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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Motion Space Analysis of Smooth Objects in Point Contacts

Rama Krishna, K January 2018 (has links) (PDF)
The present work studies instantaneous motion of smooth planar and spatial objects in unilateral point contacts. The traditional first-order instantaneous kinematic analysis is found insufficient to explain many common physical scenarios. The present work looks beyond the velocity state of motion for a comprehensive understanding through higher-order kinematic analysis of the above system. The methodology proposed herein is a Euclidean space approach to second-order motion space analysis of objects in point contacts. The geometries of the objects are approximated up to second-order in the differential vicinity of the point of contact; meaning, up to curvature at the point of contact. The instantaneous motion is approximated up to second-order kinematics, i.e., up to acceleration state. The basic approach consists of impressing an instantaneous motion upon one object while holding the other fixed which is in a single point contact initially, and observing for one of the following three states: penetration, separation, and persistence of contact between the two objects. These three states are characterized by the interference between the geometries of the objects. Penetration and separation of two curves for rotation about points on the plane is geometrically studied based on the relative configuration of the osculating circles at the point of contact. It is shown that the plane is partitioned into four regions of rotation centers. Partitioning of the plane into motion space regions at a contact provided a geometrical framework compose the motion space for multiple contacts. The applications include second-order form-closure (SFC) and synthesis of kinematic pairs. To explore the consequence of a generic motion, an analytical scheme is formulated using the screw theoretic concepts of twist and twist-derivative. It is shown that the characteristics of second-order motions at a single contact depends only upon the geometric kinematic properties of the motion; meaning, the motion characteristics are time-independent. The geometric conditions for the second-order motion that will be admissible or restrained at a contact are not available in the existing literature on \second-order mobility". The classical Euler-Savary equation for enveloping curves is found to represent the condition which is both necessary and sufficient for the second-order roll-slide motion. An elegant generalized geometric characterization of second-order motions is derived. This is made use for deriving condition of immobilization of, planar mechanisms with up to 2-degrees-of-freedom (d.o.f.), with a single point contact. Illustrative examples of four-bar and 2R-mechanisms are presented. Rapid prototyped model of the four-bar mechanism is fabricated and the SFC theory is verified satisfactorily. Through a novel use of Meusnier's theorem, rotational motion characteristics of planar curves in a point contact is used to determine the patterns and distribution of admissible axes of rotation in space for two surfaces in a single point contact. In the generalized analytical method of motion space analysis, the surfaces are locally represented in Monge's form up to second-order terms and motion is represented using twist and twist-derivative. An analytical framework for the second-order motion space analysis of surfaces with multiple contacts has been developed. Using this procedure, pairs of objects are analyzed for SFC and equivalent lower kinematic pair freedom. Revolute and planar joints with two contacts, prismatic joint with three contacts, SFC of regular concave spherical tetrahedron and regular tetrahedron with four contacts are demonstrated. Although conventional first-order studies demand seven contact points for form-closure, within the context of second-order motion, the present study established that, under special geometric conditions relative immobilization of two smooth objects can be enabled with much fewer contacts. Conditions for immobilization using three and two smooth contacts have been derived. Using contact kinematics equations based on higher-order reciprocity, an instantaneous spatial higher pair to lower pair substitute-connection which is kinematically equivalent up to acceleration analysis for two smooth surfaces in persistent point contact is derived. An illustrative example of a three-link direct-contact mechanism is presented.
42

La peur de mourir de l’enfant perturbateur : l’instabilité infantile psychogène et transitoire

Galien, Jérôme 19 September 2011 (has links)
L’« enfant perturbateur » dérange et déçoit un espoir de réussite par de mauvaises notes, ou perturbe ses parents, sa famille, ses enseignants par son agitation. Dans un tel contexte, l’adulte, qui l’accompagne dans un lieu de soin, évoque à son propos une « hyperactivité », un « trouble de la concentration », ou un « trouble du comportement ». En quelques décennies, ces motifs de consultation sont devenus majoritaires au Centre Médico-Psychopédagogique de Montpellier. Sans remettre en cause les apports de la neurobiologie, nous constatons que l’« instabilité infantile psychogène transitoire » est devenue une épidémie. A partir de notre expérience clinique, de la métapsychologie freudienne, des études de sociologie, et de celles des sciences politiques, nous soutenons la thèse suivante : l’ « enfant perturbateur » souffre d’un « complexe de déprivation » (Winnicott) qu’il traduit en termes de « peur de mourir », et si la turbulence s’exprime, c’est en tant qu’elle attire l’attention d’un adulte potentiellement secourable et que les systèmes sociaux contemporains la rendent facilement repérable. L’approche psychanalytique individuelle de l’ « enfant perturbateur » est pertinente mais peut parfois rester en suspens pendant de longues périodes, cédant le pas à l’attitude de « management » décrite par Winnicott. Ceci rend possible un mouvement de régression permettant à l’enfant de renouer avec la continuité du sentiment d’exister. Dans le transfert, l’analyste occupe alors la place de « médium malléable » (Milner, Roussillon) soumis à l’omnipotence de son patient. / The agitation of “disruptive children” disturbs or upsets their parents, family and teachers, and bad marks at school lead to disappointment in terms of hope for success. In such a context, the adults who take them for treatment mention terms such as “hyperactivity”, “concentration disorder”, or “behaviour disorder”. In just a few decades, these reasons for consulting have started to dominate at the Centre Médico-Psychopédagogique (Psychoeducational Health Centre) in Montpellier.Although we do not question the contribution of neurobiology, we have observed that“transitory psychogenic infantile instability” has become an epidemic. On the basis of our clinical experience, Freudian metapsychology, sociology and political science studies, we support the following thesis: “disruptive children” suffer from a what Winnicot calls a “deprived complex” and which he translates in terms of “fear of dying”. If there is manifest unruliness, it is to attract the attention of a potentially helpful adult and because the contemporary social systems make it easily detectable.The individual psychoanalytic approach to “disruptive children” is relevant but canremain suspended over long periods of time, giving way to the “management” attitude described by Winnicott. This makes regression possible, allowing the child to return to the continuity of a sense of being. In the transference, the psychoanalyst then plays the role of the “pliable medium” (Milner, Roussillon) subject to his patient’s omnipotence.
43

El impacto de los Ingresos Transitorios y Permanentes en el consumo de los hogares / The impact of transitory and permanent income on household consumption

Salas Quispe, Sadith Beatriz 29 October 2021 (has links)
El presente trabajo estudia como la participación de los grupos de gasto cambia ante variaciones de los ingresos, teniendo en cuenta que los ingresos son clasificados en transitorios y permanentes. La literatura supone que los hogares deben de considerar la naturaleza de esta clasificación de ingresos y, en consecuencia, los ingresos transitorios deberían de ser asignados a bienes de inversión, mientras que los ingresos permanentes deben de ser asignados a los bienes de consumo. Los resultados muestran que, ante variaciones de estos dos tipos de ingresos, la composición de los grupos de gasto varía, sin embargo, la categoría de alimentos sigue siendo la más representativa. Asimismo, se concluye que, los ingresos transitorios son asignados a los bienes de inversión, pero también son asignados a los bienes de consumo, mostrando que los hogares peruanos todavía no disciernen entre estos dos tipos de ingresos. / This paper studies how the participation of expenditure groups changes in response to changes in income, taking into account that income is classified into transitory and permanent. The literature assumes that households should consider the nature of this income classification and, consequently, transitory income should be allocated to investment goods, while permanent income should be allocated to consumption goods. The results show that, in the face of variations in these two types of income, the composition of the expenditure groups varies; however, the food category continues to be the most representative. It is also concluded that transitory income is allocated to investment goods, but it is also allocated to consumption goods, showing that Peruvian households still do not distinguish between these two types of income. / Trabajo de investigación
44

Incidence des facteurs institutionnels dans l’évolution de la structure financière des entreprises : cas d’entreprises françaises cotées à la bourse de Paris / Incidence of institutional factors in the evolution of corporate capital structure : the case of French companies listed on the Paris Stock Exchange.

Kouao, Serge Guy 17 November 2011 (has links)
S’appuyant sur les théories du financement hiérarchique et du compromis, cette recherche se donne pour objectif de tester empiriquement la relation structure financière-institution. Ces deux notions partagent des caractéristiques communes favorisant leur association conceptuelle à travers le ratio d’endettement cible spécifiquement via le comportement de conservatisme financier des entreprises. Cela ouvre de nouvelles possibilités d’analyses de ladite relation, notamment, en mobilisant le néo-institutionnalisme. Un échantillon de 204 entreprises françaises cotées à la bourse de Paris, ayant des données complètes entre 1999 et 2007, a servi à entreprendre le volet empirique de l’étude. Les principaux résultats indiquent que l’ensemble des déterminants traditionnels de la structure financière, à l’exception de la taille, joue un rôle important dans la politique de financement de ces entreprises. Le niveau de corruption et la liquidité du marché boursier français (variables institutionnelles juridico-financières) n’influencent pas le choix du niveau d’endettement, mais jouent plutôt un rôle significatif dans le choix de la maturité de la dette. Par ailleurs, la structure financière de ces entreprises converge lentement mais sûrement vers son niveau cible. / Based on the pecking order and trade-off theories, this research aims to test empirically the relationship between corporate capital structure and institution. Both concepts share common characteristics fostering their conceptual association through the target debt ratio specifically via corporate behavior of financial conservatism. This opens new possibilities for analysis of that relationship, in particular, by mobilizing the new institutionalism framework. A sample of 204 French companies listed on the Paris stock exchange, with complete data between 1999 and 2007, was used to undertake the empirical part of the study. The main results indicate that all the traditional determinants of capital structure, except the size, play an important role in the financing policy of these companies. The level of corruption and the French stock market liquidity (legal and financial institutional variables) do not influence the choice of debt level, but rather play a significant role in the choice of debt maturity. In addition, the financial structure of these companies converges slowly but surely toward its target level.

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