. None of the birth family contact variables examined in the present analyses were found to be significant predictors of further abuse/behavioural issues in care, placement stability, or restoration. Some of the significant predictors of such outcomes included: age at entry into care; pre-care mental health; previous placements, care arrangements; and caregivers support and contact with other foster carers. Overall, the present analyses highlighted that contact may not necessarily have detrimental, or beneficial impacts on children in care; however further research in this domain is required in order to identify if other contact factors may have any impact on outcomes for children in kinship or foster care.

Smartphones are becoming increasingly popular, with the result that customers prefer to carry out at least some customer services using an app on a mobile device. Among app users, smooth transfer to a live agent is seen as an important feature and this means that the company contact center need a solution to handle this as well as increasing numbers of interactions. The question this thesis tries to answer is "how can smartphone end user apps be included in the context of the company contact center"? To answer this question research was conducted regarding the possibilities of an Android smartphone, with the results of this research being used to define a use case, a state flow diagram and create a demonstration app. The thesis showed that it is possible to have an app as an online channel for customer service interactions. New possibilities in comparison to traditional telephony include that customer data such as topic, authentication, location and multimedia can be sent to the contact center before an actual interaction is started.

A volumetric contact dynamics model has been proposed by Gonthier et al. [1, 2, 3] for the purpose of rapidly generating reliable simulations of space-based manipulator contact dynamics. By assuming materials behave as a Winkler elastic foundation model, forces and moments between two bodies in contact can be expressed in terms of the volume of interference between the undeformed geometries of the bodies. Friction between bodies is modelled by a dwell-time dependent bristle model for both tangential friction, and spinning friction torque. This volumetric model has a number of advantages. Unlike point-contact models, it allows for the modelling of contact between complex geometries and scenarios where the contact surface is relatively large, while being less computationally expensive than finite element methods. Rolling resistance is included in the model through damping effects across the volume of interference. The friction model accounts for dwell-time dependent slip-stick effects, spinning friction torque, and the Contensou effect. In this thesis, an experimental validation of the volumetric contact model is presented for the first time. Models for simple geometries in contact (e.g. cylinder-on-plane, sphere-on-plane) have been developed for stationary contact and for contact with motion normal and tangential to the contact surface. Tangential motion is modelled with pure translation, pure rotation about the normal axis, and combined motion, in order to separately consider friction forces, spinning friction torque, and the Contensou effect, respectively. An apparatus has been developed to experimentally validate these models for metal-on-metal contact. The apparatus has two configurations, one for validating the normal contact models and the other for the friction models. Experimental measurements of forces and displacements are used to identify model parameters (e.g. volumetric stiffness, friction coefficients, etc.). For normal force experiments, modelling the contact forces as proportional to volume of interference was found to be a reasonable approximation. A Hertzian model was compared with the volumetric model for spherical payloads loaded quasi-statically. Using stiffnesses estimated from spherical experiments, small misalignments of the cylindrical payloads were estimated that corresponded well with measured results. Dynamic experiments suggest an inverse relationship between impact velocity and the hysteretic damping coefficient. The high normal forces applied in the friction experiments were found to create significant wear on the contact surfaces. Coefficients of friction between titanium and aluminum were found to be consistent translationally and rotationally. Friction forces from combined translation and rotation demonstrate that the Contensou effect is accurately described by the volumetric contact model.

Thesis (doctoral)--Lund University, 1994. / Added t.p. with thesis statement inserted.