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In the complex electromagnetic environment of the battlefield, the reliability and accuracy of radar equipment are facing great challenges, and the anti-jamming ability of radar directly affects the function of radar. The evaluation of radar anti-jamming effectiveness based on experimental big data has also become an important research direction of radar operational use. This paper starts with analyzing the criterion of radar anti-jamming effectiveness evaluation, sorts out the indicators of radar anti-jamming effectiveness, uses the analytic hierarchy process to establish the index weight, and uses the weighted relative deviation distance method to establish the evaluation method of radar anti-jamming performance. The research results provide reference for the evaluation of radar anti-jamming effectiveness in the exercise.

Aiming at the problem of low complexity and security of digital image encryption algorithm, a new cryptographic method based on chaotic system and DNA coding is proposed. DNA coding and fundamental operations are performed on the random matrix and plain-text images. The random matrix is produced by the improved logistic map. The methods of coding and operation are dynamically given by the random sequence produced by the hyper-chaotic system. Meanwhile, to get better diffusion effect, cipher-text feedback mechanism is proposed. In addition, the algorithm’s key is determined by the plain-text, enabling one-time encryption. The experimental analysis shows that the method has enormous key space, intense key sensitivity, high security, and can resist multiple attacks as well.

Common short bolts of equal length are widely used to support the roofs of roadways in coal mines. However, they are insufficient to keep the roof stable against large deformations, so docking long bolts with high levels of elongation that can adapt to large deformations of the surrounding rock have been adopted. This paper proposes a collaborative support method that uses long and short bolts. In this study, the mechanism of docking long bolts and collaborative support was studied. Numerical simulation, similarity simulation, and field testing were used to analyze the distribution law of the displacement, stress, and plastic failure in the surrounding rock under different support schemes. Compared with the equal-length short bolt support, the collaborative support changed the maximum principal stress of the shallow roof from tensile stress to compressive stress, and the minimum principal stress of the roof significantly increased. The stress concentration degree of the anchorage zone clearly increased. The deformation of the roof and the two sides was greatly reduced, and the subsidence shape of the shallow roof changed from serrated to a smooth curve. The roof integrity was enhanced, and the roof moved down as a whole. Plastic failure significantly decreased, and the plastic zone of the roof was within the anchorage range. The similarity simulation results showed that, under the maximum mining stress, the roof collapsed with the equal-length short bolt support but remained stable with the collaborative support. The collaborative support method was successfully applied in the field and clearly improved the stability of the surrounding rock for a large deformation roadway. Keywords: Collaborative support with long and short bolt, Docking long bolt, Numerical analysis, Similarity simulation