Animals and people can feel pain and act to correct the problem. Not so a concrete wall, which goes through life not noticing its condition as it cracks and corrodes and perhaps one day suddenly collapses. ..... These include so-called shape memory metals that return to their original shape when heated, and fluids tha turn from liquid to solid when an electric voltage is applied.
――東京大学 後期日程 理科(3月13日実施)――97年