104 research outputs found
A fractional Brownian motion model for the turbulent refractive index in lightwave propagation
It is discussed the limitations of the widely used markovian approximation
applied to model the turbulent refractive index in lightwave propagation.
It is well-known the index is a passive scalar field. Thus, the actual
knowledge about these quantities is used to propose an alternative stochastic
process to the markovian approximation: the fractional Brownian motion. This
generalizes the former introducing memory; that is, there is correlation along
the propagation path.Comment: 11 pages, no figures. Submitted and revised for Optics Communication
Method of estimation of turbulence characteristic scales
Here we propose an optical method that use phase data of a laser beam
obtained from Shack-Hartmann sensor to estimate both inner and outer scales of
turbulence. The method is based on the sequential analysis of normalized
correlation functions of Zernike coefficients. It allows excluding the value of
refractive index structural constant from the analysis and reduces the solution
of a two-parameter problem to sequential solution of two single-parameter
problems. The method has been applied to analyze the results of measurements of
the laser beam that propagated through a water cell with induced turbulence and
yielded estimates for outer and inner scales.Comment: 7 pages, 9 figure
-Function Perturbations and Boundary Problems by Path Integration
A wide class of boundary problems in quantum mechanics is discussed by using
path integrals. This includes motion in half-spaces, radial boxes, rings, and
moving boundaries. As a preparation the formalism for the incorporation of
-function perturbations is outlined, which includes the discussion of
multiple -function perturbations, -function perturbations along
perpendicular lines and planes, and moving -function perturbations. The
limiting process, where the strength of the -function perturbations
gets infinite repulsive, has the effect of producing impenetrable walls at the
locations of the -function perturbations, i.e.\ a consistent
description for boundary problems with Dirichlet boundary-condition emerges.
Several examples illustrate the formalism.Comment: 35 pages, amstex, preprint SISSA/18/93/F
Criterion for the Choice of Exposure Time in Atmospheric Turbulence Investigation with an Optical Wave
Aperture size and bandwidth requirements for measuring strong scintillation in the atmosphere
Intensity fluctuations of an atmospherically degraded beam at the focus of a large collecting lens
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