4,615 research outputs found
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
Q^2-evolution of nucleon-to-resonance transition form factors in a QCD-inspired vector-meson-dominance model
We adopt the vector-meson-dominance approach to investigate Q^2-evolution of
N-R transition form factors (N denotes nucleon and R an excited resonance) in
the first and second resonance regions. The developed model is based upon
conventional NR\gamma-interaction Lagrangians, introducing three form factors
for spin-3/2 resonances and two form factors for spin-1/2 nucleon excitations.
Lagrangian form factors are expressed as dispersionlike expansions with four or
five poles corresponding to the lowest excitations of the mesons \rho(770) and
\omega(782). Correct high-Q^2 form factor behavior predicted by perturbative
QCD is due to phenomenological logarithmic renormalization of electromagnetic
coupling constants and linear superconvergence relations between the parameters
of the meson spectrum. The model is found to be in good agreement with all the
experimental data on Q^2-dependence of the transitions N-\Delta(1232),
N-N(1440), N-N(1520), N-N(1535). We present fit results and model predictions
for high-energy experiments proposed by JLab. Besides, we make special emphasis
on the transition to perturbative domain of N-\Delta(1232) form factors.Comment: 22 pages, 22 PS figures, REVTeX 4; v2: +3 refs, minor editorial
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The Changing Face of Taxation of Virginia Business After American Woodmark and DataComp
Earth orbital teleoperator systems evaluation
The mechanical extension of the human operator to remote and specialized environments poses a series of complex operational questions. A technical and scientific team was organized to investigate these questions through conducting specific laboratory and analytical studies. The intent of the studies was to determine the human operator requirements for remotely manned systems and to determine the particular effects that various system parameters have on human operator performance. In so doing, certain design criteria based on empirically derived data concerning the ultimate control system, the human operator, were added to the Teleoperator Development Program
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