The first topic of this thesis proposes a digital video decoder for NTSC. The new fully digital design employs a DDFS (digital direct frequency synthesizer) and an adaptive digital PLL to track and lock the demodulation carrier. The complexity of the digital video decoder, hence, is drastically reduced. The overall cost of the proposed design is 6.0 mm2 (39K gates). The maximum power dissipation is 86 mW at the hightest clock rate which is 21.48 MHz. The second topic is to carry out a codec (encoder-decoder) design for interfacing variable-length and fixed-length data compression. The poor memory efficiency caused by the variable-length words converting into a fixed-length packet such that the compression can be hardwaredly and parallelly processing is significantly improved. The proposed codec is to encode more symbols in the redundant bits of the padding bits of the fixed-length packets. This novel encoding scheme relaxes the intrinsic poor bit rate of the traditional fixed-length data compression.

ABSTRACT Ibbotson and Ritter (1995) indicate that there are three anomalies in IPO markets: IPO underpricing, IPO long-run underperformance, and hot-issue market. Contrary to most of the previous studies which focus on IPO underpricing or IPO long-run performance, this dissertation examines the existence of hot-issue phenomenon in Taiwan IPO markets. ¡§Hot-Issue anomaly¡¨ means that cycle exists in both the IPO volume and IPO underpricing. Consequently, issuers tend to issue new equity to the public when faced with high average initial returns of IPOs. Ritter (1984) argues that IPOs in hot markets experience higher initial returns. Moreover, young IPOs experience more underpricing in hot markets. A possible explanation for hot-issue phenomenon is the positive feedback hypothesis: market investors positively react to IPO underpricing. When investors earn initial returns from IPOs, they are more likely to subscribe to future IPOs leading to the fact that issuers tend to issue when previous IPOs are more underpriced. Hot-issue is considered as an anomaly because underpricing or initial return is referred as an indirect cost of issuance. Issuers should try to reduce the extent of underpricing to raise IPO proceeds. From the point of view of maximizing proceeds, previous studies fail to explain the hot-issue anomaly in IPO markets. Ibbotson, Sindelar, and Ritter (1994) show that IPO hot-issue phenomenon exists not only in U.S. market but also in Germany, South Korea, and U.K. markets. To make up this gap, this dissertation first tests if there exists hot-issue anomaly in Taiwan and then examines why hot-issue anomaly exists to provide an explanation to the anomaly. I find that IPO initial return leads IPO issuance. However, issuance of IPOs does not reduce the extent of underpricing of the followed up IPOs. I further show that IPO initial return is not related to the initial return of the followed up ones. The issuance of IPOs cannot be attributed to the information of initial returns of preceding IPOs. Rather, the market information between IPO filing date and IPO issuance date is the cause for the lead-lag relation between IPO initial return and IPO issuance. IPO offer price will fully reflect to the negative recent market return but simply partially to the recent positive market return. Most of the IPO initial return can be explained by the information revealed after offer price has been set implying that the offer price is set efficiently. The large amount of IPO volume following high IPO initial return can be attributed to the positive market reaction to the preceding IPOs instead of the filed IPO pricing of preceding IPOs. Our findings explain the hot-issue anomaly. During hot markets, investors¡¦ excess demand on IPOs leads to high initial returns of IPOs. Faced with investors¡¦ excess demand, issuers attempt to issue IPOs to take advantage of investors¡¦ sentiments to maximize IPO proceeds.

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ABSTRACT In this thesis, some aspects of the non-fixed neural network for power load forecasting are discussed. Unlike traditional fixed neural network technique, the structure of neural network is non-fixed during its training and testing phases. Based on the characteristic of the desired forecasting day, the number of input node utilized is changeable. The modified learning algorithms, including fuzzy back-propagation learning algorithm and stochastic back-propagation learning algorithm, will be used in the load forecasters we developed. For precise input selection of the neural network model, the analysis of mutual relationship between load and temperature and gray relational analysis between desired forecasting load and the related previous load are studied. Two types of load forecasting, i.e., peak load forecasting and hourly load forecasting, are investigated. Short term (one-to-several-day-ahead) load forecasting is considered in this research. Hourly loads and relevant temperature data from 1992 to 1998 provided by Taipower Utility and the Central Weather Bureau is implemented for this research. For demonstrating the feasibility and superiority of the forecasters we develop, several forecasting models, including fixed neural network with constant learning rate and momentum, recursive time series model, and artificial neural network short term load forecaster (ANNSTLF) proposed by [Kho.2], are also performed for a comparison. From the results of the simulation, better performances could be obtained by the methods we proposed. Not only the over-training phenomenon is obviously reduced, the forecasting accuracy and the learning speed of the neural model are also effectively improved.

Agency theories suggest that governance matters more when agency conflicts are potentially more severe. However, empirical studies often do not control for the potential severity of agency conflicts. I show that the marginal benefit of governance varies with the free cash flow level, a proxy for the potential severity of agency conflicts. As the free cash flow level increases, higher governance quality becomes incrementally more value-enhancing, and lower governance quality becomes incrementally more value-destroying. This is consistent with the hypothesis that better governance helps resolve the agency conflicts in investment decisions when a firm has more free cash flows (Jensen, 1986). This study highlights the importance of controlling for the potential severity of agency conflicts in governance studies and provides an improved method to estimate the marginal benefit of a governance mechanism.

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No description available.

Thesis (B.S.)--Haverford College, Dept. of Mathematics, 2002. / Includes bibliographical references.

This dissertation explores catalyst technology for the production of renewable liquid fuels via thermo-chemical conversion of biomass derived syngas. Fischer-Tropsch synthesis is a process for converting syngas, i.e. a mixture of CO and H2, into energy rich long chain hydrocarbons and oxygenated compounds. This synthesis process involves a number of elementary reactions leading to an array of polymeric products. The economic operation of an FTS process lie in the interplay of both catalyst and reactor design. In relation to catalysis, the nature of chemisorbed species, and the fractional availability of active metal sites determines rate, conversion and yield. Similarly, reactor design decides the operational envelope and determines the economics of an FTS process. Eggshell cobalt catalysts are used in CO hydrogenation reactions due to their ability to maximize the use of precious cobalt metal. The thickness of the shell can be utilized to control the product yield and distribution. In this study, during catalyst synthesis stage, metal-support interaction has been exploited to control the thickness and hence, the product distribution. The catalysts are prepared using precipitation of cobalt nitrate (dissolved in ethanol) on silica support. The metal deposition rate and the location are controlled through optimized non-polar solvent imbibing, followed by water addition to a Co(NO3)2-ethanol solution and hydrolysis by urea. The eggshell coating thickness (in the absence of restricting solvent) onto silica gel substrate was modeled via theoretical equations and experimentally verified during catalyst preparation through microscopic analysis of catalyst samples. Bulk precursor solution properties such as viscosity and surface tension along with substrate properties such as tortuosity are analyzed and included in the theoretical analysis for tailoring the catalyst eggshell thickness. Polar and non-polar solvent interactions with silica gel are exploited during cobalt precipitation to control the eggshell thickness. The catalyst samples were characterized using hydrogen chemisorption studies. The catalyst was tested in a fixed bed tubular bench scale reactor using research grade synthetic feed gases (H2:CO being 2:1). Products were analyzed in a GC column fitted with flame ionized detector and the results were compared with Anderson-Schulz-Flory distribution. Liquid product analysis validated the approach used for eggshell catalyst design and synthesis. The impact of solvent and calcination conditions, on the performance of eggshell catalysts was examined. Solvents such as water and alcohol attach to the silanol groups on the silica gel surface and compete with metal salts during ion exchange and adsorption. The solution properties impact metal dispersion and interaction with metal support. The calcination conditions (static versus dynamic, oxidizing versus reducing atmosphere) also have an impact on metal dispersion and support interaction. Ethanol proved to be a better solvent for enhancing the dispersion due to its surface wetting properties. Direct reduction in dynamic hydrogen provided gradual decomposition of the cobalt precursor thus reducing agglomeration. Both the use of water as a solvent and a static air environment during calcination led to lower dispersion. The back reaction of calcination products (especially H2O) and agglomeration due to thermal expansion were competing phenomenon in a static oxidizing environment. Catalyst characterization revealed that the latter effect was pre-dominant. Catalyst performance testing was first done with pure gases (H2 & CO) in a fixed bed reactor. Additionally, to examine the technological feasibility and economic viability of producing liquid fuels from biomass via the thermo-chemical route, laboratory scale testing was done using syngas produced by gasification of pine chips. The pine chips were gasified in a tubular entrained flow gasifier operated at MSU and supplied in cylinders. The raw biomass syngas was treated using a series of adsorbents to remove tar, water and other impurities. This pre-treated gas was subjected to Fischer-Tropsch Synthesis (FTS) in a bench scale fixed bed reactor using the eggshell cobalt catalyst developed in our laboratory. Hydrogen was added to attain the 2:1 stoichiometric ratio required for the FTS reaction. The product gases were analyzed using an FTIR gas cell while liquid product was analyzed using a GC/MS HP-5 column. The eggshell catalyst produced fuel preferentially in the range of middle distillates. The activity of FTS catalyst under biomass derived syngas was lower when compared to that under pure surrogates (H2/CO) due to the presence of inert components (such as methane) in the biomass derived syngas To complement the experimental study, a comprehensive model of FTS catalytic process was developed. This included both catalyst and a fixed bed reactor model. While modeling a catalyst pellet, intra-particle diffusion limitation was taken into account. For a spherical 2mm pellet, eggshell morphology provided highest activity and selectivity. The reactor model was developed by coupling intra-pellet model with inter-pellet model via reaction term. The entire process operation starting with gas injection was considered. Presence of radial temperature profile, due to wall cooling, was confirmed by Mears criterion. Thus for a fixed time duration, a 2-dimensional reactor model, with respect to temperature and concentration, was developed. The safe operational envelopes for a fixed bed reactor, using cobalt catalyst, was narrow 473 < T < 493. The extent of catalyst pore fill changed (i) the radial thermal conductivity (ii) the overall temperature and concentration profile across the bed and (iii) the limits of safe operation without reaction runaway. Finally, hydrocarbon product selectivity also varied during startup. While the catalyst pores were being filled, effluent product mainly composed of lighter, more volatile components. Once the pores are filled, heavier products started to trickle down the bed. The economics of a large scale production of liquid fuels using this technology was explored using a CHEMCAD model of a large scale process for producing liquid fuel from biomass, a sensitivity study was conducted to determine key process parameters Two different gasification technologies were compared, one that uses only biomass (BTL process) and a second process that supplements the biomass feed with natural gas for meeting energy and hydrogen needs (BGTL process). The basis for the design was 2000 metric tons of dry biomass feed per hour. The breakeven price for synthetic crude oil was estimated at $106/bbl. for the BTL plant, and $88/bbl. for a natural gas assisted BGTL plant using current market prices for raw materials utilities and capital equipment. With the increasing availability, and falling prices of natural gas, the reforming of natural gas will provide a bridge solution in the short term for economical natural gas assisted BTL conversion, thus making it competitive in marketplace.

We construct Fuchsian groups [Gamma] of signature (0 : 2, ... ,2 ;1;0) so that the set of hyperbolic fixed points of [Gamma] will contain a given finite collection of elements in the boundary of the hyperbolic plane. We use this to establish that there are infinitely many non-commensurable non-cocompact Fuchsian groups [Delta] of finite covolume sitting in PSL₂(Q) so that the set of hyperbolic fixed points of [Delta] will contain a given finite collection of rational boundary points of the hyperbolic plane. We also give a parameterization of Fuchsian groups of signature (0:2,2,2;1;0) and investigate when particular hyperbolic elements have rational fixed points. Moreover, we include a detailed list of the group elements and their killer intervals for the known pseudomodular groups that Long and Reid found; in addition, the list contains a new list of killer intervals for a pseudomodular group not found by Long and Reid. / text