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Title: Propagation of Unit Location Uncertainty in Dense Storage Environments.
Creator: Reilly, Patrick, Pazour, Jennifer, Zheng, Qipeng, Schneider, Kellie, University of Central Florida
Abstract / Description: Effective space utilization is an important consideration in logistics systems and is especially important in dense storage environments. Dense storage systems provide high-space utilization; however, because not all items are immediately accessible, storage and retrieval operations often require shifting of other stored items in order to access the desired item, which results in item location uncertainty when asset tracking is insufficient. Given an initial certainty in item location, we use...
Show moreEffective space utilization is an important consideration in logistics systems and is especially important in dense storage environments. Dense storage systems provide high-space utilization; however, because not all items are immediately accessible, storage and retrieval operations often require shifting of other stored items in order to access the desired item, which results in item location uncertainty when asset tracking is insufficient. Given an initial certainty in item location, we use Markovian principles to quantify the growth of uncertainty as a function of retrieval requests and discover that the steady state probability distribution for any communicating class of storage locations approaches uniform. Using this result, an expected search time model is developed and applied to the systems analyzed. We also develop metrics that quantify and characterize uncertainty in item location to aid in understanding the nature of that uncertainty. By incorporating uncertainty into our logistics model and conducting numerical experiments, we gain valuable insights into the uncertainty problem such as the benefit of multiple item copies in reducing expected search time and the varied response to different retrieval policies in otherwise identical systems.
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Date Issued: 2015
Identifier: CFE0006052, ucf:50972
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006052

Title: MANAGING THE CHARACTERISTICS OF SOFTWARE PRODUCT DEVELOPMENT PROGRAMS.
Creator: Li, Yuzhu, Jiang, James, University of Central Florida
Abstract / Description: Multiple related software development projects are often managed concurrently and systematically to deliver a complex software system. This approach of managing multiple interdependent projects together to achieve a common goal is called program management (Pellegrinelli, 1997). A software development program can generate the benefits that cannot be achieved by managing projects individually. The software product development program has the special characteristics such as complexity,...
Show moreMultiple related software development projects are often managed concurrently and systematically to deliver a complex software system. This approach of managing multiple interdependent projects together to achieve a common goal is called program management (Pellegrinelli, 1997). A software development program can generate the benefits that cannot be achieved by managing projects individually. The software product development program has the special characteristics such as complexity, uncertainty and interdependence (1995). A software product development program can play an active role in managing the uncertainty and interdependence in the software development process. This dissertation is designed to examine the external communication effectiveness of the program team on the interdependence between the program and the larger organizational context. In addition, this dissertation studies the inter-project coordination effectiveness on uncertainty within a program. Based upon organizational Information Processing Theory (IPT) and Resource Dependence Theory (RDT), theoretical frameworks are developed. The proposed research models are tested by surveying software product development programs across a range of industries. The results will contribute to the understanding of multiple-project communication in a program's context. The specific interactions between coordination/communication and the product development characteristics will provide a guideline for the industrial practices.
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Date Issued: 2008
Identifier: CFE0002305, ucf:47866
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002305

Title: TWO ESSAYS ON SCREENING STRATEGIES.
Creator: Ganesh Pillai, Rajani, Xin He, Raj Echambadi, University of Central Florida
Abstract / Description: Consumers form consideration sets by screening from all available alternatives. Consumers typically utilize one of two types of screening strategies: an exclusion screening strategy wherein alternatives not worthy of further consideration are rejected or an inclusion strategy wherein worthy alternatives are selected for further evaluation. Extant literature has documented the important role played by screening strategies in decision making. However, there is very limited understanding of when...
Show moreConsumers form consideration sets by screening from all available alternatives. Consumers typically utilize one of two types of screening strategies: an exclusion screening strategy wherein alternatives not worthy of further consideration are rejected or an inclusion strategy wherein worthy alternatives are selected for further evaluation. Extant literature has documented the important role played by screening strategies in decision making. However, there is very limited understanding of when and why consumers may employ one screening strategy over the other as well the impact of the screening strategy for decision accuracy. This dissertation attempts to study the antecedent and consequence of screening strategies. Essay 1 in this dissertation, investigates the role of consumers' perceived uncertainty on the choice of screening strategy. Four studies in this essay show that when consumers are highly uncertain they are more likely to choose exclusion screening strategy; whereas when they are less uncertain they are more likely to use inclusion screening. Mediation analyses in Studies 1 and 2 show that the choice of screening strategy is primarily driven by perceived accuracy of the strategy. Study 3 demonstrates that the effect of uncertainty on the choice of screening strategy is moderated by consideration set size. When uncertain consumers form smaller sets they are more likely to use exclusion screening, but this relationship flips when they form larger consideration sets. Finally, external validity for the relationship between uncertainty and choice of screening strategy is demonstrated in Study 4 using the popular TV game show Who Wants to be a Millionaire? Essay two in this dissertation, investigates the role of perceived uncertainty and consideration set size on the relationship between screening strategy and objective accuracy of the decision. Utilizing an experimental study with an actual choice task, I demonstrate that perceived uncertainty moderates the screening strategy-decision accuracy relationship. Further, this interactive relationship is contingent on consideration set sizes. Whereas consumers with high perceived uncertainty make higher quality decisions with inclusion while forming smaller consideration sets, their decision quality is higher with exclusion when forming larger sets. Likewise, while consumers with low perceived uncertainty make more accurate decisions with exclusion when forming smaller sets, the accuracy of their decisions increases with inclusion when forming larger sets. This dissertation contributes to literature on screening strategies by explicating perceived uncertainty as a critical factor that leads to consumers preferring one screening strategy versus the other. Furthermore, it adds to our understanding of an important consequence of using screening strategies – decision accuracy.
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Date Issued: 2009
Identifier: CFE0002927, ucf:48001
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002927

Title: DEFINING RISK ASSESSMENT CONFIDENCE LEVELS FOR USE IN PROJECT MANAGEMENT COMMUNICATIONS.
Creator: Johnson, Gary, Pet-Armacost, Julia, University of Central Florida
Abstract / Description: A review of the literature regarding risk management and effective risk communications identified that very few researchers have addressed risk assessment confidence levels when using risk scoring methods. The focus of this research is to develop a definition of risk assessment confidence levels for use in internal project management communications and to evaluate its usefulness. This research defines risk assessment confidence level as "The degree of certainty that the likelihood or...
Show moreA review of the literature regarding risk management and effective risk communications identified that very few researchers have addressed risk assessment confidence levels when using risk scoring methods. The focus of this research is to develop a definition of risk assessment confidence levels for use in internal project management communications and to evaluate its usefulness. This research defines risk assessment confidence level as "The degree of certainty that the likelihood or consequence score (assigned by the risk assessor) reflects reality." A specific level of confidence is defined based on the types of analyses that were conducted to determine the risk score. A survey method was used to obtain data from a representative sample of risk assessment professionals from industry and academia to measure their opinion on the usefulness of the defined risk assessment confidence levels. The survey consisted of seven questions related to usefulness--four questions addressed the importance of stating confidence levels in risk assessments and three addressed the usableness of the proposed confidence level. Data were collected on the role and experience level of each of the respondents and the survey also included a comment section to obtain additional feedback. The survey generated 364 respondents representing a broad variety of roles associated with decision making and risk management with experience levels from fairly new to experienced risk assessors. The survey data were analyzed by calculating the proportion of respondents who gave negative, neutral and positive responses to the survey questions. An examination of the roles of the survey respondents indicated that no single group was dominant. A non-parametric Kruskal-Wallis test generally failed to reject the hypothesis that the means of the survey response distributions were identical. There was one exception which indicated that there are differences based on role and by inspection of the responses, it appears that decision makers, academics, and others more strongly support the need for confidence level information to reduce the difficulty in making risk based decisions in projects. The survey responses at a confidence level of 95% have a range of errors from 3.84 to 4.97%. Based on the results of the survey, 77 – 83% of those surveyed indicated agreement that knowing the confidence the assessors have in their assessment is important and would improve a management decision. The survey showed that 60 – 86% of the respondents agreed that the confidence levels and their definitions as presented in the survey were usable. The question with the lowest agreement (60%) was related to the way in which the individual levels were defined. The ad-hoc comments provided in the survey were divided into eleven groups based on similarity of the subject of the comment and then examined for common themes. These added additional insight into the results and useful information for future research efforts. This research validates that the use of risk assessment confidence levels is considered to be useful in project risk management. The research also identified several potential areas for future work, including determining the appropriate number of confidence levels that should be defined, refining the definition of the individual confidence level definitions, examining historical perspectives of whether the risk assessments were accurate, examining the concept of shiftability of risk assessments, further research on communication of variability of risk assessments, and research into the usefulness of risk matrices.
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Date Issued: 2008
Identifier: CFE0002352, ucf:47791
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002352

Title: LANDFILL GAS TO ENERGY: INCENTIVES & BENEFITS.
Creator: Amini, Hamid, Reinhart, Debra, University of Central Florida
Abstract / Description: Municipal solid waste (MSW) management strategies typically include a combination of three approaches, recycling, combustion, and landfill disposal. In the US approximately 54% of the generated MSW was landfilled in 2008, mainly because of its simplicity and cost-effectiveness. However, landfills remain a major concern due to potential landfill gas (LFG) emissions, generated from the chemical and biological processes occurring in the disposed waste. The main components of LFG are methane (50...
Show moreMunicipal solid waste (MSW) management strategies typically include a combination of three approaches, recycling, combustion, and landfill disposal. In the US approximately 54% of the generated MSW was landfilled in 2008, mainly because of its simplicity and cost-effectiveness. However, landfills remain a major concern due to potential landfill gas (LFG) emissions, generated from the chemical and biological processes occurring in the disposed waste. The main components of LFG are methane (50-60%) and carbon dioxide (40-50%). Although LFG poses a threat to the environment, if managed properly it is a valuable energy resource due to the methane content. Currently there are over 550 active LFG to energy (LFGTE) facilities in the US, producing renewable energy from LFG. A major challenge in designing/operating a LFGTE facility is the uncertainty in LFG generation rate predictions. LFG generation rates are currently estimated using models that are dependent upon the waste disposal history, moisture content, cover type, and gas collection system, which are associated with significant uncertainties. The objectives of this research were to: (1) Evaluate various approaches of estimating LFG generation and to quantify the uncertainty of the model outcomes based on case-study analysis, (2) Present a methodology to predict long-term LFGTE potential under various operating practices on a regional scale, and (3) Investigate costs and benefits of emitting vs. collecting LFG emissions with regards to operation strategies and regulations. The first-order empirical model appeared to be insensitive to the approach taken in quantifying the model parameters, suggesting that the model may be inadequate to accurately describe LFG generation and collection. The uncertainty values for the model were, in general, at their lowest within five years after waste placement ended. Because of the exponential nature, the uncertainty increased as LFG generation declined to low values decades after the end of waste placement. A methodology was presented to estimate LFGTE potential on a regional scale over a 25-year timeframe with consideration of modeling uncertainties. The methodology was demonstrated for the US state of Florida, and showed that Florida could increase the annual LFGTE production by more than threefold by 2035 through installation of LFGTE facilities at all landfills. Results showed that diverting food waste could significantly reduce fugitive LFG emissions, while having minimal effect on the LFGTE potential. Estimates showed that with enhanced landfill operation and energy production practices, LFGTE power density could be comparable to technologies such as wind, tidal, and geothermal. More aggressive operations must be considered to avoid fugitive LFG emissions, which could significantly affect the economic viability of landfills. With little economic motivation for US landfill owners to voluntarily reduce fugitive emissions, regulations are necessary to increase the cost of emitting GHGs. In light of the recent economic recession, it is not likely that a carbon tax will be established; while a carbon trading program will enforce emission caps and provide a tool to offset some costs and improve emission-reduction systems. Immediate action establishing a US carbon trading market with carbon credit pricing and trading supervised by the federal government may be the solution. Costs of achieving high lifetime LFG collection efficiencies are unlikely to be covered with revenues from tipping fee, electricity sales, tax credits, or carbon credit trading. Under scenarios of highly regulated LFG emissions, sustainable landfilling will require research, development, and application of technologies to reduce the marginal abatement cost, including: (1) Diverting rapidly decomposable waste to alternative treatment methods, (2) Reducing fugitive emissions through usage daily/intermediate covers with high oxidation potential, (3) Increasing the lifetime LFG collection efficiency, and (4) Increasing LFG energy value - for instance by producing high-methane gas through biologically altering the LFG generation pathway.
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Date Issued: 2011
Identifier: CFE0003960, ucf:48682
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003960

Title: DECISION SUPPORT MODEL FOR CONSTRUCTION CREW REASSIGNMENTS.
Creator: Sist, Angela, Pet-Armacost, Julia, University of Central Florida
Abstract / Description: The reassignment of crews on a construction project in response to changes occurs on a frequent basis. The factors that affect the crew reassignment decision can be myriad and most are not known with certainty. This research addresses the need for a decision support model to assist construction managers with the crew reassignment problem. The model design makes use of certainty factors in a decision tree structure. The research helped to determine the elements in the decision tree, the...
Show moreThe reassignment of crews on a construction project in response to changes occurs on a frequent basis. The factors that affect the crew reassignment decision can be myriad and most are not known with certainty. This research addresses the need for a decision support model to assist construction managers with the crew reassignment problem. The model design makes use of certainty factors in a decision tree structure. The research helped to determine the elements in the decision tree, the appropriate combination rules to use with certainty factors, and the method for combining the certainty factors and costs to develop a measure of cost for each decision option. The research employed surveys, group meetings, and individual interviews of experienced construction managers and superintendents to investigate the current methods used by decision makers to identify and evaluate the key elements of the construction crew reassignment decision. The initial research indicated that the use of certainty factors was preferred over probabilities for representing uncertainties. Since certainty factors have not been used in a traditional decision tree context, a contribution of the research is the development and testing of techniques for combining certainty factors, durations, and costs in order to represent the uncertainty and to emulate the decision process of the experts interviewed. The developed model provides the decision maker with an estimate of the upper and lower bounds of costs for each crew reassignment option. The model was applied contemporaneously to six changes on three ongoing construction projects to test the model and assess its usefulness. The model provides a previously unavailable tool for the prospective identification and estimation of productivity losses and potential costs that emanate from changes. The users indicated the model process resulted in concise and complete compilations of the elements of the crew reassignment decision and that the model outputs were consistent with the users' expectations.
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Date Issued: 2004
Identifier: CFE0000297, ucf:46212
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000297

Title: CONTROLLING RANDOMNESS: USING PROCEDURAL GENERATION TO INFLUENCE PLAYER UNCERTAINTY IN VIDEO GAMES.
Creator: Fort, Travis, McDaniel, Rudy, University of Central Florida
Abstract / Description: As video games increase in complexity and length, the use of automatic, or procedural, content generation has become a popular way to reduce the stress on game designers. However, the usage of procedural generation has certain consequences; in many instances, what the computer generates is uncertain to the designer. The intent of this thesis is to demonstrate how procedural generation can be used to intentionally affect the embedded randomness of a game system, enabling game designers to...
Show moreAs video games increase in complexity and length, the use of automatic, or procedural, content generation has become a popular way to reduce the stress on game designers. However, the usage of procedural generation has certain consequences; in many instances, what the computer generates is uncertain to the designer. The intent of this thesis is to demonstrate how procedural generation can be used to intentionally affect the embedded randomness of a game system, enabling game designers to influence the level of uncertainty a player experiences in a nuanced way. This control affords game designers direct control over complex problems like dynamic difficulty adjustment, pacing, or accessibility. Game design will be examined from the perspective of uncertainty and how procedural generation can be used to intentionally add or reduce uncertainty. Various procedural generation techniques will be discussed alongside the types of uncertainty, using case studies to demonstrate the principles in action.
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Date Issued: 2015
Identifier: CFH0004772, ucf:45386
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH0004772

Title: AN INTERVAL BASED APPROACH TO MODEL INPUT UNCERTAINTY IN DISCRETE-EVENT SIMULATION.
Creator: Batarseh, Ola, Wang, Yan, University of Central Florida
Abstract / Description: The objective of this research is to increase the robustness of discrete-event simulation (DES) when input uncertainties associated models and parameters are present. Input uncertainties in simulation have different sources, including lack of data, conflicting information and beliefs, lack of introspection, measurement errors, and lack of information about dependency. A reliable solution is obtained from a simulation mechanism that accounts for these uncertainty components in simulation. An...
Show moreThe objective of this research is to increase the robustness of discrete-event simulation (DES) when input uncertainties associated models and parameters are present. Input uncertainties in simulation have different sources, including lack of data, conflicting information and beliefs, lack of introspection, measurement errors, and lack of information about dependency. A reliable solution is obtained from a simulation mechanism that accounts for these uncertainty components in simulation. An interval-based simulation (IBS) mechanism based on imprecise probabilities is proposed, where the statistical distribution parameters in simulation are intervals instead of precise real numbers. This approach incorporates variability and uncertainty in systems. In this research, a standard procedure to estimate interval parameters of probability distributions is developed based on the measurement of simulation robustness. New mechanisms based on the inverse transform to generate interval random variates are proposed. A generic approach to specify the required replication length to achieve a desired level of robustness is derived. Furthermore, three simulation clock advancement approaches in the interval-based simulation are investigated. A library of Java-based IBS toolkits that simulates queueing systems is developed to demonstrate the new proposed reliable simulation. New interval statistics for interval data analysis are proposed to support decision making. To assess the performance of the IBS, we developed an interval-based metamodel for automated material handling systems, which generates interval performance measures that are more reliable and computationally more efficient than traditional DES simulation results.
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Date Issued: 2010
Identifier: CFE0003343, ucf:48441
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003343

Title: A Framework for Process Data Collection, Analysis, and Visualization in Construction Projects.
Creator: Akhavian, Reza, Behzadan, Amir, Oloufa, Amr, Tatari, Mehmet, University of Central Florida
Abstract / Description: Automated data collection, simulation and visualization can substantially enhance the process of designing, analysis, planning, and control of many engineering processes. In particular, managing processes that are dynamic in nature can significantly benefit from such techniques. Construction projects are good examples of such processes where a variety of equipment and resources constantly interact inside an evolving environment. Management of such settings requires a platform capable of...
Show moreAutomated data collection, simulation and visualization can substantially enhance the process of designing, analysis, planning, and control of many engineering processes. In particular, managing processes that are dynamic in nature can significantly benefit from such techniques. Construction projects are good examples of such processes where a variety of equipment and resources constantly interact inside an evolving environment. Management of such settings requires a platform capable of providing decision-makers with updated information about the status of project entities and assisting site personnel making critical decisions under uncertainty. To this end, the current practice of using historical data or expert judgments as static inputs to create empirical formulations, bar chart schedules, and simulation networks to study project activities, resource operations, and the environment under which a project is taking place does not seem to offer reliable results.The presented research investigates the requirements and applicability of a data-driven modeling framework capable of collecting and analyzing real time field data from construction equipment. In the developed data collection scheme, a stream of real time data is continuously transferred to a data analysis module to calculate the input parameters required to create dynamic 3D visualizations of ongoing engineering activities, and update the contents of a discrete event simulation (DES) model representing the real engineering process. The generated data-driven simulation model is an effective tool for projecting future progress based on existing performance. Ultimately, the developed framework can be used by project decision-makers for short-term project planning and control since the resulting simulation and visualization are completely based on the latest status of project entities.
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Date Issued: 2012
Identifier: CFE0004347, ucf:49419
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004347

Title: Creating a Consistent Oceanic Multi-decadal Intercalibrated TMI-GMI Constellation Data Record.
Creator: Chen, Ruiyao, Jones, W Linwood, Mikhael, Wasfy, Wei, Lei, Wilheit, Thomas, McKague, Darren, University of Central Florida
Abstract / Description: The Tropical Rainfall Measuring Mission (TRMM), launched in late November 1997 into a low earth orbit, produced the longest microwave radiometric data time series of 17-plus years from the TRMM Microwave Imager (TMI). The Global Precipitation Measuring (GPM) mission is the follow-on to TRMM, designed to provide data continuity and advance precipitation measurement capabilities. The GPM Microwave Imager (GMI) performs as a brightness temperature (Tb) calibration standard for the intersatellite...
Show moreThe Tropical Rainfall Measuring Mission (TRMM), launched in late November 1997 into a low earth orbit, produced the longest microwave radiometric data time series of 17-plus years from the TRMM Microwave Imager (TMI). The Global Precipitation Measuring (GPM) mission is the follow-on to TRMM, designed to provide data continuity and advance precipitation measurement capabilities. The GPM Microwave Imager (GMI) performs as a brightness temperature (Tb) calibration standard for the intersatellite radiometric calibration (XCAL) for the other constellation members; and before GPM was launched, TMI was the XCAL standard. This dissertation aims at creating a consistent oceanic multi-decadal Tb data record that ensures an undeviating long-term precipitation record covering TRMM-GPM eras. As TMI and GMI share only a 13-month common operational period, the U.S. Naval Research Laboratory's WindSat radiometer, launched in 2003 and continuing today provides the calibration bridge between the two. TMI/WindSat XCAL for their (>)9 years' period, and WindSat/GMI XCAL for one year are performed using a robust technique developed by the Central Florida Remote Sensing Lab, named CFRSL XCAL Algorithm, to estimate the Tb bias of one relative to the other. The 3-way XCAL of GMI/TMI/WindSat for their joint overlap period is performed using an extended CFRSL XCAL algorithm. Thus, a multi-decadal oceanic Tb dataset is created. Moreover, an important feature of this dataset is a quantitative estimate of the Tb uncertainty derived from a generic Uncertainty Quantification Model (UQM). In the UQM, various sources contributing to the Tb bias are identified systematically. Next, methods for quantifying uncertainties from these sources are developed and applied individually. Finally, the resulting independent uncertainties are combined into a single overall uncertainty to be associated with the Tb bias on a channel basis. This dissertation work is remarkably important because it provides the science community with a consistent oceanic multi-decadal Tb data record, and also allows the science community to better understand the uncertainty in precipitation products based upon the Tb uncertainties provided.
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Date Issued: 2018
Identifier: CFE0006987, ucf:51650
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006987

Title: Computational Fluid Dynamics Uncertainty Analysis for Payload Fairing Spacecraft Environmental Control Systems.
Creator: Groves, Curtis, Kassab, Alain, Das, Tuhin, Kauffman, Jeffrey, Moore, Brian, University of Central Florida
Abstract / Description: Spacecraft thermal protection systems are at risk of being damaged due to airflow produced from Environmental Control Systems. There are inherent uncertainties and errors associated with using Computational Fluid Dynamics to predict the airflow field around a spacecraft from the Environmental Control System. This paper describes an approach to quantify the uncertainty in using Computational Fluid Dynamics to predict airflow speeds around an encapsulated spacecraft without the use of test data...
Show moreSpacecraft thermal protection systems are at risk of being damaged due to airflow produced from Environmental Control Systems. There are inherent uncertainties and errors associated with using Computational Fluid Dynamics to predict the airflow field around a spacecraft from the Environmental Control System. This paper describes an approach to quantify the uncertainty in using Computational Fluid Dynamics to predict airflow speeds around an encapsulated spacecraft without the use of test data. Quantifying the uncertainty in analytical predictions is imperative to the success of any simulation-based product. The method could provide an alternative to traditional (")validation by test only(") mentality. This method could be extended to other disciplines and has potential to provide uncertainty for any numerical simulation, thus lowering the cost of performing these verifications while increasing the confidence in those predictions.Spacecraft requirements can include a maximum airflow speed to protect delicate instruments during ground processing. Computational Fluid Dynamics can be used to verify these requirements; however, the model must be validated by test data. This research includes the following three objectives and methods. Objective one is develop, model, and perform a Computational Fluid Dynamics analysis of three (3) generic, non-proprietary, environmental control systems and spacecraft configurations. Several commercially available and open source solvers have the capability to model the turbulent, highly three-dimensional, incompressible flow regime. The proposed method uses FLUENT, STARCCM+, and OPENFOAM. Objective two is to perform an uncertainty analysis of the Computational Fluid Dynamics model using the methodology found in (")Comprehensive Approach to Verification and Validation of Computational Fluid Dynamics Simulations("). This method requires three separate grids and solutions, which quantify the error bars around Computational Fluid Dynamics predictions. The method accounts for all uncertainty terms from both numerical and input variables. Objective three is to compile a table of uncertainty parameters that could be used to estimate the error in a Computational Fluid Dynamics model of the Environmental Control System /spacecraft system.Previous studies have looked at the uncertainty in a Computational Fluid Dynamics model for a single output variable at a single point, for example the re-attachment length of a backward facing step. For the flow regime being analyzed (turbulent, three-dimensional, incompressible), the error at a single point can propagate into the solution both via flow physics and numerical methods. Calculating the uncertainty in using Computational Fluid Dynamics to accurately predict airflow speeds around encapsulated spacecraft in is imperative to the success of future missions.
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Date Issued: 2014
Identifier: CFE0005174, ucf:50662
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005174

Title: Development of an Adaptive Restoration Tool For a Self-Healing Smart Grid.
Creator: Golshani, Amir, Sun, Wei, Qu, Zhihua, Vosoughi, Azadeh, Zhou, Qun, Zheng, Qipeng, University of Central Florida
Abstract / Description: Large power outages become more commonplace due to the increase in both frequency and strength of natural disasters and cyber-attacks. The outages and blackouts cost American industries and business billions of dollars and jeopardize the lives of hospital patients. The losses can be greatlyreduced with a fast, reliable and flexible restoration tool. Fast recovery and successfully adapting to extreme events are critical to build a resilient, and ultimately self-healing power grid. This...
Show moreLarge power outages become more commonplace due to the increase in both frequency and strength of natural disasters and cyber-attacks. The outages and blackouts cost American industries and business billions of dollars and jeopardize the lives of hospital patients. The losses can be greatlyreduced with a fast, reliable and flexible restoration tool. Fast recovery and successfully adapting to extreme events are critical to build a resilient, and ultimately self-healing power grid. This dissertation is aimed to tackle the challenging task of developing an adaptive restoration decisionsupport system (RDSS). The RDSS determines restoration actions both in planning and real-time phases and adapts to constantly changing system conditions. First, an efficient network partitioning approach is developed to provide initial conditions for RDSS by dividing large outage network into smaller islands. Then, the comprehensive formulation of RDSS integrates different recovery phases into one optimization problem, and encompasses practical constraints including AC powerflow, dynamic reserve, and dynamic behaviors of generators and load. Also, a frequency constrained load recovery module is proposed and integrated into the RDSS to determine the optimal location and amount of load pickup. Next, the proposed RDSS is applied to harness renewable energy sources and pumped-storage hydro (PSH) units by addressing the inherent variabilities and uncertainties of renewable and coordinating wind and PSH generators. A two-stage stochastic and robust optimization problem is formulated, and solved by the integer L-shaped and column-and-constraintsgeneration decomposition algorithms. The developed RDSS tool has been tested onthe modified IEEE 39-bus and IEEE 57-bus systems under different scenarios. Numerical results demonstrate the effectiveness and efficiency of the proposed RDSS. In case of contingencies or unexpected outages during the restoration process, RDSS can quickly update the restoration plan and adapt to changing system conditions. RDSS is an important step toward a self-healing power grid and its implementation will reduce the recovery time while maintaining system security.
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Date Issued: 2017
Identifier: CFE0007284, ucf:52169
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007284

Title: THE PAY EQUITY DILEMMA WOMEN FACE AROUND THE WORLD.
Creator: McMurray, Lana D, Yayla-Kullu, Muge, University of Central Florida
Abstract / Description: In this research, I examine the pay equity dilemma women face around the world and how it is different in various regions of the world. My research question focuses on "how a nation's cultural characteristics affect pay equity?" It is already documented that men are paid more than women. The goal of this study is to explain how individual characteristics of national culture (such as masculinity, individualism, power distance, and uncertainty avoidance) impacts this inequality. By increasing...
Show moreIn this research, I examine the pay equity dilemma women face around the world and how it is different in various regions of the world. My research question focuses on "how a nation's cultural characteristics affect pay equity?" It is already documented that men are paid more than women. The goal of this study is to explain how individual characteristics of national culture (such as masculinity, individualism, power distance, and uncertainty avoidance) impacts this inequality. By increasing the understanding of pay inequality, changes can be made that will improve the lives of not just women but the families of those women and the world overall. We use data from Geert Hofstede's national culture dimensions and the Global Gender Gap Report by the World Economic Forum. Our results suggest that gender gap reduces in low power distance cultures, in high individualistic cultures, in low masculine cultures, and in low uncertainty avoidance cultures. Our results provide evidence that the economic prosperity of women around the world is significantly impacted by cultural dimensions.
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Date Issued: 2018
Identifier: CFH2000372, ucf:52906
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH2000372

Title: AN UNCERTAINTY QUANTIFICATION OF THE VARIATION OF INTERNAL HEAT TRANSFER COEFFICIENTS AND THE EFFECT ON AIRFOIL LIFE.
Creator: Marsh, Jan, Kapat, Jayanta, University of Central Florida
Abstract / Description: Uncertainty in accurately knowing applied internal heat transfer coefficients inside of a cooling passage can lead to variability in predicting low cycle fatigue life of a turbine vane or blade. Under-predicting a life value for a turbine part can have disastrous effects on the engine as a whole, and can negate efforts in innovative design for advanced cooling techniques for turbine components. Quantification of this fatigue life uncertainty utilizing a computational framework is the primary...
Show moreUncertainty in accurately knowing applied internal heat transfer coefficients inside of a cooling passage can lead to variability in predicting low cycle fatigue life of a turbine vane or blade. Under-predicting a life value for a turbine part can have disastrous effects on the engine as a whole, and can negate efforts in innovative design for advanced cooling techniques for turbine components. Quantification of this fatigue life uncertainty utilizing a computational framework is the primary objective of this thesis. Through the use of probabilistic design methodologies a process is developed to simulate uncertainties of internal heat transfer coefficient, which are then applied to the aft section of a non-rotating turbine blade component, internally cooled through a multi-pass serpentine channel. While keeping all other parameters constant internal heat transfer coefficients are varied according to a prescribed uncertainty range throughout the passages. The effect on the low cycle fatigue life of the airfoil is then evaluated at three discrete locations: near the base of the airfoil, towards the tip, and at mid-span. A generic low cycle fatigue life prediction model is used for these evaluations. Even though the probabilistic design process uses independent random numbers to simulate the variation, in reality, heat transfer coefficients at points located closely together should be correlated. For this reason, an autocorrelation function is implemented. By changing the value of this function the strength of the correlation of neighboring internal heat transfer coefficients to each other over a certain distance can be controlled. In order to test the effect that this correlation strength has on the low cycle fatigue life calculation, low and high values are chosen and analyzed. The magnitude of the prescribed uncertainty range of the internal heat transfer coefficient variation is varied to further study the effects on life. Investigated values include 5%, 10% and 20% for the straight ribbed passages and 10%, 20%, and 40% for both the tip and hub turns. As expected there is a significant dependence of low cycle fatigue life to the variation in internal heat transfer coefficients. For the 20/40% case, variations in life as high as 50-60% are recorded, furthermore a trend is observed showing that as the magnitude of the uncertainty range of internal heat transfer coefficients narrows so does the range of the low cycle fatigue life uncertainty.
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Date Issued: 2010
Identifier: CFE0003496, ucf:48975
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003496

Title: A Posteriori and Interactive Approaches for Decision-Making with Multiple Stochastic Objectives.
Creator: Bakhsh, Ahmed, Geiger, Christopher, Mollaghasemi, Mansooreh, Xanthopoulos, Petros, Wiegand, Rudolf, University of Central Florida
Abstract / Description: Computer simulation is a popular method that is often used as a decision support tool in industry to estimate the performance of systems too complex for analytical solutions. It is a tool that assists decision-makers to improve organizational performance and achieve performance objectives in which simulated conditions can be randomly varied so that critical situations can be investigated without real-world risk. Due to the stochastic nature of many of the input process variables in simulation...
Show moreComputer simulation is a popular method that is often used as a decision support tool in industry to estimate the performance of systems too complex for analytical solutions. It is a tool that assists decision-makers to improve organizational performance and achieve performance objectives in which simulated conditions can be randomly varied so that critical situations can be investigated without real-world risk. Due to the stochastic nature of many of the input process variables in simulation models, the output from the simulation model experiments are random. Thus, experimental runs of computer simulations yield only estimates of the values of performance objectives, where these estimates are themselves random variables.Most real-world decisions involve the simultaneous optimization of multiple, and often conflicting, objectives. Researchers and practitioners use various approaches to solve these multiobjective problems. Many of the approaches that integrate the simulation models with stochastic multiple objective optimization algorithms have been proposed, many of which use the Pareto-based approaches that generate a finite set of compromise, or tradeoff, solutions. Nevertheless, identification of the most preferred solution can be a daunting task to the decision-maker and is an order of magnitude harder in the presence of stochastic objectives. However, to the best of this researcher's knowledge, there has been no focused efforts and existing work that attempts to reduce the number of tradeoff solutions while considering the stochastic nature of a set of objective functions.In this research, two approaches that consider multiple stochastic objectives when reducing the set of the tradeoff solutions are designed and proposed. The first proposed approach is an a posteriori approach, which uses a given set of Pareto optima as input. The second approach is an interactive-based approach that articulates decision-maker preferences during the optimization process. A detailed description of both approaches is given, and computational studies are conducted to evaluate the efficacy of the two approaches. The computational results show the promise of the proposed approaches, in that each approach effectively reduces the set of compromise solutions to a reasonably manageable size for the decision-maker. This is a significant step beyond current applications of decision-making process in the presence of multiple stochastic objectives and should serve as an effective approach to support decision-making under uncertainty.
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Date Issued: 2013
Identifier: CFE0004973, ucf:49574
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004973

Title: JEALOUSY AND ATTACHMENT 2.0: THE ROLE OF ATTACHMENT IN THE EXPRESSION AND EXPERIENCE OF JEALOUSY ON FACEBOOK.
Creator: Cole, Megan, Weger, Harry, University of Central Florida
Abstract / Description: The main objective of this research was to investigate how people use Facebook within the context of their romantic relationships from an attachment theory perspective. In the present study, a convenience sample (n = 179) completed an online survey with questions about Facebook use, attachment style, uncertainty-related behaviors, jealousy, relationship satisfaction and commitment. Results indicate that 1) there is a positive correlation between jealousy and Facebook use; 2) also, there is a...
Show moreThe main objective of this research was to investigate how people use Facebook within the context of their romantic relationships from an attachment theory perspective. In the present study, a convenience sample (n = 179) completed an online survey with questions about Facebook use, attachment style, uncertainty-related behaviors, jealousy, relationship satisfaction and commitment. Results indicate that 1) there is a positive correlation between jealousy and Facebook use; 2) also, there is a positive correlation between jealousy and the time an individual spends viewing their partnerÃ‚Â's profile; 3) further, jealousy is positively related to uncertainty-reducing behaviors. Taken together, these results support the assertion that there is a downward spiral involving jealousy and Facebook. Results also showed that there are two types of uncertainty-related behaviors: antisocial behaviors and territorial behaviors. Anxious-ambivalent attachment styles were found to engage in antisocial behaviors the most, whereas secure individuals engaged in antisocial behaviors the least. The findings provide ample areas for future research on social networking sites and relationship variables.
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Date Issued: 2010
Identifier: CFE0003078, ucf:48329
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003078

Title: UNCERTAINTY, IDENTIFICATION, AND PRIVACY: EXPERIMENTS IN INDIVIDUAL DECISION-MAKING.
Creator: Rivenbark, David, Harrison, Glenn, University of Central Florida
Abstract / Description: The alleged privacy paradox states that individuals report high values for personal privacy, while at the same time they report behavior that contradicts a high privacy value. This is a misconception. Reported privacy behaviors are explained by asymmetric subjective beliefs. Beliefs may or may not be uncertain, and non-neutral attitudes towards uncertainty are not necessary to explain behavior. This research was conducted in three related parts. Part one presents an experiment in individual...
Show moreThe alleged privacy paradox states that individuals report high values for personal privacy, while at the same time they report behavior that contradicts a high privacy value. This is a misconception. Reported privacy behaviors are explained by asymmetric subjective beliefs. Beliefs may or may not be uncertain, and non-neutral attitudes towards uncertainty are not necessary to explain behavior. This research was conducted in three related parts. Part one presents an experiment in individual decision making under uncertainty. EllsbergÃ‚Â's canonical two-color choice problem was used to estimate attitudes towards uncertainty. Subjects believed bets on the color ball drawn from EllsbergÃ‚Â's ambiguous urn were equally likely to pay. Estimated attitudes towards uncertainty were insignificant. Subjective expected utility explained subjectsÃ‚Â' choices better than uncertainty aversion and the uncertain priors model. A second treatment tested Vernon SmithÃ‚Â's conjecture that preferences in EllsbergÃ‚Â's problem would be unchanged when the ambiguous lottery is replaced by a compound objective lottery. The use of an objective compound lottery to induce uncertainty did not affect subjectsÃ‚Â' choices. The second part of this dissertation extended the concept of uncertainty to commodities where quality and accuracy of a quality report were potentially ambiguous. The uncertain priors model is naturally extended to allow for potentially different attitudes towards these two sources of uncertainty, quality and accuracy. As they relate to privacy, quality and accuracy of a quality report are seen as metaphors for online security and consumer trust in e-commerce, respectively. The results of parametric structural tests were mixed. Subjects made choices consistent with neutral attitudes towards uncertainty in both the quality and accuracy domains. However, allowing for uncertainty aversion in the quality domain and not the accuracy domain outperformed the alternative which only allowed for uncertainty aversion in the accuracy domain. Finally, part three integrated a public-goods game and punishment opportunities with the Becker-DeGroot-Marschak mechanism to elicit privacy values, replicating previously reported privacy behaviors. The procedures developed elicited punishment (consequence) beliefs and information confidentiality beliefs in the context of individual privacy decisions. Three contributions are made to the literature. First, by using cash rewards as a mechanism to map actions to consequences, the study eliminated hypothetical bias as a confounding behavioral factor which is pervasive in the privacy literature. Econometric results support the Ã‚Â"privacy paradoxÃ‚Â" at levels greater than 10 percent. Second, the roles of asymmetric beliefs and attitudes towards uncertainty were identified using parametric structural likelihood methods. Subjects were, in general, uncertainty neutral and believed Ã‚Â"badÃ‚Â" events were more likely to occur when their private information was not confidential. A third contribution is a partial test to determine which uncertain process, loss of privacy or the resolution of consequences, is of primary importance to individual decision-makers. Choices were consistent with uncertainty neutral preferences in both the privacy and consequences domains.
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Date Issued: 2010
Identifier: CFE0003251, ucf:48539
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003251

Title: STRESS AND PERFORMANCE IN UNCERTAINTY-AVOIDING INDIVIDUALS: AN INTRODUCTORY LITERATURE REVIEW.
Creator: Stowers, Kimberly, Salas, Eduardo, University of Central Florida
Abstract / Description: Uncertainty avoidance as a cultural construct has been known to affect worker stress and performance in organizations, but a review of these findings has not been done up until this point. In effort to clarify the relationship between uncertainty avoidance and stress and performance, a comprehensive literature search was performed. Findings from articles on this topic have been presented. In addition, organizational practices for accommodating uncertainty avoidance and other cultural...
Show moreUncertainty avoidance as a cultural construct has been known to affect worker stress and performance in organizations, but a review of these findings has not been done up until this point. In effort to clarify the relationship between uncertainty avoidance and stress and performance, a comprehensive literature search was performed. Findings from articles on this topic have been presented. In addition, organizational practices for accommodating uncertainty avoidance and other cultural dimensions have been explored. This review shows that uncertainty avoidance appears to be linked to higher stress, while its relationship to performance appears to depend on other factors. Best practices for accommodating uncertainty avoidance tend to include enhanced communication and structure. Ideas for future research on this topic are discussed.
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Date Issued: 2013
Identifier: CFH0004450, ucf:45125
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH0004450

Title: An Optimization of Thermodynamic Efficiency vs. Capacity for Communications Systems.
Creator: Rawlins, Gregory, Wocjan, Pawel, Wahid, Parveen, Georgiopoulos, Michael, Jones, W Linwood, Mucciolo, Eduardo, University of Central Florida
Abstract / Description: This work provides a fundamental view of the mechanisms which affect the power efficiency of communications processes along with a method for efficiency enhancement. Shannon's work is the definitive source for analyzing information capacity of a communications system but his formulation does not predict an efficiency relationship suitable for calculating the power consumption of a system, particularly for practical signals which may only approach the capacity limit. This work leverages...
Show moreThis work provides a fundamental view of the mechanisms which affect the power efficiency of communications processes along with a method for efficiency enhancement. Shannon's work is the definitive source for analyzing information capacity of a communications system but his formulation does not predict an efficiency relationship suitable for calculating the power consumption of a system, particularly for practical signals which may only approach the capacity limit. This work leverages Shannon's while providing additional insight through physical models which enable the calculation and improvement of efficiency for the encoding of signals. The proliferation of Mobile Communications platforms is challenging capacity of networks largely because of the ever increasing data rate at each node. This places significant power management demands on personal computing devices as well as cellular and WLAN terminals. The increased data throughput translates to shorter meantime between battery charging cycles and increased thermal footprint. Solutions are developed herein to counter this trend. Hardware was constructed to measure the efficiency of a prototypical Gaussian signal prior to efficiency enhancement. After an optimization was performed, the efficiency of the encoding apparatus increased from 3.125% to greater than 86% for a manageable investment of resources. Likewise several telecommunications standards based waveforms were also tested on the same hardware. The results reveal that the developed physical theories extrapolate in a very accurate manner to an electronics application, predicting the efficiency of single ended and differential encoding circuits before and after optimization.
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Date Issued: 2015
Identifier: CFE0006051, ucf:50994
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006051

Title: Integrated Sustainability Assessment Framework for the U.S. Transportation.
Creator: Onat, Nuri, Tatari, Omer, Nam, Boo Hyun, Oloufa, Amr, Pazour, Jennifer, University of Central Florida
Abstract / Description: This dissertation aims to investigate the sustainability impacts of alternative vehicle technologies and develop comprehensive sustainability assessment frameworks to analyze potential impacts of these vehicles in the U.S. In order to assess sustainability impact of vehicle alternatives, life-cycle based models has been extensively used in the literature. Although life cycle-based models are often used for environmental impacts of alternative vehicles, analysis of social and economic impacts...
Show moreThis dissertation aims to investigate the sustainability impacts of alternative vehicle technologies and develop comprehensive sustainability assessment frameworks to analyze potential impacts of these vehicles in the U.S. In order to assess sustainability impact of vehicle alternatives, life-cycle based models has been extensively used in the literature. Although life cycle-based models are often used for environmental impacts of alternative vehicles, analysis of social and economic impacts of these vehicles has gained a tremendous interest. In this regard, there is a growing interest among the international platform and academia to use the Life Cycle Sustainability Assessment framework to have more informed sustainable products, material and technology choices by considering the environmental, as well as social and economic impacts. The Life Cycle Sustainability Assessment framework is still under development and there is an ongoing research to advance it for future applications. In this dissertation, current and future needs of sustainability assessment frameworks and the U.S. transportation are identified and addressed. The major research gaps are identified as follows: (1) there has been small emphasis on effects of spatial and temporal variations on the sustainability impacts of alternative vehicle technologies, (2) no national research efforts as of now have been directed specifically toward understanding the fundamental relationship between the adoption of electric vehicles and water demand, (3) there has been a lack of understanding the dynamic complexity of transportation sustainability, encompassing feedback mechanisms, and interdependencies, for the environmental, social, and economic impacts of alternative vehicles, and (4) there is no emphasis on addressing uncertainties inherent to the U.S. transportation and its complex relationships with the environment, society, and economy.The environmental, economic, and social impacts of alternative vehicles are highly critical for truly assessing and understanding the long-term sustainability of vehicles and propose economically viable, socially acceptable, and environmentally-friendly transportation solutions for U.S. passenger transportation. This dissertation provides a more comprehensive sustainability assessment framework by realizing following objectives: (1) inclusion of spatial and temporal variations when quantifying carbon, energy, and water footprints of alternative vehicle technologies, (2) quantifying environmental, social, and economic impacts of alternative vehicle technologies, (3) capturing the dynamic relations among the parameters of U.S. transportation system, environment, society, and the economy, (4) dealing with uncertainties inherent to the U.S. transportation sector considering the complexity of the system and dynamic relationships. The results of this dissertation reveal that the results with consideration of uncertainties, temporal and spatial variations, and dynamic complex relationships among the system variables can be significantly different than those of without consideration of those. Therefore, when developing policies the robustness of proposed scenarios should be valuated with consideration of uncertainties, temporal and spatial variations as well as the dynamic feedback mechanisms. The outcomes of this study can pave the way for advancement in the state-of-the-art and state-of-the-practice in the sustainability research by presenting novel approaches to deal with uncertainties and complex systems.
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Date Issued: 2015
Identifier: CFE0005857, ucf:50904
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005857

Uncertainty (6)	+ -
uncertainty (4)	+ -
interdependence (2)	+ -
Agent Based Modeling (1)	+ -
Alternative Vehicle Technologies (1)	+ -

CFD (1)	+ -
COMPUTATIONAL FLUID DYNAMICS (1)	+ -
Confidence Level (1)	+ -
Consideration Set (1)	+ -
Construction (1)	+ -
Correlation (1)	+ -
Data-Driven (1)	+ -
Decision Accuracy (1)	+ -
Decision Support System (1)	+ -
Decision-Making (1)	+ -
Design (1)	+ -
Discrete event simulation (1)	+ -
ENVIRONMENTAL CONTROL SYSTEMS (1)	+ -
Economic analysis (1)	+ -
Electric Vehicles (1)	+ -
Ellsberg (1)	+ -
Energy (1)	+ -
Environmental Damage Cost (1)	+ -
Exploratory Modeling and Analysis (1)	+ -
Facebook (1)	+ -
Family of Models (1)	+ -
Finite Element Model (1)	+ -
GDSS (1)	+ -
GPM (1)	+ -
Geert Hofstede (1)	+ -

ETD Collection (21)	+ -
Honors Collection (3)	+ -

University of Central Florida (24)	+ -
Oloufa, Amr (3)	+ -
Xanthopoulos, Petros (3)	+ -
Jones, W Linwood (2)	+ -
Nam, Boo Hyun (2)	+ -

Pazour, Jennifer (2)	+ -
Pet-Armacost, Julia (2)	+ -
Tatari, Omer (2)	+ -
Weger, Harry (2)	+ -
Zheng, Qipeng (2)	+ -
Abdel-Aty, Mohamed (1)	+ -
Akhavian, Reza (1)	+ -
Amini, Hamid (1)	+ -
Bakhsh, Ahmed (1)	+ -
Batarseh, Ola (1)	+ -
Behzadan, Amir (1)	+ -
Catbas, Fikret (1)	+ -
Chen, Ruiyao (1)	+ -
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Das, Tuhin (1)	+ -
DeMara, Ronald (1)	+ -
Fort, Travis (1)	+ -
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Georgiopoulos, Michael (1)	+ -
Gokce, Hasan (1)	+ -
Golshani, Amir (1)	+ -
Groves, Curtis (1)	+ -
Harrison, Glenn (1)	+ -

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