16,756 research outputs found
CO2 laser waveguiding in proton implanted GaAs
Surface layers capable of supporting optical modes at 10.6 microns have been produced in n-type GaAs wafers through 300 keV proton implantation. The dominant mechanism for this effect appears to be free carrier compensation. Characterization of the implanted layers by analysis of infrared reflectivity spectra and synchronous coupling at 10.6 microns produced results in good agreement with elementary models. These results of sample characterization by infrared reflectivity and by CO2 laser waveguiding as implanted are presented and evaluated
Evaluating some computer enhancement algorithms that improve the visibility of cometary morphology
The observed morphology of cometary comae is determined by ejection circumstances and the interaction of the ejected material with the local environment. Anisotropic emission can provide useful information on such things as orientation of the nucleus, location of active areas on the nucleus, and the formation of ion structure near the nucleus. However, discrete coma features are usually diffuse, of low amplitude, and superimposed on a steep intensity gradient radial to the nucleus. To improve the visibility of these features, a variety of digital enhancement algorithms were employed with varying degrees of success. They usually produce some degree of spatial filtering, and are chosen to optimize visibility of certain detail. Since information in the image is altered, it is important to understand the effects of parameter selection and processing artifacts can have on subsequent interpretation. Using the criteria that the ideal algorithm must enhance low contrast features while not introducing misleading artifacts (or features that cannot be seen in the stretched, unprocessed image), the suitability of various algorithms that aid cometary studies were assessed. The strong and weak points of each are identified in the context of maintaining positional integrity of features at the expense of photometric information
Radar data processing and analysis
Digitized four-channel radar images corresponding to particular areas from the Phoenix and Huntington test sites were generated in conjunction with prior experiments performed to collect X- and L-band synthetic aperture radar imagery of these two areas. The methods for generating this imagery are documented. A secondary objective was the investigation of digital processing techniques for extraction of information from the multiband radar image data. Following the digitization, the remaining resources permitted a preliminary machine analysis to be performed on portions of the radar image data. The results, although necessarily limited, are reported
Dynamical quantum phase transition of a two-component Bose-Einstein condensate in an optical lattice
We study dynamics of a two-component Bose-Einstein condensate where the two
components are coupled via an optical lattice. In particular, we focus on the
dynamics as one drives the system through a critical point of a first order
phase transition characterized by a jump in the internal populations. Solving
the time-dependent Gross-Pitaevskii equation, we analyze; breakdown of
adiabaticity, impact of non-linear atom-atom scattering, and the role of a
harmonic trapping potential. Our findings demonstrate that the phase transition
is resilient to both contact interaction between atoms and external trapping
confinement.Comment: 8 pages, 8 figure
Population polygons of tektite specific gravity for various localities in australasia
Comparison of specific gravity of tektites from australia, asia, texas, and czechoslovaki
The Angular Resolution of Space-Based Gravitational Wave Detectors
Proposed space-based gravitational wave antennas involve satellites arrayed
either in an equilateral triangle around the earth in the ecliptic plane (the
ecliptic-plane option) or in an equilateral triangle orbiting the sun in such a
way that the plane of the triangle is tilted at 60 degrees relative to the
ecliptic (the precessing-plane option). In this paper, we explore the angular
resolution of these two classes of detectors for two kinds of sources
(essentially monochromatic compact binaries and coalescing massive-black-hole
binaries) using time-domain expressions for the gravitational waveform that are
accurate to 4/2 PN order. Our results display an interesting effect not
previously reported in the literature, and underline the importance of
including the higher-order PN terms in the waveform when predicting the angular
resolution of ecliptic-plane detector arrays.Comment: 13 pages, 6 figures, submitted to Phys Rev D. The current version
corrects an error in our original paper and adds some clarifying language.
The error also required correction of the graphs now shown in Figures 3
through
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