A wall currently separates the Nant Clydach tributary from the street, but the environment body, Natural Resources Wales, said building a raised flood defence wall was "not economically viable".
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但真正的问题是，理想模型往往建立在需求高峰与利用率饱和的假设之上。而真实世界中的利用率，从来不会长期维持在高位。
The James Webb Space Telescope has snapped new pictures of a cosmic cloud of gas and dust blown off by a dying star, whose fate is still unknown to scientists.