Open Access. Powered by Scholars. Published by Universities.®

Electrical and Computer Engineering Commons™

Open Access. Powered by Scholars. Published by Universities.®

2005

Discipline
Institution
Keyword
Publication
Publication Type
File Type

Articles 721 - 734 of 734

Full-Text Articles in Electrical and Computer Engineering

Interference Suppression And Parameter Estimation In Wireless Communication Systems Over Time-Varing Multipath Fading Channels, Jianqiang He Jan 2005

Interference Suppression And Parameter Estimation In Wireless Communication Systems Over Time-Varing Multipath Fading Channels, Jianqiang He

LSU Doctoral Dissertations

This dissertation focuses on providing solutions to two of the most important problems in wireless communication systems design, namely, 1) the interference suppression, and 2) the channel parameter estimation in wireless communication systems over time-varying multipath fading channels. We first study the interference suppression problem in various communication systems under a unified multirate transmultiplexer model. A state-space approach that achieves the optimal realizable equalization (suppression of inter-symbol interference) is proposed, where the Kalman filter is applied to obtain the minimum mean squared error estimate of the transmitted symbols. The properties of the optimal realizable equalizer are analyzed. Its relations with …

Go to article

Adaptive Replication And Access Control Of Multimedia Data In A P2p Environment, Sanjay Kumar Madria, Sanjeev Agarwal Jan 2005

Adaptive Replication And Access Control Of Multimedia Data In A P2p Environment, Sanjay Kumar Madria, Sanjeev Agarwal

Computer Science Faculty Research & Creative Works

This paper explores some of the ideas and solutions related to replication and access control of multimedia data in a hierarchical P2P environment. We provided overview of the techniques to generate multiresolution of multimedia data and explored error recovery and access control issues.

Go to article

The Quest For Novel Computational Paradigms And Machines, Christof Teuscher Jan 2005

The Quest For Novel Computational Paradigms And Machines, Christof Teuscher

Electrical and Computer Engineering Faculty Publications and Presentations

The quest for novel and unconventional computing machines is mainly motivated by the man-machine dichotomy and by the belief that meeting tomorrow's complex real world challenges will require new paradigms and new engineering methods to organize, train, and program such machines and to interact with them.

Go to article

Depth-Shifting Of Shallow Water Guide Source Observations, Lisa M. Zurk, Brian H. Tracey Jan 2005

Depth-Shifting Of Shallow Water Guide Source Observations, Lisa M. Zurk, Brian H. Tracey

Electrical and Computer Engineering Faculty Publications and Presentations

In theory, matched field processing offers the significant benefit of higher signal gains and increased localization capability. However, this has not been robustly observed in practice because of inherent uncertainties about details of the shallow water propagation environments which limit the prediction of the channel response. The use of guide sources to directly measure the transfer function between source and receiver arrays has been proposed as a means for reducing mismatch. However, the guide source measurement only provides a measured transfer function at the guide source location. In this paper a method of depth-shifting guide source observations is proposed, making …

Go to article

Synthesis Of Ternary Quantum Logic Circuits By Decomposition, Marek Perkowski Jan 2005

Synthesis Of Ternary Quantum Logic Circuits By Decomposition, Marek Perkowski

Electrical and Computer Engineering Faculty Publications and Presentations

Recent research in multi-valued logic for quantum computing has shown practical advantages for scaling up a quantum computer. [1,12] Multivalued quantum systems have also been used in the framework of quantum cryptography, [4] and the concept of a qudit cluster state has been proposed by generalizing the qubit cluster state. [5] An evolutionary algorithm based synthesizer for ternary quantum circuits has recently been presented, [2] as well as a synthesis method based on matrix factorization [3].In this paper, a recursive synthesis method for ternary quantum circuits based on the Cosine-Sine unitary matrix decomposition is presented.

Go to article

Effects Of Focusing-Beam Field Variations On The Stability Of Laser Oscillators, Pitak Chenkosol, Lee W. Casperson Jan 2005

Effects Of Focusing-Beam Field Variations On The Stability Of Laser Oscillators, Pitak Chenkosol, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

Semiclassical models for the dynamical behavior of single-longitudinal-mode, homogeneously broadened, unidirectional ring-laser oscillators have long been available. However, in most of these models the beam's cross section is assumed to be independent of longitudinal position in the laser, while in practical laser systems it is common for the diameter to vary with position. A model for lasers with focusing-beam field variations is developed here. Linear stability analysis shows that higher values of excitation are required to reach the type 1 instability threshold for lasers with longitudinal variations of the beam diameter than for the uniform plane-wave laser model.

Go to article

Information-Theoretic Criterion For The Performance Of Single-Photon Avalanche Photodiodes, David A. Ramirez, Majeed M. Hayat, Sergio N. Torres, Bahaa E.A. Saleh, Malvin Carl Teich Jan 2005

Information-Theoretic Criterion For The Performance Of Single-Photon Avalanche Photodiodes, David A. Ramirez, Majeed M. Hayat, Sergio N. Torres, Bahaa E.A. Saleh, Malvin Carl Teich

Electrical and Computer Engineering Faculty Research and Publications

A channel-capacity metric is introduced for assessing the performance of single-photon avalanche photodiodes (SPADs) when used as detectors in laser communication systems. This metric is employed to theoretically optimize, with respect to the device structure and operating voltage, the performance of SPADs with simple InP or In/sub 0.52/Al/sub 0.48/As-InP heterojunction multiplication regions. As the multiplication-region width increases, an increase is predicted in both the peak and the full-width at half-maximum of the channel capacity curve versus the normalized excess voltage. Calculations also show the existence of an optimal In/sub 0.52/Al/sub 0.48/As-InP heterojunction multiplication region that maximizes the peak channel capacity …

Go to article

A Suboptimal Receiver With Turbo Block Coding For Ultra-Wideband Communications, Robert H. Morelos-Zaragoza, Timothy Becker, Sim Aquino Jan 2005

A Suboptimal Receiver With Turbo Block Coding For Ultra-Wideband Communications, Robert H. Morelos-Zaragoza, Timothy Becker, Sim Aquino

Faculty Publications

In this paper, the performance of adaptive equalization and turbo product coding is investigated for pulse-based UWB communications in short-range indoor environments. The sensitivity of adaptive LMS linear and nonlinear (decision-feedback) equalizers with respect to the number of training symbols and number of taps is considered. To reduce the error performance variation with respect to changing channel conditions, a turbo product code (TPC) with two component (31,26,3) Hamming codes is proposed. We report simulation results showing that channel coding not only improves error performance, but also reduces significantly the sensitivity of UWB systems in short-range indoor wireless communications.

Go to article

Self-Assembly Of Ge Quantum Dots On Si(100)- 2×1 By Pulsed Laser Deposition, M. S. Hegazy, H. E. Elsayed-Ali Jan 2005

Self-Assembly Of Ge Quantum Dots On Si(100)- 2×1 By Pulsed Laser Deposition, M. S. Hegazy, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

Self-assembled Ge quantum dots are grown on Si(100)- 2×1 by pulsed laser deposition. The growth is studied by in situ reflection high-energy electron diffraction and postdeposition atomic force microscopy. After the completion of the wetting layer, transient hut clusters, faceted by different planes, are observed. When the height of these clusters exceeded a certain value, the facets developed into {305} planes. Some of these huts become {305}-faceted pyramids as the film mean thickness was increased. With further thickness increase, dome clusters developed on the expense of these pyramids. © 2005 American Institute of Physics. [DOI: 10.1063/1.1949285]

Go to article

Indium Growth On Si(100)-2 X 1 By Femtosecond Pulsed Laser Deposition, M. A. Hafez, M. S. Hegazy, H. E. Elsayed-Ali Jan 2005

Indium Growth On Si(100)-2 X 1 By Femtosecond Pulsed Laser Deposition, M. A. Hafez, M. S. Hegazy, H. E. Elsayed-Ali

Electrical & Computer Engineering Faculty Publications

Indium was grown on Si (100) -2×1 at room temperature by femtosecond pulsed laser deposition. Reflection high-energy electron diffraction (RHEED) was performed in situ to study film morphology and in-plane lattice spacing. Indium was found to grow on Si (100) -2×1 by the Stranski-Krastanov mode. The initial two-dimensional In layer formed in the In-2×1 structure with a lattice constant of 3.65 Å. The full-width at half-maximum (FWHM) of the specular peak decreased during the growth, indicating an increase of the In islands size. Further In growth on the initial In-2×1 layer showed the formation of hexagonal, elongated, and hemispherical islands …

Go to article

Microbubble-Based Model Analysis Of Liquid Breakdown Initiation By A Submicrosecond Pulse, J. Qian, R. P. Joshi, K. H. Schoenbach, J. Dickens, A. Neuber, M. Butcher, M. Cevallos, H. Krompholz, E. Schamiloglu, J. Gaudet Jan 2005

Microbubble-Based Model Analysis Of Liquid Breakdown Initiation By A Submicrosecond Pulse, J. Qian, R. P. Joshi, K. H. Schoenbach, J. Dickens, A. Neuber, M. Butcher, M. Cevallos, H. Krompholz, E. Schamiloglu, J. Gaudet

Electrical & Computer Engineering Faculty Publications

An electrical breakdown model for liquids in response to a submicrosecond(∼100ns) voltage pulse is presented, and quantitative evaluations carried out. It is proposed that breakdown is initiated by field emission at the interface of pre-existing microbubbles. Impact ionization within the microbubble gas then contributes to plasma development, with cathode injection having a delayed and secondary role. Continuous field emission at the streamer tip contributes to filament growth and propagation. This model can adequately explain almost all of the experimentally observed features, including dendritic structures and fluctuations in the prebreakdown current. Two-dimensional, time-dependent simulations have been carried out based on a …

Go to article

Performance Analysis And Validation Of A Recoverable Flight Control System In A Simulated Neutron Environment, Hong Zhang, W. Steven Gray, Oscar R. Gonzalez Jan 2005

Performance Analysis And Validation Of A Recoverable Flight Control System In A Simulated Neutron Environment, Hong Zhang, W. Steven Gray, Oscar R. Gonzalez

Electrical & Computer Engineering Faculty Publications

This paper introduces a class of stochastic hybrid models for the analysis of closed-loop control systems implemented with NASA's Recoverable Computer System. Such Recoverable Computer Systems have been proposed to insure reliable control performance in harsh environments. The stochastic hybrid models consist of either a stochastic finite-state automaton or a finite-state machine driven by a Markov input, which in turn drives a switched linear discrete-time dynamical system. Their stability and output tracking performance are analyzed using an extension of the existing theory for Markov jump-linear systems. For illustration, a stochastic hybrid model is used to calculate the tracking error performance …

Go to article

Optimization Of Ultraviolet Emission And Chemical Species Generation From A Pulsed Dielectric Barrier Discharge At Atmospheric Pressure, Xinpei Lu, Mounir Laroussi Jan 2005

Optimization Of Ultraviolet Emission And Chemical Species Generation From A Pulsed Dielectric Barrier Discharge At Atmospheric Pressure, Xinpei Lu, Mounir Laroussi

Electrical & Computer Engineering Faculty Publications

One of the attractive features of nonthermal atmospheric pressure plasmas is the ability to achieve enhanced gas phase chemistry without the need for elevated gas temperatures. This attractive characteristic recently led to their extensive use in applications that require low temperatures, such as material processing and biomedical applications. The agents responsible for the efficient plasma reactivity are the ultraviolet (UV) photons and the chemically reactive species. In this paper, in order to optimize the UV radiation and reactive species generation efficiency, the plasma was generated by a dielectric barrier discharge driven by unipolar submicrosecond square pulses. To keep the discharge …

Go to article

Room-Temperature Atmospheric Pressure Plasma For Biomedical Applications, Mounir Laroussi, Xinpei Lu Jan 2005

Room-Temperature Atmospheric Pressure Plasma For Biomedical Applications, Mounir Laroussi, Xinpei Lu

Electrical & Computer Engineering Faculty Publications

As low-temperature non-equilibrium plasmas come to play an increasing role in biomedical applications, reliable and user-friendly sources need to be developed. These plasma sources have to meet stringent requirements such as low temperature (at or near room temperature), no risk of arcing, operation at atmospheric pressure, preferably hand-held operation, low concentration of ozone generation, etc. In this letter, we present a device that meets exactly such requirements. This device is capable of generating a cold plasma plume several centimeters in length. It exhibits low power requirements as shown by its current-voltage characteristics. Using helium as a carrier gas, very little …

Go to article

First Prev