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Electrical and Computer Engineering

Electrical and Computer Engineering Faculty Research & Creative Works

Series

2008

Articles 151 - 158 of 158

Full-Text Articles in Engineering

Extending Voltage Range And Reducing Torque Ripple Of Five-Phase Motor Drives With Added Voltage Harmonics, Jing Huang, Keith Corzine, Shuai Lu, Chris M. Hutson Feb 2008

Extending Voltage Range And Reducing Torque Ripple Of Five-Phase Motor Drives With Added Voltage Harmonics, Jing Huang, Keith Corzine, Shuai Lu, Chris M. Hutson

Electrical and Computer Engineering Faculty Research & Creative Works

As multi-phase (defined as greater than three-phase) drives become more popular and practical, new research in this area investigates potential advantages including lower torque ripple and better power density. The added dimensions of a multi-phase machine leads to a completely different operating nature than standard three-phase machines. It can be shown physically and mathematically that certain harmonics do not contribute to torque production and therefore the torque is not directly tied to the current wave-shape. This paper utilizes this property to demonstrate a substantial increase in voltage range and a reduction in torque ripple through the use of added voltage …

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Low Complexity Soft-Input Soft-Output Block Decision Feedback Equalization, Jingxian Wu, Y. Rosa Zheng Feb 2008

Low Complexity Soft-Input Soft-Output Block Decision Feedback Equalization, Jingxian Wu, Y. Rosa Zheng

Electrical and Computer Engineering Faculty Research & Creative Works

A low complexity soft-input soft-output (SISO) block decision feedback equalizer (BDFE) is presented for turbo equalization. The proposed method employs a sub-optimum sequence-based detection, where the soft-output of the equalizer is calculated by evaluating an approximation of the sequence-based a posteriori probability (APP) of the data symbol. The sequence-based APP approximation is enabled by the adoption of both soft a priori information and soft decision feedback, and it leads to better performance and faster convergence compared to symbol-based detection methods as used by most other low complexity equalizers. The performance and convergence property of the proposed algorithm is analyzed by …

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Improved Bdfe Using A Priori Information For Turbo Equalization, Jingxian Wu, Sang-Yick Leong, Kah-Ping Lee, Chengshan Xiao, Jan C. Olivier Jan 2008

Improved Bdfe Using A Priori Information For Turbo Equalization, Jingxian Wu, Sang-Yick Leong, Kah-Ping Lee, Chengshan Xiao, Jan C. Olivier

Electrical and Computer Engineering Faculty Research & Creative Works

Turbo equalization improves communication system performance by iteratively exchanging information between soft-input soft-output (SISO) equalizer and SISO channel decoder. The trellis-based maximum a posteriori probability (MAP) algorithm serves as the optimum SISO equalizer for turbo equalization. However, MAP algorithm is unsuitable for systems with large modulation constellation size and severe inter-symbol interference (ISI) due to its prohibitively high computational complexity. In this paper, an improved SISO block decision feedback equalizer (BDFE) is proposed for low complexity turbo equalization. Unlike other sub-optimum equalizers which perform symbol by symbol detection, the proposed equalizer generates the soft output for each data bit by …

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Dual-Polarized Near-Field Microwave Reflectometer For Noninvasive Inspection Of Carbon Fiber Reinforced Polymer-Strengthened Structures, Sergey Kharkovsky, Adam C. Ryley, Vivian Stephen, R. Zoughi Jan 2008

Dual-Polarized Near-Field Microwave Reflectometer For Noninvasive Inspection Of Carbon Fiber Reinforced Polymer-Strengthened Structures, Sergey Kharkovsky, Adam C. Ryley, Vivian Stephen, R. Zoughi

Electrical and Computer Engineering Faculty Research & Creative Works

Carbon fiber reinforced polymer (CFRP) composites are increasingly being used to strengthen various components of civil, aerospace, and automotive infrastructures. Subsequent to the application of CFRP, evaluation of the structural integrity of the strengthened members becomes a critical issue. Microwave noninvasive inspection techniques have been successfully used for this purpose. To this end, a novel near-field microwave inspection system that employs a dual-polarized reflectometer for detecting defects, such as disbonds between CFRP laminates and strengthened structures, was developed. It is shown that this system is capable of automatic removal of the influence of undesired standoff distance (or surface roughness) variations. …

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Generalized Hamilton-Jacobi-Bellman Formulation-Based Neural Network Control Of Affine Nonlinear Discrete-Time Systems, Zheng Chen, Jagannathan Sarangapani Jan 2008

Generalized Hamilton-Jacobi-Bellman Formulation-Based Neural Network Control Of Affine Nonlinear Discrete-Time Systems, Zheng Chen, Jagannathan Sarangapani

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, we consider the use of nonlinear networks towards obtaining nearly optimal solutions to the control of nonlinear discrete-time (DT) systems. The method is based on least squares successive approximation solution of the generalized Hamilton-Jacobi-Bellman (GHJB) equation which appears in optimization problems. Successive approximation using the GHJB has not been applied for nonlinear DT systems. The proposed recursive method solves the GHJB equation in DT on a well-defined region of attraction. The definition of GHJB, pre-Hamiltonian function, HJB equation, and method of updating the control function for the affine nonlinear DT systems under small perturbation assumption are proposed. …

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Efficient Mrf Approach To Document Image Enhancement, Tayo Obafemi-Ajayi, Gady Agam, Ophir Frieder Jan 2008

Efficient Mrf Approach To Document Image Enhancement, Tayo Obafemi-Ajayi, Gady Agam, Ophir Frieder

Electrical and Computer Engineering Faculty Research & Creative Works

Markov random field (MRF) based approaches have been shown to perform well in a wide range of applications. Due to the iterative nature of the algorithm, the computational cost of such applications is normally high. In the context of document image analysis, where numerous documents have to be processed, this computational cost may become prohibitive. We describe a novel approach to document image enhancement using MRF. We show that by using domain specific knowledge, we are able to substantially improve computational performance by an order of magnitude. Moreover, in contrast to known techniques where patch initialization is arbitrary, in the …

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Real-Time Implementation Of A Statcom On A Wind Farm Equipped With Doubly Fed Induction Generators, Wei Qiao, Ganesh K. Venayagamoorthy, Ronald G. Harley Jan 2008

Real-Time Implementation Of A Statcom On A Wind Farm Equipped With Doubly Fed Induction Generators, Wei Qiao, Ganesh K. Venayagamoorthy, Ronald G. Harley

Electrical and Computer Engineering Faculty Research & Creative Works

Voltage stability is a key issue to achieve the uninterrupted operation of wind farms equipped with doubly fed induction generators (DFIGs) during grid faults. This paper investigates the application of a static synchronous compensator (STATCOM) to assist with the uninterrupted operation of a wind turbine driving a DFIG, which is connected to a power network, during grid faults. The control schemes of the DFIG rotor- and grid-side converters and the STATCOM are suitably designed and coordinated. The system is implemented in real-time on a real time digital simulator. Results show that the STATCOM improves the transient voltage stability and therefore …

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Multiple-Input Multiple-Output Rayleigh Flat Fading Outage Capacity Using Channel Estimation, Chris G. Potter, Kurt Louis Kosbar, Adam Panagos Jan 2008

Multiple-Input Multiple-Output Rayleigh Flat Fading Outage Capacity Using Channel Estimation, Chris G. Potter, Kurt Louis Kosbar, Adam Panagos

Electrical and Computer Engineering Faculty Research & Creative Works

Upper and lower bounds on the outage capacity for a multiple-input multiple-output (MIMO) Rayleigh flat fading wireless baseband communication environment are derived for the case when the channel is completely unknown at the transmitter and the receiver has access to channel state information (CSI) via pilot estimation. The bounds show that the channel estimation error significantly impacts the outage capacity. A change in the outage probability is also shown to have a larger impact on the outage capacity when the channel estimation error is small. To get an idea of how these bounds are affected by a temporally correlated channel, …

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