An extended two-step focusing approach (ETSFA) for processing the squinted spotlight synthetic aperture radar (SAR) data is proposed in this paper. The effect of the squint angle on the azimuth coarse focusing is analyzed and discussed. Based on the analysis results, a nonlinear shift preprocessing method is introduced, which can completely remove the squint angle impacts on the azimuth coarse focusing. Furthermore, based on the squinted spotlight SAR imaging model and the preprocessed echo data, derivations of the azimuth coarse focusing with the deramping-based technique and precise focusing with the modified Stolt-based technique are carried out in detail. Moreover, to produce an acceptable image by the proposed ETSFA for high-resolution (< 3 m) squinted spotlight SAR with large scene, a subscene processing method is introduced. The experimental results on simulated data prove the validity of the whole analysis and the proposed methods.Index Terms-Deramping-based technique, squinted spotlight synthetic aperture radar (SAR), subscene processing.
The effect of spacing in relation to word segmentation was examined for four groups of non-native Chinese speakers (American, Korean, Japanese, and Thai) who were learning Chinese as second language. Chinese sentences with four types of spacing information were used: unspaced text, word-spaced text, character-spaced text, and nonword-spaced text. Also, participants' native languages were different in terms of their basic characteristics: English and Korean are spaced, whereas the other two are unspaced; Japanese is character based whereas the other three are alphabetic. Thus, we assessed whether any spacing effects were modulated by native language characteristics. Eye movement measures showed least disruption to reading for word-spaced text and longer reading times for unspaced than character-spaced text, with nonword-spaced text yielding the most disruption. These effects were uninfluenced by native language (though reading times differed between groups as a result of Chinese reading experience). Demarcation of word boundaries through spacing reduces non-native readers' uncertainty about the characters that constitute a word, thereby speeding lexical identification, and in turn, reading. More generally, the results indicate that words have psychological reality for those who are learning to read Chinese as a second language, and that segmentation of text into words is more beneficial to successful comprehension than is separating individual Chinese characters with spaces.
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