A geometry package for generation of input data for a three-dimensional potential-flow program

The preparation of geometric data for input to three-dimensional potential flow programs was automated and simplified by a geometry package incorporated into the NASA Langley version of the 3-D lifting potential flow program. Input to the computer program for the geometry package consists of a very sparse set of coordinate data, often with an order of magnitude of fewer points than required for the actual potential flow calculations. Isolated components, such as wings, fuselages, etc. are paneled automatically, using one of several possible element distribution algorithms. Curves of intersection between components are calculated, using a hybrid curve-fit/surface-fit approach. Intersecting components are repaneled so that adjacent elements on either side of the intersection curves line up in a satisfactory manner for the potential-flow calculations. Many cases may be run completely (from input, through the geometry package, and through the flow calculations) without interruption. Use of the package significantly reduces the time and expense involved in making three-dimensional potential flow calculations

Calculation of compressible flow in and about three-dimensional inlets with and without auxiliary inlets by a higher-order panel method

A three dimensional higher order panel method was specialized to the case of inlets with auxiliary inlets. The resulting program has a number of graphical input-output features to make it highly useful to the designer. The various aspects of the program are described instructions for its use are presented

Investigation of the potentialities of photochemical laser systems. Part I - Survey and analysis Final report, 1 Feb. 1966 - 31 Jan. 1967

Photodissociative laser systems used to convert solar radiation to monochromatic coherent emission - excitation mechanisms, spectroscopy of gases absorbing light, and chemical processe

Low-Energy Excitations in an Incipient Antiferromagnet

We present fully self-consistent calculations in the fluctuation exchange approximation for the half-filled Hubbard model in 2D. A non-fermi liquid state evolves with decreasing temperature in this self-consistent model of coupled spin fluctuations and quasiparticles. The mean field phase transition to long-range antiferromagnetic order is suppressed and we find no evidence of a phase transition to long-range magnetic order. We show that the real part of the self-energy at zero energy shows a positive slope and the imaginary part of the self-energy shows a local minimum. The scale of this structure is set by the zero temperature gap in mean field theory. The growth of spin fluctuations is reflected in the evolution of sharply peaked structure in the spin fluctuation propagator around zero energy and ${\bf Q} = (\pi, \pi)$. We present calculations for the Hubbard model in 1D in a two-particle self-consistent parquet approximation. A second moment sum rule suggests that vertex corrections to the self-energy are responsible for the greater accuracy of the parquet approximation as compared to other self-consistent perturbation theories.Comment: To appear in Philosophical Magazin

Absorption of trapped particles by Jupiter's moons

Absorption effects of the four innermost moons in the radial transport equations for electrons and protons in Jupiter's magnetosphere are presented. The phase space density n at 2 R sub J for electrons with equatorial pitch angles less than 69 deg is reduced by a factor of 4.2 x 1000 when lunar absorption is included in the calculation. For protons with equatorial pitch angles less than 69 deg, the corresponding reduction factor is 3.2 x 100000. The effect of the satellites becomes progressively weaker for both electrons and protons as equatorial pitch angles of pi/2 are approached, because the likelihood of impacting a satellite becomes progressively smaller. The large density decreases which we find at the orbits of Io, Europa, and Ganymede result in corresponding particle flux decreases that should be observed by spacecraft making particle measurements in Jupiter's magnetosphere. The characteristic signature of satellite absorption should be a downward pointing cusp in the flux versus radius curve at the L-value corresponding to each satellite

Jupiter's radiation belts: Can Pioneer 10 survive?

Model calculations of Jupiter's electron and proton radiation belts indicate that the Galilean satellites can reduce particle fluxes in certain regions of the inner magnetosphere by as much as six orders of magnitude. Average fluxes should be reduced by a factor of 100 or more along the Pioneer 10 trajectory through the heart of Jupiter's radiation belts in early December. This may be enough to prevent serious radiation damage to the spacecraft

Incipient antiferromagnetism and low-energy excitations in the half-filled two-dimensional Hubbard model

We present single-particle and thermodynamic properties of the half-filled single-band Hubbard model in 2D calculated in the self-consistent fluctuation exchange approximation. The low-energy excitations at moderate temperatures and small $U$ are quasiparticles with a short lifetime. As the temperature is lowered, coupling to evolving spin fluctuations leads to the extinction of these quasiparticles, signaled by a weak pseudogap in the density of states and by a positive slope in Re $\Sigma ({\bf k}_F, \varepsilon)$ and a local maximum in $|$Im $\Sigma ({\bf k}_F, \varepsilon)|$ at $\varepsilon = 0$. We explain these results using a simple spin-fluctuation model.Comment: submitted to Physical Review Letters 9 March 199