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Title: PSEUDOQUOTIENTS: CONSTRUCTION, APPLICATIONS, AND THEIR FOURIER TRANSFORM.
Creator: Khosravi, Mehrdad, Mikusinski, Piotr, University of Central Florida
Abstract / Description: A space of pseudoquotients can be described as a space of either single term quotients (the injective case) or the quotient of sequences (the non-injective case) where the parent sets for the numerator and the denominator satisfy particular conditions. The first part of this project is concerned with the minimal of conditions required to have a well-defined set of pseudoquotients. We continue by adding more structure to our sets and discuss the effect on the resultant pseudoquotient....
Show moreA space of pseudoquotients can be described as a space of either single term quotients (the injective case) or the quotient of sequences (the non-injective case) where the parent sets for the numerator and the denominator satisfy particular conditions. The first part of this project is concerned with the minimal of conditions required to have a well-defined set of pseudoquotients. We continue by adding more structure to our sets and discuss the effect on the resultant pseudoquotient. Pseudoquotients can be thought of as extensions of the parent set for the numerator since they include a natural embedding of that set. We answer some questions about the extension properties. One family of these questions involves assuming a structure (algebraic or topological) on a set and asking if the set of pseudoquotients generated has the same structure. A second family of questions looks at maps between two sets and asks if there is an extension of that map between the corresponding pseudoquotients? If so, do the properties of the original map survive the extension? The result of our investigations on the abstract setting will be compared with some well-known spaces of pseudoquotients and Boehmians (a particular case of non-injective pseudoquotients). We will show that the conditions discussed in the first part are satisfied and we will use that to reach conclusions about our extension spaces and the extension maps. The Fourier transform is one of the maps that we will continuously revisit and discuss. Finally many spaces of Boehmians have been introduced where the initial set is a particular class of functions on either locally compact groups R and or a compact group such as a sphere. The natural question is, can we generalize the construction to any locally compact group. In some previous work such construction is discussed, however here we go further; we use characters and define the Fourier transform of integrable and square integrable Boehmians on a locally compact group. Then we discuss the properties of such transform.
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Date Issued: 2008
Identifier: CFE0002186, ucf:47893
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002186

Title: The Relationship between Agile Project Management and Project Success Outcomes.
Creator: Bergmann, Thomas, Karwowski, Waldemar, Elshennawy, Ahmad, Hancock, Peter, Mikusinski, Piotr, University of Central Florida
Abstract / Description: Agile project management (APM) has recently emerged as a new approach to managing complex projects. Some experts believe that APM will become the standard project management approach used in the 21st century. However, thus far, the role of agility in project management has not been widely investigated. In the recent past, the concept of agility has mainly been applied to software development projects. The literature on agility is still in its early stages, and further research needs to be...
Show moreAgile project management (APM) has recently emerged as a new approach to managing complex projects. Some experts believe that APM will become the standard project management approach used in the 21st century. However, thus far, the role of agility in project management has not been widely investigated. In the recent past, the concept of agility has mainly been applied to software development projects. The literature on agility is still in its early stages, and further research needs to be conducted in new project management domains.This study is intended to determine the impact of the adoption of APM on project success as perceived by project managers. This investigative approach can be applied to any project domain. In addition, the influencing effects of project complexity on the results of projects are analyzed. Through an analysis of the existing literature, critical success factors and success criteria are identified to develop a model that can be used to assess current APM practice.The research questions are answered by means of an empirical study that collected data using an online survey that was distributed to project managers located across the United States. Confirmatory factor analysis and structural equation modeling are performed to gauge the validity of the proposed research model.The study results show a significant positive relationship between APM and project success. Furthermore, a weak negative association is identified between project complexity and project success, suggesting a need for further research into and refinement of the project complexity construct. Finally, the results reveal an apparent need for additional education and certification in the field of project management, which are expected to lead to an increased use of agile approaches to project management in the future.
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Date Issued: 2018
Identifier: CFE0007391, ucf:52070
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007391

Title: A study of nonlinear dynamics of EEG responses to simulated unmanned vehicle tasks.
Creator: Xu, Ziqing, Karwowski, Waldemar, Hancock, Peter, Reinerman, Lauren, Mikusinski, Piotr, University of Central Florida
Abstract / Description: In the contemporary world, mental workload becomes higher as technology evolves and task demand becomes overwhelming. The operators of a system are usually required to complete tasks with higher complicity within a shorter period of time. Continuous operation under a high level of mental workload can be a major source of risk and human error, thus put the operator in a hazardous working environment. Therefore, it is necessary to monitor and assess mental workload. In this study, an unmanned...
Show moreIn the contemporary world, mental workload becomes higher as technology evolves and task demand becomes overwhelming. The operators of a system are usually required to complete tasks with higher complicity within a shorter period of time. Continuous operation under a high level of mental workload can be a major source of risk and human error, thus put the operator in a hazardous working environment. Therefore, it is necessary to monitor and assess mental workload. In this study, an unmanned vehicle operation with visual detection tasks was investigated by means of nonlinear analysis of EEG time series. Nonlinear analysis is considered more advantageous compared with traditional power spectrum analysis of EEG. Besides, nonlinear analysis is more capable to capture the nature of EEG data and human performance, which is a process that subjects to constant changes. By examining the nonlinear dynamics of EEG, it is more likely to obtain a deeper understanding of brain activity.The objective of this study is to investigate the mental workload under different task levels through the examination of brain activity via nonlinear dynamics of EEG time series in simulated unmanned ground vehicle visual detection tasks.The experiment was conducted by the team lead by Dr. Lauren Reinerman Jones at Institute for Simulation (&) Training, University of Central Florida. One hundred and fifty subjects participated the experiment to complete four visual detection task scenarios (1) change detection, (2) threat detection task, (3) dual task with different change detection task rates, and (4) dual task with different threat detection task rates. Their EEG was recorded during performing the tasks at nine EEG channels. This study develops a massive data processing program to calculate the largest Lyapunov exponent, correlation dimension of the EEG data. This study also develops the program for performing 0-1 test on the EEG data in Python language environment. The result of this study verifies the existence of chaotic dynamics in EEG time series, reveals the change in brain activity as the effect of changing task demand in more detailed level, and obtains new insights from the psychophysiological mental workload measurement used in the preliminary study. The results of this study verified the existence of the chaotic dynamics in the EEG time series. This study also supported the hypothesis that EEG data exhibits change in the level of nonlinearity corresponding to differed task levels. The nonlinear analysis of EEG time series data is able to discriminate the change in brain activity derived from the changes in task load. All nonlinear dynamics analysis techniques used in this study is able to find the difference of nonlinearity in EEG among task levels, as well as between single task scenario and dual task scenario.
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Date Issued: 2019
Identifier: CFE0007558, ucf:52615
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007558

Title: Iteratively Reweighted Least Squares Minimization with Prior Information: A New Approach.
Creator: Popov, Dmitriy, Li, Xin, Moore, Brian, Mikusinski, Piotr, University of Central Florida
Abstract / Description: Iteratively reweighted least squares (IRLS) algorithms provide an alternative to the more standard L1-minimization approach in compressive sensing. Daubechies et al. introduced a particularly stable version of an IRLS algorithm and rigorously proved its convergence in 2010. They did not, however, consider the case in which prior information on the support of the sparse domain of the solution is available. In 2009, Miosso et al. proposed an IRLS algorithm that makes use of this information to...
Show moreIteratively reweighted least squares (IRLS) algorithms provide an alternative to the more standard L1-minimization approach in compressive sensing. Daubechies et al. introduced a particularly stable version of an IRLS algorithm and rigorously proved its convergence in 2010. They did not, however, consider the case in which prior information on the support of the sparse domain of the solution is available. In 2009, Miosso et al. proposed an IRLS algorithm that makes use of this information to further reduce the number of measurements required to recover the solution with specified accuracy. Although Miosso et al. obtained a number of simulation results strongly confirming the utility of their approach, they did not rigorously establish the convergence properties of their algorithm. In this paper, we introduce prior information on the support of the sparse domain of the solution into the algorithm of Daubechies et al. We then provide a rigorous proof of the convergence of the resulting algorithm.
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Date Issued: 2011
Identifier: CFE0004154, ucf:49082
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004154

Title: Assessing Safety Culture among Personnel in Governmental Construction Sites at Saudi Arabia: A Quantitative Study Approach.
Creator: Alrehaili, Omar, Karwowski, Waldemar, Elshennawy, Ahmad, Hancock, Peter, Mikusinski, Piotr, University of Central Florida
Abstract / Description: Safety is an essential issue for organizations to survive, especially for hazardous industries such as the construction industry. The construction industry is considered to be one of the major industries that help in the growth of the economy and the infrastructure of all countries. Recently, scholars have paid increasing attention to the concept of safety culture due to its role in decreasing the occurrences of accidents and injuries. Safety culture has become the focus of all industries and...
Show moreSafety is an essential issue for organizations to survive, especially for hazardous industries such as the construction industry. The construction industry is considered to be one of the major industries that help in the growth of the economy and the infrastructure of all countries. Recently, scholars have paid increasing attention to the concept of safety culture due to its role in decreasing the occurrences of accidents and injuries. Safety culture has become the focus of all industries and has received much attention in recent years, especially within the construction industry. Absence of this culture is a major cause of injuries and accidents in the construction field. In the construction industry, personnel's perception of safety culture is vital to prevent accidents or behavior misconduct. Also, focusing on personnel's safety culture on construction sites provides an opportunity to decrease risks and unsafe behaviors to improve the overall safety level. Workers' performance and behaviors are shaped by their awareness and view of safety culture inside their work environment. Generally, safety performance in the construction field is still unsatisfactory based on reporting records.The present study observed the influence of safety culture on construction's personnel's safety performance on large governmental construction projects in Saudi Arabia. Construction personnel's safety performance is measured by their attitude toward violations and error behaviors. This research also exams the role of personnel's motivation toward construction safety as a mediating variable between construction safety culture and safety performance constructs, including error and violation behaviors. The research adopted a quantitative method by using a questionnaire for the purpose of data collection and analysis. A total of 434 questionnaires were collected from construction personnel including project managers, engineers, and supervisors through their voluntary participation in this study. Statistical analysis was used to analyze the data collected including descriptive statistics, confirmatory factor analysis (CFA) and structural equation modeling (SEM) techniques. Confirmatory factor analysis is used for validating each factor with its measurable items. Finally, this study applied the concept of structural equation modeling (SEM) to evaluate the correlation between all latent variables in the study's conceptualized model.The outcomes of the study show that safety culture has a direct influence on construction personnel's attitudes toward violations and an indirect effect on construction personnel's error behavior. Furthermore, safety culture has a significant effect on improving safety motivation, as well. Safety motivation for construction safety has a direct effect on errors behaviors. Conversely, safety motivation does not have a mediating effect on construction personnel's attitudes toward violations. Therefore, safety motivation's mediating role was significant only between safety culture and errors behaviors.This research has added to the existing knowledge about the important part of safety culture as a key interpreter of safety performance in construction field. The current study contributes to psychological safety through examining the influence of safety culture as the interpreter for enhancing motivation for construction safety. Additionally, this research evaluated safety culture's influence on construction personnel's attitudes toward violations and construction personnel's error behavior. The outcomes of the study are useful and recommended to be used by construction management to better pinpoint the reasons for unsafe behaviors within the construction industry. The results of this research highlights management's role in determining, and affecting, workers' behaviors.
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Date Issued: 2016
Identifier: CFE0006434, ucf:51470
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006434

Title: Agent-Based and System Dynamics Hybrid Modeling and Simulation Approach Using Systems Modeling Language.
Creator: Soyler Akbas, Asli, Karwowski, Waldemar, Geiger, Christopher, Kincaid, John, Mikusinski, Piotr, University of Central Florida
Abstract / Description: Agent-based (AB) and system dynamics (SD) modeling and simulation techniques have been studied and used by various research fields. After the new hybrid modeling field emerged, the combination of these techniques started getting attention in the late 1990's. Applications of using agent-based (AB) and system dynamics (SD) hybrid models for simulating systems have been demonstrated in the literature. However, majority of the work on the domain includes system specific approaches where the...
Show moreAgent-based (AB) and system dynamics (SD) modeling and simulation techniques have been studied and used by various research fields. After the new hybrid modeling field emerged, the combination of these techniques started getting attention in the late 1990's. Applications of using agent-based (AB) and system dynamics (SD) hybrid models for simulating systems have been demonstrated in the literature. However, majority of the work on the domain includes system specific approaches where the models from two techniques are integrated after being independently developed. Existing work on creating an implicit and universal approach is limited to conceptual modeling and structure design. This dissertation proposes an approach for generating AB-SD hybrid models of systems by using Systems Modeling Language (SysML) which can be simulated without exporting to another software platform. Although the approach is demonstrated using IBM's Rational Rhapsody(&)#174; it is applicable to all other SysML platforms. Furthermore, it does not require prior knowledge on agent-based or system dynamics modeling and simulation techniques and limits the use of any programming languages through the use of SysML diagram tools. The iterative modeling approach allows two-step validations, allows establishing a two-way dynamic communication between AB and SD variables and develops independent behavior models that can be reused in representing different systems. The proposed approach is demonstrated using a hypothetical population, movie theater and a real(-)world training management scenarios. In this setting, the work provides methods for independent behavior and system structure modeling. Finally, provides behavior models for probabilistic behavior modeling and time synchronization.
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Date Issued: 2015
Identifier: CFE0006399, ucf:51517
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006399

Title: A Simulation-Based Evaluation Of Efficiency Strategies For A Primary Care Clinic With Unscheduled Visits.
Creator: Bobbie, Afrifah, Karwowski, Waldemar, Thompson, William, Elshennawy, Ahmad, Mikusinski, Piotr, University of Central Florida
Abstract / Description: In the health care industry, there are strategies to remove inefficiencies from the health delivery process called efficiency strategies. This dissertation proposed a simulation model to evaluate the impact of the efficiency strategies on a primary care clinic with unscheduled "walk-in" patient visits. The simulation model captures the complex characteristics of the Orlando Veteran's Affairs Medical Center (VAMC) primary care clinic. This clinic system includes different types of patients,...
Show moreIn the health care industry, there are strategies to remove inefficiencies from the health delivery process called efficiency strategies. This dissertation proposed a simulation model to evaluate the impact of the efficiency strategies on a primary care clinic with unscheduled "walk-in" patient visits. The simulation model captures the complex characteristics of the Orlando Veteran's Affairs Medical Center (VAMC) primary care clinic. This clinic system includes different types of patients, patient paths, and multiple resources that serve them. Added to the problem complexity is the presence of patient no-shows characteristics and unscheduled patient arrivals, a problem which has been until recently, largely neglected. The main objectives of this research were to develop a model that captures the complexities of the Orlando VAMC, evaluate alternative scenarios to work in unscheduled patient visits, and examine the impact of patient flow, appointment scheduling, and capacity management decisions on the performance of the primary care clinic system. The main results show that only a joint policy of appointment scheduling rules and patient flow decisions has a significant impact on the wait time of scheduled patients. It is recommended that in the future the clinic addresses the problem of serving additional walk-in patients from an integrated scheduling and patient flow viewpoint.
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Date Issued: 2016
Identifier: CFE0006443, ucf:51462
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006443

Title: Investigating The Relationship Between Adverse Events and Infrastructure Development in an Active War Theater Using Soft Computing Techniques.
Creator: Cakit, Erman, Karwowski, Waldemar, Lee, Gene, Thompson, William, Mikusinski, Piotr, University of Central Florida
Abstract / Description: The military recently recognized the importance of taking sociocultural factors into consideration. Therefore, Human Social Culture Behavior (HSCB) modeling has been getting much attention in current and future operational requirements to successfully understand the effects of social and cultural factors on human behavior. There are different kinds of modeling approaches to the data that are being used in this field and so far none of them has been widely accepted. HSCB modeling needs the...
Show moreThe military recently recognized the importance of taking sociocultural factors into consideration. Therefore, Human Social Culture Behavior (HSCB) modeling has been getting much attention in current and future operational requirements to successfully understand the effects of social and cultural factors on human behavior. There are different kinds of modeling approaches to the data that are being used in this field and so far none of them has been widely accepted. HSCB modeling needs the capability to represent complex, ill-defined, and imprecise concepts, and soft computing modeling can deal with these concepts. There is currently no study on the use of any computational methodology for representing the relationship between adverse events and infrastructure development investments in an active war theater. This study investigates the relationship between adverse events and infrastructure development projects in an active war theater using soft computing techniques including fuzzy inference systems (FIS), artificial neural networks (ANNs), and adaptive neuro-fuzzy inference systems (ANFIS) that directly benefits from their accuracy in prediction applications. Fourteen developmental and economic improvement project types were selected based on allocated budget values and a number of projects at different time periods, urban and rural population density, and total adverse event numbers at previous month selected as independent variables. A total of four outputs reflecting the adverse events in terms of the number of people killed, wounded, hijacked, and total number of adverse events has been estimated. For each model, the data was grouped for training and testing as follows: years between 2004 and 2009 (for training purpose) and year 2010 (for testing). Ninety-six different models were developed and investigated for Afghanistan and the country was divided into seven regions for analysis purposes. Performance of each model was investigated and compared to all other models with the calculated mean absolute error (MAE) values and the prediction accuracy within (&)#177;1 error range (difference between actual and predicted value). Furthermore, sensitivity analysis was performed to determine the effects of input values on dependent variables and to rank the top ten input parameters in order of importance.According to the the results obtained, it was concluded that the ANNs, FIS, and ANFIS are useful modeling techniques for predicting the number of adverse events based on historical development or economic projects' data. When the model accuracy was calculated based on the MAE for each of the models, the ANN had better predictive accuracy than FIS and ANFIS models in general as demonstrated by experimental results. The percentages of prediction accuracy with values found within (&)#177;1 error range around 90%. The sensitivity analysis results show that the importance of economic development projects varies based on the regions, population density, and occurrence of adverse events in Afghanistan. For the purpose of allocating resources and development of regions, the results can be summarized by examining the relationship between adverse events and infrastructure development in an active war theater; emphasis was on predicting the occurrence of events and assessing the potential impact of regional infrastructure development efforts on reducing number of such events.
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Date Issued: 2013
Identifier: CFE0004826, ucf:49757
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004826

Title: Accelerated Life Model with Various Types of Censored Data.
Creator: Pridemore, Kathryn, Pensky, Marianna, Mikusinski, Piotr, Swanson, Jason, Nickerson, David, University of Central Florida
Abstract / Description: The Accelerated Life Model is one of the most commonly used tools in the analysis of survival data which are frequently encountered in medical research and reliability studies. In these types of studies we often deal with complicated data sets for which we cannot observe the complete data set in practical situations due to censoring. Such difficulties are particularly apparent by the fact that there is little work in statistical literature on the Accelerated Life Model for complicated types...
Show moreThe Accelerated Life Model is one of the most commonly used tools in the analysis of survival data which are frequently encountered in medical research and reliability studies. In these types of studies we often deal with complicated data sets for which we cannot observe the complete data set in practical situations due to censoring. Such difficulties are particularly apparent by the fact that there is little work in statistical literature on the Accelerated Life Model for complicated types of censored data sets, such as doubly censored data, interval censored data, and partly interval censored data.In this work, we use the Weighted Empirical Likelihood approach (Ren, 2001) to construct tests, confidence intervals, and goodness-of-fit tests for the Accelerated Life Model in a unified way for various types of censored data. We also provide algorithms for implementation and present relevant simulation results.I began working on this problem with Dr. Jian-Jian Ren. Upon Dr. Ren's departure from the University of Central Florida I completed this dissertation under the supervision of Dr. Marianna Pensky.
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Date Issued: 2013
Identifier: CFE0004913, ucf:49613
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004913

Title: Cost-Sensitive Learning-based Methods for Imbalanced Classification Problems with Applications.
Creator: Razzaghi, Talayeh, Xanthopoulos, Petros, Karwowski, Waldemar, Pazour, Jennifer, Mikusinski, Piotr, University of Central Florida
Abstract / Description: Analysis and predictive modeling of massive datasets is an extremely significant problem that arises in many practical applications. The task of predictive modeling becomes even more challenging when data are imperfect or uncertain. The real data are frequently affected by outliers, uncertain labels, and uneven distribution of classes (imbalanced data). Such uncertainties createbias and make predictive modeling an even more difficult task. In the present work, we introduce a cost-sensitive...
Show moreAnalysis and predictive modeling of massive datasets is an extremely significant problem that arises in many practical applications. The task of predictive modeling becomes even more challenging when data are imperfect or uncertain. The real data are frequently affected by outliers, uncertain labels, and uneven distribution of classes (imbalanced data). Such uncertainties createbias and make predictive modeling an even more difficult task. In the present work, we introduce a cost-sensitive learning method (CSL) to deal with the classification of imperfect data. Typically, most traditional approaches for classification demonstrate poor performance in an environment with imperfect data. We propose the use of CSL with Support Vector Machine, which is a well-known data mining algorithm. The results reveal that the proposed algorithm produces more accurate classifiers and is more robust with respect to imperfect data. Furthermore, we explore the best performance measures to tackle imperfect data along with addressing real problems in quality control and business analytics.
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Date Issued: 2014
Identifier: CFE0005542, ucf:50298
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005542

Title: Modeling of Socio-Economic Factors and Adverse Events In an Active War Theater By Using a Cellular Automata Simulation Approach.
Creator: Bozkurt, Halil, Karwowski, Waldemar, Lee, Gene, Thompson, William, Mikusinski, Piotr, University of Central Florida
Abstract / Description: Department of Defense (DoD) implemented Human Social Cultural and Behavior (HSCB) program to meet the need to develop capability to understand, predict and shape human behavior among different cultures by developing a knowledge base, building models, and creating training capacity. This capability will allow decision makers to subordinate kinetic operations and promote non-kinetic operations to govern economic programs better in order to initiate efforts and development to address the...
Show moreDepartment of Defense (DoD) implemented Human Social Cultural and Behavior (HSCB) program to meet the need to develop capability to understand, predict and shape human behavior among different cultures by developing a knowledge base, building models, and creating training capacity. This capability will allow decision makers to subordinate kinetic operations and promote non-kinetic operations to govern economic programs better in order to initiate efforts and development to address the grievances among the displeased by adverse events. These non-kinetic operations include rebuilding indigenous institutions' bottom-up economic activity and constructing necessary infrastructure since the success in non-kinetic operations depends on understanding and using social and cultural landscape. This study aims to support decision makers by building a computational model to understand economic factors and their effect on adverse events.In this dissertation, the analysis demonstrates that the use of cellular automata has several significant contributions to support decision makers allocating development funds to stabilize regions with higher adverse event risks, and to better understand the complex socio-economic interactions with adverse events. Thus, this analysis was performed on a set of spatial data representing factors from social and economic data. In studying behavior using cellular automata, cells in the same neighborhood synchronously interact with each other to determine their next states, and small changes in iteration may yield to complex formations of adverse event risk after several iterations of time. The modeling methodology of cellular automata for social and economic analysis in this research was designed in two major implementation levels as follows: macro and micro-level. In the macro-level, the modeling framework integrates population, social, and economic sub-systems. The macro-level allows the model to use regionalized representations, while the micro-level analyses help to understand why the events have occurred. Macro-level subsystems support cellular automata rules to generate accurate predictions. Prediction capability of cellular automata is used to model the micro-level interactions between individual actors, which are represented by adverse events.The results of this dissertation demonstrate that cellular automata model is capable of evaluating socio-economic influences that result in changes in adverse events and identify location, time and impact of these events. Secondly, this research indicates that the socio-economic influences have different levels of impact on adverse events, defined by the number of people killed, wounded or hijacked. Thirdly, this research shows that the socio-economic, influences and adverse events that occurred in a given district have impacts on adverse events that occur in neighboring districts. The cellular automata modeling approach can be used to enhance the capability to understand and use human, social and behavioral factors by generating what-if scenarios to determine the impact of different infrastructure development projects to predict adverse events. Lastly, adverse events that could occur in upcoming years can be predicted to allow decision makers to deter these events or plan accordingly if these events do occur.
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Date Issued: 2013
Identifier: CFE0004820, ucf:49719
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004820

Title: Safety Climate and Safety Outcomes in Aircraft Maintenance: A Mediating Effect of Employee Turnover and Safety Motivation.
Creator: Alnoaimi, Muhanna, Karwowski, Waldemar, Xanthopoulos, Petros, Hancock, Peter, Mikusinski, Piotr, University of Central Florida
Abstract / Description: Aircraft maintenance is viewed as a critical safety component in general and military aviation industries, and thus it is crucial to identify the factors that may affect aircraft maintenance. Because the safety climate is considered as a leading indicator of safety performance and safety outcomes, this study utilized this safety climate approach to develop a model which can explain the relationships between employee turnover, safety motivation, self-reported unsafe acts, reporting unsafe...
Show moreAircraft maintenance is viewed as a critical safety component in general and military aviation industries, and thus it is crucial to identify the factors that may affect aircraft maintenance. Because the safety climate is considered as a leading indicator of safety performance and safety outcomes, this study utilized this safety climate approach to develop a model which can explain the relationships between employee turnover, safety motivation, self-reported unsafe acts, reporting unsafe behaviors, incidents, and injuries in the aviation maintenance environment. This study included a sample of 283 technicians in military aircraft maintenance units who participated in a cross-sectional random survey. Data collected were analyzed using Exploratory Factor Analysis (EFA) and Structural Equation Modeling (SEM) techniques. A structural model that fitted the data was developed which predicted 64% of the variance in employee turnover, 7% of the variance in safety motivation, 20% of the variance in unsafe acts, 41% of the variance in reporting unsafe behavior, and 21% of the variance in workplace injuries. The results indicate employees who report a perception of high turnover exhibit decreased safety motivation and increased unsafe acts which lead to higher levels of workplace injuries. The perception of safety climate was identified as an antecedent to safety performance and safety outcomes. Additionally, the effects of control variables such as age and education were tested. The implications for safety management in aircraft maintenance were also discussed. This study provides directions for future research on the turnover of aircraft maintenance technicians, safety performance, and safety outcomes.
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Date Issued: 2015
Identifier: CFE0005753, ucf:50097
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005753

Title: The effects of chronic sleep deprivation on sustained attention: A study of brain dynamic functional connectivity.
Creator: He, Yiling, Karwowski, Waldemar, Xanthopoulos, Petros, Hancock, Peter, Mikusinski, Piotr, University of Central Florida
Abstract / Description: It is estimated that about 35-40% of adults in the U.S. suffer from insufficient sleep. Chronic sleep deprivation has become a prevalent phenomenon because of contemporary lifestyle and work-related factors. Sleep deprivation can reduce the capabilities and efficiency of attentional performance by impairing perception, increasing effort to maintain concentration, as well as introducing vision disturbance. Thus, it is important to understand the neural mechanisms behind how chronic sleep...
Show moreIt is estimated that about 35-40% of adults in the U.S. suffer from insufficient sleep. Chronic sleep deprivation has become a prevalent phenomenon because of contemporary lifestyle and work-related factors. Sleep deprivation can reduce the capabilities and efficiency of attentional performance by impairing perception, increasing effort to maintain concentration, as well as introducing vision disturbance. Thus, it is important to understand the neural mechanisms behind how chronic sleep deprivation impairs sustained attention.In recent years, more attention has been paid to the study of the integration between anatomically distributed and functionally connected brain regions. Functional connectivity has been widely used to characterize brain functional integration, which measures the statistical dependency between neurophysiological events of the human brain. Further, evidence from recent studies has shown the non-stationary nature of brain functional connectivity, which may reveal more information about the human brain. Thus, the objective of this thesis is to investigate the effects of chronic sleep deprivation on sustained attention from the perspective of dynamic functional connectivity.A modified spatial cueing paradigm was used to assess human sustained attention in rested wakefulness and chronic sleep deprivation conditions. Partial least squares approach was applied to distinguish brain functional connectivity for the experimental conditions. With the integration of a sliding-window approach, dynamic patterns of brain functional connectivity were identified in two experimental conditions. The brain was modeled as a series of dynamic functional networks in each experimental condition. Graph theoretic analysis was performed to investigate the dynamic properties of brain functional networks, using network measures of clustering coefficient and characteristics path length.In the chronic sleep deprivation condition, a compensation mechanism between highly clustered organization and ineffective adaptability of brain functional networks was observed. Specifically, a highly clustered organization of brain functional networks was illustrated with a large clustering coefficient. This organization suggested that brain utilizes more connections to maintain attention in the chronic sleep deprivation condition. A smaller impact of clustering coefficient variation on characteristics path lengths indicated an ineffective adaptability of brain functional networks in the chronic sleep deprivation condition. In the rested wakefulness condition, brain functional networks showed the small-world topology in general, with the average small-world topology index larger than one. Small-world topology was identified as an optimal network structure with the balance between local information processing and global integration. Given the fluctuating values of the index over time, small-world brain networks were observed in most cases, indicating an effective adaptability of the human brain to maintain the dominance of small-world networks in the rested wakefulness condition. On the contrary, given that the average small-world topology index was smaller than one, brain functional networks generally exhibited random network structure. From the perspective of dynamic functional networks, even though there were few cases showing small-world brain networks, brain functional networks failed to maintain the dominance of small-world topology in the chronic sleep deprivation condition.In conclusion, to the best of our knowledge this thesis was the first to investigate the effects of chronic sleep deprivation on sustained attention from the perspective of dynamic brain functional connectivity. A compensation mechanism between highly clustered organization and ineffective adaptability of brain functional networks was observed in the chronic sleep deprivation condition. Furthermore, chronic sleep deprivation impaired sustained attention by reducing the effectiveness of brain functional networks' adaptability, resulting in the disrupted dominance of small-world brain networks.
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Date Issued: 2015
Identifier: CFE0006036, ucf:50990
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006036

Title: A Short Window Granger Causality Approach to Identify Brain Functional Pattern Associated with Changes of Performance Induced by Sleep Deprivation.
Creator: Li, Muyuan, Karwowski, Waldemar, Xanthopoulos, Petros, Hancock, Peter, Mikusinski, Piotr, University of Central Florida
Abstract / Description: The comprehensive effect of sleep deprivation on biological and behavioral functions largely remains unknown. There is evidence to support that human sleep must be of sufficient duration and physiological continuity to ensure neurocognitive performance while we are waking. Insufficient sleep would lead to high risk of human-error related to accidents, injuries or even fatal outcomes. However, in modern society, more and more people suffer from sleep deprivation because of the increasing...
Show moreThe comprehensive effect of sleep deprivation on biological and behavioral functions largely remains unknown. There is evidence to support that human sleep must be of sufficient duration and physiological continuity to ensure neurocognitive performance while we are waking. Insufficient sleep would lead to high risk of human-error related to accidents, injuries or even fatal outcomes. However, in modern society, more and more people suffer from sleep deprivation because of the increasing social, academic or occupational demand. It is important to study the effect of sleep deprivation, not only on task performance, but also on neurocognitive functions. Recent research that has explored brain effective connectivity has demonstrated the directed inference interaction among pairs of brain areas, which may bring important insight to understand how brain works to support neurocognitive function. This research aimed to identify the brain effective connectivity pattern associated with changes of a task performance, response time, following sleep deprivation. Experiments were conducted by colleagues at Neuroergonomics Department at Jagiellonian University, Krakow, Poland. Ten healthy young women, with an average age of 23-year-old, performed visual spatial sustained-attention tasks under two conditions: (1) the rest-wakeful (RW) condition, where participants had their usual sleep and (2) the sleep-deprived (SD) condition, where participants had 3 hours less sleep than their usual sleep, for 7 nights (amounting to 21 h of sleep debt).Measures included eye tracking performance and functional magnetic resonance imaging (fMRI). In each condition, each subject's eye-position was monitored through 13 sessions, each with 46 trials, while fMRI data was recorded. There were two task performance measures, accuracy and response time. Accuracy measured the proportion of correct responses of all trials in each session. Response time measured the average amount of milliseconds until participants gazed at the target stimuli in each session. An experimental session could be treated as a short window. By splitting long trials of fMRI data into consecutive windows, Granger causality was applied based on short trials of fMRI data. This procedure helped to calculate pairwise causal influences with respect to time-varying property in brain causal interaction. Causal influence results were then averaged across sessions to create one matrix for each participant. This matrix was averaged within each condition to formulate a model of brain effective connectivity, which also served as a basis of comparison. In conclusion, significant effect of sleep deprivation was found on response time and brain effective connectivity. In addition, the change of brain effective connectivity after sleep deprivation was linked to the change of response time. First, an analysis of variance (ANOVA) showed significant difference for response time between the RW condition and the SD condition. No significant changes for accuracy were found. A paired t-test showed that response time was significantly shorter in sleep deprivation for the visual spatial sustained-attention task. Second, Granger causality analysis demonstrated a reduction of bidirectional connectivity and an increase of directed influences from low-level brain areas to high-level brain areas after sleep deprivation. This observation suggested that sleep deprivation provoked the effective connectivity engaged in salient stimuli processing, but inhibited the effective connectivity in biasing selection of attention on task and in maintaining self-awareness in day time. Furthermore, in the SD condition, attention at the visual spatial task seemed to be driven by a bottom-up modulation mechanism. Third, a relationship was found between brain effective connectivity with response time. Decreases of Granger causal influences in two directions, from medial frontal lobe to sub cortical gray nuclei and from medial parietal lobe to sub cortical gray nuclei, were associated with shorter response time in the SD condition. Additionally, an increase of Granger causal influence from medial parietal lobe to cerebellum was associated with longer response time in the SD condition.
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Date Issued: 2014
Identifier: CFE0005825, ucf:50922
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005825

Title: Extensions of S-spaces.
Creator: Losert, Bernd, Richardson, Gary, Mikusinski, Piotr, Dutkay, Dorin, Brennan, Joseph, Marinescu, Dan, University of Central Florida
Abstract / Description: Given a convergence space X, a continuous action of a convergence semigroup S on X and a compactification Y of X, under what conditions on X and the action on X is it possible to extend the action to a continuous action on Y. Similarly, given a Cauchy space X, a Cauchy continuous action of a Cauchy semigroup S on X and a completion Y of X, under what conditions on X and the action on X is it possible to extend the action to a Cauchy continuous action on Y. We answer the first question for...
Show moreGiven a convergence space X, a continuous action of a convergence semigroup S on X and a compactification Y of X, under what conditions on X and the action on X is it possible to extend the action to a continuous action on Y. Similarly, given a Cauchy space X, a Cauchy continuous action of a Cauchy semigroup S on X and a completion Y of X, under what conditions on X and the action on X is it possible to extend the action to a Cauchy continuous action on Y. We answer the first question for some particular compactifications like the one-point compactification and the star compactification as well as for the class of regular compactifications. We answer the second question for the class of regular strict completions. Using these results, we give sufficient conditions under which the pseudoquotient of a compactification/completion of a space is the compactification/completion of the pseudoquotient of the given space.
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Date Issued: 2013
Identifier: CFE0004881, ucf:49661
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004881

Title: Assessing Safety Culture among Pilots in Saudi Airlines: A Quantitative Study Approach.
Creator: Alsowayigh, Mohammad, Karwowski, Waldemar, Elshennawy, Ahmad, Lee, Gene, Hancock, Peter, Mikusinski, Piotr, University of Central Florida
Abstract / Description: In high- risk industries, such as aviation, safety is a key for organization survivor. Most accidents involve human losses and bring substantial cost to organizations. Accidents can devastate the reputation and profitability of any organization. In aviation, more than 80% of aircraft accidents are related to human errors. Safety culture has substantial impact on the success of any organization. Employees' performance and behaviors are influenced by their perception of safety culture within...
Show moreIn high- risk industries, such as aviation, safety is a key for organization survivor. Most accidents involve human losses and bring substantial cost to organizations. Accidents can devastate the reputation and profitability of any organization. In aviation, more than 80% of aircraft accidents are related to human errors. Safety culture has substantial impact on the success of any organization. Employees' performance and behaviors are influenced by their perception of safety culture within their organization. In the aviation industry, pilots are considered the last resort to prevent accidents or mishaps in the air or ground. The focus on pilots' perception of safety culture is vital to understand how the airline can influence pilots' behaviors in the flight deck, and provide opportunities to minimize risk or unsafe behavior in the future. The present study examined the effect of safety culture on safety performance among pilots of Saudi Airlines. Safety performance was measured by pilot attitude toward violations and pilot error behavior. The study further analyzed the mediating role of pilot commitment to the airline between safety culture and measures of safety performance. The study used a quantitative approach using survey questionnaire to collect the data. A total of 247 commercial airline pilots, captain and first officer, flying at Saudi Airlines voluntarily participated in the study. Confirmatory factor analysis was conducted to validate each latent construct. The study used structural equation modeling (SEM) to analyze the relationship between all variables in the study using AMOS 22 software. The study results revealed that safety culture had a direct effect on pilot attitude toward violations and indirect effect on pilot error behavior. Moreover, safety culture had strong effect on enhancing pilot commitment to the airline. The mediating role of pilot commitment to the airline was not significant, and could not mediate the relationship between safety culture and measures of safety performance. The present research contributed to the current state of knowledge about the significant role of safety culture as a main predictor of safety performance in civil aviation. The present study contributes to aviation psychology by analyzing the effect of safety culture as a predictor for improving pilot commitment to the airline. In addition, this research analyzed the effect of safety culture on pilot attitude toward violations and pilot error behavior. Study findings can be used by airline management to better identify causes of unsafe behavior inside the cockpit. The outcomes of this research emphasize the role of management in shaping and affecting employees' behaviors and attitudes.
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Date Issued: 2014
Identifier: CFE0005454, ucf:50371
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005454

Title: Integral Representations of Positive Linear Functionals.
Creator: Siple, Angela, Mikusinski, Piotr, Atanasiu, Dragu, Dutkay, Dorin, Han, Deguang, Lee, Junho, Brennan, Joseph, Huo, Qun, University of Central Florida
Abstract / Description: In this dissertation we obtain integral representations for positive linear functionals on commutative algebras with involution and semigroups with involution. We prove Bochner and Plancherel type theorems for representations of positive functionals and show that, under some conditions, the Bochner and Plancherel representations are equivalent. We also consider the extension of positive linear functionals on a Banach algebra into a space of pseudoquotients and give under conditions in which...
Show moreIn this dissertation we obtain integral representations for positive linear functionals on commutative algebras with involution and semigroups with involution. We prove Bochner and Plancherel type theorems for representations of positive functionals and show that, under some conditions, the Bochner and Plancherel representations are equivalent. We also consider the extension of positive linear functionals on a Banach algebra into a space of pseudoquotients and give under conditions in which the space of pseudoquotients can be identified with all Radon measures on the structure space. In the final chapter we consider a system of integrated Cauchy functional equations on a semigroup, which generalizes a result of Ressel and offers a different approach to the proof.
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Date Issued: 2015
Identifier: CFE0005713, ucf:50144
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005713

Safety Culture (2)	+ -
Safety Performance (2)	+ -
pseudoquotients (2)	+ -
Abstract Harmonic Analysis (1)	+ -
Adaptive neuro fuzzy inference systems (1)	+ -

Adverse events (1)	+ -
Agent-Based (1)	+ -
Agile project management (1)	+ -
Airlines (1)	+ -
Artificial neural networks (1)	+ -
Boehmians (1)	+ -
Cauchy semigroup (1)	+ -
Cauchy space (1)	+ -
Cauchy-continuous action (1)	+ -
Chronic sleep deprivation (1)	+ -
Classification (1)	+ -
Construction (1)	+ -
Control chart pattern recognition (1)	+ -
Cost-sensitive learning (1)	+ -
Dynamic functional connectivity (1)	+ -
Effective Connectivity (1)	+ -
Fuzzy inference systems (1)	+ -
Granger Causality (1)	+ -
Graph theoretic analysis (1)	+ -
Human social culture behavior (HSCB) modeling (1)	+ -
Imbalanced data (1)	+ -
Infrastructure development (1)	+ -
Levy measures (1)	+ -
MBSE (1)	+ -
Mikusinski (1)	+ -

Mikusinski, Piotr (17)	+ -
University of Central Florida (17)	+ -
Karwowski, Waldemar (12)	+ -
Hancock, Peter (7)	+ -
Elshennawy, Ahmad (4)	+ -

Xanthopoulos, Petros (4)	+ -
Lee, Gene (3)	+ -
Thompson, William (3)	+ -
Brennan, Joseph (2)	+ -
Dutkay, Dorin (2)	+ -
Alnoaimi, Muhanna (1)	+ -
Alrehaili, Omar (1)	+ -
Alsowayigh, Mohammad (1)	+ -
Atanasiu, Dragu (1)	+ -
Bergmann, Thomas (1)	+ -
Bobbie, Afrifah (1)	+ -
Bozkurt, Halil (1)	+ -
Cakit, Erman (1)	+ -
Geiger, Christopher (1)	+ -
Han, Deguang (1)	+ -
He, Yiling (1)	+ -
Huo, Qun (1)	+ -
Khosravi, Mehrdad (1)	+ -
Kincaid, John (1)	+ -
Lee, Junho (1)	+ -
Li, Muyuan (1)	+ -
Li, Xin (1)	+ -
Losert, Bernd (1)	+ -
Marinescu, Dan (1)	+ -
Moore, Brian (1)	+ -

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