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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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Diffused optical waveguides are studied using the modal and the ray tracing approach, with an emphasis on the case of a hollow waveguide with diffuse cladding. The properties of the guided modes are investigated in detail. The applications of these structures to optical circuits, integrated optics lasers and capillary gas lasers are discussed.
Lighting is one of the most critical aspects in plant production and environmental research with plants. Much research has been repeated on the effect of light intensity, spectral distribution of light and lighting cycle, but comparatively little research done on the effect of lighting direction on the growth, development and morphology of plants. When plants are grown with lamps above, light is directed downward to the plants. Downward or overhead lighting is utilized in almost all cases. However, downward lighting does not always give the best result in terms of lighting efficiency, growth, development and morphology of plants. In the present study, a sideward lighting system was developed using diffusive optical fiber belts. More higher quality tissue-cultured transplants could be produced in a reduced space with the sideward lighting system than with a downward lighting system. An application of the sideward lighting system using diffusive optical fiber belts is described and the advantages and disadvantages are discussed.
Optical diffusion method of measuring turbulence in air flows and flames
In solar energy utilization studies, correct measurements of flux arriving at other angles to optical axis must be given. Developed device (Cosine diffuser) significantly reduces measurement errors. In combination of radiation transmitter and diffuser co-operating with collimated optical instrument, relative aperture of instrument is filled.
Digital Speckle Pattern Interferometry (DSPI) is a well-established method for the measurement of diffuse objects in experimental mechanics. DSPIs are phase shifting interferometers. Three or four bucket temporal phase shifting algorithms are commonly used to provide phase shifting. These algorithms are sensitive to vibrations and can not be used to measure large optical structures far away from the interferometer. In this research a simultaneous phase shifted interferometer, PhaseCam product of 4D Technology Corporation in Tucson Arizona, is modified to be a Simultaneous phase shifted Digital Speckle Pattern Interferometer (SDSPI). Repeatability, dynamic range, and accuracy of the SDSPI are characterized by measuring a 5 cm x 5 cm carbon fiber coupon.
This article reviews diffuse optical brain imaging, a technique that employs near-infrared light to non-invasively probe the brain for changes in parameters relating to brain function. We describe the general methodology, including types of measurements and instrumentation (including the tradeoffs inherent in the various instrument components), and the basic theory required to interpret the recorded data. A brief review of diffuse optical applications is included, with an emphasis on research that has been done with psychiatric populations. Finally, we discuss some practical issues and limitations that are relevant when conducting diffuse optical experiments. We find that, while diffuse optics can provide substantial advantages to the psychiatric researcher relative to the alternative brain imaging methods, the method remains substantially underutilized in this field.
Stabilization of flat diffusion flames - optical methods for analysis of structure at velocities up to blow-out
Goddard High Resolution Spectrograph (GHRS) observations at 3.5 km/s resolution reveal several new weak unidentified interstellar absorption lines in the ultraviolet spectrum of zeta Ophiuchi. The unidentified line at 1369.13 A has the appearance and characteristics of a weak diffuse interstellar band (DIB). The line has a smooth profile similar to many optical diffuse interstellar bands (i.e., a shallow asymmetric profile), it is clearly broader than identified interstellar lines near it in wavelength, and its full width at half maximum in ergs is comparable to the widths of the weak optical DIBs. The asymmetric profile cannot be attributed to blended absorption from diffuse clouds at different velocities; at this resolution the two principal cloud complexes on the sight line at heliocentric velocities of -27 and -15 km/s are clearly separated. We compare this unidentified absorption feature to identified interstellar atomic and molecular absorption lines and optical DIBs observed on the zeta Oph and xi Per sight lines, and we conclude that it is reasonable to suggest that this absorption feature might be a DIB. This is not a unique interpretation however; the unidentified line could alternatively be due to gas in the zeta Oph H II region or a blend of unknown neutral atomic or molecular absorption lines.
A technique was devised which uses remotely sensed spectral radiances from the sea to assess the optical diffuse attenuation coefficient, K (lambda) of near-surface ocean water. With spectral image data from a sensor such as the coastal zone color scanner (CZCS) carried on NIMBUS-7, it is possible to rapidly compute the K (lambda) fields for large ocean areas and obtain K "images" which show synoptic, spatial distribution of this attenuation coefficient. The technique utilizes a relationship that has been determined between the value of K and the ratio of the upwelling radiances leaving the sea surface at two wavelengths. The relationship was developed to provide an algorithm for inferring K from the radiance images obtained by the CZCS, thus the wavelengths were selected from those used by this sensor, viz., 443, 520, 550 and 670 nm. The majority of the radiance arriving at the spacecraft is the result of scattering in the atmospheric and is unrelated to the radiance signal generated by the water. A necessary step in the processing of the data received by the sensor is, therefore, the effective removal of these atmospheric path radiance signals before the K algorithm is applied. Examples of the efficacy of these removal techniques are given together with examples of the spatial distributions of K in several ocean areas.
Models of the faint galaxy contribution to the diffuse extragalactic background light are presented, which are consistent with current data on faint galaxy number counts and redshifts. The autocorrelation function of surface brightness fluctuations in the extragalactic diffuse light is predicted, and the way in which these predictions depend on the cosmological model and assumptions of biasing is determined. It is confirmed that the recent deep infrared number counts are most compatible with a high density universe (Omega-0 is approximately equal to 1) and that the steep blue counts then require an extra population of rapidly evolving blue galaxies. The faintest presently detectable galaxies produce an interesting contribution to the extragalactic diffuse light, and still fainter galaxies may also produce a significant contribution. These faint galaxies still only produce a small fraction of the total optical diffuse background light, but on scales of a few arcminutes to a few degrees, they produce a substantial fraction of the fluctuations in the diffuse light.
Models of ionized interstellar C60 predict a strong transition in the 1.2 micrometer region, and two candidate bands have recently been detected in reddened stars. We have searched for the stronger of these bands (at 13175 A) in the Taurus dark cloud complex, to determine its response to the dark-cloud environment. None of the three lines of sight studied (two near the cloud surface, one reaching A(sub V) greater than 20(sup m)) give rise to a detectable band; in one case the equivalent width is a factor of order three below that predicted. Since such behaviour is also shown by the optical Diffuse Interstellar Bands, we suggest that the 13175 A band is a genuine DIB, but we caution against an automatic interpretation in terms of an ionic carrier.
We present 11.7 and 8.8 micron images of the central region of the Ney-Allen Nebula In Orion which reveal mid-infrared counterparts to the ionized globules previously discovered by optical and radio observations. The 0.5 arcsec full width at half maximum (FWHM) resolution images also reveal several arc-shaped structures which are associated with the compact sources. Each of the arcs points toward theta(sup 1) Ori C, providing further evidence for the strong-effects of the intense radiation and wind from this star on the central Orion Nebula. Low-resolution spectra of a few of these condensations and arcs are similar to spectra of the diffuse, optically thin silicate dust observed throughout the region. Photometry of one of the condensations, however, indicates that is cooler than the others. Simple momentum-balance arguments indicate that dust in the arcs could originate in the outflow from the compact sources and flow outward until stopped by the stellar wind and radiation pressure from theta(sup 1) Ori C.
A double-chambered gas proportional counter was constructed to detect and identify solar wind ions after acceleration by a high voltage power supply. It was determined that the best method of detecting deuterium in the solar wind is to use a tritium target as proposed for IMP H and J. The feasibility of detecting H(+) and He(+) ions of interstellar origin is considered. A program is described to carry out ground-based astronomical observations of faint, diffuse optical emission lines from interstellar gas. Hydrogen and oxygen emission lines from galactic sources were detected and the galactic and geocoronal H alpha and beta lines were clearly resolved.
Photographic and television observations made during the third flight of the Space Shuttle in March 1982 reveal the presence of a diffuse optical emission surrounding surfaces of the vehicle exposed to the atmosphere in the ram direction. The line of sight intensity of this emission is comparable to that of airglow emissions seen at the limb of the earth and competes with the brightness of stars seen within the field of view of the photographic and TV cameras. The glow emission appears to be a manifestation of an atmosphere-vehicle interaction. Light from vehicle thruster operations was also seen, as well as the optical emissions resulting from the operation of a 100 mA electron beam.
Einstein Observatory instruments were used to survey the generic properties of LMC supernova remnants (SNR). The study covered the diffuse optical bar, the 30 Dor nebula, the surrounding H I cloud, and a high fraction of the spiral arms. Twelve SNRs were identified as X-ray sources and two SNR, N157B and 0540 - 69.3, were located from radio emissions. Filamentary H-alpha emissions also revealed five other objects. X-ray intensity data indicated that density levels of the matter surrounding SNR decrease with SNR diameter. The data suggest that Sedov models for SN may not be accurate for LMC SN, which exhibit too great a luminosity scatter in the surrounding interstellar material. The emissions may be accounted for by ejecta from the SN or by multiphase interstellar material.
The X-ray source, E2000 + 223, serendipitously discovered by the Einstein Observatory, has been tentatively identified with an old nova shell. Spectroscopic observations of the diffuse optical counterpart show a heavily reddened continuum with bright forbidden S II emission lines at double lambda 6716, 6732. Radio observations at the VLA show a weak (about 1.2 mJy) extended radio source, with a nonthermal spectrum, concident with the optical emission. The observations can be best explained by assuming the object is an old nova which erupted sometime in the eighteenth or nineteenth century, similar to GK Per (Nova 1901) but at a distance of 1.4 kpc.
Self-, N2-, O2-, H2-, Ar-, and He-broadening coefficients, pressure shifts, and integrated intensities have been measured for most transitions in the Q branch of the nu3 fundamental band of methane using a difference-frequency laser spectrometer. A systematic dependence of the broadening coefficients on the tetrahedral symmetry species and order index is observed with striking similarities for N2, O2, and Ar and for H2 and He buffer gases. Comparison with earlier measurements on other bands and branches of methane indicates very little vibrational, branch, or carbon isotope dependence. Dicke narrowing is evident at intermediate pressures, yielding an average narrowing coefficient and an optical diffusion constant for each gas mixture.
The detection of UV absorption, 21 cm, H alpha and other diffuse optical emission lines from gas up to ten kiloparsecs above the plane of the Milky Way and other galaxies provides the first, opportunity to probe the rotational properties of the ionized "atmospheres" of galaxies. This rotation has implications for our understanding of the Galactic gravitational potential, angular momentum transport in the Galactic disk, and the maintenance of a Galactic dynamo. The available evidence indicates that gas rotates nearly cylindrically up to a few kiloparsecs. This is in contrast to the expectation that there should be a significant gradient in rotation speed as a function of height assuming a reasonable mass model for the Galaxy. For example, for a vertical cut at galactocentric radius R = 5 kpc in NGC 891 by Rand, the rotation speed is observed to drop by approximately 30 kilometers per second from z = 1 to 5 kpc and is expected to drop by 80 kilometers per second. Magnetic tension forces may resolve this discrepancy. Other possibilities will be examined in the near future.