Most of the computer simulations of molecules in Metal-Organic Frameworks (MOFs) to be found in the literature are done with rigid framework. But, Molecular Dynamics (MD) simulations of the self-diffusivity, Ds, of ethane within the one-dimensional 4.5 Å channels of the MOF type Zn(tbip)(H2 tbip = 5-tert-butyl isophthalic acid) presented in this work have shown not only quantitative, but also qualitative, differences in the Ds values for fixed and flexible lattices. Particularly, the dependence of Ds upon the concentration of molecules, c, is strongly influenced by the lattice flexibility. The reasons for this influence are investigated with the aid of probability density plots, free energy landscapes and barriers, along with a determination of the structural changes accompanying increasing c. It is found that for flexible lattices, the tighter, more constrained parts of the channels become wider at higher c; this allows more molecules to diffuse in the central region of the channels. The investigations for Zn(tbip) have been extended to three equimolar mixtures of ethane/ethane, CO2/ethane and CO2/methanol. The simulations take into account the lattice flexibility. The diffusional characteristics are discussed in relation to molecule properties and lattice geometry. The results show that Zn(tbip) may be a useful material for separating methane/ethane and CO2/ethane mixtures at low concentrations, and CO2/methanol mixtures at high concentrations. The temperature and concentration dependence of the self-diffusivity of propane diffusion in Zn(tbip) have been investigated as well by performing normal MD and hyper-MD with bias potential simulations. The obtained temperature dependence of the self-diffusivities is analyzed using an Arrhenius relationship, yielding the activation energy to be 9.53 kJ/mol and the pre-exponential factor to be 4.48×10-9 m2s-1. Using this hyper-MD method, interesting mechanisms of the propane molecules able to pass each other and exchange their sites in the channels can be observed. Because of mutual hindrance of propane molecules, the propane self-diffusivities decrease with increasing concentration.

Диссертация посвящена исследованию акустических характеристик реверберационной камеры. Проведены измерения звукового давления с целью исследования звукового поля в помещениях низкого и высокого уровня реверберационной камеры. Для определения диффузности поля были проведены измерения звукового давления в точках, равномерно рассредоточенных по площади камер на четырех уровнях по высоте. Исследование времени реверберации проводилось с использованием метода прерываемого шума и фиксации измерительным прибором кривой спада. Для установления характерной корреляционной связи между уровнем звукового давления в измерительных точках и расстоянием до источника звука был проведен расчет коэффициента корреляции Пирсона. Исследована степень влияния отделки помещения на величину времени реверберации. / The thesis is devoted to the study of the acoustic characteristics of reverberation chamber. Sound pressure measurements have been carried out to study the sound field in low and high level rooms of reverberation chamber. To determine the diffuse field of sound, the sound pressure was measured at points uniformly distributed over the area of the chambers at four levels in height. The reverberation time was studied using the method of interrupted noise and fixing the decay curve by the measuring instrument. To establish the characteristic correlation between the sound pressure level at the measuring points and the distance to the sound source, the Pearson correlation coefficient was calculated. The degree of influence of the finishing room on the amount of reverberation time was investigated.

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No description available.

In this study, the hydrolytic kinetics of mixtures of cotton gin waste (CGW) and recycled paper sludge (RPS) at various initial enzyme concentrations of Spezyme AO3117 and Novozymes NS50052 was investigated. The experiments showed that the concentrations of reducing sugars and the conversions of the mixtures increased with increasing initial enzyme concentration. The reducing sugar concentration and conversion of the mixture of 75% CGW and 25% RPS were higher than those of the mixture of 80% CGW and 20% RPS. The conversion of the former could reach 73.8% after a 72-hour hydrolysis at the initial enzyme loading of 17.4 Filter Paper Unit (FPU)/g substrate. A three-parameter kinetic model with convergent property based on enzyme deactivation and its analytical expression were derived. Using nonlinear regression, the parameters of the model were determined from the experimental data of hydrolytic kinetics of the mixtures. Based on this kinetic model of hydrolysis, two profit rate models, representing two kinds of operating modes with and without substrate recycling, were developed. Using the profit rate models, the optimal enzyme loading and hydrolytic time could be predicted for the maximum profit rate in ethanol production according to the costs of enzyme and operation, enzyme loading, and ethanol market price. Simulated results from the models based on the experimental data of hydrolysis of the mixture of 75% CGW and 25% RPS showed that use of a high substrate concentration and an operating mode with feedstock recycle could greatly increase the profit rate of ethanol production. The results also demonstrated that the hydrolysis at a low enzyme loading was economically required for systematic optimization of ethanol production. The development of profit rate model points out a way to optimize a monotonic function with variables, such as enzyme loading and hydrolytic time for the maximum profit rate. The study also investigated the ethanol production from the steam-exploded mixture of 75 wt% cotton gin waste and 25 wt% recycled paper sludge at various influencing factors, such as enzyme concentration, substrate concentration, and severity factor, by a novel operating mode: semi-simultaneous saccharification and fermentation (SSSF) consisting of a pre-hydrolysis and a simultaneous saccharification and fermentation (SSF). Four cases were studied: 24-hour pre-hydrolysis + 48-hour SSF (SSSF 24), 12-hour pre-hydrolysis + 60-hour SSF (SSSF 12), 72-hour SSF, and 48-hour hydrolysis + 12-hour fermentation (SHF). SSSF 24 produced higher ethanol concentration, yield, and productivity than the other operating modes. The higher temperature of steam explosion favored of ethanol production, but the higher initial enzyme concentration could not increase the final ethanol concentration though the hydrolytic rate of the substrate was increased. A mathematical model of SSSF, which consisted of an enzymatic hydrolysis model and a SSF model including four ordinary differential equations that describe the changes of cellobiose, glucose, microorganism, and ethanol concentrations with respect to residence time, was developed, and was used to simulate the data for the four components in the SSSF processes of ethanol production from the mixture. The model parameters were determined by a MATLAB program based on the batch experimental data of the SSSF. The analysis to the reaction rates of cellobiose, glucose, cell, and ethanol using the model and the parameters from the experiments showed that the conversion of cellulose to cellobiose was a rate-controlling step in the SSSF process of ethanol production from cellulose. / Ph. D.

Canada has the second largest proven oil reserves next to Saudi Arabia which is mostly located in Alberta and Saskatchewan but is unconventional heavy oil and bitumen. The tar sands are found at the surface and are mined, yet 80% of the 173 billion barrels of heavy oil and bitumen exist in-situ according to the Canadian Association of Petroleum Producers (CAPP). Two factors inhibit the economic extraction and processing of Canadian heavy oil; its enormous viscosity ranging from 1000 to over 1 million mPa.s and the asphaltene content (high molecular weight molecules containing heavy metals and sulphur). Heavy oil and bitumen were only included in the reserves estimates through the efforts of Canadian enhanced oil recovery (EOR) research. Viscosity reduction is the one common element of in-situ methods of heavy oil recovery with the exception of cold production. Currently, steam assisted gravity drainage (SAGD) and cyclic steam stimulation (CSS) are being used commercially in the field where the oil’s viscosity is reduced by injecting steam. Thermal methods are energy intensive requiring vast volumes of water such that any improvement would be beneficial. Solvent extraction is one alternative requiring no water, the solvent is recoverable and reusable, and depending on the mode of operation the heavy oil is upgraded in-situ. Vapour Extraction (VAPEX) and enhanced solvent extraction (N-SolvTM) are two such methods. VAPEX and N-Solv reduce the bitumen’s viscosity via mass transfer and a combination of mass and heat transfer, respectively. A light hydrocarbon solvent (instead of steam) is injected into an upper horizontal well where the solvent mixes with the heavy oil, reduces its viscosity and allows the oil to drain under gravity to a bottom production well. The idea of using solvents for heavy oil extraction has been around since the 1970s and both VAPEX and N-Solv are patented processes. However, there is still much to be learned about how these processes physically work. Research to date has focused on varying system parameters (including model dimensions, permeability, heavy oil viscosity, solvent type and injection rate, etc.) to observe the effect on oil production from laboratory scale models. Based on an early mass balance model by Butler and Mokrys (1989) and an improvement by Das (1995), molecular diffusion alone cannot account for the produced oil rates observed from laboratory models. Until recently, very little progress had been made towards qualifying and quantifying the mass transfer mechanisms with the exception of the diffusivity of light hydrocarbons in heavy oil. Mass transfer can only be by diffusion and convection. Differentiating and quantifying the contribution of each is complex due to the nature and viscosity of the oil. The goal of this thesis is to investigate the mass transfer mechanisms during the solvent recovery of heavy oil. Quantifying the diffusion of light hydrocarbon solvents has been an active topic of research with limited success since the mid 1990’s. The experimental approach presented here focused on capturing the rate of solvent mass transfer into the bitumen by measuring the bitumen swelling and the butane uptake independently. Unlike early pressure decay methods, the pressure is held constant to not violate the assumed equilibrium solvent concentration at the interfacial boundary condition. The high solubility of solvent in heavy oil complicates the physical modeling because simplifying assumptions of a constant diffusion coefficient, constant density and a quiescent liquid should not be used. The model was developed from first principles to predict the bitumen swelling. The form of the concentration dependent diffusivity was assumed and the diffusivity coefficients initially guessed. The swelling (moving boundary) was fixed by defining a new dimensionless space coordinate and the set of partial differential equations solved using the method of lines. Using the non-linear regression (lsqnonlin) function in MATLAB®, optimising for the difference in predicted and experimentally found bitumen heights and independently validating the result using the solvent uptake, the diffusivity of butane in heavy oil (at 25oC) was found to be Dsb = 4.78 x 10-6ωs + 4.91 x 10-6 cm2/s where ωs is the solvent mass fraction. Diffusion alone has proven inadequate in predicting oil recovery rates from laboratory scale models. It is logical to assume that convective mass transfer plays a role at mixing the solvent and bitumen while draining via gravity through the reservoir porous matrix. Solvent extraction experiments were conducted in etched glass micromodels to observe the pore scale phenomena. The pore scale mechanisms were found to differ depending on how the solvent extraction was operated, with non-condensing (VAPEX) or condensing (N-SolvTM) solvent. Observations show increased convective mixing and an increased rate of interface advancement when the solvent condenses on the bitumen surface. Evidence of trapped butane vapour being mobilised with the draining live oil and a technique of observing solvent extraction using UV light confirm that the draining live oil is on average one pore deep. While the interface appears from a distance to be uniform, at the pore scale it is not. Live oil can drain from one to two pores via capillary displacement mechanisms in one section of the interface and via film flow only in another area (James and Chatzis 2004; James et al. 2008). This work also shows the detrimental impact of having a non-condensable gas present during solvent extraction (James and Chatzis 2008). In summary, this work emphasises the mass transfer and drainage displacement mechanisms of non-condensing (VAPEX) and condensing (N-Solv) solvent extraction methods of heavy oil recovery.

Canada has the second largest proven oil reserves next to Saudi Arabia which is mostly located in Alberta and Saskatchewan but is unconventional heavy oil and bitumen. The tar sands are found at the surface and are mined, yet 80% of the 173 billion barrels of heavy oil and bitumen exist in-situ according to the Canadian Association of Petroleum Producers (CAPP). Two factors inhibit the economic extraction and processing of Canadian heavy oil; its enormous viscosity ranging from 1000 to over 1 million mPa.s and the asphaltene content (high molecular weight molecules containing heavy metals and sulphur). Heavy oil and bitumen were only included in the reserves estimates through the efforts of Canadian enhanced oil recovery (EOR) research. Viscosity reduction is the one common element of in-situ methods of heavy oil recovery with the exception of cold production. Currently, steam assisted gravity drainage (SAGD) and cyclic steam stimulation (CSS) are being used commercially in the field where the oil’s viscosity is reduced by injecting steam. Thermal methods are energy intensive requiring vast volumes of water such that any improvement would be beneficial. Solvent extraction is one alternative requiring no water, the solvent is recoverable and reusable, and depending on the mode of operation the heavy oil is upgraded in-situ. Vapour Extraction (VAPEX) and enhanced solvent extraction (N-SolvTM) are two such methods. VAPEX and N-Solv reduce the bitumen’s viscosity via mass transfer and a combination of mass and heat transfer, respectively. A light hydrocarbon solvent (instead of steam) is injected into an upper horizontal well where the solvent mixes with the heavy oil, reduces its viscosity and allows the oil to drain under gravity to a bottom production well. The idea of using solvents for heavy oil extraction has been around since the 1970s and both VAPEX and N-Solv are patented processes. However, there is still much to be learned about how these processes physically work. Research to date has focused on varying system parameters (including model dimensions, permeability, heavy oil viscosity, solvent type and injection rate, etc.) to observe the effect on oil production from laboratory scale models. Based on an early mass balance model by Butler and Mokrys (1989) and an improvement by Das (1995), molecular diffusion alone cannot account for the produced oil rates observed from laboratory models. Until recently, very little progress had been made towards qualifying and quantifying the mass transfer mechanisms with the exception of the diffusivity of light hydrocarbons in heavy oil. Mass transfer can only be by diffusion and convection. Differentiating and quantifying the contribution of each is complex due to the nature and viscosity of the oil. The goal of this thesis is to investigate the mass transfer mechanisms during the solvent recovery of heavy oil. Quantifying the diffusion of light hydrocarbon solvents has been an active topic of research with limited success since the mid 1990’s. The experimental approach presented here focused on capturing the rate of solvent mass transfer into the bitumen by measuring the bitumen swelling and the butane uptake independently. Unlike early pressure decay methods, the pressure is held constant to not violate the assumed equilibrium solvent concentration at the interfacial boundary condition. The high solubility of solvent in heavy oil complicates the physical modeling because simplifying assumptions of a constant diffusion coefficient, constant density and a quiescent liquid should not be used. The model was developed from first principles to predict the bitumen swelling. The form of the concentration dependent diffusivity was assumed and the diffusivity coefficients initially guessed. The swelling (moving boundary) was fixed by defining a new dimensionless space coordinate and the set of partial differential equations solved using the method of lines. Using the non-linear regression (lsqnonlin) function in MATLAB®, optimising for the difference in predicted and experimentally found bitumen heights and independently validating the result using the solvent uptake, the diffusivity of butane in heavy oil (at 25oC) was found to be Dsb = 4.78 x 10-6ωs + 4.91 x 10-6 cm2/s where ωs is the solvent mass fraction. Diffusion alone has proven inadequate in predicting oil recovery rates from laboratory scale models. It is logical to assume that convective mass transfer plays a role at mixing the solvent and bitumen while draining via gravity through the reservoir porous matrix. Solvent extraction experiments were conducted in etched glass micromodels to observe the pore scale phenomena. The pore scale mechanisms were found to differ depending on how the solvent extraction was operated, with non-condensing (VAPEX) or condensing (N-SolvTM) solvent. Observations show increased convective mixing and an increased rate of interface advancement when the solvent condenses on the bitumen surface. Evidence of trapped butane vapour being mobilised with the draining live oil and a technique of observing solvent extraction using UV light confirm that the draining live oil is on average one pore deep. While the interface appears from a distance to be uniform, at the pore scale it is not. Live oil can drain from one to two pores via capillary displacement mechanisms in one section of the interface and via film flow only in another area (James and Chatzis 2004; James et al. 2008). This work also shows the detrimental impact of having a non-condensable gas present during solvent extraction (James and Chatzis 2008). In summary, this work emphasises the mass transfer and drainage displacement mechanisms of non-condensing (VAPEX) and condensing (N-Solv) solvent extraction methods of heavy oil recovery.

Diffusion-weighted magnetic resonance imaging (MRI) has allowed unprecedented non-invasive mapping of brain neural connectivity in vivo by means of fiber tractography applications. Fiber tractography has emerged as a useful tool for mapping brain white matter connectivity prior to surgery or in an intraoperative setting. The advent of high angular resolution diffusion-weighted imaging (HARDI) techniques in MRI for fiber tractography has allowed mapping of fiber tracts in areas of complex white matter fiber crossings. Raw HARDI images, as a result of elevated diffusion-weighting, suffer from depressed signal-to-noise ratio (SNR) levels. The accuracy of fiber tractography is dependent on the performance of the various methods extracting dominant fiber orientations from the HARDI-measured noisy diffusivity profiles. These methods will be sensitive to and directly affected by the noise. In the first part of the thesis this issue is addressed by applying an objective and adaptive smoothing to the noisy HARDI data via generalized cross-validation (GCV) by means of the smoothing splines on the sphere method for estimating the smooth diffusivity profiles in three dimensional diffusion space. Subsequently, fiber orientation distribution functions (ODFs) that reveal dominant fiber orientations in fiber crossings are then reconstructed from the smoothed diffusivity profiles using the Funk-Radon transform. Previous ODF smoothing techniques have been subjective and non-adaptive to data SNR. The GCV-smoothed ODFs from our method are accurate and are smoothed without external intervention facilitating more precise fiber tractography. Diffusion-weighted MRI studies in amyotrophic lateral sclerosis (ALS) have revealed significant changes in diffusion parameters in ALS patient brains. With the need for early detection of possibly discrete upper motor neuron (UMN) degeneration signs in patients with early ALS, a HARDI study is applied in order to investigate diffusion-sensitive changes reflected in the diffusion tensor imaging (DTI) measures axial and radial diffusivity as well as the more commonly used measures fractional anisotropy (FA) and mean diffusivity (MD). The hypothesis is that there would be added utility in considering axial and radial diffusivities which directly reflect changes in the diffusion tensors in addition to FA and MD to aid in revealing neurodegenerative changes in ALS. In addition, applying adaptive smoothing via GCV to the HARDI data further facilitates the application of fiber tractography by automatically eliminating spurious noisy peaks in reconstructed ODFs that would mislead fiber tracking.

Chloride-induced corrosion of reinforcing steel in concrete is a worldwide problem. In order to predict how chlorides penetrate in concrete and how other ionic species in con-crete pore solution affect the penetration of chlorides, this thesis presents a numerical study on multi-phase modelling of ionic transport in concrete dominated by migration process. There are many advantages in rapid chloride migration test (RCM) method and numeri-cal approach. However, most of models in the literature predicting chloride diffusivity in concrete are diffusion models, which not consider the action of externally applied electric field. In view of this, the specific aim of this thesis is to develop a rational nu-merical migration model to simulate chloride migration tests. By using this model, the diffusion coefficient of chlorides in concrete will be efficiently predicted. Furthermore, other mechanisms of ionic transportation in composite materials can be scientifically in-vestigated in the meantime. In most existing work, researchers tend to use the assumption of electro-neutrality con-dition, which ensures that no external charge can be imported (Bockris and Reddy, 1998), to determine the electrostatic potential within concrete as well as considering a 1-D problem with only one phase structure and single species (i.e. the chlorides) for pre-dicting the ionic migration. In contrast, this thesis presents a number of sets of multi-phase migration models in more than one dimension and uses the Poisson’s equation for controlling the multi-species interactions. By solving both mass conservation and Pois-son’s equations, the distribution profiles of each ionic species and electrostatic potential at any required time are successfully obtained. Some significant factors, i.e. the influ-ence of dimensions, aggregates, interfacial transition zones (ITZs), cracks and binding effect have also been discussed in detail. The results reveal a series of important features which may not be seen from existing numerical models. For quantitative study, this thesis also provides the prediction method of chloride diffu-sivity not only by the traditional stationary diffusion models but also by the migration models presented in the thesis. The obtained results are compared with three proven analytical models, i.e., Maxwell’s model (Dormieux and Lemarchand, 2000), Brug-geman’s equation (Bruggeman’s, 1935) and the lower bound of the effective diffusion coefficient proposed by Li et al. (2012) as well as validated against experimental data sets of an accelerated chloride migration test (ACMT) brought by Yang and Su (2002).