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Articles 3961 - 3990 of 5696

Full-Text Articles in Engineering

Some Contributions On Mimo Radar, Nikolaus Lehmann Jan 2007

Some Contributions On Mimo Radar, Nikolaus Lehmann

Dissertations

Motivated by recent advances in Multiple Input Multiple Output (MIMO) wireless communications, this dissertation aims at exploring the potential of MIMO approaches in the radar context. In communications, MIMO systems combat the fading effects of the multi-path channel with spatial diversity. Further, the scattering environment can be used by such systems to achieve spatial multiplexing. In radar, a complex target consisting of several scatterers takes the place of the multi-path channel of the communication problem. A target's radar cross section (RCS), which determines the amount of returned power, greatly varies with the considered aspect. Those variations significantly impair the detection …

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Channel-Predictive Link Layer Arq Protocols In Wireless Networks, Huseyin Dogukan Cavdar Jan 2007

Channel-Predictive Link Layer Arq Protocols In Wireless Networks, Huseyin Dogukan Cavdar

Theses

Communication performance over a wireless channel should be considered according to two main parameters: energy and throughput. The reliable data transfer is a key to these goals. The reliable node-to-node data transfer is performed by link layer protocols. One prominent approach is Automatic Repeat Request (ARQ) protocol. The traditional ARQ protocols attempt to recover the erroneously transmitted frames by retransmitting those frames, regardless of the channel state. Since this channel state unaware behaviour may cause unnecessary retransmissions, traditional ARQ protocols are expected to be energy inefficient. Some ideas have been proposed such as stochastic learning automaton based ARQ, and channel …

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Polarizing Properties Of Embedded Symmetric Trilayer Stacks Under Conditions Of Frustrated Total Internal Reflection, Rasheed M.A. Azzam, Siva R. Perla Jan 2007

Polarizing Properties Of Embedded Symmetric Trilayer Stacks Under Conditions Of Frustrated Total Internal Reflection, Rasheed M.A. Azzam, Siva R. Perla

Electrical Engineering Faculty Publications

An error in the application of the design procedure described in a previous paper [Appl. Opt. 45, 1650 (2006)] has been corrected, and new revised figures are included in this erratum.

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Parallel-Slab Polarizing Beam Splitter And Photopolarimeter, R. M.A. Azzam Jan 2007

Parallel-Slab Polarizing Beam Splitter And Photopolarimeter, R. M.A. Azzam

Electrical Engineering Faculty Publications

A dielectric-slab polarizing beam splitter (PBS) is described that generates two parallel beams of orthogonal p and s linear polarizations in reflection and functions as a diattenuator in transmission. The plane-parallel slab, which is set at Brewster's angle, is uncoated on one side and has an s-polarization antireflection coating (s-ARC) on the other side. Analytical results are presented for a PBS that uses a high-index slab coated with a low-index single-layer s-ARC, which is particularly suited for the IR. A novel multistage photopolarimeter that uses two such PBSs in series is described as being capable of sequential and simultaneous measurement …

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Ultra-Wideband Orthogonal Frequency Coded Saw Correlators, Daniel Gallagher Jan 2007

Ultra-Wideband Orthogonal Frequency Coded Saw Correlators, Daniel Gallagher

Electronic Theses and Dissertations

Ultra-wideband (UWB) communication new technology with ability to share the FCC allocated frequency spectrum, large channel capacity and data rate, simple transceiver architecture and high performance in noisy environments. Such communication advantages have paved the way for emerging wireless technologies such as wireless high definition video streaming, wireless sensor networks and more. This thesis examines orthogonal frequency coded surface acoustic wave (SAW) correlators for use in advanced UWB communication systems. Orthogonal frequency coding (OFC) and pseudo-noise (PN) coding provides a means for UWB spreading of data. The use of OFC spectrally spreads a PN sequence beyond that of CDMA because …

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Study Of Soliton Stabilization In D+1 Dimensions Using Novel Analytical And Numerical Techniques, George Nehmetallah, Partha P. Banerjee Jan 2007

Study Of Soliton Stabilization In D+1 Dimensions Using Novel Analytical And Numerical Techniques, George Nehmetallah, Partha P. Banerjee

Electrical and Computer Engineering Faculty Publications

In this Chapter, we provide a brief review of the underlying nonlinear Schrödinger and associated equations that model spatio-temporal propagation in one and higher dimensions in a nonlinear dispersive environment. Particular attention is given to fast adaptive numerical techniques to solve such equations, and in the presence of dispersion and nonlinearity management, saturating nonlinearity and nonparaxiality. A unique variational approach is also outlined which helps in determining the ranges of nonlinearity and dispersion parameters to ensure stable solutions of the nonlinear equations. The propagation of 3+1 dimensional spatio-temporal pulses, or optical bullets is also modeled using a fast adaptive split-step …

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Making Olsr Aware Of Resources, Karol Kowalik, Brian Keegan, Mark Davis Jan 2007

Making Olsr Aware Of Resources, Karol Kowalik, Brian Keegan, Mark Davis

Conference papers

An important element of any routing protocol used for Wireless Mesh Networks (WMNs) is the link cost function used to represent the radio link characteristic. The majority of the routing protocols for WMNs attempt to accurately characterise the radio link quality by constructing the link cost function from the measurements obtained using active probing techniques which introduces overhead. In this paper we present a modified version of the Optimized Link State Routing (OLSR) protocol which uses the link cost function values provided the Resource Aware Routing for mEsh (RARE) module which employs passive monitoring to gather radio link information. This …

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Atmospheric Turbulence Compensation Of Point Source Images Using Asynchronous Stochastic Parallel Gradient Descent Technique On Amos 3.6 M Telescope, Mikhail Vorontsov, Jim F. Riker, Gary W. Carhart, Venkata S. Rao Gudimetla, Leonid A. Beresnev, Thomas Weyrauch Jan 2007

Atmospheric Turbulence Compensation Of Point Source Images Using Asynchronous Stochastic Parallel Gradient Descent Technique On Amos 3.6 M Telescope, Mikhail Vorontsov, Jim F. Riker, Gary W. Carhart, Venkata S. Rao Gudimetla, Leonid A. Beresnev, Thomas Weyrauch

Electrical and Computer Engineering Faculty Publications

The Stochastic Parallel Gradient Descent Technique-based Adaptive Optics (SPGD-AO) system described in this presentation does not use a conventional wavefront sensor. It uses a metric signal collected by a single pixel detector placed behind a pinhole in the image plane to drive three deformable mirrors (DMs). The system is designed to compensate the image for turbulence effects. The theory behind this method is described in detail in [1]. However this technique, while widely simulated and tested in the laboratory, was not yet verified in astronomical field site experiments. During the month of May 2007, a series of experiments with SPGD-AO …

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Adaptive Optics Performance Over Long Horizontal Paths: Aperture Effects In Multi-Conjugate Adaptive Optical Systems, Miao Yu, Mikhail Vorontsov, Svetlana Lachinova, Jim F. Riker, Venkata S. Rao Gudimetla Jan 2007

Adaptive Optics Performance Over Long Horizontal Paths: Aperture Effects In Multi-Conjugate Adaptive Optical Systems, Miao Yu, Mikhail Vorontsov, Svetlana Lachinova, Jim F. Riker, Venkata S. Rao Gudimetla

Electrical and Computer Engineering Faculty Publications

We analyze various scenarios of the aperture effects in adaptive optical receiver-type systems when inhomogeneities of the wave propagation medium are distributed over long horizontal propagation path, or localized in a few thin layers remotely located from the receiver telescope pupil. Phase aberration compensation is performed using closed-loop control architectures based on phase conjugation and decoupled stochastic parallel gradient descent (DSPGD) control algorithms. Both receiver system aperture diffraction effects and the impact of wave-front corrector position on phase aberration compensation efficiency are analyzed for adaptive systems with single or multiple wave-front correctors.

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Simulation And Study Of The Stokes Vector In A Precipitating Atmosphere, Ian Adams Jan 2007

Simulation And Study Of The Stokes Vector In A Precipitating Atmosphere, Ian Adams

Electronic Theses and Dissertations

Precipitation is a dominating quantity in microwave radiometry. The large emission and scattering signals of rain and ice, respectively, introduce large contributions to the measured brightness temperature. While this allows for accurate sensing of precipitation, it also results in degraded performance when retrieving other geophysical parameters, such as near-surface ocean winds. In particular, the retrieval of wind direction requires precise knowledge of polarization, and nonspherical particles can result in a change in the polarization of incident radiation. The aim of this dissertation is to investigate the polarizing effects of precipitation in the atmosphere, including the existence of a precipitation signal …

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Quantum Dot Energy Relaxation Mediated By Plasmon Emission In Doped Covalent Semiconductor Heterostructures, A. V. Fedorov, Anna Baranov, I. D. Rukhlenko, T. S. Perova, Kevin Berwick Jan 2007

Quantum Dot Energy Relaxation Mediated By Plasmon Emission In Doped Covalent Semiconductor Heterostructures, A. V. Fedorov, Anna Baranov, I. D. Rukhlenko, T. S. Perova, Kevin Berwick

Articles

The interaction between interface plasmons within a doped substrate and quantum dot electrons or holes has been theoretically studied in double heterostructures based on covalent semiconductors. The interface plasmon modes, the corresponding dispersion relationship, and the intraband carrier relaxation rate in quantum dots are reported. We find the critical points in the interface plasmon density of states for multilayered structures results in enhanced quantum dot intraband carrier relaxation when compared to that for a single heterostructure. A detailed discussion is made of the relaxation rate and the spectral position dependencies on the quantum dot layer thickness as well as on …

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A Map Estimator For Simultaneous Superresolution And Detector Nonunifomity Correct, Russell C. Hardie, Douglas R. Droege Jan 2007

A Map Estimator For Simultaneous Superresolution And Detector Nonunifomity Correct, Russell C. Hardie, Douglas R. Droege

Electrical and Computer Engineering Faculty Publications

During digital video acquisition, imagery may be degraded by a number of phenomena including undersampling, blur, and noise. Many systems, particularly those containing infrared focal plane array (FPA) sensors, are also subject to detector nonuniformity. Nonuniformity, or fixed pattern noise, results from nonuniform responsivity of the photodetectors that make up the FPA. Here we propose a maximuma posteriori (MAP) estimation framework for simultaneously addressing undersampling, linear blur, additive noise, and bias nonuniformity. In particular, we jointly estimate a superresolution (SR) image and detector bias nonuniformity parameters from a sequence of observed frames. This algorithm can be applied to video in …

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Modeling,Design,And Characterization Of Monolithic Bi-Directional Power Semiconductor Switch, Yue Fu Jan 2007

Modeling,Design,And Characterization Of Monolithic Bi-Directional Power Semiconductor Switch, Yue Fu

Electronic Theses and Dissertations

Bidirectional power switching devices are needed in many power management applications, particularly in lithium-ion battery protection circuitry. A monolithic bidirectional power switch fabricated with a simplified CMOS technology is introduced in this dissertation. Throughout the design process, ISE TCAD tool plays an important role. Design variables are carefully analyzed to improve the device performance or yield the best trade off. Optimization is done with the help of TCAD simulation and theoretical calculations. The device has been successfully fabricated using simplified 0.5 micron CMOS process. The experimental result shows a breakdown voltage of 25V. Due to the interdigitated source to source …

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Investigation Of Reactively Sputtered Silicon Carbon Boron Nitride (Sicbn) Thin Films For High Temperature Applications, Arun Vijayakumar Jan 2007

Investigation Of Reactively Sputtered Silicon Carbon Boron Nitride (Sicbn) Thin Films For High Temperature Applications, Arun Vijayakumar

Electronic Theses and Dissertations

The increasing demand for efficient energy systems in the last decade has brought about the development of advanced sensor systems that utilize advance detection methods to help in preventive maintenance of these essential systems. These usually are needed in hard to access environments where conditions are extreme and unfit for human interaction. Thin film based sensors deposited directly on the surfaces exposed to harsh environments can serve as ideal means of measuring the temperature of the component during operation. They provide the basic advantage of proximity to the surface and hence accurate measurement of the surface temperature. The low mass …

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Integrated Topologies And Digital Control For Satellite Power Management And Distribution Systems, Hussam Al-Atrash Jan 2007

Integrated Topologies And Digital Control For Satellite Power Management And Distribution Systems, Hussam Al-Atrash

Electronic Theses and Dissertations

This work is focused on exploring advanced solutions for space power management and distribution (PMAD) systems. As spacecraft power requirements continue to increase, paralleled by the pressures for reducing cost and overall system weight, power electronics engineers will continue to face major redesigns of the space power systems in order to meet such challenges. Front-end PMAD systems, used to interface the solar sources and battery backup to the distribution bus, need to be designed with increased efficiency, reliability, and power density. A new family of integrated single-stage power converter structures is introduced here. This family allows the interface and control …

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Four Terminal Junction Field-Effect Transistor Model For Computer-Aided Design, Hao Ding Jan 2007

Four Terminal Junction Field-Effect Transistor Model For Computer-Aided Design, Hao Ding

Electronic Theses and Dissertations

A compact model for four-terminal (independent top and bottom gates) junction field-effect transistor (JFET) is presented in this dissertation. The model describes the steady-state characteristics with a unified equation for all bias conditions that provides a high degree of accuracy and continuity of conductance, which are important for predictive analog circuit simulations. It also includes capacitance and leakage equations. A special capacitance drop-off phenomenon at the pinch-off region is studies and modeled. The operations of the junction fieldeffect transistor (JFET) with an oxide top-gate and full oxide isolation are analyzed, and a semi-physical compact model is developed. The effects of …

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Signal Processing Of An Ecg Signal In The Presence Of A Strong Static Magnetic Field, Aditya Gupta Jan 2007

Signal Processing Of An Ecg Signal In The Presence Of A Strong Static Magnetic Field, Aditya Gupta

Electronic Theses and Dissertations

This dissertation addresses the problem of elevation of the T wave of an electrocardiogram (ECG) signal in the magnetic resonance imaging (MRI). In the MRI, due to the strong static magnetic field the interaction of the blood flow with this strong magnetic field induces a voltage in the body. This voltage appears as a superimposition at the locus of the T wave of the ECG signal. This looses important information required by the doctors to interpret the ST segment of the ECG and detect diseases such as myocardial infarction. This dissertation aims at finding a solution to the problem of …

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Gate Stack And Channel Engineering: Study Of Metal Gates And Ge Channel Devices, Ravi Todi Jan 2007

Gate Stack And Channel Engineering: Study Of Metal Gates And Ge Channel Devices, Ravi Todi

Electronic Theses and Dissertations

The continued scaling of device dimensions in complementary metal oxide semiconductor (CMOS) technology within the sub-100 nm region requires an alternative high dielectric constant (high-k) oxide layer to counter high tunneling leakage currents, a metallic gate electrode to address polysilicon depletion, boron penetration and high polysilicon sheet resistance, and high mobility channel materials to boost the CMOS performance. Metal gates can also offer improved thermal and chemical stability, but their use requires that we improve our understanding of how the metal alloy phase, crystallographic orientation, and composition affect the electronic properties of the metal alloy-oxide interface. To replace n++ and …

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A Comparison And Evaluation Of Common Pid Tuning Methods, Justin Youney Jan 2007

A Comparison And Evaluation Of Common Pid Tuning Methods, Justin Youney

Electronic Theses and Dissertations

The motivation behind this thesis is to consolidate and evaluate the most common Proportional Integral Derivative (PID) controller tuning techniques used in industry. These are the tuning techniques used when the plant transfer function is not known. Many of these systems are poorly tuned because such consolidated information is not easily found in one single source such as this thesis. Once one of the tuning methods are applied almost always there will be further fine tuning needed to bring the system into the required design criteria. The purpose here is to find out which tuning technique will yield the lowest …

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Negative Bias Temperature Instability And Charge Trapping Effects On Analog And Digital Circuit Reliability, Yixin Yu Jan 2007

Negative Bias Temperature Instability And Charge Trapping Effects On Analog And Digital Circuit Reliability, Yixin Yu

Electronic Theses and Dissertations

Nanoscale p-channel transistors under negative gate bias at an elevated temperature show threshold voltage degradation after a short period of stress time. In addition, nanoscale (45 nm) n-channel transistors using high-k (HfO2) dielectrics to reduce gate leakage power for advanced microprocessors exhibit fast transient charge trapping effect leading to threshold voltage instability and mobility reduction. A simulation methodology to quantify the circuit level degradation subjected to negative bias temperature instability (NBTI) and fast transient charge trapping effect has been developed in this thesis work. Different current mirror and two-stage operation amplifier structures are studied to evaluate the impact of NBTI …

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Novel Facial Image Recognition Techniques Employing Principal Component Analysis, Moataz Mahmoud Abdelwahab Jan 2007

Novel Facial Image Recognition Techniques Employing Principal Component Analysis, Moataz Mahmoud Abdelwahab

Electronic Theses and Dissertations

Recently, pattern recognition/classification has received considerable attention in diverse engineering fields such as biomedical imaging, speaker identification, fingerprint recognition, and face recognition, etc. This study contributes novel techniques for facial image recognition based on the Two dimensional principal component analysis in the transform domain. These algorithms reduce the storage requirements by an order of magnitude and the computational complexity by a factor of 2 while maintaining the excellent recognition accuracy of the recently reported methods. The proposed recognition systems employ different structures, multicriteria and multitransform. In addition, principal component analysis in the transform domain in conjunction with vector quantization is …

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Soft Switching Multi-Resonant Forward Converter Dc To Dc Application For Communications Equipment, David Marlin Bills Jan 2007

Soft Switching Multi-Resonant Forward Converter Dc To Dc Application For Communications Equipment, David Marlin Bills

Electronic Theses and Dissertations

In the field of power electronics there is always a push to create smaller and more efficient power conversion systems. This push is driven by the industry that uses the power systems, and can be realized by new semiconductor devices or new techniques. This examination describes a novel technique for a small and highly efficient method of converting relatively high DC voltage to a very low voltage for use in the telecommunications industry. A modification to the standard Forward Resonant converter results in improvements in component stress, system efficiency, response time, and control circuitry. This examination describes background information needed …

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Comparison Of Single Stage And Two Stage Stage Grid-Tie Inverters, Keith Mansfield Jan 2007

Comparison Of Single Stage And Two Stage Stage Grid-Tie Inverters, Keith Mansfield

Electronic Theses and Dissertations

This thesis compares two methods of designing grid-tie inverters. The first design topology is a traditional two stage approach consisting of an isolated DC-DC converter on the input followed by a high switching frequency SPWM (Sinusoidal Pulse Width Modulation) stage to produce the required low frequency sine wave output. The novel second design approach employs a similar DC-DC input stage capable of being modulated to provide a rectified sine wave output voltage/current waveform. This stage is followed by a simple low frequency switched Unfolding Stage to recreate the required sine wave output. Both of the above designs have advantages and …

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Modeling And Simulations Of Electrical Breakdown And Thermal Failure In Zinc Oxide And Titanium Dioxide For High-Voltage Dielectric Applications, Guogang Zhao Jan 2007

Modeling And Simulations Of Electrical Breakdown And Thermal Failure In Zinc Oxide And Titanium Dioxide For High-Voltage Dielectric Applications, Guogang Zhao

Electrical & Computer Engineering Theses & Dissertations

The development of transmission lines with higher energy storage capabilities is an important goal for compact pulsed power systems. In this context, ceramic dielectrics are promising candidates from the standpoint of high dielectric constants and breakdown strength. Though such materials look promising, their breakdown response characteristics have not been well studied, nor adequately understood. The electrical response of dielectrics also seems to depend on the internal structure and its granularity. For example, the breakdown strength of nano-crystalline insulators such as titania and zinc oxide have been observed to depend on the internal grain size. In general, the hold-off voltage increases …

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Macrobending Fiber Loss Filter, Ratiometric Wavelength Measurement And Application, Qian Wang, Ginu Rajan, Gerald Farrell, Pengfei Wang, Yuliya Semenova, Thomas Freir Jan 2007

Macrobending Fiber Loss Filter, Ratiometric Wavelength Measurement And Application, Qian Wang, Ginu Rajan, Gerald Farrell, Pengfei Wang, Yuliya Semenova, Thomas Freir

Articles

A macrobending standard single-mode fibre (SMF28) is optimized as an edge filter, with the optimal bending radius and length determined according to the bend loss and polarization sensitivity of the bending fibre. An all-fibre ratiometric wavelength system is built and calibrated. The system's accuracy and resolution is discussed with the influence of noise of input signal and photodetectors. Finally, the ratiometric system is employed for the demodulation of FBG strain sensing.

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Synchronisms For Double Bass, Jeremy C. Baguyos Jan 2007

Synchronisms For Double Bass, Jeremy C. Baguyos

Music Faculty Publications

The Iowa State University of Science and Technology in Ames, Iowa, recently hosted the 2007 National Conference of the Society of Electro-acoustic Music In The United States (SEAMUS) from March 8th through the 10th. The annual SEAMUS conference brings together nationally recognized composers, performers, and researchers in the field of computer music for a half-week program of concerts and paper sessions. The 2007 conference featured the premier of Synchronisms No. 11 for Contrabass and Electronic Sounds by Mario Davidovsky (b. 1934). With coordination from SEAMUS, the work was commissioned by a consortium of various academic institutions. The work was composed …

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Design And Modeling Of Radiation Hardened Ldmosfet For Space Craft Power Systems, Patrick Shea Jan 2007

Design And Modeling Of Radiation Hardened Ldmosfet For Space Craft Power Systems, Patrick Shea

Electronic Theses and Dissertations

NASA missions require innovative power electronics system and component solutions with long life capability, high radiation tolerance, low mass and volume, and high reliability in space environments. Presently vertical double-diffused MOSFETs (VDMOS) are the most widely used power switching device for space power systems. It is proposed that a new lateral double-diffused MOSFET (LDMOS) designed at UCF can offer improvements in total dose and single event radiation hardness, switching performance, development and manufacturing costs, and total mass of power electronics systems. Availability of a hardened fast-switching power MOSFET will allow space-borne power electronics to approach the current level of terrestrial …

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Modeling And Digital Control Of High Frequency Dc-Dc Power Converters, Yangyang Wen Jan 2007

Modeling And Digital Control Of High Frequency Dc-Dc Power Converters, Yangyang Wen

Electronic Theses and Dissertations

The power requirements for leading edge digital integrated circuits have become increasingly demanding. Power converter systems must be faster, more flexible, more precisely controllable and easily monitored. Meanwhile, in addition to control process, the new functions such as power sequencing, communication with other systems, voltage dynamic programming,load line specifications, phase current balance, protection, power status monitoring and system diagnosis are going into today's power supply systems. Digital controllers, compared withanalog controllers, are in a favorable position to provide basic feedback control as well as those power management functions with lower cost and great flexibility. The dissertation gives an overview of …

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Maximum Energy Harvesting Control Foroscillating Energy Harvesting Systems, John Elmes Jan 2007

Maximum Energy Harvesting Control Foroscillating Energy Harvesting Systems, John Elmes

Electronic Theses and Dissertations

This thesis presents an optimal method of designing and controlling an oscillating energy harvesting system. Many new and emerging energy harvesting systems, such as the energy harvesting backpack and ocean wave energy harvesting, capture energy normally expelled through mechanical interactions. Often the nature of the system indicates slow system time constants and unsteady AC voltages. This paper reveals a method for achieving maximum energy harvesting from such sources with fast determination of the optimal operating condition. An energy harvesting backpack, which captures energy from the interaction between the user and the spring decoupled load, is presented in this paper. The …

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Comparison Of Sparse Coding And Jpeg Coding Schemes For Blurred Retinal Images., Balaji Chandrasekaran Jan 2007

Comparison Of Sparse Coding And Jpeg Coding Schemes For Blurred Retinal Images., Balaji Chandrasekaran

Electronic Theses and Dissertations

Overcomplete representations are currently one of the highly researched areas especially in the field of signal processing due to their strong potential to generate sparse representation of signals. Sparse representation implies that given signal can be represented with components that are only rarely significantly active. It has been strongly argued that the mammalian visual system is highly related towards sparse and overcomplete representations. The primary visual cortex has overcomplete responses in representing an input signal which leads to the use of sparse neuronal activity for further processing. This work investigates the sparse coding with an overcomplete basis set representation which …

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