Results 171 to 180 of about 1,756 (218)
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Noise removal in ionograms by neural network
Neural Computing & Applications, 1997A neural network approach to the extraction of 1hop F-layer traces from oblique-incidence ionograms is shown to offer performance at least comparable with conventional filtering techniques. Preprocessing in the form of background noise and vertical (horizontal) line removal is utilised prior to training a 110∶7∶100 MLP using backpropagation with ...
Markus Hagenbuchner, John Fulcher
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Journal of Atmospheric and Terrestrial Physics, 1978
Abstract The simulations of trough ionograms by Lobb and Titheridge (1977) are supplemented by calculating a trace caused by rays having a double oblique reflection in the ionosphere and not retracing their paths. It is also shown how the different parts of the traces are caused by echoes of different types.
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Abstract The simulations of trough ionograms by Lobb and Titheridge (1977) are supplemented by calculating a trace caused by rays having a double oblique reflection in the ionosphere and not retracing their paths. It is also shown how the different parts of the traces are caused by echoes of different types.
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Backscatter ionogram inversion
2003 Proceedings of the International Conference on Radar (IEEE Cat. No.03EX695), 2004A backscatter ionogram, BSI, is a plot showing the group path or time delay against operating frequency when using ground-based swept frequency radar. In the case of ground backscatter, the received signals are reflected from distant locations on the Earth's surface.
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On the simulation of backscatter ionograms
Journal of Atmospheric and Solar-Terrestrial Physics, 1997Abstract An algorithm for the simulation of backscatter ionograms is developed. Propagation is evaluated by numerically ray tracing through an ionosphere consisting of Chapman layers (major layer parameters derived from CCIR and URSI maps). Simulations are performed for a variety of model ionospheres (including some with strongly varying horizontal ...
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Automatic interpretation of oblique ionograms
Advances in Space Research, 2015Abstract We present an algorithm for the identification of trace characteristics of oblique ionograms allowing determination of the Maximum Usable Frequency (MUF) for communication between the transmitter and receiver. The algorithm automatically detects and rejects poor quality ionograms.
Alessandro Ippolito +4 more
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Journal of Atmospheric and Terrestrial Physics, 1970
Abstract Spread- F echoes are not due to partial reflection from small irregularities. Rather they are due to total reflection from large tilted surfaces of ionization. The geometry of these surfaces is examined using ionograms and airglow observations, together with Australian experiments reported in the literature.
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Abstract Spread- F echoes are not due to partial reflection from small irregularities. Rather they are due to total reflection from large tilted surfaces of ionization. The geometry of these surfaces is examined using ionograms and airglow observations, together with Australian experiments reported in the literature.
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Serum ionogram in heperpyrexia
The Indian Journal of Pediatrics, 1960Forty-five consecutive cases of pyrexia with temperatures above 103oF occurring in children ranging from one to twelve years of age were studied clinically and for serum electrolyte changes.
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Lossless compression of ionogram data
Proceedings of 13th International Conference on Digital Signal Processing, 2002A method for lossless compression of binary data is presented. To remove the redundancies among the data points, a linear predictive scheme is proposed and the coefficients are optimised in the sense of minimum mean square error. An arithmetic coder is then used to code the prediction errors.
null Hua Ye +2 more
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The analysis of night-time ionograms
Journal of Atmospheric and Terrestrial Physics, 1975Abstract The analysis of ionospheric h′(ƒ) records can give appreciable errors at night, when large amounts of ionisation may be present with plasma frequencies less than the minimum recorded frequency ƒ min . The errors depend on both the total amount of low-density ionisation, and on the ionisation gradient near ƒ min .
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Automatic scaling of polar ionograms
Antarctic Science, 2011AbstractThe Istituto Nazionale di Geosifica e Vulcanologia (INGV) software for automatic scaling of ionograms (Autoscala) was improved by introducing a system to identify D region absorption events, spread-F condition (frequency spreading in the F region), and Z-ray propagation.
Carlo Scotto, Michael Pezzopane
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