共查询到20条相似文献,搜索用时 328 毫秒
1.
本文提出了一种新型局域共振复合单元声子晶体结构, 并结合有限元方法对结构的带隙机理及低频共振带隙特性进行了分析和研究. 共振带隙产生的频率位置由所对应的局域共振模态的固有频率决定, 并且带隙宽度与局域共振模态的品质因子及其与基体之间的耦合作用强度有关. 采用局域共振复合单元结构可以实现声子晶体的多重共振, 在低频范围能打开多条共振带隙, 但受到共振单元排列方式的的影响. 由于纵向和横向局域共振模态的简并, 复合单元结构能在200 Hz以下的低频范围打开超过60%宽度的共振带隙, 最低带隙频率低至18 Hz. 这为声子晶体结构获得低频、超低频带隙提供了一种有效的方法.
关键词:
局域共振
低频带隙
复合单元
声子晶体 相似文献
2.
A new acoustic metamaterial plate is presented for the purpose of suppressing flexural wave propagation. The metamaterial unit cell is made of a plate with a lateral local resonance (LLR) substructure which consists of a four-link mechanism, two lateral resonators and a vertical spring. The substructure presents negative Young’s modulus property in certain frequency range. We show theoretically and numerically that two large low-frequency band gaps are obtained with different formation mechanisms. The first band gap is due to the elastic connection with the foundation while the second is induced by the lateral resonances. Besides, four-link mechanisms can transform the flexural wave into the longitudinal vibration which stimulates the lateral resonators to vibrate and to generate inertial forces for absorbing the energy and thus preventing the wave propagation. Frequency response function shows that damping from the vertical spring has little influence on the band gaps, although the damping can smooth the variation of frequency response (see the dotted line in Figs. 10 and 11). Increasing the damping of the lateral resonators may broaden the second band gap but deactivate its effect. This study provides guidance for flexibly tailoring the band characteristics of the metamaterial plate in noise and vibration controls. 相似文献
3.
Yang Fan Li Fei Meng Shuo Li Baohua Jia Shiwei Zhou Xiaodong Huang 《Physics letters. A》2018,382(10):679-684
Phononic crystals are known as artificial materials that can manipulate the propagation of elastic waves, and one essential feature of phononic crystals is the existence of forbidden frequency range of traveling waves called band gaps. In this paper, we have proposed an easy way to design phononic crystals with large in-plane band gaps. We demonstrated that the gap between two arbitrarily appointed bands of in-plane mode can be formed by employing a certain number of solid or hollow circular rods embedded in a matrix material. Topology optimization has been applied to find the best material distributions within the primitive unit cell with maximal band gap width. Our results reveal that the centroids of optimized rods coincide with the point positions generated by Lloyd's algorithm, which deepens our understandings on the formation mechanism of phononic in-plane band gaps. 相似文献
4.
声子晶体管路的带隙特性,可以实现管路系统在特定频率下的噪声控制.利用二维模态匹配法推导出单个内插扩张室元胞的传递矩阵,结合Bloch定理,得到声子晶体管路的能带结构计算方法;验证了二维方法在计算能带结构时的准确性.研究发现,内插扩张室声子晶体管路存在布拉格带隙和局域共振带隙.进一步研究了晶格常数以及内插管长度对能带结构的影响,结果表明,晶格常数主要控制布拉格带隙,而内插管长度对局域共振带隙有较大的影响,并研究了两种参数变化下的带隙耦合.研究结果可以为管路降噪设计提供新的思路. 相似文献
5.
Omnidirectional Single-negative Gap and in Fibonacci Sequences Composed of Single-negative Materials
Ting-yi Shang Hui-yun Zhang Yu-ping Zhang Peng Wang Jian-quan Yao 《International Journal of Infrared and Millimeter Waves》2007,28(8):671-676
The band structures of Fibonacci sequence composed of single-negative materials are studied with a transfer matrix method.
A new type of omnidirectional single-negative gaps is found in the Fibonacci sequence. In contrast to the Bragg gaps, such
an omnidirectional single-negative gap is insensitive to the incident angles and polarization, and is invariant upon the change
of the ratio of the thicknesses of two media. It is found that omnidirectional single-negative gap exists in the other Fibonacci
sequence, and it is rather stable and independence of the structure sequence. 相似文献
6.
The tunable two-dimensional photonic crystals band gap, absolute photonic band gap and semi-Dirac point are beneficial to designing the novel optical devices. In this paper, tunable photonic band gaps structure was realized by a new type two-dimensional function photonic crystals, which dielectric constants of medium columns are functions of space coordinates. However for the two-dimensional conventional photonic crystals the dielectric constant does not change with space coordinates. As the parameter adjustment, we found that the photonic band gaps structures are dielectric constant function coefficient, medium columns radius, dielectric constant function form period number and pump light intensity dependent, namely, the photonic band gaps position and width can be tuned. we also obtained absolute photonic band gaps and semi-Dirac point in the photonic band gaps structures of two-dimensional function photonic crystals. These results provide an important theoretical foundation for design novel optical devices. 相似文献
7.
A novel small size multi-band gaps phononic crystal (hPC) composed of the periodic plumbum and aluminum mass has been investigated in this paper, we calculated the dispersion relations and the displacement fields with finite element method (FEM). The influences of the geometrical parameters and materials parameters on the band structure are further investigated. We studied the influence factors of band gap by the model of origin anti-resonance. There are many flat bands in the characteristic frequency curve. The band gap covers a large range in low frequency. 相似文献
8.
9.
Photonic band structure of three-dimensional colloidal crystals with field-induced lattice structure transformation 下载免费PDF全文
By utilizing the electrorheological effect,
three-dimensional colloidal crystals can be produced, whose lattice
structure can be changed from the body-centered-tetragonal lattice
to other lattices under the application of electric fields. This
paper calculates photonic band structures of such crystals with
lattice structure transformation, and demonstrates the existence of
complete band gaps for some intermediate lattices. Thus, it becomes
possible to use the electrorheological effect to achieve photonic
crystals with desired photonic gap properties resulting from tunable
structures. 相似文献
10.
《Physics letters. A》2020,384(13):126253
This letter is concerned with acoustic wave propagation and transmission in acoustic waveguides with periodically grafted detuned Helmholtz resonators. The interplay of local resonances and Bragg band gaps in such periodic systems is examined. It is shown that, when the resonant frequencies of the resonators are tuned close to a Bragg band gap, the behavior of the Bragg band gap can be affected dramatically. Particularly, by introducing appropriately tuned resonators, the bandwidth of a Bragg band gap can be reduced to zero, leading to a very narrow pass band with great wave attenuation performance near both band edges. The band formation mechanisms of such periodic waveguides are further examined, providing explicit formulae to locate the band edge frequencies of all the band gaps, as well as the conditions to achieve very narrow pass bands in such periodic waveguides. 相似文献
11.
利用激光全息光刻技术, 在重铬酸盐明胶 感光材料中制备了掺杂有机染料的层状光子晶体. 在532 nm纳秒脉冲激光激励下, 样品的荧光光谱表现出良好的带隙特征; 随着抽运能量的增加, 在荧光带隙带边位置获得了激射光, 并进一步研究了光子晶体的带边位置与染料荧光峰的匹配对激射的影响.带边位置越靠近染料的荧光峰, 激射阈值越低, 反之则不易产生激射.该研究为超低阈值光子晶体激光器的发展提供了思路和方法.
关键词:
全息光刻
光子晶体
荧光带隙
低阈值激射 相似文献
12.
A review is presented of various composite structures containing double-negative metamaterials or two types of single-negative metamaterials. In particular, non-Bragg band gaps arising from phase-compensation or tunneling effects and their manipulation of light are stressed. The non-Bragg band gaps that are robust against incident directions, thickness randomness and are easily tuned by changing the structural parameters can not only expand our ability in controlling the flow of light, but also provide new mechanisms for the design of photonic devices. 相似文献
13.
If an ionic material is used in a photonic crystal, the lattice resonance creates a polaritonic gap in the infrared range. The interaction between a polaritonic gap and the structure gap in a 2D square photonic crystal is studied by transfer matrix photonic band structure calculations. The polaritonic gap appears for a surprisingly low volume density of the ionic material. The TM gaps are larger than the TE gaps, as in the dielectric case. By varying the lattice constant, the structure gaps can be shifted across the polaritonic gap, and the effects of merging the two gaps can be studied. 相似文献
14.
15.
We present a dual-beam multiple exposure technique that can generate complex 2-D and 3-D band gap template structures in a photosensitive material. The system parameters related to the planar interference pattern produced by two laser beams and reorientation effect of the sample relative to these planes is presented. Structures such as the 2-D, square and hexagonal arrays of dielectric “rods” and “holes” and the 3-D, cubic, Yablonovite and other profiles are given. We perform band gap calculations on these structures when the dielectric contrast has been increased using a backfill process and discuss techniques for increasing the band gap by sculpting the dielectric profile. 相似文献
16.
Flexural vibration band gaps in thin plates with two-dimensional binary locally resonant structures 下载免费PDF全文
The complete flexural vibration band gaps are studied in the thin plates
with two-dimensional binary locally resonant structures, i.e. the composite
plate consisting of soft rubber cylindrical inclusions periodically placed
in a host material. Numerical simulations show that the low-frequency gaps
of flexural wave exist in the thin plates. The width of the first gap
decreases monotonically as the matrix density increases. The frequency
response of the finite periodic thin plates is simulated by the finite
element method, which provides attenuations of over 20dB in the frequency
range of the band gaps. The findings will be significant in the application
of phononic crystals. 相似文献
17.
与介质光子晶体相比,金属光子晶体的带隙特性在毫米波和亚毫米波波段有着重要的应用价值.基于Yee网格的频域有限差分法推导得出的本征模方程,求解后能方便而又可靠地得出介质光子晶体的带隙图和场分布.但由于金属与介质的本质差异,该方法不能直接应用于金属光子晶体.文中引入了金属表面边界条件,推导了二维金属周期结构的光子带隙本征模方程.通过数值计算,得出了不同晶格结构(正方/三角格子)下两种模式(TE/TM)的全禁带特性,并与介质周期结构的禁带特性进行对比,分析了金属周期结构在模式选择和器件集成方面的优点. 相似文献
18.
与介质光子晶体相比,金属光子晶体的带隙特性在毫米波和亚毫米波波段有着重要的应用价值.基于Yee网格的频域有限差分法推导得出的本征模方程,求解后能方便而又可靠地得出介质光子晶体的带隙图和场分布.但由于金属与介质的本质差异,该方法不能直接应用于金属光子晶体.文中引入了金属表面边界条件,推导了二维金属周期结构的光子带隙本征模方程.通过数值计算,得出了不同晶格结构(正方/三角格子)下两种模式(TE/TM)的全禁带特性,并与介质周期结构的禁带特性进行对比,分析了金属周期结构在模式选择和器件集成方面的优点.
关键词:
金属光子晶体
频域有限差分法
全禁带 相似文献
19.
运用FDTD(时域有限差分法)研究了弹性波/声波通过二维正方形排列的铁/水声子晶体的传播特性.发现铁/水声子晶体在高频范围存在完全带隙,软包层铁/水声子晶体在低频范围出现共振带隙,它们分别对应于不同的带隙形成机理.通过铁/水声子晶体和软包层铁/水声子晶体的组合,可以得到从高频到低频的组合宽带隙结构,从而达到在更宽频范围内控制弹性波传播的目的;而且通过调整包层的厚度、铁芯的大小、以及填充率等结构参数,可以有效地调节组合宽带隙的频率结构. 相似文献
20.