weak non-isentropic flow

例句：

1. 1. The old man is weak from lack of exercise.
   老人由于缺乏锻炼而身体虚弱。
2. 2. The child was weak from hunger.
   孩子因为饥饿而身体虚弱。
3. 3. The weaklings were easily defeated by the stronger opponents.
   这些弱者很容易被更强的对手击败。