耦合共振型进气消声器声学特性分析

 为了拓宽消声频带、提高消声量,克服传统串并联腔体结构安装空间大等缺点,研究了一种新型耦合共振型进气消声器．利用一维平面波理论探究了Helmholtz消声器的消声机理；为准确模拟消声器突变结构处的高阶次声波,建立了并联共振腔结构和新型结构Helmholtz消声器的声学有限元计算模型；计算、分析、比较了各结构的消声特性,重点研究了新型结构尺寸参数对其共振频率与传递损失的影响．计算结果表明：由于腔体间空气耦合共振作用,两腔耦合共振型Helmholtz消声器具有3个共振频率；两共振腔连接管的长度与直径是影响该结构消声性能的关键尺寸,减小连接管长度或者增大直径都可以拓宽消声器的消声频带,提高消声性能．这将为主动、被动耦合共振型进气消声器的设计提供重要参考．  

统计能量分析方法声振预测应用研究

从声振系统激励和响应的频谱特征、预测模型的特点、精度等方面总结了统计能量分析方法（SEA）在多个领域内的应用成果,得出了含有声子系统的双壳和单壳系统是两种基本的SEA声振预测模型的结论。该系统的特点是内外的声能交换须通过声振耦合来实现,当激发的声波频率低于双壳的共振频率时,双壳系统转化为单壳系统。深入讨论了影响其SEA模型预测精度的主要因素是结构子系统的划分方式、统计能量分析参数的测量,以及有界空间内声振耦合损耗因子的正确计算。  

Microwave Resonant Transmission in a Superconducting Fabry–Perot Bilayer

Microwave resonant transmission properties in a superconducting Fabry–Perot bilayer made of a high-temperature superconductor (YBa₂Cu₃O_7−x ) and a nearly ferroelectric superconductor (n-SrTiO₃) are theoretically investigated. The effect of high-temperature superconducting layer on the unusual resonant transmittance existing in a nearly ferroelectric superconductor is investigated. It is shown that a frequency-agile two-layer coating can be obtained with the addition of the high-temperature superconducting coating. Resonant frequencies can be shifted by varying the thickness of this coating. In addition, the ultra-narrow filtering feature makes such a bilayer resonator useful in the superconducting microwave electronics, such as a frequency sampler or spectrum analyzer in the signal processing.  

Investigation of Fano resonances in the optomechanical cavity via a magnetic field

We theoretically investigate Fano resonances in a single-cavity optomechanical system, which is driven by an external force arisen from a passed current through one end of a mirror in a magnetic field. It is revealed that the asymmetric Fano shape in the optomechanical system strongly depended on the strength of the magnetic field and current intensity. Further, we study the phase of the transmitted probe light and find a tunable switch from slow to fast light and vice versa via manipulating the magnetic field.  

Analysis on transmission characteristics of nested ring resonators

The transmission characteristics of the nested ring resonator are analyzed. The intensity transmission of the resonator is obtained. Based on this, the critical coupling and coupled-resonator-induced transparency conditions are derived as length ratio of the U-shaped loop and the inner circle ring is an integer or half-integer. Accurate expressions of these two conditions are provided. Numerical calculation at some specific parameters verifies the conditions and demonstrates their variations vs. parameters of the resonator.  

Excitation techniques for resonance analysis of packages

This paper discusses the advantages and drawbacks of various excitation techniques used to detect the vibration transmissibility characteristics of packaging systems, such as resonant frequencies and damping properties. Historical and background information on the commonly used sweep sine excitation technique is presented. In addition, more recent and sophisticated techniques, such as broad‐band random excitation, random burst, pulse and chirp excitation are discussed and their usefulness highlighted. More specifically, the suitability of these excitation techniques in stimulating and detecting the non‐linear characteristics of packaging systems are considered. Some of the advantages of using low‐level and low‐duration excitation techniques to minimize potential damage to the test prototype are also expounded. Copyright © 2002 John Wiley & Sons, Ltd.