AIDS researchers say they still have much work to do on a vaccine against H.I.V.

VOA: special.2009.09.30

Delta v is positive in this direction here, the work is negative. So work on the system is positive. Work done by the system is negative.

功是负的，总而言之,外界对系统做功的符号为正。

麻省理工公开课 - 热力学与动力学课程节选

V Minus p2, V2. Minus p delta V. So the total work is the work from the left hand side plus the work on the right hand side, p1 V1- p2 V2 which is p1 V1 minus p2 V2.

负p2V2【w=-p2v2】，即负pΔ,所以全部的功就是,左边的功加上右边的功，等于。

麻省理工公开课 - 热力学与动力学课程节选