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Identificação e monitoramento do regime fluidodinamico do leito de jorro no recobrimento de particulas / Identify and monitoring of flow regimes spouted bed coating of particlesLopes, Nadia Eliza Correa 23 November 2007 (has links)
Orientadores: Osvaldir Pereira Taranto, Virginia Aparecida Silva Moris / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-10T18:40:09Z (GMT). No. of bitstreams: 1
Lopes_NadiaElizaCorrea_M.pdf: 3103834 bytes, checksum: fb203b4d1396353b5e15847051d51028 (MD5)
Previous issue date: 2007 / Resumo: O recobrimento de partículas em leito de jorro tem se mostrado bastante promissor, tendo em vista o seu potencial de aplicações em diversos produtos como comprimidos, cosméticos, sementes, fertilizantes. A maioria dos trabalhos reportados na literatura são baseados em observações visuais, em colunas construídas com material transparente, operados a pressão e temperatura ambiente. Porém, o reconhecimento visual dos regimes de escoamento não é possível em escala industrial ou com altas pressões. Logo, o objetivo desse trabalho foi identificar modificações ocorridas durante o processo de recobrimento de partículas em leito de jorro, pela comparação de observações visuais em conjunto com os espectros de potência obtidos a partir da aquisição de dados de queda de pressão em tempo real, utilizando a técnica FFT (Fast Fourier Transform). Para este estudo foram utilizadas partículas de diferentes formas, ABS e poliestireno, com diâmetro médio de 3,03 mm e 3,81 mm, respectivamente, e suspensão polimérica a base de Eudragitâ. O recobrimento foi realizado em um leito de jorro cone cilíndrico, confeccionado em acrílico com as seguintes dimensões: H = 70 cm, Dc = 14,3 cm, Di = 4 cm e ? = 60°, as condições operacionais foram pré-fixadas para cada partícula baseadas em ensaios preliminares. As flutuações da queda de pressão foram determinadas utilizando o software LabView 7.1, a uma taxa de amostragem de 400 Hz. Os resultados permitiram identificar durante o recobrimento a redução na taxa de circulação de partículas, zonas mortas e até ¿completo¿ colapso do leito, tanto por variações fluidodinâmicas visualmente observadas no leito, quanto por alteração espectral on line durante os experimentos de recobrimento. No futuro essa identificação pode ser útil como ferramenta no desenvolvimento de um sistema de controle ao processo de recobrimento / Abstract: The coating of particles in spouted has shown sufficiently promising, in view of its potential of applications in several products such as tablets, cosmetics, seeds, fertilizers. However, the works reported in literature had been predominantly based on visual observations, through columns constructed with transparent material, operated the pressure and ambient temperature. Furthermore, the visual recognition of flow regimes is not possible in industrial scale or with high pressures. Soon, the aim of this work was to identify modifications accured during the coating of particle in spouted bed, the comparison of the visual behavior with the power spectrum gotten from the acquisition of data of pressure drop in real time, using technique FFT (Fast Fourier Transform). For this study had been used particles of ABS and polystyrene, with average diameter of 3,03 mm and 3.81 mm, respectively, and aqueous polymeric suspension the base of Eudragitâ. The coating was carried through in a conical-cylindrical spouted bed, confectioned in acrylic with the following dimensions: H = 70 cm, Dc = 14,3 cm, Di = 4 cm and ? = 60°, the operational conditions had been fixed for each particle based in preliminary assays. The fluctuations of the drop pressure had been acquired using software LabView 7.1, to a rate of sampling of 400 Hz. The results had allowed to identify during the coating the reduction in the circulation rate of particle, zones deceased and until complete collapse of the spouted bed, as much for fluid-dynamics variations visually observed in the spouted bed, how much for spectral alteration during the coating experiments. In the future this identification can be useful development a control process tool / Mestrado / Engenharia de Processos / Mestre em Engenharia Química
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Padrão de sobreposição e co-ocorrência interespecífica de moscas-das-frutas (Diptera, Tephritidae, Anastrepha) em áreas antropizadas / Overlap pattern and interespecific co-ocurrence of fruit flies (Diptera, Tephritidae, Anastrepha) in anthropic areasTayron Sousa Amaral 11 March 2014 (has links)
O padrão de sobreposição de nicho e a co-ocorrência, bem como as interações positivas e negativas entre espécies de Anastrepha, com base em matrizes com dados de abundância e presença-ausência, foi avaliado. As populações de Anastrepha foram estudadas também quantativamente para avaliar sua distribuição e a flutuação populacional das espécies predominantes. O estudo foi realizado em duas áreas antropizadas, denominadas Fazenda Areão e Monte Olimpo, do campus \"Luiz de Queiroz\", Universidade de São Paulo, Piracicaba, SP. O estudo foi baseado em 52 coletas por meio de 14 armadilhas tipo McPhail distribuídas nas duas áreas. Foram coletadas 1.583 fêmeas pertencentes a 14 espécies: A. amita Zucchi, A. barbiellinii Lima, A. bistrigata Bezzi, A. daciformis Bezzi, A. distincta Greene, A. fraterculus (Wiedemann), A. grandis (Macquart), A. manihoti Lima, A. montei Lima, A. obliqua (Macquart), A. pickeli Lima, A. pseudoparallela (Loew), A. serpentina (Wiedemann) e A. sororcula Zucchi. Na Fazenda Areão, foram coletadas mais espécimes (1.041), em comparação ao Monte Olimpo (542), que, entretanto, apresentou o maior índice de diversidade de espécies. Anastrepha fraterculus, A. obliqua e A. pseudoparallela foram predominantes na Fazenda Areão; no Monte Olimpo, apenas A. fraterculus e A. pseudoparallela foram predominantes. A média de sobreposição de nicho foi maior que o esperado ao acaso para as duas áreas, portanto, os nichos ecológicos das espécies, em grande parte, se sobrepõem. O padrão de co-ocorrência indicou a ocorrência de dois pares de espécies não aleatórios que segregaram: A. pseudoparallela x A. obliqua na Fazenda Areão e A. fraterculus x A. pseudoparallela no Monte Olimpo. A segregação indica que pode haver competição por algum recurso dentro do nicho. A análise também apresentou três pares agregados: A. bistrigata x A. montei e A. fraterculus x A. barbiellinii para a Fazenda Areão e A. fraterculus x A. bistrigata para o Monte Olimpo, indicando que cada par coexiste pacificamente, sem que haja interferência na permanência das populações de moscas-das-frutas nas áreas. O nível populacional mais elevado ocorreu de agosto a dezembro, nas duas áreas, quando as temperaturas oscilaram entre 18 e 24°C, com pico populacional em setembro. / The niche overlap pattern and co-ocurrence, as well as positive and negative interactions among Anastrepha species, based on abundance matrix data and presence-absence data was evaluated. The populations of species of Anastrepha was analyzed quantitatively to evaluate its distribution and the populational fluctuation of predominant species. The study was carried out in two anthropic areas, Fazenda Areão and Monte Olimpo, at \"Luiz de Queiroz\" campus, Universidade de São Paulo, Piracicaba, SP. The research was based on 52 samplings obtained over 14 McPhail traps distributed in these two areas. It was captured 1,583 females belong 14 species: A. amita Zucchi, A. barbiellinii Lima, A. bistrigata Bezzi, A. daciformis Bezzi, A. distincta Greene, A. fraterculus (Wiedemann), A. grandis (Macquart), A. manihoti Lima, A. montei Lima, A. obliqua (Macquart), A. pickeli Lima, A. pseudoparallela (Loew), A. serpentina (Wiedemann) and A. sororcula Zucchi. It was collected more specimens (1,041) at Fazenda Areão, comparing with the ones at Monte Olimpo (542), that showed the highest species diversity index. Anastrepha fraterculus, A. obliqua and A. pseudoparallela were the predominant species at Fazenda Areão; at Monte Olimpo, only A. fraterculus and A. pseudoparallela were predominant. The niche overlap mean was higher than randomly expected for these two areas. Therefore, the species ecological niches mostly overlap. The coocurrence pattern indicated the ocurrence of two non-randomized pair of species that segregated: A. pseudoparallela x A. obliqua at Fazenda Areão, and A. fraterculus x A. pseudoparallela at Monte Olimpo. The segregation indicates that can exist three aggregated pairs: A. bistrigata x A. montei and A. fraterculus x A. barbiellinii at Fazenda Areão; and A. fraterculus x A. bistrigata at Monte Olimpo, indicating that each pair coexists pacifically, with no interference in the permanence of the fruit fly populations in the areas. The highest populational level occurred from August to December, when temperatures oscillated between 18 and 24°C, with the population peak in September.
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Amarelo da ameixeira: Modelo de colonização do hospedeiro por um fitoplasma associado à doença / Plum yellow: colonization model of the host by a phytoplasma associated with this diseaseSarah Rodrigues Galvão 18 January 2016 (has links)
A cultura da ameixeira vem despertando a atenção de produtores brasileiros, pois oferece alta rentabilidade, possibilita a prática da agricultura familiar, emprega mão de obra, recebe incentivos de programas oficiais e conta com um mercado altamente promissor. No entanto, a cultura ainda necessita de cultivares com melhor adaptação climática, qualidade de frutos e resistência às doenças. Atualmente, dentre as doenças, o \"amarelo das fruteiras de caroço\", associada a um fitoplasma, vem causando sérios problemas. Em 2013, em pomares comercias de ameixeira (Prunus salicina), instalados em Paranapanema (SP), foram observadas plantas portadoras de sintomas tipicamente induzidos por fitoplasmas, caracterizados por superbrotamento de ramos, redução no comprimento de entrenós, além de amarelecimento, deformação e redução do tamanho de folhas. Nestas plantas foi identificado um fitoplasma pertencente ao grupo 16SrI-B (Candidatus Phytoplasma asteris). Visando aumentar os conhecimentos sobre este patossistema, o objetivo desse trabalho foi estudar a dinâmica da colonização de plantas comerciais de ameixa infectadas pelo fitoplasma. Para isso, em dois pomares, amostras da parte aérea e raiz de plantas sintomáticas, pertencentes às variedades Gulfblaze e Azteca, foram coletadas mensalmente, durante um ano. O DNA total foi extraído e submetido ao PCR em tempo real para quantificar o fitoplasma nos tecidos do hospedeiro. Nessas reações foram utilizados os iniciadores universais UniRNAForward/UniRNAReverse. O fitoplasma foi detectado em todas as amostras, tanto aquelas da parte aérea quanto de raízes, em ambas as variedades estudadas. A concentração do patógeno nos tecidos do hospedeiro variou de 5,3 x 103 a 4,54 x 106 e 3,28 x 103 a 1,28 x 106 número de cópias/100ng de DNA total, na parte aérea e nas raízes, respectivamente. Os resultados mostraram uma flutuação sazonal na concentração do fitoplasma, onde as maiores concentrações foram encontradas nas épocas mais quentes do ano, principalmente no mês de dezembro, e uma redução na concentração do patógeno foi observada nas épocas mais frias, embora o fitoplasma tenha permanecido na parte aérea da planta durante a fase de dormência do hospedeiro. A variedade Gulfblaze apresentou maior concentração do patógeno comparada com a variedade Azteca. O fitoplasma associado ao amarelo da ameixeira também foi encontrado em maior concentração na copa da planta. Com base nos resultados, amostras retiradas da parte aérea e nas épocas mais quentes do ano são as mais indicadas para os procedimentos de detecção do patógeno, visando uma diagnose mais confiável. / Plum is a crop that has aroused the attention of Brazilian growers due to high profitability, family farming, incentive arrangement and promising market. However the plum culture still need of varieties with good climate adaptation, best quality fruit, and disease resistance. Currently, among the diseases, stone fruit yellows, associated with a phytoplasma have caused serious problems. In 2013, in commercial orchards of plum (Prunus salicina) located in Paranapanema (SP), plants were observed exhibiting symptoms typically induced by phytoplasmas, characterized by witches broom and shortened internodes. Besides, the leaves were yellowish, malformed, and reduced in size. In these plants was identified a phytoplasma belonging to the group 16SrI-B (Candidatus Phytoplasma asteris). The aim of the present work was to study the dynamics of colonization of commercial plants plum by the phytoplasma, in order to better understanding of the disease. Thus, in two orchards, samples from aerial parts and roots of symptomatic plants belonging to Gulfblaze and Azteca varieties were collected monthly, during a year. Total DNA was extracted and submitted to the Real Time PCR to quantify the phytoplasma in host tissues. In these reactions the universal primers UniRNAForward/UniRNAReverse were used. The phytoplasma was detected in all samples, both aerial parts and roots of the two varieties. The concentration of the pathogen in host tissues ranged from 5,3 x 103 to 4,54 x 106 and 3,28 x 103 to 1,28 x 106 number of copies/100 ng of total DNA in aerial parts and roots, respectively. The results showed a seasonal fluctuation in the concentration of phytoplasma. The highest concentrations were found in the warmer seasons of the year, especially in December, and a reduction in pathogen concentration was observed when the weather was milder, although the phytoplasma remained in aerial part of the plant during the dormant phase of the host. The Gulfblaze variety showed a higher concentration of the pathogen compared with the Azteca variety. In addition, the phytoplasma associated with the disease was found in highest concentration in the aerial part of plant. Based on the results, samples collected from the aerial part and in the warmer seasons of the year are the most recommended for pathogen detection procedures for safe diagnosis.
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Monitoramento de moscas-das-frutas (Diptera, Tephritidae, Anastrepha) em nove municípios do Estado do Valle del Cauca, Colômbia / Monitoring of fruit flies (Diptera, Tephritidae, Anastrepha) from nine municipalities of the state of the Valle del Cauca, Colombia.Marisol Giraldo Jaramillo 10 December 2007 (has links)
Neste estudo, são discutidas as moscas-das-frutas coletadas nos monitoramentos realizados pelo Instituto Colombiano Agropecuário (ICA), em nove municípios do estado do Valle del Cauca (Andalucia, Caicedonia, La Unión, Restrepo, Roldanillo, Sevilla, Toro, Tulúa e Zarzal), em diversas culturas (goiaba, mamão, café, laranja, pitahaya, etc.). Este estudo teve por objetivos: (1) identificar as espécies de Anastrepha e (2) analisar as populações das espécies mais freqüentes e numerosas. As moscas foram coletadas em armadilhas plásticas ou de vidro tipo McPhail com atrativo alimentar (proteína hidrolisada) por dois anos (janeiro de 2004 a dezembro de 2005). Nos nove municípios, foram capturadas 1.794 fêmeas de Anastrepha, sendo identificadas dez espécies: Anastrepha distincta Greene, 1934, A. grandis (Macquart, 1845), A. pallidipennis Greene, 1934, A. fraterculus (Wied., 1830), A. obliqua (Macquart, 1835), A. leptozona Hendel, 1914, A. mucronota Stone, 1942, A. serpentina (Wied., 1830), A. manihoti Lima, 1934 e A. striata Schiner, 1868. Anastrepha fraterculus foi a espécie mais freqüente (49% do total das capturas), seguida por A. striata (39,5%) e A. obliqua (7%). As sete espécies restantes, em conjunto representaram apenas 4,5% do total capturado. Anastrepha striata e A. obliqua foram coletadas nos nove municípios. Anastrepha striata foi a mais numerosa nos pomares comerciais de goiaba. Anastrepha fraterculus foi coletada em cinco municípios, mas 90% dos seus exemplares foram coletados em Sevilla e nenhum exemplar foi coletado em Roldanillo, La Unión e Toro. Esses municípios fazem parte da área selecionada para o estabelecimento do systems approach, visando à exportação de mamão aos EUA, por apresentarem áreas de baixa prevalência de A. fraterculus. Em Sevilla, foi coletado o maior número de espécies, sendo três coletadas apenas nos locais amostrados nesse município (A. distincta, A. manihoti e A. serpentina). Anastrepha leptozona e A. pallidipennis foram coletadas apenas em Toro. / This work was based on fruit flies collected during the monitoring conducted by the Instituto Colombiano Agropecuario (ICA) in nine municipalities of the Valle del Cauca province (Andalucia, Caicedonia, La Union, Restrepo, Roldanillo, Sevilla, Toro, Tulua, and Zarzal), on several crops (guava, papaya, coffee, orange, pitahaya, among others). This study had the following objectives: 1) to identify the species of Anastrepha, and 2) to analyze the populations of the most frequent and abundant species. The fruit flies were collected in plastic or glass McPhail type traps with feeding attractant (protein hydrolysate) during two years (from January, 2004 to December, 2005). In the nine municipalities, 1,794 females of Anastrepha of the following species were captured: Anastrepha distincta Greene, 1934, A. grandis (Macquart, 1845), A. pallidipennis Greene, 1934, A. fraterculus (Wied., 1830), A. obliqua (Macquart, 1835), A. leptozona Hendel, 1914, A. mucronota Stone, 1942, A. serpentina (Wied., 1830), A. manihoti Lima, 1934 and A. striata Schiner, 1868. Anastrepha fraterculus was the most frequent species captured (49% of the total captures), followed by A. striata (39.5%) and A. obliqua (7%). The other seven species accounted only for 4.5% of the total captures. Anastrepha striata and Anastrepha obliqua were captured in all nine municipalities Anastrepha striata was the most abundant on guava crops. Anastrepha fraterculus was collected in five municipalities, but 90% of the specimens were captured in Sevilla and none in Roldanillo, La Union or Toro. The former municipalities are part of the area selected to establish a systems approach under which papaya will be exported to the USA, since they bear areas of low prevalence for A. fraterculus. The highest number of species was captured in Sevilla, three were collected only in sites sampled in this municipality (A. distincta, A. manihoti, and A. serpentina). Anastrepha leptozona and A. pallidipennis were captured only in Toro.
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Fluctuations and Interactions of Brownian particles in multiple Optical Traps / Interactions et fluctuations de particules browniennes dans un réseau de pièges optiquesBérut, Antoine 07 July 2015 (has links)
Nous avons étudié expérimentalement les fluctuations de micro-particules browniennes piégées à l'aide de pinces optiques dans un réseau de puits de potentiels voisins. Nous donnons un descriptif général du montage expérimental, puis détaillons quatre utilisations différentes du système. Nous avons d'abord utilisé une unique particule dans un double puits de potentiel pour modéliser un système mémoire à deux niveaux, avec lequel nous avons vérifié le principe de Landauer sur le coût minimal en énergie pour l'effacement d'un bit d'information. Nous avons également appliqué une version détaillée d'un théorème de fluctuation à la procédure d'effacement de l'information pour retrouver la limite énergétique attendue. Nous avons ensuite étudié l'interaction hydrodynamique entre deux particules dont l'une est soumise à une température effective. Nous avons montré qu'il n'y a pas de fluctuations anormales lors de la transition sol-gel de la gélatine, contrairement à ce qui avait été observé précédemment, et que ce système ne pouvait donc pas être utilisé pour étudier des températures effectives. En revanche, nous avons montré que l'ajout d'un forçage aléatoire bien choisi sur la position d'un piège créait une température effective. Nous avons montré que le forçage d'une des particules résultait en une corrélation instantanée entre les mouvements des deux particules, et s'accompagnait d'un échange de chaleur de la particule virtuellement chaude à la particule froide en équilibre avec le bain thermique. Nous avons obtenu un bon accord entre les données expérimentales et les prédictions d'un modèle de couplage hydrodynamique. Enfin, nous décrivons l'utilisation de canaux micro-fluidiques pour réaliser un écoulement cisaillé à l'échelle micrométrique, et nous discutons de la possibilité d'interpréter un cisaillement en terme de température effective en testant une relation de fluctuation-dissipation. / We experimentally study the fluctuations of Brownian micro-particles trapped with optical tweezers arranged in various spatial configurations. We give a general description of the set-up and detail four different experiments we conducted. We first use a single particle in a double-well potential to model a two-state memory system. We verify the Landauer principle on the minimal energetic cost to erase one bit of information, and we use a detailed version of a fluctuation theorem to retrieve the expected energetic bound. We then use two particles in two different traps to study the hydrodynamic interactions between two systems kept at different effective temperatures. Contrary to what was previously observed, we show that the sol-gel transition of gelatine does not provide any anomalous fluctuations for the trapped particle when the sample is quenched below gelification temperature. However, we show that an effective temperature is created when a well chosen random noise is added on one trap position. We demonstrate that the random forcing on one particle induces an instantaneous correlation between the two particles motions, and an energy exchange from the virtually hot particle to the cold one, which is in equilibrium with the thermal bath. We show a good agreement between the experimental data and the predictions from an hydrodynamic coupling model. Finally, we describe the use of micro-fluidic channels to create a shear flow at the micron size, and we discuss the possibility to interpret the force due to the shear-flow in terms of an effective temperature by testing a fluctuation-dissipation relation.
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Three Essays in Financial EconomicsZhang, Qianying 26 May 2017 (has links)
The first paper revisits the link between interest rates and corporate bond credit spreads by applying Rigobon’s (2003) heteroskedasticity identification methodology. The second paper investigates the assumption that financial asset prices including stocks and bonds, reflect intrinsic value. The third paper decomposes the stock price into fundamental permanent, fundamental transitory, and non-fundamental shocks in order to explore the determinants of stock price fluctuations.
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Spontaneous blood oxygen fluctuation in awake and sedated brain cortex – a BOLD fMRI studyKiviniemi, V. (Vesa) 18 June 2004 (has links)
Abstract
Functional magnetic resonance imaging (fMRI) has become a leading tool in the evaluation of the human brain function. In fMRI the activation induced blood oxygenation changes in the brain can be detected with an inherent blood oxygen level dependent (BOLD) contrast. Even small blood oxygen fluctuations in a resting brain can be depicted with the BOLD contrast.
This thesis focuses on characterizing spontaneous oxygenation fluctuations of the brain by using BOLD fMRI. The effects of anesthetics on blood oxygen fluctuations were assessed in 38 children and 12 adults. The spatial distribution, frequency, synchrony, and statistical independence of the spontaneous oxygenation changes were analyzed. The role of imaging artifacts in the generation of BOLD signal fluctuations was investigated. The study aimed to develop and compare methods of detecting the nondeterministic oxygenation fluctuations of the brain.
VLF BOLD signal fluctuation in the brain cortex is induced by physiological oscillation instead of imaging artifacts. This study shows for the first time how the power and synchrony of very low frequency (VLF < 0.05 Hz) blood oxygen fluctuation significantly increases after sedation. In deeper anesthesia, the VLF fluctuation overpowers other sources of blood oxygen variation as a sign of reduced blood flow and altered hemodynamic control. Regional hemodynamic mechanisms induce non-Gaussian features on the VLF blood oxygen fluctuation that can be depicted effectively with independent component analysis. Combined use of frequency, time, and spatial domain analysis guarantees a more complete picture of brain oxygenation fluctuations.
The results of this thesis have a dualistic impact on fMRI research. First of all, VLF fluctuation alters the BOLD activation and connectivity results after sedation. Thus it has to be accounted for in the fMRI of sedated subjects. Secondly, by using the methods developed in this thesis, VLF fluctuation and other physiological BOLD signal sources can now be used in characterizing physiological alterations and pathology of the brain.
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Inquiry of Lipid Membranes Interacting with Functional Peptides and Polyphenol Drug MoleculesHo, Chian Sing 24 June 2016 (has links)
Cellular membranes are important targets for many membrane-active peptides and drug compounds. Here we are interested in deciphering how lipid membranes are perturbed by several membrane-active molecules, including the transmembrane domain of the influenza M2 protein (M2TM), aggregates formed by a synthetic polyglutamine peptide, and three polyphenol compounds (i.e., tamoxifen, genistein, and verapamil). We employ phase-separated ternary lipid model membranes in the form of giant unilamellar vesicles (GUVs) to simulate raft-like structures that have been proposed to govern many important processes in plasma membranes (e.g., intracellular singling and trafficking). Specifically, we use fluorescent microscopy to interrogate how those membrane additives modulate the phase behavior of free-standing GUVs, as well as the miscibility transition temperature (Tm). We find that M2TM increases Tm and causes vesicle budding; polyglutamine aggregates disrupt lipid membranes; and the three polyphenol compounds exert disparate effects on GUV Tm.
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Production d’énergie marine : intégration de la production éolienne offshore dans un bouquet énergétique décentralisé / Production of marine energy : integration of offshore wind generation into a decentralized energy mixIkni, Djamel 11 December 2014 (has links)
ACette thèse s’inscrit dans la continuité des travaux menés sur les problématiques des énergies renouvelables par le laboratoire GREAH. Elle est financée par la communauté de l’agglomération havraise (CODAH). Les taux de fluctuation de la puissance sont réglementés dans des codes de réseaux établis par des gestionnaires de réseau électrique dans le but de minimiser l’impact de ces fluctuations sur la fréquence et la tension du réseau. Comme l’énergie éolienne est de nature fluctuante, nous proposons dans ce rapport des solutions dans le cas où les taux de fluctuations de la production éolienne offshore dépassent ces limites. Parmi ces solutions, la capacité du parc éolien à lisser sa propre puissance ou par intégrations des unités de stockage; dans le premier cas l’utilisation d’une réserve de puissance dans les éoliennes est possible, pour créer cette réserve deux méthodes sont proposées et leurs performances évaluées. Pour deuxième solutions, une méthodologie sera proposée pour déterminer la technologie du stockage. Des propositions pour construire des parcs éoliens offshore avec des technologies en courant continu sont apparues. Pour permettre un couplage répondant et une bonne fiabilité des dispositifs d’électroniques de puissance utilisés dans la conception de ces nouveaux parcs, nous proposons dans ce rapport des convertisseurs adéquats et des stratégies de commandes qui assurent leurs stabilités. / The research work performed in this thesis is in the framework of issues related of renewable energies led by GREAH laboratory. The research work has been funded by Le Havre Municipality Assembly (CODAH). The requirements of power fluctuations in the grid are given by the grid code established by the electricity utilities companies in order to mitigate the impact of the wind power fluctuation on frequency and voltage in electrical grid. As wind energy has a fluctuating behavior, solutions have been proposed in this thesis for the situation where the power produced by an offshore wind power plant exceeds the threshold given by the grid code. Among the solutions, we can quote the ability of the wind power plant to smooth its own power production or integrate storage units. In the first case, the use of power reserve in wind turbines is possible and two methods have been proposed, and their performance evaluated. For the second solution, a methodology to find and to choose out the storage technology has been discussed. Proposals to build offshore wind farms with technologies using direct current (DC) have emerged. To get a coupling which fulfills the requirement of good reliability of power electronic devices used for the design of new wind farms, it has been proposed in this thesis adequate converters and control strategies that ensure their stability.
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Historical Analysis of Riparian Vegetation Change in Response to Shifting Management Objectives on the Middle Rio GrandePetrakis, Roy, van Leeuwen, Willem, Villarreal, Miguel L., Tashjian, Paul, Dello Russo, Regina, Scott, Christopher 22 April 2017 (has links)
Riparian ecosystems are valuable to the ecological and human communities that depend on them. Over the past century, they have been subject to shifting management practices to maximize human use and ecosystem services, creating a complex relationship between water policy, management, and the natural ecosystem. This has necessitated research on the spatial and temporal dynamics of riparian vegetation change. The San Acacia Reach of the Middle Rio Grande has experienced multiple management and river flow fluctuations, resulting in threats to its riparian and aquatic ecosystems. This research uses remote sensing data, GIS, a review of management decisions, and an assessment of climate to both quantify how riparian vegetation has been altered over time and provide interpretations of the relationships between riparian change and shifting climate and management objectives. This research focused on four management phases from 1935 to 2014, each highlighting different management practices and climate-driven river patterns, providing unique opportunities to observe a direct relationship between river management, climate, and riparian response. Overall, we believe that management practices coupled with reduced surface river-flows with limited overbank flooding influenced the compositional and spatial patterns of vegetation, including possibly increasing non-native vegetation coverage. However, recent restoration efforts have begun to reduce non-native vegetation coverage.
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