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- Title
- AUTOMATIC PARTICLE COUNTING USING AN ACOUSTIC TRANSDUCER.
- Creator
-
Haddad, George, Chen, Ruey-Hung, University of Central Florida
- Abstract / Description
-
Aerosol particle detection and determination finds important applications in the commercial, military and aerospace sectors. Monitoring of clean room environments, and spacecraft integration and check out facilities are some of the most important aplications. In the early days test filters were examined with a microscope to determine the number and size of particles that were being removed from air. Today, most of the commercially available clean room airborne particle counters work on a...
Show moreAerosol particle detection and determination finds important applications in the commercial, military and aerospace sectors. Monitoring of clean room environments, and spacecraft integration and check out facilities are some of the most important aplications. In the early days test filters were examined with a microscope to determine the number and size of particles that were being removed from air. Today, most of the commercially available clean room airborne particle counters work on a light scattering principle. They are referred to as Optical Particle Counter or OPC. Essentially, they utilize a very bright laser light source to illuminate the particles. The burst of light energy is converted into a pulse of electrical energy. By measuring the height of the signal and counting the number of pulses the sizes and quantities of particles could thus be determined. The microscope and the OPC techniques have their limitations. The microscope technique is a post contamination assessment technique and the OPC is costly, hard to maintain, lack in counting efficiency and is not mobile. This experimental study demonstrates a novel and inexpensive particle detection technique which is based on the acoustic signature of airborne particles as they are accelerated through an acoustic transducer. The transducer consists of an inlet converging nozzle, a capillary tube and an expansion section. If the air is laden with particles, as the flow accelerates through the inlet, the particles cannot follow the large change in velocity due to their inertia. Vortices are generated as air flows over the particles prior to entering the capillary. These vortices are believed to generate sound, which is amplified by the transducer acting as an organ pipe. This sound emission if measured contains frequencies that are harmonics of the natural frequency of the transducer's air column. Results show how the frequency content of the acoustic signature relates to the fundamental frequency of the transducer's air column. The transducer is able to detect micron sized particles ( 5 to 50 micron) and the sound intensity is a function of the flowrate but not of particle size. This study also shows the ability of the transducer to determine particle concentration as low as few parts per liter (ppl) and compare the data with that obtained from a commercially available aerodynamic particle sizer.
Show less - Date Issued
- 2005
- Identifier
- CFE0000367, ucf:46331
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000367
- Title
- Effect of particles on evaporation of droplet containing particles.
- Creator
-
Wei, Yan, Chen, Ruey-Hung, Deng, Weiwei, Putnam, Shawn, Wu, Thomas, University of Central Florida
- Abstract / Description
-
The evaporation of droplet containing insoluble particles has grown into an active area of research due to the needs for nanofluids for applications in heat transfer, combustion, and manufacturing desired micro/nano particles in the pharmaceutical industry. The evaporation of droplets containing particles involves complicated multiphase heat and mass transport. The evaporation process consists of two stages: the first stage consists of evaporation until a shell of particle forms or when the...
Show moreThe evaporation of droplet containing insoluble particles has grown into an active area of research due to the needs for nanofluids for applications in heat transfer, combustion, and manufacturing desired micro/nano particles in the pharmaceutical industry. The evaporation of droplets containing particles involves complicated multiphase heat and mass transport. The evaporation process consists of two stages: the first stage consists of evaporation until a shell of particle forms or when the solid to liquid ratio is sufficiently large and the second stage, where the droplet size is commonly assumed to be unchanged. The dissertation investigates the evaporation kinetics in the first stage. An experimental setup based on electrodynamic balance (EDB) is built to allow the observation of evaporation of a free standing micro size droplet. Besides experimental design, a novel theoretical model is developed to first describe the morphological evolution process in the absence of internal convection. The model accounts for the effect of particles at the droplet surface on the diffusion of liquid vapor. The gradually increasing particle number at the droplet surface reduces the area for evaporation, leading to reduction in evaporation rate in the first drying stage, contrary to previous assumptions. The evaporation in the first stage is controlled by Pe (defined as the ratio of droplet evaporation rate to the particle diffusion rate) and particle properties such as wettability. For large values of Pe, the particles concentration is high near the droplet surface, leading to the change of evaporation rate. For small values of Pe, the effect of particles on the evaporation rate of droplet in the first drying stage is small because particles are allowed sufficient time to redistribute within the droplet. The model analysis also reveals that particle wettability is an important factor affecting the first drying stage. For hydrophilic particles, the contact angle of the particles at the droplet surface is small, leading to small change of evaporation in the first stage. For the hydrophobic particles that have large contact angles, the change of evaporation rate in the first drying stage is larger. The evaporation model that accounts for the internal convection is also used to describe the evaporation process. In this model, the evaporation behavior during the first stage is controlled by the particle mobility, initial particle concentration, and droplet recession/evaporation rate. For particles with high mobility, the particle distribution within the droplet tends to be smooth. The effect of convection flow on the particles distribution becomes stronger as particle mobility decreases. Once the particles mobility is decreased to a limit at which the surface particle density is only controlled by the internal flow and the evaporation process is independent of the particles mobility. For a given internal flow field and a specific particles mobility, the duration of the first stage and the final dry particle size are both controlled by the initial particle concentration. A smaller/larger initial particle concentration results in a longer/shorter first stage and smaller/larger dry particle.
Show less - Date Issued
- 2015
- Identifier
- CFE0005903, ucf:50856
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005903
- Title
- PARTICLE SEPARATION THROUGH TAYLOR COUETTE FLOW AND DIELECTROPHORETIC TRAPPING.
- Creator
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Bock, Christopher, Chen, Quanfang, University of Central Florida
- Abstract / Description
-
As the world population approaches seven billion, a greater strain is put on the resources necessary to sustain life. One of the most basic and essential resources is water and while two thirds of the earth is covered by water, the majority is either salt water (oceans and seas) or it is too contaminated to drink. The purpose of this project is to develop a portable device capable of testing whether a specific source of water (i.e. lake, river, wellÃÂ...
Show moreAs the world population approaches seven billion, a greater strain is put on the resources necessary to sustain life. One of the most basic and essential resources is water and while two thirds of the earth is covered by water, the majority is either salt water (oceans and seas) or it is too contaminated to drink. The purpose of this project is to develop a portable device capable of testing whether a specific source of water (i.e. lake, river, well…) is potable. There are numerous filtration techniques that can remove contaminants and make even the dirtiest water clean enough for consumption but they are for the most part, very time consuming and immobile processes. The device is not a means of water purification but rather focuses on determining the content of the water and whether it is safe. Particles within the water are separated and trapped using a combination of a Taylor Couette fluid flow system and Dielectrophoretic electrodes. This paper explores Taylor Couette flow in a large gap and low aspect ratio system through theory and experimentation with early stage prototypes. Different inner cylinder radii, 2.12cm, 1.665cm and 1.075cm, were tested at different speeds approaching, at and passing the critical Taylor number, 3825, 4713 and 6923 respectively for each cylinder. Dielectrophoretic (DEP) electrodes were designed, fabricated, coated and tested using latex beads to determine the method of integrating them within the fluid flow system. Taylor Couette theory, in terms of the formation of vortices within the large gap, small aspect ratio system, was not validated during testing. The flow pattern generated was more akin to a chaotic circular Couette flow but still served to move the particles toward the outer wall. Fully integrated tests were run with limited success. Recommendations were made to pursue both circular Couette flow as the basis for particle separation and dimensional changes in the setup to allow for the formation of Taylor vortices by increasing the radius ratio but still allowing for a larger volume of fluid.
Show less - Date Issued
- 2010
- Identifier
- CFE0003129, ucf:48634
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0003129
- Title
- CONTRIBUTIONS TO AUTOMATIC PARTICLE IDENTIFICATION IN ELECTRON MICROGRAPHS: ALGORITHMS, IMPLEMENTATION, AND APPLICATIONS.
- Creator
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Singh, Vivek, Marinescu, Dan, University of Central Florida
- Abstract / Description
-
Three dimensional reconstruction of large macromolecules like viruses at resolutions below 8 \AA~ - 10 \AA~ requires a large set of projection images and the particle identification step becomes a bottleneck. Several automatic and semi-automatic particle detection algorithms have been developed along the years. We present a general technique designed to automatically identify the projection images of particles. The method utilizes Markov random field modelling of the projected images and...
Show moreThree dimensional reconstruction of large macromolecules like viruses at resolutions below 8 \AA~ - 10 \AA~ requires a large set of projection images and the particle identification step becomes a bottleneck. Several automatic and semi-automatic particle detection algorithms have been developed along the years. We present a general technique designed to automatically identify the projection images of particles. The method utilizes Markov random field modelling of the projected images and involves a preprocessing of electron micrographs followed by image segmentation and post processing for boxing of the particle projections. Due to the typically extensive computational requirements for extracting hundreds of thousands of particle projections, parallel processing becomes essential. We present parallel algorithms and load balancing schemes for our algorithms. The lack of a standard benchmark for relative performance analysis of particle identification algorithms has prompted us to develop a benchmark suite. Further, we present a collection of metrics for the relative performance analysis of particle identification algorithms on the micrograph images in the suite, and discuss the design of the benchmark suite.
Show less - Date Issued
- 2005
- Identifier
- CFE0000705, ucf:46610
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000705
- Title
- FLOW VISUALIZATION IN MICROFLUIDIC EXPANSION AND MIXING.
- Creator
-
Yakhshi Tafti, Ehsan, Kumar, Ranganathan, University of Central Florida
- Abstract / Description
-
Micro particle image velocimetry (microPIV) is a non-intrusive tool for visualizing flow in micron-scale conduits. Using this investigative instrument, two experimental studies were performed to understand flow behaviors in microfluidic channels - a sudden expansion step flow and laminar velocity profile variation in diffusion driven mixing. First, flow in a backward facing step feature (1:5 expansion ratio) in a microchannel was taken as the subject of microPIV flow visualization. The onset...
Show moreMicro particle image velocimetry (microPIV) is a non-intrusive tool for visualizing flow in micron-scale conduits. Using this investigative instrument, two experimental studies were performed to understand flow behaviors in microfluidic channels - a sudden expansion step flow and laminar velocity profile variation in diffusion driven mixing. First, flow in a backward facing step feature (1:5 expansion ratio) in a microchannel was taken as the subject of microPIV flow visualization. The onset and development of a recirculation flow was studied as a function of flow rate. This flow pattern was further used to investigate two major parameters affecting microPIV measurements; the depth-of-focus and recording time-intervals between images in a microPIV image pair. The onset of recirculation was initiated at flow rates that correspond to Reynolds numbers, Re>95, which is well beyond the typical working range of microfluidic devices (Re=0.01-10). The recirculation flow has a 3D structure due to the dimensions of the microchannel and the effect of no slip condition on the walls. Ensemble cross-correlation was found not to be sensitive to variations of depth-of-focus and the output flow fields were similar as long as the overall optical focus remained within the upper and lower bounds of the microchannel. However, variations of time intervals between images in a microPIV pair, resulted in quantitatively and qualitatively different flow patterns for a given constant flow rate and depth-of-focus. In the second experiment, the effect of the laminar velocity profile and its variation on mixing phenomena at the reduced scale is studied. It is shown that the diffusive mass flux between two miscible streams, flowing in a laminar regime in a microchannel, is enhanced if the velocity at their diffusion interface is increased. Based on this idea, an in-plane passive micromixing concept is proposed and implemented in a working device (sigma micromixer). This mixer shows considerable mixing performance by periodically varying the flow velocity profile, such that the maximum of the profile coincides with the transversely progressing diffusion fronts repeatedly throughout the mixing channel. microPIV has been used to visualize the behavior of laminar flow inside the micromixer device and to confirm the periodic variation of the velocity profile through the mixing channel.
Show less - Date Issued
- 2009
- Identifier
- CFE0002826, ucf:48079
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002826
- Title
- METAL BLACKS AS SCATTERING CENTERS TO INCREASE THE EFFICIENCY OF THIN FILM SOLAR CELLS.
- Creator
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Panjwani, Deep, Peale, Robert, University of Central Florida
- Abstract / Description
-
Metal nano particles are investigated as scattering centers on front surface of thin-film solar cells to improve efficiency. The principle is that scattering, which is enhanced near the plasmon resonance frequency of the particle and depends on particle size, increases the effective optical path length of incident light, leading to more light absorption in active layer of thin film solar cell. The particular types of particles investigated here are known as "metal-black", well known as an IR...
Show moreMetal nano particles are investigated as scattering centers on front surface of thin-film solar cells to improve efficiency. The principle is that scattering, which is enhanced near the plasmon resonance frequency of the particle and depends on particle size, increases the effective optical path length of incident light, leading to more light absorption in active layer of thin film solar cell. The particular types of particles investigated here are known as "metal-black", well known as an IR absorber for bolometric infrared detectors. Gold-black was deposited on commercial thin-film solar cells using a thermal evaporator in a nitrogen ambient at pressures of ~1 Torr. We suggest that the broad range of length scales for gold black particles, as quantified by scanning electron microscopy, gives rise to efficient scattering over a broad range of wavelengths across the solar spectrum. The solar cell efficiency was determined both as a function of wavelength and for a solar spectrum produced by a Xe lamp and appropriate filters. Up to 20% increase in short-circuit photocurrent, and a 7% increase in efficiency at the maximum power point, were observed.
Show less - Date Issued
- 2011
- Identifier
- CFE0004047, ucf:49153
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004047
- 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
-
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
- AUTOMATIC GRAPHICS AND GAME CONTENT GENERATION THROUGH EVOLUTIONARY COMPUTATION.
- Creator
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Hastings, Erin, Stanley, Kenneth, University of Central Florida
- Abstract / Description
-
Simulation and game content includes the levels, models, textures, items, and other objects encountered and possessed by players during the game. In most modern video games and simulation software, the set of content shipped with the product is static and unchanging, or at best, randomized within a narrow set of parameters. However, ideally, if game content could be constantly and automatically renewed, players would remain engaged longer in the evolving stream of content. This dissertation...
Show moreSimulation and game content includes the levels, models, textures, items, and other objects encountered and possessed by players during the game. In most modern video games and simulation software, the set of content shipped with the product is static and unchanging, or at best, randomized within a narrow set of parameters. However, ideally, if game content could be constantly and automatically renewed, players would remain engaged longer in the evolving stream of content. This dissertation introduces three novel technologies that together realize this ambition. (1) The first, NEAT Particles, is an evolutionary method to enable users to quickly and easily create complex particle effects through a simple interactive evolutionary computation (IEC) interface. That way, particle effects become an evolvable class of content, which is exploited in the remainder of the dissertation. In particular, (2) a new algorithm called content-generating NeuroEvolution of Augmenting Topologies (cgNEAT) is introduced that automatically generates graphical and game content while the game is played, based on the past preferences of the players. Through cgNEAT, the game platform on its own can generate novel content that is designed to satisfy its players. Finally, (3) the Galactic Arms Race (GAR) multiplayer online video game is constructed to demonstrate these techniques working on a real online gaming platform. In GAR, which was made available to the public and playable online, players pilot space ships and fight enemies to acquire unique particle system weapons that are automatically evolved by the cgNEAT algorithm. The resulting study shows that cgNEAT indeed enables players to discover a wide variety of appealing content that is not only novel, but also based on and extended from previous content that they preferred in the past. The implication is that with cgNEAT it is now possible to create applications that generate their own content to satisfy users, potentially significantly reducing the cost of content creation and considerably increasing entertainment value with a constant stream of evolving content.
Show less - Date Issued
- 2009
- Identifier
- CFE0002814, ucf:48143
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002814
- Title
- Improved Interpolation in SPH in Cases of Less Smooth Flow.
- Creator
-
Brun, Oddny, Wiegand, Rudolf, Pensky, Marianna, University of Central Florida
- Abstract / Description
-
ABSTRACTWe introduced a method presented in Information Field Theory (IFT) [Abramovich et al.,2007] to improve interpolation in Smoothed Particle Hydrodynamics (SPH) in cases of less smoothflow. The method makes use of wavelet theory combined with B-splines for interpolation. The ideais to identify any jumps a function may have and then reconstruct the smoother segments betweenthe jumps. The results of our work demonstrated superior capability when compared to a particularchallenging SPH...
Show moreABSTRACTWe introduced a method presented in Information Field Theory (IFT) [Abramovich et al.,2007] to improve interpolation in Smoothed Particle Hydrodynamics (SPH) in cases of less smoothflow. The method makes use of wavelet theory combined with B-splines for interpolation. The ideais to identify any jumps a function may have and then reconstruct the smoother segments betweenthe jumps. The results of our work demonstrated superior capability when compared to a particularchallenging SPH application, to better conserve jumps and more accurately interpolate thesmoother segments of the function. The results of our work also demonstrated increased computationalefficiency with limited loss in accuracy as number of multiplications and execution timewere reduced. Similar benefits were observed for functions with spikes analyzed by the samemethod. Lesser, but similar effects were also demonstrated for real life data sets of less smoothnature.SPH is widely used in modeling and simulation of flow of matters. SPH presents advantagescompared to grid based methods both in terms of computational efficiency and accuracy, inparticular when dealing with less smooth flow. The results we achieved through our research is animprovement to the model in cases of less smooth flow, in particular flow with jumps and spikes.Up until now such improvements have been sought through modifications to the models' physicalequations and/or kernel functions and have only partially been able to address the issue.This research, as it introduced wavelet theory and IFT to a field of science that, to ourknowledge, not currently are utilizing these methods, did lay the groundwork for future researchiiiideas to benefit SPH. Among those ideas are further development of criteria for wavelet selection,use of smoothing splines for SPH interpolation and incorporation of Bayesian field theory.Improving the method's accuracy, stability and efficiency under more challenging conditionssuch as flow with jumps and spikes, will benefit applications in a wide area of science. Justin medicine alone, such improvements will further increase real time diagnostics, treatments andtraining opportunities because jumps and spikes are often the characteristics of significant physiologicaland anatomic conditions such as pulsatile blood flow, peristaltic intestine contractions andorgans' edges appearance in imaging.
Show less - Date Issued
- 2016
- Identifier
- CFE0006446, ucf:51451
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0006446
- Title
- THE EFFECT OF COLLOIDAL STABILITY ON THE HEAT TRANSFER CHARACTERISTICS OF NANOSILICA DISPERSED FLUIDS.
- Creator
-
Venkataraman, Manoj, Kumar, Ranganathan, University of Central Florida
- Abstract / Description
-
Addition of nano particles to cooling fluids has shown marked improvement in the heat transfer capabilities. Nanofluids, liquids that contain dispersed nanoparticles, are an emerging class of fluids that have great potential in many applications. There is a need to understand the fundamental behavior of nano dispersed particles with respect to their agglomeration characteristics and how it relates to the heat transfer capability. Such an understanding is important for the development and...
Show moreAddition of nano particles to cooling fluids has shown marked improvement in the heat transfer capabilities. Nanofluids, liquids that contain dispersed nanoparticles, are an emerging class of fluids that have great potential in many applications. There is a need to understand the fundamental behavior of nano dispersed particles with respect to their agglomeration characteristics and how it relates to the heat transfer capability. Such an understanding is important for the development and commercialization of nanofluids. In this work, the stability of nano particles was studied by measuring the zeta potential of colloidal particles, particle concentration and size. Two different sizes of silica nano particles, 10 nm and 20 nm are used in this investigation at 0.2 vol. % and 0.5 vol. % concentrations. The measurements were made in deionized (DI) water, buffer solutions at various pH, DI water plus HCl acid solution (acidic pH) and DI water plus NaOH solution (basic pH). The stability or instability of silica dispersions in these solutions was related to the zeta potential of colloidal particles and confirmed by particle sizing measurements and independently by TEM observations. Low zeta potentials resulted in agglomeration as expected and the measured particle size was greater. The heat transfer characteristics of stable or unstable silica dispersions using the above solutions were experimentally determined by measuring heat flux as a function of temperature differential between a nichrome wire and the surrounding fluid. These experiments allowed the determination of the critical heat flux (CHF), which was then related to the dispersion characteristics of the nanosilica in various fluids described above. The thickness of the diffuse layer on nano particles was computed and experimentally confirmed in selected conditions for which there was no agglomeration. As the thickness of the diffuse layer decreased due to the increase in salt content or the ionic content, the electrostatic force of repulsion cease to exist and Van der Waal's force of agglomeration prevailed causing the particles to agglomerate affecting the CHF. The 10nm size silica particle dispersions showed better heat transfer characteristics compared to 20nm dispersion. It was also observed that at low zeta potential values, where agglomeration prevailed in the dispersion, the silica nano particles had a tendency to deposit on the nickel chromium wire used in CHF experiments. The thickness of the deposition was measured and the results show that with a very high deposition, CHF is enhanced due to the porosity on the wire. The 10nm size silica particles show higher CHF compared to 20nm silica particles. In addition, for both 10nm and 20nm silica particles, 0.5 vol. % concentration yielded higher heat transfer compared to 0.2 vol. % concentration. It is believed that although CHF is significantly increased with nano silica containing fluids compared to pure fluids, formation of particle clusters in unstable slurries will lead to detrimental long time performance, compared to that with stable silica dispersions.
Show less - Date Issued
- 2005
- Identifier
- CFE0000837, ucf:46676
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0000837
- Title
- FUNDAMENTAL ASPECTS OF REGENERATIVE CERIUM OXIDE NANOPARTICLES AND THEIR APPLICATIONS IN NANOBIOTECHNOLOGY.
- Creator
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Patil, Swanand, Seal, Sudipta, University of Central Florida
- Abstract / Description
-
Cerium oxide has been used extensively for various applications over the past two decades. The use of cerium oxide nanoparticles is beneficial in present applications and can open avenues for future applications. The present study utilizes the microemulsion technique to synthesize uniformly distributed cerium oxide nanoparticles. The same technique was also used to synthesize cerium oxide nanoparticles doped with trivalent elements (La and Nd). The fundamental study of cerium oxide...
Show moreCerium oxide has been used extensively for various applications over the past two decades. The use of cerium oxide nanoparticles is beneficial in present applications and can open avenues for future applications. The present study utilizes the microemulsion technique to synthesize uniformly distributed cerium oxide nanoparticles. The same technique was also used to synthesize cerium oxide nanoparticles doped with trivalent elements (La and Nd). The fundamental study of cerium oxide nanoparticles identified variations in properties as a function of particle size and also due to doping with trivalent elements (La and Nd). It was found that the lattice parameter of cerium oxide nanoparticles increases with decrease in particle size. Also Raman allowed mode shift to lower energies and the peak at 464 cm-1 becomes broader and asymmetric. The size dependent changes in cerium oxide were correlated to increase in oxygen vacancy concentration in the cerium oxide lattice. The doping of cerium oxide nanoparticles with trivalent elements introduces more oxygen vacancies and expands the cerium oxide lattice further (in addition to the lattice expansion due to the size effect). The lattice expansion is greater for La-doped cerium oxide nanoparticles compared to Nd-doping due to the larger ionic radius of La compared to Nd, the lattice expansion is directly proportional to the dopant concentration. The synthesized cerium oxide nanoparticles were used to develop an electrochemical biosensor of hydrogen peroxide (H2O2). The sensor was useful to detect H2O2 concentrations as low as 1µM in water. Also the preliminary testing of the sensor on tomato stem and leaf extracts indicated that the sensor can be used in practical applications such as plant physiological studies etc. The nanomolar concentrations of cerium oxide nanoparticles were also found to be useful in decreasing ROS (reactive oxygen species) mediated cellular damages in various in vitro cell cultures. Cerium oxide nanoparticles reduced the cellular damages to the normal breast epithelial cell line (CRL 8798) induced by X-rays and to the Keratinocyte cell line induced by UV irradiation. Cerium oxide nanoparticles were also found to be neuroprotective to adult rat spinal cord and retinal neurons. We propose that cerium oxide nanoparticles act as free radical scavenger (via redox reactions on its surface) to decrease the ROS induced cellular damages. Additionally, UV-visible spectroscopic studies indicated that cerium oxide nanoparticles possess auto-regenerative property by switching its oxidation state between Ce3+ and Ce4+. The auto-regenerative antioxidant property of these nanoparticles appears to be a key component in all the biological applications discussed in the present study.
Show less - Date Issued
- 2006
- Identifier
- CFE0001271, ucf:46932
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0001271
- Title
- DESIGN AND OPTIMIZATION OF NANOSTRUCTURED OPTICAL FILTERS.
- Creator
-
Brown, Jeremiah, Moharam, Jim, University of Central Florida
- Abstract / Description
-
Optical filters encompass a vast array of devices and structures for a wide variety of applications. Generally speaking, an optical filter is some structure that applies a designed amplitude and phase transform to an incident signal. Different classes of filters have vastly divergent characteristics, and one of the challenges in the optical design process is identifying the ideal filter for a given application and optimizing it to obtain a specific response. In particular, it is highly...
Show moreOptical filters encompass a vast array of devices and structures for a wide variety of applications. Generally speaking, an optical filter is some structure that applies a designed amplitude and phase transform to an incident signal. Different classes of filters have vastly divergent characteristics, and one of the challenges in the optical design process is identifying the ideal filter for a given application and optimizing it to obtain a specific response. In particular, it is highly advantageous to obtain a filter that can be seamlessly integrated into an overall device package without requiring exotic fabrication steps, extremely sensitive alignments, or complicated conversions between optical and electrical signals. This dissertation explores three classes of nano-scale optical filters in an effort to obtain different types of dispersive response functions. First, dispersive waveguides are designed using a sub-wavelength periodic structure to transmit a single TE propagating mode with very high second order dispersion. Next, an innovative approach for decoupling waveguide trajectories from Bragg gratings is outlined and used to obtain a uniform second-order dispersion response while minimizing fabrication limitations. Finally, high Q-factor microcavities are coupled into axisymmetric pillar structures that offer extremely high group delay over very narrow transmission bandwidths. While these three novel filters are quite diverse in their operation and target applications, they offer extremely compact structures given the magnitude of the dispersion or group delay they introduce to an incident signal. They are also designed and structured as to be formed on an optical wafer scale using standard integrated circuit fabrication techniques. A number of frequency-domain numerical simulation methods are developed to fully characterize and model each of the different filters. The complete filter response, which includes the dispersion and delay characteristics and optical coupling, is used to evaluate each filter design concept. However, due to the complex nature of the structure geometries and electromagnetic interactions, an iterative optimization approach is required to improve the structure designs and obtain a suitable response. To this end, a Particle Swarm Optimization algorithm is developed and applied to the simulated filter responses to generate optimal filter designs.
Show less - Date Issued
- 2008
- Identifier
- CFE0002502, ucf:47678
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002502
- Title
- THE EFFECT OF K562-IL21-2 PLASMA MEMBRANE PARTICLES ON THE PROLIFERATION OF NATURAL KILLER CELLS TO FIGHT CANCER.
- Creator
-
Prophete, Michelle, Copik, Alicja, University of Central Florida
- Abstract / Description
-
Immunotherapy has emerged as a current and future paradigm of cancer treatment, which utilizes the body's immune system to eradicate cancer. Natural Killer (NK) cells as part of the innate immune system have immense potential in their anti-tumor cytotoxic activities and host cell surveillance properties. NK cells comprise approximately five to fifteen percent of peripheral blood lymphocytes and can be proliferated in vitro using recently developed methods with co-cultures with feeder cells ...
Show moreImmunotherapy has emerged as a current and future paradigm of cancer treatment, which utilizes the body's immune system to eradicate cancer. Natural Killer (NK) cells as part of the innate immune system have immense potential in their anti-tumor cytotoxic activities and host cell surveillance properties. NK cells comprise approximately five to fifteen percent of peripheral blood lymphocytes and can be proliferated in vitro using recently developed methods with co-cultures with feeder cells (derived from engineered tumor cells) or plasma membrane (PM) particles, produced from the fore mentioned feeder cells, in combination with soluble cytokines. For efficient growth and maintenance of these NK cells, Interleukin-2 (IL-2) is utilized. IL-2 in solution, through receptor mediated signaling, stimulates proliferation of T-cells and NK cells. NK cells have lower responsiveness to IL-2 and consequently require a larger systemic dose to stimulate them as opposed to competing cell populations that have higher expression of receptors for IL-2, such as T-cells, which can have the effect of lower effective stimulation of NK cell growth. Such difference in the stimulatory capability of IL-2 toward NK cells and the short circulation lifetime of soluble IL-2 require higher dosages of soluble IL-2 for effective in vivo NK cell proliferation for therapeutic application against cancer, but is toxic. Therefore establishing another form of IL-2 delivery that improves its specific targeting to NK cells would be beneficial and may be crucial for novel therapeutic improvement. The Copik Laboratory has made an IL-2 fusion protein construct having a membrane anchor for expression of membrane-bound IL-2 on K562-41bbl-21 cells (K562-IL21). K562-IL21 cells are selectively recognized by NK cells and stimulate their proliferation and cytotoxicity. Hence, a K562-IL21 membrane-bound IL-2 form should be targeted to NK cells with IL-2 delivery. K562-IL21-2 cells were then used to prepare PM21-2 particles which have the potential to provide NK cell targeted, long-lived form of IL-2 for use as an injectable drug for in vivo adjuvant stimulation of NK cells. The presence of IL-2 on the in the PM21-2 particle product was verified by Western blot, and ELISA. Particle preparations from the modified K562 cells should possess characteristics that allow them to possibly replace soluble IL-2 and more specifically increase the numbers or anti-tumor activity of NK cell populations. The effect of PM21-2 particles was studied in in vitro culture based experiments, which tested the effectiveness the PM21-2 particles to induce selective NK cells expansion as compared to PM21 particles in the presence or absence of soluble IL-2.
Show less - Date Issued
- 2017
- Identifier
- CFH2000353, ucf:45918
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH2000353
- Title
- EFFECTS OF BINARY SOLVENT SYSTEM ON MORPHOLOGY OF PARTICLES.
- Creator
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Besana, Patrick, Deng, Weiwei, University of Central Florida
- Abstract / Description
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Recent advancements in cancer research has led to the synthesis of a new drug known as docetaxel. Meant to replace paclitaxel, its more natural counterpart whose ingredients are difficult to obtain, the drug is known to effectively treat a wide array of cancers, including breast cancer, ovarian cancer, and prostate cancer. The establishment of a synthetic alternative to paclitaxel has increased its bioavailability, thereby lowering the cost needed to utilize the drug. Still, the limiting...
Show moreRecent advancements in cancer research has led to the synthesis of a new drug known as docetaxel. Meant to replace paclitaxel, its more natural counterpart whose ingredients are difficult to obtain, the drug is known to effectively treat a wide array of cancers, including breast cancer, ovarian cancer, and prostate cancer. The establishment of a synthetic alternative to paclitaxel has increased its bioavailability, thereby lowering the cost needed to utilize the drug. Still, the limiting factor in minimizing costs is the method in which the drug is processed. Current methods in drug processing have their limitations, which include the introduction of impurities and a low effective yield due to poor powder geometry. Thus, the goal of this study looks to explore a new way to process the drug in a more efficient manner. In this study, a new method for processing docetaxel is explored on in great detail. A more direct method of using electrospray deposition is utilized for the creation of monodisperse nanoparticles, with the main intention of increasing the efficiency at which the drug is processed and prepared for drug delivery to the patient by means of injection. A key feature in electrospray deposition is its ability to produce droplets that are sized homogenously. These droplets eventually evaporate at homogenous rates. These two concepts have been exploited to consistently produce nanoparticles of the cancer drug, which is made possible by the fact that the minimal variation in droplet sizes has easily translated to minimal variation in dry particle sizes. Compared to other methods of drug processing, one other benefit that electrospray deposition conveys is that through evaporation, virtually all impurities and unwanted foreign material are eliminated. Moreover, a binary solvent system is investigated in more detail in this study, so as to determine its effects on both the evaporation of the solvent and the diffusion of the drug into nanoparticles. From there, material and geometric properties of the electrospray nozzle were explored upon in great detail, with the main goal of being able to produce a cone jet that consistently dissociates into monodisperse droplets. At the same time, controllable properties of the electrospray atomizer were investigated and continuously modified. Modifications in both the components of the solution and the operating temperature were also considered to enhance both the electrospray deposition process and the geometry of the particles. Scanning electron microscopy (SEM) characterization is continuously utilized to determine suitability of results obtained in experiments. Ultimately, the goal of this study is to determine the ideal conditions (solvent ratios, flow rate, operating temperature, electrospray atomizer nozzle configurations, etc.) in which spherical docetaxel particles sized at 100-200 nm can be produced.
Show less - Date Issued
- 2015
- Identifier
- CFH0004872, ucf:45412
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0004872
- Title
- CHARACTERIZATION OF DISPERSION AND RESIDUAL STRESS IN NANOPARTICLE REINFORCED HYBRID CARBON FIBER COMPOSITES.
- Creator
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Selimov, Alex, Raghavan,Seetha, University of Central Florida
- Abstract / Description
-
Hybrid carbon fiber reinforced composites are a new breed of materials that are currently being explored and characterized for next generation aerospace applications. Through the introduction of secondary reinforcements, such as alumina nanoparticles, hybrid properties including improved mechanical properties and stress sensing capabilities can be achieved. In order to maximize these properties, it is necessary to achieve a homogeneous dispersion of particulate filler. Utilizing the...
Show moreHybrid carbon fiber reinforced composites are a new breed of materials that are currently being explored and characterized for next generation aerospace applications. Through the introduction of secondary reinforcements, such as alumina nanoparticles, hybrid properties including improved mechanical properties and stress sensing capabilities can be achieved. In order to maximize these properties, it is necessary to achieve a homogeneous dispersion of particulate filler. Utilizing the photoluminescent properties of alumina, it is possible to compare local levels of particle concentration through emission intensities as a way to determine the effectiveness of the tested manufacturing parameters in increasing material homogeneity. Parameters of these photoluminescence emissions have been established to be stress dependent, which allows for in situ residual stress measurements. It is shown here that the application of silane coupling agents as particle surface treatments improves particle dispersion when compared to untreated samples. Reactive silane coupling agent (RSCA) treatments were found to provide for greater dispersion improvements when compared to non-reactive silane coupling agents (NRSCA). Higher resolution investigations into these samples found that treatment with a reactive coupling agent altered the stress state of particles concentrated around the fiber from a tensile stress state to a compressive stress state. This is proposed to result from bonding of the reactive groups on the coupling agent to the organic groups on the carbon fibers which adjusts the stress state of the particle. Future mechanical tests will verify the effects of the particle surface functionalization treatments on mechanical properties of the composites.
Show less - Date Issued
- 2016
- Identifier
- CFH0000233, ucf:44669
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFH0000233
- Title
- A METHODOLOGY TO STABILIZE THE SUPPLY CHAIN.
- Creator
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Sarmiento, Alfonso, Rabelo, Luis, University of Central Florida
- Abstract / Description
-
In todayÂÂ's world, supply chains are facing market dynamics dominated by strong global competition, high labor costs, shorter product life cycles, and environmental regulations. Supply chains have evolved to keep pace with the rapid growth in these business dynamics, becoming longer and more complex. As a result, supply chains are systems with a great number of network connections among their multiple components. The interactions of the network components with respect...
Show moreIn todayÂÂ's world, supply chains are facing market dynamics dominated by strong global competition, high labor costs, shorter product life cycles, and environmental regulations. Supply chains have evolved to keep pace with the rapid growth in these business dynamics, becoming longer and more complex. As a result, supply chains are systems with a great number of network connections among their multiple components. The interactions of the network components with respect to each other and the environment cause these systems to behave in a highly nonlinear dynamic manner. Ripple effects that have a huge, negative impact on the behavior of the supply chain (SC) are called instabilities. They can produce oscillations in demand forecasts, inventory levels, and employment rates and, cause unpredictability in revenues and profits. Instabilities amplify risk, raise the cost of capital, and lower profits. To reduce these negative impacts, modern enterprise managers must be able to change policies and plans quickly when those consequences can be detrimental. This research proposes the development of a methodology that, based on the concepts of asymptotic stability and accumulated deviations from equilibrium (ADE) convergence, can be used to stabilize a great variety of supply chains at the aggregate levels of decision making that correspond to strategic and tactical decision levels. The general applicability and simplicity of this method make it an effective tool for practitioners specializing in the stability analysis of systems with complex dynamics, especially those with oscillatory behavior. This methodology captures the dynamics of the supply chain by using system dynamics (SD) modeling. SD was the chosen technique because it can capture the complex relationships, feedback processes, and multiple time delays that are typical of systems in which oscillations are present. If the behavior of the supply chain shows instability patterns, such as ripple effects, the methodology solves an optimization problem to find a stabilization policy to remove instability or minimize its impact. The policy optimization problem relies upon a theorem which states that ADE convergence of a particular state variable of the system, such as inventory, implies asymptotic stability for that variable. The stabilization based on the ADE requires neither linearization of the system nor direct knowledge of the internal structure of the model. Moreover, the ADE concept can be incorporated easily in any SD modeling language. The optimization algorithm combines the advantage of particle swarm optimization (PSO) to determine good regions of the search space with the advantage of local optimization to quickly find the optimal point within those regions. The local search uses a Powell hill-climbing (PHC) algorithm as an improved procedure to the solution obtained from the PSO algorithm, which assures a fast convergence of the ADE. The experiments showed that solutions generated by this hybrid optimization algorithm were robust. A framework built on the premises of this methodology can contribute to the analysis of planning strategies to design robust supply chains. These improved supply chains can then effectively cope with significant changes and disturbances, providing companies with the corresponding cost savings.
Show less - Date Issued
- 2010
- Identifier
- CFE0002986, ucf:47977
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002986
- Title
- NUMERICAL STUDY OF ENCAPSULATED PHASE CHANGE MATERIAL (EPCM) SLURRY FLOW IN MICROCHANNELS.
- Creator
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Kuravi, Sarada, Chow, Louis, University of Central Florida
- Abstract / Description
-
Heat transfer and flow characteristics of phase change material slurry flow in microchannels with constant heat flux at the base were investigated. The phase change process was included in the energy equation using the effective specific heat method. A parametric study was conducted numerically by varying the base fluid type, particle concentration, particle size, channel dimensions, inlet temperature, base heat flux and melting range of PCM. The particle distribution inside the microchannels...
Show moreHeat transfer and flow characteristics of phase change material slurry flow in microchannels with constant heat flux at the base were investigated. The phase change process was included in the energy equation using the effective specific heat method. A parametric study was conducted numerically by varying the base fluid type, particle concentration, particle size, channel dimensions, inlet temperature, base heat flux and melting range of PCM. The particle distribution inside the microchannels was simulated using the diffusive flux model and its effect on the overall thermal performance of microchannels was investigated. Experimental investigation was conducted in microchannels of 101 µm width and 533 µm height with water as base fluid and n-Octadecane as PCM to validate the key conclusions of the numerical model. Since the flow is not fully developed in case of microchannels (specifically manifold microchannels, which are the key focus of the present study), thermal performance is not as obtained in conventional channels where the length of the channel is large (compared to length of microchannels). It was found that the thermal conductivity of the base fluid plays an important role in determining the thermal performance of slurry. The effect of particle distribution can be neglected in the numerical model under some cases. The performance of slurry depends on the heat flux, purity of PCM, inlet temperature of the fluid, and base fluid thermal conductivity. Hence, there is an application dependent optimum condition of these parameters that is required to obtain the maximum thermal performance of PCM slurry flows in microchannels.
Show less - Date Issued
- 2009
- Identifier
- CFE0002835, ucf:48080
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002835
- Title
- Enhancing Cognitive Algorithms for Optimal Performance of Adaptive Networks.
- Creator
-
Lugo-Cordero, Hector, Guha, Ratan, Wu, Annie, Stanley, Kenneth, University of Central Florida
- Abstract / Description
-
This research proposes to enhance some Evolutionary Algorithms in order to obtain optimal and adaptive network configurations. Due to the richness in technologies, low cost, and application usages, we consider Heterogeneous Wireless Mesh Networks. In particular, we evaluate the domains of Network Deployment, Smart Grids/Homes, and Intrusion Detection Systems. Having an adaptive network as one of the goals, we consider a robust noise tolerant methodology that can quickly react to changes in...
Show moreThis research proposes to enhance some Evolutionary Algorithms in order to obtain optimal and adaptive network configurations. Due to the richness in technologies, low cost, and application usages, we consider Heterogeneous Wireless Mesh Networks. In particular, we evaluate the domains of Network Deployment, Smart Grids/Homes, and Intrusion Detection Systems. Having an adaptive network as one of the goals, we consider a robust noise tolerant methodology that can quickly react to changes in the environment. Furthermore, the diversity of the performance objectives considered (e.g., power, coverage, anonymity, etc.) makes the objective function non-continuous and therefore not have a derivative. For these reasons, we enhance Particle Swarm Optimization (PSO) algorithm with elements that aid in exploring for better configurations to obtain optimal and sub-optimal configurations. According to results, the enhanced PSO promotes population diversity, leading to more unique optimal configurations for adapting to dynamic environments. The gradual complexification process demonstrated simpler optimal solutions than those obtained via trial and error without the enhancements.Configurations obtained by the modified PSO are further tuned in real-time upon environment changes. Such tuning occurs with a Fuzzy Logic Controller (FLC) which models human decision making by monitoring certain events in the algorithm. Example of such events include diversity and quality of solution in the environment. The FLC is able to adapt the enhanced PSO to changes in the environment, causing more exploration or exploitation as needed.By adding a Probabilistic Neural Network (PNN) classifier, the enhanced PSO is again used as a filter to aid in intrusion detection classification. This approach reduces miss classifications by consulting neighbors for classification in case of ambiguous samples. The performance of ambiguous votes via PSO filtering shows an improvement in classification, causing the simple classifier perform better the commonly used classifiers.
Show less - Date Issued
- 2018
- Identifier
- CFE0007046, ucf:52003
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007046
- Title
- Development of a Single Sensor Approach for Capturing Three-Dimensional, Time Resolved Flame and Velocity Information.
- Creator
-
Reyes, Jonathan, Ahmed, Kareem, Kassab, Alain, Kapat, Jayanta, University of Central Florida
- Abstract / Description
-
Performing non-intrusive measurements is the key to acquiring accurate information representative of what is being observed. The act of measuring often changes the environment being observed altering the information that is being obtained. Due to this, the community of fluid scientists have gravitated towards using laser-based measurements to observe the phenomena occurring in their experiments. The study of fluids has advanced since this point, utilizing techniques such as planar laser...
Show morePerforming non-intrusive measurements is the key to acquiring accurate information representative of what is being observed. The act of measuring often changes the environment being observed altering the information that is being obtained. Due to this, the community of fluid scientists have gravitated towards using laser-based measurements to observe the phenomena occurring in their experiments. The study of fluids has advanced since this point, utilizing techniques such as planar laser induced florescence (PLIF), particle image velocimetry (PIV), laser doppler velocimetry (LDV), particle doppler anemometry (PDA), etc. to acquire chemical species information and velocity information. These techniques, though, are inherently two-dimensional and cannot fully describe a flow field. In the area of reacting flow fields (combustion) acquiring the local fuel to air ratio information is increasingly important. Without it, scientist must rely on global one-dimensional metering techniques to correlate the fuel to air ratio of their flow field of interest. By knowing the fuel to air ratio locally and spatially across a flame, the location of products and reactants can be deduced, giving insight into any inefficiencies associated with a burner. Knowing the spatial fuel air field also gives insights into the density gradient associated with the flow field. Discussed in this work will be the development of a non-intrusive local fuel-air measurement technique and an expansion of the PIV technique into the third dimension, tomographic PIV, utilizing only one camera to do so for each measurement. The local fuel-air measurement is performed by recording two species (C2* and CH*) simultaneously and calibrating their ratio to the known fuel-air field. Tomographic PIV is performed by utilizing fiber coupling to acquire multiple viewpoints utilizing a single camera.
Show less - Date Issued
- 2019
- Identifier
- CFE0007523, ucf:52602
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0007523
- Title
- TOWARDS CALIBRATION OF OPTICAL FLOW OF CROWD VIDEOS USING OBSERVED TRAJECTORIES.
- Creator
-
Elbadramany, Iman, Kaup, David, University of Central Florida
- Abstract / Description
-
The need exists for finding a quantitative method for validating crowd simulations. One approach is to use optical flow of videos of real crowds to obtain velocities that can be used for comparison to simulations. Optical flow, in turn, needs to be calibrated to be useful. It is essential to show that optical flow velocities obtained from crowd videos can be mapped into the spatially averaged velocities of the observed trajectories of crowd members, and to quantify the extent of the...
Show moreThe need exists for finding a quantitative method for validating crowd simulations. One approach is to use optical flow of videos of real crowds to obtain velocities that can be used for comparison to simulations. Optical flow, in turn, needs to be calibrated to be useful. It is essential to show that optical flow velocities obtained from crowd videos can be mapped into the spatially averaged velocities of the observed trajectories of crowd members, and to quantify the extent of the correlation of the results. This research investigates methods to uncover the best conditions for a good correlation between optical flow and the average motion of individuals in crowd videos, with the aim that this will help in the quantitative validation of simulations. The first approach was to use a simple linear proportionality relation, with a single coefficient, alpha, between velocity vector of the optical flow and observed velocity of crowd members in a video or simulation. Since there are many variables that affect alpha, an attempt was made to find the best possible conditions for determining alpha, by varying experimental and optical flow settings. The measure of a good alpha was chosen to be that alpha does not vary excessively over a number of video frames. Best conditions of low coefficient of variation of alpha using the Lucas-Kanade optical flow algorithm were found to be when a larger aperture of 15x15 pixels was used, combined with a smaller threshold. Adequate results were found at cell size 40x40 pixels; the improvement in detecting details when smaller cells are used did not reduce the variability of alpha, and required much more computing power. Reduction in variability of alpha can be obtained by spreading the tracked location of a crowd member from a pixel into a rectangle. The Particle Image Velocimetry optical flow algorithm had better correspondence with the velocity vectors of manually tracked crowd members than results obtained using the Lukas-Kanade method. Here, also, it was found that 40x40 pixel cells were better than 15x15. A second attempt at quantifying the correlation between optical flow and actual crowd member velocities was studied using simulations. Two processes were researched, which utilized geometrical correction of the perspective distortion of the crowd videos. One process geometrically corrects the video, and then obtains optical flow data. The other obtains optical flow data from video, and then geometrically corrects the data. The results indicate that the first process worked better. Correlation was calculated between sets of data obtained from the average of twenty frames. This was found to be higher than calculating correlations between the velocities of cells in each pair of frames. An experiment was carried out to predict crowd tracks using optical flow and a calculated parameter, beta, seems to give promising results.
Show less - Date Issued
- 2011
- Identifier
- CFE0004024, ucf:49175
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004024
