演講公告

新聞標題：　( 2008-11-27 )

• 演講主題：Some Applications of the Homogenization Theory for the Periodic Structure

• 主講人：劉英宏博士(中研院應用科學研究中心)

• 演講日期：97年12月09日(星期二)<br>下午2:00-3:00

• 演講地點：(光復校區)科學一館223室

• 摘要內容：
  

  In this study, we apply the homogenization theory to periodic elastic structures and three main characteristics of that are addressed. First, we investigate band structures of phononic crystals with particular emphasis on the effects of the mass density ratio and of the contrast of elastic constants. It is shown that the density ratio rather than the contrast of elastic constants is the dominant factor that opens up phononic band gaps. Then we aimed to study propagating modes of elastic waves in
  periodic solid layers in ideal or viscous fluids. In particular, at the long wavelength limit, a three-scale homogenization analysis is developed to derive the effective group velocities in analytical forms for the shear-vertical (SV) as well as for the longitudinal-shear horizontal (P- SH) waves. It is found that propagating modes, i.e., modes with real group velocities may be supported even if the fluid phase is viscous. Finally, we propose the model of effective mass density as solid embedded into fluid for one-, two- and three-dimensionalities. The physical background of these observations is explained by applying the theory of homogenization to investigate the group velocities of the low-frequency bands at the center of symmetry Γ.

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