Engineering Commons^™

Varying Current Electro-Synthesis Of Glyoxalic Acid In Pairs In The Fixed-Bed Electrolytic Cell, Yin Sheng Chen, Xin Sheng Zhang, Ying Chun Dai, Wei Kang Yuan

Journal of Electrochemistry

As for the process of the electro oxidation of glyoxal to glyoxalic acid, the electrolytic result of either fixed bed electrolytic cell or varying current electrolysis was better than that of either flat plate electrolytic cell or constant current electrolysis. The average current density of varying current electro synthesis of glyoxalic acid in pairs was 1535 A/m 2 and the current efficiency were 85.3% and 86.7% and the selectivity were 93.9% and 94.0% for the anodic oxidation and cathodal reduction respectively. The initial composition of anodic electrolyte was 7% glyoxal and 8% hydrochloric acid (W/W) and the cathodal electrolyte consisted …

Electrochemical Synthesis And Characterization Of The Nickel Electropolyurushiol Coordination Polymer, Feng Gao, Guo-Cai Shen, Jie-Yuan Tang, Wen-Gong Zhang

Journal of Electrochemistry

The nickel electropolyurushiol coordination polymer(EPU Ni 2+ ) was obtained by the reaction between nickel chloride isopropyl alcohol solution with electropolyurushiol (EPU).The electrochemical polymerization of urushiol and the preparation of nickel electropolyurushiol coordination polymer were investigated.The coordination polymer was characterized by XPS,FT_IR,DMTA and AES methods,and its composition and structure were determined.The content of Ni 2+ reached up to 7.5%. It was shown that there was certain coordination between Ni 2+ and electropolyurushiol in the coordination polymer,thus cross_links were formed.Therefore the glass transition temperature of the coordination polymer increased and heat resistance was enhanced considerably.

Information Efficiency In Hyperspectral Imaging Systems, Stephen E. Reichenbach, Luyin Cao, Ram M. Narayanan

Department of Electrical and Computer Engineering: Faculty Publications

In this work we develop a method for assessing the information density and efficiency of hyperspectral imaging systems that have spectral bands of non-uniform width. Imaging system designs with spectral bands of nonuniform width can efficiently gather information about a scene by allocating bandwidth among the bands according to their information content. The information efficiency is the ratio of information density to data density and is a function of the scene’s spectral radiance, hyperspectral system design, and signal-to-noise ratio. The assessment can be used to produce an efficient system design. For example, one approach to determining the number and width …

On The Use Of Linda As A Framework For Distributed Database Systems, Madhan M. Thirukonda, Ronaldo Menezes

Electrical Engineering and Computer Science Faculty Publications

Linda is a coordination language capable of solving issues in distributed computing environments that relate to process synchronization, communication and creation. The expressiveness of Linda in distributed systems is such that researchers are proposing novel applications using Linda as a primary means of coordination. The examples range from peer-to-peer to groupware computing, from simple chat applications to control systems. Surprisingly, Linda has not been used in the field of distributed databases, although Linda can be helpful in solving coordination issues in a distributed database system. In this paper, we look at a possibility of using Linda in the context of …

Modeling, Fabrication, And Optimization Of Niobium Cavities – Phase I: Quarterly Progress Report November 20, 2001 - February 20, 2002, Robert A. Schill Jr., Mohamed Trabia

Transmutation Sciences Materials (TRP)

Multipacting is one of the major loss mechanisms in RF superconductivity cavities for accelerators. This loss mechanism limits the maximum amount of energy/power supported by the cavities. Optimal designs have been identified in others’ studies. In practice, these designs are not easily manufactured. Chemical etching processes used to polish the cavity walls result in a nonuniform surface etch. A nonuniform surface etch will leave some unclean areas with contaminants and micron size particles. These significantly affect multipacting. Further, a nonuniform etch will leave areas with damaged grain structure, which is not good for superconducting properties. Typically, the depth of chemical …

Nanostructures With Small- And Large-Scale Periodic And Random Rough Surfaces And Lateral Fluctuations In The Permittivity And Permeability-Scattered Near Fields, Ezekiel Bahar

Department of Electrical and Computer Engineering: Faculty Publications

The scattered electromagnetic near fields due to fluctuations in the surface height and/or lateral variations in the electromagnetic medium parameters are evaluated using a full-wave approach. Since the scales of the height and medium fluctuations considered could be significantly smaller or larger than the electromagnetic wavelengths, the familiar perturbation and physical/geometrical optics solutions cannot be used nor is it possible to investigate subwave length features based on far-field measurements. The full-wave approach employs complete field expansion that includes propagating and evanescent waves as well as lateral waves and surface waves, which are not accounted for in the perturbation and physical …

Two Mechanisms Of Blueshift Of Edge Emission In Ingan-Based Epilayers And Multiple Quantum Wells, E. Kuokstis, J. W. Yang, Grigory Simin, M. Asif Khan, R. Gaska, M. S. Shur

Faculty Publications

We present the results of a comparative photoluminescence(PL) study of GaN and InGaN-based epilayers, and InGaN/GaN multiple quantum wells(MQWs). Room-temperature PL spectra were measured for a very broad range of optical excitation from 10 mW/cm² up to 1 MW/cm². In contrast to GaN epilayers, all In-containing samples exhibited an excitation-induced blueshift of the peak emission. In addition, the blueshift of the emission in the InGaN epilayers with the same composition as the quantum well was significantly smaller. The comparison of the blueshift in the “bulk” InGaN and in the MQWs allowed us to separate two different mechanisms …

Experimental Study Of Streamers In Pure N2 And N2/O2 Mixtures And A ≈13 Cm Gap, Won J. Yi, P. F. Williams

P. F. (Paul Frazer) Williams Publications

Empirical data on streamer formation and propagation in near-atmospheric pressure N₂ and N₂/O₂mixtures are presented. The data were obtained primarily from high-speed, high-sensitivity shutter and streak photography of streamers produced in a ≈13 cm gap. The streamer propagation velocity as a function of applied voltage, polarity, total pressure, and O₂ concentration are provided. In addition, information on streamer bifurcation, and streamer shape and size is included.

The breakdown process has two phases: a fast phase featuring the propagation of streamers, and much slower phase involving the heating of the gas to form the spark …

Forces On Permeable Conductors In Magnetic Fields, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

It is often implied that the force density formula dF/dV = JXB is all that is required to calculate the force that would be experienced by any stationary current-carrying medium in a region of space containing a magnetic field. However, representations of this formula are not all compatible, and the methods of applying such formulas when the conductor or surrounding medium have permeabilities different from vacuum are not widely known. The simplest case that one might consider is that of a current-carrying wire in an otherwise uniform field. It appears that the experimental measurements corresponding to such a situation have …

High-Performance Inter-Pcb Connectors: Analysis Of Emi Characteristics, Xiaoning Ye, James L. Drewniak, Jim Nadolny, David M. Hockanson

Electrical and Computer Engineering Faculty Research & Creative Works

Electromagnetic interference (EMI) coupling associated with inter-board connection is investigated. Two experimental techniques, based on |S₂₁| measurements, including both common-mode current and near-field measurements, are reported. Both methods, as well as finite difference time domain (FDTD) modeling, were used as experimental and numerical tools for inter-printed-circuit-board (inter-PCB) connector evaluation. The EMI performance of a lab-constructed stacked-card connector, and a commercially available module-on-backplane connector were studied. EMI characteristics of the connectors are demonstrated by investigating a few aspects of the design: type of shield/ground blade for signal return, number and length of ground pins, signal pin designation, etc. Good …

Fdtd Modeling Incorporating A Two-Port Network For I/O Line Emi Filtering Design, Xiaoning Ye, James L. Drewniak

Electrical and Computer Engineering Faculty Research & Creative Works

Electromagnetic interference (EMI) filters are often utilized on I/O lines to reduce high-frequency noise form being conducted off the printed circuit board (PCB) and causing EMI problems. The filtering performance is often compromised at high frequencies due to parasitics associated with the filter itself, or the PCB layout and interconnects. Finite difference time domain (FDTD) modeling can be used to quantify the effect of PCB layout and interconnects, as well as filter type, on the EMI performance of I/O line filtering. FDTD modeling of a T-type and π-type filter consisting of surface-mount ferrites and capacitors is considered herein. The FDTD …

On Performance Analysis And Implementation Issues Of Iterative Decoding For Graph Based Codes, Xuefei Wei

Dissertations

There is no doubt that long random-like code has the potential to achieve good performance because of its excellent distance spectrum. However, these codes remain useless in practical applications due to the lack of decoders rendering good performance at an acceptable complexity. The invention of turbo code marks a milestone progress in channel coding theory in that it achieves near Shannon limit performance by using an elegant iterative decoding algorithm. This great success stimulated intensive research oil long compound codes sharing the same decoding mechanism. Among these long codes are low-density parity-check (LDPC) code and product code, which render brilliant …

On The Data Hiding Theory And Multimedia Content Security Applications, Litao Gang

Dissertations

This dissertation is a comprehensive study of digital steganography for multimedia content protection. With the increasing development of Internet technology, protection and enforcement of multimedia property rights has become a great concern to multimedia authors and distributors. Watermarking technologies provide a possible solution for this problem.

The dissertation first briefly introduces the current watermarking schemes, including their applications in video,, image and audio. Most available embedding schemes are based on direct Spread Sequence (SS) modulation. A small value pseudo random signature sequence is embedded into the host signal and the information is extracted via correlation. The correlation detection problem is …

Renegotiation Based Dynamic Bandwidth Allocation For Selfsimilar Vbr Traffic, Zafer Sahinoglu

Dissertations

The provision of QoS to applications traffic depends heavily on how different traffic types are categorized and classified, and how the prioritization of these applications are managed. Bandwidth is the most scarce network resource. Therefore, there is a need for a method or system that distributes an available bandwidth in a network among different applications in such a way that each class or type of traffic receives their constraint QoS requirements.

In this dissertation, a new renegotiation based dynamic resource allocation method for variable bit rate (VBR) traffic is presented. First, pros and cons of available off-line methods that are …

Qos Routing Source Routing Problems And Solutions, Ye Tian

Theses

The notion of Quality-of-Service has been proposed to capture qualitatively or quantitatively defined performance contracts between the service provider and the user applications. Integrated network services are designed to support Quality-of-Service (QoS). One of the primary goals for the integrated network services is to find the paths that satisfy given QoS requirements, namely QoS routing. The challenging issue in this area is to route packets subjected to multiple uncorrelated constraints because the problem is inherently NP-complete. This thesis studies the source routing heuristic approaches that bring the time complexity down to the polynomial-time for the multi-constrained path (MCP) problem. A …

Hyperbolic Position Location Estimator With Tdoas From Four Stations, Sreeram Potluri

Theses

This thesis presents a detailed derivation of a set of equations needed to locate the three dimensional position of a mobile given the locations of four fixed stations (like a global positioning system (GPS) satellite or a base station in a cell) and the signal time of arrival (TOA) from the mobile to each station. From these derived equations, a synthesizable VHDL model was developed and simulated using IEEE numen*c_std package. All the inputs and outputs were described by 32 bit vectors. From the simulations, it was observed that in the best case the mobile position was off by I …

Fabrication Considerations Of A Superconducting Transmission Line Microelectromechanical Switch, Alfredo Arturo Corrales

FIU Electronic Theses and Dissertations

Developing technologies have always faced the same problems. New applications require smaller systems, must consume less power, and provide greater sensitivity than what is currently available. This thesis provides crucial data for the manufacturing of a microelectromechanical (MEM) switch on a superconducting transmission line. New applications of front-end antennas require small, low-loss switches. MEM switches have shown insertion losses less than 0.1 dB and isolation of 50 dB at RF frequencies. Superconducting transmission lines can provide circuits with extremely low attenuation. The combination of the two can provide the best system for the need of these new applications. This thesis …

Cxquery: A Novel Xml Query Language, Peter Revesz, Yi Chen

CSE Conference and Workshop Papers

XML is becoming the data exchange standard on the Internet. Previously proposed XML query languages, such as XQuery, Quilt, YALT, Lorel, and XML-QL, lack schema definition of the query result; therefore, they are limited for defining views, integrating data, updating, and further querying, all of which are often needed in e-Business applications. We propose a novel XML query language called CXQuery, which defines the schema of the query results explicitly and can easily define views, and integrate, update, and query XML data. In addition, CXQuery can express spatial and spatio-temporal queries using a constraint-based querying approach.

Boundary Effects On Multiplication Noise In Thin Heterostructure Avalanche Photodiodes: Theory And Experiment [Al/Sub 0.6/Ga/Sub 0.4/As/Gaas], Majeed M. Hayat, Oh-Hyun Kwon, Shuling Wang, Joe C. Campbell, Bahaa E.A. Saleh, Malvin Carl Teich

Electrical and Computer Engineering Faculty Research and Publications

The history-dependent recurrence theory for multiplication noise in avalanche photodiodes (APDs), developed by Hayat et al., is generalized to include inter-layer boundary effects in heterostructure APDs with multilayer multiplication regions. These boundary effects include the initial energy of injected carriers as well as bandgap-transition effects within a multilayer multiplication region. It is shown that the excess noise factor can be significantly reduced if the avalanche process is initiated with an energetic carrier, in which case the initial energy serves to reduce the initial dead space associated with the injected carrier. An excess noise factor reduction up to 40% below the …

Wireless Lans, Jack Glas, Mihai Banu, Joachim Hammerschmidt, Vladimir I. Prodanov, Peter Kiss

Electrical Engineering

Wireless LANs based on the IEEE 802.11 standard have achieved wide customer acceptance in the enterprise environment. They are expected to continue to expand in popularity and become ubiquitous communication systems even in private and public places. This paper discusses the basics of the wireless LAN physical layer, focusing on radio transceiver specifications and design options.

Bimodal Fusion In Audio-Visual Speech Recognition, Xiaozheng Zhang, Russell M. Mersereau, Mark A. Clements

Electrical Engineering

Extending automatic speech recognition (ASR) to the visual modality has been shown to greatly increase recognition accuracy and improve system robustness over purely acoustic systems. especially in acoustically hostile environments. An important aspect of designing such systems is how to incorporate the visual component Into the acoustic speech recognizer to achieve optimal performance. In this paper, we investigate methods of Integrating the audio and visual modalities within HMM-based classification models. We examine existing integration schemes and propose the use of a coupled hidden Markov model (CHMM) to exploit audio-visual interaction. Our experimental results demonstrate that the CHMM consistently outperforms other …

Audio-Visual Speech Recognition By Speechreading, Xiaozheng Zhang, Russell M. Mersereau, Mark A. Clements

Electrical Engineering

Speechreading increases intelligibility in human speech perception. This suggests that conventional acoustic-based speech processing can benefit from the addition of visual information. This paper exploits speechreading for joint audio-visual speech recognition. We first present a color-based feature extraction algorithm that is able to extract salient visual speech features reliably from a frontal view of the talker in a video sequence. Then, a new fusion strategy using a coupled hidden Markov model (CHMM) is proposed to incorporate visual modality into the acoustic subsystem. By maintaining temporal coupling across the two modalities at the feature level and allowing asynchrony in the state …

Automatic Speechreading With Applications To Human-Computer Interfaces, Xiaozheng Zhang, Charles C. Broun, Russell M. Mersereau, Mark A. Clements

Electrical Engineering

There has been growing interest in introducing speech as a new modality into the human-computer interface (HCI). Motivated by the multimodal nature of speech, the visual component is considered to yield information that is not always present in the acoustic signal and enables improved system performance over acoustic-only methods, especially in noisy environments. In this paper, we investigate the usefulness of visual speech information in HCI related applications. We first introduce a new algorithm for automatically locating the mouth region by using color and motion information and segmenting the lip region by making use of both color and edge information …

Femtosecond Laser Utilization Methods And Apparatus And Method For Producing Nanoparticles, Dennis R. Alexander

Department of Electrical and Computer Engineering: Faculty Publications

The present invention teaches various femtosecond machining and drilling apparatus and processes for fabricating tools and the like from both traditional and non-traditional materials. Also described are novel tools such as scalpels, and nozzles fabricated from the apparatus and processes of the present invention. Likewise, the present invention may be utilized in both a novel propulsion system and the production of materials formed from nanometer sized particles and the like.

Implementation And Validation Of Range Imaging On A Uhf Radar Wind Profiler, P. B. Chilson, Tian-You Yu, Richard G. Strauch, Andreas Muschinski, Robert D. Palmer

Department of Electrical and Computer Engineering: Faculty Publications

The available range resolution of pulsed radar wind profilers is usually limited by bandwidth restrictions. Range imaging (RIM) has recently been developed as a means of mitigating these limitations by operating the wind profilers over a small set of distinct transmitter frequencies. A constrained optimization method can then be used to generate high-resolution maps of the reflectivity field as a function of range. This paper presents a description of how the RIM technique has been recently implemented on the Platteville 915-MHz tropospheric profiler, the first such implementation at UHF. Examples of data collected during a two-part experiment on 10 April …

An Airborne Low-Cost Sar For Remote Sensing: Hardware Design And Development, Ram Narayanan, Paul C. Cantu, Xiaojian Xu

Department of Electrical and Computer Engineering: Faculty Publications

An airborne low-cost synthetic aperture radar (SAR) is under development at the University of Nebraska-Lincoln. The SAR system is an X-band, stepped-chirp frequency modulation (SCFM) radar system. One of its unique features is that the waveform generation consists of a timing-controlled D/A converter and VCO arrangement to synthesize the SCFM signal, whereby allowing for less design complexity and a much lower overall system cost. In this paper, we present a brief description of the system and some computer simulation results.

Shape-Based Change Detection And Information Mining In Remote Sensing, Jiang Li, Ram M. Narayanan

Department of Electrical and Computer Engineering: Faculty Publications

Change detection is an important application of remote sensing. This paper presents our approach to retrieve and represent interesting shapes in the remotely sensed imagery using supervised classification, edge detection, and polygonal approximation techniques, and to compare the shape similarity by a computationally efficient metric. The experiments were conducted on a time series of calibrated and registered Landsat MSS images, covering the scene of the lakes at the western Nebraska. The results show the effectiveness of the shape-based change detection approach, which is potentially useful for specific applications such as the study of the lake change response to short or …

A Multiwavelength Airborne Polarimetric Lidar For Vegetation Remote Sensing: Instrumentation And Preliminary Test Results, Songxin Ran, Ram M. Narayanan

Department of Electrical and Computer Engineering: Faculty Publications

Several spaceborne and airborne lidar systems have been launched for vegetation canopy studies. Previous research has shown that lidars are useful tools for remote sensing of vegetation architecture. To support its Airborne Remote Sensing Program, the University of Nebraska has developed a multiwavelength airborne polarimetric lidar system. This system employs a Nd:YAG laser which emits radiation at two wavelengths: the fundamental at 1064 nm and the frequency-doubled at 532 nm. Both laser beams are highly linearly polarized (100: 1 extinction ratio) and have a beam divergence angle of ~4 mrad. The receiver consists of four channels, which enable dual-wavelength and …

Parameter Estimation For Transformer Modeling, Sung Don Cho

Dissertations, Master's Theses and Master's Reports - Open

Large Power transformers, an aging and vulnerable part of our energy infrastructure, are at choke points in the grid and are key to reliability and security. Damage or destruction due to vandalism, misoperation, or other unexpected events is of great concern, given replacement costs upward of $2M and lead time of 12 months. Transient overvoltages can cause great damage and there is much interest in improving computer simulation models to correctly predict and avoid the consequences.

EMTP (the Electromagnetic Transients Program) has been developed for computer simulation of power system transients. Component models for most equipment have been developed and …

Co-Polymers Of Furan With Pyrrole Or Thiophene: A Synthetic Study, Rose M. Mcconnell, Walter E. Godwin, Susan E. Baker, Kenya Powell, Martha Baskett, Amy Morara, Xiadong Ma

Journal of the Arkansas Academy of Science

The use of conductive polymers as a substitute for metallic conductors and semiconductors has attracted much attention in the literature. In particular, aromatic heterocyclic polymers constitute an important class since they possess chemical and electrical stability in both the oxidized (doped) and neutral (undoped) state. Doping a polymer allows one to vary its electrical, mechanical, optical, and thermal properties. The properties of these polymers are promising for their many technological uses such as antistatic coatings, solar cells, and electronic devises. Polyfuran is among the least common heterocyclic polymers. Polyfuran has been reported to be much less stable that either polypyrrole …