Thesis (Ph. D.)--University of Oregon, 2005. / Typescript. Includes vita and abstract. Includes bibliographical references (leaves 69-71). Also available for download via the World Wide Web; free to University of Oregon users.

Thesis (Ph. D.)--University of Rhode Island, 2005. / Typescript. Includes bibliographical references (leaves 127-134).

abstract: This thesis considers the application of basis pursuit to several problems in system identification. After reviewing some key results in the theory of basis pursuit and compressed sensing, numerical experiments are presented that explore the application of basis pursuit to the black-box identification of linear time-invariant (LTI) systems with both finite (FIR) and infinite (IIR) impulse responses, temporal systems modeled by ordinary differential equations (ODE), and spatio-temporal systems modeled by partial differential equations (PDE). For LTI systems, the experimental results illustrate existing theory for identification of LTI FIR systems. It is seen that basis pursuit does not identify sparse LTI IIR systems, but it does identify alternate systems with nearly identical magnitude response characteristics when there are small numbers of non-zero coefficients. For ODE systems, the experimental results are consistent with earlier research for differential equations that are polynomials in the system variables, illustrating feasibility of the approach for small numbers of non-zero terms. For PDE systems, it is demonstrated that basis pursuit can be applied to system identification, along with a comparison in performance with another existing method. In all cases the impact of measurement noise on identification performance is considered, and it is empirically observed that high signal-to-noise ratio is required for successful application of basis pursuit to system identification problems. / Dissertation/Thesis / M.A. Mathematics 2012

Tropical habitats have high taxonomic and ecological diversity, but they are currently subject to high rates of extinction. Amphibian populations are declining globally and while we have some understanding of the causes of these declines, it is unclear how these losses will influence ecosystem structure and function. Secondary production and trophic basis of production analyses link consumers to energy flow and reflect the relative importance of various energy sources and energy flow pathways in food webs. These techniques can yield valuable information on the roles of individual consumers in ecosystem function, and thus the ecological consequences of extinction and extirpation events. I estimated the trophic basis of production in a Panamanian headwater stream to identify major sources of energy, measure energy flow through consumers, and characterize interactions among trophic levels and functional feeding groups. I examined gut contents of 19 dominant macroinvertebrate and two dominant tadpole taxa collected during dry and wet seasons before an amphibian decline. I used previously published estimates of secondary production, assimilation efficiencies, and net production efficiencies, along with gut content data, to quantify food web structure and energy flow pathways. Overall consumption of allochthonous materials was greater than autochthonous (p < 0.001), and the dominant food sources were non-algal biofilm and vascular plant detritus. Autochthonous materials were consumed at higher rates during the dry season (p = 0.012). Total consumption rates varied within and among shredders (0.85 - 12.10 g/m2/yr), scrapers (0.46 - 0.91 g/m2/yr), filterers (1.20 - 4.67 g/m2/yr), gatherers (0.43 - 2.44 g/m2/yr) and predators (0.05 - 0.95 g/m2/yr). Overall consumption rates in pool habitats were higher compared to riffles. The degree of omnivory in the food web was much higher than has been observed in similar temperate streams. Omnivory was prevalent across all functional feeding groups, but more pronounced in predators, especially Anacroneuria (55% animal and 45% plant materials in guts). There was also an ontogenetic shift among most dominant macroinvertebrates from smaller, energy rich food sources (e.g., non-algal biofilm) to larger, less nutritious materials (e.g., vascular plant material) with increase in size. My research is the first to provide quantitative estimates of energy flow through a neotropical headwater stream food web. Information from this study is central to understanding and conserving tropical headwater streams. Further, my results, along with post-amphibian decline analyses from the same stream, will allow for a comprehensive assessment of the ecological consequences of amphibian declines.

Master of Agribusiness / Department of Agricultural Economics / Daniel M. O'Brien / In recent years, the price volatility in agricultural commodity prices, as well as agricultural input costs, has drastically increased. Today’s famer is faced with difficult decisions concerning when to market their crop, as well as when to secure various inputs. An increase in information availability, coupled with increasing price fluctuations, can make these decisions even more difficult for producers. Although seasonal trends, forecasts, and technical market analysis can be helpful, market efficiency prevents accurate prediction of agricultural prices. Because marketing decisions can be difficult to make, the easiest decision for a producer to make is to not make one at all. However, failure to make sound risk management decisions can be extremely costly to a producer. There are two primary factors that impact a producer’s bottom line: cost of production and grain marketing decisions. Each producer has their own unique cost of production that changes throughout the year. Variable input costs can be volatile within a single growing year, and often the need for certain inputs changes. Marketing decisions and timing can be an even bigger factor in a producer’s gain or loss. Since price prediction is impossible, a producer’s time may be better spent focusing on information they can control. The purpose of this thesis was to test and evaluate a cost of production, crop insurance, and grain marketing calculator with a group of corn and soybean producers in Southeast Nebraska. It is hypothesized that providing customers with a multifaceted, integrated farm management and marketing decision making tool should help them be able to make more profitable risk management and marketing decisions. By knowing how factors as changing expenses impact cost of production and how grain sales impact revenues and profitability per acre, it is hypothesized that users will make more profitable farm management and marketing decisions. In October and November of 2014, twenty corn and soybean farmers were presented with the Grain Marketing Calculator. Grain sales in the 2014 and 2015 crop years were to be entered into the calculator by participating producers as they make their grain sales. Annual production history (APH), revenue protection insurance information, actual or expected yields, and total acres of each crop were entered into the calculator during the initial producer calculator rollout. Generalized costs were entered into the calculator prior to the producer rollouts. Participants were able to change the generalized costs to their actual costs if they chose to do so. Data were gathered from the participants using the Grain Marketing Calculator in March of 2015. Participants weighted average futures sales, weighted average cash sales, percent of APH sold, and percent of total production sold were collected. In March of 2015, the same information from another group of producers who did not use the Grain Marketing Calculator was collected. The two groups average results were compared to each other and regression analyses were done to determine statistical significance of the impact on the test groups’ results. At the end of the experiment, feedback was gathered from participants and improvements were suggested.

<p> The involvement of d orbitals in the coordination of sulphur in three simple sulphur compounds ls Investigated using an ab initio approach. Comparison of minimal and extended basis set results for molecular properties such as dipole moment, molecular geometry, and force constants provides a means of establishing the importance of d orbitals In sulphur compounds and probably other second row compounds. Excited states of sulphur dioxide and ozone are studied in the hope of elucidating the respective spectra on a theoretical basis. These investigations also provide initial data for the parametrization of the semi-empirical CNDO approach for second row atoms. </p> / Thesis / Master of Science (MSc)

No description available.

Protonated epoxides feature prominently in organic chemistry as reactive intermediates. Gas-phase calculations studying the structure and ring-opening energetics of protonated ethylene oxide, propylene oxide and 2-methyl-1,2-epoxypropane were performed at the B3LYP and MP2 levels (both with the 6-311++G** basis set). Structural analyses were performed for 10 protonated epoxides using B3LYP, MP2, and CCSD/6-311++G** calculations. Protonated 2-methyl-1,2-epoxypropane was the most problematic species studied, where relative to CCSD, B3LYP consistently overestimates the C2-O bond length. The difficulty for DFT methods in modeling the protonated isobutylene oxide is due to the weakness of this C2-O bond. Protonated epoxides featuring more symmetrical charge distribution and cyclic homologues featuring less ring strain are treated with greater accuracy by B3LYP. Ion-pair separation (IPS) of THF-solvated fluorenyl, diphenylmethyl, and trityl lithium was studied computationally. Minimum-energy equilibrium geometries of explicit mono, bis and tris-solvated contact ion pairs (CIPs) and tetrakis-sovlated solvent separated ion pair (SSIPs) were modeled at B3LYP/6-31G*. Associative transition structures linking the tris-solvated CIPs and tetrakis-solvated SIPs were also located. In vacuum, B3LYP/6-31G* ΔHIPS values are 6-8 kcal/mol less exothermic than the experimentally-determined values in THF solution. Incorporation of secondary solvation in the form of Onsager and PCM single-point calculations showed an increase in exothermicity of IPS. Application of a continuum solvation model (Onsager) during optimization at the B3LYP/6-31G* level of theory produced significant changes in the Cα-Li contact distances in the SSIPs. An increase in of ion pair separation exothermicity was observed upon using both PCM and Onsager solvation models, highlighting the importance of both explicit and implicit solvation in modeling of ion pair separation. / Ph. D.

Let K be a field and Q a finite directed multi-graph. In this paper I classify all path algebras KQ and admissible orders with the property that all of their finitely generated ideals have finite Groebner bases. / Master of Science

Higher-order basis functions are widely used to model currents and fields in numerical simulations of electromagnetics problems because of the greater accuracy and computational efficiency they can provide. Different problem formulations, such as method of moments (MoM) and the finite element method (FEM) require different constraints on basis functions for optimal performance, such as normal or tangential continuity between cells. In this thesis, a method of automatically generating bases that satisfy the desired basis constraints is applied to a MoM formulation for scattering problems using surface integral equations. Numerical results demonstrate the accuracy of this approach, and show good system matrix conditioning when compared to other higher-order bases.