Digital Commons Network^™

Fast Algorithms For Layered Media, Weng Cho Chew, Bin Hu, Y. C. Pan, Lijun Jiang

Electrical and Computer Engineering Faculty Research & Creative Works

This paper gives an overview of computational electromagnetics for simulating complex structures with a large number of unknowns using integral equation method. First, it discusses the pros and cons of differential equation solvers versus integral equation solvers. Then it gives an overview of different fast algorithms for solving integral equations. It also discusses the difficulty of solving electromagnetic problems in the "twilight zone" between static and full-wave electromagnetics. Finally, it discusses various methods for fast solutions of scattering and coupling problems involving layered media both for statics and dynamic problems, and presents some numerical results. © 2005 Académie des sciences. …

A Multi-Hypothesis Approach For Salient Object Tracking In Visual Surveillance, Filiz Bunyak, Ilker Ersoy, S. R. Subramanya

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, a multiple object tracking method for visual surveillance applications is presented. Moving objects are detected by adaptive background subtraction and tracked by using a multi-hypothesis testing approach. Object matching between frames is done based on proximity and appearance similarity. a new confidence measure is assigned to each possible match. This information is arranged into a graph structure where vertices represent blobs in consecutive frames and edges represent match confidence values. This graph is later used to prune and refine trajectories to obtain the salient object trajectories. Occlusions are handled through position prediction using Kalman filter and robust …

A Warped Bandwidth Expansion Filter, Marc A. Boillot, John G. Harris

Electrical and Computer Engineering Faculty Research & Creative Works

A warped filter is presented as a new speech enhancement method to adjust formant bandwidths on a critical band scale. The warped filter enhances perceived loudness without adding signal energy by exploiting the psychoacoustic nature of the auditory system. The critical band concept in auditory theory states that when the energy in a signal remains constant, loudness increases when the energy spreads beyond a critical bandwidth. A warped filter is proposed and developed to elevate the perceived loudness of clean speech by applying non-linear bandwidth expansion to the formant regions of vowels in accordance with the critical band scale. The …

Depth-Shifting Of Shallow Water Guide Source Observations, Lisa M. Zurk, Brian H. Tracey

Electrical and Computer Engineering Faculty Publications and Presentations

In theory, matched field processing offers the significant benefit of higher signal gains and increased localization capability. However, this has not been robustly observed in practice because of inherent uncertainties about details of the shallow water propagation environments which limit the prediction of the channel response. The use of guide sources to directly measure the transfer function between source and receiver arrays has been proposed as a means for reducing mismatch. However, the guide source measurement only provides a measured transfer function at the guide source location. In this paper a method of depth-shifting guide source observations is proposed, making …

Clif Merritt And Wilderness Wildlife : Learning How To Live In Paradise, Robert N. Baker

Graduate Student Theses, Dissertations, & Professional Papers

No abstract provided.

Book Review Of Jean Stefancic & Richard Delgado, How Lawyers Lose Their Way: A Profession Fails Its Creative Minds (2005), Milton C. Regan

Georgetown Law Faculty Publications and Other Works

"How Lawyers Lose Their Way" claims that lawyers' unease stems from a distinctive source: their excessive use of and exposure to "formalism" in their work. I think that they are on to something, but the analysis in this book is too underdeveloped to provide much insight into what it is. The authors' use of the term "formalism" risks being so inclusive that it loses explanatory power. In addition, their claim that overreliance on formalism is the chief culprit in lawyers' unhappiness is vulnerable to the charge that lawyers arc suffering the effect of trends in the workplace affecting a wide …

Robust Resource Allocations In Parallel Computing Systems: Model And Heuristics, V. Shestak, Shoukat Ali, Howard Jay Siegel, A. A. Maciejewski

Electrical and Computer Engineering Faculty Research & Creative Works

The resources in parallel computer systems (including heterogeneous clusters) should be allocated to the computational applications in a way that maximizes some system performance measure. However, allocation decisions and associated performance prediction are often based on estimated values of application and system parameters. The actual values of these parameters may differ from the estimates; for example, the estimates may represent only average values, the models used to generate the estimates may have limited accuracy, and there may be changes in the environment. Thus, an important research problem is the development of resource management strategies that can guarantee a particular system …

Simulation-Based Performance Modeling For War Fighter In Loop Minefield Detection System, Abhilash Rajagopal, Sanjeev Agarwal, Sreeram Ramakrishnan

Electrical and Computer Engineering Faculty Research & Creative Works

No abstract provided.

Traces In Proximity To Gaps In Return Planes, Todd H. Hubing, Thomas Van Doren, Theodore M. Zeeff

Electrical and Computer Engineering Faculty Research & Creative Works

Coupling between circuitry on printed circuit boards can be mitigated by a variety of well-known techniques. One such technique is to isolate circuitry in different areas of the printed circuit board by strategically placing a gap in the signal return plane. However, this technique is only effective at reducing common-impedance coupling, which is generally not a significant coupling mechanism at frequencies above 1 MHz. This paper investigates the effect of a gap located between and parallel to adjacent microstrip traces. The effect of the gap on the mutual inductance and mutual capacitance is evaluated. Laboratory measurements and numerical simulations show …

Trends In Process Control Systems Security, Ann K. Miller

Electrical and Computer Engineering Faculty Research & Creative Works

The protection of critical infrastructure systems is a hotly debated topic. The very label "critical infrastructure" implies that these systems are important, and they are: they support our everyday lives, from the water and food in our homes to our physical and financial welfare. This article explores the recent evolution of programmable logic controllers (PCSs) and their environments, explains the need for improved security in these systems, and describes some of the emerging research areas that offer promise in PCS security.

Wide Area Power System Protection Using A Learning Vector Quantization Network, Ganesh K. Venayagamoorthy, Mahyar Zarghami

Electrical and Computer Engineering Faculty Research & Creative Works

This paper presents a wide area monitoring and protection technique based on a learning vector quantization (LVQ) neural network. Phasor measurements of the power network buses are monitored continuously by a LVQ network in order to alert the control room operators of possible faults. The proposed scheme could be used in a wide area monitored network to provide remedial action when primary local protection schemes for transmission lines fail to function. This technique could also be extended to the actuation of the secondary protection schemes, hence, preserving the integrity of the power network especially when the faults are spreading over …

A Dynamic Recurrent Neural Network For Wide Area Identification Of A Multimachine Power System With A Facts Device, Salman Mohagheghi, Ganesh K. Venayagamoorthy, Ronald G. Harley

Electrical and Computer Engineering Faculty Research & Creative Works

Multilayer perceptron and radial basis function neural networks have been traditionally used for plant identification in power systems applications of neural networks. While being efficient in tracking the plant dynamics in a relatively small system, their performance degrades as the dimensions of the plant to be identified are increased, for example in supervisory level identification of a multimachine power system for wide area control purposes. Recurrent neural networks can deal with such a problem by modeling the system as a set of differential equations and with less order of complexity. Such a recurrent neural network identifier is designed and implemented …

A Microphone Array System For Multimedia Applications With Near-Field Signal Targets, Y. Rosa Zheng, M. El-Tanany, R. A. Goubran, Hongchi Shi

Electrical and Computer Engineering Faculty Research & Creative Works

A microphone array beamforming system is proposed for multimedia communication applications using four sets of small planar arrays mounted on a computer monitor. A new virtual array approach is employed such that the original signals received by the array elements are weighted and delayed to synthesize a large, nonuniformly spaced, harmonically nested virtual array covering the frequency band [50, 7000] Hz of the wideband telephony. Subband multirate processing and near-field beamforming techniques are then used jointly by the nested virtual array to improve the performances in reverberant environments. A new beamforming algorithm is also proposed using a broadband near-field spherically …

A New Test Setup And Method For The Calibration Of Current Clamps, David Pommerenke, Ramachandran Chundru, Sunitha Chandra

Electrical and Computer Engineering Faculty Research & Creative Works

Current probes are widely used to measure the common mode currents in electromagnetic compatibility (EMC) applications. Often, it is necessary to characterize the ratio of measured voltage to the common mode currents up to gigahertz (GHz) frequencies. Existing calibration methods for current probes suffer from the problem of not directly measuring the current within the current clamp. Instead they either reconstruct the current from measurements at other locations or they use assumptions regarding the geometry which allows them to use a current that is measured at a different location without applying a mathematical correction. For example, by maintaining a 50-Ω …

A Novel Method Based On Neural Networks To Distinguish Between Load Harmonics And Source Harmonics In A Power System, Joy Mazumdar, Frank C. Lambert, Ganesh K. Venayagamoorthy, Ronald G. Harley

Electrical and Computer Engineering Faculty Research & Creative Works

No abstract provided.

A Robust Controller For The Manipulation Of Micro Scale Objects, Qinmin Yang, Jagannathan Sarangapani

Electrical and Computer Engineering Faculty Research & Creative Works

A suite of novel robust controllers is presented for the manipulation and handling of micro-scale objects in a micro-electromechanical system (MEMS) where adhesive, surface tension, friction and van der Waals forces are dominant. Moreover, these forces are typically unknown. The robust controller overcomes the unknown system dynamics and ensures the performance in the presence of actuator constraints by assuming that the upper bounds on these forces are known. On the other hand, for the robust adaptive controller, the unknown forces are estimated online. Using the Lyapunov approach, the uniformly ultimate boundedness (UUB) of the closed-loop manipulation error is shown for …

An Efficient Method For Supporting Multiple Types Of Services On Smart Server, Chang-Soo Kim, Yu-Hyeon Bak, Seung-Joe Bae, Jin-Mee Kim, Sang-Min Woo, Seung-Hyup Jeon, Won-Jae Lee, Hag-Young Kim

Electrical and Computer Engineering Faculty Research & Creative Works

No abstract provided.

Constitutive Commitments And Roosevelt's Second Bill Of Rights: A Dialogue, Randy E. Barnett, Cass R. Sunstein

Georgetown Law Faculty Publications and Other Works

What made the Second Bill of Rights possible? Part of the answer lies in a simple idea, one pervasive in the American legal culture during Roosevelt's time: No one really opposes government intervention. Markets and wealth depend on government. Without government creating and protecting property rights, property itself cannot exist. Even the people who most loudly denounce government interference depend on it every day. Their own rights do not come from minimizing government but are a product of government. Political scientist Lester Ward vividly captured the point: "[T]hose who denounce state intervention are the ones who most frequently and successfully …

The Place Of The User In Copyright Law, Julie E. Cohen

Georgetown Law Faculty Publications and Other Works

Copyright doctrine . . . is characterized by the absence of the user. As copyright moves into the digital age, this absence has begun to matter profoundly. As I will show, the absence of the user has consequences that reach far beyond debates about the legality of private copying, or about the proper scope of user-oriented exemptions such as the fair use and first sale doctrines. The user's absence produces a domino effect that ripples through the structure of copyright law, shaping both its unquestioned rules and its thorniest dilemmas. The resulting imbalance - empty space where one cornerstone of …

Engine Data Classification With Simultaneous Recurrent Network Using A Hybrid Pso-Ea Algorithm, Xindi Cai, Donald C. Wunsch

Electrical and Computer Engineering Faculty Research & Creative Works

We applied an architecture which automates the design of simultaneous recurrent network (SRN) using a new evolutionary learning algorithm. This new evolutionary learning algorithm is based on a hybrid of particle swarm optimization (PSO) and evolutionary algorithm (EA). By combining the searching abilities of these two global optimization methods, the evolution of individuals is no longer restricted to be in the same generation, and better performed individuals may produce offspring to replace those with poor performance. The novel algorithm is then applied to the simultaneous recurrent network for the engine data classification. The experimental results show that our approach gives …

Estimation Of Additive Noise Variance For Multiuser Cdma Systems, Jingxian Wu, Chengshan Xiao, Khaled Ben Letaief

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper, a novel additive noise variance estimation algorithm is proposed for multiuser CDMA systems experiencing time varying and frequency selective fading. The algorithm is developed by exploring the eigen-structure of the receive signal correlation matrix, which is characterized by the statistid properties of both the fading channeI and the additive white Gaussian noise. Relying only on the knowledge of the receiver signal samples, the algorithm can accurately estimate the variance of the additive noise present at the receiver of multiuser CDMA systems. The estimated noise variance can be employed along with other receiver algorithms to improve system performance.

Gene Regulatory Networks Inference With Recurrent Neural Network Models, Rui Xu, Donald C. Wunsch

Electrical and Computer Engineering Faculty Research & Creative Works

Large-scale time series gene expression data generated from DNA microarray experiments provide us a new means to reveal fundamental cellular processes, investigate functions of genes, and understand their relations and interactions. To infer gene regulatory networks from these data with effective computational tools has attracted intensive efforts from artificial intelligence and machine learning. Here, we use a recurrent neural network (RNN), trained with particle swarm optimization (PSO), to investigate the behaviors of regulatory networks. The experimental results, on a synthetic data set and a real data set, show that the proposed model and algorithm can effectively capture the dynamics of …

Image Recognition Systems With Permutative Coding, Ernst M. Kussul, Donald C. Wunsch, Tatiana N. Baidyk

Electrical and Computer Engineering Faculty Research & Creative Works

A feature extractor and neural classifier for image recognition system are proposed. They are based on the permutative coding technique which continues our investigations on neural networks. It permits us to obtain sufficiently general description of the image to be recognized. Different types of images were used to test the proposed image recognition system. It was tested on the handwritten digit recognition problem, the face recognition problem and the shape of microobjects recognition problem. The results of testing are very promising. The error rate for the MNIST database is 0.44% and for the ORL database is 0.1%.

Infrastructure Roots: Evolution Of Electric Power In The United States, Mariesa Crow

Electrical and Computer Engineering Faculty Research & Creative Works

Electricity holds a unique place in the US infrastructure. It is a commodity, a technology, and a necessity. Electric utilities must walk a fine line to balance each of these aspects. While electricity is a commodity that may be bought and sold, it must also be regulated to remain affordable for the general population. Reliability is continually balanced against the cost of upgrades and maintenance. This paper discusses the interconnection of regional area power systems in the US and the benefits such interconnection brings.

A Heuristic-Dynamic-Programming-Based Power System Stabilizer For A Turbogenerator In A Single-Machine Power System, Wenxin Liu, Ganesh K. Venayagamoorthy, Donald C. Wunsch

Electrical and Computer Engineering Faculty Research & Creative Works

Power system stabilizers (PSSs) are used to generate supplementary control signals for the excitation system in order to damp the low-frequency power system oscillations. To overcome the drawbacks of a conventional PSS (CPSS), numerous techniques have been proposed in the literature. Based on the analysis of existing techniques, a novel design based on heuristic dynamic programming (HDP) is presented in this paper. HDP, combining the concepts of dynamic programming and reinforcement learning, is used in the design of a nonlinear optimal power system stabilizer. Results show the effectiveness of this new technique. The performance of the HDP-based PSS is compared …

Why Print And Electronic Resources Are Essential To The Academic Law Library, Michelle M. Wu

Georgetown Law Faculty Publications and Other Works

Libraries have supported multiple formats for decades, from paper and microforms to audiovisual tapes and CDs. However, the newest medium, digital transmission, has presented a wider scope of challenges and caused library patrons to question the established and recognized multiformat library. Within the many questions posed, two distinct ones echo repeatedly. The first doubts the need to sustain print in an increasingly digital world, and the second warns of the dangers of relying on a still-developing technology. This article examines both of these positions and concludes that abandoning either format would translate into a failure of service to patrons, both …

A Measure Of Robustness Against Multiple Kinds Of Perturbations, Shoukat Ali, Behdis Eslamnour

Electrical and Computer Engineering Faculty Research & Creative Works

Parallel and distributed heterogeneous computing systems may operate in an environment that undergoes unpredictable changes causing certain system performance features to degrade. Such systems need robustness to guarantee limited degradation despite fluctuations in the behavior of its component parts or environment. Our previous work in this area presented a method for generating a measure of robustness for a given system. However, the focus of that approach was on a scenario where all perturbations were of the same kind, e.g., all perturbations were in message sizes or computation times, but not both message sizes and computation times. This paper gives an …

A New Microsensor System For Plant Root Zone Monitoring, Chang-Soo Kim, Sandeep Sathyan, D. M. Porterfield

Electrical and Computer Engineering Faculty Research & Creative Works

The objective of this work is to develop a new microsensor system that can monitor dissolved oxygen and hydration environment at the plant root zone. A miniaturized plant growth system is prepared including the root zone layer, either a porous ceramic tube or porous ceramic wafer on which the plant is grown, and an underlying fluidic channel to deliver nutrients and water to the root zone. We demonstrate the feasibility of using a flexible microsensor array for dissolved oxygen detection, and a four-electrode impedance microelectrode for wetness detection on the surface of a porous tube nutrient delivery system. The unique …

A Novel Method For Predicting Harmonic Current Injection From Non-Linear Loads Using Neural Networks, Joy Mazumdar, Frank C. Lambert, Ganesh K. Venayagamoorthy, Ronald G. Harley

Electrical and Computer Engineering Faculty Research & Creative Works

Generation of harmonics and the existence of waveform pollution in power system networks is one of the major problems facing the utilities. This paper proposes a neural network solution methodology for the problem of measuring the actual amount of harmonic current injected into a power network by a nonlinear load. The determination of harmonic currents is complicated by the fact that the supply voltage waveform is distorted by other loads and is rarely a pure sinusoid. A recurrent neural network trained with the backpropagation through time (BPTT) training algorithm is used to find a way of distinguishing between the load …

The Future Of Copyright, Lawrence B. Solum

Georgetown Law Faculty Publications and Other Works

Review of Free Culture: How Big Media Uses Technology and the Law to Lock Down Culture and Control Creativity by Lawrence Lessig (2004).

Sometimes technological change is so profound that it rocks the foundations of an entire body of law. Peer-to-peer (P2P) filesharing systems--Napster, Gnutella, KaZaA, Grokster, and Freenet3--are mere symptoms of a set of technological innovations that have set in motion an ongoing process of fundamental changes in the nature of copyright law. The video tape recorder begat the Sony substantial noninfringing use defense. The digital cassette recorder begat the Audio Home Recording Act. The internet begat the Digital …