Abh. techn. Wiss. Zürich, 1985 ; Diss. ETH Nr. 7888.

Actuellement, l’immense majorité des aimants supraconducteurs, notamment d’IRM, sont refroidis par un bain d’hélium liquide à pression atmosphérique. Néanmoins, ce type de refroidissement est onéreux et impose des contraintes sécuritaires importantes pour les grands volumes. Pour ces raisons, le refroidissement des aimants supraconducteurs est souhaitable sans l’hélium liquide. L’utilisation de cryogénérateur permet de refroidir par conduction solide jusqu’à 4 K et ainsi supprimer l’hélium liquide. Néanmoins, les faibles puissances disponibles combiner aux difficultés de mise en œuvre de ce type de refroidissement rendent difficile l’utilisation dans ces conditions du NbTi. En revanche à 10 K, la puissance des cryogénérateurs augmente d’un facteur 10, mais l’utilisation d’un supraconducteur à haute température critique est alors nécessaire. Notre choix s’est porté sur les conducteurs MgB2 R & W qui ont l’avantage d’être relativement économique à mettre en œuvre, mais qui ont, en revanche, le défaut d’être sensible à la déformation. Il est donc nécessaire d’être soigneux lors de leurs bobinages pour ne pas dégrader leurs performances supraconductrices. Dans le cadre de cette thèse, nous avons développé un insert froid refroidis par conduction solide permettant de mesurer le courant critique des conducteurs MgB2 R & W ainsi que des maquettes. Pour ce faire, un nouveau type de contact thermique à base de nitrure d’aluminium a été développé. En complément, nous avons conçu deux maquettes d’aimant MgB2 R & W : un solénoïde et une double galette. Cette dernière a été fabriquée (grâce à une nouvelle méthode de bobinage brevetée) et testée avec succès. / Currently, the majority of superconducting magnets, including MRI, are cooled by a bath of liquid helium at atmospheric pressure. Nevertheless, this type of cooling is expensive and imposes significant security constraints for large volumes. For these reasons, the cooling of superconducting magnets is desirable without liquid helium. Cryocooler provides dry cooling to 4 K without any liquid helium. However, the power available is low and dry cooling is difficult. In these conditions, it is complicate to use NbTi with dry cooling. But if we increase the operating temperature to 10 K, the power of cryocooler increases by a factor of ten. Nevertheless in this case, it is necessary to use of a high critical temperature superconductor. We choose to use MgB2 R & W conductors because it is relatively low cost but it has the handicap to be sensible at mechanical stress. It is therefore necessary to be careful during their winding to not degrade their superconducting performance. As part of this thesis, we have developed a dry test facility to measure the critical current of MgB2 R & W conductors as well as mock-ups. To do this, a new type of thermal contact based on aluminum nitride has been developed. In addition to this development, we designed two MgB2 R & W magnet mock-ups: a solenoid and a double pancake. The double pancake was manufactured (with a new patented winding method) and it has been successfully tested.

A study of the feeding ecology of the flounder in the Ythan estuary was carried out between October 1970 and August 1973. The diet of the fish varied along the length of the estuary. On the mudflats in the upper estuary C orophium vo lu tat or was the main food item with Nereis divers color and Hydrobia ulvae secondarily important, but on the very soft mudflats in the middle estuary small oligocbaetee (mainly Peloscolex benedeni) and polychaetes predominated in the diet. Over mussel beds 3\Terels dlveraicolor and Carcinus maenas were important and the lower and outer part elupeids were taken in large quantities by the older age groups. Intensive study on one mudflat" the Sleek of Tai'ty, showed a seasonal change in the diet; Corophi\:un being more important in the summer, and Nereis, feco. lthica,Hydrobia and P. os. io_£l. ans in the autumn and winter.. Changes in dietbetween day and night were relatively unimportant as were the differences between age classes, though the younger fish (0 & X-group) took many Crangon vulgaria, Gammarus sp. and Meomysis integer, whilst Macoma and Hydrobia wore secondarily important to the older age groups. Trapping throughout 24-hour periods showed that the stomachs of flounders were filled over the high tide period on the mudflatsf irrespective of whether high tide occurred by day or night, whereas at low water most fish had empty stomachs. However, variations in stomach fulness at high tide occurred. 0-group flounders had significantly fuller stomachs during the day than by night, but no differences were found in the >I-group. Also to show conclusively that the >I-group fill their guts to the same extent on different tides an index of gut (stomach plus intestine) fulness was determined and found not to vary significantly between day and night.

The purpose of the lecture was to investigate the historical and musical heritage of the Moravian Church, with a particular interest in the works and players of the American Moravian Trombone Choir. The historical overview of people, customs, and practices is traced from its beginnings with the Unitas Fratrum in Bohemia through the Northern Germany settlement of Herrenhut and the establishment of the American Moravian colony at Bethlehem, Pennsylvania. The musical life of the church is represented by a discussion of the early hymns of the founding fathers in Bohemia and the subsequent instrumental music of the Moravian trombone choir in America. The trombone choir played chorales that were used to call the congregation to order, announce important visitors to the town, and provide music at special occasions. Anthems were played by trombones (when players were available) in regular church services, or outside when it was necessary to double voice parts. Concerted music was played in the Bethlehem Collegium Musicum. Biographies of the players of the 18th and 19th century trombone choirs provide information attesting to the proficiency and dedication of these musicians. A list of players who contributed to the trombone choir movement since the 19th century is included, as well as information about the popularity and function of the Moravian Trombone Choir today.

Made available in DSpace on 2018-08-01T23:57:56Z (GMT). No. of bitstreams: 1 tese_10129_DissertaçãoIsraelBahiaCosta_25_07.pdf: 16020708 bytes, checksum: a8060d9a610c181587f794445940694c (MD5) Previous issue date: 2016-07-15 / O principal objetivo do presente estudo consiste em avaliar o desempenho do modelo de turbulência k-ω SST (Shear Stress Transport) em simular o escoamento e a dispersão de compostos gasosos ao redor de obstáculo cúbico isolado, sob condições de estabilidade atmosférica neutra, estável e instável. O método dos volumes finitos com malha não estruturada formada por elementos de volume tetraédricos e prismáticos é utilizado para a solução numérica das equações de conservação, através da utilização do software comercial Ansys Fluent. Foram simuladas duas configurações experimentais publicadas na literatura científica: (i) experimento em túnel de vento (MURAKAMI et al., 1990) com Re ≈ 60000, a fim de avaliar a sensibilidade das constantes empíricas do modelo de turbulência a1 (influência na viscosidade turbulenta) e Clim (influência na limitação da produção de energia cinética turbulenta nas zonas de estagnação) e comparar com outros modelos de turbulência; (ii) experimento em campo (MAVROIDIS et al., 1999) com Re ≈ 70000, com a finalidade de avaliar a influência das condições de estabilidade atmosférica na pluma de contaminantes e no decaimento temporal da concentração após a interrupção da emissão. Nesse caso, foram utilizadas as constantes empíricas que melhor reproduziram o experimento de Murakami et al. (1990). Observou-se a influência das constantes empíricas na predição do comprimento da zona de recirculação atrás do prédio e da energia cinética turbulenta. Foram encontrados valores dessas constantes que forneceram melhores resultados quando comparados aos encontrados na literatura com outros modelos de turbulência. Os campos de concentração apresentaram boa concordância aos dados experimentais de Mavroidis et al. (1999). O modelo de turbulência k-ω SST superestimou o tempo de residência do composto na esteira turbulenta, quando comparado com os resultados experimentais em campo, embora tenha obtido erros percentuais ligeiramente menores que outro modelo de turbulência (k-l), previamente simulado por Mavroidis et al. (2012). A estabilidade atmosférica não apresentou influência significativa na pluma de contaminantes para os cenários avaliados, a influência significativa foi relacionada à intensidade da velocidade do vento. Desse modo, a presença do obstáculo parece influenciar mais significativamente a intensidade de turbulência por meio das tensões cisalhantes que as condições de estabilidade atmosférica por meio do empuxo térmico.

Diss. Phil. Bern. / S.-A. aus dem Archiv für Naturgeschichte, 76. Jahrg. Berlin 1910.

Thesis (M.S.)--West Virginia University, 2008. / Title from document title page. Document formatted into pages; contains viii, 65 p. : ill. Vita. Includes abstract. Includes bibliographical references (p. 54-57).

No description available.

Texte remanié de: Diss.--Heidelberg--Neuphilologische Fakultät, 1985. / Bibliogr. p. 371-380.

Diss. Hels.