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With the improvement of image resolution in synthetic aperture radars (SARs), sea clutter characteristics become more complex, which poses new challenges to traditional ship target detection missions. In this paper, to detect ship targets quickly and efficiently in a complex background, we propose an adaptive hierarchical detection method based on a coarse-to-fine mechanism. This method constructs a new visual attention mechanism to strengthen ship targets and obtain the candidate targets adaptively by the means dichotomy method. On this basis, the precise detection results of the targets are obtained using the speed block kernel density estimation method, which maintains constant false alarm characteristics. Compared with existing methods, the adaptive hierarchical detection method has simple, fast, and accurate characteristics. Experiments based on GF-III satellite and airborne SAR datasets are presented to demonstrate the effectiveness of the proposed method.

The study attempts to identify the major sources of stress among high school chemistry teachers in Shaanxi province in China. We surveyed 101 chemistry teachers from 15 high schools in Shaanxi province in China with a self-administered questionnaire at a return rate of 72.14%. The results show among the 19-item sources of stress, investigated through factor analysis, resulted in five distinct dimensions of perceived stress: teaching workload (34% common variance), school system (11% common variance), social treatment and demands (7% common variance) and self-development demands (6% common variance), school hardware facilities (5% common variance), the top three sources of stress perceived by these chemistry teachers in descending order of mean scores: ‘social treatment and demands’, ‘parental demands’, and ‘self-development demands’. Measures such as increasing teachers wage, improving schools’ humanistic environment and school hardware facilities, creating more opportunities for the development of teachers should be given to mitigate stress of high school stress of high school at Shaanxi province in China.