Engineering Commons^™

Surface Band Bending In As-Grown And Plasma-Treated N-Type Gan Films Using Surface Potential Electric Force Microscopy, Sang-Jun Cho, Seydi Doğan, Shahriar Sabuktagin, Michael A. Reshchikov, D. Johnstone, Hadis Morkoç

Electrical and Computer Engineering Publications

The surface band bending, as well as the effect of plasma-induced damage on band bending, on GaN surfaces, was investigated. The upward band bending, measured by surface potentialelectric force microscopy (a variant of atomic force microscopy), for the as-grown n -type GaNwas about 1.0 eV which increased to ∼1.4 eV after reactive ion etching (RIE). UV illuminationdecreased the band bending by 0.3 eV with time constants on the order of seconds and hundreds of seconds for the as-grown and RIE treated GaN, respectively. This implies that there is a higher density of the surface states in the samples subjected to …

Characterization Of Ingan/Gan Multi-Quantum-Well Blue-Light-Emitting Diodes Grown By Metal Organic Chemical Vapor Deposition, K. S. Ramaiah, Y. K. Su, S. J. Cheng, B. Kerr, H. P. Liu, I. G. Chen

Electrical and Computer Engineering Publications

The structural,surface morphology, and the temperature dependence photoluminescence of InGaN(3 nm)/GaN(7 nm) 5 period multi-quantum-well blue-light-emitting diode (LED)structures grown by metal organic chemical vapor deposition(MOCVD) have been studied. Quantum dot-likestructures and strain contrast evident by black lumps were observed in the quantum wells using high-resolution transmission electron microscopy(HRTEM) analysis. Double-crystal high-resolution x-ray diffraction (HRXRD) spectra of blue LED were simulated using kinematical theory method, to obtain composition, and period thickness of well and barrier. The “S” shape character shift as red–blue–redshift of the quantum-well emission line, i.e., blue emission peak 2.667 eV at 10 K, was observed with variation of …

Decay Of Spin-Polarized Hot Carrier Current In A Quasi-One-Dimensional Spin-Valve Structure, S. Pramanik, Supriyo Bandyopadhyay, M. Cahay

Electrical and Computer Engineering Publications

We study the spatial decay of spin-polarized hot carriercurrent in a spin-valve structure consisting of a semiconductorquantum wire flanked by half-metallic ferromagnetic contacts. The current decays because of D’yakonov-Perel’ spin relaxation in the semiconductor caused by Rashba and Dresselhaus spin–orbit interactions in multi-channeled transport. The associated relaxation length is found to decrease with increasing lattice temperature (in the range from 30 to 77 K) and exhibit a nonmonotonic dependence on the electric field driving the current. The relaxation lengths are several tens of microns which are at least an order of magnitude larger than what has been theoretically calculated for …

Gan Epitaxy On Thermally Treated C-Plane Bulk Zno Substrates With O And Zn Faces, Xing Gu, Michael A. Reshchikov, Ali Teke, D. Johnstone, Hadis Morkoç, Bill Nemeth, Jeff Nause

Electrical and Computer Engineering Publications

ZnO is considered as a promising substrate for GaNepitaxy because of stacking match and close lattice match to GaN. Traditionally, however, it suffered from poor surface preparation which hampered epitaxialgrowth in general and GaN in particular. In this work, ZnO substrates with atomically flat and terrace-like features were attained by annealing at high temperature in air. GaNepitaxial layers on such thermally treated basal plane ZnO with Zn and O polarity have been grown by molecular beam epitaxy, and two-dimensional growth mode was achieved as indicated by reflection high-energy electron diffraction. We observed well-resolved ZnO and GaN peaks in the high-resolution …

Phase-Coherent Quantum Mechanical Spin Transport In A Weakly Disordered Quasi-One-Dimensional Channel, M. Cahay, S. Bandyopadhyay

Electrical and Computer Engineering Publications

A transfer matrix technique is used to model phase-coherent spin transport in the weakly disordered quasi-one-dimensional channel of a gate-controlled electron spin interferometer [S. Datta and B. Das, Appl. Phys. Lett. 56, 665 (1990)]. The model includes the effects of an axial magnetic field in the channel of the interferometer (caused by the ferromagnetic contacts), a Rashba spin-orbit interaction, and elastic (nonmagnetic) impurity scattering. We show that in the presence of an axial magnetic field, nonmagnetic impurities can cause spin relaxation in a manner similar to the Elliott-Yafet mechanism. The amplitudes and phases of the conductance oscillations of the interferometer …

Excitonic Fine Structure And Recombination Dynamics In Single-Crystalline Zno, A. Teke, Ü. Özgür, S. Doğan, X. Gu, Hadis Morkoç, B. Nemeth, J. Nause, H. O. Everitt

Electrical and Computer Engineering Publications

The optical properties of a high quality bulk ZnO, thermally post treated in a forming gas environment are investigated by temperature dependent continuous wave and time-resolved photoluminescence (PL) measurements. Several bound and free exciton transitions along with their first excited states have been observed at low temperatures, with the main neutral-donor-bound exciton peak at 3.3605 eV having a linewidth of 0.7 meV and dominating the PL spectrum at 10 K. This bound exciton transition was visible only below 150 K, whereas the A-free exciton transition at 3.3771 eV persisted up to room temperature. A-free exciton binding energy of 60 meV …

Balancedenergy Sleep Scheduling Scheme For High Density Cluster-Based Sensor Networks, Jing Deng, Yunghsiang S. Han, Wendi B. Heinzelman, Pramod K. Varshney

Electrical Engineering and Computer Science - All Scholarship

In order to conserve battery power in very dense sensor networks, some sensor nodes may be put into the sleep state while other sensor nodes remain active for the sensing and communication tasks. However, determining which of the sensor nodes should be put into the sleep state is non-trivial. As the goal of allowing nodes to sleep is to extend network lifetime, we propose and analyze a Balanced-energy Scheduling (BS) scheme in the context of cluster-based sensor networks. The BS scheme aims to evenly distribute the energy load of the sensing and communication tasks among all the nodes in the …

Printed Planar Monopole Antenna With Electromagnetically Coupled Elements, Jonathan Evans, Francisco Lerma, Max Ammann

Conference papers

In this paper, the addition of an EM-coupled element to the printed planar monopole antenna is investigated. While remaining simple to construct, modifications to the EM-coupled element are shown to reduce the lower edge frequency of the 10 dB impedance bandwidth by up to ∼19% (280 MHz at 1.5 GHz). The radiation patterns for these antennas are characteristic of monopole antennas - i.e. omnidirectional in the azimuth plane with a at the zenith - and are consistent within +/- 2 dB across their useful impedance bandwidths. By optimizing the feed arrangements on these antennas a 10 dB impedance bandwidth ratio …

Transient Photovoltage In Gan As Measured By Atomic Force Microscope Tip, M. A. Reshchikov, S. Sabuktagin, D. K. Johnstone, H. Morkoç

Electrical and Computer Engineering Publications

We studied restoration of the band bending at the surface of undoped GaN layers after illumination with above-bandgap light. The photovoltage saturated with illumination at about 0.2–0.3 eV at room temperature, although the upward band bending for GaN in the dark is of the order of 1 eV. We attribute the photovoltage effect to charging of the surface states, the density of which is estimated at about 10^12 cm^−2. Restoration of the barrier after a light pulse is simulated by a phenomenological model whereby the acceptorlike surface states are emptied of electrons under illumination and filled back in dark due …

Parameter Extraction Software For Silicon Carbide Schottky, Merged Pin Schottky And Pin Power Diode Models, Edgar Cilio

Inquiry: The University of Arkansas Undergraduate Research Journal

A software program for on-state parameter extraction is presented for the realization of a high quality model for SiC Schottky, Merged PiN Schottky, and PiN Power diodes based on McNutt and Mantooth's Comprehensive SiC Diode model [ 1 ].

The Values Of Being Small And Nimble, Joshua Shuart, Peter Christian ("Chris") Murphy

New England Journal of Entrepreneurship

Peter Christian (Chris) Murphy had worked his way up the “food chain” at AT&T for 19 years, culminating in his position as Sales Center Vice President for South Florida. When he and a coworker realized there was an opportunity in the marketplace for a small, nimble company to take advantage of emerging communications technology that a stodgy, lumbering corporation would have trouble integrating into its service package, Chris decided to jump into an entrepreneurial opportunity.

The Removal Of Motion Artifacts From Non-Invasive Blood Pressure Measurements, Paresh Thakkar

Electronic Theses and Dissertations

Modern Automatic Blood Pressure Measurement Techniques are based on measuring the cuff pressure and on sensing the pulsatile amplitude variations. These measurements are very sensitive to motion of the patient or the surroundings where the patient is. The slightest unexpected movements could offset the readings of the automatic Blood Pressure meter by a large amount or render the readings totally meaningless. Every effort must be taken to avoid subjecting the body of the patient or the patient's surroundings to motion for obtaining a reliable reading. But there are situations in which we need Blood Pressure Measurements with the patient or …

Observations Upon Entering The Kettle, Gary Spivey

Faculty Publications - Department of Electrical Engineering and Computer Science

An oft told parable relates how a frog, when dropped in a kettle of hot water, will instantly jump out. But if you drop that frog in a kettle of cold water, and slowly heat it up, the frog will not be aware of the gradual change in its environment and will die in the kettle. I had formerly limited the kettle analogy to the broad concepts of the “worldly culture” alluded to by pastors who use this imagery. Then, after completing educational experience at major state universities and a fifteen year career in industry, I decided to enter upon …

Ece3260 - Science Of Sound, Spring 2004, Paul Wheeler

Electrical and Computer Engineering - OCW

Welcome to Science of Sound. This course is offered as a regular class Fall Semesters on the USU campus in Logan, Utah. It is also available over the internet Fall, Spring, and Summer semesters, or as a yearlong independent-studies course. In each case, work is submitted using the internet. The only difference in the regular class held Fall semester is that students meet with the professor three times a week to discuss the material in the text. A teaching assistant is assigned to answer questions via the internet. The course consists of reading the text, supplementing concepts using the Internet, …

Raindrop Size Distribution Retrieval And Evaluation Using An S-Band Radar Profiler, Fang Fang

Electronic Theses and Dissertations

Vertical pointing Doppler radar profilers are used to explore the vertical structure of precipitation cloud systems and to provide validation information for use in weather research. In this thesis, a theoretical radar rain-backscatter model was developed to simulate profiler Doppler spectra as a function of assumed rain parameters, of which the raindrop size distribution (DSD) is the fundamental quantity used to describe the characteristics of rain. Also, profiler observations during stratiform rain are analyzed to retrieve the corresponding rain DSD’s. In particular, a gamma distribution model is introduced, which uses Rayleigh scattering portion of the Doppler velocity spectrum to estimate …

Analysis And Implementation Of A Synchronous Buck Converter Used As An Intermediate Stage Of An Hid Ballast, Sergey V. Vernyuk

ETD Archive

The contribution of this thesis is the analysis of a Synchronous Buck converter, used as the second stage (which controls the current through the lamp, and consequently, the lamp power) in a 3-stage High-Intensity Discharge (HID) ballast. Where previously standard Buck converters were used, this new application of the Synchronous Buck converter to a medium-power lighting ballast improves efficiency by operating the converter in a new, modified critical-conduction mode to achieve soft-switching and improve efficiency significantly. The converter and 2-loop controller will be analyzed in the three HID lamp modes of operation: open circuit, short circuit, and power control mode. …

An Asynchronous Gals Interface With Applications, Jennifer A. Smith

Electrical and Computer Engineering Faculty Publications and Presentations

A low-latency asynchronous interface for use in globally-asynchronous locally-synchronous (GALS) integrated circuits is presented. The interface is compact and does not alter the local clocks of the interfaced local clock domains in any way (unlike many existing GALS interfaces). Two applications of the interface to GALS systems are shown. The first is a single-chip shared-memory multiprocessor for generic supercomputing use. The second is an application-specific coprocessor for hardware acceleration of the Smith-Waterman algorithm. This is a bioinformatics algorithm used for sequence alignment (similarity searching) between DNA or amino acid (protein) sequences and sequence databases such as the recently completed human …

Protein Family Classification Using Structural And Sequence Information, Jennifer A. Smith

Electrical and Computer Engineering Faculty Publications and Presentations

Protein family classification usually relies on sequence information (as in the case of hidden Markov models and position-specific scoring matrices) or on structural information where some sort of average positional error between the atomic locations is used. The positional error method requires that the structure of all the proteins to be classified is known. Sequence methods have the advantage that a much larger number of proteins can be classified (since far more sequences are know than structures). However, sequence methods discard a large amount of useful information contained in the structures of the subset of proteins in the family for …

Using Information Technology To Enhance Control Engineering Education: Some Experiences, Aidan O'Dwyer

Conference papers

In the past decade, the use of computer based design and analysis tools, such as MATLAB/SIMULINK, has revolutionised practice in Control Engineering. Concepts that were previously only understandable after sustained mathematical analysis or experimental work may now be readily simulated on the computer. Over the past four years, the author has experimented with the use of MATLAB/SIMULINK, in the lecture and laboratory environment, with degree and taught masters students in control engineering at Dublin Institute of Technology (DIT). It has been found that the tool helps to increase student understanding of challenging topics, to act as motivation to further exploration …

Harmonic Distortion Caused By Ev Battery Chargers In The Distribution Systems Network And Its Remedy, Malabika Basu, Kevin Gaughan, Eugene Coyle

Conference papers

An effective way to minimise harmonic pollution in power systems is by careful design of the equipment connected to them. It is important for designers of equipment associated with emerging technologies to be aware of the potential impact of their designs on power system quality. One such upcoming technology is electric vehicle (EV) battery charging which may contribute to high harmonic distortion in the power system during the charging period. The literature notes total harmonic distortion of up to 50%. These findings are the impetus behind the present paper, where an EV battery charger has been designed, with an inherent …

Enhancing Process Performance Through Automatic Control, Aidan O'Dwyer

Conference papers

The proportional integral derivative (PID) controller is the most dominant form of automatic controller in industrial use today. With this technique, it is necessary to adjust the controller parameters according to the nature of the process. Thus, for effective control of a pasteurisation process, for example, specific values need to be chosen for the P, I and D parameters, which will be different for the values required to control, for example, a distillation column. This tailoring of controller to process is known as controller tuning.

Energy Aware Design And Analysis For Synchronous And Asynchronous Circuits, Jia Di

Retrospective Theses and Dissertations

Power dissipation has become a major concern for IC designers. Various low power design techniques have been developed for synchronous circuits. Asynchronous circuits, however. have gained more interests recently due to their benefits in lower noise, easy timing control, etc. But few publications on energy reduction techniques for asynchronous logic are available.

Power awareness indicates the ability of the system power to scale with changing conditions and quality requirements. Scalability is an important figure-of-merit since it allows the end user to implement operational policy. just like the user of mobile multimedia equipment needs to select between better quality and longer …

Modified Sierpinski Fractal Antenna, Tripti Luintel

Electronic Theses and Dissertations

Fractal antennas have the potential to provide multi-band solution through the property of self similarity that the fractal shape possess. This thesis deals with some modifications of the original Sierpinski fractal patch antenna, providing additional parameters to optimize in order to get the required radiation characteristics. A systematic study of the original Sierpinski monopole was done to gain an insight on the operation and multi-band behavior of the antenna and a similar study was done to find out why the patch version of Sierpinski lacks multi-band behavior. A Sierpinski antenna is designed by merging a grid and the fractal restoring …

Evaluation Of A Microwave Radiative Transfer Model For Calculating Sat, Simonetta Thompson

Electronic Theses and Dissertations

Remote sensing is the process of gathering and analyzing information about the earth's ocean, land and atmosphere using electromagnetic "wireless" techniques. Mathematical models, known as Radiative Transfer Models (RTM), are developed to calculate the observed radiance (brightness temperature) seen by the remote sensor. The RTM calculated brightness temperature is a function of fourteen environmental parameters, including atmospheric profiles of temperature, pressure and moisture, sea surface temperature, and cloud liquid water. Input parameters to the RTM model include data from NOAA Centers for Environmental Prediction (NCEP), Reynolds weekly Sea Surface Temperature and National Ocean Data Center (NODC) WOA98 Ocean Salinity and …

Thermal Management, Beam Control,And Packaging Designs For High Power, Te-Yuan Chung

Electronic Theses and Dissertations

Several novel techniques for controlling, managing and utilizing high power diode lasers are described. Low pressure water spray cooling for a high heat flux system is developed and proven to be an ideal cooling method for high power diode laser arrays. In order to enable better thermal and optical performance of diode laser arrays, a new and simple optical element, the beam control prism, is invented. It provides the ability to accomplish beam shaping and beam tilting at the same time. Several low thermal resistance diode packaging designs using beam control prisms are proposed, studied and produced. Two pump cavity …

Minimization Of Power Dissipation In Digital Circuits Using Pipelining And A Study Of Clock Gating Technique, Ranganath Panchangam

Electronic Theses and Dissertations

Power dissipation is one of the major design issues of digital circuits. The power dissipated by a circuit affects its speed and performance. Multiplier is one of the most commonly used circuits in the digital devices. There are various types of multipliers available depending upon the application in which they are used. In the present thesis report, the importance of power dissipation in today's digital technology is discussed and the various types and sources of power dissipation have been elaborated. Different types of multipliers have been designed which vary in their structure and amount of power dissipation. The concept of …

Autonomous Environmental Mapping In Multi-Agent Uav Systems, Linus Jan Luotsinen

Electronic Theses and Dissertations

UAV units are by many researchers and aviation specialists considered the future and cutting edge of modern flight technology. This thesis discusses methods for efficient autonomous environmental mapping in a multi-agent domain. An algorithm that emphasizes on team work by sharing the agents local map information and exploration intentions is presented as a solution to the mapping problem. General theories on how to model and implement rational autonomous behaviour for UAV agents are presented. Three different human and tactical behaviour modeling techniques are evaluated. The author found the CxBR paradigm to be the most interesting approach. Also, in order to …

Cryptarray A Scalable And Reconfigurable Architecture For Cryptographic Applications, Michael John Lomonaco

Electronic Theses and Dissertations

Cryptography is increasingly viewed as a critical technology to fulfill the requirements of security and authentication for information exchange between Internet applications. However, software implementations of cryptographic applications are unable to support the quality of service from a bandwidth perspective required by most Internet applications. As a result, various hardware implementations, from Application-Specific Integrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs), to programmable processors, were proposed to improve this inadequate quality of service. Although these implementations provide performances that are considered better than those produced by software implementations, they still fall short of addressing the bandwidth requirements of most cryptographic applications …

Planar Magnetics Design For Low-Voltage Dc-Dc Converters, Shangyang Xiao

Electronic Theses and Dissertations

The objectives of this thesis are to design planar magnetic devices based on accurate electromagnetic analysis and miniaturize magnetics within desired low profile as well as small footprint. A novel methodology based on FEM simulation is proposed. By introducing Maxwell 2D simulator, optimal interleaving structures can be found to reduce AC losses that cannot otherwise be accounted for by conventional method. And 3D simulator is employed to make the results more realistic. Thus, high-efficiency high-power density magnetics is achieved.

Performance Analysis Of Low-Power, Short-Range Wireless Transceivers, Usha Neupane

Electronic Theses and Dissertations

To address the various emerging standards like BluetoothTM, Home RF, Wi-fiTM (IEEE 802.11), ZigBeeTM etc., in the field of wireless communications, different transceivers have been designed to operate at various frequencies such as 450 MHz, 902-920 MHz, 2.4 GHz, all part of designated ISM band. Though, the wireless systems have become more reliable, compact and easy to develop than before, a detailed performance analysis and characterization of the devices should be done. This report details the performance analysis and characterization of a popular binary FSK transceiver TRF6901 from Texas Instruments. The performance analysis of the device is done with respect …