Étude de la notion documentaire et artistique dans l’oeuvre des Becher. Évolution de leurs élèves, Thomas Ruff, Andreas Gursky, Thomas Struth, Candida Höfer vers une photographie picturale et abstraite. Influence de la peinture, liée à l’enseignement de Gerhard Richter. La photo comme source d’information pour créer des images picturales chez Ruff et Richter. Utilisation du travail numérique pour s’orienter vers desimages picturales et abstraites chez Ruff et Gursky. Dimension sociologique du rapport photographie/peinture dans l’oeuvre de Thomas Struth, travail sur notre façon d’être dans le monde. Entre documentation et abstraction également, le travail de Candida Höfer sur l’espace vital, sur la structure de l’objet, évolution vers le détail, l’abstraction. Abstraction, experimentation, tendance de l’archive, axes essentiels en photographie / Study of documentary and artistic notion in the work of the Becher. Evolution of of their students, Thomas Ruff, Andreas Gursky, Thomas Strth, Candida Höfer towards a picturial and abstract photography. Pictorial influence, linked with Gerhard Richter’s teaching. Photography as source of information to create pictorial pictures by Ruff and Richter. Use of digital work by Ruff and Gursky to go towards picturealand abstract pictures. Sociological aspect in the link photography/painting in Struth’s work, on our way to exist in the world. Between documentation and abstraction too, the photographic work of Candida Höfer on vital space. Evolution on the structure of the object, on the detail, towards abstraction. Abstraction, experimentation, archival tendance, essential directions in photography

Les procédés de micro-fabrication connaissent actuellement une croissance importante dans les applications industrielles et pour des secteurs majeurs. Parmi les techniques d’usinage en micro-fabrication, le micro-fraisage est sans doute le plus polyvalent que ce soit en termes de matériau usiné ou de géométrie obtenue. La fabrication de micro-fraises est encore limitée par un certain nombre de paramètres (comme le rayon d’acuité d’arête) et demande alors à être optimisée. L’approche utilisée consistant à reproduire à petite échelle ce qui se fait de mieux à une échelle conventionnelle n’est alors plus forcément adaptée. Il en résulte que le micro-fraisage est un procédé encore mal maîtrisé (usure prématurée de l’outil, bris d’outil, trajectoire non maîtrisée, bavures…).L’objectif de la thèse est donc de comprendre les mécanismes mis en jeu lors de l’enlèvement de matière en micro-usinage et d’en établir un modèle permettant de prédire les efforts de coupe selon les conditions choisies et qui permettra par la suite de faciliter l’optimisation de la géométrie des outils coupantDans un premier temps, une étude expérimentale s’attache à observer la micro-coupe élémentaire d’un acier dur à l’aide de dispositifs réalisés dans le cadre de ces travaux. Un premier dispositif permet de mesurer les efforts d’usinage en micro-coupe élémentaire et un deuxième dispositif innovant permet d’étudier la formation du copeau par coupe interrompue.Par la suite, une démarche de modélisation de la micro-coupe élémentaire est proposée en complément de l’étude expérimentale. Une approche par loi de coupe basée sur les résultats des essais de micro-coupe élémentaire permet de modéliser les efforts d’usinage. En complément, des simulations numériques utilisant la méthode SPH donnent aussi des informations intéressantes sur la formation du copeau, notamment au niveau des zones de déformation.Enfin la loi de coupe associée à un modèle géométrique du micro-fraisage permet de prédire les efforts de coupe lors de l’usinage du même acier. Le modèle géométrique basé sur des travaux précédents a été complété pour prendre en compte la flexion d’outil ainsi que le faux-rond. Ce faux-rond est mesuré directement sur la machine à l’aide d’un moyen d’observation spécialement développé. Les résultats obtenus montrent une concordance entre les efforts expérimentaux et les efforts prédits. / Micro-manufacturing processes are undergoing a significant growth in industrial applications and in a number of major sectors. Among the micro-machining techniques, micro-milling is probably the most versatile both in terms of machined material and in terms geometrical achievability. However, micro-end-mill manufacturing is still limited by some parameters (such as cutting edge radius) and needs improvement. The top-down approach used to reproduce what is best from conventional scale to micro-scale is not necessarily suitable. As a result, micro-milling is still a poorly controlled process (tool wear, tool breakage, path control, burrs...).The aim of the thesis is to understand the mechanisms occurring during the material removal with micro-cutting and to propose a model to predict cutting forces according to cutting conditions, which will then make the optimization of micro-end-mills geometry easier.First, an experimental study is used to observe the elementary micro-cutting operation of a hardened tool steel using specially designed devices. A first device is used to measure cutting forces in elementary micro-cutting and a second innovative device is used to study chip formation by quick-stop tests.Then, modelling approaches of elementary micro-cutting are proposed to complete the experimental study. A cutting law approach based on the results of the elementary micro-cutting tests allows the cutting forces to be modelled. In addition, numerical simulations using the SPH method investigate chip formation and particularly deformation and shear zones.Finally, the proposed cutting law combined with a micro-milling geometric model allows the prediction of cutting forces when micro-milling the same hardened tool steel. The geometric model based on previous work has been completed to consider static tool deflection and run-out. This run-out is measured directly on the machine using a specially developed device. The results obtained show a good correlation between experimental and predicted forces.

La validation du modèle de réponse globale des échantillons ou des structures présente des lacunes qui peuvent être surmontés par l'utilisation de techniques de mesure de plein champ. Les techniques de mesure plein champ offrent la possibilité d'acquérir une quantité importante de données expérimentales qui pourraient être utiles dans le cadre de l'identification des paramètres de la Loi de comportement. Parmi les techniques de mesure de champ complet, le plus populaire est la corrélation d'images mono et stéréo. Les stratégies existantes pour rendre l'utilisation des données de plein champ comme la méthode de champ virtuel, la méthode écart d'équilibre, la méthode de Gap équation Constitutive et la méthode de réciprocité ont été limitées à des applications 2D. Cependant, pour un échantillon d'épaisseur finie, les effets 3D doivent être remplis. Plus important encore, dans le cas de la plasticité, triaxialité du stress joue un rôle important. Son effet doit donc être inscrits dans la modélisation du comportement de la matière. Ainsi, dans cette thèse, nous proposons une méthode pour identifier les paramètres d'une loi de comportement élasto-plastique dans lequel le modèle mécanique peut comporter cinématique 3D. La stratégie s'est avérée être le bruit robuste, presque indépendamment de la conjecture de paramètre initial et de raffinement de maillage et permet de différencier les modèles de comportement avec la même réponse globale sur la base de l'erreur de corrélation moyenne. L'identification est avérée bon pour une ou plusieurs caméras. La validation de la stratégie est faite d'acier inoxydable. La réponse globale du déplacement de charge identifié de la stratégie avec la corrélation d'image mécanique mono et stéréo est très proche des expériences. Enfin, les paramètres du matériau ont été identifiés avec l’estimation initial très différents mais tous convergent vers les mêmes valeurs finales qui montrent la solidité de la stratégie proposée. / The objective of the thesis is to formulate a strategy that gives a robust identification of constitutive law from full-field measurements taking into account 3D effects. Model validation from global response of samples or structures has shortcomings that can be overcome by the use of full-field measurement techniques. Full-field measurement techniques offer the opportunity to acquire large amount of experimental data that might be useful in the context of identification of constitutive law parameters. Among the full field measurement techniques the most popular is digital and stereo image correlation. The existing strategies to make use of full-field data like the Virtual Field Method, the Equilibrium Gap Method, the Constitutive Equation Gap Method and the Reciprocity Method were limited to 2D applications. However, for a specimen with finite thickness 3D effects must be included. Most importantly, for the case of plasticity, stress triaxiality plays an important role. Its effect must therefore be accounted for in the modelling of the constitutive behaviour of the material. Thus in this thesis we propose a method to identify the parameters of an elasto-plastic constitutive law in which the mechanical model can have 3D kinematics. The strategy has been shown to be noise robust, almost independent of initial parameter guess and mesh refinement and allows differentiating between constitutive models with same global response on the basis of mean correlation error. The identification is shown to be good for both single and multiple cameras. The strategy validation is done for stainless steel. The global identified load displacement response of the strategy for mono and stereo mechanical image correlation is very close to the experiments. Lastly, the material parameters have been identified with very different initial guess but all converge to the same final values which show the robustness of the proposed strategy.

Le procédé de tournage galetage (CoTuB) est un traitement d'usinage innovant réalisant les procédés de tournage et de galetage à billes simultanément et sur la même machine-outil. L'objectif du procédé combiné est d'améliorer l'intégrité de surface et en même temps d'augmenter la productivité par rapport aux traitements conventionnels de surface et les procédés d'usinage. En adoptant un plan d’expérience, il a été démontré qu'une amélioration considérable de l’intégrité de surface pourrait être obtenue en utilisant le nouveau procédé combiné et en sélectionnant les paramètres appropriés. Pour effectuer une étude paramétrique, un ensemble d'expériences basées sur un plan d’expérience de type Taguchi complété par une analyse de la variance (ANOVA) a été réalisée. Le but de cette étude expérimentale est d'identifier les paramètres optimaux du tournage / galetage lors du traitement de l'acier 42 Cr Mo 4 permettant de donner une intégrité de surface optimale.Pour une meilleure compréhension des phénomènes impliqués lors du procédé combiné d'usinage / galetage, des approches et méthodologies numériques ont été développées afin de reproduire le procédé combiné. Une nouvelle approche numérique, appelée «Approche Mixte», est développée et utilisée afin de simplifier la simulation du procédé combiné. Cette approche combine des données expérimentales et numériques afin de déterminer la forme et de quantifier les chargements thermiques et mécaniques exercés par l'outil de coupe sur la surface usinée sur chaque zone de cisaillement. Cette nouvelle méthode a permis d'effectuer une simulation 3D du procédé de tournage-galetage combiné et permet de simuler plusieurs passages des outils autour de la surface usinée. La simulation permet de prédire les contraintes résiduelles induites par le procédé combiné et la comparaison révèle un bon accord entre les résultats numériques et expérimentaux. / The Combined Turning-Burnishing (CoTuB) process is an innovative machining treatment that performs turning and ball-burnishing processes simultaneously and on the same machine tool. The aim of performing the combined process is to enhance surface integrity and increase productivity at the same time when compare to conventional surface treatment and machining processes. Based on adopting design of experiments, it has been depicted that a considerable improvement in surface quality could be obtained meaning the new combined process by using the suitable process parameters. In order to carry out a parametric study, a set of experiments based on Taguchi method completed with a statistical analysis of variance (ANOVA) were performed. The aim of this experimental investigation is to identify the optimal turning/burnishing parameters when treating AISI 4140 steel. This helps to get an optimal surface integrity. For a better understanding of the phenomena involved during combined machining / burnishing processes, numerical approaches and methodologies for reproducing the combined turning-burnishing process have been performed. A new approach, called the "Mixed Approach", is developed and used in order to simplify the simulation of the combined process. This approach combines experimental and numerical data in order to determine shape and to quantify thermal and mechanical loadings exerted by the cutting tool on the machined surface on each shear zone. This new method allowed to perform a 3D simulation of combined turning-burnishing and allows to model several tool passages on the machined surface. The simulation allows to predict residual stresses induced by the combined process and the comparison reveals good agreements between numerical and experimental results.

Doctorat en sciences psychologiques / info:eu-repo/semantics/nonPublished

La balistique lésionnelle, carrefour de l’expertise balistique et de la médecine légale, est fréquemment confrontée à l’évaluation et la caractérisation de plaies balistiques crâniennes. De nombreuses recherches ont été effectuées sur les traumatismes de l’extrémité cervico-céphaliques dans une vision d’amélioration de la sécurité mais celles dans le domaine de la balistique sont quasi inexistantesou empreintes de certitudes non démontrées. Le premier objectif de ce travail a été demettre en place un protocole de tirs d’essai sur des voutes crâniennes d’animal dont la structure est comparable à celle de l’homme. Ce setup original, alliant la technologie d’enregistrement vidéo à haute vitesse et l’analyse des dégâts en microtomographie, a permis de mettre en exergue des relations entre vitesse d’impact, vitesse de sortie, énergie dissipée et dommages créés. Ils contredisent souvent certaines théories jusque là proposées et répondant ainsi à notre deuxième objectif. Les nombreuses données acquises par l’expérimentation pourront utilement éclairer l’expert en balistique lésionnelle dans l’argumentation de ses hypothèses quant à l’utilisation d’un couple arme-munition plutôt qu’un autre. Cette étude propose également un nouveau modèle quant à la cinématique complète de l’interaction entre le projectile et la structure osseuse. / Wound ballistics is at the crossing between ballistics and legal medicine. It frequently has to tackle skull gunshot wounds evaluation and characterization. Many researches have been made around head and skull traumas, aiming at an improvement of security devices, but considering the field of ballistics, researches are either inexistent or marred by undemonstrated certainties. This work first aims at setting a firing protocol out, using animal skull bones that are similar with humans’. This original setup allies high speed video recordings and damage analysis with microtomography. It has shown up relationships between impact speed, exit speed, dissipated energy and observed damages. It comes in contradiction with many models formerly exposed, and hence fulfills our second objective. Important data acquired from experiments can show as very useful for wound ballistics expert to support one of his hypothesis about which firearms and ammunition type were used. This work eventually proposes a new model explaining the interaction between projectile and bone structure during damage creation.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The knowledge of previous conceptions of students is an important tool in the teaching-learning process, since it can significantly help the planning of educational activities. Solubility is a fundamental concept in Chemistry present in a wide range of everyday situations; however, it is little explored regarding previous conceptions. In this context, this study aimed to investigate the previous conceptions of high school students on solubility, to evaluate if Biology and Chemistry teachers develop experimental and interdisciplinary activities on the theme and to elaborate a booklet with experiments on solubility. The study was performed in public schools of Santa Maria-RS and Rosário do Sul-RS and involved 314 students and 30 teachers of Biology and Chemistry. In order to investigate the previous conceptions of students, we used a semi-structured questionnaire for data collection consisting of questions concerning the concept of solubility, the importance of this concept in everyday life and the existence of correlation of this content with the content studied in Biology. With regard to Biology and Chemistry teachers, we used a closed questionnaire with issues related to the workload of teachers, the realization of practical classes and the interdisciplinary approach of the solubility content. In general, we verified that students have knowledge about solubility, but little is based on scientific knowledge. Students also reported the importance of this knowledge mainly regarding the food. The results obtained also showed that most of the teachers do not work the theme solubility in an interdisciplinary way or perform experimental activities related to it. Therefore, we can conclude that some teachers still have a fragmented and compartmentalized teaching, where the student is a mere receiver of knowledge. After the analysis of the data obtained, a booklet will be prepared with experiments on solubility, which will be distributed to teachers participating the research in order to help them carry out these experiments and develop new experimental activities in the classroom. / O conhecimento das concepções prévias dos estudantes constitui uma ferramenta de grande importância no processo de ensino-aprendizagem, uma vez que estas podem auxiliar de forma significativa no planejamento de atividades pedagógicas. Um conceito fundamental em Química e pouco explorado nas investigações sobre concepções prévias é o conceito de solubilidade, o qual está presente em uma vasta gama de situações do cotidiano. Neste contexto, o presente estudo teve como objetivos: investigar as concepções prévias de estudantes do Ensino Médio sobre solubilidade; averiguar se os professores de Biologia e Química desenvolvem atividades experimentais e interdisciplinares sobre o tema; e elaborar uma apostila com experimentos sobre solubilidade. O estudo foi realizado em Escolas Públicas de Santa Maria-RS e Rosário do Sul-RS e envolveu 314 estudantes e 30 professores de Biologia e Química. A fim de investigar as concepções dos estudantes, foi utilizado para coleta de dados um questionário semi-estruturado composto por questões referentes ao conceito de solubilidade, a aplicabilidade deste conceito no dia a dia e a existência de correlação deste conteúdo com os trabalhados em Biologia. Com relação aos professores de Biologia e Química, foi utilizado um questionário fechado composto por questões referentes à carga horária dos professores, a realização de aulas práticas e a abordagem interdisciplinar do conteúdo solubilidade. De forma geral, verificou-se com este estudo, que os estudantes possuem conhecimentos sobre o tema solubilidade, porém pouco ancorados em conhecimentos científicos e que também relacionam a importância deste conhecimento principalmente com a Alimentação. Os resultados obtidos, também mostram que a maioria dos professores não trabalha o tema Solubilidade de forma interdisciplinar e nem realiza atividades experimentais sobre conteúdos relacionados. Pode-se concluir que alguns professores ainda mantêm um Ensino fragmentado e compartimentalizado, onde o estudante é um mero receptor de conhecimentos. Após a análise dos dados obtidos, será elaborada uma apostila com experimentos sobre solubilidade, a qual será distribuída aos professores participantes da pesquisa. Pretende-se auxiliá-los na execução destes experimentos e no desenvolvimento de novas atividades experimentais em sala de aula.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The experimentation has been a practice little and inadequately explored in school space assuming functions of demonstration and verification, predominantly focused on the end result. We propose, then, to focus on the process, that is, to perform a constant exploration of everything that makes up and happens while conducting an experiment. Through the careful examination of each step it is possible to discuss and contrast knowledge and, at the same time, build skills and competences. In elementary school, the student is immersed in the universe of a unified science, which allows the rescue and the recovery of a more integrated vision of scientific phenomena. In this context we recognize the potential of the process of experimentation to promote learning and scientific competences in a group of twenty six students from 3rd year of the 3rd cycle (equivalent to 9th year) of elementary public school located in a region of high social vulnerability on the outskirts of the city of Porto Alegre. Students were encouraged to develop, assemble and perform experiments, through gradual steps of familiarization with materials and devices. During the development of the activities carried out in twelve class hours interspersed with regular classes, we analyzed the actions, behaviour and material and textual production of the students, through reports, questionnaires and written records, adopting a participatory observation methodology, in order to collect qualitative aspects related to promoting competences and scientific learning arising from the process of experimentation. The assessment of the results revealed the learning of countless concepts related to the studied phenomena and the formation and consolidation of multiple and relevant competences, which are pertinent to science education. / A experimentação tem sido uma prática pouco e inadequadamente explorada no espaço escolar assumindo funções de demonstração e verificação, predominantemente centradas no resultado final. Propomos, então, focalizar o seu processo, ou seja, efetuar uma constante exploração de tudo o que compõe e acontece durante a realização de um experimento. Através do exame minucioso de cada etapa pode-se discutir e contrastar conhecimentos e, ao mesmo tempo, construir habilidades e competências. No ensino fundamental, o aluno está imerso no universo de uma Ciência unificada que permite o resgate e a valorização de uma visão mais integrada dos fenômenos científicos. Neste contexto buscamos constatar o potencial do processo de experimentação para promover aprendizagens e competências científicas em um grupo de vinte e seis alunos do 3o ano do 3o ciclo (equivalente ao 9o ano) do ensino fundamental de uma escola pública localizada numa região de alta vulnerabilidade social na periferia do município de Porto Alegre. Os alunos foram estimulados a elaborar, montar e executar experimentos, passando por etapas gradativas de familiarização com materiais e aparelhos. Durante o desenvolvimento das atividades, realizadas em doze horas-aula intercaladas com as aulas regulares, analisamos as ações, o comportamento e a produção textual e material dos alunos, por meio de relatórios, questionários e registros escritos, adotando uma metodologia de observação participativa, no intuito de coletar aspectos qualitativos relacionados à promoção de competências e aprendizagens científicas decorrentes do processo de experimentação. A avaliação dos resultados revelou a aprendizagem de inúmeros conceitos relacionados aos fenômenos estudados e a formação e consolidação de múltiplas e relevantes competências pertinentes à educação científica.

The need to economically identify rare subjects within large, poorly-mapped search spaces is a frequently-encountered problem for social scientists and managers. It is notoriously difficult, for example, to identify "the best new CEO for our company," or the "best three lead users to participate in our product development project." Mass screening of entire populations or samples becomes steadily more expensive as the number of acceptable solutions within the search space becomes rarer. The search strategy of "pyramiding" is a potential solution to this problem under many conditions. Pyramiding is a search process based upon the idea that people with a strong interest in a topic or field tend to know people more expert than themselves. In this paper we report upon four experiments empirically exploring the efficiency of pyramiding searches relative to mass screening. We find that pyramiding on average identified the most expert individual in a group on a specific topic with only 28.4% of the group interviewed - a great efficiency gain relative to mass screening. Further, pyramiding identified one of the top 3 experts in a population after interviewing only 15.9% of the group on average. We discuss conditions under which the pyramiding search method is likely to be efficient relative to screening.

South Africa is one of the countries with the highest prevalence of HIV infection in the world, particularly among the youth between the ages 15 and 24 years. The number of infections among the youth in South Africa is still increasing and this does not exclude the youth under study in the community of Eersterust. The HIV and AIDS epidemic is affecting large numbers of adolescents, throughout South Africa leading to serious psychological, social, economic and educational problems. Because of the devastating effect and rapid increase of HIV-infections among adolescents, it has become evident that not only government departments (Department of Health and Department of Education), but also community-based educational support structures (organisations) should share the responsibility by playing a pro-active role in awareness and the curbing of the spread of HIV-infection among adolescents. Various researchers have been focusing on the knowledge, attitudes and behaviour of adolescents but limited research has been done on the contribution of community-based educational support programmes with regard to creating awareness and the curbing of the further spread of HIV-infection among adolescents. This study which seeked to address the need for ongoing research in this field, attempted to investigate whether and how communitybased educational programmes address the educational needs of adolescents within a particular community, namely Eersterust. In order to determine these needs, quantitative and qualitative descriptive research approaches were utilized comprising of a questionnaire survey and focus group interviews. The questionnaire survey explored the knowledge, skills, attitudes and sexual behaviour of the 916 participants. The results from the questionnaire were utilized to determine the educational needs of adolescents. Focus group interviews were conducted with 11 adolescents who attended the educational support programmes at the Youth Development Outreach Centre and the Circle of Life Centre. The latter are two community-based organisations in the community under study (Eersterust). The focus group interviews were utilized to determine the views of the adolescents with regard to the mode of delivery and effectiveness of the community-based educational support programmes. From the data in the questionnaire the educational needs of adolescents were identified and compared with the content of the community-based educational support programmes of the two community-based support structures. The findings revealed that the community-based educational support programmes are to a large extent addressing the HIV and AIDS educational needs of the adolescents under study. The focus group interviews revealed that the participants are of the opinion that they find the programmes interesting and enriching. They benefit educationally by attending the educational programmes and they would recommend the programmes to other adolescents. The findings indicate that the educational programmes are appropriate to address the HIV and AIDS educational needs of the adolescents. The educational needs identified in the empirical research are however not fulfilled because many of the adolescents do not attend the educational programmes. There are only a few adolescents who attend these educational programmes. The latter might be a contributing factor to the high HIV-infection among adolescents. / Thesis (PhD)--University of Pretoria, 2013. / gm2013 / Early Childhood Education / unrestricted