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Articles 211 - 240 of 388
Full-Text Articles in Computer Engineering
Model-Based Edge Detector For Spectral Imagery Using Sparse Spatiospectral Masks, Biliana S. Paskaleva, Sebastian E. Godoy, Woo-Yong Jang, Steven C. Bender, Sanjay Krishna, Majeed M. Hayat
Model-Based Edge Detector For Spectral Imagery Using Sparse Spatiospectral Masks, Biliana S. Paskaleva, Sebastian E. Godoy, Woo-Yong Jang, Steven C. Bender, Sanjay Krishna, Majeed M. Hayat
Electrical and Computer Engineering Faculty Research and Publications
Two model-based algorithms for edge detection in spectral imagery are developed that specifically target capturing intrinsic features such as isoluminant edges that are characterized by a jump in color but not in intensity. Given prior knowledge of the classes of reflectance or emittance spectra associated with candidate objects in a scene, a small set of spectral-band ratios, which most profoundly identify the edge between each pair of materials, are selected to define a edge signature. The bands that form the edge signature are fed into a spatial mask, producing a sparse joint spatiospectral nonlinear operator. The first algorithm achieves edge …
A Novel On-Chip Three-Dimensional Micromachined Calorimeter With Fully Enclosed And Suspended Thin-Film Chamber For Thermal Characterization Of Liquid Samples, Benyamin Davaji, Hye Jeong Bak, Woo-Jin Chang, Chung-Hoon Lee
A Novel On-Chip Three-Dimensional Micromachined Calorimeter With Fully Enclosed And Suspended Thin-Film Chamber For Thermal Characterization Of Liquid Samples, Benyamin Davaji, Hye Jeong Bak, Woo-Jin Chang, Chung-Hoon Lee
Electrical and Computer Engineering Faculty Research and Publications
A microfabricated calorimeter (μ-calorimeter) with an enclosed reaction chamber is presented. The 3D micromachined reaction chamber is capable of analyzing liquid samples with volume of 200 nl. The thin film low-stress silicon nitride membrane is used to reduce thermal mass of the calorimeter and increase the sensitivity of system. The μ-calorimeter has been designed to perform DC and AC calorimetry, thermal wave analysis, and differential scanning calorimetry. The μ-calorimeter fabricated with an integrated heater and a temperature sensor on opposite sides of the reaction chamber allows to perform thermal diffusivity and specific heat measurements on liquid samples with same device. …
Evaluation Of The Importance Of Time-Frequency Contributions To Speech Intelligibility In Noise, Chengzhu Yu, Kamil K. Wójcicki, Philipos C. Loizou, John H. L. Hansen, Michael T. Johnson
Evaluation Of The Importance Of Time-Frequency Contributions To Speech Intelligibility In Noise, Chengzhu Yu, Kamil K. Wójcicki, Philipos C. Loizou, John H. L. Hansen, Michael T. Johnson
Electrical and Computer Engineering Faculty Research and Publications
Recent studies on binary masking techniques make the assumption that each time-frequency (T-F) unit contributes an equal amount to the overall intelligibility of speech. The present study demonstrated that the importance of each T-F unit to speech intelligibility varies in accordance with speech content. Specifically, T-F units are categorized into two classes, speech-present T-F units and speech-absent T-F units. Results indicate that the importance of each speech-present T-F unit to speech intelligibility is highly related to the loudness of its target component, while the importance of each speech-absent T-F unit varies according to the loudness of its masker component. Two …
Using The K-Means Clustering Algorithm To Classify Features For Choropleth Maps, Mark Polczynski, Michael Polczynski
Using The K-Means Clustering Algorithm To Classify Features For Choropleth Maps, Mark Polczynski, Michael Polczynski
Electrical and Computer Engineering Faculty Research and Publications
Common methods for classifying choropleth map features typically form classes based on a single feature attribute. This technical note reviews the use of the k-means clustering algorithm to perform feature classification using multiple feature attributes. The k-means clustering algorithm is described and compared to other common classification methods, and two examples of choropleth maps prepared using k-means clustering are provided.
Reliability Of Heterogeneous Distributed Computing Systems In The Presence Of Correlated Failures, Jorge E. Pezoa, Majeed M. Hayat
Reliability Of Heterogeneous Distributed Computing Systems In The Presence Of Correlated Failures, Jorge E. Pezoa, Majeed M. Hayat
Electrical and Computer Engineering Faculty Research and Publications
While the reliability of distributed-computing systems (DCSs) has been widely studied under the assumption that computing elements (CEs) fail independently, the impact of correlated failures of CEs on the reliability remains an open question. Here, the problem of modeling and assessing the impact of stochastic, correlated failures on the service reliability of applications running on DCSs is tackled. The service reliability is modeled using an integrated analytical and Monte-Carlo (MC) approach. The analytical component of the model comprises a generalization of a previously developed model for reliability of non-Markovian DCSs to a setting where specific patterns of simultaneous failures in …
On The Use Of Gaussian Approximation In Analyzing The Performance Of Optical Receivers, George El-Howayek, C. Zhang, Y. Li, J. S. Ng, J. P.R. David, Majeed M. Hayat
On The Use Of Gaussian Approximation In Analyzing The Performance Of Optical Receivers, George El-Howayek, C. Zhang, Y. Li, J. S. Ng, J. P.R. David, Majeed M. Hayat
Electrical and Computer Engineering Faculty Research and Publications
The analytical calculation of the bit error rate (BER) of digital optical receivers that employ avalanche photodiodes (APDs) is challenging due to 1) the stochastic nature of the avalanche photodiode's impulse-response function and 2) the presence of intersymbol interference (ISI). At ultrafast transmission rates, ISI becomes a dominant component of the BER, and its effect on the BER should be carefully addressed. One solution to this problem, termed the bit-pattern-dependent (PD) approach, is to first calculate the conditional BER given a specific bit pattern and then average over all possible bit patterns. Alternatively, a simplifying method, termed the bit-pattern-independent (PI) …
Speech Enhancement Using Bayesian Estimators Of The Perceptually-Motivated Short-Time Spectral Amplitude (Stsa) With Chi Speech Priors, Marek B. Trawicki, Michael T. Johnson
Speech Enhancement Using Bayesian Estimators Of The Perceptually-Motivated Short-Time Spectral Amplitude (Stsa) With Chi Speech Priors, Marek B. Trawicki, Michael T. Johnson
Electrical and Computer Engineering Faculty Research and Publications
In this paper, the authors propose new perceptually-motivated Weighted Euclidean (WE) and Weighted Cosh (WCOSH) estimators that utilize more appropriate Chi statistical models for the speech prior with Gaussian statistical models for the noise likelihood. Whereas the perceptually-motivated WE and WCOSH cost functions emphasized spectral valleys rather than spectral peaks (formants) and indirectly accounted for auditory masking effects, the incorporation of the Chi distribution statistical models demonstrated distinct improvement over the Rayleigh statistical models for the speech prior. The estimators incorporate both weighting law and shape parameters on the cost functions and distributions. Performance is evaluated in terms of the …
Non-Local Model For The Spatial Distribution Of Impact Ionization Events In Avalanche Photodiodes, David A. Ramirez, Majeed M. Hayat, Andrew S. Huntington, George M. Williams
Non-Local Model For The Spatial Distribution Of Impact Ionization Events In Avalanche Photodiodes, David A. Ramirez, Majeed M. Hayat, Andrew S. Huntington, George M. Williams
Electrical and Computer Engineering Faculty Research and Publications
We report an extension of the analytical dead space multiplication theory that provides the means to theoretically determine the spatial distribution of electron and hole impact-ionization events in an arbitrarily specified heterojunction multiplication region. The model can be used to understand the role of the dead space in regularizing the locations of impact ionization. It can also be utilized to analyze, design, and optimize new generations of ultra-low noise, multistaged gain avalanche photodiodes based upon judiciously energizing and relaxing carriers to enhance electron impact ionization and suppress hole impact ionization.
Thermal Tuning Of Mems Buckled Membrane Actuator Stiffness, Robert A. Lake, Kyle K. Ziegler, Ronald A. Coutu Jr.
Thermal Tuning Of Mems Buckled Membrane Actuator Stiffness, Robert A. Lake, Kyle K. Ziegler, Ronald A. Coutu Jr.
Electrical and Computer Engineering Faculty Research and Publications
The thermal tuning characteristics of a microelectromechanical systems (MEMS) buckled membrane exhibiting regions of both positive and negative stiffness is examined and analyzed using finite element method (FEM) simulation and through experimentation. The membranes are fabricated by releasing a silicon/silicon dioxide (Si/SiO2) laminated membrane from a silicon on insulator (SOI) wafer. The difference in thermal expansion coefficients between Si and SiO2 induces a compressive stress in the SiO2 layer causing out-of-plane buckling of the membrane. This structure is found to have positive and negative stiffness regions when actuated with a transverse force. It is demonstrated that the …
Robust And Resilient State-Dependent Control Of Continuous-Time Nonlinear Systems With General Performance Criteria, Xin Wang, Edwin E. Yaz, James Long
Robust And Resilient State-Dependent Control Of Continuous-Time Nonlinear Systems With General Performance Criteria, Xin Wang, Edwin E. Yaz, James Long
Electrical and Computer Engineering Faculty Research and Publications
A novel state-dependent control approach for continuous-time nonlinear systems with general performance criteria is presented in this paper. This controller is optimally robust for model uncertainties and resilient against control feedback gain perturbations in achieving 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, sufficient condition for the control solution can be found …
Lightweight Data Compression In Wireless Sensor Networks Using Huffman Coding, Henry P. Medeiros, Marcos C. Maciel, Richard D. Souza, Marcelo E. Pellenz
Lightweight Data Compression In Wireless Sensor Networks Using Huffman Coding, Henry P. Medeiros, Marcos C. Maciel, Richard D. Souza, Marcelo E. Pellenz
Electrical and Computer Engineering Faculty Research and Publications
This paper presents a lightweight data compression method for wireless sensor networks monitoring environmental parameters with low resolution sensors. Instead of attempting to devise novel ad hoc algorithms, we show that, given general knowledge of the parameters that must be monitored, it is possible to efficiently employ conventional Huffman coding to represent the same parameter when measured at different locations and time periods. When the data collected by the sensor nodes consists of integer measurements, the Huffman dictionary computed using statistics inferred from public datasets often approaches the entropy of the data. Results using temperature and relative humidity measurements show …
Exploiting Contextual Information For Prosodic Event Detection Using Auto-Context, Junhong Zhao, Wei-Qiang Zhang, Hua Yang, Michael T. Johnson, Jia Liu, Shanhong Xia
Exploiting Contextual Information For Prosodic Event Detection Using Auto-Context, Junhong Zhao, Wei-Qiang Zhang, Hua Yang, Michael T. Johnson, Jia Liu, Shanhong Xia
Electrical and Computer Engineering Faculty Research and Publications
Prosody and prosodic boundaries carry significant information regarding linguistics and paralinguistics and are important aspects of speech. In the field of prosodic event detection, many local acoustic features have been investigated; however, contextual information has not yet been thoroughly exploited. The most difficult aspect of this lies in learning the long-distance contextual dependencies effectively and efficiently. To address this problem, we introduce the use of an algorithm called auto-context. In this algorithm, a classifier is first trained based on a set of local acoustic features, after which the generated probabilities are used along with the local features as contextual information …
Calculation Of Magnet Losses In Concentrated-Winding Permanent-Magnet Synchronous Machines Using A Computationally Efficient Finite-Element Method, Peng Zhang, Gennadi Y. Sizov, Jiangbiao He, Dan M. Ionel, Nabeel Demerdash
Calculation Of Magnet Losses In Concentrated-Winding Permanent-Magnet Synchronous Machines Using A Computationally Efficient Finite-Element Method, Peng Zhang, Gennadi Y. Sizov, Jiangbiao He, Dan M. Ionel, Nabeel Demerdash
Electrical and Computer Engineering Faculty Research and Publications
The proposed hybrid method combines computationally efficient finite-element analysis (CE-FEA) with a new analytical formulation for eddy-current losses in the permanent magnets (PMs) of sine-wave current-regulated brushless synchronous motors. The CE-FEA only employs a reduced set of magnetostatic solutions yielding substantial reductions in the computational time, as compared with the conventional FEA. The 3-D end effects and the effect of pulsewidth-modulation switching harmonics are incorporated in the analytical calculations. The algorithms are applied to two fractional-slot concentrated-winding interior PM motors with different circumferential and axial PM block segmentation arrangements. The method is validated against 2-D and 3-D time-stepping FEA.
Microelectromechanical Systems (Mems) Resistive Heaters As Circuit Protection Devices, Ronald A. Coutu Jr., Scott A. Ostrow
Microelectromechanical Systems (Mems) Resistive Heaters As Circuit Protection Devices, Ronald A. Coutu Jr., Scott A. Ostrow
Electrical and Computer Engineering Faculty Research and Publications
With increased opportunities for the exploitation (i.e., reverse engineering) of vulnerable electronic components and systems, circuit protection has become a critical issue. Circuit protection techniques are generally software-based and include cryptography (encryption/decryption), obfuscation of codes, and software guards. Examples of hardware-based circuit protection include protective coatings on integrated circuits, trusted foundries, and macro-sized components that self-destruct, thus destroying critical components. This paper is the first to investigate the use of microelectromechanical systems (MEMS) to provide hardware-based protection of critical electronic components to prevent reverse engineering or other exploitation attempts. Specifically, surface-micromachined polycrystalline silicon to be used as meandering resistive heaters …
A Review Of Micro-Contact Physics For Microelectromechanical Systems (Mems) Metal Contact Switches, Benjamin F. Toller, Ronald A. Coutu Jr., John W. Mcbride
A Review Of Micro-Contact Physics For Microelectromechanical Systems (Mems) Metal Contact Switches, Benjamin F. Toller, Ronald A. Coutu Jr., John W. Mcbride
Electrical and Computer Engineering Faculty Research and Publications
Innovations in relevant micro-contact areas are highlighted, these include, design, contact resistance modeling, contact materials, performance and reliability. For each area the basic theory and relevant innovations are explored. A brief comparison of actuation methods is provided to show why electrostatic actuation is most commonly used by radio frequency microelectromechanical systems designers. An examination of the important characteristics of the contact interface such as modeling and material choice is discussed. Micro-contact resistance models based on plastic, elastic-plastic and elastic deformations are reviewed. Much of the modeling for metal contact micro-switches centers around contact area and surface roughness. Surface roughness and …
Automated Multi-Objective Design Optimization Of Pm Ac Machines Using Computationally Efficient Fea And Differential Evolution, Gennadi Y. Sizov, Peng Zhang, Dan M. Ionel, Nabeel Demerdash, Marius Rosu
Automated Multi-Objective Design Optimization Of Pm Ac Machines Using Computationally Efficient Fea And Differential Evolution, Gennadi Y. Sizov, Peng Zhang, Dan M. Ionel, Nabeel Demerdash, Marius Rosu
Electrical and Computer Engineering Faculty Research and Publications
The design optimization methods described in this paper are employing an ultrafast computationally efficient finite element analysis technique. A minimum number of magnetostatic solutions are used for the analysis, which makes possible the study of thousands of candidate motor designs with typical PC-workstation computational resources. A multi-objective differential evolution algorithm that considers a large number of independent stator and rotor geometric variables and performance criteria, such as average and ripple torque, losses, and efficiency, is used. The optimization method is demonstrated on different permanent magnet (PM) ac synchronous motors in the kilowatt and megawatt power ranges. For the low-power PM …
An Efficient Cost Function For The Optimization Of An N-Layered Isotropic Cloaked Cylinder, Jason V. Paul, Peter J. Collins, Ronald A. Coutu Jr.
An Efficient Cost Function For The Optimization Of An N-Layered Isotropic Cloaked Cylinder, Jason V. Paul, Peter J. Collins, Ronald A. Coutu Jr.
Electrical and Computer Engineering Faculty Research and Publications
In this paper, we present an efficient cost function for optimizing n-layered isotropic cloaked cylinders. Cost function efficiency is achieved by extracting the expression for the angle independent scatterer contribution of an associated Green's function. Therefore, since this cost function is not a function of angle, accounting for every bistatic angle is not necessary and thus more efficient than other cost functions. With this general and efficient cost function, isotropic cloaked cylinders can be optimized for many layers and material parameters. To demonstrate this, optimized cloaked cylinders made of 10, 20 and 30 equal thickness layers are presented for …
Rnn Language Model With Word Clustering And Class-Based Output Layer, Yongzhe Shi, Wei-Qiang Zhang, Jia Liu, Michael T. Johnson
Rnn Language Model With Word Clustering And Class-Based Output Layer, Yongzhe Shi, Wei-Qiang Zhang, Jia Liu, Michael T. Johnson
Electrical and Computer Engineering Faculty Research and Publications
The recurrent neural network language model (RNNLM) has shown significant promise for statistical language modeling. In this work, a new class-based output layer method is introduced to further improve the RNNLM. In this method, word class information is incorporated into the output layer by utilizing the Brown clustering algorithm to estimate a class-based language model. Experimental results show that the new output layer with word clustering not only improves the convergence obviously but also reduces the perplexity and word error rate in large vocabulary continuous speech recognition.
Dual-Carrier High-Gain Low-Noise Superlattice Avalanche Photodiodes, Jun Huang, Koushik Banerjee, Siddhartha Ghosh, Majeed M. Hayat
Dual-Carrier High-Gain Low-Noise Superlattice Avalanche Photodiodes, Jun Huang, Koushik Banerjee, Siddhartha Ghosh, Majeed M. Hayat
Electrical and Computer Engineering Faculty Research and Publications
In this paper, novel avalanche photodiode structures with alternate carrier multiplication nanometer regions, placed next to a wider electron multiplication region, to create dual-carrier feedback systems, are proposed. Gain and excess noise factor of these structures are calculated based on the dead space multiplication theory under uniform electric field. In addition, the equivalent impact ionization ratios are derived and compared. It is observed that the proposed structures can generate much higher gain compared with conventional pure electron multiplication structures under the same electric field without severely degrading the excess noise quality. Excess noise is further optimized with careful adjustment of …
Robust And Resilient Finite-Time Bounded Control Of Discrete-Time Uncertain Nonlinear Systems, Mohammad N. Elbsat, Edwin E. Yaz
Robust And Resilient Finite-Time Bounded Control Of Discrete-Time Uncertain Nonlinear Systems, Mohammad N. Elbsat, Edwin E. Yaz
Electrical and Computer Engineering Faculty Research and Publications
Finite-time state-feedback stabilization is addressed for a class of discrete-time nonlinear systems with conic-type nonlinearities, bounded feedback control gain perturbations, and additive disturbances. First, 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 and the maximum allowable bound on the gain perturbation is obtained. The developed controller is robust for all unknown nonlinearities lying in a known hypersphere with an uncertain center and all admissible disturbances. Moreover, it is resilient against any bounded perturbations that may alter the …
Distributed Multichannel Speech Enhancement Based On Perceptually-Motivated Bayesian Estimators Of The Spectral Amplitude, Marek B. Trawicki, Michael T. Johnson
Distributed Multichannel Speech Enhancement Based On Perceptually-Motivated Bayesian Estimators Of The Spectral Amplitude, Marek B. Trawicki, Michael T. Johnson
Electrical and Computer Engineering Faculty Research and Publications
In this study, the authors propose multichannel weighted Euclidean (WE) and weighted cosh (WCOSH) cost function estimators for speech enhancement in the distributed microphone scenario. The goal of the work is to illustrate the advantages of utilising additional microphones and modified cost functions for improving signal-to-noise ratio (SNR) and segmental SNR (SSNR) along with log-likelihood ratio (LLR) and perceptual evaluation of speech quality (PESQ) objective metrics over the corresponding single-channel baseline estimators. As with their single-channel counterparts, the perceptually-motivated multichannel WE and WCOSH estimators are functions of a weighting law parameter, which influences attention of the noisy spectral amplitude through …
A Novel Batch-Processing Method For Accurate Crystallographic Axis Alignment, Jun Hyun Han, Shankar Radhakrishnan, Chung-Hoon Lee
A Novel Batch-Processing Method For Accurate Crystallographic Axis Alignment, Jun Hyun Han, Shankar Radhakrishnan, Chung-Hoon Lee
Electrical and Computer Engineering Faculty Research and Publications
A new method for the accurate alignment of lithographically-defined patterns to the crystallographic axes of substrates is presented. We provide a lower (worst-case) limit of the achievable high aspect ratio using anisotropic wet chemical silicon etch for deep trenches. The method uses the fact that the intensity of light reflected from two sets of gratings, one on the photomask and the other on the substrate, is a sharp function of their relative angular misalignment. By using pre-etched gratings on the substrate formed by wet anisotropic etching, alignment accuracies better than 50 millidegrees with respect to silicon crystallographic axes have been …
Using Micro-Raman Spectroscopy To Assess Mems Si/Sio2 Membranes Exhibiting Negative Spring Constant Behavior, Lavern A. Starman, Ronald A. Coutu Jr.
Using Micro-Raman Spectroscopy To Assess Mems Si/Sio2 Membranes Exhibiting Negative Spring Constant Behavior, Lavern A. Starman, Ronald A. Coutu Jr.
Electrical and Computer Engineering Faculty Research and Publications
We introduce a novel micro-mechanical structure that exhibits two regions of stable linear positive and negative stiffness. Springs, cantilevers, beams and any other geometry that display an increasing return force that is proportional to the displacement can be considered to have a “Hookean” positive spring constant, or stiffness. Less well known is the opposite characteristic of a reducing return force for a given deflection, or negative stiffness. Unfortunately many simple negative stiffness structures exhibit unstable buckling and require additional moving components during deflection to avoid deforming out of its useful shape. In Micro-Electro-Mechanical Systems (MEMS) devices, buckling caused by stress …
Discrimination Of Photon- And Dark-Initiated Signals In Multiple Gain Stage Apd Photoreceivers, George M. Williams, David A. Ramirez, Majeed M. Hayat, Andrew S. Huntington
Discrimination Of Photon- And Dark-Initiated Signals In Multiple Gain Stage Apd Photoreceivers, George M. Williams, David A. Ramirez, Majeed M. Hayat, Andrew S. Huntington
Electrical and Computer Engineering Faculty Research and Publications
We demonstrate the ability of linear mode single carrier multiplication (SCM) avalanche photodiode (APD)-based optical receivers to discriminate single-photon-initiated avalanche events from dark-current-initiated events. Because of their random spatial origin in discrete regions of the depletion region, in the SCM APD the dark-generated carriers multiply differently than the photon-generated carriers. This causes different count distributions and necessitates different statistical descriptions of the signal contributions from photon- and dark-originating impulse responses. To include dark carriers in the performance models of the SCM APD, we considered the influence of the spatial origin of the ionization chains on a receiver's noise performance over …
Discrimination Of Individual Tigers (Panthera Tigris) From Long Distance Roars, An Ji, Michael T. Johnson, Edward J. Walsh, Joann Mcgee, Douglas L. Armstrong
Discrimination Of Individual Tigers (Panthera Tigris) From Long Distance Roars, An Ji, Michael T. Johnson, Edward J. Walsh, Joann Mcgee, Douglas L. Armstrong
Electrical and Computer Engineering Faculty Research and Publications
This paper investigates the extent of tiger (Panthera tigris) vocal individuality through both qualitative and quantitative approaches using long distance roars from six individual tigers at Omaha's Henry Doorly Zoo in Omaha, NE. The framework for comparison across individuals includes statistical and discriminant function analysis across whole vocalization measures and statistical pattern classification using a hidden Markov model (HMM) with frame-based spectral features comprised of Greenwood frequency cepstral coefficients. Individual discrimination accuracy is evaluated as a function of spectral model complexity, represented by the number of mixtures in the underlying Gaussian mixture model (GMM), and temporal model complexity, …
Multi-Gain-Stage Ingaas Avalanche Photodiode With Enhanced Gain And Reduced Excess Noise, George M. Williams, Madison Compton, David A. Ramirez, Majeed M. Hayat, Andrew S. Huntington
Multi-Gain-Stage Ingaas Avalanche Photodiode With Enhanced Gain And Reduced Excess Noise, George M. Williams, Madison Compton, David A. Ramirez, Majeed M. Hayat, Andrew S. Huntington
Electrical and Computer Engineering Faculty Research and Publications
We report the design, fabrication, and test of an InGaAs avalanche photodiode (APD) for 950-1650 nm wavelength sensing applications. The APD is grown by molecular beam epitaxy on InP substrates from lattice-matched InGaAs and InAlAs alloys. Avalanche multiplication inside the APD occurs in a series of asymmetric gain stages whose layer ordering acts to enhance the rate of electron-initiated impact ionization and to suppress the rate of hole-initiated ionization when operated at low gain. The multiplication stages are cascaded in series, interposed with carrier relaxation layers in which the electric field is low, preventing avalanche feedback between stages. These measures …
A New Look At Azimuthal Wave Propagation Constants Of An N-Layered Dielectric Coated Pec Cylinder, Jason V. Paul, Peter J. Collins, Ronald A. Coutu Jr.
A New Look At Azimuthal Wave Propagation Constants Of An N-Layered Dielectric Coated Pec Cylinder, Jason V. Paul, Peter J. Collins, Ronald A. Coutu Jr.
Electrical and Computer Engineering Faculty Research and Publications
A method for determining the azimuthal wave propagation constants supported by an n-layered dielectric coated PEC cylinder is presented. The method, based on a Green's function described in , is designed to optimally handle layered cylinders where the number of layers is extremely large as might be encountered in structures designed using transformational optics. The method is also tractable for any stratification profile without the need for individual layer analysis. We implement a recently developed numerical method to calculate Bessel functions of complex order and argument. Our method is verified by comparison with previously published results. We also present new …
Time Resolved Gain And Excess Noise Properties Of Ingaas/Inalas Avalanche Photodiodes With Cascaded Discrete Gain Layer Multiplication Regions, Georges M. Williams, David A. Ramirez, Majeed M. Hayat, Andrew S. Huntington
Time Resolved Gain And Excess Noise Properties Of Ingaas/Inalas Avalanche Photodiodes With Cascaded Discrete Gain Layer Multiplication Regions, Georges M. Williams, David A. Ramirez, Majeed M. Hayat, Andrew S. Huntington
Electrical and Computer Engineering Faculty Research and Publications
To predict pulse detection performance when implemented in high speed photoreceivers, temporally resolved measurements of a 10-stage InAlAs/InGaAs single carrier multiplication (SCM) avalanche photodiode (APD)'s avalanche response to short multi-photon laser pulses were explained using instantaneous (time resolved) pulse height statistics of the device's impulse response. Numeric models of the junction carrier populations as a function of the time following injection of a primary photo-electron were used to create the probability density functions (pdfs) of the instances of the avalanche buildup process. The numeric pdfs were used to generate low frequency gain and excess noise models, which were in good …
Forecasting Natural Gas Demand For Electric Power Generation, Ronald H. Brown, George Corliss, Richard J. Povinelli
Forecasting Natural Gas Demand For Electric Power Generation, Ronald H. Brown, George Corliss, Richard J. Povinelli
Electrical and Computer Engineering Faculty Research and Publications
No abstract provided.
Effect Of Hydrodynamic Force On Microcantilever Vibrations: Applications To Liquid-Phase Chemical Sensing, I. Dufour, E. Lemaire, B. Caillard, H. Debeda, C. Lucat, Stephen M. Heinrich, Fabien Josse, O. Brand
Effect Of Hydrodynamic Force On Microcantilever Vibrations: Applications To Liquid-Phase Chemical Sensing, I. Dufour, E. Lemaire, B. Caillard, H. Debeda, C. Lucat, Stephen M. Heinrich, Fabien Josse, O. Brand
Electrical and Computer Engineering Faculty Research and Publications
At the microscale, cantilever vibrations depend not only on the microstructure’s properties and geometry but also on the properties of the surrounding medium. In fact, when a microcantilever vibrates in a fluid, the fluid offers resistance to the motion of the beam. The study of the influence of the hydrodynamic force on the microcantilever’s vibrational spectrum can be used to either (1) optimize the use of microcantilevers for chemical detection in liquid media or (2) extract the mechanical properties of the fluid. The classical method for application (1) in gas is to operate the microcantilever in the dynamic transverse bending …