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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Metodologia para uso de simulação física no estudo da ZAC e na obtenção de diagramas CCT para soldagem / The Use of Physical Simulation on HAZ Study and CCT Diagram Attainment Dedicated to Welding

Araújo, Douglas Bezerra de 08 August 2008 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The joining of metals is often associated to metallurgical problems. Specifically, metallurgical transformations in the HAZ (Heat Affected Zone) can occur, what lead to undesirable microestructural changes. The HAZ is a difficult region for studying due to its small dimensions and high thermal gradientes. Thus, in order to overcome this limitation of the HAZ study, there are in the literature different proposes of HAZ-simulator machines (physical simulation), which uses the Joule effect for heating specific coupons that cool down by conduction and convection. This approach intends to simulate the thermal cycle in a real HAZ obtained in a real welding. However, the use of traditional coupons with cylindrical geometry presents restrictions of portraying the real case, i.e., the welding. In the cylindrical geometry option, the obtained thermal cycles do not present temperature gradients closer to the ones in real weldments. Hence, to overcome this limitation, finite elements modeling was carried out and different coupon geometries were simulated. The objective is to reach thermal cycles as close as possible to the ones obtained in a real situation, for a subsequent physical simulation. This approach showed proper and the physical and numerical present coherent results. The next step is the physical simulation validation by comparing to real weldments. This would be the most intuitive way. However, it was proposed to conduct this validation by determining CCT (Continuous Cooling Transformation) diagrams. This approach has the advantage of reaching important technological results at the same time of validating the physical simulation, since CCD diagrams dedicated to welding are very difficult to find in literature. It is possible to concluded that the physical simulation does represent the HAZ and can be used to build up CCT diagrams / Freqüentemente a união de materiais metálicos está associada a problemas metalúrgicos. Especificamente, podem ocorrer modificações metalúrgicas na ZAC (zona afetada pelo calor), levando a alterações microestruturais não adequadas. Contudo esta é uma região de difícil estudo devido a sua pequena dimensão e grandes gradientes térmicos. Assim, a fim de superar esta limitação com relação ao estudo da ZAC, existem na literatura proposições de máquinas de simulação física, que fazem uso do Efeito Joule para o aquecimento de determinados corpos de prova, que se resfriam por condução e convecção, de forma a simular o ciclo térmico obtido por soldagem real. Entretanto, o uso de corpos de provas cilíndricos apresenta restrições em retratar o caso real. Nesta opção de geometria cilíndrica, os ciclos térmicos não apresentam gradientes de temperatura que sejam fiéis àqueles encontrados em uma soldagem. Desta forma, foram realizadas simulações numéricas em elementos finitos, variando-se a geometria dos corpos de prova, de forma a obter ciclos térmicos o mais próximos da realidade para uma posterior simulação física. Esta abordagem de variação da geometria do corpo de prova calculada via simulação numérica mostrou-se adequada, onde os resultados obtidos pela simulação física e numérica mostraram-se coerentes. Como forma de validar os resultados finais obtidos via simulação física, ao invés de se conduzir soldagens reais, o que seria mais intuitivo, optou-se pelo levantamento de Diagramas CCT (Transformação em Resfriamento Contínuo) dedicados à soldagem. Este direcionamento tem a vantagem de se, concomitantemente à validação da simulação física, atingir resultados tecnologicamente muito importantes que são as curvas CCT de difícil acesso na literatura. Conclui-se pela viabilidade da simulação física em retratar a ZAC e pela viabilidade em se conseguir Diagramas CCT para soldagem. / Mestre em Engenharia Mecânica
42

Relação entre funções cognitivas e perdas adquiridas na visão de cores de pacientes com esclerose múltipla tipo remitente recorrente / Relationship between cognitive functions and acquired color vision loss in patients with relapsing-remitting type of multiple sclerosis

Rosaní Aparecida Antunes Teixeira 12 September 2012 (has links)
A Esclerose Múltipla (EM) é uma doença inflamatória autoimune caracterizada por desmielinização e degeneração do sistema nervoso central (SNC) duas a três vezes mais frequente em mulheres. A etiologia da EM é dividida em dois subtipos principais: o tipo remitente-recorrente (EMRR) mais comum, caracterizado por dois ou mais episódios de agravamento dos sintomas que envolvem diferentes locais do SNC, separados por pelo menos 1 mês e remisão dos sintomas e o tipo progressivo é a forma menos comum, caracterizada por um contínuo agravamento dos sintomas desde o início geralmente sem recaídas claras ou remissões. A presente pesquisa teve por objetivo avaliar o comprometimento da visão de cores e de sua relação com perdas de atenção, memória visual imediata, memória visual tardia, memória operacional e funções executivas dos portadores de esclerose múltipla tipo remitente recorrente. Método: participaram 41 pacientes com esclerose múltipla de idades entre 20 e 58 anos (35,4±12,2) e 37 controles com idade (34,7±12,1) e escolaridade semelhante. A discriminação de cores foi avaliada com o Cambridge Colour Test (CCT) e a avaliação de funções neuropsicológicas foram utilizados subtestes da bateria Cambridge Neuropsychological Testing Automated Battery (CANTAB) - Pattern Recognition Memory, Spatial Span, Spatial Recognition Memory, Information Sampling Task, Stop Signal Task e Rapid Information Processing; Escalas de Depressão e Ansiedade de Beck e Escala de Determinação Funcional da Qualidade de vida (DEFU). Resultados: A visão de cores está prejudicada de forma difusa em 24% dos pacientes com esclerose múltipla, tanto em pacientes com histórico de neurite óptica quando em pacientes que não tiveram neurite óptica. Na parte cognitiva, os pacientes demonstraram lentidão em executar as tarefas, comprometimento na atenção, na memória visual de curto e longo prazo, na memória operacional, na memória visuoespacial, além de lentidão no processamento de informações. Há uma relação entre alterações na visão de cores e alterações de memória visual somente em testes em que os estímulos são complexos e com inúmeros detalhes / Multiple sclerosis (MS) is an autoimmune inflammatory disease characterized by demyelination and central nervous system (CNS) degeneration. It is two times more frequent in women. It can be presented in two subtypes: the relapsing-remitting (RR), most common type, characterized by two or more episodes of focal disorders in different sites of the CNS, and remission of the symptoms; and the progressive subtype, less common, characterized by a continuous worsening of the symptoms, since the beginning, usually with no remissions. The present research evaluated color vision impairment and its relationship to attention loss, short-term memory, long-term memory, working memory and executive function in patients with the relapsing-remitting MS type. Methods: 41 patients with multiple sclerosis (20 to 58 years, 35.4 ± 12.2 in average) and 37 controls matched to age (34.7 ± 12.1 in average) and years of education participated of the study. Color vision was tested using the Cambridge Colour Test (CCT) and the neuropsychological assessment was performed using tests of the Cambridge Neuropsychological Testing Automated Battery (CANTAB) - Pattern Recognition Memory, Spatial Span, Spatial Recognition Memory, Information Sampling Task, Stop Signal Task, Rapid Information Processing the Beck Depression and Anxiety Inventories and the Functional Assessment of Multiple Sclerosis quality of life instrument. Results: Color vision was diffusely impaired in 24% of the MS patients, with or with no history of optic neuritis. Patients also showed a delay during the tasks execution, impairment in attention, short and long-term visual memory and working memory, and slowness in the information processing. There was a relationship between color vision loss and visual memory impairment, but only in tests with complex and highly detailed stimuli
43

Basinkomst – en modell för Sverige? : En litteraturstudie om vilka resultat som hittills framkommit i de experiment med basinkomst som gjorts runtom i världen, och om ett sådant transfereringssystem skulle kunna passa ”den svenska modellen”

Westberg, Henrik January 2016 (has links)
The purpose of this review is to summarize the experiments that have been presented regarding guaranteed Basic Income, performed around the world; to see if a BI might fit into ”the Swedish model”; and what further research would be needed to understand the mechanics of BI. A theory has been used, designed to compare the effects of cash transfer programs irrespective of economic level of the countries. The experiments show many similarities, such as improved school attendance and achievements, improved health, enhanced economic equality, a sense of inclusion and security, and also, where this has been studied, less crime. Where BI has been beneath the level of economic sustenance a growth of working hours including self employment has been noted, whereas in countries with an income high enough to sustain oneself a slight diminished work supply has been reported. The effects shown in the review seem to be well aligned with the visions of the Swedish welfare state, although might not be in alignment with the growing use of “work fare” in Sweden. Further research should focus on more long-lasting experiments and also to find a common ground, on which to perform them to be able to compare results.
44

Une approche socio-anthropologique de la consommation collaborative : focus sur les nouveaux rapports à la propriété / A socio-anthropological perspective on collaborative consumption : New representations of ownership

Dabadie, Isabelle 04 December 2017 (has links)
La consommation collaborative désigne un ensemble de pratiques très variées – parmi lesquelles la location, le prêt, le don, le troc ou le partage entre consommateurs –, qui remettent en question la primauté accordée à la propriété individuelle. Ce phénomène en plein essor fait l’objet de nombreuses recherches tentant de définir, de cartographier ou d’expliquer le phénomène, en identifiant ses déterminants ou en évaluant ses impacts. Peu de travaux se sont penchés sur l’arrière-plan culturel de ce mouvement. C’est l’objet de ce travail, qui étudie la consommation collaborative dans une perspective anthropologique, autour de la question, centrale, du rapport à la propriété. Cette recherche, ancrée dans la Consumer Culture Theory (CCT), adopte une approche phénoménologique centrée sur le sens des expériences vécues par les consommateurs. Elle s’appuie au plan empirique sur une ethnographie menée sur trois terrains reflétant la diversité des pratiques collaboratives – l’habitat participatif, la plaisance collaborative et les bibliothèques de vêtements. Et elle a pour première assise théorique la mobilisation d’un cadre d’analyse original – l’infrastructure cosmologique –, inspiré des travaux de Stoczkowski (2008), qui permet de révéler les traits saillants d’une vision du monde. Les résultats mettent en lumière l’émergence, au sein d’un mouvement qui reste largement consumériste, d’une contre-culture, proche de la simplicité volontaire, caractérisée par un rapport nouveau à la propriété, dans laquelle celle-ci n’est pas simplement remplacée par l’usage mais se charge d’un sens différent. Nous l’avons nommée « cosmologie de l’alter-possession ». Cette recherche permet de mieux comprendre les comportements de consommateurs qui entretiennent un rapport ambivalent aux possessions, entre détachement et recherche de liens durables, et aspirent à des formes de propriété plus ouvertes et plus collectives en réponse aux enjeux sociaux et environnementaux d’un monde aux ressources finies. / Collaborative consumption refers to a highly varied range of practices – including rentals, loans, gifts, bartering and sharing between consumers – that challenge the primacy of individual ownership. This rapidly growing phenomenon has been the subject of many research studies that have attempted to define, map or explain it by identifying its determinants or evaluating its impact. Few researchers have focused on the cultural background to this movement. That is the focus of this study, which studies collaborative consumption from an anthropological perspective, looking at the central question of our relationship with ownership. This research, rooted in Consumer Culture Theory (CCT), adopts a phenomenological approach centred on the meaning of consumer experiences. In empirical terms, it uses an ethnographic study conducted in three different fields that reflect the diversity of collaborative practices: co-housing, collaborative pleasure boating and clothes libraries. Its main theoretical foundation is the use of an original analytical framework – cosmological infrastructure, inspired by the work of Stosczkowski (2008) – which highlights the salient traits of a particular worldview. The results reveal the emergence, within a movement that remains largely consumeristic, of a counterculture that is comparable to voluntary simplicity and characterised by a new relationship with ownership, which, for proponents of this counterculture, is not only replaced by the notion of usage but is also charged with different meaning. We call this the “cosmology of alter-possession”. This research provides a better understanding of the behaviour of consumers who maintain an ambivalent relationship with possessions, somewhere between detachment and the search for lasting links, and aspire to more open and collective forms of ownership in response to the social and environmental challenges in a world with finite resources.
45

REGULATION OF L-TYPE VOLTAGE-DEPENDNET CALCIUM CHANNELS BY THE REM GTPASE

Pang, Chunyan 01 January 2008 (has links)
The Rem, Rem2, Rad, and Gem/Kir GTPases, comprise a novel subfamily of the small Ras-related GTP-binding proteins known as the RGK GTPases, and have been shown to function as potent negative regulators of high voltage-activated (HVA) Ca2+ channels upon overexpression. HVA Ca2+ channels modulate Ca2+ influx in response to membrane depolarization to regulate a wide variety of cellular functions and they minimally consist of a pore-forming α1 subunit, an intracellular β subunit, and a transmembrane complex α2/δ subunit. While the mechanisms underlying RGK-mediated Ca2+ channel regulation remain poorly defined, it appears that both membrane localization and the binding of accessory Ca2+ channel β subunits (CaVβ) are required for suppression of Ca2+ channel currents. We identified a direct interaction between Rem and the L-type Cavα1 C-terminus (CCT), but not the CCT from CaV3.2 T-type channels. Deletion mapping studies suggest that the conserved CB-IQ domain is required for Rem:CCT association, a region known to contribute to both Ca2+-dependent channel inactivation and facilitation through interactions of Ca2+-bound calmodulin (CaM) with the proximal CCT. Furthermore, both Rem2 and Rad GTPases display similar patterns of CCT binding, suggesting that CCT represents a common binding partner for all RGK proteins. While previous studies have found that association of the Rem C-terminus with the plasma membrane is required for channel inhibition, it is not required for CaVβ- subunit binding. However, Rem:CCT association is well correlated with the plasma membrane localization of Rem and more importantly, Rem-mediated channel inhibition upon overexpression. Moreover, co-expression of the proximal CB-IQ containing region of CCT (residues 1507-1669) in HIT-T15 cells partially relieves Rem blockade of ionic current. Interestingly, Ca2+/CaM disrupts Rem:CCT association in vitro. Moreover, CaM overexpression partially relieves Rem-mediated L-type Ca2+ channel inhibition and Rem overexpression alters the kinetics of calcium-dependent inactivation. Together, these data suggest that the association of Rem with the CCT represents a crucial molecular determinant for Rem-mediated L-type Ca2+ channel regulation and provides new insights into this novel channel regulatory process. These studies also suggest that instead of acting as complete Ca2+ channel blockers, RGK proteins may function as endogenous regulators for the channel inactivation machinery.
46

The difficulty of predicting risky decisions : - An experiment investigating present and future affective states influence on risk-taking

Nilsson, Lisa January 2019 (has links)
Affect and feelings states influences decision-making and risk-taking, however is it not clear yet how. This report presents a between-subject experiment on the two mechanisms, affective evaluation and affect regulation, and on how risk-taking redirects depending on which of the two is active. Incidental affect (positive, negative or neutral) was induced by pictures in an online experiment with 999 participants, who conducted the Columbia Card Task (CCT) to measure the risk-taking. The participants were informed prior to the task that gambling either makes people happy (mood-lifting cue), sad (mood-threatening cue) or has no effect on people’s mood (mood-freezing cue). The predicted results in this experiment was not found. However, the results indicate that mood changing qualities of a task can be manipulated and that further research about the interaction between incidental and integral affect is needed. The results also displayed how fleeting induced affect can be and consciousness about what affect is used is discussed.
47

Optimization Studies to Improve MSC-based Cardiac Cell Therapy : Cytokine Preconditioning and Nanoparticle Coupling

Zhou, Wanjiang 12 1900 (has links)
Contexte: La cardiopathie ischémique (IHD) reste une cause majeure de mortalité en Amérique du Nord. La thérapie cellulaire cardiaque (CCT) a émergé comme une thérapie prometteuse pour aider à guérir certaines malades cardiaques. Parmi les cellulaires avec propriétés pluripotentes, les cellules stromales mésenchymateuses (MSC) sont prometteuses. Cependant, plusieurs questions demeurent non résolues et certaines défis empêchent l'application clinique de la CCT se dans l'IHD, tels que le faible taux de rétention cellulaire in situ, le suivi des cellules in vivo post-implantation et post-acheminements et l`apoptose. Ici, le traitement préliminaire des MSC avec des facteurs de croissance et leur couplage avec des nanoparticules (NP) seront étudiés comme des méthodes pour optimiser MSC. Méthodes: Des MSCs provenant du rat (rMSC) et du cochon (pMSC) ont été isolés à partir de moelle osseuse. Les rMSC ont été préconditionnées avec SDF-1a, TSG-6 et PDGF-BB, et ensuite soumises à une hypoxie, une privation de sérum et a un stress oxydatif. Des études de cicatrisation ont également été effectués avec rMSCs préconditionnées. En parallèle, de nouvelles NP ferromagnétiques liées aux silicones ont été synthétisées. Les NPs ont été couplées aux pMSCs suivant leur fonctionnalisation avec l`anticorps, CD44, un antigène de surface du MSC bien connu. Par la suite, les études de biocompatibilité ont été réalisées sur pMSC-NP et en incluant des tests des processus cellulaires tels que la migration, l'adhésion, la prolifération et les propriétés de la différenciation. Résultats: Parmi toutes les cytokines testées, PDGF-BB a démontré la plus grande capacité à améliorer la survie de MSC dans des conditions d'hypoxie, de privation de sérum et en reponse au stress oxydatif. La conjugaison de NP a atténué la migration et la prolifération des pMSCs, mais n`a pas changé leur capacité de différenciation. Enfin, la complexe du MSC-NP est détectable par IRM. Conclusion: Nos données suggèrent que de nouvelles stratégies, telles que traitement préliminaire de PDGF-BB et le couplage des nanoparticules ferromagnétiques, peuvent être considérés comme des avenues prometteuse pour optimiser les MSCs pour la CCT. / Background: Ischemic heart disease (IHD) remains a leading cause of mortality in North America. Cardiac cell therapy (CCT) has emerged as a promising therapy to help heal the damaged heart. Among the various candidates for stem-progenitor cells, Mesenchymal Multipotential Stromal/Stem Cells (MSC) is of great promise. However, there remain unresolved issues and challenges that prevent clinical application of MSC-based CCT in IHD. Among the latter, low cellular retention rate, in vivo cell tracking and post-delivery apoptosis. Here in, growth factor preconditioning and MSC coupling to nanoparticles are investigated as methods to optimize MSC. Methods:Lewis Rat MSC (rMSC) and pig MSC (pMSC) were isolated from bone marrow. Rat MSCs were preconditioned with SDF-1a, TSG-6 and PDGF-BB, and then subjected to hypoxia, serum deprivation and oxidative stress. Wound healing assays were also done with preconditioned rat MSCs. In parallel, novel ferromagnetic silicone core-shell nanoparticles (NP) were synthesized. Pig MSCs were coupled to NPs following functionalization of the NPs with an antibody to a well-recognized MSC surface antigen, CD44. Subsequently, biocompatibility studies were performed on the pMSC-NP complex and included testing of key cellular processes such as migration, adhesion, proliferation and differentiation properties. Results: Of all cytokines used, PDGF-BB showed greatest capacity to improve MSC survival under conditions of hypoxia, serum deprivation and oxidative stress. NP conjugation has mitigated effect on the migration and proliferation of pig MSC, but do not change the differentiation capacity of MSC. Finally, the MSC-NP complex was detectable by MRI. Conclusion: Our data suggest that novel strategies, such as PDGF-BB preconditioning and ferromagnetic nanoparticle coupling, can be considered as promising avenues to optimize MSCs for CCT.
48

Anti-Poverty Policy as the Cultivation of Market Subjects: The Case of the Conditional Cash Transfer Program Oportunidades

Cannon, Kailey L. 21 February 2014 (has links)
My thesis explores the conceptual underpinnings of the acclaimed Mexican conditional cash transfer (CCT) program Oportunidades as a way of engaging broader debates about how anti-poverty policy is evolving in the wake of the World Bank’s mid-1990s legitimacy crisis. I am interested in the behaviours and attitudes—or “subjectivities”—that Oportunidades attempts to cultivate amongst participants. Whereas the majority of CCT studies tend to focus on measuring the extent to which the programs “mold” beneficiaries into the categories of being prescribed by the program, my thesis is concerned with specifying and critically examining these categories. I use a hybrid neo-Gramscian, governmentality and critical feminist theoretical framework to probe how Oportunidades beneficiaries are constructed within World Bank and Mexican government discourse, as well as in external program evaluations. I argue that Oportunidades is underpinned by an agent-centred conception of poverty and that the program promotes a kind of gendered market-conducive subjectivity amongst beneficiaries. I conclude by exploring some of the implications of the CCT model. Ma thèse explore les fondements conceptuels du Oportunidades, un programme de transferts conditionnels de fonds (TMC) Mexicain acclamé. J’utilise les TMC comme une ouverture pour élargir le débat sur la manière dont la politique anti-pauvreté évolue dans le sillage de la crise de légitimité à laquelle la Banque Mondiale a fait face dans le milieu des années 1990. Je m'intéresse aux types de comportements et d'attitudes—ou «subjectivités»—que Oportunidades essaye de cultiver chez les participants. Alors que la majorité des études sur les TMC focalisent sur l’évaluation des succès du programme à modeler les participants afin qu’ils entrent dans les catégories de personnes prescrites par le programme, mon but est la spécification et l'examen critique de ces catégories. J'utilise un cadre théorique hybride qui combine néo-gramsciennes, la gouvernementalité et des théories féministes critiques pour enquêter sur la façon dont les bénéficiaires du programme Oportunidades sont construits à l’intérieur du discours de la Banque Mondiale, du gouvernement mexicain, ainsi que dans les évaluations externes du programme. Je soutiens qu’il y a, dans le programme Oportunidades, une conception sous-entendu de la pauvreté centrée sur les comportements des individus et que le programme promeut une subjectivité sexuée des bénéficiaires qui facilite leur participation au marché. Je conclus en explorant quelques implications du modèle TMC.
49

Compensadores estáticos de reativos empregados em redes de baixa tensão com geradores distribuídos de energia / Static var compensators applied in low voltage grids with distributed generators

Almeida, Felipe Augusto Ferreira de [UNESP] 03 November 2016 (has links)
Submitted by Felipe Augusto Ferreira de Almeida null (felipeafalmeida@gmail.com) on 2016-12-20T16:56:04Z No. of bitstreams: 1 DISSERTACAO_FELIPE_FINAL.pdf: 3666708 bytes, checksum: 18899b06cbe9a7091fd3f037b0656174 (MD5) / Approved for entry into archive by Felipe Augusto Arakaki (arakaki@reitoria.unesp.br) on 2016-12-22T10:53:09Z (GMT) No. of bitstreams: 1 almeira_faf_me_bauru.pdf: 3666708 bytes, checksum: 18899b06cbe9a7091fd3f037b0656174 (MD5) / Made available in DSpace on 2016-12-22T10:53:09Z (GMT). No. of bitstreams: 1 almeira_faf_me_bauru.pdf: 3666708 bytes, checksum: 18899b06cbe9a7091fd3f037b0656174 (MD5) Previous issue date: 2016-11-03 / Instituto Federal de Educação, Ciência e Tecnologia de São Paulo (IFSP) / Este trabalho aborda o emprego do Compensador Estático de Reativos (SVC) em redes de baixa tensão com geração distribuída de energia, tendo como objetivo a compensação de tensão e de fator de potência. Os principais distúrbios de qualidade de energia elétrica em baixa tensão, bem como as normas e os limites operacionais para os principais indicadores foram revisados, visando confrontação com as situações resultantes da integração do SVC no sistema elétrico. O SVC possui operação estabelecida como carga reativa controlável em sistemas de transmissão de energia, fazendo parte dos condicionadores da tecnologia FACTS (Flexible AC Transmission Systems). A exploração desta tecnologia em outro nível de tensão é o objetivo deste trabalho. As análises foram realizadas através de simulações computacionais, desenvolvidas no ambiente MATLAB, contemplando o desenvolvimento de modelos relacionados com aplicações de RCT (Reator Controlado a Tiristor), FC (Capacitor Fixo), do CCT (Capacitor Chaveado a Tiristor) e de um sistema de geração distribuída de energia elétrica trifásico em uma rede de baixa tensão a quatro fios. A metodologia para o dimensionamento dos elementos passivos dos condicionadores é apresentada, bem como a análise dos valores de potência reativa, fator de potência, distorções harmônicas e a avaliação da necessidade de utilização ou não de filtros passivos. A teoria da potência conservativa (TPC) é a metodologia utilizada para definição das grandezas elétricas e fatores de conformidade. Por fim, as características operacionais de um SVC aplicado a uma rede de baixa tensão a quatro fios são exploradas através dos resultados de simulação, com o objetivo de demonstrar a manutenção de suas características operacionais estabelecidas, no nível de baixa tensão, e apontar aspectos diferenciados quanto à regulação de fator de potência e da forma de tensão providos pelo SVC, para servir como informação de confronto frente a outras tecnologias comumente utilizadas neste nível de tensão. / This paper discusses the use of Static Var Compensator (SVC) on low voltage grids with distributed generation with the aim of voltage and power factor compensation. The main electrical power quality disturbances at low voltage as well as the rules and operational limits for the main indicators were reviewed aiming to confront the situations resulting from SVC integration in the electrical system. SVC has established operation as controllable reactive load in power transmission systems, being part of FACTS (Flexible AC Transmission Systems) technology conditioners. The application of this technology in another level of tension is the objective of this work. The analyzes were carried out through computer simulations developed in the MATLAB environment, including the development of models related to RCT (Thyristor Controlled Reactor), FC (Fixed Capacitor), CCT (Thyristor Switching Capacitor) and a threephase electric power distributed generation system in a four-wire low voltage grid. The methodology for the dimensioning of the passive elements of the conditioners is presented, as well as the analysis of the values of reactive power, power factor, harmonic distortions and the evaluation of the need to use passive filters. The conservative power theory (CPT) is the methodology used to define the electrical magnitudes and compliance factors. Finally, the operational characteristics of a SVC applied to a low-voltage four-wire network are exploited through the simulation results, in order to demonstrate the maintenance of its established operational characteristics at the low voltage level and to point out different aspects as well as the power factor regulation and voltage form provided by the SVC, to serve as confronting information.
50

Goldmann tonometer error correcting prism: clinical evaluation

McCafferty, Sean, Lim, Garrett, Duncan, William, Enikov, Eniko, Schwiegerling, Jim, Levine, Jason, Kew, Corin 05 1900 (has links)
Purpose: Clinically evaluate a modified applanating surface Goldmann tonometer prism designed to substantially negate errors due to patient variability in biomechanics. Methods: A modified Goldmann prism with a correcting applanation tonometry surface (CATS) was mathematically optimized to minimize the intraocular pressure (IOP) measurement error due to patient variability in corneal thickness, stiffness, curvature, and tear film adhesion force. A comparative clinical study of 109 eyes measured IOP with CATS and Goldmann prisms. The IOP measurement differences between the CATS and Goldmann prisms were correlated to corneal thickness, hysteresis, and curvature. Results: The CATS tonometer prism in correcting for Goldmann central corneal thickness (CCT) error demonstrated a reduction to <+/- 2 mmHg in 97% of a standard CCT population. This compares to only 54% with CCT error <+/- 2 mmHg using the Goldmann prism. Equal reductions of similar to 50% in errors due to corneal rigidity and curvature were also demonstrated. Conclusion: The results validate the CATS prism's improved accuracy and expected reduced sensitivity to Goldmann errors without IOP bias as predicted by mathematical modeling. The CATS replacement for the Goldmann prism does not change Goldmann measurement technique or interpretation.

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