Digital Commons Network^™

Effect Of Viscoplastic Flow Rules On The Initiation And Growth Of Shear Bands At High Strain Rates, R. C. Batra, Chang-Soo Kim

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Marchand and Duffy have reported detailed measurements of the temperature and strain as a shear band develops in a HY-100 steel. Assuming their torsional tests in thin-wall tubes can be adequately modeled by a viscoplastic block undergoing overall adiabatic simple shearing deformations, we investigate the effect of modeling the viscoplastic response of the material by a.power law, and flow rules proposed by Litonski, Bodner and Partom, and Johnson and Cook. Each of these flow rules is first calibrated by using the test data at a nominal strain-rate of 3300 s-1. Then predictions from the use of these flow rules at …

Instrument Matrix Of The Four-Detector Photopolarimeter: Physical Meaning Of Its Rows And Columns And Constraints On Its Elements, R. M.A. Azzam

Electrical Engineering Faculty Publications

The four-detector photopolarimeter (FDP) is an arrangement of four photodetectors for measuring the state of polarization of light. The output current vector I of the FDP is related to the input Stokes vector S by I = AS, where A is the instrument matrix. The rows of A can be viewed as projection operators that determine the output currents of the detectors. This leads to the recognition of four special totally polarized input states, each of which maximizes the output of one detector. The associated four orthogonal states produce minimum signals. Because each detector is absorptive and its output is …

Measurement Of Magnetic Fluctuations By O-X Mode Conversion, L. L. Vahala, G. Vahala, N. Bretz

Electrical & Computer Engineering Faculty Publications

The possibility of measuring magnetic fluctuations in a fusion plasma is considered by examining the O→X mode conversion. Under certain conditions and with good angular resolution, this mode conversion can be attributed to the presence of magnetic fluctuations even though the level of these fluctuations is much lower than that of density fluctuations. Some nonideal effects such as mode polarization mismatch at the plasma edge are also discussed.

Reduced Order Robust Controllers For An Experimental Flexible Grid, Vittal S. Rao, M. Westerheide, Alok Das

Electrical and Computer Engineering Faculty Research & Creative Works

A procedure for the design and implementation of reduced-order robust controllers for active vibration control on an experimental flexible grid structure is presented. The experimental structure consists of a 5-ft x 5-ft grid made of 2-in-wide, 1/8-in-thick aluminum strips. The grid hangs vertically, being cantilevered at the top to a large T-beam anchored to a cinder block wall. The grid structure is represented by a 75-degree-of-freedom finite-element model, and the controller uses three piezoelectric accelerometer sensors to command three Non collocated DC motor torquers. The modified balance-truncation model-reduction method is used to derive a control synthesis model. These reduced-order models …

Reduced Order Modeling Methods For Turret-Gun System, Vittal S. Rao, Norman P. Coleman

Electrical and Computer Engineering Faculty Research & Creative Works

Reduced-order modeling techniques are used to design lower order robust controllers for a turret-gun system. The balance-truncation, Routh approximation, and L. Litz's (1980) modal techniques are used to derive the models. A critical comparison of the time and frequency response characteristics of the original and reduced order models is made. The spillover problem associated with a reduced-order model is investigated.

A Review Of Recent Advances In Economic Dispatch, Badrul H. Chowdhury, S. Rahman

Electrical and Computer Engineering Faculty Research & Creative Works

A survey is presented of papers and reports that address various aspects of economic dispatch. The time period considered is 1977-88. Four related areas of economic dispatch are identified and papers published in the general areas of economic dispatch are classified into these. These areas are: optimal power flow, economic dispatch in relation to AGC, dynamic dispatch, and economic dispatch with nonconventional generation sources.

A Two-Dimensional Analog Vlsi Circuit For Detecting Discontinuities In Early Vision, John G. Harris, Christof Koch, Jin Luo

Electrical and Computer Engineering Faculty Research & Creative Works

A large number of computer vision algorithms for finding intensity edges, computing motion, depth, and color, and recovering the three-dimensional shape of objects have been developed within the framework of minimizing an associated "energy" or "cost" functional. Particularly successful has been the introduction of binary variables coding for discontinuities in intensity, optical flow field, depth, and other variables, allowing image segmentation to occur in these modalities. The associated nonconvex variational functionals can be mapped onto analog, resistive networks, such that the stationary voltage distribution in the network corresponds to a minimum of the functional. The performance of an experimental analog …

Influence Of Copper Doping On The Performance Of Optically Controlled Gaas Switches, St. T. Ko, V. K. Lakdawala, K. H. Schoenbach, M. S. Mazzola

Electrical & Computer Engineering Faculty Publications

The influence of the copper concentration in silicon-doped gallium arsenide on the photoionization and photoquenching of charge carriers was studied both experimentally and theoretically. The studies indicate that the compensation ratio (N_Cu/N_Si) is an important parameter for the GaAs:Si:Cu switch systems with regard to the turn-on and turn-off performance. The optimum copper concentration for the use of GaAs:Si:Cu as an optically controlled closing and opening switch is determined.

Electrical Properties Of Hydrogenated Diamond, Sacharia Albin, Linwood Watkins

Electrical & Computer Engineering Faculty Publications

Hydrogen passivation of deep traps in diamond is demonstrated. Current‐voltage (I‐V) characteristics of polycrystalline thin film and bulk diamond were studied before and after hydrogenation. On hydrogenation, all the samples showed several orders of magnitude increase in conductivity. Hydrogenation was carried out under controlled conditions to study the changes in the I‐V characteristics of the samples. The concentration of uncompensated traps was varied systematically by hydrogenation. The concentration of electrically active hydrogen was determined from the I‐V data. It is shown that hydrogenation is an alternative to deep‐level transient spectroscopy, suitable for …

Enhanced Magneto-Optic Kerr Effects In Thin Magnetic/Metallic Layered Structures, William A. Mcgahan, Liang-Yao Chen, Z. S. Shan, David J. Sellmyer, John A. Woollam

Department of Electrical and Computer Engineering: Faculty Publications

Enhanced Kerr rotation spectra are measured in thin magnetic layers on silver. Also, variable angle of incidence spectroscopic ellipsometry is employed to measure the optical dielectric function of both the thin magnetic layer and the underlying thick silver layer. These results are explained quantitatively using the electromagnetic theory for reflection of light from multiple layers of isotropic and gyrotropic materials.

Ellipsometric Study Of Al2O3/Ag/Si And Sio2/Ag/Quartz Ashed In An Oxygen Plasma, Bhola N. De, John A. Woollam

Department of Electrical and Computer Engineering: Faculty Publications

Using monolayer-sensitive variable angle of incidence spectroscopic ellipsometry, the silver oxide growth on a silver mirror, coated with an Al₂ O₃ or SiO₂ protective layer, was investigated. The oxidation was done in a pure oxygen plasma asher. The resulting silver oxide growth was monitored accurately as a function of exposure time in the plasma asher. It was found that silver was converted to silver oxide under the protective coating, during ashing of a sample. The optical constants of a dense silver oxide thin film, created by oxidizing in the asher, were also measured.

Transient Stability Hierarchical Control In Multimachine Power Systems, A Rubbai, F. Eugenio Villaseca

Electrical and Computer Engineering Faculty Publications

The authors present the optimal transient stability control problem in a hierarchical structure for multimachine power systems. The two-level structure retains the local closed-loop controls, thereby easing its implementation on existing systems. The formulation accounts for nonlinearities and interconnections, and the optimization of the system transient performance is obtained with less computational effort. Since the computations are distributed among the many local feedback subsystems, the storage and solution times are considerably less than those required by a single overall centralized controller. This advantage becomes much stronger as the system size increases. For illustration purposes, this technique was applied successfully to …

Triggering In Trigatron Spark Gaps: A Fundamental Study, P. F. Williams, F. E. Peterkin

P. F. (Paul Frazer) Williams Publications

The trigatron has been in widespread use as a demand-triggered, high-voltage switch for more than 40 years. In spite of the popularity and maturity of the technology, there persists an uncertainty over the basic physical mechanism(s) responsible for triggering breakdown in the devices. We present the results of an empirical study of trigatrons that demonstrates that breakdown is initiated by a streamer launched from the trigger pin, independent of the trigger spark. We compare our results with those of previous workers, and discuss the generality of our conclusions.

The Electrical Characteristics Of Semi-Insulating Gallium Arsenide A Material For High Power Switches, David Clifton Stoudt

Electrical & Computer Engineering Theses & Dissertations

An experimental study of the electrical characteristics of semi-insulating gallium arsenide has been performed. The goal of this research was to aid in the development of an electron-beam controlled high-power semiconductor switch. The electrical characteristics were found to be heavily dependent on the deep level configuration of the material being investigated. Two methods of deep level characterization are discussed and their results are compared to the information given by the material manufacturer. Studies were conducted to determine both the steady-state and transient dark current characteristics of the switch. Along with being a function of the applied voltage and the deep …

Accurate Calibration Of The Four-Detector Photopolarimeter With Imperfect Polarizing Optical Elements, R. M.A. Azzam, Ali G. Lopez

Electrical Engineering Faculty Publications

The first three columns of the instrument matrix A of the four-detector photopolarimeter (FDP) are determined by Fourier analysis of the output current vector I(P) as a function of the azimuth angle P of the incident linearly polarized light. Therefore 12 of the 16 elements of A are measured free of the imperfections of the (absent) quarter-wave retarder (QWR). The effect of angular beam deviation by the polarizer is compensated for by taking the average, (1/2) [I(P) + I(P + 180°)], of the FDP output at 180°-apart, optically equivalent, angular positions of the polarizer. The remaining fourth column of A …

Evaluation Of Sorting Algorithm Performance On Single Instruction Multiple Data Machines, Dong Kuen Yang

Theses

Partitioning an application program into several tasks and executing them via parallel processing is one way to increase computation throughput and performance. But with a uniprocessor system, the performance increase will be minimal. Computer scientists have developed several multiprocessor systems to gain more speed in computation.

There are several computer architectures, such as pipeline machines, array processors and multiprocessor systems. They provide a parallel execution environment to increase the execution speed. But as the system becomes more complex, the communication traffic density between several processors increases more heavily. It has to provide some kind of control algorithm or routing function …

Reliability Prediction Of Vulcanized Fibre Using Electrical Noise As A Screening Parameter, George A. Donos

Theses

The main objective of this thesis was to find a correlation between the electrical noise generated within the body of Vulcanized Fibre in insulating service and the time of its breakdown under a synergy of electrical, thermal and mechanical stresses. Failure was defined as a material discontinuity, puncture, under accelerated life test conditions. Radio frequency measurements of the partial discharges occuring in the voids of the material were performed on 1240 samples of vulcanized fibre with 10 mil thickness. The level of electrical noise measured was used to classify the specimens into the three following categories: (a) Low Noise:0-2.8μV (0-9db), …

Robotic Arms With Flexible Links As The Links Approach Rigidity, George A. Downes

Theses

The dynamics of single link flexible robotic arms are modeled using the Bernoulli-Euler beam equation and Lagrange's equation. The Bernoulli-Euler beam equation derivation is reviewed and is studied in the limiting case as the flexiblity approaches zero. Using the Bernoulli-Euler beam equation, a procedure is developed to calculate the position of the endpoint of a link given the displacement, slope or curvature of any point on the link. Also a procedure is developed to calculate the minimum Young's modulus of elasticity, E, given a specified endpoint displacement tolerance.

A rigid link model based on Lagrange's equation and a flexible link …

Recursive System Identification Using Least Squares Method, Gholamreza Ghorbani Moghadam

Theses

Input and output sampling, in addition to computer simulations, are now an integral part of system identification. In this thesis, the concept of analyzing any time invariant continuous deterministic system will be developed by identifying a linear discrete - time system equivalent to the continuous one. In this method, two computer programs are written in pascal. The first program applies the Recursive Least Squares Method to discrete - time systems in order to estimate the system components. The second program estimates the future output of the system. Four systems have then identified using the programs.

In this process, system identification …

Design And Analysis Of An Intracranial Pressure And Temperature Sensor Telemetry System, Anshumat Parasar

Theses

This thesis presents a signal conditioning and telemetry system for an implantable pressure and temperature transducer. The initial target application is for measuring the epidural intracranial pressure in the range of 25-100 millitorr and temperature over the range 90 — 110° F. The implant, based on custom silicon IC design can be packaged within a volume of 2cm3 and will require surgical procedures for placement and removal. Effort has been made in this thesis to design the transducer, associated signal conditioning and telemetry circuits for useful operation over a wide range of power supply voltage. The implanted device is powered …

Efficient Interconnection Schemes For Vlsi And Parallel Computation, Ronald I. Greenberg

Computer Science: Faculty Publications and Other Works

This thesis is primarily concerned with two problems of interconnecting components in VLSI technologies. In the first case, the goal is to construct efficient interconnection networks for general-purpose parallel computers. The second problem is a more specialized problem in the design of VLSI chips, namely multilayer channel routing. In addition, a final part of this thesis provides lower bounds on the area required for VLSI implementations of finite-state machines. This thesis shows that networks based on Leiserson's fat-tree architecture are nearly as good as any network built in a comparable amount of physical space. It shows that these "universal" networks …

Protocol Processing Delay Analysis On Ethernet By Simulation Of Njit Ethernet, Jagdish Gangrimal Rangwani

Theses

CSMA/CD based Local Area Networks account for about 75% of the installed LAN base today. As these networks are becoming available for high channel bandwidth, it is important to identify the bottlenecks in these networks. As channels are becoming high speed, bottleneck is shifting from channel to protocol processing. This delay depends on a particular implementation of the protocol and not the protocol standard itself.

This Thesis presents the analysis of delay on Ethernet. To achieve realistic results NJIT Ethernet, as it is configured, is modelled and simulated. Traffic on this network is measured and load on each segment is …

Effects Of N>M Clos Networks On Edge Coloring And Matrix Decomposition Algorithms, Ming-Hsing Lin

Theses

Considered in this thesis are n > m Clos networks on edge coloring and matrix decomposition algorithms. This work uses a two-fold approach to examine the effects of n > m Clos networks on edge coloring and matrix decomposition algorithms. First, edge coloring and matching on bipartite multigraphs are applied to routing on Clos networks. It is demonstrated that edge coloring algorithms which find a minimum edge coloring set up the routing for n > m Clos networks with redundancy. The results presented here indicate that the Euler coloring algorithm has applications on n > m Clos networks because it has fast time complexity …

Semiconductor Pressure Sensor And Amplifier With Extended Temperature Range, Abhay Mahadeo Joshi

Theses

In this thesis work, a unique raicrosensor was designed for pressure measurements over the temperature range of -80 C to 125 C. The sensor has CMOS circuitry powered by a single voltage supply. It can be used for military and space applications including monitoring the pressure acting on the nose of the space shuttle.

The sensor consists of a thin silicon diaphragm, which is stressed by external pressure. Four resistors in a Wheatstone bridge configuration are diffused into the diaphragm. The temperature drift in the silicon sensors is dominated by the temperature dependence of the piezoresistive coefficients. The resistors are …

A Cad For Edif Pattern Generation, Mohammad Akram Khan

Theses

Generating a set of test vector for a digital circuit is the most critical step in design and test. It is very important to generate test sequence easily and efficiently. The importance is enhanced by the fact that the simulation database is being used to create test programs. A CAD tool ATPG (Automatic Test Pattern Generator) has been developed to specify and satisfy requirements of designers and test engineers. EDIF (Electronic Design Interchange Format) is followed closely. EDIF targets compatability among foundry services and CAD/CAE systems.

Spontaneous Mode Locking In Long-Cavity Xenon Lasers, Manuela Fe Tarroja, Mohammad Sharafi, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

Spontaneous mode locking in Fabry—Perot xenon lasers has been experimentally investigated for cavity lengths up to 66 m. Our results show dependence of the number of pulses per round-trip time on the cavity length and the excitation current. Other dynamical effects such as the ringing and modulation of the mode-locked pulses have been observed. A semiclassical model for the self-locking of an inhomogeneously broadened laser is also presented. Numerical results based on this model describe many dynamical features observed in our experiments.

Analytical Determination Of The Complex Dielectric Function Of An Absorbing Medium From Two Angles Of Incidence Of Minimum Parallel Reflectance, R. M.A. Azzam

Electrical Engineering Faculty Publications

The real and imaginary parts of the complex dielectric function (or complex refractive index) of an opaque substrate or a thick film can be determined from two pseudo-Brewster angles measured in two transparent incidence media of different refractive indices. This two-angle method is simple in that it involves no photometric or polarimetric analysis and in that the solution for the optical properties in terms of the measured angles is explicit, analytical, and direct (i.e. noniterative). The two-angle method is demonstrated for an opaque TiN film on a Cleartran ZnS substrate as a specific example. The effect of angle-of-incidence errors on …

Design Of Robotic Lan Controller And Map Interface, Jayesh M. Joshi

Theses

An application specific integrated circuit has been designed for use as a gateway between two local area networks. This silicon chip provides the gateway function to link the NJIT robotics network and the MAP IEEE-standardized network. This IC utilizes the available Motorola MC 68824 Token Bus Controller for the MAP data path. A special IO design compatible with an optical communication link is used to interface into the NJIT RLAN network.

The gateway IC serves as an asynchronous buffer between the 5Mbps MAP link and the 500 bps local optical link. The control protocol provides the master function for polling …

Optimal Algorithmic Testing Of Re-Programmable Logic Arrays, Arvind Chopra

Theses

This research delineates a test strategy and detailed sequence of test vectors for a new class of programmable logic devices (PLDs). This new class of devices is based on architectures that contain programmable logic arrays (PLAs) programmed by on chip integrated static RAMs or EEPROMS. The new PLD architecture poses unique testing problems which require 100% nodal test coverage. Previous PLAs/PLDs did not require that 100% of the nodes be tested since their circuits utilized fuse link crosspoints and were not dynamically reprogrammable. Such devices could be tested by a unique personality pattern that combined the application and the test …

Theory Of A Synchronously Pumped Mode-Locked Dye Laser In The Short Pump Pulse Limit, Duncan Leo Macfarlane, Lee W. Casperson

Electrical and Computer Engineering Faculty Publications and Presentations

We study the operation of a synchronously pumped mode-locked dye laser when the pump pulse is taken as a Dirac delta function, a limit that is sometimes experimentally reasonable. We find that in this limit the model simplifies considerably and that with further assumptions the physical interpretation of synchronously pumped mode-locked operation becomes apparent. Specifically, our nonlinear dynamical model reduces to the same set of equations that govern a prepumped Q-switched laser, and from this simple picture we are able to derive approximate analytic formulas for the synchronously pumped mode-locked laser pulse width and peak intensity. Additionally, we present a …