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Title: FREQUENCY-DOMAIN FARADAY ROTATION SPECTROSCOPY (FD-FRS) FOR FUNCTIONALIZED PARTICLE AND BIOMOLECULE CHARACTERIZATION.
Creator: Murdock, Richard, Putnam, Shawn, University of Central Florida
Abstract / Description: In this study, the magnetically-induced vibrations of functionalized magnetic particle suspensions were probed for the development of a novel optical spectroscopy technique. Through this work (1) the frequency-dependence of the faraday rotation in ferrofluids and (2) the extension of this system to elucidating particle size and conformation as an alternative immunoassay to costly and labor/time intensive Western Blotting and ELISA has been shown. With its sensitivity and specificity, this...
Show moreIn this study, the magnetically-induced vibrations of functionalized magnetic particle suspensions were probed for the development of a novel optical spectroscopy technique. Through this work (1) the frequency-dependence of the faraday rotation in ferrofluids and (2) the extension of this system to elucidating particle size and conformation as an alternative immunoassay to costly and labor/time intensive Western Blotting and ELISA has been shown. With its sensitivity and specificity, this method has proven to be a promising multi-functional tool in biosensing, diagnostic, and therapeutic nanomedicine efforts. Due to its ubiquitous nature in all optically-transparent materials, the faraday rotation, or circular birefringence, was developed as a robust and sensitive nanoscale biomolecule characterization technique through Brownian relaxation studies of particle suspensions. Current efforts have shown the applicability of this phenomenon in solid, pure liquid, and colloidal samples as well as simultaneous advancements of magnetic nanoparticle research in the magnetometric and magneto-optical regimes. By merging these two fields, a clinically relevant spectroscopy (fd-FRS, Frequency Domain Faraday Rotation Spectroscopy) was developed based on a newly revised model stemming from Debye relaxation theory. Through this work, an optical bench with a variable permeability core electromagnet and a frequency-domain lock-in amplifier setup (DC to 20 kHz) have been used to distinguish between Fe3O4-core nanoparticles with functionalization layers of PEG4/PEG8 polymer with future applications involving the Anti-BSA/BSA antibody/antigen couple. Particle concentrations down to 500 nM (magnetic nanoparticles) and 0.01 Volume % (magnetic beads) were studied with diameters ranging from ~200 nm to 1 um. Currently, the characteristic peak corresponding to the out-of-phase relaxation of the suspended particles has been elusive, despite a wide particle size distribution and the use of a balanced photodetector. Future work will involve highly monodisperse samples, faster scan times, and thermal characterization applications of fd-FRS.
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Date Issued: 2015
Identifier: CFH0004813, ucf:45467
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFH0004813

Title: STUDY OF GATE OXIDE BREAKDOWN AND HOT ELECTRON EFFECT ON CMOS CIRCUIT PERFORMANCES.
Creator: MA, JUN, Yuan, Jiann S., University of Central Florida
Abstract / Description: In the modern semiconductor world, there is a significant scaling of the transistor dimensions –The transistor gate length and the gate oxide thickness drop down to only several nanometers. Today the semiconductor industry is already dominated by submicron devices and other material devices for the high transistor density and performance enhancement. In this case, the semiconductor reliability issues are the most important thing for commercialization. The major reliability issues caused...
Show moreIn the modern semiconductor world, there is a significant scaling of the transistor dimensions –The transistor gate length and the gate oxide thickness drop down to only several nanometers. Today the semiconductor industry is already dominated by submicron devices and other material devices for the high transistor density and performance enhancement. In this case, the semiconductor reliability issues are the most important thing for commercialization. The major reliability issues caused by voltage are hot carrier effects (HCs) and gate oxide breakdown (BD) effects. These issues are recently more important to industry, due to the small size and high lateral field in short-channel of the device will cause high electrical field and other reliability issues. This dissertation primarily focuses on the study of the CMOS device gate oxide breakdown effect on different kinds of circuits performance, also some HC effects on circuit's performance are studied. The physical mechanisms for BD have been presented. A practical and accurate equivalent breakdown circuit model for the CMOS device was studied to simulate the RF performance degradation on the circuit level. The BD location effect has been evaluated. Furthermore, a methodology was developed to predict the BD effects on the circuit's performances with different kinds of BD location. It also provides guidance for the reliability considerations of the digital, analog, and RF circuit design. The BD effects on digital circuits SRAM, analog circuits Sample&Hold, and RF building blocks with the nanoscale device – low noise amplifier, LC oscillator, mixer, and power amplifier, have been investigated systematically. Finally 90 nm device will be used to study the HC effect on the circuit's performance. The contributions of this dissertation include: Providing a thorough study of the gate oxide breakdown issues caused by the voltage stress on the device – from device level to circuit level; Studying real voltage stress case – high frequency (950 MHz) dynamic stress, and comparing with the traditional DC stress; A simple, practical, and analytical method is derived to study the gate oxide breakdown effect including breakdown location effect and soft / hard breakdown on the digital, analog and RF circuits performances. A brief introduction and simulation for 90 nm device HC effect provide some useful information and helpful data for the industry. The gate oxide breakdown effect is the most common device reliability issue. The successful results of this dissertation, from device level to circuit level, provide an insight on how the BD affects the circuit's performance, and also provide some useful data for the circuit designers in their future work.
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Date Issued: 2009
Identifier: CFE0002856, ucf:48073
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002856

Title: A Joint Econometric Approach for Modeling Crash Counts by Collision Type.
Creator: Bhowmik, Tanmoy, Eluru, Naveen, Abdel-Aty, Mohamed, Yasmin, Shamsunnahar, University of Central Florida
Abstract / Description: In recent years, there is growing recognition that common unobserved factors that influence crash frequency by one attribute level are also likely to influence crash frequency by other attribute levels. The most common approach employed to address the potential unobserved heterogeneity in safety literature is the development of multivariate crash frequency models. The current study proposes an alternative joint econometric framework to accommodate for the presence of unobserved heterogeneity ...
Show moreIn recent years, there is growing recognition that common unobserved factors that influence crash frequency by one attribute level are also likely to influence crash frequency by other attribute levels. The most common approach employed to address the potential unobserved heterogeneity in safety literature is the development of multivariate crash frequency models. The current study proposes an alternative joint econometric framework to accommodate for the presence of unobserved heterogeneity (-) referred to as joint negative binomial-multinomial logit fractional split (NB-MNLFS) model. Furthermore, the study undertakes a first of its kind comparison exercise between the most commonly used multivariate model (multivariate random parameter negative binomial model) and the proposed joint approach by generating an equivalent log-likelihood measure. The empirical analysis is based on the zonal level crash count data for different collision types from the state of Florida for the year 2015. The model results highlight the presence of common unobserved effects affecting the two components of the joint model as well as the presence of parameter heterogeneity. The equivalent log-likelihood and goodness of fit measures clearly highlight the superiority of the proposed joint model over the commonly used multivariate approach.
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Date Issued: 2018
Identifier: CFE0007392, ucf:52740
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007392

Title: Adiabatic Film Cooling Effectiveness of a Transpiration-Cooled Leading Edge Fabricated by Laser Additive Manufacturing.
Creator: Calderon, Luisana, Kapat, Jayanta, Raghavan, Seetha, Mingareev, Ilya, University of Central Florida
Abstract / Description: Laser additive manufacturing (LAM) is an emerging technology capable of fabricating complex geometries not possibly made by investment casting methods for gas turbine applications. LAM techniques consist of building parts in a layer-by-layer process by selectively melting metal powders. In the present study, a mock leading edge segment of a turbine blade fabricated by LAM of Inconel 718 powders is investigated. For this particular design, the traditional showerhead film cooling holes have...
Show moreLaser additive manufacturing (LAM) is an emerging technology capable of fabricating complex geometries not possibly made by investment casting methods for gas turbine applications. LAM techniques consist of building parts in a layer-by-layer process by selectively melting metal powders. In the present study, a mock leading edge segment of a turbine blade fabricated by LAM of Inconel 718 powders is investigated. For this particular design, the traditional showerhead film cooling holes have been replaced by two strips containing engineered-porous regions with the purpose of simulating the effect of transpiration cooling. Transpiration cooling has been considered a promising external convective cooling method capable of providing a more uniform film and higher adiabatic film cooling effectiveness than conventional discrete film cooling. In addition, many studies have shown that this technique can yield high firing temperatures with much less coolant consumption than discrete film cooling. In this current study, adiabatic film cooling effectiveness is investigated by means of mass transfer using pressure sensitive paint (PSP). The experiments are conducted for blowing ratios ranging between M = 0.03 and M = 0.28 for a nominal density ratio of 1.5. The density ratio is obtained by using air as the mainstream flow and CO2 as the secondary flow (or coolant source). Results indicate higher coverage and film cooling effectiveness when increasing blowing ratio at the expense of higher pressure drop. In addition, the experimental results are compared to numerical analyses performed using steady state Reynolds Average Navier Stokes (RANS) simulations.
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Date Issued: 2018
Identifier: CFE0007315, ucf:52117
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007315

Title: PROFESSIONAL SCHOOL COUNSELORS' PERSPECTIVES ON THE EFFECTS OF MILITARY PARENTAL DEPLOYMENT ON SCHOOL-AGE CHILDREN AND ADOLESCENTS.
Creator: McCloud, Cheryl, Robinson, E.H. Mike, University of Central Florida
Abstract / Description: This qualitative study used an exploratory phenomenological approach to examine professional school counselors' perspectives on the effects of military parental deployment on school aged children and adolescents. The voices of school counselors who work with military connected children are absent from the literature. The research site was a professional counseling conference in Germany in the fall of 2010. Participants consisted of 12 professional school counselors who work with school-aged...
Show moreThis qualitative study used an exploratory phenomenological approach to examine professional school counselors' perspectives on the effects of military parental deployment on school aged children and adolescents. The voices of school counselors who work with military connected children are absent from the literature. The research site was a professional counseling conference in Germany in the fall of 2010. Participants consisted of 12 professional school counselors who work with school-aged children and adolescents who have experienced parental military deployment. Participants adopted pseudonyms though several indicated an affiliation with Department of Defense Dependent Schools (DODDS) and therefore offered their unique perspectives as school counselors living in military communities and working almost exclusively with military connected children and families. Data collection consisted of individual interviews with counselor participants. Data analysis consisted of coding meaningful words and phrases and yielded 33 preliminary categories that became new codes. Analysis of relationships between codes resulted in the emergence of four distinct themes: Military Life, Stages of Deployment, Role of the Counselor, and Children and Adolescents. Themes were supported by quotations of meaningful statements, thus participant voices provide thick, rich descriptions of the phenomenon. Validity strategies included peer debriefing, researcher positionality, and multiple examinations of the data set.
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Date Issued: 2011
Identifier: CFE0004046, ucf:49128
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004046

Title: The effect of carbon nanotube/organic semiconductor interfacial area on the performance of organic transistors.
Creator: Kang, Narae, Khondaker, Saiful, Leuenberger, Michael, Zhai, Lei, University of Central Florida
Abstract / Description: Organic field-effect transistors (OFETs) have attracted tremendous attention due to their flexibility, transparency, easy processiblity and low cost of fabrication. High-performance OFETs are required for their potential applications in the organic electronic devices such as flexible display, integrated circuit, and radiofrequency identification tags. One of the major limiting factors in fabricating high-performance OFET is the large interfacial barrier between metal electrodes and OSC which...
Show moreOrganic field-effect transistors (OFETs) have attracted tremendous attention due to their flexibility, transparency, easy processiblity and low cost of fabrication. High-performance OFETs are required for their potential applications in the organic electronic devices such as flexible display, integrated circuit, and radiofrequency identification tags. One of the major limiting factors in fabricating high-performance OFET is the large interfacial barrier between metal electrodes and OSC which results in low charge injection from the metal electrodes to OSC. In order to overcome the challenge of low charge injection, carbon nanotubes (CNTs) have been suggested as a promising electrode material for organic electronic devices. In this dissertation, we study the effect of carbon nanotube (CNT) density in CNT electrodes on the performance of organic field effect transistor (OFETs). The devices were fabricated by thermal evaporation of pentacene on the Pd/single walled CNT (SWCNT) electrodes where SWCNTs of different density (0-30/um) were aligned on Pd using dielectrophoresis (DEP) and cut via oxygen plasma etching to keep the length of nanotube short compared to the channel length. From the electronic transport measurements of 40 devices, we show that the average saturation mobility of the devices increased from 0.02 for zero SWCNT to 0.06, 0.13 and 0.19 cm2/Vs for low (1-5 /(&)#181;m), medium (10-15 /(&)#181;m) and high (25-30 /(&)#181;m) SWCNT density in the electrodes, respectively. The increase is three, six and nine times for low, medium and high density SWCNTs in the electrode compared to the devices that did not contain any SWCNT. In addition, the current on-off ratio and on-current of the devices are increased up to 40 times and 20 times with increasing SWCNT density in the electrodes. Our study shows that although a few nanotubes in the electrode can improve the OFET device performance, significant improvement can be achieved by maximizing SWCNT/OSC interfacial area. The improved OFET performance can be explained due to a reduced barrier height of SWCNT/pentacene interface compared to metal/pentacene interface which provides more efficient charge injection pathways with increased SWCNT/pentacene interfacial area.
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Date Issued: 2012
Identifier: CFE0004558, ucf:49252
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004558

Title: FACTORS INFLUENCING EFFECTIVENESS OF INTERORGANIZATIONAL NETWORKS AMONG CRISIS MANAGEMENT ORGANIZATIONS: A COMPARATIVE PERSPECTIVE.
Creator: Sahin, Bahadir, Wan, Thomas, University of Central Florida
Abstract / Description: Crisis management has become one of the most important public policy areas in recent decades with greater numbers of manmade and natural disasters. History showed that well-implemented crisis management policies can save lives and reduce costs in a disaster. Literature offered various suggestions for more effective crisis management policies with different techniques utilizing different theoretical frameworks. Informal relationships among crisis management employees were suggested to have a...
Show moreCrisis management has become one of the most important public policy areas in recent decades with greater numbers of manmade and natural disasters. History showed that well-implemented crisis management policies can save lives and reduce costs in a disaster. Literature offered various suggestions for more effective crisis management policies with different techniques utilizing different theoretical frameworks. Informal relationships among crisis management employees were suggested to have a positive impact on crisis management effectiveness. Yet it was not demonstrated with advanced statistical tools if there is such a relationship. This study considers crisis management effort as a network effort and employs complex adaptive systems theory in order to understand factors influencing effectiveness of crisis management networks. Complex adaptive systems theory presents that more open communication lines in a given network or an organization would increase effectiveness of it since inner processes of the network or organization would obtain more information from the chaotic environment. Quality of informal relationships (casual relationships, social capital etc.) was hypothesized as a tool to open more communication lines within an agency which would eventually increase effectiveness of the network constructed by the organization. Based on the theoretical framework, adaptiveness capacity of the agencies was also tested in order to understand a correlation between adaptation and effectiveness of crisis management networks. Multiple case-study method was employed to identify incidents that can represent crisis management in full perspective. Terrorist attacks carried upon by the same terrorist network hit New York in 2001, Istanbul in 2003, Madrid in 2004, and London in 2005 were selected. First response phase of crisis management and policy changes after and before the attacks were discussed. Public administration processes and other social-economical conditions of countries were examined in terms of crisis management structure. Names of key agencies of selected crisis management systems were suggested by a social network analysis tool-UCINET. Six key agencies per incident were targeted for surveys. Surveys included a nine-item-quality of informal relationships, four-item-adaptiveness capability, and ten-item-perceived effectiveness of crisis management networks-scales. Respondents were asked to fill in online surveys where they could refer to their colleagues in the same incidents. 230 respondents were aimed and 246 survey responses were obtained as a result. Surveys formed a structural equation model representing 23 observed factors and 2 latent constructs. Confirmatory factor analysis was utilized to validate hypothesis-driven conceptual models. Quality of informal relationships was found to have a significant positive impact on perceived crisis management network effectiveness (Standardized regression coefficient = .39). Two of the adaptiveness variables, openness to change and intra-organizational training were also positively correlated with the dependent variable of the study (Standardized regression coefficient = .40 and .26 respectively). Turkish and American groups' differences suggested a social-economical difference in societies. Majority of the respondents were some type of managers which made it possible to generalize the results for all phases of crisis management. Discussions suggested improved informal relationships among crisis management employees to provide a better crisis management during an extreme event. Collaborative social events were offered to improve crisis management effectiveness. An agency's openness to change proposed that a crisis management organization should be flexible in rules and structureto gain more efficacy. The other adaptiveness variable, intra-organizational training efforts were proposed to have certain influence on effectiveness of crisis management network. Factors built latent construct of perceived crisis management effectiveness were also found out to be important on crisis management, which of some are ability to carry out generic crisis management functions, mobilize personnel and resources efficiently, process information adequately, blend emergent and established entities, provide appropriate reports for news media etc. Study contributed to the complex adaptive system theory since the fundamentals of the theory were tested with an advanced quantitative method. Non-linear relationships within a system were tested in order to reveal a correlation as the theory suggested, where the results were convincingly positive. Crisis management networks' effectiveness was demonstrated to be validated by a ten-item-scale successfully. Future research might utilize more disaster cases both natural and manmade, search for impact of different communication tools within a system, and look at the relationships among members of crisis management networks instead looking within an organization.
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Date Issued: 2009
Identifier: CFE0002709, ucf:48173
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002709

Title: Experimental and Numerical Study of Endwall Film Cooling.
Creator: Mahadevan, Srikrishna, Kapat, Jayanta, Verma, Shashi, Vasu Sumathi, Subith, Ahmed, Kareem, Shivamoggi, Bhimsen, University of Central Florida
Abstract / Description: This research work investigates the thermal performance of a film-cooled gas turbine endwall under two different mainstream flow conditions. In the first part of the research investigation, the effect of unsteady passing wakes on a film-cooled pitchwise-curved surface (representing an endwall without airfoils) was experimentally studied for heat transfer characteristics on a time-averaged basis. The temperature sensitive paint technique was used to obtain the local temperatures on the test...
Show moreThis research work investigates the thermal performance of a film-cooled gas turbine endwall under two different mainstream flow conditions. In the first part of the research investigation, the effect of unsteady passing wakes on a film-cooled pitchwise-curved surface (representing an endwall without airfoils) was experimentally studied for heat transfer characteristics on a time-averaged basis. The temperature sensitive paint technique was used to obtain the local temperatures on the test surface. The required heat flux input was provided using foil heaters. Discrete film injection was implemented on the test surface using cylindrical holes with a streamwise inclination angle of 35? and no compound angle relative to the mean approach velocity vector. The passing wakes increased the heat transfer coefficients at both the wake passing frequencies that were experimented. Due to the increasing film cooling jet turbulence and strong jet-mainstream interaction at higher blowing ratios, the heat transfer coefficients were amplified. A combination of film injection and unsteady passing wakes resulted in a maximum pitch-averaged and centerline heat transfer augmentation of ? 28% and 31.7% relative to the no wake and no film injection case. The second part of the research study involves an experimental and numerical analysis of secondary flow and coolant film interaction in a high subsonic annular cascade with a maximum isentropic throat Mach number of ? 0.68. Endwall (platform) thermal protection is provided using discrete cylindrical holes with a streamwise inclination angle of 30? and no compound angle relative to the mean approach velocity vector. The surface flow visualization on the inner endwall provided the location of the saddle point and the three-dimensional separation lines. Computational predictions showed that the leading-edge horseshoe vortex was confined to approximately 1.5% of the airfoil span for the no film injection case and intensified with low momentum film injection. At the highest blowing ratio, the film cooling jet weakened the horseshoe vortex at the leading-edge plane. The passage vortex was intensified with coolant injection at all blowing ratios. It was seen that increasing average blowing ratio improved the film effectiveness on the endwall. The discharge coefficients calculated for each film cooling hole indicated significant non-uniformity in the coolant discharge at lower blowing ratios and the strong dependence of discharge coefficients on the mainstream static pressure and the location of three-dimensional separation lines. Near the airfoil suction side, a region of coalesced film cooling jets providing close to uniform film coverage was observed, indicative of the mainstream acceleration and the influence of three-dimensional separation lines.
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Date Issued: 2015
Identifier: CFE0005973, ucf:50775
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005973

Title: Integrated Maritime Simulation Complex Management, Quality And Training Effectiveness From The Perspective Of Modeling And Simulation In The State Of Florida, USA (A Case Study).
Creator: Sendi, Yaser, Kincaid, John, Rabelo, Luis, Lee, Gene, University of Central Florida
Abstract / Description: Naturally, maritime training simulators at all events are valuable instructional and pedagogical tools. Through the history, the maritime simulation was utilized to train prospective maritime apprentices in whom it has filled the gap left by the acute shortage of opportunities for jobs onboard vessels around the globe. However, professional seafarers are the axis of success and competitiveness in the field of maritime training. They are the ones that, who are well trained and have the...
Show moreNaturally, maritime training simulators at all events are valuable instructional and pedagogical tools. Through the history, the maritime simulation was utilized to train prospective maritime apprentices in whom it has filled the gap left by the acute shortage of opportunities for jobs onboard vessels around the globe. However, professional seafarers are the axis of success and competitiveness in the field of maritime training. They are the ones that, who are well trained and have the responsibilities of their work and the surrounding environment. In order to achieve the success along with effective training skills, both maritime companies and seafarers should implement a management of safety onboard ships, which only can be executed through the effective usage of the Bridge Resource Management (BRM) and righteous maritime simulation training.Qualitative upgrading of the maritime training process at higher education levels depends predominantly on the instructive value of the instructors' educational software and the content of these programs which contains advanced and intelligent scenarios that benefit positively in providing effective training in order to, transfer and implement their gained skills from virtual reality to the actual environment with minimal risks and additionally to avoid the unforeseen occurrences at sea. The outcomes of the evaluation have shown the instructional suitability of the maritime educational scheme and significant capabilities, it provides, as well as the domains and frameworks for its instructional development. The above facts are substantial in the refinement and improvement of the current maritime education and growth of the apprentices' capabilities and the professionalism of their skills, along with the farthest purpose of creating more educated marine navigators in the worldwide merchant fleet.This research proposes and demonstrates in details the purpose of the maritime simulation training complexes, the elements that if provided, will lead to an effective maritime simulation training, types of maritime simulation, the International Maritime Organization (IMO), its tools and its power for the effectiveness of the maritime simulation training through different conventions (&) codes and the future for the maritime simulation training, in order to emphasize and accentuate the interplay between instructors and apprentices in an integrated maritime simulation complex on which a serious maritime event is taking place.The distillation of this thesis draws an attention to the effectiveness of the partnership between maritime apprentices and their instructors across a maritime simulation training complex scheme during a virtual maritime scenario event in an advanced facilities located in the state of Florida, which is armed with modern technology, provides both added stimulation for the apprentice himself and elevates the simulator a degree toward a vessel for practical training and/or sailing.
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Date Issued: 2015
Identifier: CFE0005999, ucf:50787
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005999

Title: Growth and doping of MoS2 thin films for electronic and optoelectronic applications.
Creator: Abouelkhair, Hussain, Peale, Robert, Kaden, William, Stolbov, Sergey, Coffey, Kevin, University of Central Florida
Abstract / Description: MoS2 high absorption coefficient, high mobility, mechanical flexibility, and chemical inertness is very promising for many electronic and optoelectronic applications. The growth of high-quality MoS2 by a scalable and doping compatible method is still lacking. Therefore, the suitable dopants for MoS2 are not fully explored yet. This dissertation consists mainly of four main studies. The first study is on the growth of MoS2 thin films by atmospheric pressure chemical vapor deposition. Scanning...
Show moreMoS2 high absorption coefficient, high mobility, mechanical flexibility, and chemical inertness is very promising for many electronic and optoelectronic applications. The growth of high-quality MoS2 by a scalable and doping compatible method is still lacking. Therefore, the suitable dopants for MoS2 are not fully explored yet. This dissertation consists mainly of four main studies. The first study is on the growth of MoS2 thin films by atmospheric pressure chemical vapor deposition. Scanning electron microscope images revealed the growth of microdomes of MoS2 on top of a smooth MoS2 film. These microdomes are very promising as a broadband omnidirectional light trap for light harvesting applications. The second study is on the growth of MoS2 thin films by low pressure chemical vapor deposition (LPCVD). Control of sulfur vapor flow is essential for the growth of a pure phase of MoS2. Turning off sulfur vapor flow during the cooling cycle at 700 (&)#186;C leads to the growth of highly textured MoS2 with a Hall mobility of 20 cm2/Vs. The third study was on the growth of Ti-doped MoS2 thin films by LPCVD. The successful doping was confirmed by Hall effect measurement and secondary ion mass spectrometry (SIMS). Different growth temperatures from 1000 to 700 ? were studied. Ti act as a donor in MoS2. The fourth study is on fluorine-doped SnO2 (FTO) which has many technological applications including solar cells and transistors. FTO was grown by an aqueous-spray-based method. The main objective was to compare the actual against the nominal concentration of fluorine using SIMS. The concentration of fluorine in the grown films is lower than the concentration of fluorine in the aqueous solution.?
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Date Issued: 2017
Identifier: CFE0006847, ucf:51767
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006847

Title: Thermally induced motion, collision and mixing of levitated droplets.
Creator: Davanlou, Ashkan, Kumar, Ranganathan, Cho, Hyoung Jin, Deng, Weiwei, Mansy, Hansen, Shivamoggi, Bhimsen, University of Central Florida
Abstract / Description: This dissertation investigates the motion of a levitated droplet experimentally and analytically against the Marangoni flow in an immiscible outer fluid at higher speeds than is possible currently. Based on our earlier experiments, when a droplet is released from a height of 1.5 (-) 4 times its diameter from the liquid surface, it can overcome the impact and stay levitated at the liquid-air interface due to the existence of an air gap between the droplet and the liquid film. In order to...
Show moreThis dissertation investigates the motion of a levitated droplet experimentally and analytically against the Marangoni flow in an immiscible outer fluid at higher speeds than is possible currently. Based on our earlier experiments, when a droplet is released from a height of 1.5 (-) 4 times its diameter from the liquid surface, it can overcome the impact and stay levitated at the liquid-air interface due to the existence of an air gap between the droplet and the liquid film. In order to explain this behavior of droplet traveling against the counter-current motion, we propose a simple approach: first, the Marangoni convection inside the thin film is considered without the droplet floating on the surface. By using a level-set method and solving the Navier-Stokes equation, the free surface velocity and deformation are calculated. Then, these quantities are used to solve for droplet velocity and drag coefficient simultaneously using a force balance. In order to compare the simulation results, experiments with levitated water droplets on an immiscible carrier liquid, FC-43, were conducted for various temperature gradients, and droplet velocities were measured at different locations using high-speed imaging. The experimental results are in good agreement with the developed theoretical model. For a Reynolds number range of 2-32, it is shown that the drag coefficients are up to 66% higher than those for the fully immersed sphere at the same Reynolds numbers. A correlation is proposed to calculate the drag coefficient of levitated droplets for various temperature drops across the channel.For the first time, it is shown that it is possible to realize the natural coalescence of droplets through Marangoni effect without any external stimulation, and deliver the coalesced droplet to a certain destination through the use of surface tension gradients. The effects of the various shapes and sizes upon collision are studied. Regions of coalescence and stretching separation of colliding droplets are delineated based on Weber number and impact number. The existence of the transition line between coalescence and stretching separation in this passive mode of transport is similar to what was observed in the literature for forced coalescence at significantly higher Weber numbers. It is also found that a thermocapillary environment improves the mixing process. In order to illustrate and quantify the mixing phenomenon, the dispensed droplets were made of potassium hydroxide and phenolphthalein which is used as a pH indicator. The experiments show the possibility to reach mixing rates as high as 74% within 120 ms. This study offers new insight to thermo-coalescence and demonstrates how natural coalescence could be used to transport, mix and collect biochemical assays more efficiently. The results of this research can be engineered to enhance the performance of self-cleaning surfaces and micro-total analysis systems ((&)#181;TAS), where sample transport, filtration, chemical reactions, separation and detection are of great interest.
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Date Issued: 2015
Identifier: CFE0006213, ucf:51106
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006213

Title: RF Circuit Designs for Reliability and Process Variability Resilience.
Creator: Kritchanchai, Ekavut, Yuan, Jiann-Shiun, Sundaram, Kalpathy, Wei, Lei, Lin, Mingjie, Chow, Lee, University of Central Florida
Abstract / Description: Complementary metal oxide semiconductor (CMOS) radio frequency (RF) circuit design has been an ever-lasting research field. It has gained so much attention since RF circuits offer high mobility and wide-band efficiency, while CMOS technology provides the advantage of low cost and high integration capability. At the same time, CMOS device size continues to scale to the nanometer regime. Reliability issues with RF circuits have become more challenging than ever before. Reliability mechanisms,...
Show moreComplementary metal oxide semiconductor (CMOS) radio frequency (RF) circuit design has been an ever-lasting research field. It has gained so much attention since RF circuits offer high mobility and wide-band efficiency, while CMOS technology provides the advantage of low cost and high integration capability. At the same time, CMOS device size continues to scale to the nanometer regime. Reliability issues with RF circuits have become more challenging than ever before. Reliability mechanisms, such as gate oxide breakdown, hot carrier injection, negative bias temperature instability, have been amplified as the device size shrinks. In addition, process variability becomes a new design paradigm in modern RF circuits.In this Ph.D. work, a class F power amplifier (PA) was designed and analyzed using TSMC 180nm process technology. Its pre-layout and post-layout performances were compared. Post-layout parasitic effect decreases the output power and power-added efficiency. Physical insight of hot electron impact ionization and device self-heating was examined using the mixed-mode device and circuit simulation to mimic the circuit operating environment. Hot electron effect increases the threshold voltage and decreases the electron mobility of an n-channel transistor, which in turn decreases the output power and power-added efficiency of the power amplifier, as evidenced by the RF circuit simulation results. The device self-heating also reduces the output power and power-added efficiency of the PA. The process, voltage, and temperature (PVT) effects on a class AB power amplifier were studied. A PVT compensation technique using a current-source as an on-chip sensor was developed. The adaptive body bias design with the current sensing technique makes the output power and power-added efficiency much less sensitive to process variability, supply voltage variation, and temperature fluctuation, predicted by our derived analytical equations which are also verified by Agilent Advanced Design System (ADS) circuit simulation.Process variations and hot electron reliability on the mixer performance were also evaluated using different process corner models. The conversion gain and noise figure were modeled using analytical equations, supported by ADS circuit simulation results. A process invariant current source circuit was developed to eliminate process variation effect on circuit performance. Our conversion gain, noise figure, and output power show robust performance against PVT variations compared to those of a traditional design without using the current sensor, as evidenced by Monte Carlo statistical simulation.Finally, semiconductor process variations and hot electron reliability on the LC-voltage controlled oscillator (VCO) performance was evaluated using different process models. In our newly designed VCO, the phase noise and power consumptions are resilient against process variation effect due to the use of on-chip current sensing and compensation. Our Monte-Carlo simulation and analysis demonstrate that the standard deviation of phase noise in the new VCO design reduces about five times than that of the conventional design.
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Date Issued: 2016
Identifier: CFE0006131, ucf:51182
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006131

Title: Managing Effective Collaboration among Law Enforcement, Intelligence Services, and Military Forces in Fight against Terrorism and Organized Crime.
Creator: Demirhan, Cihan, Kapucu, Naim, Hu, Qian, Feldheim, Mary Ann, Rivera, Fernando, University of Central Florida
Abstract / Description: The fight against terrorism and organized crime require strong collaboration between public security organizations. Public security networks include several agencies that are not bound to each other with strong hierarchical ties. Because of a lack of the strong hierarchical structure, managing public networks is not similar to managing a single government agency. This study aims to examine the factors influencing network effectiveness in the public security sector. The main research questions...
Show moreThe fight against terrorism and organized crime require strong collaboration between public security organizations. Public security networks include several agencies that are not bound to each other with strong hierarchical ties. Because of a lack of the strong hierarchical structure, managing public networks is not similar to managing a single government agency. This study aims to examine the factors influencing network effectiveness in the public security sector. The main research questions of the study are: Which factors are important for effectiveness in public security networks? What is the role of inter-organizational trust among partner agencies? Which kind of leadership style will achieve the highest performance in public security networks? What is the relative importance of goal convergence and organizational culture in network effectiveness? How does the relationship between inter-organizational trust, leadership style, goal convergence and organizational culture impact network effectiveness? In order to find these relations, a self-reported survey was sent to 2,095 current and previous Turkish public security network managers. The study found that inter-organizational trust and goal convergence have a positive relationship with network effectiveness. Although facilitator leadership is found to be the most common leadership style in Turkish public security networks, it is found as inappropriate to achieve higher network effectiveness. According to the results, the co-producer network leadership is the most convenient leadership style in terms of network effectiveness. While the results of the descriptive statistics confirm that six specific features of organizational culture in public security sector have negative influence on network effectiveness, the hypothesis testing with the covariance structure model only support the negative impact of competition among partner organization. This study contributes to the literature on network effectiveness with particular proposals for the public security managers and practitioners.
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Date Issued: 2014
Identifier: CFE0005479, ucf:50350
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005479

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: Underwood, Arthur, Murray, Kenneth, Murray, Barbara, Baldwin, Lee, Hutchinson, Cynthia, University of Central Florida
Abstract / Description: 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.
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Date Issued: 2014
Identifier: CFE0005433, ucf:50406
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005433

Title: FINITE ELEMENT METHOD MODELING OF ADVANCED ELECTRONIC DEVICES.
Creator: Chen, Yupeng, Wu, Thomas, University of Central Florida
Abstract / Description: In this dissertation, we use finite element method together with other numerical techniques to study advanced electron devices. We study the radiation properties in electron waveguide structure with multi-step discontinuities and soft wall lateral confinement. Radiation mechanism and conditions are examined by numerical simulation of dispersion relations and transport properties. The study of geometry variations shows its significant impact on the radiation intensity and direction. In...
Show moreIn this dissertation, we use finite element method together with other numerical techniques to study advanced electron devices. We study the radiation properties in electron waveguide structure with multi-step discontinuities and soft wall lateral confinement. Radiation mechanism and conditions are examined by numerical simulation of dispersion relations and transport properties. The study of geometry variations shows its significant impact on the radiation intensity and direction. In particular, the periodic corrugation structure exhibits strong directional radiation. This interesting feature may be useful to design a nano-scale transmitter, a communication device for future nano-scale system. Non-quasi-static effects in AC characteristics of carbon nanotube field-effect transistors are examined by solving a full time-dependent, open-boundary Schrödinger equation. The non-quasi-static characteristics, such as the finite channel charging time, and the dependence of small signal transconductance and gate capacitance on the frequency, are explored. The validity of the widely used quasi-static approximation is examined. The results show that the quasi-static approximation overestimates the transconductance and gate capacitance at high frequencies, but gives a more accurate value for the intrinsic cut-off frequency over a wide range of bias conditions. The influence of metal interconnect resistance on the performance of vertical and lateral power MOSFETs is studied. Vertical MOSFETs in a D2PAK and DirectFET package, and lateral MOSFETs in power IC and flip chip are investigated as the case studies. The impact of various layout patterns and material properties on RDS(on) will provide useful guidelines for practical vertical and lateral power MOSFETs design.
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Date Issued: 2006
Identifier: CFE0001389, ucf:46987
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001389

Title: EFFECTS OF A COMPUTER GAME ON MATHEMATICS ACHIEVEMENT AND CLASS MOTIVATION: AN EXPERIMENTAL STUDY.
Creator: kebritchi, Mansureh, Hirumi, Atsusi, University of Central Florida
Abstract / Description: In the last few years educational computer games have gained attention as a tool for facilitating learning in different sectors of society including but not limited to military, health, and education. However, advances in computer game technology continue to outpace research on its effectiveness. Few empirical studies have investigated the effects of educational games in the context of formal K-12 settings. The purpose of this study was to examine the effects of a series of mathematics...
Show moreIn the last few years educational computer games have gained attention as a tool for facilitating learning in different sectors of society including but not limited to military, health, and education. However, advances in computer game technology continue to outpace research on its effectiveness. Few empirical studies have investigated the effects of educational games in the context of formal K-12 settings. The purpose of this study was to examine the effects of a series of mathematics computer games on mathematics achievement and motivation of high school students. In addition, the role of prior mathematics knowledge, computer skill, and English language skill of the participants on their mathematics achievement and motivation when they played the games were investigated. A total of 193 students and 10 teachers from an urban high school in the southeast of the United States of the America participated in this study. The teachers were randomly assigned to treatment and control groups. Students' mathematics achievement was measured using school district benchmark exams and a game performance test generated by the developers of the mathematics games. A mathematics motivation questionnaire based on Keller's (1987a) ARCS model of motivational design measured students' mathematics motivation. Multivariate Analysis of Co-Variance (MANCOVA) was conducted to analyze the data. In addition, interviews were conducted to cross validate the results of the quantitative data. The MANCOVA results indicated significant improvement of the mathematics achievement of the experimental versus control group. No significant improvement was found in the motivation of the experimental versus control group. However, a significant improvement was found on the motivation scores of the students who played the games in their school lab and classrooms compared to the ones who played the games only in the school labs. In addition, the findings indicated that prior mathematics knowledge, computer skill and English language skill did not play significant roles in achievement and motivation of the experimental group. Teachers' interviews revealed that these individual differences had indeed played significant roles in game-playing at the beginning of using the games, but the impacts gradually diminished as the students gained the required game-playing skills. The overall results indicated that the mathematics games used in this study were effective teaching and learning tools to improve the mathematics skills of the students. Using the games in mathematics education was suggested by the teachers as an appropriate alternative way of teaching, as one of the teachers stated: "This is definitely the way that we have to go to teach mathematics in the future." Mathematics games should be integrated with classroom activities if teachers want to increase mathematics class motivation. Teachers' helps and supports are vital in using the games effectively in a population with different prior mathematics knowledge, computer skills, and English language skills.
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Date Issued: 2008
Identifier: CFE0002066, ucf:47577
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002066

Title: DESIGN, FABRICATION AND TESTING OF A SHAPE MEMORY ALLOY BASED CRYOGENIC THERMAL CONDUCTION SWITCH.
Creator: Krishnan, Vinu Bala, Vaidyanathan, Raj, University of Central Florida
Abstract / Description: Shape memory alloys (SMAs) can recover large strains (e.g., up to 8%) by undergoing a temperature-induced phase transformation. This strain recovery can occur against large forces, resulting in their use as actuators. The SMA elements in such actuators integrate both sensory and actuation functions. This is possible because SMAs can inherently sense a change in temperature and actuate by undergoing a shape change, associated with the temperature-induced phase transformation. The objective of...
Show moreShape memory alloys (SMAs) can recover large strains (e.g., up to 8%) by undergoing a temperature-induced phase transformation. This strain recovery can occur against large forces, resulting in their use as actuators. The SMA elements in such actuators integrate both sensory and actuation functions. This is possible because SMAs can inherently sense a change in temperature and actuate by undergoing a shape change, associated with the temperature-induced phase transformation. The objective of this work is to develop an SMA based cryogenic thermal conduction switch for operation between dewars of liquid methane and liquid oxygen in a common bulk head arrangement for NASA. The design of the thermal conduction switch is based on a biased, two-way SMA actuator and utilizes a commercially available NiTi alloy as the SMA element to demonstrate the feasibility of this concept. This work describes the design from concept to implementation, addressing methodologies and issues encountered, including: a finite element based thermal analysis, various thermo-mechanical processes carried out on the NiTi SMA elements, and fabrication and testing of a prototype switch. Furthermore, recommendations for improvements and extension to NASA's requirements are presented. Such a switch has potential application in variable thermal sinks to other cryogenic tanks for liquefaction, densification, and zero boil-off systems for advanced spaceport applications. The SMA thermal conduction switch offers the following advantages over the currently used gas gap and liquid gap thermal switches in the cryogenic range: (i) integrates both sensor and actuator elements thereby reducing the overall complexity, (ii) exhibits superior thermal isolation in the open state, and (iii) possesses high heat transfer ratios between the open and closed states. This work was supported by a grant from NASA Kennedy Space Center (NAG10-323) with William U. Notardonato as Technical Officer.
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Date Issued: 2004
Identifier: CFE0000038, ucf:46136
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000038

Title: Dynamic Behavior and Performance of Different Types of Multi-Effect Desalination Plants.
Creator: Abdelkareem, Mohamed, Chow, Louis, Mansy, Hansen, Das, Tuhin, Duranceau, Steven, University of Central Florida
Abstract / Description: Water and energy are two of the most vital resources for the socio-economic development and sustenance of humanity on earth. Desalination of seawater has been practiced for some decades and is a well-established means of water supply. However, this process consumes large amounts of energy and the global energy supply is also faced with some challenges. In this research, multi-effect desalination (MED) has been selected due to lower cost, lower operating temperature and efficient in terms of...
Show moreWater and energy are two of the most vital resources for the socio-economic development and sustenance of humanity on earth. Desalination of seawater has been practiced for some decades and is a well-established means of water supply. However, this process consumes large amounts of energy and the global energy supply is also faced with some challenges. In this research, multi-effect desalination (MED) has been selected due to lower cost, lower operating temperature and efficient in terms of primary energy and electricity consumption compared to other thermal desalination systems. The motivation for this research is to address thermo-economics and dynamic behavior of different MED feed configurations with/without vapor compression (VC). A new formulation for the steady-state models was developed to simulate different MED systems. Adding a thermal vapor compressor (TVC) or mechanical vapor compression (MVC) unit to the MED system is also studied to show the advantage of this type of integration. For MED-TVC systems, results indicate that the parallel cross feed (PCF) configuration has better performance characteristics than other configurations. A similar study of MED-MVC systems indicates that the PCF and forward feed (FF) configurations require less work to achieve equal distillate production. Reducing the steam temperature supplied by the MVC unit leads to an increase in second law efficiency and a decrease in specific power consumption (SPC) and total water price. Following the fact that the MED may be exposed to fluctuations (disturbances) in input parameters during operation. Therefore, there is a requirement to analyze their transient behavior. In the current study, the dynamic model is developed based on solving the basic conservation equations of mass, energy, and salt. In the case of heat source disturbance, MED plants operating in the backward feed (BF) may be exposed to shut down due to flooding in the first effect. For all applied disturbances, the change in the brine level is the slowest compared to the changes in vapor temperature, and brine and vapor flow rates. For MED-TVC, it is recommended to limit the seawater cooling flow rate reduction to under 12% of the steady-state value to avoid dryout in the evaporators. A reduction in the motive steam flow rate and cooling seawater temperature of more than 20% and 35% of steady-state values, respectively, may lead to flooding in evaporators and plant shutdown. Simultaneous combinations of two different disturbances with opposing effects have only a modest effect on plant operation and they can be used to control and mitigate the flooding/drying effects caused by the disturbances. For the MED-MVC, the compressor work reduction could lead to plant shutdown, while a reduction in the seawater temperature will lead to a reduction in plant production and an increase in SPC.
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Date Issued: 2019
Identifier: CFE0007423, ucf:52735
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007423

Title: Explore Contributing Geometric Factors and Built-Environment on Bicycle Activity and Safety at Intersections.
Creator: Castro, Scott, Abdel-Aty, Mohamed, Cai, Qing, Eluru, Naveen, University of Central Florida
Abstract / Description: This study attempts to explore all factors associated with bicycle motor-vehicle crashes at intersections in order to improve bicycle safety and bicycle activity. Factors such as exposure (bicycle and vehicle volumes), existing facilities (bike lanes, sidewalks, shared-use paths), geometric design (# of lanes, speed limit, medians, legs, roadway conditions), and land-use were collected and evaluated using Poisson, Zero-Inflated Poisson, and Negative Binomial models in SAS 9.4 software....
Show moreThis study attempts to explore all factors associated with bicycle motor-vehicle crashes at intersections in order to improve bicycle safety and bicycle activity. Factors such as exposure (bicycle and vehicle volumes), existing facilities (bike lanes, sidewalks, shared-use paths), geometric design (# of lanes, speed limit, medians, legs, roadway conditions), and land-use were collected and evaluated using Poisson, Zero-Inflated Poisson, and Negative Binomial models in SAS 9.4 software. Increasing the bicycle travel mode can have positive lasting effects on personal health, the environment, and improve traffic conditions. Deterrents that keep users from riding bicycles more are the lack of facilities and most importantly, safety concerns. Florida has consistently been a national leader in bicyclist deaths, which made this area a great candidate to study. Vehicle and bicycle volumes for 159 intersections in Orlando, Florida were collected and compared with crash data that was obtained. All existing facilities, geometric design properties, and land-uses for each intersection were collected for analysis. The results confirmed that an increase of motor-vehicles and bicyclists would increase the risk of a crash at an intersection. The presence of a keyhole lane (bike lane in-between a through and exclusive right turn lane), was shown to be statistically significant, and although it still had a positive correlation with injury risk, it had a much lower risk of crashes than a typical bike lane at intersections. The presence of a far shared path (more than 4 feet from the edge of curb) was shown to be statistically significant in decreasing the risk of crashes between bicycles and motor-vehicles at intersections. Institutional, agricultural, residential, government, and school land uses had positive correlations and were statistically significant with increasing activity of bicyclists at intersections. This study is unique because it uses actual bicycle volume as an exposure to determine the effects of bicycle safety and activity at intersections and not many others have done this. It is important for transportation planners and designers to use this information to design better complete streets in the future.
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Date Issued: 2018
Identifier: CFE0007318, ucf:52134
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007318

Title: Surface Measurements and Predictions of Full-Coverage Film Cooling.
Creator: Natsui, Gregory, Kapat, Jayanta, Raghavan, Seetha, Vasu Sumathi, Subith, University of Central Florida
Abstract / Description: Full-coverage film cooling is investigated both experimentally and numerically. First,surface measurements local of adiabatic film cooling eeffectiveness and heat transfer augmentation for four different arrays are described. Reported next is a comparison between two very common turbulence models, Realizable k-epsilon and SST k-omega, and their ability to predict local film cooling effectiveness throughout a full-coverage array.The objective of the experimental study is the quantification of...
Show moreFull-coverage film cooling is investigated both experimentally and numerically. First,surface measurements local of adiabatic film cooling eeffectiveness and heat transfer augmentation for four different arrays are described. Reported next is a comparison between two very common turbulence models, Realizable k-epsilon and SST k-omega, and their ability to predict local film cooling effectiveness throughout a full-coverage array.The objective of the experimental study is the quantification of local heat transferaugmentation and adiabatic film cooling effectiveness for four surfaces cooled by large, both in hole count and in non-dimensional spacing, arrays of film cooling holes. The four arrays are of two different hole-to-hole spacings (P=D = X=D = 14.5; 19.8) and two different hole inclination angles (alpha = 30°; 45°), with cylindrical holes compounded relative to the flow(beta = 45°) and arranged in a staggered configuration. Arrays of up to 30 rows are tested so that the superposition effect of the coolant film can be studied. In addition, shortened arrays of up to 20 rows of coolant holes are also tested so that the decay of the coolant film following injection can be studied.Levels of laterally averaged effectiveness reach values as high as η = 0.5, and are not yet at the asymptotic limit even after 20 - 30 rows of injection for all cases studied. Levels of heat transfer augmentation asymptotically approach values of h=h0 ≈ 1.35 rather quickly, only after 10 rows. It is conjectured that the heat transfer augmentation levels off very quickly due to the boundary layer reaching an equilibrium in which the perturbation from additional film rows has reached a balance with the damping effect resulting from viscosity. The levels of laterally averaged adiabatic film cooling effectiveness far exceeding eta = 0.5 aremuch higher than expected. The heat transfer augmentation levels off quickly as opposed tothe film effectiveness which continues to rise (although asymptotically) at large row numbers. This ensures that an increased row count represents coolant well spent.The numerical predictions are carried out in order to test the ability of the two mostcommon turbulence models to properly predict full-coverage film cooling. The two models chosen, Realizable k-epsilon (RKE) and Shear Stress Transport k-omega (SSTKW), areboth two-equation models coupled with Reynolds Averaged governing equations which makeseveral gross physical assumptions and require several empirical values. Hence, the modelsare not expected to provide perfect results. However, very good average values are seen tobe obtained through these simple models. Using RKE in order to model full-coverage filmcooling will yield results with 30% less error than selecting SSTKW.
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Date Issued: 2012
Identifier: CFE0004580, ucf:49221
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0004580

Radiation (4)	+ -
side effects (4)	+ -
teacher effectiveness (4)	+ -
Florida (3)	+ -
Game-Based Training (3)	+ -

LDMOS (3)	+ -
Learning (3)	+ -
Teacher Effectiveness (3)	+ -
effectiveness (3)	+ -
media effects (3)	+ -
Adiabatic Film Cooling Effectiveness (2)	+ -
Au (2)	+ -
Cognitive Load Theory (2)	+ -
Cu (2)	+ -
Diffusion (2)	+ -
Empirical Bayes (2)	+ -
Experimental (2)	+ -
Feedback (2)	+ -
Film Cooling (2)	+ -
Florida Comprehensive Assessment Test (2)	+ -
Flow (2)	+ -
Graphene (2)	+ -
Highway Safety Manual (2)	+ -
Kondo effect (2)	+ -
Modality Effect (2)	+ -
Physiological effect (2)	+ -
Pt (2)	+ -
RF circuit performance (2)	+ -
Safety Effects (2)	+ -
Simulation (2)	+ -

ETD Collection (150)	+ -
Honors Collection (19)	+ -
PRISM: Political & Rights Issues & Social Movements (2)	+ -

University of Central Florida (164)	+ -
Murray, Barbara (9)	+ -
Abdel-Aty, Mohamed (7)	+ -
Murray, Kenneth (7)	+ -
Doherty, Walter (6)	+ -

Hancock, Peter (6)	+ -
Kapat, Jayanta (6)	+ -
Khondaker, Saiful (6)	+ -
Taylor, Rosemarye (6)	+ -
Chow, Lee (5)	+ -
Kapucu, Naim (5)	+ -
Sundaram, Kalpathy (5)	+ -
Zhai, Lei (5)	+ -
Bowers, Clint (4)	+ -
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Eluru, Naveen (4)	+ -
Hu, Qian (4)	+ -
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