If you leave the unit powered-on for 20 minutes without performing any operation, the auto power off function will turn the power off automatically, avoiding unnecessary battery consumption.

如果您离开本单位已启动的20分钟不执行任何操作，自动关机功能会自动关闭电源，避免不必要的电池消耗。

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But the experts from Codelco, the state copper producer, who have headed the rescue operation, are still taking no unnecessary chances.

不过，来自国家矿企codelco的救援负责专家却不想冒任何不必要的风险。

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Save a lot of unnecessary instructions, orders, inquiries, the management system can efficiently operation.

省却了许多无谓的请示、命令、询问，使得管理系统能高效率地运作。

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The study, published in the Lancet, could spare other women the trauma and worry of an unnecessary operation, as well as the distressing news that they may be at risk from cancer.

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"We've always felt that the whole SNH operation and the cull was completely unnecessary, " she said.

BBC: Hedgehog cull comes to an end

Opponents claim that at best, it is an unnecessary ritual, and that at worst, it is an operation that proves detrimental to the physical and psychological health of the patient.

CNN: Health