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CoordenaÃÃo de AperfeÃoamento de Pessoal de NÃvel Superior / Objetivou-se com o seguinte trabalho determinar as exigÃncias nutricionais de energia e proteÃna em ovinos Somalis Brasileira. Utilizou-se 48 ovinos Somalis Brasileira em crescimento, nÃo-castrados, com idade e peso corporal (PC) mÃdio de 60 dias e 13,47  1,76 kg, respectivamente. ApÃs um perÃodo de adaptaÃÃo de 20 dias, oito animais foram abatidos e utilizados como referÃncia para estimativas do peso de corpo vazio (PCVZ) e da composiÃÃo corporal inicial dos demais animais. Os animais remanescentes foram distribuÃdos em um delineamento em blocos casualizados, sendo os tratamentos, raÃÃes contendo diferentes nÃveis de energia metabolizÃvel (1,18; 2,07; 2,25; 2,42 e 2,69 Mcal/kg MS), com oito repetiÃÃes. O peso de abate foi determinado quando a mÃdia de peso dos animais de um dos cinco tratamentos atingiu 28 kg. A exigÃncia lÃquida de energia para mantenÃa foi estimado extrapolando-se a equaÃÃo de regressÃo do logaritmo da produÃÃo de calor, em funÃÃo do consumo de energia metabolizÃvel (CEM) para o nÃvel zero de CEM. A excreÃÃo diÃria de nitrogÃnio (N) foi estimada extrapolando-se a equaÃÃo de regressÃo de consumo de N (g/kg PC0,75/dia) em funÃÃo da retenÃÃo de N (g/kg PC0,75/dia) para o consumo zero. Foram ajustadas equaÃÃes de regressÃo do logaritmo do conteÃdo de gordura, energia e proteÃna em funÃÃo do logaritmo do PCVZ dos animais. A concentraÃÃo de energia lÃquida da dieta para mantenÃa, foi obtida dividindo-se a produÃÃo de calor em jejum, pelo CMS para manter o equilÃbrio de energia, expresso em g de MS/kg PCVZ0,75. A validaÃÃo do modelo SRNS foi realizada atravÃs do ajuste de modelo de regressÃo linear simples entre os valores preditos (variÃvel independente) e observados (variÃvel dependente), as variÃveis analisadas foram CMS e GPC. A composiÃÃo quÃmica corporal foi determinada utilizando a composiÃÃo da meia carcaÃa direita, assim como uma amostra da seÃÃo HH, obtida da meia carcaÃa esquerda. Na meia-carcaÃa esquerda resfriada, retirou-se o corte da seÃÃo HH, pela secÃÃo transversal da 9a-10a-11a costelas no ponto correspondente a 61,5% da distÃncia entre a vÃrtebra seccionada e o inÃcio da cartilagem da 12a costela, em seguida, a seÃÃo HH foi moÃda em moedor de carne industrial e homogeneizada. O ganho mÃdio diÃrio e o ganho de peso de corpo vazio aumentaram linearmente com o aumento dos nÃveis de energia metabolizÃveis. Jà o peso corporal final, peso corporal ao abate, peso de corpo vazio, consumo de matÃria seca e consumo de energia metabolizÃvel apresentaram efeito quadrÃtico (P <0,001) com o aumento do nÃvel de energia. O teor de energia e de gordura de PCVZ dos animais aumentou de 2,77 Mcal/kg e 209,17 g/kg para 3,47 Mcal/kg e 294,08 g/kg de PCVZ, respectivamente, e o PC aumentou de 13,00 para 28,70 kg. O consumo de nitrogÃnio apresentou efeito quadrÃtico, com ponto de mÃxima de 2,59 Mcal/kg MS de energia metabolizÃvel, correspondendo ao consumo mÃximo de N de 2,90 g/kg PC0,75/dia. Jà para o nitrogÃnio retido diariamente, observou-se resposta linear crescente com o aumento nos nÃveis de energia metabolizÃvel nas dietas. Observou-se uma diminuiÃÃo da quantidade de proteÃna no corpo vazio dos animais com o aumento do PCVZ, passando de 143,71 para 122,52 g/kg PCVZ, quando os animais aumentaram o peso corporal de 13,00 para 28,70 kg. A excreÃÃo diÃria de N foi estimada em 0,128 g/kg PC0,75/dia. A composiÃÃo corporal de ovinos Somalis Brasileira varia de 538,28 a 593,93 g/kg de PCVZ para Ãgua, 228,17 a 353,13 g/kg de PCVZ para gordura, 114,53 a 157,93 g/kg de PCVZ para poteÃna e 17,94 a 31,68 g/kg de PCVZ de matÃria mineral, para dietas contendo 1,18 a 2,69 Mcal/kg de MS, respectivamente. A exigÃncia lÃquida de energia para mantenÃa à 45,63 g/kg PCVZ0,75/dia. O aumento no peso dos animais de 13,00 para 28,70 kg PC eleva as deposiÃÃes de gordura de 283,75 para 398,93 g/kg GPCVZ e energia de 3,42 para 4,30 Mcal/kg GPCVZ. A exigÃncia lÃquida de proteÃna para mantenÃa à 0,80 g/kg PC0,75/dia, havendo uma diminuiÃÃo da exigÃncia lÃquida de proteÃna para GPCVZ de 119,72 para 102,07 g/kg GPCVZ, conforme o peso corporal aumenta de 13,00 para 28,70 kg. A eficiÃncia de uso da energia metabolizÃvel para mantenÃa à de 0,67. Jà a eficiÃncia de uso da energia metabolizÃvel para ganho varia de 1,85 a 0,43 para dietas contendo 1,18 a 2,69 Mcal/hg MS respectivamente. As exigÃncias lÃquidas de energia e proteÃna elevam-se com o aumento do peso corporal e aumento do ganho de peso corporal dos ovinos Somalis Brasileira. O modelo Small Ruminant Nutrition Systems à sensÃvel para predizer o consumo de matÃria seca, entretanto, subestimou em 5,18% o ganho mÃdio diÃrio de peso corporal. A seÃÃo HH estimou satisfatoriamente a composiÃÃo quÃmica de Ãgua, proteÃna e gordura na carcaÃa e no corpo vazio, enquanto o teor de minerais foi subestimado em torno de 27,07% na carcaÃa e 14,91% no corpo vazio. Os teores de Ãgua, proteÃna bruta e gordura da carcaÃa podem ser preditos pela seÃÃo HH. Por fim, a composiÃÃo quÃmica da seÃÃo HH pode ser utilizada em substituiÃÃo à composiÃÃo quÃmica da carcaÃa para predizer composiÃÃo quÃmica do corpo vazio em ovinos Somalis Brasileira. / Objetivou-se com o seguinte trabalho determinar as exigÃncias nutricionais de energia e proteÃna em ovinos Somalis Brasileira. Utilizou-se 48 ovinos Somalis Brasileira em crescimento, nÃo-castrados, com idade e peso corporal (PC) mÃdio de 60 dias e 13,47  1,76 kg, respectivamente. ApÃs um perÃodo de adaptaÃÃo de 20 dias, oito animais foram abatidos e utilizados como referÃncia para estimativas do peso de corpo vazio (PCVZ) e da composiÃÃo corporal inicial dos demais animais. Os animais remanescentes foram distribuÃdos em um delineamento em blocos casualizados, sendo os tratamentos, raÃÃes contendo diferentes nÃveis de energia metabolizÃvel (1,18; 2,07; 2,25; 2,42 e 2,69 Mcal/kg MS), com oito repetiÃÃes. O peso de abate foi determinado quando a mÃdia de peso dos animais de um dos cinco tratamentos atingiu 28 kg. A exigÃncia lÃquida de energia para mantenÃa foi estimado extrapolando-se a equaÃÃo de regressÃo do logaritmo da produÃÃo de calor, em funÃÃo do consumo de energia metabolizÃvel (CEM) para o nÃvel zero de CEM. A excreÃÃo diÃria de nitrogÃnio (N) foi estimada extrapolando-se a equaÃÃo de regressÃo de consumo de N (g/kg PC0,75/dia) em funÃÃo da retenÃÃo de N (g/kg PC0,75/dia) para o consumo zero. Foram ajustadas equaÃÃes de regressÃo do logaritmo do conteÃdo de gordura, energia e proteÃna em funÃÃo do logaritmo do PCVZ dos animais. A concentraÃÃo de energia lÃquida da dieta para mantenÃa, foi obtida dividindo-se a produÃÃo de calor em jejum, pelo CMS para manter o equilÃbrio de energia, expresso em g de MS/kg PCVZ0,75. A validaÃÃo do modelo SRNS foi realizada atravÃs do ajuste de modelo de regressÃo linear simples entre os valores preditos (variÃvel independente) e observados (variÃvel dependente), as variÃveis analisadas foram CMS e GPC. A composiÃÃo quÃmica corporal foi determinada utilizando a composiÃÃo da meia carcaÃa direita, assim como uma amostra da seÃÃo HH, obtida da meia carcaÃa esquerda. Na meia-carcaÃa esquerda resfriada, retirou-se o corte da seÃÃo HH, pela secÃÃo transversal da 9a-10a-11a costelas no ponto correspondente a 61,5% da distÃncia entre a vÃrtebra seccionada e o inÃcio da cartilagem da 12a costela, em seguida, a seÃÃo HH foi moÃda em moedor de carne industrial e homogeneizada. O ganho mÃdio diÃrio e o ganho de peso de corpo vazio aumentaram linearmente com o aumento dos nÃveis de energia metabolizÃveis. Jà o peso corporal final, peso corporal ao abate, peso de corpo vazio, consumo de matÃria seca e consumo de energia metabolizÃvel apresentaram efeito quadrÃtico (P <0,001) com o aumento do nÃvel de energia. O teor de energia e de gordura de PCVZ dos animais aumentou de 2,77 Mcal/kg e 209,17 g/kg para 3,47 Mcal/kg e 294,08 g/kg de PCVZ, respectivamente, e o PC aumentou de 13,00 para 28,70 kg. O consumo de nitrogÃnio apresentou efeito quadrÃtico, com ponto de mÃxima de 2,59 Mcal/kg MS de energia metabolizÃvel, correspondendo ao consumo mÃximo de N de 2,90 g/kg PC0,75/dia. Jà para o nitrogÃnio retido diariamente, observou-se resposta linear crescente com o aumento nos nÃveis de energia metabolizÃvel nas dietas. Observou-se uma diminuiÃÃo da quantidade de proteÃna no corpo vazio dos animais com o aumento do PCVZ, passando de 143,71 para 122,52 g/kg PCVZ, quando os animais aumentaram o peso corporal de 13,00 para 28,70 kg. A excreÃÃo diÃria de N foi estimada em 0,128 g/kg PC0,75/dia. A composiÃÃo corporal de ovinos Somalis Brasileira varia de 538,28 a 593,93 g/kg de PCVZ para Ãgua, 228,17 a 353,13 g/kg de PCVZ para gordura, 114,53 a 157,93 g/kg de PCVZ para poteÃna e 17,94 a 31,68 g/kg de PCVZ de matÃria mineral, para dietas contendo 1,18 a 2,69 Mcal/kg de MS, respectivamente. A exigÃncia lÃquida de energia para mantenÃa à 45,63 g/kg PCVZ0,75/dia. O aumento no peso dos animais de 13,00 para 28,70 kg PC eleva as deposiÃÃes de gordura de 283,75 para 398,93 g/kg GPCVZ e energia de 3,42 para 4,30 Mcal/kg GPCVZ. A exigÃncia lÃquida de proteÃna para mantenÃa à 0,80 g/kg PC0,75/dia, havendo uma diminuiÃÃo da exigÃncia lÃquida de proteÃna para GPCVZ de 119,72 para 102,07 g/kg GPCVZ, conforme o peso corporal aumenta de 13,00 para 28,70 kg. A eficiÃncia de uso da energia metabolizÃvel para mantenÃa à de 0,67. Jà a eficiÃncia de uso da energia metabolizÃvel para ganho varia de 1,85 a 0,43 para dietas contendo 1,18 a 2,69 Mcal/hg MS respectivamente. As exigÃncias lÃquidas de energia e proteÃna elevam-se com o aumento do peso corporal e aumento do ganho de peso corporal dos ovinos Somalis Brasileira. O modelo Small Ruminant Nutrition Systems à sensÃvel para predizer o consumo de matÃria seca, entretanto, subestimou em 5,18% o ganho mÃdio diÃrio de peso corporal. A seÃÃo HH estimou satisfatoriamente a composiÃÃo quÃmica de Ãgua, proteÃna e gordura na carcaÃa e no corpo vazio, enquanto o teor de minerais foi subestimado em torno de 27,07% na carcaÃa e 14,91% no corpo vazio. Os teores de Ãgua, proteÃna bruta e gordura da carcaÃa podem ser preditos pela seÃÃo HH. Por fim, a composiÃÃo quÃmica da seÃÃo HH pode ser utilizada em substituiÃÃo à composiÃÃo quÃmica da carcaÃa para predizer composiÃÃo quÃmica do corpo vazio em ovinos Somalis Brasileira. / The objective of the following work to determine the nutritional requirements of energy and protein in Brazilian Somali sheep. We used 48 sheep Brazilian Somali growing, non-castrated, age and body weight (BW) average of 60 days and 13.47  1.76 kg respectively. After a 20 day adaptation period, eight animals were slaughtered and used as a reference for estimates of empty body weight (EBW) and initial body composition of other animals. The remaining animals were distributed in a randomized block design, with the treatments, diets with different levels of metabolizable energy (1.18; 2.07; 2.25; 2.42 and 2.69 Mcal/kg DM), with eight repetitions. The weight of slaughter animals was determined when the weight average of the five treatments was 28 kg. The net energy requirement for maintenance was estimated extrapolating the logarithmic regression equation of heat production, depending on the metabolizable energy intake (MEI) to the zero level of MEI. The daily excretion of nitrogen (N) was estimated by extrapolating to N consumption regression equation (g/BW0.75 kg/day) as a function of the N retention (g/BW 0.75 kg/day) for consumption zero. They were adjusted regression of log equations fat content, protein and energy in the logarithm of EBW animals. The concentration of net energy for maintenance diet was obtained by dividing the heat production in fasting, the DMI to maintain energy balance in g DM/kg EBW0.75. The validation of the SRNS model was performed using the simple linear regression model fit between the predicted values (independent variable) and observed (dependent variable), variables were analyzed DMI and BWG. The body composition was determined using the composition of the right half carcass, as well as a sample of the section HH, obtained from the left crankcase half. In middle housing cooled left, retreated cutting the section HH, the cross section of the 9th-10th-11th rib at the point corresponding to 61.5% of the distance between the sectioned vertebrae and the beginning of the 12th rib cartilage in then, the HH section was ground in grinder industrial and homogenised meat. The average daily gain and empty body weight gain increased linearly with increasing metabolizable energy levels. But the final body weight, body weight at slaughter, empty body weight, dry matter intake and metabolizable energy intake showed a quadratic effect (P<0.001) with increasing energy level. Energy and fat EBW of the animals increased from 2.77 Mcal/kg to 209.17 g/kg to 3.47 Mcal/kg to 294.08 g/kg EBW, respectively, and increased the BW 13.00 to 28.70 kg. Consumption of nitrogen showed quadratic effect with point of maximum of 2.59 Mcal/kg DM of metabolizable energy, corresponding to the maximum consumption of N of 2.90 g/kg BW0.75/day. As for the nitrogen retained daily, there was a positive linear correlation with the increase in metabolizable energy levels in the diets. There was a decreased amount of protein in the empty body of animals with increased EBW, from 143.71 to 122.52 g/kg EBW, when the animals increased the body weight of 13.00 to 28.70 kg. The daily excretion of N was estimated at 0.128 g/BW0.75 kg/day. The body composition of Brazilian Somali sheep ranges from 538.28 to 593.93 g/kg EBW for water, from 228.17 to 353.13 g/kg EBW for fat, 114.53 to 157.93 g/kg EBW for protein and from 17.94 to 31.68 g/kg of EBW of mineral matter, for diets containing 1.18 to 2.69 Mcal/kg DM, respectively. The net energy requirement for maintenance is 45.63 g/kg EBW0.75/day. The increase in animal weight of 13.00 to 28.70 kg BW increases the deposition of fat from 283.75 to 398.93 g/kg EBW and energy of 3.42 to 4.30 Mcal/kg EBW. The protein requirement for maintenance is 0.80 g/BW0.75 kg/day, with a decreased protein requirement for EBW of 119.72 to 102.07 g/kg EBW, as the weight increases by 13.00 to 28.70 kg. The use efficiency of metabolizable energy for maintenance is 0.67. Already use efficiency of metabolizable energy for gain varies from 1.85 to 0.43 for diets containing 1.18 to 2.69 Mcal/kg DM, respectively. The net requirements of energy and protein increase with increasing body weight and increase in body weight gain of Brazilian Somali sheep. The model Small Ruminant Nutrition Systems is sensitive to predict dry matter intake, however, underestimated in 5.18% the average daily weight gain. The section HH satisfactorily estimated the chemical composition of water, protein and fat in the carcass and empty body, while the mineral content was underestimated around 27.07% 14.91% housing and empty body. The water content, crude protein and carcass fat can be predicted by section HH. Finally, the chemical composition of section HH can be used to replace the chemical composition of the carcass to predict chemical composition of empty body in Brazilian Somalis sheep. / The objective of the following work to determine the nutritional requirements of energy and protein in Brazilian Somali sheep. We used 48 sheep Brazilian Somali growing, non-castrated, age and body weight (BW) average of 60 days and 13.47  1.76 kg respectively. After a 20 day adaptation period, eight animals were slaughtered and used as a reference for estimates of empty body weight (EBW) and initial body composition of other animals. The remaining animals were distributed in a randomized block design, with the treatments, diets with different levels of metabolizable energy (1.18; 2.07; 2.25; 2.42 and 2.69 Mcal/kg DM), with eight repetitions. The weight of slaughter animals was determined when the weight average of the five treatments was 28 kg. The net energy requirement for maintenance was estimated extrapolating the logarithmic regression equation of heat production, depending on the metabolizable energy intake (MEI) to the zero level of MEI. The daily excretion of nitrogen (N) was estimated by extrapolating to N consumption regression equation (g/BW0.75 kg/day) as a function of the N retention (g/BW 0.75 kg/day) for consumption zero. They were adjusted regression of log equations fat content, protein and energy in the logarithm of EBW animals. The concentration of net energy for maintenance diet was obtained by dividing the heat production in fasting, the DMI to maintain energy balance in g DM/kg EBW0.75. The validation of the SRNS model was performed using the simple linear regression model fit between the predicted values (independent variable) and observed (dependent variable), variables were analyzed DMI and BWG. The body composition was determined using the composition of the right half carcass, as well as a sample of the section HH, obtained from the left crankcase half. In middle housing cooled left, retreated cutting the section HH, the cross section of the 9th-10th-11th rib at the point corresponding to 61.5% of the distance between the sectioned vertebrae and the beginning of the 12th rib cartilage in then, the HH section was ground in grinder industrial and homogenised meat. The average daily gain and empty body weight gain increased linearly with increasing metabolizable energy levels. But the final body weight, body weight at slaughter, empty body weight, dry matter intake and metabolizable energy intake showed a quadratic effect (P<0.001) with increasing energy level. Energy and fat EBW of the animals increased from 2.77 Mcal/kg to 209.17 g/kg to 3.47 Mcal/kg to 294.08 g/kg EBW, respectively, and increased the BW 13.00 to 28.70 kg. Consumption of nitrogen showed quadratic effect with point of maximum of 2.59 Mcal/kg DM of metabolizable energy, corresponding to the maximum consumption of N of 2.90 g/kg BW0.75/day. As for the nitrogen retained daily, there was a positive linear correlation with the increase in metabolizable energy levels in the diets. There was a decreased amount of protein in the empty body of animals with increased EBW, from 143.71 to 122.52 g/kg EBW, when the animals increased the body weight of 13.00 to 28.70 kg. The daily excretion of N was estimated at 0.128 g/BW0.75 kg/day. The body composition of Brazilian Somali sheep ranges from 538.28 to 593.93 g/kg EBW for water, from 228.17 to 353.13 g/kg EBW for fat, 114.53 to 157.93 g/kg EBW for protein and from 17.94 to 31.68 g/kg of EBW of mineral matter, for diets containing 1.18 to 2.69 Mcal/kg DM, respectively. The net energy requirement for maintenance is 45.63 g/kg EBW0.75/day. The increase in animal weight of 13.00 to 28.70 kg BW increases the deposition of fat from 283.75 to 398.93 g/kg EBW and energy of 3.42 to 4.30 Mcal/kg EBW. The protein requirement for maintenance is 0.80 g/BW0.75 kg/day, with a decreased protein requirement for EBW of 119.72 to 102.07 g/kg EBW, as the weight increases by 13.00 to 28.70 kg. The use efficiency of metabolizable energy for maintenance is 0.67. Already use efficiency of metabolizable energy for gain varies from 1.85 to 0.43 for diets containing 1.18 to 2.69 Mcal/kg DM, respectively. The net requirements of energy and protein increase with increasing body weight and increase in body weight gain of Brazilian Somali sheep. The model Small Ruminant Nutrition Systems is sensitive to predict dry matter intake, however, underestimated in 5.18% the average daily weight gain. The section HH satisfactorily estimated the chemical composition of water, protein and fat in the carcass and empty body, while the mineral content was underestimated around 27.07% 14.91% housing and empty body. The water content, crude protein and carcass fat can be predicted by section HH. Finally, the chemical composition of section HH can be used to replace the chemical composition of the carcass to predict chemical composition of empty body in Brazilian Somalis sheep.

The studies conducted on hole cleaning have been started with single phase drilling fluids for vertical holes in 1930&rsquo / s, and have reached to multiphase drilling fluids for directional and horizontal wells today. The influence of flow rate and hole inclination on cuttings transport has been well understood, and many studies have been conducted on effective hole cleaning either experimentally or theoretically. However, neither the hydraulic behavior nor the hole cleaning mechanism of gasified drilling fluids has been properly understood. The aims of this study are to investigate and analyze the hole cleaning performance of gasified drilling fluids in horizontal, directional and vertical wells experimentally, to identify the drilling parameters those have the major influence on cuttings transport, to define the flow pattern types and boundaries as well as to observe the behavior of cuttings in detail by using digital image processing techniques, and to develop a mechanistic model based on the fundamental principles of physics and mathematics with the help of the experimental observations. A mechanistic model is developed with the help of the obtained experimental data. Developed model is used for estimating optimum flow rates for liquid and gas phases for effective cuttings transport as well as for determining the total pressure losses and void fraction of each phase for a given drilling conditions. The v mechanistic model obtained using the experimental data within the scope of this study will be used to develop the hydraulic program and equipment selection to be used in the field during underbalanced drilling applications.

Proton exchange membrane fuel cells (PEMFC) are attractive energy sources for power trains in vehicles because of their low operating temperature that enables fast start-up and high power densities. Cost reduction and durability are the key issues to be solved before PEMFCs can be successfully commercialized. The major portion of fuel cell cost is associated with the catalyst layer which is typically comprised of carbon-supported Pt and ionomer. The degradation of the catalyst layer is one of the major failure modes that can cause voltage degradation and limit the service life of the fuel cell stack during operation. To develop a highly durable and better performing catalyst layer, topics such as the causes for the degradation, modes of failure, different mechanisms and effect of degradation on fuel cell performance must be studied thoroughly. Key degradation modes of catalyst layer are carbon corrosion and Pt dissolution. These two modes change the electrode structure in the membrane electrode assembly (MEA) and result in catalyst layer thinning, CO2 evolution, Pt deposition in the membrane and Pt agglomeration. Alteration of the electrode morphology can lead to voltage degradation. Accelerated stress tests (ASTs) which simulate the conditions and environments to which fuel cells are subject, but which can be completed in a timely manner, are commonly used to investigate the degradation of the various components. One of the current challenges in employing these ASTs is to relate the performance loss under a given set of conditions to the various life-limiting factors and material changes. In this study, various degradation modes of the cathode catalyst layer are isolated to study their relative impact on performance loss ‗Fingerprints‘ of identifiable performance losses due to carbon corrosion are developed for MEAs with 0.4 mg cm−2 cathode platinum loadings. The fingerprint is used to determine the extent of performance loss due to carbon corrosion and Pt dissolution in cases where both mechanisms operate. This method of deconvoluting the contributions to performance loss is validated by comparison to the measured performance losses when the catalyst layer is subjected to an AST in which Pt dissolution is predominant. The limitations of this method iv are discussed in detail. The developed fingerprint suggests that carbon loss leading to CO2 evolution during carbon corrosion ASTs contributes to performance loss of the cell. A mechanistic model for carbon corrosion of the cathode catalyst layer based on one appearing in the literature is developed and validated by comparison of the predicted carbon losses to those measured during various carbon corrosion ASTs. Practical use of the model is verified by comparing the predicted and experimentally observed performance losses. Analysis of the model reveals that the reversible adsorption of water and subsequent oxidation of the carbon site onto which water is adsorbed is the main cause of the current decay during ASTs. Operation of PEM fuel cells at higher cell temperatures and lower relative humidities accelerates Pt dissolution in the catalyst layer during ASTs. In this study, the effects of temperature and relative humidity on MEA degradation are investigated by applying a newly developed AST protocol in which Pt dissolution is predominant and involves the application of a potentiostatic square-wave pulse with a repeating pattern of 3s at 0.6 V followed by 3s at 1.0 V. This protocol is applied at three different temperatures (40°C, 60°C and 80°C) to the same MEA. A diagnostic signature is developed to estimate kinetic losses by making use of the effective platinum surface area (EPSA) obtained from cyclic voltammograms. The analysis indicates that performance degradation occurs mainly due to the loss of Pt in electrical contact with the support and becomes particularly large at 80°C. This Pt dissolution AST protocol is also investigated at three different relative humidities (100%, 50% and 0%). Electrochemical impedance spectroscopy measurements of the MEAs show an increase in both the polarization and ohmic resistances during the course of the AST. Analysis by cyclic voltammetry shows a slight increase in EPSA when the humidity increases from 50% to 100%. The proton resistivity of the ionomer measured by carrying out impedance measurements on MEAs with H2 being fed on the anode side and N2 on the cathode side is found to increase by the time it reaches its end-of-life state when operated under 0 % RH conditions.

Bone drilling is an essential part of many orthopaedic surgical procedures, including those for internal fixation and for attaching prosthetics. Drilling into bone is a fundamental skill that can be both very simple, such as drilling through long bones, or very difficult, such as drilling through the vertebral pedicles where incorrectly drilled holes can result in nerve damage, vascular damage or fractured pedicles. Also large forces experienced during bone drilling may promote crack formation and can result in drill overrun, causing considerable damage to surrounding tissues. Therefore, it is important to understand the effect of bone material quality on the bone drilling forces to select favourable drilling conditions, and improve orthopaedic procedures.

Background: This study seeks to model aspects of the regeneration of radiata pine (Pinus radiata D.Don) seedlings under a range of environmental conditions. This study investigated whether “hybrid” mechanistic models, which predict plant growth and development using empirical representations of plant physiological responses to the environment, could provide a realistic alternative to conventional empirical regeneration models. Objectives: The objectives of this study were to 1) identify the functional relationships between the environmental conditions controlling germination, establishment and growth of radiata pine seedlings, under a range of those environmental conditions as specified by temperature and available light and soil water; and 2) specify those functional relationships in hybrid mechanistic (“hybrid”) models. Methods: Radiata pine seedling germination and growth were measured under controlled environmental conditions (incubators for seed germination, growth cabinets for seedlings), and results used to adapt, parameterise and test two published hybrid models; one for germination (the hydrothermal time model); and one for seedling growth in the first six months after germination, based on plant radiation use efficiency (RUE). The hydrothermal model was tested by incubating commercial radiata pine seeds under factorial combinations of temperature and water potentials where germination was likely to occur (12.5 ºC to 32.5 ºC and 0 MPa to –1.2 MPa.). 100 seeds were germinated for each factorial combination. The hydrothermal germination model was fitted to the germination data using non-linear regression modles, will allowed simultaneous estimation of all modle parameters. Seedlings were grown in controlled growth cabinets, and their RUE was calculated as the ratio of net primary production (NPP, specified in terms of an increase in oven dry biomass), to PAR intercepted or absorbed by a seedling. Estimation of seedling RUE required development of novel techniques for non-destructive estimation of seedling oven dry weight, and measurement of PAR interception by seedlings. The effect of varying PAR flux density on RUE was tested by measuring RUE of seedlings grown at 125, 250 and 500 µmol m⁻² s⁻¹. In a second experiment, the effect of deficits in available soil water on RUE was tested by measuring RUE of seedlings grown under 250 µmol m⁻² s⁻¹ PAR flux, and at different levels of available soil water. Available soil water was specified by a soil moisture modifier factor (ƒθ) which ranges between 1 for moist soils and 0 for soils where there is insufficient water for seedling growth. This soil moisture modifier had not previously been applied in studies of tree seedling growth. Temperatures for both seedling experiments were a constant 17.5 ºC (day) and 12.5 ºC (night). Results: Hydrothermal time models accurately described radiata pine seed germination. Model predictions were closely correlated with actual seed germination over the full range of temperature and water potentials where germination was likely to occur (12.5 ºC to 32.5 ºC and 0 MPa to –1.2 MPa. The minimum temperature for germination (base temperature) was 9.0 ºC. Optimum temperatures for germination ranged from ~20ºC for slow-germinating seeds to ~27 ºC for the fastest germinating seeds. The minimum water potential for seed germination varied within the seed population, with an approximately normal distribution (base water potential = –1.38 MPa, standard deviation of 0.48 MPa). In the process of developing the model, a novel explanation for the decline in germination rates at supra-optimal temperatures was developed (Section 3.4.6), based on earlier models proposed by Alvarado & Bradford (2002) and Rowse & Finch-Savage (2003). This explanation was that the decline in germination rate was not driven just by temperature, but by accumulated hydrothermal time above the base temperature for germination (T₀). This in turn raised the base soil water potential (Ψb) towards 0, so that the reduction in germination rate arose from a reduced accumulation of hydro-time, rather than from thermal denaturation of enzymes facilitating germination – the conventional explanation for non-linear accumulation of thermal time at supra-optimal temperatures for plant development. Upwards adjustment (towards 0 MPa) of base water potentials of germinating seeds occurred also at very cold temperatures in combination with high water potentials. In both cases (very cold or else supra-optimal temperatures) this upwards adjustment in base water potentials prevented germination of part of the seed population, and is proposed as a mechanism which enables seed populations to “hedge their bets” when germinating under less than ideal germination conditions. RUE of young germinated radiata pine seedlings growing in a controlled growth cabinet was not significantly different over a range of constant PAR flux densities. Mean RUE’s were 3.22, 2.82 and 2.58 g MJ⁻¹ at 125, 250 and 500 µmol m⁻² s⁻¹ respectively. In the second experiment, the novel use of a soil moisture modifier (ƒθ) to predict RUE of seedlings subjected to water stress proved successful within a limited range of soil water stress conditions. Measured seedling transpiration and stomatal conductance were closely correlated but seedling photosynthesis was less correlated with available soil water. This result suggests that photosynthesis was not coupled with stomatal conductance when PAR flux was 250 µmol m⁻² s⁻¹, which is well below saturating irradiance for C₃ plants. Conclusions: The use of hybrid, quasi-mechanistic models to describe tree seedling growth has been seldom explored, which necessitated the development of novel experimental and analytical techniques for this study. These included a predictive model of germination decline at sub- and supra-optimal temperatures; a method for accurately estimating seedling dry weights under a range of PAR flux densities; and a novel method for estimating light interception by small seedlings. The work reported in this thesis showed that existing hybrid models (the hydrothermal time germination model and the RUE model) can be adapted to model germination and growth of radiata pine seedlings under controlled environmental conditions. Nonetheless, further research is needed before the models can be confidently used as an alternative to conventional empirical models to model regeneration in “real-world” forests. Research priorities are the performance of hydrothermal germination models under variable field conditions, and the use of the soil moisture modifier for seedlings growing on a range of soil textures and under a range of PAR fluxes.

This study aims to investigate hydraulics and the flow characteristics of drilling fluids inside annulus and to understand the mechanism of cuttings transport in horizontal and deviated wellbores. For this purpose, initially, extensive experimental studies have been conducted at Middle East Technical University, Petroleum &amp / Natural Gas Engineering Flow Loop using water and numerous drilling fluids for hole inclinations from horizontal to 60 degrees, flow velocities from 0.64 m/s to 3.05 m/s, rate of penetrations from 0.00127 to 0.0038 m/s, and pipe rotations from 0 to 120 rpm. Pressure loss within the test section and stationary and/or moving bed thickness are recorded. New friction factor charts and correlations as a function of Reynolds number and cuttings bed thickness with the presence of pipe rotation for water and drilling fluids in horizontal and deviated wellbores are developed by using experimental data. Meanwhile empirical correlations that can be used easily at the field are proposed for predicting stationary bed thickness and frictional pressure loss using dimensional analysis and the effect of the drilling parameters on hole cleaning is discussed. It has been observed that, the major variable influencing cuttings transport is fluid velocity. Moreover, pipe rotation drastically decreases the critical fluid velocity that is required to prevent the stationary cuttings bed development, especially if the pipe is making an orbital motion. A decrease in the pressure loss is observed due to the bed erosion while rotating the pipe. Cuttings transport in horizontal annulus is modeled using a CFD software for different fluid velocities, pipe rotation speeds and rate of penetrations. The CFD model is verified by using cuttings transport experiments. A mathematical model is also proposed to predict the flow characteristics of Newtonian fluids in concentric horizontal annulus with drillpipe rotation. The Navier-Stokes equations of turbulent flow are numerically solved using finite differences technique. A computer code is developed in Matlab 2007b for the proposed model. The performance of the proposed model is compared with the experimental data which were available in the literature and gathered at METU-PETE Flow Loop as well as Computational Fluids Dynamics (CFD) software. The results showed that the mechanistic model accurately predicts the frictional pressure loss and the velocity profile inside the annuli. The model&rsquo / s frictional pressure loss estimations are within an error range of &plusmn / 10%.

Dispersal, especially long-distance dispersal, is an important component in many disciplines within biology. Many species are passively dispersed by wind, not least spore-dispersed organisms. In this thesis I investigated the dispersal capacity of bryophytes by studying the colonization patterns from local scales (100 m) to landscape scales (20 km). The dispersal distances were measured from a known source (up to 600 m away) or inferred from a connectivity measure (1–20 km). I introduced acidic clay to measure the colonization rates over one season of a pioneer moss, Discelium nudum (I–III). I also investigated which vascular plants and bryophytes that had colonized limed mires approximately 20–30 years after the first disturbance (IV). Discelium effectively colonized new disturbed substrates over one season. Most spores were deposited up to 50 meters from a source but the relationship between local colonization rates and connectivity increased with distance up to 20 km (I–III). Also calcicolous wetland bryophyte species were good colonizers over similar distances, while vascular plants in the same environment colonized less frequently. Common bryophytes that produce spores frequently were more effective colonizers, while no effect of spore size was detected (IV). A mechanistic model that take into account meteorological parameters to simulate the trajectories for spores of Discelium nudum fitted rather well to the observed colonization pattern, especially if spore release thresholds in wind variation and humidity were accounted for (III). This thesis conclude that bryophytes in open habitats can disperse effectively across landscapes given that the regional spore source is large enough (i.e. are common in the region and produce spores abundantly). For spore-dispersed organisms in open landscapes I suggest that it is often the colonization phase and not the transport that is the main bottle-neck for maintaining populations across landscapes. / <p>At the time of the doctoral defence the following papesr were unpublished and had  a status as follows: Paper 2: Epubl ahead of print; Paper 3: Manuscript; Paper 4: Manuscript</p>

iv The primary objective of this study is to understand the mechanism, the hydraulics and the characteristics, of the two-phase flow in horizontal annuli. While achieving this goal, both theoretical and experimental works have been conducted extensively. The METU-PETE-CTMFL (Middle East Technical University, Petroleum and Natural Gas Engineering Department, Cuttings Transport and Multiphase Flow Laboratory) multiphase flow loop consists of 4.84 m long eccentric horizontal acrylic pipes having 0.1143m inner diameter (I.D) acrylic casing - 0.0571m outer diameter (O.D) drillpipe and 0.0932m I.D acrylic casing - 0.0488m O.D drillipipe geometric configurations. During each experiment, differential pressure loss data obtained from digital and analog pressure transmitters at a given liquid and gas flow rate were recorded. The flow patterns were identified visually. Meanwhile a mechanistic model has been developed. The flow pattern identification criteria proposed originally for twophase flow through pipes by Taitel and Dukler1 has been inherited and modified for the eccentric annular geometry. The complex geometry of eccentric annuli has been represented by a new single diameter definition, namely representative diameter dr. The representative diameter has been used while calculating the pressure losses. A computer code based on the algorithm of the proposed mechanistic model has been developed in Matlab 7.0.4. Both the flow pattern prediction and the frictional pressure loss estimation are compared with the gathered experimental data. Moreover, friction factor correlations have been developed for each flow pattern using experimental data and statistical methods. The performance of the proposed model and the friction factor correlations has been evaluated from experimental data. The mechanistic model developed in this study accurately predicts flow pattern transitions and frictional pressure losses. The model&rsquo / s pressure loss estimations are within &plusmn / 30% for two different annular flow geometries.

This thesis presents a method for modeling energy consumption in the milling process to assess their environmental impact, using a simple experimental approach. The factors influencing the environmental impact in milling processes are analyzed with life cycle assessment principles, and their climate change impact is calculated with examples of dry milling experiments. The model for predicting energy consumption is inspired by the mechanistic model of milling operation. The tangential cutting force coefficients are approximated using experimental data to estimate the spindle power. The developed model can predict energy consumption for given cutting parameters and conditions. The results of the study indicate that 1) the energy consumption of the milling process estimated by the proposed mechanistic-based model aligns well with the experimentally measured results, 2) the experimental approach used to build the model is both easy and fast, and 3) the consumption of the solid cutting tool contributes the most to the environmental impact in dry milling processes. Furthermore, the analysis presented in this thesis provides insight into how to improve energy efficiency and reduce the environmental impact of milling processes. / Denna avhandling presenterar en metod för att modellera energiförbrukning i fräsningsprocessen för att bedöma deras miljöpåverkan genom en enkel experimentell metod. Faktorer som påverkar miljöpåverkan i fräsningsprocesser analyseras med principer för livscykelbedömning och deras klimatpåverkan beräknas med exempel på torrfräsningsförsök. Modellen för att förutsäga energiförbrukningen är inspirerad av den mekaniska modellen för fräsningsoperation. Koefficienter för tangentiell skärkraft approximeras med experimentella data för att uppskatta spindelkraften. Den utvecklade modellen kan förutsäga energiförbrukningen för givna skärparametrar och villkor. Resultaten visar att 1) energiförbrukningen i fräsningsprocessen uppskattad med den föreslagna mekanikbaserade modellen överensstämmer bra med experimentellt uppmätta resultat, 2) den experimentella metoden för att bygga modellen är enkel och snabb, och 3) förbrukningen av det fasta skärverktyget bidrar mest till miljöpåverkan i torrfräsningsprocesser. Analysen som presenteras i denna avhandling ger också insikt i hur man kan förbättra energieffektiviteten och minska miljöpåverkan i fräsningsprocesser.