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Investigation of an on-off inlet shock-position control on a 16-inch ram-jet engine

Description: Report presenting an investigation of a shock-positioning control on a 16-inch ramjet engine at a range of Mach numbers and angles of attack in a supersonic wind tunnel. The static-pressure rise across the inlet normal shock was utilized in setting the diffuser at its critical condition. Results regarding the sensing pressures, engine performance, control set engine operation, pressure data, operation of the control during Mach number change, and other applications of control are provided.
Date: November 29, 1954
Creator: Wilcox, Fred A.; Perchonok, Eugene & Hearth, Donald P.
Partner: UNT Libraries Government Documents Department

Grid-based Coordinated Routing in Wireless Sensor Networks

Description: This paper discusses grid-based coordinated routing in wireless sensor networks and compares the energy available in the network over time for different grid sizes. The authors explore the quality of service of wireless sensor networks, how the coordinator nodes are elected, and the size of the grid area that will minimize the total energy consumption and extend the lifetime of the network.
Date: January 2007
Creator: Akl, Robert G. & Sawant, Uttara
Partner: UNT College of Engineering

Optimizing receiver configurations for resolution of equivalent dipole polarizabilities in situ

Description: Equivalent dipole polarizabilities are a succinct way to summarize the inductive response of an isolated conductive body at distances greater than the scale of the body. At any time lag or frequency, an equivalent dipole polarizability response is comprised of 9 parameters; six specifying an equivalent dipole polarizability matrix (which is symmetric) and three specifying the apparent location of the body center. Smith and Morrison (2002) give equations for calculating uncertainties in equivalent dipole polarizability and position based on analysis of an iterative linearized inversion. Here, the root mean squared uncertainty in polarizability is weighted and summed over a number of control points and minimized using an evolutionary algorithm for a number of instrument designs. Three families of designs are presented: single transmitter systems for use on a 2-D grid of positions with negligible error in relative instrument location, two transmitter systems for use on a line of positions with negligible error in relative instrument location, and three transmitter systems for stand alone use. Results for the one and two transmitter systems are strongly degraded by errors in instrument position, whereas the three transmitter systems are insensitive to instrument positioning errors.
Date: February 12, 2004
Creator: Smith, J. Torquil & Morrison, H. Frank
Partner: UNT Libraries Government Documents Department

Results from an International Simulation Study on Coupled Thermal,Hydrological, and Mechanical (THM) Processes near Geological NuclearWaste Repositories

Description: As part of the ongoing international DECOVALEX project, four research teams used five different models to simulate coupled thermal, hydrological, and mechanical (THM) processes near waste emplacement drifts of geological nuclear waste repositories. The simulations were conducted for two generic repository types, one with open and the other with back-filled repository drifts, under higher and lower postclosure temperatures, respectively. In the completed first model inception phase of the project, a good agreement was achieved between the research teams in calculating THM responses for both repository types, although some disagreement in hydrological responses is currently being resolved. In particular, good agreement in the basic thermal-mechanical responses was achieved for both repository types, even though some teams used relatively simplified thermal-elastic heat-conduction models that neglected complex near-field thermal-hydrological processes. The good agreement between the complex and simplified process models indicates that the basic thermal-mechanical responses can be predicted with a relatively high confidence level.
Date: October 23, 2007
Creator: Rutqvist, Jonny; Rutqvist, J.; Barr, D.; Birkholzer, J.T.; Chijimatsu, M.; Kolditz, O. et al.
Partner: UNT Libraries Government Documents Department

Comparative simulation study of coupled THM processes nearback-filled and open-drift nuclear waste repositories in Task D of theInternational DECOVALEX Project

Description: As part of the ongoing international DECOVALEX project, fourresearch teams used five different models to simulate coupled thermal,hydrological, and mechanical (THM) processes near underground wasteemplacement drifts. The simulations were conducted for two genericrepository types, one with open and the other with back-filled repositorydrifts, under higher and lower post-closure temperature, respectively. Inthe completed first model inception phase of the project, a goodagreement was achieved between the research teams in calculating THMresponses for both repository types, although some disagreement inhydrological responses are currently being resolved. Good agreement inthe basic thermal-mechanical responses was also achieved for bothrepository types, even though some teams used relatively simplifiedthermal-elastic heat-conduction models that neglect complex near-fieldthermal-hydrological processes. The good agreement between the complexand simplified process models indicates that the basic thermal-mechanicalresponses can be predicted with a relatively high confidencelevel.
Date: May 10, 2006
Creator: Rutqvist, J.; Birkholzer, J.T.; Chijimatsu, M.; Kolditz, O.; Liu,Quan-Sheng; Oda, Y. et al.
Partner: UNT Libraries Government Documents Department

A comparison of drive mechanisms for precision motion controlled stages

Description: This abstract presents a comparison of two drive mechanisms, a Rohlix{reg_sign} drive and a polymer nut drive, for precision motion controlled stages. A single-axis long-range stage with a 50 mm traverse combined with a short-range stage with a 16 {micro}m traverse at a operational bandwidth of 2.2 kHz were developed to evaluate the performance of the drives. The polymer nut and Rohlix{reg_sign} drives showed 4 nm RMS and 7 nm RMS positioning capabilities respectively, with traverses of 5 mm at a maximum velocity of 0.15 mm{sup -}s{sup -1} with the short range stage operating at a 2.2 kHz bandwidth. Further results will be presented in the subsequent sections.
Date: March 22, 2006
Creator: Buice, E S; Yang, H; Otten, D; Smith, S T; Hocken, R J; Trumper, D L et al.
Partner: UNT Libraries Government Documents Department

The Surface Wave Magnitude for the 9 October 2006 North Korean Nuclear Explosion

Description: Surface waves were generated by the North Korean nuclear explosion of 9 October 2006 and recorded at epicentral distances up to 34 degrees, from which we estimated a surface wave magnitude (M{sub s}) of 2.94 with an interstation standard deviation of 0.17 magnitude units. The International Data Centre estimated a body wave magnitude (m{sub b}) of 4.1. This is the only explosion we have analyzed that was not easily screened as an explosion based on the differences between the M{sub s} and m{sub b} estimates. Additionally, this M{sub s} predicts a yield, based on empirical M{sub s}/Yield relationships, that is almost an order of magnitude larger then the 0.5 to 1 kiloton reported for this explosion. We investigate how emplacement medium effects on surface wave moment and magnitude may have contributed to the yield discrepancy.
Date: March 11, 2008
Creator: Bonner, J; Herrmann, R; Harkrider, D & Pasyanos, M
Partner: UNT Libraries Government Documents Department

Experimental Investigation of Marquardt Shock-Positioning Control Unit on a 28-Inch Ram-Jet Engine

Description: A pneumatic proportional-plus -integral shock-positioning control unit was investigated for controlling a ram-jet engine at a flight Mach number of 2.5 and altitudes of 50,000 to 65,000 feet. A satisfactory of attack, the control action was marginal for the same control settings used at zero angle of attack.
Date: May 18, 1956
Creator: Crowl, R.; Dunbar, W. R. & Wentworth, C.
Partner: UNT Libraries Government Documents Department

Dynamic WIFI Fingerprinting Indoor Positioning System

Description: A technique is proposed to improve the accuracy of indoor positioning systems based on WIFI radio-frequency signals by using dynamic access points and fingerprints (DAFs). Moreover, an indoor position system that relies solely in DAFs is proposed. The walking pattern of indoor users is classified as dynamic or static for indoor positioning purposes. I demonstrate that the performance of a conventional indoor positioning system that uses static fingerprints can be enhanced by considering dynamic fingerprints and access points. The accuracy of the system is evaluated using four positioning algorithms and two random access point selection strategies. The system facilitates the location of people where there is no wireless local area network (WLAN) infrastructure deployed or where the WLAN infrastructure has been drastically affected, for example by natural disasters. The system can be used for search and rescue operations and for expanding the coverage of an indoor positioning system.
Date: August 2014
Creator: Reyes, Omar Costilla
Partner: UNT Libraries

INL Seismic Monitoring Annual Report: January 1, 2009 – December 31, 2009

Description: The Idaho National Laboratory (INL) has accumulated 37 years of earthquake data (1972-2009). This report covers the earthquake activity from January 1, 2009 through December 31, 2009 and is a continuation of previous annual reports on earthquake activity surrounding the eastern Snake River Plain (ESRP) and within and near the INL. It discusses the earthquake activity that has occurred around the local region and within a 161-km radius around the INL centered at 43? 39.00' N, 112? 47.00' W). It discusses the seismic station and strong motion accelerograph instrumentation used to record earthquake data and how they were analyzed. It also includes a brief discussion of continuous GPS (Global Positioning System) stations co-located at INL seismic stations.
Date: September 1, 2010
Creator: Carpenter, N. S.; Payne, S. J.; Hodges, J. M. & Berg, R. G.
Partner: UNT Libraries Government Documents Department

Adaptive and mobile ground sensor array.

Description: The goal of this LDRD was to demonstrate the use of robotic vehicles for deploying and autonomously reconfiguring seismic and acoustic sensor arrays with high (centimeter) accuracy to obtain enhancement of our capability to locate and characterize remote targets. The capability to accurately place sensors and then retrieve and reconfigure them allows sensors to be placed in phased arrays in an initial monitoring configuration and then to be reconfigured in an array tuned to the specific frequencies and directions of the selected target. This report reviews the findings and accomplishments achieved during this three-year project. This project successfully demonstrated autonomous deployment and retrieval of a payload package with an accuracy of a few centimeters using differential global positioning system (GPS) signals. It developed an autonomous, multisensor, temporally aligned, radio-frequency communication and signal processing capability, and an array optimization algorithm, which was implemented on a digital signal processor (DSP). Additionally, the project converted the existing single-threaded, monolithic robotic vehicle control code into a multi-threaded, modular control architecture that enhances the reuse of control code in future projects.
Date: December 1, 2003
Creator: Holzrichter, Michael Warren; O'Rourke, William T.; Zenner, Jennifer & Maish, Alexander B.
Partner: UNT Libraries Government Documents Department

Global positioning system pseudolite-based relative navigation.

Description: Though the Global Positioning System has revolutionized navigation in the modern age, it is limited in its capability for some applications because an unobstructed line of sight to a minimum of four satellites is required. One way of augmenting the system in small areas is by employing pseudolites to broadcast additional signals that can be used to improve the user's position solution. At the Navigation Systems Testing Laboratory (NSTL) at NASA's Johnson Space Center in Houston, TX, research has been underway on the use of pseudolites to perform precision relative navigation. Based on the findings of previous research done at the NSTL, the method used to process the pseudolite measurements is an extended Kalman filter of the double differenced carrier phase measurements. By employing simulations of the system, as well as processing previously collected data in a real time manner, sub-meter tracking of a moving receiver with carrier phase measurements in the extended Kalman filter appears to be possible.
Date: March 2004
Creator: Monda, Eric W.
Partner: UNT Libraries Government Documents Department

Wheel rolling constraints and slip in mobile robots

Description: It is widely accepted that dead reckoning based on the rolling with no slip condition on wheels is not a reliable method to ascertain the position and orientation of a mobile robot for any reasonable distance. We establish that wheel slip is inevitable under the dynamic model of motion using classical results on the accessibility and controllability in nonlinear control theory and an analytical model of rolling of two linearly elastic bodies.
Date: March 1, 1997
Creator: Shekhar, S.
Partner: UNT Libraries Government Documents Department

Implementation of an acoustic emission proximity detector for use in generating glass optics

Description: We are using the approach acoustic emission (AE) signal during a grinding operation to detect the proximity of the grinding wheel relative to a brittle material workpiece and are using this detection as a feed- back control signal in our CNC. The repeatability of the AE signal during the wheel approach is the key that allows AE to be used as a proximity detector and is demonstrated at LLNL to be about mm. We noted significant changes of the AE signal as process parameters are modified, but conclude that with a quick CNC calibration routine and holding the parameters constant during a given operation, the AE system can be successfully used to sense pre- contact wheel- to- workpiece separation. Additionally, the AE sensing system allows real- time monitoring during grinding to provide in- process information. The first prototype of an AE system on a commercially available generator is currently be tested at the Center for Optics Manufacturing.
Date: November 11, 1996
Creator: Blaedel, K. L.; Piscotty, M. A. & Taylor, J. S.
Partner: UNT Libraries Government Documents Department

Motion control design of the SDSS 2.5 mts. telescope

Description: This paper describes the control system analysis and design for the three principal axes of the 2.5 mts SDSS Telescope. The telescope requirements are good tracking performance with errors lower than 165 arcsec rms in the speed range between 0 to 45 arcsec/sec for all the axes. The pointing error is about 2 arcsec rms per axis with a maximum absolute value of 5 arcsec. The telescope has the additional requirements of slewing, between tracking areas, with maximum speed of 3 degree/sec. The dynamical model of the telescope including the friction is analyzed and based on that, the design of a PID controller for each axis is presented. The specifications for pointing and tracking mode are achieved with this design in all the range of velocities and the performance in slew-mode is acceptable. Simulations and experimental results depict the behavior of the telescope in slewing, tracking and pointing.
Date: March 24, 2000
Creator: Rivetta, C.; Briegel, C. & Czarapata, P.
Partner: UNT Libraries Government Documents Department

Robot positioning based on point-to-point motion capability

Description: This paper presents an optimal search method for determining the base location of a robot manipulator so that the robot can have a designated point-to-point (PTP) motion capabilities. Based on the topological characterization of the manipulator workspace and the definitions of various p-connectivity, a computational method is developed for enumerating various PTP motion capabilities into quantitative cost functions. Then an unconstrained search by minimizing the cost function yields the task feasible location of the robot base. This methodology is useful for placement of mobile manipulators and robotic workcell layout design.
Date: March 20, 2000
Creator: Park, Y. S.; Cho, H. S. & Koh, K. C.
Partner: UNT Libraries Government Documents Department


Description: The mechanical design considerations are discussed with respect to the currently installed X-13 and future X-29 MGU. Comparisons to the previous 2 generations of variable small-gap undulator evolution in the NSLS X-ray ring are made and design improvements noted. The design requirements and mechanical difficulties for holding, positioning and driving the magnetic arrays are explored. Structural, thermal and electrical considerations which influenced the design are then analyzed. The mechanical performance of the MGU currently installed at X-13 is examined and future installations and enhancements are presented.
Date: September 5, 2002
Partner: UNT Libraries Government Documents Department

Fiber positioning and MRS response

Description: This paper provides experimental results on the dependence of the output signal from small-area silicon photodetectors, such as MRS (Metal-Resistive layer-Semiconductor) photodiodes, on the fiber alignment.
Date: May 18, 2004
Creator: al., Pavel Polozov et
Partner: UNT Libraries Government Documents Department