Results 281 to 290 of about 32,736 (313)

Propagation experiments in low-visibility atmospheres

Applied Optics, 1978
An experimental program aimed at measuring critical channel parameters of atmospheric optical communication channels under low-visibility weather conditions is described. Multipath and angular spectrum measurements made under a variety of weather conditions over a 13.6-km line-of-sight propagation path are reported.
W H, Paik, M, Tebyani, D J, Epstein, R S, Kennedy, J H, Shapiro   +4 more
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The Propagation of Radio Waves in an Ionised Atmosphere

Mathematical Proceedings of the Cambridge Philosophical Society, 1931
Larmor has shown that if the upper atmosphere contains electrons (charge ε, mass m, density ν) and if collisions between these electrons and molecules—and also the forces between the electrons themselves—are negligible, then electric waves are propagated as if the dielectric constant of the medium were reduced by , from which it appears that, so long ...
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Parabolic Approximation for Sound Propagation in the Atmosphere

AIAA Journal, 1978
Propagation of sound in a stratified moving medium is discussed through an extension of the parabolic approximation to the acoustic equations of motion for short wavelengths. The parabolic approximation is related to the theory of geometric acoustics, and it is shown that it yields an improvement in accuracy over geometric theory.
Myers, M. K., McAninch, G. L.
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Propagation of Laser Radiation in a Turbulent Atmosphere

Applied Optics, 1973
This paper reviews the investigations of regularities of laser radiation propagation in a turbulent atmosphere carried out through 1971. Special attention is paid to the influence of laser radiation specificity-space limitation, coherence, and the possibility of its focusing on the propagation.
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Nonlinear Propagation of Aircraft Noise in the Atmosphere

AIAA Journal, 1980
Carefully controlled tests of aircraft noise propagation have shown instances of anomalously low attenuation (deficiencies in excess of 10 dB over 500 m) for frequencies in the range 5-10 kHz. These results have been explained with the aid of a statistical theory of finite-amplitude noise propagation.
C. MORFEY, G. HOWELL
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Sound Propagation in the Atmosphere

2007
Propagation of sound close to the ground outdoors involves geometric spreading, air absorption, interaction with the ground, barriers, vegetation and refraction associated with wind and temperature gradients. After a brief survey of historical aspects of the study of outdoor sound and its applications, this chapter details the physical principles ...
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On the propagation of whistling atmospherics

Journal of Atmospheric and Terrestrial Physics, 1956
Abstract It is shown that the dispersion of whistling atmospherics propagated along the lines of force of the earth's magnetic field should be greatly dependent on the geomagnetic latitude of the observing point. The change in the magnetic-field intensity along a line of force produces an upper-frequency limit for whistler propagation which, at ...
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The Propagation of a Plane Shock into a Quiet Atmosphere

Canadian Journal of Mathematics, 1953
In this note the problem of determining the propagation of a plane shock moving through a polytropic gas into an undisturbed body of the gas, leaving a non-isentropic disturbance behind it, is reduced to the solution of the problem of Cauchy for a Monge-Ampére partial differential ...
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Simulation of laser propagation in a turbulent atmosphere

Applied Optics, 2000
The split-step Fourier-transform algorithm for numerical simulation of wave propagation in a turbulent atmosphere is refined to correctly include the effects of large-scale phase fluctuations that are important for imaging problems and many beam-wave problems such as focused laser beams and beam spreading.
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Atmospheric propagation

1976
Questo capitolo, di un libro a cura di Alberto Sona, concerne la propagazione di radiazione ottica nell'atmosfera e il deterioramento della coerenza di un fascio laser. In una prima sezione ho introdotto le funzioni usate nella descrizione statistica di quantità fluttuanti, funzioni di correlazione, struttura e spettri e descritto la turbolenza ...
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