Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “profilers”

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 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Surface profile changes of scuffed bearing surfaces

A phase locked interference microscope capable of resolving depth differences to 30 A and planar displacements of 6000 A was constructed for the examination of the profiles of bearing surfaces without physical contact. This instrument was used to determine surface chemical reactivity by applying a drop of dilute alcoholic hydrochloric acid and measuring the profile of the solid surface before and after application of this probe. Scuffed bearing surfaces reacted much faster than unscuffed ones, but bearing surfaces which had been previously exposed to lubricants containing an organic chloride reacted much more slowly. In a separate series of experiments, a number of stainless steel plates were heated in a nitrogen atmosphere to different temperatures and their reactivity examined later at room temperature. The change of surface contour as a result of the probe reaction followed an Arrhenius type relation with respect to heat treatment temperature. This result could have implications on the scuffing mechanism.

Lauer, J. L.↗
NASA NTRS1983

Study to determine the IFR operational profile and problems of the general aviation single pilot

General aviation single pilot operating under instrument flight rules (GA SPIFR) was studied. The objectives of the study were to (1) develop a GA SPIFR operational profile, (2) identify problems experienced by the GA SPIFR pilot, and (3) identify research tasks which have the potential for eliminating or reducing the severity of the problems. To obtain the information necessary to accomplish these objectives, a mail questionnaire survey of instrument rated pilots was conducted. The general aviation IFR single pilot operational profile and selected data analysis examples are presented.

Weislogel, G. S.↗
NASA NTRS1983

TRAGEN: Computer program to simulate an aircraft steered to follow a specified verticle profile. User's guide

The longitudinal dynamics of a medium range twin-jet or tri-jet transport aircraft are simulated. For the climbing trajectory, the thrust is constrained to maximum value, and for descent, the thrust is set at idle. For cruise, the aircraft is held in the trim condition. For climb or descent, the aircraft is steered to follow either (a) a fixed profile which is input to the program or (b) a profile computed at the beginning of that segment of the run. For climb, the aircraft is steered to maintain the given airspeed as a function of altitude. For descent, the aircraft is steered to maintain the given altitude as a function of range-to-go. In both cases, the control variable is angle-of-attack. The given output trajectory is presented and compared with the input trajectory. Step climb is treated just as climb. For cruise, the Breguet equations are used to compute the fuel burned to achieve a given range and to connect given initial and final values of altitude and Mach number.

Source record↗
NASA NTRS1981

Vertical ozone profile results from the Nimbus-4 BUV data

A seven year data set which consists of both total ozone and ozone vertical profiles has been derived from the Nimbus-4 Backscatter Ultraviolet (BUV) experiment. The BUV experiment measures the earth's backscattered solar radiance at 12 wavelengths in the Hartley-Huggins band. The shortest 8 bands are used to determine the vertical ozone profile. The longest four bands are used to determine the total ozone. The present investigation provides a review of the major characteristics of the instrument performance and ozone results during the seven year period of the data set. Attention is given to the data coverage in time and space, the major areas of nonhomogeneous coverage, adjustments made to the basic instrument radiances, long-term trends in the radiances, rocket and balloon measurements, and problems associated with the validation of the satellite data set.

Fleig, A. J.↗
NASA NTRS1981

Algorithm for vertical ozone profile determination for the Nimbus-4 BUV data set

A description is provided of the algorithm used by the Ozone Processing Team at NASA to process seven years of Backscatter Ultraviolet (BUV) ozone profile data. The algorithm is a modification of the original retrieval algorithm developed by Mateer (1972) to process some of the early data from the BUV experiment. Principal changes made are in the first guess selection scheme, the use of all wavelengths in the inversion, and the weighting of the various wavelengths according to the errors in the radiance estimation. It is found that the described BUV ozone profile algorithm is an extremely efficient algorithm for retrieving large amounts of satellite data. The algorithm makes full use of all the available information from the measured radiances including the longer wavelength radiances which previously had not been used.

Bhartia, P. K.↗
NASA NTRS1983

Iterative optimal subcritical aerodynamic design code including profile drag

A subcritical aerodynamic design computer code has been developed, which uses linearized aerodynamics along with sweep theory and airfoil data to obtain minimum total drag preliminary designs for multiple planform configurations. These optimum designs consist of incidence distributions yielding minimum total drag at design values of Mach number and lift and pitching moment coefficients. Linear lofting is used between airfoil stations. Solutions for isolated transport wings have shown that the solution is unique, and that including profile drag effects decreases tip loading and incidence relative to values obtained for minimum induced drag solutions. Further, including effects of variation of profile drag with Reynolds number can cause appreciable changes in the optimal design for tapered wings. Example solutions are also discussed for multiple planform configurations.

Kuhlman, J. M.↗
NASA NTRS1983

Intensity dependence of the pulse profile and polarization of the Vela pulsar

Polarization measurements of the Vela pulsar PSR 0833-45 at 2295 MHz revealed that the radio pulse profile is composed of four components. The four component configuration was found to fit the observed dependence of the pulse profile on the intensity of the pulsar, and the dependence of the modulation index and power spectrum of the intensity fluctuations on the pulse-longitude. Deviations of the observed polarization position angles from those predicted by a rotating vector model were explained by the emission regions for each component being located at different distances from the star. The components are affected by retardation, aberration, and magnetic field curvature effects, all of which contribute to arrival of the components at different longitudes even though the components actually carry the position angle signature predicted by the rotating vector model.

Krishnamohan, S.↗
NASA NTRS1983

Ozone profile intercomparison based on simultaneous observations between 20 and 40 km

The vertical distribution of stratospheric ozone has been simultaneously measured by means of five different instruments carried on the same balloon payload. The launches were performed from Gap during the intercomparison campaign conducted in June 1981 in southern France. Data obtained between altitudes of 20 and 40 km are compared and discussed. Vertical profiles deduced from Electrochemical Concentration Cell sondes launched from the same location by small balloons and from short Umkehr measurements made at Mt Chiran (France) are also included in this comparison. Systematic differences of the order of 20 percent between ozone profiles deduced from solar u.v. absorption and in situ techniques are found.

Aimedieu, P.↗
NASA NTRS1983

Profiling atmospheric water vapor by microwave radiometry

High-altitude microwave radiometric observations at frequencies near 92 and 183.3 GHz were used to study the potential of retrieving atmospheric water vapor profiles over both land and water. An algorithm based on an extended kalman-Bucy filter was implemented and applied for the water vapor retrieval. The results show great promise in atmospheric water vapor profiling by microwave radiometry heretofore not attainable at lower frequencies.

Wang, J. R.↗
NASA NTRS1983

Resolution of vertical mixing-ratio profiles of atmospheric constituents retrieved from solar spectra

The relationship between the uncertainty and the resolution of the mixing-ratio profiles of absorbing gases retrieved from simulated occultation data has been investigated by analyzing sets of absorber amounts, corresponding to a constituent with a constant vertical mixing-ratio profile, along atmospheric paths observed by instruments at 0, 30, and 500 km. The vertical resolution below the instrument is limited by the number of observations and the SNR; it degrades exponentially with height and is independent of the instrument altitude; it is nearly 50 times better than the resolution obtainable above the instrument. An estimate of the resolution obtained by analyzing line shapes is included for comparison.

Shaffer, W. A.↗
NASA NTRS1983

The retrieval of atmospheric constituent mixing-ratio profiles from solar absorption spectra

Methods used to determine various atmospheric gas distributions are summarized. The experimentally determined mixing ratio profiles (the mixing ratio of a gas is the ratio of the number of gas molecules to the number of air molecules) of some atmospheric gases are shown. In most in situ experiments stratospheric gas samples are collected at several altitudes by balloon, aircraft, or rocket. These samples are then analyzed by various methods. Mixing ratio profiles of Ci, ClO, and OH were determined by laser induced fluorescence of samples. Others have analyzed gas samples by gas chromatography in order to determine the molecular abundances of CCl2F2, CCl4, CCl3F, CFCl3, CF2Cl2, CHClF2, CH3CCl3, CH4, CO, C2Cl3F3, C2Cl4, C2HCl3, C2H2, C2H4, C2H6, C3H8, C6H6, C7H8, H2, and N2O.

Shaffer, W. A.↗
NASA NTRS1984

Theoretical aspects of photoclinometric terrain profiling on the Galilean satellites

For large parts of the surfaces of the Galilean satellites there is no stereoscopic high resolution imagery, and so for shadow-free regions far from the terminator, the only method of obtaining topograpic information is photoclinometry, the technique of converting brightness variations into local surface tilts and hence into topographic profiles and contour maps. The conversion from brightness changes to slopes require knowledge of the angular photometric function for the type of planetary surface terrain being analyzed, i.e., the relationship describing the brightness of the surface as a function of the angles of incidence (I) and emergence (E) of light at a surface element. In order to investigate the effects of these changes on the shapes of topographic profiles deduced from the functions, an area of grooved terrain (lines 500-505, samples 550-650 on frame 20640.27 0060J2) using wide ranges of values of all the adjustable parameters in Hapke's new photometric function were analyzed.

Wilson, L.↗
NASA NTRS1984

Performance of a high-work low aspect ration turbine tested with a realistic inlet radial temperature profile

Experimental results are presented for a 0.767 scale model of the first stage of a two-stage turbine designed for a high by-pass ratio engine. The turbine was tested with both uniform inlet conditions and with an inlet radial temperature profile simulating engine conditions. The inlet temperature profile was essentially mixed-out in the rotor. There was also substantial underturning of the exit flow at the mean diameter. Both of these effects were attributed to strong secondary flows in the rotor blading. There were no significant differences in the stage performance with either inlet condition when differences in tip clearance were considered. Performance was very close to design intent in both cases.

Stabe, R. G.↗
NASA NTRS1984

Temperature and humidity profiles in the atmosphere from spaceborne lasers: A feasibility study

Computer simulations of the differential absorption lidar technique in a space craft for the purpose of temperature and humidity profiling indicate: (1) Current technology applied to O2 and H2O lines in the .7 to .8 micrometers wavelength band gives sufficiently high signal-to-noise ratios (up to 50 for a single pulse pair) if backscattering by aerosol particles is high, i.e. profiling accurate to 2 K for temperature and 10% for humidity should be feasible within the turbid lower troposphere in 1 km layers and with an averaging over approximately 100 pulses. (2) The impact of short term fluctuations in aerosol particle concentration is too big for a one laser system. Only a two laser system firing at a time lag of about 1 millisecond can surmount these difficulties. (3) The finite width of the laser line and the quasi-random shift of this line introduce tolerable, partly systematic errors.

Grassl, H.↗
NASA NTRS1984

Retrieval of vertical moisture profiles with microwave radiometry

A statistical correlation technique is applied to the retrieval of vertical moisture profiles from downlooking radiometric measurements of atmospheric radiation at microwave wavelengths. Only an optimum subset of available radiometer channels is selected for estimating water vapor at specific pressure levels. To test its validity the algorithm was applied, in a numerical experiment, to 50 independent tropical radiosondes over a sea surface. It was also used to retrieve continuous sequences of atmospheric moisture profiles from a set of data obtained with a 4-channel microwave radiometer carried aboard an aircraft over a land surface.

Kakar, R. K.↗
NASA NTRS1983

Stratospheric temperature profile from balloon-borne measurements of the 10.4-micron band of CO2

The technique of nonlinear least squares spectral curve fitting has been used to derive the stratospheric vertical temperature profile from balloon-borne measurements of the 10.4 micron band of CO2. The spectral data were obtained at sunset with the approximately 0.02 per cm resolution University of Denver interferometer system from a float altitude of 33.5 km near Alamogordo, New Mexico, on 23 March 1981. The r.m.s. deviation between the retrieved temperature profile and correlative radiosonde measurements is 2.2 K.

Rinsland, C. P.↗
NASA NTRS1983

Mg II profile variations of Zeta Aurigae

Variations in the Mg II 2800-A doublet of Zeta Aurigae have been observed. The Mg II profiles deviate from simple P-Cygni profiles in that they exhibit an absorption feature consistent with Chapman's (1981) interpretation of C IV absorption as evidence of a column of accretion onto the B-star component of the binary. The opening angle of the shock cone containing the accretion column is found to exceed 16 deg, implying a stellar wind velocity of approximately 67 km/s, unless the H II region temperature is unusually high. The turbulence velocity of the wind then appears to be about 33 km/s, compared to values of order 10 km/s previously determined closer to the K-star surface.

Ahmad, I. A.↗
NASA NTRS1983

The stability of coronal loops - Finite-length and pressure-profile limits

Results are described from a quickly converging, necessary-and-sufficient, MHD-stability test for coronal-loop models. The primary stabilizing influence arises from magnetic line tying at the photosphere, and this end conditions requires a series expansion of possible loop excitations. The stability boundary is shown to quickly approach a limit as the number of terms increases, providing a critical length for the loop in proportion to its transverse magnetic scale. Several models of force-free-field profiles are tested and the stability behavior of a localized current channel, embedded in an external current-free region, is shown to be superior to that of other, broader, current profiles. Pressure-gradient effects, leading to increased or decreased stability, are shown to be amplified by line tying. Long loops must either conduct low net current, or exhibit an axial-field reversal coexisting with a low-pressure core. The limits on stability depend on the magnetic aspect ratio, the plasma-to-magnetic pressure ratio, and the field orientation at the loop edge. Applications of these results to the structure of coronal loops are described.

Einaudi, G.↗