The "achievement gap" is a common term in Texas public education, often referring to academic differences in achievement among student ethnic groups within the core curriculum. Seldom is Foreign Language referenced in, nor even considered relevant to such discussions in addressing the achievement gaps that exist in our public schools, although Foreign Language holds significant influence on both students' high school and post-secondary academic trajectories. Throughout the state of Texas, it has been found that African American students are not progressing in foreign language study at the same rate and length as Hispanic, White, and Asian students; these stark achievement gaps appear to be going unmentioned, unnoticed, and/or unaddressed. This interpretive case study examined the perceptions of foreign language teachers, counselors, and administrators at a central Texas high school campus through a critical lens, regarding why they felt African American students are not progressing in foreign language courses, as compared to other student ethnic groups. Data collection for this qualitative study included individual interviews, focus group sessions, field notes, documents, and school records. For data analysis, the study employed the constant comparative method. Four general themes emerged from interviews and focus group sessions with stakeholders. These themes included deficit views, racial erasure, paralogical beliefs and behaviors, and organizational constraints, which described obstacles standing in the way of creating an equitable campus for all students. This study offers implications for educational policy, practice, and future research. For policy, Texas high school graduation requirements for foreign language should be increased and accountability measures for student learning in foreign languages should be instated. For practice, the high school should commit itself to ongoing, yearlong staff development to address equity traps at the campus. Practice should also include student performance data in foreign languages to help guide discussions about achievement gaps with African Americans and other student ethnic groups. Implications for future research include the need to examine the transferability of this study's findings to public middle school and high school campuses in Texas. Future studies should also investigate the equity trap avoidance and employment of the gaze in the context of public high school foreign language courses.

The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on September 24, 2009). Thesis advisor: Dr. Scott Kovaleski. Includes bibliographical references.

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Τα μονωτικά υλικά αποτελούν συνήθη πρακτική στο σχεδιασμό μονωτικών διατάξεων για εξοπλισμό Υψηλής Τάσης. Χαρακτηριστική περίπτωση αποτελεί η μόνωση των τυλιγμάτων Μετασχηματιστών Υψηλής Τάσης, όπου γίνεται συνδυαστική χρήση ενός κύριου μονωτικού μέσου (υγρής φύσης μονωτικό έλαιο) και δευτερευόντων (συνθετικά λεπτά φύλλα στερεής φύσεως που καλύπτουν τα τυλίγματα). Σε τέτοιου τύπου περιπτώσεις, όπου το ένα μονωτικό μέσο κυριαρχεί, οι διεπιφάνειες παίζουν καθοριστικό ρόλο, καθώς λόγω της εκεί συσσώρευσης φορέων φορτίου και άλλων ανομοιογενειών αλλάζει τη διηλεκτρική συμπεριφορά της συνδυαστική μόνωσης, με τρόπο όχι ως σήμερα εξακριβωμένο. Στόχος της παρούσας διπλωματικής είναι η διερεύνηση των επιδράσεων της εισαγωγής συνθετικού μονωτικού διαφράγματος εντός διακένου που μονώνεται από ειδικό λάδι και καταπονείται υπό γραμμικά αυξανόμενη AC τάση. Για τον λόγο αυτό χρησιμοποιήθηκε η συσκευή BAUR Oil Tester DTA 822-129-1, κομμάτι του ηλεκτρομηχανολογικού εξοπλισμού του εργαστηρίου Υψηλών Τάσεων. Επίσης η παραγωγή γραμμικά αυξανόμενης (με σταθερό ρυθμό 2 kVrms/s) AC τάσης, καθώς και η μέτρηση της τάσης διάσπασης έγιναν από τη συσκευή αυτή. Η ίδια πειραματική διαδικασία ακολουθήθηκε για συνδυασμούς ενός λαδιού ανοιχτού χρώματος με 2 διαφράγματα ιδίου τύπου από 3 διαφορετικούς τύπους (κατά δομή ή κατά πάχος ή και τα δύο) διαφραγμάτων – ήτοι συνθετικό χαρτί NOMEX 0.15mm & 0.25mm , και HYPERTHERM 0.37mm ενώ ΝΟΜΕΧ 0.15 mm δοκιμάστηκε σε συνδυασμό με ένα δεύτερο λάδι σκούρου χρώματος. Για λόγους δυνατότητας σύγκρισης δοκιμάστηκε το λάδι σκούρου χρώματος μόνο του (χωρίς διαφράγματα) και με ένα διάφραγμα. Τα αποτελέσματα και η διαγραμματική τους απεικόνιση με τις απαραίτητες παρατηρήσεις, δίνονται στην παρούσα εργασία και βασιζόμενοι σε αυτά δώσαμε και ανάλογα συμπεράσματα. Έτσι προέκυψε πως η συνδυαστική χρήση μονωτικού ελαίου και συνθετικών διαφραγμάτων μπορεί να επηρεάσει περισσότερων του ενός διηλεκτρικών μεγεθών. Η διηλεκτρική αντοχή, προσδιοριζόμενη από τη μέση τιμή της τάσης διάσπασης των δοκιμίων, παρουσιάζει σημαντικές μεταβολές. Τα διαφράγματα από χαρτί NOMEΧ παρουσιάζουν μια σχετικά σταθερή συμπεριφορά ενώ το HYPERTHERM επιδεικνύει πτωτική τάση της διηλεκτρικής του αντοχής. Το σκέτο λάδι εμφανίζει μέση τιμή διηλεκτρικής αντοχής χαμηλότερη και πιο σταθερή. Λιγότερο αναμενόμενη, ήταν η προκύπτουσα μείωση του σχετικού σφάλματος της συνδυαστικής μονωτικής διάταξης, μέγεθος που χαρακτηρίζει το στοχαστικό χαρακτήρα του συστήματος. Καλύτερα συνεργαζόμενα με το μονωτικό λάδι απεδείχθησαν τα διαφράγματα χαρτιού NOMEX 0.15 / Insulating materials are common in the design provisions for insulating high-voltage equipment. An example is the insulation of windings Transformer High Voltage, which is combined using a principal material of isolation (insulating oil liquid nature) and secondary (synthetic foil solid nature covering the windings). In this case where a material of isolation dominates, the surfaces has a special role, there due to accumulation of electrical load and other entities heterogeneity changes the dielectric behavior of the combination of insulation, so far as not verified. The objective of this diplomatic mission is to investigate the effects of the introduction of synthetic aperture in the insulating gap of special insulated from oil-stressed and under linearly increasing AC voltage. For this reason, we used the device BAUR Oil Tester DTA 822-129-1, part of the electromechanical equipment of the High Voltage Laboratory. Also, the production increased linearly (with constant rate of 2 kVrms / s) AC voltage and measuring the voltage division performed by the device. The same experimental procedure was followed for a combination of oil (type light color) with 2 paper with same type of 3 different types (in structure or thickness or both) bulkhead – i.e. synthetic paper NOMEX 0.15mm & 0.20mm, and HYPERTHERM 0.37mm -. The same bellows tested in combination with half oil dark color. For reasons of comparability tested oil dark color only (without paper) and with only one paper . The results and their diagrammatic representation with the necessary comments are given in this work and based on them and we have similar conclusion. This showed that the combined use of insulating oil and synthetic aperture can affect more than one dielectric sizes. The dielectric strength, determined by the mean breakdown voltage of essays, introduced important changes..ΝΟΜΕΧ shows less stability than HYPERTHERM and give more stable and lower dielectric strength. Less expected, but perhaps more important, was the resulting reduction of the error of combined insulating device, size characterizing the stochastic nature of the system. Better partner with the insulating oil proved the paper thick NOMEX 0.15.

Τα νευρωνικά δίκτυα αποτελούν έναν σχετικά νέο επιστημονικό χώρο, καθώς η ανάπτυξή τους έχει λάβει χώρα κυρίως τις τελευταίες δεκαετίες. Τόσο τα επιτεύγματα που έχουν σημειωθεί με τη χρήση τους, όσο και η ολοένα αυξανόμενη ενασχόληση της επιστημονικής κοινότητας με αυτά, δικαιολογούν γιατί είναι ένας τομέας που παρουσιάζει ιδιαίτερο ενδιαφέρον. Ο όρος «Τεχνητό Νευρωνικό Δίκτυο» (ΤΝΔ) ή απλά Νευρωνικό Δίκτυο αναφέρεται σε ένα μαθηματικό μοντέλο που συνίσταται από απλά στοιχεία τα οποία λειτουργούν διατεταγμένα παράλληλα και καλούνται νευρώνες. Η σύλληψη αυτών των στοιχείων έχει εμπνευστεί από τα βιολογικά νευρικά συστήματα. Ωστόσο τα νευρωνικά δίκτυα έχουν πλέον αποκοπεί τελείως απ’την βιολογία και σήμερα χρησιμοποιούνται για την επίλυση κάθε είδους προβλήματος με ηλεκτρονικό υπολογιστή. Στόχος της παρούσας εργασίας ήταν η χρήση νευρωνικών δικτύων για την εκτίμηση της τάσης διάσπασης σε μονωτικά διάκενα αέρα. Με τον όρο «μόνωση» εννοούμε τα μέτρα που λαμβάνονται για να προσδώσουν σε μία διάταξη ή συσκευή την ικανότητα να αντέχει ορισμένες διηλεκτρικές καταπονήσεις. Αυτές προέρχονται είτε από τις τάσεις που αναπτύσσονται κατά την λειτουργία της ανάμεσα στα διάφορα στοιχεία της, είτε ανάμεσα σε στοιχεία της και στοιχεία κάποιας άλλης συσκευής ή την γή. Διηλεκτρική αντοχή μιας μόνωσης καλείται η ικανότητά της να αντέχει μια ορισμένη ηλεκτρική καταπόνηση χωρίς την μόνιμη ή πρόσκαιρη καταστροφή της. Ο αέρας αποτελεί επανορθούμενο υλικό, που σημαίνει ότι μετά από μία διάσπαση ανακτά όλα τα χαρακτηριστικά που είχε πρίν απ’αυτή. Η μόνωση αέρα είναι κατ’εξοχήν εξωτερική μόνωση και συναντάται σε διάφορες διατάξεις υψηλών τάσεων, όπως π.χ. η μόνωση του ζυγού και η μόνωση κατά μήκος της επιφάνειας του μονωτήρα. Η διηλεκτρική διάσπαση ενός διακένου αέρα καθορίζεται από ένα σύνολο παραμέτρων, πιο σημαντικές από τις οποίες θεωρούνται το μήκος και η γεωμετρία του διακένου, η πολικότητα, το εύρος και η μορφή της κρουστικής καταπόνησης, καθώς και η θερμοκρασία, η πυκνότητα και η υγρασία του αέρα. Επομένως το ζητούμενο ήταν να υλοποιηθεί ένα νευρωνικό δίκτυο το οποίο να μπορεί να μάθει την συσχέτιση μεταξύ της τάσης διάσπασης και των παραμέτρων που την καθορίζουν. Η αρχιτεκτονική δικτύου που υιοθετήθηκε είναι ένα νευρωνικό δίκτυο δύο στρωμάτων εμπρόσθιας τροφοδότησης που εκπαιδεύεται με την μέθοδο της οπισθοδιάδοσης του λάθους. Ως σιγμοειδής συνάρτηση μεταφοράς στο κρυμμένο στρώμα χρησιμοποιήθηκε η υπερβολική εφαπτομένη f(x)=tanhx, ενώ ως γραμμική συνάρτηση μεταφοράς στο στρώμα εξόδου χρησιμοποιήθηκε η ταυτοτική συνάρτηση f(x)=x. Η τοπολογία αυτή είναι η πιο διαδεδομένη για τέτοιου είδους εφαρμογές. Η συλλογή των δεδομένων που καθόρισαν το πρόβλημα, δηλαδή τα διανύσματα εισόδου και εξόδου, έγινε από ένα σύνολο πειραματικών μετρήσεων που πραγματοποιήθηκαν στο εργαστήριο, για διάκενα διάταξης Ακίδα-Πλάκα και Ράβδος-Πλάκα. Σε προγραμματιστικό περιβάλλον Matlab (έκδοση R2008b), και συγκεκριμένα με χρήση του Neural Network Toolbox™ 6, αρχικά δημιουργήθηκε ένα νευρωνικό δίκτυο το οποίο δεν λάβαινε υπόψη του τις παραμέτρους που αφορούν στην γεωμετρία του διακένου. Το διάνυσμα εισόδου αποτελούνταν από 6 στοιχεία, τα οποία ήταν το μήκος του διακένου, η διάρκεια μετώπου και η διάρκεια ουράς της κρουστικής καταπόνησης, η θερμοκρασία, η ατμοσφαιρική πίεση και η υγρασία του αέρα. Το διάνυσμα της επιθυμητής εξόδου (ή αλλιώς στόχος) αποτελούνταν από μία τιμή για την τάση διάσπασης. Η εκπαίδευση του δικτύου πραγματοποιήθηκε με την χρήση του αλγόριθμου Levenberg-Marquardt. Για την διάταξη Ακίδα-Πλάκα χρησιμοποιήθηκε ένα σύνολο 70 μετρήσεων, ενώ για την διάταξη Ράβδος-Πλάκα ένα σύνολο 66 μετρήσεων. Έπειτα δόθηκε ως είσοδος στο εκπαιδευμένο δίκτυο η μήτρα εισόδου του προτύπου εκπαίδευσης. Οι ιδανικές αποκρίσεις σε αυτές τις εισόδους ήταν οι στόχοι, οπότε οι αποκρίσεις του δικτύου συγκρίθικαν με τους αντίστοιχους προς αυτές στόχους, δηλαδή τις πειραματικές τιμές για την τάση διάσπασης. Επιπλέον με χρήση του Microsoft Excel τοποθετήθηκαν σε διαγράμματα οι τιμές των στόχων και των αποκρίσεων του δικτύου συναρτήσει του μήκους διακένου ανάλογα με την μορφή της κρουστικής καταπόνησης. Η ίδια διαδικασία επαναλήφθηκε και για ένα νευρωνικό δίκτυο που λαμβάνει υπόψη του την γεωμετρία του διακένου. Για την διάταξη Ακίδα-Πλάκα στις προαναφερθείσες παραμέτρους του διανύσματος εισόδου προστέθηκαν η διάμετρος της ράβδου, το εμβαδόν της πλάκας, η ακτίνα καμπυλότητας και η γωνία του κώνου απόληξης. Αυτή τη φορά δηλαδή το διάνυσμα εισόδου αποτελούνταν από 10 στοιχεία. Για την διάταξη Ράβδος-Πλάκα το διάνυσμα εισόδου αποτελούνταν από 9 στοιχεία, αφού η ακτίνα καμπυλότητας και η γωνία του κώνου απόληξης της προηγούμενης περίπτωσης αντικαθίστανται από την ακτίνα της ημισφαιρικής απόληξης. Και για τις δύο διατάξεις το διάνυσμα στόχων αποτελούνταν από ένα στοιχείο, την τάση διάσπασης. Τα αποτελέσματα κρίνονται ικανοποιητικά, καθώς οι αποκλίσεις των αποκρίσεων του δικτύου από τις πειραματικές τιμές της τάσης διάσπασης κυμαίνονται σε αποδεκτά επίπεδα. Επομένως αποδείχθηκε ότι το εκπαιδευμένο νευρωνικό δίκτυο μπορεί να πραγματοποιήσει αξιόπιστες εκτιμήσεις για την τιμή της τάσης διάσπασης ενός μονωτικού διακένου αέρα. Ωστόσο το διάνυσμα εισόδου που δέχεται το δίκτυο θα πρέπει να χαρακτηρίζεται από τις ίδιες παραμέτρους όπως και το διάνυσμα εισόδου του προτύπου εκπαίδευσης. / Neural networks are a relatively recent scientific field, since they have mainly been developed during the last decades. There is a large interest in them, as shown by the achievements produced by their use and the rapidly growing involvement of variable scientific fields with them. The term “Artificial Neural Network” or simply “Neural Network” refers to a mathematical model being composed of simple elements which are called neurons and operate in parallel. These elements are inspired by biological nervous systems. However, Neural Networks are no longer related to biology and are nowadays being used for solving problems of any kind with the use of a computer. This paper aimed to apply Neural Networks in a way suitable for the evaluation of the breakdown voltage in insulating air gaps. Here the term “insulation” refers to any installation used to set a device capable of taking a certain amount of dielectric stress. This stress to which the device is subjected may derive from a voltage developed between the operating device’s parts, or between its parts and some other device’s parts or the ground. The dielectric endurance of an insulation expresses its ability to take a dielectric stress without being either permanently or temporarily damaged. The air is a retrievable insulating material, which means that after it has been discharged, all its characteristics are regained. The air is being widely used in external insulation installations in many High Voltage devices or parts, such as a bus insulation in a substation or the insulation along an insulator’s surface. The electric discharge of an air gap is determined by a set of parameters, the most important of them being the gap’s length and overall geometry, the polarity, width and form of the imposed impulse voltage, and the air’s temperature, pressure and humidity. The purpose of this essay was the creation of a Neural Network, which would be able to learn the correlation between the breakdown voltage of an air gap (Target) and the parameters that define its value (Inputs). The network architecture used was a two-layer feedforward backpropagation network, with the hyperbolic tangent sigmoid transfer function f(x)=tanhx in the hidden layer and the linear transfer function f(x)=x in the output layer. This network architecture is considered the most appropriate one for such applications, that is function approximation. The data that defined the problem, that is the Input and Target vectors, were assembled from a set of measurements that were made during an experimental procedure carried out in the High-Voltage laboratory of the University of Patras. The type of the air gap that was used for the experiments was a rod-plane gap, with either a cone-terminated or a hemisphere-terminated rod. At first, using the Matlab (R2008b edition) Neural Network Toolbox™ 6, a neural network that didn’t take into account the parameters regarding the gap’s geometry was created. The Input vector consisted of 6 elements, them being the gap length, the wave-front and wave-tail duration of the imposed impulse voltage, and the air temperature, pressure and humidity. The Target vector consisted of one value for the breakdown voltage. The network’s training was performed by the the Levenberg-Marquardt algorithm. For the cone-terminated rod-plane gap a set of 70 measurements was used, while for the hemisphere-terminated gap a set of 66 measurements. Then the original Inputs matrix was applied to the trained network. The desired network response (called Outputs) to these inputs is the Targets matrix, so the Outputs were compared to their corresponding Targets (lab measured breakdown voltage values). After that, using the Microsoft Excel the Targets and Outputs values were placed at diagrams (Y-Axis),diversified according to the received voltage form and associated to the gap length values (X –Axis). The same procedure was later repeated for a neural network that takes into consideration the parameters describing the gap’s geometry. Regarding the cone-terminated rod-plane gap, apart from the previously mentioned input parameters, the Input vector would also comprise the rod’s diameter, the plane’s surface,and the cone’s angle and radius of curvature. So,this time the Input vector would consist of 10 elements. Regarding the hemisphere-terminated rod-plane gap the Input vector consisted of 9 elements, given that the cone’s angle and radius of curvature were replaced by the hemisphere’s radius. In both occasions the Targets vector comprised one element, that being the breakdown voltage. The results are viewed as satisfactory, given that the deviations between the networks’s responses (Outputs) and the measured values of the breakdown voltage (Targets) are considered acceptable. Therefore, it has been proved that a well trained neural network is able of reliably estimating the value of an air gap’s breakdown voltage. Nevertheless, the network’s Inputs vector must comprise the same parameters as the original Inputs vector used for the network’s training.

This dissertation explored the academic growth in mathematics of a longitudinal cohort of 21,567 Oregon students during middle school on a state accountability test. The student test scores were used to calculate estimates of school performance based on four different accountability models (percent proficient [PP], change in PP, multilevel growth, and growth mixture). On average, 72% of Oregon eighth graders were proficient in mathematics in 2012, 71% in the average school, and 6% more students in this cohort demonstrated mathematics proficiency compared to 2011. The two-level unconditional multilevel growth model estimated the average intercept (Grade 6) to be 228.4 (SE = 0.07) scale score points with an average middle school growth rate of 5.40 scale points per year (SE = 0.02) on the state mathematics test. Student demographic characteristics were a statistically significant improvement on the unconditional model. A major shortcoming of this research, however, was the inability to find successful model convergence for any three-level growth model or any growth mixture model. A latent class growth analysis was used to uncover groups of students who shared common growth trajectories. A five-latent class solution best represented the data with the lowest BIC and a significant LMR p. Two of the latent classes were students who had high achievement in Grade 6 and demonstrated high growth across middle school and a second group with low sixth grade achievement that had below average growth in middle school. Student-level demographic predictors had statistically significant relations with growth characteristics and latent class membership. In comparing school performance based on the four different models, it was found that, although statistically correlated, the models of school performance ranked schools differently. A school’s percentage of proficient students in Grade 8 correlated moderately (r = [.60, .70]) with growth over the middle school years as estimated by the growth and LCGA models. About 70% to 80% of schools ranked more than 10 percentiles differently for every pairwise comparison of models. These results, like previous research call into question whether currently used models of school performance produce consistent and valid descriptions of school performance using state test scores.

Made available in DSpace on 2014-07-22T13:14:40Z (GMT). No. of bitstreams: 2 Rosane Cunha.pdf: 171109 bytes, checksum: cd6e7cddffc026ac78da8244af09c743 (MD5) license.txt: 1914 bytes, checksum: 7d48279ffeed55da8dfe2f8e81f3b81f (MD5) Previous issue date: 2011 / Fundação Oswaldo Cruz. Instituto Fernandes Figueira. Departamento de Ensino. Programa de Pós-Graduação em Saúde da Criança e da Mulher. Rio de Janeiro, RJ, Brasil. / O presente estudo baseia-se em parte do acervo de duas pesquisas realizadas no âmbito da Pós-Graduação em Saúde da Criança e da Mulher do Instituto Fernandes Figueira da Fundação Oswaldo Cruz, ambas aprovadas pelo Comitê de Ética em Pesquisa desse mesmo Instituto e apoiadas pelo CNPq. Pauta-se numa abordagem de pesquisa qualitativa que – ao se utilizar do método de análise das narrativas – busca identificar uma possível relação entre os sentidos atribuídos à sexualidade masculina e ao autocuidado em saúde em narrativas de homens de intervalos geracionais diferentes. Mais especificamente, busca analisar cenários, personagens e enredos sexuais presentes nessas narrativas e como esses homens situam o autocuidado em saúde no contexto da sexualidade. Os marcos conceituais teóricos são geração, masculinidade e enredo sexual. Os sujeitos deste estudo são homens, não médicos, com nível superior de escolaridade ou universitários, residentes na cidade do Rio de Janeiro. Os resultados da pesquisa são apresentados em forma de artigo científico. Conclui-se que o enredo heterossexual atravessa gerações ao reconhecer nas narrativas dos homens jovens a permanência de alguns significados culturais. Entretanto, observam-se também desfechos de conjugalidade reforçando a concepção de amor romântico, a valorização de fidelidade, a integridade e a afetividade. Esta ambivalência mostra que na geração mais jovem existe uma tensão entre mudar e permanecer. Assim, permanências e rupturas de padrões estereotipados e alguns desejos de mudanças tendem a refletir na forma como o homem contemporâneo vive e cuida de si. / This study is based on two surveys conducted at the Graduate Health of Children and Women of Instituto Fernandes Figueira, Fundação Oswaldo Cruz, both approved by the Research Ethics Committee of that Institute and supported by CNPq. The present study uses a qualitative research approach in order to establish a possible relationship between the meaning of male sexuality and health self-care, taking into account the narrative of different generations. More specifically, it seeks to analyze the different scenarios, characters and sexual scripts of these narratives and how these individuals think about health self-care in the context of sexuality. The theoretical conceptual frameworks are generation, masculinity and sexual script. This study’s subjects were male individuals, not doctors, with higher education or university, born in the city of Rio de Janeiro. The results of this research are presented in scientific article form. It is concluded that the script heterosexual crosses generations when it recognizes, in the narratives of young men, the permanence of some cultural significance. However, there are also outcomes of conjugal conception reinforcing the romantic and love ideas, the appreciation of loyalty, integrity and affection. Among the young generations, this ambiguity reflects a tension between transformation and permanence. Thus, continuities and ruptures of some desires and stereotyped patterns tend to reveal changes in the current way men live and care for themselves.

Face aux enjeux énergétiques actuels, l’électronique de puissance est un domaine de recherche de premier plan. La relative fragilité des composants présents dans les chaînes de conversion implique néanmoins de devoir prendre en compte la gestion des défaillances dès la phase de conception. La défaillance d'un composant est une situation hautement critique tant sur le plan de la sécurité environnante que sur le plan de l'indisponibilité du système qui en découle. Cette problématique de sûreté de fonctionnement constitue la ligne directive de ce travail de thèse, visant à imaginer, et concevoir des solutions permettant de sécuriser ces structures en présence de défauts. Dans cette thèse, nous étudions de nouveaux composants magnétiques offrant un excellent compromis entre la densité de puissance traitée et rendement de conversion, mais très sensibles à toutes perturbations électriques. Une méthode de pré-dimensionnement des composants magnétiques a été développée et des solutions ont été apportés pour sécuriser et maintenir le fonctionnement de la chaîne de conversion suite à l’apparition de plusieurs défauts. / In the research field, power electronics is an important issue in the actual energy challenges. Nowadays, new converters, called « multilevel or multicell converters », are used in many applications requiring high-current with high-power density. This is due to their high frequency performances and good waveforms signals. The main advantages of such converters concern the high efficiency and good system integration. Most embedded systems are required to maintain operation even if failures or faults occur. New magnetic devices called InterCell Transformers (ICTs) in multicell converters help to improve the efficiency and compactness. Nevertheless, such magnetic components are inherently sensitive to any impecfection coming from the converter. The goal of this PhD thesis is to bring solutions to make ICTs more fault tolerant. Therefore, a pre-design methodology for a robust ICT is presented in order to maintain the operation after the occurrence of one or several faults. Several solutions are presented and detailled

Made available in DSpace on 2016-08-29T14:09:21Z (GMT). No. of bitstreams: 1 tese_200_.pdf: 1888450 bytes, checksum: d447a2cd6a04ee2d9c761c7305469a49 (MD5) Previous issue date: 2006-06-29 / Este relatório técnico, configurado no formato de uma dissertação, teve como foco a qualidade na prestação de serviços, tomando como inspiração o Modelo de Lacunas preconizado por Zeithalm, Parasuraman e Berry (1990). Trata-se de uma pesquisa quantitativa, complementada por uma abordagem qualitativa, cujo objetivo foi avaliar as percepções e atendimento das expectativas dos usuários dos serviços prestados pelo Núcleo de Ensino Aberto e a Distância (Ne@ad) da Universidade Federal do Espírito Santo, por meio dos Centros regionais de Ensino Aberto e a Distância (Cre@ad). A fundamentação teórica contemplou um breve entendimento sobre a evolução da prestação de serviços no contexto do mercado; o papel da tecnologia na relação de serviços; a compreensão da educação enquanto uma relação de serviço, mesmo que diferenciada; a educação à distância; a percepção e satisfação do usuário e o modelo de gaps ou lacunas proposto por Zeithalm, Parasuraman e Berry. Para a coleta de dados foi utilizado principalmente o questionário aplicado aos usuários e coordenadores dos 13 Cre@ads. A entrevista também foi utilizada para esses segmentos incluindo, neste caso, o diretor e funcionários do Ne@ad. No geral não foram observadas diferenças nas expectativas dos usuários. Em termos das variáveis específicas algumas apresentaram discrepâncias. Na análise final observou-se a presença das lacunas entre: as expectativas do usuário e a percepção da gerência; prestação do serviço e comunicações externas; e serviço esperado e serviço percebido. Porém, ao se fazer uma análise contextual das subjetividades dos atores envolvidos no processo, percebe-se que o discurso difere sobremaneira das opiniões manifestas no questionário. / This technical report, configured in dissertation format, had as focus the quality in the rendering of services, inspirited in the Gaps Model praised by Zeithalm, Parasuraman and Berry (1990). One is a quantitative research, complemented by a qualitative approach, whose objective was to evaluate the perceptions and fullfilment of the expectations of the users of the services delivered by the Núcleo de Ensino a Distância (Ne@ad) of the Universidade Federal do Espírito Santo, through the regional Centros regionais de Ensino Aberto e a Distância (Cre@ad). The theoretical approach contemplated a brief understanding of the evolution of the rendering of services in the context of the market; the role of technology in the relation of services; the understanding of the education as a service relation, even if differentiated; the distance learning; the perception and satisfaction of the user and the model of gaps considered by Zeithalm, Parasuraman and Berry. For the data collection was used essentially questionnaire applied to users and managers of all 13 Cre@ads. The interview was utilized too for these segments including, in this case, the director and employers of Ne@ad. In general no differences in the expectations of the users were observed. In terms of the specific variables some presented discrepancies. In the final analysis was observed a presence of the gaps between: the expectations of the user and the perception of the management; service delivery and communications with the consumers; and expected service and perceived service. However, making a contextual analysis of the subjectivities of the actors involved in the process, is perceived that the speech differs excessively from the opinions manifested in the questionnaire.

O objetivo deste estudo foi comparar, por meio de mensuração das fendas na interface dentina - restauração de resina composta com utilização de algumas variáveis: fotoativação com lâmpada halógena e com LED; utilização de resina microhíbrida com partículas nanométricas Filtek Z350 ou sem estas partículas Filtek Z250; variação do sistema adesivo (Adper Single Bond 2 ou Adper Scotchbond Multi Purpose); variação da temperatura da resina composta; uso de dessensibilizante dentinário ou não; remoção do colágeno da dentina ou não e variação da intensidade de luz na fotoativação. Foram utilizados 70 molares humanos recém-extraídos, com cavidades circulares na dentina superficial de cada face proximal, foram divididos em 10 amostras para cada variável citada acima. Os dentes foram devidamente restaurados, seguindo as instruções dos fabricantes, para todos os grupos e mantidos em estufa bacteriológica por um período de 7 dias, após este período, foram polidos e as réplicas de resina epoxídica foram confeccionadas a partir de uma moldagem com silicone por adição, as mesmas foram levadas ao MEV, para a análise. As fendas foram mensuradas com o auxílio do software UTHSCSA Image tool e os dados foram submetidos à análise estatística pelo teste t de Student para a obtenção dos resultados. Com base nos resultados obtidos pode-se concluir que: os menores valores de fendas marginais foram obtidos quando da utilização de luz halógena (t=3,246 e p= 0,02) e com variação da intensidade desta luz (t= - 8,808 e p= 0,00). Os menores valores relativos de fendas, mas sem diferença estatística significante, foram encontrados, também, quando a resina Filtek Z350 foi comparada com a resina Filtek Z250 (t=-0,426 e p= 0,672) e quando o adesivo Adper Scotchbond Multi Purpose foi comparado com o Sistema Adper Single Bond 2 (t= 0,883 e p= 0,382). Os maiores valores de fendas marginais foram obtidos com a resina Filtek Z350 préaquecida a 60oC (t= -3,961 e p=0,000); com o uso de dessensibilizante dentinário (t=-3,062 e p=0,004) e com a remoção do colágeno pelo hipoclorito de sódio (t= -8,808 e p= 0,000). / The objective of this study was to compare through the cracks measurements in the dentin resin interface, using some variables: light activation with halogenic lamp and with LED; the use of micro-hybrid resin with or without nanofiller (Filtek Z350 anda Filtek Z250); variation of the adhesive systems (Adper Single Bond 2 or Scotchbond Multi Purpose); variation of the temperature in the compound resin; to use or not use the dentin desensitizing; to remove or not the dentin collagen and the light intensity variation in the light-curing. It was used 70 human extracted molars, with circular cavities in the superficial dentin of each proximal face; they were divided in 10 samples to each supra cited variable. The teeth were restored, followint the manufacturer instructions, and they were kept in a bacteriologtical kiln during a seven days period. After this time, the teeth were glossed, the resin replica were made from an addition silicone casting and these were took to the MEV, to be analyzed. The cracks were measured with the help of a UTHSCSA tool image software and the data were submited to an statistical analysis with the Student t test. The results obtained give the following conclusions: the lower values of marginal cracks were obtained when it was used the halogenic light (t = 3,246 and p = 0,02) and due the intensity variation of this light (t = 8,808 and p = 0,00). The lowest values related to the cracks were found when the Filtek Z350 resin was compared to the Filtek Z250 resin (t = 0,426 and p = 0,672), and when the Adper Scotchbond Multipurpose adhesive was compared with the Adper Single Bond 2 system (t = 0,883 and p = 0,382). The greatest values of marginal cracks were obtained with Filtek Z350 resin preheated at 60 degrees (t = -3,961 and p = 0,00); with the use of dentin desensitizing (t = -3,062 and p = 0,004) and with the removal of the collagen by using sodium hypochlorite (t = -8,808 and p = 0,000).