Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Ar”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

A comparative Rb-Sr, Sm-Nd, and K-Ar study of shocked norite 78236 - Evidence of slow cooling in the lunar crust

The sample 78236 was chipped from the top of a norite boulder at Station 8 by the Apollo 17 landing team. Jackson et al. (1975) concluded that this rock formed at a depth of 8-30 km in the lunar crust and suggested that it was excavated by a large basin-forming impact event. A petrographic description of the boulder is provided, and isotopic analyses are discussed. Attention is given to a chronology for 78236 which seems to be most consistent with radiometric and other evidence. It is proposed that cumulate norite 78236 formed deep in the lunar crust approximately 4.4 AE ago. The rock cooled slowly in the crust until it was excavated by a major basin-forming event. Excavation may have occurred about 4.2 AE ago, but the time of this event is not well constrained.

Nyquist, L. E.↗
NASA NTRS1982

Development of technique for AR coating nickel and copper metallization of solar cells FPS project product development

Experimental matrices were conducted to determine a suitable firing schedule for fritless tin printing ink. considerable difficulties were encountered with oxidation. Best results were obtained with a firing cycle consisting of 400 C for 20 minutes in nitrogen followed by 5 minutes in air at 500 C. Elimination of oxidizing conditions impaired the adhesion of both tin and copper fritless printing inks, although adhesion of fritless copper inks was obtained when fired in nitrogen with slight oxidation.

Taylor, W.↗
NASA NTRS1982

USDA-ARS Hydrology Laboratory MISWG Hydrology Workshop

Current research being conducted in remote sensing techniques for measuring hydrologic parameters and variables deals with runoff curve numbers (CN), evapotranspiration (ET), and soil moisture. The CN and ET research utilizes visible and infrared measurements. Soil moisture investigations focus on the microwave region of the electromagnetic spectrum.

Jackson, T. J.↗
NASA NTRS1985

Ignition of mixtures of SiH sub 4, CH sub 4, O sub 2, and Ar or N sub 2 behind reflected shock waves

Ignition delay times in mixtures of methane, silane, and oxygen diluted with argon and nitrogen were measured behind reflected shock waves generated in the chemical kinetic shock tube at Langley Research Center. The delay times were inferred from the rapid increase in pressure that occurs at ignition, and the ignition of methane was verified from the emission of infrared radiation from carbon dioxide. Pressures of 1.25 atm and temperatures from 1100 K to 1300 K were generated behind the reflected shocks; these levels are representative of those occurring within a supersonic Ramjet combustor. Expressions for the ignition delay time as a function of temperature were obtained from least squares curve fits to the data for overall equivalence ratios of 0.7 and 1.0. The ignition delay times with argon as the diluent were longer than those with nitrogen as the diluent. The infrared wavelength observations at 4.38 microns for carbon dioxide indicated that silane and methane ignited simultaneously (i.e., within the time resolution of the measurement). A combined chemical kinetic mechanism for mixtures of silane, methane, oxygen, and argon or nitrogen was assembled from one mechanism that accurately predicted the ignition of methane and a second mechanism that accurately predicted silane hydrogen ignition. Comparisons between this combined mechanism and experiment indicated that additional reactions, possibly between silyl and methyl fragments, are needed to develop a good silane methane mechanism.

Mclain, A. G.↗
NASA NTRS1985

A Cerenkov-delta E-Cerenkov detector for high energy cosmic ray isotopes and an accelerator study of Ar-40 and Fe-56 fragmentation

A high energy cosmic ray detector--the High Energy Isotope Spectrometer Telescope (HEIST) is described. It is a large area (0.25 m(swp 2) SR) balloon borne isotope spectrometer designed to make high resolution measurements of isotopes in the element range from neon to nickel (10 Z 28) at energies of about 2 GeV/nucleon. HEIST determines the mass of individual nuclei by measuring both the change in the Lorentz factor (delta gamma) that results from traversing the NaI stack, and the energy loss (delta E) in the stack. Since the total energy of an isotope is given by E = (gamma M), the mass M can be determined by M = delta E/delta, gamma. The instrument is designed to achieve a typical mass resolution of 0.2 amu. The isotopic composition of the fragments from the breakup of high energy An-40 and Fe-56 nuclei are measured experimentally. Isotope yields are compared with calculated yields based on semi-empirical cross-section formulae.

Lau, K. H.↗
NASA NTRS1985

Measurements of Fe and Ar fragmentation cross sections

Measurements are reported of the yields of individual isotopes of Cr to Co (Z = 24 to 27) resulting from the fragmentation of 56Fe, and the isotopes of Mg to K (Z = 12 to 19) resulting from the fragmentation of 40Ar.

Lau, K. H.↗
NASA NTRS1985

The effect of high energy (HZE) particle radiation (Ar-40) on aging parameters of mouse hippocampus and retina

Eight month old C57BL6 mice were exposed (head only) to 0.5 rad or 50 rads of Argon particles at the Lawrence Berkeley Radiation Facility, CA. Neuromotor performance was assessed monthly for six months beginning twelve weeks post-irradiation using a 'string test'. The decline in motor performance was dose-related and none of the animals was able to complete the task after four months of testing. Morphological changes were monitored six and twelve months post-irradiation by light and electron microscopy. The synaptic density in the CA-1 area of the hippocampus decreased six and twelve months after irradiation. The decrease after twelve months was less than after six months. The width of the outer nuclear layer (ONL) of the retina increased with increasing dose. The number of blood vessels between the ONL and the ganglion layer decreased twelve months after irradiation and this area did not show significant accumulation of age pigment.

Philpott, D. E.↗
NASA NTRS1988

Instantaneous velocity field measurements of a turbulent rectangular jet (AR-4) using particle image displacement velocimetry

A whole field experimental technique, commonly referred to as Particle Image Displacement Velocimetry (PIDV) is used for the measurement of the two dimensional instantaneous velocity fields in the transition region of a three dimensional jet issuing from a rectangular nozzle of an aspect ratio 4. The instability process of an initially laminar jet is studied visually and quantitatively to determine the structure and growth of the mixing region of the jet. The experiments were performed using an air jet at a Reynolds number based on the hydraulic diameter of 3600. The roll-up of the laminar shear layer into vortices and their subsequent interactions are examined.

Lourenco, L.↗
NASA NTRS1988

Cosmic-ray energy spectra between 10 and several hundred GeV per atomic mass unit for elements from Ar-18 to Ni-28 - Results from HEAO 3

Results from the Heavy Nuclei experiment on HEAO 3 are used to determine the primary abundances of Ni and Fe. Ni and Fe are found to have nearly constant relative abundances over the interval of 10 to about 500 GeV per amu. Individual secondary elements derived principally from interactions of primary Fe nuclei are shown to display a power-law decrease in relative abundance up to about 150 GeV per amu. Ar/Fe and Ca/Fe ratios of 2.6 + or - 0.7 percent and 8.8 + or - 0.7 percent, respectively, are found, confirming a fractionation of source abundances in which elements with high values of the first ionization potential are depleted relative to those with low first ionization potential.

Binns, W. R.↗
NASA NTRS1989

Advanced Recovery Systems for Advanced Launch Vehicles (ARS) phase 1 study results

The paper documents the work completed during the Advanced Recovery Systems for Advanced Launch Vehicles phase 1 study. Particular attention is given to the definition of the design of a single recovery system for the most likely near-term payload, a propulsion/avionic module (P/AM). A P/AM recovery system for phase 2 demonstration was designed which offers low cost, extremely low weight, good performance, potential for pinpoint loading, and operational flexibility.

Wailes, William K.↗
NASA NTRS1989

Some of the terrestrial effects of AR 5395

Active Region 5395 was extraordinary for both its flare production for a complete disk transit and for one of the largest geomagnetic storms on record. Some of the more dramatic terrestrial effects resulting from the flare activity are briefly discussed.

Speich, D.↗
NASA NTRS1989

Precision measurements of photoabsorption cross sections of Ar, Kr, Xe, and selected molecules at 58.4, 73.6, and 74.4 nm

Absolute absorption cross sections have been measured for the rare gases at 58.43, 73.59, and 74.37 nm with an accuracy of + or - 0.8 percent. For the molecules H2, N2, O2, CO, N2O, CO2, and CH4, precision measurements were made at 58.43 nm with an accuracy of + or - 0.8 percent. Molecular absorption cross sections are also reported at 73.59 and 74.37 nm. However, in the vicinity of these wavelengths most molecules exhibit considerable structure, and cross sections measured at these wavelengths may depend on the widths and the amounts of self-reversal of these resonance lines. A detailed discussion is given of the systematic errors encountered with the double-ion chamber used in the cross-sectional measurements. Details are also given of precision pressure measurements.

Samson, James A. R.↗
NASA NTRS1990

Properties of the large- and small-scale flow patterns in and around AR 19824

A series of magnetograms spanning just over 5 days and covering about 4 x 5 arcmin has been used to trace the photospheric motions of 170 concentrations of magnetic flux tubes in and around the decaying active region 19824. A persistent large-scale flow pattern superposed on small-scale random motions of both polarities is noted whose overall pattern resembles the flow of a river around a sand bar, and whose long-term evolution suggests a persistence of several months. The observed motions of concentrations of flux tubes are corrected for the large-scale flow in order to study their random motions.

Schrijver, C. J.↗
NASA NTRS1994

The magnetic evolution of the activity complex AR 7260: A roadmap

The active region NOAA 7260 rotated onto the north solar hemisphere as a mature bipole: a dominant negative-polarity sunspot with trailing plage and scattered small spots in attendance. The dominant p spot itself had strong magnetic fields and covered almost 400 x 10(exp -6) of a solar hemisphere. For a period of seven days beginning 14 August, 1992 this active region displayed rapid and drastic evolution: no fewer than 50 magnetic bipoles emerged in the area trailing the large sunspot, increasing the region's magnetic flux by more than 10(exp 22) Mx. This new group of sunspots formed a complex Beta gamma delta configuration with two delta spots and a high degree of magnetic shear. This region was very well observed by Yohkoh and various ground-based instruments. It presented opportunities to study new emerging flux, flares, and also the decay of a large sunspot. For the benefit of later studies we present a description of the global characteristics of this active region, a detailed 'roadmap' of its evolution during disk passage including the development of the two delta regions. We compare proper motion trends and flaring activity to observations of other delta-spots reported in the literature. We also comment on the observed outflow of magnetic elements from the decaying p spot.

Leka, K. D.↗
NASA NTRS2002

Real-Time Quantitative Analysis of H2, He, O2, and Ar by Quadrupole Ion Trap Mass Spectrometry

The use of a quadrupole ion trap mass spectrometer for quantitative analysis of hydrogen and helium as well as other permanent gases is demonstrated. The customized instrument utilizes the mass selective instability mode of mass analysis as with commercial instruments; however, this instrument operates at a greater RF trapping frequency and without a buffer gas. With these differences, a useable mass range from 2 to over 50 Da is achieved, as required by NASA for monitoring the Space Shuttle during a launch countdown. The performance of the ion trap is evaluated using part-per-million concentrations of hydrogen, helium, oxygen and argon mixed into a nitrogen gas stream. Relative accuracy and precision when quantitating the four analytes were better than the NASA-required minimum of 10% error and 5% deviation, respectively. Limits of detection were below the NASA requirement of 25-ppm hydrogen and 100-ppm helium; those for oxygen and argon were slightly higher than the requirement. The instrument provided adequate performance at fast data recording rates, demonstrating the utility of an ion trap mass spectrometer as a real-time quantitative monitoring device for permanent gas analysis.

Ottens, Andrew K.↗