The water entry problem of an asymmetric wedge with roll motion was analyzed by the method of a modified Logvinovich model (MLM). The MLM is a kind of analytical model based on the Wagner method, which linearizes the ...The water entry problem of an asymmetric wedge with roll motion was analyzed by the method of a modified Logvinovich model (MLM). The MLM is a kind of analytical model based on the Wagner method, which linearizes the free surface condition and body boundary condition. The difference is that the MLM applies a nonlinear Bernoulli equation to obtain pressure distribution, which has been proven to be helpful to enhance the accuracy of hydrodynamic loads. The Wagner condition in this paper was generalized to solve the problem of the water entry of a wedge body with rotational velocity. The comparison of wet width between the MLM and a fully nonlinear numerical approach was given, and they agree well with each other. The effect of angular velocity on the hydrodynamic loads of a wedge body was investigated.展开更多
According to JJF1059.2-2012 and CNAS-GL06, the measurement uncertainty of four indicators （semen volume, sperm motility and validity, progressive motility, abnormal sperm percentage） of boar fresh semen, as well as ...According to JJF1059.2-2012 and CNAS-GL06, the measurement uncertainty of four indicators （semen volume, sperm motility and validity, progressive motility, abnormal sperm percentage） of boar fresh semen, as well as its influencing factors, was analyzed. The results showed that the measurement uncertainty of semen volume and progressive motility caused by inspectors was low, and their measurement results reliability was high. There were small differences in measurement results of semen volume and progressive motility among inspectors. However, the measurement uncertainty of sperm motility and abnormal sperm percentage was relatively large, and great differences were found among different inspectors. Therefore, the training of inspectors＇ measuring sperm motility and abnormal sperm percentage should be strengthened, and the comparison of measurement results among inspectors should be performed in the future.展开更多
A spherical robot based on a novel double ballast masses principle is developed for military reconnaissance and unknown environment exploration. The robot is driven by two DC motors, each of which drives one ballast m...A spherical robot based on a novel double ballast masses principle is developed for military reconnaissance and unknown environment exploration. The robot is driven by two DC motors, each of which drives one ballast mass, and the two ballast masses are placed symmetrically on the major axis. Compared with the traditional ballast mass principle, the robot has featured high speed, the ability of slope climbing and obstacle overcoming in linear motion. The robot has two inputs and three DOF, which is a nonholonomic and underactuated system. The dynamic model of the robot is constructed, and the linear motion performance of robot in theory is proved by Adams simulation. The control system is briefly introduced, and the performance of the prototype is tested by experiments at last.展开更多
基金Supported by Supported by "111 Program" (B07019)
文摘The water entry problem of an asymmetric wedge with roll motion was analyzed by the method of a modified Logvinovich model (MLM). The MLM is a kind of analytical model based on the Wagner method, which linearizes the free surface condition and body boundary condition. The difference is that the MLM applies a nonlinear Bernoulli equation to obtain pressure distribution, which has been proven to be helpful to enhance the accuracy of hydrodynamic loads. The Wagner condition in this paper was generalized to solve the problem of the water entry of a wedge body with rotational velocity. The comparison of wet width between the MLM and a fully nonlinear numerical approach was given, and they agree well with each other. The effect of angular velocity on the hydrodynamic loads of a wedge body was investigated.
文摘According to JJF1059.2-2012 and CNAS-GL06, the measurement uncertainty of four indicators （semen volume, sperm motility and validity, progressive motility, abnormal sperm percentage） of boar fresh semen, as well as its influencing factors, was analyzed. The results showed that the measurement uncertainty of semen volume and progressive motility caused by inspectors was low, and their measurement results reliability was high. There were small differences in measurement results of semen volume and progressive motility among inspectors. However, the measurement uncertainty of sperm motility and abnormal sperm percentage was relatively large, and great differences were found among different inspectors. Therefore, the training of inspectors＇ measuring sperm motility and abnormal sperm percentage should be strengthened, and the comparison of measurement results among inspectors should be performed in the future.
文摘A spherical robot based on a novel double ballast masses principle is developed for military reconnaissance and unknown environment exploration. The robot is driven by two DC motors, each of which drives one ballast mass, and the two ballast masses are placed symmetrically on the major axis. Compared with the traditional ballast mass principle, the robot has featured high speed, the ability of slope climbing and obstacle overcoming in linear motion. The robot has two inputs and three DOF, which is a nonholonomic and underactuated system. The dynamic model of the robot is constructed, and the linear motion performance of robot in theory is proved by Adams simulation. The control system is briefly introduced, and the performance of the prototype is tested by experiments at last.
