Electrical and Computer Engineering Commons^™

Performance Analysis And Resource Allocation In Cdma Wireless Networks For Multimedia Services, Sebnem Zorlu

Dissertations

The proliferation of Internet and demand for wireless services necessitate large increases in capacity and data rates in order to support different multimedia services. Wireless systems will be required to support sources with a variety of traffic characteristics and quality of service requirements. This requires algorithms for admission control and resource allocation at the session, burst and packet levels. The purpose of this research is to develop and analyze optimal resource allocation strategies to maximize throughput of wireless systems with integrated services. Given the multimedia user requirements, the problem addressed can be formulated as a constrained optimization problem. The objective …

Buffer Management And Cell Switching Management In Wireless Packet Communications, Jongho Bang

Dissertations

The buffer management and the cell switching (e.g., packet handoff) management using buffer management scheme are studied in Wireless Packet Communications.

First, a throughput improvement method for multi-class services is proposed in Wireless Packet System. Efficient traffic management schemes should be developed to provide seamless access to the wireless network. Specially, it is proposed to regulate the buffer by the "Selective- Delay Push-In (SDPI)" scheme, which is applicable to scheduling delay-tolerant non-real time traffic and delay-sensitive real time traffic. Simulation results show that the performance observed by real time traffics are improved as compared to existing buffer priority scheme in …

Design Of Traffic Shaper / Scheduler For Packet Switches And Diffserv Networks : Algorithms And Architectures, Surong Zeng

Dissertations

The convergence of communications, information, commerce and computing are creating a significant demand and opportunity for multimedia and multi-class communication services. In such environments, controlling the network behavior and guaranteeing the user's quality of service is required. A flexible hierarchical sorting architecture which can function either as a traffic shaper or a scheduler according to the requirement of the traffic load is presented to meet the requirement. The core structure can be implemented as a hierarchical traffic shaper which can support a large number of connections with a wide variety of rates and burstiness without the loss of the granularity …

Optical Properties Of Photonic Crystals, Anand G. Shenoy

Theses

The ability to confine light in three dimensions has important implications for quantum optics and quantum-optical devices. Photonic crystals, the optical analog of electronic crystals, provide us a means of achieving this goal. This analogy has motivated a whole new series of experimental and theoretical searches for elusive photonic band-gap structures. Combinations of metallic and dielectric materials can be used to obtain the required three-dimensional (3D) periodic variation in the dielectric constant. This could pave the way for photonic crystal structures that have widespread applications.

The working of 3D photonic crystals into the wavelength regimes where most optoelectronic devices operate, …

Propagation And Scattering Of Collimated Beam Wave In Vegetation Using Scalar Transport Theory, Michael Yu-Chi Wu

Theses

The scalar time-dependent equation of radiative transfer is used to develop a theory of pulse beamwave propagation and scattering in a medium character ized by many random discrete scatterers which scatter energy strongly in the forward scattering direction. Applications include the scattering of highly collimated millimeter waves in vegetation and optical beams in the atmosphere. The specific problem analyzed is that of a periodic sequence of Gaussian shaped pulses normally incident from free space onto the planar boundary surface of a random medium half-space, such as a forest, that possesses a power scatter (phase) function consisting of a strong, narrow …

Performance Of Proton Exchange Membranefuel Cell With Co/H2 Fuel, Hong-Mei Yu, Zhong-Jun Hou, Bao-Lian Yi, Ke-Wan Bi, Jing-Xin Zhang, Zhi-Yin Lin, Ming Han

Journal of Electrochemistry

Fuel of proton exchange membrane fuel cell(PEMFC) mostly comes from reformatecontains CO which will poison the fuel cell electrocatalyst. The effect of CO on the performance of PEMFC was studied in this paper. The results of the experiment show that when CO is fed inPEMFC ,the cell voltage will be decreased violently,then it will become steady with some vibration. The poison will become more serious with higher CO content and weaker at higher temperature. The adsorption of CO on the electrocatalyst is reversible. The PtRu electrocatalyst is moresuitable for the electrocatalysis of CO/H₂ than Pt electrocatalyst.

Study Of The Oxidation Dynamics Of Tizro2 Metal-Ceramics, Wen-Chao Li, Li-Dong Teng

Journal of Electrochemistry

The oxidation dynamics of hot-pressed Ti-ZrO₂ metal-ceramics with the compositionof 50 vol.% Ti and 50 vol.% ZrO₂ has been studied.Thermodynamic analysis shows that Ticould react with O₂ but not with N₂ in the oxidizing process of TiZrO₂ composites at 0.1 MPa air. The oxidation dynamic behavior of Ti-ZrO₂ composites is analogous to that of pure Ti. Theactivation energy for the oxygen diffusion in Ti-ZrO₂ composites is higher than that in Ti solutions, for the presence of ZrO₂ restrains the oxygen diffusion in Ti-ZrO₂ composites. At early stagethe oxidation of Ti-ZrO_{2 …}

Preparation And Properties Of Separator For Lithium-Ion Battery, Xu-Mei Ren, Feng Wu, Chuan Wu, Han-Jun Li, Xue-Jie Huang

Journal of Electrochemistry

Lithium-ion batteries are well adapted to the new multimedia applications. PP/PE based microporous film is commonly used as separator in commercial lithium ion batteries. Herewe report a microporous film which is superior to the commercial available separator. The microporous PVDF polymer separators were prepared by the phase inversion process. The pore size of the separator is Φ 7 μm , and it's porosity is 75 %. The membrane in LiPF₆-EC/DEC showedhigh ionic conductivity (above 10^-3 S/cm at room temperature), and good mechanical properties(10³ kg/cm²). The half-cells consisted of Li/PVDF separator/MCMB showed excellent cyclingcharacteristics and …

Performance Of A Direct Methanol Fuel Cell, Zhao-Bin Wei, Jian-Guo Liu, Ya-Guang Jiao, Wei-Jiang Zhou, Wen-Zhen Li, Li-Kang Chen, Qin Xin, Bao-Lian Yi

Journal of Electrochemistry

A direct methanol fuel cell with 9cm² active area consists of Pt-Ru/C anode ,Pt/Ccathode and Nafion 115 membrane. The effect of operating conditions: methanol solution concentration, oxygen pressure and cell temperature on the cell performances was investigated. The results show that performance of single cell was enhanced by increasing oxygen pressure and celltemperature ,and a maximum power density 75 mW/cm² was obtained in the range of 250-300mA/cm² current density, 0.2 MPa oxygen pressure, 1.0 mol/L methanol concentration and 75 ℃ cell temperature. When cell operating at room temperature, a relatively low, but a stable performance of cell …

The Effect Of Preparation Condition On The Photoelectrochemical Performance Of Both The Pani Film And Tio2-Pani Composite Film On Au, Huai-Guo Huang, Hong-Ping Zhang, Zhi-Xin Zheng, Yan-Yan Xi, Ling-Ling Wu, Zhong-Hua Lin

Journal of Electrochemistry

Both the PANI (polyaniline) film and TiO₂-PANI composite film on the PATP(paminothiophenol)/Au substrate were obtained under different preparation condition by electrochemical methods, and their photoelectrochemical performances were alo studied. The resultsshowed that the photoelectrochemical performances of the films depend deeply on the comditionsof preparation. The self-assembling of PATP favors the adhesion of PANl. The partially-oxidizedPANI has a greater photoelectrochemical response than that of the reduced PANI and oxidized PANl. There is an optimum of film thickness for the photoelectrochemical performance of PANI film. Heat treating is in favor of the photoelectrochemical performance of TiO₂, but decreases …

New Progress In Studies Of Lithium Nickel Oxide As Positive Electrode Materials Of Lithium Ion Batteris, Han-San Liu, Yong Yang, Zhong-Ru Zhang, Zu-Geng Lin

Journal of Electrochemistry

Lithium nickel oxide as the positive electrode of lithium ion batteries has aroused more and more interests.This paper reviews the recent reserches on synthesis and element-substitution of LiNiO₂ cathode material,and summarizes the intrinsical relationship between properties and sturcture of the material.The developments of new synthesis methods and mutilsubstitution of the material are expecting to be studied in the future research.

Electrochemistry Characteristic Of Carbon Steel Under Biofilm And Sulfide Film, Ze-Hua Dong, Xing-Peng Guo, Jia-Shen Zheng, Li-Ming Xu

Journal of Electrochemistry

Wire Beam Electrode (WBE) made of Q235 carbon steel was applied to study theheterogeneous corrosion beneath biofilm formed by Sulfate Reducing Bacteria (SRB) in cultureand sulfide film in solution with 1% NaCl and 300 mg/L⋅S^2-. The potential, galvanic density mapping, as well as polarization curve and Electrochemical Impedance Spectrum (EIS) were measured to predict the localized corrosion under biofilm and sulfide film. As a result, the mappingshowed the potential fluctuation on the WBE suface decreased over time due to the conductivityof the biofilm and sulfide film. Therefore, the potential mapping could not be a criterion of localized corrosion …

Studies On The Formation Of Dna-Cationic Lipid Composite Films And Dna Hybridization In The Composites, Murali Sastry, Vidya Ramakrishnan, Mrunalini Pattarkine, Krishna N. Ganesh

Faculty Works

The formation of composite films of double-stranded DNA and cationic lipid molecules (octadecylamine, ODA) and the hybridization of complementary single-stranded DNA molecules in such composite films are demonstrated. The immobilization of DNA is accomplished by simple immersion of a thermally evaporated ODA film in the DNA solution at close to physiological pH. The entrapment of the DNA molecules in the cationic lipid film is dominated by attractive electrostatic interaction between the negatively charged phosphate backbone of the DNA molecules and the protonated amine molecules in the thermally evaporated film and has been quantified using quartz crystal microgravimetry (QCM). Fluorescence studies …

Inverse Synthetic Aperture Radar Imaging Using A Coherent Ultrawideband Random Noise Radar System, Daryl C. Bell, Ram M. Narayanan

Department of Electrical and Computer Engineering: Faculty Publications

The University of Nebraska-Lincoln has developed an ultrawideband random noise radar operating over the 1- to 2-GHz frequency range. The system uses the technique of heterodyne correlation, and is thus phase coherent. It has therefore been used in applications such as interferometry, polarimetry, and Doppler estimation. This assesses the performance of this radar as a range-Doppler imaging system, in particular, inverse synthetic aperture radar (ISAR). By performing turntable experiments, we examine a number of issues that arise both from the wideband nature of the radar system and from the randomness of the transmit signal. Although the ultrawideband nature of the …

7v Tristate-Capable Output Buffer Implemented In Standard 2.5v Cmos Process, Vladimir I. Prodanov, Vito Boccuzzi

Electrical Engineering

This paper describes high-voltage CMOS buffer architecture that uses low-voltage transistors. The voltage capability of the presented architecture is nearly three times larger than the voltage capability of the used MOSFET's. This buffer topology could be used to provide 3.3 V compatibility of 1.2 V and 1.5 V digital ICs implemented in standard CMOS technology. A 7 V circuit-prototype was fabricated in 0.25 /spl μ/m 2.5 V CMOS technology. Performed measurements demonstrate stress-free operationin both active and high-impedance mode.

Robust High-Pass And Notch Gm - (Grounded) C Biquads: How Many Different Topologies Are There?, Vladimir I. Prodanov

Electrical Engineering

This paper deals with Gm-C biquadratic filters that use grounded capacitors. We derive all practical HP and notch filter topologies that do not require critical component matching. The aim of this derivation was to discover new architectures. The result of this derivation is quite unexpected: there are only three distinct topologies (one notch and: two high-pass). None of them is particularly new because all reported in the literature biquad circuits are their embodiments.

Measurement Of Linewidth Enhancement Factor Of Semiconductor Lasers Using An Injection-Locking Technique, G. Liu, Xiaomin Jin, Shun-Lien Chuang

Electrical Engineering

A new method for measuring the linewidth enhancement factor of semiconductor lasers using the injection-locking technique is presented. This idea is based on the relation between the upper and lower bounds of the locked and unlocked regimes when the detuning of the pump and slave laser is plotted as a function of the injection power. Our results are confirmed with an independent measurement using amplified spontaneous emission (ASE) spectroscopy as well as our theory, which takes account of the realistic quantum-well (QW) band structure and many-body effects. This method provides a new approach to measure the linewidth enhancement factor above …

Infrared Optical Properties Of Aged Porous Gaas, S. Zangooie, Mathias Schubert, T. E. Tiwald, John A. Woollam

Department of Electrical and Computer Engineering: Faculty Publications

Aging properties of porous GaAs were investigated nondestructively using variable angle of incidence infrared spectroscopic ellipsometry. In addition to the thickness and volume porosity, properties of the solid part of the porous material are investigated in terms of the long-wavelength dielectric function and chemical composition. The high sensitivity is employed to detect and identify infrared resonant absorptions related to different vibration modes of cubic and amorphous As₂O₃. Resonances centered at 333.3, 480, 785.8, 838, and 1045.5 cm^-1 are from cubic As₂O₃, whereas resonances centered at 350, 490, and 808.5 cm^{-1 …}

Integration Of A Statcom And Battery Energy Storage, Zhiping Yang, Shen Chen, Lin Zhang, Stan Atcitty, Mariesa Crow

Electrical and Computer Engineering Faculty Research & Creative Works

The integration of an energy storage system, such as battery energy storage (BESS), into a FACTS device can provide dynamic decentralized active power capabilities and much needed flexibility for mitigating transmission level power flow problems. This paper introduces an integrated StatCom/BESS for the improvement of dynamic and transient stability and transmission capability; compare the performance of the different FACTS/BESS combinations, and provide experimental verification of the proposed controls on a scaled StatCom/BESS system

Software Engineering Metrics For Cots-Based Systems, Sahra Sedigh, Arif Ghafoor, Raymond A. Paul

Electrical and Computer Engineering Faculty Research & Creative Works

The paradigm shift to commercial off-the-shelf components appears inevitable, necessitating drastic changes to current software development and business practices. Quality and risk concerns currently limit the application of COTS based system design to noncritical applications. New approaches to quality and risk management will be needed to handle the growth of CBSs. Our metrics based approach and software engineering metrics can aid developers and managers in analyzing the return on investment in quality improvement initiatives for CBSs. These metrics also facilitate the modeling of cost and quality, although we need more complex models to capture the intricate relationships between cost and …

A Method For Evaluating The Dielectric Properties Of Composites Using A Combined Embedded Modulated Scattering And Near-Field Microwave Nondestructive Testing Technique, Dana M. Hughes, R. Zoughi

Electrical and Computer Engineering Faculty Research & Creative Works

Investigation into the derivation of the dielectric property of a material with an embedded modulated PIN diode-loaded dipole is described, using an open-ended rectangular waveguide as the irradiating source. Previous measurements of the curing of a mortar specimen show the sensitivity of this combined technique and its potential for inspecting composite structures. Modification of previous algorithms for back calculating the dielectric properties of a material with a conductor backing is considered. The modification would involve replacing the reflection at the conductor with the reflection at a modulated dipole antenna. For this, comparisons between the reflection coefficients of the dipole antenna …

Modeling Dc Power-Bus Structures With Vertical Discontinuities Using A Circuit Extraction Approach Based On A Mixed-Potential Integral Equation, Jun Fan, Hao Shi, Antonio Orlandi, James L. Knighten, James L. Drewniak

Electrical and Computer Engineering Faculty Research & Creative Works

The DC power-bus is a critical aspect in high-speed digital circuit designs. A circuit extraction approach based on a mixed-potential integral equation is presented herein to model arbitrary multilayer power-bus structures with vertical discontinuities that include decoupling capacitor interconnects. Green's functions in a stratified medium are used and the problem is formulated using a mixed-potential integral equation approach. The final matrix equation is not solved, rather, an equivalent circuit model is extracted from the first-principles formulation. Agreement between modeling and measurements is good, and the utility of the approach is demonstrated for DC power-bus design.

Overview Of Acousto-Optic Bistability, Chaos, And Logical Applications, Monish Ranjan Chatterjee, Erol Sonmez

Electrical and Computer Engineering Faculty Publications

An overview is presented of the key results in the field of acousto-optic bistability in the past two decades. It is shown that the basic acousto-optic bistable device may be described as a nonlinear dynamical system which satisfies a quadratic map. Thereafter, details are presented of several analytical methods, computer modeling approaches, including the SPICE circuit modeling technique, and experiments that have been used to understand the phenomenon.

Extensions to logical and digital applications are also discussed.

Overview Of Fuzzy Logic, Mohamed Trabia

Mechanical Engineering Faculty Presentations

The presentation includes a brief introduction to fuzzy logic and fuzzy logic controllers. These concepts are illustrated by an example of an autonomous vehicle controller.

Comparison Of Two Distributed Fuzzy Logic Controllers For Flexible-Link Manipulators, Linda Z. Shi, Mohamed Trabia

Mechanical Engineering Faculty Presentations

The paper suggests that fuzzy logic controllers present a computationally efficient and robust alternative to conventional controllers. The paper presents two possible structures for the distributed fuzzy logic controller of a single-link flexible manipulator. A linear quadratic regulator method is used to prove the effectiveness of fuzzy logic controllers.

Design Of Fuzzy Logic Controllers For Optimal Performance, Mohamed Trabia

Mechanical Engineering Faculty Presentations

While fuzzy logic controllers are generally robust, the performance of a system whose behavior is not well understood, or that has a large number of coupled inputs and outputs, may be less than optimal. In this paper, nonlinear programming techniques are used to improve the performance of a fuzzy logic controller for navigating an autonomous vehicle.

Decomposition Of Relations: A New Approach To Constructive Induction In Machine Learning And Data Mining -- An Overview, Marek Perkowski, Stanislaw Grygiel

Electrical and Computer Engineering Faculty Publications and Presentations

This is a review paper that presents work done at Portland State University and associated groups in years 1989 - 2001 in the area of functional decomposition of multivalued functions and relations, as well as some applications of these methods.

Very-Low-Specific-Resistance Pd/Ag/Au/Ti/Au Alloyed Ohmic Contact To P Gan For High-Current Devices, V. Adivarahan, A. Lunev, M. Asif Khan, J. Yang, Grigory Simin, M. S. Shur, R. Gaska

Faculty Publications

We report on Pd/Ag/Au/Ti/Au alloyed metallic contact to pGaN. An 800 °C anneal for 1 min in flowing nitrogen ambient produces an excellent ohmic contact with a specific contact resistivity close to 1×10⁻⁶ Ω cm² and with good stability under high current operation conditions. This high-temperature anneal forms an alloy between Ag,Au, and pGaN resulting in a highly p-doped region at the interface. Using x-ray photoelectron spectroscopy and x-ray diffractionanalysis, we confirm that the contact formation mechanism is the metal intermixing and alloying with the semiconductor.

Aspect Sensitivity Measurements Of Polar Mesosphere Summer Echoes Using Coherent Radar Imaging, P. B. Chilson, T.-Y. Yu, R. D. Palmer, S. Kirkwood

Department of Electrical and Computer Engineering: Faculty Publications

The Esrange VHF radar (ESRAD), located in northern Sweden (67.88) N, 21.10- E), has been used to investigate polar mesosphere summer echoes (PMSE). During July and August of 1998, coherent radar imaging (CRI) was used to study the dynamic evolution of PMSE with high temporal and spatial resolution. A CRI analysis provides an estimate of the angular brightness distribution within the radar’s probing volume. The brightness distribution is directly related to the radar reflectivity. Consequently, these data are used to investigate the aspect sensitivity of PMSE. In addition to the CRI analysis, the full correlation analysis (FCA) is used to …

Feed-Forward Compensation Scheme For Feedback Circuits, Venugopal Gopinathan, Vladimir I. Prodanov

Electrical Engineering

A feed-forward compensated negative feedback circuit comprises an operational amplifier having an inverting and a non-inverting input and an output. A feedback element is connected between the output of the operational amplifier and its inverting input to form a negative feedback loop. The inverting input of the op-amp is driven with a first transconductance amplifier which produces an output current proportional to an input voltage. A feed-forward transconductance amplifier receives the input voltage and produces an inverted output current proportional to the input voltage. A feed-forward current is injected at the output of the operational amplifier. By providing at the …