12 resultados para Balanço térmico do corpo
em Repositório Institucional da Universidade Estadual de São Paulo - UNESP
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Many social wasps are known to use thermogenesis to warm up their flight muscles and are therefore able to forage under a broad range of ambient temperatures. However it is uncertain whether there exists a possible relation between ambient temperature and thermogenic capacity for tropical species, as we lack studies focusing on these species. Therefore, we examined the use of this mechanism in the neotropical Epiponini wasp Polybia ignobilis. More specifically, we used a thermographic camera to obtain data of the surface temperatures of three body regions (head, thorax and abdomen) of wasps during foraging activities (pre-flight, flight and post-flight) in cold [initial pe- riod of foraging activity: TAM : 15 − 20◦C] and warm [final period of foraging activity: TPM : 30 − 35◦C] conditions. Thorax temperature (Tth) was always higher than head (Th) and abdomen temperature (Tabd). In general, the lowest body temperatures were observed during the pre-flight period, while the highest values occurred upon the return of the wasps from the foraging flight. Except for the pre-flight period, Tth was always higher than Tabd, indicating that heat generated at the thorax was preferentially directed to the cephalic region. Therefore we confirmed the use of thermogenesis by a neotropical social wasp, although its magnitude was found modest compared to temperate species, which suggests a link between thermal environment and thermogenic capacity. We also showed that P. ignobilis modulates heat production as a function of ambient temperature (TA), maintaining a greater temperature difference (Tbody − TA) at cooler temperatures. Finally, we identified the cephalic region of wasps as an important route for the dissipation of the heat generated during flight
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Snakes are ectothermic animals and, therefore, their physiological functions are strongly affected by temperature. For instance, the resting metabolic rate (RMR) of this animals increase with the rise in body temperature. However, metabolic determinations in ectothermic organisms, including snakes, are generally made by submitting the animals to constant temperature regimes. This experimental procedure, although widely used, accepted and certainly suitable in several cases, submit the animals to a very different situation from that experienced by them in nature. In fact, ectothermics are known by presenting extensive variations in their body temperatures trough the day and/or seasons. If this disagreement between the thermal biology of the animals and the experimental conditions, for instance over the circadian cycle, affects the determinations of metabolic rates of ectotherm animals, remains quite uncertain. Thus, this study aimed to test the effects of different thermal regimes (fluctuating vs constant) in different temperature ranges over the TMR of rattlesnakes (Crotalus durissus). Therefore, the TMR of rattlesnakes was measured by the oxygen consumption rates ( V O2) in the constant temperatures of 15°C, 20°C, 25°C, 30°C and 35°C. For fluctuating regimes, snakes were measured in thermoperiods of 12/12 hours, as follows: 15°C and 25°C; 20°C and 30°C; 25°C and 35°C. Our results show that the RMR of C. durissus rises as the temperature increases, regardless of the thermal regime. The obtained RMR in the constant regimes of 20°C and 25°C was not different from that measured in the correspondent fluctuating regimes (i.e., 15 - 25°C e 20 - 30°C). However, at constant 30°C, the RMR was significantly higher than that obtained in the 30°C fluctuating regime (25 - 35ºC). This indicates that the potential effects in submitting of snakes to different thermal regimes of its thermal biology become more important with...
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This study aims to evaluate the corrosion resistance of Ti-30Ta alloy when subjected to different strain rates. Samples of the alloy Ti-30Ta were obtained from the melting of pure elements in the arc furnace in inert atmosphere (argon gas). Then, the samples were subjected to a thermal treatment and to cold worked to obtain bars. After forging, the samples were machined in accordance with ASTME9-09 standard for carried out compression tests. To microstructural characterization, samples were sectioned longitudinal and transversally and embedded in resin. After, the wet sanding and polishing were performed, followed by a chemical attack, in order to study the microstructure under an optical microscope. Microhardness was measured on the samples that were subjected to microstructural characterization by using microhardness tester. Phases were evaluated by x-rays diffraction. Corrosion tests were carried out to evaluate the influence of deformation on the corrosion resistance. Results show that microstructure was not influenced by deformation
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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The rising in greenhouse gases emission as consequence of industrial expansion especially in developing countries is appointed as one of those reasons responsible for global warming. High-level temperatures are set as responsible for low productivity and high levels of discomfort. With the increase of worldwide energy demand, due to the population growth, this work aims to be an introductory text revising the current ventilation (mechanical and natural) and refrigeration technologies as well as low energy cooling techniques and architectural alternatives that seeks offering good ventilation and ideal buildings temperatures, making them sustainable. In addition, the text deals with the measurement instruments used to evaluate the parameters defined by international and national standards. At last, a case of study applies few concepts and technologies described in the text, introducing the results achieved, the limitations and suggestions to future works
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In a market environment increasingly competitive, the companies need to control of this process accurately, avoiding rework or rejection of materials during industrialization. This can be achieved by defining procedure that assure the maintenance of the materials characteristics, as specified initially in the projects. This graduation work has the objective of defining the best heat treatment parameter of normalizing for Heads, part of a pressure vessel, formed in P275NH material. The methodology applied is based on the execution of a sequence of Heat Treatments, using different parameters. The process variables were the cooling velocity, the hold time and the hold temperature variation. As a result of this study, it is noticed that the mechanical properties of the materials are strongly influenced by the hold temperature variation and by the cooling velocity, both determined for the heat treatment cycle
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Due to the large use of steel in several processes around the world, there is the increasingly concern to find new materials and/or optimization and improvement of the processes, as the need to reduce the cost and a productivity increase in the primary industry, such as the siderurgy. The rolling is the most used mechanical process in the world and therefore is required the development of new tools in high volume and with optimum characteristics to support the market demand. Forged rolls used are for rolling. These rolls have heat treatment that has the purpose to achieve the appropriated mechanical properties to support the variables of the rolling process. The objective of this work is to analyze the hardness profile and the microstructure a tool steel similar to AISI A2, forged in an opened die process and submitted to heat treatment with water-cooling. The results allowed plotting a hardness profile and performing a microstructure analysis, and whereby to confirm that the heat treatment is not a quenching, but it is a material beneficiation by the hardening of superficial layer, since there is no martensitic microstructure. Therefore, this paper provides the support to future studies about the possibility to perform enhancements in this thermal heat made in the rolls produced at Gerdau Plant in Pindamonhangaba
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Pós-graduação em Artes - IA
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)