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1993

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Articles 391 - 420 of 1343

Full-Text Articles in Engineering

Bs News Jul 1993

Bs News

Building Services Engineering

No abstract provided.

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Photoellipsometry Determination Of Surface Fermi Level In Gaas (100), Yi-Ming Xiong, Paul G. Snyder, John A. Woollam Jul 1993

Photoellipsometry Determination Of Surface Fermi Level In Gaas (100), Yi-Ming Xiong, Paul G. Snyder, John A. Woollam

Department of Electrical and Computer Engineering: Faculty Publications

Photoellipsometry, a new contactless optical method, is presented, Related to photoreflectance, this method utilizes spectroscopic ellipsometry with the addition of a laser pump beam directed at nearly normal incidence onto the sample surface, where photoexcited electron-hole pairs modify the built-in electric field as a result of the photovoltaic effect. The field-induced changes in the real and imaginary parts of the complex pseudodielectric function can be directly measured, and analyzed in terns of the pump beam power density or the probe beam photon energy to determine parameters, such as surface Fermi level, built-in field strength, depletion depth, broadening, critical point energies, …

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Application Of Sequence Comparison Methods To Multisensor Data Fusion And Target Recognition, Edmund W. Libby Jul 1993

Application Of Sequence Comparison Methods To Multisensor Data Fusion And Target Recognition, Edmund W. Libby

Theses and Dissertations

This research addresses methods for exploiting the joint likelihood of observed kinematic and nonkinematic (sensor signature) physical events to improve dynamic object and target recognition. A principal direction is the application of dynamic programming sequence comparison techniques to condition matching of object signatures to known models according to observed kinematics. A second direction is the application of kinematic/aspect-angle Kalman filter trackers to condition kinematic tracking according to observed signatures. These conditioning processes dramatically reduce ambiguity in object recognition, and can be used together or separately to allow computation of a posterior probabilities of object class membership using Bayesian methods. Proposals …

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Comparison Of A Distributed Kalman Filter Versus A Centralized Kalman Filter With Fault Detection Considerations, Paul J. Lawrence Jr. Jul 1993

Comparison Of A Distributed Kalman Filter Versus A Centralized Kalman Filter With Fault Detection Considerations, Paul J. Lawrence Jr.

Theses and Dissertations

This project examined the results obtained by simulating an aircraft navigation system with a partial complement of a typical avionics sensor array. Two different techniques of estimation processes were utilized and compared: the conventional Kalman and the federated filter architectures. Areas of interest include error state estimation accuracy and overall performance, residual behavior under normal and induced sensor failure conditions, and potential for failure detection and isolation. Several simulations were accomplished for each filter design and the results were compared in order to verify the validity of the newly developed federated filter architecture. Comparison of the error state estimation accuracies …

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Finite Element Analysis For An Involute Spur Gear Noise Excitation By Impact Effects, Wenbeen Li Jul 1993

Finite Element Analysis For An Involute Spur Gear Noise Excitation By Impact Effects, Wenbeen Li

Electronic Theses & Dissertations

The purpose of this study includes (1) to identify the relationship between the impact loads or backlash and the sound field pressure of impact direct noise of meshing gears, (2) to show that impact whether or not the impact direct noise contributes to the noise of overall gear system, and (3) to demonstrate how impact direct noise can be predicted. The method used to predict was finite element analysis and numerical solution. This research presents the analytical model of impact direct noise prediction for meshing gear teeth based on the data that the tooth vibration and surface are known by …

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Variable Structure End Point Control Of A Flexible Manipulator, Shailaja Chenumalla, Sahjendra N. Singh Jul 1993

Variable Structure End Point Control Of A Flexible Manipulator, Shailaja Chenumalla, Sahjendra N. Singh

Electrical & Computer Engineering Faculty Research

We treat the question of control and stabilization of the elastic multibody system developed in the Phillips Laboratory, Edwards Air Force Base, California. The controlled output is judiciously chosen such that the zero dynamics are stable or almost stable. A variable structure control (VSC) law is derived for the end point trajectory control. Although, the VSC law accomplishes precise end point tracking, elastic modes are excited during the maneuver of the arm. A Linear stabilizer is designed for the final capture of the terminal state.

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Optimizing Irrigation Management For Pollution Control And Sustainable Crop Yield, G. R. Musharrafieh, Richard C. Peralta Jul 1993

Optimizing Irrigation Management For Pollution Control And Sustainable Crop Yield, G. R. Musharrafieh, Richard C. Peralta

Civil and Environmental Engineering Faculty Publications

We developed a simulation-optimization model which maximizes crop yield while maintaining target salt concentration in the root zone, and/ or preventing salt from leaching to the groundwater. The model performs nonlinear optimization and simulation. Implicit finite difference forms of the nonlinear, transient, unsaturated water flow equation, and the convection-diffusion equation are embedded as constraints. Other constraints include nonlinear functions describing the hydraulic properties of the medium. The objectives of the management model is to develop irrigation strategies which prevent salt leaching to the groundwater when salty irrigation water is used. Five different irrigation strategies are developed for Huntington Research Farm, …

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Development And Testing Of Locally Produced Natural Rubber (Nr) And Pvc Blends, B Mutagahywa Jun 1993

Development And Testing Of Locally Produced Natural Rubber (Nr) And Pvc Blends, B Mutagahywa

Tanzania Journal of Engineering and Technology (TJET)

The mechanical properties of natural rubber - poly(vinyl chloride) blends have been studied. Tensile and tear strengths of the vulcanizates has been shown to increase with increasing proportions of PVC up to about 20 pphr. Abrasion loss and hardness decreases slightly with increasing concentration of PVC. Increased loading Of carbon black lowers the tensile and tear strength while increasing the abrasion loss and hardness values. This may be explained by the fact that PVC exists as a discontinuous rigid phase in the polymer compound. At normal loading of black (37 pphr) PVC improves processability and acts in the same way …

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Optimum Design For Spring With Orthogonal Design Method, Han Fu - Jie Jun 1993

Optimum Design For Spring With Orthogonal Design Method, Han Fu - Jie

Tanzania Journal of Engineering and Technology (TJET)

Orthogonal design method is a sort of direct optimum method, by which the op- timal result may be obtained through simple computation and analysis. This method has gained increasingly extensive interest in scientific research, engineering design, end production management as well. The orthogonal table is the basic instrument for carrying out optimum design with orthogonal design method. It is a mathernatical table established On the basis Of the idea of isostatic distribution. As various levels may appear in any column, it makes a partial experiment contain levels of all factors furthermore. RII combina- tions of any two columns may appear …

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Antecedents, Moderators And Outcomes Of Organizational Commitment, Beatus Kundi Jun 1993

Antecedents, Moderators And Outcomes Of Organizational Commitment, Beatus Kundi

Tanzania Journal of Engineering and Technology (TJET)

This study examined: (I) the impact of the BtruCturaI of tenure, job integration and organizational support on organizational (2) the mediating roles of the cultural values for performance and collectivity, and the intra—individual factorg of organizational identification and the norm of reciprocity Ln the relationahip between the structural factore and organization coamitment; and, (3) the relationghip between organizational cormitment and the ouecome variablen Of abøeneeeigm, turnover and The Bhow that job and Of the for performance a gignificant facilitator of the effecte Of the etructuraL factors on commitment; and organization identification and the norm of rec are important linkø in …

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Reduced Bandwidth For Remote Vehicle Operations, Timothy E. Noell, Fred W. Depiero Jun 1993

Reduced Bandwidth For Remote Vehicle Operations, Timothy E. Noell, Fred W. Depiero

Electrical Engineering

Oak Ridge National Laboratory staff have developed a video compression system for low-bandwidth remote operations. The objective is to provide real-time video at data rates comparable to available tactical radio links, typically 16 to 64 thousand bits per second (kbps), while maintaining sufficient quality to achieve mission objectives. The system supports both continuous lossy transmission of black and white (gray scale) video for remote driving and progressive lossless transmission of black and white images for remote automatic target acquisition. The average data rate of the resulting bit stream is 64 kbps. This system has been demonstrated to provide video of …

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A Technical Approach To Groundwater Contamination Problems, Jacqueline C. Burton, Catherine Leser, Candace M. Rose Jun 1993

A Technical Approach To Groundwater Contamination Problems, Jacqueline C. Burton, Catherine Leser, Candace M. Rose

United States Department of Energy: Publications

Argonne National Laboratory has been performing technical investigations at sites in Nebraska and Kansas that have identified groundwater contamination by carbon tetrachloride. This comprehensive program will ultimately provide the affected communities with safe drinking water. The first step in the program is to evaluate the available data and identify sites that will require an Alternate Water Supply Study (AWSS). The objective of the AWSS is to identify options for providing a safe drinking water supply to all users, in compliance with the Safe Drinking Water Act. The AWSS consists of an engineering and cost evaluation followed by implementation of the …

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Brittle Compressive Failure Of Salt-Water Columnar Ice Under Biaxial Loading, T. R. Smith, E. M. Schulson Jun 1993

Brittle Compressive Failure Of Salt-Water Columnar Ice Under Biaxial Loading, T. R. Smith, E. M. Schulson

Dartmouth Scholarship

The brittle failure of saline columnar ice was investigated under biaxial compression at and −10° and −40°C over the range 0 ≤ R A < 1 where R A is the ratio of the intermediate to major principal compressive stress. The major principal stress and the intermediate (confining) stress were orthogonal to the columnar axes (type-A confinement); both stresses and the c-axes of the grains were co-planar. The results confirm earlier work by Hausier (1981) and Timco and Frederking (1983, 1986) on saline ice and follow similar behavior to fresh-water columnar ice found by Smith and Schulson (1993) and Frederking (1977). Failure stress and failure mode are sensitive to the confinement and two regimes of behavior are found: the failure stress first rapidly increases with R A in the range 0 ≤ R A < R T and then tends to decrease for R A > R t. The transition stress ratio, R t changes from ≈0.2 at −10°C to ≈0.1 at −40°C. The failure mode changes from axial splitting to shear faulting in the loading plane for 0 < R A < R t. Above R t failure changes to a combined mode of splitting across the columns and shear faulting out of the loading plane. The failure-stress envelope is of a truncated Coulomb-type. Damage studies show wing cracks and local fragmentation of grains involving the brine pockets. The results are explained in terms of Coulombic sliding and Hertzian crack mechanics.

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Scattering Of A Light Beam From Waves At An Air-Sea Interface, Donald D. Duncan, W. H. Carter Jun 1993

Scattering Of A Light Beam From Waves At An Air-Sea Interface, Donald D. Duncan, W. H. Carter

Electrical and Computer Engineering Faculty Publications and Presentations

The authors report a new theory that describes the scattering of an upward propagating laser beam from the sea through the air-sea interface in the presence of sea waves. The sea is assumed to be a uniform dielectric and conventional scattering theory is employed by using a modification to the first Born approximation that permits treatment of surface refraction phenomena. Methods of statistical radiometry are also used in a new manner by assuming that the surface scattering function for the sea waves can be treated by a quasi-homogeneous source model to calculate the second-order correlation functions for the partially coherent …

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Vibration Suppression Of Beam Structures Traversed By Multiple Moving Loads Using A Damped Absorber, Y.H. Lin, C.H. Cho Jun 1993

Vibration Suppression Of Beam Structures Traversed By Multiple Moving Loads Using A Damped Absorber, Y.H. Lin, C.H. Cho

Journal of Marine Science and Technology–Taiwan

This paper deals with the dynamic analysis of a simply supported beam subjected to multiple discrete and distributed moving loads. Resonant vibration is observed for the support beam traversed by multiple discrete moving loads. A practical scheme is applied to reduce the excessive beam vibration to an acceptable range by using a damped absorber attached at the beam center. Lagrange's equation is used to formulated the system governing equation and Laplace transformation is applied to derive the dynamic responses for both the beam and the absorber, Various design parameters, such as the mass ratio, the tuning ratio, and the damping …

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Pitting Of Fe-Mn-Al Alloys In Nacl Solution, M Ruscak, T.P Perng Jun 1993

Pitting Of Fe-Mn-Al Alloys In Nacl Solution, M Ruscak, T.P Perng

Journal of Marine Science and Technology–Taiwan

the increase of ferrite content. However, the nearly ferritic alloy showed much better passivation behavior, presumably due to the addition of 6% Cr.In aerated solution, no or very small passive region was observed. From the immersion test, the general corrosion was found to be minor. Pitting corrosion was the primary corrosion except for the ferritic alloy. The pits were found more frequently in the ferrite phase or at the interface between the ferrite and austenite phases.

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Dehumidification Of Air Flowing In The Entrance Region Of A Channel, R.H. Yeh, W.H. Huang Jun 1993

Dehumidification Of Air Flowing In The Entrance Region Of A Channel, R.H. Yeh, W.H. Huang

Journal of Marine Science and Technology–Taiwan

The heat transfer and dehumidifying characteristics in the entrance region of the parallel plates are studied. Two-dimensional boundary layer equations are solved numerically to obtain the mass concentration for the air-vapor mixture in the inlet of a channel. A simple experiment is conducted to verify the theory. The ratio of the flow length to plate spacing is chosen to be 20/3. It shows that the average total and mass transfer colburn j-factors obtained from experimental data are higher than those of numerical analysis. Finally, the relationships between experimental data and numerical results are acquired to facilitate the prospective design of …

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Breaking Wave Spectrum And Set-Down Set-Up In Shallow Water, W.H. Yang Jun 1993

Breaking Wave Spectrum And Set-Down Set-Up In Shallow Water, W.H. Yang

Journal of Marine Science and Technology–Taiwan

To study the mean water surface in the shallow water, it is necessary to compute the wave set-up and set-down of random waves on the surf zone. Therefore, the breaking wave spectra and radiation stress must be calculated from a wide-band breaking wave model. In this study, we extend the breaking wave spectrum model (Yang, 1991) by using the Wallops spectrum in the deep water. The Wallops spectrum is based on wave dynamics theoretical analysis and no empirical coefficients to be determined by the users. It also contents correct energy (Huang et al., 1981). The breaking wave spectra, radiation stress, …

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Analysis And Simulation Of Solidification For Phase Change Materials In A Cylindrical Container, H.C. Tien, J.S. Chang Jun 1993

Analysis And Simulation Of Solidification For Phase Change Materials In A Cylindrical Container, H.C. Tien, J.S. Chang

Journal of Marine Science and Technology–Taiwan

The objective of this paper is to study the solidification problem of the phase change materials (PCM) in a thick-walled cylindrical container. Through varying each controlling parameter such as the thermophysical properties of wall (mold), wall thickness, aspect ratio of the container, initial temperature of PCM and the external cooling conditions, etc., the effect of each parameter on the solidification process is shown clearly. By knowing how a thick wall interacts with such a phase change phenomenon, it is therefore possible to well control the solidification process and also to improve the solid structure formed. In this study, convective boundary …

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Formation Of Amorphous Cu-Zr Alloy Powder By Mechanical Alloying, T.R. Chen, P.Y. Lee Jun 1993

Formation Of Amorphous Cu-Zr Alloy Powder By Mechanical Alloying, T.R. Chen, P.Y. Lee

Journal of Marine Science and Technology–Taiwan

Amorphous Cux Zr100-x alloy powder has been synthesized in the range 20 ≦ x ≦ 80 by mechanical alloying mixtures of Cu and Zr powders. This range is larger than amorphous alloys produced by the vaporquenching technique. A mixture of amorphous and crystalline phases formed at the compositions of Cu10Zr90 and Cu90Zr10. Amorphous CuxZr100-x alloy powder also has been synthesized in the range 20 ≦ X ≦ 60 by mechanical alloying mixtures of intermetallic compound Cu9Zr2 and CuZr2 powders. The temperature and activation energy for crystallization of the MA Cu-Zr amorphous powders are higher than that for vaporquenched samples. The …

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Identification Of Whirling Motions By Phase Unwrapping Technique, Rong-Juin Shyu Jun 1993

Identification Of Whirling Motions By Phase Unwrapping Technique, Rong-Juin Shyu

Journal of Marine Science and Technology–Taiwan

A method for identifying the whirling motion of a rotating shaft has been developed. This method is based on the phase unwrapping of two strain gages' signals. These two stain gages are being attached ninety degrees apart onto the rotating shaft thus observe the shaft's motion in a rotating coordinate with speed the same as that of the shaft. With such arrangement of the strain gages, the whirling motions of the shaft can be identified provided that the rotation speed of the shaft is known. These whirling motions include forward whirl and backward whirl. Equations are given to show how …

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Effects Of Anisotropy On The Hydrogen Induced Fatigue Crack Propagation Of A Banded Ferrite/Pearlite Steel, L. Tau, S.L.I. Chan, C.S. Shint Jun 1993

Effects Of Anisotropy On The Hydrogen Induced Fatigue Crack Propagation Of A Banded Ferrite/Pearlite Steel, L. Tau, S.L.I. Chan, C.S. Shint

Journal of Marine Science and Technology–Taiwan

The fatigue crack propagation (FCP) properties of AISI 4130 steel plates with a ferrite/pearlite (F/P) banded structure were evaluated both in air and electrolytic hydrogen charging environments. To understand the combined effects of hydrogen, directions of banding and elongated non-metallic inclusions on the FCP, specimens with six different orien- tations relative to the rolling direction were sampled and charged with hydrogen. When tested in air, the result reveals that the crack plane as related to the direction of banding, and the local stress concentration induced by elongated inclusions, largely affected the FCP rate. It also shows that the relative dominance …

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Second Law Analysis On Ejection Cooling System, S.P. Liaw, Y.H. Chang Jun 1993

Second Law Analysis On Ejection Cooling System, S.P. Liaw, Y.H. Chang

Journal of Marine Science and Technology–Taiwan

Ejection cooling system is analyzed by the second law of thermodynamics in this study. It is mainly consisted of a boiler, an ejector, an expansion device, a condenser, and an evaporator. Special focus is stressed on the variation of exergy in each component. The working refrigerant received exergy from boiler and pump and cons umed in other parts of the system. The coefficients of performance based on both the first and the second laws are computed respectively and thus the changes of energy and exergy in each component of the system can be readily understood. In addition, the boiler temperature, …

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Aluminum Electrodeposition From Room Temperature Molten Alcl3-Bpc Salt Bath, C.C. Yang, C.P. Chang Jun 1993

Aluminum Electrodeposition From Room Temperature Molten Alcl3-Bpc Salt Bath, C.C. Yang, C.P. Chang

Journal of Marine Science and Technology–Taiwan

The characteristics of aluminum electrodeposited layer from an ambient temperature molten salt were discussed in this study. The experimental results indicated that it is possible to carry out aluminum electrodeposition on the surface of brass and stainless steel when binary AlCI3-8P C molten electrolysis were used. The morphology of the components, characteristics and images can be detected by SEM, Auger Analysis, X-ray diffraction analysis and electrochemical polarization curves. The denser and more adhesive electrodeposited aluminum layer can be achieved by chosing proper electrolyte components (AlCI3: BPC-acidic salt bath), current forms (D.C./pulse), current density, electrolytic time and other pretreatment. In addition, …

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Numerical Study Of Spray Flame Characteristics, C.Y. Lin Jun 1993

Numerical Study Of Spray Flame Characteristics, C.Y. Lin

Journal of Marine Science and Technology–Taiwan

A numerical method was considered to calculate spray flame structure and emissions characteristics. The turbulence fluctuation was predicted using k-e-g and algebraic mixing-length-hypothesis (mlh) turbulence models. The numerical method was evaluated using a set of available experimental data. It is shown that this theoretical model predicts the data well in the near nozzle region and the predictions improve quantitatively along the axial distance. In comparing the turbulence models, the k-e-g model provides a better result for the varying-density flow of spray combustion.

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The Naval Reserve Civil Engineer Corps Environmental Engineering Program, William A. Heine, Samuel A. Vigil Jun 1993

The Naval Reserve Civil Engineer Corps Environmental Engineering Program, William A. Heine, Samuel A. Vigil

Civil and Environmental Engineering

The Navy is engaged in a national effort to bring its shore facilities into compliance with all applicable local, state, and federal environmental regulations. This work is being completed by civil service employees, consultants, and contractors under the supervision of Navy Civil Engineer Corps officers. To supplement these active duty and civilian resources, the Reserve Division of the Naval Facilities Engineering Command (RDNAVFAC) has identified Reserve officers with substantial environmental engineering skills who are being assigned to assist Navy shore activities all over the world in this essential task. The Naval Reserve Civil Engineer Corps (CEC) is composed of over …

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Predicting Seepage Of Leachate From The St. Johns Landfill To Ground And Surface Water Systems, Kevin A. Schock Jun 1993

Predicting Seepage Of Leachate From The St. Johns Landfill To Ground And Surface Water Systems, Kevin A. Schock

Dissertations and Theses

Determination of the vertical and horizontal groundwater hydraulic gradient within a landfill is the first step in determining the potential of groundwater contamination from the landfill leachate. The length of a study and the frequency at which measurements are recorded can greatly affect the description of the local groundwater environment. A more comprehensive analysis can be preformed for longer periods of study and greater measurement frequency. The intent of this study was to install a continuous groundwater level monitoring system around the st. Johns Landfill for a minimum study length of one year. This would allow a more thorough study …

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Waveform Estimation With Jitter Noise By Pseudo Symmetrical Probability Density Function, Wei-Da Hao Jun 1993

Waveform Estimation With Jitter Noise By Pseudo Symmetrical Probability Density Function, Wei-Da Hao

Dissertations and Theses

A new method for solving jitter noise in estimating high frequency waveform is proposed. It reduces the bias of the estimation in those points where all the other methods fail to achieve. It provides preliminary models for estimating percentiles in Normal, Exponential probability density function. Based on the model for Normal probability density function, a model for any probability density function is derived. The resulting percentiles, in turn, are used as estimates for the amplitude of the waveform. Simulation results show us with satisfactory accuracy.

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Performance Analysis Of A Hierarchical, Cache-Coherent, Shared Memory Based, Multi-Processor System, Raman Nayyar Jun 1993

Performance Analysis Of A Hierarchical, Cache-Coherent, Shared Memory Based, Multi-Processor System, Raman Nayyar

Dissertations and Theses

We have conducted a performance analysis of a large scale multiprocessor system based on shared buses organized in a hierarchical fashion and employing an easy to implement snoopy cache protocol. · This arrangement, named TREEBUS [ 5], presents a logical extension path for multiprocessor systems based on a single shared bus whose scalability is limited by the available system bus bandwidth [26]. The multiple, independent, hierarchical buses overcome the bus bandwidth limitation and the architecture can scale to relatively large sizes. We have developed an easy to use, reasonably accurate and computationally efficient analytic model for analyzing the performance of …

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Measurement Techniques For Noise Figure And Gain Of Bipolar Transistors, Wayne Kan Jung Jun 1993

Measurement Techniques For Noise Figure And Gain Of Bipolar Transistors, Wayne Kan Jung

Dissertations and Theses

First, the concepts of reflection coefficients, s-parameters, Smith chart, noise figure, and available power gain will be introduced. This lays out the foundation for the presentation of techniques on measuring noise figure and gain of high speed bipolar junction transistors. Noise sources in a bipolar junction transistor and an equivalent circuit including these noise sources will be presented. The process of determining the noise parameters of a transistor will also be discussed. A Pascal program and several TEKSPICE scripts are developed to calculate the stability, available power gain, and noise figure circles. Finally, these circles are plotted on a Smith …

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