Stuttgart, Univ., Diss., 2005.

Thesis (Ph. D.)--Ohio State University, 2005. / Title from first page of PDF file. Document formatted into pages; contains viii, 190 p.; also includes graphics. Includes bibliographical references (p. 186-190). Available online via OhioLINK's ETD Center

Issued also as thesis, Columbia University, under title: The metaphysics of Sir Isaac Newton.

Techn. Universiẗat, Diss., 2000--Dresden.

Thesis (Ph. D.)--Ohio State University, 2005. / Includes bibliographical references (p. 186-190). Also available online as computer text data (1 PDF file, 0.66 MB). via OhioLINK's ETD Center.

Universiẗat, Diss., 2003--Jena.

Universiẗat, Diss., 2004--Würzburg. / Erscheinungsjahr an der Haupttitelstelle: 2003.

Using the Chandra X-ray Observatory, Martini et al. (2006) found that the AGN fraction of galaxy clusters was five times higher than previous optical studies suggested. Using visual observations only, Dressler et al. (1985) estimated the AGN fraction of field galaxies to be 5%, while that of clusters was thought to be 1%. To understand the role that the environment plays in AGN fueling, the author studied a variety of environments, ranging from the field to groups to clusters. Will the AGN fraction of groups also be higher than that of the field? The author demonstrates how the AGN fraction of groups compares to that of clusters. In the following sections, the author describes the mechanics of X-ray astronomy, the group environment, and the characteristics of active galactic nuclei. The author briefly describes the possible mechanisms for AGN fueling.

Η παρούσα διδακτορική διατριβή πραγματεύεται το θέμα της αποδοτικής και με βεβαιότητα εύρεσης όλων των ριζών της παραμετρικής εξίσωσης f(x;[p]) = 0, μιας συνεχώς διαφορίσιμης συνάρτησης f με [p] ένα διάνυσμα που περιγράφει όλες τις παραμέτρους της παραμετρικής εξίσωσης και τυποποιούνται με τη μορφή διαστημάτων. Για την επίλυση αυτού του προβλήματος χρησιμοποιήθηκαν εργαλεία της Διαστηματικής Ανάλυσης. Το κίνητρο για την ερευνητική ενασχόληση με το παραπάνω πρόβλημα προέκυψε μέσα από ένα κλασικό πρόβλημα αριθμητικής ανάλυσης: την αριθμητική επίλυση συστημάτων πολυωνυμικών εξισώσεων μέσω διαστηματικής ανάλυσης. Πιο συγκεκριμένα, προτάθηκε μια ευρετική τεχνική αναδιάταξης του αρχικού πολυωνυμικού συστήματος που φαίνεται να βελτιώνει σημαντικά, κάθε φορά, τον χρησιμοποιούμενο επιλυτή. Η ανάπτυξη, καθώς και τα αποτελέσματα αυτής της εργασίας αποτυπώνονται στο Κεφάλαιο 2 της παρούσας διατριβής. Στο επόμενο Κεφάλαιο 3, προτείνεται μια μεθοδολογία για την αποδοτική και αξιόπιστη επίλυση μη-γραμμικών εξισώσεων με διαστηματικές παραμέτρους, δηλαδή την αποδοτική και αξιόπιστη επίλυση διαστηματικών εξισώσεων. Πρώτα, δίνεται μια νέα διατύπωση της Διαστηματικής Αριθμητικής και αποδεικνύεται η ισοδυναμία της με τον κλασσικό ορισμό. Στη συνέχεια, χρησιμοποιείται η νέα διατύπωση της Διαστηματικής Αριθμητικής ως θεωρητικό εργαλείο για την ανάπτυξη μιας επέκτασης της διαστηματικής μεθόδου Newton που δύναται να επιλύσει όχι μόνο κλασικές μη-παραμετρικές μη-γραμμικές εξισώσεις, αλλά και παραμετρικές (διαστηματικές) μη-γραμμικές εξισώσεις. Στο Κεφάλαιο 4 προτείνεται μια νέα προσέγγιση για την αριθμητική επίλυση του προβλήματος της Ολικής Βελτιστοποίησης με περιορισμούς διαστήματα, χρησιμοποιώντας τα αποτελέσματα του Κεφαλαίου 3. Το πρόβλημα της ολικής βελτιστοποίησης, ανάγεται σε πρόβλημα επίλυσης διαστηματικών εξισώσεων, και γίνεται εφικτή η επίλυσή του με τη βοήθεια των θεωρητικών αποτελεσμάτων και της αντίστοιχης μεθοδολογίας του Κεφαλαίου 3. Στο τελευταίο Κεφάλαιο δίνεται μια νέα αλγοριθμική προσέγγιση για το πρόβλημα της επίλυσης διαστηματικών πολυωνυμικών εξισώσεων. Η νέα αυτή προσέγγιση, βασίζεται και γενικεύει την εργασία των Hansen και Walster, οι οποίοι πρότειναν μια μέθοδο για την επίλυση διαστηματικών πολυωνυμικών εξισώσεων 2ου βαθμού. / In this dissertation the problem of finding reliably and with certainty all the zeros a pa-rameterized equation f(x;[p]) = 0, of a continuously differentiable function f is considered, where [p] is an interval vector describing all the parameters of the Equation, which are formed with interval numbers. For this kind of problem, methods of Interval Analysis are used. The incentive to this scientific research was emerged from a classic numerical analysis problem: the numerical solution of polynomial systems of equations using interval analysis. In particular, a heuristic reordering technique of the initial polynomial systems of equations is proposed. This approach seems to improve significantly the used solver. The proposed technique, as well as the results of this publication are presented in Chapter 2 of this dissertation. In the next Chapter 3, a methodology is proposed for solving reliably and efficiently parameterized (interval) equations. Firstly, a new formulation of interval arithmetic is given and the equivalence with the classic one is proved. Then, an extension of interval Newton method is proposed and developed, based on the new formulation of interval arithmetic. The new method is able to solve not only classic non-linear equations but, non-linear parameterized (interval) equation too. In Chapter 4 a new approach on solving the Box-Constrained Global Optimization problem is proposed, based on the results of Chapter 3. In details, the Box-Constrained Global Optimization problem is reduced to a problem of solving interval equations. The solution of this reduction is attainable through the methodology developed in Chapter 3. In the last Chapter of this dissertation a new algorithmic approach is given for the problem of solving reliably and with certainty an interval polynomial equation of degree $n$. This approach consists in a generalization of the work of Hansen and Walster. Hansen and Walster proposed a method for solving only quadratic interval polynomial equations

Made available in DSpace on 2014-06-11T19:30:51Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-06-06Bitstream added on 2014-06-13T21:01:24Z : No. of bitstreams: 1 carvalho_cg_dr_ilha.pdf: 1638470 bytes, checksum: ca46c8123050c9866b9ab13bc540b94d (MD5) / Este trabalho apresenta um modelo analítico para uma linha de transmissão trifásica com plano de simetria vertical. Devido às características físicas dessa linha, é possível representá-la por um sistema constituído por uma linha monofásica e por uma linha bifásica. Nesse sistema, as equações que descrevem o comportamento das grandezas nos terminais da linha monofásica são conhecidas, enquanto que as equações da linha bifásica foram obtidas utilizando uma matriz de transformação escrita explicitamente em função dos parâmetros da linha trifásica. Em seguida, as grandezas modais da linha trifásica foram convertidas para o domínio das fases e as equações resultantes representam um modelo analítico desenvolvido diretamente no domínio das fases dessa linha. Para verificar o desempenho do modelo, foram realizadas simulações considerando a energização e a incidência de uma descarga atmosférica em uma linha trifásica de 440 kV. Esses resultados foram comparados aos resultados obtidos com a linha representada por meio de um método clássico (representação nos modos) e as simulações mostraram que o modelo responde adequadamente na faixa de frequência correspondente aos procedimentos de manobra e chaveamento. O modelo desenvolvido leva em conta o efeito da frequência sobre os parâmetros longitudinais da linha e também o fato de que os parâmetros da linha são distribuídos ao longo de seu comprimento. Acredita-se que a análise das matrizes, que dão suporte ao modelo, e a validação do modelo no domínio do tempo possa dar origem, futuramente, a um modelo de linha de transmissão desenvolvido diretamente no domínio do tempo. Tal modelo, pelo fato de ser obtido diretamente das equações de propagação da linha, permitirá a obtenção de resultados de simulações, de transitórios eletromagnéticos que ocorrem... / This paper presents an analytical model to a three-phase transmission line with vertical symmetry plane. Because of physical characteristics of this line, it is possible to represent it by a system consisting of a single-phase and a two-phase line. In this system, the equations that describe the behavior of single-phase terminals quantities are known, while the two-phase equations were obtained using a transformation matrix written explicitly in terms of the parameters of three-phase line. Then, the modal quantities of three-phase line were converted into phase domain and the resulting equations represent an analytical model developed directly in phase domain of this line. To verify the performance of the model, were performed simulations considering the energization and impact of a lighting surge in a 440 kV three-phase line. These results were compared to results obtained with the line represented by a classical method (presentation modes) and simulations show that the model responds appropriately in the frequency range corresponding to the operation and switching procedures. The model developed takes into account the frequency effect on the longitudinal line parameters and also the fact that the line parameters are distributed along their length. It is believed that the matrix analysis, that support the model and the model validation in time domain may give rise in the future to a transmission line model developed directly in time domain. Such a model, because it is obtained directly from the propagation equations of line, will enable the more accurate results of simulations of electromagnetic transients that... (Complete abstract click electronic access below)