Cheung Wai-che. / Thesis (M.Phil.)--Chinese University of Hong Kong, 1978. / Bibliography: leaves 134-135.

Orientador: Jose Tomaz Vieira Pereira / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-07-23T07:55:24Z (GMT). No. of bitstreams: 1 PrattsMilanes_RafaelLincoln_M.pdf: 7529457 bytes, checksum: a46683408a5f159faa50eae4fff6c712 (MD5) Previous issue date: 1997 / Resumo: Neste trabalho tenta-se determinar as melhorias tecnológicas que devem ser feitas em um sistema de refrigeração por absorção que usa o par água-amônia como refrigerante para a fabricação de gelo. O estudo é feito sobre uma planta desse tipo que se encontra atualmente na área de serviços do Hospital das Clínicas da UNICAMP e que foi doada a esta Universidade pela empresa MADEF S.A., produtora deste tipo de fábrica no país. Foram usadas as avaliações energéticas e exergéticas, conjuntamente com o cálculo verificativo de trocadores de calor. Para conseguir isso instalou-se um sistema de aquisição de dados via computador, através do qual obtivemos os valores de pressão e temperatura da solução em diversos pontos, definidos geralmente pela entrada e saída de cada equipamento. Com estes dados determinou-se as propriedades termodinâmicas em cada ponto, com ajuda do software AQUAM, e do diagrama entalpia vs. exergia de Merkel-Bonsjakovich. A partir das avaliações energéticas e exergéticas, conseguiu-se determinar os pontos fracos do sistema, verificando os valores das irreversibilidades de cada equipamento pela aplicação do conceito de geração de entropia (Teorema de Gouy-stodola), metodologia válida para a análise de qualquer tipo de sistema. O sistema avaliado apresentou um coeficiente de operação de 0.42; as maiores irreversibilidades, 32 %, no conjunto gerador coluna de retificação; a maior eficiência exergética, 81 %, no pré-aquecedor de solução rica; e a menor, 14,29 %, no sub-resfriador de líquido. Os cálculos realizados indicam o subdimensionamento do absorvedor, do pré-resfriador de solução pobre, e do condensador evaporativo, pouco tempo de congelamento, baixa concentração de amônia no evaporador, dimensões excessivas da válvula de pressão constante e grandes perdas de calor / Abstract: It is focused the technological developments that must be done on absortion freezing systems using the couple water-ammonia as absorber refrigerant for ice inclustries. This study was made over this kind of plant which actually is found in the service area of Hospital das ClinicaslHC in UNICAMP. That plant was freely given to this University by MADEF S.A., producer of this kind of industry in Brazil. Energetic and exergetic evaluations were used jointly to verificative account of heat exchangers. To achieve this goal it was installed a data adquisition system by means of computer through which we got the pressure and temperature values of the solution in different points, genera1ly defined by input and output of each equipment. Using this data, it was determined the thermod:ynamics properties in each point, with AQUAM software help as well as enthalpy exergy diagram ofMerkel and Bonsjakovic. Since the exergetic and energetic evaluations, it was found the weak points of the system verifying irreversibility values of each equipment by applying the entropy theory concept (Gouy-Stodola's Theorem), which is considered an appropriate methodology to analyze any kind of system. The evaluated system presented a coefficient of performance, COP of 0,42, major irreversibilities representing 32% on the generator complex rectifYing column, a major exergetic efficiency, 81%, in rich solution pre-heating and the minor, 14,29%, in the liquid sub-cooling. The calcu1atedvalues indicate the absorber subdimension of the weak solution pre-cooling and of the evaporative condensation, little time of cooling, low ammonia concentration in the evaporator, excessive size of the constant pressure valve and great heat losses / Mestrado / Mestre em Planejamento de Sistemas Energéticos

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Le présent travail est consacré en premier lieu à l'investigation des limites de fonctionnement et de performances des machines frigorifiques à absorption et absorption-diffusion utilisant des mélanges d'alcanes comme fluides de travail et l'analyse en second lieu du processus d'absorption le long d'un absorbeur à film tombant en présence d'un gaz inerte. Dans le cas d'un refroidissement à l’eau les meilleures performances réalisées sont celles d'une machine utilisant le binaire C₃H₈/n-C₉H₂₀ avec un COP de l'ordre de 0.51 dans l'intervalle de la température de la chaleur motrice [110-125℃]. Une machine à absorption-diffusion utilisant ce même mélange en combinaison avec l’hydrogène permet de réaliser un COP de l'ordre de 0.44 pour une température de la chaleur motrice ne dépassant pas 120℃. Une étude approfondie est par suite menée sur l’absorption en présence d’un gaz inerte. Les résultats des l’étude ont montré entre autres que les deux résistances aux transferts de chaleur et de matière sont toutes les deux prédominantes en phase vapeur et ont révélé un taux d'absorption de l'ordre de 34% à travers une surface d'échange de 0.15m². Pour évaluer la réponse du système aux variations de ses principaux paramètres caractéristiques une étude paramétrique a été menée. Cette étude a permis d'appréhender le comportement complexe du processus d'absorption en présence d'un gaz inerte. / This work is aimed primarily to investigate the feasibility limits and the performance of absorption and absorption-diffusion cooling machines using light alkane mixture as working pairs and secondarily to analyze the absorption process along a falling film absorber in the presence of an inert gas. It is shown that in the case of water cooling the best performances are those of an absorption machine using the C₃H₈/n-C₉H₂₀ binary mixture with a COP of about 0.51 in the heat driving temperature range 110-125℃. A COP of about 0.44 is attained with an absorption-diffusion cooling machine using the same mixture in combination with hydrogen with a heat driving temperature of 120℃. A detailed study of the absorption process with the C₃H₈/n-C₉H₂₀ pair and hydrogen as inert gas is conducted. The study results show that the heat and the mass transfer resistances are both prevalent in the vapor phase. An absorption rate of about 34% through an exchange surface of 0.15m² is calculated. A parametric study is carried out to evaluate the system response to the changes of its main characteristic parameters. This study allows a better understanding of the complex behavior of the absorption process in the presence of an inert gas.

Styrene (C2H3-C6H5) is expected to have a more complex reaction process due to active reaction sites located in both vinyl group and phenyl group. Our exploration indicates that the adsorption products are coverage dependent. At low coverage, both vinyl group and phenyl group are possible to take part in the adsorption process. A new AsymT adsorption state covered two adjacent Si dimers is identified through two [4+2] cycloaddition. At high coverage, only vinyl group can interact with Si dimer to form cis and trans stereoisomers with different thermal energies and kinetic reaction barriers. STM images and vibrational frequencies are also explored to further support the experimental observations. / The adsorption of unsaturated organic molecules on reconstructed Si(100) surface is widely applied in the modification and functionalization of silicon surface to design new semiconductor materials. The present project is devoted to explore the adsorption mechanisms and the related properties of adsorption species for unsaturated organic molecules: acetylene (C2H 2), ethylene (C2H4), vinyl bromide (C2H 3Br) and styrene (C8H8) by quantum chemical calculation, based on density functional theory (DFT) method with pseudopotentials and plane wave basis set. / The investigation of vinyl bromide (C2H3Br) chemisorption on Si(100) resolves the conflicting conclusions between previous experimental and theoretical studies. The orientation of the vinyl bromide molecule relative to the titled silicon dimer is found to be an important factor for both the stability and reactivity of the precursor state. A new precursor pi-complex is identified, which is metastable and trapped by barriers around 0.1eV. Comparisons between theoretical and experimental vibrational frequencies support the conclusion that such a pi-complex is present on the surface at very low temperature. Careful analysis on the electronic structure also demonstrates that it is indeed a pi-complex rather than a diradical as previously suggested. Reaction mechanisms at higher vinyl bromide coverage are also modeled to explain the decrease in activation barrier observed in experiments. / The reaction processes for acetylene (C2H2) and ethylene (C2H4) chemisorption on the surface silicon dimer and the sub-layer silicon atoms are compared. Acetylene can undergo a new type of cycloaddition on sub-layer Si atoms (called sub-di-sigma) with no barrier, which is identified by ab initio Molecular Dynamics. The related properties including vibrational frequencies and STM images are calculated and found to be similar with those of the end-bridge adsorption structure. The identification of such a sub-di-sigma adsorption structure explains the discrepancy between STM experiments and theoretical calculations. In addition, the analysis of calculated vibrational frequencies, simulated STM images and the reaction barriers for di-sigma and end-bridge structures indicate that inter-dimer reaction for C2H4 is possible. / Zhang, Qiuji. / Adviser: Zhi Feng Liu. / Source: Dissertation Abstracts International, Volume: 70-09, Section: B, page: . / Thesis submitted in: October 2008. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 86-87). / 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.

L'atmosphère et la surface terrestre interagissent en permanence par le biais des échanges d'énergie et de matière. Ces flux jouent un rôle important dans l'étude de l'hydrologie des surfaces ou de l'écologie terrestre, ou bien encore l'étude des phénomènes météorologiques et climatiques. En effet, ils représentent les conditions aux limites des différents compartiments du système Terre et la quantification de ces échanges à différentes échelles spatiales est indispensable pour les modèles de prévision. Les mesures de flux d'énergie sont très répandues pour des mesures très localisées, in situ et au sol. Cependant, peu d'instruments de mesures permettent d'obtenir des flux intégrés sur des distances de l'ordre de la centaine de mètres à quelques kilomètres, c'est-à-dire des distances correspondant à la représentativité des pixels des images satellitaires. On compte parmi eux les scintillomètres, instrument de mesure optique, permettant de calculer les flux intégrés de chaleur sensible à partir des mesures de paramètres caractérisant l'intensité turbulente de l'atmosphère tels que le paramètre de structure de l'indice de réfraction de l'air Cn². La présence de vapeur d'eau dans l'atmosphère peut cependant perturber le signal de ces instruments. L'objectif de ce travail est le développement et la mise en oeuvre d'un scintillomètre optique permettant de mettre en évidence la contribution de l'absorption par la vapeur d'eau sur les scintillations. Les études menées à partir du développement instrumental ne s'orienteront qu'autour de la bande d'absorption à 940nm, longueur d'onde d'émission de certains scintillomètres LAS (Large Aperture Scintillometer). Au début de ma thèse, un prototype de scintillomètre, type LAS, a été conçu de façon à maitriser complètement la technologie : partie optique électronique et le traitement du signal reçu. Celui-ci a ensuite été installé au-dessus d'un site de cultures dans les environs de Toulouse, au cours des années 2007 et 2008. Les résultats obtenus avec ce prototype ont permis d'optimiser le choix de la méthode de calcul H à partir du Cn², en fonction du rapport de Bowen (rapport du flux de chaleur sensible sur le flux de chaleur latente). Les variations de l'intensité lumineuse de l'onde, menant au Cn², sont principalement dues à des effets de réfraction et de dispersion, maissont aussi sensibles à l'absorption de la vapeur d'eau. Afin de quantifier l'influence de 'absorption sur le signal Cn², j'ai utilisé 2 approches : une première approche par filtrage numérique (‘Gabor Transform'), et une seconde, par méthode chromatique. Cette dernière a nécessité de modifier considérablement le système optique du prototype LAS. Les résultats obtenus expérimentalement montrent que la contribution de l'absorption à la mesure du Cn² est en moyenne assez faible, mais qu'elle peut prendre de forte valeur, principalement lors de faibles flux H. La quantification de l'absorption par méthode hromatique est pour l'instant limité au développement technique de l'instrument. / Atmosphere, soil and vegetation are in interactions by the bias of energetic or matter exchanges. This latters have an important impact on hydrology, ecology, meteorology. Actually, they represent the boundary conditions of the Earth-Atmosphere system. Then, the quantification of these exchanges or fluxes is necessary to understand large scales phenomena and to improve forecasting models. Numerous devices are able to quantify these fluxes at local scales, but few are available to measure them over kilometres, which mean at the resolution of remote sensing datas. Amongst them, we can notice the scintillometers that are able to calculate sensible heat fluxes over distances from hundred meters to few kilometres. Actually, these devices are sensitive to variations of the refractive index of air, mainly due to turbulent eddies, defined by the structure parameter of refractive index : Cn². However, this measurement can be altered by the presence of water vapour in the air. Thus, the aim of this work is to design and make a scintillometer which is able to quantify the water vapour contribution on the Cn² measurement. In this thesis, we will focus on this contribution in the 940nm band which is the wavelength of various scintillometers LAS (Large Aperture Scintillometers). At the beginning of my PhD thesis, un scintillometer prototype has been realised in order to master the technology : optics, electronics, signal processing…This latter has been set up over crops at a few kilometres from Toulouse, between 2007 and 2008. Thanks to the results of this scintillometer, we optimize the choice on the Cn² to H algorithm, according to the Bowen ratio ß (ratio of sensible to latent heat flux). Variations of the light beam, leading to the Cn², are mainly due to refraction and dispersion effect. However, absorption can be important. In order to quantify the contribution of absorption on the Cn², 2 methods are suggested : one based on signal processing aspect (Gabor filtering), and the second one on two wavelengths propagation. To realize this latter the optics and electronics of the device have been really modified. Results show that absorption contribution is small, but can be important for low H values. Finally, the quantification of absorption by two wavelengths approach is nowadays bounded to instrumental development.

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Un changement de pH peut induire une modification des propriétés chimiques et physiques des molécules, par exemple leur interaction avec la lumière. La modélisation de tels phénomènes est complexe en raison de l’ensemble statistique des états de protonation microscopiques et de la nature quantique de la propriété étudiée. Dans cette thèse, nous présentons un protocole de calcul qui associe une méthode capable d'échantillonner à la fois ces micro-états et les changements structuraux à un pH donné, et un cadre traitant la partie pertinente de la macromolécule avec des traitements avancés de mécanique quantique et le reste du système avec la mécanique moléculaire classique. Nous rapportons également la validation de ce protocole sur le relativement petit peptide M et son application à la rhodopsine sensorielle d'Anabaena, une protéine microbienne. Nous avons pu révéler quels sont les acides aminés titrables responsables du spectre d'absorption dépendant du pH de cette biomolécule / A change in the pH can modify the chemical and physical properties of molecules such as the way they interact with light. Modeling such phenomena is complex, because of the statistical ensemble of microscopic protonation states and of the very quantum nature of the property of interest. In this thesis, we present a computational protocol which merges a method capable of sampling at the same time these microstates and the structural changes at a given pH, and a framework treating the relevant portion of the macromolecule with advanced quantum mechanics treatments and the rest of the system with classical molecular mechanics. We also report the validation of this protocol on the relatively small peptide M and its application to the anabaena sensory rhodopsin, a microbial protein. We have revealed which are the titratable amino-acids responsible for the pH-dependent absorption spectrum of this biomolecule

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