Search Results

Localized Radial Solutions for Nonlinear p-Laplacian Equation in RN

Description: We establish the existence of radial solutions to the p-Laplacian equation ∆p u + f(u)=0 in RN, where f behaves like |u|q-1 u when u is large and f(u) < 0 for small positive u. We show that for each nonnegative integer n, there is a localized solution u which has exactly n zeros. Also, we look for radial solutions of a superlinear Dirichlet problem in a ball. We show that for each nonnegative integer n, there is a solution u which has exactly n zeros. Here we give an alternate proof to that which was given by Castro and Kurepa.
Date: May 2008
Creator: Pudipeddi, Sridevi
Partner: UNT Libraries

Determining Properties of Synaptic Structure in a Neural Network through Spike Train Analysis

Description: A "complex" system typically has a relatively large number of dynamically interacting components and tends to exhibit emergent behavior that cannot be explained by analyzing each component separately. A biological neural network is one example of such a system. A multi-agent model of such a network is developed to study the relationships between a network's structure and its spike train output. Using this model, inferences are made about the synaptic structure of networks through cluster analysis of spike train summary statistics A complexity measure for the network structure is also presented which has a one-to-one correspondence with the standard time series complexity measure sample entropy.
Date: May 2007
Creator: Brooks, Evan
Partner: UNT Libraries

Analysis Of Sequential Barycenter Random Probability Measures via Discrete Constructions

Description: Hill and Monticino (1998) introduced a constructive method for generating random probability measures with a prescribed mean or distribution on the mean. The method involves sequentially generating an array of barycenters that uniquely defines a probability measure. This work analyzes statistical properties of the measures generated by sequential barycenter array constructions. Specifically, this work addresses how changing the base measures of the construction affects the statististics of measures generated by the SBA construction. A relationship between statistics associated with a finite level version of the SBA construction and the full construction is developed. Monte Carlo statistical experiments are used to simulate the effect changing base measures has on the statistics associated with the finite level construction.
Date: December 2002
Creator: Valdes, LeRoy I.
Partner: UNT Libraries

Infinite Planar Graphs

Description: How many equivalence classes of geodesic rays does a graph contain? How many bounded automorphisms does a planar graph have? Neimayer and Watkins studied these two questions and answered them for a certain class of graphs. Using the concept of excess of a vertex, the class of graphs that Neimayer and Watkins studied are extended to include graphs with positive excess at each vertex. The results of this paper show that there are an uncountable number of geodesic fibers for graphs in this extended class and that for any graph in this extended class the only bounded automorphism is the identity automorphism.
Date: May 2000
Creator: Aurand, Eric William
Partner: UNT Libraries

An Empirical Investigation of Portfolios with Little Idiosyncratic Risk

Description: The objective of this study is to answer the following research question: How large is a diversified portfolio? Although previous work is abundant, very little progress has been made in answering this question since the seminal work of Evans and Archer (1968). This study proposes two approaches to address the research question. The first approach is to measure the rate of risk reduction as diversification increases. For the first approach, I identify two kinds of risks: (1) risk that portfolio returns vary across time (Evans and Archer (1968), and Campbell et al. (2001)); and (2) risk that returns vary across portfolios of the same size (Elton and Gruber (1977), and O'Neil (1997)). I show that the times series risk reaches an asymptote as portfolio size increases. Cross sectional risk, on the other hand, does not appears to reach an asymptote as portfolio size increases. The second approach consists of comparing portfolios' performance to a benchmark portfolio that is assumed to be diversified (Statman (1987)). I develop a performance index. The performance index is calculated, for any given test portfolio, as the ratio of the Sharpe-like measure of the test portfolio to the Sharpe-like measure of the benchmark portfolio that is assumed to be diversified. The index is based on the intuition that an increase in portfolio size reduces times series risk and cross sectional risk, and increases transaction costs. Portfolio size is worth increasing as long as the marginal increase in the performance index from a decrease in risk is greater than the marginal decrease of the performance index from an increase in transaction costs. Diversification is attained when the value of the index reaches one. The results of my simulations indicate that the size of a well diversified portfolio is at the very least 30. This number can be ...
Date: May 2004
Creator: Benjelloun, Hicham
Partner: UNT Libraries

Developing Criteria for Extracting Principal Components and Assessing Multiple Significance Tests in Knowledge Discovery Applications

Description: With advances in computer technology, organizations are able to store large amounts of data in data warehouses. There are two fundamental issues researchers must address: the dimensionality of data and the interpretation of multiple statistical tests. The first issue addressed by this research is the determination of the number of components to retain in principal components analysis. This research establishes regression, asymptotic theory, and neural network approaches for estimating mean and 95th percentile eigenvalues for implementing Horn's parallel analysis procedure for retaining components. Certain methods perform better for specific combinations of sample size and numbers of variables. The adjusted normal order statistic estimator (ANOSE), an asymptotic procedure, performs the best overall. Future research is warranted on combining methods to increase accuracy. The second issue involves interpreting multiple statistical tests. This study uses simulation to show that Parker and Rothenberg's technique using a density function with a mixture of betas to model p-values is viable for p-values from central and non-central t distributions. The simulation study shows that final estimates obtained in the proposed mixture approach reliably estimate the true proportion of the distributions associated with the null and nonnull hypotheses. Modeling the density of p-values allows for better control of the true experimentwise error rate and is used to provide insight into grouping hypothesis tests for clustering purposes. Future research will expand the simulation to include p-values generated from additional distributions. The techniques presented are applied to data from Lake Texoma where the size of the database and the number of hypotheses of interest call for nontraditional data mining techniques. The issue is to determine if information technology can be used to monitor the chlorophyll levels in the lake as chloride is removed upstream. A relationship established between chlorophyll and the energy reflectance, which can be measured by satellites, enables ...
Date: August 1999
Creator: Keeling, Kellie Bliss
Partner: UNT Libraries

Landscape forest modeling of the Luquillo Experimental Forest, Puerto Rico.

Description: This thesis contributes to modeling the dynamics of forest community response to environmental gradients and disturbances over a mountain landscape. A gap model (FACET) was parameterized for species of various forest types (Tabonuco, Colorado, Dwarf and Palm), for many terrain conditions and was modified and extended to include species response to excess soil moisture and hurricanes. Landscape cover types were defined by dominance of species of each forest type and canopy height. Parameters of the landscape model (MOSAIC) were calculated from multiple runs of FACET. These runs were determined by combining terrain variables (elevation and soil) and hurricane risk. MOSAIC runs were analyzed for distribution patterns. Geographic Information Systems software was used to process terrain variables, hurricane risk and MOSAIC model output.
Date: December 2002
Creator: Abbott-Wood, Chris
Partner: UNT Libraries

Cycles and Cliques in Steinhaus Graphs

Description: In this dissertation several results in Steinhaus graphs are investigated. First under some further conditions imposed on the induced cycles in steinhaus graphs, the order of induced cycles in Steinhaus graphs is at most [(n+3)/2]. Next the results of maximum clique size in Steinhaus graphs are used to enumerate the Steinhaus graphs having maximal cliques. Finally the concept of jumbled graphs and Posa's Lemma are used to show that almost all Steinhaus graphs are Hamiltonian.
Date: December 1994
Creator: Lim, Daekeun
Partner: UNT Libraries

Three Essays in Corporate Governance

Description: Corporate governance issues have become increasingly important to financial managers and shareholders. Firms that are plagued by poor performance, incompetent managers, or excess agency costs have become the subject of a dramatic increase in shareholder activism. Dissident shareholders, who are unable to launch costly takeover bids or proxy contests, have initiated a process of governance reform through the use of shareholder sponsored proposals. Shareholder proposals are a direct attempt to reverse operating or voting policies, such as a proposal to repeal a classified board. Managers announce shareholder proposals in a proxy statement and typically include a vote recommendation against the proposal. In the first essay, I find an unfavorable stock price reaction to the announcement of a shareholder proposal. In some cases, however, management supports the proposal and negotiates an agreement with the proposing shareholder. Stock prices react favorably to a settlement announcement. If managers are willing to negotiate with shareholders, they are perceived to be acting in the best interest of shareholders. If managers are unwilling, shareholders believe a severe agency problem exists. In the second essay, the effect that ownership structure has on voting outcomes of shareholder proposals is examined. I find a direct relationship between the percentage of votes cast in favor of the proposal and levels of institutional ownership. There is an inverse relationship between the percentage of votes and managerial ownership and firm size. Large firms with powerful owner-managers present the greatest obstacle to the success of shareholder proposals. The repeal of shareholder rights plans is one of the most frequently used shareholder proposals. By adopting the rights plan, managers increase the probability of defeating a takeover, but increase their power in negotiating with a potential acquiring firm. In the third essay, I find that firms who combine a rights plan with high debt levels ...
Date: December 1993
Creator: Forjan, James M. (James Martin)
Partner: UNT Libraries

A Theory of the Role of Medium of Exchange in Mergers and Acquisitions

Description: An acquisition bid is like any other proposal for risky investment. The difference arises due to additional source of risk arising from two different sources of information asymmetry due to private knowledge held by the bidder and target. We hypothesize that the bidding process evolves in a manner to optimize bidder's investment in the target through a process of joint signalling. Medium of exchange and bid premium are used as the two signal elements simultaneously by the bidder. We develop a multiple signalling model of the bidding process which is fully revealing in equilibrium.
Date: May 1994
Creator: Tiwari, Rajesh Kumar
Partner: UNT Libraries

Dimensions in Random Constructions.

Description: We consider random fractals generated by random recursive constructions, prove zero-one laws concerning their dimensions and find their packing and Minkowski dimensions. Also we investigate the packing measure in corresponding dimension. For a class of random distribution functions we prove that their packing and Hausdorff dimensions coincide.
Date: May 2002
Creator: Berlinkov, Artemi
Partner: UNT Libraries