6 resultados para Aegean_C-40
Resumo:
Saúde e desenvolvimento
Resumo:
A thermal Energy Storage Unit (ESU) could be used to attenuate inherent temperature fluctuations of a cold finger, either from a cryocooler working or due to sudden income heat bursts. An ESU directly coupled to the cold source acts as a thermal buffer temporarily increasing its cooling capacity and providing a better thermal stability of the cold finger (“Power Booster mode”). The energy storage units presented here use an enthalpy reservoir based on the high latent heat of the liquid-vapour transition of neon in the temperature range 38 - 44 K to store up to 900 J, and that uses a 6 liters expansion volume at RT in order to work as a closed system. Experimental results in the power booster mode will be described: in this case, the liquid neon cell was directly coupled to the cold finger of the working cryocooler, its volume (12 cm3) allowing it to store 450 J at around 40 K. 10 W heat bursts were applied, leading to liquid evaporation, with quite reduced temperature changes. The liquid neon reservoir can also work as a temporary cold source to be used after stopping the cryocooler, allowing for a vibration-free environment. In this case the enthalpy reservoir implemented (24 cm3) was linked to the cryocooler cold finger through a gas gap heat switch for thermal coupling/decoupling of the cold finger. We will show that, by controlling the enthalpy reservoir’s pressure, 900 J can be stored at a constant temperature of 40 K as in a triple-point ESU.
Resumo:
Cryocoolers have been progressively replacing the use of the stored cryogens in cryogenic chains used for detector cooling, thanks to their higher and higher reliability. However, the mechanical vibrations, the electromagnetic interferences and the temperature fluctuations inherent to their functioning could reduce the sensor’s sensitivity. In order to minimize this problem, compact thermal energy storage units (ESU) are studied, devices able to store thermal energy without significant temperature increase. These devices can be used as a temporary cold source making it possible to turn the cryocooler OFF providing a proper environment for the sensor. A heat switch is responsible for the thermal decoupling of the ESU from the cryocooler’s temperature that increases when turned OFF. In this work, several prototypes working around 40 K were designed, built and characterized. They consist in a low temperature cell that contains the liquid neon connected to an expansion volume at room temperature for gas storage during the liquid evaporation phase. To turn this system insensitive to the gravity direction, the liquid is retained in the low temperature cell by capillary effect in a porous material. Thanks to pressure regulation of the liquid neon bath, 900 J were stored at 40K. The higher latent heat of the liquid and the inexistence of triple point transitions at 40 K turn the pressure control during the evaporation a versatile and compact alternative to an ESU working at the triple point transitions. A quite compact second prototype ESU directly connected to the cryocooler cold finger was tested as a temperature stabilizer. This device was able to stabilize the cryocooler temperature ((≈ 40K ±1 K) despite sudden heat bursts corresponding to twice the cooling power of the cryocooler. This thesis describes the construction of these devices as well as the tests performed. It is also shown that the thermal model developed to predict the thermal behaviour of these devices, implemented as a software,describes quite well the experimental results. Solutions to improve these devices are also proposed.
Resumo:
Cryocoolers have been progressively replacing the use of the stored cryogens in cryogenic chains used for detector cooling, thanks to their higher and higher reliability. However, the mechanical vibrations, the electromagnetic interferences and the temperature fluctuations inherent to their functioning could reduce the sensor’s sensitivity. In order to minimize this problem, compact thermal energy storage units (ESU) are studied, devices able to store thermal energy without significant temperature increase. These devices can be used as a temporary cold source making it possible to turn the cryocooler OFF providing a proper environment for the sensor. A heat switch is responsible for the thermal decoupling of the ESU from the cryocooler’s temperature that increases when turned OFF. In this work, several prototypes working around 40 K were designed, built and characterized. They consist in a low temperature cell that contains the liquid neon connected to an expansion volume at room temperature for gas storage during the liquid evaporation phase. To turn this system insensitive to the gravity direction, the liquid is retained in the low temperature cell by capillary effect in a porous material. Thanks to pressure regulation of the liquid neon bath, 900 J were stored at 40K. The higher latent heat of the liquid and the inexistence of triple point transitions at 40 K turn the pressure control during the evaporation a versatile and compact alternative to an ESU working at the triple point transitions. A quite compact second prototype ESU directly connected to the cryocooler cold finger was tested as a temperature stabilizer. This device was able to stabilize the cryocooler temperature ((≈ 40K ±1 K) despite sudden heat bursts corresponding to twice the cooling power of the cryocooler. This thesis describes the construction of these devices as well as the tests performed. It is also shown that the thermal model developed to predict the thermal behaviour of these devices,implemented as a software, describes quite well the experimental results. Solutions to improve these devices are also proposed.
Resumo:
Esta tese de doutoramento tem como campo de estudo o grafismo e a ilustração produzidos em Portugal durante os anos 40 do século XX. Ela foca a sua análise em quatro áreas de investigação: a) publicidade; b) grafismo e ilustração de jornais, revistas e livros; c) grafismo editorial produzido pelo Secretariado da Propaganda Nacional; d) grafismo de algumas publicações editadas por ocasião das exposições de Paris (1937), Nova Iorque e São Francisco (1939), e a Exposição do Mundo Português (1940). Através da pesquisa de fontes primárias – jornais, revistas, livros, anúncios, cartazes, material publicitário vário – em conjução com textos e artigos da época – procurámos fazer uma História do Design Gráfico em Portugal que tivesse em consideração não só a estética do material gráfico criado mas também a conjuntura histórica, económica, sociológica e ideológica em que esse material apareceu. Comparámos o grafismo realizado para as instituições públicas e aquele feito para as empresas privadas para concluir que há pontos de contacto entre os dois não só por os artistas serem quase sempre os mesmos mas também porque o mesmo discurso ideológico permeava tanto a propaganda do Estado Novo quanto a produção comercial ainda que houvesse a resistência de outras propostas estéticas e imaginários, como o surrealismo e o neo-realismo. António Ferro, director do Secretariado da Propaganda Nacional, soube aproveitar o talento de um núcleo de artistas para a criação de uma identidade visual para Portugal, uma identidade que sintetizasse elementos da arte popular com um enquadramento moderno. Através de múltiplas actividades essa identidade foi sendo desenvolvida e replicada mas é nas oportunidades de trabalho e experimentação dadas aos artistas modernistas portugueses que reside o verdadeiro legado de António Ferro para o Design Gráfico português.