出處
英國利物浦大學(University of Liverpool)的研究人員聲稱，只要用一種「防震遮罩」把建築物包起來，就不怕地震。
研究人員指出，就像讓軍用潛水艇、戰鬥機躲避聲納及雷達追蹤，或是讓某些小區域避開雷射光束掃描；也能用同樣方式在建築物週圍，將波長非常長的地震波重新導向，讓房子在震波中「隱形」。
「雖已經有根據這個薄板理論(thin plates)的數學模擬，但迄今並沒有進行過任何實驗。」研究團隊的領導人Sebastien Guenneau表示，他的團隊目前正在製作一個原型以確認該理論，並試圖尋找其他的應用領域：「我們的下一步是進行這種防震遮罩的實驗。」
這種防震遮罩的原理是「超材料(metamaterials)」的使用，也就是其介質規律會與隱形頻率共振，這種方法能有效地將電磁波繞過物體。當某種波無阻礙地直線前進，超材料則能在波彎過被遮蓋的物體時，稍微加快其速度。不過由另外一頭生成的同相位(in-phase)震波則似乎不會被改變。
地震會產生體波(body wave)與表面波(surface wave)兩種震波；研究人員表示，該種防震遮罩是採用超大型的超材料，如此就能抑制最具毀滅性的表面波。這種表面波會耦合成壓力與切變體波(shear-body waves)。
研究人員指出，若將大型的環狀軟性超材料圍繞在建築物地基，就可將最具毀滅性的地震表面波轉向避開整棟建築物。
目前該研究計畫仍在設計階段，研究人員還在調配要製作成大型環狀共振器的超材料；根據研究小組的電腦模擬，用等向性彈性填充物來分隔的、有多個同心層的超材料環，確實可讓地震波轉向。目前的超材料環設計，是將6種不同材料分成10層，研究人員表示將會是易於製造以應用在建築物地基。
而對該種超材料的實際驗證也在進行中，研究人員也打算嘗試將該種材料用在汽車上，看看是否能讓車禍發生時的撞擊波避開乘客。
科學家試圖利用超材料為建築物製作「防震遮罩」
Re: 科學家試圖利用超材料為建築物製作「防震遮罩」
出處
‘Invisibility Cloak’ Could Protect Against Earthquakes
20 July 2009 Liverpool, University of
Research at the University of Liverpool has shown it is possible to develop an ‘invisibility cloak’ to protect buildings from earthquakes.
The seismic waves produced by earthquakes include body waves which travel through the earth and surface waves which travel across it. The new technology controls the path of surface waves which are the most damaging and responsible for much of the destruction which follows earthquakes.
The technology involves the use of concentric rings of plastic which could be fitted to the Earth’s surface to divert surface waves. By controlling the stiffness and elasticity of the rings, waves travelling through the ‘cloak’ pass smoothly into the material and are compressed into small fluctuations in pressure and density. The path of the surface waves can be made into an arc that directs the waves outside the protective cloak. The technique could be applied to buildings by installing the rings into foundations.
Sebastien Guenneau, from the University’s Department of Mathematics, who developed the technology with Stefan Enoch and Mohamed Farhat from the Fresnel Institute (CNRS) in Marseilles, France, explained: “We are able to ‘tune’ the cloak to the differing frequencies of incoming waves which means we can divert waves of a variety of frequencies. For each small frequency range, there is a pair of rings which does most of the work and these move about a lot – bending up and down – when they are hit by a wave at their frequency.
“The waves are then directed outside the cloak where they return to their previous size. The cloak does not reflect waves – they continue to travel behind it with the same intensity. At this stage, therefore, we can only transfer the risk from one area to another, rather than eliminate it completely.”
He added: “This work has enormous potential in offering protection for densely populated areas of the world at risk from earthquakes. The challenge now is to turn our theories into real applications that can save lives – small scale experiments are underway.”
Seismic waves also include coupled pressure and shear body waves which are less destructive than surface waves. Sebastien Guenneau and Sasha Movchan at the University of Liverpool, together with Michele Brun at Cagliari University, have designed an ‘elastic’ cloak to protect against these particular seismic waves and the team is currently seeking a suitable material to accommodate the elastic parameters of the cloak.
The new research to protect against earthquakes is published in Applied Physics Letters and Physical Review Letters.
‘Invisibility Cloak’ Could Protect Against Earthquakes
20 July 2009 Liverpool, University of
Research at the University of Liverpool has shown it is possible to develop an ‘invisibility cloak’ to protect buildings from earthquakes.
The seismic waves produced by earthquakes include body waves which travel through the earth and surface waves which travel across it. The new technology controls the path of surface waves which are the most damaging and responsible for much of the destruction which follows earthquakes.
The technology involves the use of concentric rings of plastic which could be fitted to the Earth’s surface to divert surface waves. By controlling the stiffness and elasticity of the rings, waves travelling through the ‘cloak’ pass smoothly into the material and are compressed into small fluctuations in pressure and density. The path of the surface waves can be made into an arc that directs the waves outside the protective cloak. The technique could be applied to buildings by installing the rings into foundations.
Sebastien Guenneau, from the University’s Department of Mathematics, who developed the technology with Stefan Enoch and Mohamed Farhat from the Fresnel Institute (CNRS) in Marseilles, France, explained: “We are able to ‘tune’ the cloak to the differing frequencies of incoming waves which means we can divert waves of a variety of frequencies. For each small frequency range, there is a pair of rings which does most of the work and these move about a lot – bending up and down – when they are hit by a wave at their frequency.
“The waves are then directed outside the cloak where they return to their previous size. The cloak does not reflect waves – they continue to travel behind it with the same intensity. At this stage, therefore, we can only transfer the risk from one area to another, rather than eliminate it completely.”
He added: “This work has enormous potential in offering protection for densely populated areas of the world at risk from earthquakes. The challenge now is to turn our theories into real applications that can save lives – small scale experiments are underway.”
Seismic waves also include coupled pressure and shear body waves which are less destructive than surface waves. Sebastien Guenneau and Sasha Movchan at the University of Liverpool, together with Michele Brun at Cagliari University, have designed an ‘elastic’ cloak to protect against these particular seismic waves and the team is currently seeking a suitable material to accommodate the elastic parameters of the cloak.
The new research to protect against earthquakes is published in Applied Physics Letters and Physical Review Letters.