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Results for “effective changes”

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.

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At least 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Part 1: Classical laser. Part 2: The effect of velocity changing collisions on the output of a gas laser

A classical model for laser action is discussed, in which an active medium consisting of anharmonic oscillators interacts with an electromagnetic field in a resonant cavity. Comparison with the case of a medium consisting of harmonic oscillators shows the significance of nonlinearities for producing self-sustained oscillations in the radiation field. A theoretical model is presented for the pressure dependence of the intensity of a gas laser, in which only velocity-changing collisions with foreign gas atoms are included. A collision model for hard sphere, repulsive interactions was derived. Collision theory was applied to a third-order expansion of the polarization in powers of the cavity electric field (weak signal theory).

Borenstein, M.↗
NASA NTRS1972

The effects of configuration changes on the aerodynamic characteristics of a full-scale mockup of a light twin engine airplane

Wind tunnel tests of a full-scale model of a light twin engine aircraft were conducted. The angle of attack was varied from minus 4 degrees to plus 20 degrees. The sideslip range was plus or minus 8 degrees. Thrust coefficients were 0, 0.20, and 0.44. Tests were made with various nacelle configurations, modes of propeller rotation, orientation of the thrust axis, and airfoil section at Reynolds numbers of 2.96 times one million amd 2.05 times one million.

Fink, M. P.↗
NASA NTRS1976

Effects of environmental changes on marsh vegetation with special reference to salinity

A literature survey primarily concerned with brackish and salt marshes located along the eastern coast of North America and the Gulf Coast was presented. The review concentrated upon the vegetation of the marshes, particularly in regard to distribution, composition, succession, and productivity. Special efforts were made to include major works concerned with the Louisiana and Mississipi coastal marshes. It appears that spring to early summer (weeks 18-34 of the year; April - mid-July) is the best period of time to categorize the communities. It is during this time of the year that the communities appear most stable in regard to species composition. This allows a strong correlation to be drawn between the salinity of the region and the dominant species of the community. As such, this would seem to be best period in which to sample the marsh via air or land for differences in vegetation and salinity.

Smalley, A. E.↗
NASA NTRS1978

Effect of a changing G on the moment of inertia of the earth

A recent value found by Nordtvedt and Will (1972) for the rate of increase of the moment of inertia of earth resulting from a decreasing G is shown to be based on conflicting physical assumptions. The corrected result for this restricted problem yields a rate of change almost twice as large. However, in a realistic treatment, additional purely geophysical causes must also be taken into account, and these imply a decreasing moment of inertia on a scale much outweighing the increase that would occur for any acceptable value of the derivative of G. This accords with the intrinsic acceleration of angular velocity established from ancient-eclipse data.

Lyttleton, R. A.↗
NASA NTRS1979

Effects of compositional changes on the performance of a thermal barrier coating system

Systems consisting of Ni-base bond coatings containing about 16Cr, 6Al, and from 0.15 to 1.08Y (all in wt %) and zirconium oxide layers containing from 4.0 to 24.4Y2O3 were evaluated for suitability as thermal barrier systems for advanced aircraft gas turbine engine components. The evaluations were performed in a cyclic furnace between 990 and 280 C as well as between 1095 and 280 C on solid specimens; in a natural gas-oxygen torch rig between about 1200 and 100 C on solid specimens and up to 1580 C surface temperatures on air-cooled blades; and in a Mach 1.0 burner rig up to 1570 C surface temperatures on air-cooled blades. The data indicate that the best systems consist of combinations involving the Ni-16.4Cr-5.1Al-0.15Y and Ni-17.0Cr-5.4Al-0.35Y bond coatings and the 6.2Y2O3- and 7.9Y2O3- (all in wt %) stabilized zirconium oxide layers.

Stecura, S.↗
NASA NTRS1980

Influence of nonequilibrium radiation and shape change on aerothermal environment of Jovian entry body

Radiative transfer equations are derived under nonequilibrium conditions which include multilevel energy transitions. The nonequalibrium results, obtained with and without ablation injection in the shock layer, are found to be greatly influenced by the temperature distribution in the shock layer. In the absence of ablative products, the convective and radiative heating to the entry body are reduced significantly under nonequilibrium conditions. The influence of nonequilibrium is found to be greater at higher entry altitudes. With coupled ablation and carbon phenolic injection, 16 chemical species are used in the ablation layer for radiation absorption. Equilibrium and nonequilibrium results are compared under peak heating conditions. A 45 degree sphere cone, a 35 degree hyperboloid, and a 45 degree ellipsoid were used to study probe shape change. Results indicate that the shock layer flow field and heat transfer to the body are influenced significantly by the probe shape change. The effect of shape change on radiative heating of the afterbodies is found to be considerably larger for the sphere cone and ellipsoid than for the hyperboloid.

Tiwari, S. N.↗
NASA NTRS1980

A seasonal change in the effect of field-aligned currents at synchronous orbit

The expected signature of substorm field-aligned currents is described for synchronous satellites near 10 deg magnetic latitude. The main effect is a positive D perturbation premidnight and a negative D perturbation postmidnight. This behavior is illustrated for two substorms near the fall equinox. A second pair of substorms taken from winter solstice do not show the expected behavior. The absence of this effect in winter observations is verified statistically by superposed epoch analysis. A simple explanation of this behavior based on the geometry of the plane of magnetic symmetry is presented. During disturbed times at winter solstice a synchronous satellite nominally at 10 deg magnetic latitude is effectively at the magnetic equator. This distortion of the magnetic equator must be considered in future models of the disturbed magnetospheric magnetic field.

Mcpherron, R. L.↗