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Ionospheric disturbance is a major impediment to current communication systems with the signals propagating through the ionosphere. A signature of such disturbance when appearing in an ionogram, resulting from the ionosonde observation system, is known as spread-F. The spread-F statistics is therefore crucial to the design and operation of communication system. In this work, we analyze the equatorial...
In this research paper presents the observed critical frequency of E layer (foE) over Chumphon, Thailand which is located at nearly the magnetic equator (lat. 10.72° long. 99.37° dip. 3°) during September 2004 to August 2005. The foE is one of essential parameters in the International Reference Ionsphere (IRI) model. We investigate the variation of the observed foE by comparing to the Sun spot number,...
This paper proposes a new image authentication scheme, which is done in the wavelet domain. A magnitude of coefficient in selected sub-bands is determined in terms of bit plane data. An image feature is generated from this data and then signed to be a digital signature. The Signature can be embedded into host image or separately send. The feature is only 256 bytes. With the proposed scheme, image...
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