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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.
111

Chemistry and Morphology of Polymer Thin Films for Electro-Optical Application

Simon, Darren, s3027589@student.rmit.edu.au January 2006 (has links)
Thin polymer films and their properties have been investigated. The characteristics of crystalline polymers according to film thickness have been improved using polycaprolactone (PCL). The melting enthalpy of PCL has increased when the film thickness decreased and the peak melting temperature showed no significant changes with film thickness. Film thickness variation influenced surface roughness and crystal size. Optical microscope images showed the rougher surface of thicker films. The spinning time has shown no influence on film thickness and no significant changes to surface roughness. Thin films of block copolymers were used in the surface modification study; films studied included poly(styrene-b-butadiene-b-styrene) (SBS) and poly(styrene-b-isoprene-b-styrene) (SIS) and their surface modifications have been controlled using different methods of treatment. Films of SIS heated at different temperatures have shown different surface texture and roughness. Films treated at low temperature (45 °C) had smooth surfaces when compared with films heated at high temperature (120 °C and 160 °C). Phase separation of SIS heated at (120 °C and 160 °C) caused bulges of different sizes to cover the surface. The height and width of the bulges showed variation with film thickness and heating. Substrate interaction with SBS and SIS block copolymer films showed different surface texture when using the same type of substrate and different texture were obtained when SBS solutions were spun onto different substrates. It has been demonstrated that using different solvents in copolymer preparation caused different texture. Thermal and surface property variations with film thickness have been improved using amorphous polymers. Surface roughness of poly(methyl methacrylate) PMMA and disperse red 1-poly(methyl methacrylate) DR1-PMMA, PMMA has improved using thickness variation. Glass transition temperature measurement has increased when film thickness was increased. The glass transition temperature (Tg) and surface roughness of UV15 UV - curable coating polymer has been modified using UV curing and heating methods. Tg variation was observed when curing time and curing intensity were changed causing the optical properties of the polymer to be more variable. A plasma etcher caused wrinkles to occur on the surface of unheated UV15. Tg of UV15 increased when curing time increased. The Fourier Transform Infrared Spectroscopy (FTIR) spectra of cured UV15 film have shown peak variations of the ester and carbon double bond regions over the range of 1850-1700 cm-1. Urethane-Urea (UU) Polymer thin films were used to investigate optical properties and develop an optical waveguide. Absorption and transmission properties of light using non-linear optical (NLO) polymer was investigated and used in optical waveguide fabrication. Refractive indices were measured to examine UU films at two different wavelengths. A UU film of 1 µm thickness caused a maximum absorption at max = 471 nm also obtained at 810 nm wavelength. Many methods of fabrication were used; photolithography, plasma etching in a barrel reactor and thin film deposition using sputtering and evaporation. Etched depths from 1 μm to 100 μm were obtained. An optical waveguide has been prepared using plasma etching of a cured UV15 as a cladding layer on a silicon substrate.
112

Computational Analysis of Aqueous Drug Solubility – Influence of the Solid State

Wassvik, Carola January 2006 (has links)
<p>Aqueous solubility is a key parameter influencing the bioavailability of drugs and drug candidates. In this thesis computational models for the prediction of aqueous drug solubility were explored. High quality experimental solubility data for drugs were generated using a standardised protocol and models were developed using multivariate data analysis tools and calculated molecular descriptors. In addition, structural features associated with either solid-state limited or solvation limited solubility of drugs were identified.</p><p>Solvation, as represented by the octanol-water partition coefficient (log<i>P</i>), was found to be the dominant factor limiting the solubility of drugs, with solid-state properties being the second most important limiting factor.</p><p>The relationship between the chemical structure of drugs and the strength of their crystal lattice was studied for a dataset displaying log<i>P</i>-independent solubility. Large, rigid and flat molecules with an extended ring-structure and a large number of conjugated π-bonds were found to be more likely to have their solubility limited by a strong crystal lattice than were small, spherically shaped molecules with flexible side-chains.</p><p>Finally, the relationship between chemical structure and drug solvation was studied using computer simulated values of the free energy of hydration. Drugs exhibiting poor hydration were found to be large and flexible, to have low polarisability and few hydrogen bond acceptors and donors.</p><p>The relationship between the structural features of drugs and their aqueous solubility discussed in this thesis provide new rules-of-thumb that could guide decision-making in early drug discovery.</p>
113

Computational Analysis of Aqueous Drug Solubility – Influence of the Solid State

Wassvik, Carola January 2006 (has links)
Aqueous solubility is a key parameter influencing the bioavailability of drugs and drug candidates. In this thesis computational models for the prediction of aqueous drug solubility were explored. High quality experimental solubility data for drugs were generated using a standardised protocol and models were developed using multivariate data analysis tools and calculated molecular descriptors. In addition, structural features associated with either solid-state limited or solvation limited solubility of drugs were identified. Solvation, as represented by the octanol-water partition coefficient (logP), was found to be the dominant factor limiting the solubility of drugs, with solid-state properties being the second most important limiting factor. The relationship between the chemical structure of drugs and the strength of their crystal lattice was studied for a dataset displaying logP-independent solubility. Large, rigid and flat molecules with an extended ring-structure and a large number of conjugated π-bonds were found to be more likely to have their solubility limited by a strong crystal lattice than were small, spherically shaped molecules with flexible side-chains. Finally, the relationship between chemical structure and drug solvation was studied using computer simulated values of the free energy of hydration. Drugs exhibiting poor hydration were found to be large and flexible, to have low polarisability and few hydrogen bond acceptors and donors. The relationship between the structural features of drugs and their aqueous solubility discussed in this thesis provide new rules-of-thumb that could guide decision-making in early drug discovery.
114

Thermodynamic properties of humid air and their application in advanced power generation cycles

Ji, Xiaoyan January 2006 (has links)
Water or steam is added into the working fluid (often air) in gas turbines to improve the performance of gas turbine cycles. A typical application is the humidified gas turbine that has the potential to give high efficiencies, high specific power output, low emissions and low specific investment. A heat recovery system is integrated in the cycle with a humidifier for moisturizing the high-pressure air from the compressor as a kernel. Based on today’s gas turbines, the operating temperature and pressure in the humidifier are up to about 523 K and 40 bar, respectively. The operating temperature of the heat exchanger after the humidifier is up to 1773 K. The technology of water or steam addition is also used in the process of compressed air energy storage (CAES), and the operating pressure is up to 150 bar. Reliable thermodynamic properties of humid air are crucial for the process simulation and the traceable performance tests of turbomachinery and heat exchanger in the cycles. Several models have been proposed. However, the application range is limited to 400 K and 100 bar because of the limited experimental data for humid air. It is necessary to investigate the thermodynamic properties of humid air at elevated temperatures and pressures to fill in the knowledge gap. In this thesis, a new model is proposed based on the modified Redlich-Kwong equation of state in which a new cross interaction parameter between molecular oxygen and water is obtained from the fitting of the experimental data of oxygen-water system. The liquid phase is assumed to follow Henry’s law to calculate the saturated composition. The results of the new model are verified by the experimental data of nitrogen-water and oxygen-water systems from ambient temperature and pressure to 523 K and 200 bar, respectively. Properties of air-water system are predicted without any additional parameter and compared with the available experimental data to demonstrate the reliability of the new model for air-water system. The results of air-water system predicted using the new model are compared with those calculated using other real models. The comparison reveals that the new model has the same calculation accuracy as the best available model but can be used to a wider temperature and pressure range. The results of the new model are also compared with those of the ideal model and the ideal mixing model from ambient temperature and pressure to 1773 K and 200 bar to investigate the effect of the models on the thermodynamic properties of humid air. To investigate the impact of thermodynamic properties on the simulation of systems and their components, different models (ideal model, ideal mixing model and two real models) are used to calculate the thermodynamic properties of humid air in the simulation of the compressor, humidification tower, and heat exchanger in a humidified gas turbine cycle. The simulation reveals that a careful selection of a thermodynamic property model is crucial for the cycle design. The simulation results provide a useful tool for predicting the performance of the system and designing the humidified cycle components and systems. / QC 20100902
115

Crystallization Fields of Polyhalite and its Heavy Metal Analogues / Existenzgebiete des Polyhalits und seiner schwermetallhaltigen Analoga

Wollmann, Georgia 14 May 2010 (has links) (PDF)
Polyhalite is an abundant distributed mineral in rock salt formations, and considered to respond as a natural heavy metal sink because the Mg2+ ion can be substituted by other bivalent metal ions like Mn2+, Co2+, Ni2+, Cu2+ and Zn2+. One of the quantities needed to predict mineral solubilities in multi-electrolyte solutions is the solubility constant Ksol. Since polyhalite forms slowly over months or years at 298 K, the solid-liquid phase equilibria experiments were accomplished at 313 K. Enthalpies of dissolution were measured and used to extrapolate lnKsol from 313 K to 298 K. Pitzer’s equations have been applied to describe activities of solute and water, with Pitzer parameters estimated from experimental data. The solubility constants for the polyhalites were applied to calculate the solubility equilibria in the quaternary systems K+, M2+, Ca2+ / SO42- // H2O (M = Mg, Mn, Co, Cu, Zn) at 298 K and 313 K, and in case of Mg-polyhalite also in the hexary system Na+, K+, Mg2+, Ca2+ / Cl-, SO42- // H2O.
116

Freie Enthalpie binärer metallischer Legierungsschmelzen: Molekulardynamik Simulationen für NixZr1-x / Free enthalpy of binary metallic alloy melts: Molecular dynamics simulations on NixZr1-x

Küchemann, Klaus-Boris 03 November 2004 (has links)
No description available.
117

Numerical analysis using simulations for a geothermal heat pump system. : Case study: modelling an energy efficient house

Ilisei, Gheorghe January 2018 (has links)
The ground source resources are becoming more and more popular and now the ground source heat pumps are frequently used for heating and cooling different types of buildings. This thesis aims at giving a contribution in the development of the thermal modelling of borehole heat storage systems. Furthermore, its objective is to investigate the possibility of implementing of a GSHP (ground source heat pump) with vertical boreholes, in order to deliver the heating and cooling demand for a passive house and to emphasize some certain advantages of this equipment even in the case of a small building (e.g. residential house). A case study is presented to a suitable modelling tool for the estimation of the thermal behaviour of these systems GSHP by combining the outcome from different modelling programs. In order to do that, a very efficient residential solar house (EFden House – a passive residential single-family house, which was projected and built in Bucharest with academic purposes) is being analysed. The numerical results are produced using the software DesignBuilder, EED (Earth Energy Designer) and a sizing method for the length of the boreholes (ASHRAE method). The idea of using 2 different modelling programs and another sizing method for the borehole heat exchanger design (ASHRAE method) is to make sure that all the calculations and results are valid and reliable when analysing such a system theoretically (in the first phases of implementing a project), before performing a geotechnical study or a thermal response test in order to assess the feasibility of such a project beforehand. The results highlight that the length of the borehole, which is the main design parameter and also a good index in estimating the cost of the system, is directly influenced by the other fundamental variables like thermal conductivity of the grout, of the soil and the heat carrier fluid. Also, some correlations between these parameters and the COP (coefficient of performance) of the system were made. The idea of sizing the length of boreholes using two different methods shows the reliability of the modelling tool. The results showed a difference of only 2.5%.  Moreover, the length of borehole is very important as it was calculated that can trigger a difference in electricity consumption of the GSHP up to 28%. It also showed the fact that the design of the whole system can be done beforehand just using modelling tools, without performing tests in-situ. The method aims at being considered as an efficient tool to estimate the length of the borehole of a GSHP system using several modelling tools. / <p>The presentation was made via Skype due to the programme being online based</p>
118

Estudos numéricos na solução de problemas de mudança de fase

Odone, Maicon William Niebus 28 August 2014 (has links)
Submitted by Renata Lopes (renatasil82@gmail.com) on 2017-03-07T11:34:58Z No. of bitstreams: 1 maiconwilliamniebusodone.pdf: 9396542 bytes, checksum: 0a9d05fa621e639f71fa74726b219707 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2017-03-07T15:03:29Z (GMT) No. of bitstreams: 1 maiconwilliamniebusodone.pdf: 9396542 bytes, checksum: 0a9d05fa621e639f71fa74726b219707 (MD5) / Made available in DSpace on 2017-03-07T15:03:29Z (GMT). No. of bitstreams: 1 maiconwilliamniebusodone.pdf: 9396542 bytes, checksum: 0a9d05fa621e639f71fa74726b219707 (MD5) Previous issue date: 2014-08-28 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Problemas de mudança de fase líquido-sólido e/ou sólido-líquido são amplamente encontrados em diversas aplicações da indústria tais como na moldagem de diferentes tipos de peças, na aplicação de sprays térmicos para tratamento de superfícies e na fundição de materiais energéticos tais como o trinitrotolueno (TNT). Neste último caso, contrações de material, trincas e formação de vazios são frequentemente observados, devendo estes comportamentos serem previstos e evitados. Sendo assim, a simulação numérica de tais processos com algoritmos capazes de acompanhar a evolução da superfície livre, e a distribuição da temperatura no corpo durante o processo de fundição é importante. Pretende-se estudar diferentes estratégias na modelagem e solução de problemas desta natureza através das equações de transporte de massa, transferência de calor e de mudança de fase por meio do método dos volumes finitos. Na metodologia usada, os processos de solidificação e fusão são tratados por meio da aproximação do método da entalpia-porosidade baseado em malhas fixas. / Phase change problems as liquid-solid and/or solid-liquid are widely found in several industrial applications such as in molding of different parts, the application of thermal spray treatment and the casting of energy materials such as trinitrotoluene (TNT). For the latter case, material contractions, cracks and empities formation are often observed and these behaviors should be anticipated and avoided. Thus, the numerical simulation of such processes with algorithms capable to follow free surface evolution and body temperature distribution during casting process is important. In this work we study strategies in modeling and solving problems of this nature through the mass transport equations, heat transfer and phase change using the finite volume method. In the methodology used, the melting and solidification process are treated by means of the enthalpy-porosity approximation method based on fixed grids.
119

Analysis of differential diffusion phenomena in high enthalpy flows, with application to thermal protection material testing in ICP facilities

Rini, Pietro 16 March 2006 (has links)
This thesis presents the derivation of the theory leading to the determination of the governing equations of chemically reacting flows under local thermodynamic equilibrium, which rigorously takes into account effects of elemental (de)mixing. As a result, new transport coefficients appear in the equations allowing a quantitative predictions and helping to gain deeper insight into the physics of chemically reacting flows at and near local equilibrium. These transport coefficients have been computed for both air and carbon dioxide mixtures allowing the application of this theory to both Earth and Mars entry problems in the framework of the methodology for the determination of the catalytic activity of Thermal Protections Systems (TPS) materials.<p>Firstly, we analyze the influence of elemental fraction variations on the computation of thermochemical equilibrium flows for both air and carbon dioxide mixtures. To this end, the equilibrium computations are compared with several chemical regimes to better analyze the influence of chemistry on wall heat flux and to observe the elemental fractions behavior along a stagnation line. The results of several computations are presented to highlight the effects of elemental demixing on the stagnation point heat flux and chemical equilibrium composition for air and carbon dioxide mixtures. Moreover, in the chemical nonequilibrium computations, the characteristic time of chemistry is artificially decreased and in the limit the chemical equilibrium regime, with variable elemental fractions, is achieved. Then, we apply the closed form of the equations governing the behavior of local thermodynamic equilibrium flows, accounting for the variation in local elemental concentrations in a rigorous manner, to simulate heat and mass transfer in CO2/N2 mixtures. This allows for the analysis of the boundary layer near the stagnation point of a hypersonic vehicle entering the true Martian atmosphere. The results obtained using this formulation are compared with those obtained using a previous form of the equations where the diffusive fluxes of elements are computed as a linear combination of the species diffusive fluxes. This not only validates the new formulation but also highlights its advantages with respect to the previous one :by using and analyzing the full set of equilibrium transport coefficients we arrive at a deep understanding of the mass and heat transfer for a CO2/N2 mixture.<p>Secondly, we present and analyze detailed numerical simulations of high-pressure inductively coupled air plasma flows both in the torch and in the test chamber using two different mathematical formulations: an extended chemical non-equilibrium formalism including finite rate chemistry and a form of the equations valid in the limit of local thermodynamic equilibrium and accounting for the demixing of chemical elements. Simulations at various operating pressures indicate that significant demixing of oxygen and nitrogen occurs, regardless of the degree of nonequilibrium in the plasma. As the operating pressure is increased, chemistry becomes increasingly fast and the nonequilibrium results correctly approach the results obtained assuming local thermodynamic equilibrium, supporting the validity of the proposed local equilibrium formulation. A similar analysis is conducted for CO2 plasma flows, showing the importance of elemental diffusion on the plasma behavior in the VKI plasmatron torch.<p>Thirdly, the extension of numerical tools developed at the von Karman Institute, required within the methodology for the determination of catalycity properties for thermal protection system materials, has been completed for CO2 flows. Non equilibrium stagnation line computations have been performed for several outer edge conditions in order to analyze the influence of the chemical models for bulk reactions. Moreover, wall surface reactions have been examined, and the importance of several recombination processes has been discussed. This analysis has revealed the limits of the model currently used, leading to the proposal of an alternative approach for the description of the flow-surface interaction. Finally the effects of outer edge elemental fractions on the heat flux map is analyzed, showing the need to add them to the list of parameters of the methodology currently used to determine catalycity properties of thermal protection materials. / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished
120

Dissolution du dioxyde de carbone dans des solutions aqueuses d'électrolyte dans le contexte du stockage géologique : approche thermodynamique / Dissolution of carbon dioxide in aqueous electrolyte solutions, in the context of geological storage : A thermodynamic approach

Liborio, Barbara 17 February 2017 (has links)
Cette thèse porte sur l’étude de l’enthalpie de dissolution du dioxyde de carbone dans des solutions aqueuses d’électrolyte. Pour développer des modèles théoriques décrivant les systèmes {CO2-eau-sel} pour les conditions appliquées aux conditions de stockage géologique du dioxyde de carbone, il est nécessaire d’avoir des données expérimentales reliant la solubilité et l’enthalpie. Dans cette étude, une unité de mélange à écoulement construite au laboratoire a été adapté à un calorimètre SETARAM C-80 pour mesurer l’enthalpie de solution du CO2 dans des solutions aqueuses d’électrolyte (NaCl, CaCl2 et Na2SO4) aux forces ioniques comprises entre 2 et 6 et a des températures comprises entre 323.1 K et 372.9 K et des pressions allant de 2 à 16 MPa. Les données de la littérature ont été utilisées pour ajuster le modèle thermodynamique d’équilibre de phase dans l’approche Υ-φ. Le modèle thermodynamique reproduit les enthalpies expérimentales à plus ou moins 10%. Le calcul de l’enthalpie dans le modèle rigoureux est fortement dépendant des données de la littérature. Un dispositif expérimental a été mis en place pour la détermination du volume molaire du CO2 à dilution infinie, propriété nécessaire à modélisation thermodynamique. Le dioxyde de carbone à stocker peut contenir des impuretés telles que les gaz annexes (O2, N2, SOx, H2S, NyOx, H2, CO et Ar). Dans l’objective d’étudier la dissolution du CO2 dans des solutions aqueuses d’électrolyte en présence de ces impuretés, un dispositif expérimental a été mis en place pour la mesure des enthalpies de solution du SO2 dans l’eau et solutions aqueuses de NaCl et les premières résultats sont prometteurs. / This thesis studies the enthalpy of solution of carbon dioxide in electrolyte aqueous solutions. To develop theoretical models describing the systems {CO2-water-salt} under the geological storage conditions of carbon dioxide, it is necessary to have experimental data, namely solubility and enthalpy. In this study, a customized flow mixing unit was adapted to a SETARAM C-80 calorimeter to measure the enthalpy of CO2 solution in aqueous electrolyte solutions (NaCl, CaCl2 and Na2SO4) at the ionic strengths between 2 and 6 and at temperatures between 323.1 K and 372.9 K and pressures ranging from 2 to 16 MPa. Data from the literature were used to adjust the thermodynamic phase equilibrium model in the Υ-φ approach. The thermodynamic model reproduces the experimental enthalpies to plus or minus 10%. The calculation of the enthalpy in the rigorous model is strongly dependent on the data of the literature. An experimental device has been set up for the determination of the molar volume of CO2 at infinite dilution, which is necessary for thermodynamic modeling. The carbon dioxide to be stored may contain impurities such as annexes (O2, N2, SOx, H2S, NyOx, H2, CO and Ar). Under the objective of studying the influence of these impurities, an experimental apparatus has been set up for the measurement of enthalpies of solution of SO2 in water and aqueous solutions of NaCl and the first results are promising.

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