1,112 Matching Results

Search Results

Advanced search parameters have been applied.

C-Band Scanning ARM Precipitation Radar (C-SAPR) Handbook

Description: The C-band scanning ARM precipitation radar (C-SAPR) is a scanning polarimetric Doppler radar transmitting simultaneously in both H and V polarizations. With a 350-kW magnetron transmitter, this puts 125 kW of transmitted power for each polarization. The receiver for the C-SAPR is a National Center for Atmospheric Research (NCAR) -developed Hi-Q system operating in a coherent-on-receive mode. The ARM Climate Research Facility operates two C-SAPRs; one of them is deployed near the Southern Great Plains (SGP) Central Facility near the triangular array of X-SAPRs, and the second C-SAPR is deployed at ARM’s Tropical Western Pacific (TWP) site on Manus Island in Papua New Guinea.
Date: November 13, 2012
Creator: Widener, K & Bharadwaj, N
Partner: UNT Libraries Government Documents Department

Miniaturized Multi-Band Antenna Design via Element Collocation and Inductive Feed Loading

Description: In a FY09 SDRD project, four separate antennas were designed to receive signals of interest covering a broad range of frequencies. While the elements exceeded specifications, the array footprint is substantial. Research performed by the CU Microwave Active Antenna Group in collaboration with RSL, showed promise in realizing a reduced structure. This work will expand upon this previous research. This project will result in a prototype quad-band antenna.
Date: September 12, 2012
Creator: Martin, R. P.
Partner: UNT Libraries Government Documents Department

Discrete Packet Analysis for Improved Atmospheric Rejection on Modulated Laser Signals

Description: This slide-show discusses how the method of discrete packet analysis improves atmospheric compensation for quasi-CW fluorescence detection methods. This is key to improving remote sensing capabilities.
Date: July 19, 2012
Creator: O'Neill, M., McKenna, I., DiBenedetto, J., Capelle, G., Trainham, R.
Partner: UNT Libraries Government Documents Department

Precision DC Voltage Reference - Metrology Laboratory Report

Description: A precision dc voltage reference has been constructed to serve as a driver for a regulated direct current source used in the callbration of ammeters, resistors, and shunts. Variable output voltages are generated by dividing the output of a 10-V supply (CODI Semiconductor Inc. Model PVS10CA) to a nominal 0.16 and 1.6 V, selected by range switching. These voltages are applied to the input of a 320-k{Ohm}, six-decade, Kelvin-Varley divider, the output of which is used to drive the regulated direct current source. Provision has been made for precision adjustment of the input voltages to the Kelvin-Varley divider. The resolution of the output voltage is 0.625 ppm of full scale, with an estimated uncertainty of {+-}50 ppm of the setting or {+-}10 {micro}V, whichever is greater. The voltage reference is easy to use, and it has improved measurement accuracy.
Date: February 1, 1978
Creator: Kater, G.E.
Partner: UNT Libraries Government Documents Department


Description: The sonic anemometer is based on the transmission of acoustical waves traveling in opposite direction over a welldefined path, and the determination of the resulting phase between the two waves caused by the wind velocity parallel to the path. The instrument was developed for the purpose of obtainIng very low wind velocities (in the order of 1 em/sec) in an environment of extreme temperature, moisture, and pressure (120°C, saturated steam, and 70 psi). The anemometer has excellent sensitivity and performance over the desired velocity range under normal atmospheric conditions. The instrument, after calibration in the wind tunnel, was subjected to high temperatures, pressures, and steam. The results of the pressure chamber tests on the array indicate that degradation of the received amplitude signal occurs progressively with the increase in temperature, pressure, and moisture. The de resistances across the terminals of the transducers decreased considerably, and indicate that insulation is still a major problem. The effects of temperature on the array show that it is responsible for part of the signal attenuation. The results of these tests indicate the anemometer with the same transducers is capable, under atmospheric conditions, of operating to approximately 100°C. In the pressure chamber and steam environment with the present transducers, the anemometer is capable of operating to approximately 70°C. More comprehensive environmental tests will have to be performed to evaluate the factors contributing to the degradation of the signal amplitudes of the transducers. Insulation breakdown seems to be the major problem, and if this can be solved, the anemometer should be capable of operation in the extreme environment.
Date: January 1, 1968
Creator: Collins,, H. D.
Partner: UNT Libraries Government Documents Department


Description: A back-projection of filtered projection (BKFIL) reconstruction algorithm is presented that is applicable to single-photon emission computed tomography (ECT) in the presence of a constant attenuating medium such as the brain. The filters used in transmission computed tomography (TCT) - comprised of a ramp multiplied by window functions - are modified so that the single-photon ECT filter is a function of the constant attenuation coefficient. The filters give good reconstruction results with sufficient angular and lateral sampling. With continuous samples the BKFIL algorithm has a point spread function that is the Hankel transform of the window function. The resolution and s tistical properties of the filters are demonstrated by various simulations. Statistical formulas for the reconstructed image show that the square of the percent-root-mean square uncertainty (%RMS) of the reconstruction is inversely proportional to the total measured counts. The results indicate that constant attenuation can be compensated for in single-photon ECT by using an attenuation-dependent filter that reconstructs the transverse section reliably. Computer time requirements are two times that of conventional TCT or positron ECT and there is no increase in memory requirements.
Date: June 1, 1980
Creator: Gullberg, Grant T. & Budinger, Thomas F.
Partner: UNT Libraries Government Documents Department


Description: The objective of this work is to capture the potential of real-time monitoring and overcome the challenges of harsh industrial environments, Los Gatos Research (LGR) is fabricating, deploying, and commercializing advanced laser-based gas sensors for process control monitoring in industrial furnaces (e.g. electric arc furnaces). These sensors can achieve improvements in process control, leading to enhanced productivity, improved product quality, and reduced energy consumption and emissions. The first sensor will utilize both mid-infrared and near-infrared lasers to make rapid in-situ measurements of industrial gases and associated temperatures in the furnace off-gas. The second sensor will make extractive measurements of process gases. During the course of this DOE project, Los Gatos Research (LGR) fabricated, tested, and deployed both in-situ tunable diode laser absorption spectrometry (TDLAS) analyzers and extractive Off-Axis Integrated Cavity Output Spectroscopy (Off-Axis ICOS) analyzers.
Date: September 30, 2013
Creator: Gupta, Manish & Baer, Douglas
Partner: UNT Libraries Government Documents Department

Combinatorial Development of Water Splitting Catalysts Based on the Oxygen Evolving Complex of Photosystem II

Description: The use of methods to create large arrays of potential catalysts for the reaction H2O ½ O2 + 2H+ on the anode of an electrolysis system were investigated. This reaction is half of the overall reaction involved in the splitting of water into hydrogen and oxygen gas. This method consisted of starting with an array of electrodes and developing patterned electrochemical approaches for creating a different, defined peptide at each position in the array. Methods were also developed for measuring the rate of reaction at each point in the array. In this way, the goal was to create and then tests many thousands of possible catalysts simultaneously. This type of approach should lead to an ability to optimize catalytic activity systematically, by iteratively designing and testing new libraries of catalysts. Optimization is important to decrease energy losses (over-potentials) associated with the water splitting reaction and thus for the generation of hydrogen. Most of the efforts in this grant period were focused on developing the chemistry and analytical methods required to create pattern peptide formation either using a photolithography approach or an electrochemical approach for dictating the positions of peptide bond formation. This involved testing a large number of different reactions and conditions. We have been able to find conditions that have allowed us to pattern peptide bond formation on both glass slides using photolithographic methods and on electrode arrays made by the company Combimatrix. Part of this effort involved generating novel approaches for performing mass spectroscopy directly from the patterned arrays. We have also been able to demonstrate the ability to measure current at each electrode due to electrolysis of water. This was performed with customized instrumentation created in collaboration with Combimatrix. In addition, several different molecular designs for peptides that bound metals (primarily Mn) were developed and synthesized ...
Date: March 31, 2010
Creator: Woodbury, Neal
Partner: UNT Libraries Government Documents Department

High-resolution, high-transmission soft x-ray spectrometer for the study of biological samples

Description: We present a variable line-space grating spectrometer for soft x-rays that covers the photon energy range between 130 and 650 eV. The optical design is based on the Hettrick-Underwood principle and tailored to synchrotron-based studies of radiation-sensitive biological samples. The spectrometer is able to record the entire spectral range in one shot, i.e., without any mechanical motion, at a resolving power of 1200 or better. Despite its slitless design, such a resolving power can be achieved for a source spot as large as 30x3000 mu m2, which is important for keeping beam damage effects in radiation-sensitive samples low. The high spectrometer efficiency allows recording of comprehensive two-dimensional resonant inelastic soft x-ray scattering (RIXS) maps with good statistics within several minutes. This is exemplarily demonstrated for a RIXS map of highly oriented pyrolytic graphite, which was taken within 10 min.
Date: March 9, 2009
Creator: Fuchs, Oliver; Weinhardt, L.; Blum, M.; Weigand, M.; Umbach, E.; Bar, M. et al.
Partner: UNT Libraries Government Documents Department

Raman Lidar Profiles–Temperature (RLPROFTEMP) Value-Added Product

Description: The purpose of this document is to describe the Raman Lidar Profiles–Temperature (RLPROFTEMP) value-added product (VAP) and the procedures used to derive atmospheric temperature profiles from the raw RL measurements. Sections 2 and 4 describe the input and output variables, respectively. Section 3 discusses the theory behind the measurement and the details of the algorithm, including calibration and overlap correction.
Date: October 31, 2012
Creator: Newsom, RK; Sivaraman, C & McFarlane, SA
Partner: UNT Libraries Government Documents Department

Aircraft Integration and Flight Testing of 4STAR

Description: Under funding from the U.S. Dept. of Energy, in conjunction with a funded NASA 2008 ROSES proposal, with internal support from Battelle Pacific Northwest Division (PNWD), and in collaboration with NASA Ames Research Center, we successfully integrated the Spectrometer for Sky-Scanning, Sun-Tracking Atmospheric Research (4STAR-Air) instrument for flight operation aboard Battelle’s G-1 aircraft and conducted a series of airborne and ground-based intensive measurement campaigns (hereafter referred to as “intensives”) for the purpose of maturing the initial 4STAR-Ground prototype to a flight-ready science-ready configuration.
Date: October 12, 2012
Creator: Flynn, CJ; Kassianov, E; Russell, P; Redemann, J; Dunagan, S & Holben, B
Partner: UNT Libraries Government Documents Department


Description: This paper discusses instrumentation and computer based data acquisition for in-situ rock property measurements as applied to an experiment conducted at Stripa, Sweden in cooperation with the U. S. Department of Energy and the Swedish government. Electrical heaters were installed in an underground granite mass to simulate thermal loading by canisters of high-level nuclear waste. Extensometers, borehole deformation gages, vibrating wire stress meters, and thermocouples were used to monitor the thermomechanical response of the granite. A computer based data acquisition system recorded data, performed on-line computations and provided graphic output. A summary description is given of the experiment areas, heater systems, data acquisition hardware, and four types of instruments used for the in-situ rock property measurements.
Date: February 1, 1980
Creator: Binnall, Eugene P.
Partner: UNT Libraries Government Documents Department

Combinatorial Screening of Advanced Scintillators for High Resolution X-ray Detectors

Description: The lack of efficient scintillators is a major problem for developing powerful x-ray detectors that are widely used in homeland security, industrial and scientific research. Intematix has developed and applied a high throughput screening process and corresponding crystal growth technology to significantly speed up the discovery process for new efficient scintillators. As a result, Intematix has invented and fabricated three new scintillators both in powder and bulk forms, which possess promising properties such as better radiation hardness and better matching for silicon diode.
Date: May 12, 2008
Creator: Cheng, Shifan; Tao, Dejie; Lynch, Michael; Yuan, Xianglong & Li, Yiqun
Partner: UNT Libraries Government Documents Department

Condition Based Monitoring of Gas Turbine Combustion Components

Description: The objective of this program is to develop sensors that allow condition based monitoring of critical combustion parts of gas turbines. Siemens teamed with innovative, small companies that were developing sensor concepts that could monitor wearing and cracking of hot turbine parts. A magnetic crack monitoring sensor concept developed by JENTEK Sensors, Inc. was evaluated in laboratory tests. Designs for engine application were evaluated. The inability to develop a robust lead wire to transmit the signal long distances resulted in a discontinuation of this concept. An optical wear sensor concept proposed by K Sciences GP, LLC was tested in proof-of concept testing. The sensor concept depended, however, on optical fiber tips wearing with the loaded part. The fiber tip wear resulted in too much optical input variability; the sensor could not provide adequate stability for measurement. Siemens developed an alternative optical wear sensor approach that used a commercial PHILTEC, Inc. optical gap sensor with an optical spacer to remove fibers from the wearing surface. The gap sensor measured the length of the wearing spacer to follow loaded part wear. This optical wear sensor was developed to a Technology Readiness Level (TRL) of 5. It was validated in lab tests and installed on a floating transition seal in an F-Class gas turbine. Laboratory tests indicate that the concept can measure wear on loaded parts at temperatures up to 800{degrees}C with uncertainty of < 0.3 mm. Testing in an F-Class engine installation showed that the optical spacer wore with the wearing part. The electro-optics box located outside the engine enclosure survived the engine enclosure environment. The fiber optic cable and the optical spacer, however, both degraded after about 100 operating hours, impacting the signal analysis.
Date: September 30, 2012
Creator: Ulerich, Nancy; Kidane, Getnet; Spiegelberg, Christine & Tevs, Nikolai
Partner: UNT Libraries Government Documents Department

Critical Infrastructure for Ocean Research and Societal Needs in 2030

Description: The United States has jurisdiction over 3.4 million square miles of ocean—an expanse greater than the land area of all fifty states combined. This vast marine area offers researchers opportunities to investigate the ocean’s role in an integrated Earth system, but also presents challenges to society, including damaging tsunamis and hurricanes, industrial accidents, and outbreaks of waterborne diseases. The 2010 Gulf of Mexico Deepwater Horizon oil spill and 2011 Japanese earthquake and tsunami are vivid reminders that a broad range of infrastructure is needed to advance our still-incomplete understanding of the ocean. The National Research Council (NRC)’s Ocean Studies Board was asked by the National Science and Technology Council’s Subcommittee on Ocean Science and Technology, comprised of 25 U.S. government agencies, to examine infrastructure needs for ocean research in the year 2030. This request reflects concern, among a myriad of marine issues, over the present state of aging and obsolete infrastructure, insufficient capacity, growing technological gaps, and declining national leadership in marine technological development; issues brought to the nation’s attention in 2004 by the U.S. Commission on Ocean Policy. A 15-member committee of experts identified four themes that encompass 32 future ocean research questions–enabling stewardship of the environment, protecting life and property, promoting economic vitality, and increasing fundamental scientific understanding. Many of the questions in the report (e.g., sea level rise, sustainable fisheries, the global water cycle) reflect challenging, multidisciplinary science questions that are clearly relevant today, and are likely to take decades of effort to solve. As such, U.S. ocean research will require a growing suite of ocean infrastructure for a range of activities, such as high quality, sustained time series observations or autonomous monitoring at a broad range of spatial and temporal scales. Consequently, a coordinated national plan for making future strategic investments becomes an imperative to address ...
Date: April 22, 2011
Creator: National Research Council
Partner: UNT Libraries Government Documents Department

ARM Lead Mentor Selection Process

Description: The ARM Climate Research Facility currently operates more than 300 instrument systems that provide ground-based observations of the atmospheric column. To keep ARM at the forefront of climate observations, the ARM infrastructure depends heavily on instrument scientists and engineers, also known as Instrument Mentors. Instrument Mentors must have an excellent understanding of in situ and remote-sensing instrumentation theory and operation and have comprehensive knowledge of critical scale-dependent atmospheric processes. They also possess the technical and analytical skills to develop new data retrievals that provide innovative approaches for creating research-quality data sets.
Date: March 13, 2013
Creator: Sisterson, DL
Partner: UNT Libraries Government Documents Department

Ultra-high efficiency multilayer blazed gratings through deposition kinetic control

Description: Diffraction efficiency of multilayer coated blazed gratings (MBG) strongly depends on the perfection of the saw-toothshaped layers in the overall composite structure. Growth of multilayers on saw-tooth substrates should be carefully optimized in order to reduce groove profile distortion and at the same time to avoid significant roughening of multilayer interfaces. In this work we report on a new way to optimize growth of sputter-deposited Mo/Si multilayers on saw-tooth substrates through variation of the sputtering gas pressure. A new record for diffraction efficiency of 44% was achieved for a optimized MBG with groove density of 5250 lines/mm at the wavelength of 13.1 nm.
Date: January 23, 2012
Creator: Anderson, Erik; Gullikson, Eric; Salmassi, Farhad; Warwick, Tony; Yashchuk, Valeriy & Padmore, Howard
Partner: UNT Libraries Government Documents Department

Conformal growth of Mo/Si multilayers on grating substrates using collimated ion beam sputtering

Description: Deposition of multilayers on saw-tooth substrates is a key step in the fabrication of multilayer blazed gratings (MBG) for extreme ultraviolet and soft x-rays. Growth of the multilayers can be perturbed by shadowing effects caused by the highly corrugated surface of the substrates, which results in distortion of the multilayer stack structure and degradation of performance of MBGs. To minimize the shadowing effects we used an ionbeam sputtering machine with a highly collimated atomic flux to deposit Mo/Si multilayers on saw-tooth substrates. The sputtering conditions were optimized by finding a balance between smoothening and roughening processes in order to minimize degradation of the groove profile in the course of deposition and at the same time to keep the interfaces of a multilayer stack smooth enough for high efficiency. An optimal value of energy of 200 eV for sputtering Kr{sup +} ions was found by deposition of test multilayers on flat substrates at a range of ion energies. Two saw-tooth substrates were deposited at energies of 200 eV and 700 eV for the sputtering ions. It was found that reduction of the ion energy improved the blazing performance of the MBG and resulted in a 40% gain in the diffraction efficiency due to better replication of the groove profile by the multilayer. As a result of the optimization performed, an absolute diffraction efficiency of 28.8% was achieved for the 2nd blaze order of the MBG with a groove density of 7350 lines/mm at a wavelength of 13.5 nm. Details of the growth behavior of the multilayers on flat and saw-tooth substrates are discussed in terms of the Linear Continuous Model of film growth.
Date: January 23, 2012
Creator: Gawlitza, Peter; Cambie, Rossana; Dhuey, Scott; Gullikson, Eric; Warwick, Tony; Braun, Stefan et al.
Partner: UNT Libraries Government Documents Department

Sensor Development for the Large Synoptic Survey Telescope.

Description: The Large Synoptic Survey project proposes to build an 8m-class ground-based telescope with a dedicated wide field camera. The camera consists of a large focal plane mosaic composed of multi-output CCDs with extended red response. Design considerations and preliminary characterization results for the sensors are presented in this contribution to the Workshop.
Date: June 7, 2007
Creator: O'Connor,P.; Radeka, V. & Takacs, P.
Partner: UNT Libraries Government Documents Department