Classical elasticity cannot be used to explain effects related to material microstructures due to its lack of a material length scale parameter. To mitigate this deficiency, higher order elasticity theories have been developed. Two simple higher order theories and their applications are studied in this research. One is a modified couple stress theory and the other is a simplified strain gradient theory, each of which contains only one material length scale parameter in addition to the classical elastic constants. Variational formulations are provided for these two theories by using the principle of minimum total potential energy. In both cases, the governing equations and complete boundary conditions are determined simultaneously for the first time. Also, the displacement form is explicitly derived for each theory for the first time. The modified couple stress theory is applied to solve a simple shear problem, to develop a new Bernoulli-Euler beam model, and to derive the constitutive relations for hexagonal honeycomb structures, while the simplified strain gradient theory is used to solve the pressurized thick-walled cylinder problem. All these models/solutions are obtained for the first time and supplement their counterparts in classical elasticity. Numerical results obtained from the newly developed models and derived solutions and their comparisons with their counterpart results in classical elasticity reveal that the higher order theory based models and solutions have the capacity to account for microstructural effects; their counterparts in classical elasticity do not have the same capability. Nevertheless, the former are shown to recover the latter if the microstructural effects are suppressed or ignored.

Capital Assets Pricing Model (CAPM) proposed by Sharpe (1964) is the most popular model for evaluation of expected returns. Based on CAPM, beta is the only cause for the expected return. However, Banz (1981) and Reinganum (1981) argue that firm size is also influential for asset returns even beta is controlled. The size effect is called an anomaly for the pricing model based on CAPM. Besides size, Fama and French (1992) show that the Book-to-Market ratio is also significant for the stock returns. Basically, the size and Book-to-Market challenge the role of beta in evaluating the expected returns of assets. Nevertheless, Kothari, Shanken and Sloan (1995) show that beta is the only cause of asset returns if longer holding returns are conducted in the tests of the pricing model. This thesis employs two kinds of length of holding return to examine the effects of size and beta in the asset returns. For shorter holding beta, we use the weekly data while we use monthly beta for longer holding return. We find that beta and size are both positively related to asset returns. No matter which length of holding return is applied. However, the positive relation between size and expected return in Taiwan needs further investigation.

As the U.S. population continues to increase, planning for future water quantity and quality needs is important. Historically, many municipalities have relied heavily on surface water as their major source of drinking water, but recently, technological advancements have improved the economic viability of reverse-osmosis (RO) desalination of brackish-groundwater as a potable water source. Brackish-groundwater may be an alternative water source that provides municipalities an opportunity to hedge against droughts, political shortfalls, and protection from potential surface-water contamination. This research specifically focuses on investigating economies of size for conventional surface-water treatment and brackish-groundwater desalination by using results from four water treatment facilities in the Texas Lower Rio Grande Valley (LRGV). The methodology and results can have direct implications on future water planning. Economic and financial life-cycle costs were estimated for a "small"- conventional-surface water facility (2.0 million gallons per day (mgd) Olmito facility) and a "small"-brackish-groundwater desalination facility (1.13 mgd La Sara facility). Prior analyses were modified to determine similar costs for a "medium"-sized conventional surface-water facility (8.25 mgd McAllen Northwest facility) and a "medium"-sized brackish-groundwater desalination facility (7.5 mgd Southmost facility). The life-cycle costs of the "small" Olmito facility are compared to the life-cycle costs of the "medium" Northwest facility and the life-cycle costs of the "small" La Sara facility are compared against the life-cycle costs of the "medium" Southmost facility to determine the existence of economies of size. This research was facilitated by the use of the CITY H20 ECONOMICS© and the DESAL ECONOMICS© Excel® spreadsheet models previously developed by Texas AgriLife Research and Texas AgriLife Extension Service agricultural economists. Although the results are applicable to the Texas LRGV, economies of size are apparent in conventional surface-water treatment and constant economies of size are evident in brackish-groundwater desalination. This research also concludes that RO desalination of brackish-groundwater is economically competitive with conventional surface-water treatment in this region.

This thesis proposes a novel structure to realize the monolithic integra-tion of optical spot-size converter (SSC) and high-speed electroabsorption modulator (EAM). The SSC is based on a scheme of coupled asymmetric waveguide fabricated by tapered undercut waveguide. Using a selectively undercut-etching-active-region (UEAR), the laterally tapered undercut ac-tive waveguide (LTUAWG) can be processed from a wide tapered ridge waveguide using in situ control to avoid submicron photolithography as well as complex processing, such as selective area growth, selective area etching and re-growth. By monolithically integrating EAM and SSC, the EAM waveguide width can be beneficial from scaling down the waveguide size for enhancing the EAM bandwidth, while the optical coupling loss from single mode fiber can still be kept low. In this finished SSC-integrated EAM, a 1-dB misalignment tolerance of ¡Ó2.9£gm (horizontal) and ¡Ó2.2 £gm (vertical) is obtained from SSC side, which is better than the results, ¡Ó1.9£gm (horizontal) and ¡Ó1.6£gm (vertical), from EAM side. The measured far-field angles for SSC and EAM are 6.0 (horizontal) ∗ 9.3 (vertical) and 11 (horizontal) ∗ 20 (vertical) respectively. As low as mode transfer loss of -1.6 dB is obtained in such SSC. All the simulation results are quite fitted with the experiment results, realizing the function of SSC by LTUAWG. The fabricated EAM waveguide width is 2.5 £gm, leading to over 40 GHz of -3-dB electrical-to-optical (EO) response. The high efficient SSC integrated with high-speed EAM suggests that the LTUAWG technique can have potential for applications in high-speed optoelectronic fields.

Thesis (M.S.) B.Y.U. Dept. of Sociology, 1977. / Electronic thesis. Bibliography: leaves 80-89. Also available in print ed.

In this report we give a brief introduction to the multilevel models, provide a brief summary of the need for using the multilevel model, discuss the assumptions underlying use of multilevel models, and present by means of example the necessary steps involved in model building. This introduction is followed by a discussion of power and sample size determination in multilevel designs. Some formulae are discussed to provide insight into the design aspects that are most influential in terms of power and calculation of standard errors. Finally we conclude by discussing and reviewing the simulation study performed by Maas and Hox (2005) about the influence of different sample sizes at individual as well as group level on the accuracy of the estimates (regression coefficients and variances) and their standard errors. / text

This thesis discusses the effect of initial particle size and alloying of Pt nanocatalysts on the degradation of Proton Exchange Membrane Fuel Cells (PEMFC). Platinum nanocatalysts with initial particle sizes of 2.2nm, 3.2nm, 5.0nm, 6.7nm and 11.3nm were studied, before and after potential cycling. The two smallest initial particle sizes show significant degradation, while the remainder of the samples show negligible degradation after 10,000 cycles. Among the possible degradation mechanisms operating, the results show that dissolution and re-precipitation is insignificant among all the samples. On the other hand, modified electrochemical Ostwald ripening (MEOR) is the main cause for particle growth and degradation of the Pt nanocatalysts. Moreover, MEOR could also assist the coalescence of particles. Thus, controlling the Pt dissolution rate is the key factor to prevent degradation. In the case of Pt₃Co nanocatalysts, both MEOR as well as dissolution & reprecipitation play an irrelevant role in degradation. However, particle migration and coalescence seems to be more severe in Pt₃Co nanoparticles than for Pt nanoparticles. / text

published_or_final_version / Education / Doctoral / Doctor of Philosophy

published_or_final_version / Medical Sciences / Master / Master of Medical Sciences

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