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Modelo de bósons interagentes e sua relação com o BCS. / Model of interacting bosons and their relationship with the BCS.Diniz, Ricardo 04 July 1990 (has links)
Através de um hamiltoniano efetivo baseado no tratamento de NAMBU POT.90 para o BCS, no qual incluímos além do emparelhamento monopolar o emparelhamento quadrupolar, discutimos a relação entre esse modelo e o modelo de bósons interagentes. Uma aplicação e feita a cadeia o (6) do IBM, que corresponde ao limite GAMA-instável do modelo de bohr. As dificuldades encontradas e uma possível generalização para o modelo são discutidas. / The nambu mechanism for BCS theory is extended with inclusion of quadrupole pairing in adition to the usual monopole pairing. An effective Hamiltonian is constructed and its relation to the IBM is discussed. We discussed the faced difficulties and a possible generalization of the model.
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Proton-neutron pairing correlations in atomic nuclei / Corrélations d’appariement proton-neutron dans le noyau atomiqueNégréa, Daniel 10 September 2013 (has links)
La compréhension usuelle de l'appariement proton-neutron, dont les traces sont actuellement étudiées en noyaux N = Z, s'appuie sur le mécanisme de paires de Cooper et modèles BCS type. Dans cette thèse, nous présentons une approche alternative qui, contrairement aux modèles BCS, conserve exactement le nombre de particules et l'isospin. Dans cette approche, l'état fondamental de noyaux N = Z est décrit comme un condensé de quartets alpha-similaires faits de deux neutrons et deux protons couplés à l'isospin total T = 0 et de spin J total = 0. La comparaison avec des calculs exacts du modèle en couches montre que le modèle de condensation quartet (QCM) donne une description très précise de l'appariement des corrélations à noyaux N = Z, bien mieux que les modèles BCS. Il est également montré que l'appariement proton-neutron et alpha de type condensation sont importantes non seulement pour les noyaux N = Z, mais aussi pour les noyaux avec des neutrons excédentaires. Dans ce dernier cas, le condensat de quartets d'alpha coexiste avec le condensat des paires de neutrons en excès par rapport au isotopes N = Z. En utilisant le cadre de QCM, nous avons également étudié la compétition entre l’appariement proton-neutron isovectoriel et isoscalaire dans les noyaux N = Z. Nos résultats indiquent que la contribution de l'appariement isoscalaire aux corrélations d'appariement du fondamental est très faible par rapport à l'appariement isovectoriel. / The common understanding of proton-neutron pairing, whose fingerprints are currently investigated in N = Z nuclei, relies on Cooper pair mechanism and BCS-type models. In the present thesis we present an alternative approach which, contrary to BCS models, conserves exactly the particle number and the isospin. In this approach the ground state of N=Z nuclei is described as a condensate of alpha-like quartets built by two neutrons and two protons coupled to the total isospin T=0 and total spin J=0. The comparison with exact shell model calculations shows that the quartet condensation model (QCM) gives a very accurate description of pairing correlations in N=Z nuclei, much better than the BCS models. It is also shown that proton-neutron pairing and alpha-type condensation are important not only for N=Z nuclei but also for nuclei with excess neutrons. In the latter case the condensate of alpha-like quartets coexist with the condensate of the neutron pairs in excess relative to the N=Z isotope. Using the framework of QCM we have also studied the competition between the isovector and the isoscalar proton-neutron pairing in nuclei with N=Z. Our results indicate that the contribution of isoscalar pairing to the ground state pairing correlations is very small compared to the isovector pairing.
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Modelo de bósons interagentes e sua relação com o BCS. / Model of interacting bosons and their relationship with the BCS.Ricardo Diniz 04 July 1990 (has links)
Através de um hamiltoniano efetivo baseado no tratamento de NAMBU POT.90 para o BCS, no qual incluímos além do emparelhamento monopolar o emparelhamento quadrupolar, discutimos a relação entre esse modelo e o modelo de bósons interagentes. Uma aplicação e feita a cadeia o (6) do IBM, que corresponde ao limite GAMA-instável do modelo de bohr. As dificuldades encontradas e uma possível generalização para o modelo são discutidas. / The nambu mechanism for BCS theory is extended with inclusion of quadrupole pairing in adition to the usual monopole pairing. An effective Hamiltonian is constructed and its relation to the IBM is discussed. We discussed the faced difficulties and a possible generalization of the model.
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Feldstudie zur Gewichtsentwicklung und Gewichtsschätzung beim wachsenden PferdHois, Christine. Unknown Date (has links) (PDF)
Universiẗat, Diss., 2004--München.
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Efficient Computational Procedure for the Analytic Continuation of Eliashberg EquationsJohansson, Joakim, Lauren, Fredrik January 2014 (has links)
The superconducting order parameter and the mass renormalization function can be solved either at discrete frequencies along the imaginary axis, or as a function of continuous real frequencies. The latter is done with a method called analytic continuation. The analytic continuation can conveniently be done by approximating a power series to the functions, the Padè approximation. Studied in this project is the difference between the Padè approximation, and a formally exact analytic continuation of the functions. As it turns out, the Padè approximant is applicable to calculate the superconducting order parameter at temperatures sufficiently below the critical temperature. However close to the critical temperature the approximation fails, while the solution presented in this report remains reliable.
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Vergleich der unterschiedlichen Körperkonditionsbeurteilungsmethoden - body condition scoring (BCS) und Rückenfettdickenmessung (RFD) - und deren Aussagefähigkeit in Bezug auf die Fruchtbarkeit von Holstein-Friesian (HF) KühenFietze, Sebastian. Unknown Date (has links) (PDF)
Tierärztl. Hochsch., Diss., 2004--Hannover.
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Modelo de suporte ao planejamento de manutenção do sistema de bombeio centrífugo submerso de um campo petrolífero de completação secaPicanço, José Mário Barroso 31 January 2011 (has links)
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Previous issue date: 2011 / Esta dissertação apresenta uma aplicação do estudo da confiabilidade em
dados de tempo de vida de poços produtores de óleo de completação seca
equipados com bombeio centrífugo submerso. A variável resposta do estudo
é o tempo de funcionamento do poço dentro de sua normalidade até
apresentar a primeira falha relacionada ao equipamento de subsuperfície,
que cause uma parada total no funcionamento do poço. O principal objetivo
do estudo foi, com base em um conjunto de dados reais fornecidos pela
companhia petrolífera, mensurar e verificar a viabilidade técnica e econômica
de um sistema de manutenção programado baseado na política de
substituição por idade. Também foi realizada estratificação dos dados
visando a verificar a correlação de alguns fatores como localização do
campo, razão água-óleo (RAO), faixa de vazão e motivo da falha no tempo de
operações dos poços. Neste trabalho, foi feito um estudo retrospectivo com
uma amostra composta por 330 eventos de poços-colunas que estavam em
funcionamento no período de 1992 a 2010. A modelagem probabilística dos
dados foi feita através do ajuste do modelo de regressão Weibull. Os
resultados encontrados na aplicação do modelo foram considerados
satisfatórios, gerando economias em relação ao regime antigo entre 8% e
13% e em valores monetários anuais bastante significativos para o campo de
petróleo estudado
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φ photoproduction on the proton at Eγ=1.5-2.9 GeV / Eγ=1.5-2.9 GeVにおける陽子標的を用いたφ中間子光生成Mizutani, Keigo 26 March 2018 (has links)
京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第20913号 / 理博第4365号 / 新制||理||1626(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 永江 知文, 教授 鶴 剛, 教授 中家 剛 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM
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The characterization of Clostridium beijerinckii NRRL B592 cells transformed with plasmids containing the butanol-production genes under the control of constitutive promotersTollin, Craig Jeffrey 07 December 2012 (has links)
Clostridium beijerinckii is a spore-forming, obligate anaerobe that is capable of producing butanol, acetone and isopropanol. These industrial chemicals are traditionally known as solvents. The regulation of solventogenic fermentation is linked to the onset of sporulation, so that by the time the organism begins to produce solvents, it is also entering into spore formation and metabolic slowdown. The goal of this research project was to study the effect of placing the solvent-production genes from C. beijerinckii under the control of constitutive promoters from other genes, in an attempt to allow an earlier start of butanol production during the growth phase than is the case with the wild-type cells.
The aldehyde dehydrogenase from C. beijerinckii NRRL B593 (ald) and alcohol dehydrogenase from C. beijerinckii NRRL B592 (adhA) were placed under the control of the promoter from the acid-producing operon (the BCS operon) in one vector, and under the control of the promoter from the ferredoxin gene in another. In both cases, aldehyde dehydrogenase activity was produced earlier in the growth phase in transformed cells, but alcohol dehydrogenase activity was not.
The adhA gene from C. beijerinckii NRRL B592 was paired with the adhB gene from the same organism in a third vector, both under the control of the promoter from the BCS operon. In cells transformed with this vector, alcohol dehydrogenase activity was observed earlier in the growth phase than it was in wild-type NRRL B592 cells. / Ph. D.
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BCS to BEC Evolution and Quantum Phase Transitions in Superfluid Fermi GasesIskin, Menderes 29 June 2007 (has links)
This thesis focuses on the analysis of Bardeen-Cooper-Schrieffer (BCS)
to Bose-Einstein condensation (BEC) evolution in ultracold superfluid
Fermi gases when the interaction between atoms is varied. The tuning of
attractive interactions permits the ground state of the system to evolve from a weak
fermion attraction BCS limit of loosely bound and largely overlapping Cooper pairs
to a strong fermion attraction limit of tightly bound small bosonic molecules
which undergo BEC.
This evolution is accompanied by anomalous behavior of many superfluid
properties, and reveals several quantum phase transitions.
This thesis has two parts:
In the first part, I analyze zero and nonzero orbital angular momentum
pairing effects, and show that a quantum phase transition occurs for
nonzero angular momentum pairing, unlike the $s$-wave case where the BCS
to BEC evolution is just a crossover.
In the second part, I analyze two-species fermion mixtures with mass and
population imbalance in continuum, trap and lattice models. In contrast with
the crossover physics found in the mass and population balanced mixtures,
I demonstrate the existence of phase transitions between normal and
superfluid phases, as well as phase separation between superfluid (paired)
and normal (excess) fermions in imbalanced mixtures as a function of scattering
parameter and mass and population imbalance.
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