Search NASA⌕ Search

SEARCH · Search NASA

Results for “Profiling”

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 NTRS1973

Nuclear microprobe analysis of solar proton implantation profiles in lunar rock surfaces

Discussion of the results of hydrogen (proton) depth profile concentration analyses conducted on selected Apollo 16 rocks. A modeling of solar particle implantation profiles in lunar rocks is shown to trace the evolvement of these profiles under the combined influence of diffusion of atomic particles implanted in the rock, and rock surface erosion. It is also demonstrated that such diffusion may have a significant effect on the shape of the implantation profiles in certain rock materials.

Stauber, M. C.↗
NASA NTRS1974

Non-LTE profiles of the Al I autoionization lines

A non-LTE formulation is given for the transfer of radiation in the autoionizing lines of neutral aluminum at 1932 and 1936 A through both the Bilderberg and Harvard-Smithsonian model atmospheres. Numerical solutions for the common source function of these lines and their theoretical line profiles are calculated and compared with the corresponding LTE profiles. The results show that the non-LTE profiles provide a better match with the observations. They also indicate that the continuous opacity of the standard solar models should be increased in this wavelength region if the center-limb variations of observed and theoretical profiles of these lines are to be in reasonable agreement.

Finn, G. D.↗
NASA NTRS1974

The effect of Be/+/ ion implanted exponential and uniform impurity profiles on the electrical characteristics of GaAs solar cells

The high surface recombination velocity is the major deterrent to obtaining efficient GaAs solar cells. If, however, an electric field is built in at the surface, the carriers will be swept away from the surface thus minimizing the surface recombination velocity problem. It has been previously shown theoretically that an exponential impurity distribution in the doped region of the cell results in a built-in electric field. Ion implantation was used to produce solar cells with an exponential impurity profile and cells with uniform profiles. It is shown that cells with an exponential impurity profile have higher open-circuit voltage, fill factors, and spectral response than those with a uniform impurity profile.

Vaidyanathan, K. V.↗
NASA NTRS1974

Monte Carlo calculations of the surface brightness profiles of spherical dark nebulae

Theoretical surface brightness profiles of spherical dark nebulae of both uniform density and a density proportional to 1/r squared are being discussed. The albedo and asymmetry factor of the dust grains and the optical radius measured from the cloud center were the variable parameters in this study, which further assumed an isotropically incident radiation field. The occurrence of dark cores in the surface brightness profiles is examined, and their frequent existence in galactic dark nebulae is interpreted as resulting from a strongly forward scattering phase function and a high optical depth of the associated objects. The shape and depth of the profiles of the dark cores is closely related to the internal density distribution of the clouds, and it is suggested that detailed observations of the surface brightness profiles of dark nebulae will reveal important information on the type of their internal density distribution and, thus, their evolutionary status.

Witt, A. N.↗
NASA NTRS1974

Heavy ion beam probe measurements of radial potential profiles in the modified Penning discharge

A heavy ion beam probe was used to examine the radial potential profile of a plasma in the modified Penning discharge. The plasma has strong (approximately kV) electrostatic potentials near the anode ring which can be a large fraction of the injected ion beam energy. A primary (singly ionized) thallium ion beam is injected through the plasma in the midplane of a double Penning anode ring. After passage through the plasma, primary and secondary (doubly ionized) ions are detected with either a set of flat probes or an electrostatic energy analyzer. A calculation of the primary orbit through the plasma is performed to obtain an approximation to the measured primary beam trajectory. As the real radial potential profile is unknown, an adjustable model is used in the computer program. The adjustable potential profile is varied until the best agreement between measured and calculated trajectories is obtained. Secondary orbits are also predicted using the best fitting adjustable profile. The calculations indicate that secondary beams originating at more than one point in the plasma can be simultaneously observed at the electrostatic analyzer with certain primary beam initial conditions.

Kambic, G. X.↗
NASA NTRS1975

Simulation and flight studies of an approach profile indicator for VTOL aircraft

Simulation and flight investigations were conducted by using a method of providing supplementary information to the pilot in conjunction with a closed-circuit-television display during a VTOL instrument final approach including deceleration and hover. The supplementary information included range, cross range, ground speed, altitude, and rate-of-climb error and was displayed on an instrument called an approach profile indicator. The display was arranged to provide both quasi-command and situation information. Pilot comments indicated that the approach-profile-indicator display concept in conjunction with the closed-circuit television resulted in a decreased pilot workload and an increase in pilot confidence. Also, the results indicated that the approach profile repeatability was significantly improved because of the ground-speed and altitude information provided on the approach profile indicator.

Moen, G. C.↗
NASA NTRS1975

Wall-wake velocity profile for compressible non-adiabatic flows

A form of the wall-wake profile, which is applicable to flows with heat transfer, and for which a variation in y = O at y = delta, was suggested. The modified profile, which takes into account the effect of turbulent Prandtl number, was found to provide a good representation of experimental data for a wide range numbers and heat transfer. The Cf values which are determined by a least squares fit of the profile to the data agree well with values which were measured by the floating element technique. In addition, the values of delta determined by the fit correspond more closely to the outer edge of the viscous flow region than those obtained with earlier versions of the wall-wake profile.

Sun, C. C.↗
NASA NTRS1976

Wall-wake velocity profile for compressible nonadiabatic flows

The paper suggests a new form of the wall-wake profile which is applicable to flows with heat transfer, and for which the velocity gradient at the boundary-layer edge is zero. The modified profile - which takes into account the effect of turbulent Prandtl number - is found to provide a good representation of experimental data for a wide range of Mach numbers and heat transfer. The skin friction coefficient values determined by a least squares fit of the profile to the data are in good agreement with values measured by the floating element technique. The values of boundary-layer thickness determined by the fit correspond more closely to the outer edge of the viscous flow region than those obtained with earlier versions of the wall-wake profile.

Sun, C.-C.↗
NASA NTRS1977

Mean horizontal wind profiles measured in the atmospheric boundary layer about a simulated block building

Instrumented wind towers are used to measure the three components of wind about a simulated block building. The mean horizontal wind profiles over the building are compared with wind profiles measured in the absence of the building and the wind speed deficit in the wake of the building is correlated. The turbulence intensity is of the order of 20% in the undisturbed flow whereas the free stream turbulence intensity of wind-tunnel studies is generally not more than 5%. The velocity profiles measured in the undisturbed flow zones support the representation of a neutrally stable atmospheric boundary layer with a logarithmic wind profile.

Frost, W.↗
NASA NTRS1977

Lowest-order average effect of turbulence on atmospheric profiles derived from radio occultation

Turbulence in planetary atmospheres and ionospheres causes changes in angles of refraction of radio waves used in occultation experiments. Atmospheric temperature and pressure profiles, and ionospheric electron concentration profiles, derived from radio occultation measurements of Doppler frequency contain errors due to such angular offsets. The lowest-order average errors are derived from a geometrical-optics treatment of the radio-wave phase advance caused by the addition of uniform turbulence to an initially homogeneous medium. It is concluded that the average profile errors are small and that precise Doppler frequency measurements at two or more wavelengths could be used to help determine characteristics of the turbulence, as well as accuracy limits and possible correction terms for the profiles. However, a more detailed study of both frequency and intensity characteristics in radio and optical occultation measurements of turbulent planetary atmospheres and ionospheres is required to realize the full potential of such measurements.

Eshleman, V. R.↗
NASA NTRS1977

Computer Program for Calculation of a Gas Temperature Profile by Infrared Emission: Absorption Spectroscopy

A computer program to calculate the temperature profile of a flame or hot gas was presented in detail. Emphasis was on profiles found in jet engine or rocket engine exhaust streams containing H2O or CO2 radiating gases. The temperature profile was assumed axisymmetric with an assumed functional form controlled by two variable parameters. The parameters were calculated using measurements of gas radiation at two wavelengths in the infrared. The program also gave some information on the pressure profile. A method of selection of wavelengths was given that is likely to lead to an accurate determination of the parameters. The program is written in FORTRAN IV language and runs in less than 60 seconds on a Univac 1100 computer.

Buchele, D. R.↗
NASA NTRS1978

Profile design for an advanced-technology airfoil for general aviation aircraft

A profile from the NASA General Aviation Whitcomb series and NACA profiles are used as a starting point in designing an advanced airfoil for general aviation aircraft. Potential theory pressure distribution calculations, together with boundary layer calculations, permit a decrease in the null moment and an optimization of the lift characteristics of the wing. Trailing edge flap design is also improved. Wind tunnel tests are used to compare the conventional profiles, the NASA profile, and the improved design.

Welte, D.↗
NASA NTRS1977

Velocity and temperature profiles in near-critical nitrogen flowing past a horizontal flat plate

Boundary layer velocity and temperature profiles were measured for nitrogen near its thermodynamic critical point flowing past a horizontal flat plate. The heated surface was oriented both facing upward and downward. The results were compared to earlier work in which measurements were made for vertically upward flow. The boundary layer temperatures ranged from below to above the thermodynamic critical temperature. For wall temperatures below the thermodynamic critical temperature there was little variation between the velocity and temperature profiles in the three orientations. In all three orientations the point of crossing into the critical temperature region is marked by a significant flattening of the velocity and temperature profiles and also a decrease in heat transfer coefficient. As the heat flux and, consequently, wall temperature are further increased significant changes occur in the velocity and temperature profiles. Examination of near-critical heat transfer in these three flow orientations offers insights into the relative role of buoyancy forces in this regime.

Simoneau, R. J.↗
NASA NTRS1978

Interpretation of Beta Lyrae. IV - Hydrogen emission profiles and the pattern of gaseous flow in the system

The paper presents an interpretation of hydrogen emission profiles found in Beta Lyrae by attributing the asymmetry of the two emission peaks of both H-alpha and H-gamma at different phases to the absorption of an expanding-rotating gaseous stream. It is proposed that different relative shifts of the absorption line with respect to the emission line exist at different phases resulting in an apparent change in the profile with phase. Based on this idea, the expected profiles at four different phases have been computed for the H-alpha and H-gamma lines. They show a general trend close to what has been observed. Based on this same idea an apparent discrepancy between the observed results of the H-gamma profile obtained at two different epochs about 15 years apart becomes understandable. Finally a physical picture that can produce this periodic shift of the emission line relative to the absorption line is proposed and discussed.

Huang, S.-S.↗
NASA NTRS1978

Ultraviolet observations of cool stars. VI - L alpha and Mg II emission line profiles /and a search for flux variability/ in Arcturus

High-precision, high-resolution profiles of the L alpha and Mg II k chromospheric emission lines from Arcturus (alpha Boo) obtained with the Princeton Experimental Package aboard the Copernicus satellite are presented. Asymmetries seen in the profiles of these lines are probably intrinsic to the star, rather than the result of interstellar absorption. In contrast to previous observations of the Ca II K emission line, no evidence is found during a three-year period for variability in the profiles or in the total fluxes from these lines on time scales ranging from hours to months. Also presented is a flux profile of the O I 1302 line and flux upper limits for L beta, O VI 1032, Si III 1206, and O V 1218.

Mcclintock, W.↗
NASA NTRS1979

Effect on head-wind profiles and mean head-wind velocity on landing capacity flying constant-airspeed and constant-groundspeed approaches

A study was conducted to determine the effect of head-wind profiles and mean head-wind velocities on runway landing capacity for airplanes flying constant-airspeed and constant-groundspeed approaches. It was determined that when the wind profiles were encountered with the currently used constant airspeed approach method, the landing capacity was reduced. The severity of these reductions increased as the mean head-wind value of the profile increased. When constant-groundspeed approaches were made in the same wind profiles, there were no losses in landing capacity. In an analysis of mean head winds, it was determined that in a mean head wind of 35 knots, the landing capacity using constant-airspeed approaches was 13% less than for the no wind condition. There were no reductions in landing capacity with constant-groundspeed approaches for mean head winds less than 35 knots. This same result was observed when the separation intervals between airplanes was reduced.

Hastings, E. C., Jr.↗
NASA NTRS1979

Synthesis of national risk profile

The methodology used and results obtained in computing the national risk profile for carbon fibers (CF) released after an aircraft accident (fire or explosion) are presented. The computation was performed by use of twenty-six individual conditional risk profiles, together with the extrapolation of these profiles to other U.S. airports. The risk profile was obtained using 1993 CF utilization forecasts, but numbers of facilities were taken from 1972 and 1975 census data, while losses were expressed in 1977 dollars.

Source record↗
NASA NTRS1978

Remote sensing of the ozone profile in the lower stratosphere using UV and IR measurements from Nimbus-4

A method of combining the information from the infrared interferometer spectrometer (IRIS) and the backscatter ultraviolet spectrometer (BUV) on board the Nimbus-4 satellite to derive the ozone profile from 10 mb to surface is described. The radiance in the IRIS 9-micron band can be related to the ozone profile by the radiative transfer equation. The IR intensity due to ozone is dependent on the pressure broadening of spectral lines, and an estimate of a weighted mean pressure of the ozone layer can be obtained from total ozone supplied by BUV long wave intensity measurements. With the aid of the Chapman function, a model of the ozone concentration profile described by three parameters is obtained. Given the ozone concentration at 10 mb one calculates several possible combinations of the three parameters that can produce the required total ozone, and the final choice of parameter is determined from IR measurements. An ozone profile calculated in this way reproduces well the gross features of balloon ozone sounding results. Meridional cross sections of ozone concentration have also been derived which are in reasonably good agreement with balloon-derived cross-section for the northern latitudes and tropics.

Prabhakara, C.↗