Thesis (Ph. D.)--University of Chicago, Dept. of Chemistry, December 1997. / Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--University of Chicago, Dept. of History. / Includes bibliographical references. Also available on the Internet.

Thesis (M.S. in Joint Campaign Planning and Strategy)--Joint Forces Staff College, Joint Advanced Warfighting School, 2007. / Title from title screen; viewed on July 9, 2007. "April 2007." Electronic version of original print document. Includes bibliographical references (p. 77-81).

Thesis (M.A. in Security Studies (Civil-Military Relations))--Naval Postgraduate School, March 2007. / Thesis Advisor(s): Karen Guttieri. "March 2007." Includes bibliographical references (p. 99-103). Also available in print.

Thesis (PH.D.) -- Syracuse University, 2006 / "Publication number AAT 3242494."

No description available.

Σκοπός της διπλωματικής αυτής εργασίας ήταν η μελέτη των ηλεκτρομαγνητικών δυνάμεων που δημιουργούνται μέσα σε μια ασύγχρονη ηλεκτρική μηχανή, ειδικότερα των ακτινικών δυνάμεων, καθώς και η μηχανική συμπεριφορά της μηχανής λόγω των δυνάμεων αυτών. Χρησιμοποιήθηκε ένας τριφασικός ασύγχρονος κινητήρας βραχυκυκλωμένου δρομέα, ισχύος 4 kW, συνδεσμολογίας τριγώνου. Η προσομοίωση και η μελέτη έγινε με τη χρήση του προγράμματος Opera 2-D της εταιρείας Vector Fields, το οποίο χρησιμοποιεί τη μέθοδο των πεπερασμένων στοιχείων για την επίλυση των μερικών διαφορικών εξισώσεων που περιγράφουν τη ηλεκτρομαγνητική λειτουργία της μηχανής. Πρώτα γίνεται η ηλεκτρομαγνητική ανάλυση των μοντέλων της μηχανής στη μόνιμη κατάσταση. Μετά χρησιμοποιώντας τα μοντέλα αυτά, υπολογίστηκαν οι ηλεκτρομαγνητικές πιέσεις που ασκούνται σε δόντια του δρομέα και του στάτη και η συνολική ακτινική και εφαπτομενική δύναμη που ασκείται πάνω στον δρομέα. Όταν οι ιδιοσυχνότητες ταλάντωσης της μηχανής είναι κοντά στις συχνότητες που υπάρχουν στο φάσμα συχνοτήτων της ακτινικής δύναμης, δημιουργείται συντονισμός και προκαλεί θορύβους και ταλαντώσεις στη μηχανή. Για να αποφευχθούν τέτοιου είδους θόρυβοι και ταλαντώσεις υπολογίζονται τα πλάτη και οι συχνότητες της ακτινικής δύναμης καθώς και οι ιδιοσυχνότητες της μηχανής. Οι ίδιες μετρήσεις έγιναν και σε μοντέλο μηχανής με μια σπασμένη μπάρα του κλωβού. Απεικονίσθηκαν οι ακτινικές δυνάμεις και συγκρίθηκαν με αυτές του υγιούς μοντέλου στο πεδίο του χώρου, του χρόνου και της συχνότητας. Επίσης παρουσιάζεται μια μέθοδος για την ανίχνευση «υπογραφών» ηλεκτρικών σφαλμάτων, μέσω ανάλυσης Fourier της ακτινικής ηλεκτρομαγνητικής δύναμης και πίεσης. Τα αποτελέσματα δείχνουν πως η ηλεκτρομαγνητική δύναμη είναι μια καλή παράμετρος με τη χρήση της οποίας μπορεί να ανιχνευτεί το σφάλμα της σπασμένης μπάρας. / The aim of this thesis was to study the electromagnetic forces generated in an asynchronous electric machine, especially the radial forces and the mechanical behavior of the machine due to these forces. A three-phase squirrel cage asynchronous motor, 4 kW power, was used. The simulation and the study was performed using the program Opera 2-D of Vector Fields, which uses the finite element method to solve partial differential equations describing the operation of the electromagnetic machine. First of all, the electromagnetic analysis of models of the machine in steady state was performed. Using these models, the electromagnetic pressure on teeth of the rotor and stator was calculated and the total radial and tangential force exerted on the rotor was estimated. When the natural frequencies of oscillation of the machine are close to the frequencies of the radial force, coordination is generated and causes noise and vibrations in the machine. To avoid such noises and vibrations, the amplitudes and frequencies of the radial force and the natural frequencies of the machine must be calculated. The same measurements were made on a model engine with a broken bar. The radial forces were plotted and compared with those of the healthy model, in the field of space, time and frequency. Also, a method for the detection of "signatures" electrical fault, through Fourier analysis of the radial electromagnetic force and pressure is disclosed. The results showed that the electromagnetic force is a good parameter to use for the detection of the broken bar fault.

Orientador: Silvia Regina Quijadas Ara Zuliani / Banca: Maria Eunice Ribeiro Marcondes / Banca: Odete Pacubi Baierl Teixeira / Resumo: Nas últimas décadas, o Ensino de Ciências vem buscando estratégias que favoreçam o entendimento dos conteúdos científicos ou, como indica Driver (1999), a enculturação da Ciência (DRIVER, CAPECCHI E CARVALHO, MORTIMER, 2000), além da formação de alunos e professores críticos e reflexivos. O uso da argumentação em salas de aula pode se tornar grande aliada na formação de jovens pensadores e críticos, que consigam utilizar seus pensamentos em favor próprio e em conjunto, que sejam capazes de discutir problemas e propor soluções, não apenas na escola, mas em seu dia a dia. Para favorecer a argumentação, foi utilizado um minicurso investigativo com o tema "Forças intermoleculares". Nossa proposta de trabalho procurou investigar quais são as potencialidades do uso integrado desses referenciais teóricos e qual a contribuição de uma proposta de minicurso invesetigativo no desenvolvimento de habilidades de argumentação em alunos e futuros professores além de analisar a proposta investigativa utilizada. Os dados analisados foram divididos em três categorias, i) a proposta do minicurso investigativo com base na classificação de atividades de ensino proposta por Canal (2000), ii) a qualidade da argumentação com Osborne et al (2004) e iii) a atuação do professor na elaboração dos argumentos dos alunos com Mendonça e Justil (2009). Os resultados mostram que a atividade proposta favoreceu a argumetnação dos alunos e professores, possibilitando a abertura de espaços na sala de aula para que ocorra diálogo entre os alunos e os professores. Pode-se perceber o papel fundamental do professor na elaboração dos argumentos dos alunos, pois, se os mesmos não direcionarem as discussões, os argumentos podem ser mal elaborados ou mal explorados / Abstract: In recent decades, the Teaching if Science has been searching for strategies that enhance the understanding of scientific content or, as indicated by Driver (1999), enculturation of Science (DRIVER, Capecchi and CARVALHO, MORTIMER, 2000) and the training of teachers ans students to be critical and reflective. The use of argumentation in the classroom can become a great ally in forming young thinkers and critics, who can use their own behalf and thoughts together; they can discuss problems and propose solutions, not just in shool but in their day by day. To facilitate the argument we used an investigate shor course with the theme "Intermolecular Forces". Our proposal of work aimed to investigate what are the potential use of integrated theoretical and the contribution of a proposed short course in the development of investigate reasoning abilities in students and future teachers as well as used to analyze the research proposal. Data were divided into three categories, i) the proposed investigative mini course based on the classification of educational activities proposed by Canal (2000), ii) the quality of argumentation with Osborne et al (2004) and iii) the performance of teacher in preparing students with the arguments of Mendonça and Justi (2009). The results show that the proposed activity favored the argument of the students and teachers, enabling the opening of spaces in the classroom dialogue to occur between students and teachers. It can be noticed the teqacher's role in the development of students arguments, because if they do not guiding discussions arguments can be poorly designed or poorly explored / Mestre

Eccentric braced frames have been a topic of research in seismic design over the past twenty years. The idea of eccentric bracing is a relatively new method used in practice to satisfy seismic design requirements. They have been proven to give reliable results in tests using simulated earthquake events, as well as provide an economical advantage over other framing methods. Two one-story eccentric braced frame models were created using computer generated finite element analysis. The example chosen for this study are discussed further. The maximum shear stress distribution in the link beam of the frame, using finite element analysis, will be investigated herein. The results of the shear stress produced gives insight to shear forces developed in the link beam of eccentric braced frames. The results of shear forces produced are compared with those calculated by structural engineers using commonly used hand calculated equations.

In this thesis we develop analytical models for boundary layer flow through a two dimensional group of obstacles , based on the "distributed force" model. An array of obstacles is represented as a region without solid obstructions but with distributed body forces resisting the flow. Linear analyses are presented of inviscid, laminar (or constant eddy viscosity) and turbulent flow through such force distributions. For any group of obstacles, we show how to calculate the model force distribution which becomes the input for the linear analyses. The entire procedure can be iterated to take account of non-linear upstream sheltering effects. In general the model distributed force integrates to equal the actual force exerted by obstacles on the flow divided by the fraction of the array volume not occupied by solid obstacles. Turbulent stresses are modelled using a mixing length that is uniform up to a specified height and increases linearly above. Our physical arguments for a displaced mixing length above the obstacles provide an explanation for the observed coincidence between displacement height and the level of mean momentum absorption. Comparisons of the turbulent analysis results with numerical simulations and experimental data show very encouraging agreement and so support both the distributed force model and the assumptions of the mathematical analysis. From the results of the turbulent flow analysis, effective roughness and displacement heights can be calculated for the flow above the obstacles. When the displacement of the turbulent mixing length is correctly taken into account, the calculated parameters are comparable with those obtained experimentally. An analysis of plume dispersion through a group of obstacles shows how the flow field results can be applied to practical situations, and highlights the dominant effect of enhanced perturbation shear stress, especially in the obstacle roof top layer, on changes to the downstream evolution of the plume.