Computer Engineering Commons^™

Probabilistic Anomaly Detection In Natural Gas Time Series Data, Hermine Nathalie Akouemo Kengmo Kenfack, Richard J. Povinelli

Electrical and Computer Engineering Faculty Research and Publications

This paper introduces a probabilistic approach to anomaly detection, specifically in natural gas time series data. In the natural gas field, there are various types of anomalies, each of which is induced by a range of causes and sources. The causes of a set of anomalies are examined and categorized, and a Bayesian maximum likelihood classifier learns the temporal structures of known anomalies. Given previously unseen time series data, the system detects anomalies using a linear regression model with weather inputs, after which the anomalies are tested for false positives and classified using a Bayesian classifier. The method can also …

Optimal Design Of Ipm Motors With Different Cooling Systems And Winding Configurations, Alireza Fatemi, Dan M. Ionel, Nabeel Demerdash, Thomas W. Nehl

Electrical and Computer Engineering Faculty Research and Publications

Performance improvement of permanent magnet (PM) motors through optimization techniques has been widely investigated in the literature. Oftentimes the practice of design optimization leads to derivation/interpretation of optimal scaling rules of PM motors for a particular loading condition. This paper demonstrates how these derivations vary with respect to the machine ampere loading and ferrous core saturation level. A parallel sensitivity analysis using a second-order response surface methodology followed by a large-scale design optimization based on evolutionary algorithms are pursued in order to establish the variation of the relationships between the main design parameters and the performance characteristics with respect to …

Fast Multi-Objective Cmode-Type Optimization Of Pm Machines Using Multicore Desktop Computers, Alireza Fatemi, Dan M. Ionel, Nabeel Demerdash, Thomas W. Nehl

Electrical and Computer Engineering Faculty Research and Publications

Large-scale design optimization of electric machines is oftentimes practiced to achieve a set of objectives, such as the minimization of cost and power loss, under a set of constraints, such as maximum permissible torque ripple. Accordingly, the design optimization of electric machines can be regarded as a constrained optimization problem (COP). Evolutionary algorithms (EAs) used in the design optimization of electric machines including differential evolution (DE), which has received considerable attention during recent years, are unconstrained optimization methods that need additional mechanisms to handle COPs. In this paper, a new optimization algorithm that features combined multi-objective optimization with differential evolution …

Benefits Of Considering More Than Temperature Acceleration For Gan Hemt Life Testing, Ronald A. Coutu Jr., Robert A. Lake, Bradley D. Christiansen, Eric R. Heller, Christopher A. Bozada, Brian S. Poling, Glen D. Via, James P. Theimer, Stephen E. Tetlak, Ramakrishna Vetury, Jeffrey B. Shealy

Electrical and Computer Engineering Faculty Research and Publications

The purpose of this work was to investigate the validity of Arrhenius accelerated-life testing when applied to gallium nitride (GaN) high electron mobility transistors (HEMT) lifetime assessments, where the standard assumption is that only critical stressor is temperature, which is derived from operating power, device channel-case, thermal resistance, and baseplate temperature. We found that power or temperature alone could not explain difference in observed degradation, and that accelerated life tests employed by industry can benefit by considering the impact of accelerating factors besides temperature. Specifically, we found that the voltage used to reach a desired power dissipation is important, and …

Tunable Split-Ring Resonators Using Germanium Telluride, C. H. Kodama, Ronald A. Coutu Jr.

Electrical and Computer Engineering Faculty Research and Publications

We demonstrate terahertz (THz) split-ring resonator (SRR) designs with incorporated germanium telluride (GeTe) thin films. GeTe is a chalcogenide that undergoes a nonvolatile phase change from the amorphous to crystalline state at approximately 200 degrees C, depending on the film thickness and stoichiometry. The phase change also causes a drop in the material’s resistivity by six orders of magnitude. In this study, two GeTe-incorporated SRR designs were investigated. The first was an SRR made entirely out of GeTe and the second was a gold SRR structure with a GeTe film incorporated into the gap region of the split ring. These …

Conceptual Design Of Sleeve Rotor Synchronous Reluctance Motor For Traction Applications, Patel B. Reddy, Kevin Grace, Ayman M. El-Refaie

Electrical and Computer Engineering Faculty Research and Publications

Synchronous reluctance machines are very appealing for high speed traction motor design due to their robustness, simple structure, absence of magnets, and simple control. The absence of magnets means that synchronous reluctance (SynRel) machines are not susceptible to price variability and sustainability of rare-earth materials. Moreover, there are no concerns about demagnetisation or uncontrolled generation mode. However, the challenge of achieving a good constant power to speed ratio is dependent on the mechanical aspects of the design. Conventional SynRel designs perform poorly compared with the permanent magnet machines due to the presence of bridges and/or centre posts in absence of …

Integrating Nanosphere Lithography In Device Fabrication, Tod V. Laurvick, Ronald A. Coutu Jr., Robert A. Lake

Electrical and Computer Engineering Faculty Research and Publications

This paper discusses the integration of nanosphere lithography (NSL) with other fabrication techniques, allowing for nano-scaled features to be realized within larger microelectromechanical system (MEMS) based devices. Nanosphere self-patterning methods have been researched for over three decades, but typically not for use as a lithography process. Only recently has progress been made towards integrating many of the best practices from these publications and determining a process that yields large areas of coverage, with repeatability and enabled a process for precise placement of nanospheres relative to other features. Discussed are two of the more common self-patterning methods used in NSL (i.e. …

Improved Sensitivity Mems Cantilever Sensor For Terahertz Photoacoustic Spectroscopy, Ronald A. Coutu Jr., Ivan R. Medvedev, Douglas T. Petkie

Electrical and Computer Engineering Faculty Research and Publications

In this paper, a microelectromechanical system (MEMS) cantilever sensor was designed, modeled and fabricated to measure the terahertz (THz) radiation induced photoacoustic (PA) response of gases under low vacuum conditions. This work vastly improves cantilever sensitivity over previous efforts, by reducing internal beam stresses, minimizing out of plane beam curvature and optimizing beam damping. In addition, fabrication yield was improved by approximately 50% by filleting the cantilever’s anchor and free end to help reduce high stress areas that occurred during device fabrication and processing. All of the cantilever sensors were fabricated using silicon-on-insulator (SOI) wafers and tested in a custom …

Acoustic Sequences In Non-Human Animals: A Tutorial Review And Prospectus, Arik Kershenbaum, Daniel T. Blumstein, Marie A. Roch, Çağlar Akçay, Gregory Backus, Mark A. Bee, Kirsten Bohn, Yan Cao, Gerald Carter, Cristiane Cäsar, Michael Coen, Stacy L. Deruiter, Laurance Doyle, Shimon Edelman, Ramon Ferreri Cancho, Todd M. Freeberg, Ellen C. Garland, Morgan Gustison, Heidi E. Harley, Chloé Huetz, Melissa Hughes, Julia Hyland Bruno, Amiyaal Ilany, Dezhe Z. Jin, Michael T. Johnson, Chenghui Ju, Jeremy Karnowski, Bernard Lohr, Marta B. Manser, Brenda Mccowan, Eduardo Mercado Iii, Peter M. Narins, Alex Piel, Megan Rice, Roberta Salmi, Kazutoshi Sasahara, Laela Sayigh, Yu Shiu, Charles Taylor, Edgar E. Vallejo, Sara Waller, Veronica Zamora Gutierrez

Electrical and Computer Engineering Faculty Research and Publications

Animal acoustic communication often takes the form of complex sequences, made up of multiple distinct acoustic units. Apart from the well-known example of birdsong, other animals such as insects, amphibians, and mammals (including bats, rodents, primates, and cetaceans) also generate complex acoustic sequences. Occasionally, such as with birdsong, the adaptive role of these sequences seems clear (e.g. mate attraction and territorial defence). More often however, researchers have only begun to characterise – let alone understand – the significance and meaning of acoustic sequences. Hypotheses abound, but there is little agreement as to how sequences should be defined and analysed. Our …

Online Chemical Sensor Signal Processing Using Estimation Theory: Quantification Of Binary Mixtures Of Organic Compounds In The Presence Of Linear Baseline Drift And Outliers, Karthick Sothivelr, Florian Bender, Fabien Josse, Edwin E. Yaz, Antonio J. Ricco, Mary E. Mohler

Electrical and Computer Engineering Faculty Research and Publications

Compact sensor systems for on-site monitoring of groundwater for trace organic compounds in the liquid phase are currently under development in our laboratories. Potential challenges include sensor baseline drift and the presence of outliers in the data, along with difficulties extracting the contribution of individual BTEX compound (benzene, toluene, ethylbenzene, and xylenes) from the sensor response to mixtures containing multiple chemically similar compounds. As a first step, the approach presented here permits online estimation of analyte concentrations in binary mixtures of BTEX compounds in the presence of linear baseline drift and outliers. This paper investigates a sensor signal-processing approach based …

Robust Non-Permanent Magnet Motors For Vehicle Propulsion, Tsarajidy Raminosoa, David A. Torrey, Ayman M. El-Refaie, Di Pan, Stefan Grubic, Kevin Grace

Electrical and Computer Engineering Faculty Research and Publications

There has been growing interest in electrical machines that reduce or eliminate rare-earth material content. Traction applications are among the key applications where reducing cost and hence reduction or elimination of rare-earth materials is a key requirement. This paper will assess the potential of three non-permanent magnet options in the context of vehicle propulsion applications: 1) a conventional Switched Reluctance Machine (SRM), 2) a DC-biased Reluctance Machine (DCRM) and, 3) a Wound Field Flux Switching Machine (WFFSM). The three machines were designed to achieve the hybrid vehicle traction requirements of 55kW peak and 30kW continuous over a speed range going …

On The Analytical Formulation Of Excess Noise In Avalanche Photodiodes With Dead Space, Erum Jamil, Jeng Shiuh Cheong, J.P.R. David, Majeed M. Hayat

Electrical and Computer Engineering Faculty Research and Publications

Simple, approximate formulas are developed to calculate the mean gain and excess noise factor for avalanche photodiodes using the dead-space multiplication theory in the regime of small multiplication width and high applied electric field. The accuracy of the approximation is investigated by comparing it to the exact numerical method using recursive coupled integral equations and it is found that it works for dead spaces up to 15% of the multiplication width, which is substantial. The approximation is also tested for real materials such as GaAs, InP and Si for various multiplication widths, and the results found are accurate within ∼ …

Robust Multi-Criteria Optimal Fuzzy Control Of Discrete-Time Nonlinear Systems, Xin Wang, Edwin E. Yaz

Electrical and Computer Engineering Faculty Research and Publications

This paper presents a novel fuzzy control design of discrete-time nonlinear systems with multiple performance criteria. The purpose behind this work is to improve the traditional fuzzy controller performance to satisfy several performance criteria simultaneously to secure quadratic optimality with an inherent stability property together with a dissipativity type of disturbance reduction. The Takagi–Sugeno-type fuzzy model is used in our control system design. By solving a linear matrix inequality at each time step, the optimal control solution can be found to satisfy mixed performance criteria. The effectiveness of the proposed technique is demonstrated by simulation of the control of the …

A Computationally Efficient Method For Calculation Of Strand Eddy Current Losses In Electric Machines, Alireza Fatemi, Dan M. Ionel, Nabeel Demerdash, Dave A. Staton, Rafal Wrobel, Yew Chuan Chong

Electrical and Computer Engineering Faculty Research and Publications

In this paper, a fast finite element (FE)-based method for the calculation of eddy current losses in the stator windings of randomly wound electric machines with a focus on fractional slot concentrated winding (FSCW) permanent magnet (PM) machines will be presented. The method is particularly suitable for implementation in large-scale design optimization algorithms where a qualitative characterization of such losses at higher speeds is most beneficial for identification of the design solutions which exhibit the lowest overall losses including the ac losses in the stator windings. Unlike the common practice of assuming a constant slot fill factor, sf, for all …

Detection And Quantification Of Aromatic Hydrocarbon Compounds In Water Using Sh-Saw Sensors And Estimation-Theory-Based Signal Processing, Karthick Sothivelr, Florian Bender, Fabien Josse, Antonio J. Ricco, Edwin E. Yaz, Rachel E. Mohler, Ravi Kolhatkar

Electrical and Computer Engineering Faculty Research and Publications

This work investigates a sensor system for direct groundwater monitoring, capable of aqueous-phase measurement of aromatic hydrocarbons at low concentrations (about 100 parts per billion (ppb)). The system is designed to speciate and quantify benzene, toluene, and ethylbenzene/xylenes (BTEX) in the presence of potential interferents. The system makes use of polymer-coated shear-horizontal surface acoustic wave devices and a signal processing method based on estimation theory, specifically a bank of extended Kalman filters (EKFs). This approach permits estimation of BTEX concentrations even from noisy data, well before the sensor response reaches equilibrium. To utilize estimation theory, an analytical model for the …

Sensor-Based Estimation Of Btex Concentrations In Water Samples Using Recursive Least Squares And Kalman Filter Techniques, Karthick Sothivelr, Florian Bender, Fabien Josse, Edwin E. Yaz, Antonio J. Ricco

Electrical and Computer Engineering Faculty Research and Publications

This work investigates sensor signal processing approaches that can be used with a sensor system for direct on-site monitoring of groundwater, enabling detection and quantification of BTEX (benzene, toluene, ethylbenzene and xylene) compounds at μg/L (ppb) concentrations in the presence of interferents commonly found in groundwater. A model for the sensor response to water samples containing multiple analytes was first formulated based on experimental results. The first signal processing approach utilizes only RLSE (recursive least squares estimation) whereas the second, a two-step processing technique, utilizes both RLSE and bank of Kalman filters for the estimation process. The estimation techniques were …

Robust Multi-Criteria Optimal Fuzzy Control Of Continuous-Time Nonlinear Systems, Xin Wang, Edwin E. Yaz

Electrical and Computer Engineering Faculty Research and Publications

This paper presents a novel fuzzy control design of continuous-time nonlinear systems with multiple performance criteria. The purpose behind this work is to improve the traditional fuzzy controller performance to satisfy several performance criteria simultaneously to secure quadratic optimality with inherent stability property together with dissipativity type of disturbance reduction. The Takagi– Sugeno fuzzy model is used in our control system design. By solving the linear matrix inequality at each time step, the control solution can be found to satisfy the mixed performance criteria. The effectiveness of the proposed technique is demonstrated by simulation of the control of the inverted …

Plasmonic Field Confinement For Separate Absorption-Multiplication In Ingaas Nanopillar Avalanche Photodiodes, Alan C. Farrell, Pradeep Senanayake, Chung-Hong Hung, George El-Howayek, Abhejit Rajagopal, Marc Currie, Majeed M. Hayat, Diana L. Huffaker

Electrical and Computer Engineering Faculty Research and Publications

Avalanche photodiodes (APDs) are essential components in quantum key distribution systems and active imaging systems requiring both ultrafast response time to measure photon time of flight and high gain to detect low photon flux. The internal gain of an APD can improve system signal-to-noise ratio (SNR). Excess noise is typically kept low through the selection of material with intrinsically low excess noise, using separate-absorption-multiplication (SAM) heterostructures, or taking advantage of the dead-space effect using thin multiplication regions. In this work we demonstrate the first measurement of excess noise and gain-bandwidth product in III–V nanopillars exhibiting substantially lower excess noise factors …

Forecasting Design Day Demand Using Extremal Quantile Regression, David Joseph Kaftan, Jarrett L. Smalley, George F. Corliss, Ronald H. Brown, Richard J. Povinelli

Electrical and Computer Engineering Faculty Research and Publications

Extreme events occur rarely, making them difficult to predict. Extreme cold events strain natural gas systems to their limits. Natural gas distribution companies need to be prepared to satisfy demand on any given day that is at or warmer than an extreme cold threshold. The hypothetical day with temperature at this threshold is called the Design Day. To guarantee Design Day demand is satisfied, distribution companies need to determine the demand that is unlikely to be exceeded on the Design Day.

We approach determining this demand as an extremal quantile regression problem. We review current methods for extremal quantile regression. …

Real-Time Topic And Sentiment Analysis In Human-Robot Conversation, Elise Russell

Master's Theses (2009 -)

Socially interactive robots, especially those designed for entertainment and companionship, must be able to hold conversations with users that feel natural and engaging for humans. Two important components of such conversations include adherence to the topic of conversation and inclusion of affective expressions. Most previous approaches have concentrated on topic detection or sentiment analysis alone, and approaches that attempt to address both are limited by domain and by type of reply. This thesis presents a new approach, implemented on a humanoid robot interface, that detects the topic and sentiment of a user’s utterances from text-transcribed speech. It also generates domain-independent, …

Error Probabilities For Optical Receivers That Employ Dynamically Biased Avalanche Photodiodes, Georges El-Howayek, Majeed M. Hayat

Electrical and Computer Engineering Faculty Research and Publications

A novel theory was recently reported for the avalanche multiplication process in avalanche photodiodes (APDs) under dynamic reverse-biasing conditions. It has been shown theoretically that the bit-synchronized, periodic modulation of the electric field in the multiplication region can offer improvements in the gain-bandwidth product by reducing intersymbol interference in optical receivers. This paper reports a rigorous formulation of the sensitivity of optical receivers that employ dynamically biased APDs. To enable the sensitivity analysis, a recurrence theory is developed to calculate the joint probability distribution function (PDF) of the stochastic gain and avalanche buildup time in APDs that are operated under …

Survivable Cloud Network Mapping For Disaster Recovery Support, Feng Gu, Khaled B. Shaban, Nasir Ghani, Samee Khan, Mahshid R. Naeini, Majeed M. Hayat, Chadi Assi

Electrical and Computer Engineering Faculty Research and Publications

Network virtualization is a key provision for improving the scalability and reliability of cloud computing services. In recent years, various mapping schemes have been developed to reserve VN resources over substrate networks. However, many cloud providers are very concerned about improving service reliability under catastrophic disaster conditions yielding multiple system failures. To address this challenge, this work presents a novel failure region-disjoint VN mapping scheme to improve VN mapping survivability. The problem is first formulated as a mixed integer linear programming problem and then two heuristic solutions are proposed to compute a pair of failure region-disjoint VN mappings. The solution …

Improved Terahertz Modulation Using Germanium Telluride (Gete) Chalcogenide Thin Films, A. H. Gwin, C. H. Kodama, T. Laurvick, Ronald A. Coutu Jr., P. F. Taday

Electrical and Computer Engineering Faculty Research and Publications

We demonstrate improved terahertz (THz) modulation using thermally crystallized germanium telluride (GeTe) thin films. GeTe is a chalcogenidematerial that exhibits a nonvolatile, amorphous to crystalline phase change at approximately 200 °C, as well as six orders of magnitude decreased electrical resistivity. In this study, amorphous GeTe thin filmswere sputtered on sapphire substrates and then tested using THz time-domain spectroscopy (THz-TDS). The test samples, heated in-situ while collecting THz-TDS measurements, exhibited a gradual absorbance increase, an abrupt nonvolatile reduction at the transition temperature, followed by another gradual increase in absorbance. The transition temperature was verified by conducting similar thermal tests while …

Converting Medical Service Provider Data Into A Unified Format For Processing, Brandon Krugman

Master's Theses (2009 -)

Most organizations process flat files regularly. There are different options for processing files, including SQL Server Integration Services (SSIS), BizTalk, SQL import job, and other Extract, Transform, and Load (ETL) processes. All of these options have very strict requirements for file formats. If the format of the file changes, all of these options throw a catastrophic error, and implementing a fix to handle the new format is difficult. With each of the methods, the new format needs to be configured in the development environment, and the data flow must be modified to process all of the changes. Due to the …

Vocal Classification Of Vocalizations Of A Pair Of Asian Small-Clawed Otters To Determine Stress, Peter M. Scheifele, Michael T. Johnson, Michelle Fry, Benjamin Hamel, Kathryn Laclede

Electrical and Computer Engineering Faculty Research and Publications

Asian Small-Clawed Otters (Aonyx cinerea) are a small, protected but threatened species living in freshwater. They are gregarious and live in monogamous pairs for their lifetimes, communicating via scent and acoustic vocalizations. This study utilized a hidden Markov model (HMM) to classify stress versus non-stress calls from a sibling pair under professional care. Vocalizations were expertly annotated by keepers into seven contextual categories. Four of these—aggression, separation anxiety, pain, and prefeeding—were identified as stressful contexts, and three of them—feeding, training, and play—were identified as non-stressful contexts. The vocalizations were segmented, manually categorized into broad vocal type call types, and analyzed …

Establishing The Relative Merits Of Interior And Spoke-Type Permanent-Magnet Machines With Ferrite Or Ndfeb Through Systematic Design Optimization, Peng Zhang, Gennadi Y. Sizov, Dan M. Ionel, Nabeel Demerdash

Electrical and Computer Engineering Faculty Research and Publications

In this paper, a multiobjective design optimization method combining design-of-experiments techniques and differential-evolution algorithms is presented. The method was implemented and utilized in order to provide practical engineering insights for the optimal design of interior and spoke-type permanent-magnet machines. Two combinations with 12 slots and 8 poles and 12 slots and 10 poles, respectively, have been studied in conjunction with rare-earth neodymium-iron-boron (NdFeB) and ferrites. As part of the optimization process, a computationally efficient finite-element electromagnetic analysis was employed for estimating the performance of thousands of candidate designs. Three optimization objectives were concurrently considered for minimum total material cost, power …

Relating The Experimental Ionization Coefficients In Semiconductors To The Nonlocal Ionization Coefficients, Jeng Shiuh Cheong, Majeed M. Hayat, Xinxin Zhou, John P.R. David

Electrical and Computer Engineering Faculty Research and Publications

The experimentally determined impact ionization coefficients, , include intrinsically the presence of a dead-space, where carriers cannot impact ionize as they do not have sufficient energy. These, therefore, cannot be used by nonlocal ionization models, which require the enabled ionization coefficients, which describe the ionization probability after the dead-space. A relatively simple relationship is shown to exist between α'(β') and , which requires only the knowledge of the carrier threshold energies. This allows conventionally limited to the local model framework, to be used to give a very good prediction of the avalanche multiplication and excess noise for a wide range …

Investigation Of The Surface Adhesion Phenomena And Mechanism Of Gold-Plated Contacts At Superlow Making/Breaking Speed, Wanbin Ren, Cheng Chang, Yu Chen, Shengjun Xue, Ronald A. Coutu Jr.

Electrical and Computer Engineering Faculty Research and Publications

Surface adhesion phenomena of gold-plated copper contact materials are studied in conditions of nonarc load (5/15/25 V and 0.2/0.5/1 A) and superlow speed (25 and 50 nm/s) realized by a piezoactuator during the making and breaking processes. It is shown that softening and melting of local asperities leads to interface adhesion, which results from the joule heat generated by the contact resistance; it is determined that the change of contact force with time obeys the negative exponential distribution and the time constant is associated with the adhesion force directly. Based on the fitting experimental data, the relationship between the adhesion …

Using Cross-Linked Su-8 To Flip-Chip Bond, Assemble, And Package Mems Devices, Robert A. Lake, Ronald A. Coutu Jr.

Electrical and Computer Engineering Faculty Research and Publications

This paper investigates using an SU-8 photoresist as an adhesive material for flip-chip bonding, assembling, and packaging microelectromechanical systems devices. An important factor, when using SU-8 as an adhesive material is to control ultraviolet (UV) exposure during fabrication to maximize bond strength due to material cross linking. This approach is much improved over previous efforts where SU-8 bake times and temperatures where changed to alter material cross-linking. In this paper, bake times and temperatures were maintained constant and total UV exposure energy was varied. Once fabricated, bond strength was systematically tested to determine the tensile loads needed to separate bonded …

Breaking The Buildup-Time Limit Of Sensitivity In Avalanche Photodiodes By Dynamic Biasing, Majeed M. Hayat, Payman Zarkesh-Ha, George El-Howayek, Robert Efroymson, Joe C. Campbell

Electrical and Computer Engineering Faculty Research and Publications

Avalanche photodiodes (APDs) are the preferred photodetectors for direct-detection, high data-rate long-haul optical telecommunications. APDs can detect low-level optical signals due to their internal amplification of the photon-generated electrical current, which is attributable to the avalanche of electron and hole impact ionizations. Despite recent advances in APDs aimed at reducing the average avalanche-buildup time, which causes intersymbol interference and compromises receiver sensitivity at high data rates, operable speeds of commercially available APDs have been limited to 10Gbps. We report the first demonstration of a dynamically biased APD that breaks the traditional sensitivity-versus-speed limit by employing a data-synchronous sinusoidal reverse-bias that …