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1
Barsoum, Christopher. "The Thermodynamics of Planetary Engineering on the Planet Mars." Honors in the Major Thesis, University of Central Florida, 2014. http://digital.library.ucf.edu/cdm/ref/collection/ETH/id/1577.
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Mars is a potentially habitable planet given the appropriate planetary engineering efforts. In order to create a habitable environment, the planet must be terraformed, creating quasi-Earth conditions. Benchmarks for minimum acceptable survivable human conditions were set by observing atmospheric pressures and temperatures here on Earth that humans are known to exist in. By observing a positive feedback reaction, it is shown how the sublimation of the volatile southern polar ice cap on Mars can increase global temperatures and pressures to the benchmarks set for minimum acceptable survivable human conditions. Given the degree of uncertainty, utilization of pressure scale heights and the Martin extreme terrain were used to show how less than desirable conditions can still produce results where these benchmarks can be met. Methods for obtaining enough energy to sublimate the southern polar ice cap were reviewed in detail. A new method of using dark, carbonaceous Martian moon material to alter the overall average albedo of the polar ice cap is proposed. Such a method would increase Martian energy efficiency. It is shown that by covering roughly 10% of the Martian polar ice cap with dark carbonaceous material, this required energy can be obtained. Overall contributions include utilization of pressure scale heights at various suggested settlement sites, as well as polar albedo altering as a method of planetary engineering. This project serves as a foundational work for long term solar system exploration and settlement.B.S.A.E.
Bachelors
Mechanical and Aerospace Engineering
Engineering and Computer Science
Aerospace Engineering
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Haghtalab, Ali. "Thermodynamics of aqueous electrolyte solutions." Thesis, McGill University, 1990. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=74540.
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The focus of this work is the thermodynamics of aqueous solutions of strong electrolytes for both binary and multicomponent systems.A new excess Gibbs energy function to represent the deviations from ideality of binary electrolyte solutions was derived. The function consists of two contributions, one due to long-range forces, represented by the Debye-Huckel theory, and the other due to short-range forces represented by the local composition concept. The model is valid for the whole range of electrolyte concentrations, from dilute solutions up to saturation. The model consistently produces better results particularly at the higher concentration regions in which the other models deteriorate.
An electrochemical cell apparatus using Ion-Selective Electrodes (ISE) was constructed to measure the electromotive force (emf) of ions in the aqueous electrolyte mixtures. For the NaCl-NaNO$ sb3$-H$ sb2$O system, the data for the mean ionic activity coefficient of NaCl was obtained in order to show the reproducibility of literature data and to test the validity of the experimental procedure. The data for mean ionic activity coefficient of the following systems were also collected: (1) NaBr-NaNO$ sb3$-H$ sb2$O (a system with common ion); (2) NaBr-Ca(NO$ sb3$)$ sb2$-H$ sb2$O (a system with no-common-ion).
A novel mixing rule was proposed for the mean activity coefficients of electrolytes in mixtures in terms of the mean ionic activity coefficients of electrolytes in the binary solutions. The rule is applicable to multicomponent systems which obey Harned's Rule. Predictions are in excellent agreement with experimental data for ternary systems which follow the Bronsted specific ionic theory.
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Avlonitis, Dimitrios Anastassios. "Thermodynamics of gas hydrate equilibria." Thesis, Heriot-Watt University, 1992. http://hdl.handle.net/10399/803.
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Reservoir fluids are usually saturated with water at reservoir conditions and may form gas hydrates in transfer lines, which potentially may plug the system. For long subsea pipelines, methanol injection is the practical means for preventing hydrate formation and for decomposing blockages. For efficient and economical pipeline design and operation, phase boundaries, phase fractions and distribution of water and methanol among the equilibrium phases of the system must be accurately known. The system comprising reservoir fluids, water and methanol demonstrates a complex multiphase behaviour and currently no quantitatively adequate description for it has been detailed in the open literature. The problem is addressed in this thesis by a consistent application of classical equilibrium thermodynamics. At ordinary operating conditions any combination of as many as six phases can be potentially present. For the description of the vapour and all liquid phases, we use one cubic equation of state with nonconventional mixing rules developed as part of this work. Classical thermodynamics together with the cell theory of van der Waals and Platteeuw were employed for the development of a general model for the calculation of heat capacities of gas hydrates. A consistent methodology has also been developed for obtaining the potential parameters of the cell model. Thereafter, application of the model demonstrates that for nearly spherical guest molecules the classical cell theory is a strictly valid description of gas hydrates. However, complex guest molecules distort the hydrate lattice, resulting in variation of the numerical values of certain parameters of the model. This work presents an efficient algorithm for the solution of the problem of the identity of the equilibrium phases in multiphase systems where gas hydrates are potentially present. The algorithm is based on the alternative use of two equivalent forms of the Gibbs tangent plane criterion and it is believed to be more appropriate for systems involving gas hydrate equilibria than previous methods. Application of the proposed algorithm in several regions of the phase diagram of both binary and multicomponent systems shows that it can be used reliably to solve any phase equilibria problem, including the location of phase boundaries. In summary this work presents a consistent, efficient and reliable scheme for multiphase equilibrium calculations of systems containing reservoir fluids, water and methanol. Favourable results have been obtained by comparison with diverse experimental data reported in the open literature and it is believed that the proposed correlation can be used reliably for pipeline design and operation.
4
Firoozi, Sadegh. "Thermodynamics and mechanisms of lead softening." Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=100362.
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Visualization and quantitative oxidation kinetic experiments on 100 g samples of Pb-As at 600°C; thermal analysis and phase-equilibrium measurements of Pb-PbO-As2O3 samples under argon over the temperature range of 420°C to 875°C; computational thermodynamic solution modeling; and phase diagram and equilibrium calculations using FACTSage(TM) were performed to elaborate the poorly documented thermodynamics of the slags in the lead softening stage in the pyrometallurgical refining of lead. In the softening stage, the minor element impurities: arsenic, antimony and tin are removed from lead bullion by oxidation and are transferred to a skimmable oxide slag phase.It was found that optimizing an ionic molten oxide solution model that was conceptualized to contain Pb2+ and O2- with AsO3-4 and AsO3-3 ions, or with SbO3-4 and SbO3-3 ions in the respective PbO rich regions of the Pb-As-O and the Pb-Sb-O systems, was able to accurately reproduce the measured and published thermodynamic data. It was also found that the subsystems in the PbO-As2O 3-As2O5 and PbO-Sb2O3-Sb 2O5 systems showed small deviation from the ideal ionic solution model and small magnitude excess Gibbs energy parameters were sufficient to fit the predicted liquidus curves to the experimental measurements.
Arsenic in the +3 and +5 oxidation states was measured in the PbO rich region of the Pb-As-O liquid solution in the temperature range of 420°C to 875°C. The variability in the ratio of trivalent arsenic to the total arsenic content, as well as the complex variation of arsenic distribution between metal and oxide phases found strong interaction between the lead, arsenic and oxygen atoms at the 3PbO to 1AS2O3 molar ratio thus suggesting a short range ordering corresponding to the formation of AsO3-3 groupings, and indicating that the Pb3(AsO3) 2(l) species was likely to be present in the PbO rich region of the Pb-As-O system and contributing to an understanding of the Pb-As-O liquid oxide structure. Also, two new compounds (Pb3(AsO3) 2(s), Pb2AsO4(s)) were identified in the Pb-PbO-As 2O3 quenched samples via wavelength-dispersive spectrometry using the electron microprobe. The present work has application in commercial oxygen partial lead softening (OPLS), as uniquely practiced at Teck Cominco Ltd., British Columbia. There, pure oxygen gas is injected into the bath of impure bullion through a number of submerged lances in order to oxidize only part of the arsenic, antimony and tin into a slag phase. For such an operating practice, it was concluded from the visualization and quantitative oxidation experiments that the formation of solid oxides as the product of oxidation produced a physical barrier to the progress of oxidation and resulted in the commercially observed, highly-problematic, process initiation issues. When the product was liquid, there was much less of a barrier to rapid oxygen mass transfer to the minor element impurities and the softening reactions were easy to initiate. Such a change in the physical state of the products of oxidation was correlated to the optimized ternary Pb-As-O and Pb-Sb-O phase diagrams.
A current point of interest in partial lead softening is to increase the arsenic content of the slag phase. Arsenic distribution between lead bullion and slag calculated by the optimized solution model of the Pb-As-O system suggests that this can be achieved in a counter-current contacting of the slag and bullion.
5
Kust, Paul Roger. "Micellar autocatalysis and mixed micelle thermodynamics /." The Ohio State University, 1997. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487945015616522.
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Tamim, Jihane. "A continuous thermodynamics model for multicomponent droplet vaporization." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/mq20955.pdf.
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Khoshkbarchi, Mohammad Khashayar. "Thermodynamics of amino acids in aqueous electrolyte solutions." Thesis, McGill University, 1996. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=42068.
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A novel method has been developed for the measurement of the activity coefficients of an amino acid and the mean ionic activity coefficients of an electrolyte in water-electrolyte-amino acid systems. The method uses an electrochemical cell with two ion selective electrodes and a reference electrode. Activity coefficient data, at 298.15 K, for eight water-electrolyte-amino acid systems were measured. The cell consisted of a cation and an anion ion selective electrode, and the potential of each was measured versus a double junction reference electrode. The amino acids studied were glycine, DL-alanine, DL-valine and DL-serine and the electrolytes studied were NaCl and KCl. For the same systems, the solubilities at 298.15 K of the amino acids were measured at various electrolyte concentrations. The results show that the activity coefficients and the solubility of the amino acid in aqueous electrolyte solutions are strongly affected by the concentrations of both the electrolyte and the amino acid, the chemical structure of the amino acid and the nature of the cation of the electrolyte.The activity coefficients of amino acids in aqueous electrolyte solutions were modelled using a two-parameter excess Gibbs free energy model based on the contribution of a long range interaction term represented by the Bromley or the K-V model and a short range interaction term represented by the NRTL or the Wilson model.
A model based on the perturbation of a hard sphere reference system, coupled with a mean spherical approximation model, was also developed to correlate the activity coefficient of the amino acid and the mean ionic activity coefficient of the electrolyte in water-electrolyte-amino acid systems. The model can also predict the activity coefficients of amino acids in aqueous electrolyte solutions, without adjusting any parameter, at low electrolyte concentrations and slightly deviates from the experimental data at higher electrolyte concentrations.
A model was developed to correlate the solubilities of amino acids in aqueous and aqueous electrolyte solutions. The activity coefficients of amino acids in both aqueous and aqueous electrolyte solutions were represented by the perturbed mean spherical approximation model. It was shown that upon availability of independently evaluated experimental data for $ Delta h$ and $ Delta g$, the water-amino acid solubility model can accurately predict the solubility of amino acids in aqueous solutions without any adjustable parameter.
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Mountford, Paul A. C. "Molecular Thermodynamics of Superheated Lipid-Coated Fluorocarbon Nanoemulsions." Thesis, University of Colorado at Boulder, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=3721859.
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Diagnostic ultrasound is a safe, inexpensive and highly portable real-time imaging modality for viewing the human body. For over two decades, lipid-coated fluorocarbon microbubble contrast agents have been developed to help improve the diagnostic and therapeutic capabilities of ultrasound, but they have certain limitations. Recently, it was found that the microbubbles can be condensed into superheated liquid nanodrops capable of being vaporized by external optical or acoustic triggers. The compact form and vaporization effects of these phase-shift nanodrops may offer advantages over microbubbles for a number of current and future therapeutic and diagnostic applications. The goal of this dissertation work was to study the molecular thermodynamics and interfacial phenomena of these superheated phase-shift nanodrops.
In the first part of this work, a custom microscopy pressure chamber with control over temperature and pressure was used to observe microbubbles during condensation. Compression behaviors of fluorocarbon microbubbles constructed with lipid shells of varying acyl chain lengths were quantified over a broad temperature range. Microbubbles containing lipids of longer acyl chains were found to resist ideal compression and condensation. Dissolution was found to dominate as temperature approached the lipid main phase transition temperature, resulting in incomplete condensation. However, successful condensation of gas-filled microbubbles to liquid-filled nanodrops could be achieved at lower temperatures, and fluorescence microscopy showed that the lipid monolayer shell buckles and folds into surface-attached bilayer strands. The nanodrops were found to be remarkably stable when brought back to standard temperature and pressure. The temperature-pressure data were used to construct condensation phase diagrams to determine the thresholds for successful nanodrop formation.
In the second part of this study, the superheated nanodrops were vaporized back into microbubbles by changes in temperature and pressure. A custom optical chamber with control over temperature and pressure was used to track the kinetics of condensation, vaporization and dissolution of microbubble suspensions with varying fluorocarbon core and lipid shell compositions. A simple model was used to extract kinetic rates from the optical data, and Arrhenius plots were used to determine activation energies. The activation energy for thermal vaporization was found to vary with lipid acyl chain length, and a simple model of lipid intermolecular forces was used to explain this effect. Additionally, thermal vaporization was found to occur near 90% of the critical temperature of the fluorocarbon core, indicating that metastability of the superheated droplets was due to the low probability of homogenous nucleation rather than a Laplace overpressure. The superheated droplets could be reversibly vaporized and condensed to at least ten cycles, showing remarkable stability.
In the final part of this study, the tunability of vaporization was examined through the mixing of fluorocarbon gases in droplet core. A clinical ultrasound imaging system was used to track vaporization as a function of temperature and mechanical index. Discrepancies were found in the vaporization thresholds owing to mass transfer; the high solubility of the lower fluorocarbon caused it to rapidly deplete. However, a successful acoustic temperature probe was demonstrated. The experimental data from all three parts of this study were examined and explained by conventional molecular thermodynamics theory, providing new insights into the behavior and properties of these novel theranostic agents.
9
Perez, Jose L. (Jose Luiz). "Computer-aided thermodynamics modeling of a pure substance." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/35036.
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Ferguson, Todd R. (Todd Richard). "Lithium-ion battery modeling using non-equilibrium thermodynamics." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/87133.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2014.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 147-161).
The focus of this thesis work is the application of non-equilibrium thermodynamics in lithium-ion battery modeling. As the demand for higher power and longer lasting batteries increases, the search for materials suitable for this task continues. Traditional battery modeling uses dilute solution kinetics and a fit form of the open circuit potential to model the discharge. This work expands on this original set of equations to include concentrated solution kinetics as well as thermodynamics-based modeling of the open circuit potential. This modification is advantageous because it does not require the cell to be built in order to be modeled. Additionally, this modification also allows phase separating materials to be modeled directly using phase field models. This is especially useful for materials such as lithium iron phosphate and graphite, which are currently modeled using a fit open circuit potential and an artificial phase boundary (in the case of lithium iron phosphate). This thesis work begins with a derivation of concentrated solution theory, beginning with a general reaction rate framework and transition state theory. This derivation includes an overview of the thermodynamic definitions used in this thesis. After the derivation, transport and conduction in porous media are considered. Effective transport properties for porous media are presented using various applicable models. Combining concentrated solution theory, mass conservation, charge conservation, and effective porous media properties, the modified porous electrode theory equations are derived. This framework includes equations to model mass and charge conservation in the electrolyte, mass conservation in the solid intercalation particles, and electron conservation in the conducting matrix. These mass and charge conservation equations are coupled to self-consistent models of the charge transfer reaction and the Nernst potential. The Nernst potential is formulated using the same thermodynamic expressions used in the mass conservation equation for the intercalation particles. The charge transfer reaction is also formulated using the same thermodynamic expressions, and is presented in a form similar to the Butler-Volmer equation, which determines the reaction rate based on the local overpotential. This self-consistent set of equations allows both homogeneous and phase separating intercalation materials to be modeled. After the derivation of the set of equations, the numerical methods used to solve the equations in this work are presented, including the finite volume method and solution methods for differential algebraic equations. Then, example simulations at constant current are provided for homogeneous and phase separating materials to demonstrate the effect of changing the solid diffusivity and discharge rate on the cell voltage. Other effects, such as coherency strain, are also presented to demonstrate their effect on the behavior of particles inside the cell (e.g. suppression of phase separation). After the example simulations, specific simulations for two phase separating materials are presented and compared to experiment. These simulations include slow discharge of a lithium iron phosphate cell at constant current, and electrolyte-limited discharge of a graphite cell at constant potential. These two simulations are shown to agree very well with experimental data. In the last part of this thesis, the most recent work is presented, which is based on modeling lithium iron phosphate particles including coherency strain and surface wetting. These results are qualitatively compared with experimental data. Finally, future work in this area is considered, along with a summary of the thesis.
by Todd R. Ferguson.
Ph. D.
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Staron, Patrick Joseph. "Nonequilibrium thermodynamics of temperature gradient metamorphism in snow." Thesis, Montana State University, 2013. http://pqdtopen.proquest.com/#viewpdf?dispub=3560693.
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In the presence of a sufficient temperature gradient, snow evolves from an isotropic network of ice crystals to a transversely isotropic system of depth hoar chains. This morphology is often the weak layer responsible for full depth avalanches. Previous research primarily focused on quantifying the conditions necessary to produce depth hoar. Limited work has been performed to determine the underlying reason for the microstructural changes. Using entropy production rates derived from nonequilibrium thermodynamics, this research shows that depth hoar forms as a result of the snow progressing naturally toward thermal equilibrium.
Laboratory experiments were undertaken to examine the evolution of snow microstructure at the macro scale under nonequilibrium thermal conditions. Snow samples with similar initial microstructure were subjected to either a fixed temperature gradient or fixed heat input. The metamorphism for both sets of boundary conditions produced similar depth hoar chains with comparable increases in effective thermal conductivity. Examination of the Gibbs free energy and entropy production rates showed that all metamorphic changes were driven by the system evolving to facilitate equilibrium in the snow or the surroundings. This behavior was dictated by the second law of thermodynamics.
An existing numerical model was modified to examine depth hoar formation at the grain scale. Entropy production rate relations were developed for an open system of ice and water vapor. This analysis showed that heat conduction in the bonds had the highest specific entropy production rate, indicating they were the most inefficient part of the snow system. As the metamorphism advanced, the increase in bond size enhanced the conduction pathways through the snow, making the system more efficient at transferring heat. This spontaneous microstructural evolution moved the system and the surroundings toward equilibrium by reducing the local temperature gradients over the bonds and increasing the entropy production rate density.
The employment of nonequilibrium thermodynamics determined that the need to reach equilibrium was the underlying force that drives the evolution of snow microstructure. This research also expanded the relevance of nonequilibrium thermodynamics by applying it to a complicated, but well bounded, natural problem.
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Cheong, Ae-Gyeong. "Interfacial thermodynamics of liquid crystals : applications to capillary instabilities." Thesis, McGill University, 2004. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=84493.
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Most current applications and uses of liquid crystalline materials involve surfaces and interfaces. Prominent examples are high performance carbonaceous mesophase fibers, liquid crystal polymer fibers, and thermoplastic/liquid crystal polymer in-situ composites. Fundamental surface science and engineering principles are needed to optimize and design fibers and composites derived from liquid crystalline precursors. Currently non-equilibrium liquid crystal surface phenomena are not well understood. Force balance equations describing static and dynamical interfacial phenomena are available but have not been adequately used to describe the mechanics of fiber and film microstructures.This thesis explores the mechanics and stability of nematic liquid crystalline fibers embedded in inviscid and viscous matrices. A new theoretical framework for liquid crystal surface mechanics is formulated and used to model pattern formation and instability driven processes in fibers and fibrillar composites and blends. The liquid crystal Herring's formula and Laplace equation are derived and the role of liquid crystallinity is elucidated. In order to systematically analyze the role of the fundamental processes, linear stability analyses of capillary instabilities in nematic liquid crystalline fibers are performed by formulating and solving the governing nemato-capillary equations. An essential characteristic of liquid crystals, in contrast to isotropic liquids, is their mechanical anisotropy. Thus, the main parameters affecting the capillary instabilities are the isotropic and anisotropic surface tensions, the anisotropic viscosities, the bulk orientational elasticity, the isotropic viscosity of the matrix, and the surface bending modulus. Two asymptotic regimes are investigated: (a) the thin-fiber regime characterized by homogeneous bulk orientation and storage of surface elasticity, and (b) the thick-fiber regime characterized by bulk orientation distortions without surface elastic storage. Novel capillary instability mechanisms and symmetries of the instability modes for a nematic fiber embedded in a matrix are characterized. The predicted ability of capillary instabilities in nematic fibers to produce surface structures of well-defined symmetry and length scales, as well as chiral microstructures, is an important result that augments the pathways for targeted pattern formation. Deviations from classical Rayleigh capillary instabilities are identified and quantified in terms of liquid crystalline order.
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Smith, Raymond Barrett. "Nonequilibrium thermodynamics of porous electrodes for lithium-ion batteries." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111406.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2017.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 147-170).
Lithium-ion batteries are increasingly important, both in portable electronic devices and as grid stabilization for intermittent renewable sources. The varied applications involve varying requirements for safety, lifetime, and energy/power density. The broad requirement space leads to a large design space, requiring either extensive and costly experimentation or effective models. To be predictive enough to facilitate design, models must be based on underlying physics. However, battery models commonly make assumptions known to be false, such as describing phase separating materials with Fickian diffusion. In this thesis, we build on existing battery models by modifying key parts to better capture fundamental phenomena including transport and reactions in phase separating materials. First, we introduce a model of lithium transport and surface reactions within particles of graphite, which has phase separation and is the most common anode material in lithium-ion batteries. We demonstrate key features of the model, including a sensitivity to its electrochemical reaction kinetics as well as its ability to capture both single particle and porous electrode experimental data. Second, we connect a model of electrochemical kinetics that is well-established in the chemistry community to nonequilibrium thermodynamics and apply it to materials with phase separating electrodes. We demonstrate that, although it shares some characteristics with a commonly used phenomenological model, it makes distinct predictions which agree with certain experimental results. Finally, we unify these single-particle models within a volume-averaged model to describe battery behavior at the scale of full porous electrodes. The developed model and simulation software have already been applied by other researchers to help explain behavior of batteries with phase separating materials.
by Raymond Barrett Smith.
Ph. D.
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Arróyave, Raymundo 1975. "Thermodynamics and kinetics of ceramic/metal interfacial interactions." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/16625.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2004.Includes bibliographical references (p. 237-248).
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Ceramic/metal interfaces occur in a great number of important applications, such as ceramic/metal composites, microelectronics packaging, ceramic/metal seals, and so forth. Understanding the formation and evolution of such interfaces is therefore essential for the better design and optimization of these technologies. In this thesis, a methodology for the study of the thermochemical interactions at ceramic/metal interfaces, during both their formation and evolution, is proposed. Because of the importance of zirconia-based ceramics in increasingly important applications such as structural composites, thermal barrier coatings and Solid Oxide Fuel Cells, it was decided to illustrate the concepts developed in this thesis through the study of the interactions between zirconias and active metals. Semi-empirical thermodynamic models of all the phases likely to take part in the ceramic/metal interfacial interactions studied were developed. Phase diagram data and thermochemical information were critically assessed and use to adjust the thermodynamic parameters that allowed the description of the Ag-Cu-Ti, Cu-Ti-Zr, Ti-Zr-O, Cu-Ti-O and Cu-Zr-O systems. The thermodynamic models were used to predict the diffusion paths across zirconia/active metal interfaces through metastable phase diagrams calculations. Additionally, equilibrium calculations of activity diagrams were used to understand the complex interfacial reactions occurring during the active metal brazing of zirconia-based ceramics.
(cont.) By using simple one-dimensional interdiffusion simulations, it was demonstrated that the base metal in ceramic/metal joints plays an essential role in determine the thermochemical interactions at the ceramic/metal interface during ceramic/metal joining operations. In general it was found that, using all these techniques,it was possible to explain diffusion paths and reaction sequences observed in a great number of zirconia/active-metal systems, both in the solid and in the liquid states. In many cases, the morphology of the reaction layers formed at ceramic/metal interfaces determine their final properties. To address this problem, empirical thermodynamic models of the likely reaction products at zirconia/metal interfaces were coupled to kinetic models using the diffuse-interface formalism to successfully describe the formation and evolution of complex ceramic/metal interfacial structures.
by Raymundo Arróyave.
Ph.D.
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Taylor, Andrew James David. "The Capillary-Centric Model of Coupling-As-Thermodynamics." Thesis, North Dakota State University, 2015. https://hdl.handle.net/10365/27648.
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Models of ventricular-arterial coupling (VAC) have historically described the heart as a
function of its energetic interaction with the arterial system. However, these models either
represent the dynamic, adaptive cardiovascular system (CVS) in isolation or sacrifice cardiac
mechanics to use simplified, time-averaged values across the cardiac cycle. In this thesis a
facsimile CVS is constructed that characterizes ventricular-arterial interactions with intact
cardiac mechanics as a function of whole-body thermo-fluid homeostatic regulation.
Simulation results indicate proportional-integral (PI) control of heart rate and arterial
resistance is conditionally sufficient to maintain body temperature during square-wave
exercise, but further elements may be required to mimic genuine physiological responses.
These simulations of the primitive model lay the framework of capillary-centric VAC through
the perspective of coupling-as-thermodynamics.
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Louw, Christoffel. "The effect of a guided enquiry based learning approach on mechanical engineering students' understanding of thermodynamics." Thesis, Walter Sisulu University, 2012. http://hdl.handle.net/11260/d1011523.
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Personal experiences of almost 17 years as an academic in engineering education in South Africa indicate that with the current teaching methods which are in use, course outcomes as required by the South African Qualification Authority (SAQA) are not achieved in learning Thermodynamics 2 (MTHE 2). The purpose of this research was to investigate alternative methods of teaching and learning MTHE 2 which would assist to improve the students’ academic performance. The population for this research was students registered for National Diploma Mechanical Engineering and the accessible population was 40 students registered for MTHE 2 from Walter Sisulu University, Chiselhurst campus. Out of these 40 students, 20 voluntarily agreed to be the sample. The theoretical framework for this study was social constructivism. Social constructivism states that learning is an active process and the process of knowledge construction occurs in a socio-cultural context where the student and environment actively interact. The student involves himself/herself and does neither remain nor be allowed to remain just as a passive observer. This was an action research where students were exposed to Guided Enquiry Based Learning (GEBL) in groups. From a social constructivists approach to learning, GEBL was used to engage students in social groups during the teaching-learning process with specific focus on selected academic discipline. All ethical considerations applicable to a study of the present nature were adhered to and in addition, signed informed consent forms were obtained from participants prior to the study. Students were given an introduction to the concepts and principles as per the pre-set syllabus for MTHE 2 and this was followed by problem solving sessions in which they were divided into four groups of five students each. The students were given a guided enquiry- and work-based example with an additional list of questions on each module of the syllabus. They had to select the most relevant questions from the list to analyse and develop a solution for each problem. The lecturers’ role was that of a facilitator who assisted each group with problems which the group encountered. This approach engaged students more actively in the learning process and placed more responsibility on them for their own progress in learning. This process also created an atmosphere for interaction with peers and assisted them to develop interpersonal and group communication skills. Key performance indicators were developed to measure the extent to which these outcomes were achieved. The researcher made use of an instrument structured in terms of Likert-type scale in order to objectively assess the extent of achievement. Data collected from the pilot study done in 2009 indicated that GEBL improved the students’ understanding of course content and problem analysis. Quantitative data were collected by means of standard assessment i.e. semester tests, an oral test, final examination and a KPI instrument. The KPIs were formulated to measure the extent to which the outcomes for MTHE 2 had been achieved. Qualitative data were collected through 30-minute interviews, using an open-ended interview schedule, with each member of the sample. The interviews were done by a person who qualified both as an ‘insider and outsider’ in order to minimize the risk of bias and to maintain rigour in the research. In order to qualify as an ‘insider and outsider’, one ought to be as an insider: (a) from the same ethnic group, (b) qualified in Mechanical Engineering with Thermodynamics as a major course, (c) had no power disposition e.g. a former student or a laboratory assistant (excluding staff members within the mechanical engineering department) and as an outsider, one who was not part of the GEBL process. The quantitative scores from the assessments were analysed with Predictive Analysis Software (PASW) to determine the extent to which interventions had assisted student performance. The qualitative data from the interviews were analysed with N-Vivo to reveal the impact of GEBL on student learning and understanding of MTHE 2. The results indicated that with GEBL, the students’ overall scores improved from the first assessment score of 46% written on half of the first module to the final assessment score of 55% written on all seven modules. Students could handle larger volumes of work and still obtain a higher percentage. GEBL assisted students’ in recalling factual MTHE 2 concepts, understanding of MTHE 2 concepts, principles and applications. GEBL also enhanced students’ ability to communicate procedures and processes related to MTHE 2. KPIs formulated to measure the extent to which the outcomes were met in terms of student achievement indicated a 57% achievement thereof. The KPIs developed gave a percentage achievement of the specified outcomes for MTHE 2 with GEBL. Theses KPIs can be used in future to measure the effectiveness of different teaching and learning methods in terms of achieving the outcomes. It is therefore recommended that GEBL be introduced into other engineering courses also to assist students in understanding course content and in achieving the course outcomes.
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Virgo, Nathaniel D. "Thermodynamics and the structure of living systems." Thesis, University of Sussex, 2011. http://sro.sussex.ac.uk/id/eprint/6334/.
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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.
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Oliveira, F. Delly. "Electric energy system planning and the second principle of thermodynamics." Thesis, McGill University, 1995. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=39976.
Full textAbstract:
This thesis deals with the long-term planning of electric energy systems. Such systems are defined by complex interconnections of end-uses, energy conversion devices and natural resources. The planning process is usually guided by a number of design criteria, namely, economic, social and environmental impacts as well as system reliability and efficiency. The planning challenge is to find an acceptable compromise among these often conflicting objectives. System efficiency is a critical design criterion normally measuring the ratio of the system output and input energies. In electric energy systems, efficiency is normally defined according to the First Principle of Thermodynamics which states that energy cannot be destroyed. In this thesis, the definition of efficiency in electric energy system planning is broadened to include interpretations according to both the First and Second Principles of Thermodynamics. The Second Principle essentially states that the "quality" of energy decreases or, at best, remains constant in any conversion process where the quality of energy (denoted here by exergy) is a measure of the ability of a form of energy to be converted into any other form. Work, hydroelectric potential and electricity are examples of high quality energy sources while low temperatures heat end-use applications are at the low end of the quality scale. Since certain types of energy conversion processes may show high levels of exergy destruction, even though energetically efficient, it is important to design energy systems such that the energy quality of an end-use is matched as much as possible to that of the energy supply thus avoiding situation where a high quality supply is used for a low quality purpose.The electric energy industry has virtually ignored exergetic considerations in system planning due, to a large extent, to a lack of familiarity with the Second Principle and its implications. Nevertheless, exergy is an attribute which must be planned and conserved with at least the same priority as energy. It is demonstrated here that the planning of energy systems will be drastically affected when both energy and exergy are considered. However, to be able to rationally use the natural resources, exergetic analysis must become an integral part of system planning. This thesis analyses the application of the Second Principle of Thermodynamics in the planning of electric energy systems through theory, examples and case studies including economic considerations.
In order to achieve electric energy systems that are more exergetically efficient, a new type of electric energy tariff called type-of-use, is proposed. Analogous to the time-of-use rate that assigns different monetary values for the time of the day considered, the type-of-use tariff assigns a monetary value to the end-uses. Simulations are performed in different electric energy systems to demonstrate that type-of-use tariffs will indeed lead to more exergetically efficient systems.
The benefits of exergetic analysis are supported by a number of studies presented in this thesis. These studies analyse from the points of view of energetic and exergetic efficiency and cost the following: (i) A space heating system; (ii) The impact of a major introduction of electric vehicles in Canada and (iii) The long range planning of a regional electric power system consisting of two interconnected provinces.
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Kabiri-Badr, Mostafa. "Thermodynamics of salt-polymer aqueous two-phase systems: Theory and experiment." Diss., The University of Arizona, 1990. http://hdl.handle.net/10150/185088.
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A theoretical and experimental study of the phase behavior of aqueous salt-polymer two-phase systems has been done. A statistical mechanical model has been developed for the chemical potential of every component in the salt-polymer-water system. The model incorporates the effect of short-range forces by use of the isothermal-isobaric osmotic pressure expansion of Hill. The effect of long-range forces such as electrostatic interactions is incorporated with a non-primitive electrolyte model based on the work of Pailthrope et al. and on Kirkwood-Buff theory. The effect of polymer-polymer and polymer-salt interactions is represented in the model by Hill osmotic virial coefficients. The polymer molecular weight dependence of the second virial coefficients is predicted with the results of polymer scaling laws. An isopiestic experiment has been developed to measure the thermodynamic activity data required to evaluate the model parameters. Six different aqueous mixtures of polyethylene glycol 1000 and 8000 and MgSO₄, Na₂SO₄, and Na₂CO₃ were studied at 25°C, 1 ATM. Phase diagrams for these six systems were calculated from the model and compared to experiment with good agreement between them.
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Park, Jooyeon. "Computational prediction of organic crystal thermodynamics using molecular dynamics." Thesis, University of Iowa, 2015. https://ir.uiowa.edu/etd/1721.
Full textAbstract:
Computation predictions of organic crystal structure and thermodynamics are essential for material design, crystal engineering and drug development. However, accurate computational tools for organic crystal thermodynamics calculations are lacking, and experimental data set for validation of computational methods is limited. Most crystal structure predictions and stability calculations depend solely on potential energy, which is an insufficient representation of thermodynamics. This thesis proposes and validates both absolute and relative free energy calculation of small organic compounds, thus presenting an accurate computational tool that overcomes the shortcomings of potential-energy-based models.
The solubility of organic molecules can be computed from a thermodynamic cycle that decomposes standard state solubility into the sum of solid-vapor sublimation, i.e. thermodynamic stability of the crystal, and vapor-liquid solvation free energies ΔG°solubility=ΔG°sub+ΔG°solv. Crystal polymorphs have different ΔG°sub thus different solubility, which of critical importance to the pharmaceutical industry, however, robust computational methods to predict this quantity from first principles are lacking. Over the past few decades, alchemical simulation methods to compute solvation free energy using classical force fields have become widely used. However, analogous methods for determining the free energy of the sublimation/deposition phase transition are currently limited. This thesis describes an absolute thermodynamics approach based on growth of the asymmetric unit into a crystal via alchemy (GAUCHE). GAUCHE computes deposition free energy ΔG°dep=-ΔG°sub=ΔG°Vol+ΔG°Au+ΔG°Au→UG as the sum of an entropic term to account for compressing a 1 M vapor into the molar volume of the crystal asymmetric unit (VAU) plus two simulation steps. In the first simulation step, the deposition free energy ΔG°AU for a system composed of only NAU asymmetric unit (AU) molecule(s) is computed beginning from an arbitrary conformation in vacuum. In the second simulation step, the change in free energy ΔG°AU�UG to expand the asymmetric unit degrees of freedom into a unit cell (UC) composed of NUC independent molecules is computed. This latter step accounts for the favorable free energy of removing the constraint that every symmetry mate of the asymmetric unit has an identical conformation and intermolecular interactions. The current work is based on NVT simulations, which requires knowledge of the crystal space group and unit cell parameters from experiment, but not a priori knowledge of crystalline atomic coordinates. GAUCHE was applied to 5 organic molecules whose sublimation free energy has been measured experimentally, based on the polarizable AMOEBA force field and more than a microsecond of sampling per compound. The mean unsigned and root-mean-square errors were only 1.6 and 1.7 kcal/mol, respectively, which indicates that GAUCHE is capable of accurately predicting sublimation thermodynamics.
For polymorphic systems, we propose a relative thermodynamics approach, that is similar to the second simulation step of GAUCHE, where ΔG°P1→P2 is calculated instead of ΔG°AU→UG. A relative approach reduces statistical uncertainty upon convergence compared to an absolute calculation; thus, it is more appropriate due to the thermodynamic stability difference between polymorphs are often fairly small. For our paracetamol test system, the experimental free energy difference was only 0.93 kcal/mol. Although both quantum and AMOEBA potential calculations predict the form II of paracetamol as more stable crystal form than form I, our relative free energy calculation predict the opposite stability ranking, which agrees with the experiment. Decomposition of free energy into entropy and enthalpy indicates that the favorable entropy change contributes to the greater thermodynamic stability of form I over form II. Although the exact magnitude of entropy and enthalpy changes differs across literature data as well as our data, the favorable entropic contribution is consistent. Further calculations over the temperature range from 100 to 308 K show the temperature dependence of free energy, which follows the parabolic trend observed in experiments. Our results show that our relative polymorph stability methods can accurately capture temperature dependence of free-energy-based stability ranking and overcome the limitations of potential-energy-based ranking. Thus, the importance of crystal structure predictions based on free energy can be further emphasized.
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Joshi, Suvid. "MIXED SURFACTANT SYSTEMS: THERMODYNAMICS AND APPLICATIONS IN METAL OXIDE IMPRINTING." UKnowledge, 2014. http://uknowledge.uky.edu/cme_etds/29.
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In this work we study mixtures of cationic surfactant (CTAB) and sugar based surfactant(s) (octyl beta-D-glucopyranoside (C8G1), dodecyl maltoside (C12G2) and octyl beta-D-xylopyranoside (C8X1)) to understand the non-ideal thermodynamic behavior of the mixtures of cationic and non-ionic surfactants in water and synthesis of imprinted materials. The thermodynamics of micellization, mixing and dilution of these systems are studied using Isothermal Titration Calorimetry (ITC) and the experimental data obtained are modeled with a pseudo-phase separation model with non-ideal mixing described by regular solution theory. It is shown that a model accounting for enthalpy of demicellization and enthalpy of dilution based on McMillan-Mayer model is able to fit ITC data set for CTAB-C8G1 system with varying mole fractions.
In addition to measuring non-ideal mixing behavior, mixtures of cationic and saccharide-based surfactants are of interest for the molecular imprinting of oxide materials. Mixtures of CTAB and either C8G1 or C8X1 are utilized to prepare nonporous adsorbent materials which act as selective adsorbents towards the headgroup of the saccharide surfactant. The approach is based on the Stöber silica particle synthesis process in which surfactants are added to soft particles present at the onset of turbidity to imprint their surface. This approach is shown to yield particles displaying selective adsorption for sugars with different number of carbons, but also provide enantioselective adsorption of targeted saccharides. Enantioselectivity of D-glucose, D-xylose and D-maltose is demonstrated by imprinting with C8G1, C8X1 and C12G2, respectively. The imprinting technique provides the first example of selective adsorption based on non-covalent imprinting of silica for sugars.
The mixed surfactant are also used to synthesize templated porous materials incorporating titanium which are used for epoxidation catalysis. The porous materials obtained have high surface area, uniform pore sizes in the mesopore range, and provided high selectivity and activity towards epoxidation of styrene. Titanosilicate thin films are also synthesized using cationic and saccharide surfactant mixtures to understand the incorporation of the titanium into the porous material. It is demonstrated that large amounts of isolated, tetracoordinated titanium sites can be incorporated into mesoporous silica-based materials via the complexation of the titanium precursor with a saccharide-based surfactant.
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Smit, Reneé. "The nature of engineering and science knowledge in curriculum: a case study in thermodynamics." Doctoral thesis, University of Cape Town, 2017. http://hdl.handle.net/11427/25532.
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Abstract The study explores the nature of disciplinary knowledge differences and similarities between the sciences and the engineering sciences as these appear in curriculum texts. The work is presented as a case study of curriculum knowledge in thermodynamics, and the epistemic properties are investigated in four sub-cases in mechanical engineering, chemical engineering, physics and chemistry. Data was collected from prescribed undergraduate textbooks in the four disciplinary fields. The work is theoretically informed by two fields of scholarly work: the sociology of educational knowledge (in particular the work of Basil Bernstein) and the applied philosophies of science and engineering science, in order to develop a theoretical framework for analysis of the data. The framework allows the study to move beyond the typical binary classification of the sciences as 'hard-pure' and engineering sciences as 'hard-applied' disciplines. Starting from broad teleological considerations, the philosophical concepts of specialisation, idealisation and normativity are explored and developed into modalities and modal continua of variance to allow investigation of the epistemic differences and similarities in the recontextualised disciplinary knowledge from these contiguous conceptual fields. The empirical study identifies important differences in thermodynamics curriculum knowledge in terms of specialisation, normativity and idealisation across the broad disciplinary fields, rendering more complex Bernstein's notions of singulars and regions. The epistemic modalities and modes provide a way to conceive in more detail how the professional engineering science knowledge is orientated towards its field of practice. Curriculum knowledge in the engineering sciences is shown to be remarkably different from the knowledge in the sciences: both mechanical and chemical engineering knowledge emphasise particulars, rather than universals, have stronger normative aspects, and employ a limited form of idealisation in their commitment to physical realisability. By contrast, knowledge in the sciences is more universal, normativity is incidental, and idealisation is used expansively. In addition, the research findings suggest a negative correlation between idealisation and normativity as epistemic modalities: a commitment to normative concerns in the engineering sciences constrains the extent to which knowledge idealisation is pursued, compared to what is observed in the bodies of science curriculum knowledge. Furthermore, over and above differences in curriculum knowledge between the broad fields of science and engineering science, discernible variation exists between the engineering sciences investigated, raising cautions against a monolithic view of curricular epistemic properties across broad disciplinary areas.
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Gopalakrishnan, Sai Gautam. "Thermodynamics and kinetics of Mg intercalation for multivalent cathode applications." Thesis, Massachusetts Institute of Technology, 2017. http://hdl.handle.net/1721.1/111245.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2017.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 183-204).
Energy storage, especially through electrochemical mechanisms such as batteries, is crucial for sustaining the ever-increasing energy needs of the future in a fossil-free manner. While the current industrial workhorse, lithium ion batteries, has shown tremendous improvements in energy and power-densities, via both materials selection and engineering advancements, the lithium ion technology is approaching the fundamental limits of what more can be achieved. Multi-valent (MV) chemistry, that pairs an energy-dense MV metal anode (such as Mg) with a high voltage cathode has the potential to surpass the energy densities achieved by current Li-ion batteries, along with improved safety and lower costs. However, moving into newer chemistries leads to newer challenges, such as developing cathodes that can reversibly intercalate Mg at high voltages, high rates and high capacities, apart from designing electrolytes that remain stable against both the electrodes. In this thesis, I focus on the challenge of MV cathode design and I explore the thermodynamic and kinetic properties of candidate oxide cathode materials for MV batteries, including polymorphs of V₂O₅, spinel-Mn₂O₄ and layered-Mg₂Mo₃O₈, using first-principles based methods. The undercurrent of the thesis is to obtain design principles that will aid in both optimization of existing cathodes and in the identification of new candidate materials. Utilizing a diverse set of tools, I benchmark the calculated properties, including average voltage curves, lattice parameters, cation-anion decorations in structures and activation barriers for Mg diffusion, to experimental observations, where possible. Finally, this thesis should serve as a guide for other computational-theorists and experimentalists, in the search for an energy-dense MV cathode that will in turn aid in the realization of a high energy density MV battery.
by Sai Gautam Gopalakrishnan.
Ph. D.
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Kang, ShinYoung. "Ab initio prediction of thermodynamics in alkali metal-air batteries." Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/89952.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 93-100).
Electric vehicles ("EVs") require high-energy-density batteries with reliable cyclability and rate capability. However, the current state-of-the-art Li-ion batteries only exhibit energy densities near ~150 Wh/kg, limiting the long-range driving of EVs with one charge and hindering their wide-scale commercial adoption.1-3 Recently, non-aqueous metal-O₂ batteries have drawn attention due to their high theoretical specific energy.2, 4-6 Specifically, the issues surrounding battery studies involve Li-O₂ and Na-O₂ batteries due to their high theoretical specific energies of 3.5 kWh/kg (assuming Li 20 2 as a discharge product in Li-O₂ batteries) and 1.6 and 1.1 kWh/kg (assuming Na₂O₂ and NaO₂ as discharge products, respectively, in Na-O₂ batteries). Since the potential of Li-O₂ batteries as an energy storage system was first proposed in 1996,1 various studies have criticized and verified their shortcomings, such as their low power density, poor cyclability, and poor rate capability. ₇, ₈ Substantial research attempts have been made to identify the cause of the high overpotentials and electrolyte decomposition and to search for better cathode/electrolyte/anode and/or catalyst material combinations. However, Li-O₂ battery technology remains in its infancy primarily due to the lack of understanding of the underlying mechanisms. Therefore, we investigate the charging mechanism, which contributes to the considerable energy loss using first-principles calculations and propose a new charging mechanism based on experimental observations and knowledge concerning Li-ion and Na-ion batteries. Most studies on metal-O₂ batteries have mainly focused on Li-O₂ batteries. However, recently, the promising performance of Na-O₂ systems has been reported.₉, ₁₀ Although Na-O₂ batteries exhibit slightly lower theoretical specific energies than those of the Li-O₂ batteries as specified above, the chemical difference between the two alkali metals substantially distinguishes the electrochemistry properties of Na-O₂ and Li-O₂. In the Na-O₂ system, both NaO₂ and Na₂O₂ are stable compounds, while in the Li-O system, LiO₂ is not a stable compound under standard state conditions (300 K and 1 atm).₁₁, ₁₂ Presumably, due to this chemical difference, the Na-O₂ system has exhibited a much smaller charging overpotential, as low as 0.2 V, when NaO₂ is formed as a discharge product, compared with that in Li-O₂ system, >1 V. Such a low charging overpotential in Na-O₂ batteries demonstrates their potential as a next generation electrochemical system for commercially viable EVs .₉,₁₀ In this thesis, we study the thermodynamic stability of Na-O compounds to identify the phase selection conditions that affect the performance of Na-O₂ batteries.
by ShinYoung Kang.
Ph. D.
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Walton, S. Patrick (Stephen Patrick) 1973. "Thermodynamics and kinetics of antisense oligonucleotide hybridization to a structured mRNA target." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/43615.
Full textAbstract:
Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, February 2002.Includes bibliographical references (p. 165-178).
Antisense oligonucleotides have the potential to selectively inhibit the expression of any gene with a known sequence. Antisense-based therapies are under development for the treatment of infectious diseases as well as complex genetic disorders. Although there have been some remarkable successes, realizing this potential is proving difficult because of problems with oligonucleotide stability, specificity, affinity, and delivery. Each of these limitations has been addressed experimentally through the use of chemically-modified oligonucleotides and oligonucleotide conjugates, with much success in enhancing oligonucleotide efficacy. These early studies have shown that selection of target site, once considered a trivial problem, is critical to the success of antisense strategies. It has become clear that the efficacy of antisense oligonucleotides is a strong function of the structure of the target mRNA. Though single-stranded, RNA molecules are typically folded into complex three-dimensional structures, formed primarily by intramolecular Watson-Crick base-pairing. If an oligonucleotide is complementary to a sequence embedded in the three dimensional structure, the oligonucleotide may not be able to bind to its target site and exert its therapeutic effect. Because the majority of the structure of RNA molecules is due to Watson-Crick base-pairing, relatively accurate predictions of these folding interactions can be made from algorithms that locate the structure with the most favorable free energy of folding.
(cont.) Taking advantage of the predictability of RNA structures, this thesis addresses the problem of antisense target site selection, first from a theoretical and subsequently an experimental standpoint. A thermodynamic model to predict the binding affinity of oligonucleotides for their target mRNA is described and validated using multiple in vitro and cell-culture based experimental data sets. Subsequently, direct experimental comparisons with theoretical predictions are made on the well-characterized rabbit-[beta]-globin (RBG) mRNA, using a novel, centrifugal, binding affinity assay. The importance of the hybridization kinetics is also explored, as is the role of association kinetics in defining the rate of cleavage by the enzyme ribonuclease H (RNase H). Finally, the applicability of the model in identifying biologically active oligonucleotides is demonstrated.
by S. Patrick Walton.
Sc.D.
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Chookajorn, Tongjai. "Enhancing stability of powder-route nanocrystalline tungsten-titanium via alloy thermodynamics." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/88365.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 101-105).
Improvement in material properties as a result of grain size refinement to the nanoscale is often limited by an inherent tendency of these nanostructured materials to coarsen especially at the high temperatures required for processing. The structural instability stems from a large volume fraction of grain boundaries that carry an intrinsic energy penalty, but can be overcome by a consideration of the thermodynamics-based mechanism of interface energy relief via alloying. Suitable alloying conditions can provide a solute segregated grain boundary configuration that enables a nanostructured alloy to become the system's most energetically preferable state. A thermodynamics-based Monte Carlo method that captures the physics of regular solution mixing and grain boundary segregation in nanostructured alloys is developed and used to study the energetics and equilibrium structures of binary alloys. Our simulation is used to identify the alloying elements with preferable interface stabilizing capability appropriate for the high-temperature sintering requirement for powder-route nanocrystalline tungsten. Based on both alloy simulation and consideration of material properties, titanium is selected as a suitable alloying element. Nanocrystalline tungsten alloys with 0-20 atomic percent titanium content are produced by high-energy ball milling and tested at the expected sintering temperature of 1100°C. With an addition of 20 atomic percent titanium, nanocrystalline tungsten shows retention of nanoscale grain size after a one-week equilibration at 1100°C. Scanning transmission electron microscopy and atom probe tomography techniques reveal a heterogeneous distribution of titanium in the alloy with enhanced grain stability, which contradicts the expectation of a uniform solid solution by conventional bulk thermodynamics but is explicitly predicted by the alloy simulation when grain boundaries are included as possible equilibrium states. The segregation profiles from the experimental characterizations and simulated results show depletion of titanium from tungsten grain centers and enrichment of titanium well above the nominal concentration in the grain boundary vicinity in a form of complex segregation state.
by Tongjai Chookajorn.
Ph. D.
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Williams, Paul Ngcebo Tudor. "Modeling of internal combustion engine thermodynamics, valve dynamics and valve flow." Thesis, Stellenbosch : Stellenbosch University, 2002. http://hdl.handle.net/10019.1/52939.
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Thesis (MScEng)--University of Stellenbosch, 2002.ENGLISH ABSTRACT: In the design or modification of internal combustion (IC) engine components, the South African Automotive industry has always relied on either design by mother companies or quasi-empirical design methods. These methods have restricted the performance and reliability of local designs. A personal computer based model of four stroke engine operation has been developed as a rapid and cost-effective aid to users who wish to determine the performance of an engine with reasonable accuracy before dynamometer testing is possible. This model consists of a thermodynamic model of combustion and gas exchange linked to a manifold flow model. Accompanying this is a simulation of valve flow and a cam dynamic model, enabling full assessment of the optimum cam profiles and valve angles for various automotive engine configurations. The accuracy of these models has been verified by comparison with a set of engine dynamometer tests. The models have also been used with great success in local and international development projects in conjunction with local automotive manufacturers. In particular, two engine upgrade projects have been successfully completed, in which the program was used to aid the design of inlet manifolds, the selection of camshafts, and the selection of compression ratios.
AFRIKAANSE OPSOMMING: In die ontwerp of modifikasie van binnebrandenjin-komponente het die Suid-Afrikaanse Motorbedryf gewoonlik staatgemaak op óf die ontwerpe van die moedermaatskappy óf is van quasi-empiriese ontwerp metodes gebruik gemaak. Hierdie metodes het die werkverrigting en uithouvermoë van plaaslike ontwerpe beperk. 'n Rekenaar model wat die werking van 'n vierslagenjin moduleer, is ontwikkel as 'n vinnige en koste effektiewe hulpmiddel vir ontwerpers om 'n redelike akkurate voorspelling van enjin werkverrigting te verkry, voordat dynamomotor toetswerk moontlik is. Die model bestaan uit 'n termodinamise model vir ontbranding en die gas uitruilproses, gekoppel aan 'n spruitstuk vloeimodel. Die model word saam met 'n simulasie van klepvloei en 'n nok dinamiese model gebruik, wat toelaat dat 'n goeie raming van die optimum nokprofiele en klephoeke gemaak kan word vir verskeie automobielenjin konfigurasies. Die akuraatheid van hierdie modelle is bevestig deur die vergelyking van simulasie resultate met 'n omvangreike stel enjin dynamomotor toetse. Die modelle is ook met groot sukses in verskeie plaaslike en internasionale ontwikkelingsprojekte, in samewerking met die plaaslike motorbedryf, gebruik. In besonder is twee enjinontwikkelingsprojekte suksesvol voltooi, waarin die simulasie program gebruik is om die ontwerp van die inlaat spruitstuk, die keuse van nokasse en die keuse van drukverhouding te vergemaklik.
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White, Thomas J. "Development of a parametric analysis microcomputer model for evaluating the thermodynamic performance of a reciprocating Brayton cycle engine." PDXScholar, 1987. https://pdxscholar.library.pdx.edu/open_access_etds/3794.
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In this thesis, applicable data from research on IC engines have been adapted to PACE engine designs. Data from studies on heat transfer, friction, and pressure losses, in particular, have been used. Certain parameters which define operation and design characteristics appear to influence PACE engine performance very strongly. Some of the more critical parameters, notably friction and heat transfer coefficients, must be determined experimentally if accurate model results are to be expected. Pressure ratio, compressor RPM, and maximum combustor temperature, the independent operating parameters, also have a dramatic effect on engine performance. Other design or operating characteristics and working fluid properties are not controlled independently. These are dictated by the engine physical design configuration and operation, ambient conditions, and choice of fuel.
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Helminiak, Nathaniel Steven. "Construction and characterization of a single stage dual diaphragm gas gun." Thesis, Marquette University, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10641398.
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In the interest of studying the propagation of shock waves, this work sets out to design, construct, and characterize a pneumatic accelerator that performs high-velocity flyer plate impact tests. A single stage gas gun with a dual diaphragm breach allows for a non-volatile, reliable experimental testing platform for shock phenomena. This remotely operated gas gun utilizes compressed nitrogen to launch projectiles down a 14 foot long, 2 inch diameter bore barrel, which subsequently impacts a target material of interest. A dual diaphragm firing mechanism allows the 4.5 liter breech to reach a total pressure differential of 10ksi before accelerating projectiles to velocities as high as 1,000 m/s (1570-2240 mph). The projectile’s velocity is measured using a series of break pin circuits. The target response can be measured with Photon Doppler Velocimetry (PDV) and/or stress gauge system. A vacuum system eliminates the need for pressure relief in front of the projectile, while additionally allowing the system to remain closed over the entire firing cycle. Characterization of the system will allow for projectile speed to be estimated prior to launching based on initial breach pressure.
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Worm, Jeremy. "The Impact of Water Injection on Spark Ignition Engine Performance under High Load Operation." Thesis, Michigan Technological University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10684513.
Full textAbstract:
An experimental effort has been completed in which water injection was investigated as a means of enabling increases in engine output and high load efficiency. Water was injected into the intake port of a direct fuel injected, 4-cylinder, boosted engine with dual independent variable valve timing. The water was shown to increase volumetric efficiency and decrease the onset of knock which in turn enable more optimal combustion phasing. Both of these affects resulted increases in load of up to 5.5% at the same manifold pressure as the baseline case. The advancement of combustion phasing, combined with elimination of fuel enrichment resulted in an increase in full load thermal efficiency of up to 35%. Analysis is provided around these affects, as well as the phase transformation of water throughout the engine cycle.
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Breton, Andre. "Methane hydrate film growth measurements by microscopy." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18284.
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Gas Hydrates are a specific type of inclusion compound in which water molecules arrange themselves by hydrogen bonding to form cages accommodating a guest molecule of appropriate size. These compounds are thermodynamically stable at low temperatures (~ 0°C) and relatively high pressures. These conditions are typically found in deep oceans and make gas hydrates the most abundant hydrocarbon source on earth. Gas hydrates have also been investigated because they are known to plug oil pipelines. Experiments were carried out to determine how efficient VP/VC was at slowing down gas hydrate formation when compared to de-ionized water. Kinetics of formation of methane hydrate film was compared using two measurement methods: Microscopy and gas consumption. Experiments were conducted for each solution at temperatures and pressures ranging from 274-278 K and 5000-7000 kPa respectively. Gas consumption by the system and spatial movement of the hydrate film were monitored simultaneously. It was noticed that hydrate film growth measured by microscopy could be separated in two steps; initial and second growth stages. Initial growth rates measured were significantly higher than second growth rates (3 to 300 times higher). It is suspected that liquid saturation affects initial growth rates and initial film thicknesses. It was noticed that at 1 and 2°C, initial growth rates in presence of VP/VC were higher than with water. Initial growth rates with VP/VC were lower than those of water at 3°C. Results of initial film thicknesses show an inversely proportional trend with subcooling conditions. Second growth rates were shown to increase when hydrate formation driving force increased in presence of water. Results with VP/VC were significantly lower than with water and were not shown to depend noticeably on experimental conditions.Les hydrates gazeux font partis de la catégorie des complexes d’inclusion. Ce type de molécule se forme lorsque des molécules d’eau se structurent par liaisons hydrogène pour former une cage pouvant accepter une molécule «invité» d’une grandeur appropriée. Ces complexes sont thermodynamiquement stable à basse temperatures (~ 0°C) et pressions relativement élevées. Ces conditions sont reproduites dans les fonds marins. Ceux-ci abritent une énorme quantité d’hydrates gazeux, ce qui en fait la plus grande source d’hydrocarbures sur terre. Les hydrates gazeux sont également étudiés parce qu’ils se forment dans les conduits transportant du gaz ou du pétrole causant plusieurs problèmes. Une série d’expériences a été réalisée afin de déterminer l’efficacité de VP/VC à ralentir la croissance d’hydrates par rapport à une solution d’eau déionisée. La cinétique de formation d’une pellicule d’hydrate a été comparée en utilisant deux méthodes d’analyse: la microscopie et la consommation de gaz par le système. Les pressions and températures examinées pour chaque solution variaient respectivement entre 5000-7000kPa et 274-276K. La consommation de gaz et la hauteur du film étaient suivies tout au long de l’expérience. Il a été remarqué que la période de croissance du film d’hydrates mesurée par microscopie pouvait être séparée en deux phases distinctes: la croissance initiale et la deuxième croissance. La vitesse de croissance initiale mesurée était significativement supérieure à celle de la deuxième croissance (3 à 300 fois supérieure). La saturation de la phase liquide est suspectée d’influencer les valeurs de vitesse de croissance initiale ainsi que la hauteur initiale du film. La vitesse croissance initiale mesurée avec VP/VC était plus élevée qu’en présence d’eau déionisée à 1 et 2°C. Les résultats à 3°C montraient une tendance inverse. Les estimations d
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Tartibu, Lagouge K. "A multi-objective optimisation approach for small-scale standing wave thermoacoustic coolers design." Thesis, Cape Peninsula University of Technology, 2014. http://hdl.handle.net/20.500.11838/1307.
Full textAbstract:
Thesis submitted in fulfilment of the requirements for the degree
Doctor of Technology: Mechanical Engineering
in the Faculty of Engineering
at the Cape Peninsula University of Technology
2014Thermoacoustic heat engines provide a practical solution to the problem of heat management where heat can be pumped or spot cooling can be induced. This is new among emerging technology with a strong potential towards the development of sustainable and renewable energy systems by utilising solar energy or wasted heat. The most inhibiting characteristic of current thermoacoustic cooling devices is the lack of efficiency. Although simple to fabricate, the designing of thermoacoustic coolers involves significant technical challenges. The stack has been identified as the heart of the device where the heat transfer takes place. Improving its performance will make thermoacoustic technology more attractive. Existing efforts have not taken thermal losses to the surroundings into account in the derivation of the models. Although thermal losses can be neglected for large-scale applications, these losses need to be adequately covered for small-scale applications. This work explores the use of a multi-objective optimisation approach to model and to optimise the performance of a simple thermoacoustic engine. This study aims to optimise its geometrical parameters—namely the stack length, the stack height, the stack position, the number of channels and the plate spacing—involved in designing thermoacoustic engines. System parameters and constraints that capture the underlying thermoacoustic dynamics have been used to define the models. Acoustic work, viscous loss, conductive heat loss, convective heat loss and radiative heat loss have been used to measure the performance of the thermoacoustic engine. The optimisation task is formulated as a five-criterion mixed-integer nonlinear programming problem. Since we optimise multiple objectives simultaneously, each objective component has been given a weighting factor to provide appropriate user-defined emphasis. A practical example is provided to illustrate the approach. We have determined a design statement of a stack describing how the design would change if emphasis is placed on one objective in particular. We also considered optimisation of multiple objective components simultaneously and identified global optimal solutions describing the stack geometry using the augmented ε-constraint method. This approach has been implemented in GAMS (General Algebraic Modelling System). In addition, this work develops a novel mathematical programming model to optimise the performance of a simple thermoacoustic refrigerator. This study aims to optimise its geometrical parameters—namely the stack position, the stack length, the blockage ratio and the plate spacing—involved in designing thermoacoustic refrigerators. System parameters and constraints that capture the underlying thermoacoustic dynamics have been used to define the models. The cooling load, the coefficient of performance and the acoustic power loss have been used to measure the performance of the device. The optimisation task is formulated as a three-criterion nonlinear programming problem with discontinuous derivatives (DNLPs). Since we optimise multiple objectives simultaneously, each objective component has been given a weighting factor to provide appropriate user-defined emphasis. A practical example is provided to illustrate the approach. We have determined a design statement of a stack describing how the geometrical parameters described would change if emphasis is placed on one objective in particular. We also considered optimisation of multiple objective components simultaneously and identified global optimal solutions describing the stack geometry using a lexicographic multi-objective optimisation scheme. The unique feature of the present mathematical programming approach is to compute the stack geometrical parameters describing thermoacoustic refrigerators for maximum cooling or maximum coefficient of performance. The present study highlights the importance of thermal losses in the modelling of small-scale thermoacoustic engines using a multi-objective approach. The proposed modelling approach for thermoacoustic engines provides a fast estimate of the geometry and position of the stack for maximum performance of the device. The use of a lexicographic method introduced in this study improves the modelling and the computation of optimal solutions and avoids subjectivity in aggregation of weight to objective functions in the formulation of mathematical models. The unique characteristic of this research is the computing of all efficient non dominated Pareto optimal solutions allowing the decision maker to select the most efficient solution. The present research experimentally examines the influence of the stack geometry and position on the performance of thermoacoustic engines and thermoacoustic refrigerators. Thirty-six different cordierite honeycomb ceramic stacks are studied in this research. The influence of the geometry and the stack position has been investigated. The temperature difference across the stack and radiated sound pressure level at steady state are considered indicators of the performance of the devices. The general trends of the proposed mathematical programming approach results show satisfactory agreement with the experiment. One important aspect revealed by this study is that geometrical parameters are interdependent and can be treated as such when optimising the device to achieve its highest performance. The outcome of this research has direct application in the search for efficient stack configurations of small-scale thermoacoustic devices for electronics cooling.
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Yanik, Erim. "Magnetic Field and Heat Transfer Analysis of Magnetic Refrigeration Systems with Different Magnet Array Geometries." Thesis, Southern Illinois University at Edwardsville, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10808213.
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Magnetic refrigeration is one of the alternative cooling technologies that is environmental friendly and has high theoretical coefficient of performance values. This thesis study focuses on magnetic field and heat transfer enhancement of a reciprocating-type magnetic refrigeration system. A set of NdFeB 52 MGOe permanent magnets were employed to form a Halbach magnet array. Gadolinium (Gd) was used as the magnetocaloric material. It was placed concentrically within the Halbach array aperture with the working fluid running through the gap in between the magnet assembly and Gd yielding annular flow. Three different annular flow geometries namely; circular, octagonal and hexagonal cross-sections were studied. Magnetization process was analyzed theoretically, numerically and experimentally for k = 4 configuration. Numerical analysis was done by Finite Element Method Magnetics (FEMM), theoretical analysis was conducted by a mathematical model, and experimental analysis was performed on a Halbach magnet array. Obtained magnetic field results were used to calculate corresponding entropy changes and heat flux values. These values were compared to numerical heat transfer results from ANSYS and a close agreement between results were observed.
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Tapia, Carlos F. "Second law and thermoeconomic aspects of heat exchanger design /." The Ohio State University, 1986. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487267546984182.
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Eraydin, Hakan. "Nucleate pool boiling performance of small High Flux and Turbo-B tube bundles in R-114/oil mixtures." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA241936.
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Thesis (M.S. in Mechanical Engineering)--Naval Postgraduate School, December 1990.Thesis Advisor(s): Marto, Paul J. ; Memory, Steve. "December 1990." Description based on title screen as viewed on March 30, 2010. DTIC Identifier(s): Pool Boiling. Author(s) subject terms: Heat Transfer, Pool Boiling. Includes bibliographical references (p. 102-104). Also available in print.
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Hau, Jorge Luis. "Toward environmentally conscious process systems engineering via joint thermodynamic accounting of industrial and ecological systems." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1117650243.
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Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xxii, 306 p.; also includes graphics. Includes bibliographical references (p. 290-306). Available online via OhioLINK's ETD Center
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Podlesny, John Christopher 1962. "The thermodynamics and kinetics of phase separation in the lead borate glass system." Thesis, The University of Arizona, 1992. http://hdl.handle.net/10150/278088.
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Phase separation in glass systems has been studied since the turn of the century, and has developed commercial interest with the VYCOR process and recent interest in glass-ceramics. Phase separation has been studied in the lead borate glass system because it is known to separate across a fairly wide compositional range, and has been shown to undergo both stable and metastable phase separation. To further understand immiscibility in the lead borate system, an investigation has been performed to determine the immiscibility gap under nearly equilibrium conditions. Small-angle x-ray scattering (SAXS) has also been used in an attempt to characterize the kinetics of phase separation of a high-lead composition in the metastable region, using novel sample preparation methods.
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Golmohammadi, Mojdeh. "Theory and simulation of thermodynamics and flow induced order in carbonaceous mesophase binary mixtures." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97066.
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Carbonaceous mesophases (CMs) obtained from petroleum pitches and naphthalene precursors are mixtures of discotic nematic liquid crystals (DNLCs) employed to produce high performance carbon fibers (CFs). Natural pitches are usually polydisperse while synthetic ones are currently produced with very narrow molecular weight distributions.To design and control the final structure and mechanical properties of CFs three key parameters have to be considered: (i) characteristics of the raw material including the molecular weight, molecular interactions and the concentration of each species, (ii) the processing temperature and (iii) the extensional flow applied in the fiber spinning process. Experimental synthesis, processing, and characterization of CM materials are expensive due to the required equipment and operating conditions. Hence the computational modeling methodology adopted in this thesis is a cost effective tool for these novel materials. This thesis uses theory, mathematical modeling and computational simulations to characterize the effect of three above mentioned major factors on the orientational and molecular ordering behavior of a mixture of two monodisperse DNLCs, of relevance to the manufacturing of high performance CFs.The statistical mechanics Maier-Saupe model which effectively predicts the molecular ordering behavior of pure discotic systems is first extended to binary mixtures and then further extended to incorporate uniaxial extensional flow effects. Thermodynamic and thermo-rheological phase diagrams of binary lyotropic/thermotropic CM mixtures are predicted by this theory and partially validated by previous theoretical results and experimental observations. The generic thermo-rheological phase diagram which specifies the orientational structure of each component and their degree of molecular orientation under extensional spinning flow is obtained. X-ray diffraction intensity and orientational specific heat are also simulated in the present thesis, verified by available data and used as characterization tools for the orientation behavior of CM mixtures. In summary the thesis provides a new practical route for targeted structure-property relations for high performance CFs, through the chemistry and composition of the precursors, thus extending the traditional routes based on modifications of operating conditions and process geometry. At the fundamental level, the thesis presents the first dynamical model for DNLC mixtures. The models and results of the thesis are also applicable to rod-like systems under biaxial extensional flow, and DNLC under magnetic and electric fields.Les mésophases de carbone (CMs) obtenu à partir de précurseurs de bitume et de naphtalène sont des mélanges de cristaux liquides nématiques discotiques (DNLCs) utilisés pour produire les fibres de carbone (CF) à hautes performances. Le bitume naturel est généralement polydispersé tandis que celui qui est synthétique est présentement produit avec des distributions étroites du poids moléculaires.Afin de concevoir et de contrôler la structure finale et les propriétés mécaniques des CFs, trois paramètres importants doivent être pris en compte: (i) les caractéristiques de la matière première dont le poids moléculaire et les interactions moléculaires (ii) la température du processus et (iii) l'écoulement extensionnel appliqué dans le processus de filage de la fibre. La synthèse expérimentale, le traitement et la caractérisation des matériaux CM sont chers en raison de l'équipement et des conditions d'opérations requises. C'est pourquoi la méthode de modélisation numérique adoptée dans cette thèse est un outil rentable pour l'étude ces nouveaux matériaux.Cette thèse s'appuie sur la théorie, la modélisation mathématique et des simulations numériques pour caractériser l'effet de chacun des trois facteurs principaux, mentionnés ci-dessus, sur le comportement et l'orientation moléculaires d'un mélange de deux DNLCs monodispersés, relevant pour la fabrication de CFs à hautes performances.Le modèle de mécanique statistique de Maier-Saupe qui prédit efficacement l'arrangement moléculaire des systèmes discotiques purs est d'abord étendu aux mélanges binaires puis étendu afin d'incorporer les effets d'écoulement extensionnel uniaxiaux. Les diagrammes de phases de thermodynamique et de thermo-rhéologie des mélanges binaires de CM lyotrope / thermotrope prédis par cette théorie et partialement validée par les résultats théoriques et les observations expérimentales précédentes. Le diagramme de phase de thermo-rhéologie générique qui spécifie la structure d'orientation de chaque composant et leur degré d'orientation moléculaire sous extension est obtenu. L'intensité de la diffraction à rayon X ainsi que la chaleur spécifique orientée sont également simulées dans la présente thèse, vérifié par les données disponibles et utilisés comme outils de caractérisation du comportement d'orientation des mélanges de CM. En résumé, la thèse propose une nouvelle démarche pratique pour les relations ciblées propriété-structure pour les CFs à haute performance, grâce à la chimie et la composition des précurseurs, ainsi étendant les démarches traditionnelles basées sur des modifications de conditions d'exploitation et de la géométrie des processus. Au niveau fondamental, la thèse présente le premier modèle dynamique pour les mélanges DNLC. Les modèles et les résultats de cette thèse sont aussi applicables aux systèmes allongés sous écoulements extensionnel biaxial et sous l'effet de champs électriques et magnétiques.
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Patrawala, Kaushik Tanvir. "An examination of possible reversible combustion at high temperatures and pressures for a reciprocating engine." [College Station, Tex. : Texas A&M University, 2007. http://hdl.handle.net/1969.1/ETD-TAMU-1351.
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Medina, Carlos A. "Evaluation of straight and swept ramp obstacles on enhancing deflagration-to-detonation transition in pulse detonation engines." Thesis, Monterey, Calif. : Naval Postgraduate School, 2006. http://bosun.nps.edu/uhtbin/hyperion.exe/06Dec%5FMedina.pdf.
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Thesis (M.S. in Astronautical Engineering)--Naval Postgraduate School, December 2006.Thesis Advisor(s): Christopher M. Brophy. "December 2006." Includes bibliographical references (p. 107-108). Also available in print.
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Mangwiro, John Knox. "Thermodynamics and kinetics of aresenic and antimony removal from copper by sodium based slags." Thesis, Imperial College London, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266428.
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Desch, Rebecca J. "Thermodynamics and Mass Transport of Biomolecule Adsorption onto Chromatographic Media." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1382372858.
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Tanupabrungsun, Tanaporn. "Thermodynamics and Kinetics of Carbon Dioxide Corrosion of Mild Steel at Elevated Temperatures." Ohio University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1355328679.
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Brits, Johannes Hendrik Wilhelmus Machiel. "Study on the thermodynamics and kinetics of the stripping of palladium from a typical palladium organic." Master's thesis, University of Cape Town, 2005. http://hdl.handle.net/11427/11784.
Full textAbstract:
Includes bibliographical references.The aim of this thesis was to investigate the thermodynamics and the kinetics of the stripping of palladium from a typical palladium organic. The thesis firstly characterizes the thermodynamic effects of temperature and strip acid normality on the stripping of palladium and secondly investigates the kinetics of the palladium stripping reaction by exploring the effect of impeller speed and type on the overall volumetric mass transfer coefficient. which was the major focus of this thesis.
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Abdellahi, Aziz 1984. "Ab initio thermodynamics of phase-separating and cation-disordered cathodes for Li-ion batteries." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/103270.
Full textAbstract:
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2016.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 145-153).
In order to accelerate the electrification of the automotive fleet, the energy density and power density limitations of commercial Li-ion battery cathodes (layered LiMO2) must be overcome. In this thesis, we use ab initio methods to gain critical insights on two important classes of alternative Li-ion battery cathodes, namely high-capacity Li-excess cation-disordered rocksalts and high-rate LiFePO4 In the first part of this thesis (Chapters 3 and 4), we provide the first voltage-based design rules for high-capacity cation-disordered rocksalts. We demonstrate that, depending on the transition metal species, cation disorder can increase or decrease the average voltage of lithium transition metal oxides, and hence increase or decrease the total energy density of these compounds In particular, the disordered Ni3+/4+ voltage is found to be high (~4.4V), value at which it is likely to be preceded by oxygen activity. We further investigate the effect of cation-disorder on the voltage slope of lithium transition metal oxides, which controls the total capacity accessible below the stability limit of the electrolyte. We demonstrate that cation-disorder increases the voltage slope by increasing the Li site energy distribution and by enabling Li occupation of high-voltage tetrahedral sites. We further demonstrate that the voltage slope increase upon disorder is smaller for high-voltage transition metals, and that short-range ordering and Liexcess contribute in reducing the inaccessible capacity at high voltage upon disorder. In the second part of this thesis (Chapter 5), we resolve the apparent paradox between the high Li diffusivity in phase-separating LiFePO 4 and the persistence of thermodynamically unstable solid-solution states during (dis)charge at low to moderate C-rates. We demonstrate that, even under rate conditions such that relaxation to a two-phase state is kinetically possible, the thermodynamically favorable state in a single particle is not a sharp interface but rather a diffuse interface with an intermediate solid-solution region that occupies a significant fraction of the particle volume. Our results not only explain the persistence of solid-solution regions at low to moderate C-rates in nano-LiFePO4, but also explain the observations of stable intermediate solid-solution states at an ac interface in particles quenched from a solid solution.
by Aziz Abdellahi.
Ph. D.
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Kim, Yong-ju. "Phase behavior of disk-coil molecules : from bulk thermodynamics to blends with block copolymers." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/81059.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 159-164).
In this thesis, we explore the phase behavior of discotic molecules in various circumstances. We first study the thermodynamics of disk-coil molecules. The system shows rich phase behavior as a function of the relative attractive strength of coils ([lambda]), the stacking interaction strength of disks ([mu]), the number of coarse-grained monomers of the coil (Nc), and the reduced temperature (T*). At high T*, a disordered phase is dominant. At intermediate T*, lamellar, perforated lamellar, and cylinder phases appear as y and Nc are increased. At low T*, disks crystallize into ordered lamellar, ordered perforated lamellar, and ordered cylinder phases. We find that the confinement imposed on the disks by the attached coils strongly contributes to the ordered stacking of the disks. In particular, the ordered cylinder phase contains highly ordered disks stacked in parallel due to the cylindrical confinement of the coils that restricts the system to a single degree of freedom associated with the director vector of the disks. Our results are important for understanding the self-assembly of supramolecular structures of disk-coil molecules that are ubiquitous in nature, such as chlorophyll molecules. Having established the importance of confinement on the phase behavior of discotic molecules, we next study blends of discotic molecules and block copolymers (BCPs) using self-consistent field theoretic simulations. In particular we explore systems containing a single sphere, rod, or discotic molecule confined within a BCP defect and systems containing multiple discotic molecules confined within BCP cylinders. In the former case, the sphere, rod, and discotic molecules are all trapped in the defect center where the cylinders of the surrounding BCPs make a junction. The director vector of the rod molecule aligns with the axial direction of one of the cylinders, while the director vector of the discotic molecule aligns perpendicular to the axes of all the cylinders. This preferential orientation is induced by the minimized stretching energy of the BCPs for these configurations. For the system with multiple discotic molecules confined within the BCP cylinders, all director vectors are aligned with the axial direction of the cylinder when the density of disks is high to minimize both the stretching energy of the BCPs and the polymer-mediated potential between the disks. These results provide design principles for next generation optoelectronic devices based on blends of discotic molecules and BCPs.
by YongJoo Kim.
Ph.D.
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Abdel-Qader, Zainab. "The role of liquid mixing in evaporation of complex multi-component mixtures, modelling using continuous thermodynamics." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0017/MQ58435.pdf.
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Alexandridis, Paschalis. "Thermodynamics and dynamics of micellization and micelle-solute interactions in block-copolymer and reverse micellar systems." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/37749.
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Cordeiro, Helio de Miranda. "Stochastic dynamical system identification applied to combustor stability margin assessment." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/28167.
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Thesis (M. S.)--Aerospace Engineering, Georgia Institute of Technology, 2009.Committee Chair: Zinn, Ben; Committee Member: Ferri, Aldo; Committee Member: Lieuwen, Timothy; Committee Member: Prasad, J. V. R.; Committee Member: Ruzzene, Massimo.
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Garbulsky, Gerardo Damián. "Ground-state structure and vibrational free energy in first-principles models of subsitutional-alloy thermodynamics." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10911.
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