过去也有很多这样的努力，不过都失败了。

In the past, though, many such efforts have flopped.

youdao

人们在互联网初期就做过这种智能家用冰箱，不过都失败了。

This type of 'smart home' fridge has actually been attempted before, in the dot com era, and flopped.

youdao

但国际社会在京都，在哥本哈根都曾试图通过一揽子解决问题，不过两次都失败了。

But the world has twice, at Kyoto and at Copenhagen, tried to deal with the problem in one go, and failed.

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