When switching low impedances, shielding needs are minimal. Shielding is generally needed only in electrically noisy environments.

在切换低阻时，屏蔽要求是最低的。通常只有在电噪声丰富的环境下才需要屏蔽。

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Because of the high activeness of the titanium alloys, the inert gases or vacuum shielding is needed in fusion welding.

由于钛合金的活性强，熔化焊时需要用惰性气体或真空进行保护。

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But Labour says the scheme is not the change needed in the nation's diet, favouring instead better food labelling and shielding children from adverts for junk food should be the starting point.

BBC: Calories to be cut by major food and drink companies

The U.S. believes Pakistan is shielding Taliban leaders like Mullah Omar because they view them as tools that may be needed to maintain Pakistani influence in Afghanistan once U.S. troops begin to pull out, a gradual process that will start in July.

WSJ: Pakistan Rejects U.S. Criticism

One of the key technologies that is needed is a means to recycle water from astronauts back into a drinkable form, along with radiation shielding and developing ways of working and living in space for prolonged periods.

BBC: Chris Hadfield says Nasa's job is not to 'titillate'