SEARCH · Engineering Papers

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.

SourceResearch connectionFrom yearThrough year

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

At least 541 records · Page 30

All sources NASA NTRS DOE OSTI

NASA NTRS1989

Comparison of rainfall profiles retrieved from dual-frequency radar and from combined radar and passive microwave radiometric measurements

Precipitation profiles retrieved from a dual frequency X- and Ka-band radar and from an X-band radiometer are analyzed. Profiles from combined radar and microwave radiometer measurements are compared to those from dual frequency radar measurements to study the performance of the combined radar-radiometer retrievals. A method for the retrieval of rainfall rate profiles from attenuated radar returns and passive radiometric data is presented. The results suggest that the operation of a single frequency radar with multifrequency passive radiometers may provide cost-effective spaceborne measurements of global tropical rainfall distributions. The possible use of this methodology for the Tropical Rainfall Measuring Mission is considered.

Weinman, J. A.↗

NASA NTRS1990

Comparison of stratospheric ozone profiles and their seasonal variations as measured by lidar and Stratospheric Aerosol and Gas Experiment during 1988

A ground-based, high power, laser remote sensing system for measurements of stratospheric ozone concentration profiles has been in operation at the Jet Propulsion Laboratory Table Mountain Facility located in southern California, since January 1988. The seasonal variations observed in the ozone profiles, during 1988 and as a function of altitude, are described here. These profiles are compared with those from the Stratospheric Aerosol and Gas Experiment satellite instrument made within a radius of 1000 km from the lidar and also with the zonal mean measurements made in the band 34.4 +/- 5 deg. Comparison with the proposed new CIRA ozone reference model has also been carried out. The seasonal variations, between 25 and 50 km, observed by the two instruments and indicated by the reference model are in good agreement.

Mcdermid, I. Stuart↗

NASA NTRS1990

A high resolution atlas of Mg II profiles

An atlas of high dispersion Mg II profiles for standard stars of spectral types B0 through G9 is presented. The atlas contains plots of the Mg II profiles for approximately 65 stars and associated equivalent width measurements for both absorption and emission components, and the subordinate lines. The atlas is used to investigate systematic behavior of the Mg II profiles and correlation of the behavior with spectral classification.

Ewald, R.↗

NASA NTRS1991

Fully automatic guidance and control for rotorcraft nap-of-the-Earth flight following planned profiles. Volume 1: Real-time piloted simulation

Developing a single-pilot, all-weather nap-of-the-earth (NOE) capability requires fully automatic NOE (ANOE) navigation and flight control. Innovative guidance and control concepts are investigated in a four-fold research effort that: (1) organizes the on-board computer-based storage and real-time updating of NOE terrain profiles and obstacles in course-oriented coordinates indexed to the mission flight plan; (2) defines a class of automatic anticipative pursuit guidance algorithms and necessary data preview requirements to follow the vertical, lateral, and longitudinal guidance commands dictated by the updated flight profiles; (3) automates a decision-making process for unexpected obstacle avoidance; and (4) provides several rapid response maneuvers. Acquired knowledge from the sensed environment is correlated with the forehand knowledge of the recorded environment (terrain, cultural features, threats, and targets), which is then used to determine an appropriate evasive maneuver if a nonconformity of the sensed and recorded environments is observed. This four-fold research effort was evaluated in both fixed-based and moving-based real-time piloted simulations, thereby, providing a practical demonstration for evaluating pilot acceptance of the automated concepts, supervisory override, manual operation, and re-engagement of the automatic system. Volume one describes the major components of the guidance and control laws as well as the results of the piloted simulations. Volume two describes the complete mathematical model of the fully automatic guidance system for rotorcraft NOE flight following planned flight profiles.

Clement, Warren F.↗

NASA NTRS1991

Fully Automatic Guidance and Control for Rotorcraft Nap-of-the-earth Flight Following Planned Profiles. Volume 2: Mathematical Model

Developing a single-pilot, all-weather nap-of-the-earth (NOE) capability requires fully automatic NOE (ANOE) navigation and flight control. Innovative guidance and control concepts are investigated in a four-fold research effort that: (1) organizes the on-board computer-based storage and real-time updating of NOE terrain profiles and obstacles in course-oriented coordinates indexed to the mission flight plan; (2) defines a class of automatic anticipative pursuit guidance algorithms and necessary data preview requirements to follow the vertical, lateral, and longitudinal guidance commands dictated by the updated flight profiles; (3) automates a decision-making process for unexpected obstacle avoidance; and (4) provides several rapid response maneuvers. Acquired knowledge from the sensed environment is correlated with the forehand knowledge of the recorded environment (terrain, cultural features, threats, and targets), which is then used to determine an appropriate evasive maneuver if a nonconformity of the sensed and recorded environments is observed. This four-fold research effort was evaluated in both fixed-base and moving-base real-time piloted simulations; thereby, providing a practical demonstration for evaluating pilot acceptance of the automated concepts, supervisory override, manual operation, and re-engagement of the automatic system. Volume one describes the major components of the guidance and control laws as well as the results of the piloted simulations. Volume two describes the complete mathematical model of the fully automatic guidance system for rotorcraft NOE flight following planned flight profiles.

Clement, Warren F.↗

NASA NTRS1990

Retrieval of precipitation profiles from airborne radar and passive radiometer measurements - Comparison with dual-frequency radar measurements

Precipitation-rate profiles derived from a single-frequency radar and a radiometer are compared with profiles derived from a dual-frequency radar, using data obtained during the 1985-1986 Communication Research Laboratory/NASA rain measuring experiment over the Atlantic Ocean from a dual-frequency X- and Ka-band radars and an X-band passive radiometer. Profiles were retrieved using a modification of the Hitschfeld-Bordan (1954) algorithm constrained by a measurement of the path integrated extinction derived from passive radiometry. It was found that the two techniques under comparison yielded average rainfall rates that agreed within about 25 percent. It is suggested that, while a single-frequency radar operating in conjunction with multifrequency passive radiometers might provide cost-effective spaceborne measurements of tropical rainfall distributions, a dual-frequency radar might be able to remove some ambiguities that were encountered in this study.

Weinman, J. A.↗

NASA NTRS1991

Stratospheric profiles of heavy water vapor isotopes and CH3D from analysis of the ATMOS Spacelab 3 infrared solar spectra

The isotopic composition of stratospheric water vapor and methane was investigated. Stratospheric profiles of HDO, (H-18)2O, (H-17)2O, and CH3D were derived from solar occultation spectra recorded on April 30 - May 1, 1985 by the Atmospheric Trace Molecule Spectroscopy Fourier transform spectrometer aboard Spacelab 3. The profiles of the three water-vapor isotopes showed an increase in the volume mixing ratio with altitude. The measured profiles of D/H in water vapor showed a large depletion in the lower stratosphere (about 63 percent relative to standard mean ocean water, SMOW, at 20 km) and a small increase in D/H with altitude at higher altitudes, up to 34 km. The D/H ratio in stratospheric methane was close to the corresponding isotopic ratio in SMOW.

Rinsland, C. P.↗

NASA NTRS1990

The effect of small-scale roughness on the main flow profile of a laminar boundary layer

The profile distortion due to a single roughness element, to two such elements, and to many elements is investigated. Signal-averaging of the velocity difference due to the roughness being alternately present or absent is employed in order to improve accuracy. The primary objective of examining the distributed-roughness profiles for any evidence of instability-enhancing form is not met, but the results are reconsidered, and relevant hypotheses and suggestions are presented. It is noted that the reason for not meeting the objective of estimating Tollmien-Schlichting amplification from rough-wall profiles is that much of the distortion occurs close to the wall and below the element tops.

Kendall, James M., Jr.↗

NASA NTRS1991

Theoretical description of spectral line profiles of parent molecules in cometary comae

The present overview of cometary spectral-line profiles obtainable through advancements in high-resolution spectroscopic studies, which allow the retrieval of coma kinematic properties from velocity-resolved spectral-line profiles, incorporates the most important gas dynamic processes into an outflow model which is tailored to the interpretation of spectroscopic observations of parent molecules. The model is then used to study the influence on parent-molecule spectral line profile formation of the field-of-view, the expansion velocity, the kinetic temperature, and the anisotropic outflow distributions.

Hu, Hong-Yao↗

NASA NTRS1991

Comparison of aerosol extinction profiles from lidar and SAGE II data at a tropical station

Aerosol extinction profiles obtained from lidar data at Trivandrum (8.6 deg N, 77 deg E) are compared with corresponding Stratospheric Aerosol and Gas Experiment II extinction profiles. The agreement between the two is found to be satisfactory. The extinction profiles obtained by both the experiments showed a prominent peak at 23-24 km altitude in the stratosphere. The study revealed large variability in upper tropospheric extinction with location (latitude).

Parameswaran, K.↗

NASA NTRS1990

An Electronic Pressure Profile Display system for aeronautic test facilities

The NASA Lewis Research Center has installed an Electronic Pressure Profile Display system. This system provides for the real-time display of pressure readings on high resolution graphics monitors. The Electronic Pressure Profile Display system will replace manometer banks currently used in aeronautic test facilities. The Electronic Pressure Profile Display system consists of an industrial type Digital Pressure Transmitter (DPI) unit which interfaces with a host computer. The host computer collects the pressure data from the DPI unit, converts it into engineering units, and displays the readings on a high resolution graphics monitor in bar graph format. Software was developed to accomplish the above tasks and also draw facility diagrams as background information on the displays. Data transfer between host computer and DPT unit is done with serial communications. Up to 64 channels are displayed with one second update time. This paper describes the system configuration, its features, and its advantages over existing systems.

Woike, Mark R.↗

NASA NTRS1991

The analysis of apparent optical depth profiles for interstellar absorption lines

Attention is given to the apparent optical depth method, a procedure for analyzing interstellar absorption lines. Observed absorption-line profiles are converted into profiles of apparent optical depth, and apparent column density per unit velocity. By comparing the latter for a given interstellar species having two or more absorption lines which differ in the product, the presence or absence of unresolved saturated structure in the profiles can be directly inferred. The method is illustrated using absorption-line data from the IUE satellite for the highly ionized gas toward HD 64760. Additional illustrations and a study of the method's accuracy are provided through a series of numerical simulations of multicomponent interstellar absorption situations. The method is compared to the standard growth curve method for deriving interstellar column densities. The principal value of the apparent optical depth method is that the absorption-line data are directly converted into a form that provides for direct scientific interpretations of the physical conditions in the interstellar absorbing medium as a function of velocity.

Savage, Blair D.↗

NASA NTRS1992

Stress-strain analysis of a (0/90)sub 2 symmetric titanium matrix laminate subjected to a generic hypersonic flight profile

Cross ply laminate behavior of Ti-15V-3Cr-3Al-3Sn (Ti-15-3) matrix reinforced with continuous silicon carbide fibers (SCS-6) subjected to a generic hypersonic flight profile was evaluated experimentally and analytically. Thermomechanical fatigue test techniques were developed to conduct a simulation of a generic hypersonic flight profile. A micromechanical analysis was used. The analysis predicts the stress-strain response of the laminate and of the constituents in each ply during thermal and mechanical cycling by using only constituent properties as input. The fiber was modeled using a thermo-viscoplastic constitutive relation. The fiber transverse modulus was reduced in the analysis to simulate the fiber matrix interface failure. Excellent correlation was found between measured and predicted laminate stress-strain response due to generic hypersonic flight profile when fiber debonding was modeled.

Mirdamadi, Massoud↗

NASA NTRS1992

Stratospheric Backscatter, Extinction, and Lidar Ratio Profiling After the Mt. Pinatubo Eruptions

Since August 1991 the stratospheric aerosol layer is continuously monitored with a combination Raman elastic-backscatter lidar, groundbased systems. XeCl excimer laser is used as the radiation source. Signals elastically backscattered from air molecules and particles and inelastically Raman backscattered from nitrogen molecules are detected. The measurements of these two signal profiles up to 35 km height allows the separate and independent determination of aerosol extinction and backscatter properties in the perturbed lower stratosphere. The extinction coefficient is derived from the nitrogen Raman signal profile, while the backscatter coefficient is obtained from the elastic-to-inelastic backscatter signal ratio. In this way, also the extinction-to-backscatter, or lidar, ratio profile is determined. For the first time, lidar ratios are determined in the perturbed stratospheric layer by the use of remote sensing only. The lidar ratio contains information about the size range of the stratospheric particles which are assumed to be sulfuric acid droplets, and it is needed in the calculation of aerosol optical properties from data taken with a typical backscatter lidar.

Ansmann, Albert↗

NASA NTRS1992

A considerable effect of stratospheric aerosol on lidar-detected ozone profile and a three-wavelength inversion technique for both ozone and aerosol

As far as the Differential Absorption Lidar (DIAL) technique is concerned, it is important that the off-line wavelength is close to the on-line wavelength in order to avoid a messy computation of the atmospheric aerosol scattering. However, the two wavelengths of ozone-DIAL are usually considerably different. Usually, an excimer laser of 308nm (on-line) and Raman shifting of 353nm or the third harmonic of a Nd-YAG laser with 355nm (off-line) are selected for measurements of the stratospheric ozone, and there is a difference of 45nm or 47nm between them. Because of the difference there is a difference in the atmospheric scatterings of the two wavelengths. This can cause some error in the retrieved ozone profile if the aerosol scattering is neglected. This paper is devoted to a study of the effect of the stratospheric aerosol on the ozone solution, and a three-wavelength detection technique is proposed for obtaining the more exact ozone profile and the aerosol profile in the stratosphere.

Qiu, Jinhuan↗

NASA NTRS1991

Atmospheric constituent density profiles from full disk solar occultation experiments

Mathematical methods are described which permit the derivation of the number of density profiles of atmospheric constituents from solar occultation measurements. The algorithm is first applied to measurements corresponding to an arbitrary solar-intensity distribution to calculate the normalized absorption profile. The application of Fourier transform to the integral equation yields a precise expression for the corresponding number density, and the solution is employed with the data given in the form of Laguerre polynomials. The algorithm is employed to calculate the results for the case of uniform distribution of solar intensity, and the results demonstrate the convergence properties of the method. The algorithm can be used to effectively model representative model-density profiles with constant and altitude-dependent scale heights.

Lumpe, J. D.↗

NASA NTRS1991

On representation of fracture profiles by fractional integrals of a Wiener process

An enhancement of the crack diffusion model of brittle fracture is proposed. In the model, certain probabilities are evaluated as averages over the set of all virtual crack paths, and the latter are modeled as realization of a Wiener process. However, commonly observed fracture profiles are smoother. In fact, one can show that their fractal dimension is smaller than the value 3/2 for a Wiener process. Accordingly, it is proposed to represent fracture profiles by graphs of fractional integrals of a Wiener process. This allows one to employ additional fractographic information obtained from fracture profiles, e.g. their fractal dimension, in a predictive formalism, evaluating probabilities of failure.

Kunin, B.↗

NASA NTRS1992

Balmer line profiles for infalling T Tauri envelopes

The possibility that the Balmer emission lines of T Tauri stars arise in infalling envelopes rather than winds is considered. Line profiles for the upper Balmer lines are presented for models with cone geometry, intended to simulate the basic features of magnetospheric accretion from a circumstellar disk. An escape probability treatment is used to determine line source functions in nonspherically symmetric geometry. Thermalization effects are found to produce nearly symmetric H-alpha line profiles at the same time the higher Balmer series lines exhibit inverse P Cygni profiles. The infall models produce centrally peaked emission line wings, in good agreement with observations of many T Tauri stars. It is suggested that the Balmer emission of many T Tauri stars may be produced in an infalling envelope, with blue shifted absorption contributed by an overlying wind. Some of the observed narrow absorption components with small blueshifts may also arise in the accretion column.

Calvet, Nuria↗