Dissertations / Theses on the topic 'Thermodynamic behaviors'
To see the other types of publications on this topic, follow the link: Thermodynamic behaviors.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Thermodynamic behaviors.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Zhao, Yiqiang. "Thermodynamic and Dynamic Behaviors of Self-Organizing Polymeric Systems." Case Western Reserve University School of Graduate Studies / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=case1094190642.
Full text
2
Sabatini, Benjamin J. "Chemical composition, thermodynamics, and recycling : the beginnings of predictive behavioral modeling for ancient copper-based systems." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:91a4426b-8232-4f85-a39b-69e6c01c327c.
Full textAbstract:
In their attempts to understand the unwritten past of human technology and progression, archaeologists have borrowed aspects of the natural sciences to answer big questions. In one such pursuit, fundamental aspects of the sciences have been employed towards the chemical compositional analysis of copper-based artifacts, often to simply classify which is bronze, brass, or pure copper, and to explain why they are significant in limited space and time. This thesis takes the variety of identified metal types and compositions from these analyses and builds the beginnings of an ambitious thermodynamic model based on the accepted premise of consistent and widespread recycling of ancient metals over time. Following the laws of thermodynamics, in systems at equilibrium, the model predicts the outcome of metal losses over the course of ancient pyrometallurgical processes from molten systems through both volatilization and oxidation using rigorous and established mathematics and theory. Elemental loss likelihoods are modeled for all binary copper-based metals, using activity coefficients, and ternary copper and zinc-based systems, with the excess Gibbs free energy, respectively. The calculations are performed using custom-written software designed to account for hundreds of thousands of compositional permutations after the method described by Redlich and Kister (1948). The results of these calculations are given as activity (binary) and isoactivity (ternary) contour lines. Quantified tables for the oxidation and volatilization of elements from a copper melt at 1200 ºC and 1 atm are also given as rough indicators of element loss in ancient pyrometallurgical systems. A proof of concept of the models viability is also provided for binary Cu-M and ternary Cu-M-Zn (M = Ag, As, Au, Bi, Co, Fe, Ni, Pb, Sb, Sn, Zn), Cu-Sn-Pb, and Cu-Sb-As systems from the Late Bronze Age to post-medieval periods in Britain, which is based on several substantial artifact chemical datasets. For each ternary system, the interaction parameters used for higher-order calculations from the fitted behavior of each contributing binary systems are provided. Comparison of the calculated models to available experimental system assessments, and to published archaeological chemical datasets, show that in both respects the proposed modeling of ancient copper-based metal losses works. And given the near ubiquity of ancient metal use around the world, the consistency in metal production and recycling technology, and the chemical analyses available, this preliminary model can be applied virtually anywhere the technology for smelting and recycling existed. In addition to loss modeling, this thesis has the additional offshoots of predicting ancient furnace conditions based on the calculated behavior of interacting metals, and of the controlling thermodynamic factors in the ancient calamine process.
3
Lee, Won Peter. "The thermodynamic behavior of magnetite in non-ferrous smelting." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0022/NQ50091.pdf.
Full text
4
Goulko, Olga. "Thermodynamic and hydrodynamic behaviour of interacting Fermi gases." Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/241497.
Full textAbstract:
Fermionic matter is ubiquitous in nature, from the electrons in metals and semiconductors or the neutrons in the inner crust of neutron stars, to gases of fermionic atoms, like 40K or 6Li that can be created and studied under laboratory conditions. It is especially interesting to study these systems at very low temperatures, where we enter the world of quantum mechanical phenomena. Due to the Fermi-Dirac statistics, a dilute system of spin-polarised fermions exhibits no interactions and can be viewed as an ideal Fermi gas. However, interactions play a crucial role for fermions of several spin species. This thesis addresses several questions concerning interacting Fermi gases, in particular the transition between the normal and the superfluid phase and dynamical properties at higher temperatures. First we will look at the unitary Fermi gas: a two-component system of fermions interacting with divergent scattering length. This system is particularly interesting as it exhibits universal behaviour. Due to the strong interactions perturbation theory is inapplicable and no exact theoretical description is available. I will describe the Determinant Diagrammatic Monte Carlo algorithm with which the unitary Fermi gas can be studied from first principles. This algorithm fails in the presence of a spin imbalance (unequal number of particles in the two components) due to a sign problem. I will show how to apply reweighting techniques to generalise the algorithm to the imbalanced case, and present results for the critical temperature and other thermodynamic observables at the critical point, namely the chemical potential, the energy per particle and the contact density. These are the first numerical results for the imbalanced unitary Fermi gas at finite temperature. I will also show how temperatures beyond the critical point can be accessed and present results for the equation of state and the temperature dependence of the contact density. At sufficiently high temperatures a semiclassical description captures all relevant physical features of the system. The dynamics of an interacting Fermi gas can then be studied via a numerical simulation of the Boltzmann equation. I will describe such a numerical setup and apply it to study the collision of two spin-polarised fermionic clouds. When the two components are separated in an elongated harmonic trap and then released, they collide and for sufficiently strong interactions can bounce off each other several times. I will discuss the different types of the qualitative behaviour, show how they can be interpreted in terms of the equilibrium properties of the system, and explain how they relate to the coupling between different excitation modes. I will also demonstrate how transport coefficients, for instance the spin drag, can be extracted from the numerical data.
5
Lu, Xia. "Nonequilibrium thermodynamic models for the dynamic behavior of polycrystalline solids." Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/12549.
Full text
6
Iyer, Jaisree (Jaisree Kannan). "Modeling the micellization behavior of fluorosurfactants using molecular-thermodynamic theory." Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/81750.
Full textAbstract:
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering, 2013.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 (p. 267-281).
Fluorinated surfactants are an important class of surfactants because they possess properties that are far superior than those of their hydrocarbon analogs. As a result, they are used in a wide variety of applications including in paints, polishes, fire-fighting foams, and emulsion polymerization processes. However, concerns regarding the non-biodegradability and toxicity of fluorinated surfactants have prompted the search for new, benign alternative surfactant formulations that possess micellization properties comparable to those of traditional fluorinated surfactants. With this need in mind, this thesis focuses on gaining a molecular-level understanding of the micellization behavior of traditional fluorinated surfactants, and then using the acquired knowledge to design novel surfactant formulations that can reduce the use of fluorinated surfactants. Molecular-thermodynamic (MT) models were developed to calculate the various contributions to the free energy of micellization for discoidal and biaxial ellipsoidal micelles; two important micelle shapes in the context of fluorocarbon-based surfactants. These models explicitly incorporate the effect of the position-dependent curvature associated with discs and biaxial ellipsoids. Comparison between the models developed here with those that do not explicitly account for the varying curvature shows that accounting for the position-dependent curvature is extremely important in modeling these two micelle shapes. The new MT model for the free energy of micellization is also used to demonstrate the feasibility of realizing biaxial ellipsoidal micelles, a result refuted in the past in many theoretical studies on the basis of average geometrical properties of the micelle. A new computer-simulation-molecular-thermodynamic (CSMT) framework was developed to predict the micellization behavior of mixtures of fluorocarbon-based surfactants. To facilitate the practical implementation of the mixture CSMT framework, which involves the computationally intensive task of simulating several mixed micelles, an approximation to the mixture CSMT model was developed. In this approximation, relevant properties for a mixed micelle are estimated using a micelle-composition based weighted average of the analogous properties obtained from simulations of the single-component surfactant micelles for each of the surfactants comprising the mixture. Therefore, in this approximation, the need for simulating mixed micelles is eliminated. The approximation was found to compare well with the mixture CSMT model for various binary surfactant mixtures considered, except for those containing alkyl ethoxylate surfactants. A rationalization of this finding is presented. CMC predictions made using the mixture CSMT model were found to compare very well with the experimental CMCs for several binary mixtures of linear surfactants, thereby laying the foundation for using the CSMT model to predict micellization properties of mixtures of surfactants that have a more complex chemical architecture. Finally, an MT framework was also developed to predict the micellization properties of mixtures of fluorocarbon-based and hydrocarbon-based surfactants. This mixing reduces the use of fluorinated surfactants in the surfactant formulation, thereby addressing the non-biodegradability and toxicity concerns associated with fluorinated surfactants. An enthalpy of mixing contribution resulting from the interactions between the fluorocarbon tails and the hydrocarbon tails, estimated using the Regular Solution Theory, was included in the MT framework. The ability of the MT framework to predict the coexistence of two types of mixed micelles in solution was demonstrated. The MT framework predictions of micelle population distributions, CMCs, and optimal micelle compositions were compared with the experimental values for various mixtures of fluorocarbon-based and hydrocarbon-based surfactants. The models developed in this thesis provide a molecular level understanding of the micellization behavior of fluorocarbon-based surfactants and their mixtures. The models are able to predict several important micellization properties of surfactants and their mixtures that can guide surfactant formulators in the synthesis, characterization, design, and optimization of surfactant formulations that exhibit desirable properties.
by Jaisree Iyer.
Ph.D.
7
Zhong, Tingjun. "The thermodynamic behaviour and miscibility of discotic liquid crystals." Thesis, University of York, 2015. http://etheses.whiterose.ac.uk/11833/.
Full textAbstract:
This thesis is concerned with the self-organization of molecules that have disc-like shapes. The disc-like molecules may have relatively rigid structures as in polyaromatic systems, or they may have amphiphilic structures with polyaromatics at their cores, and soft outer shells made up of aliphatic chains. This research seeks to explore molecular compatibility and the ensuing structures formed by such disc- like systems through the study of phase diagrams. Thus, the thermodynamic behaviour and miscibilities of discotic liquid crystal materials were investigated by the formation of Gibbs phase diagrams and calculations using the Schröder-van Laar equation for liquid crystals that have structural common features. Polyaromatics were reviewed and investigated as they are hard discs, and are as the central cores of the molecules that form discotic liquid crystals. Existing discotic materials, such as triphenylene hexa-esters, phenyl hexa-esters, phenyl hexa-alkynes, and rod-like compounds such as benzoate esters were studied and analysed using polarized optical microscopy (POM), differential scanning calorimetry (DSC), and X-ray diffraction where appropriate, for the preparations of mixture studies. Mixture series made by triphenylene derivatives with each other, and with rod-like molecules or star-shape molecules were prepared and examined in order to investigate the potential co-miscibilities for both discotic nematic phase and hexagonal columnar phases. Mixture series made by triphenylene derivatives with polyaromatics were also prepared, and examined by POM and DSC to explore the virtual N-I phase transition temperatures for polyaromatics. These studies appear to show that nematic discotic materials are liquid crystals, whereas columnar materials exhibit 2D crystallinic soft solid phases. In addition, a novel new phase was found to form in the isotropic liquid of mixtures of polyaromatic materials, suggesting the possibility of the cubatic nematic phase being present.
8
Neal, Colleen M. "Probing the thermodynamic behavior of metal cluster ions by mass spectrometry." [Bloomington, Ind.] : Indiana University, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3297103.
Full textAbstract:
Thesis (Ph. D.)--Indiana University, Chemistry Dept., 2007.Title from dissertation home page (viewed Sept. 29, 2008). Source: Dissertation Abstracts International, Volume: 69-02, Section: B, page: 0988. Adviser: Martin F. Jarrold.
9
Draucker, Laura Christine. "Novel Solvent Systems for the Development of Sustainable Technology." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16188.
Full textAbstract:
Sustainable development in chemical engineering offers technical, industrially relevant solutions to environmental and economic issues. This work focuses on three specific issues; improving solvent selection and reducing costly experimentation, improving catalyst recovery while reducing reaction time, and producing commercial viable biofuels by cost effective pretreatments and valuable side product extractions.
Novel solvent systems are a sustainable solution because they provide the ability to replace costly solvents with cheap, benign, and recyclable systems. Specifically, this work investigated the use of one novel solvent system, Gas Expanded Liquids (GXL).When a solvent is exposed to a gas in which it is miscible at modest pressures and temperatures, the liquid solvent becomes expanded, providing a unique tunable and reversible solvent with properties that can be much different then that of the solvent itself. If you apply this gas to a mixture of two liquids of a solid dissolved in a liquid phase, it can often provide a miscibility switch, aiding in separation, crystallization, and
recovery of products or catalysts. In this work several different applications for organic
solvents expanded with carbon dioxide were studied including miscibility switches for
catalyst recycle, pretreatment of biomass for improved bio-ethanol production, and
extraction of valuable chemicals from lignin waste in the pulp and paper industry. Solid
solubility models to improve solvent selection and predict unique solvent mixtures during
crystallization were also studied. The results reported here show promise for the use of
GXL novel solvent systems and solid solubility models in many sustainable applications.
10
Assis, Andre N. "The Phosphorus Reaction in Oxygen Steelmaking: Thermodynamic Equilibrium and Metal Droplet Behavior." Research Showcase @ CMU, 2014. http://repository.cmu.edu/dissertations/464.
Full textAbstract:
Low phosphorus content steels are essential for steel applications where high ductility is required, such as thin sheets, deep drawn, pipelines and automobile exteriors. In the past, phosphorus control was not considered a big challenge in steel production in the US because iron ores with low phosphorus contents were readily available and considered cheap. However, in the last decade, the iron ore price has risen by roughly 400% and lower cost iron sources generally have higher phosphorus content. In integrated steel plants, phosphorus removal usually takes place during the oxygen steelmaking process (OSM) but in Japan a intermediate step for hot metal dephosphorization is commonly used. There are various types of OSM furnaces but the most widely used remains the top-blown Basic Oxygen Furnace (BOF). The BOF slag can be recycled to a sinter plant or directly to the blast furnace, ultimately increasing the phosphorus input in the process. In order to meet new demands for phosphorus control, it is necessary to improve our understanding on the thermodynamics and kinetics of the phosphorus partitioning reaction between slag and metal melts during steelmaking. Therefore, the present work has been divided in three strongly correlated sections: phosphorus equilibrium between metal and slag; analysis of plant data; and observations of the reaction kinetics. Phosphorus equilibrium between liquid metal and slag has been extensively studied since the 1940's. It is well known that CaO and FeO are the main slag constituents that help promote dephosphorization. On the other hand, dephosphorization decreases with temperature due to the endothermic nature of the reaction. Many correlations have been developed to predict the phosphorus partition ratio as a function of metal and slag composition as well as temperature. Nevertheless, there are still disagreements in the laboratory data and the equilibrium phosphorus partition can be predicted with an uncertainty of a factor of up to 5. The first part of the present work focuses on generating more reliable equilibrium data for BOF-type slags by approaching equilibrium from both sides of the reaction. The experimental results were combined with two other sets of data from different authors to produce a new correlation that includes the effect of SiO2 on the phosphorus partition coefficient, LP . Although the quantification of phosphorus equilibrium is extremely important, most industrial furnaces do not operate at equilibrium, usually due to liquid slag formation, kinetics and time constraints. Thus, it is important to know how close to equilibrium different furnaces operate in order to suggest optimal slag compositions to promote dephosphorization. The present work analyzed four large sets of data containing the chemical compositions of both slag and metal phase as well as the tapping temperature of each heat. Each set of data corresponded to different furnaces: one AOD (Argon Oxygen Decarburization), two top-blown BOFs and one Q-BOP or OBM. It was found that the bulk slag composition can greatly \mask" the data due to solid phases coexisting with the liquid slag. The author used the software package FactSage to estimate the amount of solids in the slag and liquid slag composition. It was found that the AOD is the reactor closest to equilibrium, followed by the Q-BOP (OBM) and the two top-blown BOFs. It was noted that the stirring conditions and slag composition are two key variables to enable optimum phosphorus removal. Also, over saturating the slag with CaO and MgO does not seem to benefit the process to any extent. Lastly, interesting observations on the behavior of small metal droplets reacting with slag are presented and discussed. It was found that dynamic interfacial phenomena at the metal-slag interface is likely to play a significant role in the kinetic behavior of the system, due to the exchange of surface active elements, such as oxygen, which dramatically lowers the interfacial tension and cause spontaneous emulsification. Although this phenomenon has been studied, actual quantification of changes in interfacial area remain a challenge. The author developed an experimental method to enable better quantification of spontaneous emulsification and two sets of experiments were carried. One with an Fe containing 0.2 wt.% P and another in a P-free system where pure iron was oxidized. It was found that phosphorus did not play a role in spontaneous emulsification and it was rapidly removed before the onset of dynamic interfacial phenomena. Emulsificaion was maybe caused by de-oxidation of the metal after phosphorus removal took place and the metal became super saturated with oxygen by an unknown reason. The estimated surface area rapidly increases by over an order of magnitude during the beginning and intermediate periods of the reaction. The metal drop breaks into hundreds of small droplets, effectively emulsifying the metal into the slag. With time, the surface area decreases and the metal droplets coalesce. Similar results were observed for an Fe droplet being oxidized. Spontaneous emulsification takes place regardless of the direction of oxygen transfer and the changes in surface area are similar for both cases. The last chapter describes the industrial relevance of the present work, summarizes the findings, revisits the hypotheses and presents potential future work where further research is encouraged.
11
Lee, Katherine Ann. "The thermodynamic and phase behaviour of catalysed reactions in supercritical fluids." Thesis, University of Leeds, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.400173.
Full text
12
Reid, Joshua Elias Samuel James. "Molecular thermodynamics and solvation behaviour of protic ionic liquid systems." Thesis, University of York, 2017. http://etheses.whiterose.ac.uk/18697/.
Full textAbstract:
Protic ionic liquids (PILs) are a class of solvents prepared from the mixing of equimolar quantities of a Brønsted acid and base resulting in both neutral and ionic species in equilibrium with one another. Their evolving application as solvents for innovative processes requires further understanding of their properties and how they originate at the molecular level. Three topics remain widely debated concerning PILs: 1) the effects of low concentrations of water as an impurity, 2) the structure–property relations in PILs and 3) the connection between PILs and their precursor components in terms of both molecular interactions and bulk properties. In this work, these three topics are studied using a variety of experimental techniques and fundamental theory for selected representative PIL systems. To clarify the effect of water at low concentrations, the statistical thermodynamic theory of solutions has been applied to quantify the interactions between species solely from thermodynamic data. Results showed both a strong composition dependence of the effect of water on the liquid structure in aprotic and protic ILs, but also that water did not significantly weaken ion–ion interactions at low concentrations. After clarifying the effects of water at low concentration on PIL behaviour, it has been shown that incorporating hydrogen bond donor functionality to the cation can increase the ionic nature of acetate PILs. This increase in ionic nature provides an excellent rationalization for the effect of cation structure on the thermodynamic and solvatochromic properties of three PILs. By studying the effect of varying composition of precursor acid and base, a deeper insight into the molecular origin of trends in bulk properties and solvation behaviour can be found. Furthermore, it has been shown that the solvation environment is highly composition dependent, offering insight into a new strategy in the application of PILs and their precursor materials as tuneable solvation media.
13
Tepesch, Patrick David. "Atomistic modeling of ceramic materials : predicting crystal structures, thermodynamic properties, and diffusion behavior." Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10936.
Full text
14
Du, Toit Adam Jacobus. "Thermodynamic behaviour of sulphur and chlorine as minor elements in metallurgical melts." Master's thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/5379.
Full textAbstract:
Includes bibliographical references (p. 137-147)This thesis is presented on the equilibrium studies that have been carried out on a series of slags, specifically chosen to cover the range of composition and conditions appropriate to the melters of the platinum group metals (PGM) producers of South Africa. New measurements have been made on the ferric to ferrous ration, sulphide capacity as well as the chloride capacity mainly for the PGM melter-type slags.
15
Tan, Geraldine. "Thermomechanical behaviour of NiTi." University of Western Australia. School of Mechanical Engineering, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0111.
Full textAbstract:
[Truncated abstract] The study of NiTi shape memory alloys, although comprehensive and diverse, still encounters numerous uncertainties and misunderstandings that often jeopardise the effective use of these alloys in various applications. One such key area is the understanding of the micromechanics and thermodynamics of the deformation mechanisms, such that their deformation behaviour can be accurately predicted and modelled. Furthermore, most research involves polycrystalline NiTi of varying compositions and processing history, both of which complicate and damage the internal structure of the matrix even before deformation. This work aims to study the micromechanisms of deformation of near-equiatomic NiTi alloys, both in polycrystalline and single crystal forms, with particular attention given to the commonly observed phenomena of Luders-like deformation behaviour and deformation induced martensite stabilisation. This work was carried out in three sections. Firstly, the tensile deformation of polycrystalline NiTi samples via martensite reorientation and stress-induced martensitic transformations was carried out. The samples were deformed to various stages of deformation and then thermally cycled to study the thermomechanical response to deformation as a means to explore the various mechanisms of deformation. Next, the deformation and post-deformation transformation behaviour of NiTi single crystals were studied to verify the effect of grain boundaries and other hypotheses raised regarding the deformation mechanisms. The single crystal samples were deformed along three low-index axial orientations. Finally, microscopic analysis was carried out on as-annealed and the deformed polycrystal and single crystal samples by means of transmission electron microscopy. The microstructural analyses accompanied the thermodynamic study and provided evidences to support various hypotheses
16
Feng, Li. "Investigation of the Relationships Between the Thermodynamic Phase Behavior and Gelation Behavior of a Series of Tripodal Trisamide Compounds." University of Akron / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=akron1342461003.
Full text
17
Logan, Kathryn Vance. "Elastic-plastic behavior of hot pressed composite titanium diboride/alumina powders produced using self-propagating high temperature synthesis." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/15853.
Full text
18
Bhinde, Tej. "Adsorption of alkyl amides : monolayer structures and mixing behaviour." Thesis, University of Cambridge, 2011. https://www.repository.cam.ac.uk/handle/1810/236781.
Full textAbstract:
In this work monolayers of alkyl amides adsorbed on a graphite surface have been successfully identified and investigated using a combination of synchrotron X-ray and neutron diffraction and Differential Scanning Calorimetry (DSC). Exceptionally stable solid layers have been observed at temperatures well above the bulk melting point, at both high multilayer coverages and, very unusually, at sub-monolayer coverages. The molecular structure of the two-dimensional crystals of these alkyl amides has been obtained from diffraction and interpreted in terms of the subtle intermolecular interactions, particularly the contribution of hydrogen bonding in monolayer assembly. Thermodynamic information provides insight on the mixing behaviour in adsorbed amide layers. A systematic study on the variation in monolayer crystal structures with alkyl chain length (between five and sixteen carbon atoms) of saturated alkyl amides using diffraction identifies that all the amide molecules investigated lie flat on the graphite surface. An odd-even variation isobserved in the monolayer crystal structures and this is supported by the melting enthalpies of the amides determined by DSC. The structure of the even members is found to support the qualitative monolayer arrangement proposed by an STM report of one member of the series, but with more quantitative insight here. Significantly, a new monolayer symmetry group for odd members of the homologous series has been identified. Characteristics of the hydrogen bond geometrybetween the molecules in the solid monolayers are reported exploiting the high level of detail available from the diffraction techniques. Secondly, the formation of solid monolayers of unsaturated alkyl amides has been reported and their crystal structures determined. This is believed to be the first report of these monolayer structures. The position and nature of the double bond have an important effect in the stability of the monolayer. Unusually, certain unsaturated amides that have a double bond conjugated with the amide group are found to form considerably more stable layers than their saturated homologues. The abnormally high melting points and enhanced stability of amide monolayers have been attributed to the existence of a network of hydrogen bonds in the layer. Phase diagrams obtained by DSC for binary mixtures of alkyl amides on graphite have been quantitatively analysed using a combination of thermodynamic models (ideal, eutectic and the regular solution models). The determined mixing behaviour is supported by conclusions based on the monolayer crystal structures of the individual components calculated using diffraction. Saturated amide mixtures that have the same plane group symmetry are found to mix non-ideally in the solid layer and phase separate if the symmetry is different, whereas the mixing behaviour of saturated/unsaturated amides considered here was found to depend on the nature of the double bond (cis/trans). Results from an initial investigation into the adsorption of alkyl amides at the polymer/air interface are also presented. This complements the study above and provides an alternative situation where amide monolayers have a central role. A reduction in the coefficient of friction is seen with increasing bulk concentration of the amide and with increasing time indicating migration of the amide to the surface. A powerful combination of surface reflection techniquesincluding neutron and X-ray reflection and ellipsometry have been used to gain uniquelyquantitative insight into this system. Initial estimates of the concentration of amides at the polystyrene surface are presented for the first time.
19
Pinna, Matteo. "Thermodynamic behaviour of gravity - attempts at a statistical derivation of the field equations." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/19487/.
Full textAbstract:
Lo scopo di questa tesi è quello di presentare una curiosa interpretazione della gravità che deriva da considerazioni statistiche ed evidenzia punti cruciali che potrebbero essere ulteriori argomenti importanti su cui poter fare ricerca scientifica. Nel tentativo di derivazione delle equazioni di
campo di Einstein attraverso un approccio statistico, fenomeni termodinamici conducono alla teoria classica della Relatività Generale, tuttavia con informazioni aggiuntive che usualmente
non compaiono quando si procede invece per la Teoria dei Campi.
Ciò nonostante, questo implica che sia necessario rivedere e accettare nuovi presupposti a livello fondamentale per quanto riguarda la natura dello spaziotempo. Tali assunzioni sono
motivate e giustificate dall'osservazione del modello statistico dal punto di vista di un sistema di riferimento privilegiato, nel momento in cui si compara il comportamento gravitazionale con la
termodinamica.
20
Robinson, Ellis Shipley. "Mixing and Phase Behavior of Organic Particles." Research Showcase @ CMU, 2014. http://repository.cmu.edu/dissertations/411.
Full textAbstract:
We have developed novel experiments aimed at understanding whether and how quickly organic aerosols (OA) mix using single-particle mass spectrometry, as different treatments of mixing in regional models significantly affect predicted mass and composition. First, we designed experiments that separate OA formation chemistry from thermodynamics to test whether two populations of particles equilibrate with eachother through the gas phase on experimental timescales. Single-particle mass spectrometry measurements from the aerosol mass spectrometer (AMS) allowed us to quantify the extent of mixing that had occurred. We calibrated this technique using pure-component aerosols with known vapor pressure and phase state, the results of which agreed with a condensation-evaporation model. We then applied these techniques to three atmospherically-relevant situations to determine that: 1) anthropogenic secondary OA (aSOA) does not mix with a surrogate for hydrophobic primary OA (POA), 2) biogenic SOA (bSOA) does not mix with hydophobic POA, and 3) bSOA shows significant mixing with aSOA. The sum of these experiments show that these complex interactions can be measured for atmospherically important systems, a first step towards quantifying activity coefficients for complex OA mixtures. We also investigated mixing within individual particles, using mixed-particles of squalane (a surrogate for hydrophobic POA) and SOA from ↵+pinene + O3 that we determined to contain two separate phases. In these experiments, after formation of the mixed-particles, we perturbed smog chamber with a heat ramp. These data revealed that squalane is able to quickly evaporate from the mixed-particles, and that almost all of the SOA is comprised of material lower in volatility than squalane (a low-volatility constituent of pump oil). For this latter “comparative volatility analysis,” we had to correct for the highly variable collection efficiency (CE) of the mixed particles to correctly calculate the mass fraction of SOA remaining. One of the larger implications of this work is highly dependent on the particle morphology, which we were not able to determine definitively: if indeed the particles are coreshell with squalane inside a thick layer of SOA, our results show that diffusivity within SOA is not ultra-low. Lastly, we present work that furthers our understanding of single-particle CE in the AMS, a quantity especially important for experiments where particle phase is dynamic or there are two separate populations of particles. We report the particle CE of SOA, ammonium sulfate, ammonium nitrate, and squalane. We also determine that half of SOA particles that give meaningful signal, do so at a time later than would be predicted based on their optically-measured flight time through the instrument. We present convincing evidence that the nature of this delay is due to particles ricocheting around the ionization region of the instrument before vaporizing on an auxillary surface near the the vaporizer. This process affects how much mass signal comes from a particle, the particle mass spectrum, and the bulk mass distribution derived from particle time-of-flight mode. Our results also show that while there is no size dependence to CE for SOA, particles that have passed through a thermodenuder have lower CE, implicating oxidation state and/or volatility as a controller of particle bounce.
21
Sundarasaradula, Doy. "A thermodynamical perspective on organisations their structure and evolution /." Access electronically, 2006. http://ro.uow.edu.au/theses/101.
Full text
22
Salah, Mohammad. "A Method to Improve the Performance of Capillary Barriers Using Heated Air Flow." Thesis, Université d'Ottawa / University of Ottawa, 2020. http://hdl.handle.net/10393/41100.
Full textAbstract:
The investigation described in this thesis is aimed at determining the effect of heated air flow on the behaviour of capillary barriers. In order to achieve the objectives of this investigation, a number of tasks were undertaken, as described hereinafter. First, a laboratory scale testing was carried out to determine the effect of heated air flow on the volumetric water content (VWC) and matric suction in a layer of soil representing the coarse grained soil layer of a capillary barrier. Several types of instruments were used to measure the VWC, matric suction, and temperature at different locations within the soil. Next, a numerical analysis was undertaken to simulate the behaviour of
the soil mass subjected to thermal changes in the laboratory experiments. Lastly, two case studies were analyzed with and without the heated air flow in the coarse grained soil layer to validate the proposed model.
The method used in this investigation was based on: (1) application of temperature change at the perimeters of the pipes installed in the coarse grained soil layer near the interface between the fine grained and coarse grained soil layers; and, (2) application of suction as a boundary condition at the perforated parts of the pipes to decrease VWC and increase matric suction in the soil mass. Using this specific method, the results of the finite element analyses of the laboratory experiments and the two case studies demonstrated that the heated air flow through the coarse grained soil layer of a capillary barrier would improve its performance as a soil cover for a number of engineering applications. Comparisons of measured and calculated values of VWC and matric suction showed good agreement providing further proof of the validity of the method.
23
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.
24
Liu, Dehua. "Thermodynamic and glass transition behavior in CO2-Polymer systems emphasizing the surface region." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1149020480.
Full text
25
Spike, M., and R. Miles. "The fundamental thermodynamic relation on contact surfaces of multicomponent nanocomposite coatings with hierarchical and adaptive behavior." Thesis, Sumy State University, 2016. http://essuir.sumdu.edu.ua/handle/123456789/47079.
Full textAbstract:
The increasing demands of modern engineering have spawned the development of new advanced materials for use. The development of advanced materials can be considered to be a typical problem of engineering optimization. In this process, an integrated engineering–physical approach is used to develop novel wear-resistant materials. Until now only a limited amount of investigations have been performed on the progression of the self-organization process during friction. Moreover studies made so far focused mostly on the characteristics of tribo-films.
26
Gernandt, Jonas. "On the phase behaviour of hydrogels : A theory of macroion-induced core/shell equilibrium." Doctoral thesis, Uppsala universitet, Institutionen för farmaci, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-188151.
Full textAbstract:
Colloidal macroions are known to interact very strongly with oppositely charged polyionic hydrogels. Sometimes this results in a non-uniform distribution of the macroions within the gel, a phenomenon that is not fully understood. This thesis is a summary of four papers on the development of a theory of the thermodynamics of macroions interacting with hydrogels, aimed at explaining the phenomenon of core/shell separation in spherical gels. It is the first theory of such interactions to use a rigorous approach to whole-gel mechanics, in which the elastic interplay between different parts of the gel is treated explicitly. The thesis shows that conventional theories of elasticity, earlier used on gels in pure solvent, can be generalised to apply also to gels in complex fluids, and that the general features of the phase behaviour are the same if mapped to corresponding system variables. It is found that the emergence of shells is due to attractions between macroions in the gel, mediated by polyions. Since the shell state is unfavourable from the perspective of the shell itself, being deformed from its preferred state, there will be a hysteresis between the uptake and the release of the macroion, like already known to occur with the uptake and release of pure solvent. Due to the elastic interplay, growth of the shell makes further growth progressively more favourable. Thus, unless there is a limited amount of macroions available the system will not reach equilibrium until complete phase transition has taken place. If the amount is limited the core/shell separation can be in equilibrium, so the volume of the solution that the gel is in contact with plays a very important part in determining the thermodynamic resting point of the system. The ability of a macroion/hydrogel to phase separate thus depends on the molecular properties whereas the ultimate fate of such a separation depends on the proportions in number between the ingoing components.
27
Benge, G. Gregory. "A comparison of thermodynamic models for the prediction of phase behavior in aqueous-polymer two-phase systems." Thesis, Virginia Polytechnic Institute and State University, 1986. http://hdl.handle.net/10919/90936.
Full textAbstract:
Aqueous-polymer two-phase systems consist of various combinations of water, polymer(s), low molecular weight component(s), and salts. These aqueous-polymer systems are comprised of two phases, each of which contains about 90 percent (by weight) water. Due to some very unique properties, these systems have been applied to separations involving biological molecules for at least a quarter of a century. In particular, these systems are inexpensive, efficient, and provide a mild (aqueous) and possibly stabilizing environment for fragile biologically-active molecules. These systems may also be designed for a high degree of selectivity. Although much effort has been expended in the area of polymer solution theory, the theory of why these systems exhibit this extraordinary two-phase behavior that characterizes them as viable liquid-liquid extraction systems for use with biologically-active molecules is not completely understood. A thermodynamic model which could accurately represent the phase equilibria exhibited by these systems would be useful for the design of systems for use in many different applications.
A potpourri of thermodynamic models and their underlying theoretical structure have been critically studied for their particular application to predicting the phase behavior of aqueouspolymer two-phase systems. In particular, the Flory-Huggins model is reviewed (with discussion of its inadequacies and subsequent modifications); the theory of Ogston; the model by Heil; several local composition models (NRTL, Wilson, and UNIQUAC); and two group-contribution models (ASOG and UNIFAC) are all discussed. The development of a solvent-electrolyte model (Chen's model) based on local composition theory (in particular the NRTL model) is reviewed, and the subsequent possible modification of this theory for solvent-polymer-electrolyte systems is discussed. The pros and cons of each model are discussed and qualitative results are given. Quantitative comparisons with experimental data are made with several of these models when appropriate data are available.
The main conclusions of this work are:
1. A major limitation to the modeling of these aqueous-polymer two-phase systems is the lack of experimental data. Sufficient, accurate data is needed for the reduction of meaningful thermodynamic parameters by which thermodynamic models can be tested for their applicability. There exists a definite need for the generation of accurate, meaningful thermodynamic data from well characterized systems.
2. The most promising model identified in this work is the theory of Ogston. First, the model is based on the virial expansion and is thus quite suitable for dilute solutions. The Ogston model is the simplest theoretically-relevant dilute-solution model. Second, it appears to be easily extended to solvent-polymer-electrolyte solutions.
3. The Flory equation of state approach appears to be promising for representing polymer solutions. The free volume dissimilarity effect on which it is based is extremely important for solvent-polymer solutions. The most important aspect of this theory is its ability to predict lower critical solution temperature (LCST) behavior -- for which the Flory-Huggins theory is totally inadequate.M.S.
28
Andersson, Martin. "Structural, thermal and thermodynamic properties of some Ln-Pd oxides and their behaviour as catalyst precursors." Doctoral thesis, Stockholms universitet, 1999. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-64279.
Full textAbstract:
The structural, thermal and thermodynamic properties of some Ln-Pd oxides of the Ln4Pd07 type are presented. The main results are; (i) Reduction of Ln4Pd07, either ex-situ by CO or in-situ by a synthetic car exhaust gas, results in a materialwith catalytic activity for car exhaust gas clean-up reactions. The obtained material consists of Pd nanoparticles situated on the surface of micron-sized grains of Ln2O3 Upon heat treatment of the reduced material in air, Lu4Pd07 i srapidly re-formed. This property May be utilised for reactivation/conditioning of aged Ln4Pd07-based catalysts; (ii) The Ln4Pd07 compounds with Ln = Nd, Sm, Eu and Gd dare isostructural and have a structure which is a triclinic distortion of the monoclinic La4Pd07 type; (iii) ΔH°, and ΔS ° f values for La4Pd07 and Nd4Pd07 have been calculated by a combination of data obtained from dissolution calorimetry and thermogravimetric analysis studies; ( iv ) Carbon nanotubes, having the so-called fishbone structure, can be prepared by heat treatment o f La4Pd07 in a 20% CO/He gas mixture for an extended period of time. Nanotubes have been extracted from the obtained La203/Pd/nanotube mixture, using a wet-chemical method.Härtill 5 uppsatser
29
Al-Abbasi, Omar Abdulaziz. "Modeling the Non-Equilibrium Behavior of Chemically Reactive Atomistic Level Systems Using Steepest-Entropy-Ascent Quantum Thermodynamics." Diss., Virginia Tech, 2013. http://hdl.handle.net/10919/24069.
Full textAbstract:
Predicting the kinetics of a chemical reaction is a challenging task, particularly for systems in states far from equilibrium. This work discusses the use of a relatively new theory known as intrinsic quantum thermodynamics (IQT) and its mathematical framework steepest-entropy-ascent quantum thermodynamics (SEA-QT) to predict the reaction kinetics at atomistic levels of chemically reactive systems in the non-equilibrium realm. IQT has emerged over the last three decades as the theory that not only unifies two of the three theories of physical reality, namely, quantum mechanics (QM), and thermodynamics but as well provides a physical basis for both the entropy and entropy production. The SEA-QT framework is able to describe the evolution in state of a system undergoing a dissipative process based on the principle of steepest-entropy ascent or locally-maximal-entropy generation. The work presented in this dissertation demonstrates for the first time the use of the SEA-QT framework to model the evolution in state of a chemically reactive system as its state relaxes to stable equilibrium. This framework brings a number of benefits to the field of reaction kinetics. Among these is the ability to predict the unique non-equilibrium (kinetic) thermodynamic path which the state of the system follows in relaxing to stable equilibrium. As a consequence, the reaction rate kinetics at every instant of time is known as are the chemical affinities, the reaction coordinates, the direction of reaction, the activation energies, the entropy, the entropy production, etc. All is accomplished without any limiting assumption of stable or pseudo-stable equilibrium. The objective of this work is to implement the SEA-QT framework to describe the chemical reaction process as a dissipative one governed by the laws of quantum mechanics and thermodynamics and to extract thermodynamic properties for states that are far from equilibrium. The F+H2-->HF+H and H+F2-->HF+F reaction mechanisms are used as model problems to implement this framework.Ph. D.
30
Mukherjee, Sundeep Johnson W. L. "Study of crystallization behavior, kinetics and thermodynamics of bulk metallic glasses using noncontact electrostatic levitation technique /." Diss., Pasadena, Calif. : California Institute of Technology, 2005. http://resolver.caltech.edu/CaltechETD:etd-01282005-111916.
Full text
31
Lebelo, Ramoshweu Solomon. "Analysis of greenhouse gas emission from reactive materials and its thermodynamics." Thesis, Cape Peninsula University of Technology, 2013. http://hdl.handle.net/20.500.11838/1302.
Full textAbstract:
Thesis (DTech(Mechanical Engineering))--Cape Peninsula University of Technology, 2013The environment is polluted by many gases of which carbon dioxide is one of them and unfortunately during the emission of carbon dioxide, oxygen, which is very important for keeping all species alive, is depleted. Increased industrial activities led to more emission of carbon dioxide and ultimately global warming arose as a result of the greenhouse effect. Global warming has resulted with high temperatures and carbon dioxide production in the atmosphere and it was necessary to come up with mathematical modelling to investigate processes that may try to reduce temperature rise, carbon dioxide emission and oxygen depletion in a stockpile of combustible material. The work done in this thesis considered three differential equations, first for temperature behaviour, second for oxygen depletion and third for carbon dioxide emission. The three equations were solved simultaneously for a reactive slab of combustible material. An exothermic reaction in a stockpile of combustible material results due to the reaction of oxygen with reactive hydrocarbon material and the products are usually heat and carbon dioxide. A detailed discussion on this part is given in chapter 1, and also some definitions of terms applied in this work, together with literature review, statement of problem, aim of the study, objectives of the study and methodology are part of the chapter. In chapter 2, the nonlinear partial differential equations governing the process are derived.
32
Uan-Zo-li, Julie Tammy. "Morphology, Crystallization and Melting Behavior of Propylene-Ethylene Statistical Copolymers." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/29143.
Full textAbstract:
In this work the morphology, crystallization and melting behavior of novel Dow Chemical propylene-ethylene copolymers were investigated.
The incorporation of ethylene units into a polypropylene chain resulted in the decrease in crystallization, melting and glass transition temperatures and overall crystallinity. Based on the shape of heat capacity curves and the dependence of the melting temperature offset on ethylene content, it was concluded that copolymers prepared using different catalyst systems exhibited different ethylene sequence length distributions.
The behavior of Dow Chemical propylene-ethylene copolymers was compared to that of copolymers prepared using traditional metallocene and Ziegler-Natta catalysts. The catalyst system used in the preparation of these new copolymers is similar to a metallocene catalyst system.
It was demonstrated that ethylene defects are partially included in the polypropylene crystal. The thermodynamic heat of fusion at the equilibrium melting temperature decreased by 44% with an increase in ethylene concentration from 0 mol% to 21.2 mol%. On the basis of calorimetric and density data, the inclusion model based on the Sanchez-Eby crystallization theory was shown to be applicable for the evaluation of the degree of crystallinity. At the same time, inadequacies were found in application of the rigid amorphous fraction model to these copolymers.
The formation of gamma-phase crystals was shown to be favored by both an increase in the ethylene content and a decrease in the crystallization rate. Increase in the ethylene content was shown to lead to a decrease in the density, length and thickness of alpha-phase crystals. It was also demonstrated that the cross-hatching morphology is present in all propylene-ethylene copolymers.Ph. D.
33
Kilit, Emel. "Critical Behaviour Of The Thermodynamic Quantities For The Thermotropic And Ferroelectric Liquid Crystals Close To The Phase Transitions." Phd thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12612963/index.pdf.
Full textAbstract:
The specific heat Cp has been showed at various temperatures in the literature, which shows a
sharp increase labeled as the lambda-transition at the critical temperature. This transition has been
observed previously among the phases of solid-nematic-isotropic liquid in p-azoxyanisole
(PAA) and anisaldazine (AAD), and among the phases of solid-smectic-cholesteric-isotropic
liquid in cholesteryl myristate (CM). In this thesis work, we analyze the experimental data for
the temperature dependence of Cp and the thermal expansion alpha_p and also pressure dependence
of alpha_p by a power-law formula. From the analysis of pressure dependence of alpha_p, we calculate
the temperature dependencies of specific heat Cp and of the isothermal compressibility kappa_T for
the phase transitions considered in PAA, AAD and CM. Our calculations for the temperature
dependence of the p and kappa_T can be compared with the experimental data when available in
the literature.
Polarization, tilt angle and the dielectric constant have been reported in the literature at various
temperatures close to the solid-smectic C*-smectic A-isotropic liquid transition in the
ferroelectric liquid crystals of A7 and C7. The mean field model with the free energy expanded in terms of the order parameters (polarization and tilt angle) has been reported in the
literature previously. In this thesis work, we apply the mean field model first time by fitting
the expressions derived for the temperature dependence of the polarization, tilt angle and
the dielectric constant to the experimental data for A7 and C7 from the literature. Since the
mean field model studied here describes adequately the observed behaviour of A7 and C7, the
expressions for the temperature dependence of the polarization, tilt angle and the dielectric
constant which we derive, can also be applied to some other ferroelectric liquid crystals to
explain their observed behaviour.
34
Gil-García, Álvaro Antonio. "Thermodynamic behaviour of supercritical water as working fluid in advanced coal-fired power plants : simulation and design study." Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7734/.
Full textAbstract:
The UK is facing an energy crisis due to the closure of old nuclear power plants which will not be replaced until Generation III nuclear reactors are built. Coal is a realistic option to fill the gap, although there is a need to use cleaner and efficient technologies as a means to comply with global environmental regulations. Supercritical coal-fired power is a viable clean coal technology; however the UK National Grid Code is built around conventional power plants, and thus compliance is uncertain. Modelling the thermal behaviour of the supercritical boiler water cycle using computational fluid dynamics is a practical method to approach compliance. The CFD models developed with the software Comsol Multiphysics were validated and verified using experimental and numerical data, respectively. Subsequently, a test-element representing one pipe from the water wall was scaled-down to match computational requirements, and tested at two different thermal boundary conditions. A strong, forcedconvective flow was revealed, with buoyancy effects at the inlet and a considerable influence of thermal acceleration. The sharp changes of the thermo-physical properties were the most influential hydrothermal factor. Heat transfer coefficient peaked near the pipe inlet, and the outlet section showed mild hydro-thermal performance, impaired by the acceleration effects.
35
Sundaram, Dilip Srinivas. "Multi-scale modeling of thermochemical behavior of nano-energetic materials." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/50225.
Full textAbstract:
Conventional energetic materials which are based on monomolecular compounds such as trinitrotoluene (TNT) have relatively low volumetric energy density. The energy density can be significantly enhanced by the addition of metal particulates. Among all metals, aluminum is popular because of its high oxidation enthalpy, low cost, and relative safety. Micron-sized aluminum particles, which have relatively high ignition temperatures and burning times, have been most commonly employed. Ignition of micron-sized aluminum particles is typically achieved only upon melting of the oxide shell at 2350 K, thereby resulting in fairly high ignition delay. Novel approaches to reduce the ignition temperatures and burning times and enhance the energy content of the particle are necessary.
Recently, there has been an enormous interest in nano-materials due to their unique physicochemical properties such as lower melting and ignition temperatures and shorter burning times. Favorably, tremendous developments in the synthesis technology of nano-materials have also been made in the recent past. Several metal-based energetic materials with nano-sized particles such as nano-thermites, nano-fluids, and metalized solid propellants are being actively studied. The “green” reactive mixture of nano-aluminum particles and water/ice mixture (ALICE) is being explored for various applications such as space and underwater propulsion, hydrogen generation, and fuel-cell technology. Strand burning experiments indicate that the burning rates of nano-aluminum and water mixtures surpass those of common energetic materials such as ammonium dinitramide (ADN), hydrazinium nitroformate (HNF), and cyclotetramethylene tetranitramine (HMX). Sufficient understanding of key physicochemical phenomena is, however, not present. Furthermore, the most critical parameters that dictate the burning rate have not been identified. A multi-zone theoretical framework is established to predict the burning properties and flame structure by solving conservation equations in each zone and enforcing the mass and energy continuities at the interfacial boundaries. An analytical expression for the burning rate is derived and physicochemical parameters that dictate the flame behavior are identified. An attempt is made to elucidate the rate-controlling combustion mechanism. The effect of bi-modal particle size distribution on the burning rate and flame structure are investigated. The results are compared with the experimental data and favorable agreement is achieved.
The ignition and combustion characteristics of micron-sized aluminum particles can also be enhanced by replacing the inert alumina layer with favorable metallic coatings such as nickel. Experiments indicate that nickel-coated aluminum particles ignite at temperatures significantly lower than the melting point of the oxide film, 2350 K due to the presence of inter-metallic reactions. Nickel coating is also attractive for nano-sized aluminum particles due to its ability to maximize the active aluminum content. Understanding the thermo-chemical behavior of nickel-aluminum core-shell structured particles is of key importance to both propulsion and material synthesis applications. The current understanding is, however, far from complete. In the present study, molecular dynamics simulations are performed to investigate the melting behavior, diffusion characteristics, and inter-metallic reactions in nickel-coated nano-aluminum particles. Particular emphasis is on the effects of core size and shell thickness on all important phenomena. The properties of nickel-coated aluminum particles and aluminum-coated nickel particles are also compared.
Considerable uncertainties pertaining to the ignition characteristics of nano-aluminum particles exist. Aluminum particles can spontaneously burn at room temperature, a phenomenon known as pyrophoricity. This is a major safety issue during particle synthesis, handling, and storage. The critical particle size below which nascent particles are pyrophoric is not well known. Energy balance analysis with accurate evaluation of material properties (including size dependent properties) is performed to estimate the critical particle size for nascent particles. The effect of oxide layer thickness on pyrophoricity of aluminum particles is studied. The ignition delay and ignition temperature of passivated aluminum particles are also calculated. Specific focus is placed on the effect of particle size. An attempt is made to explain the weak dependence of the ignition delay on particle size at nano-scales.
36
Bruckner, Robert Jack. "Simulation and Modeling of the Hydrodynamic, Thermal, and Structural Behavior of Foil Thrust Bearings." Case Western Reserve University School of Graduate Studies / OhioLINK, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=case1089304186.
Full text
37
Goswami, Ishan. "Computational and Experimental Investigation of the Critical Behavior Observed in Cell Signaling Related to Electrically Perturbed Lipid Systems." Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/97564.
Full textAbstract:
Problem Statement: The use of pulsed electric fields (PEFs) as a tumor treatment modality is receiving increased traction. A typical clinical procedure involves insertion of a pair of electrodes into the tumor and administration of PEFs (amplitude: ~1 kV/cm; pulse-width: 100 μs). This leaves a zone of complete cell death and a sub-lethal zone where a fraction of the cells survive. There is substantial evidence of an anti-tumor systemic immune profile in animal patients treated with PEFs. However, the mechanism behind such immune profile alterations remains unknown, and the effect of PEFs on cell signaling within sub-lethal zones remains largely unexplored. Moreover, different values of a PEF pulse parameter, for e.g. the pulse-widths of 100 μs and 100 ns, may have different effects on cell signaling. Thus, the challenge of answering the mechanistic questions is compounded by the large PEF parameter space consisting of different combinations of pulse-widths, amplitudes, and exposure times.
Intellectual merit: This Ph.D. research provides proof that sub-lethal PEFs can enhance anti-tumor signaling in triple negative breast cancer cells by abrogating thymic stromal lymphopoietin signaling and enhancing stimulatory proteins such as the tumor necrosis factor. Furthermore, experimental evidence produced during this Ph.D. research demonstrates that PEFs may not directly impact the intracellular mitochondrial membrane at clinically relevant field amplitudes. As demonstrated in this work, PEFs may influence the mitochondria via an indirect route such as disruption of the actin cytoskeleton and/or alteration of ionic environment in the cytoplasm due to cell membrane permeabilization. Thus, a reductionist approach to understanding the influence of PEFs on cell signaling is proposed by limiting the study to membrane dynamics. To overcome the problem of investigating the entire PEF parameter space, this Ph.D. research proposes a first-principle thermodynamic approach of scaling the PEF parameter space such that an understanding developed in one regime of PEF pulse parameter values can be used to understand other regimes of the parameter space. Demonstration of the validity of this scaling model is provided by coupling Monte-Carlo methods for density-of-states with the steepest-entropy-ascent quantum thermodynamic framework for the non-equilibrium prediction of the lipid membrane dynamics.Ph. D.
38
Räbiger, Klaus Edmund. "Fluid dynamic and thermodynamic behaviour of multiphase screw pumps handling gas-liquid mixtures with very high gas volume fractions." Thesis, University of South Wales, 2009. http://hdl.handle.net/10265/561.
Full text
39
Huang, Jia. "Rapid determination of fatigue behaviour for carbon fiber reinforced polymer laminates based on thermodynamic phenomena observed by IR thermography." Thesis, Toulouse 3, 2019. http://www.theses.fr/2019TOU30033.
Full textAbstract:
Afin de réduire le poids des structures composites et les coûts de fabrication et d'exploitation, le comportement en fatigue des stratifiés carbone fait l'objet d'une grande attention. Les objectifs de cette thèse sont de développer des méthodologies pour évaluer rapidement le comportement en fatigue des stratifiés carbone à partir de l'analyse des données thermodynamiques mesurées par une caméra infrarouge et d'examiner la corrélation entre la dissipation d'énergie et les dommages générés par la fatigue. Trois nouvelles méthodes numériques basées sur l'analyse statistique dans le traitement des données thermiques ont tout d'abord été proposées afin d'éviter les incertitudes humaines dans l'application des méthodes graphiques traditionnelles telles que la méthode de Luong et celle de Risitano. Ces trois méthodes ont toutes été évaluées en déterminant la limite de fatigue avec unicité selon les données expérimentales de la littérature. Ensuite, un modèle à deux paramètres a été proposé pour caractériser la dégradation de la rigidité des stratifiés carbone en fonction de l'augmentation du nombre de cycles. Après la calibration des paramètres et le calcul du seuil de la rigidité normalisée, toute la courbe S-N peut être obtenue dans un temps très court. Ensuite, la relation entre les phénomènes de fatigue et la génération de chaleur est étudiée. En fonction des différentes causes, la chaleur générée a été classée en deux parties : chaleur induite par le frottement interne et celle induite par l'accumulation de dommages. La production totale de chaleur correspondant aux dommages semble être indépendante de l'amplitude de la charge. Cette information peut donc être utilisée pour prédire la courbe S-N avec une bonne précisionIn order to achieve weight reduction of composite structures and reduce manufacturing and operating costs, fatigue behavior of Carbon Fiber Reinforced Polymer (CFRP) laminates has received more and more attention. The objectives of this thesis are to develop methodologies to evaluate the fatigue behavior of CFRP laminates in a short time based on the analysis of thermodynamic data measured by an infrared camera and to investigate the inherent correlation between energy dissipation and fatigue damage. Three new numerical methods based on statistical analysis for the treatment of the thermal data are firstly proposed to avoid man-made uncertainties in the traditional graphic methods such as Luong's method and Risitano's method. Those proposed methods are all evaluated by the experimental data from literature to determine the fatigue limit with uniqueness. Then, a two-parameter model is proposed to characterize the stiffness degradation of CFRP laminates with the increase of cycle numbers. After the calibration of parameters and the calculation of the normalized failure threshold stiffness, the whole S-N curve can be obtained in a very short time. Thereafter, the relationship between fatigue damage and heat generation is studied. Depending on the different causes, the generated heat is classified into two parts - induced by internal friction and induced by damage accumulation. The total heat generation corresponding to damage appears to be independent of loading amplitude, and this conclusion can also be used to predict the S-N curve with good precision
40
Lazarou, Georgia. "Development of the SAFT-γ Mie equation of state for predicting the thermodynamic behaviour of strong and weak electrolyte solutions." Thesis, Imperial College London, 2017. http://hdl.handle.net/10044/1/60588.
Full textAbstract:
The thermodynamic modelling of fluid mixtures containing electrolytes using the SAFT-γ Mie equation of state is addressed in detail in this thesis. The SAFT-γ Mie approach allows the implementation of heteronuclear molecules using a group-contribution formalism, and offers a versatile framework for developing models to describe molecules of varying chemical functionality for a broad range of physical properties. In the present work, the SAFT-γ Mie equation of state is extended to electrolyte mixtures with the incorporation of the primitive unrestricted mean spherical approximation (MSA-PM) for describing the Coulombic ion–ion interactions, and the Born solvation free energy to implicitly treat ion– solvent polar interactions. Novel reformulations of the MSA-PM and Born theories within a group-contribution framework are proposed in order to enable ionic species of any size and chemical structure to be modelled, from small inorganic ions to large non-spherical charged molecules. Taking carboxylate anions in linear alkyl chain molecules as an illustrative case study, the proposed theory is shown to effectively account for localised charge effects arising from the structural topology of the charged species. A holistic description of electrolyte solutions is employed in this work; in addition to the short-range dispersion forces and the long-range Coulombic interactions which are pertinent to such mixtures, the models developed here also account for the formation of hydrogen bonds, ion-pairing phenomena, and electrolyte dissociation equilibria. The proposed SAFT-γ Mie equation of state is used to model aqueous solutions of strong electrolytes including alkali halide salts, hydrogen halide acids, and alkali hydroxide bases. Aqueous solutions of sulphuric acid and nitric acid are studied in detail by modelling these as speciating weak electrolytes. Finally, the treatment of ion-pairing phenomena is investigated through a consideration of aqueous alkali nitrate salt solutions. This work presents a new theoretical formulation and SAFT-γ Mie group models for twenty species in total.
41
Rillard, Jean. "CO2 perturbation in aquifers : reaction kinetics and metals behavior." Thesis, Lyon 1, 2013. http://www.theses.fr/2013LYO10033/document.
Full textAbstract:
Ce travail de thèse a porté sur l'étude des perturbations hydrogéochimiques potentiellement induites par le CO2 dans un aquifère salin profond. Dans un premier temps, cet aspect a été étudié à partir de sources hydrothermales naturellement riches en CO2. Une étude de la composition chimique des eaux en fonction de l'augmentation de leur teneur en CO2 a montré une baisse de pH et un enrichissement systématique en cations majeurs et en alcalinité en fonction de la teneur en CO2. Les réactions en jeu ont été étudiées par une approche cinétique afin d'estimer la réactivité des minéraux en fonction de la perturbation en CO2, par le calcul des variations de surfaces réactives. Les résultats obtenus ont montré que la surface réactive des minéraux pouvait varier de 2 à 4 ordres de grandeur en fonction de la perturbation en CO2. Dans un second temps, une expérience d'injection d'eau saturée en CO2 a été effectuée. Une analyse de la variation de la composition chimique des eaux de l'aquifère, avant et après injection, a permis d'étudier l'impact d'une perturbation par le CO2 sur la composition de l'eau. Une attention particulière a été portée sur le comportement des métaux dissous. Les résultats ont montré une baisse du pH (de 7.3 à 5.7), accompagnée d'un enrichissement en alcalinité, cation majeurs et métaux dissous (Fe, Zn, Mn et As). Les calculs d'indice de saturation ont montré qu'une dissolution des oxydes métalliques type ferrihydrite était corrélée à l'enrichissement en métaux dissous. Une approche de cinétique chimique sur la base des résultats expérimentaux a été proposée. Cela a montré que la dissolution des oxydes métalliques obéissait à des cinétiques d'ordre complexe. Ces résultats montrent que l'effet de la perturbation par le Co2 dans les conditions choisies, engendre un enrichissement en éléments dissous, avec un effet plus significatif sur les métaux. Ces phénomènes devront être regardés de près dans l'éventualité du développement de la technologie de stockage géologique du CO2, an aquifère salin profondThe aim of this thesis was to investigate hydrogeochemical perturbation induced by CO2 in natural aquifers. In a first step, we used chemical data from natural CO2-rich hydrothermal water. We studied variation of fluid chemical composition as a function of CO2 content in order to evaluate reactivity of minerals composing the initial reservoir. Fluid chemical analyses showed decrease in pH, and systematic enrichment in alkalinity and major cations correlated to increase in CO2 content. Chemical reaction was studied by kinetic approach to estimate variation of mineral reactive surface area as function of CO2 perturbation. Results showed that mineral reactive surface area could varied by two to four orders of magnitude as a function of CO2 perturbation. In a second step a field experiment of injection of water saturated with CO2 in aquifer has been carried out. Analysis of groundwater composition before and after injection allowed to study the impact of CO2 perturbation on water-rock interaction processes. A particular focus was made on dissolved metals behavior. Results showed a decrease in pH (from 7.3 to 5.7), involved with enrichment in alkalinity by a factor two, and by approximately one order of magnitude for dissolved metals (Fe, Mn, Zn) and by a factor two for As. Saturation index showed that dissolution of metals oxide such as ferrihydrite was correlated to iron release. These results showed that, in our field experimental conditions, CO2 perturbation induced an enrichment in dissolved elements with more significant effect on dissolved metals. These results highlight the importance of proper physic-chemical characterization of fluid and reservoir rock and in-situ kinetic of reaction in the eventual option of Co2 geological storage
42
Oliveira, Júnior Arilson José de [UNESP]. "Dispositivo móvel para análise de conforto térmico e ambiência." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/144203.
Full textAbstract:
Submitted by Arilson José de Oliveira Júnior null (arilsonjr@outlook.com) on 2016-09-23T17:30:32Z
No. of bitstreams: 1
dissertação-v.16_final.pdf: 5639185 bytes, checksum: 41dab40b84e40ca63b845dee1590104f (MD5)Approved for entry into archive by Ana Paula Grisoto (grisotoana@reitoria.unesp.br) on 2016-09-27T18:21:10Z (GMT) No. of bitstreams: 1 oliveirajunior_ajo_me_bot.pdf: 5639185 bytes, checksum: 41dab40b84e40ca63b845dee1590104f (MD5)
Made available in DSpace on 2016-09-27T18:21:10Z (GMT). No. of bitstreams: 1 oliveirajunior_ajo_me_bot.pdf: 5639185 bytes, checksum: 41dab40b84e40ca63b845dee1590104f (MD5) Previous issue date: 2016-07-27
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Nos países de clima tropical, como o Brasil, um dos maiores desafios para produção animal e trabalho humano são os fatores ambientais, como altas temperaturas e umidades dentro de ambientes, assim como as tipologias das instalações, muitas vezes limitantes para o desempenho produtivo. O conforto térmico e a ambiência são áreas de estudo que tem por objetivo conceder o bem-estar para indivíduos, sejam eles animais ou seres humanos. Nos dias atuais grande parte das análises de conforto térmico no meio agrícola, ressaltando às em ambientes de produção animal, utilizam índices que possibilitam a avaliação do nível de estresse térmico de um determinado local por meio de variáveis climatológicas, como o Índice de Temperatura e Umidade – ITU, Índice de Temperatura de Globo Negro e Umidade – ITGU e Índice de Temperatura Equivalente – ITEq. Semelhantemente, em locais de trabalho humano há um limite de tolerância para exposição ao calor que deve ser monitorado mediante o chamado Índice de Bulbo Úmido Termômetro de Globo – IBUTG. Para a resolução desses índices, não há atualmente um sistema computacional específico, de hardware e software, que forneça, em tempo real, a condição térmica de um ambiente. Deste modo, o presente trabalho teve por objetivo desenvolver um sistema computacional capaz de avaliar, em tempo real, o conforto térmico de instalações de produção animal e de ambientes de trabalho humano. O sistema foi desenvolvido baseado na criação de um dispositivo portátil para coleta e transmissão das variáveis climatológicas de temperatura do ar, temperatura de globo negro e umidade relativa do ar, e do desenvolvimento de um aplicativo para smartphones e tablets Android. O dispositivo portátil foi desenvolvido utilizando um microcontrolador padrão Arduino, juntamente com sensores de temperatura e umidade relativa do ar. Para o desenvolvimento do aplicativo para dispositivos móveis, foi utilizado a linguagem de programação orientada a objetos Java no ambiente de desenvolvimento integrado Android Studio. O aplicativo para dispositivos móveis e o dispositivo portátil foram aplicados em diferentes ambientes e apresentaram correta medição de variáveis climatológicas e cálculo dos índices de conforto térmico. O dispositivo portátil demonstrou ser um produto funcional na transmissão de dados para dispositivos móveis.
In tropical weather countries, such as Brazil, one of the greatest challenges for animal production and human work environments are environmental factors, among them high temperature and humidity inside of the environments, as well as the type of facilities which are limiting for productive performance. The thermal comfort and the ambience are study areas that aims the well-being of individuals, whether they are animals or humans. It is possible to define thermal comfort as the pleasant thermal sensation of the body, in which are not necessary physiological efforts to keep the body in thermal balance. Nowadays, several analysis of thermal comfort in the agriculture environment, mainly at environments of animal production, apply indexes to make it possible the evaluation of thermal stress level of a specific place through the climatological variables, for instance, the Temperature and Humidity Index – THI, Black Globe-Humidity Index – BGHI and Heat Load Index – HLI. In the same way, at places of human work, there is a tolerance limit for heat exposition that should be monitored by the known Wet-bulb Globe Temperature Index – WBGT index. Currently, for resolution of these indexes, there is not a specific computational system (hardware and software) that provides the thermal comfort of an environment in real time. Therefore, the present work aimed to develop a computational system with features to evaluate in real time the thermal comfort of facilities of animal production and human work. The system was developed based on the creation of a mobile device to collect and transmit weather variables from the air temperature, black globe temperature and relative air humidity, and also the development of an app for smartphones and tablets. The mobile device was developed using the Arduino microcontroller, along with sensors of air temperature and relative humidity. For the development of the app it was used the Java oriented object program language, with the Android integrated development environment. The app for mobile devices and the portable device were applied in different environments and both presented a correctly measurement of climatological variables and the calculating of thermal comfort indexes. The portable device proved to be a functional product in data transmission for mobile devices.
43
Papaioannou, Vasileios. "A molecular-based group contribution equation of state for the description of fluid phase behaviour and thermodynamic derivative properties of mixtures (SAFT-γ Mie)." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/11135.
Full textAbstract:
An accurate knowledge of the thermophysical properties and phase behaviour of fluid mixtures is essential for the reliable design of products and processes across a wide range of chemical engineering applications, varying from the processing of petroleum fluids to the manufacturing of pharmaceuticals. Thermodynamic tools and, in the context of this work, group contribution (GC) methods are predictive approaches that are expected to play an important role in meeting these industrial needs. The principal focus of the work presented in this thesis is the development of a novel GC method based on the statistical associating fluid theory (SAFT): the SAFT-γ Mie approach. The method is developed based on a detailed molecular model and a realistic intermolecular potential, the Mie potential with variable attractive and repulsive ranges, for the description of interactions at a molecular level. Over the past decade, an increasing research effort has been devoted to developing formalisms that couple the accuracy of the SAFT equation of state (EoS) with the predictive capabilities of group contribution approaches. In the development of such methods one aims to overcome the limitations inherent to GC approaches based on activity coefficient models, such as in the well-established universal quasi-chemical functional group activity coefficient (UNIFAC) approach. A more recent landmark has been the development of heteronuclear methods within SAFT. The SAFT-γ EoS based on the square-well (SW) potential has been shown to describe accurately the phase behaviour of a wide variety of fluids. In the work presented in this thesis, SAFT-γ SW is applied to the study of the fluid phase behaviour of aqueous solutions of hydrocarbons. These mixtures are of high industrial relevance, and the accurate representation of their highly non-ideal nature is very challenging from a theoretical perspective. The SAFT-γ method is shown to perform comparatively well in predicting the behaviour of the systems examined. Nonetheless, some challenges are identified, such as the description of thermodynamic derivative properties and the description of near-critical fluid phase behaviour, where the performance of the method is shown to be less accurate. These challenges partially arise from the simplistic intermolecular square-well potential employed within SAFT-γ SW, which allows for a rigorous theoretical development, but fails to reproduce accurately finer aspects of the thermophysical behaviour of fluids, such as second-order derivative thermodynamic properties. These challenges are tackled here with the development of the SAFT-γ Mie GC approach, based on the versatile Mie intermolecular potential and a third-order treatment of the thermodynamics of the monomer segments. The SAFT-γ Mie method is applied to the study of the properties of two chemical families, n-alkanes and 2- ketones, and it is shown that a significant improvement over existing SAFT-based group contribution approaches can be achieved in the description of the pure component phase behaviour of the compounds studied. Moreover, the application of a realistic intermolecular potential is shown to allow for an excellent description of second-order derivative thermodynamic properties, and the accurate treatment of the intersegment interactions is shown to improve the performance of the method in the description of the near-critical fluid phase behaviour. The predictive capability of the method is demonstrated in the description of mixture fluid phase behaviour and excess thermodynamic properties in a predictive manner. Given the promising performance of the SAFT-γ Mie EoS, the method is applied to the case study of the solubility of two active pharmaceutical ingredients in organic solvents. The method is shown to satisfactorily predict the solubilities of the mixtures considered, based on limited experimental data for simple systems. Given the complexity of the mixtures studied, the performance of the SAFT-γ Mie is considered very encouraging and shows that there is great potential in the application of the method to this challenging field.
44
Tsiotas, Achilleas Athanasios. "The role of the chain extender on the phase behaviour and morphology of high hard block content thermoplastic polyurethanes : thermodynamics-structures-properties." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/the-role-of-the-chain-extender-on-the-phase-behaviour-and-morphology-of-high-hard-block-content-thermoplastic-polyurethanes-thermodynamicsstructuresproperties(d2aa856c-7cd0-46e5-a354-4b9038c87166).html.
Full textAbstract:
Thermoplastic polyurethanes (TPUs) have attracted a lot of attention over the last decades in both academic and industrial research. They are multi-block co-polymers with statistically alternating hard (HS) and soft segments (SS) along their structure. Polyurethanes owe their great versatility to the micro-phase separation that takes place between their thermodynamically incompatible HS and SS. The objective of this study was to examine how minor alternations in a specific part of the hard segment (HS) -the chain extender (CE)- affects the micro-phase separation behaviour as well as the morphology and the physical properties of linear TPUs with a high HS% w/w in their structures (≥65). For this purpose, the HS of TPUs synthesised in solution were chain extended by four different alcohols: 1,3-propanediol (13PD), 2-methyl-1,3-propanediol (2M13PD), 1,5-pentanediol (15PD) and 3-methyl-1,5-pentanediol (3M15PD). TPU samples containing the same SS and di-isocyanate were found to exhibit the highest crystallisation and phase separation degrees when extended by 13PD. TPUs containing 2M13PD and 15PD demonstrated lower degrees of phase separation. The use of a linear CE led to a higher degree of order, becoming even higher for shorter CEs. Samples incorporating 3M15PD were observed to be totally phase mixed. The reason was proposed to be an enhanced compatibility between the HS and SS resulting from the elongation of the backbone chain of the CE (better mobility) along with the introduction of the CH3 (hindering close packing and therefore crystallisation of the hard domains). This behaviour was also noticeable in SAXS, DMTA and DSC measurements through absence of scattering peaks, softening of the polymers at ambient temperatures and the presence of a single, broad glass transition at room temperature respectively. TGA of as-cast TPUs showed that severe degradation took place at temperatures higher than the observed endotherms in the DSC experiments with the exception of the 13PD. In those samples, simultaneous mixing-degradation was believed to occur during their elevated endothermic transitions. SAXS measurements revealed that the d-spacing was affected when the CE and/or the HS% w/w was altered. Higher values were observed for the linear CEs whereas introduction of chemical branches in the CE seemed to decrease the inter-lamellar spacing through an increase in the thickness of the 'inter-penetration' region. FTIR provided evidence that the phase separation of the different series was directly connected to the amount of the inter-chain hydrogen bonds in the TPU. Mechanical characterisation of the lowest available HS% w/w through tension mode DMTA and melt-rheology, confirmed that the samples with a better phase separation had higher storage moduli at room temperature as well as a higher viscosity at elevated temperatures respectively. Comparisons of the DSC data concerning the phase separation of the TPUs, showed that samples extended by 2M13PD separated upon post-melting heating, whereas the ones containing 15PD segregated upon cooling from the melt. Higher mobility for the HS and SS in the case of 15PD was suggested to be the reason. Complementary characterisation of samples with different thermal histories (melt-quenched, isothermally annealed) came to support those suggestions with additional WAXS, SAXS, and FTIR experiments. Annealing studies were only applied to samples containing 2M13PD and 15PD, since the TPUs prepared using other CEs proved unsuitable for such studies mainly due to extensive thermal degradation.
45
Niermann, Michael [Verfasser]. "Thermodynamische Eigenschaften und Umsatzverhalten von Salzhydraten zur Speicherung und Transformation von Wärme : Thermodynamic properties and conversion behavior of salt hydrates for heat storage and transformation / Michael Niermann." Hamburg : Staats- und Universitätsbibliothek Hamburg Carl von Ossietzky, 2020. http://d-nb.info/1223095843/34.
Full text
46
Hölz, Peter [Verfasser], and T. [Akademischer Betreuer] Böhlke. "A dynamic and statistical analysis of the temperature- and fatigue behavior of a race power unit – The effect of different thermodynamic states / Peter Hölz ; Betreuer: T. Böhlke." Karlsruhe : KIT Scientific Publishing, 2020. http://d-nb.info/121344781X/34.
Full text
47
Kobsch, Anaïs. "Behavior of feldspars during the Giant Impact." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEN026.
Full textAbstract:
L’hypothèse majeure pour la formation de la Lune est celle d’un Impact Géant entre deux planètes en formation, généralement appelées Théïa et Gaïa. L’agglomération du disque de débris résultant aurait ensuite formé la Lune. Cependant aucune des simulations d’impacts ne permet de reproduire totalement les observations du système Terre-Lune actuel. Une solution à ce problème pourrait être d’améliorer notre compréhension des propriétés des différents minéraux, non seulement à hautes pressions et hautes températures (typiques des impacts), mais aussi à basses pressions et hautes températures (typiques de l’état du disque dans l’espace). Comme les expériences en laboratoire ne permettent pas d’atteindre ces dernières conditions, nous réalisons ici des expériences numériques. Nous travaillons sur les feldspaths, les minéraux les plus abondants dans les croûtes lunaire et terrestre. Il existe une multitude de compositions différentes de feldspaths, ici nous nous limitons aux trois compositions extrêmes idéales : NaAlSi3O8, KAlSi3O8 et CaAl2Si2O8. Au moyen d’un ensemble de codes informatiques appelé VASP® nous obtenons de nombreuses données sur les trois feldspaths pour des températures allant d’environ 2000 à 20 000°C et des masses volumiques entre 0.5 et 6 g.cm−3. Les codes du « package » UMD développés pendant ces trois années au sein de l’équipe permettent l’analyse de ces données. Ces expériences numériques permettent de construire un diagramme de phases indicatif pour chacun des feldspaths étudiés. Nous avons visuellement identifié les conditions de pressions et températures pour lesquelles le liquide se vaporise (des bulles de gaz apparaissent). Ce gaz semble être constitué majoritairement d’atomes libres Na et K, mais aussi de petites molécules comme SiO, SiO2 ou O2. Nous avons également estimé la température critique. En dessous de cette température il est possible de voir un changement de phase liquide-gaz, mais au-dessus nous trouvons un fluide unique appelé fluide supercritique. Cette température est estimée entre 5250°C et 5750°C pour KAlSi3O8, entre 6250°C et 6750°C pour NaAlSi3O8 et entre 7250°C et 7750°C pour CaAl2Si2O8. Les propriétés des feldspaths à très hautes pressions (jusqu’à 4 000 000 de fois la pression atmosphérique) et températures (jusqu’à 20 000°C) nous permettent d’estimer l’état physique qu’une croûte planétaire composée de feldspaths pourrait avoir lors d’impacts météoritiques. Lorsque l’impact se produit sur une croûte froide (entre le zéro absolu et les conditions atmosphériques classiques) il pourrait au maximum faire fondre la croûte. Au contraire, lorsque l’impact a lieu sur une croûte chaude voire fondue (2200°C et plus) il pourrait transformer toute la croûte en fluide supercritique. Si c’était bien le cas de l’Impact Géant qui a formé la Lune, alors ce fluide supercritique ainsi créé pourrait permettre de résoudre bien des problèmes de composition chimique que les simulations d’Impact Géant présententThe impact of a planet in formation with the proto-Earth, also known as the Giant Impact, is now the main hypothesis for the Moon formation. Nevertheless, there are still discrepancies between the impact simulations and the observations of the current Earth-Moon system. To improve their models, geophysicists need a better understanding of geological materials not only at high pressures and high temperatures, typical of impacts, but also at low pressures and high temperatures, typical of the debris disc that follows the impact. Since this latter region cannot be reached by experiments we use here ab-initio molecular dynamics simulations. We work on feldspars, with formula (Ca,K,Na)(Al,Si)4O8, as they represent the major mineral component of the crust of terrestrial bodies. Using the VASP® code for numerical experiments and the home-made UMD package for post-processing, we obtain structural, transport and thermodynamic data on a wide range of temperatures (2000–7000 K) and densities (0.5–6 g.cm−3). The three feldspar end-members display a critical density between 0.4 and 0.9 g.cm−3 and critical temperatures as follows: 5000 K < TK < 5500 K, 6000 K < TNa < 6500 K and 7000 K < TCa < 7500 K. At low densities and below the critical temperatures, we can identify the start of gas bubble nucleation. The vaporization is incongruent, the gas is mostly made of free Na or K and of SiO, SiO2 or O2 molecules. There is an O2 degassing of the fluids above 4000 K at all densities. Our study at very high temperatures and pressures tells us that impacts in a cold crust would at most melt the crust, whereas impacts in a hot crust or in a magma ocean would completely bring the crust into supercritical state
48
Moradian, Farzad. "Ash Behavior in Fluidized-Bed Combustion and Gasification of Biomass and Waste Fuels : Experimental and Modeling Approach." Doctoral thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-9563.
Full textAbstract:
Over the past few decades, a growing interest in the thermal conversion of alternative fuels such as biomass and waste-derived fuels has been observed among the energy-producing companies. Apart from meeting the increasing demand for sustainable heat and power production, other advantages such as reducing global warming and ameliorating landfilling issues have been identified. Among the available thermal conversion technologies, combustion in grate-fired furnaces is by far the most common mode of fuel conversion. In recent years, Fluidized-Bed (FB) technologies have grown to become one of the most suitable technologies for combustion and gasification of biomass and waste-derived fuels.In spite of the benefits, however, some difficulties are attributed to the thermal conversion of the alternative fuels. Ash-related issues could be a potential problem, as low-grade fuels may include considerable concentrations of ash-forming elements such as K, Na, S, Ca, Mg, P, Si and Cl. These elements undergo many undesirable chemical and physical transformations during the thermal conversion, and often cause operational problems such as deposition-related issues, slag formation in furnaces, corrosion of the heat transfer surfaces, and bed agglomeration of the fluidized-beds. Ash-related problems in the utility boilers are a major concern that may result in decreased efficiency, unscheduled outages, equipment failures, increased cleaning and high maintenance costs.This thesis investigated the ash behavior and ash-related problems in two different FB conversion systems: a Bubbling Fluidized-Bed (BFB) boiler combusting solid waste, and a Dual Fluidized-Bed (DFB) gasifier using biomass as feedstock. Full-scale measurements, chemical analysis of fuel and ash, as well as thermodynamic equilibrium modeling have been carried out for the BFB boiler (Papers I-IV), to investigate the impact of reduced-bed temperature (RBT) and also co-combustion of animal waste (AW) on the ash transformation behavior and the extent of ash-related issues in the boiler. For the DFB gasifier (Paper V), a thermodynamic equilibrium model was developed to assess the risk of bed agglomeration when forest residues are used as feedstock.The experimental results showed that the RBT and AW co-combustion could decrease or even resolve the ash-related issues in the BFB boiler, resulting in a lower deposit-growth rate in the superheater region, eliminating agglomerates, and a less corrosive deposit (in RBT case). Thermodynamic equilibrium modeling of the BFB boiler gave a better understanding of the ash transformation behavior, and also proved to be a reliable tool for predicting the risk of bed agglomeration and fouling. The modeling of the DFB gasifier indicated a low risk of bed agglomeration using the forest residues as feedstock and olivine as bed material, which was in good agreement following the observations in a full-scale DFB gasifier.
49
Durairaj, Vinobalan. "A SYSTEMATIC STUDY OF THERMODYNAMIC AND TRANSPORT PROPERTIES OF LAYERED Can+1(Ru1-xCrx)nO3n+1." UKnowledge, 2008. http://uknowledge.uky.edu/gradschool_diss/661.
Full textAbstract:
Orbital degrees of freedom play vital role in prompting novel phenomena in ruthenium based Ruddlesden-Popper compounds through coupling of orbits to spin and lattice. Physical properties are then particularly susceptible to small perturbations by external magnetic fields and/or slight structural changes. Current study pertains to the impact when a more-extended 4d Ruthenium ion is replaced by a less-extended 3d Chromium ion.
Perovskite CaRuO3 (n=∞) is characterized by borderline magnetism and non- Fermi liquid behavior – common occurrences in quantum critical compounds. Remarkably, Cr substitution as low as x=0.05 abruptly drives CaRu1−xCrxO3 from a paramagnetic state to an itinerant ferromagnetic state (MS~0.4μB/f.u.), where TC=123K for x=0.22. The Cr-driven magnetism is highly anisotropic suggesting an important role of spin-orbit coupling. Unlike other chemical substitutions in the compound, Cr does not induce any Metal-Insulator transition that is expected to accompany the magnetic transition. The results indicate a coupling of Ru-4d and Cr-3d electrons that is unexpectedly favorable for itinerant ferromagnetism, which often exists delicately in the ruthenates.
Bilayered Ca3Ru2O7 (n=2), an abode of huge anisotropy, exhibits a wide range of physical properties – Colossal Magnetoresistance occurring only when the spin polarized state is avoided, Antiferromagnetic-Metallic (AFM-M) state, Quantum Oscillations (periodic in 1/B and in B) that are highly angular dependent, to mention a few. Experimental results obtained so far provide a coherent picture illustrating that orbital order and its coupling to lattice and spin degrees of freedom drive the exotic electronic and magnetic properties in this Mott-like system. Transport and thermodynamic studies on Ca3(Ru1-xCrx)2O7 (0 ≤ x ≤ 0.20) reveal that AFM-M region is broadened with x that ultimately reaches 70K for x=0.20 (~8K for x=0). In this region, electron transport is enhanced and inhibited when B is applied along crystal’s respective axes, confirming an intrinsic half-metallic behavior. Moreover, the difference in coercivities of Ru and Cr magnetic ions pave way for the first-ever observation of a strong spin-valve effect in bulk material, a quantum phenomenon so far realized only in multilayer thin films or heterostructures. This discovery opens new avenues to understand the underlying physics of spin-valves and fully realize its potential in practical devices.
50
Lei, Xiaoqin. "Theoretical modelling of coupled chemo-hydro-mechanical behaviour of unsaturated expansive clays." Thesis, Lyon, INSA, 2015. http://www.theses.fr/2015ISAL0074.
Full textAbstract:
Expansive clays used in engineering practice are usually unsaturated and are sensitive to chemical composition of the in-pore solution. To analyse the complex coupled problems involved, an efficient mathematical model which can account for these chemo-hydro-mechanical behaviours has been developed. In this thesis, expansive clays are conceptualised into three-phase multi-species porous media. Based on the modified mixture theory and irreversible thermodynamics, a thermo-electro-chemo-hydro-mechanical framework has been developed. The Clausius-Duhem inequality, which governs the dissipations associated with mechanical work, phase transformation, mass transport and thermal transport, is rigorously derived. Based on this thermodynamic framework, constitutive laws for bulk liquid and salt mass transport, free and adsorbed water inter-phase mass transfer, and the chemo-elastic-plastic deformations of soil skeleton have been developed. The model has been implemented into the FEM software Bil and validated by simulating available experimental data on Boom Clays. What’s more, the salt infiltration process into an unsaturated expansive clay layer has been simulated to illustrate the applicability of the modelArgiles gonflantes utilisées dans la pratique de l'ingénierie sont généralement insaturés et sont sensibles à la composition chimique de la solution dans les pores. Pour analyser les problèmes complexes couplés impliqués, un modèle mathématique efficace qui peut expliquer ces comportements chimio-hydro-mécanique a été développé. Dans cette thèse, argiles gonflantes sont conceptualisés dans triphasés multi-espèces de milieux poreux. Sur la base de la théorie de mélange modifié et thermodynamique irréversible, un cadre thermo-électro-chimio-hydro-mécanique a été développé. L'inégalité de Clausius-Duhem, qui régit les dissipations associés au travail mécanique, transformation de phase, le transport de masse et le transport thermique, est rigoureusement dérivée. Basé sur ce cadre thermodynamique, lois de comportement pour liquides en vrac et le sel de transport de masse, transfert de masse de l'eau entre en phase libre et adsorbé, et les déformations chimio-élastique-plastique de squelette du sol ont été développés. Le modèle a été mis en œuvre dans le logiciel FÉM Bil et validé en simulant les données expérimentales disponibles sur les argiles de Boom. Qui plus est, le processus d'infiltration de sel dans une couche d'argile gonflante insaturés a été simulée pour illustrer l'applicabilité du modèle