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Faculty Publications

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Articles 2551 - 2580 of 3294

Full-Text Articles in Engineering

Semi-Autonomous Human-Uav Interfaces For Fixed-Wing Mini-Uavs, Randal Beard, Michael A. Goodrich, Morgan Quigley Oct 2004

Semi-Autonomous Human-Uav Interfaces For Fixed-Wing Mini-Uavs, Randal Beard, Michael A. Goodrich, Morgan Quigley

Faculty Publications

Sponsorship: DARPA, AFOSR. We present several human-robot interfaces that support real-time control of a small semi-autonomous UAV. These interfaces are designed for searching tasks and other missions that typically do not have a precise predetermined flight plan. We present a detailed analysis of a PDA interface and describe how our other interfaces relate to this analysis. We then offer quantative and qualitative performance comparisons of the interfaces, as well as an analysis of their possible real-world applications.

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Electromagnetic Bias At Off-Nadir Incidence Angles, David V. Arnold, Floyd W. Millet, Karl F. Warnick Sep 2004

Electromagnetic Bias At Off-Nadir Incidence Angles, David V. Arnold, Floyd W. Millet, Karl F. Warnick

Faculty Publications

Sponsorship: JPL Subcontract 961461. Nadir and off-nadir measurements of electromagnetic (EM) bias measurements are presented and compared with an off-nadir bias model. Measurements of the bias were made during the BYU Off-Nadir Experiment (Y-ONE) in the months of March and April, 2003. Using radar measurements of the surface and backscattered power, the EM bias was computed at angles from nadir to 17º degrees. Simultaneous surface measurements from a laser rangefinder provide accurate measurements of the long wave surface parameters. An off-nadir bias model incorporating the effects of hydrodynamic modulation of short waves and tilt modulation of long waves is developed …

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High Order Convergence With A Low Order Discretization Of The 2d Mfie, Clayton P. Davis, Karl F. Warnick Sep 2004

High Order Convergence With A Low Order Discretization Of The 2d Mfie, Clayton P. Davis, Karl F. Warnick

Faculty Publications

Moment method solutions to the MFIE are often less accurate for a given grid than corresponding solutions to the EFIE. We propose that the cause of this observation is the identity operator in the MFIE and show how regularizing the identity increases the convergence rate of the discretized 2D MFIE by three orders.

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Every Polynomial-Time 1-Degree Collapses If And Only If P=Pspace, Stephen A. Fenner, Stuart A. Kurtz, James S. Royer Sep 2004

Every Polynomial-Time 1-Degree Collapses If And Only If P=Pspace, Stephen A. Fenner, Stuart A. Kurtz, James S. Royer

Faculty Publications

No abstract provided.

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Detection Of Configuration Memory Upsets Causing Persistent Errors In Sram-Based Fpgas, D. Eric Johnson, Keith S. Morgan, Michael J. Wirthlin, Michael P. Caffrey, Paul S. Graham Sep 2004

Detection Of Configuration Memory Upsets Causing Persistent Errors In Sram-Based Fpgas, D. Eric Johnson, Keith S. Morgan, Michael J. Wirthlin, Michael P. Caffrey, Paul S. Graham

Faculty Publications

Sponsorship: Los Alamos National Laboratory. FPGA designers are becoming increasingly aware of fault tolerance issues in modern FPGA designs, especially designs destined for a radiation environment. We classify errors due to upsets within the configuration bitstream into two categories; namely, persistent and non-persistent. Persistent errors generally cannot be tolerated. However, non-persistent errors can be tolerated in certain types of designs as long as they are properly accounted for. We discuss situations in which non-persistent errors are acceptable, and describe a technique for the detection of upsets causing persistent errors within the configuration memor of an SRAM-based FPGA.

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Evaluation Of Power Costs In Applying Tmr To Fpga Designs, Nathaniel Rollins, Michael J. Wirthlin, Paul S. Graham Sep 2004

Evaluation Of Power Costs In Applying Tmr To Fpga Designs, Nathaniel Rollins, Michael J. Wirthlin, Paul S. Graham

Faculty Publications

Sponsorship: Los Alamos National Laboratory. Triple modular redundancy (TMR) is a technique commonly used to mitigate against design failures caused by single event upsets (SEUs). The SEU immunity that TMR provides comes at the cost of increased design area and decreased speed. Additionally, the cost of increased power due to TMR must be considered. This paper evaluates the power costs of TMR and validates the evaluations with actual measurements. Sensitivity to design placement is another important part of this study. Power consumption costs due to TMR are also evaluated in different FPGA architectures. This study shows that power consumption rises …

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Initial Experiments In The Cooperative Control Of Unmanned Air Vehicles, Derek R. Nelson, Timothy W. Mclain, Reed S. Christiansen, Randal W. Beard, David Johansen Sep 2004

Initial Experiments In The Cooperative Control Of Unmanned Air Vehicles, Derek R. Nelson, Timothy W. Mclain, Reed S. Christiansen, Randal W. Beard, David Johansen

Faculty Publications

This paper addresses cooperative control for a team of unmanned air vehicles (UAVs). Specifically, a team of three small UAVs is controlled to perform a cooperative timing mission. Starting at loiter locations distributed around the periphery of a 2 km square battle area, the UAVs cooperatively plan paths to arrive at a target at the center of the battle area in sequence at 10 sec intervals. Cooperative path planning is performed using the methodology of coordination variables and coordination functions. Coordination and waypoint path planning are centralized on a ground station computer. Experiments have been performed using BYU’s fleet of …

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Optimal Sampling For Single-Tone Frequency Estimation, Travis E. Oliphant Aug 2004

Optimal Sampling For Single-Tone Frequency Estimation, Travis E. Oliphant

Faculty Publications

Single-tone frequency estimation from irregularly spaced samples is analyzed. The ratio of the Cramr-Rao Bound (CRB) for regularly spaced samples to the bound for irregularly spaced samples is presented and shown to be a globally convex function. It's minima and maxima over the domain of interest are identified which reveals that improvements in the CRB can be obtained using non-equally-spaced samples. For a given sampling density, the best estimates of frequency are obtained when half of the samples are taken at one end of the total available interval and the remaining samples are taken at the other end.

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Noncontact Scanning Impedance Imaging In An Aqueous Solution, Aaron R. Hawkins, Hongze Liu, Travis E. Oliphant, Stephen M. Schultz Aug 2004

Noncontact Scanning Impedance Imaging In An Aqueous Solution, Aaron R. Hawkins, Hongze Liu, Travis E. Oliphant, Stephen M. Schultz

Faculty Publications

We present a method for imaging based on noncontact electrical impedance measurements and mechanical scanning. Measurement results are shown for an initial system based on this concept. An impedance probe design is presented, applicable to the test system. Line-scan data plots of high impedance contrast structures show a good fit to a theoretical physical model. Image resolutions on the order of 100 m are indicated for the initial system. Two-dimensional impedance images of biological tissue generated by this technique are shown.

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High Efficiency 90 Degree Silica Waveguide Bend Using An Air Hole Photonic Crystal Region, J. Cai, S. Kim, Gregory P. Nordin, J. Jiang Aug 2004

High Efficiency 90 Degree Silica Waveguide Bend Using An Air Hole Photonic Crystal Region, J. Cai, S. Kim, Gregory P. Nordin, J. Jiang

Faculty Publications

We propose the hybrid integration of an air hole photonic crystal (PhC) structure with a high (0.75%) single-mode silica waveguide to achieve an ultracompact high efficiency 90 bend for transverse-magnetic polarized light. Diffraction from the periodic boundary between the PhC and silica waveguide regions is shown to seriously degrade the optical efficiency of the bend. A microgenetic algorithm ( GA) combined with a two-dimensional finite-difference time-domain method is used to modify the PhC and its boundary layer to suppress this diffraction which in turn maximizes bend efficiency. The final optimized structure has a 99.4% bend efficiency at a wavelength of …

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Percolation Paths Of Three-Dimensions In Sensitized Stainless Steel, Alisa J. Millar Henrie Aug 2004

Percolation Paths Of Three-Dimensions In Sensitized Stainless Steel, Alisa J. Millar Henrie

Faculty Publications

The study of three-dimensional percolation paths through materials is important in its contribution to understanding defect sensitive properties of materials. This work shows the importance of grain boundary character in modeling defect sensitive boundaries. Also presented are trends of percolation of sensitized grain boundaries in 304 stainless steel (304SS). Of particular interest is how open paths form in a three-dimensional model created through serial sectioning. Evidence is presented that triple or quadruple points that contain typically two boundaries with special character that intersect the percolation path break up the path. Some boundaries with no known special qualities; they are not …

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3d Analysis Of Hybrid Photonic Crystal/Conventional Waveguide 90° Bend, J. Cai, S. Kim, Gregory P. Nordin, J. Jiang Jul 2004

3d Analysis Of Hybrid Photonic Crystal/Conventional Waveguide 90° Bend, J. Cai, S. Kim, Gregory P. Nordin, J. Jiang

Faculty Publications

We present a three-dimensional (3D) analysis of a hybrid photonic crystal conventional waveguide 90° bend proposed previously [Opt. Express 10, 1334 (2002)] as an ultracompact component for large-scale planar lightwave circuit integration. Both rigorous 3D finite-difference time-domain modeling and a simple perfect mirror model analysis were carried out for different Si post heights in the photonic crystal region. Results show that the bend efficiency increases rapidly with Si post height. For a post height of 6.5 µm, this structure yields a bend efficiency of 97.3% at a wavelength of 1.55 µm for 90° bends in 2 µm X 2 µm …

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Cavity Enhancement Of The Magneto-Optic Kerr Effect For Optical Studies Of Magnetic Nanostructures, Aaron R. Hawkins, N. Qureshi, Holger Schmidt Jul 2004

Cavity Enhancement Of The Magneto-Optic Kerr Effect For Optical Studies Of Magnetic Nanostructures, Aaron R. Hawkins, N. Qureshi, Holger Schmidt

Faculty Publications

We present a study of cavity enhancement of the magneto-optic Kerr effect using dielectric multilayers in order to facilitate optical studies of individual single-domain nanomagnets. We develop a transfer matrix theory to analyze Kerr rotation from an arbitrary number of possibly lossy dielectric layers. The combination of one lossless and one thin metallic layer is found to be most favorable for studying individual nanomagnets, providing the best tradeoff between signal enhancement and spatial resolution. Accounting for the microscopic surface structure, we find good agreement between theory and experiment. Using this technique, we demonstrate Kerr enhancements by a factor of more …

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Synergetic Control Of Power Converters For Pulse Current Charging Of Advanced Batteries From A Fuel Cell Power Source, Zhenhua Jiang, Roger A. Dougal Jul 2004

Synergetic Control Of Power Converters For Pulse Current Charging Of Advanced Batteries From A Fuel Cell Power Source, Zhenhua Jiang, Roger A. Dougal

Faculty Publications

This paper presents a synergetic controller for pulse current charging of advanced batteries from a fuel cell power source. Pulse current charging protocol that has been shown to have many advantages over the traditional constant current/constant voltage protocol is applied in a fuel cell powered battery-charging station to reduce the total charging time. Strong nonlinearity and dynamics exist in such systems. In this paper, the synergetic control approach is applied to regulate the buck converters that control the pulse charging currents to the many batteries. A practical synergetic controller to coordinate pulse current charging of the battery is synthesized and …

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Measuring The Five-Parameter Grain-Boundary Distribution From Observations Of Planar Sections, Brent L. Adams, Bassem S. El-Dasher, Gregory S. Rohrer, David M. Saylor Jul 2004

Measuring The Five-Parameter Grain-Boundary Distribution From Observations Of Planar Sections, Brent L. Adams, Bassem S. El-Dasher, Gregory S. Rohrer, David M. Saylor

Faculty Publications

One of the authors (DMS) thanks his colleagues at NIST, Edwin R. Fuller, Jr. and Grady S. White, for their helpful advice and criticisms, as well as Mark D. Vaudin and James A. Warren for their critical review of this manuscript. This work was supported at CMU by the MRSEC program of the National Science Foundation under Award No. DMR-0079996. A sterological method is described for estimating the distribution of grain-boundary types in poly-crystalline materials on the basis of observations from a single planar section. The grain-boundary distribution is expressed in terms of five macroscopically observable parameters that include: three …

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Automatic Detection And Validity Of The Sea-Ice Edge: An Application Of Enhanced-Resolution Quikscat/Seawinds Data, David G. Long, Jorg Haarpaintner, Rasmus T. Tonboe, Michael L. Van Woert Jul 2004

Automatic Detection And Validity Of The Sea-Ice Edge: An Application Of Enhanced-Resolution Quikscat/Seawinds Data, David G. Long, Jorg Haarpaintner, Rasmus T. Tonboe, Michael L. Van Woert

Faculty Publications

Sea-ice edge detection is an essential task at the different national ice services to secure navigation in ice-covered seas. Comparison between the Remund and Long ice mask image from enhanced-resolution QuikScat/SeaWinds (QS) products and the analyzed ice edge from high-resolution RADARSAT synthetic aperture radar has shown that the automatically determined QS ice mask underestimates the Arctic ice extent. QS data was statistically analyzed by colocating the data with ice charts around Greenland and with the National Aeronautics and Space Administration Team's Special Sensor Microwave/Imager (SSM/I) ice concentration algorithm over the whole Arctic region. All variables, i.e., the backscatter in vertical …

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Unmanned Air Vehicle Testbed For Cooperative Control Experiments, Timothy W. Mclain, Randal W. Beard Jul 2004

Unmanned Air Vehicle Testbed For Cooperative Control Experiments, Timothy W. Mclain, Randal W. Beard

Faculty Publications

This paper describes the MAGICC Lab unmanned air vehicle (UAV) testbed at Brigham Young University. Motivation for pursuing experimental research with UAVs is given as well as a historical perspective of the UAV testbed development. Lessons learned through the development and use of the testbed over the past several years are summarized.

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Assessing The Quality Of Seawinds Rain Measurements, David G. Long, David W. Draper Jul 2004

Assessing The Quality Of Seawinds Rain Measurements, David G. Long, David W. Draper

Faculty Publications

While SeaWinds was designed to measure ocean winds, it can also measure rain over the ocean. SeaWinds on QuikSCAT active measurements of integrated columnar rain rate obtained via simultaneous wind/rain retrieval are evaluated via Monte Carlo simulation and the Cramer-Rao lower bound on estimate accuracy. Although sufficiently accurate in many conditions, the simultaneous wind/rain retrieval method used with SeaWinds on QuikSCAT data is ill-conditioned for certain wind directions and measurement geometries, sometimes yielding spurious rain rates in zero-rain conditions. To assess the validity of SeaWinds-derived rain rates, a simple empirically based rain thresholding scheme is presented, derived from simulated data. …

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New Stereology For The Recovery Of Grain-Boundary Plane Distributions In The Crystal Frame, Brent L. Adams, Ryan J. Larsen Jul 2004

New Stereology For The Recovery Of Grain-Boundary Plane Distributions In The Crystal Frame, Brent L. Adams, Ryan J. Larsen

Faculty Publications

One of the authors (RJL) is grateful to the Office of Naval Research for fellowship support. BLA acknowledges the support of the NSF through the Materials Research Science and Engineering Center, Carnegie Mellon University (Grant No. DMR-0079996). A new experimental method is given for recovering the probability-distribution function Sv(ns/g). The function Sv(na/g) is the grain-boundary area per unit volume as a function of grain-boundary plane orientation (na), given a lattice misorientation (g) between the adjoining grains. The grain-boundary normal (na) is expressed in the crystal frame in which the misorientation g originates. The proposed method recovers the three-dimensional Sv(na/g) function …

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Mutual Coupling In Mimo Wireless Systems: A Rigorous Network Theory Analysis, Michael A. Jensen, Jon W. Wallace Jul 2004

Mutual Coupling In Mimo Wireless Systems: A Rigorous Network Theory Analysis, Michael A. Jensen, Jon W. Wallace

Faculty Publications

A new framework for the analysis of multiple-input multiple-output (MIMO) wireless systems is introduced to account for mutual coupling effects in the antenna arrays. The multiport interactions at transmit and receive are characterized by representing the channel using a scattering parameter matrix. A new power constraint that limits the average radiated power is also introduced. The capacity of the MIMO system with mutual coupling is defined as the maximum mutual information of the transmit and receive vectors over all possible transmit signaling and receive loading. Full-wave electromagnetic antenna simulations combined with a simple path-based channel model are used to demonstrate …

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Simultaneous Wind And Rain Retrieval Using Seawinds Data, David G. Long, David W. Draper Jul 2004

Simultaneous Wind And Rain Retrieval Using Seawinds Data, David G. Long, David W. Draper

Faculty Publications

The SeaWinds scatterometers onboard the QuikSCAT and the Advanced Earth Observing Satellite 2 measure ocean winds on a global scale via the relationship between the normalized radar backscattering cross section of the ocean and the vector wind. The current wind retrieval method ignores scattering and attenuation of ocean rain, which alter backscatter measurements and corrupt retrieved winds. Using a simple rain backscatter and attenuation model, two methods of improving wind estimation in the presence of rain are evaluated. First, if no suitable prior knowledge of the rain rate is available, a maximum-likelihood estimation technique is used to simultaneously retrieve the …

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Experimental And Numerical Investigation Of Turbulent Flow Induced Pipe Vibration In Fully Developed Flow, Matthew T. Pittard, R. Daniel Maynes, Jonathan D. Blotter, Robert P. Evans Jun 2004

Experimental And Numerical Investigation Of Turbulent Flow Induced Pipe Vibration In Fully Developed Flow, Matthew T. Pittard, R. Daniel Maynes, Jonathan D. Blotter, Robert P. Evans

Faculty Publications

Flow-induced pipe vibration caused by fully developed pipe flow has been observed but not fully investigated when turbulent flow prevails. This article presents experimental results that indicate a strong correlation between the volume flow rate and a measure of the pipe vibration. In this work, the standard deviation of the frequency-averaged time-series signal, measured using an accelerometer attached to the pipe, is used as the measure of pipe vibration. A numerical, fluid-structure interaction (FSI) model used to investigate the relationship between pipe wall vibration and the physical characteristics of turbulent flow is also presented. This numerical FSI approach, unlike commercial …

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Use Of Collaborative Learning Exercises To Increase Student Motivation And Learning In An Introduction To Materials Engineering Course, Stacy Gleixner, Hilary Lackritz Jun 2004

Use Of Collaborative Learning Exercises To Increase Student Motivation And Learning In An Introduction To Materials Engineering Course, Stacy Gleixner, Hilary Lackritz

Faculty Publications

A collection of collaborative, in-class exercises have been designed for use in a freshmen/sophomore level Introduction to Materials Science and Engineering class. The activities are team based problems that include open ended design problems, calculation questions, and thought problems on unanswered research questions. The activities have been designed with the goal of having one or two a week embedded in a more traditional lecture setting. The exercises relate to the topics covered in most standard Introduction to Materials classes (crystal structure, mechanical properties, polymers, phase diagrams…). Each activity is designed specifically to engage the students in the lecture and excite …

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Description And Assessment Of A Business Plan Competition And New Venture Fair At San José State University, Malu Roldan, Asbjorn Osland, Michael Solt, Burton Dean Jun 2004

Description And Assessment Of A Business Plan Competition And New Venture Fair At San José State University, Malu Roldan, Asbjorn Osland, Michael Solt, Burton Dean

Faculty Publications

After the first business plan competition, in May 2003, San José State University (SJSU) faculty and community entrepreneurs serving on the university’s Silicon Valley Center for Entrepreneurship (SVCE) concluded that the process should be spread over an academic year. Hence, the New Venture Fair (NVF) was born, which was held Dec. 16, 2003. The feedback from all sources has been very positive regarding the NVF. A significant NVF exhibit was the Hewlett Packard Mobile Computing Grant (HPMCG). All teams completed projects that were impressive to most observers from the university and greater community but additional lessons were learned that will …

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Using Open-Ended Design Projects In An Open Lab To Teach Lifelong Learning Skills In An Ic Design Course, David Parent Jun 2004

Using Open-Ended Design Projects In An Open Lab To Teach Lifelong Learning Skills In An Ic Design Course, David Parent

Faculty Publications

The ABET criterion, recognition for and the ability to engage in life-long learning, is one of the most important, given that we as engineering educators can not teach every concept that students will encounter over the span of a 20-40 year career as an engineer. We believe that one method to teach and verify this critical skill in the area of Integrated Circuit (IC) design, is to have the students learn IC CAD tools by following well crafted tutorials and then complete open-ended IC design projects in an open lab. The project is supposed to be a full custom design …

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Autostereoscopic 3d Display Based On Micromirror Array, Gregory P. Nordin, C. H. Ahn, H. J. Cho, S. T. Kowel, J. H. Kulick, J. Yan Jun 2004

Autostereoscopic 3d Display Based On Micromirror Array, Gregory P. Nordin, C. H. Ahn, H. J. Cho, S. T. Kowel, J. H. Kulick, J. Yan

Faculty Publications

A novel approach for three-dimensional (3-D) display systems implemented with a micromirror array was proposed, designed, realized, and tested. The major advantages of this approach include the following: 1 micromirrors are reflective and hence achromatic (panchromatic), 2 a wide variety of displays can be used as image sources, and 3 time multiplexing can be introduced on top of space multiplexing to optimize the viewing zone arrangements. A two-view (left and right) 3-D autostereoscopic display system was first constructed. Left- and right-eye views in the forms of both still and motion 3-D scenes were displayed, and viewers were able to fuse …

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Response To Comments On “Passivity-Based Control Of Saturated Induction Motors”, Levent U. Gökdere, Marwan A. Simaan, Charles W. Brice Jun 2004

Response To Comments On “Passivity-Based Control Of Saturated Induction Motors”, Levent U. Gökdere, Marwan A. Simaan, Charles W. Brice

Faculty Publications

Contrary to the claims made in the comments to our paper, the passivity-based controller developed for induction motors has already been tested on the same demanding trajectories used for the input–output linearization controller. The experimental results show that the passivitybased controller provides closer tracking of the same mechanical trajectory, when compared with the input–output linearization controller.

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Simulation Of Hot Electron And Quantum Effects In Algan/Gan Heterostructure Field Effect Transistors, N. Braga, R. Mickevicius, R. Gaska, H. Xu, M. S. Shur, M. Asif Khan, Grigory Simin, J. Yang Jun 2004

Simulation Of Hot Electron And Quantum Effects In Algan/Gan Heterostructure Field Effect Transistors, N. Braga, R. Mickevicius, R. Gaska, H. Xu, M. S. Shur, M. Asif Khan, Grigory Simin, J. Yang

Faculty Publications

We report on simulations of electrical characteristics of AlGaN/(InGaN)/GaN heterostructurefield effect transistors with quantum and hot electroneffects taken into account. Polarization charges lead to quantum confinement of electrons in the channel and to the formation of two-dimensional electron gas. The electron quantization leads to the spread of the electronwave function into the barrier and bulk but does not have significant impact on dc electrical characteristics.Hot electrons play an important part in the charge transport by spilling over into the bulk GaN where they are captured by traps. This leads to negative differential conductivity, which is also observed experimentally. The simulation …

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Correlation And Covariance Of Satellite Scatterometer Measurements, David G. Long, Peter K. Yoho Jun 2004

Correlation And Covariance Of Satellite Scatterometer Measurements, David G. Long, Peter K. Yoho

Faculty Publications

Capable scatterometer designs have been developed that seek improved resolution through the use of higher pulse sampling rates. The high sampling rates bring the traditional scatterometry assumption of measurement independence into question. This paper uses fundamental scattering theory to derive general expressions for correlation and covariance between scatterometer measurements and provides practical analysis using current and future instruments as examples. The paper derives expressions for the measurement variance parameter Kp when measurement correlation due to Rayleigh fading effects is present and relates Kp to the statistics of multiple pulse measurements. A function of the transmit signal modulation and receive processing, …

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Growth And Transport Properties Of Complementary Germanium Nanowire Field Effect Transistors, Andrew B. Greytak, Lincoln J. Lauhon, Mark S. Gudiksen, Charles M. Lieber May 2004

Growth And Transport Properties Of Complementary Germanium Nanowire Field Effect Transistors, Andrew B. Greytak, Lincoln J. Lauhon, Mark S. Gudiksen, Charles M. Lieber

Faculty Publications

n- and p-type Ge nanowires were synthesized by a multistep process in which axial elongation, via vapor–liquid–solid (VLS) growth, and doping were accomplished in separate chemical vapor deposition steps. Intrinsic, single-crystal, Ge nanowires prepared by Au nanocluster-mediated VLS growth were surface-doped in situ using diborane or phosphine, and then radial growth of an epitaxial Ge shell was used to cap the dopant layer. Field-effect transistors prepared from these Ge nanowires exhibited on currents and transconductances up to 850 µA/µm and 4.9 µA/V, respectively, with device yields of >85%.

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