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Phononic crystal interlayer multiple scattering theory and related applications phononic crystal design

Author: QiuChunYin
Tutor: LiuZhengZuo
School: Wuhan University
Course: Condensed Matter Physics
Keywords: Dimensional phononic crystals Interlayer multiple scattering theory Negative refraction Select mode acoustic filter Directional sound source
CLC: O735
Type: Master's thesis
Year: 2005
Downloads: 323
Quote: 2
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Abstract


In this paper we derive the elastic field detail / acoustic field in two-dimensional layers multiple scattering theory and applications of phononic crystal design. More specifically: First, we expand the interlayer multiple scattering theory to two-dimensional phononic crystals, calculate the reflection and transmission coefficients. In this line of thinking, the phononic crystal is seen as a series arranged in a certain direction with a one-dimensional periodic monolayers. By calculating the scattering matrix layer multilayer system we end up with the reflection and transmission coefficients. In order to show the application of this method, we calculate the pure solid components and solid - liquid mixing component system transmission coefficient. By comparing experimental band structure calculations and ultrasonic measurements, we examined the effectiveness of this method of calculation. Then, we discuss the two-dimensional phononic crystal acoustic negative refraction behavior and ultra-lens imaging effect. We first multi-Gaussian beam incident phononic crystals, showing its acoustic negative refraction and left-handed behavior. More importantly, we have studied the effective refractive index, respectively, n ≠ -1 and n = -1 phonon crystal superlens imaging effect. In both cases, the precise numerical simulation confirms that we have obtained far field of the real image, and the law of refraction in the beam-physical analysis based entirely coincide. Then, we discuss in detail the composition of the solid component from the pure two-dimensional phononic crystal pair momentum barrier resonant tunneling state properties. Frequency continuously adjustable resistance and easy to control the quality factor makes tunneling states demonstrated in the design and optimization of the acoustic equipment broad application prospects. It is important in such a system, the vertical mode and the transverse mode of the resonant tunneling state can be completely distinguished. Therefore, the use of this state we have designed a simple and effective mode selection acoustic filter, at a desired frequency it can easily be individually selected vertical or horizontal external incident. Finally, we designed two ways directional sound sources, and predict the orientation of the sound source with a wide range of applications, such as acoustic or acoustic detection devices integrated device. A) the use of phononic crystal band-edge states, our results show that their access to high directivity and radiation enhancement possibilities. We studied numerically arranged in a square mosaic crystal acoustic phonon energy radiation source angular distribution. The results show that the angular distribution of the radiation energy and the enhancement factor strongly depends on the source relative to the position in which the symmetry of the unit cell. Finally, by using the complete band gap crystal substrate phonons, we obtained only a single branch of the directional radiation radiation, its semi-strong wide angle is approximately 5.2 degrees. B) the use of phononic crystals with planar defects resonance defect states. By the sound source placed in the two-dimensional phononic crystal resonant cavity, we obtain a semi-strong angular width of less than six degrees of radiation field. High quality factors and a large scale to improve the crystal orientation of the sound source direction. By adjusting the interval of the cavity, which

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CLC: > Mathematical sciences and chemical > Crystallography > Crystal physics > The acoustic properties of the crystal
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