Engineering Commons^™

Nonuniformly Spaced Array Elements, Daniel R. Richards Jr.

Theses and Dissertations

This thesis provides a method to reduce physical resource requirements along with cost reduction in Space Based Radar (SBR) platforms, and provides a rule of thumb for randomization effects on arrays. A trend analysis is performed on 4, 8, 12, and 16 square meter arrays. Three aperiodic thinning approaches are examined. They are an equal current density element distribution, a random periodic grid of elements, and random element distribution based a peak sidelobe indicator. According to the metrics used, the statistical and deterministic array thinning approaches performed best for these small arrays. However, the statistical arrays have a scan angle …

Post-Processing Resolution Enhancement Of Open Skies Photographic Imagery, Daniel E. Sperl

Theses and Dissertations

The Treaty on Opens Skies allows any signatory nation to fly a specifically equipped reconnaissance aircraft anywhere over the territory of any other signatory nation. For photographic images, this treaty allows for a maximum ground resolution of 30 cm. The National Air Intelligence Center (NAIC), which manages implementation of the Open Skies Treaty for the US Air Force, wants to determine if post-processing of the photographic images can improve spatial resolution beyond 30 cm, and if so, determine the improvement achievable. Results presented in this thesis show that standard linear filters (edge and sharpening) do not improve resolution significantly and …

Modeling The Statistical Time And Angle Of Arrival Characteristics Of An Indoor Multipath Channel, Michael A. Jensen, Brian D. Jeffs, A. Lee Swindlehurst, Quentin H. Spencer

Faculty Publications

Most previously proposed statistical models for the indoor multipath channel include only time of arrival characteristics. However, in order to use statistical models in simulating or analyzing the performance of systems employing spatial diversity combining, information about angle of arrival statistics is also required. Ideally, it would be desirable to characterize the full spare-time nature of the channel. In this paper, a system is described that was used to collect simultaneous time and angle of arrival data at 7 GHz. Data processing methods are outlined, and results obtained from data taken in two different buildings are presented. Based on the …

In Situ Ellipsometry Growth Characterization Of Dual Ion Beam Deposited Boron Nitride Thin Films, E. Franke, Mathias Schubert, John A. Woollam, J.-D. Hecht, G. Wagner, H. Neumann, F. Bigl

Department of Electrical and Computer Engineering: Faculty Publications

Pure hexagonal h, as well as mixed-phase cubic/hexagonal c/h boron nitride (BN) thin films were deposited onto [001] silicon substrates using the dual ion beam deposition technique. The BN thin films were grown under UHV conditions at different substrate temperatures and ion beam bombarding parameters. Thin-film growth was monitored using in situ spectroscopic ellipsometry at 44 wavelengths between 420 and 761 nm. The in situ ellipsometric Ψ and Δ data were compared with two-layer growth model calculations for the mixed-phase c/h BN, and with one-layer growth model calculations for pure h-BN growth. In situ data provide information on …

Tool-Based Integration And Code Generation Of Object Models, Michael Ray Ashby

Theses and Dissertations

Today many organizations are faced with multiple large legacy data stores in different formats and the need to use data from each data store with tools based on the other data stores' formats. This thesis presents a tool-based methodology for integrating object-oriented data models with automatic generation of code. The generated code defines a global data format, generates views of global data in individual integrated data formats, and parses data from individual formats to the global formats and from the global format to the individual formats. This allows for legacy data to be translated into the global format, and all …

Evaluation Of A Method For Kinematic Gps Carrier-Phase Ambiguity Resolution Using A Network Of Reference Receivers, Brian L. Bracy

Theses and Dissertations

New applications for GPS have driven a demand for increased positioning accuracy. The emerging GPS technology particularly affects the test community. The testing equipment and method must provide a solution that is an order of magnitude more precise than the tested equipment to achieve the desired accuracy. Carrier-phase differential GPS methods using a network of reference receivers can provide the centimeter-level accuracy required over a large geographical area. This thesis evaluates the performance of a 5-receiver network over a 50 km x 120 km area of New Mexico, using a GPS network algorithm called NetAdjust. The percentage of time a …

Comparative Analysis Of Mobility Management Schemes In A Low Earth Orbit Satellite Network, Stephen R. Conkling

Theses and Dissertations

In the 60's the United States and the Union of Soviet Socialist Republics engaged in a "space race" to be the first to put a man on the moon. Today, the space race is between large multinational telecommunication corporations with the winner receiving the financial rewards by providing communication services to the billions without even a simple telephone. Many entrants are using Low Earth Orbit (LEO) satellites to provide the communications infrastructure, but the number of customers a satellite can support is limited by bandwidth available. This resource must be used efficiently, and this involves reducing the management overhead. This …

Behavioral Igbt Modeling For Predicting High Frequency Effects In Motor Drives, Jerry L. Tichenor, S. D. Sudhoff, James L. Drewniak

Electrical and Computer Engineering Faculty Research & Creative Works

A first-order behavioral IGBT/gate drive model is proposed together with a procedure for deriving all model parameters. Despite the simplicity of the proposed model, comparison of model predictions with hardware measurements demonstrate the model to be accurate in predicting turn-on and turn-off transients.

Modeling Emi Resulting From A Signal Via Transition Through Power/Ground Layers, Wei Cui, Xiaoning Ye, Bruce Archambeault, Doug White, Min Li, James L. Drewniak

Electrical and Computer Engineering Faculty Research & Creative Works

Signal transitioning through layers on vias are very common in multi-layer printed circuit board (PCB) design. For a signal via transitioning through the internal power and ground planes, the return current must switch from one reference plane to another reference plane. The discontinuity of the return current at the via excites the power and ground planes, and results in noise on the power bus that can lead to signal integrity, as well as EMI problems. Numerical methods, such as the finite-difference time-domain (FDTD), Moment of Methods (MoM), and partial element equivalent circuit (PEEC) method, were employed herein to study this …

Cathodic Indirect Electro-Oxidation——Organic Electro-Synthesis Dimethyl Sulfone, Deng-Ping Gu, Rui-Zhi Wang, Hong-Kun Zhang, Xue-Ying Zhang, Wei Li, Bao-Qiu Cui

Journal of Electrochemistry

A cathodic indirect electro-oxidation system was established for indirect electro-oxidize dimethyl sulfoxide to dimethyl sulfone with electro-eduction generated H₂O₂ catalyzed by the pertungstate/tungstate (WO₅^2-/WO₄^2-) redox mediator. Influences of current density, pH, temperature, and the current efficiencies etc. On the cathodic indirect electro-oxidation of dimethyl sulfone were investigated for determining optimum reaction conditions. The current efficiency reached more than 70%. Mother-liquid could be recycled to use without pollution.

Effect Of Different Species Of Cobalt Additive On Performance Of Nickel Hydroxide Electrode, Xian-Xia Yuan, Yin-Dong Wang, Feng Zhan

Journal of Electrochemistry

Performances of nickel electrodes when adding or without adding Cobalt in different forms were studied, the results were interpreted by cyclic voltammetry(CV) and electrochemical impedance spectroscope (EIS). It was demonstrated that the additions of Co, CoO, CoO+Co by mechanically mixing with Ni(OH)₂ all can improve the performance of nickel electrode to some extent, and when Co is added in the form of CoO the best performance can be obtained. This can be mainly attributed to the fact that three kinds of Co additives all improved the structure of nickel hydroxide and the ability of H⁺ in electrolyte transporting …

Investigations Of Lithium Ion Battery Electrolyte Solution, Jing-Li Han, Qing-Guo Liu

Journal of Electrochemistry

Synthesis and electrochemical investigations of {LiB[(SO₃)C₆H₃(O)(COO)]OC₆H₅} in EC/DMC or DMSO/PC mixtures are presented.

The Study On Fabricating Thin Electrodes For Polymer Electrolyte Membrane Fuel Cells (Pemfc), Yong-Sheng Yang, Jing-Hua Liu, Chang-Peng Liu, Gong-Quan Sun, Chang-Zhi Li, Tian-Hong Lu

Journal of Electrochemistry

To lower platinum loading in electrodes for polymer electrolyte membrane fuel cell, a new thin electrode fabrication technique (TEFT) was developed in this work. A series of low Pt loading electrodes with smooth and uniformed surface were fabricated by the TEFT. As a result, the maximum power density of the cell with platinum loading of 1 mg/cm² and Nafion 117 membrane as electrolyte was up to 0.3 W.cm^-2. Moreover, the effects of PTFE and Nafion content in cathodes on the performance of PEMFC with low Pt loading electrodes (1 mg Pt/cm²) were examined systematically.

Sprayed And Thermally Evaporated Carbon Films As Anodes For Lithium Ion Batteries, Shu-Gao Zhang, M.Schleich Donald

Journal of Electrochemistry

Carbon films were made using spray-thermal evaporation from a kind of pyrolytic carbon powder. The films obtained with graphite structure were both potentio-statically and galvanostaically tested. Cycling patterns indicated a reduction peak on the first cycle corresponding to the formation of solid electrolyte interface, and the capacity values and x values were quite acceptable compared to theoretical ones when charging-discharging current density was suitable. Based on the experimental results, the obtained carbon films could be used as anode materials for relatively determining the electrochemical performances of cathode materials.

Studies On Electrochemical Synthesis Of 4,5-Disubstituted-1,2- Benzoquinones And The Reaction Mechanism, Xian-Zhang Bu, Gui-Wu Xiao, Lin Ma, Xing-Chum He, Ling-Quan Gu

Journal of Electrochemistry

The oxidation peak potentials (E_p) of alinine derivates and catechol in 0.1 mol/L KCl+15% alcohol solution were measured by cyclic voltammograms technique. The electrochemical oxidation condition was set according to the E_p. Three derivates of 4,5-disubstituted -1,2-benzoquinones were prepared via electrochemical oxidation-Michael addition reaction. The possible mechanism of electrochemical oxidation-Michael addition reaction is presented.

Electrochemical Characterization Of Ir-Ta-Ti Metal Oxide Coated Titanium Anodes, Ting-Yong Wang, Li-Kun Xu, Guang-Zhang Chen

Journal of Electrochemistry

Ir-Ta-Ti metal oxide coated titanium anodes of variable composition were prepared by thermal decomposition. Their micro morphorogies and electrochemical properties were characterized by scanning electron microscope, open circuit potential, cyclic voltammetry, consumption rate measurements and accelerated life test. The SEM results indicated that all coatings were of a porous and cracked-mud microstructure influenced greatly by the composition of coatings. The electrochemical measurements showed that the Ir-Ta-Ti ternary oxide-coated anodes exhibited excellent electrochemical activity and electrochemical stability in both acidic media and seawater which were affected by the composition and microstructure of the coatings. Owing to good corrosion resistance and low …

Fabrication And Examination Of Reduced Temperatrue Solid Oxide Fuel Cell Using A Supported Thin Ysz Electrolyte Substrate, Yi-Huang Zhang, Yong-Lei Dong, Yi Jiang, Zhi-Gui Lu, Jing-Wang Yan

Journal of Electrochemistry

By using a cost-effective wet process,dense yttria stabilized zirconia (YSZ) films on Ni-YSZ anode substrates have been prepared successfully. The YSZ film was characterized to be around 10 μm in thickness, sufficiently dense, uniform and crack free. A single solid oxide fuel cell fabricated from the supported YSZ film electrolyte on the anode substrate and a LSM cathode prepared on the YSZ film was tested. The power density reached to 0.1 W/cm² at 800 ℃, showing a reasonable performance. Further analysis on both electrodes shows that the anodic overpotential was much larger than IR drop (including YSZ resistance and …

Electro-Oxidation Of Glyoxal To Glyoxalic Acid, Yin-Sheng Chen, Xin-Sheng Zhang, Jun Hu, Ying-Chun Dai

Journal of Electrochemistry

An investigation has been made to obtain the glyoxalic acid by the electrochemical oxidation of glyoxal solution with hydrochloric acid under various experimental conditions.The cell used consists of a lead cathode, a DSA anode and a cation-exchange membrane of model CM001. The current efficiency and yield for glyoxalic acid generation were 80.0% and 91.1% respectively, under optimal operating conditions: velocity of electrolyte flow 1.4 m·s^-1 ,current density 450 A·m^-2, temperature 30～40 ℃, initial concentration of glyoxal and hydrochloric acid 9.1%～16.0%, 4%～6%, respectively.

Lattice And Energy Band Engineering In Alingan/Ga Heterostructures, M. Asif Khan, J. W. Yang, Grigory Simin, R. Gaska, M. S. Shur, Hans-Conrad Zur Loye, G. Tamulaitis, A. Zukauskas, David J. Smith, D. Chandrasekhar, R. Bicknell-Tassius

Faculty Publications

We report on structural, optical, and electrical properties of Al_xIn_yGa_1−x−yNGaNheterostructures grown on sapphire and 6H–SiC substrates. Our results demonstrate that incorporation of In reduces the lattice mismatch, Δa, between AlInGaN and GaN, and that an In to Al ratio of close to 1:5 results in nearly strain-free heterostructures. The observed reduction in band gap,ΔE_g, determined from photoluminescence measurements, is more than 1.5 times higher than estimated from the linear dependencies of Δa and ΔE_g on the In molar fraction. The incorporation of In and resulting changes in the built-in strain in …

Studies Of The Preparation Of Electrodes From Lead Carbonate For Lead-Acid Battery Ⅱ. The Preparation Of Paste Electrodes, Zhong-Xu Dai, Di-Hua Wang, Hao-Hao Ke, Jin-Yun Zou, Yun-Hong Zhou

Journal of Electrochemistry

The positive and negative pastes were prepared by mixing PbCO₃ and H₂SO₄ solution as well as relative additives, respectively. The effects of the various formation methods and the charge/discharge conditions on discharge capacity and active material utilization of both electrodes were examined. The results indicate that the performance of the positive electrode formed at 2.0 mA/cm² is better than that formed at higher current density under the same charge/discharge condition, the PAM utilization reaches 74.4 % under discharging at 2.0 mA/cm²; and the property of the negative electrode formed by unsymmetrical square wave …

Collaborative Distance Education In Power Engineering, Anil Pahwa, Shelli K. Starrett, Kraig J. Olejniczak, S. D. Sudhoff, Mariesa Crow

Electrical and Computer Engineering Faculty Research & Creative Works

This paper presents a perspective on offering "shared-courses," or courses simultaneously offered at two or more universities via various distance educational frameworks. Over a three year duration, two senior/graduate level courses were jointly developed and offered to the students at the University of Missouri--Rolla, the University of Arkansas, Kansas State University, and Purdue University. This paper discusses the various distance educational technologies including two-way audio/visual via ISDN line, video-tapes, and web-based conferencing. Both instructor and student reactions to these mediums are included. Pedagogical methods appropriate for these mediums are outlined. The paper concludes with recommendations and strategies for engineering institutions …

Multilevel Coded Modulation For Unequal Error Protection And Multistage Decoding—Part I: Symmetric Constellations, Robert H. Morelos-Zaragoza, Marc P. C. Fossorier, Shu Lin, Hideki Imai

Faculty Publications

In this paper, theoretical upper bounds and computer simulation results on the error performance of multilevel block coded modulations for unequal error protection (UEP) and multistage decoding are presented. It is shown that nonstandard signal set partitionings and multistage decoding provide excellent UEP capabilities beyond those achievable with conventional coded modulation. The coding scheme is designed in such a way that the most important information bits have a lower error rate than other information bits. The large effective error coefficients, normally associated with standard mapping by set partitioning, are reduced by considering nonstandard partitionings of the underlying signal set. The …

On The Assessment Of Stability And Patterning Of Speech Movements, Anne Smith, Michael T. Johnson, Clare Mcgillem, Lisa Goffman

Electrical and Computer Engineering Faculty Research and Publications

Speech requires the control of complex movements of orofacial structures to produce dynamic variations in the vocal tract transfer function. The nature of the underlying motor control processes has traditionally been investigated by employing measures of articulatory movements, including movement amplitude, velocity, and duration, at selected points in time. An alternative approach, first used in the study of limb motion, is to examine the entire movement trajectory over time. A new approach to speech movement trajectory analysis was introduced in earlier work from this laboratory. In this method, trajectories from multiple movement sequences are time- and amplitude-normalized, and the STI …

Emi From Cavity Modes Of Shielding Enclosures-Fdtd Modeling And Measurements, Min Li, Joe Nuebel, James L. Drewniak, Richard E. Dubroff, Todd H. Hubing, Thomas Van Doren

Electrical and Computer Engineering Faculty Research & Creative Works

Electromagnetic interference (EMI) from slots and apertures resulting from coupling of interior sources through enclosure cavity modes in a rectangular test enclosure is reported herein. EMI from a specially designed test enclosure with slots or apertures excited by interior sources was studied experimentally and with finite-difference time-domain (FDTD) modeling. The measurements and FDTD modeling agree well. The results indicate that radiation at cavity mode resonances through slots and apertures of nonresonant dimensions can be as significant as the radiation at aperture or slot resonances. The agreement between the FDTD modeling and measurements demonstrates the usefulness of FDTD for investigating aspects …

Microwave Near-Field Reflection Property Analysis Of Concrete For Material Content Determination, Karl Joseph Bois, Aaron D. Benally, R. Zoughi

Electrical and Computer Engineering Faculty Research & Creative Works

One of the most important parameters associated with concrete is its compressive strength. Currently, there is no reliable nondestructive testing technique that is capable of robust determination of this parameter. Concrete is a heterogeneous mixture composed of water, cement powder, sand (fine aggregate), rocks of various size or grade (coarse aggregate), and air (porosity). Water and cement powder chemically combine into a cement paste binder which, in due curing time (28 days), produces concrete with its specified compressive strength. Compressive strength of concrete is strongly influenced by its water-to-cement (w/c) ratio as well as its coarse aggregate-to-cement (ca/c) ratio. Therefore, …

Space/Time/Frequency Methods In Adaptive Radar, Christopher D. Peckham

Dissertations

Radar systems may be processed with various space, time and frequency techniques. Advanced radar systems are required to detect targets in the presence of jamming and clutter. This work studies the application of two types of radar systems.

It is well known that targets moving along-track within a Synthetic Aperture Radar field of view are imaged as defocused objects. The SAR stripmap mode is tuned to stationary ground targets and the mismatch between the SAR processing parameters and the target motion parameters causes the energy to spill over to adjacent image pixels, thus hindering target feature extraction and reducing the …

Multi-User Detection For Multi-Rate Ds/Cdma Systems, Jinwen Ma

Dissertations

Wireless cellular communication is witnessing a rapid growth in market, technology and range of services. Current and future demands for wireless communication services motivate the need for handling multi-media traffic types. In a multimedia communication system, users with different and even time-varying rates and quality of services (QoS) requirements, such as voice, image and data, must be accommodated. The use of Spread Spectrum modulation with Code Division Multiple Access (CDMA) technology is an attractive approach for economical spectrally efficient and high quality cellular and personal communication services. This dissertation explores the technologies of applying different interference cancellation techniques to multi-rate …

Integrated Product And Process Development Methodologies For Environmentally Conscious Electronic Products, Pingtao Yan

Dissertations

This research focuses on integrated product and process development (IPPD) methodologies for environmentally conscious electronic products. After a review of current research issues in the field of product and process development, a generic framework for IPPD is proposed which describes most of the concerned issues formally as constrained optimization problems. These problems may include such optimization objectives as cost, benefit, and environmental impact. Based on this framework, an IPPD methodology is proposed as a systems approach to competitive and environmentally conscious product and process development. A case study on personal computer development is performed illustrating how to apply the methodology …

Data Hiding In Multimedia - Theory And Applications, Mahalingam Ramkumar

Dissertations

Multimedia data hiding or steganography is a means of communication using subliminal channels. The resource for the subliminal communication scheme is the distortion of the original content that can be tolerated. This thesis addresses two main issues of steganographic communication schemes:

1. How does one maximize the distortion introduced without affecting fidelity of the content?

2. How does one efficiently utilize the resource (the distortion introduced) for communicating as many bits of information as possible? In other words, what is a good signaling strategy for the subliminal communication scheme?

Close to optimal solutions for both issues are analyzed. Many techniques …

Editing Mpeg2 Video In Compressed Domain, Ren Egawa

Theses

As MPEG2 becomes the heart of most digital video applications, the need to edit an MPEG2 bitstream video in compressed domain has increased. To realize this need, two major technical issues must be resolved: decoder buffer and segment extraction.

In the decoder buffer issue, the edited stream must ensure that the buffer would not overflow or underfiow as the result of the editing. This thesis invented a mathematical model that could describe the editing task and predict the editing effect on the buffer. Based on this model, the thesis then built a method to edit a stream safely. This method …