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Airborne synthetic aperture radar (SAR) raw data are affected by variable aircraft parameters due to atmospheric turbulence and aircraft properties. In order to decrease the influence of variable aircraft information, the azimuth large-aperture approach is thus applied in airborne SAR real-data processing. However, it will cause the aliasing of azimuth-signal in squint SAR mode and degrade the image quality. In this paper, a novel model of airborne squint SAR instantaneous dopper frequency is constructed at first, then the study of azimuth sub-aperture spectrum extension and azimuth time-domain aliasing is presented. After that, a modified azimuth large-aperture approach is proposed to eliminate the aliasing in azimuth time-domain. Finally, simulations and experimental results of squint SAR mode are all provided to demonstrate the validity of the proposed approach. [ABSTRACT FROM AUTHOR]

By virtue of FE-SEM and EDXA marked by Br element, the relationship between the lignin distribution and growth stress was micro-analyzed by normal wood of plantation Eucalyptus urophylla X E. grandis with different growth stress levels. The results indicated that the lignin contents of different cell wall layers were not related to the growth stress level, and the lignin content (from high level to low level) in sequence was cell corner, compound middle lamellae, S1, S2 and S3; The lignin contents in micro-morphological regions of wood fiber cell wall were decreased with the increase in growth stress and lignification process was delayed.