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- Title
- STOCHASTIC RESOURCE CONSTRAINED PROJECT SCHEDULING WITH STOCHASTIC TASK INSERTION PROBLEMS.
- Creator
-
Archer, Sandra, Armacost, Robert, University of Central Florida
- Abstract / Description
-
The area of focus for this research is the Stochastic Resource Constrained Project Scheduling Problem (SRCPSP) with Stochastic Task Insertion (STI). The STI problem is a specific form of the SRCPSP, which may be considered to be a cross between two types of problems in the general form: the Stochastic Project Scheduling Problem, and the Resource Constrained Project Scheduling Problem. The stochastic nature of this problem is in the occurrence/non-occurrence of tasks with deterministic...
Show moreThe area of focus for this research is the Stochastic Resource Constrained Project Scheduling Problem (SRCPSP) with Stochastic Task Insertion (STI). The STI problem is a specific form of the SRCPSP, which may be considered to be a cross between two types of problems in the general form: the Stochastic Project Scheduling Problem, and the Resource Constrained Project Scheduling Problem. The stochastic nature of this problem is in the occurrence/non-occurrence of tasks with deterministic duration. Researchers Selim (2002) and Grey (2007) laid the groundwork for the research on this problem. Selim (2002) developed a set of robustness metrics and used these to evaluate two initial baseline (predictive) scheduling techniques, optimistic (0% buffer) and pessimistic (100% buffer), where none or all of the stochastic tasks were scheduled, respectively. Grey (2007) expanded the research by developing a new partial buffering strategy for the initial baseline predictive schedule for this problem and found the partial buffering strategy to be superior to Selim's "extreme" buffering approach. The current research continues this work by focusing on resource aspects of the problem, new buffering approaches, and a new rescheduling method. If resource usage is important to project managers, then a set of metrics that describes changes to the resource flow would be important to measure between the initial baseline predictive schedule and the final "as-run" schedule. Two new sets of resource metrics were constructed regarding resource utilization and resource flow. Using these new metrics, as well as the Selim/Grey metrics, a new buffering approach was developed that used resource information to size the buffers. The resource-sized buffers did not show to have significant improvement over Grey's 50% buffer used as a benchmark. The new resource metrics were used to validate that the 50% buffering strategy is superior to the 0% or 100% buffering by Selim. Recognizing that partial buffers appear to be the most promising initial baseline development approach for STI problems, and understanding that experienced project managers may be able to predict stochastic probabilities based on prior projects, the next phase of the research developed a new set of buffering strategies where buffers are inserted that are proportional to the probability of occurrence. The results of this proportional buffering strategy were very positive, with the majority of the metrics (both robustness and resource), except for stability metrics, improved by using the proportional buffer. Finally, it was recognized that all research thus far for the SRCPSP with STI focused solely on the development of predictive schedules. Therefore, the final phase of this research developed a new reactive strategy that tested three different rescheduling points during schedule eventuation when a complete rescheduling of the latter portion of the schedule would occur. The results of this new reactive technique indicate that rescheduling improves the schedule performance in only a few metrics under very specific network characteristics (those networks with the least restrictive parameters). This research was conducted with extensive use of Base SAS v9.2 combined with SAS/OR procedures to solve project networks, solve resource flow problems, and implement reactive scheduling heuristics. Additionally, Base SAS code was paired with Visual Basic for Applications in Excel 2003 to implement an automated Gantt chart generator that provided visual inspection for validation of the repair heuristics. The results of this research when combined with the results of Selim and Grey provide strong guidance for project managers regarding how to develop baseline predictive schedules and how to reschedule the project as stochastic tasks (e.g. unplanned work) do or do not occur. Specifically, the results and recommendations are provided in a summary tabular format that describes the recommended initial baseline development approach if a project manager has a good idea of the level and location of the stochasticity for the network, highlights two cases where rescheduling during schedule eventuation may be beneficial, and shows when buffering proportional to the probability of occurrence is recommended, or not recommended, or the cases where the evidence is inconclusive.
Show less - Date Issued
- 2008
- Identifier
- CFE0002491, ucf:47673
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002491
- Title
- Dynamic Job-shop scheduling program(DJSP) analysis for Preventive military Helicopter maintenance system(PMS).
- Creator
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Park, Kyungjin, Lee, Gene, Rabelo, Luis, Elshennawy, Ahmad, University of Central Florida
- Abstract / Description
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Republic of Korea Army(ROKA) has been founding new attack helicopter troops since last year by adopting US main attack helicopter, AH-64E Apache, and peripheral system like pilots and mechanics training systems and their organization. The AH-64E Apache is a major attack helicopter of the US Army and all of its systems are verified in terms of the effectiveness in real operations for several decades. However, ROKA still needs their own version of systems including tactics, template, and...
Show moreRepublic of Korea Army(ROKA) has been founding new attack helicopter troops since last year by adopting US main attack helicopter, AH-64E Apache, and peripheral system like pilots and mechanics training systems and their organization. The AH-64E Apache is a major attack helicopter of the US Army and all of its systems are verified in terms of the effectiveness in real operations for several decades. However, ROKA still needs their own version of systems including tactics, template, and maintenance which are suitable for Korean terrain, climate, personnel, and so on. At least ROKA needs to have a chance to verify that the adopted system is working well with different circumstances, especially with a different maintenance system.As basic characteristics, routine maintenance and management are essential for accident prevention for a helicopter, there are specially formalized maintenance systems for every kind of helicopter respectively. It was established by a manufacturer in maintenance manuals and can be modified and integrated by users and operators. Apache also has its own maintenance schedule and system including 25-hour, 50-hour, 125-hour, and 250-hour maintenance and inspections which are implemented according to the operation hours. Those schedules are done by a task force or temporary maintenance team which is led by one or two inspectors and supported by 3~4 mechanics.Maintenance troops restrict the number of aircraft to get in the process by managing the flight hours considering the limit of manpower and equipment so that the operation rate stays above at least 80%. It is important to stipulate their capacity in need and max capacity with given personnel and facility for newly founding military troops. Especially since ROKA aviation branch is applying a more strict maintenance process, it might cause insufficiency of resources if organized by same template and procedure with the US Army. The goal of this study is to verify if existing personnel organization is affordable for new maintenance system of AH-64 Apache helicopters. As a further step ahead, this research found the most critical personnel pool and their relationship by sensitivity analysis. This research specified actual maintenance procedure and restrictions on computer and simulated virtually. During the repetition of the test, existing organization was found inadequate to satisfy all restrictions and requirements. Test pilot and inspector pool are critical to secure the successful maintenance support and to prepare for contingency. Also, there were interesting relationships between the mechanics groups. They are in supplemental relationships with each other because of the condition of one pool affects the other.
Show less - Date Issued
- 2017
- Identifier
- CFE0006776, ucf:51864
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006776
- Title
- iPads for Students with ASD: Comparing Delivery Modes for Visual Activity Schedules.
- Creator
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Gourwitz, Jillian, Martin, Suzanne, Vasquez, Eleazar, Pearl, Cynthia, Levin, Judith, Vince Garland, Krista, University of Central Florida
- Abstract / Description
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Visual Activity Schedules (VAS) are tools that present an abstract concept, such as time, in a more concrete and manageable form. VAS allow students to anticipate upcoming events and activities, develop an understanding of time, and facilitate the ability to predict change. Prior investigations have used VAS to increase on-task behavior while enhancing the student's ability to independently make transitions from one activity to another and are particularly appropriate as they capitalize on...
Show moreVisual Activity Schedules (VAS) are tools that present an abstract concept, such as time, in a more concrete and manageable form. VAS allow students to anticipate upcoming events and activities, develop an understanding of time, and facilitate the ability to predict change. Prior investigations have used VAS to increase on-task behavior while enhancing the student's ability to independently make transitions from one activity to another and are particularly appropriate as they capitalize on the visual strengths exhibited by many students with autism. Mobile devices such as the iPad are becoming a tool for teaching students with disabilities, and research is currently underway to determine the effectiveness of specific applications on student performance. This research examined the impact of VAS delivered via the iPad, compared to a paper-based VAS, on the percentage of on-task behavior and median transition time for students with autism spectrum disorder (ASD) during academic center activities in an inclusive classroom setting. An alternating-treatment, single-subject research design was used to determine whether a divergence exists between the paper-based VAS and the iPad VAS. This study included three student participants who (a) had a diagnosis of ASD as stated on the Individualized Education Plan (IEP), (b) were in grade level K-1, (c) received instruction through Language Arts activity centers taught within one classroom, and (d) had difficulty with independent on-task behavior as reported by the participant's teacher. Visual analysis of the data for on-task behavior revealed mixed results. Student 1 had a divergence between on-task behavior, with the paper-based VAS being a superior treatment condition to the iPad VAS 80% of the time. Student 2 also had a divergence between percentage of on-task behavior, with the iPad VAS being a superior treatment condition to the paper-based VAS 80% of the time. Student 3 had no clear divergence in percentage of on-task behavior between the iPad VAS and the paper-based VAS. All three participants had highly variable baseline and intervention data for transition time with a level stability range of 20% to 60%. Student 1 and Student 3 had no clear difference in transition time when comparing the paper-based VAS to the iPad VAS. Student 2 had a divergence in transition time data between the iPad VAS and the paper-based VAS, with the paper-based VAS being a superior treatment condition 90% of the time.
Show less - Date Issued
- 2014
- Identifier
- CFE0005339, ucf:50471
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005339
- Title
- BUFFER TECHNIQUES FOR STOCHASTIC RESOURCE CONSTRAINED PROJECT SCHEDULING WITH STOCHASTIC TASK INSERTIONS PROBLEMS.
- Creator
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Grey, Jennifer, Armacost, Robert, University of Central Florida
- Abstract / Description
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Project managers are faced with the challenging task of managing an environment filled with uncertainties that may lead to multiple disruptions during project execution. In particular, they are frequently confronted with planning for routine and non-routine unplanned work: known, identified, tasks that may or may not occur depending upon various, often unpredictable, factors. This problem is known as the stochastic task insertion problem, where tasks of deterministic duration occur...
Show moreProject managers are faced with the challenging task of managing an environment filled with uncertainties that may lead to multiple disruptions during project execution. In particular, they are frequently confronted with planning for routine and non-routine unplanned work: known, identified, tasks that may or may not occur depending upon various, often unpredictable, factors. This problem is known as the stochastic task insertion problem, where tasks of deterministic duration occur stochastically. Traditionally, project managers may include an extra margin within deterministic task times or an extra time buffer may be allotted at the end of the project schedule to protect the final project completion milestone. Little scientific guidance is available to better integrate buffers strategically into the project schedule. Motivated by the Critical Chain and Buffer Management approach of Goldratt, this research identifies, defines, and demonstrates new buffer sizing techniques to improve project duration and stability metrics associated with the stochastic resource constrained project scheduling problem with stochastic task insertions. Specifically, this research defines and compares partial buffer sizing strategies for projects with varying levels of resource and network complexity factors as well as the level and location of the stochastically occurring tasks. Several project metrics may be impacted by the stochastic occurrence or non-occurrence of a task such as the project makespan and the project stability. New duration and stability metrics are developed in this research and are used to evaluate the effectiveness of the proposed buffer sizing techniques. These "robustness measures" are computed through the comparison of the characteristics of the initial schedule (termed the infeasible base schedule), a modified base schedule (or as-run schedule) and an optimized version of the base schedule (or perfect knowledge schedule). Seven new buffer sizing techniques are introduced in this research. Three are based on a fixed percentage of task duration and the remaining four provide variable buffer sizes based upon the location of the stochastic task in the schedule and knowledge of the task stochasticity characteristic. Experimental analysis shows that partial buffering produces improvements in the project stability and duration metrics when compared to other baseline scheduling approaches. Three of the new partial buffering techniques produced improvements in project metrics. One of these partial buffers was based on a fixed percentage of task duration and the other two used a variable buffer size based on knowledge of the location of the task in the project network. This research provides project schedulers with new partial buffering techniques and recommendations for the type of partial buffering technique that should be utilized when project duration and stability performance improvements are desired. When a project scheduler can identify potential unplanned work and where it might occur, the use of these partial buffer techniques will yield a better estimated makespan. Furthermore, it will result in less disruption to the planned schedule and minimize the amount of time that specific tasks will have to move to accommodate the unplanned tasks.
Show less - Date Issued
- 2007
- Identifier
- CFE0001584, ucf:52850
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001584
- Title
- PLANNING AND SCHEDULING FOR LARGE-SCALEDISTRIBUTED SYSTEMS.
- Creator
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Yu, Han, Marinescu, Dan, University of Central Florida
- Abstract / Description
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Many applications require computing resources well beyond those available on any single system. Simulations of atomic and subatomic systems with application to material science, computations related to study of natural sciences, and computer-aided design are examples of applications that can benefit from the resource-rich environment provided by a large collection of autonomous systems interconnected by high-speed networks. To transform such a collection of systems into a user's virtual...
Show moreMany applications require computing resources well beyond those available on any single system. Simulations of atomic and subatomic systems with application to material science, computations related to study of natural sciences, and computer-aided design are examples of applications that can benefit from the resource-rich environment provided by a large collection of autonomous systems interconnected by high-speed networks. To transform such a collection of systems into a user's virtual machine, we have to develop new algorithms for coordination, planning, scheduling, resource discovery, and other functions that can be automated. Then we can develop societal services based upon these algorithms, which hide the complexity of the computing system for users. In this dissertation, we address the problem of planning and scheduling for large-scale distributed systems. We discuss a model of the system, analyze the need for planning, scheduling, and plan switching to cope with a dynamically changing environment, present algorithms for the three functions, report the simulation results to study the performance of the algorithms, and introduce an architecture for an intelligent large-scale distributed system.
Show less - Date Issued
- 2005
- Identifier
- CFE0000781, ucf:46595
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000781
- Title
- Sensemaking In Honors Scheduling.
- Creator
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Rowland, James, Musambira, George, Hastings, Sally, Katt, James, University of Central Florida
- Abstract / Description
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Honors courses offer students unique opportunities such as smaller class sizes, applied application of knowledge, and a closer mentorship with the faculty member. Through observation, there are some cases where courses have regularly been cancelled every term due to low enrollment. When these courses are often canceled, it can impact the honors program ability to continue to offer courses to the students. Using Weick's work on Sensemaking and principles of analyzing organizational culture,...
Show moreHonors courses offer students unique opportunities such as smaller class sizes, applied application of knowledge, and a closer mentorship with the faculty member. Through observation, there are some cases where courses have regularly been cancelled every term due to low enrollment. When these courses are often canceled, it can impact the honors program ability to continue to offer courses to the students. Using Weick's work on Sensemaking and principles of analyzing organizational culture, the study addressed how honors students are impacted by course cancellations and how they communicate about the impact. Through two focus groups with a total of eleven participants, information was gathered on how they constructed and communicated about their identity as honors students; their individual campus environments, and how those environments help to shape the communication culture they were part of; how they make scheduling decisions by extracting plausible cues from the communication they receive about course scheduling; and the impact of course cancellations on their honors experience.In defining honors and its incorporation into their identity, the students described how being in honors was a challenge to make themselves the best that they can be which included being part of an engaging community of scholars and of use to the community around. The two focus groups noted differences on how each campus provided a slightly different organizational culture: one more familiar and inviting, the other massive and resource filled, and with diversity in the type of students encountered. Course scheduling messages often were extracted from the course scheduling website, with little communication about what would be offered into the future beyond the immediate term. Students had to gather additional data from their fellow students, faculty, and the honors office. Students often searched for cues regarding time and location of the class, the impact to the degree program, and if the class will push the student in new and innovative ways to provide a deeper engagement with the material. Students were often impacted by course cancellations and the added stress of having to find replacement courses to avoid extending the time to complete the degree or risk financial repercussions with the loss of financial aid. These stressors do provide cues that can influence the degree of challenge a student is willing to accept or even degree completion.
Show less - Date Issued
- 2017
- Identifier
- CFE0006652, ucf:51249
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006652
- Title
- Shop Scheduling in the Presence of Batching, Sequence-Dependent Setups and Incompatible Job Families Minimizing Earliness and Tardiness Penalties.
- Creator
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Buchanan, Patricia, Geiger, Christopher, Mollaghasemi, Mansooreh, Pazour, Jennifer, Nazzal, Dima, University of Central Florida
- Abstract / Description
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The motivation of this research investigation stems from a particular job shop production environment at a large international communications and information technology company in which electro-mechanical assemblies (EMAs) are produced. The production environment of the EMAs includes the continuous arrivals of the EMAs (generally called jobs), with distinct due dates, degrees of importance and routing sequences through the production workstations, to the job shop. Jobs are processed in...
Show moreThe motivation of this research investigation stems from a particular job shop production environment at a large international communications and information technology company in which electro-mechanical assemblies (EMAs) are produced. The production environment of the EMAs includes the continuous arrivals of the EMAs (generally called jobs), with distinct due dates, degrees of importance and routing sequences through the production workstations, to the job shop. Jobs are processed in batches at the workstations, and there are incompatible families of jobs, where jobs from different product families cannot be processed together in the same batch. In addition, there are sequence-dependent setups between batches at the workstations. Most importantly, it is imperative that all product deliveries arrive on time to their customers (internal and external) within their respective delivery time windows. Delivery is allowed outside a time window, but at the expense of a penalty. Completing a job and delivering the job before the start of its respective time window results in a penalty, i.e., inventory holding cost. Delivering a job after its respective time window also results in a penalty, i.e., delay cost or emergency shipping cost. This presents a unique scheduling problem where an earliness-tardiness composite objective is considered.This research approaches this scheduling problem by decomposing this complex job shop scheduling environment into bottleneck and non-bottleneck resources, with the primary focus on effectively scheduling the bottleneck resource. Specifically, the problem of scheduling jobs with unique due dates on a single workstation under the conditions of batching, sequence-dependent setups, incompatible job families in order to minimize weighted earliness and tardiness is formulated as an integer linear program. This scheduling problem, even in its simplest form, is NP-Hard, where no polynomial-time algorithm exists to solve this problem to optimality, especially as the number of jobs increases. As a result, the computational time to arrive at optimal solutions is not of practical use in industrial settings, where production scheduling decisions need to be made quickly. Therefore, this research explores and proposes new heuristic algorithms to solve this unique scheduling problem. The heuristics use order review and release strategies in combination with priority dispatching rules, which is a popular and more commonly-used class of scheduling algorithms in real-world industrial settings. A computational study is conducted to assess the quality of the solutions generated by the proposed heuristics. The computational results show that, in general, the proposed heuristics produce solutions that are competitive to the optimal solutions, yet in a fraction of the time. The results also show that the proposed heuristics are superior in quality to a set of benchmark algorithms within this same class of heuristics.
Show less - Date Issued
- 2014
- Identifier
- CFE0005139, ucf:50717
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005139
- Title
- Interval Edge-Colorings of Graphs.
- Creator
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Foster, Austin, Song, Zixia, Reid, Michael, Brennan, Joseph, University of Central Florida
- Abstract / Description
-
A proper edge-coloring of a graph G by positive integers is called an interval edge-coloring if the colors assigned to the edges incident to any vertex in G are consecutive (i.e., those colors form an interval of integers). The notion of interval edge-colorings was first introduced by Asratian and Kamalian in 1987, motivated by the problem of finding compact school timetables. In 1992, Hansen described another scenario using interval edge-colorings to schedule parent-teacher conferences so...
Show moreA proper edge-coloring of a graph G by positive integers is called an interval edge-coloring if the colors assigned to the edges incident to any vertex in G are consecutive (i.e., those colors form an interval of integers). The notion of interval edge-colorings was first introduced by Asratian and Kamalian in 1987, motivated by the problem of finding compact school timetables. In 1992, Hansen described another scenario using interval edge-colorings to schedule parent-teacher conferences so that every person's conferences occur in consecutive slots. A solution exists if and only if the bipartite graph with vertices for parents and teachers, and edges for the required meetings, has an interval edge-coloring.A well-known result of Vizing states that for any simple graph $G$, $\chi'(G) \leq \Delta(G) + 1$, where $\chi'(G)$ and $\Delta(G)$ denote the edge-chromatic number and maximum degree of $G$, respectively. A graph $G$ is called class 1 if $\chi'(G) = \Delta(G)$, and class 2 if $\chi'(G) = \Delta(G) + 1$. One can see that any graph admitting an interval edge-coloring must be of class 1, and thus every graph of class 2 does not have such a coloring.Finding an interval edge-coloring of a given graph is hard. In fact, it has been shown that determining whether a bipartite graph has an interval edge-coloring is NP-complete. In this thesis, we survey known results on interval edge-colorings of graphs, with a focus on the progress of $(a, b)$-biregular bipartite graphs. Discussion of related topics and future work is included at the end. We also give a new proof of Theorem 3.15 on the existence of proper path factors of $(3, 4)$-biregular graphs. Finally, we obtain a new result, Theorem 3.18, which states that if a proper path factor of any $(3, 4)$-biregular graph has no path of length 8, then it contains paths of length 6 only. The new result we obtained and the method we developed in the proof of Theorem 3.15 might be helpful in attacking the open problems mentioned in the Future Work section of Chapter 5.
Show less - Date Issued
- 2016
- Identifier
- CFE0006301, ucf:51609
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006301
- Title
- A Comparative Study of the Effect of Block Scheduling and Traditional Scheduling on Student Achievement for the Florida Algebra 1 End-of-Course Examination.
- Creator
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Underwood, Arthur, Murray, Kenneth, Murray, Barbara, Baldwin, Lee, Hutchinson, Cynthia, University of Central Florida
- Abstract / Description
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The focus of this research was on the effect of school schedules on student achievement for ninth-grade students in a Florida school district. Data were collected from two central Florida high schools from the 2011-2012 and 2012-2013 school years. Five one-way analyses of covariance (ANCOVA) were performed to ascertain if there was any interaction between school schedules and student achievement. Examined were the interactions (a) between schedule and schools, (b) schedule and male students, ...
Show moreThe focus of this research was on the effect of school schedules on student achievement for ninth-grade students in a Florida school district. Data were collected from two central Florida high schools from the 2011-2012 and 2012-2013 school years. Five one-way analyses of covariance (ANCOVA) were performed to ascertain if there was any interaction between school schedules and student achievement. Examined were the interactions (a) between schedule and schools, (b) schedule and male students, (c) schedule and female students, (d) schedule and Black students, and (e) schedule and Hispanic students. The independent variable, school schedule, consisted of two levels: traditional schedule and A/B block schedule. The dependent variable was the spring Algebra 1 End- of-Course Examination (EOC), and the covariate was the Florida Comprehensive Assessment Test (FCAT) Mathematics Eighth-grade Development Scale Score. School schedule was not significantly related to students' spring Algebra 1 EOC scores, F(1,788) p = .932. School schedule was not significantly related to male students' spring Algebra 1 EOC scores, F(1,392) p = .698. School schedule was not significantly related to female students' spring Algebra 1 EOC scores, F(1,393) p = .579. School schedule was not significantly related to Black students' spring Algebra 1 EOC scores, F(1,186) p = .545. School schedule was not significantly related to Hispanic students' spring Algebra 1 EOC scores, F (1,184) p = .700.
Show less - Date Issued
- 2014
- Identifier
- CFE0005433, ucf:50406
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005433
- Title
- EXAMINING EMPLOYEE USE OF FAMILY-FRIENDLY BENEFITS WITH THE THEORY OF PLANNED BEHAVIOR.
- Creator
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Seiser, Heather, Fritzsche, Barbara, University of Central Florida
- Abstract / Description
-
The purpose of the present study was to investigate the factors that may be related to employees' decisions to use the family-friendly benefits (e.g., maternity/paternity leave, flexible work schedule) that are offered to them by their employers. Research has shown that both employees and organizations benefit when employees use family-friendly benefits. However, research has also shown that many employees do not take advantage of such benefits. Studies examining this issue are limited,...
Show moreThe purpose of the present study was to investigate the factors that may be related to employees' decisions to use the family-friendly benefits (e.g., maternity/paternity leave, flexible work schedule) that are offered to them by their employers. Research has shown that both employees and organizations benefit when employees use family-friendly benefits. However, research has also shown that many employees do not take advantage of such benefits. Studies examining this issue are limited, and much of the research that has been conducted is anecdotal and atheoretical. The present study overcame this problem by empirically examining the use of family-friendly benefits within the theoretical context of Ajzen's (1991) theory of planned behavior. The results of this study support the theory of planned behavior. Specifically, the results indicated that whether an individual perceived he/she had control over the use of family-friendly benefits was the most predictive of whether he/she intended to use them. Whether the individual perceived that others would approve of these behaviors was also predictive of intention to perform the behaviors. In addition, an individual's intention to take leave or use a flexible work schedule was the most predictive of whether he or she actually engaged in the behaviors. Implications for practice as well as future research directions are also discussed.
Show less - Date Issued
- 2006
- Identifier
- CFE0001399, ucf:46959
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001399
- Title
- EFFECTS OF THREE INSTRUCTIONAL SCHEDULES ON SKILL ACQUISITION AND GENERALIZATION IN THE USE OF TWO-WAY RADIOS TO REPORT TASK COMPLETION BY HIGH SCHOOL STUDENTS WITH MODERATE INTELLECTUAL DISABILITIES.
- Creator
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Perez-Turner, Geraldine, Miller, Kevin, University of Central Florida
- Abstract / Description
-
Educators of students with moderate and severe intellectual disabilities face a significant challenge in preparing their students while in school to function, acquire, and maintain skills that would facilitate successful performance in the workforce while in supported and/or independent employment after graduation. The field of special education still debates about the best way to teach students with moderate intellectual disabilities, the best setting for their instruction and the best...
Show moreEducators of students with moderate and severe intellectual disabilities face a significant challenge in preparing their students while in school to function, acquire, and maintain skills that would facilitate successful performance in the workforce while in supported and/or independent employment after graduation. The field of special education still debates about the best way to teach students with moderate intellectual disabilities, the best setting for their instruction and the best instructional schedule. The current research investigated the effectiveness and efficiency of three instructional schedules in the skill acquisition and generalization of two-way radio usage to report task completion by high school students with moderate intellectual disabilities. The instructional schedules investigated were: (a) community-based instruction only (CBI), (b) community based instruction plus simulated instruction in the classroom-same day (CBISC) and (c) simulated instruction in the classroom only (SICO). A Multiple Probe Design across participants with intermittent probe trials within each instructional group, and an added generalization phase (Horner & Baer, 1978; Tawney & Gast, 1984; Alberto & Troutman, 2003) was employed in this study. Nine high school students with moderate intellectual disabilities, three in each instructional schedule, were taught to use a two-way radio to report task completion. The results of the study revealed that the CBI instructional schedule was the overall most efficient instructional schedule for skill acquisition. Two of the CBI participants required the least number of trials to learn to use a two-way radio to report task completion. The second most efficient schedule was the CBISC and the least efficient instructional schedule was the SICO. Based on Mean scores, learning efficiency appeared to be greater for the participants in the CBI and CBISC instructional schedule. These participants required the least number of intrusive prompts. Results indicated that the SICO instructional scheduled was more efficient for only one participant. This participant only required verbal prompts for acquisition of the skill. However, participant one on the SICO instructional schedule required the most intrusive prompts of all participants across groups. For generalization, the CBISC instructional schedule appeared to be the most effective. In this schedule, the two participants that concluded the study generalized the skill across three novel settings with 100% accuracy. The SICO schedule, also had two participants generalized the skill across three novel settings; however, one participant in that group failed to generalize the skill in two settings. The CBI instructional schedule appeared to be the least effective for skill generalization in this study. In this schedule, only one participant generalized the skill in all three novel settings.
Show less - Date Issued
- 2005
- Identifier
- CFE0000398, ucf:46322
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000398
- Title
- HURRICANE EVACUATION: ORIGIN, ROUTE AND DESTINATION.
- Creator
-
Dixit, Vinayak, Radwan, Essam, University of Central Florida
- Abstract / Description
-
Recent natural disasters have highlighted the need to evacuate people as quickly as possible. During hurricane Rita in 2005, people were stuck in queue buildups and large scale congestions, due to improper use of capacity, planning and inadequate response to vehicle breakdown, flooding and accidents. Every minute is precious in situation of such disaster scenarios. Understanding evacuation demand loading is an essential part of any evacuation planning. One of the factors often understood to...
Show moreRecent natural disasters have highlighted the need to evacuate people as quickly as possible. During hurricane Rita in 2005, people were stuck in queue buildups and large scale congestions, due to improper use of capacity, planning and inadequate response to vehicle breakdown, flooding and accidents. Every minute is precious in situation of such disaster scenarios. Understanding evacuation demand loading is an essential part of any evacuation planning. One of the factors often understood to effect evacuation, but not modeled has been the effect of a previous hurricane. This has also been termed as the 'Katrina Effect', where, due to the devastation caused by hurricane Katrina, large number of people decided to evacuate during Hurricane Rita, which hit Texas three weeks after Katrina hit Louisiana. An important aspect influencing the rate of evacuation loading is Evacuation Preparation Time also referred to as 'Mobilization time' in literature. A methodology to model the effect of a recent past hurricane on the mobilization times for evacuees in an evacuation has been presented utilizing simultaneous estimation techniques. The errors for the two simultaneously estimated models were significantly correlated, confirming the idea that a previous hurricane does significantly affect evacuation during a subsequent hurricane. The results show that the home ownership, number of individuals in the household, income levels, and level/risk of surge were significant in the model explaining the mobilization times for the households. Pet ownership and number of kids in the households, known to increase the mobilization times during isolated hurricanes, were not found to be significant in the model. Evacuation operations are marred by unexpected blockages, breakdown of vehicles and sudden flooding of transportation infrastructure. A fast and accurate simulation model to incorporate flexibility into the evacuation planning procedure is required to react to such situations. Presently evacuation guidelines are prepared by the local emergency management, by testing various scenarios utilizing micro-simulation, which is extremely time consuming and do not provide flexibility to evacuation plans. To gain computational speed there is a need to move away from the level of detail of a micro-simulation to more aggregated simulation models. The Cell Transmission Model which is a mesoscopic simulation model is considered, and compared with VISSIM a microscopic simulation model. It was observed that the Cell Transmission Model was significantly faster compared to VISSIM, and was found to be accurate. The Cell Transmission model has a nice linear structure, which is utilized to construct Linear Programming Problems to determine optimal strategies. Optimization models were developed to determine strategies for optimal scheduling of evacuation orders and optimal crossover locations for contraflow operations on freeways. A new strategy termed as 'Dynamic Crossovers Strategy' is proposed to alleviate congestion due to lane blockages (due to vehicle breakdowns, incidents etc.). This research finds that the strategy of implementing dynamic crossovers in the event of lane blockages does improve evacuation operations. The optimization model provides a framework within which optimal strategies are determined quickly, without the need to test multiple scenarios using simulation. Destination networks are the cause of the main bottlenecks for evacuation routes, such aspects of transportation networks are rarely studied as part of evacuation operations. This research studies destination networks from a macroscopic perspective. Various relationships between network level macroscopic variables (Average Flow, Average Density and Average speed) over the network were studied. Utilizing these relationships, a "Network Breathing Strategy" was proposed to improve dissipation of evacuating traffic into the destination networks. The network breathing strategy is a cyclic process of allowing vehicles to enter the network till the network reaches congestion, which is followed by closure of their entry into the network until the network reaches an acceptable state. After which entrance into the network is allowed again. The intuitive motivation behind this methodology is to ensure that the network does not remain in congested conditions. The term 'Network Breathing' was coined due to the analogy seen between this strategy to the process of breathing, where vehicles are inhaled by the network (vehicles allowed in) and dissipated by the network (vehicles are not allowed in). It is shown that the network breathing improves the dissipation of vehicle into the destination network. Evacuation operations can be divided into three main levels: at the origin (region at risk), routes and destination. This research encompasses all the three aspects and proposes a framework to assess the whole system in its entirety. At the Origin the demand dictates when to schedule evacuation orders, it also dictates the capacity required on different routes. These breakthroughs will provide a framework for a real time Decision Support System which will help emergency management official make decisions faster and on the fly.
Show less - Date Issued
- 2008
- Identifier
- CFE0002051, ucf:47589
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002051
- Title
- TECHNIQUES FOR IMPROVING STUDENT ENGAGEMENT AND COMPREHENSION THROUGH THE PAIRING OF YOUNG ADULT LITERATURE WITH CLASSIC LITERATURE IN ADVANCED PLACEMENT OR HONORS TWELFTH GRADE CLASSROOMS.
- Creator
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Kopp, Julie, Kaplan, Jeffrey, University of Central Florida
- Abstract / Description
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Classics remain important to high school curriculum; however, they are also not palatable to today's students. This problem can be addressed by the use of young adult literature to help engagement and comprehension when paired with classic literature. By connecting the two, a student has the chance to learn something they will enjoy before moving on to what would be seen as efferent reading This thesis contains a review of literature on integrating young adult literature in the classroom in...
Show moreClassics remain important to high school curriculum; however, they are also not palatable to today's students. This problem can be addressed by the use of young adult literature to help engagement and comprehension when paired with classic literature. By connecting the two, a student has the chance to learn something they will enjoy before moving on to what would be seen as efferent reading This thesis contains a review of literature on integrating young adult literature in the classroom in order to view its effects on the students' engagement and comprehension. This study focuses on twelfth grade students taking Advanced Placement and Honors courses. Much of the research covers from the middle grades up to ninth grade. No direct research has been found for the twelfth grade level to have students become more avid readers past graduation. The thesis contains sample unit schedules with at least three sample lesson plans within each unit. There are explanations of how these lessons can used in conjunction with young adult literature and classical literature. Each unit covers a different classic novel list and provides the best way to engage students with increased comprehension when put into practice in any twelfth grade Advanced Placement and Honors classroom.
Show less - Date Issued
- 2013
- Identifier
- CFH0004465, ucf:45099
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004465
- Title
- DESIGN AND ANALYSIS OF EFFECTIVE ROUTING AND CHANNEL SCHEDULING FOR WAVELENGTH DIVISION MULTIPLEXING OPTICAL NETWORKS.
- Creator
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Gao, Xingbo, Bassiouni, Mostafa, University of Central Florida
- Abstract / Description
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Optical networking, employing wavelength division multiplexing (WDM), is seen as the technology of the future for the Internet. This dissertation investigates several important problems affecting optical circuit switching (OCS) and optical burst switching (OBS) networks. Novel algorithms and new approaches to improve the performance of these networks through effective routing and channel scheduling are presented. Extensive simulations and analytical modeling have both been used to evaluate...
Show moreOptical networking, employing wavelength division multiplexing (WDM), is seen as the technology of the future for the Internet. This dissertation investigates several important problems affecting optical circuit switching (OCS) and optical burst switching (OBS) networks. Novel algorithms and new approaches to improve the performance of these networks through effective routing and channel scheduling are presented. Extensive simulations and analytical modeling have both been used to evaluate the effectiveness of the proposed algorithms in achieving lower blocking probability, better fairness as well as faster switching. The simulation tests were performed over a variety of optical network topologies including the ring and mesh topologies, the U.S. Long-Haul topology, the Abilene high-speed optical network used in Internet 2, the Toronto Metropolitan topology and the European Optical topology. Optical routing protocols previously published in the literature have largely ignored the noise and timing jitter accumulation caused by cascading several wavelength conversions along the lightpath of the data burst. This dissertation has identified and evaluated a new constraint, called the wavelength conversion cascading constraint. According to this constraint, the deployment of wavelength converters in future optical networks will be constrained by a bound on the number of wavelength conversions that a signal can go through when it is switched all-optically from the source to the destination. Extensive simulation results have conclusively demonstrated that the presence of this constraint causes significant performance deterioration in existing routing and wavelength assignment (RWA) algorithms. Higher blocking probability and/or worse fairness have been observed for existing RWA algorithms when the cascading constraint is not ignored. To counteract the negative side effect of the cascading constraint, two constraint-aware routing algorithms are proposed for OCS networks: the desirable greedy algorithm and the weighted adaptive algorithm. The two algorithms perform source routing using link connectivity and the global state information of each wavelength. Extensive comparative simulation results have illustrated that by limiting the negative cascading impact to the minimum extent practicable, the proposed approaches can dramatically decrease the blocking probability for a variety of optical network topologies. The dissertation has developed a suite of three fairness-improving adaptive routing algorithms in OBS networks. The adaptive routing schemes consider the transient link congestion at the moment when bursts arrive and use this information to reduce the overall burst loss probability. The proposed schemes also resolve the intrinsic unfairness defect of existing popular signaling protocols. The extensive simulation results have shown that the proposed schemes generally outperform the popular shortest path routing algorithm and the improvement could be substantial. A two-dimensional Markov chain analytical model has also been developed and used to analyze the burst loss probabilities for symmetrical ring networks. The accuracy of the model has been validated by simulation. Effective proactive routing and preemptive channel scheduling have also been proposed to address the conversion cascading constraint in OBS environments. The proactive routing adapts the fairness-improving adaptive routing mentioned earlier to the environment of cascaded wavelength conversions. On the other hand, the preemptive channel scheduling approach uses a dynamic priority for each burst based on the constraint threshold and the current number of performed wavelength conversions. Empirical results have proved that when the cascading constraint is present, both approaches would not only decrease the burst loss rates greatly, but also improve the transmission fairness among bursts with different hop counts to a large extent.
Show less - Date Issued
- 2009
- Identifier
- CFE0002965, ucf:47958
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002965
- Title
- SCHEDULING AND RESOURCE MANAGEMENT FOR COMPLEX SYSTEMS: FROM LARGE-SCALE DISTRIBUTED SYSTEMS TO VERY LARGE SENSOR NETWORKS.
- Creator
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Yu, Chen, Marinescu, Dan, University of Central Florida
- Abstract / Description
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In this dissertation, we focus on multiple levels of optimized resource management techniques. We first consider a classic resource management problem, namely the scheduling of data-intensive applications. We define the Divisible Load Scheduling (DLS) problem, outline the system model based on the assumption that data staging and all communication with the sites can be done in parallel, and introduce a set of optimal divisible load scheduling algorithms and the related fault-tolerant...
Show moreIn this dissertation, we focus on multiple levels of optimized resource management techniques. We first consider a classic resource management problem, namely the scheduling of data-intensive applications. We define the Divisible Load Scheduling (DLS) problem, outline the system model based on the assumption that data staging and all communication with the sites can be done in parallel, and introduce a set of optimal divisible load scheduling algorithms and the related fault-tolerant coordination algorithm. The DLS algorithms introduced in this dissertation exploit parallel communication, consider realistic scenarios regarding the time when heterogeneous computing systems are available, and generate optimal schedules. Performance studies show that these algorithms perform better than divisible load scheduling algorithms based upon sequential communication. We have developed a self-organization model for resource management in distributed systems consisting of a very large number of sites with excess computing capacity. This self-organization model is inspired by biological metaphors and uses the concept of varying energy levels to express activity and goal satisfaction. The model is applied to Pleiades, a service-oriented architecture based on resource virtualization. The self-organization model for complex computing and communication systems is applied to Very Large Sensor Networks (VLSNs). An algorithm for self-organization of anonymous sensor nodes called SFSN (Scale-free Sensor Networks) and an algorithm utilizing the Small-worlds principle called SWAS (Small-worlds of Anonymous Sensors) are introduced. The SFSN algorithm is designed for VLSNs consisting of a fairly large number of inexpensive sensors with limited resources. An important feature of the algorithm is the ability to interconnect sensors without an identity, or physical address used by traditional communication and coordination protocols. During the self-organization phase, the collision-free communication channels allowing a sensor to synchronously forward information to the members of its proximity set are established and the communication pattern is followed during the activity phases. Simulation study shows that the SFSN ensures the scalability, limits the amount of communication and the complexity of coordination. The SWAS algorithm is further improved from SFSN by applying the Small-worlds principle. It is unique in its ability to create a sensor network with a topology approximating small-world networks. Rather than creating shortcuts between pairs of diametrically positioned nodes in a logical ring, we end up with something resembling a double-stranded DNA. By exploiting Small-worlds principle we combine two desirable features of networks, namely high clustering and small path length.
Show less - Date Issued
- 2009
- Identifier
- CFE0002907, ucf:48004
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002907
- Title
- A real-time crane service scheduling decision support system (CSS-DSS) for construction tower cranes.
- Creator
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Zavichi Tork, Amir, Madani Larijani, Kaveh, Oloufa, Amr, Tatari, Mehmet, Xanthopoulos, Petros, University of Central Florida
- Abstract / Description
-
The success of construction projects depends on proper use of construction equipment and machinery to a great extent. Thus, appropriate planning and control of the activities that rely on construction equipment could have significant effects on improving the efficiency of project operations. Cranes are the largest and most conspicuous construction equipment, widely used in typical construction sites. They play a major role in relocation of materials in horizontal and vertical directions on...
Show moreThe success of construction projects depends on proper use of construction equipment and machinery to a great extent. Thus, appropriate planning and control of the activities that rely on construction equipment could have significant effects on improving the efficiency of project operations. Cranes are the largest and most conspicuous construction equipment, widely used in typical construction sites. They play a major role in relocation of materials in horizontal and vertical directions on construction sites. Given the nature of activities relying on construction cranes in various stages of a project, cranes normally have control over the critical path of the project with the potential to create schedule bottlenecks and delaying the completion of the project. This dissertation intends to improve crane operations efficiency by developing a new framework for optimizing crane service sequence schedule. The crane service sequence problem is mathematically formulated as an NP-complete optimization problem based on the well-known Travel Salesman Problem (TSP) and is solved using different optimization techniques depending on the problem's size and complexity. The proposed framework sets the basis for developing near-real time decision support tools for on-site optimization of crane operations sequence. To underline the value of the proposed crane sequence optimization methods, these methods are employed to solve several numerical examples. Results show that the proposed method can create a travel time saving of 28% on average in comparison with conventional scheduling methods such as First in First out (FIFO), Shortest Job First (SJF), and Earliest Deadline First (EDF).
Show less - Date Issued
- 2013
- Identifier
- CFE0005078, ucf:50738
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005078
- Title
- Mission Analysis for Pico-Scale Satellite Based Dust Detection in Low Earth Orbits.
- Creator
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Belli, Jacob, Xu, Yunjun, Lin, Kuo-Chi, Bradley, Eric, University of Central Florida
- Abstract / Description
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A conceptual dust detection mission, KnightSat III, using pico-scale satellites is analyzed. The purpose of the proposed KnightSat III mission is to aid in the determination of the size, mass, distribution, and number of dust particles in low earth orbits through a low cost and flexible satellite or a formation of satellites equipped with a new dust detector. The analysis of a single satellite mission with an on-board dust detector is described; though this analysis can easily be extended to...
Show moreA conceptual dust detection mission, KnightSat III, using pico-scale satellites is analyzed. The purpose of the proposed KnightSat III mission is to aid in the determination of the size, mass, distribution, and number of dust particles in low earth orbits through a low cost and flexible satellite or a formation of satellites equipped with a new dust detector. The analysis of a single satellite mission with an on-board dust detector is described; though this analysis can easily be extended to a formation of pico-scale satellites. Many design aspects of the mission are discussed, including orbit analysis, power management, attitude determination and control, and mass and power budgets. Two of them are emphasized. The first is a new attitude guidance and control method, and the second is the online optimal power scheduling. It is expected that the measurements obtained from this possible future mission will provide insight into the dynamical processes of inner solar system dust, as well as aid in designing proper micro-meteoroid impact mitigation strategies for future man-made spacecraft.
Show less - Date Issued
- 2013
- Identifier
- CFE0004813, ucf:49728
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004813
- Title
- A Simulation-Based Evaluation Of Efficiency Strategies For A Primary Care Clinic With Unscheduled Visits.
- Creator
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Bobbie, Afrifah, Karwowski, Waldemar, Thompson, William, Elshennawy, Ahmad, Mikusinski, Piotr, University of Central Florida
- Abstract / Description
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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.
Show less - Date Issued
- 2016
- Identifier
- CFE0006443, ucf:51462
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006443
- Title
- A NEW FRAMEWORK FOR QOS PROVISIONING IN WIRELESS LANS USING THE P-PERSISTENT MAC PROTOCOL.
- Creator
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Anna, Kiran Babu, Bassiouni, Mostafa, University of Central Florida
- Abstract / Description
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The support of multimedia traffic over IEEE 802.11 wireless local area networks (WLANs) has recently received considerable attention. This dissertation has proposed a new framework that provides efficient channel access, service differentiation and statistical QoS guarantees in the enhanced distributed channel access (EDCA) protocol of IEEE 802.11e. In the first part of the dissertation, the new framework to provide QoS support in IEEE 802.11e is presented. The framework uses three...
Show moreThe support of multimedia traffic over IEEE 802.11 wireless local area networks (WLANs) has recently received considerable attention. This dissertation has proposed a new framework that provides efficient channel access, service differentiation and statistical QoS guarantees in the enhanced distributed channel access (EDCA) protocol of IEEE 802.11e. In the first part of the dissertation, the new framework to provide QoS support in IEEE 802.11e is presented. The framework uses three independent components, namely, a core MAC layer, a scheduler, and an admission control. The core MAC layer concentrates on the channel access mechanism to improve the overall system efficiency. The scheduler provides service differentiation according to the weights assigned to each Access Category (AC). The admission control provides statistical QoS guarantees. The core MAC layer developed in this dissertation employs a P-Persistent based MAC protocol. A weight-based fair scheduler to obtain throughput service differentiation at each node has been used. In wireless LANs (WLANs), the MAC protocol is the main element that determines the efficiency of sharing the limited communication bandwidth of the wireless channel. In the second part of the dissertation, analytical Markov chain models for the P-Persistent 802.11 MAC protocol under unsaturated load conditions with heterogeneous loads are developed. The Markov models provide closed-form formulas for calculating the packet service time, the packet end-to-end delay, and the channel capacity in the unsaturated load conditions. The accuracy of the models has been validated by extensive NS2 simulation tests and the models are shown to give accurate results. In the final part of the dissertation, the admission control mechanism is developed and evaluated. The analytical model for P-Persistent 802.11 is used to develop a measurement-assisted model-based admission control. The proposed admission control mechanism uses delay as an admission criterion. Both distributed and centralized admission control schemes are developed and the performance results show that both schemes perform very efficiently in providing the QoS guarantees. Since the distributed admission scheme control does not have a complete state information of the WLAN, its performance is generally inferior to the centralized admission control scheme. The detailed performance results using the NS2 simulator have demonstrated the effectiveness of the proposed framework. Compared to 802.11e EDCA, the scheduler consistently achieved the desired throughput differentiation and easy tuning. The core MAC layer achieved better delays in terms of channel access, average packet service time and end-to-end delay. It also achieved higher system throughput than EDCA for any given service differentiation ratio. The admission control provided the desired statistical QoS guarantees.
Show less - Date Issued
- 2010
- Identifier
- CFE0003243, ucf:48513
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003243
- Title
- Resource Allocation and Pricing in Secondary Dynamic Spectrum Access Networks.
- Creator
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Khairullah, Enas, Chatterjee, Mainak, Zou, Changchun, Lang, Sheau-Dong, Catbas, Necati, University of Central Florida
- Abstract / Description
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The paradigm shift from static spectrum allocation to a dynamic one has opened many challenges that need to be addressed for the true vision of Dynamic Spectrum Access (DSA) to materialize. This dissertation proposes novel solutions that include: spectrum allocation, routing, and scheduling in DSA networks. First, we propose an auction-based spectrum allocation scheme in a multi-channel environment where secondary users (SUs) bid to buy channels from primary users (PUs) based on the signal to...
Show moreThe paradigm shift from static spectrum allocation to a dynamic one has opened many challenges that need to be addressed for the true vision of Dynamic Spectrum Access (DSA) to materialize. This dissertation proposes novel solutions that include: spectrum allocation, routing, and scheduling in DSA networks. First, we propose an auction-based spectrum allocation scheme in a multi-channel environment where secondary users (SUs) bid to buy channels from primary users (PUs) based on the signal to interference and noise ratio (SINR). The channels are allocated such that i) the SUs get their preferred channels, ii) channels are re-used, and iii) there is no interference. Then, we propose a double auction-based spectrum allocation technique by considering multiple bids from SUs and heterogeneity of channels. We use virtual grouping of conflict-free buyers to transform multi-unit bids to single-unit bids. For routing, we propose a market-based model where the PUs determine the optimal price based on the demand for bandwidth by the SUs. Routes are determined through a series of price evaluations between message senders and forwarders. Also, we consider auction-based routing for two cases where buyers can bid for only one channel or they could bid for a combination of non-substitutable channels. For a centralized DSA, we propose two scheduling algorithms-- the first one focuses on maximizing the throughput and the second one focuses on fairness. We extend the scheduling algorithms to multi-channel environment. Expected throughput for every channel is computed by modelling channel state transitions using a discrete-time Markov chain. The state transition probabilities are calculated which occur at the frame/slot boundaries. All proposed algorithms are validated using simulation experiments with different network settings and their performance are studied.
Show less - Date Issued
- 2017
- Identifier
- CFE0006890, ucf:51723
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006890