Digital Commons Network^™

Tiling As A Loop Parallelization Technique, Hoda Ahmed Khalil

Archived Theses and Dissertations

No abstract provided.

The Gx-Tree, Amgad Mohamed Abdelkader Al-Sisi

Archived Theses and Dissertations

No abstract provided.

Anytime Algorithms For Maximal Constraint Satisfaction Problems, Noha Kaptan

Archived Theses and Dissertations

No abstract provided.

Rotational Structure Of Extremely Floppy Van Der Waals Complexes: Adiabatic Separation Of Angular And Radial Motion, P. Daniel Ward

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The adiabatic or Born-Oppenheimer approximation is often used in molecular calculations to simplify the solution to the Schrödinger equation. The basis of the approximation is the large difference in the relative motions of the nuclei and electrons in the molecule—the electrons are able to respond almost instantly to the movements of the nuclei. Thus, the nuclei may be regarded as being fixed in a certain position and the Schrödinger equation can then be solved using the potential obtained by solving the electronic problem at fixed nuclear configuration.

A similar argument can be used to decouple the angular and radial motions …

Mean-Square Error Bounds And Perfect Sampling For Conditional Coding, Xiangchen Cui

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

In this dissertation, new theoretical results are obtained for bounding convergence and mean-square error in conditional coding. Further new statistical methods for the practical application of conditional coding are developed.

Criteria for the uniform convergence are first examined. Conditional coding Markov chains are aperiodic, π-irreducible, and Harris recurrent. By applying the general theories of uniform ergodicity of Markov chains on general state space, one can conclude that conditional coding Markov chains are uniformly ergodic and further, theoretical convergence rates based on Doeblin's condition can be found.

Conditional coding Markov chains can be also viewed as having finite state space. …

Comparing Nonlinear And Nonparametric Modeling Techniques For Mapping And Stratification In Forest Inventories Of The Interior Western Usa, Gretchen Gengenbach Moisen

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Recent emphasis has been placed on merging regional forest inventory data with satellite-based information both to improve the efficiency of estimates of population totals, and to produce regional maps of forest variables. There are numerous ways in which forest class and structure variables may be modeled as functions of remotely sensed variables, yet surprisingly little work has been directed at surveying modem statistical techniques to determine which tools are best suited to the tasks given multiple objectives and logistical constraints. Here, a series of analyses to compare nonlinear and nonparametric modeling techniques for mapping a variety of forest variables, and …

Positive Solutions Obtained As Local Minima Via Symmetries, For Nonlinear Elliptic Equations, Florin Catrina

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

In this dissertation, we establish existence and multiplicity of positive solutions for semilinear elliptic equations with subcritical and critical nonlinearities. We treat problems invariant under subgroups of the orthogonal group. Roughly speaking, we prove that if enough "mass " is concentrated around special orbits, then among the functions with prescribed symmetry, there is a solution for the original problem.

Our results can be regarded as a further development of the work of Z.-Q. Wang, where existence of local minima in the space of symmetric functions was studied for the Schrödinger equation. We illustrate the general theory with three examples, all …

Theoretical Studies Of Penetration Of Magnetospheric Electric Fields To The Ionosphere, Stanislav Sazykin

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Ionospheric disturbance electric fields of magnetospheric origin play an important role in determining the global morphology and dynamics of the ionosphere of the Earth. In this work, we present a number of numerical simulations of the transient electric fields in the middle and inner magnetosphere and the ionosphere equatorward of the auroral zone caused by idealized changes in the magnetospheric driving parameters. For these studies, we use the Rice Convection Model (RCM), a large computer code of the magnetosphere-ionosphere coupling which consistently computes the electric fields, currents, and plasma densities in the magnetosphere and the electric field and currents in …

Studies On The Roles Of Atp In Nitrogenase Catalysis, Wei Wu

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Nitrogenase is the enzyme that catalyzes the reduction of nitrogen to ammonia in a reaction requiring MgATP hydrolysis. Two component proteins of nitrogenase are the iron protein (Fe protein) and the molybdenum-iron protein (MoFe protein).

Nitrogenase contains two nucleotide binding sites. During catalysis, the Fe protein binds two MgATP first. The conformational changes induced upon MgATP binding allow the Fe protein to associate with the MoFe protein. After the formation of the Fe protein-MoFe protein complex, a single electron is transferred from the Fe protein to the MoFe protein, an event that is coupled to MgATP hydrolysis in the Fe …

An Adaptive Hybrid Genetic-Annealing Approach For Solving The Map Problem On Belief Networks, Manar Hosny

Archived Theses and Dissertations

Genetic algorithms (GAs) and simulated annealing (SA) are two important search methods that have been used successfully in solving difficult problems such as combinatorial optimization problems. Genetic algorithms are capable of wide exploration of the search space, while simulated annealing is capable of fine tuning a good solution. Combining both techniques may result in achieving the benefits of both and improving the quality of the solutions obtained. Several attempts have been made to hybridize GAs and SA. One such attempt was to augment a standard GA with simulated annealing as a genetic operator. SA in that case acted as a …

Single Phase Flow Modeling In Packed Beds: Discrete Cell Approach Revisited, Y. Jiang, M. R. Khadilkar, M. (Muthanna) H. Al-Dahhan, M. P. Dudukovic

Chemical and Biochemical Engineering Faculty Research & Creative Works

A Discrete Cell Model (DCM), based on the Minimization of the Total Rate of Energy Dissipation, is Applied to Compute the Fluid Velocity Field in Two-Dimensional Packed Beds. the Analysis of the Individual Terms of the Energy Dissipation Rate Equation is Also Presented. the Results Obtained by DCM Are Validated Both by Comparing Them with the Solutions of Ensemble-Averaged Momentum and Mass Conservation Equations (CFDLIB Code) and by Available Experimental Results. the Differences between DCM and CFD Simulations Were Found to Be Confined to within a 10% Band over a Wide Range of Reynolds Numbers (Re' = 5-171). Thus, a …

Enhancing Partitionable Group Membership Service In Asynchronous Distrib Systems, Marwa Mohamed Mansour

Archived Theses and Dissertations

No abstract provided.

Annealed Disorder, Rare Regions, And Local Moments: A Novel Mechanism For Metal-Insulator Transitions, Dietrich Belitz, Theodore R. Kirkpatrick, Thomas Vojta

Physics Faculty Research & Creative Works

It is shown that, for noninteracting electron systems, annealed magnetic disorder leads to a new mechanism, and a new universality class, for a metal-insulator transition. The transition is driven by a vanishing of the thermodynamic density susceptibility rather than by localization effects. The critical behavior in d = 2 + ∈ dimensions is determined, and the underlying physics is discussed. It is further argued that annealed magnetic disorder, in addition to underlying quenched disorder, describes local magnetic moments in electronic systems.

Genuine Saddle Point And Nucleation Potential For Binary Systems, Jinsong Li, Igor L. Maksimov, Gerald Wilemski

Physics Faculty Research & Creative Works

A generalized nucleation potential is constructed for binary systems. The potential consists of the reversible work of cluster formation plus additional terms arising from various kinetic effects. We show that the major nucleation flux passes through the saddle point (termed the genuine saddle point) of this generalized nucleation potential. The generalized nucleation potential reduces to the kinetic potential of a unary system when one component vanishes. The genuine saddle point concept provides a convenient way to identify systems and conditions for which the ridge crossing phenomenon occurs. Our theory agrees approximately with exact numerical results.

Management Of An Accounting Practice Handbook, Volume 2. Administration, May 2000, American Institute Of Certified Public Accountants (Aicpa)

Guides, Handbooks and Manuals

No abstract provided.

Iron And Acid Removal From Acid Mine Drainage In Open Limestone Systems, Qingyun Sun

Graduate Theses, Dissertations, and Problem Reports (ETD)

Passive systems, like wetlands, anoxic limestone drains, and open limestone channels, show promise for treating acid mine drainage (AMD) discharges. Open limestone channels have been developed for over ten years and the treatment effectiveness of AMD by open limestone systems shows wide variation. The variation is due to site conditions (slope and size of the limestone channel) but more importantly to the surface area of the limestone and iron concentrations in the water. Iron in AMD coats the limestone in open limestone systems thereby reducing the surface area available for reaction. Over time, the limestone appears to lose its ability …

Porosity Distribution Prediction Using Artificial Neural Networks, Fahad Abdullah Al-Qahtani

Graduate Theses, Dissertations, and Problem Reports (ETD)

Reservoir characterization plays a very important role in the petroleum industry, especially to the economic success of the reservoir development. Heterogeneity can complicate the evaluation of reservoir properties. Porosity is the primary key to a reliable reservoir model.;Several studies in the literature indicated that accurate evaluation of reservoir properties can be made by the analysis of electric logs. Stringtown oil field in Tyler and Wetzel counties in the northwestern part of West Virginia was selected to conduct this study.;Artificial Neural Networks (ANN) is one of the latest technologies available to the petroleum industry. The objective of this study was to …

Gas Production Forecasting Using Automatic Type Curve Matching, Walter Jonathan Diazgranados

Graduate Theses, Dissertations, and Problem Reports (ETD)

As the demand for natural gas has increased in the last years, also the need for forecast reliable gas recoveries. Gas type curves are one of the methods utilized to estimate future well performance. The purpose of this study is the utilization of the Aminian et al type curves to model gas well performance. Unlike other studies developed in the past, Aminian et al type curves account for important factors ignored in the derivation of the proposed theoretical solutions. Thus, the pressure dependency of gas viscosity and compressibility, as well as the pressure loss owing to non-Darcy flow, make of …

Low Seasonal Temperatures Promote Life Cycle Synchronization, Janette Lee Jenkins

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

In this paper, we discuss how seasonal temperature variation and dormancy can synchronize the development of exothermic organisms. Using a simple aging model, it is shown that minimal seasonal temperature variation and periods of dormancy during extreme temperature conditions are sufficient to establish stable, univoltine ovipositional cycles. Dormancy, in fact, promotes synchronous oviposition emergence. The mountain pine beetle, an important insect living in extreme temperature conditions and showing no evidence of diapause, invites direct application of this model. Simulations using mountain pine beetle parameters are used to determine temperature regimes for which stable, ovipositional cycles exist.

Is It Time For Cooperative Learning To Enter American Classrooms?, Donna Sewell

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

Education's raison d'etre is to prepare students with the skills necessary for a productive and happy life within society. The fact that many educational institutions are experiencing a disconcerting number of students dropping out of school (and sometimes life itself) may be an indicator that this preparation is less than adequate in meeting their needs. In fact, the needs of a high school graduate today are so different and far-reaching than what they were 30-50 years ago, it will be easier to group them according to a change in economics, transformed demographics and changes in social situations and practices. Each …

Virulence Of Cryphonectria Hypoviruses From Previous Release Sites, Paul Henry Chaloux

Graduate Theses, Dissertations, and Problem Reports (ETD)

In 1994 and 1995, Cryphonectria parasitica isolates singly or doubly infected with hypoviruses in the CHV3 genus, and lacking distinctive morphological abnormalities, were recovered near plots formerly used to release hypoviruses. This study tested the hypothesis that North American hypoviruses are evolving decreased virulence, and investigated hypovirus interactions affecting virulence in double-infections. Families of single conidial progeny (SCP), differing in infection status, and derived from six recovered, three release, and three comparison isolates were tested in three field experiments. All release isolates and four recovered isolates were debilitated by their CHV3-gh2-type hypoviruses. CHV3-sr2-type hypoviruses never caused debilitation. In family SG3-2 …

Re-Evaluation Of Wave Transmission Coefficients For Submerged Breakwater Physical Models, Harry Charles Friebel

Theses and Dissertations

Increasing interest in utilizing submerged breakwaters and artificial reefs for shoreline stabilization requires accurate models and relationships for predicting wave attenuation. The objective of this paper is to develop an empirical model as an improvement to existing wave transmission models. This will provide the required design criteria for use in future submerged breakwater designs. An extensive study of existing literature on submerged breakwaters and associated wave attenuation was performed, followed by a detailed statistical analysis of existing data sets to determine an alternate model for the wave transmission coefficient. A total of five data sets from physical model studies were …

Structural And Magnetic Properties Of Mechanically Milled Smco5:C, E. M. Kirkpatrick, Diandra Leslie-Pelecky

Diandra Leslie-Pelecky Publications

Mechanically milling SmCo₅ powder significantly increases coercivity and remanence ratio by introducing defects; however, these defects can be removed by room-temperature aging, with a resultant decrease in coercivity. A series of (SmCo₅) _x:C1–_x (0.15 ≤ x ≤1) samples has been fabricated to investigate the effect of C on oxidation protection and magnetic properties. SmCo₅ was premilled for 1 h, then added to C powder and milled for times ranging from 15 min to 7 h. X-ray diffraction indicates the presence of crystalline graphite and SmCo₅ for milling times ≤ 6 h and also …

Nanostructure And Magnetic Properties Of Composite Copt:C Films, M. Yu, Yi Liu, David J. Sellmyer

David Sellmyer Publications

The nanostructure and magnetic properties of composite CoPt:C films at room temperature were investigated as a function of annealing temperature, carbon concentration, and film thickness. CoPt:C films with a variety of carbon concentrations were fabricated by cosputtering Co, Pt, and C onto water-cooled Si(100) substrates followed by annealing. X-ray diffraction and transmission electron microscopy analyses indicate that nanocrystallites of face-centered-tetragonal (fct) CoPt phase, which has a uniaxial magnetocrystalline anisotropy constant of about 5×10⁷ erg/cm³, can be formed in carbon matrix when the annealing temperature is higher than 600 °C. The grain sizes of the fct CoPt crystallites …

Magnetic And Structural Properties Of Smco7-XCuX Alloys, I.A. Al-Omari, Y. Yeshurun, Jian Zhou, David J. Sellmyer

David Sellmyer Publications

We report the structural and magnetic properties of SmCo_7-xCu_x, where x= 0, 0.1, 0.2, 0.3, 0.4, 0.5, and 0.7. X-ray diffraction shows that these alloys from the disordered hexagonal TbCu₇-type structure. For large values of x (x≥0.8) the hexagonal TbCu₇-type structure cannot be formed. X-ray diffraction on magnetically aligned samples show that these samples have uniaxial anisotropy. The lattice parameters (a and c) are dependent on the Cu concentration, and the unit cell volume is found to increase with x. The saturation magnetization decreases with x …

Temperature Dependence Of Magnetic Hysteresis Of RcoX:Co Nanocomposites (R=Pr And Sm), J. Ping Liu, Ralph Skomski, Yi Liu, David J. Sellmyer

David Sellmyer Publications

The temperature dependence of magnetic hysteresis of RCo_x:Co (R=Pr and Sm) nanocomposite films is reported. These films are prepared by dc and rf sputtering and subsequent thermal processing. It is found that the squareness of the hysteresis loops deteriorates with decreasing temperature. This is attributed to the enhanced magnetic anisotropy of the hard phases at low temperatures. The analysis of the magnetic reversal process shows that the anisotropy enhancement leads to a transition from cooperated to independent behavior. This analysis agrees well with the experimental results.

Hysteresis-Loop Overskewing In The Light Of A Novel Nucleation Mode, Ralph Skomski, J. Ping Liu, David J. Sellmyer

David Sellmyer Publications

It is demonstrated that the magnetostatic demagnetizing factor is not the only sample-shape dependent contribution to the hysteresis loop. There are also exchange contributions, which lead to interesting effects, particularly in nanostructures. An example is the recently discovered bulging mode in two-phase nanomagnets. The bulging mode exhibits the angular symmetry of the coherent mode, but it is incoherent due to its radial variation and gives rise to negative demagnetizing factors.

Structure And Magnetic Properties Of Smco7-XTiX With Tbcu7-Type Structure, Jian Zhou, I.A. Al-Omari, J. Ping Liu, David J. Sellmyer

David Sellmyer Publications

The SmCo_7-xTi_x, x = 0–0.56 bulk samples are prepared by arc melting. X-ray diffraction indicates that samples with 0.2<x7-type structure phase and other minor phases appear for other values of x, which indicates that Ti helps stabilize the 1-7 phase. The lattice parameters ratio (c/a) increases with increasing Ti concentration. Room temperature saturation magnetization and Curie temperature decrease with increasing x. X-ray diffraction and magnetization measurements on aligned samples show that all samples studied have uniaxial anisotropy. The anisotropy field is found to increase with increasing x reaching …

Magnetic Properties Of Cluster-Beam-Synthesized Cobalt: Noble-Metal Films, J.M. Meldrim, Y. Qiang, Yi Liu, H. Haberland, David J. Sellmyer

David Sellmyer Publications

A cluster-beam deposition technique has been used to produce magnetic clusters embedded in a nonmagnetic matrix. We report here on films with cobalt clusters of average diameter of 5.5 nm embedded both in Cu and Ag. Volumetric concentrations of Co ranged from 10% to 50%. Magnetization and low temperature hysteresis loops, both field cooled (FC) and zero-field cooled (ZFC), have been measured between 4.2 and 300 K. The FC and ZFC magnetization bifurcate at or above room temperature with the clusters having a nonzero remanence at room temperature. Low temperature hysteresis loops exhibit a two-phase nature with one phase displaying …

Magnetic Spectroscopy And Characterization Of La0.65Pb0.35Mno3, M. I. Chipara, Shireen Adenwalla, Peter A. Dowben, Qin Lan Xu, Sy_Hwang Liou, R. Shoemaker

Peter Dowben Publications

Crystalline films of La_0.65Pb_0.35MnO₃ grown on Si (100) substrates by rf sputtering have been investigated by ferromagnetic resonance and MOKE. The dependence of the ferromagnetic resonance line parameters on the sample orientation and temperature is investigated. An expression for the angular dependence of the resonance field on the orientation of the sample is proposed, based on the assumption that close to the Curie temperature the Zeeman and demagnetizing terms are dominant. MOKE data support this hypothesis. The temperature dependence of the magnetization at saturation, in relative units, estimated from ferromagnetic resonance agrees with SQUID data. …