15,244 research outputs found
Integrated filter and detector array for spectral imaging
A spectral imaging system having an integrated filter and photodetector array is disclosed. The filter has narrow transmission bands which vary in frequency along the photodetector array. The frequency variation of the transmission bands is matched to, and aligned with, the frequency variation of a received spectral image. The filter is deposited directly on the photodetector array by a low temperature deposition process. By depositing the filter directly on the photodetector array, permanent alignment is achieved for all temperatures, spectral crosstalk is substantially eliminated, and a high signal to noise ratio is achieved
Relationships between dust grain components responsible for observed interstellar extinction and polarization
Ultraviolet extinction properties of interstellar dust are well observed. The amount of extinction measured in the visible (E(B-V)), at the 2200 A feature (E(BUMP)), and in the far ultraviolet (E(1550-V)) are only vaguely correlated indicating that at least 3 fairly independent populations of grains contribute to the overall extinction curve. A search of literature was made for polarimetric observations of the 1415 stars included in the extinction catalog derived from the Astronomical Netherlands Satellite (ANS) data. It was found that about 900 of the stars had at least one unfiltered polarimetric observation, p (%). In addition, 150 stars had calculated values of lambda sub max (wavelength at which maximum polarization occurs). The lambda sub max and p/E(B-V) parameters are discussed
UNITED STATES PERSPECTIVE: SOUTHERN AGRICULTURE AND THE WORLD ECONOMY: THE MULTILATERAL TRADE NEGOTIATIONS
International Relations/Trade,
Transient and diffusion analysis of Hg Cd Te
The solution of the one dimensional planar interface solidification problem is presented. Numerical solutions are applied to experimental solute profiles to determine the effective diffusion constant for Hg Co Te. Progress on the design and construction of a high gradient furnace is reported
P wave velocity variations in the Coso Region, California, derived from local earthquake travel times
Inversion of 4036 P wave travel time residuals from 429 local earthquakes using a tomographic scheme provides information about three-dimensional upper crustal velocity variations in the Indian Wells Valley-Coso region of southeastern California. The residuals are calculated relative to a Coso-specific velocity model, corrected for station elevation, weighted, and back-projected along their ray paths through models defined with layers of blocks. Slowness variations in the surface layer reflect local geology, including slow velocities for the sedimentary basins of Indian Wells and Rose valleys and relatively fast velocities for the Sierra Nevada and Argus Mountains. In the depth range of 3–5 km the inversion images an area of reduced compressional velocity in western and northern Indian Wells Valley but finds no major velocity variations beneath the Coso volcanic field to the north. These results are consistent with a recent study of anomalous shear wave attenuation in the Coso region. Between 5 and 10 km depth, low-velocity areas (7% slow) appear at the southern end of the Coso volcanics, reaching east to the Coso Basin. Numerical tests of the inversion's resolution and sensitivity to noise indicate that these major anomalies are significant and well-resolved, while other apparent velocity variations in poorly sampled areas are probably artifacts. The seismic data alone are not sufficient to uniquely characterize the physical state of these low-velocity regions. Because of the Coso region's history of Pleistocene bimodal volcanism, high heat flow, geothermal activity, geodetic deformation, and seismic activity, one possibility is to link the zones of decreased P velocity to contemporary magmatic activity
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