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Faculty Publications

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Articles 2341 - 2370 of 3295

Full-Text Articles in Engineering

Aeronautical Telemetry Using Multiple-Antenna Transmitters, Michael A. Jensen, Michael D. Rice, Adam L. Anderson Jan 2007

Aeronautical Telemetry Using Multiple-Antenna Transmitters, Michael A. Jensen, Michael D. Rice, Adam L. Anderson

Faculty Publications

The placement of multiple antennas on an air vehicle is one possible practice for overcoming signal obstruction created by vehicle maneuvering during air-to-ground transmission. Unfortunately, for vehicle attitudes where more than one of these antennas has a clear path to the receiving station, this practice also leads to self-interference nulls, resulting in dramatic degradation in the average signal integrity. This paper discusses application of unitary space-time codes such as the Alamouti transmit diversity scheme and unitary differential space-time codes to overcome the self-interference effect observed in such systems. The mathematical foundations of these techniques within the context of this application …

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Obstacle And Terrain Avoidance For Miniature Aerial Vehicles, Timothy Mclain, Jeff Saunders, Blake Barber, Randall W. Beard, Stephen R. Griffiths Jan 2007

Obstacle And Terrain Avoidance For Miniature Aerial Vehicles, Timothy Mclain, Jeff Saunders, Blake Barber, Randall W. Beard, Stephen R. Griffiths

Faculty Publications

Unmanned aerial vehicles (UAVs) are playing increasingly prominent roles in defense programs and strategy around the world. Technology advancements have enabled the development of large UAVs (e.g., Global Hawk, Predator) and the creation of smaller, increasingly capable UAVs. The focus of this Chapter is on smaller fixed-wing miniature aerial vehicles (MAVs), which range in size from % to 2 m in wingspan. As recent conflicts have demonstrated, there are numerous military applications for MAVs including reconnaissance, surveillance, battle damage assessment, and communications relays.

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Compliant High-Precision E-Quintet Ratcheting (Cheqr) Mechanism For Safety And Arming Devices, John A. Kennedy, Larry L. Howell, William Greenwood Jan 2007

Compliant High-Precision E-Quintet Ratcheting (Cheqr) Mechanism For Safety And Arming Devices, John A. Kennedy, Larry L. Howell, William Greenwood

Faculty Publications

Ratchet and pawl mechanisms are used in safety applications to provide mechanical isolation between inputs and an output to insure that extreme environmental conditions do not inadvertently allow an unexpected output. These devices have become smaller and are approaching a size regime where traditional precision components, such as precision bearings and springs, are not available. This paper introduces the Compliant High-precision E-Quintet Ratcheting (CHEQR) mechanism as a means of exploiting the advantages of compliant mechanisms to create safety devices that eliminate the need for bearings and springs. The pseudo-rigid-body model was used to design a mechanism with the desired force-deflection …

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A Cognitive Robotics Approach To Comprehending Human Language And Behaviors, Deryle W. Lonsdale, D. Paul Benjamin, Damian Lyons Jan 2007

A Cognitive Robotics Approach To Comprehending Human Language And Behaviors, Deryle W. Lonsdale, D. Paul Benjamin, Damian Lyons

Faculty Publications

The ADAPT project is a collaboration of researchers in linguistics, robotics and artificial intelligence at three universities. We are building a complete robotic cognitive architecture for a mobile robot designed to interact with humans in a range of environments, and which uses natural language and models human behavior. This paper concentrates on the HRI aspects of ADAPT, and especially on how ADAPT models and interacts with humans.

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Effects Of Moisture On Ignition Behavior Of Moist California Chaparral And Utah Leaves, Thomas H. Fletcher, Brent M. Pickett, Steven G. Smith, Gregory S. Spittle, Megan M. Woodhouse, Elizabeth Haake, David R. Weise Jan 2007

Effects Of Moisture On Ignition Behavior Of Moist California Chaparral And Utah Leaves, Thomas H. Fletcher, Brent M. Pickett, Steven G. Smith, Gregory S. Spittle, Megan M. Woodhouse, Elizabeth Haake, David R. Weise

Faculty Publications

Individual cuttings from eight plant species native to California chaparral or Utah were burned in a well-controlled, well-instrumented facility. Gas temperatures above a flat-flame burner were controlled at 987 C and 10 mol% O2, resulting in a heat flux at the leaf surface varying from 80–140 kW/m2. High moisture leaves were observed to burst due to the rapid escape of vapor from the leaf interior. Bubbles in or on the leaf surface were observed for leaves with moderate moisture contents. A large number of leaf temperature measurements were made, along with measurements of the ignition time …

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High-Pressure Turbine Deposition In Land-Based Gas Turbines From Various Synfuels, Thomas H. Fletcher Jan 2007

High-Pressure Turbine Deposition In Land-Based Gas Turbines From Various Synfuels, Thomas H. Fletcher

Faculty Publications

Ash deposits from four candidate power turbine synfuels were studied in an accelerated deposition test facility. The facility matches the gas temperature and velocity of modern first-stage high-pressure turbine vanes. A natural gas combustor was seeded with finely ground fuel ash particulate from four different fuels: straw, sawdust, coal, and petroleum coke. The entrained ash particles were accelerated to a combustor exit flow Mach number of 0.31 before impinging on a thermal barrier coating (TBC) target coupon at 1150°C. Postexposure analyses included surface topography, scanning electron microscopy, and x-ray spectroscopy. Due to significant differences in the chemical composition of the …

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Heat And Mass Transport In Heat Pipe Wick Structures, Brian D. Iverson, Tyler W. Davis, Suresh V. Garimella, Mark T. North, Sukhvinder S. Kang Jan 2007

Heat And Mass Transport In Heat Pipe Wick Structures, Brian D. Iverson, Tyler W. Davis, Suresh V. Garimella, Mark T. North, Sukhvinder S. Kang

Faculty Publications

A novel experimental approach is developed for characterizing the performance of heat pipe wick structures. This approach simulates the actual operation of wick structures in a heat pipe. Open, partially submerged, sintered copper wicks of varying pore size are studied under the partially saturated conditions found in normal heat pipe operation. A vertical wick orientation, where the capillary lift is in opposition to gravity, is selected to test the wicks under the most demanding conditions. Mass transport measurements of the working fluid, in addition to the temperature field, are obtained for the porous wicks under the action of a discrete …

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A Bayesian Perspective On Estimating Mean, Variance, And Standard-Deviation From Data, Travis E. Oliphant Dec 2006

A Bayesian Perspective On Estimating Mean, Variance, And Standard-Deviation From Data, Travis E. Oliphant

Faculty Publications

This article shows how to compute confidence intervals for mean, standard-deviation, and variance using Bayesian methods. The method is implemented in SciPy as scipy.stats.bayes_mvs After reviewing some classical estimators for mean, variance, and standard-deviation and showing that un-biased estimates are not usually desirable, a Bayesian perspective is employed to determine what is known about mean, variance, and standard deviation given only that a data set in-fact has a common mean and variance. Maximum-entropy is used to argue that the likelihood function in this situation should be the same as if the data were independent and identically distributed Gaussian. A non-informative …

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Information Infrastructure For Integrated Ecohydraulic And Water Resources Modeling And Assessment, R. Wallace, K. Pathak, M. Fife, Norman L. Jones, J. P. Holland, D. Stuart, J. Harris, C. Butler, D. R. Richards Dec 2006

Information Infrastructure For Integrated Ecohydraulic And Water Resources Modeling And Assessment, R. Wallace, K. Pathak, M. Fife, Norman L. Jones, J. P. Holland, D. Stuart, J. Harris, C. Butler, D. R. Richards

Faculty Publications

Watershed management increasingly requires ecohydraulic modeling and assessment within a regional context, rather than on a project-by-project basis. Such holistic modeling and assessment require evaluation capabilities across multiple temporal and spatial scales. Thus, modeling and assessment tools must be integrated in a scientifically and computationally effective infrastructure. The US Army Engineer Research and Development Center, in concert with the Hydrologic Engineering Center and its academic partners, including Brigham Young University, is establishing a comprehensive set of hydroinformatics modeling and assessment tools for ecohydraulic and water resources management applications, all linked based on a common data and information infrastructure. This paper …

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Vision-Based Target Geo-Location Using A Fixed-Wing Miniature Air Vehicle, D. Blake Barber, Joshua D. Redding, Timothy W. Mclain, Randal W. Beard, Clark N. Taylor Dec 2006

Vision-Based Target Geo-Location Using A Fixed-Wing Miniature Air Vehicle, D. Blake Barber, Joshua D. Redding, Timothy W. Mclain, Randal W. Beard, Clark N. Taylor

Faculty Publications

This paper presents a method for determining the GPS location of a ground-based object when imaged from a fixed-wing miniature air vehicle (MAV). Using the pixel location of the target in an image, with measurements of MAV position and attitude, and camera pose angles, the target is localized in world coordinates. The main contribution of this paper is to present four techniques for reducing the localization error. In particular, we discuss RLS filtering, bias estimation, flight path selection, and wind estimation. The localization method has been implemented and flight tested on BYU’s MAV testbed and experimental results are presented demonstrating …

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Predicting On-Orbit Static Single Event Upset Rates In Xilinx Virtex Fpgas, Joshua Engel, Keith S. Morgan, Michael J. Wirthlin, Paul S. Graham Nov 2006

Predicting On-Orbit Static Single Event Upset Rates In Xilinx Virtex Fpgas, Joshua Engel, Keith S. Morgan, Michael J. Wirthlin, Paul S. Graham

Faculty Publications

Sponsorship: Department of Energy, Los Alamos National Laboratory. This document describes the methodology used to predict single-event upset rates for Xilinx Virtex FPGAs based on the CREME96 orbit modeling tool. Using this methodology, SEU upset rates are obtained for several Xilinx Virtex FPGAs including Virtex, Virtex-II, and Virtex-4. Further, SEU upset rates are obtained for a variety of orbits for each of these FPGAs.

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Simulation Of A Carbon Nanotube-Based Compliant Parallel-Guiding Mechanism: A Nanomechanical Building Block, Martin L. Culpepper, Christopher M. Dibiasio, Robert M. Panas, Spencer P. Magleby, Larry L. Howell Nov 2006

Simulation Of A Carbon Nanotube-Based Compliant Parallel-Guiding Mechanism: A Nanomechanical Building Block, Martin L. Culpepper, Christopher M. Dibiasio, Robert M. Panas, Spencer P. Magleby, Larry L. Howell

Faculty Publications

The authors report the behavior of a nanoscale parallel-guiding mechanism wherein the compliant components are single-walled carbon nanotubes. Parallel-guiding mechanisms are often the building blocks of macro- and microscale mechanical systems. The authors present results that provide insight into the performance of a parallel-guiding mechanism for nanoscale devices. The device exhibits a range over 75% of the device size, i.e., 5.5 nm, when actuated with 6.4 nN. Below 3.6 nN, displacements are due to bulk elastic bending of the nanotubes. Above 5.2 nN, displacements are governed by the hingelike bending of kinks in the nanotubes. van der Waals forces are …

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Santa Clara County Soft First Story Multi Unit Building Survey, Guna S. Selvaduray, S. Vukazich, J. Tran Nov 2006

Santa Clara County Soft First Story Multi Unit Building Survey, Guna S. Selvaduray, S. Vukazich, J. Tran

Faculty Publications

The objective of this survey was to provide data to emergency managers in Santa Clara County on the number of soft first-story multifamily dwellings (MFD) located in their communities using a cost-effective town-gown partnership. Target areas of cities were found by identifying areas containing residential units of two or more stories that had four or more living units. The survey found that 2,630, or 36%, of the 7,391 MFD in Santa Clara County are of the soft first-story construction type. It was found that one out of every nine apartment units in Santa Clara County is located in a soft …

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Time-Varying Mimo Channels: Measurement, Analysis, And Modeling, Michael A. Jensen, Jon W. Wallace Nov 2006

Time-Varying Mimo Channels: Measurement, Analysis, And Modeling, Michael A. Jensen, Jon W. Wallace

Faculty Publications

communication nodes is analyzed. A wide-band 8 times 8 sounder is employed to measure the response of indoor and outdoor channels at 2.55 and 5.2 GHz. The rate of channel temporal variation is then quantified in terms of information theoretic metrics that indicate the loss in channel quality as transmit and receive channel state information becomes increasingly outdated. Finally, these metrics are used to investigate the ability of two different modeling strategies-a random matrix model and a physical time-varying cluster model-to capture the channel temporal variation.

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Anisotropic High Aspect Ratio Etch Development For Fluorinated Polymers With Stress Relief Technique, S. Kim, Gregory P. Nordin, N. Rahmanian Nov 2006

Anisotropic High Aspect Ratio Etch Development For Fluorinated Polymers With Stress Relief Technique, S. Kim, Gregory P. Nordin, N. Rahmanian

Faculty Publications

The authors have developed an anisotropic, high aspect ratio (18:1) etch for perfluorocyclobutyl (PFCB) polymers with trenches as narrow as 800 nm using a CO/O2 etch chemistry in an inductively coupled plasma reactive ion etcher. Anisotropy is achieved by carbon sidewall passivation. The motivation for this etch development is to use the air trenches as very compact waveguide splitters [S. Kim et al., Opt. Eng. 45, 054602 (2006)] The authors report a new trench widening mechanism due to tensile stress of the PFCB films and a method of avoiding this widening through the use of additional stress relief trenches on …

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An M/M/1 Retrial Queue With Unreliable Server, Nathan P. Sherman, Jeffrey P. Kharoufeh Nov 2006

An M/M/1 Retrial Queue With Unreliable Server, Nathan P. Sherman, Jeffrey P. Kharoufeh

Faculty Publications

We analyze an unreliable M/M/1 retrial queue with infinite-capacity orbit and normal queue. Retrial customers do not rejoin the normal queue but repeatedly attempt to access the server at i.i.d. intervals until it is found functioning and idle. We provide stability conditions as well as several stochastic decomposability results.

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Potential Energy Surfaces For Small Alcohol Dimers I: Methanol And Ethanol, Richard L. Rowley, Tapani A. Pakkanen, Christopher M. Tracy Oct 2006

Potential Energy Surfaces For Small Alcohol Dimers I: Methanol And Ethanol, Richard L. Rowley, Tapani A. Pakkanen, Christopher M. Tracy

Faculty Publications

Potential energy landscapes for homogeneous dimers of methanol and ethanol were calculated using counterpoise (CP) corrected energies at the MP2/6-311+G(2df,2pd) level. The landscapes were sampled at approximately 15 dimer separation distances for different relative monomer geometries, or routes, given in terms of a relative monomer yaw, pitch, and roll and the spherical angles between the monomer centers (taken as the C atom attached to the O). The 19 different routes studied for methanol and the 22 routes examined for ethanol include 607 CP corrected energies. Both landscapes can be adequately represented by site-site, pairwise-additive models, suitable for use in molecular …

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Modeling Arsenic Partitioning In Coal-Fired Power Plants, Constance L. Senior, David O. Lignell, Adel F. Sarofim, Arun Mehta Oct 2006

Modeling Arsenic Partitioning In Coal-Fired Power Plants, Constance L. Senior, David O. Lignell, Adel F. Sarofim, Arun Mehta

Faculty Publications

Vapor-phase arsenic in coal combustion flue gas causes deactivation of the catalysts used in selective catalytic reduction (SCR) systems for NOx control. A one-dimensional model has been developed to predict the behavior of arsenic in the postcombustion region of a coal-fired boiler as a function of gas residence time. The purpose of the model is to calculate the partitioning of arsenic between the vapor phase from volatilization and arsenic on the ash particles due to surface reaction and/or condensation at temperatures characteristic of SCR systems. The model accounts for heterogeneous condensation of arsenic on the fly ash, as well …

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Optical Emission Study Of Nonthermal Plasma Confirms Reaction Mechanisms Involving Neutral Rather Than Charged Species, Morris D. Argyle, Gui-Bing Zhao, Maciej Radosz Oct 2006

Optical Emission Study Of Nonthermal Plasma Confirms Reaction Mechanisms Involving Neutral Rather Than Charged Species, Morris D. Argyle, Gui-Bing Zhao, Maciej Radosz

Faculty Publications

Charge transfer reactions are commonly used to explain NOX conversion in nonthermal plasma. An analysis of optical emission spectra induced by pulsed corona discharge in NOX-containing argon suggests that, in fact, the contribution of charge transfer reactions to NOX conversion in nonthermal plasma is negligible. During electrical discharge in such gas mixtures, NO(B), an electronic excited state of NO formed due to the dissociative recombination reactions of NO2+ and N2O+ and the optical emission of NO(B) could be a proof that cations are responsible for NOX conversion. However, the optical emission of NO(B) is not observed, leading to the conclusion …

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Fabrication And Characterization Of Poly(Propylene Fumarate) Scaffolds With Controlled Pore Structures Using 3-Dimensional Printing And Injection Molding, Kee-Won Lee, Shanfeng Wang, Lichun Lu, Esmaiel Jabbari, Bradford L. Currier, Michael J. Yaszemski Oct 2006

Fabrication And Characterization Of Poly(Propylene Fumarate) Scaffolds With Controlled Pore Structures Using 3-Dimensional Printing And Injection Molding, Kee-Won Lee, Shanfeng Wang, Lichun Lu, Esmaiel Jabbari, Bradford L. Currier, Michael J. Yaszemski

Faculty Publications

Poly(propylene fumarate) (PPF) is an injectable, biodegradable polymer that has been used for fabricating preformed scaffolds in tissue engineering applications because of in situ crosslinking characteristics. Aiming for understanding the effects of pore structure parameters on bone tissue ingrowth, 3-dimensional (3D) PPF scaffolds with controlled pore architecture have been produced in this study from computer-aided design (CAD) models. We have created original scaffold models with 3 pore sizes (300, 600, and 900 µm) and randomly closed 0%, 10%, 20%, or 30% of total pores from the original models in 3 planes. PPF scaffolds were fabricated by a series steps involving …

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Low-Frequency Ultrasound Increases Outer Membrane Permeability Of Pseudomonas Aeruginosa, Christopher M. Runyan, John C. Carmen, Benjamin L. Beckstead, Jared L. Nelson, Richard A. Robison, William G. Pitt Sep 2006

Low-Frequency Ultrasound Increases Outer Membrane Permeability Of Pseudomonas Aeruginosa, Christopher M. Runyan, John C. Carmen, Benjamin L. Beckstead, Jared L. Nelson, Richard A. Robison, William G. Pitt

Faculty Publications

Low-frequency ultrasound has been investigated as an adjuvant to antimicrobial therapy, targeted at both planktonic and biofilm (sessile) organisms. Our previous work showed that ultrasound (US) effectively enhances the bactericidal activity of certain antibiotics against planktonic cultures (Pitt et al., 1994; Rediske et al., 1999) and in vitro biofilms (Johnson et al., 1998; Qian et al., 1999) and in vivo biofilms (Carmen et al., 2004b, 2005; Rediske et al., 2000) of gram-positive and gram-negative bacteria. Ultrasound was shown to increase the transport of antibiotics through biofilms (Carmen et al., 2004a) which could account for some (or all) of the enhanced …

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A New Class Of Miniature Embedded Inverted-F Antennas (Ifas) For 2.4 Ghz Wlan Application, Mohammed Z. Azad, Mohammod Ali Sep 2006

A New Class Of Miniature Embedded Inverted-F Antennas (Ifas) For 2.4 Ghz Wlan Application, Mohammed Z. Azad, Mohammod Ali

Faculty Publications

A new class of miniature printed embedded inverted-F antennas are proposed for operation in the 2.4-2.485 GHz wireless local-area network band. One of the proposed antennas on FR4 substrate (dielectric constant = 4.4) measures 9.2 mm by 4.1 mm and has a bandwidth of 3.5%. The peak gain of this antenna is 1.4 dBi. An overall size reduction of 70% is achieved compared to a conventional inverted-F antenna. Effects of dielectric loss tangent and material conductivity on the bandwidth and efficiency of these antennas are also investigated. Finally, two embedded antenna elements are analyzed to demonstrate the feasibility for a …

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The 1.6-Kv Algan/Gan Hfets, N. Tipirneni, Alexei Koudymov, V. Adivarahan, Jinwei Yang, Grigory Simin, Asif Khan Sep 2006

The 1.6-Kv Algan/Gan Hfets, N. Tipirneni, Alexei Koudymov, V. Adivarahan, Jinwei Yang, Grigory Simin, Asif Khan

Faculty Publications

The breakdown voltages in unpassivated nonfield-plated AlGan/GaN HFETs on sapphire substrates were studied. These studies reveal that the breakdown is limited by the surface flashover rather than by the AlGan/GaN channel. after elimination of the surface flashover in air, the breakdown voltage scaled linearly with the gate-drain spacing reaching 1.6 kV at 20 mu m. The corresponding static ON-resistance was as low as 3.4 m Omega(.)cm(2). This translates to a power device figure-of-merit V-BR(2)/R-ON = 7.5 x 10(8) V-2 . n(-1) cm(-2), which, to date, is among the best reported values for an AlGan/GaN HFET.

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Melt Detection In Antarctic Ice Shelves Using Scatterometers And Microwave Radiometers, David G. Long, Lucas B. Kunz Sep 2006

Melt Detection In Antarctic Ice Shelves Using Scatterometers And Microwave Radiometers, David G. Long, Lucas B. Kunz

Faculty Publications

Ku-band dual-polarization radar backscatter measurements from the SeaWinds-on-QuikSCAT scatterometer are used to determine periods of surface freeze and melt in the Antarctic ice shelves. The normalized horizontal-polarization radar backscatter (sigmao) and backscatter polarization ratio are used in maximum-likelihood estimation of the ice state. This method is used to infer the daily ice-surface conditions for 25 study locations located on the Ronne, Ross, Larsen, Amery, Shackleton, and other ice shelves. The temporal and spatial variations of the radar response are observed for various neighborhood sizes surrounding each given location during the study period. Criteria for determining the dates of melt onset …

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Maximizing Miniature Aerial Vehicles, Stephen Griffiths, Jeffery Brian Saunders, Andrew Curtis, Blake Barber, Timothy W. Mclain, Randal W. Beard Sep 2006

Maximizing Miniature Aerial Vehicles, Stephen Griffiths, Jeffery Brian Saunders, Andrew Curtis, Blake Barber, Timothy W. Mclain, Randal W. Beard

Faculty Publications

Despite the tremendous potential demonstrated by miniature aerial vehicles (MAV) in numerous applications, they are currently limited to operations in open air space, far away from obstacles and terrain. To broaden the range of applications for MAVs, methods to enable operation in environments of increased complexity must be developed. In this article, we presented two strategies for obstacle and terrain avoidance that provide a means for avoiding obstacles in the flight path and for staying centered in a winding corridor.

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Comparison Of Microcantilever Hg Sensing Behavior With Thermal Higher Order Modes For As-Deposited Sputtered And Thermally Evaporated Au Films, Gregory P. Nordin, Michael A. George, Ashwini R. Kadam Sep 2006

Comparison Of Microcantilever Hg Sensing Behavior With Thermal Higher Order Modes For As-Deposited Sputtered And Thermally Evaporated Au Films, Gregory P. Nordin, Michael A. George, Ashwini R. Kadam

Faculty Publications

As-deposited sputtered and thermally evaporated Au films are studied for Hg sensing with rectangular Si microcantilevers. Microcantilever deflection and frequency shifts in the first four thermally induced flexural modes are measured for each type of Au film as a function of Hg exposure. All thermally induced higher order modes show shifts in their frequencies for Hg exposures when the Au is sputter deposited whereas typically only the third and fourth order modes show frequency shifts when the Au is thermally evaporated. A technique is employed in order to vary Au coverage along a microcantilever surface. The shifts in the thermal …

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Systematic Design Process For Slanted Graing Couplers,, Gregory P. Nordin, J. Jiang, B. Wang Aug 2006

Systematic Design Process For Slanted Graing Couplers,, Gregory P. Nordin, J. Jiang, B. Wang

Faculty Publications

We have developed a systematic design process for recently proposed slanted grating couplers (SGCs) that operates in the strong coupling regime. Based on rigorous analysis of SGC properties, this design process utilizes the k-vector diagram and a rigorous grating leaky-mode solver to intentionally enforce the phase-match and Bragg conditions. We demonstrate that the resultant SGC designs have performance similar to those obtained by parallel micro-genetic algorithm (µGA) optimization with the twodimensional finite-difference time-domain (2D FDTD) method. Only two 2D FDTD simulations are necessary in the later stages of our systematic design process. Therefore the time saving is tremendous compared to …

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Methane Conversion In Pulsed Corona Discharge Reactors, Morris D. Argyle, Gui-Bing Zhao, Sanil John, Ji-Jun Zhang, Linna Wang, Suresh S. Muknahallipatna, Jerry C. Hamann, John F. Ackerman, Ovid A. Plumb Aug 2006

Methane Conversion In Pulsed Corona Discharge Reactors, Morris D. Argyle, Gui-Bing Zhao, Sanil John, Ji-Jun Zhang, Linna Wang, Suresh S. Muknahallipatna, Jerry C. Hamann, John F. Ackerman, Ovid A. Plumb

Faculty Publications

This work reports the effect of capacitance, cathode material, gas flow rate and specific energy input on methane conversion, energy efficiency and product selectivity in a co-axial cylinder pulsed corona discharge reactor. Ethan and acetylene appear to be formed from dimerization of CH3 radicals and CH radicals, respectively, while ethylene is formed mainly from the dehydrogenation of ethane. At a given power input, low capacitance with high pulse frequency results in higher methane conversion and energy efficiency than operation at high capacitance with low pulse frequency. Platinum coated stainless steel cathodes slightly enhance methane conversion relative to stainless steel cathodes, …

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A Compact Digitally Controlled Fuel Cell/Battery Hybrid Power Source, Zhenhua Jiang, Roger A. Dougal Aug 2006

A Compact Digitally Controlled Fuel Cell/Battery Hybrid Power Source, Zhenhua Jiang, Roger A. Dougal

Faculty Publications

A compact digitally controlled fuel cell/battery hybrid power source is presented in this paper. The hybrid power source composed of fuel cells and batteries provides a much higher peak power than each component alone while preserving high energy density, which is important and desirable for many modern electronic devices, through an appropriately controlled dc/dc power converter that handles the power flow shared by the fuel cell and the battery. Rather than being controlled to serve only as a voltage or current regulator, the power converter is regulated to balance the power flow to satisfy the load requirements while ensuring the …

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Cross-Layer Issues In Mac Protocol Design For Mimo Ad Hoc Networks, Michael A. Jensen, A. Lee Swindlehurst, Michele Zorzi, James R. Zeidler, Adam L. Anderson, Bhaskar Rao, John Proakis, Srikanth Krishnamurthy Aug 2006

Cross-Layer Issues In Mac Protocol Design For Mimo Ad Hoc Networks, Michael A. Jensen, A. Lee Swindlehurst, Michele Zorzi, James R. Zeidler, Adam L. Anderson, Bhaskar Rao, John Proakis, Srikanth Krishnamurthy

Faculty Publications

In this article, we discuss research and design issues that arise in the development of networking protocols for an ad hoc network where nodes are equipped with multiple antenna elements and have the ability to perform signal processing operations as required by adaptive beamforming, interference cancellation, and space-time coding.

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