Open Access. Powered by Scholars. Published by Universities.®

Computer Engineering Commons™

Open Access. Powered by Scholars. Published by Universities.®

Marquette University

Discipline
Keyword
Publication Year
Publication
Publication Type
File Type

Articles 271 - 300 of 411

Full-Text Articles in Computer Engineering

Modeling And Parametric Design Of Permanent-Magnet Ac Machines Using Computationally Efficient Finite-Element Analysis, Gennadi Y. Sizov, Dan M. Ionel, Nabeel Demerdash Jun 2012

Modeling And Parametric Design Of Permanent-Magnet Ac Machines Using Computationally Efficient Finite-Element Analysis, Gennadi Y. Sizov, Dan M. Ionel, Nabeel Demerdash

Electrical and Computer Engineering Faculty Research and Publications

Computationally efficient finite-element analysis (FEA) (CE-FEA) fully exploits the symmetries of electric and magnetic circuits of sine-wave current-regulated synchronous machines and yields substantial savings of computational efforts. Motor performance is evaluated through Fourier analysis and a minimum number of magnetostatic solutions. The major steady-state performance indices (average torque, ripple and cogging torque, back-electromotive-force waveforms, and core losses) are satisfactorily estimated as compared with the results of detailed time-stepping (transient) FEA. In this paper, the CE-FEA method is presented and applied to a parametric design study for an interior-permanent-magnet machine. Significant reduction of simulation times is achieved (approximately two orders of …

Go to article

Fault-Tolerant Operation Of Delta-Connected Scalar- And Vector-Controlled Ac Motor Drives, Ahmed Mohamed Sayed Ahmed, Nabeel Demerdash Jun 2012

Fault-Tolerant Operation Of Delta-Connected Scalar- And Vector-Controlled Ac Motor Drives, Ahmed Mohamed Sayed Ahmed, Nabeel Demerdash

Electrical and Computer Engineering Faculty Research and Publications

Operation and analysis of delta-connected ac motor-drive systems under fault-tolerant open-phase mode of operation is introduced in this paper for both scalar- and vector-controlled motor-drive systems. This technique enables the operation of the three-phase motor upon a failure in one of its phases without the need of a special fault-detection algorithm. It is mainly used to significantly mitigate torque pulsations, which are caused by an open-delta configuration in the stator windings. The performance of the fault-tolerant system was verified using a detailed time stepping finite element simulation as well experimental tests for a 5-hp 460-V induction motor-drive system and the …

Go to article

Analysis Of The Detection Of Organophosphate Pesticides In Aqueous Solutions Using Hydrogen-Bond Acidic Coating On Sh-Saw Devices, Arnold Kweku Mensah-Brown, Darlington Mlambo, Fabien Josse Phd, Susan C. Schneider Phd May 2012

Analysis Of The Detection Of Organophosphate Pesticides In Aqueous Solutions Using Hydrogen-Bond Acidic Coating On Sh-Saw Devices, Arnold Kweku Mensah-Brown, Darlington Mlambo, Fabien Josse Phd, Susan C. Schneider Phd

Electrical and Computer Engineering Faculty Research and Publications

The work presented in this paper focuses on the synthesis and characterization of a hybrid organic/inorganic chemically sensitive layer for rapid detection and analysis of OPs in aqueous solutions using SH-SAW devices. Coated SH-SAW devices on 36° YX-LiTaO and 42.75° YX-Quartz (ST-90° X Quartz), are used to determine the optimum operating conditions for achieving rapid sensor responses with high sensitivity. Three analytes (parathion-methyl, parathion, and paraoxon), having similar molecular mass and volume, are used to evaluate the performance of the hybrid organic/inorganic coating in terms of sensor properties of interest including sensitivity, selectivity, reproducibility. It is shown that the coating …

Go to article

Phone Lattice Reconstruction For Embedded Language Recognition In Lvcsr, Yuxiang Shan, Yan Deng, Jia Liu, Michael T. Johnson Apr 2012

Phone Lattice Reconstruction For Embedded Language Recognition In Lvcsr, Yuxiang Shan, Yan Deng, Jia Liu, Michael T. Johnson

Electrical and Computer Engineering Faculty Research and Publications

An increasing number of multilingual applications require language recognition (LRE) as a frontend, but desire low additional computational cost. This article demonstrates a novel architecture for embedding phone based language recognition into a large vocabulary continuous speech recognition (LVCSR) decoder by sharing the same decoding process but generating separate lattices. To compensate for the prior bias introduced by the pronunciation dictionary and the language model of the LVCSR decoder, three different phone lattice reconstruction algorithms are proposed. The underlying goals of these algorithms are to override pronunciation and grammar restrictions to provide richer phonetic information. All of the new algorithms …

Go to article

Srrs Embedded With Mems Cantilevers To Enable Electrostatic Tuning Of The Resonant Frequency, E. A. Moore, Derrick Langley, Matthew E. Jussaume, L. A. Rederis, C. A. Lundell, Ronald A. Coutu Jr., Peter J. Collins, Lavern A. Starman Apr 2012

Srrs Embedded With Mems Cantilevers To Enable Electrostatic Tuning Of The Resonant Frequency, E. A. Moore, Derrick Langley, Matthew E. Jussaume, L. A. Rederis, C. A. Lundell, Ronald A. Coutu Jr., Peter J. Collins, Lavern A. Starman

Electrical and Computer Engineering Faculty Research and Publications

A microelectromechanical systems (MEMS) cantilever array was monolithically fabricated in the gap region of a split ring resonator (SRR) to enable electrostatic tuning of the resonant frequency. The design consisted of two concentric SRRs each with a set of cantilevers extending across the split region. The cantilever array consisted of five beams that varied in length from 300 to 400 μm, with each beam adding about 2 pF to the capacitance as it actuated. The entire structure was fabricated monolithically to reduce its size and minimize losses from externally wire bonded components. The beams actuate one at a time, longest …

Go to article

Geometrical Considerations For The Design Of Liquid-Phase Biochemical Sensors Using A Cantilever's Fundamental In-Plane Mode, L. A. Beardslee, Fabien Josse, Stephen M. Heinrich, I. Dufour, O. Brand Mar 2012

Geometrical Considerations For The Design Of Liquid-Phase Biochemical Sensors Using A Cantilever's Fundamental In-Plane Mode, L. A. Beardslee, Fabien Josse, Stephen M. Heinrich, I. Dufour, O. Brand

Electrical and Computer Engineering Faculty Research and Publications

The influence of the beam geometry on the quality factor and resonance frequency of resonant silicon cantilever beams vibrating in their fundamental in-plane flexural mode in water has been investigated. Compared to cantilevers vibrating in their first out-of-plane flexural mode, utilizing the in-plane mode results in reduced damping and reduced mass loading by the surrounding fluid. Quality factors as high as 86 have been measured in water for cantilevers with a 20 μm thick silicon layer. Based on the experimental data, design guidelines are established for beam dimensions that ensure maximal Q-factors and minimal mass loading by the surrounding …

Go to article

Low-Loss Meta-Atom For Improved Resonance Response, Derrick Langley, Ronald A. Coutu Jr., Peter J. Collins Mar 2012

Low-Loss Meta-Atom For Improved Resonance Response, Derrick Langley, Ronald A. Coutu Jr., Peter J. Collins

Electrical and Computer Engineering Faculty Research and Publications

Measurements of a meta-atom integrated with a low noise amplifier into the split-ring resonator are presented. A comparison is made between baseline meta-atoms and one integrated with a GaAs low noise amplifier. S-parameter measurements in a RF strip-line show the resonant frequency location. The resonance null is more prominent for the integrated meta-atom. Biasing the low noise amplifier from 0 to 7 VDC showed that the resonant null improved with biasing voltage. As the biasing voltage increases, the transmission null reduced from -11.82 to -23.21 dB for biases from 0 to 7 VDC at resonant frequency.

Go to article

(Mu-Ctl-01-12) Towards Model Driven Game Engineering In Simsys: Requirements For The Agile Software Development Process Game, C. Shaun Longstreet, Kendra M. L. Cooper Mar 2012

(Mu-Ctl-01-12) Towards Model Driven Game Engineering In Simsys: Requirements For The Agile Software Development Process Game, C. Shaun Longstreet, Kendra M. L. Cooper

Center for Teaching and Learning Technical Reports

Software Engineering (SE) and Systems Engineering (Sys) are knowledge intensive, specialized, rapidly changing disciplines; their educational infrastructure faces significant challenges including the need to rapidly, widely, and cost effectively introduce new or revised course material; encourage the broad participation of students; address changing student motivations and attitudes; support undergraduate, graduate and lifelong learning; and incorporate the skills needed by industry. Games have a reputation for being fun and engaging; more importantly immersive, requiring deep thinking and complex problem solving. We believe educational games are essential in the next generation of e-learning tools. An extensible, freely available, engaging, problem-based game platform …

Go to article

Analyzing Logistic Map Pseudorandom Number Generators For Periodicity Induced By Finite Precision Floating-Point Representation, Kyle Persohn, Richard J. Povinelli Mar 2012

Analyzing Logistic Map Pseudorandom Number Generators For Periodicity Induced By Finite Precision Floating-Point Representation, Kyle Persohn, Richard J. Povinelli

Electrical and Computer Engineering Faculty Research and Publications

Because of the mixing and aperiodic properties of chaotic maps, such maps have been used as the basis for pseudorandom number generators (PRNGs). However, when implemented on a finite precision computer, chaotic maps have finite and periodic orbits. This manuscript explores the consequences finite precision has on the periodicity of a PRNG based on the logistic map. A comparison is made with conventional methods of generating pseudorandom numbers. The approach used to determine the number, delay, and period of the orbits of the logistic map at varying degrees of precision (3 to 23 bits) is described in detail, including the …

Go to article

Distributed Multichannel Speech Enhancement With Minimum Mean-Square Error Short-Time Spectral Amplitude, Log-Spectral Amplitude, And Spectral Phase Estimation, Marek B. Trawicki, Michael T. Johnson Feb 2012

Distributed Multichannel Speech Enhancement With Minimum Mean-Square Error Short-Time Spectral Amplitude, Log-Spectral Amplitude, And Spectral Phase Estimation, Marek B. Trawicki, Michael T. Johnson

Electrical and Computer Engineering Faculty Research and Publications

In this paper, the authors present optimal multichannel frequency domain estimators for minimum mean-square error (MMSE) short-time spectral amplitude (STSA), log-spectral amplitude (LSA), and spectral phase estimation in a widely distributed microphone configuration. The estimators utilize Rayleigh and Gaussian statistical models for the speech prior and noise likelihood with a diffuse noise field for the surrounding environment. Based on the Signal-to-Noise Ratio (SNR) and Segmental Signal-to-Noise Ratio (SSNR) along with the Log-Likelihood Ratio (LLR) and Perceptual Evaluation of Speech Quality (PESQ) as objective metrics, the multichannel LSA estimator decreases background noise and speech distortion and increases speech quality compared to …

Go to article

A Mems Photoacoustic Detector Of Terahertz Radiation For Chemical Sensing, Nathan Glauvitz, S. Blazevic, Ronald A. Coutu Jr., Michael Kistler, Ivan R. Medvedev, Douglas T. Petkie Jan 2012

A Mems Photoacoustic Detector Of Terahertz Radiation For Chemical Sensing, Nathan Glauvitz, S. Blazevic, Ronald A. Coutu Jr., Michael Kistler, Ivan R. Medvedev, Douglas T. Petkie

Electrical and Computer Engineering Faculty Research and Publications

A piezoelectric Microelectromechanical system (MEMS) cantilever pressure sensor was designed, modeled, fabricated, and tested for sensing the photoacoustic response of gases to terahertz (THz) radiation. The sensing layers were comprised of three thin films; a lead zirconate titanate (PZT) piezoelectric layer sandwiched between two metal contact layers. The sensor materials were deposited on the silicon device layer of a silicon-on-insulator (SOI) wafer, which formed the physical structure of the cantilever. To release the cantilever, a hole was etched through the backside of the wafer and the buried oxide was removed with hydrofluoric acid. Devices were then tested in a custom …

Go to article

Characterizing Metal-Insulator-Transition (Mit) Phase Change Materials (Pcm) For Rf And Dc Micro-Switching Elements, Brent L. Danner, Ronald A. Coutu Jr. Jan 2012

Characterizing Metal-Insulator-Transition (Mit) Phase Change Materials (Pcm) For Rf And Dc Micro-Switching Elements, Brent L. Danner, Ronald A. Coutu Jr.

Electrical and Computer Engineering Faculty Research and Publications

Metal-insulator transition (MIT) phase-change materials (PCM) are material compounds that have the ability to be either conductors or insulators depending on external stimuli. A micromachined test structure for applying external electric fields across MIT wire segments was designed and fabricated. Using this novel test structure, Germanium Telluride (GeTe) and Vanadium Oxide (VOx) were successfully transitioned from a conductor to an insulator. The resistivity of the GeTe wire segments increased three to five orders of magnitude with ∼40 V applied to the parallel plates of the test structure. The VOx wires exhibited an order of magnitude transition in resistivity with ∼20 …

Go to article

Continuous Time-Varying Biasing Approach For Spectrally Tunable Infrared Detectors, Woo-Yong Jang, Majeed M. Hayat, Payman Zarkesh-Ha, Sanjay Krishna Jan 2012

Continuous Time-Varying Biasing Approach For Spectrally Tunable Infrared Detectors, Woo-Yong Jang, Majeed M. Hayat, Payman Zarkesh-Ha, Sanjay Krishna

Electrical and Computer Engineering Faculty Research and Publications

In a recently demonstrated algorithmic spectral-tuning technique by Jang et al. [Opt. Express 19, 19454-19472, (2011)], the reconstruction of an object’s emissivity at an arbitrarily specified spectral window of interest in the long-wave infrared region was achieved. The technique relied upon forming a weighted superposition of a series of photocurrents from a quantum dots-in-a-well (DWELL) photodetector operated at discrete static biases that were applied serially. Here, the technique is generalized such that a continuously varying biasing voltage is employed over an extended acquisition time, in place using a series of fixed biases over each sub-acquisition time, which totally …

Go to article

Multiplication Theory For Dynamically Biased Avalanche Photodiodes: New Limits For Gain Bandwidth Product, Majeed M. Hayat, David A. Ramirez Jan 2012

Multiplication Theory For Dynamically Biased Avalanche Photodiodes: New Limits For Gain Bandwidth Product, Majeed M. Hayat, David A. Ramirez

Electrical and Computer Engineering Faculty Research and Publications

Novel theory is developed for the avalanche multiplication process in avalanche photodiodes (APDs) under time-varying reverse-biasing conditions. Integral equations are derived characterizing the statistics of the multiplication factor and the impulse-response function of APDs, as well as their breakdown probability, all under the assumption that the electric field driving the avalanche process is time varying and spatially nonuniform. Numerical calculations generated by the model predict that by using a bit-synchronous sinusoidal biasing scheme to operate the APD in an optical receiver, the pulse-integrated gain-bandwidth product can be improved by a factor of 5 compared to the same APD operating under …

Go to article

A Suspended Nanogap Formed By Field-Induced Atomically Sharp Tips, Jun Hyun Han, Kyung Song, Shankar Radhakrishnan, Sang Ho Oh, Chung Hoon Lee Jan 2012

A Suspended Nanogap Formed By Field-Induced Atomically Sharp Tips, Jun Hyun Han, Kyung Song, Shankar Radhakrishnan, Sang Ho Oh, Chung Hoon Lee

Electrical and Computer Engineering Faculty Research and Publications

A sub-nanometer scale suspended gap (nanogap) defined by electric field-induced atomically sharp metallic tips is presented. A strong local electric field (>109 V=m) across micro/nanomachined tips facing each other causes the metal ion migration in the form of dendrite-like growth at the cathode. The nanogap is fully isolated from the substrate eliminating growth mechanisms that involve substrate interactions. The proposed mechanism of ion transportation is verified using real-time imaging of the metal ion transportation using an in situ biasing in transmission electron microscope (TEM). The configuration of the micro/nanomachined suspended tips allows nanostructure growth of a wide variety of …

Go to article

A New Ensemble Learning Method For Temporal Pattern Identification, Wenjing Zhang, Xin Feng Jan 2012

A New Ensemble Learning Method For Temporal Pattern Identification, Wenjing Zhang, Xin Feng

Electrical and Computer Engineering Faculty Research and Publications

In this paper we present a method for identification of temporal patterns predictive of significant events in a dynamic data system. A new hybrid model using Reconstructed Phase Space (MRPS) and Hidden Markov Model (HMM) is applied to identify temporal patterns. This method constructs phase space embedding by using individual embedding of each variable sequences. We also employ Hidden Markov Models (HMM) to the multivariate sequence data to categorize multi-dimensional data into three states, e.g. normal, patterns and events. A support vector machine optimization method is used to search an optimal classifier to identify temporal patterns that are predictive of …

Go to article

A Very Robust Algan/Gan Hemt Technology To High Forward Gate Bias And Current, Bradley D. Christiansen, Eric R. Heller, Ronald A. Coutu Jr., Ramakrishna Vetury, Jeffrey B. Shealy Jan 2012

A Very Robust Algan/Gan Hemt Technology To High Forward Gate Bias And Current, Bradley D. Christiansen, Eric R. Heller, Ronald A. Coutu Jr., Ramakrishna Vetury, Jeffrey B. Shealy

Electrical and Computer Engineering Faculty Research and Publications

Reports to date of GaN HEMTs subjected to forward gate bias stress include varied extents of degradation. We report an extremely robust GaN HEMT technology that survived—contrary to conventional wisdom—high forward gate bias (+6 V) and current (>1.8 A/mm) for >17.5 hours exhibiting only a slight change in gate diode characteristic, little decrease in maximum drain current, with only a 0.1 V positive threshold voltage shift, and, remarkably, a persisting breakdown voltage exceeding 200 V.

Go to article

New Perspective On Passively Quenched Single Photon Avalanche Diodes: Effect Of Feedback On Impact Ionization, David A. Ramirez, Majeed M. Hayat, Graham J. Rees, Xudong Jiang, Mark A. Itzler Jan 2012

New Perspective On Passively Quenched Single Photon Avalanche Diodes: Effect Of Feedback On Impact Ionization, David A. Ramirez, Majeed M. Hayat, Graham J. Rees, Xudong Jiang, Mark A. Itzler

Electrical and Computer Engineering Faculty Research and Publications

Single-photon avalanche diodes (SPADs) are primary devices in photon counting systems used in quantum cryptography, time resolved spectroscopy and photon counting optical communication. SPADs convert each photo-generated electron hole pair to a measurable current via an avalanche of impact ionizations. In this paper, a stochastically self-regulating avalanche model for passively quenched SPADs is presented. The model predicts, in qualitative agreement with experiments, three important phenomena that traditional models are unable to predict. These are: (1) an oscillatory behavior of the persistent avalanche current; (2) an exponential (memoryless) decay of the probability density function of the stochastic quenching time of the …

Go to article

Electrostatically Tunable Meta-Atoms Integrated With In Situ Fabricated Mems Cantilever Beam Arrays, Ronald A. Coutu Jr., Peter J. Collins, Elizabeth A. Moore, Derrick Langley, Matthew E. Jussaume, Lavern A. Starman Oct 2011

Electrostatically Tunable Meta-Atoms Integrated With In Situ Fabricated Mems Cantilever Beam Arrays, Ronald A. Coutu Jr., Peter J. Collins, Elizabeth A. Moore, Derrick Langley, Matthew E. Jussaume, Lavern A. Starman

Electrical and Computer Engineering Faculty Research and Publications

Two concentric split ring resonators (SRRs) or meta-atoms designed to have a resonant frequency of 14 GHz are integrated with microelectromechanical systems cantilever arrays to enable electrostatic tuning of the resonant frequency. The entire structure was fabricated monolithically to improve scalability and minimize losses from externally wire-bonded components. A cantilever array was fabricated in the gap of both the inner and outer SRRs and consisted of five evenly spaced beams with lengths ranging from 300 to 400 μm. The cantilevers pulled in between 15 and 24 V depending on the beam geometry. Each pulled-in beam increased the SRR gap capacitance …

Go to article

Stochastically Resilient Observer Design For A Class Of Continuous-Time Nonlinear Systems, Chung Seop Jeong, Edwin E. Yaz, Yvonne I. Yaz Sep 2011

Stochastically Resilient Observer Design For A Class Of Continuous-Time Nonlinear Systems, Chung Seop Jeong, Edwin E. Yaz, Yvonne I. Yaz

Electrical and Computer Engineering Faculty Research and Publications

This work addresses the design of stochastically resilient or non-fragile continuous-time Luenberger observers for systems with incrementally conic nonlinearities. Such designs maintain the convergence and/or performance when the observer gain is erroneously implemented due possibly to computational errors i.e. round off errors in computing the observer gain or changes in the observer parameters during operation. The error in the observer gain is modeled as a random process and a common linear matrix inequality formulation is presented to address the stochastically resilient observer design problem for a variety of performance criteria. Numerical examples are given to illustrate the theoretical results.

Go to article

Robust And Resilient Finite-Time Control Of A Class Of Discrete-Time Nonlinear Systems, Mohammad N. Elbsat, Edwin E. Yaz Sep 2011

Robust And Resilient Finite-Time Control Of A Class Of Discrete-Time Nonlinear Systems, Mohammad N. Elbsat, Edwin E. Yaz

Electrical and Computer Engineering Faculty Research and Publications

In this paper, we address the finite-time state-feedback stabilization of a class of discrete-time nonlinear systems with conic type nonlinearities, bounded feedback control gain perturbations, and additive disturbances. Sufficient conditions for the existence of a robust and resilient linear state feedback controller for this class of systems are derived. Then, using linear matrix inequality techniques, a solution for the controller gain is obtained. The developed controller is robust for all unknown nonlinearities lying in a hyper-sphere and all admissible disturbances. Moreover, it is resilient against any bounded perturbations that may alter the controller’s gain by at most a prescribed amount. …

Go to article

Robust And Resilient State Dependent Control Of Discrete-Time Nonlinear Systems With General Performance Criteria, Xin Wang, Edwin E. Yaz, Yvonne I. Yaz Sep 2011

Robust And Resilient State Dependent Control Of Discrete-Time Nonlinear Systems With General Performance Criteria, Xin Wang, Edwin E. Yaz, Yvonne I. Yaz

Electrical and Computer Engineering Faculty Research and Publications

A novel state dependent control approach for discrete-time nonlinear systems with general performance criteria is presented. This controller is robust for unstructured model uncertainties, resilient against bounded feedback control gain perturbations in achieving optimality for general performance criteria to secure quadratic optimality with inherent asymptotic stability property together with quadratic dissipative type of disturbance reduction. For the system model, unstructured uncertainty description is assumed, which incorporates commonly used types of uncertainties, such as norm-bounded and positive real uncertainties as special cases. By solving a state dependent linear matrix inequality at each time step, sufficient condition for the control solution can …

Go to article

Characterizing Multi-Walled Carbon Nanotube Synthesis For Field Emission Applications, Benjamin L. Crossley, Nathan Glauvitz, Betty T. Quinton, Ronald A. Coutu Jr., Peter J. Collins Aug 2011

Characterizing Multi-Walled Carbon Nanotube Synthesis For Field Emission Applications, Benjamin L. Crossley, Nathan Glauvitz, Betty T. Quinton, Ronald A. Coutu Jr., Peter J. Collins

Electrical and Computer Engineering Faculty Research and Publications

No abstract provided.

Go to article

Novel Microelectromechanical Systems Image Reversal Fabrication Process Based On Robust Su-8 Masking Layers, Scott A. Ostrow Ii, Ronald A. Coutu Jr. Jul 2011

Novel Microelectromechanical Systems Image Reversal Fabrication Process Based On Robust Su-8 Masking Layers, Scott A. Ostrow Ii, Ronald A. Coutu Jr.

Electrical and Computer Engineering Faculty Research and Publications

This paper discusses a novel fabrication process that uses a combination of negative and positive photoresists with positive tone photomasks, resulting in masking layers suitable for bulk micromachining high-aspect ratio microelectromechanical systems (MEMS) devices. MicroChem's negative photoresist Nano™ SU-8 and Clariant's image reversal photoresist AZ 5214E are utilized, along with a barrier layer, to effectively convert a positive photomask into a negative image. This technique utilizes standard photolithography chemicals, equipment, and processes, and opens the door for creating complementary MEMS structures without added fabrication delay and cost. Furthermore, the SU-8 masking layer is robust enough to withstand aggressive etch chemistries …

Go to article

Fault-Tolerant Technique For Δ-Connected Ac-Motor Drives, Ahmed Mohamed Sayed Ahmed, Behrooz Mirafzal, Nabeel Demerdash Jun 2011

Fault-Tolerant Technique For Δ-Connected Ac-Motor Drives, Ahmed Mohamed Sayed Ahmed, Behrooz Mirafzal, Nabeel Demerdash

Electrical and Computer Engineering Faculty Research and Publications

A fault-tolerant technique for motor-drive systems is introduced in this paper. The technique is merely presented for ac motors with Δ-connected circuits in their stator windings. In this technique, the faulty phase is isolated by solid-state switches after the occurrence of a failure in one of the stator phases. Then, the fault-tolerant technique manages current-flow in the remaining healthy phases. This technique is to significantly mitigate torque pulsations, which are caused by an open-Δ configuration in the stator windings. The performance of the fault-tolerant technique was experimentally verified using a 5-hp 460-V induction motor-drive system and the results are presented …

Go to article

Multispectral Classification With Bias-Tunable Quantum Dots-In-A-Well Focal Plane Arrays, Biliana S. Paskaleva, Woo-Yong Jang, Yagya D. Sharma, Sanjay Krishna, Majeed M. Hayat Jun 2011

Multispectral Classification With Bias-Tunable Quantum Dots-In-A-Well Focal Plane Arrays, Biliana S. Paskaleva, Woo-Yong Jang, Yagya D. Sharma, Sanjay Krishna, Majeed M. Hayat

Electrical and Computer Engineering Faculty Research and Publications

Mid-wave and long-wave infrared (IR) quantum-dots-in-a-well (DWELL) focal plane arrays (FPAs) are promising technology for multispectral (MS) imaging and sensing. The DWELL structure design provides the detector with a unique property that allows the spectral response of the detector to be continuously, albeit coarsely, tuned with the applied bias. In this paper, a MS classification capability of the DWELL FPA is demonstrated. The approach is based upon: 1) imaging an object repeatedly using a sequence of bias voltages in the tuning range of the FPA and then 2) applying a classification algorithm to the totality of readouts, over multiple biases, …

Go to article

Reliability Testing Of Algan/Gan Hemts Under Multiple Stressors, Bradley D. Christiansen, Ronald A. Coutu Jr., Eric R. Heller, Brian S. Poling, Glen D. Via, Ramakrishna Vetury, Jeffrey B. Shealy Apr 2011

Reliability Testing Of Algan/Gan Hemts Under Multiple Stressors, Bradley D. Christiansen, Ronald A. Coutu Jr., Eric R. Heller, Brian S. Poling, Glen D. Via, Ramakrishna Vetury, Jeffrey B. Shealy

Electrical and Computer Engineering Faculty Research and Publications

We performed an experiment on AlGaN/GaN HEMTs with high voltage and high power as stressors. We found that devices tested under high power generally degraded more than those tested under high voltage. In particular, the high-voltage-tested devices did not degrade significantly as suggested by some papers in the literature. The same papers in the literature also suggest that high voltages cause cracks and pits. However, the high-voltage-tested devices in this study do not exhibit cracks or pits in TEM images, while the high-power-tested devices exhibit pits.

Go to article

Propagation Of Plate Acoustic Waves In Contact With Fluid Medium, Nagaraj Ghatadi Suraji Apr 2011

Propagation Of Plate Acoustic Waves In Contact With Fluid Medium, Nagaraj Ghatadi Suraji

Master's Theses (2009 -)

The characteristics of acoustic waves propagating in thin piezoelectric plates in the presence of a fluid medium contacting one or both of the plate surfaces are investigated. If the velocity of plate wave in the substrate is greater than velocity of bulk wave in the fluid, then a plate acoustic wave (PAW) traveling in the substrate will radiate a bulk acoustic wave (BAW) in the fluid. It is found that, under proper conditions, efficient conversion of energy from plate acoustic waves to bulk acoustic waves and vice versa can be obtained. For example, using the fundamental anti symmetric plate wave …

Go to article

Sensitivity Of High-Speed Lightwave System Receivers Using Inalas Avalanche Photodiodes, Daniel S.G. Ong, Majeed M. Hayat, John P.R. David, Jo Shien Ng Feb 2011

Sensitivity Of High-Speed Lightwave System Receivers Using Inalas Avalanche Photodiodes, Daniel S.G. Ong, Majeed M. Hayat, John P.R. David, Jo Shien Ng

Electrical and Computer Engineering Faculty Research and Publications

Calculations based on a rigorous analytical model are carried out to compare the sensitivity of optical receivers that use InP and In0.52Al0.48As avalanche photodiodes (APDs). The model includes the effects of intersymbol interference, tunneling current, avalanche noise and its correlation with the stochastic avalanche duration, dead space, and transimpedance amplifier noise. For a 10-Gb/s system with a bit-error rate of 10-12, the optimum receiver sensitivity predicted for In0.52Al0.48As and InP APDs is -28.6 and -28.1 dBm, respectively, corresponding to a reduction of 11% in optical signal power for receivers using …

Go to article

Versatile Spectral Imaging With An Algorithm-Based Spectrometer Using Highly Tuneable Quantum Dot Infrared Photodetectors, Peter Vines, Chee Hing Tan, John P.R. David, Ram S. Attaluri, Thomas E. Vanderveldt, Sanjay Krishna, Woo-Yong Jang, Majeed M. Hayat Feb 2011

Versatile Spectral Imaging With An Algorithm-Based Spectrometer Using Highly Tuneable Quantum Dot Infrared Photodetectors, Peter Vines, Chee Hing Tan, John P.R. David, Ram S. Attaluri, Thomas E. Vanderveldt, Sanjay Krishna, Woo-Yong Jang, Majeed M. Hayat

Electrical and Computer Engineering Faculty Research and Publications

We report on the implementation of an algorithm-based spectrometer capable of reconstructing the spectral shape of materials in the mid-wave infrared (MWIR) and long-wave infrared (LWIR) wavelengths using only experimental photocurrent measurements from quantum dot infrared photodetectors (QDIPs). The theory and implementation of the algorithm will be described, followed by an investigation into this algorithmic spectrometer's performance. Compared to the QDIPs utilized in an earlier implementation, the ones used here have highly varying spectral shapes and four spectral peaks across the MWIR and LWIR wavelengths. It has been found that the spectrometer is capable of reconstructing broad spectral features of …

Go to article

First Prev Next Last