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At least 397 records · Page 22
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

SAGA: A project to automate the management of software production systems

The current work in progress for the SAGA project are described. The highlights of this research are: a parser independent SAGA editor, design for the screen editing facilities of the editor, delivery to NASA of release 1 of Olorin, the SAGA parser generator, personal workstation environment research, release 1 of the SAGA symbol table manager, delta generation in SAGA, requirements for a proof management system, documentation for and testing of the cyber pascal make prototype, a prototype cyber-based slicing facility, a June 1984 demonstration plan, SAGA utility programs, summary of UNIX software engineering support, and theorem prover review.

Campbell, R. H.↗
NASA NTRS1984

Mesoscale analysis of VAS 6.7 micron image data for several case studies

Several case studies are examined in an attempt to relate Visible infrared spin scan radiometers Atmospheric Sounder (VAS) water vapor channel radiance data to atmospheric moisture. Since the 6.7 micrometer channel detects radiation emitted by atmospheric water vapor from a rather thick layer, a scheme is developed which weighted rawinsonde observations of relative humidity in a similar manner. A comparison of the two fields (weighted relative humidity values from gridded rawinsonde observations and the VAS water vapor image) indicates that even when mesoscale data are used, the technique only presented a smooth representation of the radiance field. This weighting function is dependent on both the temperature and moisture distribution of the atmosphere. Cross sections of relative humidity from the mesoscale rawinsondes are produced which sliced the water vapor imagery in particularly interesting regions (areas of high and low blackbody temperatures). Comparisons are then made between the cross sections and the variations in the VAS radiance data along the cross section line. Bright regions in the water vapor imagery (cold blackbody temperatures) are often associated with thin layers of high relative humidity or thick layers of only moderately moist air. The reverse also applies, i.e., dark regions (warm blackbody temperatures) in the imagery corresponded well with very dry regions in the cross sections.

Jedlovec, G. J.↗
NASA NTRS1983

Neutron-transmutation-doped germanium bolometers

Six slices of ultra-pure germanium were irradiated with thermal neutron fluences between 7.5 x 10 to the 16th and 1.88 x 10 to the 18th per sq cm. After thermal annealing the resistivity was measured down to low temperatures (less than 4.2 K) and found to follow the relationship rho = rho sub 0 exp(Delta/T) in the hopping conduction regime. Also, several junction FETs were tested for noise performance at room temperature and in an insulating housing in a 4.2 K cryostat. These FETs will be used as first stage amplifiers for neutron-transmutation-doped germanium bolometers.

Palaio, N. P.↗
NASA NTRS1984

Minimum wafer thickness by rotated ingot ID wafering

The efficient utilization of materials is critical to certain device applications such as silicon for photovoltaics or diodes and gallium-gadolinium-garnet for memories. A variety of slicing techniques has been investigated to minimize wafer thickness and wafer kerf. This paper presents the results of analyses of ID wafering of rotated ingots based on predicted fracture behavior of the wafer as a result of forces during wafering and the properties of the device material. The analytical model indicated that the minimum wafer thickness is controlled by the depth of surface damage and the applied cantilever force. Both of these factors should be minimized. For silicon, a minimum thickness was found to be approximately 200 x 10 - 6th m for conventional sizes of rotated ingot wafering. Fractures through the thickness of the wafer rather than through the center supporting column were found to limit the minimum wafer thickness. The model suggested that the use of a vacuum chuck on the wafer surface to enhance cleavage fracture of the center supporting core and, with silicon, by using 111-line-type ingots could have potential for reducing minimum wafer thickness.

Chen, C. P.↗
NASA NTRS1984

Prospects for three-dimensional projective and tomographic imaging radar networks

Results of a study demonstrating the feasibility of broadband and speckle-free projective imaging of a complex shaped scattering object in the 6-17 GHz range with centimeter resolution are presented. It is shown how angular, spectral, and polarization diversities can be combined in the data acquisition process with a unique target-derived reference technique to access the three-dimensional Fourier space of the scatterer cost-effectively. Imagea retrieval algorithms, based on the projection slice theorem and knowledge of object symmetry, are utilized in obtaining images of a model aircraft with near optical resolution. The implications for high-resolution three-dimensional tomographic imaging radar networks are discussed.

Farhat, N. H.↗
NASA NTRS1984

Chip level modeling of LSI devices

The advent of Very Large Scale Integration (VLSI) technology has rendered the gate level model impractical for many simulation activities critical to the design automation process. As an alternative, an approach to the modeling of VLSI devices at the chip level is described, including the specification of modeling language constructs important to the modeling process. A model structure is presented in which models of the LSI devices are constructed as single entities. The modeling structure is two layered. The functional layer in this structure is used to model the input/output response of the LSI chip. A second layer, the fault mapping layer, is added, if fault simulations are required, in order to map the effects of hardware faults onto the functional layer. Modeling examples for each layer are presented. Fault modeling at the chip level is described. Approaches to realistic functional fault selection and defining fault coverage for functional faults are given. Application of the modeling techniques to single chip and bit slice microprocessors is discussed.

Armstrong, J. R.↗
NASA NTRS1986

Constant-Pressure Sawing

Attachment for reciprocating power-saw maintains nearly constant cutting pressure even though kerf length varies. Attachment developed for wire saws used to slice cylindrical silicon ingots into wafers for semiconductor devices. By maintaining constant pressure, attachment helps to ensure smooth, flat, uniform wafers. Principle adaptable to straight, toothed saws as well as to wire saws.

Orris, G. M.↗
NASA NTRS1984

Do the Arching HI Filaments Show in Local Reddening Data?

Probable dust counterparts of arching structures are investigated in two cases: (1) the Eridanus expanding shell; and (2) the extended Sco-Cen feature. Color excess data may be used to derive distance and dimension estimates of these structures. Color excesses from two areas SA 121 and SA 144 situated on the position of the 3.2 to 6.3 km/s velocity-slice are applied. Some stratification of the color excesses is noticed for both areas but extreme patchiness typifies particularly the dust in the SA 144 region.

Knude, J.↗
NASA NTRS1985

Texture etching of (100) silicon for solar cells

A chemical means of creating the proper kind of light collection texture on (100) silicon slices is discussed. Texturing of (100) silicon surfaces in sodium or potassium hydroxides occurs by the growth of a reaction product in a random array of surface sites, which leads to pyramids remaining at the sites after other parts of the surface dissolve away. A new texture-promoting influence, a proximity effect, was discovered in this work. An attempt was made to quantify the various promotional effects. The purpose of the present paper is to: (1) explain in detail the attempt at understanding and quantifying texturing; (2) give an experimental description with observations on the proximity effect and the effect of additions of water glass that were discovered during this work; and (3) show that the precipitate or growth models account for almost all of the known promotional effects.

Dyer, L. D.↗
NASA NTRS1985

Remarks on preparation of indandione detection reagents

A modified Claisen condensation with sliced sodium at a higher temperature was recommended for the production of ungranulated charcoal. A new ninhydrin production method by oxidation of benzaldiketohydrinden using available reagents was tried and was unsuccessful. Triketohydrinden was obtained by boiling ninhydrin in acetic acid anhydrides.

Stepan, J.↗
NASA NTRS1984

A summary of JPL single event upset test data from May 1982, through January 1984

A summary of single event upset data for 42 device types (including RAMs, 4-bit slices, microprocessors, 4-bit counters, and flip-flops) studied at 11 different accelerator tests (performed chiefly with the Berkeley 88-inch cyclotron and the Cal Tech Van de Graaff) is presented. All bipolar and NMOS RAMs were found to be SEU sensitive, some with very low LET thresholds. Some CMOS or CMOS/SOS RAMs were hard; and the CMOS microprocessors were hard, but the bipolar and NMOS microprocessors were soft. Several devices were found to exhibit a cross section that depends strongly on LET, even when the LET is well above the LET threshold. A ranking of hardness is presented for the logic devices tested.

Nichols, D. K.↗
NASA NTRS1984

The Single Event Upset (SEU) response to 590 MeV protons

The presence of high-energy protons in cosmic rays, solar flares, and trapped radiation belts around Jupiter poses a threat to the Galileo project. Results of a test of 10 device types (including 1K RAM, 4-bit microP sequencer, 4-bit slice, 9-bit data register, 4-bit shift register, octal flip-flop, and 4-bit counter) exposed to 590 MeV protons at the Swiss Institute of Nuclear Research are presented to clarify the picture of SEU response to the high-energy proton environment of Jupiter. It is concluded that the data obtained should remove the concern that nuclear reaction products generated by protons external to the device can cause significant alteration in the device SEU response. The data also show only modest increases in SEU cross section as proton energies are increased up to the upper limits of energy for both the terrestrial and Jovian trapped proton belts.

Nichols, D. K.↗
NASA NTRS1984

Effect of localized polycrystalline silicon properties on solar cell performance

Several forms of polycrystalline silicon, mostly from cast ingots, (including UCP, SILSO and HEM) were studied. On typical slices, localized properties were studied in two ways. Small area (about 2.5 sq mm) mesa diodes were formed, and localized photovoltaic properties were measured. Also a small area (about .015 sq mm) light spot was scanned across the cells; the light spot response was calibrated to measure local diffusion length directly. Using these methods, the effects of grain boundaries, or of intragrain imperfections were correlated with cell performance. Except for the fine grain portion of SILSO, grain boundaries played only a secondary role in determining cell performance. The major factor was intra-grain material quality and it varied with position in ingots and probably related to solidification procedure.

Leung, D.↗
NASA NTRS1984

Mesoscale analysis of 6.7 micron image data from the VISSR Atmospheric Sounder (VAS) for several case studies

Several case studies are examined in an attempt to relate Visible infrared spin scan radiometers Atmospheric Sounder (VAS) water vapor channel radiance data to atmospheric moisture. Since the 6.7 micrometer channel detects radiation emitted by atmospheric water vapor from a rather thick layer, a scheme is developed which weighted rawinsonde observations of relative humidity in a similar manner. A comparison of the two fields (weighted relative humidity values from gridded rawinsonde observations and the VAS water vapor image) indicates that even when mesoscale data are used, the technique only presented a smooth representation of the radiance field. This weighting function is dependent on both the temperature and moisture distribution of the atmosphere. Cross sections of relative humidity from the mesoscale rawinsondes are produced which sliced the water vapor imagery in particularly interesting regions (areas of high and low blackbody temperatures). Comparisons are then made between the cross sections and the variations in the VAS radiance data along the cross section line. Bright regions in the water vapor imagery (cold blackbody temperatures) are often associated with thin layers of high relative humidity or thick layers of only moderately moist air. The reverse also applies, i.e., dark regions (warm blackbody temperatures) in the imagery corresponded well with very dry regions in the cross sections.

Jedlovec, G. J.↗
NASA NTRS1985

Velocity selective flow visualization in a free supersonic nitrogen jet with the resonant Doppler velocimeter

The use of the resonant Doppler velocimeter for flow visualization in a free supersonic nitrogen jet is demonstrated experimentally. In the experiment reported here, room-temperature nitrogen at 12.7 psi expands through a Mach 3.4 converging diverging nozzle into a plenum chamber; small amount of sodium is injected through a heated needle centered 0.5-in. upstream of the nozzle throat. The beam of a single frequency dye laser is expanded into a sheet of light with a cylindrical beam expander and directed counter to the jet to spatially resolve any slice across the core of the flow. By tuning the laser to different frequencies, particular velocity and density fields can be highlighted.

Zimmermann, M.↗
NASA NTRS1985

Theoretical analysis of Wolter/LSM X-ray telescope systems

A ray tracing analysis has been performed for the spectral slicing zoom X-ray telescope for configurations in which a convex layered synthetic microstructure (LSM) optic is placed in front of the prime focus or a concave LSM optic is placed behind the prime focus. The analysis has considered the geometrical shape of the LSM optic to be either a hyperboloid, sphere, ellipsoid or constant optical path aspheric element for two configurations of the glancing incidence X-ray telescope: the ATM Experimental S-056 Wolter I system and the Stanford/MSFC Wolter-Schwarzchild nested system. For the different systems the RMS blur circle radii, the point spread function (PSF), the full width half maximum (FWHM) of the PSF have been evaluated as a function of field angle and magnification of the secondary to determine resolution of the system. The effects of decentration and tilt of the selected LSM element on the performance of the system have been studied to determine mounting and alignment tolerances.

Shealy, D. L.↗
NASA NTRS1986

Polyphase thrust tectonic in the Barberton greenstone belt

In the circa 3.5 by-old Barberton greenstone belt, the supracrustal rocks form a thick and strongly deformed thrust complex. Structural studies in the southern part of the belt have shown that 2 separate phases of over-thrusting (D sub 1 and D sub 2) successively dismembered the original stratigraphy. Thrust nappes were subsequently refolded during later deformations (D sub 3 and D sub 4). This report deals with the second thrusting event which, in the study region appears to be dominant, and (unlike the earlier thrusting), affects the entire supracrustal pile. The supracrustal rocks form a predominantly NE/SW oriented, SE dipping tectonic fan (the D sub 2 fan) in which tectonic slices of ophiolitic-like rocks are interleaved with younger sedimentary sequences of the Diepgezet and malalotcha groups. Structural and sedimentological data indicate that the D sub 2 tectonic fan was formed during a prolonged, multi-stage regional horizontal shortening event during which several types of internal deformation mechanisms were successively and/or simultaneously active. Movement appears to have been predominantly to the NW and to the N. During D sub 2, periods of quiescence and sedimentation followed periods of thrust propagation. Although the exact kinematics which led to the formation of this fan is not yet known, paleoenvironmental interpretations together with structural data suggest that D sub 2 was probably related to (an) Archean collision(s).

Paris, I. A.↗