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- Title
- CASE STUDIES OF READING PERFORMANCE OF MALE STUDENTS AND THE SINGLE-SEX CLASSROOM.
- Creator
-
Basilo, Eric, Murray, Barbara, University of Central Florida
- Abstract / Description
-
Data from standardized test scores shows boys are falling further behind in literacy each year. Thanks to countless hours of research, we can pinpoint some of the causes for this decline. The major challenge educators face is how to keep boys interested in reading while placed in classrooms not necessarily designed to meet their needs. One option being explored is the use of single-sex classrooms. For over 160 years in the United States, public school single-sex classrooms have existed. The...
Show moreData from standardized test scores shows boys are falling further behind in literacy each year. Thanks to countless hours of research, we can pinpoint some of the causes for this decline. The major challenge educators face is how to keep boys interested in reading while placed in classrooms not necessarily designed to meet their needs. One option being explored is the use of single-sex classrooms. For over 160 years in the United States, public school single-sex classrooms have existed. The thought is that by separating boys and girls for academic classes, certain distractions will be eliminated, the environment can be adapted to accommodate the needs of boys, and teachers can teach in a style more appropriate to the gender. This study investigated how successful single-sex classrooms are in promoting student achievement. By taking data from the National Association for Single-Sex Public Education (NASSPE), and standardized test scores from selected states, the study looked at any statistical differences that occurred within schools containing academic, single-sex classrooms, and coeducational classrooms. Further, the study investigated whether significant differences occurred between gender groups within schools containing single-sex classrooms and those within coeducational ones. Finally, the study looked at presentation methods within these classes. Findings of the study indicated that for single-sex classes to be effective, further research must occur in order to develop best-teaching practices applicable to each gender. The study also demonstrated the need for professional development opportunities for single-sex classroom teachers, as success in such classrooms was found to be possible and demonstrable. Furthermore, the study indicated a need to identify students who would most benefit from inclusion in a single-sex classroom.
Show less - Date Issued
- 2008
- Identifier
- CFE0002019, ucf:47618
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002019
- Title
- Development of an Efficient Molecular Single-Electron Transport Spectroscopy.
- Creator
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Rodriguez Garrigues, Alvar, Gonzalez Garcia, Enrique, Flitsiyan, Elena, Ishigami, Marsahir, University of Central Florida
- Abstract / Description
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In this thesis I present a complete and detailed guide for the development process and fabrication of efficient single-electron transistors (SETs) and a better single-molecule magnets (SMMs) deposition yield. Starting from a commercial Si/SiO2 wafer I show the steps for the deposition of different layers to fabricate a SET as well as the improvements achieved in those for a completely functional SET device. The development process is based on a combination of optical lithography and e-beam...
Show moreIn this thesis I present a complete and detailed guide for the development process and fabrication of efficient single-electron transistors (SETs) and a better single-molecule magnets (SMMs) deposition yield. Starting from a commercial Si/SiO2 wafer I show the steps for the deposition of different layers to fabricate a SET as well as the improvements achieved in those for a completely functional SET device. The development process is based on a combination of optical lithography and e-beam lithography with metal deposition in ultra-high vacuum. The improvements involve a better conductance in the Al gate component, with a controlled formation of the superficial oxide layer and a faster feedback electromigration-induced breaking of Au nanowires for the creation of nanogaps at room temperature. The gate component is improved by increasing its thickness and exposing it to plasma oxidation for the complete oxidation of its surface. The nanowire breaking is realized at room temperature to make use of the surface tension of Au, which, after a previous feedback procedure, eventually opens the final gap in the nanowire. Finally, I demonstrate a new technique that allows increasing the yield of having a SMM connected in the nanowire gap. This new technique is based on monitoring the resistance of the broken nanowires during the SMM deposition from a controlled liquid solution at room temperature. When the resistance ((>)G? for open gaps) drops to values below Mega-ohms (characteristic resistance of a molecule bridging the gap) for a number of nanowires in the chip, the device is then ready for low temperature measurements.
Show less - Date Issued
- 2013
- Identifier
- CFE0004742, ucf:49775
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004742
- Title
- Electronic transport and correlations in single magnetic molecule devices.
- Creator
-
Romero, Javier, Mucciolo, Eduardo, Del Barco, Enrique, Stolbov, Sergey, Hernandez, Florencio, University of Central Florida
- Abstract / Description
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In this dissertation, we study the most important microscopic aspects that grant molecules such as Single Molecule Magnets (SMMs) their preferential spin direction. We do so by proposing and solving a model that includes correlations between electrons occupying atomic orbitals. In addition, we study the relation between the non-equilibrium electronic transport signatures in a SMM model weakly coupled to a three-terminal single electron transistor device, and the interference features of the...
Show moreIn this dissertation, we study the most important microscopic aspects that grant molecules such as Single Molecule Magnets (SMMs) their preferential spin direction. We do so by proposing and solving a model that includes correlations between electrons occupying atomic orbitals. In addition, we study the relation between the non-equilibrium electronic transport signatures in a SMM model weakly coupled to a three-terminal single electron transistor device, and the interference features of the SMM model in the presence of a magnetic field. Finally, we investigate the equilibrium transport features in a giant-spin model of a SMM in the Kondo regime. We study how the magnetic field modulation of the energy in a highly anisotropic molecule can affect the conductance of the molecule in the Kondo regime.
Show less - Date Issued
- 2014
- Identifier
- CFE0005407, ucf:50420
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005407
- Title
- THE VIOLENT OVERTHROW OF PERSONALIST REGIMES COMPARED TO THE PEACEFUL COLLAPSE OF SINGE PARTY REGIMES: CASE STUDIES OF LIBYA UNDER QADDAFI AND THE USSR UNDER GORBACHEV.
- Creator
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Austin, Victoria, Dolan, Thomas, University of Central Florida
- Abstract / Description
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Personalist regimes tend to be violently overthrown while single party states tend to non-violently collapse from within. This paper analyzes Libya under Qaddafi as a personalist regime, and USSR under Gorbachev as a single party state, and seeks to ascertain through case studies and process tracing the reasons for the violent overthrow of personalist regimes compared to the peaceful collapse of single party regimes. Both regime types create the problems that result in their downfall, and...
Show morePersonalist regimes tend to be violently overthrown while single party states tend to non-violently collapse from within. This paper analyzes Libya under Qaddafi as a personalist regime, and USSR under Gorbachev as a single party state, and seeks to ascertain through case studies and process tracing the reasons for the violent overthrow of personalist regimes compared to the peaceful collapse of single party regimes. Both regime types create the problems that result in their downfall, and both kinds of downfall are accelerated by the public appearance of weakness.
Show less - Date Issued
- 2013
- Identifier
- CFH0004536, ucf:45198
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004536
- Title
- Lateral Power MOSFETs Hardened Against Single Event Radiation Effects.
- Creator
-
Shea, Patrick, Shen, Zheng, Yuan, Jiann-Shiun, Malocha, Donald, University of Central Florida
- Abstract / Description
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The underlying physical mechanisms of destructive single event effects (SEE) from heavy ion radiation have been widely studied in traditional vertical double-diffused power MOSFETs (VDMOS). Recently lateral double-diffused power MOSFETs (LDMOS), which inherently provide lower gate charge than VDMOS, have become an attractive option for MHz-frequency DC-DC converters in terrestrial power electronics applications. There are growing interests in extending the LDMOS concept into radiation-hard...
Show moreThe underlying physical mechanisms of destructive single event effects (SEE) from heavy ion radiation have been widely studied in traditional vertical double-diffused power MOSFETs (VDMOS). Recently lateral double-diffused power MOSFETs (LDMOS), which inherently provide lower gate charge than VDMOS, have become an attractive option for MHz-frequency DC-DC converters in terrestrial power electronics applications. There are growing interests in extending the LDMOS concept into radiation-hard space applications. Since the LDMOS has a device structure considerably different from VDMOS, the well studied single event burn-out (SEB) or single event gate rapture (SEGR) response of VDMOS cannot be simply assumed for LDMOS devices without further investigation. A few recent studies have begun to investigate ionizing radiation effects in LDMOS devices, however, these studies were mainly focused on displacement damage and total ionizing dose (TID) effects, with very limited data reported on the heavy ion SEE response of these devices. Furthermore, the breakdown voltage of the LDMOS devices in these studies was limited to less than 80 volts (mostly in the range of 20-30 volts), considerably below the voltage requirement for some space power applications. In this work, we numerically and experimentally investigate the physical insights of SEE in two different fabricated LDMOS devices designed by the author and intended for use in radiation hard applications. The first device is a 24 V Resurf LDMOS fabricated on P-type epitaxial silicon on a P+ silicon substrate. The second device is a much different 150 V SOI Resurf LDMOS fabricated on a 1.0 micron thick N-type silicon-on-insulator substrate with a 1.0 micron thick buried silicon dioxide layer on an N-type silicon handle wafer. Each device contains internal features, layout techniques, and process methods designed to improve single event and total ionizing dose radiation hardness. Technology computer aided design (TCAD) software was used to develop the transistor design and fabrication process of each device and also to simulate the device response to heavy ion radiation. Using these simulations in conjunction with experimentally gathered heavy ion radiation test data, we explain and illustrate the fundamental physical mechanisms by which destructive single event effects occur in these LDMOS devices. We also explore the design tradeoffs for making an LDMOS device resistant to destructive single event effects, both in terms of electrical performance and impact on other radiation hardness metrics.
Show less - Date Issued
- 2011
- Identifier
- CFE0004165, ucf:49044
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004165
- Title
- NURSING ATTITUDES TOWARD THE USE OF REPROCESSED SINGLE-USE MEDICAL DEVICES.
- Creator
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Maben-Tenney, Laura, Loerzel, Victoria, University of Central Florida
- Abstract / Description
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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
- A Solid State VHF Single Sideband Transmitter.
- Creator
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Roos, Ermi, McCarter, Ed R., Engineering
- Abstract / Description
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Florida Technological University College of Engineering Thesis; This research report investigates a unique method of generating single sideband power, which is particularly useful in transistorized transmitters operating at VHF frequencies. Radio frequency power id developed by class C amplifiers, rather than conventional class A or B amplifiers. Currently, VHF power transistors are not well adapted for use as linear amplifiers, and will function far better in the class C mode. A prototype...
Show moreFlorida Technological University College of Engineering Thesis; This research report investigates a unique method of generating single sideband power, which is particularly useful in transistorized transmitters operating at VHF frequencies. Radio frequency power id developed by class C amplifiers, rather than conventional class A or B amplifiers. Currently, VHF power transistors are not well adapted for use as linear amplifiers, and will function far better in the class C mode. A prototype VHF transmitter which develops single sideband power with nonlinear amplifiers was designed and constructed. The transmitter characteristics were measured and analyzed to establish the feasibility of the new design.
Show less - Date Issued
- 1973
- Identifier
- CFR0004779, ucf:52958
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFR0004779
- Title
- DESIGN AND MODELING OF RADIATION HARDENED LATERAL POWER MOSFETS.
- Creator
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Landowski, Matthew, Shen, Zheng, University of Central Florida
- Abstract / Description
-
Galactic-cosmic-rays (GCR) exist in space from unknown origins. A cosmic ray is a very high energy electron, proton, or heavy ion. As a GCR transverses a power semiconductor device, electron-hole-pairs (ehps) are generated along the ion track. Effects from this are referred to as single-event-effects (SEEs). A subset of a SEE is single-event burnout (SEB) which occurs when the parasitic bipolar junction transistor is triggered leading to thermal runaway. The failure mechanism is a complicated...
Show moreGalactic-cosmic-rays (GCR) exist in space from unknown origins. A cosmic ray is a very high energy electron, proton, or heavy ion. As a GCR transverses a power semiconductor device, electron-hole-pairs (ehps) are generated along the ion track. Effects from this are referred to as single-event-effects (SEEs). A subset of a SEE is single-event burnout (SEB) which occurs when the parasitic bipolar junction transistor is triggered leading to thermal runaway. The failure mechanism is a complicated mix of photo-generated current, avalanche generated current, and activation of the inherent parasitic bipolar transistor. Current space-borne power systems lack the utility and advantages of terrestrial power systems. Vertical-double-diffused MOSFETs (VDMOS) is by far the most common power semiconductor device and are very susceptible to SEEs by their vertical structure. Modern space power switches typically require system designers to de-rate the power semiconductor switching device to account for this. Consequently, the power system suffers from increased size, cost, and decreased performance. Their switching speed is limited due to their vertical structure and cannot be used for MHz frequency applications limiting the use of modern digital electronics for space missions. Thus, the Power Semiconductor Research Laboratory at the University of Central Florida in conjunction with Sandia National Laboratories is developing a rad-hard by design lateral-double-diffused MOSFET (LDMOS). The study provides a novel in-depth physical analysis of the mechanisms that cause the LDMOS to burnout during an SEE and provides guidelines for making the LDMOS rad-hard to SEB. Total dose radiation, another important radiation effect, can cause threshold voltage shifts but is beyond the scope of this study. The devices presented have been fabricated with a known total dose radiation hard CMOS process. Single-event burnout data from simulations and experiments are presented in the study to prove the viability of using the LDMOS to replace the VDMOS for space power systems. The LDMOS is capable of higher switching speeds due to a reduced drain-gate feedback capacitance (Miller Capacitor). Since the device is lateral it is compatible with complimentary-metal-oxide-semiconductor (CMOS) processes, lowering developing time and fabrication costs. High switching frequencies permit the use of high density point-of-load conversion and provide a fast dynamic response.
Show less - Date Issued
- 2009
- Identifier
- CFE0002795, ucf:48113
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002795
- Title
- AN EXPLORATORY QUANTITATIVE AND QUALITATIVE ANALYSIS OF STUDENT PERFORMANCE IN SINGLE-GENDER CLASSROOMS IN ONE FLORIDA ELEMENTARY SCHOOL: 2006-2009.
- Creator
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Haynes, Lloyd, Taylor, Rosemarye, University of Central Florida
- Abstract / Description
-
ABSTRACT The purpose of this study was to determine the relationship of participation in single-gender classrooms on student performance on the reading and mathematics developmental scale scores (DSS) of third, fourth, and fifth grade students on the Florida Comprehensive Assessment Test (FCAT). The FCAT is a standardized test that is administered to all grade 3 through grade 10 public school students in the state of Florida and has been used to assess students' achievement in reading and...
Show moreABSTRACT The purpose of this study was to determine the relationship of participation in single-gender classrooms on student performance on the reading and mathematics developmental scale scores (DSS) of third, fourth, and fifth grade students on the Florida Comprehensive Assessment Test (FCAT). The FCAT is a standardized test that is administered to all grade 3 through grade 10 public school students in the state of Florida and has been used to assess students' achievement in reading and mathematics. Students in grades 4, 8, and 10 have also been assessed in science and writing. This study was concerned only with FCAT reading and mathematics scores. The elementary school whose standardized test scores were utilized in this study was comprised of working class families. The standardized test scores were generated by third, fourth, and fifth grade students who were enrolled in (a) single-gender all boys' classes, (b) single-gender all girls' classes, and (c) mixed-gender or traditional classes that contained both boys and girls. The analysis of data presented in this study was inconclusive with respect to the advantage of the single-gender educational setting over the mixed-gender educational setting. The analysis of the data produced the following results. During the school years 2005-2006, 2006-2007, 2007-2008, and 2008-2009, there were 80 opportunities for a given class type to achieve the highest reading DSS mean, reading DSS median, mathematics DSS mean, or mathematics DSS median. The single-gender boys' class achieved the highest DSS 44 times (55%), the mixed-gender classes achieved the highest DSS 29 times (36%), and the single-gender girls' class achieved the highest DSS 7 times (9%).
Show less - Date Issued
- 2011
- Identifier
- CFE0003885, ucf:48745
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003885
- Title
- Exchange coupling in molecular magnets: Zero, one and three dimensions.
- Creator
-
Amjad, Asma, Gonzalez Garcia, Enrique, Klemm, Richard, Peale, Robert, Hill, Stephen, University of Central Florida
- Abstract / Description
-
Molecular magnets with different dimensionality, whether they are zero-dimensional single-molecule magnets (SMM) or one-dimensional single-chain magnets (SCM) are very interesting, since they allow probing the fundamental aspects bordering quantum and classical physics at the nanoscale level. This dissertation covers experimental studies of two Mn-based exchange-coupled molecule-based magnets and two Co-based single-chain magnets, using both dc Hall-effect magnetometry and electron paramagnet...
Show moreMolecular magnets with different dimensionality, whether they are zero-dimensional single-molecule magnets (SMM) or one-dimensional single-chain magnets (SCM) are very interesting, since they allow probing the fundamental aspects bordering quantum and classical physics at the nanoscale level. This dissertation covers experimental studies of two Mn-based exchange-coupled molecule-based magnets and two Co-based single-chain magnets, using both dc Hall-effect magnetometry and electron paramagnet resonance (EPR) techniques. In these multi-dimensional systems, the spin of the molecule exhibits quantum mechanical behavior at low temperature. It is quite interesting to observe the effect of magnetic exchange interactions on the magnetic properties of various complexes; hence they strongly affect the magnetic behavior.In this dissertation, the research is initiated with the study of low-magnetic-nuclearity molecules, starting with a spectroscopic study of a significantly anisotropic Mn(IV) monomer. At low temperature the molecule possesses easy-plane type anisotropy of a remarkable magnitude. Although the molecule is not a single-molecule magnet, the remarkable anisotropy can initiate synthesis of newer and better molecular magnets with Mn(IV) as the main building block. Furthermore, the interplay between the magnetic anisotropy and the inter-ion exchange interactions (J) within the molecule are probed for a dimer and a trimer where the magnetic core is comprised of two and three ions respectively. In the Mn-based case of the dimer, the low coupling between the atoms leads to significant state mixing, thus making it impossible to assign the individual spin states to the dimer or to the respective individual Mn(II) ions. In the case of the trimer, lowering of the symmetry achieved by fine tuning of the inter-ion exchange interactions leads to relieving of frustration in the antiferromagnetic (AF) triangular Mn(III) system, resulting in a well defined ground state and significant zero field splitting. Also a clear hysteretic behavior observed in this system demonstrates its SMM nature at low temperature. Finally, high-field high-frequency magnetic and spectroscopic studies performed on two cobalt-based SCMs reveal that formation of magnetic domains by exchange interactions within the chain are strongly influenced by thermal fluctuations. The chain possesses a uniaxial anisotropy with the quantization axis lying along the length of the chain. Moreover it is shown that modulation of the magnitude of inter- and intra-chain interactions results in a three-dimensional dynamics in one of the samples. Interestingly, detailed dc magnetic studies show a tunable crossover between one- and three-dimensional magnetic dynamics as a function of temperature and/or magnetic field sweep rate. Our voyage through several molecular systems of different dimensionality have allowed us to expand our understanding of the role of exchange interactions on the magnetic behavior in molecular magnetism.
Show less - Date Issued
- 2013
- Identifier
- CFE0004806, ucf:49723
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004806
- Title
- SOLAR-BASED SINGLE-STAGE HIGH-EFFICIENCY GRID-CONNECTED INVERTER.
- Creator
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Tian, Feng, BATARSEH, ISSA, University of Central Florida
- Abstract / Description
-
Renewable energy source plays an important role in the energy cogeneration and distribution. Traditional solar-based inverter system is two stages in cascaded, which has a simpler controller but low efficiency. A new solar-based single-stage grid-connected inverter system can achieve higher efficiency by reducing the power semiconductor switching loss and output stable and synchronized sinusoid current into the utility grid. Controlled by the digital signal processor, the inverter can also...
Show moreRenewable energy source plays an important role in the energy cogeneration and distribution. Traditional solar-based inverter system is two stages in cascaded, which has a simpler controller but low efficiency. A new solar-based single-stage grid-connected inverter system can achieve higher efficiency by reducing the power semiconductor switching loss and output stable and synchronized sinusoid current into the utility grid. Controlled by the digital signal processor, the inverter can also draw maximum power from the solar array, thereby maximizing the utilization of the solar array. In Chapter 1, a comparison between the traditional two-stage inverter and the single-stage inverter is made. To increase the ability of power processing and enhance the efficiency further, a full-bridge topology is chosen, which applies the phase-shift technique to achieve zero-voltage transition. In Chapter 2, average-mode and switch-mode Pspice simulations are applied. All the features of the inverter system are verified, such as stability, zero voltage transition and feed-forward compensation, etc. All these simulation results provide useful design tips for prototyping. In Chapter 3, a phase-shift controller is designed based on UCC3895. Also, a detailed design procedure is given, including key components selection, transformer and inductor design and driver circuits design. In Chapter 4, experimental results of a prototype DC/DC converter are presented and analyzed. By optimization of the circuit, the problems of the prototype are solved and the prototype is working stably. The thesis' conclusion is given in Chapter 5.
Show less - Date Issued
- 2005
- Identifier
- CFE0000468, ucf:46414
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000468
- Title
- THE EFFECTS OF INQUIRY AND SINGLE-GENDER GROUPING ON SECOND GRADE GIRLS' ATTITUDES AND PARTICIPATION IN SCIENCE.
- Creator
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Estrada, Elsy, Jeanpierre, Bobby, University of Central Florida
- Abstract / Description
-
Disparities between males and females in attitudes toward science have been the focus of extensive investigations. Studies have found that females feel intimidated by their male peers in science and mathematics classes, making girls less likely to participate. Their confidence in these areas decreases and they become less likely to follow related career paths. Researchers and educators are at task to find methods to provide equal learning opportunities for all students. The purpose of this...
Show moreDisparities between males and females in attitudes toward science have been the focus of extensive investigations. Studies have found that females feel intimidated by their male peers in science and mathematics classes, making girls less likely to participate. Their confidence in these areas decreases and they become less likely to follow related career paths. Researchers and educators are at task to find methods to provide equal learning opportunities for all students. The purpose of this action research was to investigate the effects of single-gender grouping and inquiry-based teaching on girls' participation and attitude in science class. This study took place in a second grade classroom at a suburban school in the fall of 2005. Surveys and interviews were used to investigate students' attitudes before and after working with inquiry learning single-gender groups. Using observations, female students' participation was recorded according to the kind of participation they exhibited – passive/assisting, active/leading, or active/manipulating. Students maintained journals to record their understanding of science content and rated the lessons. In addition to improving female students' attitudes towards science, inquiry learning fostered an increase in active student participation. Six out of the eight female students perceived that girls participated more in single-gender groups during the study than they did before the study in their regular mixed-gender groups. However, they did not report a change in their own participation in relation to their peers after working in single-gender groups. Further research with control groups was suggested with a larger and more socio-economically diverse population.
Show less - Date Issued
- 2006
- Identifier
- CFE0000991, ucf:46703
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000991
- Title
- CONTROLLED DEPOSITION OF MAGNETIC MOLECULES AND NANOPARTICLES ON ATOMICALLY FLAT GOLD SURFACES.
- Creator
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Haque, Md. Firoze, del Barco, Enrique, University of Central Florida
- Abstract / Description
-
In this thesis I am presenting a detailed study to optimize the deposition of magnetic molecules and gold nanoparticles in atomically flat surfaces by self-assembling them from solution. Epitaxially grown and atomically flat gold surface on mica is used as substrate for this study. These surfaces have roughness of the order one tenth of a nanometer and are perfect to image molecules and nanoparticles in the 1-10 nanometers range. The purpose of these studies is to find the suitable parameters...
Show moreIn this thesis I am presenting a detailed study to optimize the deposition of magnetic molecules and gold nanoparticles in atomically flat surfaces by self-assembling them from solution. Epitaxially grown and atomically flat gold surface on mica is used as substrate for this study. These surfaces have roughness of the order one tenth of a nanometer and are perfect to image molecules and nanoparticles in the 1-10 nanometers range. The purpose of these studies is to find the suitable parameters and conditions necessary to deposit a monolayer of nano-substance on chips containing gold nanowires which will eventually be used to form single electron transistors by electromigration breaking of the nanowire. Maximization of the covered surface area is crucial to optimize the yield of finding a molecule/nanoparticle near the gap formed in the nanowire after electromigration breaking. Coverage of the surface by molecules/nanoparticles mainly depends on the deposition time and concentration of the solution used for the self-assembly. Deposition of the samples under study was done for different solution concentrations and deposition times until a self-assembly monolayer covering most of the surface area is obtained. Imaging of the surfaces after deposition was done by tapping-mode AFM. Analysis of the AFM images was performed and deposition parameters (i.e. coverage or molecule/particle size distribution) were obtained. The subjects of this investigation were a molecular polyoxometalate, a single-molecule magnet and functionalized gold nanoparticles. The obtained results agree with the structure of each of the studied systems. Using the optimized deposition parameters found in this investigation, single-electron transport measurements have been carried out. Preliminary results indicate the right choice of the deposition parameters.
Show less - Date Issued
- 2008
- Identifier
- CFE0002338, ucf:47795
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002338
- Title
- Electronic, Optical, and Magnetic Properties of Graphene and Single-Layer Transition Metal Dichalcogenides in the Presence of Defects.
- Creator
-
Khan, Mahtab, Leuenberger, Michael, Mucciolo, Eduardo, Saha, Haripada, Tetard, Laurene, Schoenfeld, Winston, University of Central Florida
- Abstract / Description
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Two-dimensional (2D) materials, such as graphene and single-layer (SL) transition metal dichalcogenides (TMDCs), have attracted a lot of attention due to their fascinating electronic and optical properties. Graphene was the first 2D material that has successfully been exfoliated from bulk graphite in 2004. In graphene, charge carriers interacting with the honeycomb lattice of carbonatoms of graphene to appear as massless Dirac fermions. Massless quasiparticles with linear dispersion are also...
Show moreTwo-dimensional (2D) materials, such as graphene and single-layer (SL) transition metal dichalcogenides (TMDCs), have attracted a lot of attention due to their fascinating electronic and optical properties. Graphene was the first 2D material that has successfully been exfoliated from bulk graphite in 2004. In graphene, charge carriers interacting with the honeycomb lattice of carbonatoms of graphene to appear as massless Dirac fermions. Massless quasiparticles with linear dispersion are also observed in surface states of 3D topological insulators and quantum Hall edgestates. My first project deals with the two-dimensional Hong-Ou-Mandel (HOM) type interferenceexperiment for massless Dirac fermions in graphene and 3D topological insulators. Since masslessDirac fermions exhibit linear dispersion, similar to photons in vacuum, they can be used to observethe HOM interference intensity pattern as a function of the delay time between two massless Dirac fermions. My further projects and the major part of this dissertation deal with single-layer (SL) transition metal dichalcogenides (TMDCs), such as MoS$_2$, WS$_2$, MoSe$_2$ and WSe$_2$, which have recently emerged as a new family of two-dimensional (2D) materials with great interest, not only from the fundamental point of view, but also because of their potential application to ultrathin electronic and optoelectronic devices. In contrast to graphene, SL TMDCs are direct band semiconductors and exhibit large intrinsic spin-orbit coupling (SOC), originating from the d orbitals of transition metal atoms. Wafer-scale production of SL TMDCs is required for industrial applications. It has been shown that artificially grown samples of SL TMDCs through various experimental techniques, such as physical vapor deposition (PVD), chemical vapor deposition (CVD), and molecular beam epitaxy (MBE), are not perfect, instead certain type of imperfections such as point defects are always found to be present in the grown samples. Defects compromise the crystallinity of the sample, which results in reduced carrier mobility and deteriorated optical efficiency. However, defects are not always unwanted; in fact, defects can play an important role in tailoring electronic, optical, and magnetic properties of materials. Using Density functional theory we investigate the impact of point defects on the electronic, optical, and magnetic properties of SL TMDCs. First, we show that certain vacancy defects lead to localized defect states, which in turn give rise to sharp transitions in in-plane and out-of-plane optical susceptibilities of SL TMDCs. Secondly, we show that a naturally occurring antisite defect Mo$_S$ in PVD grown MoS$_2$ is magnetic in nature with a magneticmoment of 2$\mu_B$, and remarkably exhibit an exceptionally large atomic scale magnetic anisotropy energy (MAE) of ~ 500 eV. Both magnetic moment and MAE can be tuned by shifting the position of the Fermi level which can be achieved either by gate voltage or by chemical doping. Thirdly, we argue that the antisite defect Se$_W$ in WSe$_2$ leads to long lived localized excited states, which can explain the observed single quantum emitters in CVD grown WSe$_2$ samples, with potential application to quantum cryptography.
Show less - Date Issued
- 2018
- Identifier
- CFE0007030, ucf:52047
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007030
- Title
- THREE-PORT MICRO-INVERTER WITH POWER DECOUPLING CAPABILITY FOR PHOTOVOLTAIC (PV) SYSTEMS APPLICATIONS.
- Creator
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Harb, Souhib, Batarseh, Issa, University of Central Florida
- Abstract / Description
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The Photovoltaic (PV) systems have been realized using different architectures, starting with the string and centralized PV system to the modular PV system. Presently, decentralized inverters are being developed at the PV panel power level (known as AC – PV Modules). Such new PV systems are becoming more attractive and many expect this will be the trend of the future. The AC-Module PV system consists of an inverter attached to one PV panel. This integration requires...
Show moreThe Photovoltaic (PV) systems have been realized using different architectures, starting with the string and centralized PV system to the modular PV system. Presently, decentralized inverters are being developed at the PV panel power level (known as AC – PV Modules). Such new PV systems are becoming more attractive and many expect this will be the trend of the future. The AC-Module PV system consists of an inverter attached to one PV panel. This integration requires that both devices have the same life-span. Although, the available commercial inverters have a relatively short life-span (10 years) compared to the 25 –year PV. It has been stated in literature that the energy storage capacitor (electrolytic type) in the single-phase inverter is the most vulnerable electronic component. Hence, many techniques such as (power decoupling techniques) have been proposed to solve this problem by replacing the large electrolytic capacitor with a small film capacitor. This thesis will present a quick review of these power decoupling techniques, and proposes a new three-port micro-inverter with power decoupling capability for AC-Module PV system applications.
Show less - Date Issued
- 2010
- Identifier
- CFE0003357, ucf:48474
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003357
- Title
- SINGLE PARENT, FIRST-GENERATION COLLEGE STUDENTS WHO TRANSFER TO A BACHELOR'S DEGREE INSTITUTION: A PHENOMENOLOGICAL INVESTIGATION.
- Creator
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Snyder, Kevin, Cintron, Rosa, University of Central Florida
- Abstract / Description
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This qualitative, phenomenological research study was conducted to investigate the influences of self-efficacy on the college experiences and beliefs about capabilities of single parent, first-generation, transfer students. Consistent and strong levels of self-efficacy were revealed within each of the eight participants. Major participant themes identified through the Pattern Recognition Flowchart include that (a) children are a primary source of motivation and influence, (b) education is the...
Show moreThis qualitative, phenomenological research study was conducted to investigate the influences of self-efficacy on the college experiences and beliefs about capabilities of single parent, first-generation, transfer students. Consistent and strong levels of self-efficacy were revealed within each of the eight participants. Major participant themes identified through the Pattern Recognition Flowchart include that (a) children are a primary source of motivation and influence, (b) education is the pathway for a better future and career, (c) participants possess strong academic and personal efficacy, (d) participants possess a support network and (e) first-generation status serves as a motivating factor. Minor themes include that participants (a) were influenced by strong role models and positive encouragement and (b) possessed an ability to persevere through significant obstacles. While several of the themes corroborated extant research, some themes supported a unique perspective for this growing student population.
Show less - Date Issued
- 2010
- Identifier
- CFE0003564, ucf:48902
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003564
- Title
- IMAGING AND SPECTROSCOPY OF CONDUCTING POLYMER-FULLERENE COMPOSITE MATERIALS.
- Creator
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Tenery, Daeri, Gesquiere, Andre, University of Central Florida
- Abstract / Description
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Since the development and optical study of conjugated (conducting) polymers it has become apparent that chain conformation and aggregation at the molecular scale result in complex heterogeneous nanostructured bulk materials for which a detailed insight into morphological, spectroscopic as well as optoelectronic properties and mechanisms is overwhelmingly difficult to obtain. Nanoparticles composed of the conjugated polymer poly (MEH-PPV) and nanocomposite nanoparticles consisting of MEH-PPV...
Show moreSince the development and optical study of conjugated (conducting) polymers it has become apparent that chain conformation and aggregation at the molecular scale result in complex heterogeneous nanostructured bulk materials for which a detailed insight into morphological, spectroscopic as well as optoelectronic properties and mechanisms is overwhelmingly difficult to obtain. Nanoparticles composed of the conjugated polymer poly (MEH-PPV) and nanocomposite nanoparticles consisting of MEH-PPV doped with 1-(3-methoxycarbonylpropyl)-1-phenyl-C61 (PCBM) were prepared as model systems to study these materials at the length scale of one to a few domains. The MEH-PPV and PCBM doped nanoparticles were analyzed by single imaging/particle spectroscopy (SPS) and revealed molecular scale information on the structure-property relationships of these composite materials. The data obtained from SPS were investigated in terms of spectral difference between doped and undoped nanoparticles. The doped nanoparticles are blue shifted by approximately 5-10 nm, have an additional blue shoulder, and show different vibronic structure than the undoped nanoparticles. Specifically, relative intensity of the 0-1 transition is lower than for the undoped nanoparticles. These data are indicative of differences in molecular order between both nanoparticle systems, detected at the molecular scale. In addition, the effect of electrical fields present in devices on the interfacial charge transfer properties was evaluated. Furthermore, these nanoparticles were incorporated into the lipid nanotubes to study the diffusion process of the single MEH-PPV nanoparticles inside the lipid nanotubes. Our data shows a clear proof of concept that diffusion of nanoparticles inside the hollow lipid nanotubes can be studied on a single particle basis, which will allow us to study diffusion processes quantitatively and mechanistically within the framework of developing a biocompatible drug and gene delivery platform.
Show less - Date Issued
- 2009
- Identifier
- CFE0002708, ucf:48155
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002708
- Title
- Optimization of Molecular Beacon-Based Multicomponent Probes for Analysis of Nucleic Acids.
- Creator
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Stancescu, Maria, Kolpashchikov, Dmitry, Clausen, Christian, Koculi, Eda, Balaeff, Alexander, Shuler, Michael, University of Central Florida
- Abstract / Description
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Detection of single nucleotide substitutions (SNS) in DNA and RNA has a growing importance in biology and medicine. One traditional approach for recognition of SNS takes advantage of hybridization probes that bind target nucleic acids followed by measuring ?Tm, the difference in melting temperatures of matched and mismatched hybrids. The approach enables SNS differentiation at elevated temperatures (usually 40-65oC) often only in a narrow range of (
Show moreDetection of single nucleotide substitutions (SNS) in DNA and RNA has a growing importance in biology and medicine. One traditional approach for recognition of SNS takes advantage of hybridization probes that bind target nucleic acids followed by measuring ?Tm, the difference in melting temperatures of matched and mismatched hybrids. The approach enables SNS differentiation at elevated temperatures (usually 40-65oC) often only in a narrow range of (<)10oC and requires high-resolution melting devices. Here we demonstrate that a specially designed DNA probe (X sensor) can broaden ?Tm from ~10oC to ~16oC and distinguish SNS in the interval of ~5-40oC. Therefore, there is no need for heating or measuring Tm for accurate SNS differentiation. Our data indicate that this wide differentiation range is in part due to the non-equilibrium hybridization conditions. Further we explored the idea that it is possible to improve the performance of an X sensor operable in close to equilibrium conditions by shifting its operability to non-equilibrium conditions. One way to achieve this is to introduce as many as possible structured ligands in analyte's dissociated state. Here we show that by introducing the maximum possible conformational constraints in X probe it is possible to shift its operation to non-equilibrium conditions and to improve its selectivity at temperatures (<)15oC. Thus, this work points towards a new strategy for the design of highly selective hybridization sensors which operate in non-equilibrium conditions at close to room temperature. The X sensors could be utilized in qPCR, microarrays, as well as RNA analysis in living cells and for ambient temperature point-of-care diagnostics. In the last part of this work, X sensors were used in real time detection of PCR products. The sensors were optimized to operate in PCR buffer with optimal Mg2+ concentration. They were able to detect the target amplicon together with nonspecific products. The results presented here suggest that X sensors might be adopted for real time PCR format.
Show less - Date Issued
- 2015
- Identifier
- CFE0006009, ucf:51006
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006009
- Title
- Optical Parity Time Metasurface Structures.
- Creator
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El Halawany, Ahmed, Christodoulides, Demetrios, Rahman, Talat, Peale, Robert, Likamwa, Patrick, University of Central Florida
- Abstract / Description
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In the last few years, optics has witnessed the emergence of two fields namely metasurfaces and parity-time (PT) symmetry. Optical metasurfaces are engineered structures that provide unique responses to electromagnetic waves, absent in natural materials. Optical metasurfaces are known for their reduced dimensionality i.e. subwavelength and consequently lower losses are anticipated. The other paradigm is the PT symmetric materials, also known as photonic synthetic matter. PT symmetry has...
Show moreIn the last few years, optics has witnessed the emergence of two fields namely metasurfaces and parity-time (PT) symmetry. Optical metasurfaces are engineered structures that provide unique responses to electromagnetic waves, absent in natural materials. Optical metasurfaces are known for their reduced dimensionality i.e. subwavelength and consequently lower losses are anticipated. The other paradigm is the PT symmetric materials, also known as photonic synthetic matter. PT symmetry has emerged from quantum mechanics when a new class of non-Hermitian Hamiltonian quantum systems was highlighted to have real eigenvalues, hence eradicating Hermiticity of the Hamiltonian as an essential condition to the existence of real eigenvalues.The first half of the thesis is focused on the experimental and numerical realization of PT symmetric metasurfaces. A systematic methodology is developed to implement this class of metasurfaces in both one-dimensional and two-dimensional geometries. In two dimensional systems, PT symmetry can be established by employing either H-like diffractive elements or diatomic oblique Bravais lattices. It is shown that the passive PT symmetric metasurfaces can be utilized to appropriately engineer the resulting far-field characteristics. Such PT-symmetric structures are capable of eliminating diffraction orders in specific directions, while maintaining or even enhancing the remaining orders. Later, it is shown a first ever attempt of PT metasurface fabricated on a flexible polymer (polyimide) substrate. The studied PT metasurface exhibits the ability to direct light, i.e. Poynting vector in a desired direction. Herein, the light scattered from the fabricated device in the undesired direction is attenuated by at least an order of magnitude. The proposed PT symmetric metasurface is essentially diatomic Honeycomb Bravais lattice, where both the passive and lossy elements exist side by side on each site separated by 50 nm. The unidirectionality of the studied metasurface is not limited to a single wavelength, on the contrary, it is observed to be effective on the entire visible band (400 (-) 600 nm). The PT symmetric meatsurface is also fabricated on a high strength substrate; sapphire (Al2O3). An excellent agreement between the experimental and numerical (COMSOL) results is found for both substrates. Customized modifications to the current design can open avenues to study the unidirectionality of metasurfaces to different optical bands, for example IR.The second part of the thesis deals with the theoretical modeling of the dynamics of an electron that gets trapped by means of decoherence and quantum interference in the central quantum dot (QD) of a semiconductor nanoring (NR) made of five QDs, between 100 and 300 K. The electron's dynamics is described by a master equation with a Hamiltonian based on the tight-binding model, taking into account electron(-)LO phonon interaction. Based on this configuration, the probability to trap an electron with no decoherence is almost 27%. In contrast, the probability to trap an electron with decoherence is 70% at 100 K, 63% at 200 K and 58% at 300 K. Our model provides a novel method of trapping an electron at room temperature.This setup is then used to propose a theoretical model for an electrically driven single photon source operating at high temperatures. It is shown that the decoherence, which is usually the main obstacle for operating single photon sources at high temperatures, ensures an efficient operation of the presented electrically driven single photon source at high temperatures. The single-photon source is driven by a single electron source attached to a heterostructure semiconductor nanoring. The electron's dynamics in the nanoring and the subsequent recombination with the hole is described by the generalized master equation with a Hamiltonian based on tight-binding model, taking into account the electron-LO phonon interaction. As a result of decoherence, an almost 100% single photon emission with a strong antibunching behavior i.e. g(2)(0) (<)(<) 1 at high temperature up to 300 K is achieved.
Show less - Date Issued
- 2016
- Identifier
- CFE0006454, ucf:51421
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006454
- Title
- Internal Degrees of Freedom and Spin Transitions in Single Molecule Magnets.
- Creator
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Atkinson, James, Del Barco, Enrique, Chen, Bo, Mucciolo, Eduardo, Luis, Fernando, University of Central Florida
- Abstract / Description
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This thesis covers a range of work detailing the transitions between spin eigenstates in molecular magnet systems. Broadly speaking, these transitions can be divided into two kinds: Those that involve a the tunneling of spin through a potential barrier to a resonant state on the other side, a phenomenon known as quantum tunneling of magnetization, and those that occur through the absorption or emission of a photon. In this latter case, the energy of the photon must match the difference...
Show moreThis thesis covers a range of work detailing the transitions between spin eigenstates in molecular magnet systems. Broadly speaking, these transitions can be divided into two kinds: Those that involve a the tunneling of spin through a potential barrier to a resonant state on the other side, a phenomenon known as quantum tunneling of magnetization, and those that occur through the absorption or emission of a photon. In this latter case, the energy of the photon must match the difference between two eigenstates with a difference in angular momentum of ?. We will detail research performed on single molecule magnets, a class of systems that has established itself as an exemplar of higher-order spin interaction. Specifically, we will present the results of studies focused on two Manganese based systems, both of which represent good examples of single molecule magnet behavior. By performing magnetization measurements below the temperature threshold where these systems' polarizations become hysteretic, we find that the precise form of the observed resonant tunneling features (which includes evidence for strong interference of geometric phase a.k.a. Berry phase) can be related to the specifics of the intramolecular interaction. We have analyzed our results using the (")giant spin(") model (which approximates the system as a single spin) as well as with a (")multi-spin(") method which considers all interactions between the ions in the molecular core. We will also discuss the results of measurements performed on a crystalline sample under stress (uniaxial pressure). The data has been analyzed in a framework in which a physical distortion is modelled as a modification of the molecular anisotropy, with different directions of applied stress represented as changes to different parameters governing the molecular energy landscape. This analysis includes simulation of the magnetic relaxation through a master equation approach to the spin-phonon interaction.Finally, our discussion will outline efforts toward understanding the coherent behavior of spin systems. The (")weak(") and (")strong(") coupling between a photon and spin represent two regimes of an interaction by which the information within a spin can be accessed and manipulated. We will discuss the challenges involved in exploring these regimes, both from a theoretical and experimental standpoint. The purpose of this experiment dovetails with those outlined above in attempting to form an intimate basis of knowledge describing the universal relationships to spin at the most fundamental level.
Show less - Date Issued
- 2016
- Identifier
- CFE0006524, ucf:51381
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006524
