• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 116
  • 102
  • 40
  • 19
  • 18
  • 8
  • 7
  • 5
  • 4
  • 4
  • 3
  • 2
  • 2
  • 2
  • 2
  • Tagged with
  • 376
  • 171
  • 84
  • 77
  • 67
  • 56
  • 49
  • 47
  • 41
  • 36
  • 36
  • 32
  • 31
  • 27
  • 26
  • 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.
351

Problemet utan namn? : Neuroser, stress och kön i Sverige från 1950 till 1980 / The Problem that had no Name? : Neurosis, Stress and Gender in Sweden 1950-1980

Björk, Maria January 2011 (has links)
Focusing on Sweden between 1950 and 1980, this doctoral dissertation analyzes and problematizes the process in which a discourse about neurosis and nervous troubles gradually evolved into a discourse about stress. The thesis aims to show how the medical and general discussion about diffuse or vague symptoms transformed and rearticulated ideas and views on society and man, citizenship, gender roles, and medicine. It shows how the discourse on neuroses tended to locate sickness and deviance in the individual, whereas its subsequent transformation into a discourse on stress located the pathological in an external, societal sphere. A particularly prominent issue in the study concerns the role that gender, and in particular female gender, has played in these discourses, and how the place of the feminine can be understood in relation to stress and neuroses. The dissertation shows that female gender was not central to the discourse on neuroses and stress  during the studied period. On the contrary, gender was subordinated to ideas about man and citizenship within the greater context of society and culture. The dissertation takes its starting point in the Swedish 1950’s, often characterized as the era of ”The Strong Society” or ”The People’s Home”. During this period, the neurosis discourse was fixed and remained unchanged. In practice, neurosis was a diagnosis that provided such symptoms that were otherwise difficult to measure and assess with a theory of origin. Neuroses were believed to principally affect a certain category of individuals, who, due to their constitution or disposition, were held to be particularly susceptible to neurotic sufferings. During the 1960s the belief in The Strong Society and its notion of ideal citizenship began to crumble. It was against this background that the Swedish medical profession started discussing ”stress”. Stress, in contrast, could afflict anyone and everyone, according to “the father of stress” Hans Selye and Swedish stress researchers. Stress was assumed to be a potential cause of ”nervous troubles” and disease, but was never considered to be a disease in itself. The concept of the individual as a citizen now gave way for the notion of the individual as a primarily biological organism. Within the stress discourse in the 1960s, the primacy of the universal normal (male) man was a recurring focal point. In the 1970s, the stress researchers distanced themselves from Selyes’ concept of stress by focusing on individual factors. In the discussion about stress during the 1970s, the ”constitutionally weak” individual of the 1950s and the biological organism of the 1960s blended into a hybrid construction of a unique, biological individual.
352

Visualisering av svarstider mellan mobila klienter och datacenter / Visualisation of Latencies Between Mobile Clients and Datacenters

Sidenvall, Adrian, Truong, Andy, Boman, Erik, Szreder, Mikael, Lind, Oskar, Eriksson, Simon, Petersson, Simon January 2015 (has links)
Rapporten är en sammanställning av gruppens samlade erfarenheter och lärdomar av ett projekt vars syfte var att utveckla ett verktyg som ska visualisera svarstider mellan mobila klienter och datacenter. Genom att använda kontinuerlig prototypning har gruppen kunnat arbeta på ett användarna sätt för att uppfylla kundens verkliga behov. För att uppnå detta användes utvecklingsmetodiken Kanban. Under projektets gång anpassades metodiken för att bättra passa in i arbetet. Projektets användartester har lett till sammanfattande erfarenheter om visualisering av data. Visualiseringar som projektgruppen ansetts tydliga uppfattades inte alltid på samma sätt av användarna. Att visualisera flera parametrar på en världskarta anses vara problematiskt då kartan i sig endast består av länder. För visualisering av flera parametrar måste då även externa användas, exempelvis cirklar eller andra former.
353

Μελέτη συστήματος παροχής ηλεκτρικών τάσεων σε εργαστηριακό χώρο : παρεμβάσεις σε σύστημα ελέγχου PLC μέσω του προγράμματος SCADA / Study of a laboratory voltage supply system and construction with a PLC via SCADA application

Παπαδόπουλος, Βασίλειος 28 August 2009 (has links)
Το έτος 1987 στο Τμήμα Ηλεκτρολόγων Μηχανικών και Τεχνολογίας Υπολογιστών του Πανεπιστήμιου Πατρών και συγκεκριμένα στο Εργαστήριο Ηλεκτρομηχανικής Μετατροπής Ενέργειας του Τμήματος Ηλεκτρολόγων Μηχανικών, στα πλαίσια εκπαιδευτικών και ερευνητικών σκοπών, εγκαταστάθηκε ένα πλήρες αυτοματοποιημένο σύστημα παράγωγης και παροχής ηλεκτρικών τάσεων. Σκοπός του συστήματος ήταν η παροχή 10 διαφορετικών τύπων τάσεων σε 15 συγκεκριμένες θέσεις εργασίας στο χώρου του Εργαστηρίου. Το σύστημα ήταν πλήρως αυτοματοποιημένο, καθώς χρησιμοποιήθηκε προγραμματιζόμενος λογικός ελεγκτής (PLC) που ήταν επιφορτισμένος με τον έλεγχο, την εποπτεία και τη διαχείριση του Συστήματος. Επίσης υπήρχε προσωπικός Η/Υ άμεσα συνδεδεμένος στο σύστημα, μέσω του όποιου ο διαχειριστής του μπορούσε να παρακολουθεί, να διαχειρίζεται και να διανέμει τον κάθε τύπο από τις προσφερόμενες παροχές. Το σύστημα με την πάροδο του χρόνου εμφάνισε βασικά λειτουργικά προβλήματα, με αποτέλεσμα να μειωθεί δραστικά ο αριθμός των παρεχόμενων τύπων τάσεων, αλλά και η ικανότητα διαχείρισης και διανομής αυτών που παρέχονταν. Πιο συγκεκριμένα, το τμήμα τoυ προγραμματιζόμενoυ λογικού ελεγκτή (PLC) και του συνδεδεμένου Η/Υ του συστήματος ουσιαστικά και πρακτικά είχε τεθεί πλέον πλήρως εκτός λειτουργίας. Στόχος και σκοπός της παρούσας εργασίας ήταν η λύση των προβλημάτων του προαναφερθέντος συστήματος με τελικό αποτέλεσμα την κανονική και ομαλή λειτουργία του. Η λύση που προτείνεται είναι η υλοποίηση και η ενσωμάτωση ενός σύγχρονου δικτύου αυτοματισμού με τη χρήση σύγχρονων PLC (επιλέχθηκε η εταιρεία OMRON) καθώς και η ενσωμάτωση ενός συστήματος εποπτικού και διαχειριστικού ελέγχου, λογισμικό τύπου SCADΑ της ίδιας εταιρείας. Αναλύονται διεξοδικά τόσο ο τρόπος παραγωγής των τάσεων με τα αντίστοιχα κυκλώματα ισχύος όσο και ο τρόπος διανομής και διαχείρισης αυτών με τα αντίστοιχα κυκλώματα αυτοματισμού. Εμπεριέχονται εκτενείς αναφορές στα σύγχρονα PLC, στον τρόπο λειτουργίας και προγραμματισμού τους καθώς και ο τρόπος με τον οποίο είναι δυνατό να ενσωματωθούν και να λειτουργήσουν πλήρως στο υπάρχον σύστημα. Γίνεται μια εισαγωγή στα σύγχρονα συστήματα διαχείρισης και εποπτικού ελέγχου (SCADA) ώστε να μπορεί ο κάθε αναγνώστης, χωρίς να χρειάζονται υψηλού επιπέδου γνώσεις, να κατανοήσει τη χρησιμότητα και τη λειτουργία τους και μελετείται ο τρόπος με τον οποίο θα υλοποιηθεί το παραπάνω δίκτυο αυτοματισμού με τη χρήση των PLC και με την παρουσία του εποπτικού συστήματος SCADA. Γίνεται πλήρης αναφορά σε έναν πολύ βασικό τομέα του Ηλεκτρολόγου Μηχανικού στη σύγχρονη εποχή: τον υπολογισμό κόστους προμήθειας, εγκατάστασης και κατασκευής όλων των στοιχείων του εγχειρήματος και μελετούνται όλες οι παράλληλες επιλογές για την καλύτερη δυνατή λειτουργία του και την περαιτέρω ανάπτυξη και βελτίωση του. / The year 1987 in the Department of Electrical and Computer Engineering University of Patras and specifically in Electromechanical Energy Conversion Laboratory Department of Electrical Engineering, in educational and research purposes, installed a complete automated system for producing and providing electrical voltages. This system was able to provide 10 different types of voltages in 15 stations in the area of Laboratory. The system was fully automated, used a Programmable Logic Controller (PLC), which was responsible for monitoring, supervision and management system. Also there was a PC directly connected to the system, through which the administrator can monitor, manage and distribute each type of voltage. The system through the walking time showed major operational problems. As a result, the number of the types of voltages and the ability to manage and distribute those provided reduced drastically. Specifically, the part of programmable logic controller (PLC) and the connected computer system effectively and practically has run out of order. The purpose of this work was the solution of problems of the system and ultimately with final result the normal and smooth operation. The solution proposed is the implementation and integration of a modern network automation using modern PLC (the company chosen is OMRON) and the incorporation of a supervisory control and data acquisition application and (SCADA) software of the same company. Analyzed in detail both the production voltages with the respective power circuits and the method of distribution and management of the automation circuits. Contained extensive references to contemporary PLC, in operations and programming, and how it is possible to integrate and operate fully in the existing system. There is an introduction to SCADA to enable each reader without the need for high-level knowledge to understand the utility and operation, and considering how we implement the above automation network using a PLC and SCADA application. We mention a very important area of Electrical Engineering in the modern era: counting the cost of supply, installation and construction of all elements of the project and consider all parallel options for optimal operation and further development and improvement.
354

Untersuchungen und Kalkulationstabellen zur Schätzung der N2-Fixierleistung und der N-Flächenbilanz beim Anbau von Lupinus albus und Lupinus luteus in Reinsaat und von Vicia faba und Pisum sativum in Reinsaat und im Gemenge mit Avena sativa / Estimation of the nitrogen fixation and the N balance in cultivations of Lupinus albus and Lupinus luteus as sole crops and of Vicia faba and Pisum sativum as sole crops and in mixed stands with Avena sativa - resarches and calculation charts -

Jost, Britta 11 July 2003 (has links)
No description available.
355

Un langage contrôlé pour les instructions nautiques du Service Hydographique et Océanographique de la Marine / A controlled language for the french national Hydrographic and Oceanographic Service Coast Pilot Books instructions nautiques

Sauvage-Vincent, Julie 16 January 2017 (has links)
Les langages contrôlés sont des langages artificiellement définis utilisant un sous-ensemble du vocabulaire, des formes morphologiques, des constructions syntaxiques d'une langue naturelle tout en en éliminant la polysémie. En quelque sorte, ils constituent le pont entre les langages formels et les langues naturelles. De ce fait, ils remplissent la fonction de communication du médium texte tout en étant rigoureux et analysables par la machine sans ambiguïté. En particulier, ils peuvent être utilisés pour faciliter l'alimentation de bases de connaissances, dans le cadre d'une interface homme-machine.Le Service Hydrographique et Océanographique de la Marine (SHOM) publie depuis 1971 les Instructions nautiques, des recueils de renseignements généraux, nautiques et réglementaires, destinés aux navigateurs. Ces ouvrages complètent les cartes marines. Elles sont obligatoires à bord des navires de commerce et de pêche. D'autre part, l'Organisation Hydrographique Internationale (OHI) a publié des normes spécifiant l'échange de données liées à la navigation et notamment un modèle universel de données hydrographiques (norme S-100, janvier 2010). Cette thèse se propose d'étudier l'utilisation d'un langage contrôlé pour représenter des connaissances contenues dans les Instructions nautiques, dans le but de servir de pivot entre la rédaction du texte par l'opérateur dédié, la production de l'ouvrage imprimé ou en ligne, et l'interaction avec des bases de connaissances et des outils d'aide à la navigation. En particulier on étudiera l'interaction entre le langage contrôlé des Instructions nautiques et les cartes électroniques correspondantes. Plus généralement, cette thèse se pose la question de l'évolution d'un langage contrôlé et des ontologies sous-jacentes dans le cadre d'une application comme les Instructions nautiques, qui ont la particularité d'avoir des aspects rigides (données numériques, cartes électroniques, législation) et des aspects nécessitant une certaine flexibilité (rédaction du texte par des opérateurs humains, imprévisibilité du type de connaissance à inclure par l'évolution des usages et des besoins des navigants). De manière similaire aux ontologies dynamiques que l'on rencontre dans certains domaines de connaissance, on définit ici un langage contrôlé dynamique. Le langage contrôlé décrit dans cette thèse constitue une contribution intéressante pour la communauté concernée puisqu'il touche au domaine maritime, domaine encore inexploité dans l'étude des langages contrôlés, mais aussi parce qu'il présente un aspect hybride, prenant en compte les multiples modes (textuel et visuel) présents dans le corpus constitué par les Instructions nautiques et les documents qu'elles accompagnent. Bien que créé pour le domaine de la navigation maritime, les mécanismes du langage contrôlé présentés dans cette thèse ont le potentiel pour être adaptés à d'autres domaines utilisant des corpus multimodaux. Enfin, les perspectives d'évolution pour un langage contrôlé hybride sont importantes puisqu'elles peuvent exploiter les différents avantages des modes en présence (par exemple, une exploitation de l'aspect visuel pour une extension 3D). / Controlled Natural Languages (CNL) are artificial languages that use a subset of the vocabulary, morphological forms and syntactical constructions of a natural language while eliminating its polysemy. In a way, they constitute the bridge between formal languages and natural languages. Therefore, they perform the communicative function of the textual mode while being precise and computable by the machine without any ambiguity. In particular, they can be used to facilitate the population or update of knowledge bases within the framework of a human-machine interface.Since 1971, the French Marine Hydrographic and Oceanographic Service (SHOM) issues the French Coast Pilot Books Instructions nautiques , collections of general, nautical and statutory information, intended for use by sailors. These publications aim to supplement charts, in the sense that they provide the mariner with supplemental information not in the chart. They are mandatory for fishing and commercial ships. On the other hand, the International Hydrographic Organization (IHO) issued standards providing information about navigational data exchange. Among these standards, one of a particular interest is the universal model of hydrographic data (S-100 standard, January, 2010).This thesis analyses the use of a CNL to represent knowledge contained in the Instructions nautiques. This CNL purpose is to act as a pivot between the writing of the text by the dedicated operator, the production of the printed or online publication, and the interaction with knowledge bases and navigational aid tools. We will focus especially on the interaction between the Instructions nautiques Controlled Natural Language and the corresponding Electronic Navigational Charts (ENC).More generally, this thesis asks the question of the evolution of a CNL and the underlying ontologies involved in the Instructions nautiques project. Instructions nautiques have the particularity of combining both strictness (numerical data, electronic charts, legislation) and a certain amount of flexibility (text writing by human operators, unpredictability of the knowledge to be included due to the evolution of sailors¿ practices and needs). We define in this thesis a dynamic CNL in the same way that dynamic ontologies are defined in particular domains. The language described in this thesis is intended as an interesting contribution for the community involved in CNL. Indeed, it addresses the creation of a CNL for the unexploited domain of maritime navigation, but its hybrid aspects as well through the exploration of the multiple modalities (textual and visual) coexisting in a corpus comprising ENC and their companion texts. The mechanisms of the CNL presented in this thesis, although developed for the domain of the maritime navigation, have the potential to be adapted to other domains using multimodal corpuses. Finally, the benefits in the future of a controlled hybrid language are undeniable: the use of the different modalities in their full potential can be used in many different applications (for example, the exploitation of the visual modality for a 3D extension).
356

Difficulties in the comprehension and interpretation of a selection of graph types and subject-specific graphs displayed by senior undergraduate biochemistry students in a South African university

Van Tonder, André 11 1900 (has links)
A carefully constructed set of 16 graphical tasks related to key biochemistry concepts was designed and administered to a group of 82 students in their final year of B.Sc. study. The test mean score of 48,3% ( 12,1) was low and characterised by gender and ethnic differences. There was a moderate linear relationship between biochemistry grades obtained by the students over two years of study and their graphical literacy (r = 0,433). The majority of the students exhibited slope/height confusion and only seven students (8,5%) were able to answer the two items corresponding to Kimura‘s Level F, the most complex and difficult level of graphical literacy. Eye tracking data gave valuable insights into different strategies used by students while interpreting graphs and is a valuable tool for assessing graphical literacy. These findings confirmed other studies where researchers have found a widespread lack of graph comprehension among biological science students. / Institute of Science and Technology Education / M. Sc. (Science Education)
357

Provas sem palavras: uma ponte entre a intuição e a linguagem matemática / Proofs without words: a bridge between intuition and mathematical language

Ortega, Regina Cássia de Souza 18 April 2018 (has links)
O presente trabalho tem por objetivo divulgar e explorar as Provas sem Palavras no âmbito do Ensino Fundamental e Médio para, posteriormente, servir de possível material de consulta por parte de professores, na busca de melhores métodos de explicação sobre importantes assuntos desenvolvidos em sala. Dessa forma, imagina-se que a compreensão dos alunos através da visualização fortalecerá de maneira significativa a aquisição do conhecimento. Para tanto, são sugeridos diversos temas onde a visualização é desenvolvida e explicada, seja através de relato, seja através de demonstrações matemáticas. / The aim of the present work is to disseminate and explore the Proof Without Words in the scope of elementary and high school to be used later as a possible reference material for teachers in the search for better methods of explanation on important subjects developed in the classroom. In this way, it is imagined that students’ comprehension through visualization will significantly strengthen the acquisition of knowledge. In order to do so, several themes are suggested where the visualization is developed and explained, either through storytelling or through mathematical demonstrations.
358

Avaliação do padrão de crescimento na síndrome de Noonan em pacientes com mutações identificadas nos genes PTPN11, SOS1, RAF1 e KRAS / Growth pattern of patients with Noonan syndrome with identified mutations in PTPN11, SOS1, RAF1 e KRAS genes

Alexsandra Christianne Malaquias de Moura Ribeiro 30 May 2011 (has links)
A Síndrome de Noonan (SN) é caracterizada por baixa estatura proporcionada de início pós-natal, dismorfismos faciais, cardiopatia congênita e deformidade torácica. A frequência da SN é estimada entre 1:1000 e 1:2500 nascidos vivos, com distribuição semelhante em ambos os sexos. A herança é autossômica dominante com penetrância completa, porém a maioria dos casos é esporádica. Até o momento, mutações em genes da via RAS-MAPK (PTPN11, KRAS, SOS1, RAF1, MEK1, NRAS e SHOC2) foram identificadas em aproximadamente 70% dos pacientes. Uma das principais características fenotípicas da SN é a baixa estatura pós-natal, embora o mecanismo fisiopatológico do déficit de crescimento nesta síndrome ainda não esteja totalmente esclarecido. Estudos que avaliaram o padrão de crescimento linear em crianças com SN foram realizados anteriormente ao conhecimento do diagnóstico molecular dessa síndrome. No presente estudo, avaliamos a frequência de mutação nos genes PTPN11, SOS1, RAF1 e KRAS em 152 pacientes com SN e o padrão de crescimento linear (altura) e ponderal [índice de massa corpórea (IMC)] dos pacientes com mutação identificada. No total, mutações nos genes relacionados foram encontradas em 99 pacientes (65%) do nosso estudo, com predominância do gene PTPN11 (47%), seguido do SOS1 (9%), RAF1 (7%) e KRAS (3%). Foram construídas curvas específicas para SN de Altura e IMC para idade e sexo utilizando o método LMS. Os pacientes com SN apresentaram crescimento pré-natal preservado, porém o comprometimento do crescimento pós-natal foi observado desde o primeiro ano de vida, atingindo uma altura final de -2,5 e -2,2 desvios-padrão da média para população brasileira em homens e mulheres, respectivamente. O prejuízo da altura foi maior nos pacientes com mutação no gene RAF1 em comparação com os genes PTPN11 e SOS1. O IMC dos pacientes com SN apresentou queda de 1 desvio-padrão em relação à média da população brasileira normal. O comprometimento do IMC foi menor nos pacientes carreadores de mutação no RAF1. Pacientes com mutação nos genes PTPN11 e SOS1 apresentaram maior frequência de estenose de valva pulmonar, enquanto a miocardiopatia hipertrófica foi mais frequente nos pacientes com mutação no gene RAF1. A variabilidade fenotípica observada nos pacientes com mutação no PTPN11 não pode ser explicada pelo grau que estas mutações influenciam a atividade tirosina fosfatase da SHP-2 nem pela presença de polimorfismos no gene KRAS. Com a análise dos éxons 3, 8 e 13 do PTPN11, seguido dos éxons 6 e 10 do SOS1 e éxon 7 do RAF1 identificamos 86% dos pacientes carreadores de mutações nos genes relacionados, propondo uma forma mais eficiente de avaliação molecular na SN. Acreditamos que a variabilidade fenotípica presente nessa síndrome esteja diretamente ligada aos diferentes papéis exercidos pelas proteínas que participam da via RAS/MAPK. Entretanto, mais estudos em relação à via RAS/MAPK serão necessários para esclarecer as questões relacionadas ao crescimento e outras características fenotípicas da SN / Noonan Syndrome (NS) is characterized by distinctive facial features, short stature and congenital heart defects. The estimated prevalence is 1:1000 to 1:2500 live births, affecting equally both sexes. It is an autosomal dominant disorder with complete penetrance, but most cases are sporadic. To date, mutations in the RAS/MAPK pathway genes (PTPN11, KRAS, SOS1, RAF1, MEK1, NRAS and SHOC2) were identified in approximately 70% of patients. One of the cardinal signs of NS is proportional postnatal short stature although the physiopathological mechanism of growth impairment remains unclear. The current knowledge about the natural history of growth associated with NS was described before molecular diagnosis era. In this study, we performed PTPN11, SOS1, RAF1, and KRAS mutation analysis in a cohort of 152 NS patients and studied the natural linear (height) and ponderal growth [body mass index (BMI)] of NS patients with related mutations. Mutations in NS-causative genes were found in 99 patients (65%) of our cohort. The most common mutated gene was PTPN11 (47%), followed by SOS1 (9%), RAF1 (7%) and KRAS (3%). Sex-specific percentile curves for height and BMI were constructed using the LMS method. NS patients had birth weight and length within normal ranges but the postnatal growth impairment was observed during the first year of life, reaching a final height of -2.3 and -2.2 standard deviations from the mean for Brazilian healthy men and women, respectively. Postnatal growth impairment was higher in RAF1 mutation patients than in patients with SOS1 and PTPN11 mutations. BMI values in NS patients were lower in comparison with normal Brazilian population. BMI values were higher in patients with RAF1 mutations than in patients with other genotypes. Patients with mutations in PTPN11 and SOS1 genes were more likely to have pulmonary valve stenosis, whereas hypertrophic cardiomyopathy was more common in patients with mutations in the gene RAF1. The intensity of constitutive tyrosine phosphatase activity of SHP-2 due to PTPN11 mutations, as well as the presence of polymorphisms in KRAS gene did not influence the phenotype of NS patients with mutation in PTPN11 gene. Analysis of exons 3, 8 and 13 of PTPN11 gene, followed by exons 6 and 10 of SOS1 gene and exon 7of RAF1 gene identified 86% of patients harboring mutations in related genes, suggesting a more efficient evaluation of NS molecular diagnosis. We believe that the phenotypic variability in this syndrome is directly linked to the different roles played by proteins that participate in RAS/MAPK pathway. However, further studies in RAS/MAPK pathway are needed to clarify issues related to growth and other phenotypic characteristics of SN
359

Essays on multivariate generalized Birnbaum-Saunders methods

MARCHANT FUENTES, Carolina Ivonne 31 October 2016 (has links)
Submitted by Rafael Santana (rafael.silvasantana@ufpe.br) on 2017-04-26T17:07:37Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Carolina Marchant.pdf: 5792192 bytes, checksum: adbd82c79b286d2fe2470b7955e6a9ed (MD5) / Made available in DSpace on 2017-04-26T17:07:38Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Carolina Marchant.pdf: 5792192 bytes, checksum: adbd82c79b286d2fe2470b7955e6a9ed (MD5) Previous issue date: 2016-10-31 / CAPES; BOLSA DO CHILE. / In the last decades, univariate Birnbaum-Saunders models have received considerable attention in the literature. These models have been widely studied and applied to fatigue, but they have also been applied to other areas of the knowledge. In such areas, it is often necessary to model several variables simultaneously. If these variables are correlated, individual analyses for each variable can lead to erroneous results. Multivariate regression models are a useful tool of the multivariate analysis, which takes into account the correlation between variables. In addition, diagnostic analysis is an important aspect to be considered in the statistical modeling. Furthermore, multivariate quality control charts are powerful and simple visual tools to determine whether a multivariate process is in control or out of control. A multivariate control chart shows how several variables jointly affect a process. First, we propose, derive and characterize multivariate generalized logarithmic Birnbaum-Saunders distributions. Also, we propose new multivariate generalized Birnbaum-Saunders regression models. We use the method of maximum likelihood estimation to estimate their parameters through the expectation-maximization algorithm. We carry out a simulation study to evaluate the performance of the corresponding estimators based on the Monte Carlo method. We validate the proposed models with a regression analysis of real-world multivariate fatigue data. Second, we conduct a diagnostic analysis for multivariate generalized Birnbaum-Saunders regression models. We consider the Mahalanobis distance as a global influence measure to detect multivariate outliers and use it for evaluating the adequacy of the distributional assumption. Moreover, we consider the local influence method and study how a perturbation may impact on the estimation of model parameters. We implement the obtained results in the R software, which are illustrated with real-world multivariate biomaterials data. Third and finally, we develop a robust methodology based on multivariate quality control charts for generalized Birnbaum-Saunders distributions with the Hotelling statistic. We use the parametric bootstrap method to obtain the distribution of this statistic. A Monte Carlo simulation study is conducted to evaluate the proposed methodology, which reports its performance to provide earlier alerts of out-of-control conditions. An illustration with air quality real-world data of Santiago-Chile is provided. This illustration shows that the proposed methodology can be useful for alerting episodes of extreme air pollution. / Nas últimas décadas, o modelo Birnbaum-Saunders univariado recebeu considerável atenção na literatura. Esse modelo tem sido amplamente estudado e aplicado inicialmente à modelagem de fadiga de materiais. Com o passar dos anos surgiram trabalhos com aplicações em outras áreas do conhecimento. Em muitas das aplicações é necessário modelar diversas variáveis simultaneamente incorporando a correlação entre elas. Os modelos de regressão multivariados são uma ferramenta útil de análise multivariada, que leva em conta a correlação entre as variáveis de resposta. A análise de diagnóstico é um aspecto importante a ser considerado no modelo estatístico e verifica as suposições adotadas como também sua sensibilidade. Além disso, os gráficos de controle de qualidade multivariados são ferramentas visuais eficientes e simples para determinar se um processo multivariado está ou não fora de controle. Este gráfico mostra como diversas variáveis afetam conjuntamente um processo. Primeiro, propomos, derivamos e caracterizamos as distribuições Birnbaum-Saunders generalizadas logarítmicas multivariadas. Em seguida, propomos um modelo de regressão Birnbaum-Saunders generalizado multivariado. Métodos para estimação dos parâmetros do modelo, tal como o método de máxima verossimilhança baseado no algoritmo EM, foram desenvolvidos. Estudos de simulação de Monte Carlo foram realizados para avaliar o desempenho dos estimadores propostos. Segundo, realizamos uma análise de diagnóstico para modelos de regressão Birnbaum-Saunders generalizados multivariados. Consideramos a distância de Mahalanobis como medida de influência global de detecção de outliers multivariados utilizando-a para avaliar a adequacidade do modelo. Além disso, desenvolvemos medidas de diagnósticos baseadas em influência local sob alguns esquemas de perturbações. Implementamos a metodologia apresentada no software R, e ilustramos com dados reais multivariados de biomateriais. Terceiro, e finalmente, desenvolvemos uma metodologia robusta baseada em gráficos de controle de qualidade multivariados para a distribuição Birnbaum-Saunders generalizada usando a estatística de Hotelling. Baseado no método bootstrap paramétrico encontramos aproximações da distribuição desta estatística e obtivemos limites de controle para o gráfico proposto. Realizamos um estudo de simulação de Monte Carlo para avaliar a metodologia proposta indicando seu bom desempenho para fornecer alertas precoces de processos fora de controle. Uma ilustração com dados reais de qualidade do ar de Santiago-Chile é fornecida. Essa ilustração mostra que a metodologia proposta pode ser útil para alertar sobre episódios de poluição extrema do ar, evitando efeitos adversos na saúde humana.
360

Damage localization in civil engineering structures using dynamic strain measurements / Localisation de défauts dans les structures de génie civil à partir de mesures dynamiques de déformations

Tondreau, Gilles 26 April 2013 (has links)
This thesis focuses on the development of a new method for the continuous<p>monitoring of civil engineering structures in order to locate small damages automatically. A<p>review of the very wide literature on Structural Health Monitoring (SHM) points first out that<p>the methods can be grouped in four categories based on their need or not of a numerical model,<p>as well as their need or not of information of the damaged structure to be applied. This state<p>of the art of the SHM methods highlights the requirement to reach each levels of SHM, which<p>is in particular for the localization of small damages in civil engineering structures the needs<p>for a non-model based output-only damage sensitive feature extraction technique. The origin of<p>the local sensitivity of strains to damages is also analyzed, which justifies their use for damage<p>localization.<p>A new method based on the modal filtering technique which consists in combining linearly<p>the sensor responses in a specific way to mimic a single degree of freedom system and which<p>was previously developed for damage detection is proposed. A very large network of dynamic<p>strain sensors is deployed on the structure and split into several independent local sensor networks.<p>Low computational cost and fast signal processing techniques are coupled to statistical<p>control charts for robust and fully automated damage localization.<p>The efficiency of the method is demonstrated using time-domain simulated data on a simply<p>supported beam and a three-dimensional bridge structure. The method is able to detect and<p>locate very small damages even in the presence of noise on the measurements and variability<p>of the baseline structure if strain sensors are used. The difficulty to locate damages from acceleration<p>sensors is also clearly illustrated. The most common classical methods for damage<p>localization are applied on the simply supported beam and the results show that the modal filtering<p>technique presents much better performances for an accurate localization of small damages<p>and is easier to automate.<p>An improvement of the modal filters method referred to as adaptive modal filters is next<p>proposed in order to enhance the ability to localize small damages, as well as to follow their<p>evolution through modal filters updating. Based on this study, a new damage sensitive feature<p>is proposed and is compared with other damage sensitive features to detect the damages with<p>modal filters to demonstrate its interest. These expectations are verified numerically with the<p>three-dimensional bridge structure, and the results show that the adaptation of the modal filters<p>increases the sensitivity of local filters to damages.<p>Experimental tests have been led first to check the feasibility of modal filters to detect damages<p>when they are used with accelerometers. Two case studies are considered. The first work<p>investigates the experimental damage detection of a small aircraft wing equipped with a network<p>of 15 accelerometers, one force transducer and excited with an electro-dynamic shaker. A<p>damage is introduced by replacing inspection panels with damaged panels. A modified version<p>of the modal filtering technique is applied and compared with the damage detection based principal<p>component analysis of FRFs as well as of transmissibilities. The three approaches succeed<p>in the damage detection but we illustrate the advantage of using the modal filtering algorithm as<p>well as of the new damage sensitive feature. The second experimental application aims at detecting<p>both linear and nonlinear damage scenarios using the responses of four accelerometers<p>installed on the three-storey frame structure previously developed and studied at Los Alamos<p>National Labs. In particular, modal filters are shown to be sensitive to both types of damages,<p>but cannot make the distinction between linear and nonlinear damages.<p>Finally, the new method is tested experimentally to locate damages by considering cheap<p>piezoelectric patches (PVDF) for dynamic strain measurements. Again, two case studies are investigated.<p>The first work investigates a small clamped-free steel plate equipped with 8 PVDFs sensors, and excited with a PZT patch. A small damage is introduced at different locations by<p>fixing a stiffener. The modal filters are applied on three local filters in order to locate damage.<p>Univariate control charts allow to locate automatically all the damage positions correctly.<p>The last experimental investigation is devoted to a 3.78m long I-steel beam equipped with 20<p>PVDFs sensors and excited with an electro-dynamic shaker. Again, a small stiffener is added to<p>mimic the effect of a small damage and five local filters are defined to locate the damage. The<p>damage is correctly located for several positions, and the interest of including measurements<p>under different environmental conditions for the baseline as well as overlapping the local filters<p>is illustrated.<p>The very nice results obtained with these first experimental applications of modal filters<p>based on strains show the real interest of this very low computational cost method for outputonly<p>non-model based automated damage localization of real structures. / Doctorat en Sciences de l'ingénieur / info:eu-repo/semantics/nonPublished

Page generated in 0.092 seconds