Electrical and Computer Engineering Commons^™

Ti/Al/Ni/Au Ohmic Contacts For Alinn/Aln/Gan-Based Heterojunction Field-Effect Transistors, Lin Zhou, Jacob H. Leach, Xianfeng Ni, Hadis Morkoç, David J. Smith

Electrical and Computer Engineering Publications

The microstructure of AuNiAlTi/Al0.84In0.16N/AlN/GaNOhmic contacts annealed from 700 to 900 °C has been determined using transmission electron microscopy and associated analytical techniques. Intermixing and phase separation of the metal contact layers was observed to degrade the surface roughness. An optimal contact performance was obtained for contacts annealed at 800 °C and was attributed to the formation of TiN contact inclusions that had penetrated through the AlInN layers into the GaN layers underneath. These TiN contact inclusions had an inverted mushroom shape with a density of ∼108 cm−2, and they were invariably located at the positions of mixed-type threading dislocations. These …

Hot Electron Effects On Efficiency Degradation In Ingan Light Emitting Diodes And Designs To Mitigate Them, X. Ni, X. Li, J. Lee, S. Liu, V. Avrutin, Ü. Özgür, H. Morkoç, A. Matulionis

Electrical and Computer Engineering Publications

Hot electrons and the associated ballistic and quasiballistic transport, heretofore neglected endemically, across the active regions of InGaN light emitting diodes (LEDs) have been incorporated into a first order simple model which explains the experimental observations of electron spillover and the efficiency degradation at high injection levels. The model is in good agreement with experiments wherein an adjustable barrier hot electron stopper, commonly called the electron blocking layer (EBL), is incorporated. The model is also in agreement with experiments wherein the electrons are cooled, eliminating hot electrons, inside a staircase electron injector (SEI) prior to their injection into the active …

On The Use Of A Dynamic Hybrid Tempo Detection Model For Beat Tracking, Mikel Gainza

Conference papers

In this paper, an approach that estimates the times at which musical beats occur is presented. The system uses a hybrid multi-band decomposition in order to estimate the music tempo. Following this, beat events are tracked by using a dynamic programming approach, which is updated by using short time tempo estimates. The hybrid decomposition is used in order to calculate the tempo by using different onset detection functions in different frequency bands. In addition, a method that estimates which frequency bands provide reliable periodicities is also presented. The accuracy of the model is evaluated by comparing the presented system against …

Electromagnetic Fields, Power Losses, And Resistance Of High-Frequency Magnetic Devices, Daniel Joseph Whitman

Browse all Theses and Dissertations

The operation of dc-dc PWM converters requires magnetic components that operate at high frequencies and carry large currents. At such frequencies the skin and proximity effects cause a substantial increase in power losses and ac resistance. This thesis reviews existing one dimensional analytical work on the prediction of these losses and, beginning with an inductor, derives expressions for the electromagnetic fields and power losses within the winding as well as the ac resistance of the device. The results of the inductor analysis are then extended to examine these quantities in transformers of various winding configurations. It is shown that proximity …

Efficacy Of A Final Lab Practicum And Lab Reports For Assessment In A Fundamentals Electric Circuits Laboratory, Edward Carl Greco Jr., James D. Reasoner, Daniel W. Bullock, Carlos Castillo, Patricia Buford, Gill Richards

Faculty Publications - Electrical Engineering

In a fundamental electrical engineering laboratory course, the traditional team based approach to laboratory structure with two or more members per lab team was not as effective for teaching basic laboratory skills and knowledge as a lab structure that allowed students to perform laboratory exercises individually throughout the semester. The laboratory report was insensitive and insufficient to measure the difference in the laboratory abilities and knowledge from these two groups. In order to assess the students' laboratory knowledge and abilities, it was necessary to develop a new assessment instrument that would be sufficient for this purpose. The students' performance on …

Response-Calibration Techniques For Antenna-Coupled Infrared Sensors, Peter Krenz

Electronic Theses and Dissertations

Infrared antennas are employed in sensing applications requiring specific spectral, polarization, and directional properties. Because of their inherently small dimensions, there is significant interaction, both thermal and electromagnetic, between the antenna, the antenna-coupled sensor, and the low-frequency readout structures necessary for signal extraction at the baseband modulation frequency. Validation of design models against measurements requires separation of these effects so that the response of the antenna-coupled sensor alone can be measured in a calibrated manner. Such validations will allow confident extension of design techniques to more complex infrared-antenna configurations. Two general techniques are explored to accomplish this goal. The extraneous …

The Size Ellect On The Infrared Spectra Of Condensed Media Under Conditions Of Id, 2d And 3d Dielectric Confinement, Igor I. Shaganov, Tatiana S. Perova, Vasily A. Melnikov, Kevin Berwick

Articles

A general expression for the dielectric loss spectrum of an absorbing composite medium was obtained from a Maxwell-Garnett general equation. This expression was simplified for the cases of one, two and three dimensional dielectric confinement in both ordered and disordered thin layers, rods (wires) and spheres of absorbing medium which are considered as mesoparticles or mesoscopic molecules. This theoretical approach was verified experimentally using high purity organic liquids with strong absorption bands in the infrared range. Three organic liquids, namely benzene, chloroform and carbon disulphide, were measured in various dielectric confinement configurations using Fourier Transform Infrared (FTIR) spectroscopy with a …

Double Quantum Dot Photoluminescence Mediated By Incoherent Reversible Energy Transport, S. Yu Kruchinin, A. V. Federov, A. V. Baranov, T. S. Perova, Kevin Berwick

Articles

We present a theoretical study of the stationary photoluminescence of two, direct-gap, semiconductor nanocrystals, taking into account electronic excitation energy-transfer processes due to electrostatic interaction. The results obtained here allow for the incoherent reversible energy transport that occurs when the intraband relaxation rate in a quantum dot acceptor is comparable to, or less than, the energy-transfer rate. We investigate the secondary emission of two different electronic level schemes that can be realized experimentally, obtain analytical expressions for the luminescence differential cross section, and perform an analysis of its spectrum. It is shown that when excitation is not in resonance with …

A Macrobending Singlemode Fiber Refractive Index Sensor For Low Refractive Index Liquids, Pengfei Wang, Yuliya Semenova, Yong Li, Qiang Wu, Gerald Farrell

Articles

An all-fiber refractive index sensor with a simple configuration is proposed and investigated. The proposed fiber refractometer consists of a full-loop structure of bare high-bend loss singlemode fiber-1060XP, employing the well-known whispering gallery mode (WGM) effect induced by the evanescent wave excitation to measure the refractive index of an external medium. A competitive sensitivity is achieved (average 725.76nm/RIU at a bend diameter of 19.3mm) compared with other fiber-optic sensors, plus benefits resulting from simplicity, low cost and ease of fabrication.

Study Of The Effect Of Source Signal Bandwidth On Ratiometric Wavelength Measurement, Qiang Wu, Yuliya Semenova, Ginu Rajan, Pengfei Wang, Gerald Farrell

Articles

We derive an analytic equation for a ratiometric wavelength measurement system and analyze the influence of the optical source signal bandwidth. Our investigation shows that in a particular optical sensing system, the higher the bandwidth of the optical signal, the better resolution the system will achieve. Experiments based on two types of optical signals (output signal of a tunable laser and a fiber Bragg grating) were carried out, and experimental results verified both the simulation results and the theoretical analysis.

Fuzzy Logic Learning For Predictive Feedback Estimation In A Radiant Heat System, Matthew R. Rickey

Browse all Theses and Dissertations

High temperature thermal testing is used to validate the effectiveness of thermal protection systems (TPS) and to simulate aerodynamic heating in high speed flight vehicle structures. Silicon controlled rectifiers (SCR) are utilized to drive resistive heating elements and producing temperatures up to 5000 degrees Fahrenheit. Thermocouples used to provide feedback to the control system have a high probability of failure at extreme temperatures. Traditional solutions include switching to redundant thermocouples, changing to an open-loop control scheme, or using power as the control signal. The first methods is limited in that redundant thermocouples are also not completely reliable. Both open-loop control …

The Effects Of Harmonics On Power Quality And Energy Efficiency, Alan Harrison

Other resources

By making our electricity supply more secure, reliable and versatile will mean that we reduce our reliance upon oil, gas and solid fuels, which mostly exist outside of Ireland and the European community. The majority of our fuel is imported and this makes our economy dependent on outside interests and out of our control. Even more importantly as the world’s fossil fuel reserves are running out and electricity demand is ever increasing.

If we make our electricity networks secure and designed to the highest standards we can import and export electrical energy more easily as our demands change, for example …

Speed Control For Simple Heat Engine, Kat Devirgilio

Honors Capstone Projects and Theses

No abstract provided.

Toward A Distributed Actuation And Cognition Means For A Miniature Soft Robot, Xiaoting Yang

Electronic Theses and Dissertations

This thesis presents components of an on-going research project aimed towards developing a miniature soft robot for urban search and rescue (USAR). The three significant contributions of the thesis are verifying the water hammer actuation previous work, developing an estimator of water hammer impulse direction from hose shape, and creating the infrastructure for distributed cognitive networks. There are many technical issues in designing soft robots, in terms of perception, actuation, cognition, power, physical structure and so on. We are focusing on actuation and cognition issues in this thesis. We investigated water hammer actuation as an alternative system which provides a …

Facility Power Usage Modeling And Short Term Prediction With Artificial Neural Networks, Sunny Wan, Xiao-Hua Yu

Electrical Engineering

Residential and commercial buildings accounted for about 68% of the total U.S. electricity consumption in 2002. Improving the energy efficiency of buildings can save energy, reduce cost, and protect the global environment. In this research, artificial neural network is employed to model and predict the facility power usage of campus buildings. The prediction is based on the building power usage history and weather conditions such as temperature, humidity, wind speed, etc. Different neural network configurations are discussed; satisfactory computer simulation results are obtained and presented.

Multi-Node Toa-Doa Cooperative Los-Nlos Localization : Enabling High Accuracy And Reliability, Zhonghai Wang

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

This dissertation investigates high performance cooperative localization in wireless environments based on multi-node time-of-arrival (TOA) and direction-of-arrival (DOA) estimations in line-of-sight (LOS) and non-LOS (NLOS) scenarios. Here, two categories of nodes are assumed: base nodes (BNs) and target nodes (TNs). BNs are equipped with antenna arrays and capable of estimating TOA (range) and DOA (angle). TNs are equipped with Omni-directional antennas and communicate with BNs to allow BNs to localize TNs; thus, the proposed localization is maintained by BNs and TNs cooperation.

First, a LOS localization method is proposed, which is based on semi-distributed multi-node TOA-DOA fusion. The proposed technique …

2009/10 Research, Development, And Activities, College Of Engineering And Applied Sciences

Electrical and Computer Engineering Newsletter

• Design of iPhone Game Applications for the Eyes on the Earth Initiative
• Printed Electronics Research and Sensor Development
• Dual-Use Ground Vehicle Condition-Based Maintenance
• TS-Type Fuzzy Automaton for Software Agents
• NEW DEAN – College of Engineering & Applied Sciences
• Nonlinear Circuits and Systems Laboratory
• ECE supporting Sunseeker Solar Rayce Team
• DOE Strategic Training and Education in Power Systems (STEPS) Funding

Ab Initio Simulations Of Hydrogen And Lithium Adsorption On Silicene, Tim H. Osborn

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The energies and temperature-dependent dynamics of hydrogen and lithium chemisorption on a silicon nanosheet, called silicene, were studied using density functional theory and molecular-dynamics (MD) simulations. Silicene has a buckled honeycomb structure, and has been fabricated as suspended monolayer sheets and nanoribbons in recent experiments. We calculated the adsorption energies of hydrogen and lithium on silicene for different adsorption ratios between 3.1% and 100%. The studies will clarify the characteristics of these novel and promising nanomaterials, and pave the way for their applications.

For Hydrogen, the adsorption energy had a maximum of 3.01 eV/H for complete hydrogenation, and decreased by …

On Iterative Decoding Of Two-Level Superposition Codes For Cooperative Broadcasting Based On Qpsk And 4-Pam Constellations, Robert H. Morelos-Zaragoza

Faculty Publications

This paper considers iterative decoding of two-level superposition codes used in cooperative broadcasting over wireless networks. The coding scheme consists of two low-density parity-check (LDPC) codes combined using Plotkin's |u|u + v|-construction and provides two levels of error protection. Coding for cooperative broadcasting differs from conventional single-source broadcast coding. Instead of binary addition of subcode codewords performed by a single-source encoder, in superposition coding two modulated subcode sequences, produced by two coordinated and independent sources, are combined at the antenna of the receiver. Expressions are derived for the bit metrics, or log-likelihood ratio values, used by an iterative decoder for …

Analysis And Design Of A Feedback Controlled Adaptive Pneumatic Cast, Susan Renee Mueller

Electronic Theses and Dissertations

A pneumatic system with PID control for an actively controlled cast is designed. The cast is intended to aid healing of diabetic foot ulcers by relieving pressure from the sole of a patient's foot and distributing it to the calf. This is accomplished by a pneumatic system which maintains set pressure in multiple air bladders. The research began by defining an electrical circuit analogous to a single supply subsystem. Tests are performed to determine the coefficients for each component. These coefficients are used in a mathematical model to better understand the response of the system to pressure input. A controller …