16,575 research outputs found
Electronic equipment, systems, and techniques: A compilation
Electronic circuits with specialized computer applications and control circuits are presented. Patent information is included
Evaluation of the potential of one to three SEASAT-SMMR channels in retrieving sea surface temperature
The scanning multichannel microwave radiometer (SMMR) aboard the SEASAT satellite measured emitted radiation in both horizontal and vertical polarizations at microwave frequencies of 6.6, 10.69, 18.0, 21.0 and 37.0 GHz. Retrieval algorithms, for sea surface temperature (SST) determination, from subsets of one to three SMMR channels are obtained by a two step statistical technique. The technique first selects the best subsets of a given size defined by an R2 criterion (coefficient of determination), of a given size by the application of an efficient 'leaps and bounds' technique on a statistical data base. It then performs a regression analysis on the selected subsets. The statistical data base employed a large (600) set of seasonally and geographically diverse atmospheric and surface parameters for radiative transfer calculations. The results of the study of one to three channel subset retrieval algorithms indicate the possibility of using 6.6V, 6.6H and 18V channels for SST determination from SEASAT-SMMR data
Interacting galaxies and cosmological parameters
We propose a (physical)-geometrical method to measure the present rates of
the density cosmological parameters for a Friedmann-Lemaitre universe. The
distribution of linear separations between two interacting galaxies,when both
of them undergo a first massive starburst, is used as a standard of length.
Statistical properties of the linear separations of such pairs of
``interactivated'' galaxies are estimated from the data in the Two Degree Field
Galaxy Redshift Survey. Synthetic samples of interactivated pairs are generated
with random orientations and a likely distribution of redshifts. The resolution
of the inverse problem provides the probability densities of the retrieved
cosmological parameters. The accuracies that can be achieved by that method on
matter and cosmological constant densities parameters are computed depending on
the size of ongoing real samples. Observational prospects are investigated as
the foreseeable surface densities on the sky and magnitudes of those objects.Comment: 8 pages, 6 figure
Near-Optimal Cayley Expanders for Abelian Groups
We give an efficient deterministic algorithm that outputs an expanding generating set for any finite abelian group. The size of the generating set is close to the randomized construction of Alon and Roichman [Alon and Roichman, 1994], improving upon various deterministic constructions in both the dependence on the dimension and the spectral gap. By obtaining optimal dependence on the dimension we resolve a conjecture of Azar, Motwani, and Naor [Azar et al., 1998] in the affirmative. Our technique is an extension of the bias amplification technique of Ta-Shma [Ta-Shma, 2017], who used random walks on expanders to obtain expanding generating sets over the additive group of ???. As a consequence, we obtain (i) randomness-efficient constructions of almost k-wise independent variables, (ii) a faster deterministic algorithm for the Remote Point Problem, (iii) randomness-efficient low-degree tests, and (iv) randomness-efficient verification of matrix multiplication
Development of carbon dioxide laser doppler instrumentation detection of clear air turbulence
The analytical, experimental, and developmental aspects of an airborne, pulsed, carbon dioxide laser-optical radar system are described. The laser detects clear air turbulence and performs Doppler measurements of this air-motion phenomenon. Conclusions and recommendations arising from the development of the laser system are presented
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