SEARCH · Search NASA
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.
In the present paper, the theory of parametric upconversion is extended to describe the mixing of two focused optical beams with unequal confocal parameters. The results obtained apply particularly well to the case where focusing of one input beam is limited to physical constraints, e.g., damage. The effects of phase matching, walk-off, and diffraction are examined.
Two large, complex deep-focus earthquakes are analyzed, using body waves, to determine the relative locations and equivalent forces of the component events. Details of the source mechanism determination are given, with special emphasis on the means of comparing results for double-couple and more general models. The formalism includes a description of a method for calculating the confidence ellipses around the principal axes of the moment tensor. An interpretation of the results suggests that the mechanism of deep-focus earthquakes is controlled by the buoyancy of the slab and the change in viscosity at the 650 km discontinuity.
The surface density of quasars brighter than a given threshold is enhanced near a galaxy by the gravitational focusing of light from those quasars that are nearly co-aligned with individual stars in the galaxy halo. The focusing can intensify and make detectable quasars which would otherwise have been below the threshold. If galaxies have massive haloes of macroscopic objects then the resulting enhancement could explain the apparent association between quasars and galaxies with discrepant redshifts found in a statistical analysis. Therefore, such quasar-galaxy associations need not require the abandonment of the cosmological interpretation of the redshift.
The performance of a ground-prototype of an apparatus for recycling isoelectric focusing was evaluated in an effort to provide technology for large scale purification of peptide hormones, proteins, and other biologicals. Special emphasis was given to the effects of gravity on the function of the apparatus and to the determination of potential advantages deriveable from its use in a microgravity environment. A theoretical model of isoelectric focusing sing chemically defined buffer systems for the establishment of the pH gradients was developed. The model was transformed to a form suitable for computer simulations and was used extensively for the design of experimental buffers.
An automatic focusing system designed around an ultrasonic range measurement is described. Besides maintaining the focus, subject distance is a by-product which could lighten the NOVA computational effort. An automatic head tracking unit is also discussed. It is intended to reduce the search time required when track is lost. An X-Y ultrasonic measurement is also made in this design to control the deflection mirrors.
An abbreviated version of a mathematical model of the steady state in isoelectric focusing is presented. Details of the mathematical transformations leading to a model suitable for computer implementation and numerical solution are given in the Appendix. The model describes the structure of concentration, pH, conductivity and potential gradients arising from the focusing of electrochemically defined ampholytes. Some of the results of computer simulations of two and three component systems are of particular interest to the experimentalist and are presented together with experimental validation of this model.
Detector using two whirling wires measures focus of beam in electronbeam welder. Multiple-wire beam-sampling method provides for simple nullmeter focus indication easily controlled by operator. Detector not only operates at high beam currents but eliminates need for oscilloscope.
The stationary self-focusing of the Gauss wave beam is considered in a nonhomogeneous medium in the case of local nonlinearity. Equations of the aberrationless approximation for the beam width, the field on the beam axis and the refraction factor are integrated on a computer. Self-focusing in dependence of the nonlinearity level and initial divergence, the dissipation, the length of nonhomogeneity of the dielectric permittivity nondisturbed by a beam, and the diffraction parameter are investigated.
The Mars Orbiter Water Mission (MOWM) is discussed as an example of a low-cost, low-risk focused-science Mars mission which might be implemented in the near term within recently imposed fiscal constraints. MOWM is designed to act as a follow-on to the Viking results in the areas of comparative climatology and water, carbon dioxide and dust inventories. The STS-compatible space vehicle would be based on proven earth-orbiting satellite hardware, fulfilling requirements for both spinning and despun components, operation with nonoptimum solar cell orientation, PAM-A upper stage compatibility, and data storage for delayed transmission. Study results have shown the technical and economic feasibility of missions based on any of four submitted designs which meet these requirements, and of low-cost, well-focused science objective Mars missions in general.
The potential of space electrophoresis is conditioned by the fact that all electrophoretic techniques require the suppression of gravity-caused convection. Isoelectric focusing (IEF) is a powerful variant of electrophoresis, in which amphoteric substances are separated in a pH gradient according to their isoelectric points. A new apparatus for large scale IEF, utilizing a recycling principle, has been developed. In the ground-based prototype, laminar flow is provided by a series of parallel filter elements. The operation of the apparatus is monitored by an automated array of pH and ultraviolet absorption sensors under control of a desk-top computer. The apparatus has proven to be useful for the purification of a variety of enzymes, snake venom proteins, peptide hormones, and other biologicals, including interferon produced by genetic engineering techniques. In planning for a possible space apparatus, a crucial question regarding electroosmosis needs to be addressed To solve this problem, simple focusing test modules are planned for inclusion in an early Shuttle flight.
The focused parabolic antenna has far field pattern characteristics in the radiating near field region. Therefore, it can provide fine resolutions in the across range dimensions. The technique of focusing the parabolic antenna is discussed and applied to a 2-1/2 foot parabolic antenna at X-band. The results of the pattern measurements at various ranges from 2.8 m to 5 m are provided.
An improved technique to determine the subreflector translations required to properly focus a Cassegrainian antenna, under gravity loading, at a full range of elevation angles, is presented. This technique is applied to the 34-m antenna configuration installed at stations DSS-15 (Goldstone, California) and DSS-45 (Australia). The subreflector lateral and axial translations, to be stored into the antenna-control systems, are computed and tabulated. The relationships that govern the main parameters are also presented for future subreflector focusing analysis under wind and thermal loadings.
Recent measurements of the energy spectrum of the plasma-focus-generated deuteron beam yield as spectrum of the form N(E)=(approx.) E to the -2.7 for 1MeV E 13 MeV. Other measurements show that the beta 1 electron beam which is generated simultaneously with the deuteron beam is interrupted into segments of spacing 25ps and duration approximately 4ps. A stuttering-electro-magnetic-ram (ser) model of the plasma focus in proposed which is similar to Raudorf's electronic ram which produces a similar spectrum for an electron beam for 1Mev E 10MeV. It is proposed that the cosmic ray spectrum and the giganic galactic jets are both generated by ser action near the centers of active galaxies.
A test method particularly suited for X-ray telescopes was evaluated experimentally. The method makes use of a focused ring formed by an annular aperture when using a point source at a finite distance. This would supplement measurements of the best focus image which is blurred when the test source is at a finite distance. The telescope used was the Technology Mirror Assembly of the Advanced X-ray Astrophysis Facility (AXAF) program. Observed ring image defects could be related to the azimuthal location of their sources in the telescope even though in this case the predicted sharp ring was obscured by scattering, finite source size, and residual figure errors.
Some remote sounding applications require utilization of interference filters with very high out-of-band rejection (OBR) performance. In this paper, the advantages to be gained in achieving high OBR by the use of two serially ganged interference filters mounted in a wedge configuration near a focus are discussed. Degradation of OBR due to scattering effects is examined, and a quantitative technique to estimate such effects in dual wedged filters mounted at a focus is presented. An approach to the design of filter elements to be used in the dual wedged configuration is given that accounts for scatter. An application of this design approach to the CLAES 10.81 micron filter is described.
The problem of designing a computerized experiment monitoring system for use in a space station or elsewhere is examined. It is shown that the essential challenge of such a system - attaining a reasonable expected running time - can be attacked using the concept of focus of attention and by exploiting parallelism. The use of the Contract Net Protocol for the latter purpose is discussed. The use of ideas from information science to help focus a programs's efforts on those computations likely to bring results is addressed, and the incorporation of those ideas into a design in order to aid the system in deciding upon the best course of action is considered.
The objective of the program was the definition and development of optimal methods for electrophoretic separations in microgravity. The approach is based on a triad consisting of ground based experiments, mathematical modeling and experiments in microgravity. Zone electrophoresis is a rate process, where separation is achieved in uniform buffers on the basis of differences in electrophoretic mobilities. Optimization and modeling of continuous flow electrophoresis mainly concern the hydrodynamics of the flow process, including gravity dependent fluid convection due to density gradients and gravity independent electroosmosis. Optimization of focusing requires a more complex model describing the molecular transport processes involved in electrophoresis of interacting systems. Three different focusing instruments were designed, embodying novel principles of fluid stabilization. Fluid stability was achieved by: (1) flow streamlining by means of membrane elements in combination with rapid fluid recycling; (2) apparatus rotation in combination with said membrane elements; and (3) shear stress induced by rapid recycling through a narrow gap channel.
A static plasma grating has been demonstrated experimentally (Wu et al., 1988) in a large-optical-cavity focused-ion-beam-distributed-Bragg-reflector (FIB-DBR) GaAlAs/GaAs laser diode. The grating is formed by implanting stripes of dopants with a focused ion beam. The dopants ionize to form periodic fluctuations in the carrier concentration which, through the Kramers-Kronig relations, form an index grating. A model of the grating strength for optimizaton of the laser design is developed and presented. The computed results show that the coupling coefficient k can be increased by more than an order of magnitude over the 15/cm experimentally. Therefore, FIB-DBR or FIB-distributed-feedback (DFB) lasers with performance comparable to that of conventional DBR (or DFB) lasers can be expected.