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MEASURING THE EFFECT OF ERRATIC DEMANDON SIMULATED MULTI-CHANNEL MANUFACTURINGSYSTEM PERFORMANCE
Title
MEASURING THE EFFECT OF ERRATIC DEMANDON SIMULATED MULTI-CHANNEL MANUFACTURINGSYSTEM PERFORMANCE.
Creator
Kohan, Nancy, Kulonda, Dennis, University of Central Florida
Abstract / Description
ABSTRACT To handle uncertainties and variabilities in production demands, many manufacturing companies have adopted different strategies, such as varying quoted lead time, rejecting orders, increasing stock or inventory levels, and implementing volume flexibility. Make-to-stock (MTS) systems are designed to offer zero lead time by providing an inventory buffer for the organizations, but they are costly and involve risks such as obsolescence and wasted expenditures. The main concern of make-to...
Show moreABSTRACT To handle uncertainties and variabilities in production demands, many manufacturing companies have adopted different strategies, such as varying quoted lead time, rejecting orders, increasing stock or inventory levels, and implementing volume flexibility. Make-to-stock (MTS) systems are designed to offer zero lead time by providing an inventory buffer for the organizations, but they are costly and involve risks such as obsolescence and wasted expenditures. The main concern of make-to-order (MTO) systems is eliminating inventories and reducing the non-value-added processes and wastes; however, these systems are based on the assumption that the manufacturing environments and customers' demand are deterministic. Research shows that in MTO systems variability and uncertainty in the demand levels causes instability in the production flow, resulting in congestion in the production flow, long lead times, and low throughput. Neither strategy is wholly satisfactory. A new alternative approach, multi-channel manufacturing (MCM) systems are designed to manage uncertainties and variabilities in demands by first focusing on customers' response time. The products are divided into different product families, each with its own manufacturing stream or sub-factory. MCM also allocates the production capacity needed in each sub-factory to produce each product family. In this research, the performance of an MCM system is studied by implementing MCM in a real case scenario from textile industry modeled via discrete event simulation. MTS and MTO systems are implemented for the same case scenario and the results are studied and compared. The variables of interest for this research are the throughput of products, the level of on-time deliveries, and the inventory level. The results conducted from the simulation experiments favor the simulated MCM system for all mentioned criteria. Further research activities, such as applying MCM to different manufacturing contexts, is highly recommended.
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Date Issued
2004
Identifier
CFE0000240, ucf:46275
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0000240
Investigating the universality and comprehensive ability of measures to assess the state of workload
Title
Investigating the universality and comprehensive ability of measures to assess the state of workload.
Creator
Abich, Julian, Reinerman, Lauren, Lackey, Stephanie, Szalma, James, Taylor, Grant, University of Central Florida
Abstract / Description
Measures of workload have been developed on the basis of the various definitions, some are designed to capture the multi-dimensional aspects of a unitary resource pool (Kahneman, 1973) while others are developed on the basis of multiple resource theory (Wickens, 2002). Although many theory based workload measures exist, others have often been constructed to serve the purpose of specific experimental tasks. As a result, it is likely that not every workload measure is reliable and valid for all...
Show moreMeasures of workload have been developed on the basis of the various definitions, some are designed to capture the multi-dimensional aspects of a unitary resource pool (Kahneman, 1973) while others are developed on the basis of multiple resource theory (Wickens, 2002). Although many theory based workload measures exist, others have often been constructed to serve the purpose of specific experimental tasks. As a result, it is likely that not every workload measure is reliable and valid for all tasks, much less each domain. To date, no single measure, systematically tested across experimental tasks, domains, and other measures is considered a universal measure of workload. Most researchers would argue that multiple measures from various categories should be applied to a given task to comprehensively assess workload. The goal for Study 1 to establish task load manipulations for two theoretically different tasks that induce distinct levels of workload assessed by both subjective and performance measures was successful. The results of the subjective responses support standardization and validation of the tasks and demands of that task for investigating workload. After investigating the use of subjective and objective measures of workload to identify a universal and comprehensive measure or set of measures, based on Study 2, it can only be concluded that not one or a set of measures exists. Arguably, it is not to say that one will never be conceived and developed, but at this time, one does not reside in the psychometric catalog. Instead, it appears that a more suitable approach is to customize a set of workload measures based on the task. The novel approach of assessing the sensitivity and comprehensive ability of conjointly utilizing subjective, performance, and physiological workload measures for theoretically different tasks within the same domain contributes to the theory by laying the foundation for improving methodology for researching workload. The applicable contribution of this project is a stepping-stone towards developing complex profiles of workload for use in closed-loop systems, such as human-robot team interaction. Identifying the best combination of workload measures enables human factors practitioners, trainers, and task designers to improve methodology and evaluation of system designs, training requirements, and personnel selection.
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Date Issued
2013
Identifier
CFE0005119, ucf:50675
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005119
Principals' Perceptions and Self-efficacy in Relation to School Security
Title
Principals' Perceptions and Self-efficacy in Relation to School Security.
Creator
Jones, Julian, Taylor, Rosemarye, Doherty, Walter, Kennedy, Mary, Wolf, Ross, University of Central Florida
Abstract / Description
Principals in the nation's schools have been tasked with managing crisis incidents that may occur with students and others on their campuses on a daily basis. The purposes of this study were to determine the differences, if any, that existed in Central Florida public school principals' perceptions regarding school security, their perceived confidence to address critical crisis incidents on their campuses, their perceptions of the likelihood critical incidents would occur, their perceptions of...
Show morePrincipals in the nation's schools have been tasked with managing crisis incidents that may occur with students and others on their campuses on a daily basis. The purposes of this study were to determine the differences, if any, that existed in Central Florida public school principals' perceptions regarding school security, their perceived confidence to address critical crisis incidents on their campuses, their perceptions of the likelihood critical incidents would occur, their perceptions of interaction with law enforcement, the critical incidents they fear the most, and their perceptions of factors impacting the incidents they fear the most. Principal subgroup mean responses to the Principal Safety and Security Perceptions Survey in the three areas of Bandura's (1997) triadic reciprocal causation were examined in the context of principals' gender, longevity, student enrollment, grade configuration, free and reduced lunch rate, presence of a law enforcement officer, and presence of a security plan. Findings revealed significant differences between categorical groups of principals in multiple areas. It was determined that significant differences in principals' perceptions warrant further study. Recommendations for practice include security policy development and practical application of noted trends.
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Date Issued
2015
Identifier
CFE0005636, ucf:50217
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005636
Transient and Distributed Algorithms to Improve Islanding Detection Capability of Inverter Based Distributed Generation
Title
Transient and Distributed Algorithms to Improve Islanding Detection Capability of Inverter Based Distributed Generation.
Creator
Alhosani, Mohamed, Qu, Zhihua, Mikhael, Wasfy, Haralambous, Michael, Behal, Aman, Xu, Chengying, University of Central Florida
Abstract / Description
Recently, a lot of research work has been dedicated toward enhancing performance, reliability and integrity of distributed energy resources that are integrated into distribution networks. The problem of islanding detection and islanding prevention (i.e. anti-islanding) has stimulated a lot of research due to its role in severely compromising the safety of working personnel and resulting in equipment damages. Various Islanding Detection Methods (IDMs) have been developed within the last ten...
Show moreRecently, a lot of research work has been dedicated toward enhancing performance, reliability and integrity of distributed energy resources that are integrated into distribution networks. The problem of islanding detection and islanding prevention (i.e. anti-islanding) has stimulated a lot of research due to its role in severely compromising the safety of working personnel and resulting in equipment damages. Various Islanding Detection Methods (IDMs) have been developed within the last ten years in anticipation of the tremendous increase in the penetration of Distributed Generation (DG) in distribution system. This work proposes new IDMs that rely on transient and distributed behaviors to improve integrity and performance of DGs while maintaining multi-DG islanding detection capability.In this thesis, the following questions have been addressed: How to utilize the transient behavior arising from an islanding condition to improve detectability and robust performance of IDMs in a distributive manner? How to reduce the negative stability impact of the well-known Sandia Frequency Shift (SFS) IDM while maintaining its islanding detection capability? How to incorporate the perturbations provided by each of DGs in such a way that the negative interference of different IDMs is minimized without the need of any type of communication among the different DGs?It is shown that the proposed techniques are local, scalable and robust against different loading conditions and topology changes. Also, the proposed techniques can successfully distinguish an islanding condition from other disturbances that may occur in power system networks. This work improves the efficiency, reliability and safety of integrated DGs, which presents a necessary advance toward making electric power grids a smart grid.
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Date Issued
2013
Identifier
CFE0005295, ucf:50567
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005295

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