In this study, a ground moving target focusing and motion parameter estimation method based on modified secondorder keystone transform (MSOKT) have been proposed for a synthetic aperture radar. Firstly, a cross-track velocity matching compensation function is derived to remove range walk migration and estimate the cross-track velocity of the moving target. Secondly, an MSOKT is proposed to remove the range curvature and Doppler frequency migration simultaneously. Lastly, a well-focused result of the moving target is obtained, and the motion parameters of the moving target are estimated. Compared with the traditional KT-based method, the proposed method works well in situations where Doppler centre blur and Doppler spectrum ambiguity are present. The computational complexity of the proposed method is considerably lower than that of the traditional optimum method, such as Radon-Lv's distribution. Simulation and real data processing results validate the effectiveness of the proposed method.

A series of linear 2,5-tetraphenylsilole-vinylene-type polymers were successfully synthesized for the first time. The tetraphenylsilole moieties were linked at their 2,5-positions through a vinylene bridge with p-dialkoxybenzenes to obtain polymer PSVB and with 3,6-carbazole to obtain polymer PSVC. For comparison, 2,5-tetraphenylsilole-ethyne-type polymer PSEB was also synthesized, in which the vinylene bridge of PSVB was replaced with an ethyne bridge. Very interestingly, the bridging group (vinylene or ethyne) had a significant effect on the photophysical properties of the corresponding polymers. The fluorescence peak of PSEB at 504 nm in solution originated from the emission of its silole moieties, whereas PSVB and PSVC emitted yellow light and no blueish-green emission from the silole moieties was observed, thus demonstrating that the emissions of PSVB and PSVC were due to their polymer backbones. More importantly, the 2,5-tetraphenylsilole-ethyne polymer exhibited a pronounced aggregation-enhanced emission (AEE) effect but the 2,5-tetraphenylsilole-vinylene polymer was AEE-inactive. Moreover, both AEE-active 2,5-tetraphenylsilole-ethyne polymer and AEE-inactive 2,5-tetraphenylsilole-vinylene polymers were successfully applied as fluorescent chemosensors for the detection of explosive compounds.

The platform of multi-channel synthetic aperture radar/ground moving target indication (MC-SAR/GMTI) system may encounter the problem of curvilinear trajectory due to the existence of acceleration in several applications, e.g. manoeuvring responding, orbital motion, and longtime observing. The curvilinear trajectory changes the attitude of the array, which leads to instantaneous baseline changing during echo reception. Thus, the traditional constant baseline range model is no longer valid since it will introduce severe phase error. In this Letter, a general range model that it applies to both stationary and moving targets for MC-SAR/GMTI is proposed. Simulation results of the point spread functions demonstrate that the proposed model can achieve good performance.

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