View All Items
(1 - 20 of 78)
Pages
- Title
- USABILITY OF VARIOUS INPUT DEVICES ON A STEERING TASK.
- Creator
-
Fund, Ian, McConnell, Daniel, University of Central Florida
- Abstract / Description
-
In this study we examined the differences of performance of various input devices on a steering task. Two paths were created, one easy and one hard, with the harder path having more turning points to navigate with one of three different input devices: mouse and keyboard, Xbox 360 controller, and a joystick. Participants were also exposed to low or high stress conditions. High stress was caused by playing loud short bursts of music over headphones worn by participants during testing. Results...
Show moreIn this study we examined the differences of performance of various input devices on a steering task. Two paths were created, one easy and one hard, with the harder path having more turning points to navigate with one of three different input devices: mouse and keyboard, Xbox 360 controller, and a joystick. Participants were also exposed to low or high stress conditions. High stress was caused by playing loud short bursts of music over headphones worn by participants during testing. Results indicated the mouse and keyboard performed better in all cases. There was no significant difference between the Xbox controller and joystick. No differences were found in the low and high stress conditions. Differences in sex were found, even when controlling for video game experience. These findings indicate that the mouse and keyboard is the best device to use on a steering task.
Show less - Date Issued
- 2015
- Identifier
- CFH0004763, ucf:45362
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004763
- Title
- NURSING ATTITUDES TOWARD THE USE OF REPROCESSED SINGLE-USE MEDICAL DEVICES.
- Creator
-
Maben-Tenney, Laura, Loerzel, Victoria, University of Central Florida
- Abstract / Description
-
BACKGROUND: Before the implementation of single-use devices (SUD) in health care, medical equipment was sterilized and reused. Now many medical devices are used once and then thrown away, contributing to the 5.9 million tons of medical waste produced yearly. This project explores nursing attitudes toward single-use medical devices, evaluates current recycling practices and examines whether student nurses would be likely to use reprocessed SUDs in their practice if given the option....
Show moreBACKGROUND: Before the implementation of single-use devices (SUD) in health care, medical equipment was sterilized and reused. Now many medical devices are used once and then thrown away, contributing to the 5.9 million tons of medical waste produced yearly. This project explores nursing attitudes toward single-use medical devices, evaluates current recycling practices and examines whether student nurses would be likely to use reprocessed SUDs in their practice if given the option. METHODOLOGY: After obtaining IRB approval, students enrolled in nursing research courses were invited to participate in this exploratory study. 157 undergraduate nursing students completed the 46-question survey. Descriptive statistics were used to analyze the survey results, independent t-tests were used to compare groups and content analysis was used to analyze open-ended responses. RESULTS: The typical student was female, age 30, licensed as a registered nurse and enrolled in the RN to BSN program. Most students (84.7%) viewed themselves as environmentally conscious, and most recycle at home (75.5%) and at work (54.7%). Most agreed (96.8%) that hospitals produce a lot of hazardous waste and that it is the hospitals responsibility for environmentally friendly waste disposal. The majority also agreed (80%) that nurses have the ability to impact waste production at a hospital. More than half (67.7%) agreed that SUD disposal contributes to environmental pollution and many (76.6%) felt that nurses should be responsible for environmental health concepts. Most (81.6%) felt that SUDs should be thrown out after one use and few (28.5%) felt that SUDs can be reused if sterilized. Most (74.0%) also believed that SUD reuse contributes to hospital acquired infections, but a little more than half (56.3%) were willing to reuse a SUD that had only touched intact skin if sterilized for reuse. Additionally, most respondents (79.1%) would consider joining a green team at work. Those who recycle at home were more likely to identify as environmentally conscious than those who do not recycle at home. No generational differences existed when considering environmental consciousness. Generation X was more likely to recycle at home than Generation Y, but no generational differences existed when analyzing work recycling habits. Generation X was also more likely to see single-use device disposal as contributing to environmental pollution than Generation Y. Home recyclers were more likely to agree that nurses have the ability to decrease the amount of hospital trash production, and more likely to join a green team than non-recyclers. They also believed that SUD disposal contributes to environmental pollution, SUDs can be reused if sterilized, and disagreed that SUD reuse contributes to hospital acquired infections when compared to those who do not recycle at home. Discussion: While most students agree that hospitals produce large amounts of waste and should be responsible for the disposal of it in an environmentally friendly manner, most are hesitant to use reprocessed SUDs as a means to make the hospital more environmentally friendly. Student responses indicated the largest perceived barriers to SUD reuse were fears of inadequate sterilization and fears of the spread of disease. CONCLUSIONS: Most students, especially home recyclers, believe themselves to be environmentally conscious and most were willing to consider reusing some SUDs. Translating this belief into action can happen through education in line with the Scope and Standards of practice for nursing, as well as establishing the safety of SUDs through further research.
Show less - Date Issued
- 2012
- Identifier
- CFH0004243, ucf:44939
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004243
- Title
- Simulation Model to Evaluate Performance of Operational Systems and their Impact on Repair Shop Activity at a Navy Field Site.
- Creator
-
Newell, James T., Doering, R. D., Engineering
- Abstract / Description
-
University of Central Florida College of Engineering Thesis; This paper presents the background and procedures leading to development of a simulation model to analyze the impact of certain decision variables on operational system performance and workloads as the repair facility of a typical Navy field site. The research examines the impact of maintenance support concepts, as implemented by changes in the decision variables, associated with the broader application of Automatic Test Equipment....
Show moreUniversity of Central Florida College of Engineering Thesis; This paper presents the background and procedures leading to development of a simulation model to analyze the impact of certain decision variables on operational system performance and workloads as the repair facility of a typical Navy field site. The research examines the impact of maintenance support concepts, as implemented by changes in the decision variables, associated with the broader application of Automatic Test Equipment. The initial effort consisted of data collection and field site surveys which culminated in defining a work flow model illustrating typical repair facility operations. The work flow model is translated into a computer simulation model. The baseline model contains all the values for failure rates, delay times, and probability decision parameters derived from the available data. The simulation model is then exercised and the output data recorded for comparison with historical data to validate the model and provide a baseline for comparison as the decision parameters are varied. Of the variables exercised, it appreas that the Built-in-Test (BIT), or Self-test capability, is one of the more important design considerations in the original operating systems.
Show less - Date Issued
- 1979
- Identifier
- CFR0008133, ucf:52959
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFR0008133
- Title
- Young Children's Fine Motor iPad Gestures When Performed Alone and in Dyads.
- Creator
-
Nguyen, Lap, Culp, Anne, Szente, Judit, Hughes-Brand, Nicola Shea, University of Central Florida
- Abstract / Description
-
Since the release of the first iPad in 2010, over 200 million have been sold worldwide. In the short time since the iPad's release, the devices have become popular in classrooms. The purpose of this study was twofold: 1) to document the fine motor iPad gestures of 2 , 3-, and 4-year-old children who used iPads by themselves and in dyads and 2) to conduct international comparisons regarding such observed fine motor iPad gestures. In this study, I examined seven iPad gestures: (a) tap, (b) drag...
Show moreSince the release of the first iPad in 2010, over 200 million have been sold worldwide. In the short time since the iPad's release, the devices have become popular in classrooms. The purpose of this study was twofold: 1) to document the fine motor iPad gestures of 2 , 3-, and 4-year-old children who used iPads by themselves and in dyads and 2) to conduct international comparisons regarding such observed fine motor iPad gestures. In this study, I examined seven iPad gestures: (a) tap, (b) drag/slide, (c) free rotate, (d) drag and drop, (e) pinch, (f) spread, and (g) flick. This study had five components. The first component involved observations of the iPad gestures of a sample of Orlando, Florida, children operating iPads by themselves. The first component was a partial replication of the 2013 and 2014 studies conducted by Aziz et al. The second component of this study involved observations of the iPad gestures of the Orlando children operating iPads in dyads. In the third component of this study, I compared the iPad gestures of the Orlando children with the gestures of a sample of 2-, 3-, and 4-year-old children from London. In the fourth component of this study, I compared the iPad gestures of the Orlando children with the gestures of a sample of 2-, 3-, and 4-year-old children from Malaysia. In the fifth component, I compared the iPad gestures of the Orlando sample when the children were paired with classmates and asked to play with the iPads in dyads, rather than operating iPads by themselves. Biographical information was collected, including (a) child's age, (b) household income, (c) child's gender, (d) child's ethnic origin, (e) types of mobile devices in the household, (f) daily usage of mobile devices, (g) people with whom the child used mobile devices, (h) earliest age of device usage, and (i) the primary language spoken at home.
Show less - Date Issued
- 2016
- Identifier
- CFE0006541, ucf:51352
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006541
- Title
- PHYSICAL ERGONOMIC AND MENTAL WORKLOAD FACTORS OF MOBILE LEARNING AFFECTING PERFORMANCE OF ADULT DISTANCE LEARNERS: STUDENT PERSPECTIVE.
- Creator
-
Jones, Rochelle, McCauley-Bush, Pamela, University of Central Florida
- Abstract / Description
-
Distance education is the fastest growing educational modality because of advances information technology has made over the past 25 years. Adult learners have become the fastest growing population in distance education. Adult learners, through technical tools and devices they use on the job, have become more digitally literate and mobile, making the ability to access class work on the go a necessity. Mobile learning or m-learning (learning that uses wireless, portable, mobile computing, and...
Show moreDistance education is the fastest growing educational modality because of advances information technology has made over the past 25 years. Adult learners have become the fastest growing population in distance education. Adult learners, through technical tools and devices they use on the job, have become more digitally literate and mobile, making the ability to access class work on the go a necessity. Mobile learning or m-learning (learning that uses wireless, portable, mobile computing, and communication devices) is becoming an extension of distance learning, providing a channel for students to learn, communicate, and access educational material outside the traditional classroom environment. For adult learners, this modality allows them to take advantage of accessing material using mobile devices they use for job related activities. Despite the portability and readiness to information mobile devices provide its users, cognitive and physical ergonomic issues may impact learner performance. These issues may stem from information overload and physical discomfort from extended use of the mobile device which may negatively affect the overall success and satisfaction of m-learning environments. The purpose of this study was to examine the relationship between physical ergonomic discomfort, subjective workload, physiological response, and the impact on student performance while using mobile technology to read course material. Activity Theory was used as the theoretical foundation that guided the study. Eighty-four research participants, all over the age of 25, read a passage using one of two distance education modalities: desktop computer or mobile device. While reading the passage, one of three task load levels was imposed on participants: none, low or high. Each participant endured three trials, repeating the same task for each trial. After each trial, participants completed an achievement test and the NASA-TLX assessment. The results from this study provided evidence that mobile learning technologies with increased levels of task load introduced physical ergonomic discomfort and affected perceptions of mental workload in participants. The study also provided evidence that mobile learning technologies with increased levels of task load affected the performance (reading and learning) of participants. Study results provided insight into capabilities and limitations of students in their use of mobile devices for educational purposes. The limitations identified need to be further examined to aid in building successful m-learning environments with the goal of mobile device usage not affecting student performance.
Show less - Date Issued
- 2009
- Identifier
- CFE0002658, ucf:48212
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002658
- Title
- Digital Architecture for a Computer Based Imaging System.
- Creator
-
McIntosh, John O., Petrasko, Brian, Engineering
- Abstract / Description
-
University of Central Florida College of Engineering Thesis; There is a great need for a graphic simulation system used as a training device to take the place of actual flying. A good system will greatly reduce the cost of training men as well as cut down on casualties. Several systems have been tried and are now in use. Among them are two that are worthy of more study. These are the CCTV or model board and the digital systems. Both have several disadvantages that create a need for a new...
Show moreUniversity of Central Florida College of Engineering Thesis; There is a great need for a graphic simulation system used as a training device to take the place of actual flying. A good system will greatly reduce the cost of training men as well as cut down on casualties. Several systems have been tried and are now in use. Among them are two that are worthy of more study. These are the CCTV or model board and the digital systems. Both have several disadvantages that create a need for a new system. One such system is an optically based digitally processes system that combines the best features of two previous systems. This system uses charge-coupled-device memories that are digitally accessed by a microcomputer based system. The information from the CCD's is then processed and calculations are performed on it to transform it into a form that can be displayed on a cockpit-like screen. The system also allows for interaction between the pilot and itself.
Show less - Date Issued
- 1979
- Identifier
- CFR0008131, ucf:52966
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFR0008131
- Title
- DESIGN AND MODELING OF RADIATION HARDENED LDMOSFET FOR SPACE CRAFT POWER SYSTEMS.
- Creator
-
Shea, Patrick, Shen, John, University of Central Florida
- Abstract / Description
-
NASA missions require innovative power electronics system and component solutions with long life capability, high radiation tolerance, low mass and volume, and high reliability in space environments. Presently vertical double-diffused MOSFETs (VDMOS) are the most widely used power switching device for space power systems. It is proposed that a new lateral double-diffused MOSFET (LDMOS) designed at UCF can offer improvements in total dose and single event radiation hardness, switching...
Show moreNASA missions require innovative power electronics system and component solutions with long life capability, high radiation tolerance, low mass and volume, and high reliability in space environments. Presently vertical double-diffused MOSFETs (VDMOS) are the most widely used power switching device for space power systems. It is proposed that a new lateral double-diffused MOSFET (LDMOS) designed at UCF can offer improvements in total dose and single event radiation hardness, switching performance, development and manufacturing costs, and total mass of power electronics systems. Availability of a hardened fast-switching power MOSFET will allow space-borne power electronics to approach the current level of terrestrial technology, thereby facilitating the use of more modern digital electronic systems in space. It is believed that the use of a p+/p-epi starting material for the LDMOS will offer better hardness against single-event burnout (SEB) and single-event gate rupture (SEGR) when compared to vertical devices fabricated on an n+/n-epi material. By placing a source contact on the bottom-side of the p+ substrate, much of the hole current generated by a heavy ion strike will flow away from the dielectric gate, thereby reducing electrical stress on the gate and decreasing the likelihood of SEGR. Similarly, the device is hardened against SEB by the redirection of hole current away from the base of the device's parasitic bipolar transistor. Total dose hardness is achieved by the use of a standard complementary metal-oxide semiconductor (CMOS) process that has shown proven hardness against total dose radiation effects.
Show less - Date Issued
- 2007
- Identifier
- CFE0001966, ucf:47468
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001966
- Title
- CAMERA SYSTEM SUPPORT FOR HIGHWAY TRANSPORTATION USING MOBILE DEVICES.
- Creator
-
Minh, Le, Hua, Kien A., University of Central Florida
- Abstract / Description
-
With the very fast growing technology in wireless, advancement in hardware and the dramatically falling cost of mobile computing devices such as PDA, handheld device, People nowadays can have a personal device that fits in their hand but has computing power as a desktop did few years ago. The same device now is able to communicate over a wireless network and view office document at the same time. The combination of size, power and flexibility makes the personal devices increasingly appear in...
Show moreWith the very fast growing technology in wireless, advancement in hardware and the dramatically falling cost of mobile computing devices such as PDA, handheld device, People nowadays can have a personal device that fits in their hand but has computing power as a desktop did few years ago. The same device now is able to communicate over a wireless network and view office document at the same time. The combination of size, power and flexibility makes the personal devices increasingly appear in many aspects of life.In this proposal, we focus on a simple yet useful application of mobile devices and wireless capabilities. The application can help commuters in traffic system to find an optimal route based on video camera surveillance information. This surveillance information is made available to the user through his/her handheld devices. As an example, suppose we have installed several cameras along the expressway. If commuters can access to these cameras, they can observe the situation currently happening along the way, and decide which path would be the most effective to avoid the traffic congestion. This application will eventually improve the effectiveness of current traffic system since it will help to reduce traffic congestions.
Show less - Date Issued
- 2004
- Identifier
- CFE0000094, ucf:46090
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000094
- Title
- LIQUID CRYSTAL MATERIALS AND TUNABLE DEVICES FOR OPTICAL COMMUNICATIONS.
- Creator
-
Du, Fang, Wu, Shin-Tson, University of Central Florida
- Abstract / Description
-
In this dissertation, liquid crystal materials and devices are investigated in meeting the challenges for photonics and communications applications. The first part deals with polymer-stabilized liquid crystal (PSLC) materials and devices. Three polymer-stabilized liquid crystal systems are developed for optical communications. The second part reports the experimental investigation of a novel liquid-crystal-infiltrated photonic crystal fiber (PCF) and explores its applications in fiber-optic...
Show moreIn this dissertation, liquid crystal materials and devices are investigated in meeting the challenges for photonics and communications applications. The first part deals with polymer-stabilized liquid crystal (PSLC) materials and devices. Three polymer-stabilized liquid crystal systems are developed for optical communications. The second part reports the experimental investigation of a novel liquid-crystal-infiltrated photonic crystal fiber (PCF) and explores its applications in fiber-optic communications. The curing temperature is found to have significant effects on the PSLC performance. The electro-optic properties of nematic polymer network liquid crystal (PNLC) at different curing temperatures are investigated experimentally. At high curing temperature, a high contrast, low drive voltage, and small hysteresis PNLC is obtained as a result of the formed large LC micro-domains. With the help of curing temperature effect, it is able to develop PNLC based optical devices with highly desirable performances for optical communications. Such high performance is generally considered difficult to realize for a PNLC. In fact, the poor performance of PNLC, especially at long wavelengths, has hindered it from practical applications for optical communications for a long time. Therefore, the optimal curing temperature effect discovered in this thesis would enable PSLCs for practical industrial applications. Further more, high birefringence LCs play an important role for near infrared photonic devices. The isothiocyanato tolane liquid crystals exhibit a high birefringence and low viscosity. The high birefringence LC dramatically improves the PSLC contrast ratio while keeping a low drive voltage and fast response time. A free-space optical device by PNLC is experimentally demonstrated and its properties characterized. Most LC devices are polarization sensitive. To overcome this drawback, we have investigated the polymer-stabilized cholesteric LC (PSCLC). Combining the curing temperature effect and high birefringence LC, a polarization independent fiber-optical device is realized with over 30 dB attenuation, ~12 Vrms drive voltage and 11/28 milliseconds (rise/decay) response times. A polymer-stabilized twisted nematic LC (PS TNLC) is also proposed as a variable optical attenuator for optical communications. By using the polarization control system, the device is polarization independent. The polymer network in a PS TNLC not only results in a fast response time (0.9/9 milliseconds for rise/decay respectively), but also removes the backflow effect of TNLC which occurs in the high voltage regime.
Show less - Date Issued
- 2005
- Identifier
- CFE0000485, ucf:46361
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000485
- Title
- DESIGN AND IMPLEMENTATION OF A HARDWARE LEVEL CONTENT NETWORKING FRONT END DEVICE.
- Creator
-
Buboltz, Jeremy, Kocak, Taskin, University of Central Florida
- Abstract / Description
-
The bandwidth and speed of network connections are continually increasing. The speed increase in network technology is set to soon outpace the speed increase in CMOS technology. This asymmetrical growth is beginning to causing software applications that once worked with then current levels of network traffic to flounder under the new high data rates. Processes that were once executed in software now have to be executed, partially if not wholly in hardware. One such application that could...
Show moreThe bandwidth and speed of network connections are continually increasing. The speed increase in network technology is set to soon outpace the speed increase in CMOS technology. This asymmetrical growth is beginning to causing software applications that once worked with then current levels of network traffic to flounder under the new high data rates. Processes that were once executed in software now have to be executed, partially if not wholly in hardware. One such application that could benefit from hardware implementation is high layer routing. By allowing a network device to peer into higher layers of the OSI model, the device can scan for viruses, provide higher quality-of-service (QoS), and efficiently route packets. This thesis proposes an architecture for a device that will utilize hardware-level string matching to distribute incoming requests for a server farm. The proposed architecture is implemented in VHDL, synthesized, and laid out on an Altera FPGA.
Show less - Date Issued
- 2007
- Identifier
- CFE0001888, ucf:47390
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001888
- Title
- INVESTIGATION OF HIGH-K GATE DIELECTRICS AND METALS FOR MOSFET DEVICES.
- Creator
-
Seshadri, Sriram, Sundaram, Kalpathy, University of Central Florida
- Abstract / Description
-
Progress in advanced microlithography and deposition techniques have made feasible high- k dielectric materials for MOS transistors. The continued scaling of CMOS devices is pushing the Si-SiO2 to its limit to consider high-k gate dielectrics. The demand for faster, low power, smaller, less expensive devices with good functionality and higher performance increases the demand for high-k dielectric based MOS devices. This thesis gives an in-depth study of threshold voltages of PMOS and NMOS...
Show moreProgress in advanced microlithography and deposition techniques have made feasible high- k dielectric materials for MOS transistors. The continued scaling of CMOS devices is pushing the Si-SiO2 to its limit to consider high-k gate dielectrics. The demand for faster, low power, smaller, less expensive devices with good functionality and higher performance increases the demand for high-k dielectric based MOS devices. This thesis gives an in-depth study of threshold voltages of PMOS and NMOS transistors using various high-k dielectric materials like Tantalum pent oxide (Ta2O5), Hafnium oxide (HfO2), Zirconium oxide (ZrO2) and Aluminum oxide (Al2O3) gate oxides. Higher dielectric constant may lead to high oxide capacitance (Cox), which affects the threshold voltage (VT) of the device. The working potential of MOS devices can be increased by high dielectric gate oxide and work function of gate metal which may also influence the threshold voltage (VT). High dielectric materials have low gate leakage current, high breakdown voltage and are thermally stable on Silicon Substrate (Si). Different kinds of deposition techniques for different gate oxides, gate metals and stability over silicon substrates are analyzed theoretically. The impact of the properties of gate oxides such as oxide thickness, interface trap charges, doping concentration on threshold voltage were simulated, plotted and studied. This study involved comparisons of oxides-oxides, metals-metals, and metals-oxides. Gate metals and alloys with work function of less than 5eV would be suitable candidates for aluminum oxide, hafnium oxide etc. based MOSFETs.
Show less - Date Issued
- 2005
- Identifier
- CFE0000667, ucf:46549
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000667
- Title
- Stochastic-Based Computing with Emerging Spin-Based Device Technologies.
- Creator
-
Bai, Yu, Lin, Mingjie, DeMara, Ronald, Wang, Jun, Jin, Yier, Dong, Yajie, University of Central Florida
- Abstract / Description
-
In this dissertation, analog and emerging device physics is explored to provide a technology plat- form to design new bio-inspired system and novel architecture. With CMOS approaching the nano-scaling, their physics limits in feature size. Therefore, their physical device characteristics will pose severe challenges to constructing robust digital circuitry. Unlike transistor defects due to fabrication imperfection, quantum-related switching uncertainties will seriously increase their sus-...
Show moreIn this dissertation, analog and emerging device physics is explored to provide a technology plat- form to design new bio-inspired system and novel architecture. With CMOS approaching the nano-scaling, their physics limits in feature size. Therefore, their physical device characteristics will pose severe challenges to constructing robust digital circuitry. Unlike transistor defects due to fabrication imperfection, quantum-related switching uncertainties will seriously increase their sus- ceptibility to noise, thus rendering the traditional thinking and logic design techniques inadequate. Therefore, the trend of current research objectives is to create a non-Boolean high-level compu- tational model and map it directly to the unique operational properties of new, power efficient, nanoscale devices.The focus of this research is based on two-fold: 1) Investigation of the physical hysteresis switching behaviors of domain wall device. We analyze phenomenon of domain wall device and identify hys- teresis behavior with current range. We proposed the Domain-Wall-Motion-based (DWM) NCL circuit that achieves approximately 30x and 8x improvements in energy efficiency and chip layout area, respectively, over its equivalent CMOS design, while maintaining similar delay performance for a one bit full adder. 2) Investigation of the physical stochastic switching behaviors of Mag- netic Tunnel Junction (MTJ) device. With analyzing of stochastic switching behaviors of MTJ, we proposed an innovative stochastic-based architecture for implementing artificial neural network (S-ANN) with both magnetic tunneling junction (MTJ) and domain wall motion (DWM) devices, which enables efficient computing at an ultra-low voltage. For a well-known pattern recognition task, our mixed-model HSPICE simulation results have shown that a 34-neuron S-ANN imple- mentation, when compared with its deterministic-based ANN counterparts implemented with dig- ital and analog CMOS circuits, achieves more than 1.5 ? 2 orders of magnitude lower energy consumption and 2 ? 2.5 orders of magnitude less hidden layer chip area.
Show less - Date Issued
- 2016
- Identifier
- CFE0006680, ucf:51921
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006680
- Title
- PHASE SHAPING IN THE INFRARED BY PLANAR QUASI-PERIODIC SURFACES COMPRISED OF SUB-WAVELENGTH ELEMENTS.
- Creator
-
Ginn, James, Boreman, Glenn, University of Central Florida
- Abstract / Description
-
Reflectarrays are passive quasi-periodic sub-wavelength antenna arrays designed for discrete reflected phase manipulation at each individual antenna element making up the array. By spatially varying the phase response of the antenna array, reflectarrays allow a planar surface to impress a non-planar phasefront upon re-radiation. Such devices have become commonplace at radio frequencies. In this dissertation, they are demonstrated in the infrared for the first time – at frequencies as...
Show moreReflectarrays are passive quasi-periodic sub-wavelength antenna arrays designed for discrete reflected phase manipulation at each individual antenna element making up the array. By spatially varying the phase response of the antenna array, reflectarrays allow a planar surface to impress a non-planar phasefront upon re-radiation. Such devices have become commonplace at radio frequencies. In this dissertation, they are demonstrated in the infrared for the first time – at frequencies as high as 194 THz. Relevant aspects of computational electromagnetic modeling are explored, to yield design procedures optimized for these high frequencies. Modeling is also utilized to demonstrate the phase response of a generalized metallic patch resonator in terms of its dependence on element dimensions, surrounding materials, angle of incidence, and frequency. The impact of realistic dispersion of the real and imaginary parts of the metallic permittivity on the magnitude and bandwidth of the resonance behavior is thoroughly investigated. Several single-phase reflectarrays are fabricated and measurement techniques are developed for evaluating these surfaces. In all of these cases, there is excellent agreement between the computational model results and the measured device characteristics. With accurate modeling and measurement, it is possible to proceed to explore some specific device architectures appropriate for focusing reflectarrays, including binary-phase and phase-incremental approaches. Image quality aspects of these focusing reflectarrays are considered from geometrical and chromatic-aberration perspectives. The dissertation concludes by briefly considering two additional analogous devices – the transmitarray for tailoring transmissive phase response, and the emitarray for angular control of thermally emitted radiation.
Show less - Date Issued
- 2009
- Identifier
- CFE0002707, ucf:48186
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002707
- Title
- Determination of Frequency-Based Switch Triggers for Optimal Vibration Reduction via Resonance Frequency Detuning.
- Creator
-
Lopp, Garrett, Kauffman, Jeffrey, Das, Tuhin, Xu, Yunjun, University of Central Florida
- Abstract / Description
-
Resonance frequency detuning (RFD) is a piezoelectric-based vibration reduction approach that applies to systems experiencing transient excitation through the system's resonance(-)for example, turbomachinery experiencing changes in rotation speed, such as on spool-up and spool-down. This technique relies on the inclusion of piezoelectric material and manipulation of its electrical boundary conditions, which control the stiffness of the piezoelectric material. Resonance frequency detuning...
Show moreResonance frequency detuning (RFD) is a piezoelectric-based vibration reduction approach that applies to systems experiencing transient excitation through the system's resonance(-)for example, turbomachinery experiencing changes in rotation speed, such as on spool-up and spool-down. This technique relies on the inclusion of piezoelectric material and manipulation of its electrical boundary conditions, which control the stiffness of the piezoelectric material. Resonance frequency detuning exploits this effect by intelligently switching between the open-circuit (high stiffness) and short-circuit (low stiffness) conditions as the excitation approaches resonance, subsequently shifting the natural frequency to avoid this resonance crossing and limit the response. The peak response dynamics are then determined by the system's sweep rate, modal damping ratio, electromechanical coupling coefficient, and, most importantly, the trigger (represented here in terms of excitation frequency) that initiates the stiffness state switch. This thesis identifies the optimal frequency-based switch trigger over a range of sweep rates, damping ratios, and electromechanical coupling coefficients. With perfect knowledge of the system, the optimal frequency-based switch trigger decreases approximately linearly with the square of the coupling coefficient. Furthermore, phase of vibration at the time of the switch has a very small effect; switching on peak strain energy is marginally optimal. In practice, perfect knowledge is unrealistic and an alternate switch trigger based on an easily measurable parameter is necessary. As such, this thesis also investigates potential methods using the open-circuit piezoelectric voltage response envelope and its derivatives. The optimal switch triggers collapse to a near linear trend when measured against the response envelope derivatives and, subsequently, an empirical control law is extracted. This control law agrees well with and produces a comparable response to that of the optimal control determined using perfect and complete knowledge of the system.
Show less - Date Issued
- 2015
- Identifier
- CFE0005829, ucf:50909
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005829
- Title
- Advanced liquid crystal displays with supreme image qualities.
- Creator
-
Chen, Haiwei, Wu, Shintson, Moharam, Jim, Likamwa, Patrick, Dong, Yajie, University of Central Florida
- Abstract / Description
-
Several metrics are commonly used to evaluate the performance of display devices. In this dissertation, we analyze three key parameters: fast response time, wide color gamut, and high contrast ratio, which affect the final perceived image quality. Firstly, we investigate how response time affects the motion blur, and then discover the 2-ms rule. With advanced low-viscosity materials, new operation modes, and backlight modulation technique, liquid crystal displays (LCDs) with an unnoticeable...
Show moreSeveral metrics are commonly used to evaluate the performance of display devices. In this dissertation, we analyze three key parameters: fast response time, wide color gamut, and high contrast ratio, which affect the final perceived image quality. Firstly, we investigate how response time affects the motion blur, and then discover the 2-ms rule. With advanced low-viscosity materials, new operation modes, and backlight modulation technique, liquid crystal displays (LCDs) with an unnoticeable image blur can be realized. Its performance is comparable to an impulse-type display, like cathode ray tube (CRT). Next, we propose two novel backlight configurations to improve an LCD's color gamut. One is to use a functional reflective polarizer (FRP), acting as a notch filter to block the unwanted light, and the other is to combine FRP with a patterned half-wave plate to suppress the crosstalk between blue and green/red lights. In experiment, we achieved 97.3% Rec. 2020 in CIE 1976 color space, which is approaching the color gamut of a laser projector. Finally, to enhance an LCD's contrast ratio, we proposed a novel device configuration by adding an in-cell polarizer between LC layer and color filter array. The CR for a vertically-aligned LCD is improved from 5000:1 to 20,000:1, and the CR for a fringe field switching LCD is improved from 2000:1 to over 3000:1. To further enlarge CR to fulfill the high dynamic range requirement, a dual-panel LCD system is proposed and the measured contrast ratio exceeds 1,000,000:1. Overall speaking, such an innovated LCD exhibits supreme image qualities with motion picture response time comparable to CRT, vivid color to laser projector, and contrast ratio to OLED. Along with other outstanding features, like high peak brightness, high resolution density, long lifetime, and low cost, LCD would continue to maintain its dominance in consumer electronics in the foreseeable future.
Show less - Date Issued
- 2017
- Identifier
- CFE0006864, ucf:51758
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006864
- Title
- Monolithically Integrated InP-based Unidirectional Circulators Utilizing non-Hermiticity and Nonlinearity.
- Creator
-
Aleahmad, Parinaz, Christodoulides, Demetrios, Delfyett, Peter, Likamwa, Patrick, Moya Cessa, Hector Manual, University of Central Florida
- Abstract / Description
-
The need to integrate critical optical components on a single chip has been an ongoing quest in both optoelectronics and optical communication systems. Among the possible devices, elements supporting non-reciprocal transmission are of great interest for applications where signal routing and isolation is required. In this respect, breaking reciprocity is typically accomplished via Faraday rotation through appropriate magneto-optical arrangements. Unfortunately, standard light emitting...
Show moreThe need to integrate critical optical components on a single chip has been an ongoing quest in both optoelectronics and optical communication systems. Among the possible devices, elements supporting non-reciprocal transmission are of great interest for applications where signal routing and isolation is required. In this respect, breaking reciprocity is typically accomplished via Faraday rotation through appropriate magneto-optical arrangements. Unfortunately, standard light emitting optoelectronic materials like for example III-V semiconductors, lack magneto-optical properties and hence cannot be directly used in this capacity. To address these issues, a number of different tactics have been attempted in the last few years. These range from directly bonding garnets on chip, to parametric structures and unidirectional nonlinear arrangements involving ring resonators, to mention a few. Clearly, of importance will be to realize families of non-reciprocal devises that not only can be miniaturized and readily integrated on chip but they also rely on physical processes that are indigenous to the semiconductor wafer itself. Quite recently we have theoretically shown that such unidirectional systems can be implemented, provided one simultaneously exploits the presence of gain/loss processes and optical nonlinearities. In principle, these all-dielectric structures can be broadband, polarization insensitive, color-preserving, and can display appreciable isolation ratios provided they are used under pulsed conditions. In this study, we experimentally demonstrate a compact, monolithically integrated unidirectional 4(&)#215;4 optical circulator, based on non-reciprocal optical transmission through successive amplification/attenuation stages and elements with very large resonance nonlinearities associated with InGaAsP quantum wells. Our results indicate that isolation ratios over 20dB can be experimentally achieved in pulse-mode operation. Our design can be effortlessly extended to other existing optoelectronic device systems beyond InP.
Show less - Date Issued
- 2016
- Identifier
- CFE0006522, ucf:51373
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006522
- Title
- Advanced Metrology and Diagnostic Loss Analytics for Crystalline Silicon Photovoltaics.
- Creator
-
Schneller, Eric, Schoenfeld, Winston, Thomas, Jayan, Fenton, James, Coffey, Kevin, Sundaram, Kalpathy, University of Central Florida
- Abstract / Description
-
Characterization plays a key role in developing a comprehensive understanding of the structure and performance of photovoltaic devices. High quality characterization methods enable researchers to assess material choices and processing steps, ultimately giving way to improved device performance and reduced manufacturing costs. In this work, several aspects of advanced metrology for crystalline silicon photovoltaic are investigated including in-line applications for manufacturing, off-line...
Show moreCharacterization plays a key role in developing a comprehensive understanding of the structure and performance of photovoltaic devices. High quality characterization methods enable researchers to assess material choices and processing steps, ultimately giving way to improved device performance and reduced manufacturing costs. In this work, several aspects of advanced metrology for crystalline silicon photovoltaic are investigated including in-line applications for manufacturing, off-line applications for research and development, and module/system level applications to evaluate long-term reliability. A frame work was developed to assess the cost and potential value of metrology within a manufacturing line. This framework has been published to an on-line calculator in an effort to provide the solar industry with an intuitive and transparent method of evaluating the economics of in-line metrology. One important use of metrology is in evaluating spatial non-uniformities, as localized defects in large area solar cells often reduce overall device performance. Techniques that probe spatial uniformity were explored and analysis algorithms were developed that provide insights regarding process non-uniformity and its impact on device performance. Finally, a comprehensive suite of module level characterization was developed to accurately evaluate performance and identify degradation mechanisms in field deployed photovoltaic modules. For each of these applications, case-studies were used to demonstrate the value of these techniques and to highlight potential use cases.
Show less - Date Issued
- 2016
- Identifier
- CFE0006499, ucf:51386
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006499
- Title
- TUNABLE LIQUID CRYSTAL PHOTONIC DEVICES.
- Creator
-
Fan, Yun-Hsing, Wu, Shin-Tson, University of Central Florida
- Abstract / Description
-
Liquid crystal (LC)-based adaptive optics are important for information processing, optical interconnections, photonics, integrated optics, and optical communications due to their tunable optical properties. In this dissertation, we describe novel liquid crystal photonic devices and their fabrication methods. The devices presented include inhomogeneous polymer-dispersed liquid crystal (PDLC), polymer network liquid crystals (PNLC) and phase-separated composite film (PSCOF). Liquid crystal...
Show moreLiquid crystal (LC)-based adaptive optics are important for information processing, optical interconnections, photonics, integrated optics, and optical communications due to their tunable optical properties. In this dissertation, we describe novel liquid crystal photonic devices and their fabrication methods. The devices presented include inhomogeneous polymer-dispersed liquid crystal (PDLC), polymer network liquid crystals (PNLC) and phase-separated composite film (PSCOF). Liquid crystal/polymer composites could exist in different forms depending on the fabrication conditions. In Chap. 3, we demonstrate a novel nanoscale PDLC device that has inhomogeneous droplet size distribution. In such a PDLC, the inhomogeneous droplet size distribution is obtained by exposing the LC/monomer with a non-uniform ultraviolet (UV) light. An electrically tunable-efficiency Fresnel lens is devised for the first time using nanoscale PDLC. The tunable Fresnel lens is very desirable to eliminate the need of external spatial light modulator. Different gradient profiles are obtained by using different photomasks. The nanoscale LC droplets are randomly distributed within the polymer matrix, so that the devices are polarization independent and exhibit a fast response time. Because of the small droplet sizes, the operating voltage is higher than 100 Vrms. To lower the driving voltage, in Chap. 2 and Chap. 3, we have investigated a polymer-network liquid crystal (PNLC) using a rod-like monomer structure. Since the monomer concentration is only about 5%, the operating voltage is below 10 Vrms. The PNLC devices are polarization dependent. To overcome this shortcoming, stacking two cells with orthogonal alignment directions is a possibility. In Chap. 3, another approach to lower the operating voltage is to use phase-separated composite film (PSCOF) where the LC and polymer are separated completely to form two layers. Without multi-domain formed in the LC cell, PSCOF is free from light scattering. Using PNLC and PSCOF, we also demonstrated LC blazed grating and Fresnel lens. The diffraction efficiency of these devices is continuously controlled by the electric field. Besides Fresnel lens, another critical need for imaging and display is to develop a system with continuously tunable focal length. A conventional zooming system controls the lens distance by mechanical motion along the optical axis. This mechanical zooming system is bulky and power hungry. To overcome the bulkiness, in Chap. 4 we developed an electrically tunable-focus flat LC spherical lens which consists of a spherical electrode imbedded in the top flat substrates while a planar electrode on the bottom substrate. The electric field from the spherical and planar electrodes induces a centrosymmetric gradient refractive index distribution within the LC layer which, in turn, causes the focusing effect. The focal length is tunable by the applied voltage. A tunable range from 0.6 m to infinity is achieved. Microlens array is an attractive device for optical communications and projection displays. In Chap. 5, we describe a LC microlens array whose focal length can be switched from positive to negative or vise versa by the applied voltage. The top spherical electrode glass substrate is flattened with a polymer layer. The top convex substrate and LC layer work together like a zoom lens. By tuning the refractive index profile of the LC layer, the focal length of the microlens array can be switched from positive to negative or vise versa. The tunable LC microlens array would be a great replacement of a conventional microlens array which can be moved by mechanical elements. The fast response time feature of our LC microlens array will be very helpful in developing 3-D animated images. A special feature for LC/polymer composites is light scattering. The concept is analogous to the light scattering of clouds which consist of water droplets. In Chap. 6, we demonstrate polymer network liquid crystals for switchable polarizers and optical shutters. The PNLC can present anisotropic or isotropic light scattering behavior depending on the fabrication methods. The use of dual-frequency liquid crystal and special driving scheme leads to a sub-millisecond response time. The applications for display, light shutters, and switchable windows are emphasized. Although polymer networks help to reduce liquid crystal response time, they tend to scatter light. In Chap. 7, for the first time, we demonstrate a fast-response and scattering-free homogeneously-aligned PNLC light modulator. Light scattering in the near-infrared region is suppressed by optimizing the polymer concentration such that the network domain sizes are smaller than the wavelength. As a result, the PNLC response time is ~300X faster than that of a pure LC mixture except that the threshold voltage is increased by ~25X. The PNLC cell also holds promise for mid and long infrared applications where response time is a critical issue.
Show less - Date Issued
- 2005
- Identifier
- CFE0000545, ucf:46439
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000545
- Title
- MODELING,DESIGN,AND CHARACTERIZATION OF MONOLITHIC BI-DIRECTIONAL POWER SEMICONDUCTOR SWITCH.
- Creator
-
Fu, Yue, Shen, Z.John, University of Central Florida
- Abstract / Description
-
Bidirectional power switching devices are needed in many power management applications, particularly in lithium-ion battery protection circuitry. A monolithic bidirectional power switch fabricated with a simplified CMOS technology is introduced in this dissertation. Throughout the design process, ISE TCAD tool plays an important role. Design variables are carefully analyzed to improve the device performance or yield the best trade off. Optimization is done with the help of TCAD simulation and...
Show moreBidirectional power switching devices are needed in many power management applications, particularly in lithium-ion battery protection circuitry. A monolithic bidirectional power switch fabricated with a simplified CMOS technology is introduced in this dissertation. Throughout the design process, ISE TCAD tool plays an important role. Design variables are carefully analyzed to improve the device performance or yield the best trade off. Optimization is done with the help of TCAD simulation and theoretical calculations. The device has been successfully fabricated using simplified 0.5 micron CMOS process. The experimental result shows a breakdown voltage of 25V. Due to the interdigitated source to source design, the inter-terminal current flowing path is effectively reduced to a few microns. The experimental result shows an ultra low specific on resistance. In comparison with other bi-directional power semiconductor switches by some major semiconductor manufacturers, the proposed BDS device has less than one half of the specific on resistance, thus substantially lower on state power loss of the switch. The proposed BDS device has a unique NPNPN structure, in comparison with NPNP structure, which is the analytical structure for CMOS latch-up, the proposed device inherently exhibits a better latch up immunity than CMOS inverter, thanks to the negative feed back mechanism of the extra NPN parasitic BJT transistor. In order to implement the device into simulators like PSPICE or Cadence IC Design, a compact model named variable resistance model has been built. This simple analytical model fits quite well with experimental data, and can be easily implemented by Verilog-A or other hardware description languages. Also, macro modeling is possible provided that the model parameters can be extracted from experimental curves. Several advanced types of BDS devices have been proposed, they exceed the basic BDS design in terms of breakdown voltage and /or on resistance. These advanced structures may be prominent for further improvement of the basic BDS device to a higher extend. Some cell phone providers such as Nokia is already asking for higher breakdown voltage of BDS device, due to the possibility of incidentally insert the battery pack into the cell phone with wrong pin polarity. Hopefully, the basic BDS design or one of these advanced types may eventually be implemented into the leading brand cell phone battery packs.
Show less - Date Issued
- 2007
- Identifier
- CFE0001605, ucf:47168
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001605
- Title
- PROCESSING AND STUDY OF CARBON NANOTUBE / POLYMER NANOCOMPOSITES AND POLYMER ELECTROLYTE MATERIALS.
- Creator
-
Harish, Muthuraman, Huo, Qun, University of Central Florida
- Abstract / Description
-
The first part of the study deals with the preparation of carbon nanotube/polymer nanocomposite materials. The dispersion of multi-walled carbon nanotubes (MWNTs) using trifluoroacetic acid (TFA) as a co-solvent and its subsequent use in polymer nanocomposite fabrication is reported. The use of carbon nanotube/ polymer nanocomposite system for the fabrication of organic solar cells is also studied. TFA is a strong but volatile acid which is miscible with many commonly used organic solvents....
Show moreThe first part of the study deals with the preparation of carbon nanotube/polymer nanocomposite materials. The dispersion of multi-walled carbon nanotubes (MWNTs) using trifluoroacetic acid (TFA) as a co-solvent and its subsequent use in polymer nanocomposite fabrication is reported. The use of carbon nanotube/ polymer nanocomposite system for the fabrication of organic solar cells is also studied. TFA is a strong but volatile acid which is miscible with many commonly used organic solvents. Our study demonstrates that MWNTs can be effectively purified and readily dispersed in a range of organic solvents including dimethyl formamide (DMF), tetrahydrofuran (THF), and dichloromethane when mixed with 10 vol% trifluoroacetic acid (TFA). X-ray photoelectron spectroscopic analysis revealed that the chemical structure of the TFA-treated MWNTs remained intact without oxidation. The dispersed carbon nanotubes in TFA/THF solution were mixed with poly(methyl methacrylate) (PMMA) to fabricate polymer nanocomposites. A good dispersion of nanotubes in solution and in polymer matrices was observed and confirmed by SEM and optical microscopy study. Low percolation thresholds of electrical conductivity were observed from the fabricated MWNT/PMMA composite films. A carbon nanotube/ polymer nanocomposites system was also used for the fabrication of organic solar cells. A blend of single-wall carbon nanotubes (SWNTs) and poly3-hexylthiophene (P3HT) was used as the active layer in the device. The device characteristics showed that the fabrication of the solar cells was successful without any shorts in the circuit. The second part of the study deals with the preparation and characterization of electrode and electrolyte materials for lithium ion batteries. A system of lithium trifluoroacetate/ PMMA was used for its study as the electrolyte in lithium battery. A variety of different processing conditions were used to prepare the polymer electrolyte system. The conductivity of the electrolyte plays a critical role in the high power output of a battery. A high power output requires fast transport of lithium ions for which the conductivity of the electrolyte must be at least 3 x 10^-4 S/cm. Electrochemical Impedance Spectroscopy (EIS) was used to determine the conductivity of the polymer electrolyte films. Among the different processing conditions used to prepare the polymer electrolyte material, wet films of PMMA/salt system prepared by using 10vol% of TFA in THF showed the best results. At about 70wt% loading of the salt in the polymer, the conductivity obtained was about 1.1 x 10^-2 S/cm. Recently, the use of vanadium oxide material as intercalation host for lithium has gained widespread attention. Sol-gel derived vanadium oxide films were prepared and its use as a cathode material for lithium ion battery was studied. The application of carbon nanotubes in lithium ion battery was explored. A carbon nanotube /block copolymer (P3HT-b-PS) composite was prepared and its potential as an anode material was evaluated.
Show less - Date Issued
- 2007
- Identifier
- CFE0001941, ucf:47436
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001941
