资深农民工分享 http://blog.sciencenet.cn/u/马红孺 上海交通大学机动学院教授http://www.physics.sjtu.edu.cn/hrma

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科大遮音程序 助造「隐形」潜艇

已有 7363 次阅读 2008-6-17 06:19 |个人分类:生活点滴

 

这是香港文汇报最近的一个报道,写的还比较靠谱。

科大遮音程序 助造「隐形」潜艇


http://www.wenweipo.com   [2008-06-14]   放大图片

 ■科大讲座教授陈子亭等的研究发现,为「遮音层」提供必要的数学理论基础。西班牙科学家应用他们的研究成果,刊出「遮音层」蓝图,利用新技术制造特殊隔音材料,可造「隐形」潜艇。图为一艘法国核动力攻击潜艇。资料图片

 【本报讯】西班牙科学家应用香港科技大学及美国杜克大学早前的研究成果,在《新物理学期刊》中刊出「遮音层」的蓝图。这一蓝图的原理,是利用新技术制造特殊材料,遮在物体外达到完全隔音,或在声纳检测下完全隐形的效果,预计新技术可应用在建筑及军事上,例如建造隔音屋、音响效果更佳的音乐厅及「隐形」潜艇等。有关的蓝图是建基于香港科大物理系讲座教授陈子亭及研究人员陈焕阳(Huanyang Chen音译)于月前发表的研究,为「遮音层」提供必要的数学理论基础。

 陈子亭及陈焕阳月前发表的研究,发现了在数学上原用于平面几何的「遮音方程序」,能转化为可于现实立体世界应用的直流电导电性方程序,为制作「遮音层」提供了重要的理论基础。陈子亭主要从事材料物理的研究,早在2000年,他参与的科大研究小组亦研制了一种新颖的声学材料,透过将声波全反射达到在日常生活中消除噪音的目的,这一研究广获肯定;他近年亦有进行纳米材料技术研究,现身兼科大 William Mong纳米科学及技术研究所所长。

 伦敦帝国学院的隐形科技专家彭德莱教授表示,遮盖研究多年前已有成果,例如杜克大学前年便成功令一条小铜圆柱在微波检测下完全隐形;至于迄今仍未有「遮音层」,是因为未研究出所需物料所致。

生产「音波水晶」做隔音实验

 有份参与「遮音层」研究的巴伦西亚理工大学桑切斯-德埃萨博士表示,「遮音层」的原理是令射向物件的声波不反射开去,并绕过物件继续前进,就如河水绕过河中的石头一样,相信利用一层层排列好的圆柱状的微型「音波水晶」,便可达到这效果。在计算机模拟实验中,只需200层「音波水晶」便可有效阻隔噪音,不过,「遮音层」实际厚薄将视乎需阻隔的声音波长而异。

 他下一步有意生产「音波水晶」进行实验,来验证模拟实验的结果。

 

 

最近的另一报道“美研制超级新材料 可实现噪音消失”http://www.sciencenet.cn/htmlnews/2008/6/207963.html  则有点让人不知所云,云遮雾罩的感觉。

事实上,这是来自sciencedaily的一个报道的翻译和外推,只是翻译的比较乱。 这里是原文的链接

http://www.sciencedaily.com/releases/2008/06/080612193837.htm

 

原文如下:

Nuisance Noise Silenced By Acoustic Cloak

ScienceDaily (Jun. 13, 2008) — Researchers in Spain have proven that metamaterials, materials defined by their unusual man-made cellular structure, can be designed to produce an acoustic cloak -- a cloak that can make objects impervious to sound waves, literally diverting sound waves around an object.

The research builds on recent theoretical research which has sought ways to produce materials that can hide objects from sound, sight and x-rays.

Daniel Torrent and José Sánchez-Dehesa from the Wave Phenomena Group, Department of Electronics Engineering at the Polytechnic University of Valencia, cite theoretical work published early last year in NJP by researchers from Duke University in North Carolina, US, as the starting point for their more practical approach.

To realise the cloak physically, the Spanish research team calculated how metamaterials constructed with sonic crystals, solid cylinders in a periodic array that can scatter sound waves, could be used in a multilayered structure to divert sound completely around an object.

The researchers performed multiple simulations to test their theory. They investigated the optimum number of layers required to completely divert sound and how thin the materials could be made to maintain their use but also ensure that they are easy to implement.

Results were very encouraging, showing that optimum cloaking requires approximately 200 layers of the metamaterial but that there is scope for much thinner materials to be used than technology can currently produce. So, put simply, watch this space.

José Sánchez-Dehesa, one of the lead researchers, writes, "We hope that this proposal will motivate future experimental work demonstrating the materials' performance."

One of the first uses of the material is likely to be warships, hoping to avoid sonar radars which pick up on the noise that ships emit, but if developments continue apace it could be used in concert halls to direct noise away from problem spots or even as a way to deal with noisy neighbours.

Journal reference: Acoustic cloaking in two dimensions: a feasible approach.13 June, 2008 New Journal of Physics (NJP).

根据我们最近的研究和理解,这篇文章建议的方法其实并不feasible. 大体上是他们以前的想法加上南京大学组最近的建议提出的一个方案。



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