Open Access. Powered by Scholars. Published by Universities.®
- Discipline
- Keyword
-
- Oceanographic techniques (2)
- UAV (2)
- Unmanned aircraft (2)
- Alumina-supported vanadia (1)
- Aluminum (1)
-
- Atmospheric techniques (1)
- Backscatter (1)
- Bistable (1)
- Catalyst structure (1)
- Channel capacity (1)
- Compliant mechanism (1)
- Cooperative control (1)
- Cooperative timing (1)
- Covariance matrices (1)
- Dislocations (1)
- Elasticity (1)
- Electromagnetic wave polarisation (1)
- Electron backscatter diffraction patterns (1)
- Electron backscattering diffraction (1)
- Error analysis (1)
- Ethene (1)
- FPGA Reliability (1)
- Grain boundaries (1)
- I/O (1)
- Indicator kriging (1)
- Indoor radio (1)
- LDBM (1)
- Linear displacement (1)
- MIMO systems (1)
- MODFLOW (1)
Articles 1 - 16 of 16
Full-Text Articles in Engineering
On-Chip Actuation Of An In-Plane Compliant Bistable Micromechanism, Michael S. Baker, Larry L. Howell
On-Chip Actuation Of An In-Plane Compliant Bistable Micromechanism, Michael S. Baker, Larry L. Howell
Faculty Publications
A compliant bistable micromechanism has been developed which can be switched in either direction using on-chip thermal actuation. The energy storage and bistable behavior of the mechanism is achieved through the elastic deflection of compliant segments. The Pseudo-Rigid-Body Model was used for the compliant mechanism design, and for analysis of the large deflection flexible segments. To achieve on-chip actuation, the mechanism design was optimized to allow it to be switched using linear motion thermal actuators. The modeling theory and analysis are presented for three design iterations, with two iterations fabricated in the MUMP's process and the third in the SUMMiT …
An Assessment Of Seawinds On Quikscat Wind Retrieval, David Draper, David G. Long
An Assessment Of Seawinds On Quikscat Wind Retrieval, David Draper, David G. Long
Faculty Publications
The scatterometer ocean wind retrieval process produces several possible solutions or ambiguities at each point, requiring a separate ambiguity selection step to infer a unique wind vector field. An ambiguity selection error occurs when the selected wind vector is not the closest ambiguity to the true wind. The current ambiguity selection routine for SeaWinds is ad hoc, but performs well under most circumstances. Factors such as instrument noise and rain can also cause the estimated wind flow to deviate from the true wind. A quality assurance (QA) analysis is performed to assess the ambiguity selection effectiveness and noise level of …
Mapping The Mesoscale Interface Structure In Polycrystalline Materials, Brent L. Adams, C. L. Bauer, D. Casasent, A. Morawiec, S. Ozdemir, A. Talukder, Chialin T. Wu
Mapping The Mesoscale Interface Structure In Polycrystalline Materials, Brent L. Adams, C. L. Bauer, D. Casasent, A. Morawiec, S. Ozdemir, A. Talukder, Chialin T. Wu
Faculty Publications
This work was supported primarily by the MRSEC Program of the National Science Foundation under Award Numbers DMR-9632556 and DMR-0079996. A new experimental approach to the quantitative characterization of polycrystalline microstructure by scanning electron microscopy is described. Combining automated electron backscattering diffraction with conventional scanning contrast imaging and with calibrated serial sectioning, the new method (Mesoscale Interface Mapping System, MIMS) recovers precision estimates of the 3-dimensional idealized aggregate function G(x). This function embodies a description of lattice phase and orientation (limiting resolution ~ 1 degree) at each point x (limiting spatial resolution ~ 100 nanometers), and therefore contains a complete …
Modeling The Thermal Behavior Of A Surface-Micromachined Linear-Displacement Thermomechanical Microactuator, Christian D. Lott, Timothy W. Mclain, John N. Harb, Larry L. Howell
Modeling The Thermal Behavior Of A Surface-Micromachined Linear-Displacement Thermomechanical Microactuator, Christian D. Lott, Timothy W. Mclain, John N. Harb, Larry L. Howell
Faculty Publications
Thermomechanical microactuators possess a number of desirable attributes including ease of fabrication and large force and displacement capabilities relative to other types of microactuators. These advantages provide motivation for improving thermomechanical microactuator designs that are more energy efficient and thus better suited for low-power applications. To this end, this paper describes the development and experimental validation of a finite-difference thermal model of a thermomechanical in-plane microactuator (TIM). Comparisons between the model and experimental results demonstrate the importance of including the temperature dependence of several parameters in the model. Strategies for reducing the power and energy requirements of the TIM were …
Viewpoint: Experimental Recovery Of Geometrically Necessary Dislocation Density In Polycrystals, Brent L. Adams, Bassem S. El-Dasher, Anthony D. Rollett
Viewpoint: Experimental Recovery Of Geometrically Necessary Dislocation Density In Polycrystals, Brent L. Adams, Bassem S. El-Dasher, Anthony D. Rollett
Faculty Publications
The authors wish to thank The Alcoa Technical Research Center for supplying the specimens and performing the compression tests. This work was supported primarily by the MRSEC program of the National Science Foundation under DMR-0079996. Application of electron backscattering diffraction methods to recover estimates of the geometrically necessary dislocation density is described. The limitations of the method arising from the opacity of crystalline materials and the spatial and angular resolution limits are discussed.
Experimental Demonstration Of Multiple Robot Cooperative Target Intercept, Timothy W. Mclain, Randal W. Beard, Jed M. Kelsey
Experimental Demonstration Of Multiple Robot Cooperative Target Intercept, Timothy W. Mclain, Randal W. Beard, Jed M. Kelsey
Faculty Publications
This paper presents experimental results for the simultaneous intercept of preassigned targets by a team of mobile robots. The robots are programmed to mimic the dynamic behavior of unmanned air vehicles in constant-altitude flight. In proceeding to their targets, robots must avoid both known static threats and pop-up threats. An overview of the cooperative control strategy followed is given, as well as a description of the robot hardware and software used. Experimental results demonstrating simultaneous intercept of targets by the robot team are presented.
Autonomous Hierarchical Control Of Multiple Unmanned Combat Air Vehicles (Ucavs), Timothy Mclain, Randal W. Beard, Sai-Ming Li, Jovan D. Boskovic, Sanjeev Seereeram, Ravi Prasanth, Jayesh Amin, Raman K. Mehra
Autonomous Hierarchical Control Of Multiple Unmanned Combat Air Vehicles (Ucavs), Timothy Mclain, Randal W. Beard, Sai-Ming Li, Jovan D. Boskovic, Sanjeev Seereeram, Ravi Prasanth, Jayesh Amin, Raman K. Mehra
Faculty Publications
In this paper we present a hierarchical control scheme that enables multiple UCAVs to achieve demanding missions in hostile environments autonomously. The objective is to use a swarm of UCAVs for a SEAD type mission: fly the UCAVs in a formation to an enemy territory populated with different kinds of threats, collect enemy information or destroy certain targets, and return to the base, all without human intervention. The scheme is an integration of four distinct components, including: (1) high level Voronoi diagram based path planner to avoid static threats; (2) low level path planner to avoid popup threats; (3) differential …
Validation Of Sea Ice Motion From Quikscat With Those From Ssm/I And Buoy, David G. Long, Yunhe Zhao, Antony K. Liu
Validation Of Sea Ice Motion From Quikscat With Those From Ssm/I And Buoy, David G. Long, Yunhe Zhao, Antony K. Liu
Faculty Publications
Arctic sea ice motion for the period from October 1999 to March 2000 derived from QuikSCAT and ocean buoy observations. Special Sensor Microwave/Imager (SSM/I) data using the wavelet analysis method agrees well with ocean buoy observations. Results from QuikSCAT and SSM/I are compatible when compared with buoy observations and complement each other. Sea ice drift merged from daily results from QuikSCAT, SSM/I, and buoy data gives more complete coverage of sea ice motion. Based on observations of six months of sea ice motion maps, the sea ice motion maps in the Arctic derived from QuikSCAT data appear to have smoother …
Modeling The Indoor Mimo Wireless Channel, Michael A. Jensen, Jon W. Wallace
Modeling The Indoor Mimo Wireless Channel, Michael A. Jensen, Jon W. Wallace
Faculty Publications
This paper demonstrates the ability of a physically based statistical multipath propagation model to match capacity statistics and pairwise magnitude and phase distributions of measured 4 x 4 and 10 x 10 narrow-band multiple-input multiple-output data (MIMO) at 2.4 GHz. The model is compared to simpler statistical models based on the multivariate complex normal distribution with either complex envelope or power correlation. The comparison is facilitated by computing channel element covariance matrices for fixed sets of multipath statistics. Multipolarization data is used to demonstrate a simple method for modeling dual-polarization arrays.
In-Plane Linear-Displacement Bistable Microrelay, Troy Gomm, Larry L. Howell, Richard H. Selfridge
In-Plane Linear-Displacement Bistable Microrelay, Troy Gomm, Larry L. Howell, Richard H. Selfridge
Faculty Publications
This paper investigates the Linear Displacement Bistable Mechanism (LDBM) for use in microrelays. The LDBM, thermal actuators, and contacts are integrated to demonstrate a relay design. The performance of the relay is characterized using relay performance metrics, including size (1.92 mm2), contact force (23.4 μN), switching time (340 μs), breakdown voltage (> 475 V), and isolation (> 235 V). The actuation voltage and current are 11 V and 85 mA, respectively. AC characteristics, including contact-to-contact crosstalk and AC isolation are also measured. The testing results demonstrate that it is feasible to use the LDBM as a microrelay and that it …
Effect Of Catalyst Structure On Oxidative Dehydrogenation Of Ethane And Propane On Alumina-Supported Vanadia, Morris D. Argyle, Kaidong Chen, Alexis T. Bell, Enrique Iglesia
Effect Of Catalyst Structure On Oxidative Dehydrogenation Of Ethane And Propane On Alumina-Supported Vanadia, Morris D. Argyle, Kaidong Chen, Alexis T. Bell, Enrique Iglesia
Faculty Publications
The catalytic properties of Al2O3-supported vanadia with a wide range of VOx surface density (1.4-34.2 V/nm2) and structure were examined for the oxidative dehydrogenation of ethane and propane. UV-visible and Raman spectra showed that vanadia is dispersed predominately as isolated monovanadate species below ~2.3 V/nm2. As surface densities increase, two-dimensional polyvanadates appear (2.3-7.0 V/nm2) along with increasing amounts of V2O5 crystallites at surface densities above 7.0 V/nm2. The rate constant for oxidative dehydrogenation (k1) and its ratio with alkane and alkene combustion (k2/k1 and k3/k1, respectively) were compared for both alkane reactants as a function of vanadia surface density. Propene …
Using Transition Probability Geostatistics With Modflow, Norman L. Jones, J. R. Walker, S. F. Carle
Using Transition Probability Geostatistics With Modflow, Norman L. Jones, J. R. Walker, S. F. Carle
Faculty Publications
This paper describes a technique for applying the transition probability geostatistics method for stochastic simulation to a MODFLOW model. Transition probability geostatistics has several advantages over traditional indicator kriging methods, including a simpler and more intuitive framework for interpreting geological relationships and the ability to simulate juxtapositional tendencies such s fining-upwards sequences. The indicator arrays generated by the transition probability simulation are converted to layer elevation and thickness arrays for use with the new Hydrogeologic Unit Flow (HUF) package in MODFLOW 2000. This makes it possible to preserve complex heterogeneity while using reasonably sized grids.
Surface Micromachined Force Gauges: Uncertainty And Reliability, Jonathan W. Wittwer, Troy Gomm, Larry L. Howell
Surface Micromachined Force Gauges: Uncertainty And Reliability, Jonathan W. Wittwer, Troy Gomm, Larry L. Howell
Faculty Publications
Surface micromachining of micro-electro-mechanical systems (MEMS), like all other fabrication processes, has inherent variation that leads to uncertain material and dimensional parameters. By considering the effects of these variations during the design of micro force gauges, the gauge uncertainty and reliability can be estimated. Without means of calibrating micro gauges, these effects are often significant when compared to experimental repeatability. The general force gauge model described in this paper can be used to measure a wide range of forces, and simple design changes can lead to improved accuracy in measurement. A method of probabilistic design is described that is not …
Evaluation Of A Compound Probability Model With Tower-Mounted Scatterometer Data, David G. Long, Benjamin E. Barrowes
Evaluation Of A Compound Probability Model With Tower-Mounted Scatterometer Data, David G. Long, Benjamin E. Barrowes
Faculty Publications
Six months of data from the YSCAT94 experiment conducted at the CCIW WAVES research platform on Lake Ontario, Canada, are analyzed to evaluate a compound probability model. YSCAT was an ultrawideband small footprint (ap 1 m) microwave scatterometer that operated at frequencies of 2-18 GHz, incidence angles from 0° to 60°, both h-pol and v-pol, and which tracked the wind using simultaneous weather measurements. The probability distribution function of the measured instantaneous backscattered amplitude (p(a)) is compared to theoretical distributions developed from-the composite model and a simple wave spectrum. Model parameters of the resulting Rayleigh/generalized lognormal distribution probability density function …
Reliability Of Programmable Input/Output Pins In The Presence Of Configuration Upsets, Paul S. Graham, Nathaniel Rollins, Michael J. Wirthlin, Michael P. Caffrey
Reliability Of Programmable Input/Output Pins In The Presence Of Configuration Upsets, Paul S. Graham, Nathaniel Rollins, Michael J. Wirthlin, Michael P. Caffrey
Faculty Publications
Sponsorship: Los Alamos National Laboratories (LA-UR-02-3163). Field programmable gate arrays (FPGAs) are an attractive alternative for space-based remote sensing applications. However, SRAM-based FPGAs are sensitive to radiation induced single-event upsets within the configuration memory. Such configuration upsets may change the logic, routing, and operating modes of a user FPGA design. Upsets within the configuration of an I/O block are especially troublesome as they may impact the operation of other system components. This paper will evaluate the operation of the I/O block within the Xilinx Virtex FPGA in the presence of configuration memory upsets and introduce techniques for detecting and repairing …
Spectral Integration Of Microstructure And Design, Brent L. Adams, B. Henrie, M. Lyon, H. Garmestani, Surya R. Kalidindi
Spectral Integration Of Microstructure And Design, Brent L. Adams, B. Henrie, M. Lyon, H. Garmestani, Surya R. Kalidindi
Faculty Publications
Support of the Army Research Office is greatly appreciated. Mechanical design can be conducted in a framework where consideration of microstructure as a continuous design variable is facilitated by the use of a Fourier space. Selection of the mechanical framework for the problem (e.g., mechanical constitutive model and homogenization relations) dictates the dimensionality of the pertinent microstructure representation. Microstructure is comprised of basic elements that belong to the local state space. Local state includes crystallographic phase and orientation, and other parameters such as composition. The local state space is transformed into an isomorphic set in Fourier space. The universe of …