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Santiago, Pelaez Zapata Daniel. "Beyond the Sea Surface : Exploring Ocean Wave Measurements From Multiple Perspectives." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASM004.
Повний текст джерелаАнотація:
Cette thèse explore les mesures de vagues océaniques sous plusieurs perspectives, étendant l'analyse au-delà de leur manifestation visuelle à la surface de la mer. Les limitations existantes dans les technologies de mesure entravent une compréhension complète d'aspects tels que le spectre directionnel des vagues, les processus de déferlement et les essaims de bulles générées par les vagues. Cette étude intègre des données provenant de différentes plates-formes, y compris de capteurs installés au fond, de bouées de surface et de satellites, abordant les limitations de couverture spatiale et temporelle. Une nouvelle technique basée sur la transformation en ondelettes pour l'estimation du spectre directionnel de vagues est présentée, montrant des performances cohérentes et des avantages par rapport aux méthodes conventionnelles. L'analyse de la propagation directionnelle des vagues révèle des distributions étroites au pic spectral et un élargissement asymétrique aux fréquences plus basses et plus élevées. La thèse compare également les données des bouées GPS avec les observations satellitaires de la mission CFOSAT/SWIM. Les propriétés acoustiques des vagues océaniques sont examinées à travers des mesures d'essaims de bulles, révélant une relation entre la vitesse du vent, la profondeur de l'essaim de bulles et la couverture d'écume. Le rôle de la circulation de Langmuir dans le transport des essaims de bulles est mis en évidence. Le bruit sous-marin et sa corrélation avec les variables environnementales sont étudiés à l'aide d'un hydrophone monté sur le fond. Dans l'ensemble, la thèse fournit une description complète des vagues océaniques, offrant des perspectives précieuses sur les interactions complexes entre l'air et la merThis thesis explores ocean wave measurements from multiple perspectives, extending the analysis beyond their visual manifestation on the sea surface. Existing limitations in measurement technologies hinder a full understanding of aspects such as directional wave spectrum, wave breaking processes, and wave-induced bubble plumes. This study integrates data from various platforms, including bottom-mounted sensors, surface buoys, and satellites, addressing spatial and temporal coverage limitations. A novel wavelet-based technique for directional wave spectrum estimation is presented, showing consistent performance and advantages over conventional methods. Analysis of directional wave spreading reveals narrow distributions at the spectral peak and asymmetric broadening at lower and higher frequencies. The thesis also compares GPS buoy data with satellite-based observations from the CFOSAT/SWIM mission. The acoustic properties of ocean waves are examined through measurements of bubble plumes, revealing a relationship between wind speed, bubble plume depth, and whitecapping coverage. The role of Langmuir circulation in transporting bubble plumes is highlighted. Underwater noise and its correlation with environmental variables are investigated using a bottom-mounted hydrophone. Overall, the thesis provides a comprehensive description of ocean waves, offering valuable insights into complex air-sea interactions
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Bilson, Richard C. "Implementing overload and polymorphism in Cforal." Waterloo, Ont. : University of Waterloo, [Dept. of Computer Science], 2003. http://etd.uwaterloo.ca/etd/rcbilson2003.pdf.
Повний текст джерелаАнотація:
Thesis (M.Math.)--University of Waterloo."A thesis presented to the University of Waterloo in fulfillment of the thesis requirement for the degree of Master of Mathematics in Computer Science". Includes bibliographical references.
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Aspler, Julia, and Elsa Axelsson. "The role of CFOs in family business acquisitions." Thesis, Internationella Handelshögskolan, Jönköping University, IHH, Företagsekonomi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-48620.
Повний текст джерелаАнотація:
Abstract Background & Problem: Many family firms face a change in ownership in the near future. Acquisitions of family firms can therefore be a solution for the change in ownership. Due to special family firm characteristics, acquisitions of such companies can be complicated. Previous research shows that accountants and CFOs have a positive effect on the firm’s survival and growth. However, the CFOs’ roles in family business acquisitions have not been studied before. Purpose: The purpose of this research is to explore what roles accountants and CFOs have in acquisitions of family firms. Method: The base of this study is an abductive research approach with a qualitative research strategy. The main method was semi-structured interviews that was complemented with a document study of official documents from websites. Conclusion: The empirical findings and analysis revealed that the CFOs in family firm acquisitions are important, but the CFOs’ roles in acquirer and acquiree differ. The CFOs in the selling family business is more of a bean counter in the process and provide material. The CFOs in the acquiring group is more of a business partner, conducting analyses and are involved in strategic decisions. The process of acquiring family firms is a special situation for the CFOs in the acquiring group since they need to adapt to the family firms’ informal culture.
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Malmros, Catrine, and Johnson Andrea. "Brandpåverkan på skyddskonstruktioner i funktionsskyddsrum : En undersökning av resthållfasthet i betongbalkar." Thesis, Mälardalens högskola, Akademin för ekonomi, samhälle och teknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:mdh:diva-40032.
Повний текст джерелаАнотація:
In the beginning of the 21st century decisions were made regarding the decommission of the total defence in Sweden. Since then the security policy situation has changed, regarding both the risk of war and other types of treats such as terrorism. Due to this the total defence is now being re-established. The Swedish Fortifications Agency and Research Institutes of Sweden (RISE) has initiated the Centre of excellence for fortification (CFORT) to support the development of competence in fortification. In case of a crisis or war secured function shelters constitutes a significant part of the Swedish total defence by protecting important technology and activity.The purpose of this bachelor thesis is to investigate the remaining load bearing capacity in concrete constructions in secured function shelters after exposure to fire. This will provide a foundation for further research within the area of the effects of fire in secured function shelters. To achive this, experiments were conducted on nine concrete beams which were casted according to calculations based on the structural codes of the Swedish Fortifications Agency (FKR). Since fully scaled beams are difficult to manage and would not fit in the equipment being used, the beams were casted in a smaller size; 2000 x 150 x 210 mm. Samples of the concrete and the reinforcement were sent to the Swedish Cement and Concrete Research Institute (CBI) for tests which provided actual values of the compressive strength, yield point and modulus of elasticity. Six of the beams were in pairs exposed to fire in a specially built oven according to three different temperature curves. All the beams were later subjected to load until failure. Calculations regarding load bearing capacity were executed with both theoretical and actual values obtained from CBI. The results were compared to the results from the loading tests. During the last fire experiment the beams spalled, most likely due to the quickly rising temperature. The loading test showed that the strength of the beams which had not spalled were not significantly lower than the unaffected beams. Those beams showed a reduction of only 0 – 6 %. However, the beams which had spalled showed a reduce in strength of approximately 20 %.Centrum för fortifikatorisk kompentens
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Alsuhaibani, Azzam A. "The Impact of Social Ties between CEOs and CFOs on Financial Reporting Quality." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1532084149612262.
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Dimitrov, Dara K. "The Creation of Sustainable Development: What it means to CFOs in New Zealand." The University of Waikato, 2009. http://adt.waikato.ac.nz/public/adt-uow20090304.163356/index.html.
Повний текст джерела
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Nolli, Luciana Marangni. "Ayahuasca : potencial terapêutico na dependência ao álcool e atividade neural da proteína cFOS em modelo experimental." reponame:Repositório Institucional da UnB, 2018. http://repositorio.unb.br/handle/10482/34164.
Повний текст джерелаАнотація:
Dissertação (mestrado)—Universidade de Brasília, Faculdade de Ciências da Saúde, Programa de Pós-Graduação em Ciências Farmacêuticas, 2018.Fundação de Apoio à Pesquisa do Distrito Federal (FAP-DF).
As opções farmacológicas para o tratamento do alcoolismo possuem limitações, e estudos em humanos têm mostrado ser a ayahuasca, uma bebida psicoativa ancestral de uso religioso/ritualístico com ação serotoninérgica, uma possível opção terapêutica. Os objetivos deste estudo foram avaliar o impacto da ayahuasca no consumo de álcool por ratos Wistar que consumiram álcool durante 8 semanas segundo o protocolo IA2BC (intermittent access to 2-botttle choice), avaliar a expressão da proteína cFos e substância Nissl em regiões cerebrais relevantes no processo de dependência e o comportamento dos animais nos testes de campo aberto e labirinto em cruz elevado. Na 8o semana do protocolo IA2BC, os ratos foram divididos em 5 grupos de 12 animais e tratados por 5 dias com H2O (controle), naltrexona, um antagonista opioide utilizado no tratamento da dependência, ou com ayahuasca (Aya) nas doses 0,5, 1 e 2 X a dose ritualística. Um grupo sadio (n=4) não exposto ao álcool foi sacrificado na 7º semana e os outros grupos 18 dias depois do tratamento. O tratamento com naltrexona ou ayahuasca não diminuíram o consumo de álcool com relação à linha de base (7º. Semana), mas o consumo foi menor no grupo naltrexona em relação ao grupo H2O. A exposição ao álcool aumentou a expressão da cFos em todas as áreas cerebrais, de maneira significante principalmente no cortex medial pré-frontal e núcleo accumbens. Com relação ao grupo controle H2O, a cFos foi signficativamente menor no cortex medial pré-frontal para o grupo Aya0,5. O tratamento com naltrexona aumentou signficativamente a expressão de cFos no núcleo accumbens e estriado em relação ao grupo controle. A exposição ao álcool aumentou a densidade de corpusculos de Nissl nas regiões neurais investigadas para os grupos H2O, naltrexona e Aya2, grupos que também apresentaram aumento do peso do cérebro em relação ao grupo sadio. O tratamento com a naltrexona ou ayahuasca não tiveram impacto significativo no comportamento dos ratos expostos ao álcool nos testes comportamentais. O potencial da ayahuasca no tratamento da dependência ao álcool deve ser melhor investigado utilizando outros protocolos de exposição e tratamento. Adicionalmente, o aumento da expressão da cFos no estriado e núcleo accumbens em animais tratados com naltrexona (significativo) e ayahuasca não era esperado, e demanda estudos futuros.
Pharmacological options to treat alcohol addiction are limited, and human studies have demonstrated that ayahuasca, an ancestral infusion with serotoninergic action used in religious ceremonies, has a potential use in the treatment. The objectives of this studies were to evaluate the effect of ayahuasca treatment on alcohol consumption of Wistar rats exposed to alcohol during 8 weeks according to the IA2BC protocol (intermittent access to 2-bottle choice), evaluate the cFos expression and Nissl substance in neural areas relevant to chemical addiction, and the animal behavior in the open field and elevated plus-maze tests. On the 8th week of the IA2BC protocol, the animals were divided in 5 groups of 12 animals and treated daily for 5 days with H2O, naltrexone, an opioid antagonist used to treat alcohol addiction, and ayahuasca (Aya) at the 0.5, 1 or 2x the religious doses. A naïve group (n=4) not exposed to alcohol was sacrificed at the end of the 7th week and the other groups 18 hours after the last treatment. Treatment with either naltrexone or ayahuasca did not decrease the alcohol consumption compared to the baseline (7th week), but the consumption in naltrexone treated rats was significantly lower compared to the H2O group. Exposure to alcohol increase cFos expression in all regions, an increase that was significant mainly in the medial orbital cortex and accumbens nu, core regions. cFos was significantly lower in the Aya0.5 group compared with the H2O group in the medial orbital cortex. There was a significant increase in the cFos in the accumbens nu core and striatum for the naltrexone group. The exposure to alcohol increased the number of Nissl substance in the H2O, naltrexone and Aya2 groups, which also showed an increased brain weight compared to the naïve group. Treatment with naltrexone or ayahuasca did not have significant impact on the behavior of the animals in both tests. The potential of ayahuasca treatment on alcohol addiction/consumption needs to be further investigated using other treatment protocols. In addition, the increase of cFos in the accumbens nu core and striatum in rats treated with naltrexone (significant) or ayahuasca was not expected and also requires further investigation.
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Han, Feng. "Tournament Incentives vs. Equity Incentives of CFOs: The Effect on Firms' Risk Taking and Earnings Management." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc984224/.
Повний текст джерелаАнотація:
My dissertation consists of two essays on CFOs' promotion-based tournament incentives and performance-based equity incentives. The first essay examines the joint implications of CFOs' tournament incentives and equity incentives for firms' risk-taking. With the pay gap between the CEO and the CFO as the proxy for the CFO's tournament incentives, I find that the relationship between a firm's risk taking and the CFO's tournament incentives is non-monotonic. In particular, I show that below a certain level, increase in pay gap is associated with increase in firm risk taking (e.g., higher leverage, lower cash holding balance and higher R&D intensity). However, after reaching a certain level, the CEO-CFO pay gap negatively impacts risk-taking, as increase in pay gap is associated with lower leverage, higher cash holding balance and lower R&D intensity. With the CFO's pay-performance sensitivity as the proxy for the CFO's equity incentives, I find that the CFO's equity incentives negatively impact firm's R&D intensity, but have no significant impact on broader financial decisions such as capital structure and cash policy. Collectively, my findings indicate that CFO incentives play an important role in firm's risk-taking behaviors, and the effect of the CFO's tournament incentives is more pronounced. The second essay studies the impact of tournament incentives and equity incentives for CFOs on firms' earnings management, including accrual-based earnings management (e.g., total accruals, abnormal accruals) and real activities manipulation (e.g., abnormal discretionary expenditures, abnormal production costs). Measuring the CFO's tournament incentives as the pay gap between the CEO and the CFO, I show that the CFO's tournament incentives positively influence total accruals and abnormal accruals. Meanwhile, the CFO's equity incentives, measured as the CFO's pay-performance sensitivity, are found positively related to real activities manipulation proxies and total accruals. My findings show a consistent pattern before and after the passage of SOX (Sarbanes-Oxley Act of 2002), but the incentives' effects on earnings management have become less significant in the post-SOX period. Overall, the CFOs' tournament and equity incentives both play an important role in earnings management, but their relative importance lies in different earnings management techniques.
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Redon, Marie. "Evolution of the CFOs along with the Financialization process in France, a study of their reciprocal relationships." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLED028/document.
Повний текст джерелаАнотація:
Cette thèse étudie l'évolution des carrières, des rôles et de l’influence des Directeurs Financiers au regard du processus de financiarisation en France. En analysant la financiarisation et les Directeurs Financiers à travers une approche institutionnaliste, cette recherche présente leurs relations réciproques depuis les années 1980. Alors que le processus de financiarisation a influencé l'évolution de la profession de Directeur Financier, ces derniers ont de leur côté contribué à la financiarisation de différentes manières. Au moyen d'une approche méthodologique mixte, basée sur 1 040 Curriculum Vitae de Directeurs Financiers et 58 entretiens, cette thèse offre une étude approfondie et à grande échelle de l'évolution des Directeurs Financiers au regard du processus de financiarisation en FranceThis dissertation investigates the evolution of the Chief Financial Officers’ (CFO) backgrounds, roles and agencies along with the financialization process in France. By studying financialization and CFOs from an institutional perspective, it presents their reciprocal relationships since the 1980s. While the financialization process has influenced the evolution of the CFO profession, CFOs also have various repercussions on financialization. Thanks to 1,040 resumes of CFOs and 58 interviews analyzed through a multiphase mixed method, this dissertation offers both a large scale and an in-depth study of the evolution of the CFOs along with the financialization process
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Anisimova, Margarita [Verfasser]. "Investigating the long-term effects of spike-timing-dependent plasticity and the activity-dependence of cFos expression in hippocampal pyramidal neurons using optogenetics : Untersuchung der Langzeiteffekte der Spike-Timing-abhängigen Plastizität und der Aktivitätsabhängigkeit der cFos-Expression in Hippocampus-Pyramiden-Neuronen mittels Optogenetik / Margarita Anisimova." Hamburg : Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky, 2020. http://d-nb.info/1225041856/34.
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Baumann, Bernd [Verfasser]. "Spezifische Funktionen von cFos bei der zellulären Antwort auf UV-Strahlung und bei der Genregulation durch extrazelluläre Stimuli / B. Baumann." Karlsruhe : KIT-Bibliothek, 1997. http://d-nb.info/1108446647/34.
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Chamelete, André [UNESP]. "Avaliação da expressão dos genes cFOS, IL-1b, CYP1a1 e CYP1b1 em Danio rerio expostos a Benzo[a]pireno e tratados com ligantes do receptor P2X7." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/134243.
Повний текст джерелаАнотація:
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
O BaP é um contaminante ambiental capaz de causar inflamação e desregulação de vias celulares. Pela ação da CYP1a1 e CYP1b1, é convertido a metabólitos mais reativos. A literatura mostra que o BaP aumenta a expressão de algumas citocinas próinflamatórias, como a IL-1, porém, são bem contraditórios os relatos sobre o efeito do BaP no cFOS, o qual apresenta papel importante na proliferação, na formação de tumores e, possivelmente, na inflamação. O objetivo deste estudo foi de elucidar a participação do receptor purinérgico P2X7 sobre a expressão dos genes IL-1 e cFOS, durante exposição ao BaP. Foi empregado as técnicas de qPCR para quantificação de expressão gênica, e testes de correlação e regressão entre IL-1 e cFOS. A exposição ao BaP induziu a expressão dos dois genes, além das enzimas do seu metabolismo. Quando bloqueado o receptor P2X7, além de uma menor indução das CYPs, os níveis de IL-1 e cFOS caíram abaixo dos níveis controle, sugerindo a participação do P2X7. Os testes de correlação e regressão mostraram uma relação forte direta entre IL-1 e cFOS, reforçando o papel do cFOS na inflamação.
BaP is an environmental contaminant capable to cause inflammation and impair cellular pathways. CYP1a1 and CYP1b1 convert it to more reactive metabolites. Studies show that BaP enhances some proinflammatory citokines expression, like IL-1, yet reports about BaP affecting cFOS, which plays important role in proliferation, tumor formation and inflammation, are controversial. This work aimed to elucidate whether P2X7 purinergic receptor plays a role in IL-1 and cFOS expression during BaP exposure. We applied qPCR techniques to quantify gene expression, correlation and regression assays. Our results showed that BaP raised both IL-1 and cFOS genes expression, besides CYPs ones. Morevoer, when blocking P2X7 receptor, IL-1 and cFOS expression dropped under normal levels, which suggest P2X7 participation, in addition to a smaller enzymes induction. Correlation and regression assays exhibited a strong straight relationship between IL-1 and cFOS expression, reinforcing the role of cFOS in inflammation.
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Pereira, Júlio Guilherme Viana Gaspar do Amaral. "Fatores que influenciam as decisões da estrutura de capital e métodos de avaliação de investimento usados pelos CFOs das empresas portuguesas." Master's thesis, Instituto Superior de Economia e Gestão, 2017. http://hdl.handle.net/10400.5/14748.
Повний текст джерелаАнотація:
Mestrado em Contabilidade, Fiscalidade e Finanças EmpresariaisO presente trabalho aborda duas temáticas com elevado grau de complementariedade na formação do valor das empresas: 1) A estrutura de capital das empresas; 2) Utilização de modelos de avaliação de investimentos. Tendo como ponto de partida o estudo de Graham & Harvey (2001) ao mercado norte-americano e canadiano, foi realizado um inquérito aos responsáveis financeiros de 142 empresas a operar no mercado português. Os resultados obtidos indicam que a dimensão, a maturidade das empresas e a rendibilidade das vendas afetam negativamente o endividamento. O grau de utilização dos métodos de avaliação de investimento manifestou-se superior no PRC, TIR e VAL. Quanto maior a dimensão e o número de anos de atividade das empresas, maior é o uso do PRC e TIR. A idade dos CFOs influenciou negativamente o uso dos diferentes métodos e a formação dos CFOs mostrou-se determinante para o maior uso dos modelos. A flexibilidade para alterar o rácio de endividamento das empresas evidenciou-se baixo. Foi clara também, uma combinação entre a maturidade da dívida e a vida útil dos ativos. O financiamento através do aumento do capital próprio e por emissão de dívida convertível foi, em geral, pouco utilizado. A Teoria Tradicionalista (Durand), a Teoria do Pecking-Order e a Teoria da Sinalização foram as que obtiveram maior nível de concordância.
This study analyzes two complementary subjects in the formation of companies? corporate value: 1) The capital structure; 2) Use of evaluation appraisal methods. Based on Graham & Harvey (2001) study of the North American and Canadian markets, a survey was conducted among financial managers of 142 companies operating in the Portuguese market. The results show that the companies' size, the maturity and the profitability negatively affect the companies' indebtedness. The degree of utilization of the evaluation appraisal methods was higher in the capital recovery factor, internal rate of return and net present value. The greater the companies' size and number of years of activity, the greater the use of capital recovery factor and internal rate of return. The age of CFOs negatively influenced the use of the different methods, the qualifications of CFOs was determinant for the greater use of the models. The flexibility to change the company debt ratio was low. Additionally, the results show a combination of debt maturity and asset life. Financing through the increase in equity and the convertible debt issuance was, in general, less used. The Traditionalist Theory (Durand), the Pecking-Order Theory and Incentive-signalling approach obtained the highest level of agreement.
info:eu-repo/semantics/publishedVersion
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Faure, Alexis. "Etude fonctionnelle des automatismes comportementaux chez le rat." Paris 6, 2005. http://www.theses.fr/2005PA066089.
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Santini, Tales Roberto de Souza. "Projeto e análise de aplicações de circuladores ativos para a operação em frequências de ultrassom Doppler de ondas contínuas." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/18/18153/tde-19082014-090655/.
Повний текст джерелаАнотація:
Os circuladores tradicionais são amplamente utilizados em telecomunicações e defesa militar para o simultâneo envio e recepção de sinais por um único meio. Esses circuitos passivos, fabricados a partir de materiais ferromagnéticos, possuem a desvantagem do aumento de dimensões, peso e custos de fabricação com a diminuição da frequência de operação definida no projeto destes dispositivos, inviabilizando sua aplicação em frequências abaixo de 500 MHz. O circulador ativo surgiu como uma alternativa aos tradicionais, tendo aplicações em frequências desde o nível DC até a ordem de dezenas de gigahertz. As suas maiores aplicações ocorrem quando são necessários dispositivos compactos, de baixo custo e de baixa potência. Os primeiros circuitos propostos possuíam uma grande limitação em termos de frequência de operação e de potência entregue à carga. Entretanto, com os avanços tecnológicos na eletrônica, tais problemas podem ser amenizados atualmente. Neste trabalho é apresentado o desenvolvimento de um circuito circulador ativo para a utilização em instrumentação eletrônica, em particular para a operação em frequências na ordem das utilizadas em equipamentos de ultrassom Doppler de ondas contínuas, na faixa de 2 MHz a 10 MHz. As possíveis vantagens da implementação de circuladores em sistemas de ultrassom estão relacionadas ao incremento da relação sinal-ruído, aumento da área de recepção do transdutor, simplificação da construção do transdutor, simplificação do circuito de demodulação/ processamento, e maior isolação entre os circuitos de transmissão e recepção de sinais. Na fase inicial, o circulador ativo proposto é modelado por equacionamento, utilizando-se tanto o modelo ideal dos amplificadores operacionais como o seu modelo de resposta em frequência. Simulações computacionais foram executadas para confirmar a validade do equacionamento. Um circuito montado em placa de prototipagem rápida foi apresentado, e testes de prova de conceito em baixas frequências foram realizados, mostrando uma grande semelhança entre o teórico, o simulado e o experimental. A segunda parte contou com o projeto do circuito circulador para a operação em maiores frequências. O circuito proposto é composto por três amplificadores operacionais de realimentação por corrente e vários componentes passivos. Uma análise de sensibilidade utilizando os métodos de Monte-Carlo e análise do pior caso foi aplicada, resultando em um perfil de comportamento frente às variações dos componentes do circuito e às variações da impedância de carga. Uma placa de circuito impressa foi projetada, utilizando-se de boas práticas de leiaute para a operação em altas frequências. Neste circuito montado, foram realizados os seguintes testes e medições: comportamento no domínio do tempo, faixa dinâmica, nível de isolação em relação à amplitude do sinal, largura de banda, levantamento dos parâmetros de espalhamento, e envio e recepção de sinais por transdutor de ultrassom Doppler de ondas contínuas. Os resultados dos testes de desempenho foram satisfatórios, apresentando uma banda de transmissão de sinais para frequências de 100 MHz, isolação entre portas não consecutivas de 39 dB na frequência de interesse para ultrassom Doppler e isolação maior que 20 dB para frequências de até 35 MHz. A faixa dinâmica excedeu a tensão de 5 Vpp, e o circuito teve bom comportamento no envio e na recepção simultânea de sinais pelo transdutor de ultrassom.Traditional circulators are widely used in both telecommunications and military defense for sending and receiving signals simultaneously through a single medium. These passive circuits which are manufactured from ferromagnetic materials, have the disadvantages of having suffered an increase in dimensions, weight, and manufacturing costs along with the decrease in the operation frequency established in the designs of such devices, thus preventing their useful employment in frequencies below 500 MHz. The active circulator emerged as an alternative to the traditional ones, and has applications on frequencies ranging from a DC level to levels involving dozens of gigahertz. It is applicable when compact devices are made necessary, at a low cost, and for low frequencies. The first circuits to be introduced had a major limitation in terms of operating frequency and power delivered to the load. However, due to technological advances in electronics, problems such as the aforementioned can now be minimized. This research work presents the development of an active circulator circuit to be used in electronic instrumentation, particularly for operation at frequencies such as those used in continuous wave Doppler ultrasound equipment, ranging from 2 MHz to 10 MHz. The advantages made possible by implementing ultrasound systems with circulators are related to an increase in the signal-to-noise ratio, an increase in the transducers reception area, a simplified construction of the transducer, simplification of the demodulation/processing circuit, and a greater isolation between the transmission circuits and signal reception. In the initial phase, the proposed active circulator was modeled by means of an equating method, using both the ideal model of operational amplifiers and the model of frequency response. Computer simulations were carried out in order to confirm the validity of the equating method. A circuit mounted upon a breadboard was introduced and proof of concept assessments were performed at low frequencies, showing a great similarity among the theoretical, simulated and experimented data. The second phase is when the circulator circuits design was developed in order make its operation at higher frequencies possible. The proposed circuit is comprised of three currentfeedback operational amplifiers and several passive components. A sensitivity analysis was carried out using Monte-Carlo methods and worst-case analyses, resulting in a certain behavioral profile influenced by variations in circuit components and variations in load impedance. A printed circuit board was designed, employing good practice layout standards so that operation at high frequencies would be achieved. The following evaluations and measurements were performed on the circuit that was assembled: time domain behavior, dynamic range, isolation level relative to signal amplitude, bandwidth, survey of the scattering parameters, and transmission and reception of signals by a continuous wave Doppler ultrasound transducer. The results of the performance tests were satisfactory, presenting a 100 MHz signal transmission band, isolation between non-consecutive ports of 39 dB at the frequency of interest to the Doppler ultrasound, and an isolation greater than 20 dB for frequencies of up to 35 MHz. The dynamic range exceeded the 5Vpp and the circuit performed satisfactorily in the simultaneous transmission and reception of signals through the ultrasound\'s transducer.
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Olímpio, Regiane Marques Castro. "Efeito da triiodotironina (T3) e estrógeno (E2) Sobre a expressão gênica e proteica de Rankl, OPG E c-Fos em osteoblastos derivados de células tronco mesenquimais humanas." Botucatu, 2017. http://hdl.handle.net/11449/151414.
Повний текст джерелаАнотація:
Orientador: Célia Regina NogueiraResumo: O tecido ósseo é extremamente complexo e regulado por fatores sistêmicos e locais, apresentando considerável atividade metabólica que envolve a remoção do osso mineralizado pelos osteoclastos, seguida pela formação da matriz óssea pelos osteoblastos. A associação de triiodotironina (T3) e estrógeno (E2) pode levar a uma resposta complexa à atividade do tecido ósseo sendo que o T3 possui efeito tanto sobre a reabsorção como na formação óssea e o E2, em baixo nível, pode levar a osteoporose e no estado normal garante a supressão de citocinas, a partir do sistema RANKL, OPG e c-Fos, que participam ativamente no remodelamento ósseo. Dessa forma, muitos estudos têm sido realizados com o objetivo de verificar a ação hormonal sobre o metabolismo ósseo. Entre essas pesquisas, têm sido isoladas células-tronco mesenquimais (CTMs) a partir do tecido adiposo humano e diferenciadas em osteoblastos. Baseado nisso, o objetivo do nosso trabalho foi avaliar o efeito do T3 e E2 nas concentrações infrafisiológica (T3I/ 10-10M e E2I/ 10-9M); fisiológicas (T3F/10-9M e E2F/10-8M) e suprafisiológicas (T3S/10-8M) separadamente e em diferentes associações de T3I (T3I+E2I e T3I+E2F); T3F (T3F+E2I e T3F+E2F) e T3S (T3S+E2I e T3S + E2F) e diferentes associações de E2I (E2I+T3I e E2I+T3F e E2I+T3S); E2F (E2F+T3I e E2F+T3F e E2F+T3S) sobre a expressão gênica e proteica de RANKL, OPG e c-FOS. Quando associados, a maioria desses hormônios aumentou os níveis gênicos da célula estudada. Em c... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: Bone tissue is extremely complex and is regulated by systemic and local factors, presenting a considerable metabolic activity involving the removal of mineralized bone by osteoclasts in balance with the formation of bone matrix by osteoblasts. The association of triiodothyronine (T3) and estrogen (E2) may lead the activity of bone tissue to complex responses, due to T3 effects on both bone formation and reabsorption, and E2 being able to lead to osteoporosis when at low levels, or, at normal levels, maintain the suppression of the cytokines RANKL, OPG, and c-FOS, which take part actively on bone remodeling. To date, many studies have been done to verify hormone actions on bone metabolism. Among them, mesenchymal stem cells (MSC) have been isolated from human adipose tissue and differentiated into osteoblasts. The aim of our study was to evaluate the effect of both T3 and E2 on RANKL, OPG, and c-FOS gene and protein expression, at infra- (T3I, 10-10M; E2I, 10-9M), physiological (T3F, 10-9M; E2F, 10-8M) supra- (T3S, 10-8M) and doses. Cells were treated with hormones separately or in all possible combinations of T3 and E2 doses. The majority of associated treatments increased gene expression levels of all genes. We can state that the doses included in this study, of both hormones, efficiently increase the expression of the analyzed genes, especially when associated.
Doutor
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Chamalete, André. "Avaliação da expressão dos genes cFOS, IL-1b, CYP1a1 e CYP1b1 em Danio rerio expostos a Benzo[a]pireno e tratados com ligantes do receptor P2X7 /." São José do Rio Preto, 2016. http://hdl.handle.net/11449/134243.
Повний текст джерелаАнотація:
Orientador: Marcelo CamposBanca: Claudiana Lameu Gomes
Banca: Camila Nomura Boscolo
Resumo: O BaP é um contaminante ambiental capaz de causar inflamação e desregulação de vias celulares. Pela ação da CYP1a1 e CYP1b1, é convertido a metabólitos mais reativos. A literatura mostra que o BaP aumenta a expressão de algumas citocinas próinflamatórias, como a IL-1, porém, são bem contraditórios os relatos sobre o efeito do BaP no cFOS, o qual apresenta papel importante na proliferação, na formação de tumores e, possivelmente, na inflamação. O objetivo deste estudo foi de elucidar a participação do receptor purinérgico P2X7 sobre a expressão dos genes IL- 1 e cFOS, durante exposição ao BaP. Foi empregado as técnicas de qPCR para quantificação de expressão gênica, e testes de correlação e regressão entre IL-1 e cFOS. A exposição ao BaP induziu a expressão dos dois genes, além das enzimas do seu metabolismo. Quando bloqueado o receptor P2X7, além de uma menor indução das CYPs, os níveis de IL- 1e cFOS caíram abaixo dos níveis controle, sugerindo a participação do P2X7. Os testes de correlação e regressão mostraram uma relação forte direta entre IL-1e cFOS, reforçando o papel do cFOS na inflamação
Abstract: BaP is an environmental contaminant capable to cause inflammation and impair cellular pathways. CYP1a1 and CYP1b1 convert it to more reactive metabolites. Studies show that BaP enhances some proinflammatory citokines expression, like IL-1, yet reports about BaP affecting cFOS, which plays important role in proliferation, tumor formation and inflammation, are controversial. This work aimed to elucidate whether P2X7 purinergic receptor plays a role in IL-1 and cFOS expression during BaP exposure. We applied qPCR techniques to quantify gene expression, correlation and regression assays. Our results showed that BaP raised both IL-1 and cFOS genes expression, besides CYPs ones. Morevoer, when blocking P2X7 receptor, IL-1 and cFOS expression dropped under normal levels, which suggest P2X7 participation, in addition to a smaller enzymes induction. Correlation and regression assays exhibited a strong straight relationship between IL-1 and cFOS expression, reinforcing the role of cFOS in inflammation
Mestre
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Lücht, Christian [Verfasser]. "Molekulare Pathomechanismen osteoblastärer Differenzierung bei Urämie: Tumor-Nekrose-Faktor-alpha induziert über extrazellulär aktivierte Kinasen und Aktivatorprotein 1/cFOS eine Induktion von Interleukin-6-Expression / Christian Lücht." Berlin : Medizinische Fakultät Charité - Universitätsmedizin Berlin, 2019. http://d-nb.info/1180994515/34.
Повний текст джерела
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Lagarrigue, Sandrine. "Surexpression constitutive de cfos et cjun dans des cellules epitheliales de foie de rat : intervention de ces oncoproteines sur la proliferation et la transformation cellulaires in vitro." Rennes 1, 1994. http://www.theses.fr/1994REN10035.
Повний текст джерелаАнотація:
Les proteines cfos et cjun sont les composants du facteur de transcription ap1 qui est implique, entre autres, dans le controle de la proliferation cellulaire. Les genes cfos et cjun, genes de reponse precoce et homologues cellulaires d'oncogenes viraux, peuvent apres surexpression, entrainer une transformation cellulaire in vitro. Mes resultats completent les donnees concernant les consequences de la surexpression de cfos ou de cjun sur la proliferation et la transformation in vitro. Plusieurs lignees de cellules epitheliales de foie de rat (rlec) ont ete etablies par transfection stable: certaines surexpriment la proteine cfos (lignee 43c), d'autres surexpriment la proteine cjun (lignee cj-a). La surexpression constitutive de la proteine cjun ne semble pas modifier le comportement des rlec. Neanmoins, l'etude de la modification de l'etat de phosphorylation de la proteine cjun dans les cellules cj-a a permis de mettre en evidence, pour la premiere fois, les faits suivants: i) les igfs (insulin-like growth factor i et ii), comme le tpa, induisent une augmentation globale de l'etat de phosphorylation de la proteine cjun, ii) la phosphorylation de cjun mais aussi sa surexpression semblent etre deux evenements necessaires a la transformation in vitro des rlec. Par contre, la seule surexpression de cfos dans les rlec entraine une stimulation de croissance de ces cellules et conduit a leur transformation. De plus, elle augmente leur sensibilite a l'inhibition de croissance due au tgf1, faisant du modele 43c, un outil original pour l'etude de l'intervention de la proteine cfos dans les mecanismes d'action du tgf1. Par ailleurs, plusieurs molecules (vitamines a,c et e et flavonoides) ont ete testees pour leur eventuel pouvoir anti-transformant sur les deux modeles cj-a traite au tpa et 43c. Seule, l'acide retinoique (ar) reprime la transformation in vitro de ces deux systemes cellulaires. Cette reversion par l'ar de la transformation du clone cj-a pourrait etre expliquee par la diminution de l'affinite de ap1 au tre (en presence de sites rare) ainsi que l'inhibition des expressions des proteines cfos et cjun induites par le tpa
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Peine, Anja Stefanie [Verfasser]. "Auswirkungen des Duftstoffes 2,5-dihydro-2,4,5-trimethylthiazolin auf das räumliche Lernverhalten und die mRNA Expression von cFos und dem Corticotropin Releasing Factor in einem Glutamat-Decarboxylase67-Mausmodell / Anja Stefanie Peine." Magdeburg : Universitätsbibliothek, 2017. http://d-nb.info/1141230429/34.
Повний текст джерела
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Sabine, Amélie. "Activation angiogénique de cultures primaires de cellules endothéliales humaines : implication du complexe de transcription AP-1." Lyon, École normale supérieure (sciences), 2008. http://www.theses.fr/2008ENSL0506.
Повний текст джерела
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Zhao, Yuming. "Phenotypic analysis of osteoclast lineage in c-fos mutant mice." Thesis, King's College London (University of London), 2003. https://kclpure.kcl.ac.uk/portal/en/theses/phenotypic-analysis-of-osteoclast-lineage-in-cfos-mutant-mice(fafcec7f-6480-4f8c-87b6-3cca60a475fb).html.
Повний текст джерела
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Malerba, Gioacchino. "Progetto di un nodo sensore attivo a basso voltaggio per analisi ad ultrasuoni." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/17355/.
Повний текст джерелаАнотація:
In questo elaborato è descritto il progetto di un nodo sensore attivo piezoelettrico adatto per applicazioni nell'ambito del monitoraggio strutturale, in particolare per l'analisi ad ultrasuoni. Tale tecnica si avvale di almeno una coppia di sensori: un pulsatore attivo e un ricevitore passivo. A tal proposito, i più utilizzati sono i trasduttori piezoelettrici, i quali trovano un largo impiego anche nell'ambito biomedico.
Le attrezzature commerciali utilizzate in questo campo allo stato dell'arte hanno grande ingombro, costi elevati e un alto voltaggio. Tuttavia, tramite un'analisi preliminare sulla struttura da monitorare è possibile individuare le zone di maggiore stress e quindi inserire i sensori in modo mirato, riducendo l'ingombro e il peso dell'elettronica utilizzata.
In questo contesto si inserisce il lavoro di tesi, il cui obiettivo è il progetto di un nodo sensore attivo piccolo, leggero, a basso costo e a basso consumo di potenza, idoneo per essere installato permanentemente sulle strutture. Si è passati dalla definizione del problema alle possibili implementazioni circuitali utilizzando il software LTspice, fino alla scelta finale dei componenti fisici che sintetizzassero il blocco di driver/demodulatore, rispettivamente pilotando l'elemento piezoelettrico e demodulando il segnale PWM generato dal microcontrollore.
Dopo aver utilizzato un induttore (flottante) per svolgere l'adattamento di impedenza, sono stati testati due componenti di natura induttiva: doppio circuito di Antoniou e doppio giratore. Nella fase successiva sono state disaccoppiate la funzione di driver e demodulatore, realizzate prima da un VFA e un filtro passa-basso e poi, nello step finale, da un CFOA e un filtro passa-basso.
Come risultato finale è stato ottenuto un nodo sensore attivo, la cui tensione di uscita è caratterizzata da una dinamica pari a 6 V circa e una frequenza di risonanza di 20 KHz.
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Σαμιώτης, Παναγιώτης. "Σχεδίαση μιγαδικών φίλτρων χαμηλής τάσης τροφοδοσίας με χρήση CFOAs". Thesis, 2010. http://nemertes.lis.upatras.gr/jspui/handle/10889/3872.
Повний текст джерелаАнотація:
Οι συνεχώς αυξανόμενες ανάγκες της σημερινής αγοράς για φορητές ηλεκτρονικές συσκευές και τηλεπικοινωνιακά συστήματα χαμηλής τάσης τροφοδοσίας και χαμηλής κατανάλωσης ισχύος, καθιστά απαραίτητη τη σχεδίαση ενεργών βαθμίδων οι οποίες θα είναι ικανές να λειτουργήσουν σε ένα περιβάλλον όπου μία απλή τάση τροφοδοσίας μικρότερη ή ίση με 1.5V είναι διαθέσιμη. Έτσι, στην εργασία αυτή θα γίνει μια μελέτη διαφορετικών ενεργών βαθμίδων που δύνανται να λειτουργήσουν στο περιβάλλον αυτό, συγκρίνοντας τις δυνατότητες τους. Η μελέτη αυτή αφορά στις ενεργές βαθμίδες CCII και CFOA, καθώς και σε παραλλαγές τους που αφορούν στη λειτουργία των βαθμίδων αυτών με διαφορική τάση εισόδου (DVCCII και DVCFOA).Απώτερος σκοπός της σύγκρισης των βαθμίδων αυτών, αποτελεί η εφαρμογή τους στη σχεδίαση και υλοποίηση μιγαδικών φίλτρων. Έτσι, έπειτα από μία πλήρη περιγραφή των μιγαδικών φίλτρων ώστε να κατανοηθεί η λειτουργία τους, αλλά και των προβλημάτων που εισάγουν την ανάγκη χρήσης τέτοιων φίλτρων, θα μελετηθεί η χρησιμότητα καθεμιάς από τις παραπάνω ενεργές βαθμίδες στη σχεδίαση μιγαδικών φίλτρων ανώτερης τάξης, τα οποία πληρούν τις προδιαγραφές της εκάστοτε τεχνολογίας. Συγκεκριμένα θα γίνει η σχεδίαση και υλοποίηση ενός μιγαδικού φίλτρου 12ης τάξης ικανού να λειτουργεί (κατ’ επιλογή) τόσο για ένα κανάλι μετάδοσης μέσω του πρωτοκόλλου Bluetooth, όσο και για ένα κανάλι μετάδοσης μέσω του πρωτοκόλλου ZigBee.Τελικό βήμα της εργασίας, αποτελεί η φυσική σχεδίαση του κυκλώματος που θα προκύψει, ώστε να επαληθευτεί η ορθή λειτουργία του σε ένα περισσότερο ρεαλιστικό περιβάλλον.The ever-increasing needs of today's market for portable electronic devices and telecommunication systems of low voltage and low power consumption, necessitates the design of active building blocks that are likely to operate in an environment where a single supply voltage less than or equal to 1.5V is available. Thus, this work will be a study of different active building blocks that may operate in this environment, comparing their abilities. The study refers to active building blocks CCII and CFOA, as well as variations related to their operation involving differential input voltage (DVCCII and DVCFOA). The ultimate goal of comparing these blocks is their application in the design and implementation of complex filters. Thus, after a full description of complex filters to understand their functioning and the problems that introduce the need to use such filters, the usefulness of each of these blocks will be studied in the design of higher-order complex filters, which meet the specifications of each technology. In particular a 12th order complex filter able to function (optional) for both a transmission channel over Bluetooth Protocol, and a transmission channel over ZigBee Protocol, will be designed and implemented. Final step of the work is the physical layout of the circuit, so as to verify the proper functioning in a more realistic environment.
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CHEN, TING-RUI, and 陳廷睿. "CFOs’ Incentives and Debt Financing." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/rw65k4.
Повний текст джерелаАнотація:
碩士國立雲林科技大學
財務金融系
105
This study investigates the effect of Cheief financial officers’（CFOs’） risk-taking incentives on corporate financial policies. The sample includes S&P 500 firms over year 2006 to 2012. The results show that the risk-taking incentives of CFOs does not significantly relate to capital structure decision. However, the risk-taking incentives of CFOs significantly influence their firms’ financing policies. We find CFOs’ risk-decreasing（-increasing） incentives are associated with safer（risker） debt-maturity choices.
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JI, HONG-JHENG, and 紀洪政. "Overconfidence CFOs and Firm Performance." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/e85psv.
Повний текст джерелаАнотація:
碩士國立雲林科技大學
財務金融系
106
Literature show that overconfidence executives may lead to the distortions of corporate investment. Overconfident executives overestimate their return of the investment projects and think external funds as overpricing. Therefore, they overinvest when they have sufficient internal funds but reduce investment if they need to request external fund. By using the sample of S&P 500 firms, this study investigates the relation of overconfident CFOs and investment. The CFOs are regarded as overconfident if they hold in-the-money options. The results show that overconfident CFOs overinvest and have higher cash-flow investment sensitivity.
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CHEN, PO-YU, and 陳柏毓. "The Design of Voltage-Mode Biquadratic Filters and Oscillators Using CFOAs." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/fsmxb6.
Повний текст джерелаАнотація:
碩士明志科技大學
電子工程系碩士班
107
This thesis presents two voltage-mode biquadratic filters based on current-feedback operational amplifiers (CFOAs). Both proposed voltage-mode biquadratic filters employ three CFOAs, three resistors and two grounded capacitors with two inputs and three outputs. The use of grounded capacitors makes the proposed circuits ideal for integrated circuit (IC) implementation. Both proposed configurations simultaneously provide low-pass (LP), band-pass (BP), and band-reject (BR) voltage responses at high-input impedance terminal. Further, both circuits can be also obtained high-pass (HP) voltage response. Both circuits offer orthogonal controllability of the quality factor and resonance angular frequency. Moreover, each of the proposed voltage-mode filters can be easily transformed into a voltage-mode quadrature oscillator. Finally, OrCAD PSpice simulation and experimental results using AD844s ICs from Analog Devices have been included to verify the workability of the proposed CFOA-based circuit designs.
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Ράικος, Γιώργος. "Σχεδίαση τελεστικών ενισχυτών με ανατροφοδότηση ρεύματος (CFOAs) για εφαρμογές χαμηλής τάσης τροφοδοσίας". Thesis, 2007. http://nemertes.lis.upatras.gr/jspui/handle/10889/2923.
Повний текст джерелаАнотація:
Είναι γνωστό ότι τα κυκλώματα των τελεστικών ενισχυτών (Op-Amps) είναι από τις βασικότερες δομικές βαθμίδες στον χώρο της σχεδίασης αναλογικών ολοκληρωμένων κυκλωμάτων. Μια εναλλακτική δομή του τελεστικού ενισχυτή αποτελεί το κύκλωμα ενός Current Feedback Operational Amplifier (CFOA). Ένας CFOA είναι ουσιαστικά ένας μεταφορέας ρεύματος (Current Conveyor-CCII) σε σειρά με έναν ακολουθητή τάσης (Voltage Follower), και είναι ιδιαιτέρως χρήσιμος κατά την σχεδίαση κυκλωμάτων χαμηλής τάσης τροφοδοσίας.
Στην εργασία αυτή μελετήθηκαν τέσσερις δομές CFOA, σχεδιασμένες για λειτουργία με χαμηλή τάση τροφοδοσίας, και χρησιμοποιήθηκαν για τον σχεδιασμό φίλτρων με τις μεθόδους Leapfrog, τοπολογικής εξομοίωσης και κυματική.
Στο πρώτο κεφάλαιο αναφέρονται οι γενικές αρχές που ισχύουν στην σχεδίαση κυκλωμάτων για λειτουργία με χαμηλή τάση τροφοδοσίας καθώς και τις πιο συχνά χρησιμοποιούμενες τεχνικές σχεδίασης.
Στο δεύτερο κεφάλαιο μελετώνται αναλυτικά οι τέσσερις δομές CFOA συγκρίνοντας τους βασικότερους παράγοντες απόδοσής τους. Τα κυκλώματα των CFOA που μελετώνται βασίζονται σε πρόσφατα δημοσιευμένες δομές Current Conveyor (CCII).
Στο τρίτο κεφάλαιο αναλύεται η μέθοδος σχεδίασης φίλτρων Leapfrog, και χρησιμοποιείται για την σχεδίαση ενός Butterworth φίλτρου 3ης τάξης. Ως δομική βαθμίδα για την σχεδίαση αυτού του φίλτρου χρησιμοποείται ο CFOA [2]. Το τρίτο κεφάλαιο ολοκληρώνεται με την παρουσίαση των βασικότερων παραγώντων απόδοσης.
Στο τέταρτο κεφάλαιο παρουσιάζεται η τοπολογική μέθοδος σχεδίασης φίλτρων, στην οποία γίνεται τοπολογική αντικατάσταση πηνίου, σε παθητικό φίλτρο, από ισοδύναμο κύκλωμα με ενεργά στοιχεία. Και στην περίπτωση αυτή η δομική μονάδα σχεδιασμού είναι ο CFOA [2].
Στο πέμπτο κεφάλαιο παρουσιάζεται η σχεδίαση ενός Butterworth φίλτρου 3ης τάξης με την κυματική μέθοδο. Η σχεδίαση πραγματοποιήθηκε χρησιμοποιώντας ως δομική βαθμίδα τον CFOA [1].
Στο έκτο κεφάλαιο παρουσιάζεται η φυσική σχεδίαση (layout) του Butterworth φίλτρου 3ης τάξης που σχεδιάστηκε με την leapfrog μέθοδο στο τρίτο κεφάλαιο. Η φυσική σχεδίαση πραγματοποιήθηκε με την χρήση του λογισμικού Cadence και του περιβάλλοντος Virtuoso που περιλαμβάνει για την φυσική σχεδίαση αναλογικών ηλεκτρονικών κυκλωμάτων .
Τέλος στο έβδομο κεφάλαιο γίνεται σύγκριση των αποτελεσμάτων εξομοίωσης των δομών CFOA’s αλλά και των αποτελεσμάτων εξομοίωσης των φίλτρων που σχεδιάστηκαν στα παραπάνω κεφάλαια . Επίσης παρουσιάζονται κάποιες προτάσεις για μελλοντική και περαιτέρω έρευνα.Operational amplifier is one of most important analog building block. An alternative structure for operational amplifier is a Current Feedback Operational Amplifier (CFOA). A CFOA is essentially consists of a current conveyor (CCII) connecting with a Voltage Follower (VF). The usage of CFOA for the low-voltage analog IC design is quite useful. In this work four different CFOA structures, designed for low-voltage operation, were considered. Also the aforementioned CFOAs were used to build a butterworth filter with Leapfrog method, topological simulation method and wave method. In first chapter the basic design rules and the most common design techniques for low-voltage IC design is presented. In chapter 2 the four structures of CFOAs circuits were considered, under the light of comparison of most critical factors of operation. The CFOAs circuits were based in most resent published topologies of Current Conveyor (CCII). In chapter 3 the Leapfrog method for filters design was discussed. Also a 3rd order butterworth filter is designed based on this method. The CFOA of ref [2] is the main building lock to construct this filter. In chapter 4 another method for filter design is presented named topological simulation method. According to this method passive elements such as inductors and capacitors are replaced by active elements. The main building block is also CFOA of ref [2]. In Chapter 5 a 3rd order butterworth filter based on wave method is designed. In this case the main building block was the CFOA circuit of ref [1]. Chapter 6 presents the layout of the 3rd order butterworth filter which designed at chapter 3 with leapfrog method. The layout design was implemented using Virtuoso environment of Cadence design framework II platform. Chapter 7 conclude this work presenting the simulated comparison results for all four CFOAs circuits and the 3rd order butterworth filters that were designed with the three different methods. Some thoughts for further research in the this subject are also presented.
29
Li, Shih-Sheng, and 李世聖. "Estimation of Multiuser CFOs in OFDMA Systems." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/nffu6m.
Повний текст джерелаАнотація:
碩士國立臺灣大學
電信工程學研究所
106
Recently, orthogonal frequency-division multiple access (OFDMA) has been widely adopted in many wireless communication standards. However, the OFDMA-based systems are sensitive to the frequency synchronization error, i.e. carrier frequency offset (CFO), which destroys the orthogonality among the subcarriers. In the uplink OFDMA systems, the received signal at the base station (BS) is composed of all active users with individual CFO. This frequency synchronization error is normally partitioned into an acquisition stage followed by a tracking stage at the BS. CFO induces both intercarrier interference (ICI) and multiple-access interference (MAI), which degrade the performance of systems significantly. Therefore, the estimation and the correction of the frequency synchronization error is a crucial and challenging topic in uplink OFDMA systems. Most existing CFO estimation methods are derived under the certain carrier assignment scheme (CAS). In the thesis, we introduce several new estimation methods that can be applied to generalized-CAS (GCAS). Both blind and pilot-aided methods are considered. In the first part, we first review on estimator using the constant-modulus (CM) constellation and then propose several blind estimations of multiple CFOs, such as virtual carrier based (VC-based), VC-CM based and kurtosis-based (KT-based) estimators. In addition, we develop a closed form solution for CFO tracking and obtain a 2-stage algorithm for the VC-based estimator. The complexity of these closed form solutions are very low. In the second part, for pilot-aided scheme, we propose a new algorithm for the joint estimation of CFO and channel response. We also incorporate the VC in the CFO estimation to further the estimation accuracy. Low complexity closed form solutions are also derived. Moreover, numerical simulations are provided to show the effectiveness of the proposed methods and to compare the performances with other existing methods.
30
Spiller, Michelle Ann. "The independent influence of CFOs on firms' financial reporting." Thesis, 2019. http://hdl.handle.net/10453/137101.
Повний текст джерелаАнотація:
University of Technology Sydney. Faculty of Business.This thesis provides evidence on two research questions regarding the independent influence of CFOs on firms’ financial reporting. Chapter 2 examines the effect of relative CFO power on financial reporting integrity and Chapter 3 investigates changes in financial reporting integrity surrounding routine versus non-routine CFO turnover. The primary proxy for financial reporting integrity is the recognition of non-current asset impairments in response to indicators of impairment which remains a key focus area of regulatory scrutiny and inquiry. Based on a sample of 1,781 Australian firm-years over the period 2007 to 2015, the evidence in Chapter 2 illustrates that firms record less timely non-current asset impairments (in the presence of adverse economic circumstances and worsening financial performance) as the degree of relative CFO power increases. 463 Australian CFO changes between 1 July 2007 and 30 June 2015 are examined in Chapter 3 which finds that new CFOs use asset write-offs as a vehicle to engage in ‘big bath’ accounting in the year of a non-routine appointment. The results in Chapter 3 also indicate that (irrespective of the nature of the CFO change) CFOs bias earnings upward in the period prior to their departure. The results are consistent with respect to a number of sensitivity tests and alternative proxies for financial reporting integrity. While CFOs, therefore, have the capacity to exert independent influence over firms’ reported results the balance of findings suggest that CFOs act in self-interest. In other words, CFOs’ financial reporting decisions are opportunistically motivated by their own compensation and career incentives and the personal costs they face. The evidence in this thesis is, therefore, contrary to the view that CEO pressure is a primary driver of CFOs’ involvement in earnings manipulation.
31
Wu, Chi-Hung, and 吳奇鴻. "Realizations of voltage-mode quadrature oscillators using CFOA and DVCCTA active components." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/cpv3jv.
Повний текст джерелаАнотація:
碩士明志科技大學
電子工程系碩士班
104
In this study, to realize voltage-mode second-order sinusoidal quadrature oscillators, three new circuit configurations are presented. First proposed oscillator employs two current-feedback operational amplifiers (CFOAs), two grounded capacitors, and three resistors. The proposed oscillator exhibits the following advantageous features: (i) independent adjustment of condition of oscillation and frequency of oscillation, (ii) two low output impedance sinusoidal voltages with 90o phase difference, (iii) employment of two grounded capacitors ideal for integrated circuit implementation, and (iv) low active and passive sensitivity performance. The second proposed oscillator employs a single differential voltage current conveyor transconductance amplifier (DVCCTA), one grounded resistor, and two grounded capacitors. The proposed oscillator exhibits the following advantageous features: (i) independent and electronic adjustment of condition of oscillation and frequency of oscillation, (ii) two quadrature sinusoidal voltage signals with 90o phase difference, (iii) employment of two grounded capacitors ideal for integrated circuit implementation, and (iv) low active and passive sensitivity performance. The last proposed oscillator employs a single DVCCTA, two grounded resistor, and two grounded capacitors. The proposed oscillator exhibits the following advantageous features: (i) independent adjustment of condition of oscillation and frequency of oscillation, (ii) electronic adjustment of frequency of oscillation, (iii) three quadrature sinusoidal voltage signals with 90o phase difference, (iv) employment of two grounded capacitors ideal for integrated circuit implementation, and (v) low active and passive sensitivity performance. Finally, we use HSPICE to prove the accuracy of the circuit with TSMC 0.18µm process technology. The results show close agreement between theory and simulation. In addition to simulation, the first proposed quadrature oscillator has been validated by using commercially available AD844-type of CFOAs.
32
HARSH, AMAN. "IMPLEMENTATION OF VARIOUS FILTERS USING OTRA." Thesis, 2016. http://dspace.dtu.ac.in:8080/jspui/handle/repository/15279.
Повний текст джерелаАнотація:
The low-voltage and low-power mixed mode circuit design has gained importance with the
advent of the portable electronic and mobile communication systems. More and more mixed
mode circuit blocks, are being integrated onto a single chip in an effort to reduce overall cost and
space and to improve system performance. This requires the scaling of CMOS technology. The
reliability and density factors associated with technology scaling demand for downsized supply
voltages. This trend of continuous reduction of the supply voltage poses serious challenges to the
analog designers. To circumvent this conflict instead of using costly CMOS technologies with
lower thresholds, it is desirable to use low voltage circuit techniques that are compatible with
standard CMOS processes. In the last few decades the current-mode processing has emerged as
an alternative design technique. Ever shrinking feature size of devices on ICs and
consequential reduction of power supply voltage can be handled by operating in the current
domain, as current mode circuits are designed for lower voltage swings. While fundamentally
any design techniques is limited by device characteristics, there may be specific applications
where current-mode circuits provide one or more of the following advantages: higher
bandwidth, better signal linearity, higher slew rates, lower power consumption, and better
accuracy. Additionally, current-mode circuits are often less complex than the voltage-mode
circuits, which may lead to significant chip area savings. Emergence of various current-mode
analog building blocks is outcome of the considerable progress in current-mode analog signal
processing. Operational trans-resistance amplifier (OTRA) among those is of relatively recent
origin.
33
Lin, Jia-An, and 林家安. "The Effect of Pay Gap between CEOs and CFOs on Financial Reporting Quality." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/92sq3y.
Повний текст джерелаАнотація:
碩士國立臺灣大學
會計學研究所
107
This paper examines the effect of pay gap between CEOs and CFOs on financial reporting quality. In this study, all samples are selected from the Compustat and Execucomp database during the period of years 2006–2017. The empirical results show that pay gap has differential impacts on discretionary accruals and real activity manipulation. Larger short-term pay gap increases real activity manipulation, whereas larger long-term pay gap increases discretionary accrual management. The findings provide implications to corporate decision-making regarding the compensation policy. In addition to the pay level and pay structure, the compensation committee should also consider the pay gap between CEOs and CFOs.
34
GARG, KAMINI. "MODIFIED CFOA AND ITS APPLICATION FOR THE SIMULATION OF INDUCTOR, FILTER AND INVERSE FILTER." Thesis, 2012. http://dspace.dtu.ac.in:8080/jspui/handle/repository/14126.
Повний текст джерелаАнотація:
The recent trend in electronics has been towards reducing the size of circuits, a trend which
culminated in the development of integrated circuits, but it has been proven impractical to
achieve a comparable reduction in the size of inductors because of the relation between the
size of inductor and the quality factor. Also inductors are seldom used at low frequencies
because at very low frequency the size and weight of inductors become exceedingly large and
quality factor becomes very low. Fortunately, active circuits can sometimes synthesize the
equivalent of an inductor with high quality factor.
In this dissertation, we have presented a modified current feedback operational
amplifier (MCFOA), which is more suitable for realizing simulated inductors and active
filters. New grounded inductor and floating inductor have been simulated using a minimum
number of passive components based on one or two modified current feedback operational
amplifiers (MCFOAs) and the result is validated with the implementation of RL high pass
filter.
To show the flexibility of the proposed MCFOA, a single input three output (SITO)
voltage mode filter and three input single output (TISO) voltage mode filters employing a
single MCFOA have been simulated using the PSPICE program.
In communication, control and instrumentation systems an electrical signal may get
altered by many linear or nonlinear transformation caused by the signal processors or
transmission system. To recover these distortions of the signal, a system is required that has
inverse transfer characteristics of the original system. Inverse filter can correct these
distortions because it has frequency response, which is the reciprocal of the frequency
response of the system that caused the, distortion.
In this dissertation, inverse filters have been designed using both the Modified current
feedback operational amplifier (MCFOA) and standard AD844 CFOA. The workability of
the proposed inverse filters is demonstrated by PSPICE simulations.
35
Kao, Bo-Yuan, and 高伯元. "The effect of the Seniority and Education Mismatch between CPAs and CFOs on Audit Fees." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/z2vn9y.
Повний текст джерелаАнотація:
碩士國立政治大學
會計學系
107
The purpose of this study is to explore the effect of the seniority and education mismatch between CPAs and CFOs on audit fees. This study analyzes the listed companies at stock exchange market and at over-the-counter market that have disclosed audit fees in 2010-2017 in Taiwan. The empirical results show that the mismatch of seniority between the CPAs and CFOs is positively associated with the audit fees and that there is no association between the educational mismatch and audit fees. Specifically, the audit fees are higher for firms in which CPAs are senior to CFOs in terms of working experience. It suggests that the one with greater seniority may have a stronger bargaining power for the audit fees. While we do not find the association between the educational mismatch and audit fees, the non-result is possibly due to a sample self-selection bias. In addition, the further analysis of the study finds that the positive association between the mismatch of seniority and the audit fees occurs in all audit firms.
36
Lawson, Bradley. "The Influence of Individual Audit Committee Chairs, CEOs, and CFOs on Corporate Reporting and Operating Decisions." Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-08-11457.
Повний текст джерелаАнотація:
This paper examines the association between individual managers and corporate reporting and operating decisions. To examine this question, I develop a dataset of 241 individual CEOs and CFOs, as well as audit committee chairs, covering the period of 1988 to 2009. Although audit committee chairs are tasked with monitoring insiders and not actually preparing the financial results, research suggests that each of these management groups could exert their individual "styles" on the reporting and operating decisions. Using this dataset, I find that each of these groups significantly influence accounting- and non-accounting-based corporate decisions. Also, I examine whether the influence of these individuals is impacted by characteristics of the corporation's operating environment. Using individual proxies for managerial discretion and job demands, as well as developing index measures for each of these constructs, I find that the influence of these particular managers is not impacted by the amount of discretion they have or their perceived job demands. Last, I find evidence that observable demographic measures explain some of the managers' decisions. These results add to the literature concerning the importance of individual managers to corporate decisions because they suggest that managers besides the CFO can significantly influence reporting and operating decisions, and the influence of these managers extends beyond accrual-based techniques to include real activities management decisions.
37
楊苓梓. "The Relative Power of CFOs and Audit Committees and Choice of Audit Firm: Evidence from China." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/bhn2tt.
Повний текст джерелаАнотація:
碩士國立政治大學
會計學系
106
The objective of this thesis is to examine whether the relative power of CFOs and audit committees has an effect on its firms’ choice of audit firms. Using a sample of Chinese listed firms during 2007~2016, I find that: (1) companies with more powerful CFOs are more likely to hire lower-quality auditors, as measured by non-top10 audit firm; (2) The effect of CFOs’ relative power on the choice of audit firms is weaker for state-owned enterprises than for private enterprises.
38
Lin, Bo-Tung, and 林柏彤. "The Relation between Female CFOs, Female Audit Committee Members and Financial Restatement： Extensive Study on the role of Female CPAs." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/54779016381359830202.
Повний текст джерелаАнотація:
碩士國立中興大學
會計學研究所
104
In order to understand the importance of gender, the study examines the effect of female CFOs and female audit committee members on the likelihood of financial restatements separately. The study also considers whether female CPAs would strengthen the relation mentioned above, since financial statements are audited by CPAs. Using the listed and OTC companies in Taiwan from 2006 to 2014 as empirical data, empirical results indicate that female CFOs have a significantly negative association with the occurrences of financial restatements, and when there is at least one female audit committee member in companies, a significantly negative association between female audit members and financial restatements exists. Moreover, if there is at least one female CPA in the composition of CPAs, it strengthens the negative relation between female CFOs and financial restatements significantly, but on the other side, the study doesn’t find that it strengthens the relation between female audit committee members and financial restatements. Besides, the empirical results of the sensitivity tests show that the higher the proportion of female audit committee members is, the less the likelihood of financial restatements occurs. However, when there are different definitions for CPAs, the study couldn’t consistently document that they strengthen the effects of female CFOs and female audit committee members on the likelihood of financial restatements.
39
Nock, Tanya Gwendolyn. "Development of an Enzyme Immunoassay and Cellular Function Assays to Probe the Function of Teneurin C-terminal Associated Peptide (TCAP)." Thesis, 2010. http://hdl.handle.net/1807/24270.
Повний текст джерелаАнотація:
The teneurin C-terminal associated peptides (TCAP) are a family of four predicted peptides that are expressed in all metazoans where the teneurins have been studied to date. Of the four peptides, TCAP-1 has been studied most extensively. In vitro, TCAP-1 increases neuronal proliferation and neurite outgrowth. In vivo, the peptide reduces CRF-induced behavioural responses in rats. Despite the large body of evidence indicating a strong biological role for TCAP-1, little is known about the chemistry and solubility of the peptide, or the signaling pathway(s) mediating these effects. The aim of this research was to appropriately solubilize the peptide and to develop detection assays for its study in greater detail. I have now established an appropriate formulation of TCAP-1 and developed an immunoassay to assess its concentrations in tissues and in circulation. Also, by examining a number of transcriptional response elements, I have found two assays for probing the signal transduction mechanisms of this peptide.
40
Itankar, Yogendra Umesh. "Equalization Algorithms And Performance Analysis In Cyclic-Prefixed Single Carrier And Multicarrier Wireless Systems." Thesis, 2012. https://etd.iisc.ac.in/handle/2005/2314.
Повний текст джерелаАнотація:
The work reported in this thesis is divided in to two parts.
In the first part, we report a closed-form bit error rate (BER) performance analysis of orthogonal frequency division multiple access (OFDMA) on the uplink in the presence of carrier frequency offsets (CFOs) and/or timing offsets (TOs) of other users with respect to a desired user. We derive BER expressions using probability density function (pdf) and characteristic function approaches, for a Rician faded multi-cluster multi-path channel model that is typical of indoor ultrawideband channels and underwater acoustic channels. Numerical and simulation results show that the BER expressions derived accurately quantify the performance degradation due to non-zero CFOs and TOs.
Ultrawideband channels in indoor/industrial environment and underwater acoustic channels are severely delay-spread channels, where the number of multipath components can be of the order of tens to hundreds. In the second part of the thesis, we report low complexity equalization algorithms for cyclic-prefixed single carrier (CPSC)systems that operate on such inter-symbol interference(ISI) channels characterized by large delay spreads. Both single-input single-output and multiple-input multiple-output(MIMO) systems are considered. For these systems, we propose a low complexity graph based equalization carried out in frequency domain. Because of the noise whitening effect that happens for large frame sizes and delay spreads in the frequency domain processing, improved performance compared to time domain processing is shown to be achieved. Since the graph based equalizer is a soft-input soft-output equalizer, iterative techniques(turbo-equalization) between detection and decoding are shown to yield good coded BER performance at low complexities in convolutional and LDPC coded systems. We also study joint decoding of LDPC code and equalization of MIMO-ISI channels using a joint factor graph.
41
Itankar, Yogendra Umesh. "Equalization Algorithms And Performance Analysis In Cyclic-Prefixed Single Carrier And Multicarrier Wireless Systems." Thesis, 2012. http://hdl.handle.net/2005/2314.
Повний текст джерелаАнотація:
The work reported in this thesis is divided in to two parts.
In the first part, we report a closed-form bit error rate (BER) performance analysis of orthogonal frequency division multiple access (OFDMA) on the uplink in the presence of carrier frequency offsets (CFOs) and/or timing offsets (TOs) of other users with respect to a desired user. We derive BER expressions using probability density function (pdf) and characteristic function approaches, for a Rician faded multi-cluster multi-path channel model that is typical of indoor ultrawideband channels and underwater acoustic channels. Numerical and simulation results show that the BER expressions derived accurately quantify the performance degradation due to non-zero CFOs and TOs.
Ultrawideband channels in indoor/industrial environment and underwater acoustic channels are severely delay-spread channels, where the number of multipath components can be of the order of tens to hundreds. In the second part of the thesis, we report low complexity equalization algorithms for cyclic-prefixed single carrier (CPSC)systems that operate on such inter-symbol interference(ISI) channels characterized by large delay spreads. Both single-input single-output and multiple-input multiple-output(MIMO) systems are considered. For these systems, we propose a low complexity graph based equalization carried out in frequency domain. Because of the noise whitening effect that happens for large frame sizes and delay spreads in the frequency domain processing, improved performance compared to time domain processing is shown to be achieved. Since the graph based equalizer is a soft-input soft-output equalizer, iterative techniques(turbo-equalization) between detection and decoding are shown to yield good coded BER performance at low complexities in convolutional and LDPC coded systems. We also study joint decoding of LDPC code and equalization of MIMO-ISI channels using a joint factor graph.
42
Raghunath, K. "Performance Analysis Of Multiuser/Cooperative OFDM Systems With Carrier Frequency And Timing Offsets." Thesis, 2009. https://etd.iisc.ac.in/handle/2005/1048.
Повний текст джерелаАнотація:
Multiuser and cooperative orthogonal frequency division multiplexing(OFDM) systems are being actively researched and adopted in wireless standards, owing to their advantages of robustness to multipath fading, modularity, and ability to achieve high data rates. In OFDM based systems, perfect frequency and timing synchronization is essential to maintain orthogonality among the subcarriers at the receiver. In multiuser OFDM on the uplink, timing offsets (TOs) and/or carrier frequency offsets (CFOs) of different users, caused due to path delay differences between different users, Doppler and/or poor oscillator alignment, can destroy orthogonality among subcarriers at the receiver. This results in multiuser interference (MUI)and consequent performance degradation. In this thesis, we are concerned with the analysis and mitigation of the effect of large CFOs and TOs in multiuser OFDM systems, including uplink orthogonal frequency division multiple access (OFDMA),uplink single-carrier frequency division multiple access(SC-FDMA), and cooperative OFDM.
Uplink OFDMA: In the first part of this thesis, we analytically quantify the effect of large CFOs and TOs on the signal-to-interference plus noise ratio(SINR) and uncoded bit error rate(BER) performance of uplink OFDMA on Rayleigh and Rician fading channels, and show analytical results to closely match with simulation results. Such an SINR/BER analysis for uplink OFDMA in the presence of both large CFOs as well as TOs has not been reported before. We also propose interference cancelling(IC) receivers to mitigate the performance degradation caused due to large CFOs and TOs of different users.
SC-FDMA versus OFDMA: An issue with uplink OFDMA is its high peak-to-average power ratio(PAPR).Uplink SC-FDMA is proposed in the standards as a good low-PAPR alternative to uplink OFDMA; e.g., SC-FDMA has been adopted in the uplink of 3GPP LTE. A comparative investigation of uplink SC-FDMA and OFDMA from a sensitivity to large CFOs and TOs view point has not been reported in the literature. Consequently, in the second part of the thesis, we carry out a comparative study of the sensitivity of SC-FDMA and OFDMA schemes to large CFOs and TOs of different users on the uplink. Our results show that while SC-FDMA achieves better performance due to its inherent frequency diversity advantage compared to OFDMA in the case of perfect synchronization, its performance can get worse than that of OFDMA in the presence of large CFOs and TOs. We further show that use of low-complexity multistage IC techniques, with the knowledge of CFOs and TOs of different users at the receiver, can restore the performance advantage of SC-FDMA over OFDMA.
Cooperative OFDM: Cooperative OFDM is becoming popular because of its ability to provide spatial diversity in systems where each node has only one antenna. In most studies on cooperative communications, perfect time synchronization among cooperating nodes is assumed. This implies that the transmissions from different cooperating nodes reach the destination receiver in orthogonal time slots. In practice, however, due to imperfect time synchronization, orthogonality among different nodes’ signals at the destination receiver can be lost, causing inter-symbol interference(ISI).In the third part of the thesis, we investigate cooperative OFDM communications using amplify-and-forward(AF) protocol at the relay, in the presence of imperfect timing synchronization. We derive analytical expressions for the ISI as function of timing offset for cooperative OFDM with AF protocol, and propose an IC receiver to mitigate the effects of timing offset induced ISI.
43
Raghunath, K. "Performance Analysis Of Multiuser/Cooperative OFDM Systems With Carrier Frequency And Timing Offsets." Thesis, 2009. http://hdl.handle.net/2005/1048.
Повний текст джерелаАнотація:
Multiuser and cooperative orthogonal frequency division multiplexing(OFDM) systems are being actively researched and adopted in wireless standards, owing to their advantages of robustness to multipath fading, modularity, and ability to achieve high data rates. In OFDM based systems, perfect frequency and timing synchronization is essential to maintain orthogonality among the subcarriers at the receiver. In multiuser OFDM on the uplink, timing offsets (TOs) and/or carrier frequency offsets (CFOs) of different users, caused due to path delay differences between different users, Doppler and/or poor oscillator alignment, can destroy orthogonality among subcarriers at the receiver. This results in multiuser interference (MUI)and consequent performance degradation. In this thesis, we are concerned with the analysis and mitigation of the effect of large CFOs and TOs in multiuser OFDM systems, including uplink orthogonal frequency division multiple access (OFDMA),uplink single-carrier frequency division multiple access(SC-FDMA), and cooperative OFDM.
Uplink OFDMA: In the first part of this thesis, we analytically quantify the effect of large CFOs and TOs on the signal-to-interference plus noise ratio(SINR) and uncoded bit error rate(BER) performance of uplink OFDMA on Rayleigh and Rician fading channels, and show analytical results to closely match with simulation results. Such an SINR/BER analysis for uplink OFDMA in the presence of both large CFOs as well as TOs has not been reported before. We also propose interference cancelling(IC) receivers to mitigate the performance degradation caused due to large CFOs and TOs of different users.
SC-FDMA versus OFDMA: An issue with uplink OFDMA is its high peak-to-average power ratio(PAPR).Uplink SC-FDMA is proposed in the standards as a good low-PAPR alternative to uplink OFDMA; e.g., SC-FDMA has been adopted in the uplink of 3GPP LTE. A comparative investigation of uplink SC-FDMA and OFDMA from a sensitivity to large CFOs and TOs view point has not been reported in the literature. Consequently, in the second part of the thesis, we carry out a comparative study of the sensitivity of SC-FDMA and OFDMA schemes to large CFOs and TOs of different users on the uplink. Our results show that while SC-FDMA achieves better performance due to its inherent frequency diversity advantage compared to OFDMA in the case of perfect synchronization, its performance can get worse than that of OFDMA in the presence of large CFOs and TOs. We further show that use of low-complexity multistage IC techniques, with the knowledge of CFOs and TOs of different users at the receiver, can restore the performance advantage of SC-FDMA over OFDMA.
Cooperative OFDM: Cooperative OFDM is becoming popular because of its ability to provide spatial diversity in systems where each node has only one antenna. In most studies on cooperative communications, perfect time synchronization among cooperating nodes is assumed. This implies that the transmissions from different cooperating nodes reach the destination receiver in orthogonal time slots. In practice, however, due to imperfect time synchronization, orthogonality among different nodes’ signals at the destination receiver can be lost, causing inter-symbol interference(ISI).In the third part of the thesis, we investigate cooperative OFDM communications using amplify-and-forward(AF) protocol at the relay, in the presence of imperfect timing synchronization. We derive analytical expressions for the ISI as function of timing offset for cooperative OFDM with AF protocol, and propose an IC receiver to mitigate the effects of timing offset induced ISI.