Like plano-convex lenses, double convex lenses have positive focal lengths and form...chromatic aberration almost exactly canceled at unit conjugate radio. Double-convex lenses have shorter focal lengths than plano-convex lenses...
convex凸體 cam凸輪 http://www.china-customs.com/big5/customs/data/2005/10663.htm 這邊還有一些術語 參考看看 ：）
...and the position is not the same21. different brands have different concave/convex removable suction power22. different branded toilet tissue flat layout of the concave/convex...