When simulating a thermohydraulic system, the general assumption isthat the conservation equations for mass, energy and momentum apply.And in such systems both liquid and gas exist, in this project liquidwater and steam. This report examines two different approaches tosimulate a thermohydraulic system. One is called 6-equation model,where separate conservation equations exist for both gas and liquid.The other is known as 3-equation model, where the conservationequations describe a mix of the two states. This examination is doneby modeling an experiment known as FIX-II in the software APROS, whichis capable of using both the 3- and 6-equation model. This reportshows that in several cases, both equation models give quite goodresults. However, whereas the 3-equation model in some cases, mainlypressure, were able to produce results more in line with experimentaldata, it struggled when it comes to counter current flow. Countercurrent flow, or CCF, means that gas and liquid flow in oppositedirections, something that the 3-equation model is unable to handle.For experiment 3051 this leads to a break flow in the 3-equation modelthat significantly deviates from experimental data. Generally, it isconcluded that the 3-equation model needs to be used with cautionbecause of its inability to deal with CCF. Besides CCF, there is alsoa significant difference between the two equation models in how heatflow is calculated. This difference in heat flow is the main reasonfor differences in pressure between the two equation models, which inturn caused the difference in break flow.

The focus of the world is on the reduction of greenhouse gases, such as carbon dioxide, which contribute to the global warming currently experienced. Because most of the carbon dioxide emitted into the atmosphere is from fossil fuel combustion, alternative energy sources were developed and others are currently under study to see whether they will be good alternatives. One of these alternative sources of energy is the combustion of wood instead of coal. The advantages of wood are that it is a neutral carbon fuel source and that currently installed infrastructure used to combust coal can be retrofitted to combust wood or a mixture of wood and coal in an attempt to reduce the carbon dioxide emissions. Spent nuclear fuel has to be cooled so that the decay heat generated does not melt the containment system, which could lead to the unintentional release of radioactive material to the surroundings. The heat transfer mechanisms involved in the cooling have historically been analysed by assuming that the fluid and solid phases are at local thermal equilibrium (LTE) in order to simplify the analysis. The exergy destruction of the combustion of pine wood in an adiabatic combustor was investigated in this thesis using analytical and computational methods. The exergy destruction of the combustion process was analysed by means of the second law efficiency, which is the ratio of the maximum work that can be achieved by a Carnot engine extracting heat from the combustor, and the optimum work of the combustor. This was done for theoretical air combustion and various excess air combustions, with varied inlet temperatures of the incoming air. It was found that the second law efficiency reached an expected maximum for theoretical air combustion, and this held true for all varying air inlet temperatures. However, it was found that as the air inlet temperature was increased more and more, the maximum second law efficiency was the same for all excess air combustions, including the theoretical air combustion. It was also found that the results of the analytical and commercial computational fluid dynamics code compared well. Another analysis was conducted of irreversibilities generated due to combustion in an adiabatic combustor burning wood. This was done for a reactant mixture varying from a rich to a lean mixture. A non-adiabatic non-premixed combustion model of a numerical code was used to simulate the combustion process where the solid fuel was modelled by using the ultimate analysis data. The entropy generation rates due to the combustion and frictional pressure drop processes were computed to eventually arrive at the irreversibilities generated. It was found that the entropy generation rate due to frictional pressure drop was negligible when compared with that due to combustion. It was also found that a minimum in irreversibilities generated was achieved when the air-fuel mass ratio was 4.9, which corresponded to an equivalent ratio of 1.64, which was lower than the respective air-fuel mass ratio and equivalent ratio for complete combustion with theoretical amount of air of 8.02 and 1. Studieswere conducted to numerically analyse irreversibilities generated due to combustion in an adiabatic combustor burning wood. The first study analysed the effect of changing the incoming air temperature from 298 K to 400 K. The second study analysed the effect of changing the wall condition of the combustor from adiabatic to negative heat flux (that is heat leaving the system) for an incoming air temperature of 400 K. The irreversibilities generated in the combustor were calculated by computing the entropy generation rates due to the combustion, heat transfer and frictional pressure drop processes. For the first part of the study, it was found that for the minimum irreversibilities generated in the adiabatic combustor, the optimal air-fuel ratio (AF) corresponding to minimum irreversibilities slightly reduced from 4.9 to 4.8. In the second part of the study, it was found that by changing the wall condition from adiabatic to heat flux on the combustor, the AF corresponding to the minimum irreversibilities increased from 4.8 to 6. For the third part of the study, the combustor with a heat flux wall condition and a wall thickness simulated at an AF of 6, the sum of twice the wall thickness and the optimum diameter always added up to 0.32 m, resulting in the minimum irreversibilities. An analytical model was developed to minimise the thermal resistance of an air-cooled porous matrix made up of solid spheres with internal heat generation. This was done under the assumption of LTE. It was found that the predicted optimum sphere diameter and the minimum thermal resistance were both robust in that they were independent of the heat generation rate of the solid spheres. Results from the analytical model were compared with those from a commercial numerical porous model using liquid water and air for the fluid phase, and wood and silica for the solid phase. The magnitudes of the minima of both the temperature difference and the thermal resistance seemed to be due to equal contribution from the thermal conduction heat transfer inside the solid spheres and heat transfer in the porous medium. Because the commercial numerical porous model modelled only the heat transfer occurring in the porous medium, it expectedly predicted half of the magnitudes of the minima of the temperature difference and thermal resistance of those by the analytical model. / Thesis (PhD)--University of Pretoria, 2017. / Mechanical and Aeronautical Engineering / PhD / Unrestricted

No description available.

Title: Modelling of plasma-solid interaction Author: Jan Nožka Department: Institute of Theoretical Physics Supervisor: prof. RNDr. Rudolf Hrach, DrSc., Department of Surface and Plasma Science Abstract: This work is devoted to computer modeling of the low-temperature argon plasma discharge. We created one basic particle model and one basic fluid model. Furthermore, we created a model of electron-electron interaction in three dimensions. This model is able to stabilize nonequilibrium electron gas in the expected equilibrium. This model was developed to investigate the influence of electron-electron scattering on the acceleration of electrons above the speed that is sufficient for excitation or ionization of neutral argon atom. At the end of this work there are results that shed a light on the importance of this interaction in comparison with the amount of fast electrons that are present in the plasma due to electric filed field.

Submitted by Socorro Pontes (socorrop@ufersa.edu.br) on 2017-04-11T19:49:29Z No. of bitstreams: 1 JacinaraHGML_TESE.pdf: 2277274 bytes, checksum: 6f35ba41b855fe18662b6c316e37bc38 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-04-13T14:42:13Z (GMT) No. of bitstreams: 1 JacinaraHGML_TESE.pdf: 2277274 bytes, checksum: 6f35ba41b855fe18662b6c316e37bc38 (MD5) / Approved for entry into archive by Vanessa Christiane (referencia@ufersa.edu.br) on 2017-04-13T14:59:04Z (GMT) No. of bitstreams: 1 JacinaraHGML_TESE.pdf: 2277274 bytes, checksum: 6f35ba41b855fe18662b6c316e37bc38 (MD5) / Made available in DSpace on 2017-04-13T14:59:14Z (GMT). No. of bitstreams: 1 JacinaraHGML_TESE.pdf: 2277274 bytes, checksum: 6f35ba41b855fe18662b6c316e37bc38 (MD5) Previous issue date: 2016-12-05 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The Morada Nova sheep is an important locally adapted genetic resource from the Brazilian Semiarid. However, the genetic variability of these animals has been reduced due to the selection criteria adopted by breeders who only select to breed traits. One of these criteria is related to coat color, where the animals of red variety with dark and light tonality are discarded, as well as all animals of the white variety, with the justification that they are less adapted to the semiarid environment. Thus, in the present thesis was built in order to evaluate all characteristics related to the adaptation of Morada Nova sheep with different hair and coat color. Four groups were used according to coat color: (1) dark red animals, (2) intermediate red, (3) light red, and (4) white-coated animals. Forty Morada Nova ewes were observed in each of three herds for 7 consecutive months. In the first study we evaluated the thermal exchanges of sensible and latent heat loss in the different groups. All groups maintained homeothermy even when exposed to high solar radiation. The red coat animals increased respiratory rate in conditions of greater thermal stress. This fact was not observed in the white variety, which showed higher skin evaporation. In the second study, were evaluated hair coat characteristics and their association in the heat transfer from animals to the environment as well as physiological responses of animals. The largest differences found in the coat characteristics were recorded between the extremes of coat color: dark red and white. The white variety exhibited characteristics that promoted the protection of the skin, while red variety had characteristics which favored heat dissipation. It was concluded that Morada Nova sheep have good adaptability to the Semiarid environment, regardless of the coat color, and should be used in farming systems, preserved and multiplied / A raça Morada Nova é um importante recurso genético localmente adaptado do semiárido brasileiro, e apresentam características adaptativas exclusivas dessa região do Brasil no qual foi formada ao longo de anos de seleção natural. Porém, a variabilidade genética desses animais vem reduzindo devido aos critérios de seleção adotado pelos criadores que visam somente o padrão racial. Um desses critérios está relacionado com a cor do pelame, no qual são descartados os animais de pelagem vermelha escura e clara, assim como a variedade branca com a justificativa que são menos adaptados ao ambiente semiárido. Com isso, a presente tese foi construída com o objetivo de avaliar todas as características ligadas à adaptação dos animais da raça Morada Nova com diferentes cores de pelame. Foram avaliados, por um período de sete meses consecutivos, três rebanhos comerciais sendo que cada rebanho foram acompanhadas 40 matrizes. Os animais foram divididos em grupos de forma que os com pelame vermelho foram classificados em: (1) tonalidade escura, (2) tonalidade intermediária e (3) tonalidade clara. Os animais de pelame branco foram classificados como grupo 4. A tese foi dividida em dois artigos, sendo que no primeiro foram avaliadas as trocas térmicas de calor sensível e latente nos diferentes grupos. Foi observado que todos os grupos conseguiram manter a homeotermia, mesmo expostos à elevada radiação solar. Os mecanismos sensíveis foram pouco expressivos para a perda de calor, enquanto que os mecanismos latentes foram mais eficientes na termólise em todos os grupos. Os animais de pelagem vermelha elevaram muito a frequência respiratória nas condições de maior estresse térmico, fato que não foi verificado nos animais com pelagem branca, que apresentaram maior evaporação cutânea. No segundo artigo foram avaliadas as características morfológicas de pelame e sua associação com a transferência térmica de calor, assim como as respostas fisiológicas dos animais. As maiores diferenças encontradas para essas características foram em relação aos extremos de cor de pelagem: vermelho escuro e branco. Os resultados mostraram que a variedade branca apresentou características que promovem a proteção da epiderme, enquanto que os animais da variedade vermelha apresentaram características que favorecem a dissipação de calor. Contudo, pode-se afirmar que todos os animais da raça Morada Nova representam importante material genético bem adaptados a região equatorial semiárida, e devem ser utilizados nos sistemas de criação, conservados e multiplicados / 2017-04-11

Um dos problemas mais importantes que precisa ser resolvido, tanto pela física de partículas como pela cosmologia, é a existência de assimetria bariônica. Entre os cenários mais atrativos para a geração dinâmica da assimetria bariônica (Bariogênese) encontra- se a denominada Leptogênese. Nesse cenário, cria-se uma assimetria leptônica que será convertida em assimetria bariônica por processos não perturbativos mediados por sphalerons. Na realização mais simples da Leptogênese, que será estudada nesta dissertação, neutrinos pesados de mão direita, produzidos termicamente, decaem violando CP, gerando um assimetria leptônica nesses decaimentos. O principal atrativo deste cenário é que conecta duas escalas aparentemente diferentes: a escala da geração de assimetria leptônica e a escala das massas e oscilações dos neutrinos ativos mediante o mecanismo de See-Saw. O estudo usual da Leptogênese utiliza equações de Boltzmann para determinar a evolução temporal da assimetria. Porém, a equação de Boltzmann é uma equação semiclássica, dado que envolve, por um lado, uma função clássica no espaço de fases, a função de distribuição, mas, por outro, os termos de colisão envolvem quantidades obtidas na teoria quântica de campos à temperatura nula. Em particular, a formulação de Boltzmann não permite descrever fenômenos quânticos como oscilações coerentes e efeitos de decoêrencia e interferência. Uma descrição quântica completa da evolução da assimetria leptônica na leptogênese deve, de fato, ser obtida no contexto da teoria quântica de campos fora do equilíbrio térmico. O formalismo de Schwinger-Keldysh permite realizar isso. Nesta dissertação descreveremos a leptogênese no formalismo de Schwinger-Keldysh para o caso em que são adicionados ao espectro de partículas do Modelo Padrão três neutrinos de mão direita, sem fazer qualquer suposição sobre a hierarquia de massas. / One of the most important problems that is needed to solve by the Elementary Particle Physics as well as by the Cosmology is the existence of baryonic asymmetry. Among the most attractive scenarios of dynamic generation of baryonic asymmetry (Baryogenesis) is the so-called Leptogenesis. In that scenario, a leptonic asymmetry is treated in such a way that it will be converted in baryonic asymmetry by non-perturbative processes mediated by sphalerons. In the simplest realization of Leptogenesis, that will be studied in this disertation, heavy right-handed neutrinos, produzed thermally, decay violating CP generating a leptonic asymmetry in these decays. The principal attractive of this scenario is that it connects two apparently different scales, the scale of leptonic asymmetry generation and the scale of masses and oscillations of the active neutrinos through the See-Saw mechanism. The usual study of the leptogenesis uses Boltzmann equations in order to determine the temporal evolution of the asymmetry. However, the Boltzmann equation is a semiclassical equations, since, on one side, it is formulated for a classical function in phases space, the distribution function, but, on the other hand, the collision term involves quantities obtained in the Quantum Field Theory at zero temperature. In particular, Boltzmann formulation does not allow to describe quantum phenomena such coherent oscillations and effects of decoherence and interference. Indeed, a proper quantum description of the evolution of the leptonic asymmetry must be obtained in the context of the Non-Equilibrium Quantum Field Theory. The Schwinger-Keldysh formalism allows to perform this. In this dissertation, leptogenesis is described using the Schwinger-Keldysh formalism for the case in which there are three right-handed neutrinos without a definite mass hierarchy.

Um dos problemas mais importantes que precisa ser resolvido, tanto pela física de partículas como pela cosmologia, é a existência de assimetria bariônica. Entre os cenários mais atrativos para a geração dinâmica da assimetria bariônica (Bariogênese) encontra- se a denominada Leptogênese. Nesse cenário, cria-se uma assimetria leptônica que será convertida em assimetria bariônica por processos não perturbativos mediados por sphalerons. Na realização mais simples da Leptogênese, que será estudada nesta dissertação, neutrinos pesados de mão direita, produzidos termicamente, decaem violando CP, gerando um assimetria leptônica nesses decaimentos. O principal atrativo deste cenário é que conecta duas escalas aparentemente diferentes: a escala da geração de assimetria leptônica e a escala das massas e oscilações dos neutrinos ativos mediante o mecanismo de See-Saw. O estudo usual da Leptogênese utiliza equações de Boltzmann para determinar a evolução temporal da assimetria. Porém, a equação de Boltzmann é uma equação semiclássica, dado que envolve, por um lado, uma função clássica no espaço de fases, a função de distribuição, mas, por outro, os termos de colisão envolvem quantidades obtidas na teoria quântica de campos à temperatura nula. Em particular, a formulação de Boltzmann não permite descrever fenômenos quânticos como oscilações coerentes e efeitos de decoêrencia e interferência. Uma descrição quântica completa da evolução da assimetria leptônica na leptogênese deve, de fato, ser obtida no contexto da teoria quântica de campos fora do equilíbrio térmico. O formalismo de Schwinger-Keldysh permite realizar isso. Nesta dissertação descreveremos a leptogênese no formalismo de Schwinger-Keldysh para o caso em que são adicionados ao espectro de partículas do Modelo Padrão três neutrinos de mão direita, sem fazer qualquer suposição sobre a hierarquia de massas. / One of the most important problems that is needed to solve by the Elementary Particle Physics as well as by the Cosmology is the existence of baryonic asymmetry. Among the most attractive scenarios of dynamic generation of baryonic asymmetry (Baryogenesis) is the so-called Leptogenesis. In that scenario, a leptonic asymmetry is treated in such a way that it will be converted in baryonic asymmetry by non-perturbative processes mediated by sphalerons. In the simplest realization of Leptogenesis, that will be studied in this disertation, heavy right-handed neutrinos, produzed thermally, decay violating CP generating a leptonic asymmetry in these decays. The principal attractive of this scenario is that it connects two apparently different scales, the scale of leptonic asymmetry generation and the scale of masses and oscillations of the active neutrinos through the See-Saw mechanism. The usual study of the leptogenesis uses Boltzmann equations in order to determine the temporal evolution of the asymmetry. However, the Boltzmann equation is a semiclassical equations, since, on one side, it is formulated for a classical function in phases space, the distribution function, but, on the other hand, the collision term involves quantities obtained in the Quantum Field Theory at zero temperature. In particular, Boltzmann formulation does not allow to describe quantum phenomena such coherent oscillations and effects of decoherence and interference. Indeed, a proper quantum description of the evolution of the leptonic asymmetry must be obtained in the context of the Non-Equilibrium Quantum Field Theory. The Schwinger-Keldysh formalism allows to perform this. In this dissertation, leptogenesis is described using the Schwinger-Keldysh formalism for the case in which there are three right-handed neutrinos without a definite mass hierarchy.

No description available.

doctoral thesis, Ph.D, University of California, Berkeley, Berkeley, CA. / Published through the Information Bridge: DOE Scientific and Technical Information. "LBNL--55855" Gedik, Nuh. USDOE Director. Office of Science. Office of Basic Energy Sciences 05/20/2004. Report is also available in paper and microfiche from NTIS.

Cette thèse traite de la manipulation de l'énergie dans trois systèmes quantiques ouverts différents dans la limite de couplage faible système-environnement, et leurs dynamiques respectives sont décrites par une équation maîtresse quantique markovienne. Dans le premier chapitre, le calcul d'une telle équation est réalisé pour un système particulier, et diverses notions de thermodynamique quantique sont introduites. Pour le premier système physique, on analyse le transport d'énergie le long de chaînes atomiques (entre 2 et 7 atomes) soumises à un rayonnement de corps noir proche de la température ambiante. Il est montré que l'efficacité du transport peut atteindre des valeurs remarquables, surpassant 100% et atteignant jusqu'à 1400% dans certaines configurations. De plus, lorsque l'efficacité est amplifiée, la portée du transport est également considérablement augmentée. Le chapitre suivante traite aussi du transport d'énergie dans des chaînes atomiques. Le système quantique est placé à l'interface d'un isolant topologique photonique (ITP), qui supporte un plasmon polariton de surface (PPS) insensible à la réflexion. Le PPS se propage le long de la chaîne atomique et assiste le transport d'énergie. La comparaison est faite entre PPSs réciproque et unidirectionnel en termes d'efficacité du transport, et il est démontré que ce dernier produit une meilleure efficacité, de plus d'un ordre de grandeur. De surcroît, divers aspects pratiques dus aux propriétés des ITPs sont mis en avant, notamment la robustesse du transport d'énergie en présence de défauts sur le parcours du PPS. Enfin, un système quantique immergé dans un champ électromagnétique hors équilibre thermique est étudié. Il est composé d'un système à trois niveaux d'énergie, jouant le rôle de machine thermique quantique à absorption, ainsi que de N atomes à deux niveaux ("qubits") qui sont affectés par l'action de la machine. Il est montré que la machine est capable de délivrer des tâches thermiques d'intensité significative sur les qubits, y compris lorsque leur nombre augmente. De plus, il est mis en évidence qu'en raison d'interactions qubit-qubit, les tâches réalisées par la machine sont distribuées parmi l'ensemble du système des qubits en interaction, de sorte que dans certains cas, même les qubits complètement découplés de la machine subissent une modification de température considérable. Ce mécanisme de distribution des tâches est analysé à travers les corrélations entre différentes partitions du système quantique. Par ailleurs, le contrôle des tâches thermiques est également discuté. / This thesis deals with energy management in open quantum systems. Three different systems are under study in the limit of weak system-environment coupling, and their dynamics is described by Markovian quantum master equations. In the first chapter, the complete derivation of such equation is performed in a specific case, and several notions of quantum thermodynamics are introduced. In the first system, energy transport is investigated along atomic chains (between 2 and 7 atoms) embedded in blackbody radiation around room temperature. It is shown that the transport efficiency can reach remarkable values, exceeding 100% and reaching 1400% in some configurations. Moreover, when the efficiency is amplified, the transport range is also considerably increased. The following chapter also deals with energy transport in atomic chains. The quantum system is located at the interface of a photonic topological insulator (PTI), supporting a unidirectional surface-plasmon-polariton (SPP) immune to backscattering. The SPP propagates along the chain and assists energy transport. Comparison is made between reciprocal and unidirectional SPPs in terms of transport efficiency, and it is shown that the latter can yield an efficiency larger by one order of magnitude. In addition, several practical aspects stemming from PTIs are highlighted, including the robustness of energy transport in the presence of defects on the SPP path. In the last chapter, a quantum system embedded in an out-of-thermal-equilibrium electromagnetic field is investigated. It is composed of a three-level atom playing the role of an absorption quantum thermal machine, as well as N two-level atoms ('qubits'), with N=1,...,6, which are the target bodies. It is demonstrated that the machine is able to perform significant thermal tasks on the qubits, even when their number is increased. Moreover, it is pointed out that due to qubit-qubit interactions, the tasks delivered by the machine are distributed throughout the system of interacting qubits, such that in some cases the temperature of the qubits which are completely decoupled from the machine can still be considerably affected by it. This task-distribution mechanism is investigated by means of the correlations between different subparts of the system. In addition, the tuning of thermal tasks is discussed.