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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Study of interfacial condensation in a nuclear reactor core makeup tank

Ma, Chang Chun 13 December 1993 (has links)
Steam interfacial condensation in a core makeup tank was simulated using the code RELAP5/MOD3 version 8.0 to predict the violent pressure oscillation phenomena in a core makeup tank. Six base cases were carried out to study the effects of back pressure and of vacuum conditions produced in the core makeup tank by rapid steam condensation. The effect of varying the liquid conduction thermal layer thickness was studied. In addition, the code's ability to predict condensation heat transfer was evaluated. Violent pressure oscillations were found in the early period of a transient. The violent pressure oscillations had no effect on the total amount of injection water from core makeup tank. The conduction thermal layer thickness was found to only effect the liquid temperature history. The current version of RELAP5/MOD3 was found to be incapable of dealing with the condensation heat transfer problem in which the volume liquid temperature is lower than the temperature of the heat structure which is connected to that hydraulic volume. / Graduation date: 1994
52

An FPGA-based 3D Graphics System / Ett FPGA-baserat 3D-grafiksystem

Knutsson, Niklas January 2005 (has links)
This report documents the work done by the author to design and implement a 3D graphics system on an FPGA (Field Programmable Gate Array). After a preamble with a background presentation to the project, a very brief introduction in computer graphics techniques and computer graphics theory is given. Then, the hardware available to the project, along with an analysis of general requirements is examined. The following chapter contains the proposed graphics system design for FPGA implementation. A broad approach to separate the design and the eventual implementation was used. Two 3D pipelines are suggested - one fully capable high-end version and one which use minimal resources. The documentation of the effort to implement the minimal graphics system previously discussed then follows. The documentation outlines the work done without going too deep into detail, and is followed by the largest of the tests conducted. Finally, chapter seven concludes the project with the most important project conclusions and some suggestions for future work.
53

Downcore Distribution of Holocene Foraminifera in the Jhuoshuei River Delta

Yang, Chun-Chih 01 August 2012 (has links)
Two drilled cores were collected from the Jhuoshuei River delta for this study, which is focused on the analyses of sedimentological, statistical analysis, AMS C14 dating and paleoenvironment interpretation based on the benthic foraminiferal fossils. Foraminiferal shell do not exist between 30000 and 12000 yr B.P., indicating the environment of this sections might be terrestrial. Between 12000 and 8000 yr B.P., the southern core do not have traces of foraminifera, suggesting the deposition site was terrestrial. The northern core contains the benthic foraminiferal shell between 12000 and 9000 yr B.P. The foraminiferal assemblage indicates the sedimentation might be a inner shelf like enviroment. An estuarine like environment was suggested between 9000 and 8000 yr B.P.. Between 8000 and 6000 yr B.P., foraminiferal cluster analysis indicates a middle to inner shelf environment at the southern core site; a inner shelf at the northern core. From 6000 to 3000 yr B.P., foraminiferal cluster analysis indicates a inner shelf at the south core while northern core foraminifera became fewer and the environment gradually changing to terrestrial facies. From 3000 yr B.P. upwards, foraminiferal cluster analysis indicates a shallower inner shelf at the southern core. From 2000 yr B.P. to today, the southern core changed to terrestrial.
54

Metal and Polymer Foam Hybrid Materials: Design, Fabrication and Analysis

Campbell, Julianna 12 January 2010 (has links)
Two novel hybrid materials for use in sandwich cores of structural materials are designed, manufactured and mechanically tested. Each material is a hybrid of metal and polymer foam. One set of hybrids is fabricated using an aluminium micro-truss filled with varying densities of polyurethane foam. Increases up to 120% in stiffness, 372% in strength, 740% in resilience and 106% in impact energy over the aluminium micro-truss are obtained from compression and impact testing. Furthermore, the stiffness of these hybrids can be tailored according to the density of the polyurethane foam. Another set of hybrids is fabricated using a rapid prototyped ABS polymer truss that is foamed and electroplated with nanocrystalline nickel. Increases up to 1525% in stiffness, 1165% in strength and 650% in energy absorption over the foamed ABS truss are obtained. Furthermore, the gain in strength, stiffness and energy absorption outweigh the gain in density in these hybrid materials.
55

Metal and Polymer Foam Hybrid Materials: Design, Fabrication and Analysis

Campbell, Julianna 12 January 2010 (has links)
Two novel hybrid materials for use in sandwich cores of structural materials are designed, manufactured and mechanically tested. Each material is a hybrid of metal and polymer foam. One set of hybrids is fabricated using an aluminium micro-truss filled with varying densities of polyurethane foam. Increases up to 120% in stiffness, 372% in strength, 740% in resilience and 106% in impact energy over the aluminium micro-truss are obtained from compression and impact testing. Furthermore, the stiffness of these hybrids can be tailored according to the density of the polyurethane foam. Another set of hybrids is fabricated using a rapid prototyped ABS polymer truss that is foamed and electroplated with nanocrystalline nickel. Increases up to 1525% in stiffness, 1165% in strength and 650% in energy absorption over the foamed ABS truss are obtained. Furthermore, the gain in strength, stiffness and energy absorption outweigh the gain in density in these hybrid materials.
56

Abrupt Holocene climate change: evidence from a new suite of ice cores from Nevado Coropuna, southwestern Peru and recently exposed vegetation from the Quelccaya Ice Cap, southeastern Peru /

Buffen, Aron Maurice, January 2008 (has links)
Thesis (M.S.)--Ohio State University, 2008. / Title from first page of PDF file. Includes bibliographical references (p. 109-128).
57

Space-time analysis of reactivity measurements

MOREIRA, JOAO M.L. 09 October 2014 (has links)
Made available in DSpace on 2014-10-09T12:32:01Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T13:56:54Z (GMT). No. of bitstreams: 1 12899.pdf: 8071135 bytes, checksum: c51cd9839b73c11d92a566a85488515f (MD5) / Tese (Doutoramento) / IPEN/T / University of Michigan
58

Enrichment of surface ice stable water isotope ratios following sublimation

Dennis, Donovan 07 November 2018 (has links)
Stable isotopes of water preserved in glaciers and icesheets have revolutionized our understanding of terrestrial paleoclimate. Post-deposition alteration of the stable water isotope ratios in snow and ice can obscure the original meteoric signal, therefore altering the interpretation of δ18O and δD as records of paleo-temperatures in ice. The effects of sublimation on δ18O and δD are not well-understood for massive (non-snow) ice and have been largely overlooked, particularly within the experimental literature. We present results from a series of environmental chamber experiments investigating alteration of the in-situ signal following sublimation. Our data suggest that sublimation enriches the ice remaining after sublimation in 18O and D. This is observed both in surface ice and in the signal of the ice at depth. These results could have important implications for studies utilizing surface ice δ18O and δD for reconstructions of paleoclimate.
59

Rosas são vermelhas e violetas são azuis? A influência das emoções sobre a percepção de cores

Moura, Jadde Emmylle Silva de 17 April 2018 (has links)
Submitted by Automação e Estatística (sst@bczm.ufrn.br) on 2018-08-01T23:06:14Z No. of bitstreams: 1 JaddeEmmylleSilvaDeMoura_DISSERT.pdf: 1612798 bytes, checksum: aef54b5521355bd929dc0d8a6b6f8771 (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2018-08-03T22:39:41Z (GMT) No. of bitstreams: 1 JaddeEmmylleSilvaDeMoura_DISSERT.pdf: 1612798 bytes, checksum: aef54b5521355bd929dc0d8a6b6f8771 (MD5) / Made available in DSpace on 2018-08-03T22:39:41Z (GMT). No. of bitstreams: 1 JaddeEmmylleSilvaDeMoura_DISSERT.pdf: 1612798 bytes, checksum: aef54b5521355bd929dc0d8a6b6f8771 (MD5) Previous issue date: 2018-04-17 / Conselho Nacional de Desenvolvimento Científico e Tecnológico - CNPq / As cores não são apenas um estímulo estético, elas também afetam diretamente a cognição e o comportamento humano. Estudos denominados de psicodinâmica e psicologia das cores, por exemplo, indicam que as cores de um objeto, ou de um local, podem induzir emoções. As emoções, por sua vez, também interferem na visão e percepção das cores, devido à capacidade de determinados estados emocionais induzirem alterações em importantes neurotransmissores, afetando diretamente a excitação que por sua vez provoca contrações ou dilatações na pupila, alterando a quantidade de luz que chega até a retina. Emoções negativas como a tristeza, por exemplo, prejudicariam a percepção visual da cor por desencadear reações que promovem quedas nos níveis de dopamina, e interromperem a contração da pupila, consequentemente prejudicando a sensibilidade ao contraste cromático. Já estados emocionais positivos, como a alegria, poderiam ser responsáveis por ampliar a atenção visual. A presente pesquisa objetivou observar a influência dos estados emocionais de alegria ou tristeza sobre a percepção de cores da visão humana. Investigamos tal influência em indivíduos com visão em cores normal e em indivíduos daltônicos. A pesquisa contou com a participação de 74 homens com idades entre 18 e 35 anos, daltônicos e não daltônicos. Todos os participantes foram submetidos ao Inventário de Depressão de Beck (BDI), ao Teste de Ishihara, e ao teste de percepção de cores de Lanthonny D-40 Hue, e assistiram a um vídeo de aproximadamente 3 minutos de estímulo emocional durante o qual houve monitoramento da contração pupilar. Após a exibição dos vídeos os participantes realizaram novamente o teste de percepção de cores e foi avaliado se houve ou não mudança significativa no desempenho da capacidade de sua percepção cromática. Os dados resultantes deste trabalho sugerem que há influência significativa da emoção tanto sobre a percepção de cores quanto para o tamanho da pupila. Sendo assim, como hipotetizado inicialmente, não apenas informações semânticas, mas também aspectos emocionais parecem estar envolvidos na cognição visual e consequentemente na percepção de cores da visão humana. / Colors are not just an aesthetic stimulus, they also directly affect human cognition and behavior. Studies of psychodynamics and color psychology, for example, indicate that the colors of an object, or a place, can induce emotions. Emotions, in turn, also interfere with color vision and perception, due to the ability of certain emotional states to induce changes in important neurotransmitters, directly affecting the excitation, which in turn causes contractions or dilations in the pupil, altering the amount of light that reaches the retina. Negative emotions such as sadness, for example, would impair the visual perception of color by triggering reactions that promote falls in dopamine levels, and disrupt pupil contraction, consequently impairing sensitivity to chromatic contrast. Already positive emotional states, such as joy, could be responsible for expanding visual attention. The present research observed the occurrence of the influence of the emotional states of joy or sadness on the perception of colors of the human vision. We investigate how that influence affects individuals with normal color vision and colorblind individuals, who in turn can no longer distinguish certain colors, the research had the participation of 74 men between the ages of 18 and 35, colorblind and non-colorblind. All participants were submitted to the Beck Depression Inventory (BDI), the Ishihara Test, and the Lanthonny D-40 Hue color perception test and watched a video of approximately 3 minutes of emotional stimulation. After the videos were taken, the participants again performed the color perception test. We evaluated whether there was a significant change in the performance of the ability of their color perception. The data resulting from this work suggest that there is significant influence of emotion on both color perception and pupil size. Thus, as hypothesized initially, not only semantic information, but also emotional aspects seem to be involved in visual cognition and consequently in color perception of human vision.
60

Comparação entre sinais e sintomas clínicos e variáveis hemodinâmicas obtidas por ecocardiografia em pacientes com insuficiência cardiáca crônica

Silva Neto, Luís Beck da January 2000 (has links)
Resumo não disponível.

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