Engineering Commons^™

Structural Characterization Of Aluminum Films Deposited On Sputtered-Titanium Nitride/ Silicon Substrate By Metalorganic Chemical Vapor Deposition From Dimethylethylamine Alane, Xiaodong Li, Byoung-Youp Kim, Shi-Woo Rhee

Faculty Publications

Alfilmsdeposited on sputtered‐TiN/Si substrate by metalorganic chemical vapor deposition(MOCVD) from dimethylethylamine alane (DMEAA) were characterized using x‐ray diffraction(XRD),Auger electron spectroscopy(AES),atomic force microscopy(AFM), and transmission electron microscopy (TEM). The TiN filmsputtered on the Si has a preferred orientation along the growth direction with the 〈111〉 of the film parallel to the Si〈111〉. Sputtering of the TiN film on the Si induced strains at the interface. The TiN/Si interface is flat while the Al/TiN interface is rough. There exist many dislocations at the Al/TiN interface. The Al₂O₃ phase was formed at the Al/TiN interface during the early stages of …

A Massively Parallel Computation Strategy For Fdtd: Time And Space Parallelism Applied To Electromagnetics Problems, Michael A. Jensen, Amir Fijany, Yahya Rahmat-Samii, Jacob Barhen

Faculty Publications

We present a novel strategy for incorporating massive parallelism into the solution of Maxwell's equations using finite-difference time-domain methods. In a departure from previous techniques wherein spatial parallelism is used, our approach exploits massive temporal parallelism by computing all of the time steps in parallel. Furthermore, in contrast to other methods which appear to concentrate on explicit schemes such as Yee's (1966) algorithm, our strategy uses the implicit Crank-Nicolson technique which provides superior numerical properties. We show that the use of temporal parallelism results in algorithms which offer a massive degree of coarse grain parallelism with minimum communication and synchronization …

Integrating Reconstructed Scatterometer And Advanced Very High Resolution Radiometer Data For Tropical Forest Inventory, David G. Long, Perry J. Hardin

Faculty Publications

A scientific effort is currently underway to assess tropical forest degradation and its potential impact on Earth's climate. Because of the large continental regions involved, Advanced Very High Resolution Radiometer (AVHRR) imagery and its derivative vegetation index products with resolutions between 1 and 12 km are typically used to inventory the Earth's equatorial vegetation. Archival AVHRR imagery is also used to obtain a temporal baseline of historical forest extent. Recently however, 50-km Seasat-A Scatterometer (SASS) Ku-band imagery (acquired in 1978) has been reconstructed to = 4-km resolution, making it a supplement to AVHRR imagery for historical vegetation assessment. In order …

Traffic Control For Automated Highway Systems: A Conceptual Framework, H.-S. Jacob Tsao

Faculty Publications

This paper proposes a conceptual framework for designing a traffic control scheme. It adopts a top-down approach to defining major design steps starting with high-level feature definition. With the desired features defined, the top-down approach then identifies and defines moves and related planning and movement functions that are required for supporting the desired features. The paper takes a systems view and identifies the safety issues regarding the movement coordination of the large number of vehicles on an Automated Highway System (AHS).

A Pixel Scale Digital-To-Analog Converter Array For Liquid Crystal On Vlsi Displays, Gregory P. Nordin, S. T. Kowel, J. H. Kulick, R. G. Lindquist, P. J. Nasiatka, A. Thomsen

Faculty Publications

A pixel scale digital to analog converter and driver for liquid crystal (LC) cells is presented. The circuit is a compact CMOS logic gate that sums pulse density modulation (pdm) signals. Low pass filtering of the pdm signal is 'done by the LC material. The circuit is suitable to implement large arrays of converters as, for example, in display applications. It is applicable in LC on silicon displays where gray scale data are stored and converted at each pixel site. Advantages over the commonly used active matrix technology include the removal of all analog circuitry, no need for refresh, reduced …

Electromagnetic Boundary Conditions And Differential Forms, Karl F. Warnick, Richard H. Selfridge, David V. Arnold

Faculty Publications

A new representation for electromagnetic boundary conditions involving a boundary projection operator defined using the interior and exterior products of the calculus of differential forms is developed. This operator expresses boundary conditions for fields represented by differential forms of arbitrary degree. With vector analysis, the field intensity boundary conditions require the cross product, whereas the flux boundary conditions use the inner product. With differential forms, the field intensity and flux density boundary conditions are expressed using a single operator. This boundary projection operator is readily applied in practice, so that this work extends the utility of the calculus of differential …

Liquid Crystal-On-Silicon Implementation Of The Partial Pixel Three-Dimensional Display Architecture, M. W. Jones, Gregory P. Nordin, M. Friends, S. T. Kowel, J. H. Kulick, R. G. Lindquist, P. J. Nasiatka

Faculty Publications

We report the implementation of a liquid crystal-on-silicon, three-dimensional 13-D2 diffractive display based on the partial pixel architecture. The display generates multiple stereoscopic images that are perceived as a static 3-D scene with one-dimensional motion parallax in a manner that is functionally equivalent to a holographic stereogram. The images are created with diffraction gratings formed in a thin liquid crystal layer by fringing electric fields from transparent indium tin oxide interdigitated electrodes. The electrodes are controlled by an external drive signal that permits the 3-D scene to be turned on and off. The display has a contrast ratio of 5.8, …

Real-Time Three-Dimensional Display Based On The Partial Pixel Architecture, Gregory P. Nordin, M. W. Jones, S. T. Kowel, J. H. Kulick, R. G. Lindquist

Faculty Publications

We previously reported several static three-dimensional (3-D) display implementations of the partial pixel architecture [J. Opt. Soc. Am. A 12, 73 (1995)]. We report herein our f irst real-time 3-D display based on this architecture. The display is functionally equivalent to a real-time holographic stereogram. It is autostereoscopic and provides horizontal motion parallax. The display device is composed of a diffractive optical element (fabricated with standard photolithographic techniques) and a separate conventional liquidcrystal display. The display has been used to play back a precomputed animated 3-D scene at video frame rates using a standard VGA video output.

Upgrading A Cd-Rom Network For Multimedia Applications, Margaret Sylvia

Faculty Publications

Checking the servers, PCs, and network connections for bottlenecks in serving multimedia across the network are steps that will alleviate speed and connectivity issues for users.

On Primitive Bch Codes With Unequal Error Protection Capabilities, Robert H. Morelos-Zaragoza, Shu Lin

Faculty Publications

Presents a class of binary primitive BCH codes that have unequal-error-protection (UEP) capabilities. The authors use a previous result on the span of their minimum weight vectors to show that binary primitive BCH codes, containing second-order punctured Reed-Muller (RM) codes of the same minimum distance, are binary-cyclic UEP codes. The values of the error correction levels for this class of binary LUEP codes are estimated.

Pulse Width Modulation Drive Technique For High Resolution Liquid Crystal Gratings, Gregory P. Nordin, S. T. Kowel, J. H. Kulick, R. G. Lindquist, P. J. Nasiatka, A. Thomsen

Faculty Publications

We report the use of a pulse-width modulation drive technique for high-resolution liquid-crystal gratings and show how the grating diffraction efficiency depends on the duty cycle of the drive signal. We identify a regime in which the diffraction efficiency is linearly proportional to the duty cycle, thereby providing a linear drive characteristic.

Otter: A Testbed Submersible For Robotics Research, Tim Mclain, H H. Wang, R L. Marks, S D. Fleischer, D W. Miles, G A. Sapilewski, S M. Rock, M J. Lee, R C. Burton

Faculty Publications

Untethered, unmanned submersibles (UUSs) have the potential of becoming useful tools in nuclear reactor inspection and repair and waste-site cleanup and survey, in addition to subsea exploration. Classical "hand-in-glove" control methods used currently by tethered, remotely-operated vehicles (ROVs) are unsuitable for UUS systems which have, at best, limited communications. The Stanford Aerospace Robotics Laboratory (ARL) has joined with the Monterey Bay Aquarium Research Institute (MBARI) in a program to develop new methods of controlling UUS systems.

As a part of this effort, a submersible testbed has been built to test and develop new technologies that will make UUSs useful tools …

A Staggered-Diamond Design For Automated/Manual-Hov Highway-To-Highway Interchanges And Constraints On Ahs Design For Accommodating Automated Highway Change, Jacob Tsao

Faculty Publications

This paper consists of two components. The First component addresses a key AHS infrastructure support issue—providing eight extra connector ramps, in addition to the eight existing highway-to-highway connector ramps for the conventional manual traffic, at a highway-to-highway interchange for accommodating continuous automated driving from one highway to the crossing highway. The proposed staggered-diamond design requires only four, instead of eight, separate structures and hence greatly increases the feasibility of AHS infrastructure support. However, the reduced infrastructure complexity at such interchanges could still constrain considerably the design, operation and evolution of AHS. This is the focus of the second component. The …

Stage Definition For Ahs Deployment And An Ahs Evolutionary Scenario, Jacob Tsao

Faculty Publications

Pros and cons of various mature Automated Highway Systems (AHS) have been a subject of intense study. However, such discussions are nothing but intellectual exercises unless the issue of how to evolve, in a planned and managed fashion, the current highway systems towards these mature AHS is also addressed. Since full functionality of a mature AHS cannot be realized suddenly, discrete functional steps must be identified and optimized. This paper defines an evolutionary stage towards a mature AHS as any discernible functional increment whose realization may encounter considerable difficulties requiring a significant amount of conscious effort to overcome. A good …

Multilevel Block Coded 8-Psk Modulations Using Unequal Error Protection Codes For The Rayleigh Fading Channel, Robert H. Morelos-Zaragoza, Tadeo Kamasi, Shu Lin

Faculty Publications

This paper introduces new block coded 8-PSK modulations with unequal error protection (UEP) capabilities for Rayleigh fading channels. The design of efficient block coded modulations (BCM) over 8-PSK signal sets, for the specific purpose of UEP, over Rayleigh fading channels is considered. UEP is desirable in communications systems where part of the source information is more important, or error sensitive, such as the transmission of coded speech and data broadcasting. The proposed block modulation codes are based on the multilevel construction of Imai and Hirakawa (1977). It is shown that the use of binary linear UEP (LUEP) codes as component …

Qpsk Block-Modulation Codes For Unequal Error Protection, Robert H. Morelos-Zaragoza, Shu Lin

Faculty Publications

Unequal error protection (UEP) codes find applications in broadcast channels, as well as in other digital communication systems, where messages have different degrees of importance. Binary linear UEP (LUEP) codes combined with a Gray mapped QPSK signal set are used to obtain new efficient QPSK block-modulation codes for unequal error protection. Several examples of QPSK modulation codes that have the same minimum squared Euclidean distance as the best QPSK modulation codes, of the same rate and length, are given. In the new constructions of QPSK block-modulation codes, even-length binary LUEP codes are used. Good even-length binary LUEP codes are obtained …

Linearly-Constrained Entropy Maximization Problem With Quadratic Costs And Its Applications To Transportation Planning Problems, Shu-Cherng Fang, Jacob Tsao

Faculty Publications

Many transportation problems can be formulated as a linearly-constrained convex programming problem whose objective function consists of entropy functions and other cost-related terms. In this paper, we propose an unconstrained convex programming dual approach to solving these problems. In particular, we focus on a class of linearly-constrained entropy maximization problem with quadratic cost, study its Lagrangian dual, and provide a globally convergent algorithm with a quadratic rate of convergence. The theory and algorithm can be readily applied to the trip distribution problem with quadratic cost and many other entropy-based formulations, including the conventional trip distribution problem with linear cost, the …

Em Interaction Of Handset Antennas And A Human In Personal Communications, Michael A. Jensen, Yahya Rahmat-Samii

Faculty Publications

In personal communications, the electromagnetic interaction between handset-mounted antennas and the nearby biological tissue is a key consideration. This paper presents a thorough investigation of this antenna-tissue interaction using the finite-difference time-domain (FDTD) electromagnetic simulation approach with detailed models of real-life antennas on a transceiver handset. The monopole, side-mounted planar inverted F, top-mounted bent inverted F, and back-mounted planar inverted F antennas are selected as representative examples of external and internal configurations. Detailed models of the human head and hand are implemented to investigate the effects of the tissue location and physical model on the antenna performance. Experimental results are …

Hydrogen-Atom Direct-Entry Mechanism Into Metal Membranes, G. Zheng, Branko N. Popov, Ralph E. White

Faculty Publications

The hydrogen-atom direct-entry mechanism is used to explain why the steady-state hydrogen permeation current density through a metal membrane is directly proportional to the cathodic current density, i_c, and is independent of the membrane thickness when i_c is small.

A Boundary-Layer Model Of A Parallel-Plate Electrochemical Reactor For The Destruction Of Nitrates And Nitrites In Alkaline Waste Solutions, Shailesh Prasad, John W. Weidner, Andrew E. Farell

Faculty Publications

Electrochemical processes appear to be attractive for treating low level nuclear wastes. The development of a simple divided electrochemical-cell model operating in a batch mode, used for the reduction of nitrates and nitrites from nuclear wastes, is presented. This model, based on a boundary-layer approach, is simple and yet encompasses the key features of a previously developed distributed-parameter model that includes diffusion, migration, and convection as the flux components. Because it dramatically reduces computation time, this boundary-layer model is well suited for use in a complex interactive flowsheet model and for optimization studies. The boundary-layer model is used to predict …

A Parallel-Plate Electrochemical Reactor Model For The Destruction Of Nitrate And Nitrite In Alkaline Waste Solutions, D. H. Coleman, Ralph E. White, D. T. Hobbs

Faculty Publications

A parallel-plate electrochemical reactor model with multiple reactions at both electrodes and anolyte and catholyte recirculation tanks was modeled for the electrochemical destruction of nitrate and nitrite species in an alkaline solution. The model can be used to predict electrochemical reaction current efficiencies and outlet concentrations of species from the reactor, given inlet feed conditions and cell operating conditions. Also, predictions are made for off-gas composition and liquid-phase composition in the recirculation tanks. The results of case studies at different applied potentials are shown here. At lower applied potentials, the model predictions show that the destruction process is more energy …

Thermophoretic Sampling Of Coal-Derived Soot Particles During Devolatilization, Jinliang Ma, Thomas H. Fletcher, Brent W. Webb

Faculty Publications

Thermophoretic sampling of soot particles formed during high-temperature coal devolatilization is performed in order to examine soot particle sizes and shapes. Coal particles are injected along the centerline of a laminar flow flat flame burner, where a fuel-rich methane-air flame is used as a heat source. Volatiles released from the coal particles form a cloud of soot particles at high temperatures in the absence of oxygen. A carbon-coated microscope grid is briefly inserted into the soot cloud, where the temperature gradient between the soot particles and the cold grid surface causes the migration of soot particles and results in deposition. …

Undergraduate Engineering Ceramics Laboratory Development, Guna S. Selvaduray

Faculty Publications

No abstract provided.

Electrochemical Determination Of The Diffusion Coefficient Of Hydrogen Through An Lani4.25Al0.75 Electrode In Alkaline Aqueous Solution, G. Zheng, Branko N. Popov, Ralph E. White

Faculty Publications

The constant potential and constant current discharge techniques were used to determine the hydrogen diffusion coefficients in an LaNi_4.25Al_0.75 electrode. The values obtained were 2.97 × 10^–11 and 3.30 × 10^–11 cm²/s, respectively. The advantages and disadvantages of these two techniques are discussed.

The Effect Of Current And Nickel Nitrate Concentration On The Deposition Of Nickel Hydroxide Films, Christopher C. Streinz, Andrew P. Hartman, Sathya Motupally, John W. Weidner

Faculty Publications

An electrochemical quartz crystal nanobalance (EQCN) has been utilized to measure the mass of Ni(OH)₂ films electrochemically deposited from Ni(NO₃)₂ solutions. The objective of this work was to quantify electrochemical deposition as a function of deposition conditions. The changing mass recorded on the EQCN was demonstrated to be the result of Ni(OH)₂ deposition. Deposited mass was observed to increase proportionally with applied charge as suggested by previous investigators. Most significantly, the rate of deposition was found to decrease more than an order of magnitude as the Ni(NO₃)₂ concentration increased from 0.2 to …

Proton Diffusion In Nickel Hydroxide Films: Measurement Of The Diffusion Coefficient As A Function Of State Of Charge, Sathya Motupally, Christopher C. Streinz, John W. Weidner

Faculty Publications

Electrochemical impedance spectroscopy (EIS) was used to measure the solid-state diffusion coefficient of protons in nickel hydroxide films at room temperature as a function of state of charge (SOC). A model for the complex faradaic impedance of the nickel hydroxide active material is presented and used to extract the diffusion coefficient of protons from the EIS data. Impedance data over a range of frequencies can be used to extract a constant diffusion coefficient without the knowledge of the initial mobile proton concentration or the form of the charge-transfer kinetic expression. The proton diffusion coefficient is a strong function of SOC …

The Effect Of Temperature And Ethanol On The Deposition Of Nickel Hydroxide Films, Christopher C. Streinz, Sathya Motupally, John W. Weidner

Faculty Publications

The objective of this work was to determine the effect of the temperature and the ethanol content of the Ni(NO₃)₂ solution on: (i) the efficiency of electrochemical deposition of nickel hydroxide; and (ii) the molecular weight of the deposited film. An electrochemical quartz crystal nanobalance (EQCN) was used to measure the mass of films electrochemically deposited from Ni(NO₃)₂ solutions and constant current discharges were used to determine the electrochemical capacity of the films. The data indicates that increasing the temperature increases both the efficiency of the deposition reaction and the …

Electrowinning Of Non-Noble Metals With Simultaneous Hydrogen Evolution At Flow-Through Porous Electrodes I. Theoretical, Mahmoud M. Saleh, John W. Weidner, Badr G. Ateya

Faculty Publications

A mathematical model is developed to simulate the electrowinning of non-noble metals (e.g., Zn, Cr) within flow-through porous electrodes under the conditions of simultaneous evolution of hydrogen gas bubbles. The results of the model are presented as a function of several dimensionless groups representing kinetics, mass transfer, ohmic resistance, and gas bubbles. These coupled, nonlinear effects are investigated by examining the distributions of the metal reduction and hydrogen evolution currents, coulombic efficiency of the metal electrowinning reaction, and gas void fractions under a series of limiting conditions. The gas bubbles accentuate the nonuniform distribution of the potential and …

Electrowinning Of Non-Noble Metals With Simultaneous Hydrogen Evolution At Flow-Through Porous Electrodes Ii. Experimental, Mahmoud M. Saleh, John W. Weidner, Bahgat E. Ei-Anadouli, Badr G. Ateya

Faculty Publications

This paper presents an interpretation of the experimental results obtained on the electrowinning of zinc at a flow-through porous electrode in light of a mathematical model which was presented in Part I. The process is accompanied by simultaneous hydrogen evolution within the electrode, which increases the pore electrolyte resistivity and decreases the coulombic efficiency. We measured polarization curves, coulombic efficiencies, and current distributions under various conditions of zincate concentrations, flow rates, cell current, and electrode thickness. Reasonable agreement between the measured and predicted current distributions was obtained only under conditions of high electrolyte flow rates, low cell currents, and thinner …

Electrochemical Determination Of The Diffusion Coefficient Of Hydrogen Through An Lani4.25Al0.75 Electrode In Alkaline Aqueous Solution, G. Zheng, Branko N. Popov, Ralph E. White

Faculty Publications

The constant potential and constant current discharge techniques were used to determine the hydrogen diffusion coefficients in an LaNi_4.25Al_0.75 electrode. The values obtained were 2.97 × 10^–11 and 3.30 × 10^–11 cm²/s, respectively. The advantages and disadvantages of these two techniques are discussed.