Thesis (M. Phil.)--University of Hong Kong, 2002. / Includes bibliographical references (leaves 106-113).

Fine grained soils, in particular clays of high plasticity, are known to have very low values of hydraulic conductivity. This low permeability causes several problems related to vegetation growth and stormwater runoff. One way to improve the permeability of clay soils is by using coarse aggregates as a fill material. Recently, Expanded Shale has been widely applied as an amendment to improve drainage properties of clayey soils. However, limited effort has been made to quantify the effect of Expanded Shale on the hydraulic conductivity or on the volume change of fine grained soils. Specifically, the field and laboratory tests required to quantify the amounts of Expanded Shale to be mixed with clays to obtain desired hydraulic conductivity values have not been conducted. This paper presents the results of a series of laboratory fixed-wall permeameter tests conducted on naturally occurring clay deposits in the Austin area with different plasticity. The testing program comprised of clay samples with different quantities of Expanded Shale aggregates by volume, ranging between 0 and 50%, and compacted at two different compaction efforts (60% and 100% of the standard Proctor compaction effort). The laboratory test results indicate that the hydraulic conductivity of the three soils increases by at least an order of magnitude when the Expanded Shale is mixed in quantities between 25 to 30% by volume depending on the compaction effort. Expanded Shale amended samples also showed lower swelling potential with increasing amendment quantities. Moreover, when the clay with the higher plasticity was mixed with 25% Expanded Shale, the compression and recompression ratios decreased by 25% and 15% respectively. / text

published_or_final_version / Economics and Finance / Doctoral / Doctor of Philosophy

Mudstones compose nearly 70% of the volume of sedimentary basins, yet they are among the least studied of sedimentary rocks. Their low permeability and high compressibility contribute to overpressure around the world. Despite their fundamental importance in geologic processes and as seals for anthropogenic-related storage, a systematic, process-based understanding of the interactions between porosity, compressibility, permeability, and pore-size distribution in mudstones remains elusive. I use sediment mixtures composed of varying proportions of natural mudstone such as Boston Blue Clay or Nankai mudstone and silt-sized silica to study the effect of composition on permeability and compressibility during burial. First, to recreate natural conditions yet remove variability and soil disturbance, I resediment all mixtures in the laboratory to a total stress of 100 kPa. Second, in order to describe the systematic variation in permeability and compressibility with clay fraction, I uniaxially consolidate the resedimented samples to an effective stress equivalent to about 2 km of burial under hydrostatic conditions. Scanning electron microscope images provide insights on microstructure. My experiments illuminate the controls on mudstone permeability and compressibility. At a given porosity, vertical permeability increases by an order of magnitude for clay contents ranging from 59% to 34% by mass whereas compressibility reduces by half at a given vertical effective stress. I show that the pore structure can be described by a dual-porosity system, where one rock fraction is dominated by silt where large pores are present and the majority of flow occurs and the other fraction is dominated by clay where limited flow occurs. I use this concept to develop a coupled compressibility-permeability model in order to predict porosity, permeability, compressibility, and coefficient of consolidation. These results have fundamental implications for a range of problems in mudstones. They can be applied to carbon sequestration, hydrocarbon trapping, basin modeling, overpressure distribution and geometry as well as morphology of thrust belts, and an understanding of gas-shale behavior. / text

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The cockroach, with its large brain and physiological resilience, holds many advantages for the development of behavioral paradigms. The work presented here provides a foundation for, and describes the results of, the implementation of studies of neural correlates of learning and memory on restrained animals.Using the antennal projection response (APR) as an indicator of learning and retention, several learning paradigms have been developed. A visual-olfactory associative and a gustatory-olfactory aversive conditioning paradigm demonstrated a plastic behavior that could be driven in an intact and immobilized cockroach. Conditioning the APR to a visual cue paired with an olfactory cue characterized the role of unilateral and bilateral olfactory input in learning and memory. While unilateral olfactory input is sufficient to learn a visual-olfactory association, bilateral olfactory input is necessary for long-term retention of the association. This comparison identified a critical time period in which memory is consolidated. This time period was subsequently used to analyze gene expression during memory consolidation.The split-brain cockroach preparation was developed to investigate what parts of the brain are necessary and sufficient for learning and retention of a visual-olfactory association; this preparation was also used to examine learning-induced changes in test tissue versus control tissue provided by the same animal. Evidence suggests that half of a brain is sufficient for a visual-olfactory association to be established and sufficient for retention of that association between 12 and 24 hours. However, the entire brain is necessary for long-term memory to be established. Using the split-brain cockroach simultaneously as the control and the test subject, learning-induced alterations in the microglomerular synaptic complexes of the calyces were identified in the trained half, but not in the naïve half.Using the APR, spatial learning and memory was examined. Multiple representations of space were revealed in the brain of the cockroach. Cockroaches represent space in terms of an olfactory gradient map, as well as the visuospatial relationship between objects. When both representations of space can be utilized by the cockroach to localize a cue, the positional visual cue is the one that determines the behavioral response.

With the rapid advance of information technologies, human beings increasingly rely on computers to accumulate, process, and make use of data. Knowledge discovery techniques have been proposed to automatically search large volumes of data for patterns. Knowledge discovery often requires a set of relevant features to represent the specific domain. My dissertation presents a framework of feature engineering for knowledge discovery, including feature construction, feature selection, and feature consolidation.Five essays in my dissertation present novel approaches to construct, select, or consolidate features in various applications. Feature construction is used to derive new features when relevant features are unknown. Chapter 2 focuses on constructing informative features from a relational database. I introduce a probabilistic relational model-based approach to construct personal and social features for identity matching. Experiments on a criminal dataset showed that social features can improve the matching performance. Chapter 3 focuses on identifying good features for knowledge discovery from text. Four types of writeprint features are constructed and shown effective for authorship analysis of online messages. Feature selection is aimed at identifying a subset of significant features from a high dimensional feature space. Chapter 4 presents a framework of feature selection techniques. This essay focuses on identifying marker genes for microarray-based cancer classification. Our experiments on gene array datasets showed excellent performance for optimal search-based gene subset selection. Feature consolidation is aimed at integrating features from diverse data sources or in heterogeneous representations. Chapter 5 presents a Bayesian framework to integrate gene functional relations extracted from heterogeneous data sources such as gene expression profiles, biological literature, and genome sequences. Chapter 6 focuses on kernel-based methods to capture and consolidate information in heterogeneous data representations. I design and compare different kernels for relation extraction from biomedical literature. Experiments show good performances of tree kernels and composite kernels for biomedical relation extraction.These five essays together compose a framework of feature engineering and present different techniques to construct, select, and consolidate relevant features. This feature engineering framework contributes to the domain of information systems by improving the effectiveness, efficiency, and interpretability of knowledge discovery.

China now is one of the most attractive destinations for foreign direct investment (FDI) and mergers and acquisitions (M&As) have become an increasingly important mode of FDI entry in China since its accession to the World Trade Organization. M&As in China are expected to play a vital role in the restructuring of its inefficient State-owned enterprises. This thesis characterizes and analyzes the evolving Chinese legal regime governing M&As in the context of the ongoing economic reform. In addition, it identifies the antitrust issues arising from foreign acquisitions of Chinese domestic enterprises, which can result in market dominance and restrictive practices in China. The thesis concludes that China's M&A regime can be improved and aligned more closely with international practices as its economy becomes further integrated into the world economy.

This thesis presents an empirical investigation of the role of competition in determining (1) bidder firm behaviour in, and (2) the resulting valuation effects of, corporate takeovers. The study is based on the most comprehensive sample currently available of interfirm tender offers for publicly traded U. S. target firms during the period 1971-1990. Corporate takeover contests differ in complex ways with respect to the asymmetric information and bargaining environment, distributions of bidder reservation values and target share ownership, and information acquisition costs. There is substantial theoretical work examining the strategic role of the choice of payment method, bidder elimination and target management resistance, and of particular interest in this thesis, pre-bid acquisition of target shares ("toehold") and its impact on the subsequent tender offer price. Despite a voluminous empirical literature on corporate acquisitions, systematic evidence on the extent and role of bidder toeholds on bidding strategies is sparse. While the toehold has been shown to be prevalent in takeover contests, the extant empirical literature contains few results pointing to the strategic role suggested by theory. The lack of statistical significance may reflect a combination of small samples, weak experimental design, and biases in estimation. This thesis remedies the small sample problem by examining more than 1350 takeover contests in the U. S. from 1971 to 1990. The experimental design is improved by including a larger set of sample controls, and addressing the bias issue by estimating a set of equations which simultaneously determines the toehold and the takeover premium. The wealth effects of takeover contests are estimated as a function of toeholds, the number of bids/bidders, the outcome of the bid, and the target management response. Other empirical issues, including the effect of toeholds on the probability of target management resistance and emergence of a second bid in the contest, are also examined. Finally, a new econometric technique is developed for simultaneously estimating event probabilities and conditional expected event returns in order to determine whether entering the takeover auction, and responding to rival bids for the target shares, on average enhances the wealth of the initial bidders' shareholders.

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