It is necessary to clarify radio duct properties in order to estimate propagation characteristics for radio system design. In this paper, radio duct properties are statistically analyzed using aerological data observed at six typical stations in Japan over seven years, and meteorological data observed near the ground by a balloon or tower. Radio refractivity gradient statistics are then compared with duct occurrence probability and fading occurrence probability. Consequently, it was possible to evaluate quantitatively a probability of duct occurrence using refractivity statistics. Certain properties of the radio duct were also quantitatively obtained.
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A method is proposed wherein printed documents are segmented into the following three areas: headline area, textline area, and attached area. Then the character lines constituting headline and textline are extracted. This paper describes: 1) the combination of the global features of the document such as projection profiles and stroke densities, and the local features of the document such as circumscribed rectangles are used; 2) the basic features of document elements such as character line periodicity in the textline area, so that a single method can be applied to segment document elements in differently formatted documents.
An experimental result of this method applied to eight Japanese and English printed documents of both horizontal and vertical lines showed that 98.4 percent of the headlines in headline area, 99.9 percent of the textlines in textline area, and 83.3 percent of diagrams in the attached area were segmented successfully.
The result confirms that this method is effective in segmenting document elements, and applicable to a variety of documents. Part of document processing is implemented in the experiment by special hardware for speed.
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