A new methodology is developed to calculate density of states of interstellar and atmospheric clusters that takes account of their loosely bound nature and incorporates kinetically important angular momentum constraints explicitly. The method is based on classical phase space integration for the intermonomer modes of the cluster with imposition of the constraints of selected total energy and total angular momentum. It achieves considerable efficiency via essentially analytic evaluation of the momentum space integrals coupled with efficient Monte Carlo sampling of configurations. The derivation for the equation for the density of states is outlined and all steps in the simplification of the accessible momentum space volume are detailed. The method is tested rigorously against an entirely analytic result obtained for the ideal case of a dimer with spherical top fragments and no interaction potential. Interstellar applications of the new approach are presented for (HCN)2 and (CO)2. The new intermononmer density of states has been integrated over metastable states to obtain the intermonomer partition function, which in turn is used to calculate the metastable equilibrium constants for interstellar clusters, which in turn is used tocalculate the second order rate constant of overall dimer formation in the interstellar environment. Atmospheric applications of the new approach are presented for (H2O)2. The new intermonomer density of states is convoluted with the intramonomer density of states to obtain the convoluted density of states. This convoluted density of states is then integrated over total energy and angular momentum to obtain the anharmonic partition function, which in turn is used to calculate the equilibrium constant for atmospheric clusters, which in turn is used to calculate the third order rate constant for overall dimer formation in the atmospheric environment. Kinetic quantities are also calculated with the intermonomer and convoluted density of states for interstellar and atmospheric clusters, respectively. These densities of states are combined with RRKM theory to compute unimolecular dissociation rate constants, which are then averaged with respect to the thermal capture flux distribution to compute average lifetimes as a function of temperature.

A new methodology is developed to calculate density of states of interstellar and atmospheric clusters that takes account of their loosely bound nature and incorporates kinetically important angular momentum constraints explicitly. The method is based on classical phase space integration for the intermonomer modes of the cluster with imposition of the constraints of selected total energy and total angular momentum. It achieves considerable efficiency via essentially analytic evaluation of the momentum space integrals coupled with efficient Monte Carlo sampling of configurations. The derivation for the equation for the density of states is outlined and all steps in the simplification of the accessible momentum space volume are detailed. The method is tested rigorously against an entirely analytic result obtained for the ideal case of a dimer with spherical top fragments and no interaction potential. Interstellar applications of the new approach are presented for (HCN)2 and (CO)2. The new intermononmer density of states has been integrated over metastable states to obtain the intermonomer partition function, which in turn is used to calculate the metastable equilibrium constants for interstellar clusters, which in turn is used tocalculate the second order rate constant of overall dimer formation in the interstellar environment. Atmospheric applications of the new approach are presented for (H2O)2. The new intermonomer density of states is convoluted with the intramonomer density of states to obtain the convoluted density of states. This convoluted density of states is then integrated over total energy and angular momentum to obtain the anharmonic partition function, which in turn is used to calculate the equilibrium constant for atmospheric clusters, which in turn is used to calculate the third order rate constant for overall dimer formation in the atmospheric environment. Kinetic quantities are also calculated with the intermonomer and convoluted density of states for interstellar and atmospheric clusters, respectively. These densities of states are combined with RRKM theory to compute unimolecular dissociation rate constants, which are then averaged with respect to the thermal capture flux distribution to compute average lifetimes as a function of temperature.

A new methodology is developed to calculate density of states of interstellar and atmospheric clusters that takes account of their loosely bound nature and incorporates kinetically important angular momentum constraints explicitly. The method is based on classical phase space integration for the intermonomer modes of the cluster with imposition of the constraints of selected total energy and total angular momentum. It achieves considerable efficiency via essentially analytic evaluation of the momentum space integrals coupled with efficient Monte Carlo sampling of configurations. The derivation for the equation for the density of states is outlined and all steps in the simplification of the accessible momentum space volume are detailed. The method is tested rigorously against an entirely analytic result obtained for the ideal case of a dimer with spherical top fragments and no interaction potential. Interstellar applications of the new approach are presented for (HCN)2 and (CO)2. The new intermononmer density of states has been integrated over metastable states to obtain the intermonomer partition function, which in turn is used to calculate the metastable equilibrium constants for interstellar clusters, which in turn is used tocalculate the second order rate constant of overall dimer formation in the interstellar environment. Atmospheric applications of the new approach are presented for (H2O)2. The new intermonomer density of states is convoluted with the intramonomer density of states to obtain the convoluted density of states. This convoluted density of states is then integrated over total energy and angular momentum to obtain the anharmonic partition function, which in turn is used to calculate the equilibrium constant for atmospheric clusters, which in turn is used to calculate the third order rate constant for overall dimer formation in the atmospheric environment. Kinetic quantities are also calculated with the intermonomer and convoluted density of states for interstellar and atmospheric clusters, respectively. These densities of states are combined with RRKM theory to compute unimolecular dissociation rate constants, which are then averaged with respect to the thermal capture flux distribution to compute average lifetimes as a function of temperature.

The need for renewable and cleaner sources of energy has made biofuels an interesting alternative to fossil fuels, especially in the case of butanol isomers, with their favorable blend properties and low hygroscopicity. Although C4 alcohols are prospective fuels, some key reactions governing their pyrolysis and combustion have not been adequately studied, leading to incomplete kinetic models. Butanol reactions kinetics is poorly understood. Specifically, the unimolecular and H-assisted tautomerism of propen-2-ol to acetone, which are included in butanol combustion kinetic models, are assigned rate parameters based on the analogous unimolecular tautomerism vinyl alcohol ↔ acetaldehyde and H addition to the double bound of iso-butene, respectively. In an attempt to update current kinetic models for tert- and 2-butanol, a theoretical kinetic study of the unimolecular and H-assisted tautomerism, i-C3H5OH⟺CH3COCH3 and i-C3H5OH+Ḣ⟺CH3COCH3+Ḣ, was carried out by means of CCSD(T,FULL)/aug-cc-pVTZ//CCSD(T)/6-31+G(d,p) and CCSD(T)/aug-cc-pVTZ//M062X/cc-pVTZ ab initio calculations, respectively. For H-assisted tautomerism, the reaction takes place in two consecutive steps: i-C3H5OH+Ḣ⟺CH3ĊOHCH3 and CH3ĊOHCH3⟺CH3COCH3+Ḣ. Multistructural torsional anharmonicity and variational transition state theory were considered in a wide temperature and pressure range (200 K – 3000 K, 0.1 kPa – 108 kPa). It was observed that decreasing pressure leads to a decrease in rate constants, describing the expected falloff behavior for both isomerizations. Results for unimolecular tautomerism differ from vinyl alcohol ↔ acetaldehyde analogue reactions, which shows lower rate constant values. Tunneling turned out to be important, especially at low temperatures. Accordingly, pyrolysis simulations in a batch reactor for tert- and 2-butanol with computed unimolecular rate constants showed important differences in comparison with previous results, such as larger acetone yield and quicker propen-2-ol consumption. In the combustion and pyrolysis batch reactor simulations, using all the rate constants computed in this work, H-assisted reactions are limited because H radicals become abundant once the propen-2-ol has been consumed by other reactions, such as the non-catalyzed tautomerism i-C3H5OH⟺CH3COCH3, which becomes one of the main source of acetone. The intermediate radical (CH3ĊOHCH3) is formed exclusively from tert-butanol, with its concentration in 2-butanol oxidation being smaller because the secondary alcohol is unable to produce the radical directly. In all cases, the intermediate is converted effectively to acetone.

A flotation model has been proposed that is applicable in a turbulent environment. It is the first turbulent model that takes into account hydrodynamics of the flotation cell as well as all relevant surface forces (van der Waals, electrostatic, and hydrophobic) by use of the Extended DLVO theory. The model includes probabilities for attachment, detachment, and froth recovery as well as a collision frequency. A review of the effects fluids have on the flotation process has also been given. This includes collision frequencies, attachment and detachment energies, and how the energies of the turbulent system relate to them. Flotation experiments have been conducted to verify this model. Model predictions were comparable to experimental results with similar trends. Simulations were also run that show trends and values seen in industrial flotation systems. These simulations show the many uses of the model and how it can benefit the industries that use flotation. / Ph. D.

The FT-Raman techniques were developed to quantify reactions that follow on mixing aqueous solutions of bis-(1,3-diaminopropane)diaquacobalt( III) ion ([Co(tn)2(0H)(H20)]2+) and p-nitrophenylphosphate (PNPP). For the development and validation of the kinetic modelling technique, the well-studied inversion of sucrose was utilized. Rate constants and concentrations could be estimated using calibration solutions and modelling methods. It was found that the results obtained are comparable to literature values. Hence this technique could be further used for the [Co(tn)2(0H)(H20)]2+ assisted hydrolysis of PNPP. It was found that rate constants where the pH is maintained at 7.30 give results which differ from those where the pH is started at 7.30 and allowed to change during the reaction. The average rate constant for 2:1 ([Co(tn)2(0H)(H20)]2+:PNPP reactions was found to be approximately 3 x 104 times the unassisted PNPP hydrolysis rate. / Chemistry / M. Sc. (Chemistry)

Atmospheric aldol self-reactions of octanal, heptanal and hexanal in a range of aqueous H2SO4 w/v% concentrations as a catalyst were studied in both bulk liquid-liquid experiments and gas-liquid experiments. Initially, a new practical methodology was developed and enhanced to monitor aldol reactions in aqueous acidic media. The evaluation of a quenching and extracting method were performed, confirming the suitability, reliability and reproducibility of the extraction method. In bulk studies, aldol products of the three aldehydes were separated and identified by preparative HPLC, GC-MS and NMR. The major aldol products observed at high acid concentrations were alpha,β-unsaturated aldehyde (dimer), trialkyl benzene (trimer) and tetraalkylcycloocta-tetraene (tetramer). The trimer of octanal was formed as trioxane in low sulfuric acid concentration and the possible mechanism accretion reaction pathways of high and low acid concentrations are proposed in this study. A systematic kinetic study of octanal, heptanal and hexanal in the bulk experiments at 65, 60 and 55 w/v% H2SO4 at 294 K were monitored using gas chromatographic equipped with a flame ionisation detector (GC-FID). The rate constants were generally estimated using second order kinetics and observed to increase as a function of sulfuric acid concentrations and also as the chain length of aliphatic aldehyde increased. The aldol self-reaction in the bulk experiment was too fast at room temperature to be easily measured using a quenching method therefore attempts were made to follow the reaction at low temperature (0 °C). The result at low temperature indicated that the rate constant of aldehyde was reduced but there was an issue of rapid rise in temperature as a result of mixing concentrated sulfuric acid with aqueous solution of the aldehyde. A gas bubbling system was developed which better simulates atmospheric reality, and which also resolves the issue of temperature rise on mixing. Two different methodologies were used: one in which the aldehyde was continually added, and one where a fixed amount was added from the gas phase and the reaction was then allowed to proceed, monitored at selected time intervals. The precision and accuracy of the fixed method was then further improved by the addition of an internal standard (IS). Using this, the concentrations of aliphatic aldehydes (C6-C8) were calibrated using an experimentally determined response factor and used to follow the loss of the reactant aldehydes. Similar methods were applied to the aldol dimers (C6-C8), which were purified and used to calibrate the chromatographic response. The rate constant for octanal, heptanal and hexanal at 76 wt% and 294 K were 0.0969 M-1 s-1, 0.1497 M-1 s-1 and 0.2622 M-1 s-1 respectively. There are some observations based upon the results presented in this thesis that may be of atmospheric significance: (i) phase separation between organic and aqueous layers in both the bulk experiment and in the bubbling system; (ii) the acid strength dependence and concentration-dependence of the various products; (iii) the faster rates than previously reported, and variation between bulk and bubbling; and (v) the time-dependent colour changes. Further work to explore these observations is proposed.

The DMPO type spin trap 5,5-Dimethyl-1-pyrroline N-oxide (DMPO) and the exceptionally similar spin trap 2-ethoxycarbonyl-2-methyl-3,4-dihydro-2H-pyrrole-l-oxide (EMPO) are widely studied in computational and theoretical works. This particular study examines the addition reactions that both these molecules undergo with the carcinogenic hydroxyl radical. This work used a relatively new approximation method, called the correlation consistent composite approach or ccCA, for carrying out quantum mechanical calculations to give the free energies of the products and reactants of the reactions. The free energies are to be used to extrapolate the rate constants of the reactions from the Arrhenius equation. Though both the spin traps studied have been widely examined and assessed in both theoretical and experimental work, accurately calculated rate constants have not been previously obtained using computational methods. The results obtained here will help to assess the efficiency and the accuracy of the ccCA method, as well as lead to the design of better, more novel spin traps.

An experimental study of the effect of initial conditions on the development of Rayleigh Taylor Instabilities (RTI) at low Atwood numbers (order of 10-4) was performed in the water channel facility at TAMU. Initial conditions of the flow were generated using a controllable, highly reliable Servo motor. The uniqueness of the study is the system’s capability of generating the required initial conditions precisely as compared to the previous endeavors. Backlit photography was used for imaging and ensemble averaging of the images was performed to study mixing width characteristics in different regimes of evolution of Rayleigh-Taylor Instability (RTI). High-speed imaging of the flows was performed to provide insights into the growth of bubble and spikes in the linear and non-linear regime of instability development. RTI are observed in astrophysics, geophysics and in many instances in nature. The vital role of RTI in the feasibility and efficiency of the Inertial Confinement Fusion (ICF) experiment warrants a comprehensive study of the effect of mixing characteristics of RTI and its dependence on defining parameters. With this broader objective in perspective, the objectives of this present investigation were mainly threefold: First was the validation of the novel setup of the Water channel system. Towards this objective, validation of Servo motor, splitter plate thickness effects, density and temperature measurements and single-mode experiments were performed. The second objective was to study the mixing and growth characteristics of binary and multi-mode initial perturbations seeking an explanation of behavior of the resultant flow structures by performing the first ever set of such highly controlled experiments. The first-ever set of experiments with highly controlled multi-mode initial conditions was performed. The final objective of this study was to measure and compare the bubble and spike velocities with single-mode initial conditions with existing analytical models. The data derived from these experiments would qualitatively and quantitatively enhance the understanding of dependence of mixing width on parametric initial conditions. The knowledge would contribute towards a generalized theory for RTI mixing with specified dependence on various parameters, which has a wide range of applications. The system setup was validated to provide a reliable platform for the novel multi-modal experiments to be performed in the future. It was observed that the ensemble averaged mixing width of the binary system does not vary significantly with the phase-difference between the modes of a binary mode initial condition experiment, whereas it varies with the amplitudes of the component modes. In the exponential and non-linear regimes of evolution, growth rates of multi-mode perturbations were found to be higher than the component modes, whereas saturation growth rates correspond to the dominant wavelength. Quadratic saturation growth rate constants, alpha were found to be about 0.07 ± 0.01 for binary and multi modes whereas single-mode data measured alpha about 0.06 ± 0.01. High-speed imaging was performed to measure bubble and spike amplitudes to obtain velocities and growth rates. It was concluded that higher temporal and spatial resolution was required for accurate measurement. The knowledge gained from the above study will facilitate a better understanding of the physics underlying Rayleigh-Taylor instability. The results of this study will also help validating numerical models for simulation of this instability, thereby providing predictive capability for more complex configurations.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20413号 / 工博第4350号 / 新制||工||1674(附属図書館) / 京都大学大学院工学研究科化学工学専攻 / (主査)教授 宮原 稔, 教授 田門 肇, 教授 山本 量一 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM