Results 191 to 200 of about 18,997 (237)

Tracking atmospheric ducts using radar clutter: evaporation duct tracking using kalman filters

2007 IEEE Antennas and Propagation Society International Symposium, 2007
This paper addresses the problem of tracking evaporation ducts in marine environments. The method tracks the evolution of the range and height-dependent index of refraction using the radar sea clutter. A split-step fast Fourier transform (FFT) based parabolic equation (PE) approximation to the wave equation is used to compute the clutter return in ...
Caglar Yardim, Peter Gerstoft, William S. Hodgkiss   +2 more
openaire   +1 more source

Retrieving evaporation duct heights from measured propagation factors

IET International Conference on Radar Systems 2007, 2007
The knowledge of refractivity is very important for coverage prediction. This problem is common above sea, where the particular atmospheric conditions lead to atmospheric ducts which strongly modify the range of the radar compared to the standard atmosphere coverage. The most common duct which is almost always present is the evaporation duct.
R. Douvenot, V. Fabbro, H.H. Fuchs, H. Essen, C. Bourlier, J. Saillard, Y. Hurtaud   +6 more
openaire   +2 more sources

Polarization dependence of transient signals in evaporation ducts

Radio Science, 1978
The evaporation duct model used is that of Kahan and Eckart and consists of a discontinuous drop of the otherwise constant relative permittivity at the upper duct boundary. The earth is assumed to be a perfect conductor and ideally plane. We determine the electrical field strength exactly at some fixed point within the duct layer, having chosen a ...
H. Zimmer, K. J. Langenberg, K.‐D. Becker   +2 more
openaire   +1 more source

MMW propagation in warm water evaporation ducts

2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM), 2013
This paper focuses on Ka-band (35 GHz) propagation in maritime evaporation ducts using M-profiles derived from high resolution radiosonde observations from locations with warm sea surface temperature (> 25°C) and large M-deficits (ΔM > 60 M-units), and the equivalent ln-linear model fits to the radiosonde M-profiles.
openaire   +1 more source

Application of Laser Technology in Evaporation Duct Detection

Applied Mechanics and Materials, 2011
Aiming at how to detect evaporation duct environment accurately in real time, method of detecting atmospheric duct by using laser technique was put forward. From the model of air refractive index of radar band, theoretical relationship between laser scattering properties of aerosol over the ocean and vertical change characteristics of the air humidity ...
Le Dong Wang, Jian Gan Wang, Tao Liu
openaire   +1 more source

Evaporation Duct Communication: Test Plan Part 2

1991
Abstract : This document is a continuation and expansion of an earlier study that examines the feasibility of using the evaporation duct to support an alternative high-speed communication system for Navy applications. This Evaporation Duct Communication (EDCOM) experiment is a unique opportunity to evaluate another communication channel that can ...
L. T. Rogers, K. D. Anderson
openaire   +1 more source

Estimating evaporation duct heights from radar sea echo

Radio Science, 2000
The evaporation duct is a downward refracting layer that results from the rapid decrease in humidity with respect to altitude occurring in the atmospheric surface layer above bodies of water. The evaporation duct affects radar detection ranges at frequencies of approximately 1 GHz and above.
L. Ted Rogers, Claude P. Hattan, Janet K. Stapleton   +2 more
openaire   +1 more source

The transient response above an evaporation duct

Journal of Physics D: Applied Physics, 1998
The transient electromagnetic field generated by a vertical electric dipole above an evaporation duct is investigated theoretically. The evaporation duct model used is that previously described by Kahan and Eckart. A vertical electric dipole, above the surface layer, is taken as the source of the electromagnetic field. We determine the electrical field
openaire   +1 more source

Failure of large-scale pilot evaporator duct nozzle

Engineering Failure Analysis, 2015
Abstract Failure investigation was carried out on a 12'' water evaporator duct nozzle of a large-scale steam flood pilot which is used to inject steam into a heavy crude oil reservoir. The nozzle contained cracks at the pipe, shell, pad and welds. All the materials are made of UNS31803 grade 2205 duplex stainless steel.
H.M. Shalaby, B. Al-Wakaa, N. Tanoli
openaire   +1 more source

94-GHz propagation in the evaporation duct

IEEE Transactions on Antennas and Propagation, 1990
One-way, low-altitude radio propagation measurements at 94 GHz and simultaneous surface meteorological measurements were made on a 40.6 km, over-horizon, over-water path along the southern California coast to assess the effects of the evaporation duct on signal propagation.
openaire   +1 more source