Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1980. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND SCIENCE. / Includes bibliographical references. / by Chang-Shung Chai. / Ph.D.

Fazemos inicialmente uma breve exposição sobre os fundamentos da Termodinâmica Clássica Holotrópica, desenvolvida por N. Bernardes. Esta consiste em formular o problema da Termodinâmica tomando como grandeza fundamental a entropia de um universo ( - sistema Isolado); no caso de um universo clássico composto esta é igual a soma das entropias de suas partes. Postulamos um principio dinâmico suficiente para a validade da segunda lei da Termodinâmica, o qual implica que os máximos dessa soma são estados estacionários estáveis do universo. Somos levados naturalmente a perguntar o que acontece se a entropia do universo possuir mais do que um máximo; a resposta a isso é o tratamento que daremos ao fenômeno de transição de fase. Analisamos em detalhe o universo composto por um corpo pequeno (cuja entropia é por hipótese analítica) e reservatórios de calor e trabalho. Para que a entropia do universo possua mais que um máximo a entropia do corpo pequeno não pode ser côncava em todo seu domínio; assumindo uma forma particular para ela (deslocamento de Bernardes) analisaremos o equilíbrio entre duas fases e o comportamento em torno do ponto onde a curva de coexistência termina (ponto crítico isolado). Com isto será possível dar uma visão clara e bastante intuitiva do fenômeno de transição de fase dito \"de primeira ordem\". Tendo em mente o significado físico das transformadas de Legendre da entropia do corpo pequeno (transparente na formulação holotrópica) compreenderemos o sentido das descontinuidades de primeira e segunda ordem que afetam as funções termodinâmicas que descrevem o equilíbrio do universo, com o que não veremos razão alguma para classificar as transições de fase da maneira que assim fez Ehrenfest. Veremos também, e isto é muito importante, que a Termodinâmica Clássica não consegue explicar a singularidade no calor específico que se verifica experimentalmente num ponto crítico, sendo que esta falha é intrínseca ou à Termodinâmica clássica ou à hipótese da entropia do corpo pequeno ser contínua e diferenciável. / We make initially a short exposition about the fundaments of Holotropic classical thermodynamics, developed by N. Bernardes. This is the formulation of the thermodynamic problem taking the entropy of a universe (isolated system) as the fundamental variable. In a classical composite universe it is the sum of the entropies of its parts. We postulate a dynamic principle sufficient for the validity of the second law of Thermodynamics, which implies that the maxima of that sum are stable stationary states of the universe. We arrive at the question about what occurs when the entropy of the universe possesses more than one maximum; the answer is the treatment we will give to the phenomena of phase transition. We analyze in detail the universe composed by a small body (whose entropy is analytical by hypothesis) and heat and work reservoirs. The entropy of the small body must be not concave in all of its dominium for the entropy of universe to have more than one maximum; we make a particular choice for it (Bernardes displacement) in order to analyze equilibrium between two phases and the behavior around the point where the coexistence curve terminates (isolated critical point). With this it will be possible to have a clear and intuitive grasp of the phenomena called \"first order\" phase transition. Keeping in mind the physical meaning of the Legendre transforms of the entropy of the small body we will understand the meaning of the first and second order discontinuities that affect the thermodynamic functions which describe the equilibrium state of the universe. We will see no reason to classify phase transitions the way Ehrenfest did. We will see also, and this is a very important thing, that classical Thermodynamics cannot explain the singularity that occurs in specific heat at a critical point. This failure is intrinsic to classical Thermodynamics or to the hypothesis that the small body entropy is a continuous and differentiable function.

A finalidade deste trabalho é estabelecer as conexões entre física de buracos negros e termodinâmica, atentando para eventuais semelhanças e diferenças entre ramos aparentemente bem diversos da física moderna. Tais conexões foram inicialmente buscadas e estabelecidas na década de 1970, graças ao trabalho de S. Hawking e Jacob D. Bekenstein, entre outros, e sucessivamente aprofundadas nos anos subseqüentes, notadamente na última década. O mérito maior do primeiro foi estabelecer a emissão de radiação com espectro térmico por buracos negros em geral, mesmo aqueles desprovidos de rotação e carga (buracos negros de Schwarzschild). O segundo encarregou-se de correlacionar leis termodinâmicas clássicas com processos envolvendo buracos negros. Neste trabalho, procuramos inicialmente estudar os buracos negros de Schwarzschild e Kerr-Newman no tocante às suas propriedades gerais, bem como o problema do movimento de partículas nos espaços-tempos em questão, para discutir-se brevemente o problema de extração de energia de buracos negros, como apontado por Penrose e outros. Estabelecidas as propriedades gerais, pode-se enfim derivar a Termodinâmica destes buracos, correlacionando-se entropia e área, e obter expressões para a temperatura de corpo negro dos mesmos - em perfeita consonância com a derivação de Hawking, não abordada aqui, feita através da Teoria Quântica de Campos. Com a temperatura, pode-se estudar as capacidades térmicas, reveladores de propriedades típicas de buracos negros não compartilhadas por sistemas clássicos. A reboque destas, entra a discussão sobre a estabilidade termodinâmica de buracos negros em ensembles canônicos e microcanônicos, através do método das séries lineares, de Poincaré, fechando o presente trabalho. Assim, os capítulos 1 e 2 tratam das soluções de Schwarzschild e Kerr-Newman, respectivamente, abordando-lhes as propriedades gerais e o problema do movimento de partículas, materiais ou não, nessas geometrias. O capítulo 3 estabelece as pontes entre Termodinâmica e buracos negros, sendo crucial para o restante do trabalho. No capítulo 4 estudamos temperaturas e capacidades térmicas de diversos buracos negros, e finalmente no capítulo 5 vem o problema da estabilidade termodinâmica dos buracos negros. / In the present work, we have established the connections between black-hole physics and thermodynamics, searching for similarities and differences between these two branches of physicxs, which might look quite far apart. Such links were first sought for and established during the 1970s, thanks to the pioneering work of S. Hawking and Jacob D. Bekenstein, among others, and continuously developed in the following years, notably in the last decade. Hawking's major achievement was the prediction, from arguments based on Quantum Field Theory, that black holes radiate with a thermal spectrum, even the uncharged and nonrotating ones (the Schwarzschild black holes). Bekenstein's biggest merit was to find the link between classical thermodynamical laws and processes involving black holes. In this work, we started with Schwarzschild and Kerr-Newman black holes, working out their general properties, as well as the problem of particle motion in such spacetimes, so that we could briefly discuss the issue of energy extraction from black holes, as established by Penrose and others. Once the general features of these black holes were known, it was possible to derive the black-hole thermodynamics, due to a simple relation between black-hole entropy and area. Expressions for the black-hole temperature were then easily obtained, in perfect agreement with Hawking's own derivation, not considered here. With temperatures at hand, heat capacities could be thoroughly examined, showing intrinsic properties of black holes, not shared by classical systems. The question of thermodynamic stability of black holes arose naturally from heat capacity analysis, and we have analysed black holes in both the microcanonical and canonical ensembles, in the light of Poincaré's linear series method, completing the current work. Chapters 1 and 2 deal with the Schwarzschild and Kerr-Newman solutions, respectively, deriving their general features and working out particle motion in these geometries. Chapter 3 establishes the links between black-hole physics and thermodynamics, being of crucial importance for the subsequent chapters. Chapter 4 provides an extensive study of black-hole temperatures and heat capacities, paving the way for the last chapter, Chapter 5, concerning to thermodynamic stability of black holes.

Ever growing population and increased energy consumption across all industries has resulted in higher atmospheric concentration of the greenhouse gases (GHG) and therefore an increase in the planet's average temperature, which has led to increasingly demanding and more strict legislations on pollutant sources, and more specifically, the automotive industry. As a consequence of all this, the demand for research into alternative energy sources has greatly increased. In this study combustion characteristics, engine performance, and exhaust emission of diesel-ethanol and diesel-gasoline are investigated in an optical direct injection diesel engine. In particular, effects of different substitution ratios and diesel injection strategies are studied when the total fuel energy is kept constant. The three main substitution ratios used in this study include 45% (45% of fuel energy from port-injected ethanol/gasoline and 55% from direct injection diesel), 60%, and 75%. The engine used for this investigation is a Ricardo Hydra single cylinder optical engine running at 1200 rpm. In-cylinder pressure measurement is used for calculating all engine parameters, heat release rate, and efficiency. In addition to the thermodynamic analysis of the combustion parameters, high speed camera was used alongside with a copper vapor laser or the high speed image intensifier in the high speed video imaging for the optical analysis of the effect of the above-mentioned parameters on autoignition and combustion processes, while Horiba particulate analyser and AVL smoke meter were utilized in monitoring and recording emissions for every tested condition. Depending on the testing conditions, such as injection strategy and intake conditions, both dual-fuel operations were able to deliver high efficiency and improved emissions compared to that of a pure diesel engine operation, with the diesel-gasoline operation offering more consistency in improved thermal efficiency, and the diesel-ethanol operation delivering lower emission output. The optical analysis of the combustion represents the main difference in the flame propagation, distribution and quality for each substitute fuel and its substitution percentage, as well as the condition under examination.

1. A Diffusion-Absorption-Refrigeration (DAR) system for air conditioning (DAAC) is developed. It is directly driven by heat, uses a bubble pump to replace the mechanical pump, uses three-component working fluid, and operates under the same system pressure level. Hence, it is quiet, long lasting and environmental friendly. To investigate the practicality of using the DAAC system for air conditioning, the thermodynamic model is derived first, and then an experimental prototype is built for validation. From the experimental results under various operating conditions, it is found that the bubble pump is the key component that dominates the system performance, so it should be designed carefully with respect to the designed cooling capacity and operating condition. Meanwhile, the system also shows good performance under the ambient temperature disturbance. / 2. A novel absorption air conditioning system based on solar energy and energy storage is proposed. This system uses Lithium-Bromide water solution as refrigerant and is powered by solar energy. Moreover, a new energy storage technique is also proposed to transform and store the solar energy in the form of chemical potential difference of the working fluid. Thus, the system flexibility and energy usage efficiency are improved. To validate the system design, the thermodynamic models for the air conditioning system are developed. Then by computer simulation, the system characteristics and performance are achieved under the proposed operation strategy. It is found that the proposed air conditioning system is energy efficient with high energy storage density and shows great potential in the future. / 3. A complex absorption air conditioning system is proposed by using an advanced energy storage technology called Variable Mass Energy Transformation and Storage (VMETS). This system is based on both compression and absorption refrigeration, uses water-LiBr or ammonia-water as working fluid, and can shift the off-peak electric energy for effective air conditioning. The key of the technology is to regulate the chemical potential by controlling the refrigerant mass fraction in the working fluid with respect to time. By using a solution storage tank and a refrigerant storage tank, the energy transformation and storage can be carried out at the desirable time to provide the low cost air conditioning efficiently. Based on the derived system models, the system characteristics and performance under two system strategies, full-storage and partial-storage strategies, are investigated in details. By computer simulation, it is found that the VMETS technology has high energy conversion efficiency. / 4. A novel thermoelectric air conditioning system is developed. Different from the conventional air conditioning systems, this system is based on the thermoelectric effect and semiconductor technology. It consists of thermoelectric (TE) modules, a power supply, a water circulation system and a computer control system. The thermoelectric system has three functions: heating, cooling, and power generation. To improve the efficiency, it uses the so-called symbiotic generation to optimize the energy usage. In order to investigate the system performance, a theoretical model is developed. By computer simulation, it is found that the system can achieve acceptable performance for cooling and heating under a typical condition. A small experimental model is also built, and the testing result confirms the simulation results. / 5. An intelligent thermal comfort controller is developed to improve the comfort level for air conditioning system. This controller adopts Predicted Mean Vote (PMV) as the control objective rather than the conventional temperature control, and takes six variables into consideration. Meanwhile, a kind of direct neural network (NN) control algorithm is designed by combining a proposed energy saving strategy. By computer simulation, it is found that this controller can achieve high comfort level and energy saving for the conventional Heating, Ventilation and Air-Conditioning (HVAC) systems. Moreover, a compact thermal comfort controller is also developed for the DAAC system. / 6. A cost-effective Fault Detection and Diagnosis (FDD) method is proposed for HVAC system to maintain the energy saving and thermal comfort. It combines the model-based method and the neural network classifier, so it is called Model-Based Fault Detection and Diagnosis method (MBFDD). To validate the performance, the MBFDD is applied to a HVAC system by simulation. Based on the derived system models, the output variables sensitive to the faults can be selected. After pre-processing the acquired data under normal and faulty conditions, the MBFDD based on neural network classifier can be trained first, and then used for on-line monitoring and FDD. The simulation results show that this method is efficient for the HVAC system, and is able to enhance the comfort level and energy saving as well as the system health and safety. / Air conditioning system plays an important role in modern living. Every year millions of air conditioning systems are made and sold. Consequently, even small technological improvement may add up to significant energy saving. Currently, most of the air conditioning systems are based on the compression refrigeration technology, which uses electricity as power and chlorofluorocarbon (CFCs) as refrigerant. Facing the ever-increasing energy and environmental crisis in the world, developing energy-efficient and environmental-friendly air conditioning system is of great importance. / This thesis presents the research on developing air conditioning systems by employing several kinds of technologies: (1) absorption refrigeration technology; (2) bubble pump technology; (3) energy storage technology; (4) renewable energy technology; (5) thermoelectric refrigeration technology; (6) thermal comfort control technology; and (7) fault detection and diagnosis technology. Based on these technologies, this thesis addresses the following topics: / Liang Jian. / "June 2006." / Adviser: Ruxu Du. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6700. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (p. 175-194). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.

This work investigates the hydrodynamics of the expansion of the bubbles of the broken symmetry phase during the electroweak phase transition in the early universe, in which SU(2) electroweak symmetry is broken and fundamental particles acquire mass through the Higgs mechanism. The electroweak phase transition has received renewed attention as a viable setting for the production of the matter-antimatter asymmetry of the universe. The relevant mechanisms are strongly dependent on key parameters like the expansion velocity of the walls of bubbles of the new phase. In addition, the key dynamical parameters of the phase transition may generate signatures (like gravitational waves) which may become detectable in the near future. This work builds on existing hydrodynamical studies of the growth of bubbles of the broken symmetry phase and adapts them to novel scenarios, producing predictions of the wall velocity. The early universe at the time of the electroweak phase transition is modelled as a perfect relativistic fluid. A fundamental problem is to account for the interaction between the so-called cosmic 'plasma' and the bubble wall, which may slow down wall propagation and produce a steady state with finite velocity. This 'friction' is accounted for by a separate term in the hydrodynamical equations. This work adapts existing microphysical calculations of the friction to two physical models chosen because of their suitability as regards producing the baryon asymmetry of the universe: 1) An extension of the Standard Model with dimension-6 operators (for which this is the first calculation of the wall velocity ever produced) and 2) The Light Stop Scenario (LSS) of the Minimal Supersymmetric Standard Model (MSSM) (for which this is the first 2-loop calculation). The predicted values of the wall velocity are coherent and consistent with previous studies, confirming, in particular, the prediction of a low wall velocity for the LSS.

Non-equilibrium physical systems, be they biological or otherwise, are powered by differences in intensive thermodynamic variables, which result in flows of matter and energy through the system. This thesis is concerned with the response of physical systems and ecosystems to complex types of boundary conditions, where the flows and intensive variables are constrained to be functions of one another. I concentrate on what I call negative feedback boundary conditions, where the potential difference is a decreasing function of the flow. Evidence from climate science suggests that, in at least some cases, systems under these conditions obey a principle of maximum entropy production. Similar extremum principles have been suggested for ecosystems. Building on recent work in theoretical physics, I present a statisticalmechanical argument in favour of this principle, which makes its range of application clearer. Negative feedback boundary conditions can arise naturally in ecological scenarios, where the difference in potential is the free-energy density of the environment and the negative feedback applies to the ecosystem as a whole. I present examples of this, and develop a simple but general model of a biological population evolving under such conditions. The evolution of faster and more efficient metabolisms results in a lower environmental energy density, supporting an argument that simpler metabolisms could have persisted more easily in early environments. Negative feedback conditions may also have played a role in the origins of life, and specifically in the origins of individuation, the splitting up of living matter into distinct organisms, a notion related to the theory of autopoiesis. I present simulation models to clarify the concept of individuation and to back up this hypothesis. Finally I propose and model a mechanism whereby systems can grow adaptively under positive reinforcement boundary conditions by the canalisation of fluctuations in their structure.

Fazemos inicialmente uma breve exposição sobre os fundamentos da Termodinâmica Clássica Holotrópica, desenvolvida por N. Bernardes. Esta consiste em formular o problema da Termodinâmica tomando como grandeza fundamental a entropia de um universo ( - sistema Isolado); no caso de um universo clássico composto esta é igual a soma das entropias de suas partes. Postulamos um principio dinâmico suficiente para a validade da segunda lei da Termodinâmica, o qual implica que os máximos dessa soma são estados estacionários estáveis do universo. Somos levados naturalmente a perguntar o que acontece se a entropia do universo possuir mais do que um máximo; a resposta a isso é o tratamento que daremos ao fenômeno de transição de fase. Analisamos em detalhe o universo composto por um corpo pequeno (cuja entropia é por hipótese analítica) e reservatórios de calor e trabalho. Para que a entropia do universo possua mais que um máximo a entropia do corpo pequeno não pode ser côncava em todo seu domínio; assumindo uma forma particular para ela (deslocamento de Bernardes) analisaremos o equilíbrio entre duas fases e o comportamento em torno do ponto onde a curva de coexistência termina (ponto crítico isolado). Com isto será possível dar uma visão clara e bastante intuitiva do fenômeno de transição de fase dito \"de primeira ordem\". Tendo em mente o significado físico das transformadas de Legendre da entropia do corpo pequeno (transparente na formulação holotrópica) compreenderemos o sentido das descontinuidades de primeira e segunda ordem que afetam as funções termodinâmicas que descrevem o equilíbrio do universo, com o que não veremos razão alguma para classificar as transições de fase da maneira que assim fez Ehrenfest. Veremos também, e isto é muito importante, que a Termodinâmica Clássica não consegue explicar a singularidade no calor específico que se verifica experimentalmente num ponto crítico, sendo que esta falha é intrínseca ou à Termodinâmica clássica ou à hipótese da entropia do corpo pequeno ser contínua e diferenciável. / We make initially a short exposition about the fundaments of Holotropic classical thermodynamics, developed by N. Bernardes. This is the formulation of the thermodynamic problem taking the entropy of a universe (isolated system) as the fundamental variable. In a classical composite universe it is the sum of the entropies of its parts. We postulate a dynamic principle sufficient for the validity of the second law of Thermodynamics, which implies that the maxima of that sum are stable stationary states of the universe. We arrive at the question about what occurs when the entropy of the universe possesses more than one maximum; the answer is the treatment we will give to the phenomena of phase transition. We analyze in detail the universe composed by a small body (whose entropy is analytical by hypothesis) and heat and work reservoirs. The entropy of the small body must be not concave in all of its dominium for the entropy of universe to have more than one maximum; we make a particular choice for it (Bernardes displacement) in order to analyze equilibrium between two phases and the behavior around the point where the coexistence curve terminates (isolated critical point). With this it will be possible to have a clear and intuitive grasp of the phenomena called \"first order\" phase transition. Keeping in mind the physical meaning of the Legendre transforms of the entropy of the small body we will understand the meaning of the first and second order discontinuities that affect the thermodynamic functions which describe the equilibrium state of the universe. We will see no reason to classify phase transitions the way Ehrenfest did. We will see also, and this is a very important thing, that classical Thermodynamics cannot explain the singularity that occurs in specific heat at a critical point. This failure is intrinsic to classical Thermodynamics or to the hypothesis that the small body entropy is a continuous and differentiable function.

Este trabalho, realizado com o auxílio da termodinâmica computacional, dá continuação a um estudo sistemático, que trata dos fundamentos dos tratamentos termoquímicos metalúrgicos relacionados à nitretação e à nitrocarburação. O estudo concentrou-se nas ligas da família ABNT 10XX, do aço ABNT 4140 e do aço ferramenta AISI M2. A composição das ligas utilizadas na simulação, contudo, não correspondem exatamente à comercial. Uma simplificação foi necessária para que a simulação do processo fosse facilitada. O uso da termodinâmica computacional como ferramenta para determinação das fases presentes (ou que podem vir a se formar) em um sistema a certa temperatura e pressão simulando o processo de nitretação mostrou-se uma valiosa ferramenta de análise.Apesar de, na prática, estes prognósticos ainda dependerem de uma cinética micro ou macroscópica favorável para ser verdadeiros, a comparação dos resultados obtidos com a literatura mostrou uma boa concordância nos resultados, validando, assim, o emprego desta técnica de análise. Assim, além deste estudo ser um avanço na compreensão das fases que participam das microestruturas (nitretos e carbonitretos) que se formam nas ligas estudadas, também pode ser utilizado como um balizador na definição de parâmetros que permitam a seleção destas fases finais desejadas, economizando tempo e recursos na realização de ensaios experimentais. / This work, accomplished with the help of computational thermodynamics, provides the development of a systematic study concerning the basis of the thermochemical treatments related to nitriding and nitrocarburising. This study focused on the alloys of the ABNT 10XX family, on the ABNT 4140 steel and on the AISI M2 tool steel. However, the compositions used in the simulation do not correspond exactly to the commercial composition of the alloy, for they had their composition simplified in order to facilitate the simulation process. The use of computational thermodynamics as a tool to determine the phase present (or that can be formed) in a system under a specific temperature and pressure, simulating the nitriding process, proved to be a valuable analysis tool. Nevertheless, in practice, these prognostics still depend on a micro or macro kinetics in order to be true; the comparison of the results obtained with those found in the literature showed good agreement of results, validating, thus, the use of this analysis technique. So, besides this study being an advance when it comes to understanding phases (nitrides and carbonitrides) that are formed in the studied alloys, it can also be used as a mark in defining parameters that allow the selection of final desired structures, saving time and resources.

Metabolism is a key attribute of life on Earth at multiple spatial and temporal scales, involved in processes ranging from cellular reproduction to biogeochemical cycles. While metabolic network modeling approaches have enabled significant progress at the cellular-scale, extending these techniques to address questions at both the ecosystem and planetary-scales remains highly unexplored. In this thesis, I integrate various multi-scale metabolic network modeling approaches to address key questions with regard to both the long-term evolution of metabolism in the biosphere and the metabolic processes that take place in complex microbial communities. The first portion of my thesis work, focused on the evolution of ancient metabolic networks, attempts to model the emergence of ecosystem-level metabolism from simple geochemical precursors. By integrating network-based algorithms, physiochemical constraints, and geochemical estimates of ancient Earth, I explored whether a complex metabolic network could have emerged without phosphate, a key molecular component in modern-day living systems, known to be poorly available at the onset of life. We found that phosphate may have not been essential in early living systems, and that thioesters may have been the primitive energy currency in ancient metabolic networks. By generalizing this approach to explore the scope of geochemical scenarios that could have given rise to living systems, I found that other key biomolecules, including fixed nitrogen, may have not been required at the earliest stages in biochemical evolution. The second portion of my thesis deals with a different aspect of ecosystem-level metabolism, namely the role of metabolism in shaping the structure of microbial communities. I studied the relationship between metabolism and microbial community assembly using microbial communities grown in synthetic laboratory environments. We found that a generalized statistical consumer-resource model recapitulates the emergent phenomena observed in these experiments. Future work could seek to better clarify the connection between the fundamental rules that led to life’s emergence over 4 billion years ago and the laws that shape microbial ecosystems today. An ecosystems-level metabolic perspective may aid in our understanding of both the emergence and maintenance of the biosphere.