Optical analyzer technique are used to measure the sound speed as a function of pressure for shocked multiphase alloy 93 W containing 93%W, with 4.2%Ni-2.45%Fe-0.35%Co alloy as binder, all in wt.%. Below 250 GPa, the ...Optical analyzer technique are used to measure the sound speed as a function of pressure for shocked multiphase alloy 93 W containing 93%W, with 4.2%Ni-2.45%Fe-0.35%Co alloy as binder, all in wt.%. Below 250 GPa, the speed increases with pressure, then a bulk“softening” process occurs at 250 to 340 GPa, afterwards the speed again rises with pressure and coincides with the calculated bulk sound speed, showing a fluid-like behavior for this alloy. Lindemann melting law calculations were made for both the binder and the tungsten. The results showed that 250 GPa corresponds approximately to the pressure for the binder beginning to melt, and 340GPa corresponds to that for tungsten. Therefore, we believe that the shock-induced “softening” mechanism for this kind of multiphase alloys can be attributed to the binder melting.展开更多
The Hugoniot equation-of-state(EOS)of porous iron with an average initial density of 6.904g/cm^(3) has been measured in the pressure range from 90 to 160GPa,and a good straight fitting D=2.997+1.603u has accordingly b...The Hugoniot equation-of-state(EOS)of porous iron with an average initial density of 6.904g/cm^(3) has been measured in the pressure range from 90 to 160GPa,and a good straight fitting D=2.997+1.603u has accordingly been obtained,where D is the shock wave velocity and u the particle velocity,both in units of km/s.Combining this with the Hugoniot EOS of non-porous iron,the Grüneisen EOS and the Rankine-Hugoniot energy conservation relation,and taking the possible solid-liquid transition correction,we have calculated the Grüneisen parameterγof iron and obtained the resultγ0ρ0=γρ=const,withγ0=1.945 andρ0=7.856g/cm^(3),ρbeing the density.展开更多
文摘针对无人机通过视觉对地面动态目标跟踪过程中视角固定易丢失目标,以及在着陆过程中由于成像畸变严重、画面不稳定导致定位精度差的问题,提出随动视觉跟踪的跟踪控制策略和基于视觉联合磁引导的获取无人机高精度相对位姿的方法.在跟踪过程中,设计新型信标图案供无人机进行视觉识别获取目标的方位,识别速度可以达到5 ms/帧,通过随动视觉跟踪完成实时跟踪.在着陆过程中,在动态目标上设置磁源,利用无人机检测磁场特性并通过BP神经网络解算相对位置;在信标图案内设置平行线特征,用于近镜头时辅助视觉解算相对角度.在获取无人机相对位姿后,进行相应的运动控制即可完成着陆.实验结果表明,跟踪过程稳定可靠,抗干扰能力强;着陆精度高,着陆误差小于2 cm.
基金the Science Foundation of China Academy of Engineering Physics,Contract No.9301002.
文摘Optical analyzer technique are used to measure the sound speed as a function of pressure for shocked multiphase alloy 93 W containing 93%W, with 4.2%Ni-2.45%Fe-0.35%Co alloy as binder, all in wt.%. Below 250 GPa, the speed increases with pressure, then a bulk“softening” process occurs at 250 to 340 GPa, afterwards the speed again rises with pressure and coincides with the calculated bulk sound speed, showing a fluid-like behavior for this alloy. Lindemann melting law calculations were made for both the binder and the tungsten. The results showed that 250 GPa corresponds approximately to the pressure for the binder beginning to melt, and 340GPa corresponds to that for tungsten. Therefore, we believe that the shock-induced “softening” mechanism for this kind of multiphase alloys can be attributed to the binder melting.
基金Supported by the Science and Technology Foundation of China Academy of Engineering Physics under contract No.990110.
文摘The Hugoniot equation-of-state(EOS)of porous iron with an average initial density of 6.904g/cm^(3) has been measured in the pressure range from 90 to 160GPa,and a good straight fitting D=2.997+1.603u has accordingly been obtained,where D is the shock wave velocity and u the particle velocity,both in units of km/s.Combining this with the Hugoniot EOS of non-porous iron,the Grüneisen EOS and the Rankine-Hugoniot energy conservation relation,and taking the possible solid-liquid transition correction,we have calculated the Grüneisen parameterγof iron and obtained the resultγ0ρ0=γρ=const,withγ0=1.945 andρ0=7.856g/cm^(3),ρbeing the density.
