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標題: | 可調式二維聲子晶體波傳現象 Acoustic wave propagation of tunable two-dimensional phononic crystal |
作者: | Chen-Che Tsai 蔡政哲 |
指導教授: | 宋家驥(Chia-Chi Sung) |
關鍵字: | 聲子晶體,填充率,定向聲源,負折射,共振腔,頻溝, phononic crystal,filling ratio,collimating acoustic wave beam,negative refraction,resonant cavity,band gap, |
出版年 : | 2011 |
學位: | 碩士 |
摘要: | 近年來,於聲子晶體領域之研究發現了重要的特殊形式物理特性。有別於在早期聲子晶體的研究與探討主要集中於能隙的應用與計算,如濾波器、波導或共振腔的設計,根據近期文獻研究發現在其傳導區擁有異常之頻散現象,發現聲子晶體具有負折射特性,使得該方面之研究更成為最近學術界的熱門話題。
本文旨在研究利用此異常頻散現象以及調整幾何形狀排列的改變應用於定向聲源、減噪模組等討論,並以有限元素法( Finite Elementary Method )模擬其波傳結果。 在定向聲源的工作中,為了使點波源自我準則現象更明顯,我們改變了二維聲子晶體排列方式以及選擇其中較佳的結果和文獻中利用共振腔定向聲源方式作比較,使其便於實作上架置於並且達到更好的效果;減噪模組方面我們將三組填充率、填充物半徑、晶格常數皆不同的聲子晶體作組合,由於此三組聲子晶體各自的濾波頻段不同,將其疊合在一起以達到寬頻段濾波的效果,將人耳可聽到的頻段能量過濾掉。有別於以往設計聲子晶體來產生窄頻濾波效果,這種擁有寬頻濾波效果的多層聲子晶體可應需求不同應用於傳統研究領域外的地方。 本論文將藉由可調式二維聲子晶體改變其原始規則形態探討週期性結構所衍伸出的多種特殊物理現象發展適用的二維聲子晶體波傳理論。 這些二維聲子晶體波傳理論進可發展至三維聲子晶體以及應用在未來的生醫領域與機械領域上。 Many dispersion characteristics of phononic crystal are investigated. Such as negative refraction have become hot topics of scientific research in recent years. The arrayed arrangement tunable dispersion characteristics of phononic crystals are observed. By controlling the arrayed arrangement, we can tune the refractive direction and adjust the location of focus and then the tunable acoustic superlens can be designed. There has been much research into the collimation of light source beams by photonic crystals. However, this effect has seldom been achieved using phononic crystals (PCs). On the other hand, it has been shown that acoustic waves may be collimated by resonant cavities in 2D PCs to obtain high directivity. We focuses on the collimation of an acoustic point source by negative refraction in 2D PCs. The advantages of this method are: experiment apparatus is uncomplicated; the divergence angle is only about 5° in the far region; and it has low attenuation when propagating energy. And we also combine three different form 2D PCs become a multilayered PCs to obtain wide frequency bandwidth(20Hz~20kHz) effect. In this method, we can reduce noise which people can hear. It is anticipated that this collimating beam method and multilayered PCs may be applied in 2D and 3D acoustic assembled devices or in ultrasonic and sonar detection devices. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/32918 |
全文授權: | 有償授權 |
顯示於系所單位: | 工程科學及海洋工程學系 |
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