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81.
Constitutive computational modelling foundation of piezoelectronic microstructures and application to high-frequency microchip DSAW resonators 总被引:1,自引:0,他引:1
This paper establishes a piezoelectric constitutive computational approach based on generalized eigenvalue and multivariable
finite element solutions with potential applications to accurate and effective analysis of layered piezoelectric microstructures
of arbitrary geometries and different anisotropic materials, to ease the limitation of current computer capacity in analyzing
large-scale high-frequency disturbed surface acoustic waves (DSAW) by mounted electrodes in piezoelectric devices such as
microchip SAW resonators. A new incompatible generalized hybrid/mixed element GQM5 is also proposed for improving predictions
of the piezoelectric surface mount thermal stresses that are shear-dominated. The (generalized) plane strain constitutive
model is numerically verified for piezoelectric finite element computation. With the help of computational piezoelectricity
(electro-mechanics) for general layered structures with metal electrodes and anisotropic piezoelectric substrates, some new
interesting, reliable and fundamental constitutive finite element results are obtained for high-frequency piezoelectric and
mechanical SAW propagations and can be used for further applications. The ST-cut FEA results agree quite well with available
exact and lab solutions for free surface case.
The project supported by SRF for ROCS, SEM of China, the past Rutgers Univer-Seiko Epson Joint Fund and Zhejiang Provincial
NSF 相似文献
82.
求解二维结构-声耦合问题的一种半数值半解析方法 总被引:2,自引:1,他引:2
基于传递矩阵法和虚拟源强模拟技术提出了一种求解在谐激励作用下二维结构-声相互作用问题的半数值半解析法.在足够小的积分步长内,文中对任意形状弹性环沿周向曲线坐标的非齐次状态微分方程组,建立了一种齐次扩容方法.对于外声场,采用多圆形虚拟源强配置方案。并在每一条圆形配置曲线上将源强密度函数用Fourier级数展开,同时结合快速Fourier变换法,提出了一种高精度、高效率求解任意形状二维孔穴Helmholtz外问题的快速算法.在耦合方程的求解方面,根据叠加原理,将外激励和虚拟源强的Fourier级数展开项作为广义力分别作用在弹性环上,借助齐次扩容方法和精细积分法求得弹性环的状态向量,再利用流固交接条件和最小二乘法直接建立了耦合系统的求解方程.文中给出了二个典型弹性环在集中谐激励力作用下声辐射算例,计算结果表明该文方法较通常采用的混合FE-BE法更为有效. 相似文献
83.
84.
A.O. Borisyuk 《Flow, Turbulence and Combustion》1998,61(1-4):269-284
An acoustic model of a larger human blood vessel is developed. This model takes into account the main features of the acoustic
generation and propagation of noise in the human chest from the source (turbulent pressure fluctuations in blood flow) to
a receiver resting on the skin, and allows the consideration of a simple stenotic narrowing in the vessel. The low Mach number
turbulent wall pressure models of Corcos, Chase, Ffowcs Williams, and Smol'yakov and Tkachenko are used to describe random
sources in the vessel. The relationships obtained permit one to analyse the dependence of the resultant acoustic field in
the thorax on the parameters of the blood flow and the vessel, and show the possibility of finding characteristic signs of
the presence of a stenosis by comparison of noise fields from intact and diseased arteries.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
85.
何军 《应用数学和力学(英文版)》2007,28(11):148-1494
An analytical moment-based method for calculating structural first failure times under non-Gaussian stochastic behavior is proposed.In the method,a power series that constants can be obtained from response moments (skewness,kurtosis,etc.) is used firstly to map a non-Gaussian structural response into a standard Gaussian process,then mean up-crossing rates,mean clump size and the initial passage probability of a critical barrier level by the original structural response are estimated,and finally,the formula for calculating first failure times is established on the assumption that corrected up-crossing rates are independent.An analysis of a nonlinear single-degree-of-freedom dynamical system excited by a Gaussian model of load not only demonstrates the usage of the proposed method but also shows the accuracy and efficiency of the proposed method by comparisons between the present method and other methods such as Monte Carlo simulation and the traditional Ganssian model. 相似文献
86.
A NOVEL SEMI-ANALYTICAL METHOD FOR SOLVING ACOUSTIC RADIATION FROM LONGITUDINALLY STIFFENED INFINITE NON-CIRCULAR CYLINDRICAL SHELLS IN WATER 总被引:2,自引:0,他引:2
XiangYu HuangYuying 《Acta Mechanica Solida Sinica》2005,18(1):1-12
Based on the extended homogeneous capacity high precision integration method and the spectrum method of virtual boundary with a complex radius vector, a novel semi-analytical method, which has satisfactory computation effectiveness and precision, is presented for solving the acoustic radiation from a submerged infinite non-circular cylindrical shell stiffened by longitudinal ribs by means of the Fourier integral transformation and stationary phase method. In this work,besides the normal interacting force, which is commonly adopted by some researchers, the other interacting forces and moments between the longitudinal ribs and the non-circular cylindrical shell are considered at the same time. The effects of the number and the size of the cross-section of longitudinal ribs on the characteristics of acoustic radiation are investigated. Numerical results show that the method proposed is more efficient than the existing mixed FE-BE method. 相似文献
87.
A. N. Kudryavtsev S. G. Mironov T. V. Poplavskaya I. S. Tsyryul’nikov 《Journal of Applied Mechanics and Technical Physics》2006,47(5):617-627
The evolution of disturbances in a hypersonic viscous shock layer on a flat plate excited by slow-mode acoustic waves is considered
numerically and experimentally. The parameters measured in the experiments performed with a free-stream Mach number M
∞ = 21 and Reynolds number Re
L = 1.44 · 105 are the transverse profiles of the mean density and Mach number, the spectra of density fluctuations, and growth rates of
natural disturbances. Direct numerical simulation of propagation of disturbances is performed by solving the Navier-Stokes
equations with a high-order shock-capturing scheme. The numerical and experimental data characterizing the mean flow field,
intensity of density fluctuations, and their growth rates are found to be in good agreement. Possible mechanisms of disturbance
generation and evolution in the shock layer at hypersonic velocities are discussed.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 5, pp. 3–15, September–October, 2006. 相似文献
88.
Nonlinear vortical structures and soliton formation are investigated for electron temperature gradient instability in a two-electron temperature non-Maxwellian magnetoplasma. The inhomogeneity in magnetic field is also considered. A new set of nonlinear equations, using transport equations of Braginskii”s model, are formulated to study the nonlinear structures. A modified linear dispersion relation of coupled electron temperature gradient (ETG) mode and electron acoustic wave is derived. The ETG instability is found to increase with increase in ηec value that increases with sharp density gradients. The results are applied to auroral region of earth's magnetosphere and the calculated values of the nonlinear electric field of fast solitary waves are found to be in agreement with the Viking satellite observations. 相似文献
89.
Sandor Kristyan 《International journal of quantum chemistry》2013,113(10):1479-1492
The reduction of the electronic Schrodinger equation or its calculating algorithm from 4N‐dimensions to a nonlinear, approximate density functional of a three spatial dimension one‐electron density for an N electron system which is tractable in practice, is a long‐desired goal in electronic structure calculation. In a seminal work, Parr et al. (Phys. Rev. A 1997, 55, 1792) suggested a well behaving density functional in power series with respect to density scaling within the orbital‐free framework for kinetic and repulsion energy of electrons. The updated literature on this subject is listed, reviewed, and summarized. Using this series with some modifications, a good density functional approximation is analyzed and solved via the Lagrange multiplier device. (We call the attention that the introduction of a Lagrangian multiplier to ensure normalization is a new element in this part of the related, general theory.) Its relation to Hartree–Fock (HF) and Kohn–Sham (KS) formalism is also analyzed for the goal to replace all the analytical Gaussian based two and four center integrals (∫gi( r 1)gk( r 2)rd r 1d r 2, etc.) to estimate electron‐electron interactions with cheaper numerical integration. The KS method needs the numerical integration anyway for correlation estimation. © 2012 Wiley Periodicals, Inc. 相似文献
90.
Cavitation in thin layer of liquid metal has potential applications in chemical reaction, soldering, extraction, and therapeutic equipment. In this work, the cavitation characteristics and acoustic pressure of a thin liquid Ga–In alloy were studied by high speed photography, numerical simulation, and bubble dynamics calculation. A self-made ultrasonic system with a TC4 sonotrode, was operated at a frequency of 20 kHz and a max output power of 1000 W during the cavitation recording experiment. The pressure field characteristic inside the thin liquid layer and its influence on the intensity, types, dimensions, and life cycles of cavitation bubbles and on the cavitation evolution process against experimental parameters were systematically studied. The results showed that acoustic pressure inside the thin liquid layer presented alternating positive and negative characteristics within 1 acoustic period (T). Cavitation bubbles nucleated and grew during the negative-pressure stage and shrank and collapsed during the positive-pressure stage. A high bubble growth speed of 16.8 m/s was obtained and evidenced by bubble dynamics calculation. The maximum absolute pressure was obtained at the bottom of the thin liquid layer and resulted in the strongest cavitation. Cavitation was divided into violent and weak stages. The violent cavitation stage lasted several hundreds of acoustic periods and had higher bubble intensity than the weak cavitation stage. Cavitation cloud preferentially appeared during the violent cavitation stage and had a life of several acoustic periods. Tiny cavitation bubbles with life cycles shorter than 1 T dominated the cavitation field. High cavitation intensities were observed at high ultrasonication power and when Q235B alloy was used because such conditions lead to high amplitudes on the substrate and further high acoustic pressure inside the liquid. 相似文献