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- Title
- EFFICIENCY IMPROVEMENT TECHNIQUES FOR HIGH VOLTAGE CAPACITOR CHARGING METHODS.
- Creator
-
Islas, Michael, Batarseh, Issa, University of Central Florida
- Abstract / Description
-
The goal of this thesis is to design and fabricate a DC-to-DC converter for use in high-voltage capacitor charging applications. The primary objectives include increasing the efficiency and reducing the cost of traditional methods used for this application. Traditional methods were not designed specifically for high-voltage capacitor charging and were thus very primitive and exhibited lower efficiency. Prior methods made use of a high voltage power supply and a current limiting resistor or...
Show moreThe goal of this thesis is to design and fabricate a DC-to-DC converter for use in high-voltage capacitor charging applications. The primary objectives include increasing the efficiency and reducing the cost of traditional methods used for this application. Traditional methods were not designed specifically for high-voltage capacitor charging and were thus very primitive and exhibited lower efficiency. Prior methods made use of a high voltage power supply and a current limiting resistor or control scheme. The power supply would often only operate efficiently at a single voltage value and would thus function poorly over a range used in charging a capacitor. The resistor would also dissipate a fair amount of power, also limiting efficiency. This design makes use of a traditional flyback topology utilizing a controller developed specifically for this application, centering the design approach on the LT3750. Hence, taking full advantage of the efficiency improving control scheme it provides. Additionally, through the use of advanced techniques to eliminate noise and power losses, the efficiency may be significantly improved. A detailed theoretical analysis of the charger is also presented. The analysis will then be applied to optimization techniques to select ideal component values to meet specific design specifications. In this research, a specifically designed and developed prototype will be used to experimentally verify the theoretical work and optimization techniques.
Show less - Date Issued
- 2009
- Identifier
- CFE0002899, ucf:48025
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002899
- Title
- Nonlinear dynamic modeling, simulation and characterization of the mesoscale neuron-electrode interface.
- Creator
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Thakore, Vaibhav, Hickman, James, Mucciolo, Eduardo, Rahman, Talat, Johnson, Michael, Behal, Aman, Molnar, Peter, University of Central Florida
- Abstract / Description
-
Extracellular neuroelectronic interfacing has important applications in the fields of neural prosthetics, biological computation and whole-cell biosensing for drug screening and toxin detection. While the field of neuroelectronic interfacing holds great promise, the recording of high-fidelity signals from extracellular devices has long suffered from the problem of low signal-to-noise ratios and changes in signal shapes due to the presence of highly dispersive dielectric medium in the neuron...
Show moreExtracellular neuroelectronic interfacing has important applications in the fields of neural prosthetics, biological computation and whole-cell biosensing for drug screening and toxin detection. While the field of neuroelectronic interfacing holds great promise, the recording of high-fidelity signals from extracellular devices has long suffered from the problem of low signal-to-noise ratios and changes in signal shapes due to the presence of highly dispersive dielectric medium in the neuron-microelectrode cleft. This has made it difficult to correlate the extracellularly recorded signals with the intracellular signals recorded using conventional patch-clamp electrophysiology. For bringing about an improvement in the signal-to-noise ratio of the signals recorded on the extracellular microelectrodes and to explore strategies for engineering the neuron-electrode interface there exists a need to model, simulate and characterize the cell-sensor interface to better understand the mechanism of signal transduction across the interface. Efforts to date for modeling the neuron-electrode interface have primarily focused on the use of point or area contact linear equivalent circuit models for a description of the interface with an assumption of passive linearity for the dynamics of the interfacial medium in the cell-electrode cleft. In this dissertation, results are presented from a nonlinear dynamic characterization of the neuroelectronic junction based on Volterra-Wiener modeling which showed that the process of signal transduction at the interface may have nonlinear contributions from the interfacial medium. An optimization based study of linear equivalent circuit models for representing signals recorded at the neuron-electrode interface subsequently proved conclusively that the process of signal transduction across the interface is indeed nonlinear. Following this a theoretical framework for the extraction of the complex nonlinear material parameters of the interfacial medium like the dielectric permittivity, conductivity and diffusivity tensors based on dynamic nonlinear Volterra-Wiener modeling was developed. Within this framework, the use of Gaussian bandlimited white noise for nonlinear impedance spectroscopy was shown to offer considerable advantages over the use of sinusoidal inputs for nonlinear harmonic analysis currently employed in impedance characterization of nonlinear electrochemical systems. Signal transduction at the neuron-microelectrode interface is mediated by the interfacial medium confined to a thin cleft with thickness on the scale of 20-110 nm giving rise to Knudsen numbers (ratio of mean free path to characteristic system length) in the range of 0.015 and 0.003 for ionic electrodiffusion. At these Knudsen numbers, the continuum assumptions made in the use of Poisson-Nernst-Planck system of equations for modeling ionic electrodiffusion are not valid. Therefore, a lattice Boltzmann method (LBM) based multiphysics solver suitable for modeling ionic electrodiffusion at the mesoscale neuron-microelectrode interface was developed. Additionally, a molecular speed dependent relaxation time was proposed for use in the lattice Boltzmann equation. Such a relaxation time holds promise for enhancing the numerical stability of lattice Boltzmann algorithms as it helped recover a physically correct description of microscopic phenomena related to particle collisions governed by their local density on the lattice. Next, using this multiphysics solver simulations were carried out for the charge relaxation dynamics of an electrolytic nanocapacitor with the intention of ultimately employing it for a simulation of the capacitive coupling between the neuron and the planar microelectrode on a microelectrode array (MEA). Simulations of the charge relaxation dynamics for a step potential applied at t = 0 to the capacitor electrodes were carried out for varying conditions of electric double layer (EDL) overlap, solvent viscosity, electrode spacing and ratio of cation to anion diffusivity. For a large EDL overlap, an anomalous plasma-like collective behavior of oscillating ions at a frequency much lower than the plasma frequency of the electrolyte was observed and as such it appears to be purely an effect of nanoscale confinement. Results from these simulations are then discussed in the context of the dynamics of the interfacial medium in the neuron-microelectrode cleft. In conclusion, a synergistic approach to engineering the neuron-microelectrode interface is outlined through a use of the nonlinear dynamic modeling, simulation and characterization tools developed as part of this dissertation research.
Show less - Date Issued
- 2012
- Identifier
- CFE0004797, ucf:49718
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0004797