Browsing by Author "Sohel, Malkiat Singh"
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Item Generalized ray tracing in a most general ocean(1969) Sohel, Malkiat Singh; Hayre, H. S.; Shehadeh, Nazmi M.The problem of ray tracing in a water mass moving with an exponentially decaying velocity in three-dimensional space is representative of, for instance, the Gulf Stream in the Gulf of Mexico and river deltas and most of all, many other restricted channels lying between large land masses around the world including tidal effects in many areas. A general expression for the curvature of the ray path in an ocean channel whose watermass is assumed to be moving with a three-dimensional mass velocity decreasing exponentially is derived under the assumption that the speed of sound decreases exponentially with depth. The ray path data for the source located at various depths and for initial ray depression angles of [theta][subscript o] = 20°, 30°, 45° and 60°, respectively, for both still and moving watermass, both at constant velocity and spatially varying mass velocity. The percentage error in each case is calculated and presented. The speed of sound variations data available off the Florida coast is analyzed for random variation of the speed of sound with depth superimposed on the usual exponential variation. Its statistical parameter, density function, mean, variance, auto-correlation and decorrelation distance are calculated and presented. The expression for the curvature of ray path in moving inhomogeneous medium, assuming the above model, is also presented.Item Rough surface Doppler return spectra(1972) Sohel, Malkiat Singh; Hayre, Harbhajan S.; Schneider, William P.; Blumberg, Randolph; Finch, Robert D.; Collins, R. EugeneIn this study doppler return spectra, from a two-dimensional random rough ocean surface are investigated for both radar and sonar signals. Theoretical expressions of the doppler spectra are derived and their numerical values are calculated using a computer and an analysis of the resulting data is presented. Certain approximations in the previously reported work are removed and/or modified for the case of a one-dimensional random rough surface and the case of the two-dimensional surface is also solved. In order to develop the theoretical doppler spectrum expressions, Kirchhoff-Huygen integral approach is used. Shadowing and multiple scattering effects are not considered. For the sonar case, a frequency of 50 kilohertz ([lambda] = wavelength = 3.0CM) is employed and for the radar case a frequency of 20 gigahertz ([lambda] = wavelength = 1.5CM) is used. [...]