Made available in DSpace on 2014-06-11T19:22:21Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-02-06Bitstream added on 2014-06-13T19:07:46Z : No. of bitstreams: 1 rocha_v_me_guara.pdf: 8713768 bytes, checksum: 78a8daf2c93d3384356543e4273f0b6d (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho teve por objetivo estudar a propriedade do plasma em pressão atmosférica para esterilização de materiais termossensíveis. Para testar a propriedade do plasma frio de esterilizar materiais termossensíveis, concentramos nossos experimentos no plasma gerado por descarga com barreira dielétrica (DBD). Para realizar nossos experimentos usamos os microrganismos Cândida albicans ATCC18804, Escherichia coli ATCC23922, Bacillus subtilis ATCC19659, e Staphylococcus aureus ATCC 6538. Primeiramente, realizamos descarga DBD sobre uma placa de microtitulação contendo suspensões de microrganismos, mas observamos que, neste caso, a descarga DBD não teve eficácia na esterilização, devido a não penetração das entidades reativas (ozônio, UV), dentro desse volume de microrganismos. Modificamos nosso sistema, colocando um eletrodo adaptado a uma placa de Petri, e aplicamos a descarga DBD sobre os microrganismos em suspensão semeados em Agar. Realizamos exposição de 2, 5, 10, 15 e 20 minutos, com 1,1W de potência, tensão de 40kV pico-a-pico e aproximadamente 1 cm de distância entre o eletrodo superior e o meio de cultura. Observamos o crescimento dos meios de cultura tratados (contagem de UFC) e analisamos a morfologia dos microrganismos tratados em comparação com as amostras sem tratamento, através de microscopia eletrônica de varredura (MEV). Através desses experimentos, pudemos observar que, no caso de superfícies, o plasma é um método de esterilização eficiente e rápido. Isso porque, durante a descarga são formados ozônio, fótons UV, e partículas livres carregadas, que podem contribuir para o efeito esterilizante / The objective of this work was to investigate the application of plasma at atmospheric pressure for sterilization of termosensitive materials. To test the capability of cold plasma to sterilize termosensitive materials, we concentrated our study on the plasma generated by a dielectric barrier discharge (DBD). In our experiments we used the microorganisms Candida albicans ATCC18804, Escherichia coli ATCC23922, Bacillus subtilis ATCC19659, and Staphylococcus aureus ATCC 6538. Firstly, we produce a DBD discharge in a microtitulation plate containing suspensions of the microorganism and no sterilization effect was observed. This is due to the fact that no penetration of the reactivates species (ozone, UV) inside of the volume of microorganisms. We modified our system, putting an adapted electrode on the cover of a Petri plate, and we applied the DBD discharge on microorganisms in suspension sowed in Agar. We used different times of treatment (2, 5, 10, 15 and 20 minutes), with mean power of 1,1W, 40kV pick-to-pick voltage and approximately 1 cm of distance between the superior electrode and the culture media. We evaluate the growth on the treated culture media (counting the colony-forming unit - CFU) and also analyzed the morphology of the treated microorganisms in comparison with the samples without treatment, through scanning electronic microscopy (SEM). Through these experiments, we could observe that, applied on a surfaces, the plasma is an efficient and fast sterilization method. This is because during the discharge are formed ozone, UV photons, and free particles, that can contribute to the effect of sterilization

In addition, two unknown vibronic bands have been observed in the 12150 cm-1 region and 12450 cm-1 region. From the observed linewidths, isotopic shift of the transition frequency and appearance of intricate spectral pattern, it is plausible that these bands may be due to C2 under the perturbation of a state inaccessible by dipole transition. Further analysis of these bands are underway. / The unprecedented sensitivity and resolution achieved by our spectrometer allows the measurement of the very weak Phillips band system (A 1piu - X1Sigmag +) of C2 in the plasma of methane and helium at a ratio of 1:170 generated under very mild ac hollow cathode discharge conditions. A total of eleven vibronic bands of the Phillips system have been observed in the region from 10300 cm-1 to 14250 cm-1 and analyzed based on the previous work. Combining the observed transition frequencies with those from Douay et al. [J. Mol. Spectrosc. 131, 250 (1988)], a set of spectroscopic constants for both the X1Sigma g+ and A1piu states have been obtained using least-squares fitting. Excellent agreement has been found between determined molecular constants and those found in the literature. The observation of the high upsilon levels in the 1piu state allows the determination of high order anharmonic constants oeze and oeae for the first time. / This thesis reports the construction of a custom-designed experimental setup for the high resolution near infrared spectroscopic studies of molecular ions and radicals generated in gaseous plasma. The home-built near infrared spectrometer system has a frequency resolution of 500 kHz and a frequency accuracy of ∼0.0010 cm-1 with a detection sensitivity of DeltaI/I of 10-6 using zero background concentration modulated phase sensitive detection scheme. An in-house program has been designed for data acquisition, frequency calibration and data processing and storage. / Yeung, Shun Hin. / Source: Dissertation Abstracts International, Volume: 72-04, Section: B, page: . / Thesis (Ph.D.)--Chinese University of Hong Kong, 2010. / Includes bibliographical references (leaves 129-134). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. Ann Arbor, MI : ProQuest Information and Learning Company, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese.

O campo magnético crítico superior e a temperatura crítica são calculadas para supercondutores com impurezas. Na avaliação das funções de Green do problema são usadas as autofunções exatas de um elétron em um campo magnético constante, ao invés da aproximação semi-clássica comumente utilizada. / The upper critical field and the Critical Temperature of a dirty superconductor are calculated. To evaluate the Green Functions we avoid the semi-classical aproximation by using the exact eletrons eigenstates in a magnetic field.

Orientador: Helmut Karl Bockelmann / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica / Made available in DSpace on 2018-09-26T18:20:22Z (GMT). No. of bitstreams: 1 Kayama_MiltonEiji_D.pdf: 5536651 bytes, checksum: 2a4fabce98ccec64ad3f1c3a6fcdba86 (MD5) Previous issue date: 1987 / Resumo: A reconexão de tinhas magnéticas e a formação da configuração reversa de campo (FRC) foi estudada num theta-pincn sem espelhos magnéticos. O plasma foi diagnosticado por sondas magnética múltiplas, sonda diamagnética compensada (sonda de fluxo excluído), espectroscopia na região do visível e fotografia ultra-rápida. Foi observado um valor da resistividade efetiva no plasma maior que o predito classicamente. O tempo de reconexão das linhas magnéticas foi menor que 0,2 microseg; esta reconexão rápida mostrou boa concordância com modelos teóricos que associam este fenômeno às instabilidades de ruptura (tearing) e de Krusk al- Schwartzschild / Abstract: The reconnection of magnetic field Iines and the formation of field reversed configuration (FRC) were studied on a mirrorless theta-pinch. The applied diagnostics were multiple magnetic probe, compensated diamagnetic probe (excluded flux probe). visible spectroscopy and fast photograph. We observe an high, value on the effective plasma resistivity, greater than the classic Spitzer resistivity value. A fast reconnection was also observed, in a time less than 0.2 microsec; this phenomena is in good agreement with theoretical models which associate it to the resistive tearing mode instability and the Kruskal- Schwartzschild instability / Doutorado / Mestre em Engenharia Elétrica

Las actividades que se desarrollan en las ciudades dinamizan la economía global; no obstante, estos procesos urbanos son, actualmente, intensivos en emisión de gases de efecto invernadero (GEI). Es de interés mundial reducir estas emisiones con la transición a sistemas de bajo consumo de carbono. Para ello, se implementa, en los subsistemas urbanos, tecnologías de captación de recursos endógenos donde se aborda el nexo energía – agua – alimento. El estudio posee dos objetivos: (i) determinar el grado de autosuficiencia energética, hídrica y alimentaria para afianzar la seguridad respectiva; (ii) cuantificar la reducción de GEI respecto del contexto actual. Asimismo, la investigación se sustenta en: (a) prevenir la discontinuidad del suministro y reducir la dependencia de fuentes externas; (b) el cumplimiento del compromiso medioambiental del Acuerdo de París, Convención Marco de las Naciones Unidas sobre el Cambio Climático (2016). Para el análisis, se han seleccionado tres ciudades por cada región geográfica de Perú: Ica, Ayacucho y Pucallpa; cada una con una climatología, morfología urbana y un mix eléctrico regional particular. Estas ciudades son representativas porque se encuentran en las regiones climatológicas donde se concentra la mayor parte de la población nacional. Por ello, éstas se han caracterizado en demanda y oferta con datos de energía solar incidente, temperatura, pluviometría y consumo de agua, electricidad y alimentos. Posteriormente, a partir del plano urbano, ArcGis 10.3 cuantifica la superficie de cubierta disponible. Como último paso para obtener el potencial real, se aplican una serie de factores de corrección por área y eficiencia. Los resultados indican que los recursos endógenos permiten satisfacer la demanda; específicamente, en energía. Asimismo, el análisis ambiental con el método IPCC 2013 en Simapro v8.2 evidencia una importante reducción de emisiones de GEI, la cual varía en cada ciudad según el mix eléctrico particular con el que es comparado. Finalmente, a través del análisis de sensibilidad, se determina valores ideales que ciertos parámetros de crecimiento urbano deben mantener para afianzar la seguridad entre el nexo urbano descrito y la sostenibilidad ambiental. / Cities concentrate global development through different economic activities. However, currently urban processes are highly intensive in terms emission of greenhouse gas (GHG) emissions. The reduction of these emissions is a global concern that has triggered the transition to low carbon systems. Thus, it is imperative to implement technologies of endogenous resources in urban subsystems that can deal with the energy-water–food nexus. Therefore, this dissertation has two main objectives. On the one hand, to determine the selfsufficiency factor in energy, water and food to strengthen their respective security. On the other hand, the establishment of a quantification framework to calculate GHG emission reductions with respect to the current situation. The importance of this study is based on an effort to decentralize the supply of energy, water and food in urban environments, reducing the dependence on external sources. For this, the underutilization of rooftops was identified as a potential vector to generate endogenous resources in cities. Three cities (i.e., Ica, Ayacucho and Pucallpa) were selected for analysis, each of them representing a particular climatic region of Peru. These cities were deemed representative because they are in the climatic regions where most of the Peruvian population is concentrated. Hence, they were characterized by their demand and supply through data of incident solar energy, temperature, precipitation and water, electricity and food consumption. Subsequently, based on land registry plans, ArcGis 10.3 quantify the surface of available rooftops. As the final step to obtain the real potential, correction factors were applied by area and efficiency. The results indicate that endogenous resources allow meeting the demand of electricity, water and horticulture products. In addition, environmental analysis using Life Cycle Assessment with the IPCC 2013 assessment method showed that there is a significant reduction of GHG emissions, which varies in each city due to the particular electric mix of comparison. Finally, through the sensitivity analysis, particular values that certain parameters of urban growth should keep are determined in order to secure the safety between the urban nexus and the environmental sustainability. / Tesis

This thesis describes physics research carried out at the Columbia Neutral Torus (CNT) stellarator after its adaptation from a non-neutral plasma experiment to a device relevant to magnetic fusion energy research. Results are presented in the areas of plasma heating and related topics (microwave-assisted plasma start-up, overdense heating, inversion of stellarator images), as well as to stellarator stability and related topics (high β, error fields). This thesis also describes the engineering improvements which enabled the said adaptation of CNT. The first step of that process involved the installation of a low-power, pulsed 2.45 GHz magnetron. In those initial experiments it was found that the simultaneous use of microwave start-up and of an emissive hot cathode resulted in non-linearly increased electron densities, implying a synergy between the two start-up methods. Then, a 10 kW, 2.45 GHz heating system was commissioned including a custom-designed transmission line and launch antenna. Highly overdense plasmas (a factor of 4 above the cutoff density) were obtained with this system, both for O-mode and X-mode polarization. The analysis of Langmuir probe profiles of density and temperature required the accurate mapping of the minor radius in the plasma, which motivated a study of CNT error fields. This resulted in a new numerical method for inferring coil misalignments from flux surface measurements. The improved knowledge of the actual magnetic field geometry of CNT permitted to develop and successfully apply an inversion technique to experimental plasma images. This technique (“onion peeling”) reconstructs radial emissivity profiles, and can be considered a 3D generalization of Abel inversion. Finally, simulations of high-β plasma equilibria in different CNT magnetic configurations indicate that (1) ballooning stability limits should be accessible at volume-averaged β as low as 0.9% and (2) ballooning-stable β values as high as 3.0% should be attainable with heating powers as low as 40-100 kW and 1-3 MW respectively, according to stellarator energy confinement scaling laws.

The first study of magnetohydrodynamic (MHD) equilibria and external kink modes in shaped plasmas on the High Beta Tokamak - Extended Pulse (HBT-EP) is described. A new poloidal field coil and high-current, low-voltage capacitive power supply was designed and installed. The new coil significantly modifies the shape of the plasma cross section and provides a new research tool for the study of kink mode structure and control. When fully energized, the coil creates a magnetic separatrix, which defines the boundary between confined and unconfined plasma. The separatrix is set by a poloidal field null called an “X-point”, which is on the inboard side of the torus, above the midplane. Several arrays of magnetic sensors observe and characterize the plasma equilibrium and the MHD fluctuations from kink modes. Free-boundary plasma equilibria are reconstructed using standard methods that minimize the mean-square error between the numerically reconstructed equilibria and various measurements. Reconstructions of shaped plasma equilibria show the creation of fully diverted plasmas with shaped outer boundaries. The reconstructions are confirmed by direct measurements using arrays of magnetic sensors and a moveable Langmuir probe to measure the outermost closed flux surface. Measurements of individual kink modes are obtained from the magnetic fluctuations using a technique known as biorthogonal decomposition. External kink modes that naturally arise in shaped plasmas are observed and described. The poloidal structure of modes in shaped plasmas are found to be similar to those that arise in circular plasmas, except near the X-point. The magnetic signature of kink modes on the surface of the plasma are calculated using the ideal MHD code DCON. For plasmas with an X-point, DCON shows a short-wavelength, low amplitude structure near the X-point. The code VALEN is used to calculate the perturbed magnetic field measured at the sensors due to the DCON mode at the plasma surface. VALEN includes the effects of sensor/plasma separation and eddy currents induced in conducting structures by rotation of the modes. Good agreement is found between the measured mode structures and the ideal kink mode structures calculated at the sensors by VALEN. A distributed array of forty active control coils was used to perturb the plasma equilibria, and for both shaped and circular equilibria, the structure of the response to the perturbation was found to be the same as the that of the dominant naturally occurring mode in that equilibrium. Finally, the magnitude of the plasma’s response to applied magnetic perturbations was found to be comparable between shaped and unshaped plasmas, even though separation between the sensors and the boundary of the shaped plasmas increases relative to circular plasmas with the same plasma current and radial positions. In addition to demonstrating a new research tool for study of kink modes on HBT-EP, this research demonstrates the importance of accurate electromagnetic calculations, including eddy currents, when comparing measured and predicted mode structure.

The primary achievement of this study is the development of a new approach for optimizing the plasma shape in a tokamak fusion energy reactor. In the interest of producing the largest possible fusion power output, the shape is optimized to allow for the highest possible beta - the ratio of the fluid to magnetic pressure - that can be sustained without the onset of magnetohydrodynamic (MHD) instabilities. To this end, the study explores the beta-domain that is stabilizable by bulk plasma rotation, with rotation timescales comparable to the resistive dissipation time of the plasma tearing surfaces or of the surrounding vacuum chamber. Modern feedback control systems are able to apply external magnetic fields which are phased to emulate the effect of plasma rotation, making the technique applicable even to large tokamaks with inadequate plasma rotation. In order to explore how the rotationally stabilizable beta-domain is affected by plasma shaping, a new semi-analytic MHD model of a tokamak has been developed. In addition to shaped toroidal tokamak geometry, the model contains dissipative effects resulting from resistivity in both the plasma and in the vacuum-chamber wall. The inclusion of plasma and wall resistivity introduces a lower beta-limit, associated with the onset of an unstable MHD mode, which can become dominated by either resistive-plasma (tearing) or resistive-wall effects in different parts of the parameter space. The computation time for analyzing the mode stability is greatly reduced by approximating the plasma current to reside in a thin layer, a form known as a sharp-boundary model. With fast calculations that focus on the key physics of these MHD instabilities, the model is able to explore qualitative trends of rotational stabilizability over a broad range of plasma shapes. Results of this study predict that varying the elongation or triangularity of the plasma cross-section can lead to qualitatively different beta-limits for the rotationally stabilizable domain. As the shape is varied, the upper bound in beta for rotational stabilization is found to switch from resistive-wall dominated behavior to resistive-plasma dominated behavior. The optimal plasma shape, associated with the highest beta-limit achievable with plasma rotation, is shown to be at the crossing point between the two domains. This discovery provides a basis for understanding existing experimental results and lays the groundwork for more quantitative studies with larger codes.

This thesis presents simulation and experimental work on feedback control of the \emph{phase} of non-rotating magnetic islands (locked modes) in the DIII-D tokamak, as well as its application to synchronized modulated current drive, for stability studies and control of the locked mode \emph{amplitude}. A numerical model has been developed to predict mode dynamics under the effect of various electromagnetic torques, due to the interaction with induced currents in the wall, error fields, and applied resonant magnetic perturbations (RMPs). This model was adapted to predict entrainment capabilities on ITER, suggesting that small (5~cm) islands can be entrained in the sub-10~Hz frequency range. Simulations and subsequent experiments on DIII-D demonstrated a novel technique to prevent locked modes. Preemptive entrainment applies a rotating RMP before a neoclassical tearing mode fully decelerates such that it will be entrained by the RMP and mode rotation can be sustained. A feedback control algorithm was designed and implemented on DIII-D to offer the ability to prescribe any toroidal phase to the mode and to allow for smoother entrainment. Experimental results confirmed simulation predictions of successful entrainment, and demonstrated one possible application to electron cyclotron current drive (ECCD). Feedback-controlled mode rotation and pre-programmed ECCD modulation were synchronized at DIII-D. This allowed a fine control of the ECCD deposition relative to the island O-point. Experiments exhibited a modulation of the saturated island width, in agreement with time-dependent modeling of the modified Rutherford equation. This work contributes to control and suppression of locked modes in future devices, including ITER.

Submitted by WELLINGTON DAVIS ZORNETA null (wdavisz@gmail.com) on 2017-03-07T22:01:44Z No. of bitstreams: 1 DEFESA_WELLINGTON_07_03_17.docx: 3122710 bytes, checksum: a1c5031dbf83a250882078bb3596eec3 (MD5) / Rejected by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br), reason: Solicitamos que realize uma nova submissão seguindo as orientações abaixo: A versão final da dissertação/tese deve ser submetida no formato PDF (Portable Document Format). O arquivo PDF não deve estar protegido e a dissertação/tese deve estar em um único arquivo, inclusive os apêndices e anexos, se houver. Por favor, corrija o formato do arquivo e realize uma nova submissão. Agradecemos a compreensão. on 2017-03-10T19:09:00Z (GMT) / Submitted by WELLINGTON DAVIS ZORNETA null (wdavisz@gmail.com) on 2017-03-11T10:46:25Z No. of bitstreams: 1 DEFESA_WELLINGTON_07_03_17.pdf: 2349479 bytes, checksum: a8a3c7d452a376d189825c87f032576b (MD5) / Rejected by LUIZA DE MENEZES ROMANETTO (luizamenezes@reitoria.unesp.br), reason: Solicitamos que realize uma nova submissão seguindo as orientações abaixo: No campo “Versão a ser disponibilizada online imediatamente” foi informado que seria disponibilizado o texto completo porém no campo “Data para a disponibilização do texto completo” foi informado que o texto completo deverá ser disponibilizado apenas 6 meses após a defesa. Caso opte pela disponibilização do texto completo apenas 6 meses após a defesa selecione no campo “Versão a ser disponibilizada online imediatamente” a opção “Texto parcial”. Esta opção é utilizada caso você tenha planos de publicar seu trabalho em periódicos científicos ou em formato de livro, por exemplo e fará com que apenas as páginas pré-textuais, introdução, considerações e referências sejam disponibilizadas. Se optar por disponibilizar o texto completo de seu trabalho imediatamente selecione no campo “Data para a disponibilização do texto completo” a opção “Não se aplica (texto completo)”. Isso fará com que seu trabalho seja disponibilizado na íntegra no Repositório Institucional UNESP. Por favor, corrija esta informação realizando uma nova submissão. Agradecemos a compreensão. on 2017-03-16T20:39:25Z (GMT) / Submitted by WELLINGTON DAVIS ZORNETA null (wdavisz@gmail.com) on 2017-03-16T21:12:53Z No. of bitstreams: 1 DEFESA_WELLINGTON_07_03_17.pdf: 2349479 bytes, checksum: a8a3c7d452a376d189825c87f032576b (MD5) / Approved for entry into archive by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br) on 2017-03-22T14:31:53Z (GMT) No. of bitstreams: 1 zornetta_wd_me_guara.pdf: 2349479 bytes, checksum: a8a3c7d452a376d189825c87f032576b (MD5) / Made available in DSpace on 2017-03-22T14:31:53Z (GMT). No. of bitstreams: 1 zornetta_wd_me_guara.pdf: 2349479 bytes, checksum: a8a3c7d452a376d189825c87f032576b (MD5) Previous issue date: 2017-01-26 / Os gases siderúrgicos disponíveis em empresas do setor como resultado de seus principais processos de transformação são o gás de coqueria (COG), o gás de alto forno (BFG) e o gás de aciaria (LDG); que são bastante valorizados pelo fato de minimizarem a necessidade de emprego de gás natural ou outra fonte combustível. As centrais termelétricas estão entre as principais consumidoras desses combustíveis, e a distribuição de combustíveis siderúrgicos para as mesmas é um problema discutido na literatura técnica como uma forma de minimizar os desequilíbrios entre a geração e o consumo dos mesmos. Ao mesmo tempo, busca-se maximizar a eficiência energética da empresa e a confiabilidade/disponibilidade do seu suprimento às unidades consumidoras sem queima direta nas torres de queima (flares). A presente proposta de pesquisa tem por objetivo modelar e propor soluções para a otimização da distribuição de gases combustíveis em centrais termelétricas em ciclo combinado gás/vapor considerando os impactos que a troca de combustíveis operam sobre o acionador principal (no caso, o conjunto a gás) em termos de sua resposta à intercambiabilidade entre combustíveis. As modificações propostas neste trabalho otimizam simultaneamente a distribuição de gases subproduto no sistema de gases siderúrgicos; foram avaliadas 56 combinações de combustíveis, o que resultou numa faixa de potência ideal para a aplicação do estudo entre 30 MW e 80 MW, e outra faixa entre 10 MW e 30 MW que deve ser evitada quando o objetivo é a receita liquida positiva. O estudo de caso mostra que o modelo proposto encontra a solução ideal em termos de redução de custo total quando se aplica o uso do COG na mistura com GN, bem como na substituição do GN por uma mistura de gases de processo COG e BFG, o que resultou nos três melhores resultados de receita líquida encontrados nesta análise.