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Title: Cascaded plasmon resonances for enhanced nonlinear optical response.
Creator: Toroghi, Seyfollah, Kik, Pieter, Vanstryland, Eric, Kuebler, Stephen, Hagan, David, Belfield, Kevin, University of Central Florida
Abstract / Description: The continued development of integrated photonic devices requires low-power, small volume all-optical modulators. The weak nonlinear optical response of conventional optical materials requires the use of high intensities and large interaction volumes in order to achieve significant light modulation, hindering the miniaturization of all-optical switches and the development of lightweight transmission optics with nonlinear optical response. These challenges may be addressed using plasmonic...
Show moreThe continued development of integrated photonic devices requires low-power, small volume all-optical modulators. The weak nonlinear optical response of conventional optical materials requires the use of high intensities and large interaction volumes in order to achieve significant light modulation, hindering the miniaturization of all-optical switches and the development of lightweight transmission optics with nonlinear optical response. These challenges may be addressed using plasmonic nanostructures due to their unique ability to confine and enhance electric fields in sub-wavelength volumes. The ultrafast nonlinear response of free electrons in such plasmonic structures and the fast thermal nonlinear optical response of metal nanoparticles, as well as the plasmon enhanced nonlinear Kerr-type response of the host material surrounding the nanostructures could allow ultrafast all-optical modulation with low modulation energy. In this thesis, we investigate the linear and nonlinear optical response of engineered effective media containing coupled metallic nanoparticles. The fundamental interactions in systems containing coupled nanoparticles with size, shape, and composition dissimilarity, are evaluated analytically and numerically, and it is demonstrated that under certain conditions the achieved field enhancement factors can exceed the single-particle result by orders of magnitude in a process called cascaded plasmon resonance. It is demonstrated that these conditions can be met in systems containing coupled nanospheres, and in systems containing non-spherical metal nanoparticles that are compatible with common top-down nanofabrication methods such as electron beam lithography and nano-imprint lithography. We show that metamaterials based on such cascaded plasmon resonance structures can produce enhanced nonlinear optical refraction and absorption compared to that of conventional plasmonic nanostructures. Finally, it is demonstrated that the thermal nonlinear optical response of metal nanoparticles can be enhanced in carefully engineered heterogeneous nanoparticle clusters, potentially enabling strong and fast thermal nonlinear optical response in system that can be produced in bulk through chemical synthesis.
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Date Issued: 2014
Identifier: CFE0005556, ucf:50272
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005556

Title: EFFECTS OF REDUCED RAS AND VOLUME ON ANAEROBIC ZONE PERFORMANCE FOR A SEPTIC WASTEWATER BIOLOGICAL PHOSPHOROUS REMOVAL SYSTEM.
Creator: Magro, Daniel, Randall, Andrew, University of Central Florida
Abstract / Description: Enhanced Biological Phosphorous Removal (EBPR) performance was found to be adequate with reduced Return Activated Sludge (RAS) flows (50% of available RAS) to the anaerobic tank and smaller than typical anaerobic zone volume (1.08 hours hydraulic retention time or HRT). Three identical parallel biological nutrient removal (BNR) pilot plants were fed with strong, highly fermented (160 mg/L VFAs), domestic/industrial wastewater from a full scale wastewater treatment facility (WWTF). The pilot...
Show moreEnhanced Biological Phosphorous Removal (EBPR) performance was found to be adequate with reduced Return Activated Sludge (RAS) flows (50% of available RAS) to the anaerobic tank and smaller than typical anaerobic zone volume (1.08 hours hydraulic retention time or HRT). Three identical parallel biological nutrient removal (BNR) pilot plants were fed with strong, highly fermented (160 mg/L VFAs), domestic/industrial wastewater from a full scale wastewater treatment facility (WWTF). The pilot plants were operated at 100%, 50%, 40% and 25% RAS (percent of available RAS) flows to the anaerobic tank with the remaining RAS to the anoxic tank. In addition, varying anaerobic HRT (1.08 and 1.5 hours), and increased hydraulic loading (35% increase) was examined. The study was divided in four Phases, and the effect of these process variations on EBPR were studied by having one different variable between two identical systems. The most significant conclusions were that only bringing part of the RAS to the anaerobic zone did not decrease EBPR performance, instead changing the location of P release and uptake. Bringing less RAS to the anaerobic and more to the anoxic tank decreased anaerobic P release and increased anoxic P release (or decreased anoxic P uptake). Equally important is that with VFA rich influent wastewater, excessive anaerobic volume was shown to hurt overall P removal even when it resulted in increased anaerobic P release. Computer modeling with BioWin and UCTPHO was found to predict similar results to the pilot test results. Modeling was done with reduced RAS flows to the anaerobic zone (100%, 50%, and 25% RAS), increased anaerobic volume, and increased hydraulic loading. The most significant conclusions were that both models predicted EBPR did not deteriorate with less RAS to the anaerobic zone, in fact, improvements in EBPR were observed. Additional scenarios were also consistent with pilot test data in that increased anaerobic volume did not improve EBPR and increased hydraulic loading did not adversely affect EBPR.
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Date Issued: 2005
Identifier: CFE0000329, ucf:46285
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000329

Title: ATTACHMENT STYLE'S IMPACT ON THE PERCEPTION OF SELF-VERIFYING AND SELF-ENHANCING COMFORTING MESSAGES.
Creator: Shellabarger, Krista, Weger, Harry, University of Central Florida
Abstract / Description: This study investigates the connection between one's adult attachment style and one's evaluation of verifying or enhancing comforting messages. Drawing from research by Swann (2005) and Katz and Joiner (2002), the hypothesis predicted that an individual would prefer verifying messages over enhancing messages regardless of attachment style. A research question was also posed: Will an individual's adult attachment style moderate the degree to which a person perceives the...
Show moreThis study investigates the connection between one's adult attachment style and one's evaluation of verifying or enhancing comforting messages. Drawing from research by Swann (2005) and Katz and Joiner (2002), the hypothesis predicted that an individual would prefer verifying messages over enhancing messages regardless of attachment style. A research question was also posed: Will an individual's adult attachment style moderate the degree to which a person perceives the communication of verifying or enhancing messages as helpful or effective? In an effort to find these answers, a questionnaire was completed by 251 individuals. Results indicate a preference for verifying messages among participants regardless of attachment style. This is consistent with the findings of Katz and Joiner (2002) and Swann (2005). However, results did not indicate a significant difference between attachment style and a preference of enhancing or verifying messages.
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Date Issued: 2008
Identifier: CFE0002324, ucf:47822
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002324

Title: Investigation of Heat Transfer Enhancement Within a Concentric Annulus.
Creator: Hanhold, Alexander, Kapat, Jayanta, Ahmed, Kareem, Vasu Sumathi, Subith, University of Central Florida
Abstract / Description: Effective heat exchange is key for many energy applications including heat exchangers, heat extraction from heat source, and heat rejection to ambient thermal sink. This study focuses on the investigation for a specific heat exchange configuration, namely heat removal within a concentric annular passage using helical turbulators and jet impingement. Numerical testing was used to see how the different geometric parameters affect the heat transfer and pressure drop within the annulus by using...
Show moreEffective heat exchange is key for many energy applications including heat exchangers, heat extraction from heat source, and heat rejection to ambient thermal sink. This study focuses on the investigation for a specific heat exchange configuration, namely heat removal within a concentric annular passage using helical turbulators and jet impingement. Numerical testing was used to see how the different geometric parameters affect the heat transfer and pressure drop within the annulus by using helicoil turbulators. A vast range of designs were studied by changing the turbulator shape, pitch, and blockage ratio while maintaining a constant Reynolds number of 25,000. CFD was performed in STARCCM+ using the realizable ?-? turbulence model. Results show that turbulence and heat transfer increase with a higher blockage ratio and smaller pitch but the pressure drop is subsequently increased as well. The square turbulator promoted higher heat transfer compared to the circle turbulator but the pressure drop was significantly increased when the helix angle was greater than 20(&)deg; and blockage ratio greater than 0.48.Experimental and numerical efforts were used to find the heat transfer due to impingement jets on the target surface. Multiple flows as a function of jet Reynolds number ranging from 16,000-33,000 were tested for two geometries. Temperature Sensitive Paint (TSP) was utilized to observe local heat transfer. It was observed that jet degradation occurs after the 6th row of stream-wise impingement jets for both cases experimentally and it was difficult to numerically capture the effect of the cross flow from previous jets but managed to follow the same trend. The numerical results showed that they can be used with good agreement to predict the surface averaged Nusselt number to be within the 12% uncertainty found from experimental efforts. Geometry B was determined to perform better in terms of heat transfer as opposed to Geometry A with the same pressure loss.
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Date Issued: 2017
Identifier: CFE0007286, ucf:52155
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007286

Title: CONNECTING SELF ENHANCEMENT AND SELF VERIFICATION MESSAGES IN FRIENDSHIPS.
Creator: Bloch, Ann, Weger, Harry, University of Central Florida
Abstract / Description: This study investigates the connection between self-enhancement and self-verification and confirmation and emotional support. The hypotheses predicted that there is a positive relationship between confirmation and self-enhancement and self-verification; people feel good about themselves when confirmed by friends, people feel that friends know them well when they are confirmed. The hypotheses also predicted that there would be a positive relationship between emotional support and self...
Show moreThis study investigates the connection between self-enhancement and self-verification and confirmation and emotional support. The hypotheses predicted that there is a positive relationship between confirmation and self-enhancement and self-verification; people feel good about themselves when confirmed by friends, people feel that friends know them well when they are confirmed. The hypotheses also predicted that there would be a positive relationship between emotional support and self-enhancement and self-verification; people feel good when friends provide emotional support, and people feel that friends know them well when provided emotional support. A research question was also posed: Does family functioning have an effect on perceptions of self-enhancement and self-verification messages? To find the answers, a questionnaire was completed by 279 individuals. The results indicate two types of enhancement messages; a more specific and positive form of enhancement and more global (and negative) self perception of rejection. The findings are interesting and unique to self-enhancement in communication research which provides many avenues for continued research. Results also suggest that different elements of confirming communication influences perceptions of enhancement in different ways, emotional support predicts verification.
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Date Issued: 2009
Identifier: CFE0002939, ucf:47975
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002939

Title: EXPERIMENTAL STUDIES OF THE HEAT TRANSFER CHARACTERISTICS OF SILICA NANOPARTICLE WATER-BASED DISPERSION IN POOL BOILING USING NICHROME FLAT RIBBONS AND WIRES.
Creator: Vazquez, Diane, Kumar, Ranganathan, University of Central Florida
Abstract / Description: This work deals with a study of enhanced critical heat flux (CHF) and burnout heat flux (BHF) in pool boiling of water with suspended silica nanoparticles using ribbon-type and wire heaters. Previously our group and other researchers have reported three-digit percentage increase in critical heat flux in silica nanofluids. This study investigates the effect of various heater surface dimensions and cross-sectional shapes on pool boiling heat transfer characteristics of water and water-based...
Show moreThis work deals with a study of enhanced critical heat flux (CHF) and burnout heat flux (BHF) in pool boiling of water with suspended silica nanoparticles using ribbon-type and wire heaters. Previously our group and other researchers have reported three-digit percentage increase in critical heat flux in silica nanofluids. This study investigates the effect of various heater surface dimensions and cross-sectional shapes on pool boiling heat transfer characteristics of water and water-based nanofluids. CHF and BHF were analyzed for circular and rectangular cross-section nichrome wires and ribbons of increasing sizes in the range of 0.32mm to 2.38mm width, approaching a flat-plate scenario. Experimental trends showed that the CHF and BHF in water pool boiling decrease as heater surface area increases, and for similar surface area, the wire had a 25% higher CHF than that of the ribbon. For concentrations from 0.1vol% to 2vol%, various properties such as viscosity, pH, and surface tension as well as silica deposition on surface and glowing length of ribbon were measured in order to study the possible factors in the heat transfer behavior of nanofluids. The deposition of the particles on the wire allows high heat transfer through inter-agglomerate pores, resulting in a nearly 3-fold increase in burnout heat flux at very low concentrations. Results have shown a maximum of up to 340% CHF enhancement for ribbon-type heaters, and the relationship of CHF with respect to nanoparticle concentration has been found to be non-monotonic with a peak around 0.2vol% to 0.4vol%. Visualization of boiling experiments aided with determination of relative bubble sizes, nucleation, and flow regimes. The surface morphology of the heater was investigated using SEM and EDS analyses, and it was inferred that the 2vol% concentration deposition coating had higher porosity and rate of deposition compared with 0.2vol% case.
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Date Issued: 2010
Identifier: CFE0003141, ucf:48635
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003141

Title: Cavity-Coupled Plasmonic Systems for Enhanced Light-Matter Interactions.
Creator: Vazquez-Guardado, Abraham, Chanda, Debashis, Christodoulides, Demetrios, Abouraddy, Ayman, Moharam, Jim, Leuenberger, Michael, University of Central Florida
Abstract / Description: Light-matter interaction is a pivotal effect that involves the synergetic interplay of electromag- netic fields with fundamental particles. In this regard localized surface plasmons (LSP) arise from coherent interaction of the electromagnetic field with the collective oscillation of free electrons in confined sub-wavelength environments. Their most attractive properties are strong field en- hancements at the near field, highly inhomogeneous, peculiar temporal and spatial distributions and...
Show moreLight-matter interaction is a pivotal effect that involves the synergetic interplay of electromag- netic fields with fundamental particles. In this regard localized surface plasmons (LSP) arise from coherent interaction of the electromagnetic field with the collective oscillation of free electrons in confined sub-wavelength environments. Their most attractive properties are strong field en- hancements at the near field, highly inhomogeneous, peculiar temporal and spatial distributions and unique polarization properties. LSP systems also offer a unique playground for fundamental electromagnetic physics where micro-scale systemic properties can be studied in the macro-scale. These important properties and opportunities are brought up in this work where I study hybrid cavity-coupled plasmonic systems in which the weak plasmonic element is far-field coupled with the photonic cavity by properly tuning its phase. In this work I preset the fundamental understand- ing of such a complex systems from the multi-resonance interaction picture along experimental demonstration. Using this platform and its intricate near fields I further demonstrate a novel mech- anism to generate superchiral light: a field polarization property that adds a degree of freedom to light-matter interactions at the nanoscale exploited in advanced sensing applications and surface effect processes. Finally, the detection of non-chiral analytes, such as proteins, neurotransmit- ters or nanoparticles, and more complex chiral analytes, such as proteins and its conformation states, amino acids or chiral molecules at low concentrations is demonstrated in several biosensing applications. The accompanied experiential demonstrations were accomplished using the nanoim- printing technique, which places the cavity-coupled hybrid plasmonic system as a unique platform towards realistic applications not limited by expensive lithographic techniques.
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Date Issued: 2018
Identifier: CFE0007418, ucf:52708
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007418

Title: Assessment, Optimization, and Enhancement of Ultrafiltration (UF) Membrane Processes in Potable Water Treatment.
Creator: Boyd, Christopher, Duranceau, Steven, Cooper, Charles, Randall, Andrew, University of Central Florida
Abstract / Description: This dissertation reports on research related to ultrafiltration (UF) membranes in drinking water applications. A pilot-scale investigation identified seasonal surface water quality impacts on UF performance and resulted in the development of a dynamic chemically enhanced backwash protocol for fouling management. Subsequent analysis of UF process data revealed limitations with the use of specific flux, transmembrane pressure (TMP), and other normalization techniques for assessing UF process...
Show moreThis dissertation reports on research related to ultrafiltration (UF) membranes in drinking water applications. A pilot-scale investigation identified seasonal surface water quality impacts on UF performance and resulted in the development of a dynamic chemically enhanced backwash protocol for fouling management. Subsequent analysis of UF process data revealed limitations with the use of specific flux, transmembrane pressure (TMP), and other normalization techniques for assessing UF process fouling. A new TMP balance approach is presented that identifies the pressure contribution of membrane fouling and structural changes, enables direct process performance comparisons at different operating fluxes, and distinguishes between physically and chemically unresolved fouling. In addition to the TMP balance, a five component optimization approach is presented for the systematic improvement of UF processes on the basis of TMP variations. Terms are defined for assessing process event performance, a new process utilization term is presented to benchmark UF productivity, and new measures for evaluating maintenance procedures are discussed. Using these tools, a correlation between process utilization and operating pressures was established and a sustainable process utilization of 93.5% was achieved. UF process capabilities may be further enhanced by pre-coating media onto the membrane surface. Silicon dioxide (SiO2) and powdered activated carbon (PAC) are evaluated as pre-coating materials, and the applicability of the TMP balance for assessing pre-coated membrane performance is demonstrated. The first use of SiO2 as a support layer for PAC in a membrane pre-coating application is presented at the laboratory-scale. SiO2-PAC pre-coatings successfully reduced physically unresolved fouling and enhanced UF membrane organics removal capabilities.
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Date Issued: 2013
Identifier: CFE0005088, ucf:50758
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0005088

Title: THE IMPACT OF CO-TEACHING ON STUDENT LEARNING OUTCOMES IN SECONDARY SOCIAL STUDIES CLASSROOMS IMPLEMENTING CONTENT ENHANCEMENT ROUTINES.
Creator: Zgonc, Kimberly, Dieker, Lisa, University of Central Florida
Abstract / Description: The purpose of this study was to examine if differences exist in student learning outcomes between students who are instructed in a co-taught or non co-taught environment in secondary social studies classrooms implementing Content Enhancement Routines (CER). This study examined student and teacher data from seventeen matched pairs of co-taught and non co-taught middle and high school general education social studies teachers who participated in professional development in CER and professional...
Show moreThe purpose of this study was to examine if differences exist in student learning outcomes between students who are instructed in a co-taught or non co-taught environment in secondary social studies classrooms implementing Content Enhancement Routines (CER). This study examined student and teacher data from seventeen matched pairs of co-taught and non co-taught middle and high school general education social studies teachers who participated in professional development in CER and professional development in co-teaching if applicable. Of the 34 participating teachers, 23 were visited by school district personnel to verify implementation of CER. Five co-teaching teams, each consisting of a general and special educator, completed a Coteaching Rating Scale (CtRS) (n=10) to analyze the level of co-teaching occurring in the classroom (beginning, compromising or collaborating stage). A systematic sample of students (n = 907) completed a CER Student Perception Survey to examine perceived differences of the use of CER in co-taught and non co-taught social studies classrooms. Student state assessment scores (n = 318) in co-taught and non co-taught classrooms were analyzed to distinguish differences in student learning gains. Specifically this study investigated if differences in student performance occur when a special educator is present in the classroom. Results indicate that although there was no statistically significant difference in student learning outcomes between the two settings, the impact of teacher preparation, professional development and the implementation of CER in the secondary social studies classroom may be determining factors in student success.
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Date Issued: 2007
Identifier: CFE0001645, ucf:47226
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0001645

Title: A PROBE INTO LEARNING APPROACHES AND ATTITUDES TOWARDS TECHNOLOGY-ENHANCED LANGUAGE LEARNING (TELL) IN CHINESE INSTRUCTION.
Creator: Yuan, Rong, Orwig, Gary, University of Central Florida
Abstract / Description: This quantitative research, carried out at the military environment at the Defense Language Institute investigated whether learning approaches could predict learners' language proficiency and learners' attitude towards technology-enhanced language learning (TELL). In addition, it also examined whether learners' demographic factors, such as age, educational backgrounds, prior experience in foreign language learning and in TELL as well as their ability to use PC and the World Wide Web could...
Show moreThis quantitative research, carried out at the military environment at the Defense Language Institute investigated whether learning approaches could predict learners' language proficiency and learners' attitude towards technology-enhanced language learning (TELL). In addition, it also examined whether learners' demographic factors, such as age, educational backgrounds, prior experience in foreign language learning and in TELL as well as their ability to use PC and the World Wide Web could predict the above mentioned language proficiency and attitude. A cluster sampling method was adopted and data was collected in four Chinese departments at the institute. Both the learning approaches inventory ASSIST and the attitudes towards TELL survey were administered to 158 Chinese language learners. 137 valid responses were obtained. All data were input into SPSS for regression and correlation analyses. Conclusions of the study are as follows: 1. The surface and apathetic approach (p<.01) was a significant predictor for both learners' measured language proficiency and their self-perception of academic performance. 2. The strategic approach was a positive predictor for learners' attitudes towards TELL; whereas, surface and apathetic approach was a negative predictor for learners' attitudes towards TELL. 3. None of the learners' demographic variables could not predict either learners' language proficiency or their attitudes towards TELL. Implications for instructional design, curriculum development, teacher education, as well as relevant research issues were discussed.
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Date Issued: 2005
Identifier: CFE0000829, ucf:46675
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000829

Title: The effects of dynamic versus isometric postactivation potentiation on collegiate female rowers.
Creator: Harat, Idan, Fukuda, David, Stout, Jeffrey, Wells, Adam, University of Central Florida
Abstract / Description: Post-activation potentiation (PAP) has been shown to improve acute power-based performance, and the potential to enhance rowing performance. To examine PAP effects with rowing performance, 40 collegiate female rowers performed isometric potentiating (ISO), dynamic potentiating (DYN) and typical control (CON) warm-up protocols, after which they completed a three-minute all-out test (3MT) to evaluate their total distance, peak power, mean power, critical power, anaerobic working capacity (W')...
Show morePost-activation potentiation (PAP) has been shown to improve acute power-based performance, and the potential to enhance rowing performance. To examine PAP effects with rowing performance, 40 collegiate female rowers performed isometric potentiating (ISO), dynamic potentiating (DYN) and typical control (CON) warm-up protocols, after which they completed a three-minute all-out test (3MT) to evaluate their total distance, peak power, mean power, critical power, anaerobic working capacity (W') and stroke rate. Fifteen-second splits for distance and mean power were also analyzed. The PAP protocols were performed on a rowing ergometer, in a movement pattern that simulated rowing. ISO consisted of 5 (&)#215; 5-second static muscle actions with the ergometer handle rendered immovable with a nylon boat-strap, while DYN consisted of 2 (&)#215; 10-second all-out rowing bouts, separated by a 2-minute rest interval. A two-way (condition by experience level) interaction was found for distance, mean power and W' with significant differences (DYN (>) CON; 5.6 m, 5.9W and 1561.6 J) for more experienced rowers ((>)3.75 years; n=19) and no differences for less experienced rowers (n=18). A main effect for stroke rate was found with DYN(>)CON (1 s/min). Split analysis of mean power output revealed a two-way (condition by 15s split) interaction independent from experience level. Mean power in DYN was significantly greater than CON and ISO in the 15-30, 30-45, 45-60 and 60-75 second intervals. These results suggest that dynamic PAP may be beneficial for experienced rowers and that these strategies might benefit a greater power output over shorter distances regardless of experience. Future studies should investigate potential benefits of this protocol over a full race distance and identify the difference between experienced and less experienced rowers.
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Date Issued: 2019
Identifier: CFE0007465, ucf:52665
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007465

Title: HIGH HEAT FLUX SPRAY COOLING WITH AMMONIA ON ENHANCED SURFACES.
Creator: Bostanci, Huseyin, Chow, Louis, University of Central Florida
Abstract / Description: Many critical applications today, in electronics, optics and aerospace fields, among others, demand advanced thermal management solutions for the acquisition of high heat loads they generate in order to operate reliably and efficiently. Current competing technologies for this challenging task include several single and two phase cooling options. When these cooling schemes are compared based on the high heat flux removal (100-1000 W/cm2) and isothermal operation (within several oC across the...
Show moreMany critical applications today, in electronics, optics and aerospace fields, among others, demand advanced thermal management solutions for the acquisition of high heat loads they generate in order to operate reliably and efficiently. Current competing technologies for this challenging task include several single and two phase cooling options. When these cooling schemes are compared based on the high heat flux removal (100-1000 W/cm2) and isothermal operation (within several oC across the cooled device) aspects, as well as system mass, volume and power consumption, spray cooling appears to be the best choice. The current study focused on high heat flux spray cooling with ammonia on enhanced surfaces. Compared to some other commonly used coolants, ammonia possesses important advantages such as low saturation temperature, and high heat absorbing capability. Moreover, enhanced surfaces offer potential to greatly improve heat transfer performance. The main objectives of the study were to investigate the effect of surface enhancement on spray cooling performance, and contribute to the current understanding of spray cooling heat transfer mechanisms. These objectives were pursued through a two stage experimental study. While the first stage investigated enhanced surfaces for the highest heat transfer coefficient at heat fluxes of up to 500 W/cm2, the second stage investigated the optimized enhanced surfaces for critical heat flux (CHF). Surface modification techniques were utilized to obtain micro scale indentations and protrusions, and macro (mm) scale pyramidal, triangular, rectangular, and square pin fins. A third group, multi-scale structured surfaces, combined macro and micro scale structures. Experimental results indicated that micro- and macrostructured surfaces can provide heat transfer coefficients of up to 534,000 and 426,000 W/m2oC at 500 W/cm2, respectively. Multi-scale structured surfaces offered even a better performance, with heat transfer coefficients of up to 772,000 W/m2oC at 500 W/cm2, corresponding to a 161% increase over the reference smooth surface. In CHF tests, the optimized multi-scale structured surface helped increase maximum heat flux limit by 18%, to 910 W/cm2 at nominal liquid flow rate. During the additional CHF testing at higher flow rates, most heaters experienced failures before reaching CHF at heat fluxes above 950 W/cm2. However, the effect of flow rate was still characterized, suggesting that enhanced surfaces can achieve CHF values of up to 1,100 W/cm2 with 67% spray cooling efficiency. The results also helped shed some light on the current understanding of the spray cooling heat transfer mechanisms. Data clearly proved that in addition to fairly well established mechanisms of forced convection in the single phase regime, and free surface evaporation and boiling through secondary nucleation in the two phase regime, enhanced surfaces can substantially improve boiling through surface nucleation, which can also be supported by the concept of three phase contact lines, the regions where solid, liquid and vapor phases meet. Furthermore, enhanced surfaces are capable of retaining more liquid compared to a smooth surface, and efficiently spread the liquid film via capillary force within the structures. This unique advantage delays the occurrence of dry patches at high heat fluxes, and leads to higher CHF.
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Date Issued: 2010
Identifier: CFE0003290, ucf:48502
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003290

Title: DESIGN AND FABRICATION OF SPACE VARIANT MICRO OPTICAL ELEMENTS.
Creator: Srinivasan, Pradeep, LiKamWa, Patrick, University of Central Florida
Abstract / Description: A wide range of applications currently utilize conventional optical elements to individually transform the phase, polarization, and spectral transmission/reflection of the incident radiation to realize the desired system level function. The material properties and the feasibility of fabrication primarily impact the device and system functionality that can be realized. With the advancement in micro/nano patterning, growth, deposition and etching technology, devices with novel and multiplexed...
Show moreA wide range of applications currently utilize conventional optical elements to individually transform the phase, polarization, and spectral transmission/reflection of the incident radiation to realize the desired system level function. The material properties and the feasibility of fabrication primarily impact the device and system functionality that can be realized. With the advancement in micro/nano patterning, growth, deposition and etching technology, devices with novel and multiplexed optical functionalities have become feasible. As a result, it has become possible to engineer the device response in the near and far field by controlling the phase, polarization or spectral response at the micro scale. One of the methods that have been explored to realize unique optical functionalities is by varying the structural properties of the device as a function of spatial location at the sub-micron scale across the device aperture. Spatially varying the structural parameters of these devices is analogous to local modifications of the material properties. In this dissertation, the optical response of interference transmission filters, guided mode resonance reflection filters, and diffraction gratings operated in Littrow condition with strategically introduced spatial variation have been investigated. Spatial variations in optical interference filters were used to demonstrate wavelength tunable spatial filters. The effect was realized by integrating diffractive and continuous phase functions on the defect layer of a one-dimensional photonic crystal structure. Guided mode resonance filters are free space optical filters that provide narrow spectral reflection by combining grating and waveguide dispersion effects. Frequency dependent spatial reflection profiles were achieved by spatially varying the grating fill fraction in designed contours. Diffraction gratings with space variant fill fractions operating in Littrow condition were used to provide graded feedback profiles to improve the beam quality and spatial brightness of broad area diode lasers. The fabrication of space variant structures is challenging and has been accomplished primarily by techniques such as ruling, electron beam writing or complex deposition methods. In order to vary the desired structural parameter in a designed manner, a novel technique for the fabrication of space variant structures using projection lithography with a fidelity that rivals any of the current technologies was also developed as a part of this work. The devices exhibit wavelength dependent beam shaping properties in addition to spatial and spectral filtering and have potential applications in advanced imaging systems, graded reflectivity laser mirrors, and engineered illumination. The design, modeling, microfabrication and experimental characterization of space variant micro optical elements with novel optical functionalities are presented.
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Date Issued: 2009
Identifier: CFE0002843, ucf:48066
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0002843

Title: Novel solid state lasers based on volume Bragg gratings.
Creator: Hale, Evan, Glebov, Leonid, Divliansky, Ivan, Schulzgen, Axel, Vodopyanov, Konstantin, Lyakh, Arkadiy, University of Central Florida
Abstract / Description: Since their invention in 1960, lasers have revolutionized modern technology, and tremendous amounts of innovation and development has gone into advancing their properties and efficiencies. This dissertation reports on further innovations by presenting novel solid state laser systems based on the volume Bragg gratings (VBGs) and the newly developed holographic phase mask (HPMs) for brightness enhancement, dual wavelength operation, and mode conversion. First, a new optical element was created...
Show moreSince their invention in 1960, lasers have revolutionized modern technology, and tremendous amounts of innovation and development has gone into advancing their properties and efficiencies. This dissertation reports on further innovations by presenting novel solid state laser systems based on the volume Bragg gratings (VBGs) and the newly developed holographic phase mask (HPMs) for brightness enhancement, dual wavelength operation, and mode conversion. First, a new optical element was created by pairing the HPM with two surface gratings creating an achromatic holographic phase mask. This new optical device successfully performed transverse mode conversion of multiple narrow line laser sources operating from 488 to 1550 nm and a broadband mode locked femtosecond source with no angular tuning. Also, two types of HPMs were tested on high power Yb fiber lasers to demonstrate high energy mode conversion.Secondly, the effects of implementing VBGs for brightness enhancement of passively Q-switched systems with large Fresnel numbers was investigated. Implementing VBGs for angular mode selection allowed for higher pulse energies to be extracted without sacrificing brightness and pulse duration. This technique could potentially be applied to construct compact cavities with 1 cm diameter beams and nearly diffraction limited beam quality.Lastly, a spectral beam combining approach was applied to create Tm3+ and Yb3+ based narrowband dual-wavelength pump sources for terahertz generation, using VBGs as frequency selectors and beam combiners. Comparison of pulse duration and synchronization was done between passive and active Q-switching operation. An experimental set up for THz generation and detection using high sensitive detectors was created, and modeling of terahertz conversion efficiencies were done
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Date Issued: 2019
Identifier: CFE0007812, ucf:52333
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007812

Title: Estimation and clustering in statistical ill-posed linear inverse problems.
Creator: Rajapakshage, Rasika, Pensky, Marianna, Swanson, Jason, Zhang, Teng, Bagci, Ulas, Foroosh, Hassan, University of Central Florida
Abstract / Description: The main focus of the dissertation is estimation and clustering in statistical ill-posed linear inverse problems. The dissertation deals with a problem of simultaneously estimating a collection of solutions of ill-posed linear inverse problems from their noisy images under an operator that does not have a bounded inverse, when the solutions are related in a certain way. The dissertation defense consists of three parts. In the first part, the collection consists of measurements of temporal...
Show moreThe main focus of the dissertation is estimation and clustering in statistical ill-posed linear inverse problems. The dissertation deals with a problem of simultaneously estimating a collection of solutions of ill-posed linear inverse problems from their noisy images under an operator that does not have a bounded inverse, when the solutions are related in a certain way. The dissertation defense consists of three parts. In the first part, the collection consists of measurements of temporal functions at various spatial locations. In particular, we studythe problem of estimating a three-dimensional function based on observations of its noisy Laplace convolution. In the second part, we recover classes of similar curves when the class memberships are unknown. Problems of this kind appear in many areas of application where clustering is carried out at the pre-processing step and then the inverse problem is solved for each of the cluster averages separately. As a result, the errors of the procedures are usually examined for the estimation step only. In both parts, we construct the estimators, study their minimax optimality and evaluate their performance via a limited simulation study. In the third part, we propose a new computational platform to better understand the patterns of R-fMRI by taking into account the challenge of inevitable signal fluctuations and interpretthe success of dynamic functional connectivity approaches. Towards this, we revisit an auto-regressive and vector auto-regressive signal modeling approach for estimating temporal changes of the signal in brain regions. We then generate inverse covariance matrices fromthe generated windows and use a non-parametric statistical approach to select significant features. Finally, we use Lasso to perform classification of the data. The effectiveness of theproposed method is evidenced in the classification of R-fMRI scans
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Date Issued: 2019
Identifier: CFE0007710, ucf:52450
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007710

Title: EFFECT OF ACETIC OR CITRIC ACID ULTRAFILTRATION RECYCLE STREAMS ON COAGULATION PROCESSES.
Creator: Boyd, Christopher, Duranceau, Steven, University of Central Florida
Abstract / Description: Integrating ultrafiltration (UF) membranes in lieu of traditional media filters within conventional surface water coagulation-flocculation-sedimentation processes is growing in popularity. UF systems are able to produce low turbidity filtered water that meets newer drinking water standards. For typical drinking water applications, UF membranes require periodic chemically enhanced backwashes (CEBs) to maintain production; and citric acid is a common chemical used for this purpose. Problems may...
Show moreIntegrating ultrafiltration (UF) membranes in lieu of traditional media filters within conventional surface water coagulation-flocculation-sedimentation processes is growing in popularity. UF systems are able to produce low turbidity filtered water that meets newer drinking water standards. For typical drinking water applications, UF membranes require periodic chemically enhanced backwashes (CEBs) to maintain production; and citric acid is a common chemical used for this purpose. Problems may arise when the backwash recycle stream from a citric acid CEB is blended with raw water entering the coagulation basin, a common practice for conventional surface water plants. Citric acid is a chelating agent capable of forming complexes that interfere with alum or ferric chloride coagulation. Interference with coagulation negatively affects settled water quality. Acetic acid was investigated as a potential substitute for citric acid in CEB applications. A jar testing study was conducted to compare the impacts of both citric acid and acetic acid on the effectiveness of aluminum sulfate (alum) and ferric chloride coagulants. Citric acid was found to adversely affect coagulation at lower acid to coagulant (A/C) molar ratios than acetic acid, and a coagulation interference threshold was identified for both acids based on settled water turbidity goals recommended by the U.S. Environmental Protection Agency (EPA). Pilot testing was conducted to assess the viability of acetic acid as a UF CEB chemical. Acetic acid CEBs maintained pilot performance in combination with sodium hypochlorite CEBs for filtering a raw California surface water. It is believed that this is the first ultrafiltration membrane process application of acetic acid CEBs for municipal potable water production in the United States.
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Date Issued: 2011
Identifier: CFE0003723, ucf:48779
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0003723

Title: Biological Nutrient Removal (BNR) Process Optimization and Recovery of Embedded Energy Using Biodiesel By-product.
Creator: Salamah, Sultan, Randall, Andrew, Duranceau, Steven, Chopra, Manoj, University of Central Florida
Abstract / Description: Enhanced biological phosphorus removal (EBPR) as well as biological nitrogen removal require a carbon source to be carried out. Volatile fatty acid (VFAs) (mainly acetic and propionic acids) are the major driving force for EBPR. Many domestic wastewaters have an insufficient amount of VFAs. However, carbon sources such as acetic and propionic acids can be produced using primary solids fermentation process. Due to the cost of VFA production, an external carbon source can be added to the...
Show moreEnhanced biological phosphorus removal (EBPR) as well as biological nitrogen removal require a carbon source to be carried out. Volatile fatty acid (VFAs) (mainly acetic and propionic acids) are the major driving force for EBPR. Many domestic wastewaters have an insufficient amount of VFAs. However, carbon sources such as acetic and propionic acids can be produced using primary solids fermentation process. Due to the cost of VFA production, an external carbon source can be added to the biological nutrient removal (BNR) system that can be fermented to provide the desired VFAs. Glycerol (biodiesel by-product) offers a solution to reduce carbon addition cost if can be fermented to acetic and propionic acid or can be used directly as an external carbon substrate for EBPR and denitrification. Using glycerol in wastewater treatment can also offset the biodiesel plant disposal cost and reduce the BNR chemical cost. The main objective of this study was to optimize the prefermentation process and optimize the BNR system using glycerol as an external carbon source. In this work, Optimization of the prefermentation process using glycerol, mixing, and hydrogen gas addition was evaluated. EBPR performance within an A2O-BNR system was evaluated using either a direct glycerol method to the anaerobic zone or by co-fermentation with primary solids. Also, optimization of the nitrogen removal (specifically denitrification) efficiency of a 5-stage BardenphoTM BNR system using either a direct glycerol method to the second anoxic zone or by co-fermentation with primary solids was evaluated. It was found in this study that glycerol was an efficient external carbon substrate for EBPR as well as biological nitrogen removal. The prefermentation experiment showed that glycerol co-fermentation with primary solids produced significantly higher (p(<)0.05) VFAs than primary solids fermentation alone, even more than the possible value from the added glycerol (427 mg-COD/L). The increased VFAs imply that the glycerol addition stimulated additional fermentation of primary solids. Lowering the prefermenter mixing energy (50 to 7 rpm) resulted in a significant increase in VFAs production (80%). Also, purging the headspace of the prefermenter with hydrogen gas did not lead to more VFAs, but significantly (p(<)0.05) increased the propionic acid to acetic acid ratio by 41%. In the A2O-BNR pilot plant experiment, it was found that glycerol is a suitable renewable external substrate to drive enhanced EBPR as well as denitrification. The results from both locations of glycerol addition (direct vs. fermented) were beneficial to the BNR system. Both systems had similar effluent quality and achieved total nitrogen (TN) and total phosphorus (TP) removals up to 86% and 92% respectively. The 5-stage BardenphoTM BNR experiment investigated the location of glycerol addition (direct vs. fermented) on the performance of denitrification in the second anoxic zone and the overall performance. The results from both systems were that glycerol was beneficial to the BNR system and had virtually similar effluent quality. Both systems achieve complete denitrification and excellent removal of TN and TP up to 95% and 89% respectively. Also, the pilot that received fermented glycerol had significantly higher VFAs loading and lower observed yield. The side-stream prefermenter effluent flowing to the second anoxic reactor did not cause high effluent ammonia (NH3) concentration. In summary, the location at which glycerol was added did not affect effluent quality for nitrogen and phosphorus. However, glycerol addition and mixing energy did impact prefermenter performance and effluent quality.
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Date Issued: 2017
Identifier: CFE0006788, ucf:51826
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0006788

Title: SPECTRAL SIGNATURE MODIFICATION BY APPLICATION OF INFRARED FREQUENCY-SELECTIVE SURFACES.
Creator: Monacelli, Brian, Boreman, Glenn, University of Central Florida
Abstract / Description: It is desirable to modify the spectral signature of a surface, particularly in the infrared (IR) region of the electromagnetic spectrum. To alter the surface signature in the IR, two methods are investigated: thin film application and antenna array application. The former approach is a common and straightforward incorporation of optically-thin film coatings on the surface designated for signature modification. The latter technique requires the complex design of a periodic array of passive...
Show moreIt is desirable to modify the spectral signature of a surface, particularly in the infrared (IR) region of the electromagnetic spectrum. To alter the surface signature in the IR, two methods are investigated: thin film application and antenna array application. The former approach is a common and straightforward incorporation of optically-thin film coatings on the surface designated for signature modification. The latter technique requires the complex design of a periodic array of passive microantenna elements to cover the surface in order to modify its signature. This technology is known as frequency selective surface (FSS) technology and is established in the millimeter-wave spectral regime, but is a challenging technology to scale for IR application. Incorporation of thin films and FSS antenna elements on a surface permits the signature of a surface to be changed in a deterministic manner. In the seminal application of this work, both technologies are integrated to comprise a circuit-analog absorbing IR FSS. The design and modeling of surface treatments are accomplished using commercially-available electromagnetic simulation software. Fabrication of microstructured antenna arrays is accomplished via microlithographic technology, particularly using an industrial direct-write electron-beam lithography system. Comprehensive measurement methods are utilized to study the patterned surfaces, including infrared spectral radiometry and Fourier-transform infrared spectrometry. These systems allow for direct and complementary spectral signature measurements--the radiometer measures the absorption or emission of the surface, and the spectrometer measures its transmission and reflection. For the circuit-analog absorbing square-loop IR FSS, the spectral modulation in emission is measured to be greater than 85% at resonance. Other desirable modifications of surface signature are also explored; these include the ability to filter radiation based on its polarization orientation and the ability to dynamically tune the surface signature. An array of spiral FSS elements allows for circular polarization conditioning. Three techniques for tuning the IR FSS signature via voltage application are explored, including the incorporation of a pn junction substrate, a piezoelectric substrate and a liquid crystal superstrate. These studies will ignite future explorations of IR FSS technology, enabling various unique applications.
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Date Issued: 2005
Identifier: CFE0000589, ucf:46471
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0000589

Title: Optical Properties of Single Nanoparticles and Two-dimensional Arrays of Plasmonic Nanostructures.
Creator: Zhou, Yadong, Zou, Shengli, Harper, James, Zhai, Lei, Chen, Gang, Zheng, Qipeng, University of Central Florida
Abstract / Description: The tunability of plasmonic properties of nanomaterials makes them promising in many applications such as molecular detection, spectroscopy techniques, solar energy materials, etc. In the thesis, we mainly focus on the interaction between light with single nanoparticles and two-dimensional plasmonic nanostructures using electrodynamic methods. The fundamental equations of electromagnetic theory: Maxwell's equations are revisited to solve the problems of light-matter interaction, particularly...
Show moreThe tunability of plasmonic properties of nanomaterials makes them promising in many applications such as molecular detection, spectroscopy techniques, solar energy materials, etc. In the thesis, we mainly focus on the interaction between light with single nanoparticles and two-dimensional plasmonic nanostructures using electrodynamic methods. The fundamental equations of electromagnetic theory: Maxwell's equations are revisited to solve the problems of light-matter interaction, particularly the interaction of light and noble nanomaterials, such as gold and silver. In Chapter 1, Stokes parameters that describe the polarization states of electromagnetic wave are presented. The scattering and absorption of a particle with an arbitrary shape are discussed. In Chapter 2, several computational methods for solving the optical response of nanomaterials when they are illuminated by incident light are studied, which include the Discrete Dipole Approximation (DDA) method, the coupled dipole (CD) method, etc. In Chapter 3, the failure and reexamination of the relation between the Raman enhancement factor and local enhanced electric field intensity is investigated by placing a molecular dipole in the vicinity of a silver rod. Using a silver rod and a molecular dipole, we demonstrate that the relation generated using a spherical nanoparticle cannot simply be applied to systems with particles of different shapes. In Chapter 4, a silver film with switchable total transmission/reflection is discussed. The film is composed of two-dimensional rectangular prisms. The factors affecting the transmission (reflection) as well as the mechanisms leading to the phenomena are studied. Later, in Chapter 5 and 6, the sandwiched nano-film composed of two 2D rectangular prisms arrays and two glass substrates with a continuous film in between is examined to enhance the transmission of the continuous silver film.
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Date Issued: 2018
Identifier: CFE0007117, ucf:51943
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007117

Title: Use of Video-Enhanced Debriefing in Clinical Nursing Skill Acquisition: Indwelling Urinary Catheterization as an Exemplar.
Creator: Hoyt, Erica, Gill, Michele, Clark, M. H., Chase, Susan, Gonzalez, Laura, University of Central Florida
Abstract / Description: Nursing students struggle to acquire and maintain clinical psychomotor skills. Hiring agencies bear the cost of retraining graduate nurses inept with skills learned early in their nursing curriculum. Improperly performed clinical skills pose a risk to patient safety, resulting in pain and suffering for the patient. This empirical study aimed to determine if video-enhanced debriefing (VED) improved initial skill validation scores, skill feedback, satisfaction with learning, and reduced skill...
Show moreNursing students struggle to acquire and maintain clinical psychomotor skills. Hiring agencies bear the cost of retraining graduate nurses inept with skills learned early in their nursing curriculum. Improperly performed clinical skills pose a risk to patient safety, resulting in pain and suffering for the patient. This empirical study aimed to determine if video-enhanced debriefing (VED) improved initial skill validation scores, skill feedback, satisfaction with learning, and reduced skill decay among first-semester, pre-licensure BSN students performing female indwelling urinary catheterization (IUC) in a simulated clinical setting compared to no debriefing. Participants received standard instruction, then video-recorded their IUC skill. Participants randomized into the VED group individually participated in an advocacy/inquiry debriefing with the principal investigator while viewing their performance video. Both groups completed a summative IUC skill validation per standard course instruction and submitted their skill performance ratings. All participants completed a survey including their perceived IUC knowledge, amount of skill practice, learning satisfaction with VED, and an evaluation of their skill performance feedback. All participants re-recorded their IUC skill and received performances ratings with the same instruments again ten weeks after the initial skill validation. The analysis revealed that VED did not improve nursing skills, knowledge, practice, or perceptions of the learning experience compared to the video-only group. Nursing students in the VED condition did rate their skill performance feedback higher than those in the video-only group. Students improved performance in both conditions, showing that learning via video is an effective teaching strategy to enhance student's satisfaction with learning, to engage in repetitive practice with feedback, and to improve learning.
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Date Issued: 2019
Identifier: CFE0007656, ucf:52504
Format: Document (PDF)
PURL: http://purl.flvc.org/ucf/fd/CFE0007656

enhancement (4)	+ -
CEB (2)	+ -
heat transfer (2)	+ -
Acetic Acid (1)	+ -
Backwash Recycle (1)	+ -

Biosensing (1)	+ -
Cascaded Field Enhancement (1)	+ -
Chemically Enhanced Backwash (1)	+ -
Citric Acid (1)	+ -
Clinical competence (1)	+ -
Coagulation (1)	+ -
Coagulation Interference (1)	+ -
Confirmation (1)	+ -
Continuous metal film (1)	+ -
Coupling mode (1)	+ -
Debriefing (1)	+ -
Deliberate practice (1)	+ -
Discrete Dipole Approximation (1)	+ -
Distributed estimation (1)	+ -
Dopamine Sensing (1)	+ -
Dynamic Contrast Enhanced imaging (1)	+ -
EBPR (1)	+ -
Emotional Support (1)	+ -
Enhanced Light-Matter Interaction (1)	+ -
Enhanced electric fields. (1)	+ -
Fano Resonance (1)	+ -
Feedback (1)	+ -
Foucault (1)	+ -
Friendship (1)	+ -
Functional Laplace deconvolution (1)	+ -

University of Central Florida (23)	+ -
Duranceau, Steven (3)	+ -
Randall, Andrew (3)	+ -
Boyd, Christopher (2)	+ -
Weger, Harry (2)	+ -

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Atia, George (1)	+ -
Bagci, Ulas (1)	+ -
Belfield, Kevin (1)	+ -
Belfield, Kevin D. (1)	+ -
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