Current Search:  Fourier transformations (x)

View All Items

  • CSV Spreadsheet
(1 - 5 of 5)
Digital Image Processing by the Two-Dimensional Discrete Fourier Transform Method
Title
Digital Image Processing by the Two-Dimensional Discrete Fourier Transform Method.
Creator
Joels, Lyman F., null, null, Engineering
Abstract / Description
Florida Technological University College of Engineering Thesis; The present study was conducted to ascertain undergraduate views about the effectiveness of International Teaching Assistants (ITAs) in the American classroom. The study was administered to a stratified cluster sampling by college of the target population, undergraduate students at the University of Central Florida, in Orlando, Florida. The instrument used, Questionnaire of Undergraduates about International Teaching Assistants ...
Show moreFlorida Technological University College of Engineering Thesis; The present study was conducted to ascertain undergraduate views about the effectiveness of International Teaching Assistants (ITAs) in the American classroom. The study was administered to a stratified cluster sampling by college of the target population, undergraduate students at the University of Central Florida, in Orlando, Florida. The instrument used, Questionnaire of Undergraduates about International Teaching Assistants (QUITA) as developed by Wanda Fox (1990), is composed of a total of 40 items regarding personal and academic background, cultural exposure to and views about non-native speakers of English, and ITA-classroom effectiveness and problem-solving strategies. On the basis of data from the Fall 1998 semester, approximately 15% of the total number of ITA-taught course sections per college were surveyed. The subjects responded anonymously using computerized answer sheets. Upon completion of the data collection phase, all surveys were analyzed for response frequencies. In addition, background and demographic information regarding the participants and information regarding undergraduate exposure to IT As and IT A instruction were also summarized. The Likert-type items were combined to reveal an overall ATITA (Attitude toward International Teaching Assistants) score. The results of the ATITA portion of the study indicate that undergraduate student views toward IT As and IT A instruction are between neutral and mildly positive. Furthermore, survey responses indicated that undergraduates resolve conflicts involving IT As through personal means. The closing recommendations suggest maintaining open lines of communication between undergraduates, ITAs, and administrators alike.
Show less
Date Issued
1973
Identifier
CFR0004782, ucf:52960
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFR0004782
STRUCTURAL TRANSITION DURING FIBRILLOGENESIS OF AMYLOID ? PEPTIDE
Title
STRUCTURAL TRANSITION DURING FIBRILLOGENESIS OF AMYLOID ? PEPTIDE.
Creator
Sidrak, George, Tatulian, Suren, University of Central Florida
Abstract / Description
Alzheimer's Disease (AD) is a neurodegenerative disease marked by progressive neuronal cell death, leading to dementia. AD is the most common disease that results in dementia and largely affects the elderly, with five million people in the United States diagnosed with the disease as of 2015 and approximately 35 million people worldwide. Diseases resulting in dementia cost the US healthcare system an estimated $172 billion in 2010 and that cost is expected to increase as the population ages...
Show moreAlzheimer's Disease (AD) is a neurodegenerative disease marked by progressive neuronal cell death, leading to dementia. AD is the most common disease that results in dementia and largely affects the elderly, with five million people in the United States diagnosed with the disease as of 2015 and approximately 35 million people worldwide. Diseases resulting in dementia cost the US healthcare system an estimated $172 billion in 2010 and that cost is expected to increase as the population ages and as diagnostic techniques improve so that more people are treated (Holtzman, 2011). The disease was first reported by psychiatrist Alois Alzheimer at the onset of the 20th century, when one of his patients "suffered memory loss, disorientation, hallucinations and delusions and died at the age of 55," then was found to have severe brain atrophy post-mortem (Cipriani, Dolciotti, Picchi, & Bonuccelli, 2011). There are palliative treatments available that marginally slow disease progression but there is currently no cure for the disease (Awasthi, Singh, Pandey, & Dwivedi, 2016). More research is needed to develop effective therapeutic strategies to combat the disease. Currently, AD cytotoxicity is believed to be caused by increased amyloid ? (A?) peptide plaque deposition in the brain, as described by the amyloid cascade hypothesis (Barage & Sonawane, 2015). The current understanding is that oligomers of A? peptide lead to neuronal death through multiple mechanisms, most notably hyper-phosphorylation of the tau protein. Having a better understanding of the structural changes in the fibrillization process of A? will provide a broader insight into mechanisms of cell death and open new possibilities for pharmacological treatments, which is what this research intends to provide.
Show less
Date Issued
2017
Identifier
CFH2000178, ucf:45994
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFH2000178
Signal processing with Fourier analysis, novel algorithms and applications
Title
Signal processing with Fourier analysis, novel algorithms and applications.
Creator
Syed, Alam, Foroosh, Hassan, Sun, Qiyu, Bagci, Ulas, Rahnavard, Nazanin, Atia, George, Katsevich, Alexander, University of Central Florida
Abstract / Description
Fourier analysis is the study of the way general functions may be represented or approximatedby sums of simpler trigonometric functions, also analogously known as sinusoidal modeling. Theoriginal idea of Fourier had a profound impact on mathematical analysis, physics, and engineeringbecause it diagonalizes time-invariant convolution operators. In the past signal processing was atopic that stayed almost exclusively in electrical engineering, where only the experts could cancelnoise, compress...
Show moreFourier analysis is the study of the way general functions may be represented or approximatedby sums of simpler trigonometric functions, also analogously known as sinusoidal modeling. Theoriginal idea of Fourier had a profound impact on mathematical analysis, physics, and engineeringbecause it diagonalizes time-invariant convolution operators. In the past signal processing was atopic that stayed almost exclusively in electrical engineering, where only the experts could cancelnoise, compress and reconstruct signals. Nowadays it is almost ubiquitous, as everyone now dealswith modern digital signals.Medical imaging, wireless communications and power systems of the future will experience moredata processing conditions and wider range of applications requirements than the systems of today.Such systems will require more powerful, efficient and flexible signal processing algorithms thatare well designed to handle such needs. No matter how advanced our hardware technology becomeswe will still need intelligent and efficient algorithms to address the growing demands in signalprocessing. In this thesis, we investigate novel techniques to solve a suite of four fundamentalproblems in signal processing that have a wide range of applications. The relevant equations, literatureof signal processing applications, analysis and final numerical algorithms/methods to solvethem using Fourier analysis are discussed for different applications in the electrical engineering /computer science. The first four chapters cover the following topics of central importance in thefield of signal processing: Fast Phasor Estimation using Adaptive Signal Processing (Chapter 2) Frequency Estimation from Nonuniform Samples (Chapter 3) 2D Polar and 3D Spherical Polar Nonuniform Discrete Fourier Transform (Chapter 4)iv Robust 3D registration using Spherical Polar Discrete Fourier Transform and Spherical Harmonics(Chapter 5)Even though each of these four methods discussed may seem completely disparate, the underlyingmotivation for more efficient processing by exploiting the Fourier domain signal structureremains the same. The main contribution of this thesis is the innovation in the analysis, synthesis, discretization of certain well-known problems like phasor estimation, frequency estimation, computations of a particular non-uniform Fourier transform and signal registration on the transformed domain. We conduct propositions and evaluations of certain applications relevant algorithms suchas, frequency estimation algorithm using non-uniform sampling, polar and spherical polar Fourier transform. The techniques proposed are also useful in the field of computer vision and medical imaging. From a practical perspective, the proposed algorithms are shown to improve the existing solutions in the respective fields where they are applied/evaluated. The formulation and final proposition is shown to have a variety of benefits. Future work with potentials in medical imaging, directional wavelets, volume rendering, video/3D object classifications, high dimensional registration are also discussed in the final chapter. Finally, in the spirit of reproducible research, we release the implementation of these algorithms to the public using Github.
Show less
Date Issued
2017
Identifier
CFE0006803, ucf:51775
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0006803
Theoretical Study of Laser Beam Quality and Pulse Shaping by Volume Bragg Gratings
Title
Theoretical Study of Laser Beam Quality and Pulse Shaping by Volume Bragg Gratings.
Creator
Kaim, Sergiy, Zeldovich, Boris, Flitsiyan, Elena, Leuenberger, Michael, Likamwa, Patrick, University of Central Florida
Abstract / Description
The theory of stretching and compressing of short light pulses by the chirped volume Bragg gratings (CBG) is reviewed based on spectral decomposition of short pulses and on the wavelength-dependent coupled wave equations. The analytic theory of diffraction efficiency of a CBG with constant chirp and approximate theory of time delay dispersion are presented. Based on those, we performed comparison of the approximate analytic results with the exact numeric coupled-wave modeling. We also study...
Show moreThe theory of stretching and compressing of short light pulses by the chirped volume Bragg gratings (CBG) is reviewed based on spectral decomposition of short pulses and on the wavelength-dependent coupled wave equations. The analytic theory of diffraction efficiency of a CBG with constant chirp and approximate theory of time delay dispersion are presented. Based on those, we performed comparison of the approximate analytic results with the exact numeric coupled-wave modeling. We also study theoretically various definitions of laser beam width in a given cross-section. Quality of the beam is characterized by the dimensionless beam propagation products (?x???_x)?? , which are different for each of the 21 definitions. We study six particular beams and introduce an axially-symmetric self-MFT (mathematical Fourier transform) function, which may be useful for the description of diffraction-quality beams. Furthermore, we discuss various saturation curves and their influence on the amplitudes of recorded gratings. Special attention is given to multiplexed volume Bragg gratings (VBG) aimed at recording of several gratings in the same volume. The best shape of a saturation curve for production of the strongest gratings is found to be the threshold-type curve. Both one-photon and two-photon absorption mechanism of recording are investigated. Finally, by means of the simulation software we investigate forced airflow cooling of a VBG heated by a laser beam. Two combinations of a setup are considered, and a number of temperature distributions and thermal deformations are obtained for different rates of airflows. Simulation results are compared to the experimental data, and show good mutual agreement.
Show less
Date Issued
2015
Identifier
CFE0005638, ucf:50210
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0005638
Experimental confirmation of ballistic nanofriction and quasiparticle interference in Dirac materials.
Title
Experimental confirmation of ballistic nanofriction and quasiparticle interference in Dirac materials.
Creator
Lodge, Michael, Ishigami, Masahiro, Kaden, William, Schelling, Patrick, Del Barco, Enrique, Roy, Tania, University of Central Florida
Abstract / Description
This dissertation is broadly divided into two parts. The first part details the development and usage of an experimental apparatus to measure the dry nanofriction for a well-defined interface at high sliding speeds. I leverage the sensitivity of a quartz crystal microbalance (QCM) to determine the drag coefficient of an ensemble of gold nanocrystals sliding on graphene at speeds up to 11 cm/s. I discuss the theories of velocity-dependent friction, especially at high sliding speeds, and QCM...
Show moreThis dissertation is broadly divided into two parts. The first part details the development and usage of an experimental apparatus to measure the dry nanofriction for a well-defined interface at high sliding speeds. I leverage the sensitivity of a quartz crystal microbalance (QCM) to determine the drag coefficient of an ensemble of gold nanocrystals sliding on graphene at speeds up to 11 cm/s. I discuss the theories of velocity-dependent friction, especially at high sliding speeds, and QCM modeling. I also discuss our synthesis protocols for graphene and molybdenum disulfide, as well as our protocol for fabricating a clean, graphene-laminated QCM device and nanocrystal ensemble. The design and fabrication of our QCM oscillator circuit is presented in detail. The quantitatively-measured the drag coefficient is compared against molecular dynamics simulations at both low and high sliding speeds. We show evidence of a predicted ultra-low friction regime and find that the interaction energy between gold nanocrystals and graphene is lower than previously assumed. In the second part of this dissertation, I detail the band structure measurement of a novel semimetal using scanning tunneling microscopy. In particular, I measured the energy-dependenceof quasiparticle interference patterns at the surface of zirconium silicon sulfide (ZrSiS), a topological nodal line semimetal whose charge carrier quasiparticles possess a pseudospin degree offreedom. The aims of this study were to (1) discover the shape of the band structure above the Fermi level along a high-symmetry direction, (2) discover the energetic location of the line node inthe same high-symmetry direction, and (3) discover the selection rules for k transitions. This study confirms the predicted linearity in E(k) of the band structure above the Fermi level. Additionally,we observe an energy-dependent mechanism for pseudospin scattering. This study also provides the first experimentally-derived estimation of the line node position in E(k).
Show less
Date Issued
2018
Identifier
CFE0007218, ucf:52222
Format
Document (PDF)
PURL
http://purl.flvc.org/ucf/fd/CFE0007218