可视密码 visual cryptography

外视密度 Apparent density ; Density apparent

煤视密度 apparent density of coal

视密卡 cam

密切注视 Keep close watch on ; keep an eye open ; Keep an eye on

严密监视的列车 Closely Watched Trains ; Closely Observed Trains ; Ostre Sledovane Vlaky

视密度的测定 Determination of apparent density

可视密码方案 NPBVCS

可视密码技术的研究 Study of Visual Cryptography Technology