Dissertations / Theses: 'Kinetics'

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Leung, Suet-ying, and 梁雪瑩. "A study of step kinetics by kinetic Monte Carlo simulation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2002. http://hub.hku.hk/bib/B31226322.

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JUNIOR, JOSE HENRIQUE NOLDIN. "THE REDUCTION KINETICS KINETICS OF SELF-REDUCING BRIQUETTES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2002. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=3667@1.

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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO
O presente trabalho, apresenta uma análise do impacto das variáveis, temperatura, tipo de atmosfera e composição dos materiais ferrosos e carbonosos, sobre a cinética da auto- redução, em dois tipos de briquetes auto-redutores, na faixa de temperatura de 1000 à 1300 graus Celsius. É apresentado um breve histórico da ciência de redução dos óxidos de ferro, além das características relevantes dos principais processos de auto-redução e uma análise dos principais trabalhos correlatos disponíveis na literatura, procurando evidenciar os aspectos termodinâmicos e cinéticos destes estudos. São discutidos detalhes do aparato disponível, o procedimento experimental, a caracterização das amostras, e os resultados obtidos. A partir da análise dos resultados, foi determinando a energia de ativação aparente (E0) igual à 177,10 kJ/mol e o fator de freqüência pré-exponencial da equação de Arrehnius (Constante da taxa 0) igual à 0,97x10-3 s-1. Foi observado que aumentos na temperatura de teste, diminuição na vazão de N2 e uso de atmosfera de CO, melhoraram significativamente a cinética de redução dos briquetes auto- redutores, aumentando os graus de conversão obtidos. Os resultados confirmaram que a reação de Boudouard se apresenta como a etapa controladora do processo até 1200 graus Celsius C, quando o controle passa a ser misto, sofrendo também a influência da reação química de redução dos óxidos de ferro. A importância destes resultados e observações experimentais para o desenvolvimento e projeto dos processos emergentes de auto-redução são destacados.
The present work, analyzes the impact of the key variables, temperature, reduction atmosphere and composition of the ferrous and carbonaceous materials, on the kinetics of self- reducing briquettes, for two types of samples, over the temperature range 1000 - 1300 Celsius Degree. A brief history of the ironmaking science is presented, covering the most relevant features of the main self-reduction processes and a survey of the main published researches on the same subject relating to thermodynamic and kinetic aspects. The experimental procedure, details of the apparatus used, the experimental parameters, characterization of the samples and the results are described. Based on the results obtained, the kinetic parameters were evaluated determining the apparent activation energy (E0) as 177,10 kJ/mol and the pre-exponential frequency factor of the Arrehnius equation (ê0) as 0,97x10-3 s-1. It is observed that, increasing the temperature, decreasing the inert gas flow (N2) and using CO atmosphere, improves significantly the kinetics of reduction of self-reducing briquettes, raising the rate of iron oxide reduction. The results confirm that the Boudouard reaction is the rate limiting step of the overall reaction, up to 1200 Celsius Degree, when a mixed control starts, where the influence of the iron oxides reduction shall be also considered. The significance of this experimental results and observations to the design and the development of an innovative self-reduction smelting process are highlighted.

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3

Rodway, G. H. "Interface kinetics." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.258163.

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Maguire, N. "Transient Kinetics." Thesis, Queen's University Belfast, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527839.

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Lang, Matthew H. "Polyelectrolyte adsorption kinetics." Diss., Georgia Institute of Technology, 1994. http://hdl.handle.net/1853/5792.

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Morin, Bertrand. "Kinetics of quenches." Thesis, McGill University, 1993. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=41218.

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Order-disorder transitions have been studied for many years. The great number of experiments done on binary alloys makes condensed matter physics very appealing since it allows theory and experiment to progress side by side.
Using field theoretic methods, we study many aspects of physical systems such as binary alloys, which are taken out of thermodynamic equilibrium. In the introduction, an expose of basic notions is given. In the second chapter, we review an analytical method describing phase separation processes resulting from a critical quench. Physically, the latter phenomena could represent an initially disordered binary alloy, in which, following a drop in temperature, the atoms spontaneously order into a crystalline lattice. We will then study the effect a conserved field has on the kinetics of phase separation. This conserved field represents the local concentration of atoms of the alloy. In Chapter 4, we describe a theory formulated to explain some non-trivial relaxation of the structure factor seen experimentally for an initially ordered system suddenly cooled. Finally, we propose a theoretical model describing polymorphous crystallization. The model is studied via computer simulations. The results so obtained are compared to the experiment.

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Whyte, Andrew Robert. "Laser photofragment kinetics." Thesis, University of Canterbury. Chemistry, 1988. http://hdl.handle.net/10092/8319.

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We report here several studies of the kinetics of reactions of free radical species in the gas phase. The radicals were produced by ultraviolet laser photolysis of stable precursor molecules in the presence of various reactant gases together with an excess of inert bath gas. The ensuing reactions were followed by means of either time-resolved laser-induced fluorescence (LIF) measurements of relative radical concentrations, or time-resolved resonance fluorescence measurements of the relative concentrations of product atoms. From the LIF measurements, bimolecular rate coefficients have been obtained at room temperature for the reactions CN + N → N₂ + C [(1.00 ±0.13) x 10⁻¹⁰ cm³s⁻¹], CN + O₂ → products [(1.27 ±0.23) x 10⁻¹⁰ cm³s⁻¹], NH₂ + N → products [(1.21 ±0.14) x 10⁻¹ⁱ cm³s⁻¹], NH₂ + NO → products [(1.81 ±0.12) x 10⁻¹ⁱ cm³s⁻¹], NH₂ + NO₂ → products [(2.11 ±0.18) x 10⁻¹ⁱ cm³s⁻¹], NH + NO → products [(5.78 ±0.64) x 10⁻¹ⁱ cm³s⁻¹], NH + NO₂ →products [(1.61 ±0.14) x 10⁻¹ⁱ cm³s⁻¹]. The rate coefficients for the reactions of NH have also been determined over the temperature range 269 - 377 K, yielding activation energies of 0 ±2 kJ mol⁻¹ (NH + NO) and - 9.5 ±3.2 kJ mol⁻¹ (NH + NO₂). In addition to the rate coefficient measurements the nature of the products of the NH₂ + N reaction has been investigated by measuring the relative yields of product hydrogen atoms via resonance fluorescence. The time dependence of the H atom concentration is consistent with production of H by the reaction NH₂ + N → N₂ + H + H. The same method has been used to establish that H atoms are not produced in the reaction between NH₂ + NO. These results have been interpreted in relation to the mechanisms of the reactions concerned. In particular, the nature of the primary products of the NH₂ + NO reaction is still uncertain; the present results on the NH₂ + NO and NH + NO systems indicate that OH is not a primary product of the former reaction, contrary to previous suggestions. This uncertainty and the results of a recent theoretical study of the kinetics of the NH₂ + NO reaction have raised questions about the nature of the reaction potential energy surface. Using the methods of ab initio molecular orbital theory we have determined the structures, relative energies and vibrational frequencies of a range of species which occur along the reaction coordinates leading to several alternative sets of products. The results of this investigation have been compared to those of earlier experimental and theoretical studies of the NH₂ + NO reaction.

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Lee, Khai S. "Kinetics of wetting." Thesis, Loughborough University, 2008. https://dspace.lboro.ac.uk/2134/33866.

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Wetting and de-wetting processes play an important role in many natural and technological processes. In many cases, wetting is an essential prerequisite for application, for example in paint films, crop sprays, cosmetics, pharmaceutical tablets and in preparation of suspensions. Both equilibrium and dynamic processes of wetting are important in coatings. In many industrial and medical applications, some strategies to control drop-spreading on solid surfaces are being developed. One possibility is that a surfactant, a surface-active polymer, a polyelectrolyte or their mixture are added to a liquid (usually water). Recently discovered trisiloxane and other silicone-based surfactants show very unusual behaviour.

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Lin, Chuhong. "Interfacial electrochemical kinetics." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:03207db0-6625-4b20-9c10-ba69ee21d8c6.

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The first two chapters in this thesis introduce the fundamental knowledge underpinning electrochemistry and numerical simulation. The rest of the thesis comprises three parts: investigation of charge transfer at the electrode-electrolyte interface; a kinetic study of electrocatalytic reactions at micro- and nano-electrodes; and the evaluation of electrochemical detection of single enzymes. In the first part the inner-sphere electron transfer is discussed under different situations where the breakage or formation of the chemical bond, the reorganization of the solvent and the influence of the electrical double layer are taken into consideration. Two important half-cell reactions in the field of fuel cells, the hydrogen oxidation reaction and the oxygen reduction reaction, are taken as examples and discussed in Chapter 3 and Chapter 4. The second part focuses primarily on the influence of the electrode size and geometry on electrocatalytic reactions. The kinetics reflecting both the mass transport of the reacting species and the electrocatalytic reaction are investigated. The application of simulation enables the measurement of the kinetic parameters and the determination of rate-determining factors in different experimental situations. The hydrogen oxidation reaction on nanoparticles is investigated in Chapter 5. Homogeneous and heterogeneous EC' (E: electrochemical step; C': catalytic step) reactions are discussed in Chapter 6, respectively. In the last section, the possible detection of single enzymes via the nano-impact electrochemical technique is explored in Chapter 7. The kinetics of the electrode system containing a freely-diffusing enzyme and a microelectrode is investigated and the experimental conditions required for the measurement of enzyme activity predicted.

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Kotchoubey, Jurij. "POLCA-T Neutron Kinetics Model Benchmarking." Thesis, KTH, Reaktorteknologi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-176096.

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The demand for computational tools that are capable to reliably predict the behavior of a nuclear reactor core in a variety of static and dynamic conditions does inevitably require a proper qualification of these tools for the intended purposes. One of the qualification methods is the verification of the code in question. Hereby, the correct implementation of the applied model as well as its flawless implementation in the code are scrutinized. The present work concerns with benchmarking as a substantial part of the verification of the three-dimensional, multigroup neutron kinetics model employed in the transient code POLCA-T. The benchmarking is done by solving some specified and widely used space-time kinetics benchmark problems and comparing the results to those of other, established and well-proven spatial kinetics codes. It is shown that the obtained results are accurate and consistent with corresponding solutions of other codes. In addition, a sensitivity analysis is carried out with the objective to study the sensitivity of the POLCA-T neutronics to variations in different numerical options. It is demonstrated that the model is numerically stable and provide reproducible results for a wide range of various numerical settings. Thus, the model is shown to be rather insensitive to significant variations in input, for example. The other consequence of this analysis is that, depending on the treated transient, the computing costs can be reduced by, for instance, employing larger time-steps during the time-integration process or using a reduced number of iterations. Based on the outcome of this study, one can finally conclude that the POLCA-T neutron kinetics is modeled and implemented correctly and thus, the model is fully capable to perform the assigned tasks.

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Rivera, Díaz del Castillo Pedro Eduardo José. "Kinetics of precipitation reactions." Thesis, University of Cambridge, 2002. https://www.repository.cam.ac.uk/handle/1810/221870.

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Trejo-Gallardo, Jaime. "Modeling chalcopyrite leaching kinetics." Thesis, University of British Columbia, 2007. http://hdl.handle.net/2429/240.

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Chalcopyrite (CuFeS2) is the most abundant of the copper sulfides and also one of the most refractory for leaching. Several processing routes have been proposed to overcome drawbacks associated with environmental problems related to copper extraction from this mineral. Atmospheric leaching in acidic ferric sulfate is regarded as being particularly attractive over other hydrometallurgical systems. However, the challenge has been to overcome the problem of slow extraction rates due to passivity encountered at high solution potentials in this system. This highlights the need to investigate better operating conditions to optimize copper extraction and prevent the problem of passivation, and to develop suitable modeling tools to assess and diagnose leaching performance. In this work, a dissolution rate expression for chalcopyrite leaching in acidic ferric sulfate media is proposed accounting for effects in the active and passive regions under potentials from 415 to 550 mV (Ag/AgCl). A model of chemical speciation in the bulk solution elucidates the idea of passivation caused by precipitation of ferric species and their consequent adsorption onto the chalcopyrite surface. Electrochemical studies on massive samples of chalcopyrite involving characterization and modeling of the anodic and cathodic half-cell reactions of chalcopyrite leaching together with mixed potential considerations lead to the development of the mathematical expression for dissolution rate. The mathematical model was calibrated with electrochemical parameters and results are in good agreement with real leaching data from batch tests for solution potential regions where passivity is not observed. On the other hand, the passive region was modeled by means of adjusting parameters related to adsorption energies of the passivating species. Results of the model for this region deviate from real data as potential becomes higher probably due to diffusion resistance through a layer composed of ferric complexes.

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13

Song, Zhiqiang. "Kinetics of emulsion polymerization." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/10148.

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Seddon, N. "Mercury bromide laser kinetics." Thesis, University of Hull, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.377398.

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Zaman, Flora. "Kinetics of enzyme models." Thesis, University of Kent, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263701.

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Camplejohn, Richard Stephen. "Cell kinetics and cancer." Thesis, University of Newcastle Upon Tyne, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.327272.

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Mas, Elodie A. "Exploiting kinetics in nanoscience." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440269.

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18

Rushworth, Philip John. "Quantitative asymmetric reaction kinetics." Thesis, University of Warwick, 2011. http://wrap.warwick.ac.uk/45827/.

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The comparison of catalysts for producing chiral materials is of vital importance in the improvement of reaction scope and efficacy. Here we describe a new method of analysing the kinetics of the stereodetermining steps in asymmetric reactions by performing ligand/catalyst competition experiments against an internal standard and measuring the enantiomeric excess obtained at a variety of ratios of ligand/catalyst to internal standard. From these enantiomeric excess measurements, we can establish the relative rate of reaction between the ligand/catalyst systems and the internal standard, allowing us to make indirect comparisons of the rates at which the ligands/catalysts perform the reaction. Here we take this method and apply it to three common synthetic procedures: the Sharpless asymmetric dihydroxylation, the asymmetric Michael addition of malonates to nitroalkenes and palladium catalysed asymmetric allylation reaction.

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Yang, Li-yin 1952. "Crystallization kinetics of diphenylhydantoin." Thesis, The University of Arizona, 1989. http://hdl.handle.net/10150/277190.

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The crystallization kinetics of diphenylhydantoin (DPH) has been studied at constant conditions in a small mixed suspension mixed product removal (MSMPR) crystallizer. Supersaturation is created by changing the pH of a DPH solution in the crystallization vessel. Crystal size distributions (CSD's) are measured by an in situ zone sensing method. Effects of pH and supersaturation on crystallization kinetics and CSD are summarized. The effect of an additive on the crystal growth of DPH has been studied in a batch system. Avoidance of nucleation in the early stages of crystallization is essential to the effect investigated.

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Henstridge, Martin Carl. "Studies in electrode kinetics." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:562136fd-3a23-464e-8829-c1b37052a29a.

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This thesis is concerned with the study of electrode kinetics, which we shall examine via comparison between theory with experiment. As such the first two chapters outline the basic principles of electrochemical experiments and their simulation. First, we examine the properties of voltammetry at porous electrodes by means of both simulations and experiments. We then introduce the symmetric Marcus-Hush (SMH) model of electrode kinetics as an alternative to the empirical Butler-Volmer model. First, we examine different methods for modeling the voltammetry of kinetically inhomogeneous electroactive monolayers. Next, we perform a critical evaluation of the SMH model for solution-phase systems through extensive comparison to experiments under diffusion-only and convective mass transport conditions using both cyclic and square wave voltammetry. The model is compared with the Butler-Volmer model throughout and is ultimately found to be poorly suited to the parameterisation of electrode kinetics, despite its foundations in the microscopic Marcus theory. We then introduce the asymmetric Marcus-Hush model, which removes the assumption that the Gibbs energy curves for reactant and product have the same curvature. This modification results in an additional parameter which quantifies the asymmetry of the system. A similar evaluation of this model is then undertaken for both surface-bound and solution phase systems and the asymmetric model is found to be a great deal more successful than its symmetric predecessor. Finally we outline a novel technique for extracting kinetic information directly from experimental cyclic voltammetry. The method is simple to implement and is general to all electrode geometries with one-dimensional symmetry.

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Sililo, Bernard Liswani. "Modelling uranium leaching kinetics." Diss., University of Pretoria, 2016. http://hdl.handle.net/2263/61336.

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The uranium price decline has negatively impacted on the uranium mining industry. This decline in price requires that uranium metallurgical processes be made to operate more efficiently. Some key parameters that influence the dissolution and kinetics of leaching uraninite (one of the main minerals from which uranium can be extracted) are pH, oxidationreduction potential and iron concentration. A good understanding of the effect these parameters have on the leach kinetics would lead to an efficient operation of metallurgical processes. The objective of this work was therefore to investigate the effects of these key drivers on leach kinetics of Rӧssing Uranium ore. Added to this, was an attempt to come up with a mathematical model which can successfully replicate the leach kinetics. A series of laboratory leach experiments were performed on Rӧssing ore where the pH, oxidationreduction potential and total iron were varied, one at a time, to establish the effects they have on the leach kinetics and on the uranium extraction. Analysis of the data collected from this study showed that the leach kinetics are more dependent on the oxidation-reduction potential, followed by the iron concentration and least affected by the pH. It was further shown that oxidation-reduction potential is a function of total iron. An integral method was used to analyse the kinetic data. A literature study reveals that uraninite dissolution follows first order kinetics, but of interest in these results was that the uranium dissolution was found to closely follow the second order. Further research is recommended to look at ascertaining these results. Two models were developed, one using regression and the other by curve fitting method. Both models could fit the experimental data well enough.
Dissertation (MSc)--University of Pretoria, 2016.
Materials Science and Metallurgical Engineering
MSc
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22

Olinde, Lindsay. "Sediment Oxygen Demand Kinetics." Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/42437.

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Hypolimnetic oxygen diffusers increase sediment oxygen demand (SOD) and, if not accounted for in design, can further exacerbate anoxic conditions. A study using extracted sediment cores, that included both field and laboratory experiments, was performed to investigate SOD kinetics in Carvinâ s Cove Reservoir, a eutrophic water supply reservoir for Roanoke, Virginia. A bubble-plume diffuser is used in Carvinâ s Cove to replenish oxygen consumed while the reservoir is thermally stratified. The applicability of zero-order, first-order, and Monod kinetics to describe transient and steady state SOD was modeled using analytical and numerical techniques. Field and laboratory experiments suggested that first-order kinetics characterize Carvinâ s Cove SOD. SOD calculated from field experiments reflected diffuser flow changes. Laboratory experiments using mini-diffusers to vary dissolved oxygen concentration and turbulence were conducted at 4Â°C and 20Â°C. Similar to field observations, the laboratory results followed changes in mini-diffuser flow. Kinetic-temperature relationships were also observed in the laboratory experiments. A definitive conclusion could not be made on the broad applicability of first-order kinetics to Carvinâ s Cove SOD due to variability within field experiments. However, in situ experiments are underway that should assist in the overall understanding of the reservoirâ s SOD kinetics.
Master of Science

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Ebanks, Keira C. "Kinetics of Peptide Aggregation." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/31830.

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The most thermodynamically stable biological structure is the cross-beta secondary structure of the "amyloid"or "prion". As a testament to its stability, the amyloid occurs naturally in 2 rare instances: as a mechanism to protect or destroy life. Pathogenic amyloids are the signature of neurological disorders such as Alzheimer's and Parkinson's disease and bovine spongiform encephalopathy (BSE), which have no effective treatments or known cures. Pathogenic amyloids appear as nanometer sized "plaques" that self-assemble over time. The plaques usually are well-organized crystalline/fibrous structures ~10-20 nm in diameter and >100 nm long. "Functional" amyloids are very rare in nature and serve the direct purpose to proliferate life. Stalks to protect eggs, fibers to coat spores, and adhesive proteins of bacteria, algae, fungi, and mollusks are examples. Functional amyloids can be larger than pathogenic amyloids by 1-2 orders of magnitude. There is a burgeoning research field based on emulating the amyloid. This is because it can be formed from a host of proteins or peptides simply by denaturing them enough to form a cross-beta secondary structure and has a modulus of >10 GPa. As a general reference, "protein" is usually a very high molecular weight, naturally occurring molecule and "peptide" is a much smaller portion of a natural protein or a non-natural molecule synthesized from a few amino acids. Researchers are increasingly attempting to take advantage of the functional amyloid. It is still not understood how the functional amyloid self-assembles or why it can be larger than the pathogenic amyloid. We have identified a potential pathway to large functional amyloids that involves a long alpha-helix containing protein (the "adder") undergoing an alpha to beta transition in the presence of a hydrophobic beta-sheet template. Testing our hypothesis against proteins found in natural large functional amyloids seems to suggest it is a ubiquitous process. The resulting material is a fiber composite similar to the native structures.
Master of Science

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Viselgienė, Gintarė. "The kinetics of silver electrodeposition from sulfite solutions." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20100623_093628-71686.

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Silver electrodeposition from sulfite electrolytes is considered to be one of the most promising processes to replace the extremely toxic traditional cyanide-based silver plating solutions with the additional advantage, that sulfite electrolytes can be successfully applied for silver deposition for micro-electro-mechanical systems (MEMSs). Mechanism of metal complexes electroreduction is an important result, especially when it may have a wide range of applications in the future. However, electrodeposition also has several shortcomings, including sulfite ion oxidation by oxygen in air and relatively negligible cathodic current densities, which are too low for qualitative galvanotechnique. There are very few works dedicated to the chemistry and electrochemistry of silver sulfite complexes. Most publications related with this subject are concerned with the questions of applicability. The main objective of this study was the investigation of the silver sulfite complexes electroreduction kinetics. To achieve this goal, we studied the dependence of the exchange current density on the free sulfite ions concentration in a series of isopotential solutions. Our studies also allowed to determine the mechanism of this electrochemical charge transfer reaction.
Naudojant chronopotenciometrijos metodą buvo tirta sidabro elektronusodinimo iš sulfitinių tirpalų kinetika. Eksperimentiniai tyrimai patvirtino negausius žinomus literatūrinius duomenis, kad sidabro elektrokristalizacija iš sulfitinių elektrolitų yra apsprendžiama lėta sidabro ad-atomų kristalizacija galvaninės dangos paviršiuje. Tai ypač akivaizdu pusiausvyrinio potencialo srityje. Nustatyta, kad patikimiausi rezultatai, tiriant krūvio pernešimo stadiją, gaunami maksimaliai nutolus nuo pusiausvyros potencialo. Tai lengviausia realizuoti chronopotenciometrijos sąlygomis, o nustatytas mainų srovės tankis svyruoja tarp 0,9 (kai tirpalo sudėtis 0,003 ir 0,115 ) iki 2,46 (kai tirpalo sudėtis 0,1 ir 0,77 ). Patikimiausi rezultatai buvo gauti matuojant mainų srovės tankių priklausomybes nuo laisvų sulfito jonų koncentracijos izopotencialių ( 0,300 ) tirpalų serijoje. Visuose izopotencialiuose tirpaluose buvo nustatyti krūvio pernašos viršįtampiai -60 – -160 intervale. Naudojantis lygtimi ir mainų srovės tankio priklausomybės nuo laisvų sulfito jonų koncentracijos grafiku iš eksperimentinių duomenų nuolinkio kampo apskaičiuotas reakcijos laipsnis 0,67. Atsižvelgiant į galimas paklaidas, tikėtina, kad jis yra lygus 1. Gauti rezultatai rodo, kad artimas vienetui reakcijos laipsnis sulfito jonų atžvilgiu atitinka teiginį, jog betarpiškai fazių sąlyčio riboje redukuojasi kompleksinė dalelė . Atsiradusios paklaidos greičiausiai yra susiję su tirpalo komponentų... [toliau žr. visą tekstą]

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Setta, Feth-Allah. "Calcium carbonate and barium sulphate scale formation kinetics : a surface scale deposition kinetic model." Thesis, University of Leeds, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.595798.

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Scale formation is one of the major flow assurance problems in the water treatment and in the oil and gas sectors. Calcium carbonate (CaCO3) is the most common scale encountered in industry. Barium sulphate (BaSO4) scale is the most difficult to deal with as it is highly insoluble and requires chemical and/or physical treatments. Scale build up results in reduced water flow through pipes and could lead to an entire shutdown of installations leading to important financial losses. Nowadays, the main ways to treat and prevent scale formation are periodic squeeze treatments and/or the continuous injection of scale inhibitors. The use of nitrogen and phosphorous compounds, such as polyphosphino carboxylic acid (PPCA), has already been shown to significantly decrease calcium carbonate scale formation. However, the discharge of such inorganic chemicals into the environment represents a real threat and green inhibitors (such as Polymaleic acid (PMA), Poly-Aspartate (PA) and Carboxymethyl-inulin (CMI) are an altemative. A simultaneous comparison of their inhibition effects on scale precipitation and deposition has been carried out in this study. Several different scale preCipitation prediction models have been developed. However, these models are based on thermodynamics and give, at most, a scale tendency to form. Scale Deposition rate equations or prediction of scale deposition have been largely ignored. Moreover, no attempts have been made to associate precipitation data in the bulk solution with deposition data on a solid surface. If a comparison is made with corrosion prediction where a time-based rate is given (in millimetres per year), then it can be seen that a scale kinetic deposition model would be more useful for the flow assurance and the integrity management. This study present a first attempt for a calcium carbonate and barium sulphate scale deposition kinetic model giving an amount of scale (quantity as a mass or thickness) on a stainless steel surface in function of the saturation index, the temperature, the pressure and flow regime

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Zhang, Ziji. "Theoretical and computational study of coupling of soot, gas kinetics and radiation in diffusion flames using reduced mechanisms /." Digital version accessible at:, 1998. http://wwwlib.umi.com/cr/utexas/main.

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Boström, Fredrik. "Single-cycle kinetics for QCM biosensors for high throughput nanoparticle characterization application." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-298942.

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Characterizing nanoparticles to be able to understand how they functions in the body is important for development of drugs. Furthermore with increasing number of nanoparticle product the nanotoxicity of nanoparticles is important to understand. This report is a part of the EU-project Nanoclassifier which purpose is to “develop a cost effective, high throughput screening platform for characterization of the bionanointerface and its cell-binding partners”. Single-cycle kinetic was used to determine the number of binding epitopes on polystyrene nanoparticle with transferrin corona. The number of available epitopes describes how active the Nanoparticle will be in the body. For this purpose Single-cycle kinetic methodology was successfully used on nanoparticles. Single-cycle kinetic methodology has great potential to become the standard method for high throughput nanoparticle epitope characterization.

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WATKINS, JOSEPH ABRA. "SPECTRAL AND KINETIC PROPERTIES OF CHLOROBIUM THIOSULFATOPHILUM CYTOCHROME C-555 (ELECTROSTATICS, REDOX KINETICS, CIRCULAR DICHROISM)." Diss., The University of Arizona, 1986. http://hdl.handle.net/10150/183975.

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The spectral and kinetic properties of Chlorobium thiosulfatophilum cytochrome c-555 have been investigated and are compared to analogous properties of procaryotic and eucaryotic c-type cytochromes. The circular dichroism spectra are similar for c-type cytochromes of a given class and effects arising from specific amino acid substitutions are determined. The oxidation-reduction state dependence of the spectra in the near-ultraviolet region is interpreted in terms of changes in hydrogen bonding and polarity of the environment of aromatic amino acid residues in close proximity to heme iron resulting from small structural changes. An electrostatic model of bimolecular rate constants is developed to adequately describe the electric field effects for accurate computation of intrinsic rate constants. Structural models of bimolecular complexes of cytochrome c and flavodoxin or cytochrome b₅, developed by other investigators, are used to constrain the dielectric coefficients of the electrostatic model. Using these constraints, the relative contributions of ionic and dipolar interactions to the intermolecular electrostatic potential energies are estimated for several c-type cytochrome reactions. The ionic contribution is adequately described by the charged residue interactions in the region of intermolecular contact, and the dipolar contribution is adequately described by the molecular dipole moment. Oxidation-reduction reactions of cytochrome c-555 with small molecule reagents suggest a mechanism of electron transfer that is similar to other c-type cytochromes. In general, electron transfer may be preceded by formation of a bimolecular collision complex or may occur during the collision. Further, the ionic strength dependence of second-order rate constants indicates that molecular electric fields significantly affect the bimolecular reaction rates. Calculated intrinsic rate constants are dependent on the difference between oxidation-reduction potentials of the reactants as predicted by Marcus outer sphere electron transfer theory. The mechanism of reduction of c-type cytochromes by flavodoxin semiquinone is similar to the mechanism of electron transfer reactions involving small molecules. Thus, principles involved in protein-small molecule reactions are also involved in protein-protein reactions.

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29

Boddapati, Aparna. "Modeling cure depth during photopolymerization of multifunctional acrylates." Thesis, Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/33934.

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The photopolymerization of multifunctional acrylates leads to the formation of a complex and insoluble network due to cross-linking. This characteristic is a useful property for stereolithography applications, where solid parts of the desired shape are cured using a pre-determined energy exposure profile. Traditionally, the required energy exposure is determined using a critical energy--depth of penetration, or Ec--Dp, model. The parameters Ec and Dp, are usually fit to experimental data at a specific resin composition and cure intensity. As a result, since the Ec--Dp model does not explicitly incorporate cure kinetics, it cannot be used for a different set of process conditions without first obtaining experimental data at the new conditions. Thus, the Ec--Dp model does not provide any insight when a new process needs to be developed, and the best processing conditions are unknown. The kinetic model for multifunctional acrylate photopolymerization presented here is based on a set of ordinary differential equations (ODE), which can be used to predict part height versus exposure condition across varying resin compositions. Kinetic parameter information used in the model is obtained by fitting the model to double bond conversion data from Fourier Transform Infrared Spectroscopy (FTIR) measurements. An additional parameter, the critical conversion value, is necessary for determining the formation of a solid part of the desired height. The initial rate of initiation, Ri, combines all the factors that impact part height, and therefore, it is an important quantity that is required in order to find the critical conversion value. The critical conversion value is estimated using the Ri and Tgel value from microrheology measurements. Information about network connectivity, which can be used to get properties such as molecular weight, cannot be derived from models using traditional mass-action kinetics for the cross-linking system. Therefore, in addition to modeling the reaction using the ODE based model, the results from a statistical model based on Kinetic Monte Carlo (KMC) principles are also shown here. The KMC model is applicable in situations where the impact of chain length on the kinetics or molecular weight evolution is of interest. For the present project, the detailed information from network connectivity was not required to make part height predictions, and the conversion information from the ODE model was sufficient. The final results show that the kinetic ODE model presented here, based on the critical conversion value, captures the impact of process parameters such as initiator concentration, light intensity, and exposure time, on the final part height of the object. In addition, for the case of blanket cure samples, the part height predictions from the ODE model make comparable predictions to the Ec--Dp model. Thus, the ODE model presented here is a versatile tool that can be used to determine optimum operating conditions during process development.

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30

Marais, Charles Guillaume. "Thermodynamics and kinetics of sorption /." Link to the online version, 2008. http://hdl.handle.net/10019/1944.

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31

Kempen, Antoine. "Solid state phase transformation kinetics." [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=964251191.

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32

Tacon, Geoffrey Reginald Russell. "Mathematical modelling of liver kinetics /." [St. Lucia, Qld.], 2005. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe19399.pdf.

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33

Hedfors, Cecilia. "Lipase chemoselectivity - kinetics and applications." Licentiate thesis, KTH, School of Biotechnology (BIO), 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10232.

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A chemoselective catalyst is preferred in a chemical reaction where protecting groups otherwise are needed. The two lipases Candida antarctica lipase B and Rhizomucor miehei lipase showed large chemoselectivity ratios, defined as (k_cat/K_M)_OH/ (k_cat/K_M)_SH, in a transacylation reaction with ethyl octanoate as acyl donor and hexanol or hexanethiol as acyl acceptor (paper I). The chemoselectivity ratio of the uncatalyzed reaction was 120 in favour of the alcohol. Compared to the uncatalyzed reaction, the chemoselectivity was 730 times higher for Candida antarctica lipase B and ten times higher for Rhizomucor miehei lipase. The K_M towards the thiol was more than two orders of magnitude higher than the K_M towards the corresponding alcohol. This was the dominating contribution to the high chemoselectivity displayed by the two lipases. In a novel approach, Candida antarctica lipase B was used as catalyst for enzymatic synthesis of thiol-functionalized polyesters in a one-pot reaction without using protecting groups (paper II). Poly(e-caprolactone) with a free thiol at one of the ends was synthesized in an enzymatic ring-opening polymerization initiated with mercaptoethanol or terminated with either 3-mercaptopropionic acid or g-thiobutyrolactone.

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34

Gheorghita, Ligia. "Passivation kinetics at semiconductor interfaces." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0016/NQ46347.pdf.

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35

Xia, Qi. "Gas absorption kinetics in STR's." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0032/NQ64694.pdf.

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36

Vaidyaraman, Sundar. "Kinetics of the bosch reaction." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/10277.

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37

Lance, Christine Marie. "Repassivation kinetics of dental amalgam." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/19648.

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38

Ozdemir, Metin. "Morphological kinetics of facetted crystals." Diss., Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/27898.

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39

Xia, Qi 1962. "Gas absorption kinetics in STR's." Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36732.

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Experiments were carved out in a stirred tank reactor with both two phase and three phase systems. A systematic examination of the effect of solid particles on parameters such as volumetric liquid-side mass transfer coefficient kLa, specific interfacial area a, gas holdup epsilong, bubble size dB, and average bubble residence time tau, was conducted. Both dimensional and dimensionless correlations were generated and conclusions were drawn.
The work was carried out in the context of the industrial experience that stirred tank reactors are widely used in both metallurgical and chemical engineering processes that often involve gas absorption in two and three phase systems. The effect of solids loading on the oxygen absorption rate in stirred tank reactors is complex due to the interactions between bubbles and solid particles, and also between other parameters. The measurement of some parameters, such as bubble size, specific interfacial area, volumetric mass transfer coefficient, is difficult, and there are many discrepancies in the literature with respect to the form of the correlation for oxygen absorption rate and bubble size and also the explanation of the internal mechanisms.
The present work found that kLa decreased with increasing solids volume fraction. This decrease was as much as 50% when solids loading was increased from 0 (water) to 14 vol% at a superficial gas velocity of 0.64 cm/s and a impeller speed of 400 rpm. The primary reason for this was due to the enhancing effect of solids on bubble coalescence and the increase of slurry density. Kolmogroff's turbulence theory was proved not applicable to the present STR and conditions. The cause for this was believed to be due to the fact that the power density in the STR was far from homogeneous, and the dynamic equilibrium between bubble breakup and the bubble coalescence was not established.
Bubble size, dB, was found to be increased by increasing solids volume fraction. The increase was due to the direct enhancing effect of solids on bubble coalescence and due to less bubble recirculation, i.e., change of the bulk flow pattern, with increased solids loading. There was no direct relationship found between a change of the apparent viscosity of slurry and a change of bubble size. Therefore, the manner by which many people incorporated apparent viscosity into the correlation of dB is inappropriate.
To properly describe the extent of bubble coalescence in three phase systems, a new parameter, the coalescence factor, fc, was defined in the present work. It was found that the coalescence factor decreased with increasing solids volume fraction and power input, but decreased with increasing superficial gas velocity.

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40

Moonga, B. S. "The kinetics of protiodecarbonylation reactions." Thesis, Brunel University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375474.

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41

Harding, Mark S. "The kinetics of interfacial processes." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336113.

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42

Heard, Dwayne Ellis. "Laser studies of chemical kinetics." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.258025.

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43

Till, Ulrike. "Recombination kinetics of radical pairs." Thesis, University of Oxford, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267949.

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44

Lewis, L. A. "Oxidation kinetics of zinc vapour." Thesis, University of Manchester, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487650.

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45

Kononova, Anna. "Memetic computing in chemical kinetics." Thesis, University of Leeds, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.531526.

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46

Demetriou, D. A. "Numerical simulations of interface kinetics." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.598490.

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This dissertation's goal is concerned with the development and numerical study of a continuum model, that describes a variety of interface growth phenomena such as fluid displacement in porous media, crystal growth and flux-lines in type-II superconductors. The continuum model is the Quenched-Edwards-Wilkinson (QEW), which is well established in the literature and we restrict ourselves in providing a brief 'derivation' in terms of symmetry considerations. A crucial part of the model is the quenched random medium where the interface moves. The 'adequate' generation of the random background is a crucial ingredient of the simulations and we use a method first employed in fluid mechanics, but never before used in this field. Massive parallel simulations of the resulting system allowed us to verify the presence of a well defined depinning transition between a pinned and moving interface. This is characterized by the presence of a spatial system size (above a certain system size) independent threshold force. The transition appears to fit well the conjecture that the ensemble and time averaged centre of mass velocity, v_cm, scales with the applied external driving force, F, according to v_cm ~ ((F)/(F)_c-1)^θwhere F_c is the threshold force and θ the velocity critical exponent. The velocity exponent is expected to be a 'universal' quantity independent of model parameters. Based on our work we estimate θ = 0.61 ± 0.06.

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47

Suwatchara, Danu. "Experimental advances in electrode kinetics." Thesis, University of Oxford, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639734.

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At the present, numerous kinetic theories are available to electrochemists in describing chemical reactions at the electrode. These exist in varying degree of complexity, ranging from simplistic empirical formulae to more rigorous models that account for microscopic physical phenomena pertiaining to the reactive species and their environment. However, experimental work documented in support of the validity and comparison between these theories is scarce. This is largely due to difficulty in attaining and controlling the experimental conditions where applicability of the theories break down. As such, the current work utilizes state-of-the-art · electrochemical experimental techniques in order to test some of the most prominent electrode kinetics theories via comparison to simulations. This is done with the aim of identifying their limitations and providing new insight into fundamental mechanistic processes that occur during an electrochemical reaction.

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48

Daly, P. J. "Dissolution kinetics of calcium carbonate." Thesis, University of Liverpool, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372693.

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49

Brownless, George Peter. "The combustion kinetics of hydrofluorocarbons." Thesis, University of Leeds, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343477.

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50

Nelson, Dorothy Caroline. "Reaction kinetics of gasless pyrotechnics." Thesis, University of Leeds, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.293701.

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Dissertations / Theses on the topic 'Kinetics'

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