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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.
81

Etude de l’effet du vieillissement thermique sur le comportement en fatigue ducomposite de poly (sulfure de phénylène) renforcé par des fibres de verre (PPS/FV) / Study of thermal aging effect on fatigue behaviors of a short glass fiber reinforced Polyphenylene Sulfide (PPS/GF) composite

Zuo, Peiyuan 18 December 2018 (has links)
Dans ce travail, l’effet du vieillissement thermique sur le comportement en fatigue ducomposite de poly (sulfure de phénylène) renforcé par fibres de verre (PPS/FV) a été étudié. Ce matériau est d’abord étudié par différentes méthodes d’analyse afin de déterminer ses caractéristiques physicochimiqueset mécaniques. Ensuite, le matériau subit un vieillissement thermo-oxydatif accéléré à différentes températures comprises entre 100 °C et 200 °C. Certaines caractéristiques du matériau sont d’ailleurs suivies au cours du vieillissement. A partir des résultats obtenus, un mécanisme d’oxydation estproposé et un modèle cinétique est développé. La validité de ce modèle est vérifiée par les résultats expérimentaux, essentiellement obtenus par la spectrométrie infrarouge. L’effet du vieillissement sur lecomportement mécanique est étudié par les deux axes suivants : D’abord d’une manière indirecte en étudiant l’évolution de la morphologie de la phase cristalline au cours du temps et ensuite par la méthode directe. Dans cette méthode directe, premièrement, le comportement en fatigue et en traction-traction duPPS/FV a été étudié en faisant varier la fréquence et l’amplitude de la sollicitation. La courbe de Wöhler est tracée en fonction du nombre de cycles à la rupture. Il a été constaté que le vieillissement modifie lepositionnement et l’allure de la courbe de Wöhler. Ensuite les éprouvettes vieillies à différentes températures sont testées en fatigue (traction-traction) avec une amplitude maximale (σmax=40 MPa) et un rapport de chargement (R=0,1) afin de suivre l’influence de la dégradation thermo-oxydative au cours du vieillissement. Il a été constaté que l’oxydation a un effet néfaste sur le comportement en fatigue du PPS/FV. Ce matériau perd significativement de ses performances même au début du vieillissement etsurtout à haute température de vieillissement. La perte de la performance en fatigue du matériau s’accentue au fur et à mesure que le processus d’oxydation se poursuit. / In this work, the effect of thermal aging on the fatigue behavior of a glass fiber reinforced poly (phenylene sulfide) composite (PPS/GF) was studied. This material is first characterized by differentmethods of analysis to determine its physicochemical and mechanical characteristics. Subsequently, thematerial undergoes accelerated thermo-oxidative aging at different temperatures between 100 °C and 200 °C. Some characteristics of this material are followed during thermal aging. From the results obtained, an oxidation mechanism is proposed and a kinetic model is developed. The validity of this model is verifiedby the experimental results, essentially obtained by infrared spectrometry. The effect of thermal aging on mechanical behavior is studied in two ways: Firstly, indirect manner by studying the evolution of the morphology of the crystalline phase over time and subsequently by the direct method. In this directmethod, firstly the tension-tension fatigue behavior of PPS/GF was studied by varying the frequency and amplitude of stress. The Wöhler curve is plotted on the basis of the number of cycles at break. Thermalaging has been found to alter the position and shape of the Wöhler curve. Then the samples aged at different temperatures were tested by tension-tension fatigue with a maximum amplitude (σmax = 40 MPa)and a loading ratio (R = 0.1) to follow the influence of thermo-oxidative degradation during aging. It has been found that thermal aging has a detrimental effect on the fatigue behavior of PPS/GF. This material loses its performance significantly even at the beginning of aging, especially in high aging temperature.The loss of fatigue performance grows in the oven as the oxidation process continues.
82

Änderungsflexibilität in der kundenindividuellen Fertigung

Wünsch, Daniela 14 April 2011 (has links) (PDF)
Die Anforderungen des Marktes in Bezug auf Flexibilität und Geschwindigkeit, welchen sich Produktionsunternehmen stellen müssen, nehmen immer weiter zu. Die Kunden wollen in jeder Hinsicht individuell bedient werden. Sie wollen das Produkt nach ihren Vorstellungen konfigurieren können, es in kurzer Zeit zur Verfügung gestellt bekommen und trotzdem bei Bedarf individuelle Änderungen integrieren können. Aus diesem Grund muss ein Produktionsunternehmen sowohl in der Planungs- als auch in der Ausführungsphase flexibel auf Änderungen, die vom Kunden ausgelöst werden oder durch interne Ereignisse erforderlich sind, reagieren können. Studien unter produzierenden Unternehmen haben gezeigt, dass im Fall der Notwendigkeit nachträglicher Änderungen das Produktionsplanungs- und steuerungssystem oft nicht miteinbezogen wird, insbesondere dann, wenn die Änderungen sehr prozessnah stattfinden. Da Änderungen jedoch heutzutage keine Seltenheit mehr sind, führt dies dazu, dass die im System gehaltenen Daten häufig von dem tatsächlichen Produkti-onsablauf abweichen. Eine im Rahmen der Arbeit durchgeführte Analyse führender ERP-Systeme und MES hat gezeigt, dass dieses Problem auf Systemunzulänglichkeiten zurückzuführen ist. Auf Basis der Systemuntersuchung schlägt die Arbeit deshalb ein Konzept für ein flexibles Produktionspla-nungs- und -steuerungssystem vor: das PPS II-System. Dieses System soll gewährleisten, dass nachträgliche Änderungen, die durch interne oder externe Ereignisse ausgelöst werden, in die Produktionsplanung integriert werden können. Die Architektur des PPS II-Systems basiert auf der Idee, die starre Trennung zwischen den Planungs- und Steuerungssystemen der Fertigung aufzulösen. Um dies zu gewährleisten, besteht das PPS II-System aus lose gekoppelten Services, deren Zusammenwirken das Verhalten des Systems beschreibt. Die Funktionalität des PPS II-Systems orientiert sich am Konzept der prozessnahen Gestaltungsentscheidung, welches die Ausführungszeit, die zu verwendenden Materialien und die einzusetzenden Ressourcen auf Basis verschiedener Abstraktionen erst unmittelbar vor Produktionsbeginn bestimmt. Eine umfangreiche theoretische und praktische Evaluierung bestätigt, dass das PPS II-System auf diese Weise sehr flexibel auf Änderungen reagieren kann. / Today, production companies face big challenges, in particular with regards to flexibility and speed. Their customers want to be served individually in every respect. They want to configure the product individually and receive it as fast as possible. However, they also want to be able to integrate late changes. For this reason, a production company must be able to react to changes in the planning phase as well as in the production phase in a very flexible way. Such changes might be initiated by the customers or they might be necessary due to internal events. Surveys, which analyzed the processes of production companies, have revealed that their production planning and control systems are often not involved if late changes are necessary. This is particularly true, if the changes occur shortly before the production starts. Therefore, system data deviate from the real production procedure often already in the planning phase. An analysis of leading ERP systems and MES carried out in this thesis has shown that the reason for the problems is the limited flexibility of these systems. On the basis of the analysis, this thesis proposes a new concept for a flexible production and control system: the PPC II system. This system should ensure that late changes triggered by internal or external events can be integrated in the production schedule. The architecture of the PPC II system is based on the idea to eliminate the separation between the planning system and the control system. To reach this goal, the system consists of loosely coupled services that are flexibly orches-trated to control production processes. The PPC II system realizes the concept of late order freeze. Process-relevant decisions for the execution time, the used materials, and the resources are made shortly before production starts. A comprehensive theoretical and practical evaluation verifies that the PPC II system is able to react flexible to changes.
83

機率比例抽樣設計之建構

陳靜宜, Chen, Ching-Yi Unknown Date (has links)
當考慮不等機率抽樣設計時,若存在一輔助訊息與我們欲估計之未知量成比例,則機率比例抽樣設計(probability proportional to size sampling design),記為PPS機率抽樣設計,是一個不錯的選擇。Horvitz-Thompson估計量在 PPS 機率抽樣設計之下變異數較小。換句話說,可以更精確地估計母體總和。本文提出一個由Hedayat-Lin方法推廣而得之新演算法,利用本演算法可建構出一些PPS機率抽樣設計。此種設計不僅能不偏的估計Horvitz-Thompson估計量之變異數,且能確保此估計量為非負值。 / When unequal probability sampling design is under consideration, and when there exists auxiliary information which is proportional to the unknown quantity that we want to estimate, probability proportional to size sampling design, abbreviated as PPS sampling design, is a good choice. Under PPS sampling design, Horvitz-Thompson estimator has small variance. In this paper, a new algorithm, which is a generalization of Hedayat-Lin's procedure, is given. Using this algorithm, a PPS(N, n) sampling design can be constructed. This design not only provides unbiased estimate of the variance of Horvitz-Thompson estimator but also assures its non-negativity.
84

Explorer les trajectoires de patients via les bases médico-économiques : application à l'infarctus du myocarde / Exploring trajectories of patients via medico-economic databases : application to myocardial infarction

Pinaire, Jessica 17 October 2017 (has links)
Avec environ 120 000 personnes atteintes chaque année, 12 000 décès suite à la première crise et 18 000 décès après une année, l'infarctus du myocarde est un enjeu majeur de santé publique. Cette pathologie nécessite une hospitalisation et une prise en charge dans une unité de soins intensifs de cardiologie. Pour étudier cette pathologie, nous nous sommes orientés vers les bases hospitalières du PMSI.La collecte des données hospitalières dans le cadre du PMSI génère sur le plan national des bases de données de l'ordre de 25 millions d'enregistrements par an.Ces données, qui sont initialement recueillies à des fins médico-économiques, contiennent des informations qui peuvent avoir d'autres finalités : amélioration de la prise en charge du patient, prédiction de l'évolution des soins, planification de leurs coûts, etc.Ainsi émerge un autre enjeu : celui de fournir des outils d'explorations des trajectoires hospitalières des patients à partir des données issues du PMSI. Par le biais de plusieurs objectifs, les travaux menés dans le cadre de cette thèse ont pour vocation de proposer des outils combinant des méthodes issues de trois disciplines : informatique médicale, fouille de données et biostatistique.Nous apportons quatre contributions.La première contribution concerne la constitution d'une base de données de qualité pour analyser les trajectoires de patients. La deuxième contribution est une méthode semi-automatique pour la revue systématique de la littérature. Cette partie des travaux délimite les contours du concept de trajectoire dans le domaine biomédical. La troisième contribution est l'identification des parcours à risque dans la prédiction du décès intra-hospitalier. Notre stratégie de recherche s'articule en deux phases : 1) Identification de trajectoires types de patients à l'aide d'outils issus de la fouille de données ; 2) Construction d'un modèle de prédiction à partir de ces trajectoires afin de prédire le décès. Enfin, la dernière contribution est la caractérisation des flux de patients à travers les différents évènements hospitaliers mais aussi en termes de délais d'occurrences et de coûts de ces évènements. Dans cette partie, nous proposons à nouveau une alliance entre une méthode de fouille de données et de classification de données longitudinales. / With approximately 120,000 people affected each year, 12,000 deaths from the first crisis and 18,000 deaths after one year, myocardial infarction is a major public health issue. This pathology requires hospitalization and management in an intensive care cardiology unit. We study this pathology using the French national Prospective Paiement System (PPS) databases.The collection of national hospital data within the framework of the PPS generates about 25 million records per year.These data, which are initially collected for medico-economic purposes, contain information that may have other purposes: improving patient care, predicting the evolution of care, planning their costs, etc.Another emerging issue is that of providing tools for exploring patients' hospital trajectories using data from the PPS. Through several objectives, this thesis aims to suggest tools combining methods from three disciplines: medical computing, data mining and biostatistics.We make four contributions.The first contribution concerns the constitution of a quality database to analyze patient trajectories. The second contribution is a semi-automatic method for the systematic review of the literature. This part of the work delineates the contours of the trajectory concept in the biomedical field. The third contribution is the identification of care trajectories in the prediction of intra-hospital death. Our research strategy is divided into two phases: 1) Identification of typical patient trajectories using data mining tools; 2) Construction of a prediction model from these trajectories to predict death. Finally, the last contribution is the characterization of patient flows through the various hospital events, also considering of delays and costs. In this contribution, we propose a combined-data mining and a longitudinal data clustering technique.
85

Friction and Wear Performance of Experimentally Developed Self-lubricating PPS/PTFE Composites

Lagrama, Kimberly Rose January 2019 (has links)
Demanding applications, as well as the push to eliminate the need for fossil-fuel based lubricants, create the need for the development of high-performance polymers. Polyphenylene Sulfide (PPS) is an example of a high-performance polymer and has a high service temperature, good dimensional stability, and excellent chemical resistance. However, it has a low impact strength and is very brittle in neat form. Another high-performance polymer, Polytetrafluoroethylene (PTFE), provides low friction in dry sliding conditions and can deposit polymer transfer films onto the counterface but exhibits high wear rates in neat form. To take advantage of the desirable characteristics of both polymers, PPS/PTFE-based composites were produced through the Injection Molding process. The individual disadvantages of these polymers were further improved by incorporating the following fillers: SCF, GO and CNT. The tribological performance under dry sliding conditions and two different loads were investigated as well as the microhardness and degree of crystallinity of the materials. The DSC results showed that the incorporation of reinforcements did not significantly alter the total degree of crystallinity in the material. PPS/PTFE and the composites have significantly lower specific wear rates and coefficient of friction values compared to neat PPS and PTFE. The composites have higher microhardness and friction coefficient values (60N and 100N) compared to PPS/PTFE. For both loads, composites SCFCNT, 5SCF and 10SCF had the lowest specific wear rates recorded where a synergistic effect between SCF and CNT has been observed. The filler loading content did not affect the friction performance of the composites in both loads. However, for composites with SCF as the only reinforcement, the increase in wt% content of SCF increased the specific wear rate at 60N and decreased the specific wear rate at 100N. SEM images of the pin surfaces show that the governing wear mechanisms in the polymer blend and composites are abrasive and adhesive wear. The reduction of the specific wear rate values is also accompanied by the improvement in the uniformity of the observed transfer film formation.
86

Purchasing Power Parity (PPP) Deviations: The case of Zimbabwe and it’s five neighbouring countries (1997 – 2016).

Mudavanhu, Tinashe January 2019 (has links)
Economic decline in Zimbabwe has manifested in several ways, one of which is in the form of persistent trade deficits. This is not unique to Zimbabwe alone, with trade imbalances also extending to its neighbouring countries. The purpose of this study is to investigate whether PPP deviations can be used to manage bilateral trade balances in such a way that parties concerned benefit from the trade proportionally. The literature review analysed research done on the validity of PPP theory in developing and developed countries all over the world. Studies generally confirmed that the long-run PPP holds strong for developed countries and weak for developing countries. The study makes use of secondary yearly data from international financial institutions and employs unit root tests and the Engle Granger cointegration test to investigate the Purchasing Power Parity theory. In addition, Granger causality tests were also performed on the observed deviations and trade balances to find out if a relationship is present. It was noted that PPP theory does not hold between Zimbabwe and its neighbouring countries (Botswana, Namibia, Zambia, South Africa, and Mozambique). As such, PPP deviations cannot be used to improve bilateral trade balances between Zimbabwe and its trading partners.
87

A prescrição de psicofármacos em uma região de saúde do Estado de São Paulo : análise e reflexão sobre uma prática /

Lamb, Ieda Garms Macedo January 2008 (has links)
Orientador: Abilio da Costa Rosa / Banca: Maria Jacira da Silva Simões / Banca: Sílvio Yasui / Resumo: Este trabalho de pesquisa analisou a dispensação de psicofármacos prescritos na rede extra-hospitalar do SUS, de 2002 a 2006, em uma Região de Saúde do Estado de São Paulo. Essa prescrição de psicofármacos é entendida, aqui, enquanto componente do dispositivo de medicalização, na concepção de Illich e Foucault e enquanto parte de um mesmo paradigma, o PPHM, conforme proposto por Costa-Rosa. A alta prevalência de transtornos psíquicos, em função de fatores complexos, mais agravados na atualidade, e as alardeadas taxas de medicalização do sofrimento psíquico indicam a grande relevância de investigar o fenômeno com profundidade, considerando que, de acordo com dados obtidos até 2006, em 25 municípios do referido Estado, as prescrições de psicofármacos foram significativas. Utilizou-se o método epidemiológico, baseado em dados secundários fornecidos pelo Farmanet, para o Programa Estadual (SP) de Assistência Farmacêutica na área de Saúde Mental. Os dados referentes aos psicofármacos dispensados foram expressos em DDD (Dose Diária Definida) por mil habitantes/dia, para cada classe terapêutica. As classes terapêuticas mais dispensadas foram antidepressivos, estabilizadores de humor e ansiolíticos, enquanto os antipsicóticos mantiveram dispensação estável, no mesmo período. O estudo realizado apontou grande possibilidade de ocorrência da medicalização do sofrimento psíquico, com suas consequências iatrogênicas. Esta análise pretende fornecer contribuições, neste momento difícil em que as políticas e as práticas próprias do Paradigma Psicossocial tanto lutam para se firmar, em todo o país, como alternativa teórico-técnica e ética ao Paradigma Psiquiátrico Hospitalocêntrico Medicalizador (PPHM). / Abstract: This research analysis the dispensation of psychopharmacs prescribed in the extrahospitalar network of SUS, from 2002 to 2006, in a health region of the State of São Paulo, Brazil. This prescription of psychopharmacs, is understood here, while the component of medicalization disposition, according to Illich and Foucault and while comes from the some pattern, the PPHM, according to Costa-Rosa. The high prevalency of psychic disturbance, because of complex factors, more aggravated nowadays, and boasted toxes of psychei suffering medicalization indicate the great importance to investigate this phenomenon deeper, considering that, according to obtained data until 2006, in 25 cities of the refered State, the presciptions of psychopharmacs were meaningful. It is utilized the epidemiologyc method, with secundary data supplied by the Farmanet, for the State wide Program (SP) of Pharmaceutical Assistence in the Mental Health field. The refering data of exempted psychopharmacs were expressed in DDD (Daily Dosage Definite) by a thousand in habitants per day, for each therapeutic class. The most exempted classes were antidepressives, humor stabilizers and ansioulitics, while the antipsychots maintained stable exemptation, in the some period. The realized study indicated great possibility of medicalization occurance od psychic suffering, with their iatrogenic consequences. This analysis intends to supply contribution, in this hard time, where politics and owen acts of the Psychosocial Patern fight to be solid, in the whole country as a tecnique theorical and ethical alternative to the Medicalizatior Hospitalocentric Psychiatric Pattern (PPHM). / Mestre
88

Pesquisas sob amostragem informativa utilizando o FBST / Surveys under informative sampling using the FBST

Azerêdo, Daniel Mendes 28 May 2013 (has links)
Pfeffermann, Krieger e Rinott (1998) apresentaram uma metodologia para modelar processos de amostragem que pode ser utilizada para avaliar se este processo de amostragem é informativo. Neste cenário, as probabilidades de seleção da amostra são aproximadas por uma função polinomial dependendo das variáveis resposta e concomitantes. Nesta abordagem, nossa principal proposta é investigar a aplicação do teste de significância FBST (Full Bayesian Significance Test), apresentado por Pereira e Stern (1999), como uma ferramenta para testar a ignorabilidade amostral, isto é, para avaliar uma relação de significância entre as probabilidades de seleção da amostra e a variável resposta. A performance desta modelagem estatística é testada com alguns experimentos computacionais. / Pfeffermann, Krieger and Rinott (1998) introduced a framework for modeling sampling processes that can be used to assess if a sampling process is informative. In this setting, sample selection probabilities are approximated by a polynomial function depending on outcome and auxiliary variables. Within this framework, our main purpose is to investigate the application of the Full Bayesian Significance Test (FBST), introduced by Pereira and Stern (1999), as a tool for testing sampling ignorability, that is, to detect a significant relation between the sample selection probabilities and the outcome variable. The performance of this statistical modelling framework is tested with some simulation experiments.
89

Bayesian Predictive Inference Under Informative Sampling and Transformation

Shen, Gang 29 April 2004 (has links)
We have considered the problem in which a biased sample is selected from a finite population, and this finite population itself is a random sample from an infinitely large population, called the superpopulation. The parameters of the superpopulation and the finite population are of interest. There is some information about the selection mechanism in that the selection probabilities are linearly related to the measurements. This is typical of establishment surveys where the selection probabilities are taken to be proportional to the previous year's characteristics. When all the selection probabilities are known, as in our problem, inference about the finite population can be made, but inference about the distribution is not so clear. For continuous measurements, one might assume that the the values are normally distributed, but as a practical issue normality can be tenuous. In such a situation a transformation to normality may be useful, but this transformation will destroy the linearity between the selection probabilities and the values. The purpose of this work is to address this issue. In this light we have constructed two models, an ignorable selection model and a nonignorable selection model. We use the Gibbs sampler and the sample importance re-sampling algorithm to fit the nonignorable selection model. We have emphasized estimation of the finite population parameters, although within this framework other quantities can be estimated easily. We have found that our nonignorable selection model can correct the bias due to unequal selection probabilities, and it provides improved precision over the estimates from the ignorable selection model. In addition, we have described the case in which all the selection probabilities are unknown. This is useful because many agencies (e.g., government) tend to hide these selection probabilities when public-used data are constructed. Also, we have given an extensive theoretical discussion on Poisson sampling, an underlying sampling scheme in our models especially useful in the case in which the selection probabilities are unknown.
90

Planung und Steuerung von Produktion und Recycling in kreislaufwirtschaftlich ausgeprägten Unternehmensnetzwerken : ein Supply Chain Management orientierter Ansatz /

Martens, Heiko. January 2007 (has links) (PDF)
Zugl.: @Göttingen, Universiẗat, Diss., 2006.

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