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The study on the motion characteristics of bullet in muzzle flow field is of great practical signi- ficance to the better understanding of the effect of muzzle flow on a bullet, and it also has a realistic meaning for improving the firing accuracy of weapon systems. The high-speed photography and shadowgraph method are used to study the motion characteristics of 5.8 mm bullet in the muzzle flow field. Based on chamber pressure data observed in experiment, the force and motion of bullet in muzzle flow field are studied by using coupled interior ballistic computational fluid dynamics method. The experimental result shows that the clear flow field and bullet motion can be captured by using the designed test scheme; the numerical calculation indicates that the motion of bullet in the muzzle flow field is not always accelerated. The effects of the coronal air mass and the core jet of propellant gas are the main cause to lead to the change in bullet velocity. At the moment of axial force conversion, there is still shock wave at the bottom of the bullet. [ABSTRACT FROM AUTHOR]

For the purpose of the use of bearing-frequency target motion analysis on underwater static platform, a target motion parameter estimation method is proposed according to bearings and frequency information. The initial value in the iteration of the Kalman filter is set with the least square estimation, resulting in faster convergence and more accurate estimation results. Real test results show that the proposed method has good convergence rate and accuracy, which can be used effectively to achieve the underwater passive localization of target. [ABSTRACT FROM AUTHOR]