In this report a phase locked loop (PLL) system for grid voltage phase tracking has been investigated. The grid voltage phase angle contains critical information for connecting a power plant, such as a wave energy converter, to the grid. A synchronous reference frame PLL system with PI-regulator gains calculated with the symmetrical optimum method has been designed and simulations in SIMULINK have been made. For ideal grid conditions the phase angle was tracked fast and accurate. For non-ideal conditions the phase angle was tracked but with less accuracy, due to slow dynamics of the system, but still within acceptable margins. In order to test this system further it has to be implemented in a control system and tested when connected to the grid.

A high efficiency driver is designed for light emitting diode (LED) street lamps in the thesis. The main power conversion circuit employs a phase-controlled rectifier to convert the power from the ac mains of 110/220 V, 60 Hz directly into a dc source, providing the required output current for the street lamps formed by arrayed high brightness white LEDs. The phase-controlled rectifier of the LED driver circuit can be a conventional semi-converter or a rectifier with symmetrical phase control, which makes use of thyristors and power transistors, respectively, to regulate the LED current by means of adjusting the conduction angles in a cycle of the ac line. The phase-controlled rectifiers may exclude the use the bulky electrolyte capacitor with acceptable variation in the chromaticity and the color temperature. Operating at the low frequency, the phase-controlled rectifiers can avoid the problems of electromagnetic interference caused by high-frequency switching and adopt low cost power switches. Furthermore, a relatively high power factor can be achieved when the line source voltage varies within a small allowable range. The research is targeted to a design of a 200 W LED street lamp. To facilitate the changes of the control functions and circuit parameters, the control circuit is realized with a microcontroller. In addition, over-voltage/current protections can be included easily. Experimental results demonstrate that the phase-controlled rectifiers with appropriately designated circuit parameters can approach a power factor of 0.92 and a circuit efficiency of 93% at the rated output.

Symmetrical Multilevel Diversity Coding (SMDC) is a network compression problem for which a simple separate coding strategy known as superposition coding is optimal in terms of achieving the entire admissible rate region. Carefully constructed induction argument along with the classical subset entropy inequality of Han played a key role in proving the optimality. This thesis considers a generalization of SMDC for which, in addition to the randomly accessible encoders, there is also an all-access encoder. It is shown that superposition coding remains optimal in terms of achieving the entire admissible rate region of the problem. Key to our proof is to identify the supporting hyperplanes that define the boundary of the admissible rate region and then build on a generalization of Han's subset inequality. As a special case, the (R0,Rs) admissible rate region, which captures all possible tradeoffs between the encoding rate, R0, of the all-access encoder and the sum encoding rate, Rs, of the randomly accessible encoders, is explicitly characterized. To provide explicit proof of the optimality of superposition coding in this case, a new sliding-window subset entropy inequality is introduced and is shown to directly imply the classical subset entropy inequality of Han.

This thesis is to develop a novel polishing tool system fitted for convex and concave symmetrical surface of combined surface. There are two design goals in this system. First, this system can be used to polish a concave or convex cone surface with various dimensions and angle cones by adjusting its geometric feature of structure. Second, this polishing tool is expected to have high life expectancy in real applications. Because of the advantages, an efficiency and controllable polishing system would be developed.An inference process, based on a top-down planning strategy, was used to obtain the concept design of polishing tool. There are two major parts in the structure of polishing tool system. The first one is its elastic structure. Both its geometric configuration and loading applied at work are adjustable. The second one is the polishing tool of cylindrical shape. With this specific geometric feature, the effect of tool wear on polishing rate is minimized. The finite element method was adopted to analyze the deformation characteristics of the elastic structure. Accordingly, an optimal design about the shape and dimension of elastic structure was determined. The experimental study showed that the developed polishing system had the property of high repeatability in machining rate. It was also demonstrated that the machining rate of system was insensitive to the tool wear during the polishing process. This advantage may allow this system to gain significant benefit in reducing the need of tool replacement. Finally, it was shown that the experimental trends of machining rate due to the change of applied load or polishing speed followed that of cylindrical polishing system. Both of them can be properly predicted based on the lubricating theories.

Įprasti elektromechaninių vykdymo sistemų dinamikos optimizavimo metodai – kiekybinis ir simetrinis optimumai turi savų privalumų bei trūkumų ir yra pagrįsti pastovios struktūros greičio reguliatoriais: proporciniu (P) ir proporciniu integruojančiu (PI). Siekiant suderinti kiekybinio ir simetrinio optimumų tiekiamus privalumus bei pašalinti jų trūkumus, užtikrindamas elektromechaninės vykdymo sistemos greičio dinaminį nuokrypį neviršijantį 5 % ir nulinį greičio statinį nuokrypį ištirtas P-PI valdymo dėsnio kintamos struktūros reguliatorius. Remiantis ITAE integraliniu kokybės rodikliu nustatyta geriausią elektromechaninės vykdymo sistemos dinamikos kokybę užtikrinanti greičio reguliatoriaus valdymo dėsnio perjungimo parametro priklausomybė nuo statinės apkrovos. Atlikti elektros pavaros su kintamos struktūros greičio reguliatoriumi veikimo imitacijos tyrimai MATLAB/Simulink programa. Nustatyta, kad P-PI kintamos struktūros reguliatorius užtikrina nuo 60,7 % iki 83,15 % geresnę elektromechaninės vykdymo sistemos dinamikos kokybę nei pastovios struktūros simetrinio optimumo reguliatorius (PI). Tačiau naudojant P-PI kintamos struktūros reguliatorių gaunama nuo 2,76 % iki 13,67 % blogesnė sistemos dinamikos kokybė nei PI-P-PI kintamos struktūros reguliatoriaus atveju. / Classical dynamics optimization methods of the electromechanical servo drives are the quantitative and symmetrical optimums. These methods have advantages and disadvantages and are based on the fixed structure velocity controllers – proportional (P) and proportional-integrating (PI). In order to coordinate the advantages and eliminate disadvantages of the quantitative and symmetrical optimum methods have been investigated the P-PI variable structure velocity controller in the electromechanical servo drive. The P-PI variable structure velocity controller ensures that the dynamic error does not exceed 5 % and enables avoiding the static velocity error. According to the ITAE (Integral of Time multiplied by Absolute Error) quality indicator it was determined the control law switching parameter dependence on the static load ensuring the best dynamical quality of the electromechanical servo system. The investigations have been accomplished simulating the electromechanical servo system with P-PI variable structure velocity controller using MATLAB/Simulink program. It has been determined that P-PI variable structure velocity controller ensures from 60,7 % to 83,15 % better dynamical quality of the electromechanical servo system compared to the fixed structure controller (PI) of the symmetrical optimum. But using P-PI variable structure velocity controller the dynamical quality declines from 2,76 % to 13,67 % compared to the PI-P-PI variable structure velocity controller.

The rapid changes in the world of online technology during the last two decades brought along new challenges and opportunities for public relations practitioners. Literature has proven that the interactive capabilities of web-based technology have the possibility to build and maintain relationships with stakeholders and create two-way symmetrical communication opportunities. One such technology is an intranet, which could have an immense impact on an organisation's internal communication environment. If managed and applied correctly the intranet has the possibility to build two-way symmetrical relationships with an organisation's internal stakeholders - often described as one of the organisation's most strategic stakeholder groups. In this applied research study, the contribution of an international mining organisation's intranet to internal two-way symmetrical communication was explored and described. An extensive literature study was conducted to determine how an intranet could contribute theoretically to two-way symmetrical communication. The empirical findings were obtained by means of two main research methods: a qualitative content analysis and semi-structured interviews with middle management employees. The content analysis described how the basic principles of two-way symmetrical communication were applied on the Lonmin Platinum intranet. The semistructured interviews with middle management explored and described how they perceived and used the intranet with regard to two-way symmetrical communication. It was concluded that the Lonmin intranet did not contribute to two-way symmetrical communication. A critical conclusion is that an intranet as a mediated communication medium could not contribute to two-way symmetrical communication if the internal communication climate does not facilitate the specific values related to the Excellence Theory and two-way symmetrical communication principles. Another conclusion is that Lonmin's intranet was too technologically focussed. There was no management of strategic communication or ownership, and as a result the intranet did not contribute to two-way symmetrical communication in the organisation. It is suggested that future studies describe the contribution of the Lonmin intranet to two-way symmetrical communication after the communication department had commenced with strategic intranet management. The relation between the contribution of the intranet to two-way symmetrical communication in the organisation and the general communication climate could also be explored in future research studies. / Thesis (M.A. (Communication Studies))--North-West University, Potchefstroom Campus, 2007.

The rapid changes in the world of online technology during the last two decades brought along new challenges and opportunities for public relations practitioners. Literature has proven that the interactive capabilities of web-based technology have the possibility to build and maintain relationships with stakeholders and create two-way symmetrical communication opportunities. One such technology is an intranet, which could have an immense impact on an organisation's internal communication environment. If managed and applied correctly the intranet has the possibility to build two-way symmetrical relationships with an organisation's internal stakeholders - often described as one of the organisation's most strategic stakeholder groups. In this applied research study, the contribution of an international mining organisation's intranet to internal two-way symmetrical communication was explored and described. An extensive literature study was conducted to determine how an intranet could contribute theoretically to two-way symmetrical communication. The empirical findings were obtained by means of two main research methods: a qualitative content analysis and semi-structured interviews with middle management employees. The content analysis described how the basic principles of two-way symmetrical communication were applied on the Lonmin Platinum intranet. The semistructured interviews with middle management explored and described how they perceived and used the intranet with regard to two-way symmetrical communication. It was concluded that the Lonmin intranet did not contribute to two-way symmetrical communication. A critical conclusion is that an intranet as a mediated communication medium could not contribute to two-way symmetrical communication if the internal communication climate does not facilitate the specific values related to the Excellence Theory and two-way symmetrical communication principles. Another conclusion is that Lonmin's intranet was too technologically focussed. There was no management of strategic communication or ownership, and as a result the intranet did not contribute to two-way symmetrical communication in the organisation. It is suggested that future studies describe the contribution of the Lonmin intranet to two-way symmetrical communication after the communication department had commenced with strategic intranet management. The relation between the contribution of the intranet to two-way symmetrical communication in the organisation and the general communication climate could also be explored in future research studies. / Thesis (M.A. (Communication Studies))--North-West University, Potchefstroom Campus, 2007.

Dois surtos de intoxicação por selênio em suínos que ocorreram no estado do Paraná são descritos. Foram acometidos leitões em fase de creche, 16 de um lote de 100 com 27 dias de idade (surto 1) e 350 de 2285 com 22 dias de idade (surto2) apresentaram poliomielomalácia simétrica focal. Animais que sobreviveram aos surtos desenvolveram lesões de casco características de intoxicação crônica por selênio. Os sinais clínicos iniciaram após 6 dias e 30 horas da introdução da ração com alto teor de selênio nos surtos 1 e 2, respectivamente. O surgimento dos sinais foi abrupto, os animais começavam com andar cambaleante, evoluiam para paralisia dos membros pélvicos e progrediam para paralisia dos membros torácicos e tetraparesia. Os animais do surto 1 não tinham alterações de comportamento e mantinham estado de alerta e animais do surto 2 apresentaram quadros de depressão. Macroscopicamente, observaram-se focos circulares amarelados com áreas deprimidas mais escura, em alguns animais, restritas ao corno ventral da substância cinzenta (H medular) em intumescências cervical e lombar. Microscopicamente, essas áreas corresponderam à malácia da substância cinzenta, caracterizada por microcavitações, perda neuronal, cromatólise, neuronofagia, infiltrado de células Gitter, microgliose, astrócitos de Alzheimer tipo II e proliferação de células endoteliais evidenciadas na imuno-histoquímica (IHQ) para fator de von Willebrand. 9Continua) No segundo surto, dois animais apresentaram vacuolização difusa do citoplasma de neurônios. Em um animal, Astrócitos gemistocíticos foram observados. Na IHQ para Proteína Ácida Glial Fibrilar (GFAP), obteve-se marcação positiva na maioria dos animais e, na IHQ para Proteína S-100, obteve-se marcação em alguns casos. Além dessas alterações medulares, foram encontrados, em dois animais lesões de polioencefalomalácia em porções do tronco encefálico. Fragmentos de fígado de oito animais e ração de ambos os surtos foram encaminhados para dosagem de selênio. Em amostras de ração, detectou-se 3,38 ppm (surto 1) e 154 ppm (surto 2) e em amostras de fígado teve dosagens superiores a 3,34 ppm. No surto 2, foi realizada uma visita onde seis suínos foram eutanasiados para monitoramento de níveis hepáticos de selênio, sendo dois animais controles e quatro sobreviventes do surto. Quarenta e dois dias após a retirada da ração, os níveis de selênio foram inferiores ao controle e ao nível considerado em quadros de intoxicação (3 ppm). / Two outbreaks of selenium poisoning occurred in pigs in Cruzeiro do Iguaçu and Dois Vizinhos, both of the located in Paraná State. The affected pigs were in the post-weaning period, 16 out of 100 were 27 days of age (outbreak 1) and 350 out of 2285 were 22 days of age (outbreak 2). Affected animals showed signs of focal symmetrical poliomyelomalacia. Surviving pigs developed lesions in hoof, which are characteristic of chronic poisoning by selenium. Clinical signs were observed 6 days and 30 hours after the introduction of the feed with high selenium content in outbreaks 1 and 2, respectively. The appearance of the signs was abrupt, beginning with gait and progressing to paralysis of rear limbs and the forelimbs, or tetraparesis. Animals of outbreak 1 were alert and had no behaviors changes and animals of outbreak 2 showed depression. Macroscopically, in some animals there were yellow circular focus with dark areas, restricted to the ventral horn of the gray matter of spinal cord in cervical and lumbar intumescence. Microscopically, these areas corresponded to gray substance malacia characterized by microcavitation, neuronal loss, chromatolysis, Gitter cell infiltrate, neuronophagia, microgliosis, Alzheimer type II astrocytes and proliferation of endothelial cells, which were labeled by immunohistochemistry (IHC) for von Willebrand factor. In the second outbreak, two animals showed a diffuse cytoplasm vacuolization of the neurons. Gemistocytic astrocytes were observed in one animal. In most affected pigs, positive in test for glial fibrillary acid protein (GFAP) was observed, but only in some cases, there was positive anti-S-100 IHC. In addition these spinal cord changes were seen polioencephalomalacia in portions of the brainstem in two animals. Liver samples from eight animals and feed samples from both outbreaks were referred to determine selenium concentration. Selenium dosages in feed samples were 3.38 ppm (outbreak 1) and 154 ppm (outbreak 2) and in liver samples were above 3.34 ppm. Additions six animals were euthanized for monitoring hepatic levels of selenium, two were control animals and four were survivors of the second outbreak. 42 days after the withdrawal of the diet, selenium levels were lower than in internal control and the level seen in intoxication outbreaks (3 ppm).

Made available in DSpace on 2014-06-11T19:22:34Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-07-20Bitstream added on 2014-06-13T20:09:48Z : No. of bitstreams: 1 costa_llh_me_bauru.pdf: 1092988 bytes, checksum: 490b62551f9555ff7b869527de5680f6 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho apresenta um estudo dos fenômenos de desequilíbrio e assimetria que podem ocorrer em sistemas trifásicos, no qual foram estudadas duas abordagens. A primeira delas é a abordagem tradicional de análise de fenômenos de desequilíbrio e assimetria, proposta por Fortescue, denominadas Componentes Simétricas ou Componentes de Sequência. Essa proposta desenvolvida no domínio da frequência foi estudada também no domínio do tempo, após sua adaptação. Isso porque as componentes simétricas generalizadas, nova abordagem de análise de desequilíbrio, está desenvolvida no domínio do tempo. Ambas as propostas de análise do desequilíbrio e assimetria trifásicos são aplicadas à sistemas trifásicos periódicos não senoidais. Enquanto que as componentes simétricas de Fortescue, para serem calculadas, necessitam que o sistema trifásico não senoidal seja decomposto nas harmônicas da série de Fourier, as componentes simétricas generalizadas podem ser aplicadas diretamente ao sistema não senoidal. O desenvolvimento de ambas as abordagens para um sistema periódico não senoidal resulta em relação entre ambas as propostas de análise de desequilíbrio e assimetria As relações entre as componentes simétricas generalizadas e as componentes simétricas de Fortescue são a principal contribuição deste trabalho. Baseado nas componentes simétricas generalizadas, novos indicadores de desequilíbrio são propostos. Os novos indicadores são comparados com os indicadores de desequilíbrio clássicos, os quais foram desenvolvidos a partir da proposta de Fortescue. Por fim, uma aplicação é desenvolvida na qual foram aplicados os conceitos estudados. Nesta aplicação, uma tensão trifásica não senoidal desequilibrada alimenta um motor de indução trifásico / This work presents a study of the phenomena of unbalance and asymmetry which may occur in three-phase systems which two approaches were studied. The first one is the traditional approach of analysis of phenomena of unbalance and asymmetry, proposed by Fortescue, called Symmetrical Components or Sequence Components. This proposal developed in the frequency domain was also studied in the time domain after adaptation. This because of the generalized symmetrical components, new approach to the analysis of unbalance and asymmetry is developed in the time domain. Both proposals for analysis if the unbalance and asymmetry in three-phase systems are applied to the periodic non-sinusoidal three-phase systems. While the symmetrical components of Fortescue, to be calculated, require that the non-sinusoidal three-phase system is decomposed into harmonic Fourier series, the generalized symmetrical components can be applied directly to the non-sinusoidal system. The development of both approaches to a periodic non-sinusoidal system results in relationships between both proposals for analysis of unbalance and asymmetry. The relationships between the symmetrical components and the generalized symmetrical components of Fortescue are the main contribution of this work. Based on the generalized symmetrical components, new indicators of unbalance are proposed. The new new indicators are compared with the classical indicators of unbalance, which were developed from the proposed Fortescue. Finally, an application is developed with the concepts studied. In this application, an unbalanced non-sinusoidal three-phase voltage supplies a three-phase induction motor

Dois surtos de intoxicação por selênio em suínos que ocorreram no estado do Paraná são descritos. Foram acometidos leitões em fase de creche, 16 de um lote de 100 com 27 dias de idade (surto 1) e 350 de 2285 com 22 dias de idade (surto2) apresentaram poliomielomalácia simétrica focal. Animais que sobreviveram aos surtos desenvolveram lesões de casco características de intoxicação crônica por selênio. Os sinais clínicos iniciaram após 6 dias e 30 horas da introdução da ração com alto teor de selênio nos surtos 1 e 2, respectivamente. O surgimento dos sinais foi abrupto, os animais começavam com andar cambaleante, evoluiam para paralisia dos membros pélvicos e progrediam para paralisia dos membros torácicos e tetraparesia. Os animais do surto 1 não tinham alterações de comportamento e mantinham estado de alerta e animais do surto 2 apresentaram quadros de depressão. Macroscopicamente, observaram-se focos circulares amarelados com áreas deprimidas mais escura, em alguns animais, restritas ao corno ventral da substância cinzenta (H medular) em intumescências cervical e lombar. Microscopicamente, essas áreas corresponderam à malácia da substância cinzenta, caracterizada por microcavitações, perda neuronal, cromatólise, neuronofagia, infiltrado de células Gitter, microgliose, astrócitos de Alzheimer tipo II e proliferação de células endoteliais evidenciadas na imuno-histoquímica (IHQ) para fator de von Willebrand. 9Continua) No segundo surto, dois animais apresentaram vacuolização difusa do citoplasma de neurônios. Em um animal, Astrócitos gemistocíticos foram observados. Na IHQ para Proteína Ácida Glial Fibrilar (GFAP), obteve-se marcação positiva na maioria dos animais e, na IHQ para Proteína S-100, obteve-se marcação em alguns casos. Além dessas alterações medulares, foram encontrados, em dois animais lesões de polioencefalomalácia em porções do tronco encefálico. Fragmentos de fígado de oito animais e ração de ambos os surtos foram encaminhados para dosagem de selênio. Em amostras de ração, detectou-se 3,38 ppm (surto 1) e 154 ppm (surto 2) e em amostras de fígado teve dosagens superiores a 3,34 ppm. No surto 2, foi realizada uma visita onde seis suínos foram eutanasiados para monitoramento de níveis hepáticos de selênio, sendo dois animais controles e quatro sobreviventes do surto. Quarenta e dois dias após a retirada da ração, os níveis de selênio foram inferiores ao controle e ao nível considerado em quadros de intoxicação (3 ppm). / Two outbreaks of selenium poisoning occurred in pigs in Cruzeiro do Iguaçu and Dois Vizinhos, both of the located in Paraná State. The affected pigs were in the post-weaning period, 16 out of 100 were 27 days of age (outbreak 1) and 350 out of 2285 were 22 days of age (outbreak 2). Affected animals showed signs of focal symmetrical poliomyelomalacia. Surviving pigs developed lesions in hoof, which are characteristic of chronic poisoning by selenium. Clinical signs were observed 6 days and 30 hours after the introduction of the feed with high selenium content in outbreaks 1 and 2, respectively. The appearance of the signs was abrupt, beginning with gait and progressing to paralysis of rear limbs and the forelimbs, or tetraparesis. Animals of outbreak 1 were alert and had no behaviors changes and animals of outbreak 2 showed depression. Macroscopically, in some animals there were yellow circular focus with dark areas, restricted to the ventral horn of the gray matter of spinal cord in cervical and lumbar intumescence. Microscopically, these areas corresponded to gray substance malacia characterized by microcavitation, neuronal loss, chromatolysis, Gitter cell infiltrate, neuronophagia, microgliosis, Alzheimer type II astrocytes and proliferation of endothelial cells, which were labeled by immunohistochemistry (IHC) for von Willebrand factor. In the second outbreak, two animals showed a diffuse cytoplasm vacuolization of the neurons. Gemistocytic astrocytes were observed in one animal. In most affected pigs, positive in test for glial fibrillary acid protein (GFAP) was observed, but only in some cases, there was positive anti-S-100 IHC. In addition these spinal cord changes were seen polioencephalomalacia in portions of the brainstem in two animals. Liver samples from eight animals and feed samples from both outbreaks were referred to determine selenium concentration. Selenium dosages in feed samples were 3.38 ppm (outbreak 1) and 154 ppm (outbreak 2) and in liver samples were above 3.34 ppm. Additions six animals were euthanized for monitoring hepatic levels of selenium, two were control animals and four were survivors of the second outbreak. 42 days after the withdrawal of the diet, selenium levels were lower than in internal control and the level seen in intoxication outbreaks (3 ppm).