Many industrial processes handling organic solvents produce volatile organic compounds (VOCs). These VOCs not only cause environmental pollution, but also represent an economic loss. VOC removal and recovery have become a big issue that needs to be addressed. Traditional techniques for VOCs removal include carbon adsorption, condensation, and absorption, and none is efficient enough to meet every need. Membrane separation has emerged as an excellent alternative or complementary technology for VOC separation. Separation of VOCs from nitrogen by composite hollow fiber membranes is studied in this thesis. Microporous hollow fiber membranes were spun from polyvinylidene fluoride (PVDF) using the phase inversion method, and the hollow fibers were coated with a thin layer of poly(ether block amide) (PEBA), thereby forming composite membranes. PVDF was chosen as the substrate material because of its excellent thermal and chemical stabilities and good mechanical strength, and PEBA was selected as the active separating layer because of its good permselectivity and film forming properties. In PEBA polymer, the hard polyamide blocks provide high mechanical strength, and the soft polyether blocks provide flexibility and elasticity. This study is focused on the preparation and characterization of PEBA/PVDF composite hollow fiber membranes. The membranes were tested for the removal of representative VOCs including hexane, heptane and cyclohexane, which are the main components of gasoline, and dimethyl carbonate (DMC), ethanol, methanol, and methyl t-butyl ether (MTBE) that are the oxygenates and octane number enhancers of gasoline. The separation of gasoline vapor from nitrogen was also investigated. It was found that the PEBA/PVDF composite hollow fiber membranes are effective for the separation of hydrocarbon vapors from nitrogen. The effects of hollow fiber membrane preparation conditions on the membrane performance were studied, and the separation performance of the composite hollow fiber membranes at various operating conditions (e. g. feed concentration, operating temperature) was evaluated.

The method of separation of variables facilitates the integration of the Hamilton-Jacobi equation by reducing its solution to a series of quadratures in the separable coordinates. The case in which the metric tensor is diagonal in the separable coordinates, that is, orthogonal separability, is fundamental. Recent theory by Benenti has established a concise geometric (coordinate-independent) characterisation of orthogonal separability of the Hamilton-Jacobi equation on a pseudoRiemannian manifold. It generalises an approach initiated by Eisenhart and developed by Kalnins and Miller. Benenti has shown that the orthogonal separability of a system via a point transformation is equivalent to the existence of a Killing tensor with real simple eigen values and orthogonally integrable eigenvectors. Applying a moving frame formalism, we develop a method that produces the orthogonal separable coordinates for low dimensional Hamiltonian systems. The method is applied to a two dimensional Riemannian manifold of arbitrary curvature. As an illustration, we investigate Euclidean 2-space, and the two dimensional surfaces of constant curvature, recovering known results. Using our formalism, we also derive the known superseparable potentials for Euclidean 2-space. Some of the original results presented in this thesis were announced in [8, 9, 10].

This thesis provides an introduction to and analysis of the problem of determining nuclear magnetic resonance (NMR) relaxation times of porous media by using the so-called Carr-Purcell-Meiboom-Gill (CPMG) technique. We introduce the principles of NMR, the CPMG technique and the signals produced, porous effects on the NMR relaxation times and discuss various numerical methods for the inverse problem of extracting the relaxation times from CPMG signals. The numerical methods for solving Fredholm integral equations of the first kind are sketched from a series expansion perspective. A method of using arbitrary constituent functions for improving the performance of non-negative least squares (NNLS) is developed and applied to several synthesized data sets and real experimental data sets of saturated porous glass gels. The data sets were obtained by the author of this thesis and the experimental procedure will be presented. We discuss the imperfections in the assumptions on the physical and numerical models, the numerical schemes, and the experimental results, which may lead to new research possibilities.

Pik1p, one of three phosphatidylinositol 4-kinases in the fission yeast, <i>Schizosaccharomyces pombe</i>, was found previously to interact with Cdc4p, a myosin essential light chain that is required for cytokinesis. The involvement of pik1 in cell cycle control was investigated. A fluorescently tagged Pik1p fusion protein was associated with Golgi throughout the cycle, and was found at the medial division plane of the cell during late cytokinesis. This latter distribution has not been reported previously. Gene deletion in diploid cells and tetrad analysis revealed that pik1 is essential for cell viability and is required for spore germination. The terminal phenotype of a temperature-sensitive, loss-of-function allele (pik1-td) indicated that pik1 is involved in cytokinesis: particularly for suppression of secondary septum material deposition, for suppression of initiation of supernumerary septa, and for cell separation. Contractile ring formation was normal in pik1-td cells at the restrictive temperature although the pattern of F-actin patches was disrupted. The F-actin patches were dispersed throughout the cytoplasm. Accumulation of extra inner membranous or vesicle-like structures was observed in these cells. The <i>S. pombe</i> nmt1 promoter and attenuated versions of it were found to be useful for complementation studies in <i>S. cerevisiae</i>. Heterologous expression of <i>S. pombe</i> pik1 complemented the essential functions of a temperature-sensitive allele (pik1﷓101) of its orthologue in <i>Saccharomyces cerevisiae</i> that were lost at the restrictive temperature. A residue required for <i>S. pombe</i> Pik1p lipid kinase activity, D709, was also required for this complementation. A residue, R838, which is required for interactions between Pik1p and Cdc4p was not required for this complementation. The timing and localization of Pik1p to the division plane of the cell late in cytokinesis combined with analysis of the terminal phenotype of a loss-of-function allele, indicate that Pik1p and/or its derived phosphoinositides are required for regulation of septation and cell separation. Pik1p may be involved in the transport, possibly via vesicular transport, of enzymes required for hydrolysis of the primary septum. It may be involved in signaling pathways that lead to the initiation of septation and to the cessation of the deposition of secondary septum material.

No description available.

Proton exchange membrane (PEM) fuel cells, with low operating temperatures and high power density, are a reasonable candidate for use in mobile power generation. One large drawback to their use is that their fuel reformer requires not only fuel but also water, thereby requiring two separate reservoirs to be available. PEM fuel cells exhaust enough water in their oxidant stream to potentially meet the needs of the fuel reformer. If this water could be recovered and routed to the fuel reformer it would markedly increase the portability of PEM fuel cells. The goal of this research was to test a previously designed axial flow moisture separator. The separator was employed in a test bed which utilized compressed, heated air mixed with steam to simulate the oxidant exhaust conditions of a 25 kW PEM fuel cell. The simulated exhaust was saturated with water. The mixture was expanded through the turbine side of an automotive turbocharger, which dropped the temperature and pressure of the mixture, causing water to condense, making it available for separation. The humid air mixture was passed over an axial flow centrifugal separator and water was removed from the flow. The separator was tested in a variety of conditions with and without passing chilled water through the separator. The axial separator was tested independently, with a flow straightener preceding it, and with a commercially available centrifugal moisture separator in series following it. It was shown that cooling makes a significant impact on the separation rate while adding a flow straightener does not. Separation efficiencies of 19% on average were experienced without cooling, while efficiencies of 50% were experienced with 3.1 kW of cooling. The separation efficiency of the two moisture separators combined was found to be 31.7% which is 165% that of the axial separator alone under uncooled conditions.

Based on the recent successes in stochastic linear programming and mixed integer programming, in this thesis we combine these two important areas of mathematical programming; specifically we study stochastic integer programming. We first study a simple and important stochastic integer programming problem, called stochastic uncapacitated lot-sizing (SLS), which is motivated by production planning under uncertainty. We describe a multi-stage stochastic integer programming formulation of the problem and develop a family of valid inequalities, called the (Q, S) inequalities. We establish facet-defining conditions and show that these inequalities are sufficient to describe the convex hull of integral solutions for two-period instances. A separation heuristic for (Q, S) inequalities is developed and incorporated into a branch-and-cut algorithm. A computational study verifies the usefulness of the inequalities as cuts. Then, motivated by the polyhedral study of (Q, S) inequalities for SLS, we analyze the underlying integer programming scheme for general stochastic integer programming problems. We present a scheme for generating new valid inequalities for mixed integer programs by taking pair-wise combinations of existing valid inequalities. The scheme is in general sequence-dependent and therefore leads to an exponential number of inequalities. For some special cases, we identify combination sequences that lead to a manageable set of all non-dominated inequalities. For the general scenario tree case, we identify combination sequences that lead to non-dominated inequalities. We also analyze the conditions such that the inequalities generated by our approach are facet-defining and describe the convex hull of integral solutions. We illustrate the framework for some deterministic and stochastic integer programs and we present computational results which show the efficiency of adding the new generated inequalities as cuts.

Organic/inorganic materials have a high potential to enable major advances in membrane performance. It has previously been impossible to develop polymeric systems with adequate transport properties for xylene purification. Zeolite membranes have been created with the appropriate selectivities; however low productivity, low mechanical durability, and high capital costs have kept these materials from being utilized. So-called mixed matrix hybrid organic/inorganic membranes combine the mechanical durability and cost effectiveness of polymeric membranes with the enhanced performance of zeolitic structures. This project will focus on investigating polymeric and molecular sieve materials for mixed matrix membrane use in xylene isomer separation as a model system. Torlon polyamide-imide has unique properties that should be potentially useful in a mixed matrix composite. Silicalite will be investigated as the dispersed phased given its proven applicability with xylene isomers. The overarching goal is to establish an approach for creation of mixed matrix materials that can be broadly applied to challenging organic separations. This project has three specific goals: (1) characterization of Torlons inherent properties, processing ability, and important transport potential, (2) characterization of zeolite matching properties and the effect of interfacial engineering on these properties, and (3) development of appropriate approaches to combine the sieve and polymer to obtain a hybrid material with properties that match theoretically predicted separation property enhancements relative to the neat polymer. High temperature pervaporation will be used to evaluate material transport properties, as this experimental setup closely mimics the high activity vapor streams found in many industrial xylene processes. The results of this research will be used to develop a protocol for development of future mixed matrix membranes that may be applied to a variety of organic liquid systems.

An acoustic field is used to increase the critical heat flux of a copper boiling heat transfer surface. The increase is a result of the acoustic effects on the vapor bubbles. Experiments are being performed to explore the effects of an acoustic field on vapor bubbles in the vicinity of a rigid heated wall. Work includes the construction of a novel heater used to produce a single vapor bubble of a prescribed size and at a prescribed location on a flat boiling surface for better study of an individual vapor bubble s reaction to the acoustic field. Work also includes application of the results from the single bubble heater to a calibrated copper heater used for quantifying the improvements in critical heat flux.

The control system is an original and sound system of this Country. The Founder of this Country, Dr. Sun Yat-sen, proposed after he established this Republic that the control power should be practiced by an independent body to highlight the functions of such power, rather than putting it under the legislative power as in the 3-Separated Powers common to many Western countries. This thesis begins by examining the status and nature of control power in the 5-Separated Powers as in the constitutional regime of this Country from a perspective of separation of powers. It follows by exploring the evolution of mandates of the Control Yuan as a result of various constitutional amendments during the 1990s when the Government undertook constitutional amendments engineering for the promotion of democratic development. This thesis then analyzes the impact of such constitutional amendments upon the practice of control power from existing laws and regulations relevant to the control power and provides the views of this author. It then analyzes the status quo of the practice of functions of the Third Control Yuan by its Members, in comparison to the statistics on the functional practice of the Second Control Yuan, so as to comprehend the efficacy of the practice of functions of the Third Control Yuan. In the conclusion, the author puts forward his own findings and suggestions on the practice of control power by the Third Control Yuan.