Secretary of Defense Robert Gates said that while no one expects the world will achieve the goal of "zero nuclear weapons" anytime soon, the new treaty is a major step toward greater security with fewer nuclear weapons: "It is clear that we can accomplish goals with fewer nuclear weapons."

VOA: standard.2010.03.26

Going from two to three, that's an adiabatic expansion, so q is equal to zero in that step.

从第二点到第三点，是绝热膨胀，因此q等于零。

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