Engineering Commons^™

Scaling Of The Silicon-On-Insulator Si And Si1-Xgex P-Mosfets, Marijan PeršUn

Dissertations and Theses

Two-dimensional numerical simulation was used to study the scaling properties of SOI p-MOSFETs. Based on the design criteria for the threshold voltage and DIBL, a set of design curves for different designs was developed. Data for subthreshold slope, SCE and threshold voltage sensitivity to silicon film thickness are also given. Results show that short-channel effects can be controlled by increasing the doping level or by thinning the silicon film thickness. The first approach is more effective for p+ gate design with high body doping, while the second approach is much more effective for n+ gate design with low body doping. …

Data Allocation For Distributed Programs, Liono Setiowijoso

Dissertations and Theses

This thesis shows that both data and code must be efficiently distributed to achieve good performance in a distributed system. Most previous research has either tried to distribute code structures to improve parallelism or to distribute data to reduce communication costs. Code distribution (exploiting functional parallelism) is an effort to distribute or to duplicate function codes to optimize parallel performance. On the other hand, data distribution tries to place data structures as close as possible to the function codes that use it, so that communication cost can be reduced.

In particular, dataflow researchers have primarily focused on code partitioning and …

Seasonal Hidden Markov Models For Stochastic Time Series With Periodically Varying Characteristics, Arthur M. Lewis

Dissertations and Theses

Novel seasonal hidden Markov models (SHMMs) for stochastic time series with periodically varying characteristics are developed. Nonlinear interactions among SHMM parameters prevent the use of the forward-backward algorithms which are usually used to fit hidden Markov models to a data sequence. Instead, Powell's direction set method for optimizing a function is repeatedly applied to adjust SHMM parameters to fit a data sequence. SHMMs are applied to a set of meteorological data consisting of 9 years of daily rain gauge readings from four sites. The fitted models capture both the annual patterns and the short term persistence of rainfall patterns across …

Ohmic Contact To Ion Implanted Gallium Arsenide Antimonide For Application To Indium Aluminum Arsenide-Gallium Arsenide Antimonide Heterostructure Insulated-Gate Field Effect Transistors, Kenneth G. Merkel Ii

Theses and Dissertations

The p-channel In_0.52Al_0.48As-GaAs_1-xSb_x heterostructure insulated-gate field effect transistor (p-HIGFET) is a candidate for complementary integrated circuits due to superior cutoff characteristics and low gate leakage current. Advancement of the In_0.52Al_0.48As-GaAs_1-xSb_x p-HIGFET requires improved source-drain design. Five main tasks were accomplished to achieve this goal. First, thermal limits of the In_0.52Al_0.48As-GaAs_0.51Sb_0.49 HIGFET were investigated. Second, the temperature dependence of band gap and impurity energies were determined for beryllium doped In_0.52Al_0.48. Third, high acceptor concentrations were obtained …

Tolerance Theory Of Periodic Surfaces, James A. Godsey

Theses and Dissertations

Two formulations for the far field statistical average power pattern of a strip grating with errors in strip and slit width are presented. The first formulation utilizes the Born approximation in which the unknown aperture fields are replaced by the incident fields. The second formulation utilizes an approximation which satisfies the edge condition. Approximations for the scattered fields are first derived using PEC surface equivalence for a TEz polarized plane wave incident upon a strip grating consisting of an infinite PEC screen cut by a number of infinitely long slits. Babinet's principle is then used to obtain approximations for the …

Modeling And Development Of A Cellular Micro-Kernel, K. Balaji

Masters Theses

A novel cellular load distribution strategy was designed and implemented on transputers by Dr. Richard Taylor and Dr. Don Goodeve at the University of York, United Kingdom. Based upon the above proposed strategy, a statistical model was developed using the Cellular Automata Theory. The theoretical model drives the implementation process of the cellular micro-kernel on the nCUBE 2S system. The load distribution and the performance characteristics for snake and L type transmission modes, and for uniform and non-uniform distribution of destination processors of the micro-kernel has been measured and compared with our theoretical model. The results show good agreement between …

Determination Of The Temperature Coefficients Of Selected Material Constants Of Dilithium Tetraborate, Gregory S. Weaver

Theses and Dissertations

The first and second order temperature coefficients of the material constants c^E₁₁, c^E₁₂, c^E₄₄, c^E₆₆, and e¹⁵ of dilithium tetraborate (Li₂B₄O₇) have been measured over a temperature range of 20°C to 150°C. An improved resonator method was used to measure the fundamental zero mass loading antiresonant frequencies of selected pure-mode orientations of Li₂B₄O₇. Material constants extraction was performed using a linear least squares matrix method. The resulting material constant curves were fit with a third …

Scattering From Finite By Infinite Periodic Arrays With Arbitrary Piecewise-Linear Slot Elements, Paul R. Barre

Theses and Dissertations

A numerical model for analyzing electromagnetic scattering from a planar Frequency Selective Surface (FSS) is developed. The model can represent an FSS with multiple arrays of arbitrary piecewise linear scatterers in a stratified dielectric medium. The FSS's arrays are finite by infinite, accounting for edge effects, where a periodic array element is formed from the piecewise linear connection of thin slots in a groundplane. The stratified dielectric medium is defined as an arbitrary stack of lossless dielectric slabs that sandwich the user defined arrays, simulating an FSS. The Surface Equivalence theorem is used to construct an equivalent problem based on …

Design And Development Of Microswitches For Micro-Electro-Mechanical Relay Matrices, Mark W. Phipps

Theses and Dissertations

Many different micro-electro-mechanical switches were designed in the Multi-User MEMS processes (MUMPs) and deep x-ray lithography and electroforming (LIGA) processes. The switches were composed of actuators that operated based upon either electrostatic forces or thermal forces. A thermally activated beam flexure actuator that operated based upon differential heating was used extensively. This actuator, which was fabricated in the MUMPs process, was able to deflect up to 12 microns with a total input power of less than 25 mW. The thermal resistance, which was needed to model this actuator, was determined from a material constant, 1.9 ± 0.08 m^1.5-°C-W …

Optimal Mixed-Norm Control Synthesis For Discrete-Time Linear Systems, David R. Jacques

Theses and Dissertations

A mixed-norm approach to control synthesis for discrete time linear systems is developed. Specifically, the problem of minimizing the H₂ norm of a transfer function, subject to a combination of ℓ₁ and-or H_∞ norm constraints on dissimilar but related transfer functions is considered. The uniqueness of the optimal solution is shown, and numerical methods for approximating the optimal solution to within arbitrary accuracy are developed. These methods generally result in high order compensators which can not be implemented in most practical applications. In response to this, a numerical method is developed which solves for suboptimal solutions of …

Design, Fabrication, Modeling, And Testing Of Surface-Micromachined Micromirror Devices, M. Adrian Michalicek

Theses and Dissertations

The Flexure-Beam Micromirror Device (FBMD) is a phase-only piston style spatial light modulator demonstrating properties which can be used for phase adaptive- corrective optics. This thesis presents a complete study of new designs of FBMDs and other micromirror devices, from original design considerations through final device testing and verification of ideal and advanced models. The models relate the electrical and mechanical properties of the device by equating the electrostatic force of a parallel- plate capacitor with the counteracting spring force of the device's support flexures. For the advanced model of the Flexure-Beam micromirror device, the capacitor solution is derived via …

Grain-Size Optimization And Scheduling For Distributed Memory Architectures, Jing-Chiou Liou

Dissertations

The problem of scheduling parallel programs for execution on distributed memory parallel architectures has become the subject of intense research in recent, years. Because of the high inter-processor communication overhead in existing parallel machines, a crucial step in scheduling is task clustering, the process of coalescing heavily communicating fine grain tasks into coarser ones in order to reduce the communication overhead so that the overall execution time is minimized.

The thesis of this research is that the task of exposing the parallelism in a given application should be left to the algorithm designer. On the other hand, the task of …

Investigation Of Hybrid Message-Passing And Shared-Memory Architectures For Parallel Computer : A Case Study : Turbonet, Xi Li

Dissertations

Several DSP (Digital Signal Processing) algorithms are developed for the MIT TurboNet parallel computer. In contrast to other parallel computers that implement exclusively in hardware either the message-passing or the shared-memory communication paradigm, or employ distributed shared-memory architectures characterized by inefficient implementation of the shared-memory paradigm, the hybrid architecture of TurboNet supports direct, efficient implementation of both paradigms. Three versions of each algorithm are developed, if possible, corresponding to message-passing, shared-memory, and hybrid communications, respectively. Theoretical and experimental comparisons of algorithms are employed in the analysis of performance. The results prove that the hybrid versions generally achieve better performance than …

A Modified Lrt-Based Spread-Spectrum Receiver Using Spatial And Temporal Processing, Jeffrey L. Cutcher

Theses

The problem of demodulating a direct-sequence (DS) spread-spectrum signal in the presence of single-tone or narrow-band interference and multi-path is discussed. A likelihood-ratio test (LRT) receiver is presented which consists of a whitening filter and a RAKE correlator.

A modified LRT receiver structure is then considered where the whitening filter is replaced by an antenna array with corresponding tap coefficients. The array spatially removes the interference by estimating it's angle-of-arrival. Using the array has an advantage over the original LRT receiver when a narrow-band interference is present. Both receivers are identical in performance under the single-tone interference model.

A third …

Radiation Damage Studies In Gate Oxides, Sandeep G. Bharathi

Theses

Detailed investigation of the effects of Gamma-ray irradiation on the electrical properties such as current-voltage arid capacitance-voltage characteristics in thermally grown SiO₂ films in the thickness range of 15 to 120 nm on silicon substrates is presented in this thesis. The structures used in this study are Al/Poly/SiO₂/Si/Al and Al/SiO₂/Si/Al MOS capacitors. Based on the electrical characterization studies, we observe that irradiation causes generation of positive charges in the oxide leading to a shift of the high frequency Capacitance-Voltage (C-V) curves. An increase in surface state density at the SiO₂-Si interface with increase …

A Defect Detection Algorithm For Sequential And Parallel Computers, Ralf Hross

Theses

The comparison of images containing a single object of interest, where one of them contains a model object, is frequently used for defect detection/identification. This is often a problem of interest to industrial applications. To make this task more efficient, the implementation on parallel computers should be a major objective. This thesis introduces sequential and parallel versions of an algorithm that compares original(reference) and processed images in the time and frequency domains. The emphasis is on parallel implementation. This comparison may help to detect changes in images. Extracted data is also compared to database data in an attempt to pinpoint …

A Vhdl Design Of A Reconfigurable Cache Memory System, Tiffany M. Brooks

Honors Capstone Projects and Theses

No abstract provided.

Bandwidth And Additive Bandwidth Of Graphs, Maria Kujawski

Honors Capstone Projects and Theses

No abstract provided.

Testability Design And Testability Analysis Of A Cube Calculus Machine, Lixin Zhou

Dissertations and Theses

Cube Calculus is an algebraic model popular used to process and minimize Boolean functions. Cube Calculus operations are widely used in logic optimization, logic synthesis, computer image processing and recognition, machine learning, and other newly developing applications which require massive logic operations. Cube calculus operations can be implemented on conventional general-purpose computers by using the appropriate "model" and software which manipulates this model. The price that we pay for this software based approach is severe speed degradation which has made the implementation of several high-level formal systems impractical. A cube calculus machine which has a special data path designed to …

Identification And Evaluation Of Monitoring Techniques For The Performance Of A Communication Network, Maureen E. Borgia

Theses and Dissertations

This study investigates the application of statistical process control methods to monitoring the performance of a communication network. The methods applied include four different types of control charts. The literature search uncovered only one previous study that used a control chart to monitor a communication network. Using a case study of a communication network, four important issues for proper control chart usage are emphasized. These issues are: proper data collection rate due to autocorrelation, proper subgrouping of the data, ensuring that count data conforms to the assumptions of the binomial probability model before implementing p or np control charts, and …

Effects Of Varying Coupling Impedance, Finite Length, And Asynchronous Harmonics On High Power Bwo Performance, Larald Dean Moreland

Electrical and Computer Engineering ETDs

A systematic study of high power backward wave oscillators (BWOs) was performed using the Sinus-6 repetitively-pulsed relativistic electron beam accelerator. Peak output power of up to 550 MW was measured in a frequency range of 9.2 to 9.8 GHz with pulse lengths up to 10 ns. The experimental results were compared with numerical simulations using TWOQUICK, a 2.5 D, relativistic, fully electromagnetic, particle-in-cell (PIC) code. It was observed that a significant increase in microwave efficiency can be obtained by using a BWO with a spatially varying coupling impedance instead of the traditional uniform distribution. Based on experiments using variations of …

Hardware/Software Codesign And Simulation With The Occam Programming Language, Roy L. Krans

Masters Theses

Hardware/software codesign is an increasingly popular method for improving system performance and adaptability while minimizing cost. The goal of this design approach is to achieve the desired system characteristics (performance, fault tolerance, cost, power consumption, etc.) by carefully distributing the system functions among hardware and software components. Popular tools for describing this dual hardware/software functionality are behavioral languages such as C++ and Ada. These languages typically include facilities for both traditional sequential programming as well as behavioral modeling.

This thesis examines the effectiveness of occam as a behavioral language and its role in hardware/software codesign. The occam language is used …

An Investigation Of The Speed And Power Limitations Of A Copper-Doped Gallium Arsenide Photoconductive Switch, David Clifton Stoudt

Electrical & Computer Engineering Theses & Dissertations

The processes of persistent photoconductivity followed by photo-quenching are demonstrated in copper-compensated, silicon-doped, semi-insulating gallium arsenide. These processes allow a switch to be developed that can be closed by the application of one laser pulse (λ = 1.06 μm) and opened by the application of a second laser pulse with a wavelength equal to twice that of the first laser (λ= 2.13 μm). Switch closure is primarily achieved by elevating electrons from a deep copper center which has been diffused into the material. The opening phase is a two-step process which relies initially on the absorption of the 2-μm laser …

Automatic Synthesis Of Vlsi Layout For Analog Continuous-Time Filters, David Lyle Robinson

Dissertations and Theses

Automatic synthesis of digital VLSI layout has been available for many years. It has become a necessary part of the design industry as the window of time from conception to production shrinks with ever increasing competition. However, automatic synthesis of analog VLSI layout remains rare.

With digital circuits, there is often room for signal drift. In a digital circuit, a signal can drift within a range before hitting the threshold which triggers a change in logic state. The effect of parasitic capacitances for the most part, hinders the timing margins of the signal, but not its functionality. The logic functionality …

Investigation Of Ground Target Detection Methods In Fully Polarimetric Wide Angle Synthetic Aperture Radar Images, Wayne B. Mclaggan

Theses and Dissertations

Target detection is a high priority of the Air Force for the purpose of reconnaissance and bombardment. This research investigates and develops methods to distinguish ground targets from clutter (i.e. foliage, landscape etc.) in Wide Angle Synthetic Aperture Radar (WASAR) images. WASAR uses multiple aspect angle SAR images of the same target scene. The WASAR data was generated from a pre-release software package (XPATCH-ES) provided by the sponsor (WL-AARA). A statistical analysis and feature extraction is performed on the XPATCH-ES data. Polarimetric and wide angle covariance matrices are estimated and analyzed. From an analysis of the wide angle covariance matrix …

Tree Restructuring Approach To Mapping Problem In Cellular Architecture Fpgas, Narahari Ramineni

Dissertations and Theses

This thesis presents a new technique for mapping combinational circuits to Fine-Grain Cellular-Architecture FPGAs. We represent the netlist as the binary tree with decision variables associated with each node of the tree. The functionality of the tree nodes is chosen based on the target FPGA architecture. The proposed tree restructuring algorithms preserve local connectivity and allow direct mapping of the trees to the cellular array, thus eliminating the traditional routing phase. Also, predictability of the signal delays is a very important advantage of the developed approach. The developed bus-assignment algorithm efficiently utilizes the medium distance routing resources (buses). The method …

Design Of A Digital Compensation Filter, Nader Fakhry

Dissertations and Theses

The 24-bit Motorola DSP56001 processor will be used in combination with the DSP56ADC16 and the PCM-56 to design a good FIR compensation filter. Our objective is to digitize the input analog signal, and to compensate for the attenuation in the magnitude response of the digital sine wave. Two different experiments will be conducted, a hands on approach, and a simulation program. The first one will be realized directly, using the DSP system. We will determine the magnitude response of the system, and then deduce the coefficients of the FIR sin(x)/x filter. A look up table will store those values which …

Theory, Design And Applications Of Linear Transforms For Information Transmission, Adil Benyassine

Dissertations

The aim of this dissertation is to study the common features of block transforms, subband filter banks, and wavelets, and demonstrate how discrete uncertainty can be applied to evaluate these different decomposition techniques. In particular, we derive an uncertainty bound for discrete-time functions. It is shown that this bound is the same as that for continuous-time functions, if the discrete-time functions have a certain degree of regularity.

This dissertation also deals with spectral modeling in filter banks. It is shown, both theoretically and experimentally, that subspectral modeling is superior to full spectrum modeling if performed before the rate change. The …

Design And Micro-Fabrication Of Tantalum Silicide Cantilever Beam Threshold Accelerometer, Chang Joo Kim

Dissertations

Microfabricated threshold accelerometers were successfully designed and fabricated following a careful analysis of the electrical, mechanical, and fabrication issues inherent to micron-sized accelerometers. A uniform cantilever beam was chosen because of the simplicity of design and fabrication. New models for the electrostatic force exerted on the cantilever beam were developed and calculations were made that accurately predicted the electrical characteristics of the accelerometer. The calculations also provided design guidelines for optimizing the accelerometer dimensions. Computer simulation demonstrated that the error of the electrostatic force, calculated using the most accurate model, was within 2% of the actual force which was obtained …

Electrical Characteristics Of Novel Heterojunction Diodes Of Thin Relaxation Semiconductors/P-Si/, Hyung Joo Lee

Dissertations

The relaxation semiconductor is defined as one in which the dielectric relaxation time (τd;resistivity times permittivity) is greater than lifetime (τo). Non-hydrogenated amorphous Silicon Carbide (SiC) and KrF excimer laser induced disordered Si were used for the relaxation semiconductors. Both semiconductors have high resistivity, wide energy gap, and numerous defects. A novel diode, consisting of those semiconductors on p-type crystalline Silicon (c-Si), was fabricated. In the diode structure, an injecting contact was made on the relaxation material and a Schottky barrier contact was made on the c-Si.

Electrical characteristics of both diodes were found to have interesting …