Manipulation Of Sound Properties By Acoustic Metasurface And Metastructure
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Manipulation of Sound Properties by Acoustic Metasurface and Metastructure
This thesis focuses on the manipulation of sound properties by artificial materials. It elaborates on the fundamental design of acoustic metasurfaces and metastructures as the extension of metamaterials, and their functionality in the manipulation of sound properties. A broad and comprehensive guideline of designing acoustic metasurfaces and metastructures is also provided. Based on the proposed subwavelength metasurfaces and the metastructures with a simplified layout, multiple potential applications are demonstrated. This thesis will appeal to acoustic engineers and researchers who are interested in designing acoustic artificial structures.
Nanomaterials, Metamaterials, and Smart Materials: Synthesis and Characterization
Author: Kamal I. M. Al-Malah
language: en
Publisher: Bentham Science Publishers
Release Date: 2025-07-02
Nanomaterials, Metamaterials, and Smart Materials: Synthesis and Characterization explores the science and technology behind nanomaterials, metamaterials, and smart materials, focusing on their synthesis, characterization, and applications. It bridges fundamental concepts with cutting-edge research, covering material classification, size-dependent properties, fabrication challenges, and real-world applications in energy, healthcare, and electronics. Societal and ethical considerations are also discussed, providing a well-rounded perspective on material advancements. Key Features: - Comprehensive Coverage: Explores nanomaterials, metamaterials, and smart materials, from foundational principles to advanced applications. - Practical Learning Tools: Includes prerequisite concepts, video resources, and end-of-chapter problems for self-assessment. - Interdisciplinary Approach: Connects physics, chemistry, and engineering to real-world applications. - Extensive References: Provides citations for further exploration and deeper learning.
Nonlocality and Willis Coupling in Acoustic Metamaterials and Metasurfaces
Acoustic metamaterials and metasurfaces are artificial materials and surfaces composited with meta-atoms and inclusions at the subwavelength scale but behave homogeneously in the macroscopic scale with unusual properties in the manipulation of sound waves. Most of the research in this field has focused so far on the study of the local response of the materials and surface properties but neglected the nonlocality. This dissertation focuses on the study of nonlocal phenomena in acoustics, and explore their unusual abilities in the control and manipulation of sound waves. The dissertation starts with the exploration of pressure-velocity coupling phenomena, also known as Willis coupling or acoustic bianisotropy, in a single subwavelength inclusion and derived general bounds on the Willis response of acoustic scatterers, indicating these bounds can be reached through proper design. A systematic design approach of reciprocal Willis inclusion has been outlined for the realistic implementation of acoustic inclusions with Willis response from zero, mild to maximum. My study shows that reciprocal Willis responses can be mainly attributed to geometrical asymmetries. By breaking the system’s time-reversal symmetry through bias flow, Willis coupling has also been observed in geometry-symmetrical systems. Then, I changed my viewpoint from single inclusion to the collective response of metamaterials at the macroscopic level. By combining moving media with zero-index acoustic propagation, giant bianisotropy and extreme nonreciprocity were achieved in the metamaterials with modest mechanical motion. This special acoustic response was utilized to induce non-reciprocal positive-to-negative sound refraction and the non-reciprocal metamaterial lens which could focus object when the excitation is from a specific side. Finally, the study was extended to metasurface, and explore their unusual properties by considering the strong coupling between neighboring elements. The general impedance relation with the consideration of coupling between neighboring elements was proposed and the mechanism was applied to the design of nonlocal passive metasurfaces which could overcome the limitations of local designs, and achieve unitary efficiency for extreme beam steering. The nonlocal metasurface has also been applied to the design of acoustic hyperbolic metasurface requiring extreme anisotropic impedance which was considered impossible in the local metasurface