Modeling of imperfect repair through perfect renewal process uses an ‘‘as good as new’’ repair assumption and nonhomogeneous Poisson process uses an ‘‘ABAO’’ repair assumption. In practice, repair actions do not result in such extreme situations but in a complex transitional one, that is, general repair. This article discusses generalized renewal process for an aero engine as repairable compone...

by Christopher O. Porter Aero-optical aberrations associated with turbulent compressible flow fields can seriously degrade the performance of an optical system; the effect of these aberrations increases as the wavelength of the transiting light becomes shorter, and so is particularly strong at visible and near-infrared wavelengths. These aero-optic aberrations originate from both spatialand tem...

An experimental study of the two-dimensional transition from turbulent boundary layer over small backward-facing steps is presented in order to investigate the effect of the separation bubble behind the back-step on the aero-optical environment, as well as to demonstrate the capacity for characterizing complex flow fields using non-intrusive optical measurement techniques such as the Malley Pro...

by Ryan T. Kelly Aero-optical disturbances produced from turbulent compressible flow-fields can seriously degrade the performance of an optical signal. At compressible flight speeds these disturbances stem from the density variations present in turbulent boundary-layers and free-shear layers; however helicopters typically operate at incompressible speeds which nearly eliminates the aberrating e...

As a beam of light traverses through a non-uniform index-of-refraction field, adjacent light rays become advanced or retarded with respect to one another. This in turn creates an aberrated line of constant phase known as an aberrated optical wavefront. Such phase distortions significantly degrade the beam’s far-field intensity pattern resulting in a loss of system performance. Aberrations induc...

In the present paper, a comparison between five different shell finite elements, including the Linear Triangular Element, Linear Quadrilateral Element, Linear Quadrilateral Element based on deformation modes, 8-node Quadrilateral Element, and 9-Node Quadrilateral Element was presented. The shape functions and the element equations related to each element were presented through a detailed mathem...

by Mohammed S. Kamel Reliable prediction of optical wavefront distortions induced by compressible turbulent flow surrounding an aperture is crucial to the development of airborne laser systems. Large-eddy simulation (LES) with a wall model provides a promising highfidelity simulation method for high-Reynolds-number aero-optical flows by avoiding the severe near-wall resolution requirement. In t...

Particulate matter and photo-oxidant processes in the Eastern Mediterranean have been studied using the UAM-AERO mesoscale air quality model in conjunction with the NILU-CTM regional model. Meteorological data were obtained from the RAMS prognostic meteorological model. The modeling domain includes the eastern Mediterranean area between the Greek mainland and the island of Crete. The modeling s...