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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Analysis of forest disturbance using TM and AVHRR data

A methodology that will be used to determine the proportions of undisturbed, successional vegetation and recently disturbed land cover within coniferous forests using remotely sensed data from the advanced very high resolution radiometer (AVHRR) is presented. The method uses thematic mapper (TM) data to determine the proportions of the three stages of forest disturbance and regrowth for each AVHRR pixel in the sample areas, and is then applied to interpret all AVHRR imagery. Preliminary results indicate that there are predictable relationships between TM spectral response and the disturbance classes. Analysis of ellipse plots from a TM classification of the disturbed forested landscape indicates that the forest classes are separable in the red (0.63-0.69 micron) and near-infrared (0.76-0.90 micron) bands, providing evidence that the proportion of disturbance classes may be determined from AVHRR data.

Spanner, Michael A.↗
NASA NTRS1991

Wheat yield estimation at the farm level using TM Landsat and agrometeorological data

A model for estimating wheat yields on the farm level was developed, that integrates the Landsat TM data and agrometeorological information. Results obtained for a test site in southern Brasil for years of 1986 and 1987 show that the vegetation index derived from Landsat TM could account for the 60 to 40 percent wheat-yield variability observed between the two crop years. Compared to results using either the Landsat TM vegetation index or the agrometeorological data alone, the joint use of both types of data in a single model yielded a significant improvement.

Rudorff, B. F. T.↗
NASA NTRS1991

Detection of soil erosion within pinyon-juniper woodlands using Thematic Mapper (TM) satellite data

The sensitivity of Landsat TM data for detecting soil erosion within pinyon-juniper woodlands, and the potential of the spectral data for assigning the universal soil loss equation (USLE) crop managemnent (C) factor to varying cover types within the woodlands are assessed. Results show greatly accelerated rates of soil erosion on pinyon-juniper sites. Percent cover by pinyon-juniper, total soil-loss, and total nonliving ground cover accounted for nearly 70 percent of the variability in TM channels 2, 3, 4, and 5. TM spectral data were consistently better predictors of soil erosion than the biotic and abiotic field variables. Satellite data were more sensitive to vegetation variation than the USLE C factor, and USLE was found to be a poor predictor of soil loss on pinyon-juniper sites. A new string-to-ground soil erosion prediction technique is introduced.

Price, Kevin P.↗
NASA NTRS1992

Interpretation of SAR imagery of the Greenland ice sheet using coregistered TM imagery

Landsat TM images are coregistered with a Seasat SAR image of the margin of the Greenland ice sheet and used in the interpretation of features in the SAR data. A winter TM image is used to provide topographic information while a summer TM image provides information on the pattern of melt and the location of lakes. It is shown that: (1) the snow line is easily detectable in SAR imagery; (2) areas of higher radar backscatter in the bare-ice zone most often correspond to areas full of crevasses too small to resolve in the SAR images; (3) subsurface scattering causes significant blurring of features in SAR imagery; and (4) the band of surface lakes occurring above the snow line corresponds to at least a portion of the wet-snow zone.

Bindschadler, Robert↗
NASA NTRS1994

Modified LaRC(TM)-IA Polyimides

Modified versions of thermoplastic polyimide LaRC(TM)-IA incorporate various amounts of additional, rigid moieties into backbones of LaRC(TM)-IA molecules. Modified versions more resistant to solvents and exhibit higher glass-transition temperatures, yet retain melt-flow processability of unmodified LaRC(TM)-IA.

St. Clair, Terry L.↗
NASA NTRS1994

PalymSys (TM): An extended version of CLIPS for construction and reasoning using blackboards

This paper describes PalymSys(TM) -- an extended version of the CLIPS language that is designed to facilitate the implementation of blackboard systems. The paper first describes the general characteristics of blackboards and shows how a control blackboard architecture can be used by AI systems to examine their own behavior and adapt to real-time problem-solving situations by striking a balance between domain and control reasoning. The paper then describes the use of PalymSys in the development of a situation assessment subsystem for use aboard Army helicopters. This system performs real-time inferencing about the current battlefield situation using multiple domain blackboards as well as a control blackboard. A description of the control and domain blackboards and their implementation is presented. The paper also describes modifications made to the standard CLIPS 6.02 language in PalymSys(TM) 2.0. These include: (1) a dynamic Dempster-Shafer belief network whose structure is completely specifiable at run-time in the consequent of a PalymSys(TM) rule, (2) extension of the run command including a continuous run feature that enables the system to run even when the agenda is empty, and (3) a built-in communications link that uses shared memory to communicate with other independent processes.

Bryson, Travis↗
NASA NTRS1994

Effect Of Molecular Weight On Adhesive Properties Of The Phenylethynyl-Terminated Polyimide LARC(sup TM)-PETI-5

Future civilian aircraft will require the use of advanced adhesive systems with high temperature capabilities. One such material has been developed at the NASA Langley Research Center, a phenylethynyl-terminated polyimide given the designation LARC(sup TM)-PETI-5. Recent work has shown the advantages of similar phenylethynyl-terminated polyimides as films, moldings, adhesives, and composite matrix resins. Phenylethynyl-terminated oligomers provide greater processing windows than materials which incorporate simple ethynyl endcaps. Since these low molecular weight, low melt viscosity oligomers thermally cure without the evolution of volatile by-products, they provide an excellent means of producing polymers with high glass transition temperatures, excellent solvent resistance, and high mechanical properties. Three different versions of LARC(sup TM)-PETI-5 with theoretical number average molecular weights (M(sub n)s) of 250, 5000, and 10000 g/mol were synthesized in this work. Differential Scanning Calorimetry (DSC) measurements were performed on the dry powder form of these materials to establish cure conditions which result in high glass transition temperatures (T(sub g)s). Lap shear specimens were prepared from adhesive tape made from each material and with the thermal cure conditions determined from the DSC data. The tensile shear data established processing conditions which provided the best adhesive strengths. Further testing was performed to establish the properties of LARC(sup TM)-PETI-5 as an adhesive material and to determine its solvent resistance.

Cano, Roberto J.↗
NASA NTRS2000

LARC(tm) RP46 Polyimide Low Cost High Temperature Technology

The LARC(tm) RP46 polyimide was developed in 1991 at NASA Langley Research Center as an ultra-high-performance composite matrix resin for use in aircraft engine components, as well as a more environmentally friendly alternative to commercially available high temperature matrix resins. The LARC(tm) RP46 polyimide is prepared with non-toxic 3,4'-oxyldianiline(ODA). This chemistry has led to several improved performance characteristics over similar high temperature polyimides. These improvements include: (1) 700 F use temperature; (2) Significantly less moisture absorption; (3) Better chemical corrosion resistance; (4) Greater microcracking resistance; (5) Higher structural durability. The 700 F use temperature LARC(tm) RP46 is 150 F higher than that of commonly used PMR-type high temperature resins. In addition, it features significantly less moisture absorption and is therefore less susceptible to moisture induced damage. It also has better corrosion resistance to chemicals, greater microcracking resistance, and higher durability with regard to structural integrity.

Pater, Ruth H.↗
NASA NTRS2000

BOREAS RSS-15 SIR-C and Landsat TM Biomass and Landcover Maps of the NSA

As part of BOREAS, the RSS-15 team conducted an investigation using SIR-C, X-SAR, and Landsat TM data for estimating total above-ground dry biomass for the SSA and NSA modeling grids and component biomass for the SSA. Relationships of backscatter to total biomass and total biomass to foliage, branch, and bole biomass were used to estimate biomass density across the landscape. The procedure involved image classification with SAR and Landsat TM data and development of simple mapping techniques using combinations of SAR channels. For the SSA, the SIR-C data used were acquired on 06-Oct-1994, and the Landsat TM data used were acquired on 02-Sep-1995. The maps of the NSA were developed from SIR-C data acquired on 13-Apr-1994. The data files are available on a CD-ROM (see document number 20010000884), or from the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

Hall, Forrest G.↗
NASA NTRS2001

Automated Tow Placed LaRC(TM)-PETI-5 Composites

LaRC(TM)-PETI-5 is a PhenylEthynyl-Terminated Imide resin developed at NASA Langley Research Center (LaRC) during the 1990s. It offers a combination of attractive composite and adhesive properties. IM7/LaRC(TM)-PETI-5 composites exhibit thermal and thermo-oxidative stability typical of polyimides, superior chemical resistance and processability, excellent mechanical properties, toughness and damage tolerance. It was selected for study in the High Speed Research program aimed at developing technologies for a future supersonic aircraft, the High Speed Civil Transport, with a projected life span of 60 000 h at a cruise speed up to Mach 2.4. Robust autoclave processing cycles for LaRC(TM)-PETI-5 composites have been thoroughly designed and demonstrated, which involved hand lay-up of solvent-ladened 'wet' prepregs. However, this type of processing is not only costly but also environmentally unfriendly. Volatile management and shrinkage could become serious problems in the fabrication of large complex airframe structural subcomponents. Robotic tow placement technology utilizing 'dry' material forms represents a new fabrication process which overcomes these deficiencies. This work evaluates and compares mechanical properties of composites fabricated by heated head automated tow placement (dry process) with those obtained by hand lay-up/autoclave fabrication (wet process). Thermal and rheological properties of the robotically as-placed uncured composites were measured. A post-cure cycle was designed due to the requirement of the PETI-5 resin for a 370 C/1 h hold to reach full cure, conditions which cannot be duplicated during heated head robotic placement. Mechanical properties such as 0 degree flexural strength and modulus, open hole tensile and compressive strength and moduli, reduced section compression dogbone compressive strength, and modified zippora-medium small (MZ-MS) tensile and compressive properties were obtained on the post-cured panels. These properties compared favourably with those obtained from the wet process.

Hou, T. H.↗
NASA NTRS2003

Helium Cryo Testing of a SLMS(TM) (Silicon Lightweight Mirrors) Athermal Optical Assembly

SLMS (TM) a thermal technology has been demonstrated in the small 4-foot helium cryogenic test chamber located at the NASA/MSFC X-Ray Calibration Facility (XRCF). A SLMS (TM) Ultraviolet Demonstrator Mirror (UVDM) produced by Schafer under a NASA/MSFC Phase I SBIR was helium cryo tested both free standing and bonded to a Schafer designed prototype carbon fiber reinforced silicon carbide (Cesic) mount. Surface figure data was obtained with a test measurement system that featured an Instantaneous Phase Interferometer (IPI) by ADE Phase Shift. The test measurement system s minimum resolvable differential figure deformation and possible contributions from test chamber ambient to cryo window deformation are under investigation. The free standing results showed differential figure deformation of 10.4 nm rms from 295K to 27K and 3.9 nm rms after one cryo cycle. The surface figure of the UVDM degraded by lambda/70 rms HeNe once it was bonded to the prototype Cesic mount. The change was due to a small astigmatic aberration in the rototype Cesic mount due to lack of finish machining and not the bonding technique. This effect was seen in SLMST (TM) optical assembly results, which showed differential figure deformation of 46.5 nm rms from 294K to 27K, 42.9 nm rms from 294K to 77K, 28.0 nm rms from 294K to 193K and 6.2 nm rms after one cryo cycle.

Jacoby, Marc T.↗
NASA NTRS2005

Actively Cooled SLMS(TM) Technology for HEL Applications

Mr. Jacoby is the Chief Scientist for Schafer's Lightweight Optical Systems business area with twenty four years experience in laser and optical systems for space and military applications. He and colleague Dr. Goodman conceived and developed Silicon Lightweight Mirrors (SLMS(TM)) technologies for space applications from the extreme UV to FAR IR wavelengths. Schafer has demonstrated two different methods for actively cooling our Silicon Lightweight Mirrors (SLMS(TM)) technology. Direct internal cooling was accomplished by flowing liquid nitrogen through the continuous open cell core of the SLMS(TM) mirror. Indirect external cooling was accomplished by flowing liquid nitrogen through a CTE matched Cesic square-tube manifold that was bonded to the back of the mirror in the center. Testing was done in the small 4-foot thermal/vacuum chamber located at the NASA/MSFC X-Ray Calibration Facility. Seven thermal diodes were located over the front side of the 5 inch diameter mirror and one was placed on the outlet side of the Cesic manifold. Results indicate that the mirror reaches steady state at 82K in less than four minutes for both cooling methods. The maximum temperature difference of the eight diodes was less than 200 mK when the mirror was internally cooled and covered with MLI to insulate it from the large 300 K aluminum plate that was used to mount it.

Jacoby, Marc T.↗
NASA NTRS1997

Quasi four-level Tm:LuAG laser

A quasi four-level solid-state laser is provided. A laser crystal is disposed in a laser cavity. The laser crystal has a LuAG-based host material doped to a final concentration between about 2% and about 7% thulium (Tm) ions. For the more heavily doped final concentrations, the LuAG-based host material is a LuAG seed crystal doped with a small concentration of Tm ions. Laser diode arrays are disposed transversely to the laser crystal for energizing the Tm ions.

Jani, Mahendra G.↗
NASA NTRS2007

Tm:germanate Fiber Laser: Tuning And Q-switching

A Tm:germanate fiber laser produced >0.25 mJ/pulse in a 45 ns pulse. It is capable of producing multiple Q-switched pulses from a single p ump pulse. With the addition of a diffraction grating, Tm:germanate f iber lasers produced a wide, but length dependent, tuning range. By s electing the fiber length, the tuning range extends from 1.88 to 2.04 ?m. These traits make Tm:germanate lasers suitable for remote sensin g of water vapor.

Barnes, Norman P.↗
NASA NTRS2006

Optical Properties of Tm(3+) Ions in Alkali Germanate Glass

Tm-doped alkali germanate glass is investigated for use as a laser material. Spectroscopic investigations of bulk Tm-doped germanate glass are reported for the absorption, emission and luminescence decay. Tm:germanate shows promise as a fiber laser when pumped with 0.792 m diodes because of low phonon energies. Spectroscopic analysis indicates low nonradiative quenching and pulsed laser performance studies confirm this prediction by showing a quantum efficiency of 1.69.

Walsh, Brian M.↗
NASA NTRS2008

Review of Tm and Ho Materials; Spectroscopy and Lasers

A review of Tm and Ho materials is presented, covering some fundamental aspects on the spectroscopy and laser dynamics in both single and co-doped systems. Following an introduction to 2- m lasers, applications and historical development, the physics of quasi-four level lasers, energy transfer and modeling are discussed in some detail. Recent developments in using Tm lasers to pump Ho lasers are discussed, and seen to offer some advantages over conventional Tm:Ho lasers. This article is not intended as a complete review, but as a primer for introducing concepts and a resource for further study.

Walsh, Brian M.↗
NASA NTRS2015

Surface Temperature Measurements from a Stator Vane Doublet in a Turbine Engine Afterburner Flame Using a YAG:Tm Thermographic Phosphor

Luminescence-based surface temperature measurements were obtained from a YAG:Tm-coated stator vane doublet exposed to the afterburner flame of a J85 test engine at University of Tennessee Space Institute (UTSI). The objective of the testing was to demonstrate that reliable surface temperatures based on luminescence decay of a thermographic phosphor producing short-wavelength emission could be obtained from the surface of an actual engine component in a high gas velocity, highly radiative afterburner flame environment. YAG:Tm was selected as the thermographic phosphor for its blue emission at 456 nm (1D23F4 transition) and UV emission at 365 nm (1D23H6 transition) because background thermal radiation is lower at these wavelengths, which are shorter than those of many previously used thermographic phosphors. Luminescence decay measurements were acquired using a probe designed to operate in the afterburner flame environment. The probe was mounted on the sidewall of a high-pressure turbine vane doublet from a Honeywell TECH7000 turbine engine coated with a standard electron-beam physical vapor deposited (EB-PVD) 200-m-thick TBC composed of yttria-stabilized zirconia (YSZ) onto which a 25-m-thick YAG:Tm thermographic phosphor layer was deposited by solution precursor plasma spray (SPPS). Spot temperature measurements were obtained by measuring luminescence decay times at different afterburner power settings and then converting decay time to temperature via calibration curves. Temperature measurements using the decays of the 456 and 365 nm emissions are compared. While successful afterburner environment measurements were obtained to about 1300C with the 456 nm emission, successful temperature measurements using the 365 nm emission were limited to about 1100C due to interference by autofluorescence of probe optics at short decay times.

thermographic phosphor↗
DOE OSTI2020

Electrolytically Assisted Surface Decontamination (EASD{sup TM}) for POCO Operations - 20282

NNL in collaboration with C-Tech Innovation Ltd and Sellafield Ltd has been exploring innovative technologies to enable a significant reduction of radiological hazards within facilities during the Post Operational Clean Out (POCO) phase of a nuclear plant's life cycle. Reducing the hazard by effectively decontaminating plants in-situ during POCO delivers huge cost reductions for future decommissioning operations. These cost reduction benefits are realized by reducing the number and complexity of remote operations as well as lowering the long-term waste disposal costs. Whilst chemical decontamination can achieve the desired level of decontamination, applying aggressive chemical reagents is hazardous, potentially difficult to control and requires there to be complimentary effluent treatment and waste routes. This work has aimed to develop flexible and controllable decontamination processes which could be operated without the additional complexity and issues associated with chemical decontamination. The processes needed to be relatively fast and effective to minimize the time operators would spend in an active area. In addition, there was a driver to produce decontamination methodologies which generated a secondary waste compatible with current routes and which takes advantage of current waste capacity. The strategy therefore was to come up with a solution that works with, rather than against, the science and engineering behind process plants at Sellafield. Electrolytically Assisted Surface Decontamination (EASD{sup TM}) is an innovative electrochemical decontamination process (developed by NNL and C-Tech Innovation Ltd) that can remove activity from contaminated metal in very short time periods. Application of the patented electric waveform to the surface when treating contaminated metal with nitric acid has been shown to significantly enhance the decontamination performance. When compared to proposed baseline washout procedures at Sellafield, the only change to the process is the applied electrical waveform which is temporary and controllable. The current causes dissolution of the metal surface being decontaminated which leads to activity transferring from the plant item into the nitric acid effluent stream. This innovation has the potential to transform the POCO process and allow a nitric acid based washout approach to deliver POCO quickly and cost effectively within the existing infrastructure. Several devices have now been designed that incorporate this EASD{sup TM} technology and enable the decontamination process to be applied to a range items commonly identified as being contaminated during nuclear decommissioning programmes such as pipework, tanks and hotspots of walls/floors. Inactive and active laboratory-scale testing has been completed using both simulated and 'real-life' contaminated (low level waste) metallic items retrieved from different nuclear sites. Active trials demonstrated that contaminated items could be treated to free release levels within minutes. Engineering scale tests are currently being performed, with guidance from Sellafield's system engineers and plant managers, to provide the necessary re-assurance the designed devices could be successfully deployed in an on-plant scenario. The final stage of this development work is to carry out an active demonstration of the decontamination technology on Thorp at Sellafield. This paper aims to highlight progress made to date with the EASD{sup TM} technology and, more specifically, the development of an in-situ decontamination device for deployment within radioactive pipework. (authors)

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE W↗