Digital Commons Network^™

Novel Model Of Cerebrospinal Fluid Dynamics Based On Hemodynamically Driven Cyclic Brain Compliance Variation, Bruno A. Mantilla

Dissertations

This study provides a novel explanation for the CerebrQ-Spinal Fluid (CSF) flow pattern observed in phase contrast cine-MRJ studies. CSF dynamics has been traditionally explained as a bulk flow from the site of production to the site of absorption. Studies done with phase contrast cine-MRI show a more complex CSF movement, that is not explainable by the bulk flow paradigm. This study describes a mechanism explaining how the energy delivered by the heart in each cycle is responsible not only for the blood flow, but also for the CSF circulation. This mechanism is based on a cyclic variation of brain …

The Model-Based Systematic Development Of Logis Online Graphing Instructional Simulator, Darrel R. Davis

USF Tampa Graduate Theses and Dissertations

This Developmental Research study described the development of an interactive online graphing instructional application and the impact of the Analysis Design Development Implementation Evaluation (ADDIE) model on the development process. An optimal learning environment was produced by combining Programmed Instruction and Adaptive Instruction principles with a graphing simulator that implemented guided contingent practice. The development process entailed the creation and validation of three instruments measuring knowledge, skills, and attitudes, which were components of the instruction.

The research questions were focused on the influence of the ADDIE model on the development process and the value of the LOGIS instructional application. The …

Continuous Simulation Of Groundwater Use And Effluent Discharge In Catfish (Ictalurus Punctatus) Ponds At Five Locations In The Southeast U.S, Sugeng Triyono

Theses and Dissertations

Long-term climatological data were used to evaluate the effectiveness of a drop/add management strategy to reduce groundwater use and effluent discharge in catfish ponds in the southeast U.S.. A drop/add approach is based on the creation of a storage volume in the pond for rainfall collection. The storage volume is created by allowing water level in the pond to decrease until some minimum level is reached. When the minimum level is reached, the pond is partly refilled, leaving the remaining volume available to capture incident precipitation. In this way, the role of precipitation in the water budget is increased. In …

A Wind And Rain Backscatter Model Derived From Amsr And Seawinds Data, Seth Niels Nielsen

Theses and Dissertations

The SeaWinds scatterometers aboard the QuikSCAT and ADEOS II satellites were originally designed to measure wind vectors over the ocean by exploiting the relationship between wind-induced surface roughening and the normalized radar backscatter cross-section. Recently, an algorithm for simultaneously retrieving wind and rain (SWR) from scatterometer measurements was developed that enables SeaWinds to correct rain-corrupted wind measurements and retrieve rain rate data. This algorithm is based on co-locating Tropical Rainfall Measuring Mission Precipitation Radar (TRMM PR) and SeaWinds on QuikSCAT data. In this thesis, a new wind and rain radar backscatter model is developed for the SWR algorithm using a …

Bathymetric Alterations Due To Urbanization And Their Effects On Residual Salinity, Flow Field And Transport Time For Tampa Bay, Florida, Amanda J. Linville

USF Tampa Graduate Theses and Dissertations

Growth and development over the past one hundred years has resulted in the construction of causeways and navigational channels in Tampa Bay. Urbanization has lead to bathymetric alterations of the bay, and thus has effectively changed the residual salinity, flow fields, and transport time in Tampa Bay. In this study a numerical ocean model of Tampa Bay was first used to simulate the circulation for 2001-2003 using present day bathymetry. Then, an identical simulation was performed using the bathymetry generated from 1879 depth soundings. The residual (30-day time average) circulation fields and salinity, along with transport times was intercompared for …

An Improved Model For Calculating Heats Of Dilution And Equilibrium Constants For High Temperature Aqueous Electrolyte Solutions, Xiaoyun Lin

Theses and Dissertations

At high temperatures, the properties of aqueous electrolyte systems differ markedly from those at 25°C. For mixed-electrolyte dilute solutions at high temperatures, the degree of ion-association is sufficiently large that the association equilibrium must be incorporated in any model describing the solutions. These association reactions usually do not occur to a measurable extent at room temperature. Oscarson and co-workers have designed a correlation model based on the excess Gibbs energy which can correlate log K and ∆H values as well as the heats of dilution for aqueous electrolyte systems as a function of temperature (T) and ionic strength (I) from …

Channel Modeling Applied To Robust Automatic Speech Recognition, Alexander G. Sklar

Open Access Theses

In automatic speech recognition systems (ASRs), training is a critical phase to the system?s success. Communication media, either analog (such as analog landline phones) or digital (VoIP) distort the speaker?s speech signal often in very complex ways: linear distortion occurs in all channels, either in the magnitude or phase spectrum. Non-linear but time-invariant distortion will always appear in all real systems. In digital systems we also have network effects which will produce packet losses and delays and repeated packets. Finally, one cannot really assert what path a signal will take, and so having error or distortion in between is almost …

Model Of Early Universe With H+2, Tae Song Lee

UNLV Retrospective Theses & Dissertations

The aim of this thesis is to improve existing models of the Early Universe by adding vibrationally resolved reactions to a standard model. Stancil, Lepp, and Dalgarno (1996, 1998) have developed a standard chemical model for molecules in the Early Universe. Galli and Palla (1998) have shown that vibrational excitation may be important in this model by forcing the vibrational level of H+2 to be either v=0 or v=9. I studied a consistent model for the vibrational levels including level dependent formation and destruction as well as transition between the levels.

Atmospheric Dispersion Model Validation For Low Wind Speed Conditions, Patrick Shawn Sawyer

UNLV Retrospective Theses & Dissertations

Atmospheric plume dispersion models are used for a variety of purposes including emergency planning and response to hazardous material releases, determining force protection actions in the event of a WMD attack and for locating sources of pollution. This paper provides a review of previous studies that examine the accuracy of atmospheric plume dispersion models for chemical releases. It considers the principles used to derive air dispersion plume models and looks at three specific models currently in use; ALOHA, EPIcode and SCIPUFF. Results from this study indicate over-prediction bias by the EPIcode and SCIPUFF models and under-prediction bias by the ALOHA …

Extending The Delone And Mclean Information Systems Success Model For E-Commerce Website Success, Joy Wendy Wu

UNLV Retrospective Theses & Dissertations

Website evaluation can continuously improve the performance of websites and increase sales. However, the lack of a comprehensive framework as guidance hampered this task. The main purpose of this research is to provide a comprehensive framework for e-commerce websites evaluation by extending the DeLone and McLean Information System Success Model. A new dimension---"Relationship quality" is proposed to the model. The study also tries to identify characteristics of e-commerce websites that impact the user's satisfaction; A survey questionnaire was distributed to web users, and a total of 295 responses were obtained. The data was processed through Statistical Package for the Social …

Estimating The Effects Of Casino Marketing Activities On Slot Business Volume: A Model For Leisure Services Businesses, Lisa Birtciel Young

UNLV Retrospective Theses & Dissertations

This study researched the effect of marketing promotions on gaming volume (i.e., coin-in). Specifically, this study attempted (1) to gain an understanding of the relationship between specific marketing promotions (slot tournaments, special events, product prize drawings, and no marketing promotions) and gaming volume; and (2) to estimate the magnitude of incremental revenue for each type of promotion. A conceptual model was proposed to examine the effect of the different types of marketing promotions on gaming volume, including two other variables (holidays and day-of-the-week) previously found to influence gaming volume; Secondary data were collected from a Las Vegas Strip property for …

A General Mathematical Model Of Stenoses, Jordan Jimmy Crabbe

UNLV Retrospective Theses & Dissertations

Incidence and the prevalence rate of stroke in the United States has been of great concern to the Centers for Disease Control and prevention (CDC), National Center for Health Statistics (NCHS), the American Society of Stroke, American Stroke Association and the U.S. government as a whole; Many mathematical models of the stroke problem have been proposed and solved using diverse methods and computations. Most of the models are based on the stenoses, occlusion or rupture of the artery and the formation of cerebral aneurysms, which all lead to the occurrence of stroke; This paper utilizes a direct approach to change …

A Model For Programming Characteristics Of Sonos Type Flash With High-Kappa Dielectrics, Varun Jain

UNLV Retrospective Theses & Dissertations

Silicon Oxide Nitride Oxide Silicon (SONOS) FLASH memories have recently gained a lot of attention due to better retention and scaling opportunities over the conventional Floating Gate FLASH memories. The constant demand for device scaling, to attain higher density, higher performance, and low cost per bit, has posed charge leakage problems. SONOS type devices with high-kappa storage layers and/or high-kappa blocking oxide have been proposed to alleviate the demand for constant tunnel oxide scaling. In comparison to conventional FLASH, these devices operate at lower voltages, exhibit higher programming speeds, comparable retention times, less over-erase problem and better compatibility with low …

Diffusion Model For Lightning Radiative Transfer Using Spherical Geometry, James Beguah Odei

UNLV Retrospective Theses & Dissertations

A one-speed Boltzmann transport theory, with diffusion approximations, is applied to study the radiative transfer properties of lightning in optically thick thunder clouds. The cloud is modeled in terms of spherical geometry and studies on the effects of multiple scattering are considered. Mathematically, the cloud is composed of a homogeneous distribution of spherical water droplets. Computationally, the cloud is treated as a nuclear reactor, with photons replaced by neutrons. Diffusion techniques common in nuclear reactor analyses are applied as in [1]. Relevant numerical techniques will be used to simulate the Cloud Results for the obtained intensity distribution will be compared …

Development Of A Flood Forecasting Model For Flamingo Tropicana Watershed In The Las Vegas Valley, Satya Prakash Chataut

UNLV Retrospective Theses & Dissertations

Floods are among the most frequent natural phenomenon that occur due to excessive precipitation. Accurate and current forecasting of floods is necessary to avoid social and economic losses. Forecasting floods in an event of intense rain allows the concerned agencies to adopt appropriate measures such as warnings and evacuations and to initiate corrective and remedial efforts before disaster strikes (Chapman and Canaan, 2001); Las Vegas has experienced rapid population growth since the 1990s. This has brought large-scale increase in impervious land surface due to the expansion of residential, commercial, and industrial area in the valley. The increase in impervious area …

A Diffusion Model Of Lightning Radiative Transfer Using Cylindrical Geometry, Rina Alfonso Santos

UNLV Retrospective Theses & Dissertations

Clouds come in different shapes and sizes and are made up of different constituents. Realistic clouds are composed of heterogeneous distribution of constituents (ice particle, needle shaped objects, cubic, hexagonal, etc.). For tractability of solutions and smoothness of calculations, assumptions are made. The assumption is viable due to multiple scattering effect for propagation of radiation in random media. In Koshak et al. (1994), "Diffusion Model for Lightning Radiative Transfer", the cloud was treated as a nuclear reactor in order to obtain forms that can be readily computable and a simple geometry was chosen, i.e., a homogeneous rectangular parallelepiped Cloud In …

Creating And Testing The Higher Education Leadership Competencies (Helc) Model: A Study Of Athletics Directors, Senior Student Affairs Officers, And Chief Academic Officers, Zachary A Smith

UNLV Retrospective Theses & Dissertations

The purpose of this study was threefold: to extend existing knowledge of McDaniel's (2002) qualitative inquiry of higher education leadership competencies by testing her theory using quantitative methods; to either affirm or create a new, more refined model of higher education leadership competencies based on the results of the data analysis; and finally, to compare the similarities and differences of important competencies necessary for effective leadership between and within three groups of leaders in higher education: athletics directors (ADs), senior student affairs officers (SSAOs), and chief academic officers (CAOs); Goodness of fit results indicated McDaniel's 4-category model of higher education …

Examining Women Faculty Experiences Using The Model Of Human Occupation Perspective: A Qualitative Approach In One Community College, Christine R Privott

UNLV Retrospective Theses & Dissertations

Occupations for women in the academy have been changing over the last century. Contemporary studies that have looked at women faculty work have been mixed in their findings about the relationship between gender and job satisfaction. Few studies have focused on two-year-college models of women's experiences as faculty; Set in the context of occupational science theories, this qualitative study explored the daily work of women faculty in one community college. The concept of faculty work was viewed through Kielhofner's Model of Human Occupation, which suggests that occupations are made up of three subsystems of human action or doing: volition, habituation, …

Signal Processing Of An Ecg Signal In The Presence Of A Strong Static Magnetic Field, Aditya Gupta

Electronic Theses and Dissertations

This dissertation addresses the problem of elevation of the T wave of an electrocardiogram (ECG) signal in the magnetic resonance imaging (MRI). In the MRI, due to the strong static magnetic field the interaction of the blood flow with this strong magnetic field induces a voltage in the body. This voltage appears as a superimposition at the locus of the T wave of the ECG signal. This looses important information required by the doctors to interpret the ST segment of the ECG and detect diseases such as myocardial infarction. This dissertation aims at finding a solution to the problem of …

An Algorithm For Determining Satellite Attitude By Comparing Physical Feature Models To Edges Detected In Satellite Or Ground-Based Telescope Imagery, Eric Brian Reinhart

Electronic Theses and Dissertations

This thesis discusses the development and performance of an algorithm created to calculate satellite attitude based on the comparison of satellite "physical feature" models to information derived from edge detection performed on imagery of the satellite. The quality of this imagery could range from the very clear, close-up imagery that may come from an unmanned satellite servicing mission to the faint, unclear imagery that may come from a ground-based telescope investigating a satellite anomaly. Satellite "physical feature" models describe where an edge is likely to appear in an image. These are usually defined by physical edges on the structure of …

Porosity And Permeability Of Bimodal Sediment Mixtures Using Natural Sediment, Peter M. Phillips

Browse all Theses and Dissertations

Porosity and permeability are parameters that affect the flow of ground water in the subsurface and have significant implications on the modeling of fate and transport of contaminants. However, little has been done to quantitatively examine the effect on porosity and permeability of packing in bimodal mixtures of natural sediment. This study compares measurements of porosity and permeability on model bimodal sediment mixtures with predictions from petrophysical models. The main goal is to evaluate how well these petrophysical models predict porosity and permeability in bimodal mixtures of natural sediment. The effect of the volume fraction of fines on porosity and …

Development And Validation Of A Computational Musculoskeletal Model Of The Elbow Joint, Justin Paul Fisk

Theses and Dissertations

Musculoskeletal computational modeling is a versatile and effective tool which may be used to study joint mechanics, examine muscle and ligament function, and simulate surgical reconstructive procedures. While injury to the elbow joint can be significantly debilitating, questions still remain regarding its normal, pathologic, and repaired behavior. Biomechanical models of the elbow have been developed, but all have assumed fixed joint axes of rotation and ignored the effects of ligaments. Therefore, the objective of this thesis was to develop and validate a computational model of the elbow joint whereby joint kinematics are dictated by three-dimensional bony geometry contact, ligamentous constraints, …

Predicting Northern Goshawk Dynamics Using An Individual-Based Spatial Model, Melanie A. Smith

Graduate Student Theses, Dissertations, & Professional Papers

The northern goshawk (Accipiter gentilis) is a US Forest Service Region 2 Sensitive Species, requiring the Black Hills National Forest to manage for its viability. Previous studies have suggested that a model integrating goshawk population demographics, habitat availability, and territoriality would have the ability to predict population dynamics including goshawk locations, population size, and population viability. An individual-based spatial model was created for the Black Hills goshawk population. This project focused on evaluating our current understanding of goshawk dynamics, and making individual- and population-level predictions as appropriate following model validation. The model simulated demographics and behavior of individuals and usage …