Um importante diferencial competitivo das empresas distribuidoras de energia elétrica é a gestão da utilização dos seus ativos elétricos. Dentre eles destaca-se o transformador de potência em função de sua importância estratégica no fornecimento de energia aos grandes centros de carga. Para minimizar os impactos operacionais e sociais associados às interrupções constantemente monitoradas para que haja controle efetivo e garantia de funcionamento adequado e otimizado. O monitoramento das suas principais características é um ponto crítico que deve ser constantemente aprimorado, pela indiscutível importância destes ativos elétricos na continuidade do fornecimento de energia elétrica. Este trabalho apresenta proposta para avaliação em tempo real de falhas em transformadores de potência, para que sejam monitorados remotamente pela distribuidora, através do seu respectivo centro de operação do sistema elétrico, propiciando assertividade e rápida tomada de decisão gerencial em ocorrências de falhas internas, reduzindo os custos associados à interrupção do fornecimento de energia elétrica, diminuindo significativamente os tempos de restabelecimento do fornecimento e consequentemente minimizando impactos nos principais Indicadores de qualidade operacional da distribuidora. / An important competitive edge of electric power distribution companies is their electric assets utilization management. Among them stands outs the power transformers because of its strategic importance in the energy supply to high demand areas. To minimize operational and social impacts associated to the electric energy supply interruptions these equipments must to have their main characteristics constantly monitored to have effective control and optimizer functioning warranty. The main characteristics monitoring is a critical point which must be constantly improved, for the unquestionable importance of these electric assets in the electric energy supply continuity. This work shows a proposal to the real time power transformer failure, to remote monitoring by the utilities thru its respective electric system operation center, enabling assertively and fast management decision making in internal failure occurrences, reducing costs associated with electric energy supply interruption, decreasing the supply reestablishing times and consequently minimizing the impacts on the main distribution operational quality indicators.

Neste trabalho s€o apresentadas as medidas do coeficiente de multiplica€o gasosa (α) no isobutano puro obtidas com uma cƒmara de placas paralelas protegida contra descargas por um eletrodo de vidro (anodo) de elevada resistividade (ρ = 2 x 1012.cm). O m†todo empregado foi o de Townsend pulsado, onde a ioniza€o prim‡ria † produzida pela incidˆncia de um feixe de laser de nitrogˆnio em um eletrodo met‡lico (catodo). As correntes el†tricas medidas com a cƒmara operando em regime de ioniza€o e de avalanche foram utilizadas para o c‡lculo do coeficiente de multiplica€o gasosa pela solu€o da equa€o de Townsend para campos el†tricos uniformes. A t†cnica utilizada foi validada pelas medidas do coeficiente de multiplica€o gasosa no nitrogˆnio, um g‡s amplamente estudado, e para o qual se tem dados bem estabelecidos na literatura. Os coeficientes de multiplica€o gasosa do isobutano foram medidos em fun€o do campo el†trico reduzido no intervalo de 139Td a 208Td. Os valores obtidos foram comparados com os simulados pelo programa Imonte (vers€o 4.5) e com os ‰nicos dados existentes na literatura, recentemente obtidos pelo nosso grupo. Esta compara€o demonstrou que os resultados s€o concordantes dentro dos erros experimentais. / In this work it is presented measurements of gaseous multiplication coefficient (α) in pure isobutane obtained with a parallel plate chamber, protected against discharges by one electrode (anode) of high resistivity glass (ρ = 2 x 1012.cm). The method applied was the Pulsed Townsend, where the primary ionization is produced through the incidence of a nitrogen laser beam onto a metallic electrode (cathode). The electric currents measured with the chamber operating in both ionization and avalanche regimes were used to calculate the gaseous multiplication coefficient by the solution of the Townsend equation for uniform electric fields. The validation of the technique was provided by the measurements of gaseous multiplication coefficient in pure nitrogen, a widely studied gas, which has well-established data in literature. The coefficients in isobutane were measured as a function of the reduced electric field in the range of 139Td up to 208Td. The obtained values were compared with those simulated by Imonte software (version 4.5) and the only experimental results available in the literature, recently obtained in our group. This comparison showed that the results are concordant within the experimental errors.

Neste trabalho, duas equações modedlo na área da dinâmica de gases rarefeitos, são derivadas a partir de algumas soluções exatas da equação linearizada de Boltzmann homogênea e não homogênea. Em adição, uma versão analítca do método de ordenadas discretas é usado para resolver problemas clássicos nesta área, descritos pelo "Modelo S". Resultados numéricos são apresentados para os problemas de fluxo de Couette, fluxo de Poiseuille, "Creep" Térmico, Deslizamento Térmico e problema de Kramers.

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2018-01-31T16:50:00Z No. of bitstreams: 1 2016 - Bruna Caroline Franzan.pdf: 2183556 bytes, checksum: 2e937393a56f483356ba48da8c23210a (MD5) / Made available in DSpace on 2018-01-31T16:50:00Z (GMT). No. of bitstreams: 1 2016 - Bruna Caroline Franzan.pdf: 2183556 bytes, checksum: 2e937393a56f483356ba48da8c23210a (MD5) Previous issue date: 2016-07-22 / CAPES / This study aimed to evaluate the feces of horses as an inoculum source to apply to in vitro fermentation tests when roughage is used as the substrate. The design was completely randomized in a 2x2 factorial arrangement. The first factor is hydration time of the substrate: 0 and 12 hours; and the second factor evaluated was the feces dilution with nutritive solution (weight: weight): 1:1 and 1:3. The variables cumulative gas production and degradation of nutrients the design was completely randomized in split plots, with the effect of incubation time as subplots. Three stallions were used as feces donors. After 28 days of adaptation to the diet and management, the feces were collected directly from the rectum of animals. After collection, the feces had been mixed with the nutritive solution in the ratio (weight:weight): 1:1 and 1:3 and kept in a water bath at 39 ? C constantly sprayed with CO2. After one hour, the material was filtered and 10 ml of inoculum had been added to previously prepared bottles. The fermentation bottles were prepared as follows: put 1 g of Coastcross hay and 90 ml of nutritive solution was added at the moment of inoculation or 12 hours before inoculation procedure. The variables bacteria count after 24 h of inoculation, the dry matter degradation (DMD), the organic matter degradation (OMD) and the neutral detergent fiber degradation (NDFD) at 24, 48 and 72 h of fermentation, as well the ammonia nitrogen content (NH3-N), pH and the cumulative gases production over 72 h had been evaluated. The nonlinear regression model adjusted the cumulative gases production. The results were submitted to ANOVA 5%, and the averages compared by SNK test at 5%. There was no significant effect of hydration and dilution factors in OMD, NDFD, NH3-N and the concentration of Lactobacillus spp., Streptococcus spp., cellulolytic bacteria and total anaerobic bacteria. The significant dilution effect in the pH was observed and the significant hydration effect in DMD. The interaction between incubation time and the hydration time of the substrate was detected over the cumulative gases production, with values significantly different starting at eight hours of incubation until the end of process. There was no proper fit to the proposed model, since the L parameter was not significant. The soluble nutrients of the Coastcross hay became available due to the hydration process, therefore, has used for the initial development of the microorganisms reducing the lag phase period of 2.32 (without hydration) to 0.24 h. In conclusion, the hydration of the dehydrated substrate is a strategy that increases the fermentation substrate extension and degradation of dry matter. Moreover, lag phase time was reduced. / Este trabalho teve como objetivo utilizar as fezes de equinos como fonte de in?culo em ensaios de fermenta??o in vitro com alimentos volumosos. Utilizou-se o delineamento inteiramente ao acaso em arranjo fatorial 2x2. O primeiro fator foi o tempo de hidrata??o do substrato: 0 e 12 horas; e o segundo fator foi a dilui??o das fezes com solu??o nutritiva na rela??o (peso:peso): 1:1 e 1:3. Para as vari?veis produ??o cumulativa de gases e degrada??o dos nutrientes o delineamento utilizado foi inteiramente ao acaso em esquema de parcelas subdivididas, com o efeito tempo de incuba??o na subparcela. Tr?s garanh?es foram utilizados como doadores de fezes. Ap?s 28 dias de adapta??o ? dieta e ao manejo, as fezes foram coletadas diretamente no reto dos animais. Ap?s a coleta, as fezes foram misturadas com a solu??o nutritiva na rela??o (peso:peso): 1:1 e 1:3 e mantidas em banho maria a 39?C constantemente borrifadas com CO2. Ap?s uma hora, o material foi filtrado e adicionou-se 10 mL de in?culo em frascos previamente preparados. Nos frascos de fermenta??o colocou-se 1 g do feno de Coastcross e, 90 mL de solu??o nutritiva adicionada no momento da inocula??o ou 12 horas antes da inocula??o. Avaliou-se a contagem bacteriol?gica 24 h ap?s a inocula??o, a degrada??o da mat?ria seca (DMS), mat?ria org?nica (DMO) e da fibra em detergente neutro (DFDN) nos tempos de 24, 48 e 72 h, o teor de nitrog?nio amoniacal (N-NH3), pH e a produ??o cumulativa de gases at? 72 h, a qual foi ajustada pelo modelo de regress?o n?o linear unicompartimental. Os resultados foram submetidos ? ANOVA 5% de signific?ncia, e as m?dias comparadas pelo teste SNK ? 5%. N?o houve efeito significativo dos fatores hidrata??o e dilui??o na DMO, DFDN, N-NH3 e na concentra??o de Lactobacillus spp., Streptococus spp., bact?rias celulol?ticas e bact?rias anaer?bias totais. Houve efeito da dilui??o no pH final e efeito da hidrata??o na DMS. Houve intera??o entre o tempo de incuba??o e o tempo de hidrata??o do substrato na produ??o cumulativa de gases, com valores apresentando diferen?a significativa a partir de oito horas p?s incuba??o. N?o houve ajuste adequado ao modelo proposto, pois o par?metro L n?o foi significativo. A hidrata??o do feno de Coastcross disponibilizou nutrientes sol?veis para o desenvolvimento inicial dos microrganismos, reduzindo o per?odo de fase lag de 2,32 para 0,24 h. Conclui-se que a hidrata??o do substrato volumoso desidratado ? uma estrat?gia que aumenta o volume de gases provenientes da fermenta??o do substrato e a degrada??o da mat?ria seca, al?m disso, reduz o per?odo de fase lag.

Tese de mestrado integrado. Engenharia do Ambiente. Ramo de Gestão. Faculdade de Engenharia. Universidade do Porto. 2011

Tese de mestrado integrado. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 2010

Estágio realizado na AlgaFuel e orientado pelo Doutor Vítor Verdelho Vieira / Tese de mestrado integrado. Engenharia Química. Faculdade de Engenharia. Universidade do Porto. 2008

Peat soils store a large fraction of the global soil carbon (C) pool and comprise 95% of wetland C stocks. They also have the capability to produce and release significant amounts of greenhouse gasses (CO2, CH4) into the atmosphere. Most studies of wetland soil C and gas flux dynamics have been done in expansive peatlands in northern boreal and subarctic biomes. However, wetlands in temperate and tropical climates are vastly understudied despite accounting for more than 20% of the global peatland C stock and storing large amounts of biogenic gasses Although studies investigating greenhouse gas dynamics from peatlands have increased during the last decade, the spatial and temporal distribution of these gases still remains highly uncertain, mainly due to the limitations in terms of spatial and temporal resolution and invasive nature of most methods traditionally used. This thesis combines a series of field and laboratory studies at several sites in the Greater Everglades as examples to show the potential of hydrogeophysical methods to better understand: 1) the belowground C distribution and overall contribution to the global C stocks of certain wetlands (Chapter 2); and 2) the spatial and temporal variability in both C accumulation and releases from peat soil monoliths from several wetland sites in the Greater Everglades (Chapter 3 and 4). To estimate belowground C in the field, I used a combination of indirect non-invasive geophysical methods (GPR), aerial imagery, and direct measurements (coring) to estimate the contribution of subtropical depressional wetlands to the total C stock of pine flatwoods landscape at the Disney Wilderness Preserve (DWP, Orlando, FL). Three-dimensional (3D) GPR surveys were used to define the thickness of stratigraphic layers from the wetland surface to the mineral soil interface within depressional wetlands. Depth-profile cores in conjunction with C core analysis were utilized to visually confirm depths of each interface and estimate changes in soil C content with depth and were ultimately used to estimate total peat volume and C stock for each depressional wetland. Aerial photographs were used to develop a relationship between surface area and total wetland C stock, that were applied to estimate total landscape C stock of all depressional wetlands throughout the entire preserve. Additionally, low-frequency GPR surveys were conducted to image the stratigraphy underneath the peat basin of depressional wetlands to depict lithological controls on the formational processes of depressional wetlands at the DWP. Spatial and temporal variability in biogenic greenhouse gas (i.e. methane and carbon dioxide) production and release were investigated at the laboratory scale. Two 38 liter (0.5 m x 0.23 m x 0.3 m) peat monoliths from two different wetland ecosystems in central Florida (sawgrass peatland and a wet prairie) were compared in order to understand whether changes in matrix properties influence gas dynamics in a controlled environment (i.e. constant temperature). Gas content variability (i.e. build-up and release) within the peat matrix was estimated using a series of high frequency (1.2 GHz) GPR transects along each sample about three times a week. An array of gas traps (eight per sample) fitted with time-lapse cameras were also used in order to constrain GPR measurements and capture gas releases at 15-minute intervals. Gas chromatography was performed on gas samples extracted from the traps to determine CH4 and CO2 content. Also, at the lab scale, temporal variability in biogenic gas accumulation and release was investigated in a large 0.073 m3 peat monolith from the Blue Cypress Preserve in central Florida. An autonomous rail system was constructed in order to estimate gas content variability (i.e. build-up and release) within the peat matrix using a series of continuous GPR transects along the sample. This system ran virtually nonstop using high frequency (1.2 GHz) antennas. GPR measurements were again constrained with an array of gas traps (6) fitted with time-lapse cameras and gas chromatography. The aim of this study is to better constrain temporal scale, and better understand the heterogeneous nature (both in time and space) of gas releases from peat soils. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

Trace gases can have a significant impact on the Earth's climate, and the analysis of changes in these gases and an understanding of how much of these changes are a result of human activity is important for understanding global climate change. Methane (CH4) is the second only to CO2 in radiative forcing over the last 200 years, and its concentration in the atmosphere has more than doubled since 1750. Sources and sinks of CH4 have characteristic isotopic effects, which shift the relative concentration of the methane isotopologues. Spectroscopic techniques for of analysis the isotopic composition of methane have been evolving since the early 1990's, and promise real-time, in-situ measurements that would provide unprecedented information on the methane atmospheric cycle. Here we present our development and results of a new optical spectroscopic isotope ratio instrument using cavity ringdown spectroscopy in the near IR region using the ν2+2ν3 overtone band. This region has limited interference from other molecules, and an advantageous juxtaposition of a 13CH4 triplet, and a single 12CH4 peak, allowing near-simultaneous measurement of both isotopologues. We present the results of two datasets showing high linearity over a wide range of isotope ratios, which achieved a precision of ±4 /. We present analysis of the data and consider the effects of temperature and molecular interference.

Memoria para optar al Título Profesional de Ingeniera Forestal / El dióxido de carbono (CO2) y el metano (CH4) son los principales gases de efecto invernadero (GEI), cuyo aumento sostenido en la atmósfera contribuye al calentamiento global y al cambio climático. El ecosistema esclerófilo de Chile, es un nodo de biodiversidad global cada vez más amenazado, por la actividad humana. El objetivo de este estudio fue verificar si las plantas de este ambiente emiten CH4 en la luz (fotosíntesis) y oscuridad (respiración autotrófica), en seis especies de árboles y arbustos contrastantes (Cryptocarya alba, Quillaja saponaria, Lithraea cáustica, Acacia caven, Colliguaja odorifera y Retanilla trinervia) de los matorrales y los bosques esclerófilos de Chile Central, comparando un verano caluroso y seco frente a un invierno húmedo de temperaturas moderadas. También se esperaba evaluar la relación de los factores ambientales sobre el control de los flujos de CH4 en las plantas. Usando cámaras estáticas, se midieron los flujos de CO2 y CH4 de las plantas mediante un analizador de gases infrarrojo y cromatografía de gases, respectivamente. Las tasas de fotosíntesis fueron mucho mayores en invierno que en verano, aumentando generalmente en la serie: C. alba, L. caustica, Q. saponaria, C. odorifera, R. trinervia y A. caven. La respiración de ramas fue mayor en invierno que en verano, y además mayor en el grupo formado por A. caven, R. trinervia y C. odorifera en comparación con las especies esclerófilas C. alba, L. caustica y Q. saponaria, probablemente asociado a la menor fracción de follaje de rama en el primer grupo comparado con el segundo. Las plantas en la luz durante el verano -generalmente- capturaron CH4, mientras que en invierno, los flujos de CH4 en la plant,a no fueron significativamente diferentes de cero, excepto para A. caven que fue una fuente de éste a la atmósfera (intervalo de confianza del 95%, 12-151 nmol m-2 s-1). En la oscuridad, las plantas generalmente fueron sumideros de CH4 durante el verano, no así en invierno donde no fueron significativamente diferente de cero. La mayor captura de CH4 se observó en R. trinervia en verano (intervalo de confianza del 95%, 89-287 nmol m-2 s-1) en comparación con las otras especies. Los flujos de CH4 en las plantas y en el suelo siguieron un patrón similar que sugiere una fuerte correlación entre ellos. Los flujos de CH4 en el suelo fueron generalmente negativos en el verano capturando CH4 (sumideros) y positivos en invierno (fuentes); que se corresponde con las plantas que capturan CH4 en verano y sin flujos en invierno excepto para A.caven, que emite. Esto sugiere un mecanismo de difusión simple, mediante el cual el CH4 producido en el suelo por metanogénesis en invierno se transporta por el árbol hacia las copas y se libera a través de lenticelas y estomas; mientras que lo opuesto ocurre en verano cuando los metanotrofos del suelo capturan CH4 y generan un gradiente por el cual el CH4 se mueve hacia el suelo desde la atmósfera a través de la planta donde es capturado. Palabras