Studying dynamics of magnetization relaxation in excited magnetic materials is important both for understanding the rates and pathways of magnetization relaxation and for the potential use in spin-based electronics and data storage devices in the future. Previous studies have demonstrated that the size of nanocrystals is an important factor for energy relaxation in quantum dots and metal nanoparticles. Since magnetization relaxation is one of energy relaxation pathways, the size of nanocrystals may be also an important factor for magnetization relaxation in nanoscale magnetic materials. The goal of this study is to have a better understanding of magnetization relaxation in nanoscale magnetic materials. In particular, we focused on the correlation between the nanocrystal size and the rates of spin-lattice relaxation (SLR), a magnetization relaxation pathway, in magnetic nanocrystals. The size-dependent magnetization relaxation rate after optically induced demagnetization in colloidal Fe3O4 nanocrystals was measured by using time-resolved Faraday rotation (FR). Fe3O4 nanocrystals were chosen as the model system to study the correlation between the size of nanocrystals and the rates of SLR due to the wellestablished synthetic procedure of making nanocrystals with various sizes and narrow size dispersion. Faster SLR rates were observed in smaller Fe3O4 nanocrystals. The results suggested the surface of nanocrystals have higher efficiency of SLR than the interior region by using a simple model to analyze the SLR rates of Fe3O4 nanocrystals with various sizes. Higher efficiency of SLR at the surface may be due to the stronger spin-orbit coupling at the surface relative to the interior region. In addition to magnetization dynamics studies, the effect of oxidation on static FR in iron oxide nanocrystals (between Fe3O4 and y-Fe2O3) was studied. The results indicated FR signal is linearly correlated to the strength of optical transition between Fe2 and Fe3 in Fe3O4 for a given size of nanocrystals.

Atmospheric pressure microplasmas are uniquely characterized by their very high energy densities and also by their small discharge sizes. These properties allow for unique applications in plasma processing technologies. We have investigated the operational characteristics of microplasmas at higher energy densities and smaller sizes by operating microplasma configurations at high pressure conditions. We studied the discharge and analyzed its variation with changes in current and pressure. The discharge was analyzed by microscopic visualization and data from the images and was processed to measure the current density and estimate charged particle density. By increasing the pressure beyond 200 psi and by minimizing the discharge current required for sustaining the plasma, we have been able to achieve discharge sizes of 7 mu m in nitrogen and as small as 20 μm in helium. Optical emission spectroscopic studies were carried out to measure gas temperature and vibrational temperature using the nitrogen 2nd positive system. With increase in pressure, the transition from non-equilibrium plasma to equilibrium plasma was also studied using the OES temperature measurements. iv Temperature measurements are also used to estimate normalized current densities. Normalized current density results obtained after introducing the corrected effective pressure based on the increased gas temperature are close to the value of 400 mu A /cm^2*Torr^2 obtained for low pressure normal glow discharges in nitrogen. This research presents further validation of the general operational characteristics of microplasmas being pressure scaled versions of normal glow discharges. Attained energy densities are ten to twenty times higher than in atmospheric pressure microplasmas. Discharge sizes are also significantly smaller, decreasing with increasing pressure, but the scaling is with density ‘nd’ rather than pressure ‘Pd’ due to the increase in gas temperature with pressure, indicating a dependence on collisional processes. We can infer that at higher pressures, the operational characteristics of more complex plasma discharges like dielectric barrier discharges, RF plasmas, etc. follow scaling patterns, transitions and limits similar to the microplasma discharge studied in this thesis.

This paper probes into institutional investor¡¦s impact on Taiwan¡¦s stock market and its shareholding ratio in the relation of return. We aim to find out an effective return index of degree in order to provide another reference basis for investors. This research uses listed companies from 1999 to 2003 as sample. The analysis result shows that Taiwan has gone against the phenomenon of book-to-market and size effect in the past five years, and institutional investors¡¦ partiality is one of the reasons causing this phenomenon. The stock with high share of all kinds of institutional investors is expected to have high return in addition. In consideration of the momentum of the share of all kinds of institutional investors, we are unable to prove that the stock which has the positive momentum of share of all kinds of institutional investors will yield high return. The size factor and book-to-market ratio factor at the regular value prove whether institutional investors still have the ability to select stocks. The result proves that the group with high share of all kinds of institutional investors still has high return under the same book-to-market ratio and size factor, and proves that institutional investors indeed have better tactics in selecting stocks.

Water and R-134a sprays as they impinge on the flat endplate of a circle are studied experimentally. In order to optimize water and R-134a sprays cooling efficiency, a detailed characterization and understanding of the spray formation is essentially needed. The effects of the jet exit velocity and Weber number on spray segregation are investigated. An optical image system was used to quantify the droplet size and distribution. LDV measurements were used to characterize the local velocity and velocity fluctuation distribution from a commercial available nozzle in both axial and radial directions. It is found in the water spray that local mean droplet diameter (SMD) decreases as jet exit velocity increases and as jet proceeds further downstream as well. Furthermore, the SMD and radial velocity are found to be the largest at the outer edges of the water spray. In contrast, the radial velocity is found to be the smallest at the outer edges of the R-134a spray. The SMD and radial velocity continuously decrease across both the water spray and R-134a spray toward the jet axis; while the corresponding axial velocity is the maximum there. Moreover, the R-134a spray jet heat transfer in non-boiling regime was shown to be dependent on the velocity of the impinging jets in terms of Weber number and other related parameters which are in good agreement with those of previous studies.

The effects of abrasive particle size and tool surface roughness on tool and work wears of a polishing process were investigated. It was aimed to obtain a polishing condition that could result in a high work wear while the tool wear was low. An analytical study was first done to examine how the various operating conditions affected the wear rates of tool and work. It was done from a wear model developed by Su and Horng [1]. This model was further extended in the study to allow the wear rate analysis for an abrasive particle with ellipsoid shape. It was shown that an enhancement of abrasive particle size or tool surface roughness would increase the work wear while decrease the tool wear. Several sets of experiments were conducted to confirm the predictions of analytical study. It was shown that the experimental trends were the same as the analytical ones. Finally, the possible causes of observed phenomena and the limitations of the study were discussed.

Along with the rising and flourishing development of the modern technology and human knowledge, the demands for optical-electric products and communication systems are getting more and more. By combining the semi-conductor technology process with micro optical elements, a complete micro optical system can be integrated. The functions of a micro optical system include beam-splitting, beam-light offsetting, focusing, and switching, etc. Letting micro optical elements be integrated on a substrate, the fix and alignment problems, which are caused by the relative displacements between the elements, can be improved. Also, the production rate can be increased and cost can be reduced if the products are made by micro mold and array fabricated process. Thus, the technology of the Micro Optical Electro Mechanical System is widely applied to manufacture the products of optical-electric and communication, such as the backlight module of a LCD, projector, and optical fiber communication system, etc. The main purpose of this study is to design and fabricate a microball-lens array, and to apply it to couple optical fibers. The proposed product is a 3D micro-ball-lens array with vertical and non-vertical focus directions and better coupling efficiency. A v-groove is fabricated by using semi-conductor technology in order to fix the micro-ball-lens array and optical fiber such that an optical fiber switch coupling system can be obtained. The packaging of the optical fiber switch coupling system is formed by UV-cure and a microcap which is fabricated by MEMS. It can provide the protection to the system. Also, the completed system can achieve the demands of the industry fields such as precise localization, cost reduction and so on.

Electro¡VAbsorption Modulator has become a very important element in optical fiber communication due to its capability of integrating with other semiconductor devices. In order to get high-speed performance, the small size of waveguides is necessary. But it also brings to high coupling loss, resulting in low optical fiber link. In general, the waveguide mode is elliptical shape with sizes of 1¡Ñ2£gm to 1¡Ñ3£gm, which will definitely lead to high mode mismatch as adapted to conventional single¡Vmode optical fibers of 8£gm circular mode and cause 7~10 dB insertion loss[21]. Typically, micro lens, tapered fibers or taper optical waveguides are used to confine optical fiber mode to waveguide in order to reduce the insertion loss. In the thesis, we have developed a novel structure of tapered optical spot-size mode converter monolithically integrated with traveling-wave electro-absorption modulator (TWEAM) by using whole wet-etching processing. The optical waveguides are fabricated by wet-etching and subsequent selective undercut etching. By adjusting the wet-etching time, the waveguide core for TWEAM and the tapered spot-size mode converter can thus be engineered. The selective undercut wet etching not only can reduce the optical scattering loss, but also decrease the parasitic capacitance, leading to high optical and microwave transmission of TWEAM. Based on the model described in literature [4-8] and also Beam Propagation Method (BPM), the optical index of epi-layers is used to calculate the three¡Vdimension modal of optical mode and coupling efficiency. The microwave equivalent circuit is used to calculate and design device structure. In this thesis, the Spot¡VSize Converter monolithically with Traveling¡VWave Electro¡VAbsorption Modulator device is successfully fabricated and demonstrated. TWEAM integrated spot-size optical mode converter is measured and compared with single TWEAM (without converter) with optical wavelength of from 1550nm to 1570nm. The average optical insertion loss of about 4dB is found. The maximum extinction-ratio is about 21dB with modulation efficiency of 21dB/V, E-O response about 12GHz of ¡V3dB bandwidth at 50£[ termination is demonstrated.

Structure properties of water clusters are investigated in this study by means of molecular dynamics simulations. The oxygen density profile, dipole moment and hydrogen bond properties of water clusters are all examined. The temperature dependence and size dependence of the structure properties are also explored in the present study. Upon the molecular dynamics simulations, the flexible three-centered (F3C) water potential is used to model the inter- and intra-actions of the water molecule. It is found that as the temperature rises, the density of the oxygen and the average number of hydrogen bonds per water molecule will decrease. The effect of cluster size, however, is less significant on the structure properties. The differences between the structural properties for the surface region and those for the interior region of the cluster are also investigated. It is found that as the temperature rises, the average number of hydrogen bonds per water molecule decreases, but the ratio of surface water molecules increases. After comparing the water densities in interior regions and the average number of hydrogen bonds in those regions, we find there is no apparent size effect on water molecules in the interior region, whereas the size of the water cluster has a significant influence on the behavior of water molecules at the surface region.

Software cost estimation is essential for software companies to be more competitive and more profitable. The objective of this thesis is to study current software size estimation practices adopted by Turkish software companies, to identify best prac-tices, and to suggest appropriate methods that can help companies to reduce errors in their software size estimations.

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