Indeed, background leakage is so pervasive that water suppliers accept 3,500 litres of water per kilometre of pipe per day as the minimum achievable loss.

事实上，底面渗漏现象随处可见，供水商也接受了每日每千米管道3500升的最低漏水量。

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Indeed, background leakage is so pervasive that water suppliers accept 3, 500 litres of water per kilometre of pipe per day as the minimum achievable loss.

事实上，底面渗漏现象随处可见，供水商也接受了每日每千米管道3500升的最低漏水量。

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Some end value condition derived by variational method in accordance with the least energy loss principle and their mechanical background are also dealt with.

同时从能量最小原理出发，用变分的方法推导出几种端值条件，说明它们的力学背景。

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