Thesis (Ph. D.)--University of Washington, 2008. / Vita. Includes bibliographical references (p. 63-64).

Thesis (Ph.D.)--University of California, Berkeley, 1961. / "Chemistry, UC-4" -t.p. "TID-4500 (16th Ed.)" -t.p.

Thesis (Ph. D.)--University of Rhode Island, 2005. / Typescript. Includes bibliographical references (leaves 74-76).

Many-objective optimization problems (MaOPs), in which the number of objectives is greater than three, are common in various applications, and have drawn many scholars' attention. Evolutionary multiobjective optimization (EMO) algorithms have been successfully applied to solve bi- and tri-objective optimization problems. However, MaOPs are more challenging compared with the bi- and tri-objective optimization problems. The performances of most existing classical EMO algorithms generally deteriorate over the number of objectives. Thus, this thesis presents a weight design method to modify classical decomposition-based EMO algorithms for solving MaOPs, and a novel objective extraction method to transform the MaOP into a problem with few objectives.;Additionally, performance metrics play an important role in understanding the strengths and weaknesses of an algorithm. To the best of our knowledge, there is no direct performance metric for the objective reduction algorithms. Their performance can only be indirectly evaluated by the metrics, such as IGD-metric and H-metric, of the solutions obtained by an EMO algorithm equipped with the objective reduction method. This thesis presents a direct performance metric featuring the simplicity and usability of the objective reduction algorithms. Meanwhile, we propose a novel framework for many-objective test problems, which features both simple and complicated Pareto set shape, and is scalable in terms of the numbers of the objectives and the essential objectives. Also, we can control the importance of essential objectives.;As some MaOPs may have redundant or correlated objectives, it is desirable to reduce the number of the objectives in such circumstances. However, the Pareto solution of the reduced problem obtained by most existing objective reduction methods may not be the Pareto solution of the original MaOP. Thus, this thesis proposes an objective extraction method for MaOPs. It formulates the reduced objective as a linear combination of the original objectives to maximize the conflict between the reduced objectives. Subsequently, the Pareto solution of the reduced problem obtained by the proposed algorithm is that of the original MaOP, and the proposed algorithm can preserve the non-dominant relation as much as possible. We compare the proposed objective extraction method with three objective reduction methods, i.e., REDGA, L-PCA and NL-MVU-PCA. The numerical studies show the effectiveness and robustness of the proposed approach.;The decomposition-based EMO algorithms, e.g. MOEA/D, M2M, have demonstrated the effectiveness in dealing with MaOPs. Nevertheless, these algorithms need to design the weight vectors, which has significant effects on the algorithms' performance. Especially, when the Pareto front of the problem is incomplete, these algorithms cannot obtain a set of uniform solutions by using the conventional weight design methods. Not only can self-organizing map (SOM) preserve the topological properties of the input data by using the neighborhood function, but also its display is more uniform than the probability density of the input data. This phenomenon is advantageous to generate a set of uniform weight vectors based on the distribution of the individuals. Therefore, we propose a novel weight design method based on SOM, which can be integrated with most of the decomposition-based EMO algorithms. In this thesis, we choose the existing M2M algorithm as an example for such integration. This integrated algorithm is then compared with the original M2M and two state-of-the-art algorithms, i.e. MOEA/D and NSGA-II on eleven redundancy problems and eight non-redundancy problems. The experimental results show the effectiveness of the proposed approach.

This thesis examines the catalytic characteristics of two materials with respect to the decomposition of Formic Acid. The decomposition of formic acid proceeds via two principal reaction pathways: dehydration and dehydrogenation. Dehydrogenation is a valuable reaction producing Hydrogen suitable for use in fuel cells whereas the dehydration pathway produces carbon monoxide, a poison for many fuel cell materials. One of the surface species, the formate ion, is also implicated in other important chemical reactions, most notably the water gas shift and the decomposition of methanol. The author seeks to document various intermediate surface species associated with the two reaction pathways with hope to use this information to future tailoring of catalysts for greater selectivity.

I investigated the role of a flood in particulate organic matter (POM) dynamics of the Little Tennessee river/floodplain ecosystem in western North Carolina, USA. I measured litter inputs, leaf breakdown, floodplain litter, and aboveground herbaceous net primary production at 12 sites. Annual litter inputs (274-625 g m-2 y-1) were typical of a temperate deciduous forest, but lower than other floodplain forests in the eastern United States. Mean aboveground herbaceous net primary production ranged from 61-439 g m-2 y-1 and leaf breakdown rates of 4 tree species ranged from 0.001-0.010 d-1. Following a flood on 8 January 1998, sites were separated into three inundation classes: inundated, partially-inundated, and non-inundated. Sites inundated by a January flood had significantly less forest floor leaf litter and coarse woody debris after the flood. There was no significant change at the partially-inundated or non-inundated sites. In addition, there was no significant difference in herbaceous material between pre- and post-flood collections for any inundation classes. Litter input, leaf breakdown, and floodplain litter standing crop data suggest that flood entrainment of POM from the floodplain of Little Tennessee River is a source of POM to the active channel. The impact of floods on the floodplain POM dynamics, however, is highly dependent on the time of year and magnitude of the flood, and on the structure of floodplain tree assemblages, which is strongly influenced by anthropogenic land use. Compared to direct litterfall and instream primary production, the floodplain may be a small annual source of POM for the river. / Master of Science

Olefin metathesis is an outstandingly versatile methodology for the catalytic assembly of carbon-carbon bonds. Metathesis methodologies have been widely embraced since the advent of easily-handled ruthenium catalysts. However, industrial implementation has lagged. Problems of reliability and productivity arising from catalyst decomposition have impeded broad uptake of metathesis in process chemistry. Such challenges also hamper deployment of metathesis in forefront applications such as chemical biology. Better understanding of the mechanisms by which catalysts decompose can thus improve performance in demanding applications, as well as providing guidelines for informed process and catalyst design. Oxygen is often viewed as a relatively innocuous contaminant in reactions promoted by these late transition metal catalysts. Indeed, multiple reports comment on the desirability and operational simplicity of metathesis in air. We suspected, however, that deleterious impacts of O2 may be masked by the high catalyst loadings typically deployed in such reports. The first part of this thesis focuses on examining the robustness of leading metathesis catalysts toward oxygen. Systems examined include the classic, dominant N-heterocyclic carbene (NHC) derivatives, as well as recent breakthrough analogues containing cyclic alkyl amino carbene (CAAC) ligands. Both are shown to be decomposed by oxygen, but the CAAC catalysts are found to be not only more productive, but significantly more O2-tolerant. This is important as it overturns the widespread belief that high catalyst activity is invariably a trade-off against higher sensitivity. Studies of the initial oxidation event for the second-generation Grubbs catalyst RuCl2(H2IMes)(PCy3)(=CHPh) suggest that [2+2] cycloaddition of O2, as well as bimolecular decomposition of the four- coordinate species generated by PCy3 oxidation, account for ca. 90% of the observed decomposition. A previously-proposed pathway involving attack of O2 at the benzylidene ligand appears to be a minor contributor. In Chapter 3 of this thesis, a new strategy for inhibiting catalyst decomposition is examined. Specifically, cationic metathesis catalysts were encapsulated within a supramolecular resorcinarene capsule, which self-assembles around the catalysts in water-saturated toluene. Encapsulation nearly doubles RCM yields relative to the parent, neutral catalyst in water-saturated toluene. The increased catalyst productivity is enabled by site-isolation of the catalyst within the capsule, which prevents bimolecular decomposition, and by the hydrophobic nature of the capsule interior, which limits decomposition by water. A final study focuses on attempts to identify a more robust catalyst via ligand redesign. Examined for this purpose are recently reported, electron-rich pyridinylide aminophosphines (PyAPs; these take the general form R2P–N=Ar), which exhibit enhanced s-donor properties relative to NHCs. Strategies for incorporation of PyAP ligands into Ru metathesis catalysts are developed, and the catalytic activity of these species is described. PyAP catalysts are found be significantly less active than the corresponding NHC catalysts, despite their higher donicity. Poor performance results from facile catalyst decomposition. Where the N=Ar group lacks substituents at the ortho sites, o- metalation enables decomposition of the precatalyst. More problematically, the nitrogen atom appears to participate in nucleophilic attack on the key, metathesis-enabling [Ru]=CHR functionality, limiting the potential use of this class of phosphine in metathesis. Criteria for the development of more robust second-generation phosphine catalysts are proposed.

An increasing trend in mass mortality events (MMEs) has been observed in recent years, leading to an increased study of these events and their causes. Still to be investigated are the immediate and long-term effects of these environmental disturbances. Microbial communities found on and within the carcass are a major contributor to decomposition. With an increased biomass from several carcasses, transfer of these microbes to secondary death events may be affected. For this project, several simulated MMEs were used in conjunction with a secondary death event to observe the effects of transfer between the microbial communities and changes in the communities over time. It was found that microbial diversity decreases over time as decomposition progresses, and that an initial difference which can be observed between skin and internal microbial communities homogenizes over time. This result will contribute to an understanding of microbial succession and the impact of increasing MMEs.

No description available.

No description available.