本文以二維圓柱層狀聲學斗篷做為最佳化設計對象，分別由材料參數、斗篷層數及厚度等因素分析探討最佳化方法，使得層狀斗篷散射降至最低。最佳化過程使用Nelder-Mead method和Genetic algorithms兩種數值方法尋求參數最佳解，找出最適合層狀斗篷的材料參數及厚度配置，可使斗篷有很好的表現；但最佳化方法有其適用範圍，本文中藉由調整斗篷尺寸、層數、材料範圍…等參數，隨著不同因素的改變，觀察其對最佳化方法結果的影響，可發現若斗篷尺寸、層數變化設定在適當的範圍中，則最佳化方法能明顯表現出成果；反之若斗篷尺寸、層數變化設定在不適當的範圍中，則無論如何努力，最佳化方法都很難有效發揮其功能，達到改善層狀斗篷隱形效果的功能。因此在本文中致力於探討最佳化方法與其結果，並討論最佳化方法所適用範圍，以期能掌握最佳化方法的性質，善用其優點，幫助設計出具有更好隱形效果的層狀斗篷。

In this thesis, we present an optimized design of multilayered cylindrical acoustic cloak. The optimization procedure adjusts the material parameters, number of layers, and the thickness of the cloak to reduce the maximum scattering by an object. We utilize a Nelder-Mead method and a genetic algorithm to search for the optimal solution of material parameters and thickness distributions of the cloak. Selected examples for acoustic cloak comprised of isotropic and anisotropic layers are demonstrated in our study. We find that the optimized design can indeed reduce the scattering and the cloak performance can be much improved. The limition of the proposed optimization design is also discussed. It is hoped that the proposed optimization process can provide an efficient way in the design and fabrication of acoustic cloak.

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