不完全连续三层微梁谐振器中热弹性阻尼研究

基于Euler-Bernoulli梁理论和二维傅里叶热传导定律,针对两端固定约束边界条件,通过截面分割法得到不完全连续三层微梁的固有频率,利用格林函数法求解波动温度场分布函数。然后利用能量法,建立了热弹性阻尼（Thermoelastic damping,TED）解析模型。通过ANSYS有限元数值解与MATLAB解析解对比,验证了所建模型的正确性。结果表明：(1)TED中厚度方向的收敛速度远大于长度方向收敛速度,TED对厚度方向上的热传递更为敏感;(2)在此结构基层开槽处两端无限接近时,可以简化为完全连续微梁结构模型;(3)若微梁长恒定不变,随着开槽长度的增加,TED呈减小趋势;(4)通过基层的开槽,此结构微梁的最大弹性势能以及热能损失都会降低;(5)在基层中进行刻蚀开槽时,槽的长度与厚度的比值应取较大值。     

微谐振器结构性能的有限元分析

微谐振器是试飞测试系统的重要组成部件,微谐振器的性能影响到试飞测试系统的精确度.为了提高微谐振器的性能,在传统结构的基础上,提出改变微谐振器中折叠梁、驱动梳齿等结构的尺寸来改善其性能.运用有限元法对不同结构尺寸下的微谐振器进行模态、品质因子分析.仿真结果表明,横向微谐振器的一阶模态频率的大小很大程度上受到折叠梁尺寸的影响;静电梳齿的尺寸设计中,梳齿的宽度是影响驱动力和品质的一个关键因素.仿真结果表明,对提高微谐振器的性能具有一定的指导意义.     

双层微梁结构谐振器中波动温度场的研究

针对两端固定双层微梁结构谐振器,利用格林函数,求解了一维热传导时梁中的波动温度场分布函数.通过解析模型计算结果与有限元数值模型计算结果的比较,验证了所得解析模型的有效性,并讨论两种模型的优缺点.研究结果表明:波动温度的幅值仅为平衡温度的0.06％左右,由于波动温度场产生的热应变也非常小;激振频率对波动温度场的影响非常大;微梁的总长度与材料比对温度场也有影响.     

静电驱动微梁谐振器的厚度形态误差特性分析

本文研究了一类双极板静电驱动两端固支微梁谐振器.考虑中性面拉伸和厚度形态误差,建立了微谐振器连续体模型.厚度形态误差通过设置参数方程实现,方程中包含误差参数λ,用于调整误差影响程度.利用伽辽金法和Newton-Cotes法将系统化简为单自由度模型.首先,通过COMSOL Multiphysics有限元软件对理论求得的静电力进行了仿真验证.然后,推导了不考虑厚度形态误差时系统的吸合情况,发现系统在特定情况下可以出现二次吸合现象.通过改变误差参数,分析了厚度形态误差对吸合情况的影响.最后,利用多尺度法求出系统小幅振动下的响应,研究了厚度形态误差对等效固有频率和系统软硬特性的影响.     

基于微环谐振器的甲烷传感器

提出了一种新型的基于微环谐振器的甲烷传感器。该传感器通过微环表层的穴番A涂层来增加微环的有效折射率,使微环谐振器中谐振波长随甲烷浓度的增加而向右漂移;通过测量输出光信号的谐振波长推算出甲烷浓度。理论分析结果表明,该传感器的谐振波长变化范围在一个自由光谱范围内,甲烷浓度测量范围为0~15%;对比SOI材料和聚合物材料、单面敏感膜和三面敏感膜的测量结果,得出聚合物材料三面敏感膜微环的谐振波长变化幅度较大,测量灵敏度为60pm。     

微机械谐振器的快速测试方法

为了缩短微机械谐振器的测量时间,提高测量效率.提出了一种针对压阻检测的微谐振器的频率特性测试新方法,该方法利用欧姆鉴相器,积分器和微处理器实现对微弱信号的有效检测.欧姆鉴相器以检测电阻为鉴相器,利用欧姆定律实现参考信号和被测信号的乘法鉴相运算;通过积分器实现对鉴相结果的积分运算,抑制干扰和噪声;微处理器用于对积分数据的...     

等效模型分析微机械薄膜谐振器的力学特性

通过引入折合的概念,将多层微机械谐振悬臂梁等效为单层结构,建立了多层微悬臂梁的弯曲振动方程,结合边界条件求出了微悬臂梁的固有频率。等效概念的引入大大简化了多层微机械谐振器件振动特性的理论分析过程,与传统只考虑绝对占优层的方法相比,等效模型不仅更加精确,而且突出了多层微机械谐振梁中的主要矛盾,为多层微机械谐振式器件的结构优化设计奠定了基础。     

计入空气阻尼的MEMS微谐振器非线性动力学研究

针对横向振动MEMS微谐振器,计入非线性空气阻尼力,对微谐振器非线性动力学特性进行研究.建立微谐振器非线性动力学模型,计入滑移边界条件和稀薄气体效应,利用FLUENT和MATLAB对Navier-Stokes方程和动力学方程进行求解.经过与国外实验对比,可得出考虑非线性阻尼力的平板振幅值非常接近实验值,振幅峰-峰值误差仅为6%,且优于线性动力学的分析结果.为MEMS器件非线性动力学特性分析提供理论依据.     

I形MEMS谐振器的电阻差分检测方法

为克服Ｉ2形MEMS谐振器输入端（热执行）与输出端（压阻敏感）直接耦合所造成的输出信号品质较差的缺点,设计并制作了一种电阻差分检测电路。该电路通过外接电阻的方法,产生与输出信号中耦合成分幅值相同、相位相反的差分信号。将差分信号与谐振器输出信号相组合,从而实现解耦的目的。实验结果表明,电阻差分检测可有效消除了输出信号中的耦合成分,使频谱响应曲线得到更直观的体现。与其他消除耦合信号的技术方案相比（混频检测电路、惰性谐振器等）,电阻差分检测法电路设计简单,无需改动器件的加工工艺,有利于满足未来器件小型化要求。     

I~2形MEMS谐振器的电阻差分检测方法

为克服I2形MEMS谐振器输入端(热执行)与输出端(压阻敏感)直接耦合所造成的输出信号品质较差的缺点,设计并制作了一种电阻差分检测电路。该电路通过外接电阻的方法,产生与输出信号中耦合成分幅值相同、相位相反的差分信号。将差分信号与谐振器输出信号相组合,从而实现解耦的目的。实验结果表明,电阻差分检测可有效消除了输出信号中的耦合成分,使频谱响应曲线得到更直观的体现。与其他消除耦合信号的技术方案相比(混频检测电路、惰性谐振器等),电阻差分检测法电路设计简单,无需改动器件的加工工艺,有利于满足未来器件小型化要求。     

Switched beam dielectric resonator antenna array with six reconfigurable radiation patterns

A single feed, four element rectangular Dielectric Resonator Antenna (DRA) array, with beam switching capability is proposed. A wide impedance bandwidth of more than 25% at the center frequency of 1.95 GHz is achieved. Each DRA has two excitation strips and four parasitic patches. The six cases are discussed; each case corresponds to a diverse radiation pattern. The antenna beam is switched in azimuth (θ = 45°) at Φ = 0°, 60°, 120°, 180°, 240°, and 300°. The antenna gain is found to be more than 7 dB in most of the frequency band of interest. A passive prototype is developed and tested to validate simulation results. The comparison between the simulated and measured reflection coefficients and the radiation patterns for the six cases is presented. A good agreement between the measured and simulated results is observed. © 2016 Wiley Periodicals, Inc. Int J RF and Microwave CAE 26:519–530, 2016.     

热弹耦合梁方程组在非线性边界条件下的整体吸引子

本文研究了一类在非线性边界条件下的热弹耦合梁方程组的初边值问题,首先通过先验估计证明系统存在唯一的整体解,其次通过证明系统存在有界吸收集和半群的渐近光滑性得到整体吸引子的存在性.     

Support loss for beam undergoing coupled vibration of bending and torsion in rocking mass resonator

Rocking mass resonator is widely used to design various sensors and actuators, which is a dual-axial symmetry resonator with high sensitivity. Q_support is the dominant energy loss mechanism influencing its high sensitivity. The anchor types and support loads applied to attachment points of rocking mass resonator are analyzed. Then support loss is simplified as a model with a beam attached to a finite thickness plate at its end. The general formulations for power radiated into support structure are given. An accurate analytical model of support loss for rocking mass resonator has been developed and verified by experiments. When the thickness of resonator is 240 μm, the measured Q can achieve a value of 589.1; while the thickness of resonator is reduced to 60 μm, the measured Q can achieve a value more than 8500. The derived model is general and might be applicable to various micro beam resonators and anchor types, providing significant insight to design of high-Q rocking mass devices.     

Vibration and flutter of wind turbine blade modeled as anisotropic thin-walled closed-section beam

Based on a variational asymptotic analytical model, vibration and aeroelastic stability of rotor blades modeled as anisotropic thin-walled closed-section beams are systematically addressed. The analysis is applied to a laminated composite construction of the circumferentially asymmetric stiffness (CAS) that produces bending-twist coupling. The vibration characteristics of composite beam are determined by the Extended Galerkin Method. The unsteady aerodynamic loads and centrifugal force are integrated with t...     

Wide‐bandwidth dielectric resonator antenna with omni‐directional radiation patterns for beam focusing properties in a circular array

Investigation results are presented for a cylindrical dielectric resonator antenna (DRA) with a central airgap, which is excited using a coaxial probe connected to a wire monopole. By selecting the proper values of airgap and monopole heights, a desired impedance bandwidth (S₁₁ ≤ ?10 dB) from 40% to 67% can be achieved. The proposed DRA provides monopole like omni‐directional radiation patterns with low crosspolarization levels throughout the bandwidth. Prototype DRA was fabricated with equal heights of the airgap and monopole and experimentally verified for both the impedance matching and radiation performance. Simulated and measured bandwidths of 67% and 64%, respectively, were obtained with acceptable peak realized gain. The simulated and measured radiation patterns agree well. Furthermore, this DRA is investigated for beam focusing properties when implemented in a circular array consisting of four‐elements on a circular finite ground plane. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:92–101, 2014.     

用激光束成像法测量双E型硅弹性膜应变

用激光束成像法对双E型传感器的硅弹性膜应变进行的研究,测出了该弹性膜的应变情况,此方法对其它结构形式的敏感芯片应变的研究也有一定的参考价值。     

A state‐of‐art review on performance improvement of dielectric resonator antennas

This article outlines a compressive review on investigation carried out targeting to gain, circular polarization (CP), and mutual coupling reduction in dielectric resonator antenna (DRA). The DRA has already been created a separate position in antenna engineering domain because of its adept characteristics, such as wide bandwidth, high efficiency, low‐loss, and mainly 3D‐design flexibility which is rarely available in conventional antennas. In this context, the research on gain, circular polarization, and mutual coupling are quite interesting and being carried out from the last two decades. The ultimate aim of this article is to (i) give an overview of different techniques adopted in context to gain, CP, and mutual coupling reduction; (ii) give a compressive review of notable research carried out targeting to these three characteristics; and (iii) find out the research gap concentration for furtherance of the same.     

旋转粘弹性夹层梁非线性自由振动特性研究

对旋转粘弹性夹层梁的非线性自由振动特性进行了分析.基于Kelvin-Voigt粘弹性本构关系和大挠度理论,建立了旋转粘弹性夹层梁的非线性自由振动方程,并使用Galerkin法将偏微分形式振动方程化为常微分振动方程.采用多重尺度法对非线性常微分振动方程进行求解,通过小参数同次幂系数相等获得微分方程组,并通过求解方程组及消除久期项来获得旋转粘弹性夹层梁非线性自由振动的一次近似解.用数值方法讨论了粘弹性夹层厚度、转速和轮毂半径对梁固有频率的影响.结果表明:固有频率随转速增大而增大,随夹层厚度增大而减小,随轮毂半径的增大而增大.     

沿轴向飞行粘弹性夹层梁热弹耦合振动响应分析

研究了沿轴向飞行粘弹性夹层梁的热弹耦合振动响应.考虑材料变形与传热的相互影响,建立了轴向运动粘弹性夹层梁的热弹耦合振动控制方程;将方程中激励项(温度函数与外激力)拟合为时间的函数,采用伽辽金法得到方程的位移解,并在每一个微小的时间段内采用迭代收敛的数值方法对热传导方程进行求解得到温度场.使用数值方法讨论了轴向飞行运动速度和热载荷持续时间对其振动响应的影响.研究表明:稳定振动时飞行速度对位移影响较大,对温度影响较小;热冲击对振动位移响应有较大影响,并改变振动特性.