Digital Commons Network^™

Development Of A Methodology For Numerical Simulation Of A D C Arc Discharge In A Liquid Dielectric, Christopher James Lewis

Theses and Dissertations

The majority of literature regarding the numerical simulation of arc discharges in gaseous environments has used a plasma physics approach. Virtually all simulations treat the discharge as an idealized gaseous plasma, which can be described by temperature, pressure, and electric field. This approach can work well if the media is a shielding gas such as Argon; however, the approach does not work well for processes such as underwater welding, EDM, and underwater discharges used to generate high purity particles. The reason these discharges do not have many extensive simulation efforts as described in the literature is because they occur in …

Prediction Of Fluid Viscosity Through Transient Molecular Dynamic Simulations, Jason Christopher Thomas

Theses and Dissertations

A novel method of calculating viscosity from molecular dynamics simulations is developed, benchmarked, and tested. The technique is a transient method which has the potential to reduce CPU requirements for many conditions. An initial sinusoidal velocity profile is overlaid upon the peculiar velocities of the individual molecules in an equilibrated simulation. The transient relaxation of this initial velocity profile is then compared to the corresponding analytical solution of the momentum equation by adjusting the viscosity-related parameters in the constitutive equation that relate the shear rate to the stress tensor. The newly developed Transient Molecular Dynamics (TMD) method was tested for …

Biological Simulations And Biologically Inspired Adaptive Systems, Edgar Alfredo Duenez-Guzman

Doctoral Dissertations

Many of the most challenging problems in modern science lie at the interface of several fields. To study these problems, there is a pressing need for trans-disciplinary research incorporating computational and mathematical models. This dissertation presents a selection of new computational and mathematical techniques applied to biological simulations and problem solving: (i) The dynamics of alliance formation in primates are studied using a continuous time individual-based model. It is observed that increasing the cognitive abilities of individuals stabilizes alliances in a phase transition-like manner. Moreover, with strong cultural transmission an egalitarian regime is established in a few generations. (ii) A …

Computational Investigations Of Characteristic Performance Improvements For Subkilogram Laser Micropropulsion, Richard Joel Thompson

Masters Theses

Experimental investigations have evaluated the feasibility of using laser-driven plasma microthrusters for small-thrust, high-specific-impulse space maneuvers, particularly for micro- and nanosatellite missions. Recent work made use of the Mach2 hydromagnetics code for the construction of an adequate computational model of the micro-thruster opera- tion. This thesis expounds on this previous work by extending the computational modeling capabilities, allowing for the determination of plasma plume properties and characteristic performance assessment of the microthruster; this allows for further computational investi- gation of the performance improvements achieved by new design considerations. Two par- ticular design changes are implemented and measured: (i) the simulation …

Probabilistic Remediation Evaluation Model For Chlorinated Solvents Considering Uncertainty, Hailian Liang

All Dissertations

The complex processes and expensive costs of source and plume remediation of dense, non-aqueous phase liquid (DNAPL) complicate the decision-making process for site remediation. Selection of remediation alternatives has been a big challenge due to the lack of tools that simultaneously evaluate the effectiveness of source and plume remediation and access the uncertainties in all major parameters. In this research, a new probabilistic remediation model, Probabilistic Remediation Evaluation Model for Chlorinated solvents sites (PREMChlor), has been developed. This is achieved through linking the analytical model REMChlor to a Monte Carlo modeling simulation package GoldSim via a FORTRAN Dynamic Link Library …

Comparing Cognitive Decision Models Of Iowa Gambling Task In Indivituals Following Temporal Lobectomy, Jenny Vennukkah Jeyarajah

Mathematics Theses

This study examined the theoretical basis for decision making behavior of patients with right or left temporal lobectomy and a control group when they participated in the Iowa Gambling Task. Two cognitive decision models, Expectancy Valence Model and Strategy Switching Heuristic Choice Model, were compared for best fit. The best fitting model was then chosen to provide the basis for parameter estimation (sources of decision making, i.e. cognitive, motivational, and response processes) and interpretation. Both models outperformed the baseline model. However comparison of G2 means between the two cognitive decision models showed the expectancy valence model having a higher mean …

Smooth Flexible Models Of Nonhomogeneous Poisson Processes Fit To One Or More Process Realizations, Shalaka C. Deo

Theses

Simulation is a technique of creating representations or models of real world systems or processes and conducting experiments to predict behavior of actual systems. Input modeling is a critical aspect of simulation modeling. Stochastic input models are used to model various aspects of the system under uncertainty including process times and interarrival times. This research focuses on input models for nonstationary arrival processes that can be represented as nonhomogeneous Poisson processes (NHPPs). In particular, a smooth flexible model for the mean-value function (or integrated rate function) of a general NHPP is estimated. To represent the mean-value function, the method utilizes …

The Impact Of A Simulation Based Leader Development Training Program On Transformational And Transactional Leadership Behavior, Robin Louise Mccoy Phd

Dissertations

Organizations devote considerable resources developing employees' capacity for leadership because they believe that "leaders" are essential in the operations of their organizations. Unfortunately, organizations do not have the time or resources to send their employees off for lengthy leader development training programs. This has contributed to the growing popularity of short-term training programs which are relatively inexpensive to conduct. However, researchers are increasingly requesting more empirical studies that examine the impact of these programs, yet these requests have remained largely disregarded. Additionally, there is a lack for developing methodologies to determine whether or not involvement in a short-term program facilitates …

Evaluating The Performance Of Propensity Scores To Address Selection Bias In A Multilevel Context: A Monte Carlo Simulation Study And Application Using A National Dataset, Jeremy Andrew Lingle

Educational Policy Studies Dissertations

When researchers are unable to randomly assign students to treatment conditions, selection bias is introduced into the estimates of treatment effects. Random assignment to treatment conditions, which has historically been the scientific benchmark for causal inference, is often impossible or unethical to implement in educational systems. For example, researchers cannot deny services to those who stand to gain from participation in an academic program. Additionally, students select into a particular treatment group through processes that are impossible to control, such as those that result in a child dropping-out of high school or attending a resource-starved school. Propensity score methods provide …

Genes And Symptoms Of Schizophrenia: Modifiers, Networks, And Interactions In Complex Disease, Sarah Bergen

Theses and Dissertations

Understanding the genetic foundations of schizophrenia and the resultant symptom manifestations is an important step as we work toward development of new prevention and treatment strategies. This work has sought better understanding of this disease through use of three subject cohorts and two studies using simulated data exploring features of complex disease. First, we probed the symptoms of schizophrenia in subjects of African and European ancestry drawn from the Genetic Association Information Network (GAIN) schizophrenia study and found significant differences between groups, particularly in affective symptoms. The genetic basis of symptom variation was then explored in a selection of candidate …

Improving Ad-Hoc Team Performance Using Video Games, Jeff David Craighead

USF Tampa Graduate Theses and Dissertations

This dissertation examined the effects of distributed, multiplayer training video games on the performance of distributed teams of robot operators. Two hypotheses were tested, the first hypothesis stated that online, game-based team training will improve the performance of an ad-hoc team versus an ad-hoc team formed of individually trained teammates. The second hypothesis stated that the fractal dimension of a robot's path can be used as an indicator of its operator's skill. Forty-one volunteers participated in an experiment in which they played a distributed, online training game which showed them the basics of operating an Inuktun Extreme VGTV for a …

Probing The Early Stages Of Polyglutamine Aggregation With Computational Methods, Andreas Vitalis

All Theses and Dissertations (ETDs)

Exonic CAG repeat diseases are a class of neurodegenerative age-of-onset diseases caused by an unstable trinucleotide expansion in a coding region of a gene. The most prominent example is Huntington's disease: HD) whose symptoms are characterized by loss of motor control and cognitive deficits. For all nine of the known CAG repeat diseases, pathology is ascribed to the mutant proteins which carry expanded stretches of glutamine residues: polyglutamine). The length of the polyglutamine segment is inversely correlated with the disease age-of-onset. Protein aggregates are routinely found in postmortem tissue samples of brains of HD patients. These findings suggest a prominent …

Development Of A Nonlinear Ride Quality Model To Aid In Tweelå© Parameter Selection, Marc Paradiso

All Theses

The ride comfort of a vehicle is very important to both automotive and tire manufacturers. Unfortunately the ride comfort provided by the tire has an inverse relationship with the handling ability of the vehicle. Michelin has sought to decouple ride comfort and handling capability by developing a non-pneumatic tire they have dubbed the TWEEL©. To better understand what effects fitting a TWEEL with specific characteristics would have on the ride comfort of a vehicle a computer simulation was developed to study the effects of TWEEL stiffness and deflection on ride comfort.
The vehicle model used in the simulation is a …

Simulation, Kriging, And Visualization Of Circular-Spatial Data, William James Morphet

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The circular dataimage is defined by displaying direction as the color at the same direction in a color wheel composed of a sequence of two-color gradients with color continuity between gradients. The resulting image of circular-spatial data is continuous with high resolution. Examples include ocean wind direction, Earth's main magnetic field, and rocket nozzle internal combustion flow. The cosineogram is defined as the mean cosine of the angle between random components of direction as a function of distance between observation locations. It expresses the spatial correlation of circular-spatial data. A circular kriging solution is developed based on a model fitted …

A Graph-Based Factor Screening Method For Synchronous Data Flow Simulation Models, Gregory Tauer

Theses

This thesis develops a method for identifying important input factors in large system dynamics models from an analysis based on those models' underlying structures. The identification of important input factors is commonly called factor screening and is a key step in the analysis of simulation models with many input parameters. Models under investigation are system dynamics models implemented as synchronous data flow programs, a model of computation that requires encoding the model components' dependencies in a graph format. The developed method views this graph as a stochastic process and attempts to rank the importance of inputs, or source nodes, with …

If Animals Could Talk, Matthew Moore

Art and Design Theses

This paper is an investigation of the ideas and philosophies that have played a role in the creation of my thesis exhibition entitled If Animals Could Talk. While my research into the subject of animals and more specifically human/animal interaction has covered a wide spectrum, this paper focuses on several texts including, “Why Look at Animals,” by John Berger and “Simulation and Simulacra” by Jean Baudrillard as being influential in the development of my artwork. This paper also analyzes the work of several artists dealing with human/animal relations. Those artists include Sanna Kannisto, Neeta Madahar and Douglas Gordon.

Neuromechanical Analysis Of Locust Jumping, David Wayne Cofer

Biology Dissertations

The nervous systems of animals evolved to exert dynamic control of behavior in response to the needs of the animal and changing signals from the environment. To understand the mechanisms of dynamic control, we need a means of predicting how individual neural and body elements will interact to produce the performance of the entire system. We have developed a neuromechanical application named AnimatLab that addresses this problem through simulation. A computational model of a body and nervous system can be constructed from simple components and situated in a virtual world for testing. Simulations and live experiments were used to investigate …

A Method For Introducing Artificial Perception (Ap) To Improve Human Behavior Representation (Hbr) Using Agents In Synthetic Environments, Randall Bartholomew Garrett

Computational Modeling & Simulation Engineering Theses & Dissertations

While psychology has shown that perception is very important for the human decision process, agent perception has not been covered in sufficient detail within the agent directed simulation field. To contribute to such a solution, an open challenge lies in capturing the knowledge of human sciences, such as psychology, and making this knowledge usable for engineers. This dissertation addresses perception by describing an experimental method where agent perception simulates human perception. In particular, it presents engineering methods based on accepted psychological approaches resulting in a proof of concept. To prove the feasibility, an Artificial Perception (AP) meta-model is presented using …

2-D Finite Element Modeling For Nanoindentation And Fracture Stress Analysis, Chi Chen

USF Tampa Graduate Theses and Dissertations

In Chapter 1, a brief introduction of nanoindentation and finite element method is presented. General procedures have been developed based on FEM modeling of nanoindentation data to obtain the mechanical properties of thin films. Selected FEM models are illustrated in detail.

In Chapter 2, nanoindentation test is simulated using finite element method based on contact mechanics approach. The relationship between load and indentation depth is obtained. The numerical results show good agreement with experimental data. It is shown that FEM is an effective tool for simulation of nanoindentation tests of metallic films. However, limitations caused by simplification of models and …

Predicting The Medical Management Requirements Of Large Scale Mass Casualty Events Using Computer Simulation, Scott A. Zuerlein

USF Tampa Graduate Theses and Dissertations

Recent events throughout the world and in the US lend support to the belief that another terrorist attack on the US is likely, perhaps probable. Given the potential for large numbers of casualties to be produced by a blast using conventional explosives, it is imperative that health systems across the nation consider the risks in their jurisdictions and take steps to better prepare for the possibility of an attack. Computer modeling and simulation offers a viable and useful methodology to better prepare an organization or system to respond to a large scale event. The real question, given the shortage, and …

Unified Large And Small Signal State-Space Based Modeling And Symbolic Simulation For Pwm Converters, Ehab Shoubaki

Electronic Theses and Dissertations

In this Dissertation, which concentrates on discrete modeling for control purposes of DC/DC converters and simulation through symbolic techniques. A Unified Discrete State-Space Model for power converters in CCM is presented. Two main approaches to arriving at the discrete model are used. The first approach involves an impulse function approximation of the duty cycle modulation of the converter switches, and this approach results in a small signal discrete model. The Second approach is direct and does not involve any approximation of the modulation, this approach yields both a large signal nonlinear discrete model and a linear small signal model. Harmonic …

Safety And Operational Evaluation Of Dynamic Lane Merging In Work Zones, Rami Harb

Electronic Theses and Dissertations

Traffic safety and mobility of roadway work zones have been considered to be one of the major concerns in highway traffic safety and operations in Florida. In intent to expose Florida's work zones crash characteristics, the Florida Traffic Crash Records Database for years 2002, 2003 and 2004 were explored. Statistical models were estimated and Florida's work zone crash traits for single vehicle crashes and two-vehicle crashes were drawn. For the single-vehicle crashes, trucks were found more likely to be involved in single vehicle crashes in freeway work zones compared to freeways without work zones. Straight level roadways are significantly affected …

Dod Acquisition Workforce Education: An Sba Education Case Study, Richard Davenport

Electronic Theses and Dissertations

A Department of Defense (DoD) M&S education task force is in the process of studying the Modeling and Simulation (M&S) education of the acquisition workforce. Historically, DoD acquisition workforce education is not referred to as education, but rather what the Defense Acquisition University (DAU) refers to as "practitioner training, career management, and services." The DAU is the organization primarily responsible for training the DoD acquisition corps in conjunction with service schools and strategic partners in the civilian sector. DAU programs primarily focus on program management, contracting, and management of logistics across the system life cycle. Further, the examples and cases …

Presence-Dependent Performance Differences Between Virtual Simulations And Miniature Worlds, Andre Huthmann

Electronic Theses and Dissertations

The purpose of simulation is to avoid reality-based constraints by the implemen-tation of a synthetic model. Based on this advantage, interactive simulations have conquered all areas of applications from acquisition, and training, to research. Simulation results are transferred in many ways into reality and conclusions are drawn from the simulation to the application. Many anecdotal observations on human-in-the-loop simulations have shown a significant difference in actor behavior between simulations and reality-based applications. It seems that the factors that makes simulation so attractive, namely the absence of constraints and especially of imminent danger for persons and equipment, influence the behavior and …

Developing New Indices For The Identification Of Poor Effort, Scott A. Magnuson

ETD Archive

The purpose of this study is to gather data in order to develop new indices to aid clinicians in more accurately distinguishing between patients feigning posttraumatic stress disorder (PTSD) and those with genuine PTSD. Participants were administered a battery of tests that included the Digit Span, Digit Symbol, Trail Making Test (TMT), and Rey Auditory Verbal Learning Test (RAVLT) twice, once while performing genuinely and again while simulating PTSD. The results of this study found that trails 21-25 of part A of the TMT are a good indicator of poor effort. This measurement was found to have high sensitivity (90.7 …

The Effect Of Virtual Clinical Gaming Simulations On Student Learning Outcomes In Medical-Surgical Nursing Education Courses, Robin A. Lewis

Theses, Dissertations and Capstones

The purpose of this study was to determine what the effects of virtual clinical simulation instruction were on the learning outcomes of students in higher education medical-surgical nursing education courses. This study fills a gap in the literature by adding data to the body of knowledge related to the use of this strategy for practical application in the classroom. This study used a causal comparative design. Data were acquired from the ATI Content Mastery Series (CMS) 2.1 Medical Surgical Examination ™ information for the fall 2006 through fall 2008 academic semesters. Additionally, data were collected using a pre- and post-course …

Evaluating Ecological Studies In Epidemiology, Brenden T. Dufault

Digitized Theses

The purpose of this research was twofold. The first objective was to assess the quality of modern cross-sectional ecological studies with a bibliometric review. The second objective was to investigate via simulation study the reliability of common ecological regression models for analysing count data.

The bibliometric review found that the quality and areas of application of the ecological literature is quite diverse. However, a large proportion of studies exhibited poor statistical practice and provided insufficient amounts of justification and information.

Linear, weighted linear, Poisson, and negative binomial regression were included in the simulation study based on their prevalence in the …

Confidence Interval Estimation Of The Area Under The Receiver Operating Characteristic Curve In The Presence Of Measurement Error, Yanhong Li

Digitized Theses

Diagnosis of diseases is often based on biomarkers with continuous measurements. The discriminative ability of a biomarker can be depicted by a receiver operating characteristic (ROC) curve, which shows simultaneously the proportions of both ab­ normal and normal subjects correctly diagnosed at various cutoff points in the marker values. The area (A) under the ROC curve is commonly used to measure the ability of the marker to distinguish between two populations. Many biomarkers are subject to measurement error, which must be taken into account in statistical inference for A to avoid misleading results. Assuming a normal distribution for biomarker values, …

The Calibration, Validation, And Comparison Of Vissim Simulations Using The Two-Fluid Model, Jeremy Crowe

Electronic Theses and Dissertations

The microscopic traffic simulation program VISSIM is a powerful tool that has been used by transportation engineers and urban planners around the world. A VISSIM simulation is meant to depict the performance of the physical road network through the use of modeling tools and behavioral parameters. The process which gets the model to the point of matching real world conditions is called calibration and requires a means of relating the real world to the simulated world. The topic of this thesis discusses a new means of calibration using the two-fluid model. The two-fluid model is a macroscopic modeling technique which …

Project Management: A Simulation-Based Optimization Method For Dynamic Time-Cost Tradeoff Decisions, Radhamés A. Tolentino Pena

Theses

Project managers face difficult decisions with regard to completing projects on time and within the project budget. A successful project manager not only needs to assure that the project is completed, but also desires to make optimal use of resources and maximize the profitability of the project. The goal of this research is to address the time-cost tradeoff problem associated with selecting from among project activity alternatives under uncertainty. Specifically, activities that make up a project may have several alternatives each with an associated cost and stochastic duration. The final project cost is a result of the time and cost …