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Electrical and Computer Engineering Faculty Research & Creative Works

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Articles 2131 - 2160 of 3518

Full-Text Articles in Engineering

A Pulse-Based Feature Extractor For Spike Sorting Neural Signals, Christy L. Rogers, John G. Harris, Jose C. Principe, Justin C. Sanchez Sep 2007

A Pulse-Based Feature Extractor For Spike Sorting Neural Signals, Christy L. Rogers, John G. Harris, Jose C. Principe, Justin C. Sanchez

Electrical and Computer Engineering Faculty Research & Creative Works

Spike sorting is often required for analyzing neural recordings to isolate the activity of single neurons. Wave shape analysis in the spike sorting procedure provides a means to detect spikes while minimizing the influence of false alarms. As neural recording techniques allow for recording hundreds of electrodes, power is too limited in neural implants for current spike sorting algorithms. Even with spike sorting at the back end where more power is available, the bandwidth is too limited to transmit enough information for current spike sorting techniques. A low-power pulse-based feature extractor presented in the paper is a solution to the …

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Wireless, In Vivo Neural Recording Using A Custom Integrated Bioamplifier And The Pico System, David Cheney, Aik Goh, Jie Xu, Karl Gugel, John G. Harris, Justin C. Sanchez, Jose C. Principe Sep 2007

Wireless, In Vivo Neural Recording Using A Custom Integrated Bioamplifier And The Pico System, David Cheney, Aik Goh, Jie Xu, Karl Gugel, John G. Harris, Justin C. Sanchez, Jose C. Principe

Electrical and Computer Engineering Faculty Research & Creative Works

This paper describes a wireless system for sampling multiple channels of neural activity based on a low-power, custom 80dB-gain integrated bio amplifier, Texas Instrument's MSP430 microprocessors, and Nordic Semiconductor's ultra-low power, high bandwidth RF transmitter/receivers. The system's features are presented as well as results of spike potentials from a live subject. © 2007 IEEE.

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Blueprint For Iteratively Hardening Power Grids Employing Unified Power Flow Controllers, William M. Siever, Ann K. Miller, Daniel R. Tauritz Sep 2007

Blueprint For Iteratively Hardening Power Grids Employing Unified Power Flow Controllers, William M. Siever, Ann K. Miller, Daniel R. Tauritz

Electrical and Computer Engineering Faculty Research & Creative Works

A stable electricity supply is vital for modern society. However, many parts of our power transmission grid are operating near their operational limits. Such stressed systems are vulnerable to cascading failures, where a few small faults can induce a cascade of failures potentially leading to a major blackout The unified power flow controller (UPFC), the most powerful highspeed, semi-conductor based power flow device, can be used as a theoretical model to study how these devices can be used to improve power grid resilience. The blueprint presented here can be used to iteratively identify critical weaknesses in power grids and to …

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A Probabilistic Approach To Measuring Robustness In Computing Systems, Behdis Eslamnour, Shoukat Ali Sep 2007

A Probabilistic Approach To Measuring Robustness In Computing Systems, Behdis Eslamnour, Shoukat Ali

Electrical and Computer Engineering Faculty Research & Creative Works

System builders are becoming increasingly interested in robust design. We believe that a methodology for generating robustness metrics will help the robust design research efforts and, in general, is an important step in the efforts to create robust computing systems. the purpose of the research in this paper is to quantify the robustness of a resource allocation, with the eventual objective of setting a standard that could easily be instantiated for a particular computing system to generate a robustness metric. We present our theoretical foundation for a robustness metric and give its instantiation for a particular system. © 2007 IEEE.

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Development And Laboratory Trials Of The Light-Based High-Resolution Target Movement Monitor For Monitoring Convergence At Underground Mines, B. D. Apel, B. R. Gray, Randy Hays Moss, Steve Eugene Watkins, T. H. Jones Sep 2007

Development And Laboratory Trials Of The Light-Based High-Resolution Target Movement Monitor For Monitoring Convergence At Underground Mines, B. D. Apel, B. R. Gray, Randy Hays Moss, Steve Eugene Watkins, T. H. Jones

Electrical and Computer Engineering Faculty Research & Creative Works

This paper describes a development and laboratory evaluation of the light-based high-resolution target movement monitor which can be used to measure convergence at underground excavations with submillimeter accuracy. The monitor is based on unique measurement technology which was developed at the University of Missouri-Rolla. This system has the potential for high accuracy detection and monitoring of positional changes (as small as 0.1mm with the current laboratory implementation) presented by many types of targets located in close proximity to or at far distances from the monitor. The sensitivity of the system to camera resolution and the error analysis as a function …

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Change In Voltage Distortion Predictions At The Pcc Due To Changing Nonlinear Load Current Profile Using Plant Startup Data, Joy Mazumdar, Frank C. Lambert, Ganesh K. Venayagamoorthy, Ronald G. Harley Sep 2007

Change In Voltage Distortion Predictions At The Pcc Due To Changing Nonlinear Load Current Profile Using Plant Startup Data, Joy Mazumdar, Frank C. Lambert, Ganesh K. Venayagamoorthy, Ronald G. Harley

Electrical and Computer Engineering Faculty Research & Creative Works

Customer loads connected to electricity supply systems may be broadly categorized as either linear or nonlinear. Nonlinear loads inject harmonics in a power distribution network. The interaction of the nonlinear load harmonics with the network impedances creates voltage distortions at the point of common coupling (PCC) which in turn affects other loads connected to the same PCC. When several nonlinear loads are connected to the PCC, it is difficult to predict mathematically how each nonlinear load is affecting the voltage distortion level at the PCC. Typically, customers with nonlinear loads apply harmonic filtering techniques to clean up their current and …

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Plug-In Hybrid Vehicles -- A Vision For The Future, Mehdi Ferdowsi Sep 2007

Plug-In Hybrid Vehicles -- A Vision For The Future, Mehdi Ferdowsi

Electrical and Computer Engineering Faculty Research & Creative Works

One of the unique advantages of plug-in hybrid vehicles is their capability to integrate the transportation and electric power generation sectors in order to improve the efficiency, fuel economy, and reliability of both systems. This goal is performed via integration of the onboard energy storage units of plug-in vehicles with the power grid by power electronic converters and communication systems. Employing energy storage systems improves the efficiency and reliability of the electric power generation, transmission, and distribution. Similarly, combining an energy storage system with the power train of a conventional vehicle results in a hybrid vehicle with higher fuel efficiency. …

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Increased Performance Of Battery Packs By Active Equalization, Jonathan W. Kimball, Brian T. Kuhn, Philip T. Krein Sep 2007

Increased Performance Of Battery Packs By Active Equalization, Jonathan W. Kimball, Brian T. Kuhn, Philip T. Krein

Electrical and Computer Engineering Faculty Research & Creative Works

Battery packs for most applications are series strings of electrochemical cells. Due to manufacturing variations, temperature differences, and aging, the individual cells perform differently. When a complete pack is charged and discharged as a single two-terminal circuit element, some cells are chronically overcharged, undercharged, or overdischarged, all of which act to reduce cell life. The performance and life of the complete pack is limited by the weakest cell. Many methods have been proposed and explored to mitigate this problem. In the present work, a switched-capacitor converter is shown to be a simple and effective method to maintain equal cell or …

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Self-Healing Control With Multifunctional Gate Drive Circuits For Power Converters, Peng Xiao, Ganesh K. Venayagamoorthy, Keith Corzine, Robert S. Woodley Sep 2007

Self-Healing Control With Multifunctional Gate Drive Circuits For Power Converters, Peng Xiao, Ganesh K. Venayagamoorthy, Keith Corzine, Robert S. Woodley

Electrical and Computer Engineering Faculty Research & Creative Works

Many commercial and military transport systems have fault diagnostic functions implemented to help protect the device when a severe fault occurs. However, most present systems do not contain prognostics capability which would allow operators to observe an unhealthy system component in its pre- fault condition. In industry applications, scheduled downtime can result in considerable cost avoidance. The next technology step is self-healing system components which observe not only potential problems, but can also take steps to continue operation under abnormal conditions - whether due to long-term normal wear-and-tear or sudden combat damage. In this paper, current and voltage information using …

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Robust Tuning Of Modern Power System Stabilizers Using Bacterial Foraging Algorithm, B. Sumanbabu, S. Mishra, B. K. Panigrahi, Ganesh K. Venayagamoorthy Sep 2007

Robust Tuning Of Modern Power System Stabilizers Using Bacterial Foraging Algorithm, B. Sumanbabu, S. Mishra, B. K. Panigrahi, Ganesh K. Venayagamoorthy

Electrical and Computer Engineering Faculty Research & Creative Works

IEEE Std 421.5, revised by the IEEE excitation system subcommittee introduced a new type of power system stabilizer model, the multiband power system stabilizers (IEEE PSS4B). Although it requires two input signals, like the widely used IEEE PSS2B, the underlying principle of the new IEEE PSS4B makes it sharply different. This paper presents a method based on Bacterial Foraging Algorithm (BFA) to simultaneously tune these modern power system stabilizers (PSSs) in multimachine power system. Simulation results of multi-machine power system validate the efficiency of this approach. the proposed method is effective for the tuning of multi-controllers in large power systems.

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A Memetic Algorithm Configured Via A Problem Solving Environment For The Hamiltonian Cycle Problems, X. S. Chen, Meng-Hiot Lim, Donald C. Wunsch Sep 2007

A Memetic Algorithm Configured Via A Problem Solving Environment For The Hamiltonian Cycle Problems, X. S. Chen, Meng-Hiot Lim, Donald C. Wunsch

Electrical and Computer Engineering Faculty Research & Creative Works

Algorithm Development Environment for Permutation-based problems (ADEP) is a software environment for configuring meta-heuristics for solving combinatorial optimization problems. This paper describes the key features of ADEP and how the environment was used to generate a Memetic Algorithm (MA) solution for Hamiltonian Cycle Problems (HCP). The effectiveness of the MA algorithm is demonstrated through computer simulations and its performance is compared with backtracking and other heuristic techniques such as Simulated Annealing, Tabu Search, and Ant Colony Optimization.

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Defect-Tolerant Gate Macro Mapping & Placement In Clock-Free Nanowire Crossbar Architecture, Ravi Bonam, Yong-Bin Kim, Minsu Choi Sep 2007

Defect-Tolerant Gate Macro Mapping & Placement In Clock-Free Nanowire Crossbar Architecture, Ravi Bonam, Yong-Bin Kim, Minsu Choi

Electrical and Computer Engineering Faculty Research & Creative Works

Recently, we proposed a new clock-free nanowire crossbar architecture based on a delayinsensitive paradigm called Null Convention Logic (NCL). The proposed architecture has simple periodic structure that is suitable for non-deterministic nanoscale assembly and does not require a clock distribution network - so it is intrinsically free from timing-related failure modes. Even though the proposed architecture offers improved manufacturability, it is still not free from defects. This paper elaborates on the different programming techniques to map a given threshold gate macro on a random PGMB (Programmable Gate Macro Block) with predefined dimension. Defect-Aware and Defect Unaware approaches have been considered …

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Reliability Modeling For The Advanced Electric Power Grid, Ayman Z. Faza, Sahra Sedigh, Bruce M. Mcmillin Sep 2007

Reliability Modeling For The Advanced Electric Power Grid, Ayman Z. Faza, Sahra Sedigh, Bruce M. Mcmillin

Electrical and Computer Engineering Faculty Research & Creative Works

The advanced electric power grid promises a self-healing infrastructure using distributed, coordinated, power electronics control. One promising power electronics device, the Flexible AC Transmission System (FACTS), can modify power flow locally within a grid. Embedded computers within the FACTS devices, along with the links connecting them, form a communication and control network that can dynamically change the power grid to achieve higher dependability. The goal is to reroute power in the event of transmission line failure. Such a system, over a widespread area, is a cyber-physical system. The overall reliability of the grid is a function of the respective reliabilities …

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Distributed Energy Resources: Issues And Challenges, Badrul H. Chowdhury, Chung-Li Tseng Aug 2007

Distributed Energy Resources: Issues And Challenges, Badrul H. Chowdhury, Chung-Li Tseng

Electrical and Computer Engineering Faculty Research & Creative Works

No abstract provided.

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A Duplex Theory Of Spike Coding In The Early Stages Of The Auditory System, Ismail Uysal, Harsha Sathyendra, John G. Harris Aug 2007

A Duplex Theory Of Spike Coding In The Early Stages Of The Auditory System, Ismail Uysal, Harsha Sathyendra, John G. Harris

Electrical and Computer Engineering Faculty Research & Creative Works

We propose a duplex theory of spike coding in the early stages of the auditory system based on the intensity and noise levels of the acoustic stimuli. According to this concept, at low intensity levels, where auditory nerve firings cannot generate a high enough synchrony among neuron ensembles, rate coding is more likely favored against phase-locking via synchrony coding. To the contrary, at conversational intensity levels, phase synchrony coding is preferred due to its superior and highly noise robust performance. The theory is supported by both evidence from biology, as well as from experimental simulations using biologically plausible models of …

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Miso Damping Controller Design For A Tcsc Using Particle Swarm, Swakshar Ray, Ganesh K. Venayagamoorthy, Balarko Chaudhuri, Rajat Majumder Aug 2007

Miso Damping Controller Design For A Tcsc Using Particle Swarm, Swakshar Ray, Ganesh K. Venayagamoorthy, Balarko Chaudhuri, Rajat Majumder

Electrical and Computer Engineering Faculty Research & Creative Works

This paper presents a new approach for designing multi-input-single-output (MISO) damping controller for a TCSC in a multi-machine power system. The damping controller design uses particle swarm optimization (PSO) to determine the coefficients of single or multi-stage lead-lag compensators. The classical technique works well in the design of lead-lag compensators for SISO controllers. But, there is no proper step-by-step procedure to achieve the desired performance characteristics for a MISO controller. Hence, in this paper, a computational optimization tool has been used to determine the optimal gains and time constants of a linear MISO damping controller. The damping controller is implemented …

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Making The Power Grid More Intelligent, Salman Mohagheghi, Ronald G. Harley, Ganesh K. Venayagamoorthy Aug 2007

Making The Power Grid More Intelligent, Salman Mohagheghi, Ronald G. Harley, Ganesh K. Venayagamoorthy

Electrical and Computer Engineering Faculty Research & Creative Works

Summary form only given. This paper focuses on the applications of intelligent techniques for improving the performances of the power system controllers. Intelligent control techniques lay the foundation of the next generation of nonlinear controllers and have the advantage of further improving the controller's performance by incorporating heuristics and expert knowledge into its design. Most of these techniques are independent of any mathematical model of the power system, which proves to be a considerable advantage.

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Redundancy Optimization For Clock-Free Nanowire Crossbar Architecture, Yadunandana Yellambalase, Ravi Bonam, Minsu Choi Aug 2007

Redundancy Optimization For Clock-Free Nanowire Crossbar Architecture, Yadunandana Yellambalase, Ravi Bonam, Minsu Choi

Electrical and Computer Engineering Faculty Research & Creative Works

In this paper a method is being proposed to find the optimal dimension of Programmable Gate Macro Block (PGMB) in clock-free nanowire crossbar architecture. A PGMB is a nanowire crossbar matrix with discrete number of rows and columns on which the NCL (Null Convention Logic) gates can be programmed. This method uses inherent redundancy to route through defective crosspoints. A 6 X 10 defect-free crossbar can be used to program any of the 27 threshold gates. Due to imperfections and variations in nanoscale manufacturing process, high defect densities are anticipated. Thus, such defects should be located when tested and the …

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Clock-Free Nanowire Crossbar Architecture Based On Null Convention Logic (Ncl), Ravi Bonam, Shikha Chaudhary, Yadunandana Yellambalase, Minsu Choi Aug 2007

Clock-Free Nanowire Crossbar Architecture Based On Null Convention Logic (Ncl), Ravi Bonam, Shikha Chaudhary, Yadunandana Yellambalase, Minsu Choi

Electrical and Computer Engineering Faculty Research & Creative Works

There have been numerous nanowire crossbar architectures proposed till date, although all of them are envisioned to be synchronous (i.e., clocked). The clock is an important part in a circuit and it needs to be connected to all the components to synchronize their operation. Considering non-deterministic nature of nanoscale integration, realizing them on a nano wire crossbar system would be quite cumbersome. Unlike the conventional clocked counterparts, a new clock-free crossbar architecture is proposed to resolve the issues with clocked counterparts in this paper, where the use of clock is eliminated from the architecture. This has been done by implementing …

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Disbond Thickness Evaluation Employing Multiple-Frequency Near-Field Microwave Measurements, Mohamed A. Abou-Khousa, R. Zoughi Aug 2007

Disbond Thickness Evaluation Employing Multiple-Frequency Near-Field Microwave Measurements, Mohamed A. Abou-Khousa, R. Zoughi

Electrical and Computer Engineering Faculty Research & Creative Works

Near-field microwave nondestructive evaluation (NDE) techniques have shown great potential for disbond detection in multilayer dielectric composite structures. The high detection capability associated with these techniques stems from the fact that near-field microwave signals are sensitive to minute variations in the dielectric properties and geometry of the medium in which they propagate. In the past, the sensitivity of the near-field microwave NDE techniques to the presence and properties of disbonds in multilayer dielectric composites has been investigated extensively. However, a quantitative disbond thickness estimation method has yet to be introduced. In this paper, we propose a maximum-likelihood (ML) disbond thickness …

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Optimal Control Of A Photovoltaic Solar Energy System With Adaptive Critics, Richard L. Welch, Ganesh K. Venayagamoorthy Aug 2007

Optimal Control Of A Photovoltaic Solar Energy System With Adaptive Critics, Richard L. Welch, Ganesh K. Venayagamoorthy

Electrical and Computer Engineering Faculty Research & Creative Works

This paper presents an optimal energy control scheme for a grid independent photovoltaic (PV) solar system consisting of a PV array, battery energy storage, and time varying loads (a small critical load and a larger variable non-critical load). The optimal controller design is based on a class of adaptive critic designs (ACDs) called the action dependant heuristic dynamic programming (ADHDP). The ADHDP class of ACDs uses two neural networks, an "action" network (which actually dispenses the control signals) and a "critic" network (which critics the action network performance). An optimal control policy is evolved by the action network over a …

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Optimal Scheduling Of Generator Maintenance Using Modified Discrete Particle Swarm Optimization, Yusuf Yare, Ganesh K. Venayagamoorthy Aug 2007

Optimal Scheduling Of Generator Maintenance Using Modified Discrete Particle Swarm Optimization, Yusuf Yare, Ganesh K. Venayagamoorthy

Electrical and Computer Engineering Faculty Research & Creative Works

This paper presents a modified discrete particle swarm optimization (PSO) based technique for generating optimal preventive maintenance schedule of generating units for economical and reliable operation of a power system while satisfying system load demand and crew constraints. While GA and other analytical methods might suffer from premature convergence and the curse of dimensionality, heuristics based swarm intelligence can be an efficient alternative. PSO is known to effectively solve large scale multi-objective optimization problems. Here, a modified discrete PSO approach is proposed for the GMS optimization problem in order to overcome the limitations of the conventional methods and come up …

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Parameter Optimization Of Pss Based On Estimated Hessian Matrix From Trajectory Sensitivities, Jung-Wook Park, Ganesh K. Venayagamoorthy, Seung-Mook Baek Aug 2007

Parameter Optimization Of Pss Based On Estimated Hessian Matrix From Trajectory Sensitivities, Jung-Wook Park, Ganesh K. Venayagamoorthy, Seung-Mook Baek

Electrical and Computer Engineering Faculty Research & Creative Works

This paper describes the optimal tuning for the output limits of the power system stabilizer (PSS), which can improve the system damping performance immediately following a large disturbance. The non-smooth nonlinear parameters such as the saturation limits of the PSS cannot be tuned by the conventional methods based on linear approaches. To implement the systematic optimal tuning for the output limits of the PSS, a feedforward neural network (FFNN) is applied to the hybrid system model based on the differential-algebraic-impulsive-switched (DAIS) structure. The FFNN is firstly designed to identify the trajectory sensitivities obtained from the DAIS structure. Thereafter, it estimates …

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Hand-Assembled Cable Bundle Modeling For Crosstalk And Common-Mode Radiation Prediction, Shishuang Sun, Geping Liu, James L. Drewniak, David Pommerenke Aug 2007

Hand-Assembled Cable Bundle Modeling For Crosstalk And Common-Mode Radiation Prediction, Shishuang Sun, Geping Liu, James L. Drewniak, David Pommerenke

Electrical and Computer Engineering Faculty Research & Creative Works

A statistical cable bundle model is developed to account for the random disturbance of the wire positions along hand-assembled cable bundles. The nonuniform random bundles are modeled as n-cascaded segments of a uniform multiconductor transmission line. At each section, all wire positions are disturbed with random numbers obeying a Gaussian distribution. In addition, a spline interpolation function is used to improve the continuity of wires winding along the bundle. The wire crosstalk and the common-mode (CM) current distribution along the bundle can be calculated with simulation program with integrated circuit emphasis (SPICE)-like solvers. By injecting the CM current along the …

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Applications Of Diffusion Maps In Gene Expression Data-Based Cancer Diagnosis Analysis, Rui Xu, Donald C. Wunsch, Steven Damelin Aug 2007

Applications Of Diffusion Maps In Gene Expression Data-Based Cancer Diagnosis Analysis, Rui Xu, Donald C. Wunsch, Steven Damelin

Electrical and Computer Engineering Faculty Research & Creative Works

Early detection of a tumor's site of origin is particularly important for cancer diagnosis and treatment. The employment of gene expression profiles for different cancer types or subtypes has already shown significant advantages over traditional cancer classification methods. One of the major problems in cancer type recognition-oriented gene expression data analysis is the overwhelming number of measures of gene expression levels versus the small number of samples, which causes the curse of dimension issue. Here, we use diffusion maps, which interpret the eigenfunctions of Markov matrices as a system of coordinates on the original data set in order to obtain …

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Direction Of Arrival Estimation Based On Support Vector Regression: Experimental Validation And Comparison With Music, Andrea Randazzo, Mohamed A. Abou-Khousa, Matteo Pastorino, R. Zoughi Aug 2007

Direction Of Arrival Estimation Based On Support Vector Regression: Experimental Validation And Comparison With Music, Andrea Randazzo, Mohamed A. Abou-Khousa, Matteo Pastorino, R. Zoughi

Electrical and Computer Engineering Faculty Research & Creative Works

In this letter, the problem of estimating the directions of arrival (DOAs) of coherent electromagnetic waves impinging upon a uniform linear array (ULA) is considered. In particular, an efficient DOA estimation approach based on the support vector regression is assessed using experimental measurements. Moreover, the obtained results are compared with those yielded by the multiple signal classification (MUSIC) algorithm.

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Dhp-Based Wide-Area Coordinating Control Of A Power System With A Large Wind Farm And Multiple Facts Devices, Wei Qiao, Ganesh K. Venayagamoorthy, Ronald G. Harley Aug 2007

Dhp-Based Wide-Area Coordinating Control Of A Power System With A Large Wind Farm And Multiple Facts Devices, Wei Qiao, Ganesh K. Venayagamoorthy, Ronald G. Harley

Electrical and Computer Engineering Faculty Research & Creative Works

Wide-area coordinating control is becoming an important issue and a challenging problem in the power industry. This paper proposes a novel optimal wide-area monitor and wide-area coordinating neurocontroller (WACNC), based on wide-area measurements, for a power system with power system stabilizers, a large wind farm, and multiple flexible ac transmission system (FACTS) devices. The wide-area monitor is a radial basis function neural network (RBFNN) that identifies the input-output dynamics of the nonlinear power system. Its parameters are optimized through a particle swarm optimization (PSO) based method. The WACNC is designed by using the dual heuristic programming (DHP) method and RBFNNs. …

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Approximate Dynamic Programming And Neural Networks On Game Hardware, Ryan J. Meuth, Donald C. Wunsch Aug 2007

Approximate Dynamic Programming And Neural Networks On Game Hardware, Ryan J. Meuth, Donald C. Wunsch

Electrical and Computer Engineering Faculty Research & Creative Works

Modern graphics processing units (GPU) and game consoles are used for much more than simply 3D graphics applications and video games. From machine vision to finite element analysis, GPU's are being used in diverse applications, collectively called General Purpose computation onf graphics processor units (GPGPU). Additionally, game consoles are entering the market of high performance computing as inexpensive nodes in computing clusters. This paper explores the capabilities and limitations of modern GPU's and game consoles, surveying the ADP and neural network technologies that can be applied to these devices.

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A Time-To-First-Spike Cmos Image Sensor, Xiaochuan Guo, Xin Qi, John G. Harris Aug 2007

A Time-To-First-Spike Cmos Image Sensor, Xiaochuan Guo, Xin Qi, John G. Harris

Electrical and Computer Engineering Faculty Research & Creative Works

A time-to-first spike (TTFS) imager was designed such that each pixel outputs a single digital pulse whose timing encodes pixel illumination. For still image applications, this time representation provides a tremendous increase in dynamic range, similar to that of other existing time-based imagers. However, a major advantage of the TTFS imager is that this wide dynamic range can be achieved even for 30 frames/s video applications. A prototype 32x32 TTFS image sensor was fabricated in AMI 0.5 μm CMOS technology. The prototype chip demonstrates a 104 dB dynamic range (limited by the optical equipment), 42 μV/electron conversion gain, 1.25 nA/cm …

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Method Of Measuring Permittivity Of Composite Materials With Hexagonal Ferrite Inclusions, Alexander A. Kitaytsev, Gulnur N. Zhumabayeva, Marina Koledintseva Jul 2007

Method Of Measuring Permittivity Of Composite Materials With Hexagonal Ferrite Inclusions, Alexander A. Kitaytsev, Gulnur N. Zhumabayeva, Marina Koledintseva

Electrical and Computer Engineering Faculty Research & Creative Works

A new simple method for measuring complex permittivity of substantially lossy composite materials is presented. In this method, a sample of the material under study should completely fill in the cross-section of the single-mode transmission line (waveguide), and the length of the sample must be an integer of a half-wavelength in the waveguide filled with this material. The oscillator frequency is swept linearly, the minima of the reflection coefficient are measured, and then analytical formulas are used to calculate real and imaginary parts of permittivity. The method was tested on magneto- dielectric samples containing hexagonal ferrite powders, as well on …

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