Gas inFusion? is a novel remedial technology that dissolves CO₂ into water under pressure for NAPL recovery. As the supersaturated liquid flows through the porous medium gas evolution occurs in situ as the system returns to thermodynamic equilibrium. The evolution of gas bubbles leads to NAPL recovery by two mechanisms: 1) volatilization and 2) mobilization by the NAPL spreading in a film around the rising bubbles. Laboratory experiments by Li demonstrated that injecting the supersaturated water into a porous medium minimized the buoyancy driven flow of gas and the fingering phenomena that limit typical gas sparging. The distribution of carbon dioxide at partial pressures (p_CO2) above the applicable hydrostatic pressure and the evolved gas phase were determined in two field experiments conducted in the relatively homogeneous fine to medium sand at CFB Borden. First, CO₂-supersaturated water was injected into a single point located approximately 4 metres below ground surface. Then this injection was repeated with pumping of two nearby wells to see if the lateral distribution of CO₂ gas could be controlled hydraulically. Groundwater monitoring of p_CO2 above the hydrostatic pressure and geophysical surveys (neutron measurements, surface ground penetrating radar (GPR), and cross-borehole GPR) to find zones of induced gas content were supported by hydraulic monitoring and physical observations of gas bubble distribution at the water table. <br /><br /> Based on the results of these tests, enhanced CO₂ levels above the hydrostatic pressure were observed up to 5. 5-7. 0 m from the injection point and the gas phase up to ~5. 3 m. It was not possible to determine the impact hydraulic control had on the lateral distribution of CO₂ due to problems with the experiment. The distribution of the gas phase was heterogeneous with CO₂ gas pockets forming below low permeability layers, as evidenced by surface GPR, permeameter tests, and grain size analyses. These gas pockets accumulated until sufficient pressure built up to overcome the displacement pressure of these lower permeability layers. At this point there is evidence of CO₂ breakthrough in the cross-borehole GPR data and physical observations of gas bubbles at the water table. These observations are consistent with previous investigations, which indicate that although the Borden aquifer is homogeneous, distinct horizontal layering is present with sufficient variations in permeability/displacement pressure to trap and cause some lateral spreading of a gas phase. The evidence of channeling and the impact of heterogeneities on gas distribution are consistent with air sparging studies.

Bibliography: leaves 278-289. / xi, 324 leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / This thesis reports on experimental investigation of the growth and aggregation of calcium oxalate mono-dydrate in metastable saline solutions using batch and continuous systems. The physical chemistry of calcium oxalate mono-hydrate in aqueous solutions is considered. A tubular crystalliser to be used as an in vitro system is described. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemical Engineering, 1996?

Thesis (M.S.)--Chemical Engineering, Georgia Institute of Technology, 2005. / Ronald W. Rousseau, Committee Chair ; William J. Koros, Committee Member ; Angus P. Wilkinson, Committee Member ; David J. am Ende, Committee Member. Includes bibliographical references.

Thesis (Ph.D.)--Chemical Engineering, Georgia Institute of Technology, 2009. / Committee Chair: Dr Rousseau, Ronald W; Committee Co-Chair: Dr Grover Gallivan, Martha; Committee Member: Dr Realff, Matthew; Committee Member: Dr Garmestani, Hamid; Committee Member: Dr Nenes, Athanasios.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

Nucleation is the first step in the formation of a new phase in a thermodynamic system. The Classical Nucleation Theory (CNT) is the traditional theory used to describe this phenomenon. The object of this thesis is to investigate nucleation beyond one of the most significant limitations of the CNT: the assumption that the surface tension of a nucleating cluster of the new phase is independent of the cluster’s size and has the same value that it would have in the bulk of the new phase. In order to accomplish this, we consider a microscopic, two-dimensional Lattice Gas Automata (LGA) model of precipitate nucleation in a supersaturated system, with model input parameters Ess (solid particle-to-solid particle bonding energy), Esw (solid particle-to-water particle bonding energy), η (next-to-nearest neighbour bonding coeffiicent in solid phase), and Cin (initial solute concentration). The LGA method was chosen for its advantages of easy implementation, low memory requirements, and fast computation speed. Analytical results for the system’s concentration and the crystal radius as functions of time are derived and the former is fit to the simulation data in order to determine the system’s equilibrium concentration. A mean first-passage time (MFPT) technique is used to obtain the nucleation rate and critical nucleus size from the simulation data. The nucleation rate and supersaturation are evaluated using a modification to the CNT that incorporates a two-dimensional, radius-dependent surface tension term. The Tolman parameter, δ, which controls the radius-dependence of the surface tension, decreases (increases) as a function of the magnitude of Ess (Esw), at fixed values of η and Esw (Ess). On the other hand, δ increases as η increases while Ess and Esw are held constant. The constant surface tension term of the CNT, Σ0, increases (decreases) with increasing magnitudes of Ess (Esw) fixed values of Esw (Ess), and increases as η is increased. Together, these results indicate an increase in the radius-dependent surface tension, Σ, with respect to increasing magnitude of Ess relative to the magnitude of Esw. Σ0 increases linearly as a function of the change in energy during an attachment or detachment reaction, |ΔE|, however with a slope less than that predicted for a crystal that is uniformly packed at maximum density.

Experimental design has applications in many fields, from medicine to manufacturing. Incorporating statistics into both the planning and analysis stages of the experiment will ensure that appropriate data are collected to allow for meaningful analysis and interpretation of the results. If the number of factors of interest is very large, or if the experimental runs are very expensive, then a supersaturated design (SSD) can be used for factor screening. These designs have n runs and k > n - 1 factors, so there are not enough degrees of freedom to allow estimation of all of the main effects. This paper will first review some of the current techniques for the construction and analysis of SSDs, as well as the analysis challenges inherent to SSDs. Analysis techniques of Sure Independence Screening (SIS) and Iterative Sure Independence Screening (ISIS) are discussed, and their applications for SSDs are explored using simulation, in combination with the Smoothly Clipped Absolute Deviation (SCAD) approach for down-selecting and estimating the effects.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1981. / MICROFICHE COPY AVIALABLE IN ARCHIVES AND ENGINEERING. / Bibliography: leaves 118-119. / by Jane Ellen Martini. / M.S.

Batch crystallization is used widely in the production of high-value added species. It is widely recognized that product properties, some of which may be related directly to the utility of the drug, and downstream processes, such as tableting, are influenced by crystal morphology, size, and shape. The ability to observe on-line the evolution of the population density and detect a polymorphic transformation would constitute a major asset in understanding crystallizer operation and the phenomena that influence product quality. Focused-beam reflectance measurement (FBRM) is among the process analytical technologies (PAT) that hold promise for enhanced monitoring of pharmaceutical crystallization. It is based on scattering of laser light and provides a methodology for on-line monitoring of a representation of the crystal population in either batch or continuous crystallization systems. Properly installed, the FBRM allows on-line determination of the chord-length density, which is a complex function of crystal geometry and is statistically related to the population density. A model based on the geometry of the crystal was therefore established to relate both densities and thus enable computation of the population density from a measured chord length density. The evolution of the population density as a function of time leads to the estimation of the supersaturation and therefore allows the determination of the systems kinetics. From there, the population balance can be solved. Paracetamol is a common substance which exhibit polymorphism and is mainly used as an analgesic and antipyretic drug. The developed model was here applied to batch cooling crystallization of paracetamol from ethanol solutions; this system was used to explore the utility of FBRM data in detection of the polymorphic transformations. As different shapes generate different chord length densities, a transition from one polymorphic form with one specific crystal habit to another can be tracked through the FBRM. The purpose of the present study is to use the FBRM to monitor the evolution of the crystallization process, develop a model describing the evolution of the process, and monitor polymorphic transformation. The end results would be the possibility to implement a better control of the crystallization process that would ensure that downstream processing and product quality meet expectations.

abstract: In this dissertation two research questions in the field of applied experimental design were explored. First, methods for augmenting the three-level screening designs called Definitive Screening Designs (DSDs) were investigated. Second, schemes for strategic subdata selection for nonparametric predictive modeling with big data were developed. Under sparsity, the structure of DSDs can allow for the screening and optimization of a system in one step, but in non-sparse situations estimation of second-order models requires augmentation of the DSD. In this work, augmentation strategies for DSDs were considered, given the assumption that the correct form of the model for the response of interest is quadratic. Series of augmented designs were constructed and explored, and power calculations, model-robustness criteria, model-discrimination criteria, and simulation study results were used to identify the number of augmented runs necessary for (1) effectively identifying active model effects, and (2) precisely predicting a response of interest. When the goal is identification of active effects, it is shown that supersaturated designs are sufficient; when the goal is prediction, it is shown that little is gained by augmenting beyond the design that is saturated for the full quadratic model. Surprisingly, augmentation strategies based on the I-optimality criterion do not lead to better predictions than strategies based on the D-optimality criterion. Computational limitations can render standard statistical methods infeasible in the face of massive datasets, necessitating subsampling strategies. In the big data context, the primary objective is often prediction but the correct form of the model for the response of interest is likely unknown. Here, two new methods of subdata selection were proposed. The first is based on clustering, the second is based on space-filling designs, and both are free from model assumptions. The performance of the proposed methods was explored visually via low-dimensional simulated examples; via real data applications; and via large simulation studies. In all cases the proposed methods were compared to existing, widely used subdata selection methods. The conditions under which the proposed methods provide advantages over standard subdata selection strategies were identified. / Dissertation/Thesis / Doctoral Dissertation Statistics 2020