A number of field experiments measuring the fluctuating intensity of a laser beam propagating along horizontal paths in the maritime environment is performed over sub-kilometer distances at the United States Naval Academy. Both above the ground and over the water links are explored. Two different detection schemes, one photographing the beam on a white board, and the other capturing the beam directly using a ccd sensor, gave consistent results. The probability density function (pdf) of the fluctuating intensity is reconstructed with the help of two theoretical models: the Gamma-Gamma and the Gamma-Laguerre, and compared with the intensity's histograms. It is found that the on-ground experimental results are in good agreement with theoretical predictions. The results obtained above the water paths lead to appreciable discrepancies, especially in the case of the Gamma-Gamma model. These discrepancies are attributed to the presence of the various scatterers along the path of the beam, such as water droplets, aerosols and other airborne particles. Our paper's main contribution is providing a methodology for computing the pdf function of the laser beam intensity in the maritime environment using field measurements.

It is experimentally demonstrated that the class of partially coherent, partially polarized optical beams can be efficiently used for reduction in scintillations on propagation through turbulent air. The experiment involving the electromagnetic beam generation and its interaction with turbulent air simulator is discussed in details. The collected data is in solid agreement with the recently published theoretical predictions.

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Irradiance fluctuations of a pseudo Multi-Gaussian Schell Model beam propagating in the maritime environment is explored as a function of spatial light modulator cycling rate and estimated atmospheric turnover rate. Analysis of the data demonstrates a strong negative correlation between the scintillation index of received optical intensity and cycling speed for the estimated atmospheric turnover rate.

Abstract. Analytic steady solutions of inhomogeneous simple shear with isothermal and stress boundary conditions are found. The material is assumed to be thermoviscous and inertia and heat conduction effects are included. The basic inhomogeneous solution is spatially dependent, but time independent. Bifurcation of this solution, as the parameters vary, is analyzed. It is shown that there is a critical value of the parameter, corresponding to thermal softening, below which two steady state solutions exist for specified values of other parameters. A linear perturbation method, which gives rise to a linear set of partial differential equations (with spatially dependent coefficients), is used to distinguish the stable branch of the bifurcation diagram. After separation of variables, the existence of eigenvalues and eigenfunctions of the resulting fourth-order system is demonstrated. An asymptotic solution to the eigenvalue problem, for the case when an appropriate parameter is set equal to zero, is obtained explicitly. An integral method is then used in the general case to obtain a sufficient condition for stability.

We report on experimental generation of Electromagnetic Bessel-Gaussian Schellmodel [EBGSM] beams via incoherent superposition of two mutually orthogonal electric field components, both originated from a laser source, whose phases are spatially modified by two nematic liquid crystal Spatial Light Modulators. The EBGSM beam is then passed through a weakly fluctuating turbulent channel and examined for contrast in its fluctuating intensity. It is demonstrated that after passing through turbulence the electromagnetic beam exhibits reduction in the scintillation index on the order of 50%, as compared with that for an equivalent scalar beam, in strong agreement with recent theoretical predictions.

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To accurately model the stress transfer through a square-ended sandwich structure core and/or a square-ended adhesive layer, a biharmonic Airy stress function solution is derived using a spectral decomposition and a collocation expansion. The solution satisfies the zero stress conditions at the traction-free surfaces and the matched displacement conditions at the top and bottom material interfaces. The stress field is investigated for an idealized state of pure shear. For this example case, the shear and normal stress fields are found to be finite and differentiable everywhere in the domain. This includes finite valued stresses at the sharp corners of an elastic medium. The resulting stress components are compared with the Goland-Reissner, the Closed Form Higher Order, and COMSOL finite element models. The Spectral/ Collocation model is found to be superior owing to the satisfaction of the differential equations of deformation compatibility. It is also demonstrated that highly refined structural mechanics finite element models are unable to handle the stress-free conditions at corners of the traction-free surfaces.