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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.
11

Densidade energética: relação com variáveis demográficas, de estilo de vida, nutricionais e socioeconômicas em amostra representativa da população adulta do município de São Paulo / Energy density: association with demographic, lifestyle, nutritional and socioeconomic variables in a representative sample of adult population in the city of São Paulo.

Stella, Roberta Horschutz 05 September 2008 (has links)
Introdução - A densidade energética (DE), definida como a quantidade de energia por unidade de peso, é um importante fator na ingestão de alimentos e no valor calórico total da alimentação. Dessa forma, é uma característica da dieta que pode estar envolvida na qualidade da alimentação e no controle de peso. Objetivo - Analisar a relação entre a DE da dieta com variáveis demográficas, de estilo de vida, nutricionais e socioeconômicas em amostra representativa da população adulta do Município de São Paulo. Métodos - Foram utilizados dados secundários do projeto em Políticas Públicas, intitulado \"Inquérito de Saúde no Município de São Paulo - ISA-Capital\". Trata-se de um estudo transversal, de base populacional. O grupo de estudo foi composto por adultos, de ambos os sexos (N=710). O consumo alimentar foi medido através do método Recordatório de 24 horas. O consumo relatado foi transformado em energia e nutrientes com a utilização do software Nutrition Data System (NDS). A DE da dieta foi estimada através de três métodos: 1- inclusão de todos os alimentos e bebidas; 2- inclusão de todos os alimentos e bebidas calóricas que contenham, no mínimo, 5 Kcal/100g; 3- inclusão de todos os alimentos e exclusão de todas as bebidas. Para avaliar as relações entre a densidade energética da dieta e as variáveis demográficas, de estilo de vida, e socioeconômicas de interesse, foi utilizada a análise de regressão linear múltipla. Resultados: A população estudada foi composta por 56,7% de mulheres, 61,1% da etnia branca e 60,1% com situação conjugal unida/casada. A idade mínima foi de 20 anos e a idade máxima de 59 anos, com média de 36,2 anos. Os valores médios encontrados para a DE1, DE2 e DE3 foram 1,32 kcal/g (EP=0,01), 1,35 kcal/g (EP=0,01) e 1,95 kcal/g (EP=0,02), respectivamente. No modelo múltiplo, a escolaridade do indivíduo e a situação de trabalho \"em atividade\" associaram-se inversamente, ajustado por etnia para DE1 e DE2. Para DE3, foi verificada associação direta para etnia \"outras\" e inversa para hábito de fumar \"ex-fumante\". Conclusões: As médias de densidade energética encontradas no estudo mostraram-se superiores aos poucos estudos populacionais Resumo disponíveis. Os resultados apontados pelos diferentes métodos de cálculo da densidade energética sugerem que a contribuição dos líquidos não pode ser subestimada. / Introduction: Energy density (ED), defined as the amount of energy per unit weight, is a major factor related to food intake and total dietary energy. It is a dietary component that may be involved with diet quality and weight control. Objective: To assess the association between dietary ED and demographic, lifestyle, nutritional and socioeconomic variables in a representative sample of adult population in the city of São Paulo. Methods: A population-based, cross-sectional study was conducted based on secondary data from the Public Policies project, \"Health Survey in the City of São Paulo - ISA-Capital\". The study sample comprised both male and female adults (N=710). Food intake was measured using a 24-hour food recall. The reported intake was converted into energy and nutrients by the Nutrition Data System (NDS) program. Dietary ED was estimated through three different approaches: 1- inclusion of all foods and beverages; 2- inclusion of all energetic foods and beverages with a calorie content of at least 5 kcal/100 g; 3- inclusion of all foods and exclusion of all beverages. A multiple linear regression analysis was carried out to assess the associations between dietary ED and the study variables. Results: In the sample studied, 56.7% were women, 61.1% were White and 60.1% were either married or living with a partner. Mean age was 36.2 years, ranging between 20 and 59 years. Mean ED1, ED2 and ED3 were 1.32 kcal/g (SE=0.01), 1.35 kcal/g (SE=0.01) and 1.95 kcal/g (SE=0.02), respectively. In the multiple regression analysis, schooling and \"active\" working status were inversely associated, after adjusting for ethnicity, with ED1 and ED2. For ED3, there was found a direct association with \"other\" ethnicity and an inverse association with \"former smoking\". Conclusions: Mean energy densities found in the study were higher than those reported in few other population-based studies available. The results obtained through the different approaches for ED estimation indicate that the contribution of liquids should not be underestimated.
12

Energy Quantity Estimation in Radiated Acoustic Fields

Whiting, Eric B. 01 September 2016 (has links)
Energy quantities, which are calculated from pressure and particle velocity, yield a great deal of information about acoustic fields. Errors in pressure or particle velocity estimation lead to bias errors the estimation of energy quantities. The bias errors arise from different probe configurations and processing methods. Two processing methods are examined: the traditional method and the recently developed Phase and Amplitude Gradient Estimation (PAGE) method. These two methods are compared to investigate how each estimates pressure and particle velocity and the subsequent bias errors in a plane wave, standing wave, and spherical spreading wave field. Analytical expressions are derived for the energy quantity estimation using ideal one-dimensional probes. A simulation of the field from a baffled circular piston and measurements using ideal two-dimensional probes is computed. Compared to the traditional method, the PAGE method significantly extends the range of frequencies for which the results are accurate. It is found that a probe with a center microphone significantly reduces the estimation error and extends the usable range of frequencies. The PAGE method with unwrapping, perfectly matches the analytical results for plane waves, while the traditional method is only good at wavelengths that are large compared to the probe size. Furthermore, the PAGE method has a constant bias error in spherical wave fields due to the 1/r decrease in pressure. The traditional method has a frequency dependent bias error that is much worse at higher frequencies. Lastly, the PAGE method has the same or worse error for the standing wave. As an application of energy quantities, acoustic intensity is used to develop an equivalent source model for jet noise from an F-22 at military and afterburner engine conditions. An optimization is used to find the best-matching wavepacket model for measured intensity vectors. The results are compared to another intensity method of estimating the source region and source directivity, and the two methods have good agreement.
13

The response of the growing pig to changes in energy intake achieved through changes in dietary energy concentration versus restriction of feed intake

Marriott, Jennifer P. 04 October 2010 (has links)
This study was undertaken to compare the effects of changing energy intake, either by restricting feed intake or by altering dietary energy concentration, on the growth performance of pigs. The relative abilities of the DE, ME and NE systems to predict pig growth performance were also evaluated. A total of 72 barrows, having initial body-weights of 30 ± 2 kg, were randomly assigned to one of nine dietary treatments. These treatments were organized in a 3 x 3 factorial arrangement consisting of three dietary energy concentrations (2.18, 2.29 and 2.40 Mcal NE/kg) and three levels of feed allowance (80, 90 and 100% of ad libitum). Actual feed allowances of 79, 91 and 100% of ad libitum were achieved. No interactive effects of feeding level and dietary energy concentration were observed (P > 0.10). Increases in feed allowance from 79 to 91 to 100% of ad libitum resulted in increases in daily intakes of feed (P < 0.0001) and energy (P < 0.0001). Improvements in the rate (P < 0.0001) and efficiency (P < 0.0001) of body-weight gain were also noted. Additionally, feeding level affected the amount of energy available for body-weight gain on a daily (P < 0.0001) but not on a total (P > 0.10) basis. The efficiency with which dietary energy was used for weight gain was unaffected by feeding level (P > 0.10). Increases in dietary energy concentration were accompanied by decreases in daily feed intakes (P = 0.0016); however, dietary energy concentration did not affect daily energy intakes (P > 0.10). Neither average daily gains nor feed conversion efficiencies were affected by changes in dietary energy concentration (P > 0.10). Additionally, there were no differences among energy concentration treatments in terms of the amount of dietary energy available for body-weight gain (P > 0.10) or the efficiency with which it was used (P > 0.10). No differences were observed between the DE, ME and NE systems in terms of their abilities to predict the growth performance of pigs. The present study demonstrates that the energy intake of pigs can be effectively manipulated via adjustments in feeding level and that changes in dietary energy density, over the range studied here, are unable to affect changes in energy intake. This finding indicates that extreme caution should be used when extrapolating data obtained from studies in which feed allowance was manipulated to scenarios (e.g. commercial practice) in which energy density is to be altered, and vice versa.
14

Characterizing High-Energy-Density Propellants for Space Propulsion Applications

Kokan, Timothy Salim 05 April 2007 (has links)
There exists wide ranging research interest in high-energy-density matter (HEDM) propellants as a potential replacement for existing industry standard fuels for liquid rocket engines. The U.S. Air Force Research Laboratory, the U.S. Army Research Lab, the NASA Marshall Space Flight Center, and the NASA Glenn Research Center each either recently concluded or currently has ongoing programs in the synthesis and development of these potential new propellants. In order to perform conceptual designs using these new propellants, most conceptual rocket engine powerhead design tools (e.g. NPSS, ROCETS, and REDTOP-2) require several thermophysical properties of a given propellant over a wide range of temperature and pressure. These properties include enthalpy, entropy, density, viscosity, and thermal conductivity. Very little thermophysical property data exists for most of these potential new HEDM propellants. Experimental testing of these properties is both expensive and time consuming and is impractical in a conceptual vehicle design environment. A new technique for determining these thermophysical properties of potential new rocket engine propellants is presented. The technique uses a combination of three different computational methods to determine these properties. Quantum mechanics and molecular dynamics are used to model new propellants at a molecular level in order to calculate density, enthalpy, and entropy. Additivity methods are used to calculate the kinematic viscosity and thermal conductivity of new propellants. This new technique is validated via a series of verification experiments of HEDM compounds. Results are provided for two HEDM propellants: quadricyclane and 2-azido-N, N-dimethylethanamine (DMAZ). In each case, the new technique does a better job than the best current computational methods at accurately matching the experimental data of the HEDM compounds of interest. A case study is provided to help quantify the vehicle level impacts of using HEDM propellants. The case study consists of the National Aeronautics and Space Administrations (NASA) Exploration Systems Architecture Study (ESAS) Lunar Surface Access Module (LSAM). The results of this study show that the use of HEDM propellants instead of hypergolic propellants can lower the gross weight of the LSAM and may be an attractive alternative to the current baseline hypergolic propellant choice.
15

Heteroatom-containing carbons for high energy density supercapacitor

Chung, Kang Ko January 2013 (has links)
The supercapacitor is one of the most important energy storage devices as its construction allows for addressing many of the drawbacks related to batteries, but the low energy density of current systems is a major issue. In this doctoral dissertation, with a view to attaining high energy density supercapacitor systems that can be comparable to those for batteries, new heteroatom-containing carbons in the form of particles and three-dimensional films were investigated. A nitrogen-containing material, acrodam, was chosen as the carbon precursor due to the inexpensiveness, high carbonization yield, oligomerizability, etc. The carbon particles were prepared from acrodam together with caesium acetate as a meltable flux agent, and disclosed excellent properties in hydroquinone-loaded sulphuric acid electrolyte with high energy densities (up to 133.0 Wh kg–1) and sufficient cycle stabilities. These properties are already now comparable to those of batteries. Besides, conductive carbon three-dimensional films were fabricated using acrodam oligomer as the precursor by the inexpensive spin coating method. The films were found to be homogeneous, flat, void- and crack-free, and high conductivities (up to 334 S cm–1) could be obtained at the carbonization temperature of 1000 ºC. Furthermore, a porous carbon three-dimensional film could be formed using an organic template at the first attempt. This finding demonstrates the film’s potentiality for various applications such as supercapacitor electrode; the essential absence of contact resistance within the network should contribute to effective transportation of electron within the electrode. The progress made in this dissertation will open a new way to further enhancement of energy density for supercapacitor as well as other applications that exceeds the current properties. / Der Superkondensator ist einer der wichtigsten Energiespeicher da seine Konstruktion die Lösung vieler Nachteile von Batterien erlaubt. Allerdings weisen derzeitige Systeme noch zu geringe Energiedichten auf. Um Superkondensatoren mit Energiedichten vergleichbar zu Batterien zu ermöglichen, wurden in der vorliegenden Dissertation neue, heteroatomhaltige Kohlenstoffe in Form von Partikeln und Filmen untersucht. Aufgrund geringer Kosten, hohen Ausbeuten, Polymerisierbarkeit usw. wurde die stickstoffhaltige Substanz Acrodam als Kohlenstoffvorstufe verwendet. Die Kohlenstoffpartikel wurden ausgehend von Acrodam zusammen mit Cäsiumacetat als schmelzbares Flussmittel hergestellt und wiesen ausgezeichnete Eigenschaften in Hydrochinon geladenen Schwefelsäure-Elektrolyten mit hohen Energiedichten (bis zu 133,0 Wh kg–1) und guten Zyklusstabilitäten auf. Diese Eigenschaften sind bereits jetzt vergleichbar mit denen von Batterien. Weiterhin wurden unter Verwendung von Acrodamoligomeren als Vorstufe und mit Hilfe der kostengünstigen Rotationsbeschichtung leitfähige, dreidimensionale Kohlenstofffilme hergestellt. Bei einer Karbonisierungstemperatur von 1000 °C konnten die Materialien als homogene, flache, Hohlraum-und Riss-freie Filme erhalten werden, die eine hohe Leitfähigkeit (bis zu 334 S cm–1) aufwiesen. Darüber hinaus konnte mit einem organischen Templat ein dreidimensionaler, poröser Kohlenstoff geformt werden. Dies zeigt das Potential der Filme für verschiedene Anwendungen wie Superkondensatorelektroden; die Abwesenheit von Übergangswiderständen im Netzwerk sollte zu einem effizienten Transport von Elektronen in der Elektrode beitragen. Die Ergebnisse dieser Dissertation werden neue Wege zur Verbesserung der Energiedichte von Superkondensatoren sowie weiteren Anwendungen eröffnen.
16

Factors affecting overwinter mortality and early marine growth in the first ocean year of juvenile Chinook salmon in Quatsino Sound, British Columbia

Middleton, Katherine Rose 03 August 2011 (has links)
Evidence suggests that the variability in recruitment of adult Pacific salmon is related to smolt survival during the first ocean year. Specifically, the first few weeks and first marine winter may be two critical periods of high mortality during early marine life. Mortality during early marine residency has been attributed to predation and size-dependent factors while high mortality during the first winter may be due to energy deficits and failure to reach a certain size by the end of the growing season. My study assessed factors influencing overwinter mortality and early marine growth in juvenile Chinook salmon (Oncorhynchus tshawytscha) from Marble River, Quatsino Sound, British Columbia. Juvenile salmon were collected during November 2005 and 2006 (fall) and March 2006 and 2007(winter). Mortality rates over the first winter derived from catch per unit effort across seasons ranged between 80-90% in all years. These are the first estimations of overwinter mortality in juvenile Pacific salmon. Fish size distributions showed no evidence of size-selective overwinter mortality between fall and winter fish in either 2005-2006 or 2006-2007. Otolith microstructure analyses showed no significant difference in circulus increment widths during the first four weeks after marine entry. Similarities in increment width indicated that early marine growth did not differ between fall and winter fish during early marine residency in 2006. These observations show that the high overwinter mortality rates of juvenile Chinook salmon in Quatsino Sound are not size-dependent. Total plankton biomass was significantly lower in the winter season but size distribution, gut fullness and energy density data did not show evidence of starvation. No correlation was found between early marine growth, size, energy accumulation and high mortality in Marble River juvenile Chinook salmon during their first ocean winter in Quatsino Sound. Possible factors influencing these high mortality rates may include non size-selective predation, disease, local environmental influences or an as yet unknown source. Future work should continue to focus on understanding the relationship between early marine survival and adult recruitment. The expansion of growth comparisons geographically and chronologically while determining the effects of predatory mortality on juvenile Chinook salmon along the north Pacific continental shelf and beyond are imperative to fully understanding this complex marine life stage. / Graduate
17

Spatially fixed and moving virtual sensing methods for active noise control.

Moreau, Danielle J. January 2010 (has links)
Local active noise control systems generate a zone of quiet at the physical error sensor location. While significant attenuation is achieved at the error sensor, local noise control is not without its problems, chiefly that the zone of quiet is generally small and impractically sized. It may be inconvenient to place the error sensor at the desired location of attenuation, such as near an observer’s ear, preventing the small zone of quiet from being centered there. To overcome the problems encountered in local active noise control, virtual acoustic sensors have been developed to shift the zone of quiet away from the physical sensor position to a spatially fixed desired location. The general aim of the research presented in this thesis is to improve and extend the spatially fixed and moving virtual sensing algorithms developed for active noise control thus far and hence increase the scope and application of local active noise control systems. To achieve this research aim, a number of novel spatially fixed and moving virtual sensing algorithms are presented for local active noise control. In this thesis, a spatially fixed virtual sensing technique named the Stochastically Optimal Tonal Diffuse Field (SOTDF) virtual sensing method is developed specifically for use in pure tone diffuse sound fields. The SOTDF virtual sensing method is a fixed gain virtual sensing method that does not require a preliminary identification stage nor models of the complex transfer functions between the error sensors and the sources. SOTDF virtual microphones and virtual energy density sensors that use both pressure and pressure gradient sensors are developed using the SOTDF virtual sensing method. The performance of these SOTDF virtual sensors is investigated in numerical simulations and using experimental measurements made in a reverberation chamber. SOTDF virtual sensors are shown to accurately estimate the pressure and pressure gradient at a virtual location and to effectively shift the zone of quiet away from the physical sensors to the virtual location. In numerically simulated and post-processed experimental control, both virtual microphones and virtual energy density sensors achieve higher attenuation at the virtual location than conventional control strategies employing their physical counterpart. As it is likely that the desired location of attenuation is not spatially fixed, a number of moving virtual sensing algorithms are also developed in this thesis. These moving virtual sensing algorithms generate a virtual microphone that tracks the desired location of attenuation as it moves through a three-dimensional sound field. To determine the level of attenuation that can be expected at the ear of a seated observer in practice, the performance of the moving virtual sensing algorithms in generating a moving zone of quiet at the single ear of a rotating artificial head is investigated in real-time experiments conducted in a modally dense three dimensional cavity. Results of real-time experiments demonstrate that moving virtual sensors provide improved attenuation at the moving virtual location compared to either fixed virtual sensors or fixed physical sensors. As an acoustic energy density cost function spatially extends the zone of quiet generated at the sensor location, a fixed three-dimensional virtual acoustic energy density sensing method is also developed for use in a modally dense three-dimensional sound field. The size of the localised zone of quiet achieved by minimising either the acoustic energy density or the squared pressure at the virtual location with the active noise control system is compared in real-time experiments conduced in a modally dense three-dimensional cavity. Experimental results demonstrate that minimising the virtual acoustic energy density provides improved attenuation in the sound field and a larger 10 dB zone of quiet at the virtual location than virtual microphones. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1522526 / Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2010
18

Densidade energética: relação com variáveis demográficas, de estilo de vida, nutricionais e socioeconômicas em amostra representativa da população adulta do município de São Paulo / Energy density: association with demographic, lifestyle, nutritional and socioeconomic variables in a representative sample of adult population in the city of São Paulo.

Roberta Horschutz Stella 05 September 2008 (has links)
Introdução - A densidade energética (DE), definida como a quantidade de energia por unidade de peso, é um importante fator na ingestão de alimentos e no valor calórico total da alimentação. Dessa forma, é uma característica da dieta que pode estar envolvida na qualidade da alimentação e no controle de peso. Objetivo - Analisar a relação entre a DE da dieta com variáveis demográficas, de estilo de vida, nutricionais e socioeconômicas em amostra representativa da população adulta do Município de São Paulo. Métodos - Foram utilizados dados secundários do projeto em Políticas Públicas, intitulado \"Inquérito de Saúde no Município de São Paulo - ISA-Capital\". Trata-se de um estudo transversal, de base populacional. O grupo de estudo foi composto por adultos, de ambos os sexos (N=710). O consumo alimentar foi medido através do método Recordatório de 24 horas. O consumo relatado foi transformado em energia e nutrientes com a utilização do software Nutrition Data System (NDS). A DE da dieta foi estimada através de três métodos: 1- inclusão de todos os alimentos e bebidas; 2- inclusão de todos os alimentos e bebidas calóricas que contenham, no mínimo, 5 Kcal/100g; 3- inclusão de todos os alimentos e exclusão de todas as bebidas. Para avaliar as relações entre a densidade energética da dieta e as variáveis demográficas, de estilo de vida, e socioeconômicas de interesse, foi utilizada a análise de regressão linear múltipla. Resultados: A população estudada foi composta por 56,7% de mulheres, 61,1% da etnia branca e 60,1% com situação conjugal unida/casada. A idade mínima foi de 20 anos e a idade máxima de 59 anos, com média de 36,2 anos. Os valores médios encontrados para a DE1, DE2 e DE3 foram 1,32 kcal/g (EP=0,01), 1,35 kcal/g (EP=0,01) e 1,95 kcal/g (EP=0,02), respectivamente. No modelo múltiplo, a escolaridade do indivíduo e a situação de trabalho \"em atividade\" associaram-se inversamente, ajustado por etnia para DE1 e DE2. Para DE3, foi verificada associação direta para etnia \"outras\" e inversa para hábito de fumar \"ex-fumante\". Conclusões: As médias de densidade energética encontradas no estudo mostraram-se superiores aos poucos estudos populacionais Resumo disponíveis. Os resultados apontados pelos diferentes métodos de cálculo da densidade energética sugerem que a contribuição dos líquidos não pode ser subestimada. / Introduction: Energy density (ED), defined as the amount of energy per unit weight, is a major factor related to food intake and total dietary energy. It is a dietary component that may be involved with diet quality and weight control. Objective: To assess the association between dietary ED and demographic, lifestyle, nutritional and socioeconomic variables in a representative sample of adult population in the city of São Paulo. Methods: A population-based, cross-sectional study was conducted based on secondary data from the Public Policies project, \"Health Survey in the City of São Paulo - ISA-Capital\". The study sample comprised both male and female adults (N=710). Food intake was measured using a 24-hour food recall. The reported intake was converted into energy and nutrients by the Nutrition Data System (NDS) program. Dietary ED was estimated through three different approaches: 1- inclusion of all foods and beverages; 2- inclusion of all energetic foods and beverages with a calorie content of at least 5 kcal/100 g; 3- inclusion of all foods and exclusion of all beverages. A multiple linear regression analysis was carried out to assess the associations between dietary ED and the study variables. Results: In the sample studied, 56.7% were women, 61.1% were White and 60.1% were either married or living with a partner. Mean age was 36.2 years, ranging between 20 and 59 years. Mean ED1, ED2 and ED3 were 1.32 kcal/g (SE=0.01), 1.35 kcal/g (SE=0.01) and 1.95 kcal/g (SE=0.02), respectively. In the multiple regression analysis, schooling and \"active\" working status were inversely associated, after adjusting for ethnicity, with ED1 and ED2. For ED3, there was found a direct association with \"other\" ethnicity and an inverse association with \"former smoking\". Conclusions: Mean energy densities found in the study were higher than those reported in few other population-based studies available. The results obtained through the different approaches for ED estimation indicate that the contribution of liquids should not be underestimated.
19

Symmetry breaking in nuclear mean-field models

Ryssens, Wouter 08 September 2016 (has links)
Dans les années 1970, Vautherin et Brink ont effectué les premiers calculs auto-consistents du problème à N-corps nucléaire en utilisant une interaction de Skyrme. Aujourd’hui la méthode de la fonctionnelle de densité (EDF) ou la méthode champ-moyen est toujours utilisée à grande échelle pour étudier la structure nucléaire. Le premier point fort de cette méthode est sa simplicité computationnelle qui permet de l'appliquer dans l'entièreté de la charte nucléaire, des noyaux les plus légers aux éléments super lourds à plus que 250 nucléons. Depuis le début des années 1980, les initiales `BFH', représentant Paul Bonche, Hubert Flocard et Paul-Henri Heenen, ont signé un grand nombre des papiers depuis 1984. Ces trois scientifiques sont les auteurs de trois codes numériques iconiques EV8, CR8 et EV4. Des versions évoluées de ces codes sont toujours utilisées fréquemment aujourd’hui par des nombreux chercheurs. Au fil des années, deux désavantages de ces trois codes sont apparus. Le premier désavantage est lié à la physique: bien que EV8, EV4 et CR8 offrent à l'utilisateur accès à une variété de combinaisons de symétries conservées et brisées, un grand nombre n'est pas accessible. De plus en plus souvent, les applications traitant des noyaux exotiques demandent des calculs champ-moyen qui sont moins limités par les symétries imposées. Le deuxième désavantage est d'une nature plus pratique: le maintien au même niveau d'une combinaison de trois codes qui ont des buts comparables est difficile. Le projet de mon doctorat était de construire un code qui unifie et généralise les fonctionnalités de EV8, CR8 et EV4. Aujourd'hui MOCCa, un acronyme de MOdular Cranking Code, est capable de reproduire toutes les fonctionnalités des codes BFH. De plus, il est maintenant possible d'effectuer des calculs champ-moyen pour un nombre des combinaisons de symétries conservées et brisées, offrant un domaine d'applications énorme. Quatre symétries ont été toujours imposées dans les codes BFH, et sont maintenant toutes soumises au choix de l'utilisateur, qui peut les conserver où les briser indépendamment. Ceci résulte en 16 modes d'opération différents du code, dont tous ont des intérêts physiques pour décrire des phénomènes nucléaires. La déformation octupolaire du 224Ra et les bandes chirales du 138Nd sont des exemples récents d'intérêt expérimental, dont la description théorique est maintenant abordable avec un seul outil. Cet outil fait preuve d'une grande complexité: sur le plan physique, des méthodes ont été développées pour résoudre les équations du champ-moyen en l'absence des symétries facilitant le problème, tandis que sur le plan pratique, le traitement d'un nombre de degrés de liberté non-physiques a eté amelioré. La dernière partie de la thèse, la plus importante probablement du point de vue des futurs collaborateurs, est pour cette raison constituée d'un manuel d'utilisateur. Deux applications de la méthode sont ainsi présentées: la description des transitions de forme dans les isotopes de Radium et une étude de l'évolution des rayons de charge dans la chaîne isotopique du mercure démontrent la viabilité de la méthode. / Option Physique du Doctorat en Sciences / info:eu-repo/semantics/nonPublished
20

Development of Methods to Propagate Energy Density and Predict Farfield Directivity Using Nearfield Acoustic Holography

Woolston, Scott Richard 09 July 2009 (has links) (PDF)
Acoustical-based imaging systems have found merit in determining the behavior of vibrating structures. This thesis focuses on the continued development of the nearfield acoustic holography (NAH) approach. Conventional NAH consists of first measuring the pressure field on a two-dimensional conformal surface and then propagating this data back to the vibrating structure to obtain information about the source, such as the normal velocity distribution. Recent work has been done which incorporates particle velocity information into the traditional NAH measurements to reduce the number of measurements required. This advancement has made NAH a more affordable tool for acoustical imaging and sound field characterization. It is proposed that the inclusion of velocity information into traditional NAH can further increase its usefulness. By propagating the velocity and pressure values independently and recombining them on the reconstruction surface, the pressure field and energy density fields can be predicted at any point in the sound field. It is also proposed that the same NAH measurement can be used to predict farfield directivity. The inclusion of velocity values into the NAH technique also provides a means for predicting energy density (ED) anywhere within the acoustic field. These two developments would allow a single NAH measurement to provide much more information about an acoustic source and its radiated sound field. Experimental testing shows that NAH is successful at predicting the shape of the resulting ED field and directivity pattern with some error in amplitude. The best performance of the technique is with a planer source resulting in an average amplitude error of 18.5% over the entire field.

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