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In this study, forced cooling of heat sinks mounted on CPU&rsquo / s was investigated. Heat sink effectiveness, effect of turbulence models, effect of radiation heat transfer and different heat sink geometries were numerically analyzed by commercially available computational fluid dynamics softwares Icepak and Fluent. The numerical results were compared with the experimental data and they were in good agreement. Conjugate heat transfer is simulated for all the electronic cards and packages by solving Navier-Stokes equations. Grid independent, well converged and well posed models were run and the results were compared. The best heat sink geometry is selected and it is modified in order to have lower maximum temperature distribution in the heat sink.

CO2 emission is very important, because it is responsible for about 60% of the &quot / Greenhouse Effect&quot / . The major objectives of this study were to prepare a CO2 emission inventory of Turkey based on districts and provinces by using the fuel consumption data with respect to its sources, to find the CO2 uptake rate of forests in Turkey based on provinces and districts, and to estimate the ground level concentration of CO2 across Turkey using U.S. EPA&#039 / s ISCLT3 model for the preparation of ground level concentration maps. The basic sources of the CO2 emission were taken as households, manufacturing industries, thermal power plants and road vehicles. The sinks of the CO2 were forests. The CO2 uptake by forests was calculated using the annual increment of forest biomass. The results of the CO2 emission inventory conducted in this study between the years 1990 and 2003 showed that the CO2 emission in 1990 was 142.45 million tones/year and the highest emission was calculated in 2000 with a value of 207.97 million tones/year. The regional distribution of CO2 emission showed that the Marmara Region emits the highest regional CO2 emission throughout the years with an average value of 54.76 million tones/year. It was also calculated that Marmara and Aegean Regions are responsible for half of the CO2 emission of Turkey. The results of the CO2 uptake calculations showed that the CO2 uptake of forests in the coastal zone was higher that that in the inland zone. The CO2 uptake in the Central Anatolia, Eastern Anatolia and South-Eastern Anatolia Regions were 2.6, 1.9 and 1.1 million tones/year, respectively. The maximum CO2 uptake is in the Black Sea Region with a value of 16.4 million tones/year. The highest ground level CO2 concentartions without any sink effect were always obtained in the Marmara Region. However, the forest areas in this region decrease the concentrations considerably. The dispersion model performance is determined highly without the results of the year 2002.

This thesis is primarily focused on flow-field upstream of hydropower intakes, with emphasis on the use of temperature control curtains and predicting the flow acceleration zone. By reviewing the available literature, it is concluded that the flow-field upstream of hydropower intake systems can be modeled by potential flow theory. The understanding of near intake flow-field can be useful in fish entrainment studies and in designing fish repulsion systems. To control downstream river temperatures, a flexible curtain was installed upstream of several dams in California. Flow downstream of the curtain was analyzed using a Computational Fluid Dynamic (CFD) solver with rigorous validation by experimental data. The experiment was conducted with a 4 beam Acoustic Doppler Velocimeter (ADV) probe. The study shows that wall jet properties downstream of the curtain are affected by the water depth and the inlet Reynolds number. Empirical expressions were developed to predict jet properties and the wall shear stress. Flow upstream of the curtain was analyzed using potential flow theories with validation by the CFD solver. In this part, a theory based on Schwarz-Christoffel transformation was developed to predict the flow-field upstream of the curtain without accounting for any density stratification in the water body. It is observed that the acceleration zone upstream of the curtain can be affected by sink opening size, its location and water depth. The effect of boundaries on flow upstream of a line sink and the interaction of multiple sinks were analyzed. The effect of stratification on a line sink is also analyzed. A theory is developed to predict the incipient withdrawal condition when a sink is located on the horizontal bottom. The theory is also extended to a tilted bottom. The effect of boundaries on the incipient withdrawal condition is analyzed. When only one layer is being withdrawn, it is shown that a homogenous equation can be applied to a stratified condition by assuming an upper layer boundary at the interface. In addition to these works, a despike algorithm for ADV data is developed, and a numerical analysis on central difference scheme is presented. / Water Resources Engineering

Les fréquences de fonctionnement élevées des puces semi-conductrices génèrent des flux de chaleurs importants qu'il est nécessaire d'évacuer pour éviter la destruction de la puce. Un module standard dans le domaine de l'électronique de puissance est composé d'une puce en silicium, d'un isolant électrique (substrat) et d'un dissipateur thermique (drain) permettant l'évacuation de la chaleur. Cette chaleur induit des contraintes thermomécaniques dues à la dilatation différentielle des matériaux.Deux concepts nouveaux proposés permettent de palier ces problèmes et d'augmenter la fiabilité générale des systèmes électroniques. Le premier est la conception et l'élaboration d'un drain composite à propriétés thermiques adaptatives (coefficient de dilatation thermique et conductivité thermique). Dans le deuxième, une nouvelle méthode d'assemblage est présentée. Elle permet, au moyen d'un film métallique Sn ou Au, de créer des composés intermétalliques stables dans le temps. / The high operating frequencies of semiconductor chips generate heat fluxes it is important to be evacuated in order to avoid the destruction of the chip. A standard module in the field of power electronics is composed of a silicon chip, an electrical insulator (substrate) and a heat sink (drain) for the evacuation of heat. This heat induces thermomechanical stresses due to differential expansion of materials.Two new concepts proposed can overcome these problems and increase the overall reliability of electronic systems. The first is the design and development of a drain composite adaptive thermal properties (thermal expansion coefficient and thermal conductivity). In the second, a new assembly method is presented. It allows, by means of a metal film Sn or Au, intermetallic compounds to create stable over time.

Doctor of Philosophy / Department of Agronomy / S.V. Krishna Jagadish / Sorghum (Sorghum bicolor (L.) Moench) is one of the hardiest crop to abiotic stresses compared with other grain crops. However early stage chilling, terminal heat and drought stress are three most damaging abiotic stresses that have limited sorghum productivity in the US Great plains and other locations having similar environmental conditions. Three studies were conducted with an overall goal aimed at increasing grain sorghum’s resilience to harsh climatic conditions. In the first study, four promising chilling stress tolerant sorghum advanced breeding lines, a known early stage chilling tolerant Chinese landrace (Shan Qui Red - SQR) and a susceptible US elite cultivar (RTx430) as checks were assessed for chilling tolerance during emergence and early growth under field and controlled environments. Aerial phenotyping using unmanned aircraft systems (UAS) fitted with multispectral camera was used to capture reflectance-based vegetation indices (NDVI and NDRE) in field experiments. Some advanced breeding lines with superior agronomic background also recorded significantly better emergence, seedling growth and vigor compared to SQR under chilling conditions. Aerial phenotyping indices from images taken between 30 and 60 days after emergence were consistently correlated with destructive measurements under early plantings, indicating their effectiveness in differentiating chilling responses. Second study was conducted to understand physiological mechanisms inducing heat stress resilience in sorghum during flowering. A diverse set of sorghum inbreds and selected hybrids were tested under greenhouse, growth chamber facilities and field conditions. A highly conserved early-morning-flowering mechanism was observed across all the inbreds and hybrids, with the peak anthesis wherein >90% of florets completed flowering within 30 min after dawn. The conserved response was consistent even under drought stress and heat stress exposure imposed at different times of the day. Our findings report a novel heat escaping early-morning-flowering mechanism effectively employed by sorghum to minimize heat stress impact at anthesis. Another experiment with sequential increase in daytime temperature treatments suggest heat stress induced loss in pollen viability to be a key factor resulting in reduced seed-set and grain yield. The findings suggest heat stress could have a greater impact on post-pollen germination processes such as fertilization, embryo formation and development. We identified a heat tolerant genotype “Macia” which appears to be a promising donor for developing improved heat tolerant sorghum hybrids. In the third study, a bi-parental recombinant inbred lines (RILs) mapping population developed from elite post flowering drought susceptible cultivar (RTx430) and a known drought tolerant cultivar (SC35) were evaluated under wide spectrum of environments and moisture conditions. Several novel and major QTL for grain yield, panicle neck diameter, effective quantum yield of photosystem II and chlorophyll content were identified. The genomic regions and the candidate genes within these regions can potentially help in improving source and sink dynamics in sorghum under diverse environments. The findings from these studies will complement ongoing efforts in developing future sorghum with enhanced resilience to different abiotic stresses that continue to limit sorghum productivity.

Le système Zambèze localisé sur le versant est de l'Afrique est caractérisé par un système turbiditique de très grande dimension (x 100 km) et est associé à terre au troisième plus grand bassin versant d'Afrique (1 320 000 km2) après ceux du Nil et du Congo. A ce jour, peu d'études ont porté sur l'évolution du système terre - mer depuis le bassin versant en érosion jusqu'au bassin en sédimentation. Ce travail s'attachera à : [1] caractériser et à discuter l'origine des déformations enregistrées dans le système sédimentaire Zambèze depuis 155 Ma, [2] quantifier les bilans érosion - sédimentation du système du Zambèze, pour une meilleure compréhension du routage sédimentaire. / The Zambezi system located on the eastern slope of Africa is characterized by a turbiditic system of very large size (x 100 km) and is associated onshore to the third largest watershed in Africa (1,320,000 km2) after those of the Nile and Congo. Few studies have examined the evolution of the land - sea system from the eroding catchment to the sedimentation basin. This work will focus on: [1] characterize and discuss the origin of the deformations recorded in the Zambezi sedimentary system since 155 Ma, [2] quantify the erosion-sedimentation balances of the Zambezi system, for a better understanding of the sedimentary routing

Submitted by JORGE ANDRES ARROYAVE ORTEGON (jaarroyaveo@unal.edu.co) on 2018-08-20T15:11:59Z No. of bitstreams: 1 Dissertação_Jorge_Arroyave_Versão_Final_FC(1).pdf: 6142009 bytes, checksum: 185f73f2530ec7bc30607d8a9e004919 (MD5) / Approved for entry into archive by Cristina Alexandra de Godoy null (cristina@adm.feis.unesp.br) on 2018-08-20T20:10:47Z (GMT) No. of bitstreams: 1 arroyaveortegon_ja_me_ilha.pdf: 6142009 bytes, checksum: 185f73f2530ec7bc30607d8a9e004919 (MD5) / Made available in DSpace on 2018-08-20T20:10:47Z (GMT). No. of bitstreams: 1 arroyaveortegon_ja_me_ilha.pdf: 6142009 bytes, checksum: 185f73f2530ec7bc30607d8a9e004919 (MD5) Previous issue date: 2018-04-27 / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A energia solar pode ser aproveitada como fonte de energia térmica para aquecimento de água, por exemplo, em coletores solares ou como fonte de energia elétrica usando sistemas de células fotovoltaicas. Entretanto, as células fotovoltaicas, geralmente, de custos relativamente altos, têm algumas restrições relacionadas a altas temperaturas de operação e distribuições de temperatura não homogêneas levando a redução da vida útil e eficiência elétrica de tais sistemas. Essas limitações têm sido o foco de pesquisas, a fim de melhorar as eficiências elétricas, regular as temperaturas de operação e reduzir os materiais necessários para fabricação das células. Assim, este projeto de pesquisa tem como objetivo avaliar o desempenho de um dissipador de calor, baseado em microcanais retangulares paralelos, no resfriamento de uma célula fotovoltaica de alta concentração (HCPV-High Concentration Photovoltaic Cell), utilizando-se de análise teórica (modelo térmico), simulação numérica (usando o software comercial CFD ANSYS® Fluent v15) e de uma bancada experimental. Neste trabalho, foram consideradas as condições de máxima radiação (denominado de pior cenário, quando a célula não gera eletricidade e todo o calor deve ser dissipado) e de radiação média ao longo do período considerado. Os dados climatológicos foram obtidos do site Canal Clima - UNESP, com dados historicos do clima na região noroeste paulista. Foi realizada uma revisão do estado da arte a fim de compreender como os sistemas de geração elétrica fotovoltaica podem ser otimizados pelo uso de concentradores solares e materiais mais eficientes (células de junção-múltipla). A influência da temperatura nestes sistemas e como sistemas de resfriamento podem melhorar seu desempenho também foram analisados. Uma bancada experimental permitiu validar os resultados teóricos e numéricos obtidos. Comprovou-se que o uso de dissipador de calor baseado em microcanais pode permitir um controle efetivo da temperatura da célula HCPV, melhorando sua eficiência de conversão de energia solar em energia elétrica. O dissipador de calor foi avaliado sob condições de fluxo de calor constante, variando-se a velocidade mássica, G, no intervalo de 300 kg/m2s a 1500 kg/m2s. Assim, foi possível manter a superfície da célula a uma temperatura de 40°C, aproximadamente, para uma queda de pressão de, em média, 6 kPa. Os resultados das três análises apresentaram comportamentos similares e a concordância entre eles foi razoável, considerando as limitações de cada abordagem. / Solar energy can be used as a source of thermal energy in solar collectors, for example, or as a source of electricity using photovoltaic cell systems. However, photovoltaic cells requires high investments having some restrictions related to high operating temperatures and nonhomogeneous temperature distributions, leading to a reduction in the useful life and electrical efficiency. These limitations have been the focus of researches in order to improve electrical efficiencies, to regulate operating temperatures, and to reduce required materials in the cells. Thus, this research project aims to evaluate the performance of a heat sink based on parallel rectangular microchannels for cooling of a high concentration photovoltaic cell (HCPV), using theoretical analysis (thermal model), numerical simulation (using commercial software CFD ANSYS® Fluent v15) and an experimental bench. In this work, it was considered the conditions of maximum radiation (named worst scenario, when the cell does not generate electricity and all the heat must be dissipated) and the average radiation over the period considered. These climatological data were obtained from the Canal Clima – UNESP site, in the northwestern region of São Paulo state. A review on the subject was carried out in order to understand how solar photovoltaic systems can be optimized using solar concentrators and more efficient materials (multiple-junction cells). The influence of temperature and cooling systems were analyzed. An experimental bench was built, which allowed the validation of the theoretical and numerical results. The use of microchannel heat sinks can allow an effective temperature control of the HCPV cell, improving its efficiency of converting thermal energy into electrical energy. The heat sink was evaluated for different heat flux values and for mass velocity, G, in a range of 300 kg/m2s to 1500 kg/m2s. It was possible to maintain the high concentration cell at 40 °C with a pressure drop of 6 kPa, for the worst scenario. The three analyzes presented similar behavior and the agreement between them was reasonable, considering the approaches limitations. / FAPESP 2013/15431-7 / CNPq 458702/2014-5

Understanding energy fluxes within and between floodplain water bodies, and between rivers and their floodplains is essential for comprehending the dynamics of modern, altered river systems. Floodplain aquatic invertebrates may move between habitats deliberately (through emergence and dispersal) or through passive transport during flooding. This movement may represent a significant flux of energy and an essential food web subsidy. I assessed the usefulness of the stable isotopes of hydrogen and oxygen (D and 18O respectively) for identifying the origins and movements of macroinvertebrates in Mississippi River floodplain water bodies. I sampled water and invertebrates from the Mississippi River, intermittent and permanent floodplain wetlands, and tributaries during 2007 and 2008. Results showed consistent relationships between δD and δ18O signatures in invertebrate tissues and their home water bodies. I also investigated whether δD and δ18O could be used as a multivariate "fingerprint" to trace a captured invertebrate back to its environment of origin. Results showed that δD can be a useful tracer of the movement of floodplain invertebrates in some cases, although δ18O is likely not suitable for that purpose.

Made available in DSpace on 2014-06-11T19:26:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-02-04Bitstream added on 2014-06-13T19:54:53Z : No. of bitstreams: 1 silva_ac_me_botfca.pdf: 604510 bytes, checksum: 71c5f7d364ff5ed33d5d61f19025419f (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O trabalho teve como objetivo avaliar, a viabilidade da metodologia para avaliação da translocação e alocação de fotoassimilados, utilizando o isótopo estável do carbono-13 como marcador, assim como, avaliar a relação fonte-dreno nos diferentes órgãos bem como, saber em que órgão se encontraria o carbono-13 após determinados intervalos de tempo, em plantas em estádio reprodutivo da espécie Ficus carica L. Para tanto, uma folha da figueira considerada adulta através da caracterização fotossintética com um medidor portátil de fotossíntese IRGA-6400, foi colocada dentro de uma câmara de acrílico construída para este fim, e submetida a um ambiente com enriquecimento de 13CO2 por 30 minutos. Após 24 horas, os diferentes órgãos presentes nas plantas foram coletados no experimento órgãos drenos, nas demais plantas seguiu-se a experimentação tempo de alocação, onde as plantas de Ficus carica L. foram arrancadas ao longo das horas: 6, 24, 48, 72, 120, 168, 360. Após o tempo especificado as partes (meristema apical, folhas, ramos, caule e sistema radicular) das plantas em estudo foram coletados e imediatamente imersos em nitrogênio líquido (-196 ºC), para evitar que os tecidos permanecessem vivos e conseqüentemente pudessem consumir os fotoassimilados no processo da respiração. As amostras, previamente identificadas foram secas em estufa de circulação forçada a 65º C por 72 horas, em seguida moídas em moinho criogênico, para que houvesse uma perfeita homogeneização, sendo posteriormente analisadas no espectrômetro de massas de razão isotópica, para a determinação do enriquecimento relativo de 13C. Naturalmente a planta apresenta valores de enriquecimento relativo de 13C - 27,92‰, alocando acima de 90% da massa seca e do carbono total nas partes lenhosas. Os resultados obtidos indicaram que figueira se caracteriza como uma planta do ciclo... / The work have planned be quizzed, the feasability of the methodology for evaluation of the fhotosynthates translocation and allocation, using the carbon 13 stable isotope a marker, evaluate the source-sink relation in the different organs and, know in that organ would be found the carbon-13 after determined time periods, in Ficus carica L. plants in reproductive stadium. A fig tree leaf considered adult through the photosynthetic with a portable meter of photosynthesis IRGA-6400 characterization. Was put inside a acrylic chamber, and submitted to an environment with 13CO2 enrichment for 30 minutes. After 24 hours, the different organs present in the plants were collected in the drains organs experiment, in the other plants followed the allocation time experimentation where the plants of Ficus carica L. were lurches to the long one of the hours: 6, 24, 48, 72, 120, 168, 360. After the time specified the studied plant parts (meristem, sheets, branches, stem and system roots) were collected and immediately immersed in liquid nitrogen (-196 ºC), for avoid that the fabrics remained alive and consequently could consume the fhotosynthates in the breath trial. The samples, previously identified were droughts in of circulation forced to 65º C for 72 hours, right away ground in cryogenic mill, for that had a perfect homogenization, being subsequently analyzed in the mass spectrometry of isotopic reason, for the relative enrichment... (Complete abstract click electronic access below)