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Anchor Nodes Placement for Effective Passive Localization

Description: Wireless sensor networks are composed of sensor nodes, which can monitor an environment and observe events of interest. These networks are applied in various fields including but not limited to environmental, industrial and habitat monitoring. In many applications, the exact location of the sensor nodes is unknown after deployment. Localization is a process used to find sensor node's positional coordinates, which is vital information. The localization is generally assisted by anchor nodes that are also sensor nodes but with known locations. Anchor nodes generally are expensive and need to be optimally placed for effective localization. Passive localization is one of the localization techniques where the sensor nodes silently listen to the global events like thunder sounds, seismic waves, lighting, etc. According to previous studies, the ideal location to place anchor nodes was on the perimeter of the sensor network. This may not be the case in passive localization, since the function of anchor nodes here is different than the anchor nodes used in other localization systems. I do extensive studies on positioning anchor nodes for effective localization. Several simulations are run in dense and sparse networks for proper positioning of anchor nodes. I show that, for effective passive localization, the optimal placement of the anchor nodes is at the center of the network in such a way that no three anchor nodes share linearity. The more the non-linearity, the better the localization. The localization for our network design proves better when I place anchor nodes at right angles.
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Date: August 2010
Creator: Pasupathy, Karthikeyan
Partner: UNT Libraries

Simulation of local watershed nutrient and sediment delivery to Lake Texoma.

Description: A hydrologic model and watershed export model was used to estimate the loading of nutrients and total suspended solids from un-gaged local watersheds associated with Lake Texoma. Discharge to the reservoir from local watersheds was predicted using a modification of the curve number method in HEC Hydrologic Modeling System (HEC-HMS). Event mean concentrations were applied to land use to estimate loadings of nutrients and TSS. Total discharge from the local watersheds was estimated to be 3.02 x 107 cubic meters for a study window of March 1 to May 31, 1997, less than 10 percent of the input to the lake from the Red River and Washita River systems. Loadings were estimated to be 33,553 kg nitrogen, 4,401 kg phosphorus, and 3,423,140 kg TSS. The models and results obtained from their application appear to have potential utility for use in a water quality management decision support system for the reservoir.
Date: May 2004
Creator: Upton, Alexandra C.
Partner: UNT Libraries

Bias and Precision of the Squared Canonical Correlation Coefficient under Nonnormal Data Conditions

Description: This dissertation: (a) investigated the degree to which the squared canonical correlation coefficient is biased in multivariate nonnormal distributions and (b) identified formulae that adjust the squared canonical correlation coefficient (Rc2) such that it most closely approximates the true population effect under normal and nonnormal data conditions. Five conditions were manipulated in a fully-crossed design to determine the degree of bias associated with Rc2: distribution shape, variable sets, sample size to variable ratios, and within- and between-set correlations. Very few of the condition combinations produced acceptable amounts of bias in Rc2, but those that did were all found with first function results. The sample size to variable ratio (n:v)was determined to have the greatest impact on the bias associated with the Rc2 for the first, second, and third functions. The variable set condition also affected the accuracy of Rc2, but for the second and third functions only. The kurtosis levels of the marginal distributions (b2), and the between- and within-set correlations demonstrated little or no impact on the bias associated with Rc2. Therefore, it is recommended that researchers use n:v ratios of at least 10:1 in canonical analyses, although greater n:v ratios have the potential to produce even less bias. Furthermore,because it was determined that b2 did not impact the accuracy of Rc2, one can be somewhat confident that, with marginal distributions possessing homogenous kurtosis levels ranging anywhere from -1 to 8, Rc2 will likely be as accurate as that resulting from a normal distribution. Because the majority of Rc2 estimates were extremely biased, it is recommended that all Rc2 effects, regardless of which function from which they result, be adjusted using an appropriate adjustment formula. If no rationale exists for the use of another formula, the Rozeboom-2 would likely be a safe choice given that it produced the greatest ...
Date: August 2006
Creator: Leach, Lesley Ann Freeny
Partner: UNT Libraries

Modeling Infectious Disease Spread Using Global Stochastic Field Simulation

Description: Susceptibles-infectives-removals (SIR) and its derivatives are the classic mathematical models for the study of infectious diseases in epidemiology. In order to model and simulate epidemics of an infectious disease, a global stochastic field simulation paradigm (GSFS) is proposed, which incorporates geographic and demographic based interactions. The interaction measure between regions is a function of population density and geographical distance, and has been extended to include demographic and migratory constraints. The progression of diseases using GSFS is analyzed, and similar behavior to the SIR model is exhibited by GSFS, using the geographic information systems (GIS) gravity model for interactions. The limitations of the SIR and similar models of homogeneous population with uniform mixing are addressed by the GSFS model. The GSFS model is oriented to heterogeneous population, and can incorporate interactions based on geography, demography, environment and migration patterns. The progression of diseases can be modeled at higher levels of fidelity using the GSFS model, and facilitates optimal deployment of public health resources for prevention, control and surveillance of infectious diseases.
Date: August 2006
Creator: Venkatachalam, Sangeeta
Partner: UNT Libraries

Simulation Study of Hybrid Ground Source Heat Pump System in the Hot-Humid Climate

Description: The beachfront hotel with hybrid geothermal heat pump system (HyGSHP), located in the hot-humid climate, is simulated by TRNSYS in the thesis, and the simulation results are validated by the measured data. The simulation of alternative HVAC systems, complete ground source heat pump and conventional air source heat pump, are included to conduct the comparative study with HyGSHP based on the energy consumption and life cycle analysis. The advantages and disadvantages of HyGSHP are discussed in the thesis. Two ground source heat exchanger parameters, U-tube size and grout materials, are investigated in order to study the effects on the ground heat exchanger thermal performance. The preliminary work and results are shown in the thesis.
Date: August 2011
Creator: Zhu, Jiang
Partner: UNT Libraries

An Empirical Evaluation of Communication and Coordination Effectiveness in Autonomous Reactive Multiagent Systems

Description: This thesis describes experiments designed to measure the effect of collaborative communication on task performance of a multiagent system. A discrete event simulation was developed to model a multi-agent system completing a task to find and collect food resources, with the ability to substitute various communication and coordination methods. Experiments were conducted to find the effects of the various communication methods on completion of the task to find and harvest the food resources. Results show that communication decreases the time required to complete the task. However, all communication methods do not fare equally well. In particular, results indicate that the communication model of the bee is a particularly effective method of agent communication and collaboration. Furthermore, results indicate that direct communication with additional information content provides better completion results. Cost-benefit models show some conflicting information, indicating that the increased performance may not offset the additional cost of achieving that performance.
Date: May 2005
Creator: Hurt, David
Partner: UNT Libraries

Social Network Simulation and Mining Social Media to Advance Epidemiology

Description: Traditional Public Health decision-support can benefit from the Web and social media revolution. This dissertation presents approaches to mining social media benefiting public health epidemiology. Through discovery and analysis of trends in Influenza related blogs, a correlation to Centers for Disease Control and Prevention (CDC) influenza-like-illness patient reporting at sentinel health-care providers is verified. A second approach considers personal beliefs of vaccination in social media. A vaccine for human papillomavirus (HPV) was approved by the Food and Drug Administration in May 2006. The virus is present in nearly all cervical cancers and implicated in many throat and oral cancers. Results from automatic sentiment classification of HPV vaccination beliefs are presented which will enable more accurate prediction of the vaccine's population-level impact. Two epidemic models are introduced that embody the intimate social networks related to HPV transmission. Ultimately, aggregating these methodologies with epidemic and social network modeling facilitate effective development of strategies for targeted interventions.
Date: August 2009
Creator: Corley, Courtney David
Partner: UNT Libraries

FACET Simulation in the Imataca Forest Reserve, Venezuela: Permanent Plot Data and Spatial Analysis

Description: Tree diameter data from 29 years of observations in six permanent plots was used to calculate the growth rate parameter of the FACET gap model for 39 species in the Imataca forests in Venezuela. The compound topographic index was used as a measure of differential soil water conditions and was calculated using geographic information systems. Growth rate values and topographic conditions typical of hill and valley were input to FACET to simulate dynamics at the species level and by ecological and functional groups. Species shade-tolerance led to expected successional patterns. Drought-tolerant/saturation-intolerant species grew in the hills whereas drought-intolerant/saturation-tolerant species occurred in the valleys. The results help to understand forest composition in the future and provide guidance to forest management practices.
Date: May 2006
Creator: Figuera, Dilcia
Partner: UNT Libraries

Comparisons of Improvement-Over-Chance Effect Sizes for Two Groups Under Variance Heterogeneity and Prior Probabilities

Description: The distributional properties of improvement-over-chance, I, effect sizes derived from linear and quadratic predictive discriminant analysis (PDA) and from logistic regression analysis (LRA) for the two-group univariate classification were examined. Data were generated under varying levels of four data conditions: population separation, variance pattern, sample size, and prior probabilities. None of the indices provided acceptable estimates of effect for all the conditions examined. There were only a small number of conditions under which both accuracy and precision were acceptable. The results indicate that the decision of which method to choose is primarily determined by variance pattern and prior probabilities. Under variance homogeneity, any of the methods may be recommended. However, LRA is recommended when priors are equal or extreme and linear PDA is recommended when priors are moderate. Under variance heterogeneity, selecting a recommended method is more complex. In many cases, more than one method could be used appropriately.
Date: May 2003
Creator: Alexander, Erika D.
Partner: UNT Libraries

Supply Chain Network Evolution: Demand-based Drivers of Interfirm Governance Evolution

Description: Which form of exchange governance performs better in a dynamic environment? This remains an unanswered question in the transaction cost analysis (TCA) and relational exchange literatures. Some researchers purport that transactional governance provides superior performance by providing firms the flexibility to change suppliers. Others suggest that relational governance leads to superior performance because of the willingness of both parties to adapt. Reviews of TCA have turned up ambivalent empirical findings with regard to the effects of uncertainty despite a track record of strong empirical support for other predictions. Because most of TCA and relational exchange theories' predictions enjoy strong support, this research builds upon these theories to propose a theoretical modeling framework for a dynamic environment in a supply chain network (SCN) setting. This dissertation extends TCA and relational exchange to a dynamic, network environment. It uses the approach of building a simulation in order to study in detail the relationship between key exchange factors and the selection of transactional and relational exchange governance over time. This research effort extended TCA theory with a complex adaptive model of supply chain network governance evolution that attempts to link environmental, network, production, firm and exchange factors in a continuously evolving loop. The proposed framework expands transaction cost analysis' explanatory power. Results partially support past scholarly proposal that uncertainty functions as an antecedent of asset specificity rather than as an independent construct affecting governance outcome dependent upon which form of uncertainty is being considered. The successful simulation of supply chain networks as complex adaptive systems shift the focus from deterministic, confirmatory models of exchange to an exploratory, positive model. Instead of exchange governance as an outcome, it is the catalyst of the evolutionary process.
Date: August 2007
Creator: Gravier, Michael J.
Partner: UNT Libraries

Simulation Approaches for System of Systems: Event-Based versus Agent Based Modeling

Description: This paper from the 2015 Conference on Systems Engineering Research conference proceedings reviews different modeling techniques and uses two converse techniques, i.e. agent-based and event-based modeling, to run a simulation of hypothetical systems collaborating into a system of systems.
Date: March 16, 2015
Creator: Baldwin, W. Clifton; Sauser, Brian & Cloutier, Robert
Item Type: Article
Partner: UNT College of Business

First Principle Calculations of the Structure and Electronic Properties of Pentacene Based Organic and ZnO Based Inorganic Semiconducting Materials

Description: In this thesis, I utilize first principles density functional theory (DFT) based calculations to investigate the structure and electronic properties including charge transfer behaviors and work function of two types of materials: pentacene based organic semiconductors and ZnO transparent conducting oxides, with an aim to search for high mobility n-type organic semiconductors and fine tuning work functions of ZnO through surface modifications. Based on DFT calculations of numerous structure combinations, I proposed a pentacene and perfluoro-pentacene alternating hybrid structures as a new type of n-type semiconductor. Based on the DFT calculations and Marcus charge transfer theory analysis, the new structure has high charge mobility and can be a promising new n-type organic semiconductor material. DFT calculations have been used to systematically investigate the effect of surface organic absorbate and surface defects on the work function of ZnO. It was found that increasing surface coverage of organic groups and decreasing surface defects lead to decrease of work functions, in excellent agreement with experimental results. First principles based calculations thus can greatly contribute to the investigating and designing of new electronic materials.
Date: May 2012
Creator: Li, Yun
Partner: UNT Libraries

A Global Stochastic Modeling Framework to Simulate and Visualize Epidemics

Description: Epidemics have caused major human and monetary losses through the course of human civilization. It is very important that epidemiologists and public health personnel are prepared to handle an impending infectious disease outbreak. the ever-changing demographics, evolving infrastructural resources of geographic regions, emerging and re-emerging diseases, compel the use of simulation to predict disease dynamics. By the means of simulation, public health personnel and epidemiologists can predict the disease dynamics, population groups at risk and their geographic locations beforehand, so that they are prepared to respond in case of an epidemic outbreak. As a consequence of the large numbers of individuals and inter-personal interactions involved in simulating infectious disease spread in a region such as a county, sizeable amounts of data may be produced that have to be analyzed. Methods to visualize this data would be effective in facilitating people from diverse disciplines understand and analyze the simulation. This thesis proposes a framework to simulate and visualize the spread of an infectious disease in a population of a region such as a county. As real-world populations have a non-homogeneous demographic and spatial distribution, this framework models the spread of an infectious disease based on population of and geographic distance between census blocks; social behavioral parameters for demographic groups. the population is stratified into demographic groups in individual census blocks using census data. Infection spread is modeled by means of local and global contacts generated between groups of population in census blocks. the strength and likelihood of the contacts are based on population, geographic distance and social behavioral parameters of the groups involved. the disease dynamics are represented on a geographic map of the region using a heat map representation, where the intensity of infection is mapped to a color scale. This framework provides a tool for public health personnel and ...
Date: May 2012
Creator: Indrakanti, Saratchandra
Partner: UNT Libraries

Regional Economic Impact of Texas Motor Speedway: A Simulation

Description: This study proposes a method for measuring the regional economic impact of a relatively new sport: stock car racing. Although research on the economic impact of most major league sports is abundant, little has been written on stock car racing. The purpose of this paper is to estimate, through a simulation, the regional economic impact of Texas Motor Speedway. The study finds that the Texas Motor Speedway boosted economic activity by $87,179,367 in 1998 from racetrack operations, and supported 5,300 jobs paying $22,293,135 in earnings. In addition, expenditures by speedway visitor from outside the region are estimated at $22,985,200, further increasing the total local economic activity by $49 million.
Date: August 2000
Creator: Rattner, Laura E.
Partner: UNT Libraries

Reactions and Interfacial Behaviors of the Water–Amorphous Silica System from Classical and Ab Initio Molecular Dynamics Simulations

Description: Due to the wide application of silica based systems ranging from microelectronics to nuclear waste disposal, detailed knowledge of water-silica interactions plays an important role in understanding fundamental processes, such as glass corrosion and the long term reliability of devices. In this dissertation, atomistic computer simulation methods have been used to explore and identify the mechanisms of water-silica reactions and the detailed processes that control the properties of the water-silica interfaces due to their ability to provide atomic level details of the structure and reaction pathways. The main challenges of the amorphous nature of the silica based systems and nano-porosity of the structures were overcome by a combination of simulation methodologies based on classical molecular dynamics (MD) simulations with Reactive Force Field (ReaxFF) and density functional theory (DFT) based ab initio MD simulations. Through the development of nanoporous amorphous silica structure models, the interactions between water and the complex unhydroxylated internal surfaces identified the unusual stability of strained siloxane bonds in high energy ring structure defects, as well as the hydroxylation reaction kinetics, which suggests the difficulty in using DFT methods to simulate Si-O bond breakage with reasonable efficiency. Another important problem addressed is the development of silica gel structures and their interfaces, which is considered to control the long term residual dissolution rate in borosilicate glasses. Through application of the ReaxFF classical MD potential, silica gel structures which mimic the development of interfacial layers during silica dissolution were created A structural model, consisting of dense silica, silica gel, and bulk water, and the related interfaces was generated, to represent the dissolution gel structure. High temperature evolution of the silica-gel-water (SGW) structure was performed through classical MD simulation of the system, and growth of the gel into the water region occurred, as well as the formation of intermediate range structural ...
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Date: May 2016
Creator: Rimsza, Jessica M
Partner: UNT Libraries

Modeling and Simulation of the Vector-Borne Dengue Disease and the Effects of Regional Variation of Temperature in the Disease Prevalence in Homogenous and Heterogeneous Human Populations

Description: The history of mitigation programs to contain vector-borne diseases is a story of successes and failures. Due to the complex interplay among multiple factors that determine disease dynamics, the general principles for timely and specific intervention for incidence reduction or eradication of life-threatening diseases has yet to be determined. This research discusses computational methods developed to assist in the understanding of complex relationships affecting vector-borne disease dynamics. A computational framework to assist public health practitioners with exploring the dynamics of vector-borne diseases, such as malaria and dengue in homogenous and heterogeneous populations, has been conceived, designed, and implemented. The framework integrates a stochastic computational model of interactions to simulate horizontal disease transmission. The intent of the computational modeling has been the integration of stochasticity during simulation of the disease progression while reducing the number of necessary interactions to simulate a disease outbreak. While there are improvements in the computational time reducing the number of interactions needed for simulating disease dynamics, the realization of interactions can remain computationally expensive. Using multi-threading technology to improve performance upon the original computational model, multi-threading experimental results have been tested and reported. In addition, to the contact model, the modeling of biological processes specific to the corresponding pathogen-carrier vector to increase the specificity of the vector-borne disease has been integrated. Last, automation for requesting, retrieving, parsing, and storing specific weather data and geospatial information from federal agencies to study the differences between homogenous and heterogeneous populations has been implemented.
Date: August 2016
Creator: Bravo-Salgado, Angel D
Partner: UNT Libraries

Cyber-Physical Systems Can Make Emergency Response Smart

Description: This paper from the Humanitarian Technology: Science, Systems and Global Impact 2015 conference proceedings discusses the Smart Emergency Response System prototype built in the context of the SmartAmerica Challenge 2013-2014 by a team of nine organizations led by MathWorks.
Date: July 7, 2015
Creator: Zander, Justyna; Mosterman, Pieter J.; Padir, Taskin; Wan, Yan & Fu, Shengli
Item Type: Paper
Partner: UNT College of Engineering

Ability of Offenders with Psychopathic Traits to Simulate Cognitive and Affective Empathy

Description: The accurate assessment of psychopathy constitutes a critical component of forensic assessments addressing offender populations. Among the core characteristics of psychopathy, the interpersonal component of deception and empathic deficits are prominently observed in offenders with psychopathic traits. Given the negative consequences of being classified as a psychopath, offenders may be likely to minimize their psychopathic traits. In particular, no research has investigated whether offenders with psychopathic traits are able to simulate empathy in an effort to mask their cognitive or affective empathy deficits (e.g., lack of remorse about offenses). The present study aims to contribute to the literature with regard to the simulation of empathy. Using a mixed between- and within-subjects design, 81 male detainees were placed into (a) a low psychopathy group, (b) a moderate psychopathy group, or (c) a high psychopathy group based on the Psychopathy Checklist – Revised. For the within-subjects component, all offenders answered empathy questionnaires under genuine and simulation conditions. Results indicate the sample possessed cognitive empathy, but did not display affective empathy under genuine instructions. Under simulation instructions, participants significantly increased their scores on several empathy measures. The implications of simulated empathy and comparisons between groups regarding simulation abilities are discussed.
Date: August 2013
Creator: Robinson, Emily V.
Partner: UNT Libraries

Methodological Issues in Malingering Research: The Use of Simulation Designs

Description: The accurate determination of malingering relies on the use of validated and clinically relevant assessment measures. Simulation design is the most often-used research design to accomplish this. However, its external validity is sometimes questioned. The goal of the thesis was to systematically evaluate these major elements: situation, incentives, and coaching. The situation in simulation studies can vary from relevant (academic failure in a college population) to irrelevant (capital murder) for the samples being studied. Incentives refer to the external motivation given to improve simulators' performance and can be positive (extra credit and monetary reward) or negative (extra time and effort). Finally, coaching refers to whether the participant receives any information on detection strategies that are designed to identify feigners. Using a large undergraduate sample in a factorial design, results indicate that a scenario familiar to the participants generally improved the believability of their responses. Coaching also improved the ability to feign convincingly, while incentive type was not associated with any change in scores. The implications of these findings for future research designs and the connection to practice are discussed.
Date: December 2010
Creator: Gillard, Nathan D.
Partner: UNT Libraries