Sum rules for variational wavefunctions.
Sum rule properties of finite set of wave functions obtained from application of variational principles to basis functions linear combinations
Dalgarno, A.↗
SEARCH · Engineering Papers
Results for “functional properties”
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.
Elastic properties of a micro-breccia, igneous rock and lunar fines from Apollo 11 mission
Micro-breccia, igneous rocks and lunar fines elastic properties at ambient conditions and as function of pressure, discussing near surface mare region models
Anderson, O. L.↗
Effects of electrostatic rocket material deposited on solar cells.
If solar arrays on solar-electric spacecraft protrude into the exhaust hemisphere of the electric thrusters, they will receive fluxes (usually small) of both propellant and accelerator grid atoms. Unlike propellants, grid materials have low vapor pressures and will not reevaporate. An analysis is presented of degradation in the optical, thermal, and electrical performance of solar cells resulting from thin deposits of grid material (aluminum and molybdenum) on various array surfaces. The classical optical theory of thin films, heat balance equations, and a typical relationship for solar cell efficiency vs temperature are used to compute curves showing optical properties, temperature, and power output as functions of film thickness. The results compare favorably with available experimental data. It is shown that a few monolayers of metal deposition on the illuminated surface will seriously degrade cell performance. A means of estimating the arrival rate of these materials is provided.
Kemp, R. F.↗
Signal sequence detection given noisy, common background image sets.
The optimum processing (likelihood functional) is found for a set of M images, each the sum of a member of a signal sequence due to an object to be detected and its parameters estimated, a sample function of a noise field, and a sample function of a common background field. The noise fields are independent, zero mean, white Gaussian fields, all independent of the background field. The latter is assumed to be either (1) completely unknown or of known mean and covariance functions with (2) a certain fluctuation property or (3) Gaussian. Three equivalent forms of the optimum processing are found: (1) a summation of generalized matched filterings of the images, (2) a summation of matched filtering of certain generalized differences of the images, and (3) a summation of 'estimator-correlator' type filterings. The detection performance and optimum signal/image selection under the Neyman-Pearson criterion is given, and is shown that optimum processor and signal design can completely eliminate any effect of the background on detectability.
Harger, R. O.↗
Nonstationary atmospheric boundary layer turbulence simulation
Report on a new and general technique for simulating atmospheric turbulence-like random processes which are statistically homogeneous along the horizontal and nonhomogeneous along the vertical. This technique is general in the sense that it can be used for a broad class of similar problems. Like the other presently available schemes, the techniques presented are based on the Dryden hypothesis and Taylor's frozen eddy hypothesis; however, they go a step further by utilizing certain self-similarity properties of the Dryden spectral density function which permits the development of height invariant filters. These filters are in turn used to generate vertically homogeneous (statistically) random processes from which turbulence at any specified level in the boundary layer can be simulated, thus facilitating the simulation of a nonstationary turbulence process along the flight path of an aircraft during take-off or landing.
Fichtl, G. H.↗
High purity silica reflective heat shield development
A high purity slip cast silica material has been developed for use as a reflective heat shield for entries into the atmospheres of the outer planets. The several stages leading to the development of this material are described and details of raw material selection, preparation of the slip material and casting techniques are discussed. Optical (reflectance and transmittance), physical and chemical properties measurements were performed as a function of the important material and processing variables. Performance analysis of a reflective heat shield fabricated from the high purity silica slip shows that approximately 90 percent of the radiant bow shock energy incident on the heat shield during entry into the atmosphere of Jupiter will be reflected.
Blome, J. C.↗
Graphite fiber reinforced thermoplastic resins
The results of a program designed to optimize the fabrication procedures for graphite thermoplastic composites are described. The properties of the composites as a function of temperature were measured and graphite thermoplastic fan exit guide vanes were fabricated and tested. Three thermoplastics were included in the investigation: polysulfone, polyethersulfone, and polyarylsulfone. Type HMS graphite was used as the reinforcement. Bending fatigue tests of HMS graphite/polyethersulfone demonstrated a gradual shear failure mode which resulted in a loss of stiffness in the specimens. Preliminary curves were generated to show the loss in stiffness as a function of stress and number of cycles. Fan exit guide vanes of HMS graphite polyethersulfone were satisfactorily fabricated in the final phase of the program. These were found to have stiffness and better fatigue behavior than graphite epoxy vanes which were formerly bill of material.
Navak, R. C.↗
A scaling law for energy transfer by inelastic electron-molecule collisions in mixtures
The equation governing the electron energy distribution in the presence of a spatially uniform electric field in a weakly ionized gas was reformulated into an integral equation for the logarithmic slope of the distribution function. For gas mixtures in which the dominant electron energy loss mechanism is by vibrational excitation of the molecules, this equation is suitable for approximate analysis and exact numerical solution by iteration. Superelastic collisions are easily included in this formulation, and do not seriously effect the convergence of the numerical scheme. The approximate analytical results are only qualitatively correct, but suggest appropriate parameters which correlate the exact numerical results very well. The distribution function as well as certain gross properties such as net energy transfer into vibration, mean energy, and drift velocity depend primarily on a single nondimensional parameter involving only E/N and the cross sections.
Bienkowski, G. K.↗
Stratospheric Aerosol Measurement (SAM 2) experiment
The Stratospheric Aerosol Measurement 2 (SAM 2) is used to map the concentration and optical properties of stratospheric aerosols as a function of altitude, latitude, and longitude. The vertical distribution of the stratospheric aerosols in the polar regions of both hemispheres is provided.
Mccormick, M. P.↗
Radiation effects in GaAs AMOS solar cells
The results of radiation damage produced in AMOS (Antireflecting-Metal-Oxide-Semiconductor) cells with Sb2O3 interfacial oxide layers by 1-MeV electrons are presented. The degradation properties of the cells as a function of irradiation fluences were correlated with the changes in their spectral response, C-V, dark forward, and light I-V characteristics. The active n-type GaAs layers were grown by the OM-CVD technique, using sulfur doping in the range between 3 x 10 to the 15th power and 7 x 10 to the 16th power/cu cm. At a fluence of 10 to the 16th power e/sq cm, the low-doped samples showed I sub sc degradation of 8% and V sub oc degradation of 8%. The high-doped samples showed I sub sc and V sub oc degradation of 32% and 1%, respectively, while the fill factor remained relatively unchanged for both. AMOS cells with water vapor-grown interfacial layers showed no significant change in V sub oc.
Shin, B. K.↗
A cloud physics radiometer
The paper describes the design features and capabilities of a seven-channel cloud physics radiometer (CPR) for remote sensing of cloud properties. The CPR channel characteristics and functions are tabulated and diagrammed. Each of the first three channels utilizes a photo-multipler detector, with the high-voltage power supply integrated with the tube into a single unit. In operation a heater is used to keep the optics temperature at or above 273 K and this temperature is constantly monitored. The last four channel detectors and filters are all cooled to the temperature of liquid nitrogen. The inclined scanning mirror rotates at a rate of 3.48 rps. Registration pulses are triggered and recorded as the mirror enters and leaves the + or -45 deg earth observation region. The ice-cloud, water cloud, snow discriminator detector has worked quite well in general. Interesting radiometer data have been obtained and their analysis is under way. The combination of the CPR and the Cloud Lidar System will make possible sophisticated remote sensing cloud studies.
Kyle, H. L.↗
Dual-spin spacecraft nutation control using articulated payloads
A technique is presented for achieving active control of nutation on a dual-spin spacecraft with an articulated payload through use of the payload's control system. Using the Orbiting Solar Observatory (OSO)-8 as an illustration, the closed-form solution to the nutation/control system dynamic interaction is presented. Control system design criteria are developed which establish the basic stability of the interaction. Design procedures are described to achieve the most effective nutation damping. Limitations on the amount of damping which can be achieved are characterized as functions of spacecraft and payload mass properties and servo-design parameters. The design techniques presented are verified through a series of on-orbit tests recently conducted on the OSO-8 spacecraft.
Slafer, L. I.↗
Field research on the spectral properties of crops and soils, volume 1
The experiment design, data acquisition and preprocessing, data base management, analysis results and development of instrumentation for the AgRISTARS Supporting Research Project, Field Research task are described. Results of several investigations on the spectral reflectance of corn and soybean canopies as influenced by cultural practices, development stage and nitrogen nutrition are reported as well as results of analyses of the spectral properties of crop canopies as a function of canopy geometry, row orientation, sensor view angle and solar illumination angle are presented. The objectives, experiment designs and data acquired in 1980 for field research experiments are described. The development and performance characteristics of a prototype multiband radiometer, data logger, and aerial tower for field research are discussed.
Bauer, M. E.↗
Ion temperature troughs induced by a meridional neutral air wind in the night-time equatorial topside ionosphere
A mathematical model was constructed to calculate O(+) and H(+) concentrations, field-aligned velocities, and electron temperatures in the night-time equatorial topside ionosphere. The model is used to establish the ability of F-region neutral air winds to produce observed ion temperature distributions, and to study the properties of ion temperature troughs as functions of altitude, latitude, and ionospheric composition. The O(+) - H (+) transition height represents an altitude limit above which the ion cooling from adiabatic expansion of the plasma is very small; the northern and southern edges of the ion temperature troughs are restricted to the limiting dip altitudes determined by magnetic field line geometry and by the functional form of the F-region neutral wind velocity.
Bailey, G. J.↗
Turbulence in sound excited jets - Measurements and theory
The mechanisms by which the turbulent structure of an axisymmetric jet is modified by the presence of an acoustic excitation are examined. A model is described in which the excitation triggers instability waves at the jet exit. As these waves propagate downstream they extract energy from the mean flow and transfer it to the random turbulence. This results in an increase of the random turbulence levels and a more rapid mixing and spreading for the jet. Models are introduced for the Reynolds stress and the 'wave-induced stress'. It is shown that at high frequencies the presence of the instability wave may reduce the random turbulence levels. Numerical calculations are presented for both the radial and axial variation in the time-averaged properties of the flow as a function of excitation conditions. The calculations are compared with measurements of fluctuating velocity and pressure in a round jet with a Reynolds number of 375,000, based on jet diameter and exit velocity.
Morris, P. J.↗
Photothermal characterization of encapsulant materials for photovoltaic modules
A photothermal test matrix and a low cost testing apparatus for encapsulant materials of photovoltaic modules were defined. Photothermal studies were conducted to screen and rank existing as well as future encapsulant candidate materials and/or material formulations in terms of their long term physiochemical stability under accelerated photothermal aging conditions. Photothermal characterization of six candidate pottant materials and six candidate outer cover materials were carried out. Principal products of photothermal degradation are identified. Certain critical properties are also monitored as a function of photothermal aging.
Liang, R. H.↗
Measuring and Modeling of the Dielectric Properties and Attenuation of Vegetation
The dielectric properties and attenuation of vegetation was measured and modeled. The purpose was to: (1) measure the microwave dielectric properties of vegetation material as a function of moisture content and microwave frequency; (2) develop dielectric mixing models for the vegetation-water mixture; (3) develop a model for the loss factor of a vegetation canopy; (4) relate the results of (1) and (2) to (3); and (5) test the model in (3) against direct canopy transmission measurements.
F Ulaby↗
Microwave dielectric properties of plant materials
Three waveguide transmission systems covering the 1-2, 3.5-6.5, and 7.5-8.5 GHZ bands were used to measure the dielectric properties of vegetation material as a function of moisture content and microwave frequency. The materials measured included, primarily, the leaves and stalks of corn and wheat. Dielectric measurements also were made of the liquid included in the vegetation material after it was extracted from the vegetation by mechanical means. The extracted liquids were found to have an equivalent NaCl salinity of about 10 per mil, which can have a significant effect on the dielectric loss at frequencies below 5 GHz. The results of attempts to model the dielectric constant of the vegetatioon-water mixture in terms of the dielectric constants and volume fractions of its constituent parts (i.e., bulk vegetation, air, bound water, and free water) are discussed. Additionally, measurements of the temporal variations in the total attenuation at 10.2 GHz are presented for a corn canopy and a soybean canopy.
Ulaby, F. T.↗