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- Title
- MODELING AND OPTIMIZATION OF BODY DIODE REVERSE RECOVERY CHARACTERISTICS OF LDMOS TRANSISTORS.
- Creator
-
Deschaine, Wesley, Shen, John, University of Central Florida
- Abstract / Description
-
As switching speeds for DC-DC converter applications keep becoming faster and faster and voltage requirements become smaller and smaller, the need for new device structures becomes more prevalent. Designers of these new structures will need to make sure they take into consideration the different power losses associated with the different structures and make modifications to reduce or if possible eliminate them. A new 30V LDMOS device has been created and is being implemented into a...
Show moreAs switching speeds for DC-DC converter applications keep becoming faster and faster and voltage requirements become smaller and smaller, the need for new device structures becomes more prevalent. Designers of these new structures will need to make sure they take into consideration the different power losses associated with the different structures and make modifications to reduce or if possible eliminate them. A new 30V LDMOS device has been created and is being implemented into a synchronous buck converter for future DC-DC conversions. This new lateral device has a Figure of Merit of 80mÙ*nC, representing a 50% reduction from the conventional trench MOSFET. The only draw back with this new device is that the body diode power loss has increased significantly. There are two principal goals of this research. The first is to reduce the body diode reverse recovery characteristics of a 30V LDMOS transistor without employing an additional Schottky diode, increasing the Figure of Merit, or decreasing the breakdown voltage past 30 volts. The second is to achieve 75% reduction in reverse recovery charge (Qrr) through each solution. Four solutions will be presented in this study and have been verified through extensive ISE-TCAD device and circuit simulation.
Show less - Date Issued
- 2006
- Identifier
- CFE0001081, ucf:46778
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001081
- Title
- SYNCHRONIZATION IN ADVANCED OPTICAL COMMUNICATIONS.
- Creator
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Kim, Inwoong, Li, Guifang, University of Central Florida
- Abstract / Description
-
All-optical synchronization and its application in advanced optical communications have been investigated in this dissertation. Dynamics of all-optical timing synchronization (clock recovery) using multi-section gain-coupled distributed-feedback (MS-GC DFB) lasers are discussed. A record speed of 180-GHz timing synchronization has been demonstrated using this device. An all-optical carrier synchronization (phase and polarization recovery) scheme from PSK (phase shift keying) data is proposed...
Show moreAll-optical synchronization and its application in advanced optical communications have been investigated in this dissertation. Dynamics of all-optical timing synchronization (clock recovery) using multi-section gain-coupled distributed-feedback (MS-GC DFB) lasers are discussed. A record speed of 180-GHz timing synchronization has been demonstrated using this device. An all-optical carrier synchronization (phase and polarization recovery) scheme from PSK (phase shift keying) data is proposed and demonstrated for the first time. As an application of all-optical synchronization, the characterization of advanced modulation formats using a linear optical sampling technique was studied. The full characterization of 10-Gb/s RZ-BPSK (return-to-zero binary PSK) data has been demonstrated. Fast lockup and walk-off of the all-optical timing synchronization process on the order of nanoseconds were measured in both simulation and experiment. Phase stability of the recovered clock from a pseudo-random bit sequence signal can be achieved by limiting the detuning between the frequency of free-running self-pulsation and the input bit rate. The simulation results show that all-optical clock recovery using TS-DFB lasers can maintain a better than 5 % clock phase stability for large variations in power, bit rate and optical carrier frequency of the input data and therefore is suitable for applications in ultrafast optical packet switching. All-optical timing synchronization of 180-Gb/s data streams has been demonstrated using a MS-GC DFB laser. The recovered clock has a jitter of less than 410 fs over a dynamic range of 7 dB. All-optical carrier synchronization from phase modulated data utilizes a phase sensitive oscillator (PSO), which used a phase sensitive amplifier (PSA) as a gain block. Furthermore, all-optical carrier synchronization from 10-Gb/s BPSK data was demonstrated in experiment. The PSA is configured as a nonlinear optical loop mirror (NOLM). A discrete linear system analysis was carried out to understand the stability of the PSO. Complex envelope measurement using coherent linear optical sampling with mode-locked sources is investigated. It is shown that reliable measurement of the phase requires that one of the optical modes of the sampling pulses be locked to the optical carrier of the data signal to be measured. Carrier-envelope offset (CEO) is found to have a negligible effect on the measurement. Measurement errors of the intensity profile and phase depend on the pulsewidth and chirp of the sampling pulses as well as the detuning between the carrier frequencies of the data signal and the center frequency of the sampling source. Characterization of the 10-Gb/s RZ-BPSK signal was demonstrated using the coherent detection technique. Measurements of the optical intensity profile, chirp and constellation diagram were demonstrated. A CW local oscillator was used and electrical sampling was performed using a sampling scope. A novel feedback scheme was used to stabilize homodyne detection.
Show less - Date Issued
- 2006
- Identifier
- CFE0001239, ucf:52894
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001239
- Title
- Sparse signal recovery under sensing and physical hardware constraints.
- Creator
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Mardaninajafabadi, Davood, Atia, George, Mikhael, Wasfy, Vosoughi, Azadeh, Rahnavard, Nazanin, Abouraddy, Ayman, University of Central Florida
- Abstract / Description
-
This dissertation focuses on information recovery under two general types of sensing constraints and hardware limitations that arise in practical data acquisition systems. We study the effects of these practical limitations in the context of signal recovery problems from interferometric measurements such as for optical mode analysis.The first constraint stems from the limited number of degrees of freedom of an information gathering system, which gives rise to highly constrained sensing...
Show moreThis dissertation focuses on information recovery under two general types of sensing constraints and hardware limitations that arise in practical data acquisition systems. We study the effects of these practical limitations in the context of signal recovery problems from interferometric measurements such as for optical mode analysis.The first constraint stems from the limited number of degrees of freedom of an information gathering system, which gives rise to highly constrained sensing structures. In contrast to prior work on compressive signal recovery which relies for the most part on introducing additional hardware components to emulate randomization, we establish performance guarantees for successful signal recovery from a reduced number of measurements even with the constrained interferometer structure obviating the need for non-native components. Also, we propose control policies to guide the collection of informative measurements given prior knowledge about the constrained sensing structure. In addition, we devise a sequential implementation with a stopping rule, shown to reduce the sample complexity for a target performance in reconstruction.The second limitation considered is due to physical hardware constraints, such as the finite spatial resolution of the used components and their finite aperture size. Such limitations introduce non-linearities in the underlying measurement model. We first develop a more accurate measurement model with structured noise representing a known non-linear function of the input signal, obtained by leveraging side information about the sampling structure. Then, we devise iterative denoising algorithms shown to enhance the quality of sparse recovery in the presence of physical constraints by iteratively estimating and eliminating the non-linear term from the measurements. We also develop a class of clipping-cognizant reconstruction algorithms for modal reconstruction from interferometric measurements that compensate for clipping effects due to the finite aperture size of the used components and show they yield significant gains over schemes oblivious to such effects.
Show less - Date Issued
- 2019
- Identifier
- CFE0007675, ucf:52467
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007675
- Title
- An Evaluation of Anxiety Following Substance Abuse Withdrawal and Assessment of Somatic Treatments presently Available with a Focus on Cranial Electrotherapy Stimulation.
- Creator
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Hutchison, Janet, Neff, Donna, Weiss, Josie, Covelli, Maureen, Seikel Thomas, Stacy, University of Central Florida
- Abstract / Description
-
Addictive disorders/substance use disorders (SUDS) affect almost everyone in the United States, either directly or indirectly. The cost of substance abuse to the social and economic structure in the United States is huge. Anxiety is one of the most frequently mentioned symptoms which lead to relapse during the early weeks of recovery due to neurohormonal changes in the limbic system as well as cortisol production which occur during this time. Present research in the treatment of anxiety in...
Show moreAddictive disorders/substance use disorders (SUDS) affect almost everyone in the United States, either directly or indirectly. The cost of substance abuse to the social and economic structure in the United States is huge. Anxiety is one of the most frequently mentioned symptoms which lead to relapse during the early weeks of recovery due to neurohormonal changes in the limbic system as well as cortisol production which occur during this time. Present research in the treatment of anxiety in substance abuse and long term recovery is focused on genetics and pharmaceuticals, however most pharmaceuticals produce sedation. Additional therapies in early recovery, which decrease the symptoms of anxiety while enhancing cognitive ability to learn and apply coping skills, are needed.Purpose: The purpose of this dissertation was to identify the natural degradation of anxiety symptoms occurring during the first few weeks following detox from alcohol or opiates. To identify non pharmacological methods in use to decrease anxiety symptoms during this period, and then examine whether treatment with Cranial Electrotherapy Stimulation (CES) would enhance the degradation of anxiety symptoms. Methods and Results: The initial prospective study of 53 men in residential treatment, measured anxiety on entry, 30 and 60 days. The results found that increased anxiety measured prior to a participant leaving against medical advice was more significant than increased anxiety measured on admission. The follow-on pilot study in the same residential program was a double-blind experimental study using CES with active and placebo CES units loaned from the manufacturer. The intervention was conducted during the first 3 weeks of opiate/alcohol abstinence; a period identified when anxiety peaks, and dropout rate is high. There were 29 men in the experimental group and 31 in the placebo group. Salivary cortisol and state anxiety were measured on the first and final day of CES treatment. Anxiety was also measured at study enrollment and at 30 days when study enrollment was terminated. The results were statistically inconclusive as both the placebo and CES (experimental) groups trended downward; however the trend was greater in the CES group. Discussion/Implications: Anxiety was identified as a significant factor in leaving treatment early. Cranial Electrotherapy Stimulation appears to decrease anxiety in non-substance abusing populations. However, these finding were not supported in this substance abusing population during the first month of recovery. Although CES appeared to be the most promising alternative therapy, more research is needed in the use of this and other emerging therapies for the treatment of anxiety symptoms during this early recovery period.
Show less - Date Issued
- 2016
- Identifier
- CFE0006118, ucf:51169
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006118
- Title
- Study of High Efficiency Micro Thermoelectric Energy Harvesters.
- Creator
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Pedrosa, Steven, Chen, Quanfang, Cho, Hyoung, Xu, Yunjun, University of Central Florida
- Abstract / Description
-
Thermal energy sources, including waste heat and thermal radiation from the sun, are important renewable energy resources. Thermal energy can be converted into electricity by thermoelectric phenomena; the thermoelectric phenomena can also be operated in reverse when provided an electric current, producing a temperature gradient across the device. Thermoelectric devices are scalable, renewable, and cost effective products that offer capabilities to harness waste heat or environmental heat...
Show moreThermal energy sources, including waste heat and thermal radiation from the sun, are important renewable energy resources. Thermal energy can be converted into electricity by thermoelectric phenomena; the thermoelectric phenomena can also be operated in reverse when provided an electric current, producing a temperature gradient across the device. Thermoelectric devices are scalable, renewable, and cost effective products that offer capabilities to harness waste heat or environmental heat sources, and convert the captured heat into usable electricity. The operating principle of a thermoelectric device requires that a temperature gradient be present across the device, which induces the flow of electrons from the hot side of the device to the cold side. Thermoelectric devices are currently hampered by the low conversion efficiencies and strict operating temperatures for certain materials. This study investigates the main factors affecting efficiencies of thermoelectric devices as energy harvesters and aims to optimize the devices for maximum efficiency and lower costs by using microfabrication processes and self-assembled materials for complete thermoelectric modules (TEMs). By first establishing operating conditions and a desired mode of operation, optimization equations have been established to determine device dimensions and performance parameters. Compact integration realized by microfabrication technologies that allow for multiple output voltages from a single chip was also investigated. Additionally, cost savings were found by reducing the number of fabrication processing steps and eliminating the need for precious metals during fabrication. The optimized design proposed in this study utilizes copper electrodes and requires fewer applications of photoresist than previous proposed designs. In fabrication of thin film based micro devices, the film quality and the composition of the film are essential elements for producing TEMs with desired efficiencies. Although Bi2Te3 has been investigated as thermoelectric material, this study determined that there was a possibility that both N-type and P-Type Bi2Te3 could be created from a single electrolyte solution by controlling the amount of Te present in the film. Films were produced with both AC and DC signals and varied composition of Te at.% of Bi2Te3 was achieved by controlling the average current density during electrochemical deposition. A linear relationship was established between the average current density and the resultant Te content. SEM and EDS were used to characterize the morphology and the composition of the thin films created. With the fabricated thermoelectric materials, analytical models could be developed using known material properties of thermoelectric films with a given Te content. The analytical results obtained by the developed optimization equations were comparable with the FEA models produced by using COMSOL, a multiphysics program with powerful solving algorithms that was used to evaluate designs. Further improvements to device performance can be achieved by designing a segmented thermoelectric device with multiple layers of thermoelectric material to allow the device to operate across a larger temperature gradient.
Show less - Date Issued
- 2011
- Identifier
- CFE0004486, ucf:49318
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004486
- Title
- Failing the Failed: A Treatise on the Need for a Research Based Pedagogical Approach to Credit Recovery.
- Creator
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Scott, Kelly, Boote, David, Robinson, Edward, Vitale, Thomas, Hayes, Burnice, University of Central Florida
- Abstract / Description
-
The purpose of this dissertation in practice is to address the problem of online credit recovery. Although online enrollments have skyrocketed in recent years and all preliminary research indicates a large percentage of those enrollments are from students seeking credit recovery, much of the curriculum currently being offered is not research-based. Following a literature review focused on the history of credit recovery as well as successful current methods, we designed CRIT (Credit Recovery...
Show moreThe purpose of this dissertation in practice is to address the problem of online credit recovery. Although online enrollments have skyrocketed in recent years and all preliminary research indicates a large percentage of those enrollments are from students seeking credit recovery, much of the curriculum currently being offered is not research-based. Following a literature review focused on the history of credit recovery as well as successful current methods, we designed CRIT (Credit Recovery Instructional Treatment), a research-based approach to curriculum design for credit recovery. CRIT is a standards based curriculum relying on criterion based assessments. This approach was then applied in the creation of specific curriculum for English 4 credit recovery and as a general approach for all subjects. A step by step evaluation plan for current and proposed approaches for credit recovery was then defined. Additionally, we provide a detailed implementation strategy specific to our organization but easily retrofitted for other organizations. We focus on the organization of Florida Virtual School (FLVS), a state run K-12 virtual school run as a special school district in Florida because it is a familiar organization; however, the model and results may be generalizable for online or traditional education.
Show less - Date Issued
- 2014
- Identifier
- CFE0005289, ucf:50565
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005289
- Title
- Failing the Failed: A treatise on the need for a research based pedagogical approach to credit recovery.
- Creator
-
Smith, Elise, Boote, David, Robinson, Edward, Vitale, Thomas, Hayes, Burnice, University of Central Florida
- Abstract / Description
-
The purpose of this dissertation in practice is to address the problem of online credit recovery. Although online enrollments have skyrocketed in recent years and all preliminary research indicates a large percentage of those enrollments are from students seeking credit recovery, much of the curriculum currently being offered is not research-based. Following a literature review focused on the history of credit recovery as well as successful current methods, we designed CRIT (Credit Recovery...
Show moreThe purpose of this dissertation in practice is to address the problem of online credit recovery. Although online enrollments have skyrocketed in recent years and all preliminary research indicates a large percentage of those enrollments are from students seeking credit recovery, much of the curriculum currently being offered is not research-based. Following a literature review focused on the history of credit recovery as well as successful current methods, we designed CRIT (Credit Recovery Instructional Treatment) a research-based approach to curriculum design for credit recovery. CRIT is a standards based curriculum relying on criterion based assessments. This approach was then applied in the creation of specific curriculum for English 4 credit recovery and as a general approach for all subjects. A step by step evaluation plan for current and proposed approaches for credit recovery was then defined. Additionally we provide a detailed implementation strategy specific to our organization but easily retrofitted for other organizations. We focus on the organization of Florida Virtual School (FLVS), a state run k-12 virtual school run as a special school district in Florida because it is a familiar organization. However, the model and results may be generalizable for online or traditional education.
Show less - Date Issued
- 2014
- Identifier
- CFE0005290, ucf:50568
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005290
- Title
- The Effects of Corporate Social Responsibility on Service Recovery Evaluations in Casual Dining Restaurants.
- Creator
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Albus, Heidi, Ro, Hee Jung, Parsa, Haragopal, Kwun, David, University of Central Florida
- Abstract / Description
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This study examined the effects of Corporate Social Responsibility (CSR) on service recovery in terms of customer satisfaction, repeat patronage, word of mouth, and consumer trust in casual dining restaurants. More specifically, this study proposed that CSR will have a halo effect on negative service recovery incidents and mitigate the adverse effects of the poor recovery. An experimental study consisting of a 3x2 between subjects factorial design was used. Three CSR conditions (positive,...
Show moreThis study examined the effects of Corporate Social Responsibility (CSR) on service recovery in terms of customer satisfaction, repeat patronage, word of mouth, and consumer trust in casual dining restaurants. More specifically, this study proposed that CSR will have a halo effect on negative service recovery incidents and mitigate the adverse effects of the poor recovery. An experimental study consisting of a 3x2 between subjects factorial design was used. Three CSR conditions (positive, negative, and no CSR) were matched with two service recovery conditions (positive or negative). Four hundred and eighteen subjects were recruited by a reputed marketing research firm. Results of this study showed that CSR and service recovery have a significant effect on customer satisfaction, repeat patronage, word of mouth, and consumer trust in casual dining restaurants. Furthermore, the results showed that CSR enhances the positive effects of good service recovery.
Show less - Date Issued
- 2012
- Identifier
- CFE0004348, ucf:49418
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004348
- Title
- RECOVERY OF HYDROGEN AND HELIUM FROM THEIR MIXTURES USING METAL HYDRIDES.
- Creator
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Oztek, Muzaffer, Hampton, Michael, University of Central Florida
- Abstract / Description
-
Waste streams of hydrogen and helium mixtures are produced at the Kennedy Space Center during purging of the hydrogen systems and supply lines. This process is done prior to and after hydrogen servicing. The purged waste gases are lost to the atmosphere, resulting in an annual loss of 2 million and 0.1 million standard cubic meters of helium and hydrogen, respectively. Recovery of these gases will have an economic benefit. Metals, alloys, and intermetallics are known to react with hydrogen in...
Show moreWaste streams of hydrogen and helium mixtures are produced at the Kennedy Space Center during purging of the hydrogen systems and supply lines. This process is done prior to and after hydrogen servicing. The purged waste gases are lost to the atmosphere, resulting in an annual loss of 2 million and 0.1 million standard cubic meters of helium and hydrogen, respectively. Recovery of these gases will have an economic benefit. Metals, alloys, and intermetallics are known to react with hydrogen in favorable conditions; therefore, they have the possibility of serving as separating and recovery agents. In this study, Mg2Ni, VTiNi and LaNi5 were studied for the separation of H2 from He, using differential scanning calorimetry and thermal volumetric analysis. The ability of LaNi5 to react with hydrogen reversibly at room temperature was verified, and further analysis focused on this compound. Size reduction and activation of LaNi5 by mechanical milling was investigated using different milling parameters for the purpose of activating the material for hydrogen absorption. Because it has been shown that addition of aluminum to LaNi5 resulted in improved hydriding and dehydriding properties, that system was studied further here. In this study, aluminum was added to LaNi5 by mechanical milling. Hydriding properties and elemental compositions of the samples were determined afterwards. The hydrogen absorption rate and capacity were compared to that of LaNi5. Both LaNi5 and its Al doped derivatives exhibited a reduced rate of hydrogen uptake and a reduced hydrogen capacity in the presence of helium. The effects of coating the samples with either gold-palladium or platinum were investigated. It was observed that coating the samples with Pt reduced the negative effect of He, whereas AuPd coating did not have any effect. Larger scale studies were done using a continuous U-tube hydride reactor, built and tested for separation of H2¬ from a 20:80 H2:He mixture. The amount of hydrogen retained in the bed was determined and found to be less than that for the batch systems.
Show less - Date Issued
- 2005
- Identifier
- CFE0000660, ucf:46507
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000660
- Title
- EFFECTS OF ENERGY-BASED THERAPIES ON POSTOPERATIVE RECOVERY: AN INTEGRATIVE REVIEW OF THE LITERATURE.
- Creator
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Wooten, Emily M, Bushy, Angeline, D'Amato-Kubiet, Leslee, University of Central Florida
- Abstract / Description
-
Associated with health care reform, there has been a growing interest among healthcare professionals regarding use of energy-based therapies as a complementary therapeutic intervention. The purpose of this integrative literature review was to examine the impact of energy-based therapies (i.e. healing touch, reiki, therapeutic touch) on patients� postoperative recovery. The methodology included identifying appropriate peer-reviewed, English-language research articles on the topic area that...
Show moreAssociated with health care reform, there has been a growing interest among healthcare professionals regarding use of energy-based therapies as a complementary therapeutic intervention. The purpose of this integrative literature review was to examine the impact of energy-based therapies (i.e. healing touch, reiki, therapeutic touch) on patients� postoperative recovery. The methodology included identifying appropriate peer-reviewed, English-language research articles on the topic area that were published between 2006 to 2018. Following a search in select data bases, articles focusing on the topic were critiqued, analyzed and synthesized by the researcher. Consistent and inconsistent findings along with gaps in the literature are noted. In general, the research supported positive postoperative recovery outcomes when energy-based therapies were included along with standard postoperative nursing care. This theses highlights implication for nursing practice, education, and policy and identifies study limitations. Given that research is limited on this topic area, additional studies are needed to establish supporting evidence to ascertain the effects of energy-based therapies when used as a complementary postoperative intervention.
Show less - Date Issued
- 2018
- Identifier
- CFH2000456, ucf:45865
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000456
- Title
- SETTING THE STAGE FOR A SOBER COMMUNITY ON CAMPUS.
- Creator
-
DeLisa, John, Chicurel, Steven, University of Central Florida
- Abstract / Description
-
In the last thirty years, a movement in America helps students struggling with substance abuse and dependency. Only recently, in the 1970s to be precise, has there been any significant documentation that unveils the problem of substance abuse in college. Schools like Texas Tech University and Kennesaw State University are in the forefront helping hundreds of thousands of students who struggle to have a safe and productive college experience. These schools provide support systems, scholarships...
Show moreIn the last thirty years, a movement in America helps students struggling with substance abuse and dependency. Only recently, in the 1970s to be precise, has there been any significant documentation that unveils the problem of substance abuse in college. Schools like Texas Tech University and Kennesaw State University are in the forefront helping hundreds of thousands of students who struggle to have a safe and productive college experience. These schools provide support systems, scholarships, and mentorship to those students who are free from drug use and dependence and are looking to further their education. It is my intent to demonstrate a growing need for these support systems and present a theatrical work that will raise awareness of this issue. Oftentimes, the issue of substance abuse is an embarrassing and uncomfortable topic for people to discuss. There are issues of denial at both the personal and academic level. By using theatre as a means to present this topic in a non-confrontational, engaging, and thoughtful manner, I contend that there can be progress in bringing Collegiate Recovery Programs to colleges nationwide. My play, A Way Back, will add to the canon of substance abuse plays with an emphasis on substance abuse recovery in college.
Show less - Date Issued
- 2014
- Identifier
- CFH0004580, ucf:45159
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004580
- Title
- LOW REYNOLDS NUMBER WATER FLOW CHARACTERISTICS THROUGH RECTANGULAR MICRO DIFFUSERS/NOZZLES WITH A PRIMARY FOCUS ON MAJOR/MINOR PRESSURE LOSS, STATIC PRESSURE RECOVERY, AND FLOW SEPARATION.
- Creator
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Hallenbeck, Kyle, Chew, Larry, University of Central Florida
- Abstract / Description
-
The field of microfluidics has recently been gathering a lot of attention due to the enormous demand for devices that work in the micro scale. The problem facing many researchers and designers is the uncertainty in using macro scaled theory, as it seems in some situations they are incorrect. The general idea of this work was to decide whether or not the flow through micro diffusers and nozzles follow the same trends seen in macro scale theory. Four testing wafers were fabricated using PDMS...
Show moreThe field of microfluidics has recently been gathering a lot of attention due to the enormous demand for devices that work in the micro scale. The problem facing many researchers and designers is the uncertainty in using macro scaled theory, as it seems in some situations they are incorrect. The general idea of this work was to decide whether or not the flow through micro diffusers and nozzles follow the same trends seen in macro scale theory. Four testing wafers were fabricated using PDMS soft lithography including 38 diffuser/nozzle channels a piece. Each nozzle and diffuser consisted of a throat dimension of 100μm x 50μm, leg lengths of 142μm, and half angles varying from 0o – 90o in increments of 5o. The flow speeds tested included throat Reynolds numbers of 8.9 – 89 in increments of 8.9 using distilled water as the fluid. The static pressure difference was measured from the entrance to the exit of both the diffusers and the nozzles and the collected data was plotted against a fully attached macro theory as well as Idelchik's approximations. Data for diffusers and nozzles up to HA = 50o hints at the idea that the flow is neither separating nor creating a vena contracta. In this region, static pressure recovery within diffuser flow is observed as less than macro theory would predict and the losses that occur within a nozzle are also less than macro theory would predict. Approaching a 50o HA and beyond shows evidence of unstable separation and vena contracta formation. In general, it appears that there is a micro scaled phenomenon happening in which flow gains available energy when the flow area is increased and looses available energy when the flow area decreases. These new micro scaled phenomenon observations seem to lead to a larger and smaller magnitude of pressure loss respectively.
Show less - Date Issued
- 2008
- Identifier
- CFE0002391, ucf:47772
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002391
- Title
- Comparative nutrient removal with innovative green soprtion media for groundwater and stormwater co-treatment.
- Creator
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Wen, Dan, Chang, Ni-bin, Nam, Boo Hyun, Kibler, Kelly, Wanielista, Martin, Zheng, Qipeng, University of Central Florida
- Abstract / Description
-
As indicated by the National Academy of Engineering, the understanding of nitrogen cycle has been deemed as one of 14 grand challenges in engineering of the 21st century. Due to rapid population growth and urbanization, the stormwater runoff increased in quantity as well as its nutrient concentrations, which may trigger serious environmental issues such as eutrophication in aquatic systems and ecosystem degradation. This study focuses on stormwater and groundwater quality control via...
Show moreAs indicated by the National Academy of Engineering, the understanding of nitrogen cycle has been deemed as one of 14 grand challenges in engineering of the 21st century. Due to rapid population growth and urbanization, the stormwater runoff increased in quantity as well as its nutrient concentrations, which may trigger serious environmental issues such as eutrophication in aquatic systems and ecosystem degradation. This study focuses on stormwater and groundwater quality control via Biosorption Activated Media (BAM) which can be applied to enhance the nutrient removal potential as an emerging Best Management Practices (BMPs). BAM was tested in this study with respect to two changing environmental factors including the presence of toxins such as copper and the addition of carbon sources that may affect the removal effectiveness. In addition, the impacts on microbial ecology in BAM within the nitrification and denitrification processes due to those changing environmental conditions were explored through the identification of microbial population dynamics under different environmental conditions. To further enhance the recovery and reuse of the adsorbed ammonia as possible soil amendment or even fertilizer, a new media called Iron Filing Green Environmental Media (IFGEM) was developed based on BAM, with the inclusion of iron filings as a key component for nitrate reduction. The functionality of IFGEM was analyzed through a serious column studies with respect to several key factors, including varying influent nutrient concentrations, pH values, and temperature. The results of the column studies demonstrate promising nutrient removal and recovery potential simultaneously under changing factors.
Show less - Date Issued
- 2018
- Identifier
- CFE0007770, ucf:52394
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007770
- Title
- ASSESSMENT OF AQUIFER STORAGE AND RECOVERY IMPACT ON PHOSPHORUS STABILITY IN LAKE SEDIMENT.
- Creator
-
Liu, Sha, Chang, Ni-bin, University of Central Florida
- Abstract / Description
-
Lake Okeechobee, the second largest natural freshwater lake in the United States, had experienced a historical drought in 2007-2008 and the inflow to Lake Okeechobee has been reduced by 40% of the average daily mean between warm phase and cold phase due to the impact of Atlantic Multidecadal Oscillation in the past six decades. To cope with this water resources management problem, the US Army Corps of Engineers (USACE) proposed the largest national implementation plan of aquifer storage and...
Show moreLake Okeechobee, the second largest natural freshwater lake in the United States, had experienced a historical drought in 2007-2008 and the inflow to Lake Okeechobee has been reduced by 40% of the average daily mean between warm phase and cold phase due to the impact of Atlantic Multidecadal Oscillation in the past six decades. To cope with this water resources management problem, the US Army Corps of Engineers (USACE) proposed the largest national implementation plan of aquifer storage and recovery (ASR) project in the Kissimmee River Basin. Routine operation of ASR will deliver recovered water from ASR wells into the lake with different water quality parameters resulting in some concerns about the phosphorus stability issues at the sediment bed, which may lead to eutrophication problems. To explore the potential impacts of ASR operation on phosphorus stability in terms of adsorption, desorption, and diffusion processes, this research presented a systematic assessment based on five different mixing ratios between ASR water and lake water, and explored the sensitivity with respect to the chemical equilibrium between lake water and ASR water to predict the phosphorus stability changes in lake sediment. A series of lab-scale batch and column tests in support of a mechanistic modeling analysis provided a holistic chemical assessment as to how the phosphorus stability may be influenced by different mixing ratios. It led to an observation that the ratio of 1:10 between ASR water and lake water proved to be an optical ratio to avoid eutrophication and bring ecological benefits based on a suite of criteria.
Show less - Date Issued
- 2010
- Identifier
- CFE0003277, ucf:48527
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003277
- Title
- Effects of an Acute High-Volume Isokinetic Intervention on Inflammatory and Strength Changes: Influence of Age.
- Creator
-
Gordon, Joseph, Hoffman, Jay, Stout, Jeffrey, Fukuda, David, University of Central Florida
- Abstract / Description
-
PURPOSE: The purpose of this study was to compare the effects of a high volume isokinetic intervention on lower body strength and inflammation, as well as markers of muscle damage in the subsequent 48 hours between younger and middle-aged men. METHODS: 19 healthy, recreationally trained men were randomly assigned to two groups, younger adults (YA: 21.8 (&)#177; 2.0 y; 90.7 (&)#177; 11.6 kg; 21.5 (&)#177; 4.1 % body fat), or middle-aged adults (MA: 47.0 (&)#177; 4.4 y; 96.0 (&)#177; 21.5; 24.8...
Show morePURPOSE: The purpose of this study was to compare the effects of a high volume isokinetic intervention on lower body strength and inflammation, as well as markers of muscle damage in the subsequent 48 hours between younger and middle-aged men. METHODS: 19 healthy, recreationally trained men were randomly assigned to two groups, younger adults (YA: 21.8 (&)#177; 2.0 y; 90.7 (&)#177; 11.6 kg; 21.5 (&)#177; 4.1 % body fat), or middle-aged adults (MA: 47.0 (&)#177; 4.4 y; 96.0 (&)#177; 21.5; 24.8 (&)#177; 6.3 % body fat). Both groups reported to the human performance laboratory (HPL) on four separate occasions. On the first visit (D1), anthropometric assessment, as well as a familiarization session with the isokinetic dynamometer, was performed. A muscle damaging protocol (HVP) was performed on the second visit (D2) consisting of 8 sets of 10 repetitions at 60(&)deg;(&)#183;sec-1 on the isokinetic dynamometer. An assessment protocol (AP) was performed to assess performance decrements between the YA and MA groups. For this protocol, a maximal voluntary isometric contraction (MVIC) was performed, as well as 3 isokinetic kicks at 2 different speeds (240(&)deg;(&)#183;sec-1 and 60(&)deg;(&)#183;sec-1). For the MVIC, values for peak torque (PKT), average torque (AVGT), rate of torque development at 100 ms (RTD100), and 200 ms (RTD200) were recorded. For the isokinetic kicks at 240(&)deg;(&)#183;sec-1 (ISK240) and 60(&)deg;(&)#183;sec-1 (ISK60), values were also recorded for peak torque (PKT), average torque (AVGT), as well as peak power (PP), and average power (AVGP). The AP was performed before the HVP (BL), immediately after the HVP (IP), 120 minutes after the HVP (120P), as well as one (24H) and two (48H) days following the HVP. Blood draws were also taken at BL, IP, 24H, and 48H, as well as 30 minutes (30P), and 60 minutes (60P) following the HVP to assess circulating levels of creatine kinase (CK), myoglobin (Mb), c-reactive protein (CRP), and interleukin 6 (IL-6). Ultrasound assessment was also performed at BL and IP as well to assess changes in muscle morphology as a result of the intervention. Performance, blood, and ultrasound markers were analyzed using a repeated measures ANOVA to observe between group comparisons for all of the outcome variables. RESULTS: There were no group differences observed for isometric or isokinetic peak torque or average torque, nor were there differences in isokinetic peak power or average power between the two groups as a result of the intervention. There were, however, differences in the pattern for rate of torque development at 100 ms and 200 ms between the two groups. RTD 100 was decreased at IP and 48H in YA, with MA showing decreases at IP, but also 120P and 24H unlike YA. RTD200 was decreased at all time points in YA, while MA was decreased at IP, 24H, and 48H, but not 120P. For markers of muscle damage and inflammation, there were no differences in the response of Mb, CK, CRP, or IL-6 between groups. CONCLUSIONS: Age does not appear to be a driving factor in the inflammatory or muscle damage response from a high volume isokinetic intervention. Though changes in peak torque and average torque from a high volume isokinetic intervention do not seem to differ between younger and middle-aged adults, the rate of torque production at 100ms and 200ms is different between groups. This suggests that while recovery to average or maximal strength after an exercise bout may not be affected greatly by age, the rate of neuromuscular recovery from exercise may be primarily affected by other factors such as training status.
Show less - Date Issued
- 2017
- Identifier
- CFE0006594, ucf:51259
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006594
- Title
- I'M BEING FRAMED: PHASE RETRIEVAL AND FRAME DILATION IN FINITE-DIMENSIONAL REAL HILBERT SPACES.
- Creator
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Greuling, Jason L, Han, Deguang, University of Central Florida
- Abstract / Description
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Research has shown that a frame for an n-dimensional real Hilbert space offers phase retrieval if and only if it has the complement property. There is a geometric characterization of general frames, the Han-Larson-Naimark Dilation Theorem, which gives us the necessary and suffcient conditions required to dilate a frame for an n-dimensional Hilbert space to a frame for a Hilbert space of higher dimension k. However, a frame having the complement property in an n-dimensional real Hilbert space...
Show moreResearch has shown that a frame for an n-dimensional real Hilbert space offers phase retrieval if and only if it has the complement property. There is a geometric characterization of general frames, the Han-Larson-Naimark Dilation Theorem, which gives us the necessary and suffcient conditions required to dilate a frame for an n-dimensional Hilbert space to a frame for a Hilbert space of higher dimension k. However, a frame having the complement property in an n-dimensional real Hilbert space does not ensure that its dilation will offer phase retrieval. In this thesis, we will explore and provide what necessary and suffcient conditions must be satisfed to dilate a phase retrieval frame for an n-dimensional real Hilbert space to a phase retrieval frame for a k-dimensional real Hilbert.
Show less - Date Issued
- 2018
- Identifier
- CFH2000319, ucf:45868
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000319
- Title
- Development of an Adaptive Restoration Tool For a Self-Healing Smart Grid.
- Creator
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Golshani, Amir, Sun, Wei, Qu, Zhihua, Vosoughi, Azadeh, Zhou, Qun, Zheng, Qipeng, University of Central Florida
- Abstract / Description
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Large power outages become more commonplace due to the increase in both frequency and strength of natural disasters and cyber-attacks. The outages and blackouts cost American industries and business billions of dollars and jeopardize the lives of hospital patients. The losses can be greatlyreduced with a fast, reliable and flexible restoration tool. Fast recovery and successfully adapting to extreme events are critical to build a resilient, and ultimately self-healing power grid. This...
Show moreLarge power outages become more commonplace due to the increase in both frequency and strength of natural disasters and cyber-attacks. The outages and blackouts cost American industries and business billions of dollars and jeopardize the lives of hospital patients. The losses can be greatlyreduced with a fast, reliable and flexible restoration tool. Fast recovery and successfully adapting to extreme events are critical to build a resilient, and ultimately self-healing power grid. This dissertation is aimed to tackle the challenging task of developing an adaptive restoration decisionsupport system (RDSS). The RDSS determines restoration actions both in planning and real-time phases and adapts to constantly changing system conditions. First, an efficient network partitioning approach is developed to provide initial conditions for RDSS by dividing large outage network into smaller islands. Then, the comprehensive formulation of RDSS integrates different recovery phases into one optimization problem, and encompasses practical constraints including AC powerflow, dynamic reserve, and dynamic behaviors of generators and load. Also, a frequency constrained load recovery module is proposed and integrated into the RDSS to determine the optimal location and amount of load pickup. Next, the proposed RDSS is applied to harness renewable energy sources and pumped-storage hydro (PSH) units by addressing the inherent variabilities and uncertainties of renewable and coordinating wind and PSH generators. A two-stage stochastic and robust optimization problem is formulated, and solved by the integer L-shaped and column-and-constraintsgeneration decomposition algorithms. The developed RDSS tool has been tested onthe modified IEEE 39-bus and IEEE 57-bus systems under different scenarios. Numerical results demonstrate the effectiveness and efficiency of the proposed RDSS. In case of contingencies or unexpected outages during the restoration process, RDSS can quickly update the restoration plan and adapt to changing system conditions. RDSS is an important step toward a self-healing power grid and its implementation will reduce the recovery time while maintaining system security.
Show less - Date Issued
- 2017
- Identifier
- CFE0007284, ucf:52169
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007284
- Title
- Promoting Recovery in Trauma Affected Children: Developing a School-Based Professional DevelopmentTool for Teacher Awareness and Intervention.
- Creator
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Ioannides Sperber, Ellen, Hewitt, Randall, Hopp, Carolyn, Vitale, Thomas, Van Horn, Stacy, University of Central Florida
- Abstract / Description
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ABSTRACT The problem of practice addressed in this paper is the need for professional development training in the educational setting on the social, emotional, academic, cognitive, and behavioral needs of students who have experienced a traumatic event. The need identified exists due to the lack of knowledge, interest, and opportunity to partake in professional development training in an effort to understand the impact trauma has on academic achievement and the toll that is placed on the...
Show moreABSTRACT The problem of practice addressed in this paper is the need for professional development training in the educational setting on the social, emotional, academic, cognitive, and behavioral needs of students who have experienced a traumatic event. The need identified exists due to the lack of knowledge, interest, and opportunity to partake in professional development training in an effort to understand the impact trauma has on academic achievement and the toll that is placed on the school environment. The purpose of this paper is to review research on childhood trauma, examine the psychological impact on student academic achievement, foster child resiliency, and develop a foundation for effectuating change through a school-based intervention program that concentrates on promoting recovery in affected children. Traumatic events are a very real part of life that becomes a societal problem when a very young mind has to cope with the aftermath of the event. A survey and two interviews were administered to inform the professional development framework of the needs of students and teachers along with research on social-emotional learning, psychological resilience, and recovery methods offering an informative vehicle for change that will significantly impact the child's life. Cultivating Resilience Through The Arms of Academics is a school-based professional development framework designed to educate teaching professionals on the psycho-social needs of trauma affected children while providing systematic interventions designed to help these children with the factors necessary for healing to the extent allowable by the public school system. Schools are targeted to provide the interventions necessary for healing due to their extensive influence on the children they serve. This program will provide children with an emotionally safe environment thus establishing a school climate that is conducive for learning. The interventions in the program promote healing for trauma victims, assist teachers by providing strategies to engage the trauma affected students, and addresses the psycho-social competence and educational performance of all children in the educational population.
Show less - Date Issued
- 2016
- Identifier
- CFE0006689, ucf:52874
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006689
- Title
- Design, Synthesis and Characterization of Biomimetic, Bioinspired and Bio-related Functional Polymers for Atmospheric Water Recovery.
- Creator
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Alqassar, Abdullah, Chang, Ni-bin, Leon, Lorraine, Zheng, Qipeng, University of Central Florida
- Abstract / Description
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Atmospheric water recovery in changing environments has received wide attention in environmental science and engineering communities due to rapid population growth and frequent droughts. This study is focused on the design, synthesis, and characterization of biomimetic, bioinspired, and bio-related functional polymers (b3p) to help resolve the water supply issue especially in arid or semi-arid regions. It is aimed to develop unique synthetic methods to access well-defined polymers with the...
Show moreAtmospheric water recovery in changing environments has received wide attention in environmental science and engineering communities due to rapid population growth and frequent droughts. This study is focused on the design, synthesis, and characterization of biomimetic, bioinspired, and bio-related functional polymers (b3p) to help resolve the water supply issue especially in arid or semi-arid regions. It is aimed to develop unique synthetic methods to access well-defined polymers with the aid of nanomaterials and metal to produce next generation polymer materials for better atmospheric water recovery. The design of such new b3p is bioinspired by some skin materials of biological species such as frogs, beetles, or spiders. Such synthetic efforts are also coupled with fundamental studies of the polymer functions and structures, providing renewed understanding of how molecular structure and processing parameters associated with different nanomaterials impact macroscopic properties. This research was conducted by using a class of cross-linked hydrophilic copolymers known as hydrogels that exhibit a high fluid absorbency, up to 1,000 times to their own weight. Using free radical polymerization to cross-link two different monomers, such as Acrylamide (Am) and Acrylic Acid (Aa) loaded with Calcium Chloride (CaCl2) and coated with gold nanoparticles (Au-Np's), can produce novel thermally-responsive hydrophilic copolymer (e.g. Poly (Am-co-Aa)/Au-Np's/CaCl2) that was placed inside a controlled structure for testing. The new b3p materials can adsorb water vapor in the evening via a swelling process and discharge water vapor in the morning via a deswelling process to harvest the atmospheric water for recovery and reuse. The new b3p materials demonstrated high average swelling percentage of about 3541% when placed in water under a temperature range of [20-30oC] for 5 hours. The hydrogel loaded with 3.3701ivgrams CaCl2 was placed in the furnace under relative humidity percentage (RH) range of [80-90%] and can absorb up to 27% of the atmospheric water undergoing the same time. The research concludes that the proposed synthetic method contributes to solving such contemporary challenge in green chemistry to some extent. Further studies are needed to deeply investigate the ability of this new hydrogel to load more dissolved solids such as CaCl2.
Show less - Date Issued
- 2019
- Identifier
- CFE0007776, ucf:52370
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007776
- Title
- INDIVIDUAL REACTIONS TO ORGANIZATIONAL ETHICAL FAILURES AND RECOVERY ATTEMPTS: A RECOVERY PARADOX?.
- Creator
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Caldwell, James, Schminke, Marshall, University of Central Florida
- Abstract / Description
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ABSTRACT The vast majority of behavioral ethical research focuses on the antecedents of unethical behavior. Consequently, questions involving the consequences of organizational unethical behavior remain largely unanswered. Therefore, extant business ethics research largely neglects the impacts of organizational unethical behavior on individuals. Moreover, questions involving what organizations can do to correct or recover from having engaged in unethical behavior as well as individual...
Show moreABSTRACT The vast majority of behavioral ethical research focuses on the antecedents of unethical behavior. Consequently, questions involving the consequences of organizational unethical behavior remain largely unanswered. Therefore, extant business ethics research largely neglects the impacts of organizational unethical behavior on individuals. Moreover, questions involving what organizations can do to correct or recover from having engaged in unethical behavior as well as individual responses to those efforts are also mostly ignored. Therefore, the purpose of this study is to investigate the impact of unethical activity on employees and explore organizations that have failed ethically and their attempts at recovery. This study explores two issues. First, how do employees react to organizational unethical behavior (OUB) and to what extent are those reactions dependent on contextual and individual factors? Second, to what extent can organizations recover from the negative impacts of ethical failure? More specifically, is it possible for organizations that fail in their ethical responsibilities to recover such that they are paradoxically "better-off" than their counterparts that never failed in the first place? To explore these issues I review, integrate and draw upon the ethical decision-making and service failure recovery literatures for theoretical support. Empirical testing included two studies. The first was a field study using survey data acquired from the Ethics Resource Center (ERC) in which over 29,000 participants were asked about their perceptions of ethics at work. Second, a supplemental field study was conducted in which 100 employees rated the characteristics of unethical acts (e.g. severity). Results revealed a negative direct effect of severity and controllability of the OUB on perceptions of organizational ethicality and a negative direct effect of controllability of the OUB on organizational satisfaction. Ethical context moderated the relationship between OUB controllability and perceived organizational ethicality. Partial support was found for the moderating effects of ethical context on the relationship between OUB severity and perceived organizational ethicality. Results also supported an ethical failure recovery paradox.
Show less - Date Issued
- 2009
- Identifier
- CFE0002655, ucf:48243
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002655
