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Articles 1 - 30 of 37
Full-Text Articles in Electrical and Computer Engineering
Thin 3d Multiplication Regions In Plasmonically Enhanced Nanopillar Avalanche Detectors, Pradeep Senanayake, Chung-Hong Hung, Alan C. Farrell, David A. Ramirez, Joshua Shapiro, Chi-Kang Li, Yuh-Renn Wu, Majeed M. Hayat, Diana L. Huffaker
Thin 3d Multiplication Regions In Plasmonically Enhanced Nanopillar Avalanche Detectors, Pradeep Senanayake, Chung-Hong Hung, Alan C. Farrell, David A. Ramirez, Joshua Shapiro, Chi-Kang Li, Yuh-Renn Wu, Majeed M. Hayat, Diana L. Huffaker
Electrical and Computer Engineering Faculty Research and Publications
We demonstrate a nanopillar (NP) device structure for implementing plasmonically enhanced avalanche photodetector arrays with thin avalanche volumes (∼ 310 nm × 150 nm × 150 nm). A localized 3D electric field due to a core–shell PN junction in a NP acts as a multiplication region, while efficient light absorption takes place via surface plasmon polariton Bloch wave (SPP-BW) modes due to a self-aligned metal nanohole lattice. Avalanche gains of ∼216 at 730 nm at −12 V are obtained. We show through capacitance–voltage characterization, temperature-dependent breakdown measurements, and detailed device modeling that the avalanche region is on the order of …
Stress Monitoring Of Post-Processed Mems Silicon Microbridge Structures Using Raman Spectroscopy, Lavern A. Starman, Ronald A. Coutu Jr.
Stress Monitoring Of Post-Processed Mems Silicon Microbridge Structures Using Raman Spectroscopy, Lavern A. Starman, Ronald A. Coutu Jr.
Electrical and Computer Engineering Faculty Research and Publications
Inherent residual stresses during material deposition can have profound effects on the functionality and reliability of fabricated Micro-Electro-Mechanical Systems (MEMS) devices. Residual stress often causes device failure due to curling, buckling, or fracture. Typically, the material properties of thin films used in surface micromachining are not well controlled during deposition. The residual stress; for example, tends to vary significantly for different deposition methods. Currently, few nondestructive techniques are available to measure residual stress in MEMS devices prior to the final release etch. In this research, micro-Raman spectroscopy is used to measure the residual stresses in polysilicon MEMS microbridge devices. This …
Fabrication Process Comparison And Dynamics Evaluation Of Electrothermal Actuators For A Prototype Mems Safe And Arming Devices, Scott A. Ostrow Ii, Robert A. Lake, J. P. Lombardi Iii, Ronald A. Coutu Jr., Lavern A. Starman
Fabrication Process Comparison And Dynamics Evaluation Of Electrothermal Actuators For A Prototype Mems Safe And Arming Devices, Scott A. Ostrow Ii, Robert A. Lake, J. P. Lombardi Iii, Ronald A. Coutu Jr., Lavern A. Starman
Electrical and Computer Engineering Faculty Research and Publications
Electrothermal actuators fabricated using the Polysilicon Multi-User MEMS Process (PolyMUMPs) and the Sandia Ultra-Planar, Multi-Level MEMS Technology 5 (SUMMiT V) have been investigated for use in integrated microelectromechanical systems (MEMS) safe and arming devices. The fabricated electrothermal actuators have been dynamically tested to determine and compare the responses of devices from both processes. Furthermore, the integration of these devices into a safe and arming device were tested and investigated for each process. Initial results indicate that the SUMMiT devices provide the most optimum results based on consistency of operation and reliability.
Sar-Based Vibration Estimation Using The Discrete Fractional Fourier Transform, Qi Wang, Matthew Pepin, Ryan J. Beach, Ralf Dunkel, Tom Atwood, Balu Santhanam, Walter Gerstle, Armin W. Doerry, Majeed M. Hayat
Sar-Based Vibration Estimation Using The Discrete Fractional Fourier Transform, Qi Wang, Matthew Pepin, Ryan J. Beach, Ralf Dunkel, Tom Atwood, Balu Santhanam, Walter Gerstle, Armin W. Doerry, Majeed M. Hayat
Electrical and Computer Engineering Faculty Research and Publications
A vibration estimation method for synthetic aperture radar (SAR) is presented based on a novel application of the discrete fractional Fourier transform (DFRFT). Small vibrations of ground targets introduce phase modulation in the SAR returned signals. With standard preprocessing of the returned signals, followed by the application of the DFRFT, the time-varying accelerations, frequencies, and displacements associated with vibrating objects can be extracted by successively estimating the quasi-instantaneous chirp rate in the phase-modulated signal in each subaperture. The performance of the proposed method is investigated quantitatively, and the measurable vibration frequencies and displacements are determined. Simulation results show that the …
Analysis Of The Detection Of Organophosphate Pesticides In Aqueous Solutions Using Polymer-Coated Sh-Saw Sensor Arrays, Tian Newman
Master's Theses (2009 -)
The shear horizontal surface acoustic wave (SH-SAW) device was investigated as a micro-chemical sensor for the direct, rapid and in-situ monitoring of chemical contaminants in groundwater and wastewater. The chemical contaminants of interest are organo-phosphate-based compounds (parathion, parathion-methyl, and paraoxon). The polymers used as partially chemically selective coatings are 2,2’-diallylbisphenol A - 1,1,3,3,5,5-hexamethyltrisiloxane (BPA-HMTS), and 2,2’-diallylbisphenol A- polydimethylsiloxane (BPA-PDMS), polyepichlorohydrin (PECH). The experimental results indicate that the analyte/polymer interaction is a result of mass loading and viscoelastic changes in the polymer. BPA-HMTS, BPA-PDMS, and PECH have the highest to lowest sensitivity towards parathion, parathion-methyl, and paraoxon respectively. The polymers tested …
Modeling And Control Of A Doubly-Fed Induction Generator For Wind Turbine-Generator Systems, Xin Jing
Modeling And Control Of A Doubly-Fed Induction Generator For Wind Turbine-Generator Systems, Xin Jing
Master's Theses (2009 -)
Wind energy plays an increasingly important role in the world because it is friendly to the environment. During the last decades, the concept of a variable-speed wind turbine (WT) has been receiving increasing attention due to the fact that it is more controllable and efficient, and has good power quality. As the demand of controllability of variable speed WTs increases, it is therefore important and necessary to investigate the modeling for wind turbine-generator systems (WTGS) that are capable of accurately simulating the behavior of each component in the WTGS. Therefore, this thesis will provide detailed models of a grid-connected wind …
Investigating A Horizontal Helical Antenna For Use In The Phantom Monopole Configuration, Mattison Lemieux
Investigating A Horizontal Helical Antenna For Use In The Phantom Monopole Configuration, Mattison Lemieux
Master's Theses (2009 -)
Recently, the phantom monopole configuration was successfully simulated using wire loop antennas. The wire loop antennas have an undesirable input impedance, making them difficult to match and implement. A new type of antenna that has a more desirable impedance while still maintaining the same near magnetic field and far field radiation pattern is investigated in this work. The research done focuses on a horizontally placed helical antenna. There is little research done on a horizontally placed helical antenna so several different parameters of this antenna were investigated. A normal mode helical antenna was chosen because of its size and impedance. …
Hybrid Coupler Implemented As A Phase Shifter, John P. Vitale
Hybrid Coupler Implemented As A Phase Shifter, John P. Vitale
Master's Theses (2009 -)
Phase shifters are two-port microwave devices which take an input signal and output a phase shifted version of the signal. These devices can be used in phased antenna arrays, frequency translators, and IQ modulator/demodulator systems. The goal for this work is to construct a hybrid coupler phase shifter which will provide a 90 degree phase shift to a signal with a center frequency of 1800 MHz over a 5% bandwidth. This work is novel because the hybrid coupler phase shifter has not been extensively studied. Some papers have provided rough guidelines for constructing these shifters, but there is little exploration …
Electroluminescence From Zno Nanostructure Synthesizes Between Nanogap, Cheng Jiang
Electroluminescence From Zno Nanostructure Synthesizes Between Nanogap, Cheng Jiang
Master's Theses (2009 -)
This thesis presents the investigation of a nanoscale light-emitting diode (LED) device. The nanoscale LED has a great potential to be used as a light source for biomedical screening and fluorescence lifetime spectroscopy. It can also be developed to a single photon emitter for the application of quantum computing. The nano-LED has the electrical structure of a metal-semiconductor-metal (MSM) junction. The MSM junction has been formed on the nanogap device that is fabricated on a SOI wafer by optical lithography and KOH solution silicon etching. The Ni evaporated on the surface of the nanogap device performs the metal contact for …
Noise Impacts From Professional Dog Grooming Forced-Air Dryers, Peter M. Scheifele, Michael T. Johnson, David C. Byrne, John G. Clark, Ashley Vandlik, Laura W. Kretschmer, Kristine E. Sonstrom
Noise Impacts From Professional Dog Grooming Forced-Air Dryers, Peter M. Scheifele, Michael T. Johnson, David C. Byrne, John G. Clark, Ashley Vandlik, Laura W. Kretschmer, Kristine E. Sonstrom
Electrical and Computer Engineering Faculty Research and Publications
This study was designed to measure the sound output of four commonly used brands of forced-air dryers used by dog groomers in the United States. Many dog groomers have questions about the effect of this exposure on their hearing, as well as on the hearing of the dogs that are being groomed. Readings taken from each dryer at 1 meter (the likely distance of the dryer from the groomer and the dog) showed average levels ranging from 105.5 to 108.3 dB SPL or 94.8 to 108.0 dBA. Using the 90 dBA criterion required by the US Occupational Safety and Health …
Bayesian Speaker Adaptation Based On A New Hierarchical Probabilistic Model, Wen-Lin Zhang, Wei-Qiang Zhang, Bi-Cheng Li, Dan Qu, Michael T. Johnson
Bayesian Speaker Adaptation Based On A New Hierarchical Probabilistic Model, Wen-Lin Zhang, Wei-Qiang Zhang, Bi-Cheng Li, Dan Qu, Michael T. Johnson
Electrical and Computer Engineering Faculty Research and Publications
In this paper, a new hierarchical Bayesian speaker adaptation method called HMAP is proposed that combines the advantages of three conventional algorithms, maximum a posteriori (MAP), maximum-likelihood linear regression (MLLR), and eigenvoice, resulting in excellent performance across a wide range of adaptation conditions. The new method efficiently utilizes intra-speaker and inter-speaker correlation information through modeling phone and speaker subspaces in a consistent hierarchical Bayesian way. The phone variations for a specific speaker are assumed to be located in a low-dimensional subspace. The phone coordinate, which is shared among different speakers, implicitly contains the intra-speaker correlation information. For a specific speaker, …
Ambient Habitat Noise And Vibration At The Georgia Aquarium, Peter M. Scheifele, Michael T. Johnson, Laura W. Kretschmer, John G. Clark, D. Kemper, G. Potty
Ambient Habitat Noise And Vibration At The Georgia Aquarium, Peter M. Scheifele, Michael T. Johnson, Laura W. Kretschmer, John G. Clark, D. Kemper, G. Potty
Electrical and Computer Engineering Faculty Research and Publications
Underwater and in-air noise evaluations were completed in performance pool systems at Georgia Aquarium under normal operating conditions and with performance sound tracks playing. Ambient sound pressure levels at in-pool locations, with corresponding vibration measures from life support system (LSS) pumps, were measured in operating configurations, from shut down to full operation. Results indicate noise levels in the low frequency ranges below 100 Hz were the highest produced by the LSS relative to species hearing thresholds. The LSS had an acoustic impact of about 10 dB at frequencies up to 700 Hz, with a 20 dB re 1 μPa impact …
Unconventional Uses Of Microcantilevers As Chemical Sensors In Gas And Liquid Media, I. Dufour, Fabien Josse, Stephen M. Heinrich, C. Lucat, C. Ayela, F. Ménil, O. Brand
Unconventional Uses Of Microcantilevers As Chemical Sensors In Gas And Liquid Media, I. Dufour, Fabien Josse, Stephen M. Heinrich, C. Lucat, C. Ayela, F. Ménil, O. Brand
Electrical and Computer Engineering Faculty Research and Publications
The use of microcantilevers as (bio)chemical sensors usually involves the application of a chemically sensitive layer. The coated device operates either in a static bending regime or in a dynamic flexural mode. While some of these coated devices may be operated successfully in both the static and the dynamic modes, others may suffer from certain shortcomings depending on the type of coating, the medium of operation and the sensing application. Such shortcomings include lack of selectivity and reversibility of the sensitive coating and a reduced quality factor due to the surrounding medium. In particular, the performance of microcantilevers excited in …
Performance And Reliability Of Non-Markovian Heterogeneous Distributed Computing Systems, Jorge E. Pezoa, Majeed M. Hayat
Performance And Reliability Of Non-Markovian Heterogeneous Distributed Computing Systems, Jorge E. Pezoa, Majeed M. Hayat
Electrical and Computer Engineering Faculty Research and Publications
Average service time, quality-of-service (QoS), and service reliability associated with heterogeneous parallel and distributed computing systems (DCSs) are analytically characterized in a realistic setting for which tangible, stochastic communication delays are present with nonexponential distributions. The departure from the traditionally assumed exponential distributions for event times, such as task-execution times, communication arrival times and load-transfer delays, gives rise to a non-Markovian dynamical problem for which a novel age dependent, renewal-based distributed queuing model is developed. Numerical examples offered by the model shed light on the operational and system settings for which the Markovian setting, resulting from employing an exponential-distribution assumption …
Design, Analysis, And Construction Of An Equal Split Wilkinson Power Divider, Logan J. Berens
Design, Analysis, And Construction Of An Equal Split Wilkinson Power Divider, Logan J. Berens
Master's Theses (2009 -)
The Wilkinson power divider is a well known device in the RF/microwave community used for splitting or combining signals. It is composed of simple transmission lines and a resistor, and takes advantage of the properties of quarter-wavelength transmission line sections to provide ideal power divider characteristics. Three different equal split Wilkinson power dividers are designed to operate near 1800 MHz and constructed using typical microstrip fabrication techniques. The three power dividers each feature a unique design to help determine how the microstrip layout can impact isolation and return loss. A circuit analysis of the general Wilkinson power divider schematic is …
Multivariate Temporal Patterns Detection Using Reconstructed Phase Space And Gaussian Mixture Model In Dynamic Data System, Xin Feng, Wenjing Zhang
Multivariate Temporal Patterns Detection Using Reconstructed Phase Space And Gaussian Mixture Model In Dynamic Data System, Xin Feng, Wenjing Zhang
Electrical and Computer Engineering Faculty Research and Publications
No abstract provided.
Finite-Time Control And Estimation Of Nonlinear Systems With Disturbance Attenuation, Mohammad N. Elbsat
Finite-Time Control And Estimation Of Nonlinear Systems With Disturbance Attenuation, Mohammad N. Elbsat
Dissertations (1934 -)
This dissertation addresses the mixed criteria finite-time bounded controller and observer design of certain classes of nonlinear systems. Finite-time bounded controllers and observers are used to guarantee performance bounds on the transient response of the systems considered. A robust and resilient mixed criteria state-feedback controller design is developed for a class of nonlinear systems with conic-type nonlinearities lying within a hypersphere of uncertain center, additive disturbances, and controller gain perturbations in discrete and continuous-time. Furthermore, a robust and resilient mixed criteria state-dependent state-feedback controller design is developed for a class of nonlinear systems with state dependent system matrices and state-dependent …
Modeling And Parametric Design Of Permanent-Magnet Ac Machines Using Computationally Efficient Finite-Element Analysis, Gennadi Y. Sizov, Dan M. Ionel, Nabeel Demerdash
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 …
Using Inductance As A Tuning Parameter For Rf Meta-Atoms, Derrick Langley, Ronald A. Coutu Jr., Peter J. Collins
Using Inductance As A Tuning Parameter For Rf Meta-Atoms, Derrick Langley, Ronald A. Coutu Jr., Peter J. Collins
Electrical and Computer Engineering Faculty Research and Publications
The resonant frequency of metamaterials structured with split ring resonator (SRR) meta-atoms is determined primarily through the capacitance and inductance of the individual meta-atoms. Two designs that vary inductance incrementally were modeled, simulated, fabricated, and tested to investigate the role inductance plays in metamaterial designs. The designs consisted of strategically adding sections to the SRR to increase the inductance, but in a manner that minimized capacitance variations. Each design showed a shift in resonant frequency that was proportional to the length of the added section. As the length of each section was increased, the resonant frequency shifted from 2.78 GHz …
Fault-Tolerant Operation Of Delta-Connected Scalar- And Vector-Controlled Ac Motor Drives, Ahmed Mohamed Sayed Ahmed, Nabeel Demerdash
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 …
Wireless Medical Sensor Networks: Design Requirements And Enabling Technologies, Cecilia H. Vallejos De Schatz, Henry P. Medeiros, Fabio K. Schneider, Paulo J. Abatti
Wireless Medical Sensor Networks: Design Requirements And Enabling Technologies, Cecilia H. Vallejos De Schatz, Henry P. Medeiros, Fabio K. Schneider, Paulo J. Abatti
Electrical and Computer Engineering Faculty Research and Publications
This article analyzes wireless communication protocols that could be used in healthcare environments (e.g., hospitals and small clinics) to transfer real-time medical information obtained from noninvasive sensors. For this purpose the features of the three currently most widely used protocols—namely, Bluetooth® (IEEE 802.15.1), ZigBee (IEEE 802.15.4), and Wi-Fi (IEEE 802.11)—are evaluated and compared. The important features under consideration include data bandwidth, frequency band, maximum transmission distance, encryption and authentication methods, power consumption, and current applications. In addition, an overview of network requirements with respect to medical sensor features, patient safety and patient data privacy, quality of service, and interoperability …
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
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 …
Phone Lattice Reconstruction For Embedded Language Recognition In Lvcsr, Yuxiang Shan, Yan Deng, Jia Liu, Michael T. Johnson
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 …
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
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 …
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
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 …
Low-Loss Meta-Atom For Improved Resonance Response, Derrick Langley, Ronald A. Coutu Jr., Peter J. Collins
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.
Analyzing Logistic Map Pseudorandom Number Generators For Periodicity Induced By Finite Precision Floating-Point Representation, Kyle Persohn, Richard J. Povinelli
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 …
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
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 …
A Suspended Nanogap Formed By Field-Induced Atomically Sharp Tips, Jun Hyun Han, Kyung Song, Shankar Radhakrishnan, Sang Ho Oh, Chung Hoon Lee
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 …
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
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 …