Neste trabalho é abordada a estimação de parâmetros de motores de indução trifásicos através de métodos diferentes daqueles normalizados por normas técnicas. Inicialmente é apresentada uma revisão bibliográfica dos principais métodos alternativos encontrados na literatura, onde são discutidas as vantagens e desvantagens de cada um deles. Também é abordado o problema da variação dos parâmetros durante a operação do motor devido a fenômenos como o efeito pelicular e a saturação no ferro. São propostos três métodos de estimação dos parâmetros da máquina de indução trifásica que utilizam apenas medições de tensões e correntes do estator. O primeiro método utiliza a impedância instantânea vista dos terminais do estator na estimação dos parâmetros. O segundo é baseado em ensaios de decaimento, visando a obtenção do valor de regime permanente da constante de tempo do rotor. Já o terceiro método proposto envolve a aplicação do primeiro método em segmentos do conjunto de dados, denominados de janelas móveis, a fim de se obter a variação dos parâmetros com a frequência das tensões e correntes induzidas no rotor. Esta variação ocorre principalmente devido ao efeito pelicular. São apresentados algoritmos para a estimação das grandezas não medidas porém necessárias nos métodos propostos, tais como a velocidade do rotor, fluxo do estator e torque eletromagnético. Também é realizada a estimação dos parâmetros mecânicos do motor. Os três métodos são validados através de simulações e experimentos envolvendo motores de diferentes potências, onde é possível observar os efeitos da variação dos parâmetros. Por fim, a eficácia dos métodos é avaliada através de comparações entre as correntes obtidas da simulação do motor com os parâmetros estimados e as correntes efetivamente medidas durante os ensaios. Observa-se que no caso do motor de baixa potência, admitir a variação dos parâmetros não melhora os resultados. Por outro lado, no caso dos motores de maior potência os erros envolvidos quando se admite variação nos parâmetros com a frequência do rotor é consideravelmente menor do que os erros obtidos através da simulação com parâmetros constantes. / In this work, the estimation of the parameters of three phase induction motor is approached through alternative methods. Firstly, it is presented a literature review of the commonly used methods, where the advantages and disadvantages of each one are discussed. The problem of parameter variation during the motor operation due to phenomena as skin-effect and iron saturation is also discussed. Three methods aiming at the estimation of the induction motors parameters are presented, where only stator voltages and currents measurements are required. The first method uses the instantaneous impedance as seen from the stator terminals for the parameter estimation. The second one is based on deceleration tests, aiming to obtain the steady-state value of the rotor time constant. The third method involves the application of the first method to segments of the data, named moving windows. The objective is to assess the parameter variation with the rotor frequency, mainly due to skin-effect. Algorithms for estimation of quantities such as rotor speed, stator flux and electromagnetic torque are presented. A method to estimate mechanical parameters is also presented. The three methods are validated through simulation and experimental tests with motors of different power. Using the proposed methods, it is possible to observe the parameter variation effects. Finally, the accuracy of the methods is evaluated through comparisons between the stator currents simulated with the estimated parameters and the measured currents. In the case of low power motor, no significant improvement in the results were observed when varying parameters are assumed. On the other hand, in the case of high power motors the errors considering varying parameters with the rotor frequency are considerably lower than those obtained through simulation with constant parameters.

'Hot particle' skin dosimetry calculations are commonly performed using homogeneous dose-point kernels (DPK) in conjunction with scaling and backscatter models to account for non-homogeneous geometries. A new scaling model for determining the actual DPK for beta-particles transmitted by a high-Z source material has been developed. The model is based on a determination of the amount of mono-energetic electron absorption that occurs in a given source thickness through the use of EGSnrc (Electron Gamma Shower) Monte Carlo simulations. Integration over a particular beta spectrum provides the beta-particle DPK following self-absorption as a function of source thickness and radial depth in water, thereby accounting for spectral hardening that may occur in higher-Z materials. Beta spectra of varying spectral shapes and endpoint energies were used to test our model for select source materials with 7.42 < Z ��� 94. A new volumetric backscatter model has also been developed. This model corrects for beta-particle backscattering that occurs both in the source medium and in the atmosphere surrounding the source. Hot particle backscatter factors are constructed iteratively through selective integration of point-source backscatter factors over a given source geometry. Selection criteria are based on individual source-point positions within the source and determine which, if any, backscatter factors are used. The new scaling model and backscatter model were implemented into the DPK-based code VARSKIN 4 for extensive dose testing and verification. Verification results were compared to equivalent Monte Carlo simulations. The results demonstrate that significant improvements can be made to DPK-based models when dealing with high-Z volumetric sources in non-homogeneous geometries. / Graduation date: 2013

Die vorliegende Arbeit beschäftigt sich mit modernen geregelten Niederspannungsdrehstromantrieben. Es wird insbesondere auf das Problem der Stromverdrängung bei Maschinen mittlerer bis großer Leistung eingegangen. Für hohe Frequenzen in Verbindung mit hohen Ständernuten kommt es dabei zu einer gravierenden Erhöhung der Ständerwicklungsverluste infolge der Stromverdrängung. Diese führt sowohl zu einem starken Anstieg der mittleren Erwärmung der Maschine als auch zu Heißpunkten in der Ständerwicklung. Aufgrund ihres Einsatzes als Prüfstandsmotor werden moderne geregelt betriebene Induktionsmotoren gezielt zu Drehschwingungen angeregt. Eine ähnliche Problematik findet man in abgwandelter Form auch bei Maschinen der Querschneiderindustrie, welche Spielzeiten im zehntel Sekundenbereich aufweisen. Bei diesen Induktionsmaschinen kommt es aufgrund der zyklischen Drehmomentänderung zu einem Stromverdrängungseffekt in den Stäben des Kurzschlusskäfigs. Es entsteht damit eine zusätzliche Verlustquelle, die wesentlich zur Erwärmung des Läufers beiträgt. Nach dem heutigen Stand der Wissenschaft geht man bei der Stromregelung von einem Trägheitsverhalten 1.Ordnung für die Übertragungsfunktion der Induktionsmaschine aus. Die vorliegende Arbeit erweitert dieses Modell unter Berücksichtigung der Läuferstromverdrängung. / This study focuses on modern controlled low voltage three phase machines, especially, on the problem of the skin effect in machines of middle and high power range. Due to the skin effect, a severe increase of the dissipation power of the slot windings can be observed for high frequencies with deep slots. This causes a sharp rise of the temperature of the machine as well as hot spots in the stator winding. As a result of its use as test bench applications, modern controlled induction machines are purposefully stimulated for torsional vibration. A similar difficulty can be found in machines for the cross cutter industry, which can be applied in the tenth part of a second, for instance. Because of the cyclical change of the torque in these induction machines, a skin effect results in the bars of the squirrel-cage. Here, an additional source of dissipation, which adds considerably to the heating of the rotor, emerges. Following the state of today’s science, at the current control loop an PT1-element can be assumed for the transfer function of induction machines. This study expands the model with regard to the rotor skin effect.

The high-density integrated circuit (IC) gives rise to geometrically complex multiscale chip-package structures whose electromagnetic performance is difficult to predict. This motivates this dissertation to work on an efficient full-wave transient solver that is capable of capturing all the electromagnetic behaviors of such structures with high accuracy and reduced computational complexity compared to the existing methods. In this work, the unconditionally stable Laguerre-FDTD method is adopted as the core algorithm for the transient full-wave solver. As part of this research, skin-effect is rigorously incorporated into the solver which avoids dense meshing inside conductor structures and significantly increases computational efficiency. Moreover, as an alternative to typical planar interconnects for next generation high-speed ICs, substrate integrated waveguide, is investigated. Conductor surface roughness is efficiently modeled to accurately capture its high-frequency loss behavior. To further improve the computational performance of chip-package co-simulation, a novel transient non-conformal domain decomposition method has been proposed. Large-scale chip-package structure can be efficiently simulated by decomposing the computational domain into subdomains with independent meshing strategy. Numerical results demonstrate the capability, accuracy and efficiency of the proposed methods.

Στα πλαίσια αυτής της διπλωματικής εργασίας θα εξετάσουμε το πρόβλημα της εξασθένισης που παρουσιάζεται σε ένα BPL (Broadband over powerlines) network (ευζωνικό δίκτυο), αξιολογώντας την αρνητική επιρροή των διαφόρων καταστρεπτικών παραγόντων και ειδικότερα του επιδερμικού φαινομένου (skin effect). Τα BPL συστήματα εισάγουν μια καινοτόμα τεχνολογία ευρυζωνικής πρόσβασης στο διαδίκτυο και όχι μονό, η οποία δείχνει να ανταποκρίνεται στις σύγχρονες απαιτήσεις, προσφέροντας ικανοποιητική ποιότητα υπηρεσιών και μειώνοντας το κόστος υλοποίησης τους. Δεν χρειάζεται επενδύσεις για νέα υποδομή, αφού οι γραμμές ηλεκτρικής ισχύος καλύπτουν σχεδόν όλες τις κατοικημένες περιοχές του πλανήτη. Ιδιαίτερα σε αραιοκατοικημένες περιοχές με ελάχιστη τηλεπικοινωνιακή κάλυψη και υποδομή, η τεχνολογία BPL είναι ίσως η μοναδική λύση για ευρυζωνικές υπηρεσίες. Είναι κατανοητή τώρα η ανάγκη που προκύπτει για περεταίρω διερεύνηση του επιδερμικού φαινομένου, ενός παράγοντα που ενεργεί αρνητικά στη διάδοση του σήματος, διαμέσου του BPL δικτύου. Στο πρώτο κεφάλαιο θα μιλήσουμε γενικά για την BPL τεχνολογία, πώς και πού ξεκίνησε. Θα δώσουμε ένα γενικό ορισμό με μια μικρή εισαγωγή στα συστήματα BPL. Στο δεύτερο κεφάλαιο θα ασχοληθούμε με τα δίκτυα πρόσβασης, με άλλα λόγια την δομή των δικτύων πρόσβασης BPL καθώς επίσης και τα βασικά στοιχεία των δικτύων. Γίνεται μια εκτενής παρουσίαση των τοπολογιών και της αρχιτεκτονικής των δικτύων BPL και τελευταία παρουσιάζεται η εμπορική αξιοποίηση στις διάφορες εφαρμογές χρήσης της BPL τεχνολογίας. Στο τρίτο κεφάλαιο θα μιλήσουμε για το επιδερμικό φαινόμενο, που εμφανίζεται, πώς επηρεάζει και τι προκαλεί στις BPL εφαρμογές. Γίνεται αναφορά στα καλώδια, αλλά και στα δίκτυα διαμέσου των οποίων βρίσκει εφαρμογές η BPL τεχνολογία, και συνάμα εμφανίζεται το επιδερμικό φαινόμενο. Στο τέταρτο κεφάλαιο παρουσιάζεται μια πειραματική εργασία, όπου φαίνεται ο τρόπος με τον οποίον το επιδερμικό φαινόμενο επιδρά στο εσωτερικό των καλωδίων, ένα πρόγραμμα σε Matlab όπου γίνεται εμφανής η σχέση της συχνότητας με το επιδερμικό βάθος. Τέλος, παρουσιάζουμε τα συμπεράσματα που προκύπτουν από όλη την εργασία. / --

This dissertation is composed of three parts of major contributions. In Chapter II, we discuss analytical study of contaminant transport from a finite source in a finite-thickness aquifer. This chapter provides analytical solutions of contaminant transport from one-, two-, and three-dimensional finite sources in a finite-thickness aquifer using Green's function method. A library of unpublished analytical solutions with different finite source geometry is provided. A graphically integrated software CTINT is developed to calculate the temporal integrations in the analytical solutions and obtain the final solutions of concentration. In Chapter III, we obtained solutions of groundwater flow to a finite-diameter horizontal well including wellbore storage and skin effect in a three-dimensionally anisotropic leaky aquifer. These solutions improve previous line source solutions by considering realistic well geometry and offer better description of drawdown near the horizontal well. These solutions are derived on the basis of the separation of the source and the geometric functions. The graphically integrated computer program FINHOW is written to generate type curves of groundwater flow to a finite-diameter horizontal well. The influence of the finite-diameter of the well, the wellbore storage, the skin effect, the leakage parameter, and the aquifer anisotropy is thoroughly analyzed. In Chapter IV, a general theory of groundwater flow to a fractured or non-fractured aquifer considering wellbore storage and skin effect is provided. Solutions for both leaky confined and water table aquifers are provided. The fracture model used in this study is the standard double-porosity model. The storage of the aquitard (the leaky confining layer) is included in the formula. A program denoted FINHOW2 is written to facilitate the calculation. Sensitivity of the solution to the confined versus unconfined conditions, fractured versus non-fractured conditions, and wellbore storage and skin effects is analyzed.

Ultraviolet (UV) radiation damages both eukaryotic and prokaryotic cells by causing the formation of free radicals which damage cell membranes and DNA. Antioxidant vitamins have been shown to protect cells from UV-induced damage by scavenging free radicals. The protection of skin and its normal flora is necessary for the health of individuals in resisting diseases caused by microorganisms and delaying the long-term damage caused by UV radiation.This research investigated the effects of the antioxidants vitamin A and ascorbic acid, as well as UV-irradiation on both prokaryotic (Staphylococcus epidermidis) cells and eukaryotic (human fibroblast skin) cells. This information is important in determining the effects of vitamin treatment on skin and its normal flora.Results indicate that ascorbic acid is rapidly (within six hours) degraded after being dissolved in water or medium. Treatment of cells with ascorbic acid must take into account this rapid degradation. S.epidermidis cells were protected from UV-induced damage by treatment with ascorbic acid but were more sensitive to UV-irradiation when treated with vitamin A. Human fibroblast cells treated with ascorbic acid did not exhibit morphological changes when compared to untreated cells. / Department of Biology

Thesis (Ph. D.)--University of Hawaii at Manoa, 2004. / Includes bibliographical references (leaves 198-219). / Also available by subscription via World Wide Web / xvii, 219 leaves, bound ill., some col. 29 cm

Neste trabalho é abordada a estimação de parâmetros de motores de indução trifásicos através de métodos diferentes daqueles normalizados por normas técnicas. Inicialmente é apresentada uma revisão bibliográfica dos principais métodos alternativos encontrados na literatura, onde são discutidas as vantagens e desvantagens de cada um deles. Também é abordado o problema da variação dos parâmetros durante a operação do motor devido a fenômenos como o efeito pelicular e a saturação no ferro. São propostos três métodos de estimação dos parâmetros da máquina de indução trifásica que utilizam apenas medições de tensões e correntes do estator. O primeiro método utiliza a impedância instantânea vista dos terminais do estator na estimação dos parâmetros. O segundo é baseado em ensaios de decaimento, visando a obtenção do valor de regime permanente da constante de tempo do rotor. Já o terceiro método proposto envolve a aplicação do primeiro método em segmentos do conjunto de dados, denominados de janelas móveis, a fim de se obter a variação dos parâmetros com a frequência das tensões e correntes induzidas no rotor. Esta variação ocorre principalmente devido ao efeito pelicular. São apresentados algoritmos para a estimação das grandezas não medidas porém necessárias nos métodos propostos, tais como a velocidade do rotor, fluxo do estator e torque eletromagnético. Também é realizada a estimação dos parâmetros mecânicos do motor. Os três métodos são validados através de simulações e experimentos envolvendo motores de diferentes potências, onde é possível observar os efeitos da variação dos parâmetros. Por fim, a eficácia dos métodos é avaliada através de comparações entre as correntes obtidas da simulação do motor com os parâmetros estimados e as correntes efetivamente medidas durante os ensaios. Observa-se que no caso do motor de baixa potência, admitir a variação dos parâmetros não melhora os resultados. Por outro lado, no caso dos motores de maior potência os erros envolvidos quando se admite variação nos parâmetros com a frequência do rotor é consideravelmente menor do que os erros obtidos através da simulação com parâmetros constantes. / In this work, the estimation of the parameters of three phase induction motor is approached through alternative methods. Firstly, it is presented a literature review of the commonly used methods, where the advantages and disadvantages of each one are discussed. The problem of parameter variation during the motor operation due to phenomena as skin-effect and iron saturation is also discussed. Three methods aiming at the estimation of the induction motors parameters are presented, where only stator voltages and currents measurements are required. The first method uses the instantaneous impedance as seen from the stator terminals for the parameter estimation. The second one is based on deceleration tests, aiming to obtain the steady-state value of the rotor time constant. The third method involves the application of the first method to segments of the data, named moving windows. The objective is to assess the parameter variation with the rotor frequency, mainly due to skin-effect. Algorithms for estimation of quantities such as rotor speed, stator flux and electromagnetic torque are presented. A method to estimate mechanical parameters is also presented. The three methods are validated through simulation and experimental tests with motors of different power. Using the proposed methods, it is possible to observe the parameter variation effects. Finally, the accuracy of the methods is evaluated through comparisons between the stator currents simulated with the estimated parameters and the measured currents. In the case of low power motor, no significant improvement in the results were observed when varying parameters are assumed. On the other hand, in the case of high power motors the errors considering varying parameters with the rotor frequency are considerably lower than those obtained through simulation with constant parameters.

Orientador: Prof. Dr. Francisco Eugenio Mendonça da Silveira / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Física, 2017. / Através do estudo da teoria cinética dos dínamos, onde se destaca o dínamo ou processo de Ponomarenko, nos deparamos com uma análise, até agora desenvolvida na literatura, restrita à aproximação em que a superfície que encerra o escoamento responsável pelo efeito dínamo é considerada dielétrica. Este trabalho oferece um tratamento analítico do processo de Ponomarenko onde essa mesma superfície, que confina o movimento do fluido, passa a ser condutora, o que permite o surgimento do efeito skin. Será apresentada, portanto, uma solução geral, da qual é possível deduzir, em certas condições, a relação de dispersão, já conhecida na literatura, para o qual o efeito dínamo é considerado importante e, em outras, a relação de dispersão ainda não conhecida, em que o efeito skin se torna importante. Por fim, apresentamos novamente a solução geral que contém ambos os efeitos, considerando duas aproximações caracterizadas como: dínamo de baixa rotação e dínamo de alta rotação. Que serão úteis para indicarem a tendência do sistema em relação ao efeito dínamo. / Through the study of the kinematic dynamo theory, where the Ponomarenko dynamo stands out, we come across an analysis, until now developed in the literature, restricted to the approximation in which the surface, that contains the flow responsible for the dynamo effect, is considered dielectric. This work offers an analytical treatment of the Ponomarenko process, where the surface that confines the movement of the fluid, becomes conductive, which allows the appearance of the skin effect. A general solution will, therefore, be presented, from which it is possible to derive, under certain conditions, the dispersion relation already known in the literature, for which the dynamo effect is considered important and, others, the new dispersion relation, in which the skin effect becomes important. Finally, we present, again, the general skin effect solution that contains both effects, considering two approaches, characterized as: slowly rotation dynamo and fastly rotation dynamo. They will be useful to indicate the tendency of the system exhibit to the dynamo effect.