开孔屏蔽腔内传输线负载所受电磁干扰的解析算法

外界电磁场通过孔缝耦合进入屏蔽腔,并经由线缆对腔内电子设备造成干扰,这是电磁兼容中需要考虑的重要问题,而数值法分析此类尺寸跨度大的电磁问题效率过低。基于电磁拓扑和等效电路法,提出一种快速计算外界平面波辐照下开孔屏蔽腔内传输线负载所受电磁干扰的解析算法。首先利用电磁拓扑将整个耦合问题分解为两个独立的子问题：外界平面波辐照下开孔空腔内的耦合场问题与耦合场辐照下孤立传输线的响应问题,然后提出基于等效电路法求解空腔内耦合电场的计算方法,最后利用场线耦合BLT方程求解耦合电场对孤立传输线负载造成的电磁干扰。经CST仿真验证,该解析算法能有效计算任意位置开(多)孔屏蔽腔内任意放置传输线负载所受的电磁干扰。相比于数值法,该解析算法不仅花费更少的计算时间与资源,且能用于参数影响规律的研究。     

Measurement of the frequency response of a diaphragm-based pressure sensor by use of a pulsed excimer laser

We present a novel method for measuring the frequency response of a diaphragm-based optical fiber Fabry-Perot interferometric pressure sensor. The impulse response of the sensor to the radiation pressure generated by an excimer laser pulse is measured. The Fourier transform of the impulse response yields the frequency response of the pressure sensor. Experimental results show that it is a convenient and efficient method for measurement of the frequency response of diaphragm-based pressure sensors.     

A time-varying identification method for mixed response measurements

The proper orthogonal decomposition is a method that may be applied to linear and nonlinear structures for extracting important information from a measured structural response. This method is often applied for model reduction of linear and nonlinear systems and has been applied recently for time-varying system identification. Although methods have previously been developed to identify time-varying models for simple linear and nonlinear structures using the proper orthogonal decomposition of a measured structural response, the application of these methods has been limited to cases where the excitation is either an initial condition or an applied load but not a combination of the two. This paper presents a method for combining previously published proper orthogonal decomposition-based identification techniques for strictly free or strictly forced systems to identify predictive models for a system when only mixed response data are available, i.e. response data resulting from initial conditions and loads that are applied together. This method extends the applicability of the previous proper orthogonal decomposition-based identification techniques to operational data acquired outside of a controlled laboratory setting. The method is applied to response data generated by finite element models of simple linear time-invariant, time-varying, and nonlinear beams and the strengths and weaknesses of the method are discussed.     

模拟封闭声场脉冲响应的圆锥束跟踪法

本文简要介绍了声场脉冲响应计算机模拟技术的基本状况,给出了一种将虚源法和声线法相结合的模拟方法－圆锥束跟踪法的原理和算法,并将其对一个实例的计算结果与虚源法进行了比较,最后对其实现过程中需要注意的问题进行了讨论。     

The measurement of the free field impulse response of microphones in a laboratory environment

A method is presented of measuring the free field frequency and impulse response of microphones by using a pulse technique in an ordinary laboratory environment. The pressure transient generated by exciting a loudspeaker with a narrow pulse is detected at some point in the loudspeaker's far field by a “reference” microphone whose response is assumed flat over the frequency range of interest. The microphone to be tested is then substituted in exactly the same position and its response to the transient measured. The outputs of the two microphones are accurately sampled and deconvolved by using a discrete Fourier transform technique to give the magnitude and phase parts of the “test” microphone's frequency response, and hence, via the discrete Fourier transform, its response to a delta function of pressure propagating in the free field. The computed impulse responses are presented and the accuracy of the method discussed.To illustrate the use of the method, the free field frequency response and free field correction curves of a one inch instrumentation microphone are measured. The method is then used to measure the pressure which occurs at the centre of the flat end-face of a long a cylinder when excited by an impulse of acoustic pressure propagating in the free field from various angles of incidence.     

Using experimental design to characterize the effect of structural elements on acoustical response of hand-free phone

This article presents an adaptation of the experimental design method (more precisely called “statistical design and analysis of experiments” and referred to as DOE) to acoustics. Experimental design is an efficient method to find an empirical relation whenever a theoretical one cannot be obtained or would be too difficult to obtain. This technique is not common in acoustics where it has been used in a few application cases to determine what product or process parameters affect the acoustic response. The response variable was single valued whereas, in the proposed method, it is an array of values, a frequency spectrum which constitutes a more practical tool for an advanced acoustic analysis. The results are presented on a spectrum plot where the factor effect is given in the physical quantity (dB) and the Fisher test of significance is presented as two plots of the lower and upper significance limits (also in dB). The method is applied to a hand-free telephone where, for subsequent modeling purposes, the method determines which structural factors affect the telephone acoustic response and what are the associated frequency ranges. This adaptation of the DOE method is validated with the verification of the results in three ways: first, with a complementary experimental design, second, with a more classical experimental method, and, third, with a computer simulation.     

谐和与随机噪声联合作用Duffing单边约束系统的响应

研究了Duffing单边约束系统在谐和与随机噪声联合激励下的响应问题. 用谐波平衡法和摄动法分析了系统在确定性谐和激励和随机激励联合作用下的响应,用随机平均法讨论了随机扰动项对系统响应的影响. 在一定条件下,当约束距离较大时对应于不同的初始条件,系统具有两个非碰撞的稳态响应;而当约束距离不大时,对应于不同的初始条件,系统也可以有两个不同的稳态响应,其中一个是发生碰撞的响应,而另外一个则不发生碰撞. 数值模拟表明该方法是有效的. 关键词： Duffing单边约束系统 随机响应 谐波平衡法 摄动法     

Time and frequency response of structures with frequency dependent,non-proportional linear damping

A method to compute the non-stationary time and frequency response of structures with a frequency-dependent non-proportional linear damping, called the resonance modes method, is presented in this paper. It consists of two main steps. The first step aims at spotting the structure resonance modes, which are the solutions of the matrix nonlinear eigenvalue problem obtained using the finite element method in the complex plane. This step requires a complex eigensolver and an iterative scheme, a perturbation technique or a combination of both. The second step uses the computed resonance modes and an analytical expression of the inverse Laplace transform to deduce the time or frequency response of structures to general excitations. The response of an aluminum plate damped with an elastomer treatment to a point-force excitation, computed with the classical modal approach, the direct solution and the presented method shows its precision and efficiency. An acoustic power computation finally validates the implementation of a fast variant, based on the perturbation technique, for vibroacoustic applications.     

Seismic response of underwater members of variable cross section

This paper is concerned with a method for solving seismic response problems of a pile of variable cross section with a tip inertia subjected to a sea bottom seismic displacement. The analysis developed here is based on an elastodynamic theory in which the effects of the continuously distributed mass and rigidity of the pile are included. The method includes use of Fourier series expansion, the Laplace transform, the transfer matrix method and the residue theorem in order to deal with the complex seismic displacement and arbitrarily shaped piles; considerable simplification of the calculations is thus achieved. The theoretical results given are applicable to seismic response problems for a pile of arbitrary shape with a tip inertia, excited by arbitrary displacements. As an application of the present theoretical results, the dynamic response has been calculated for hollow piles of curved conical shape with tip inertias and double taper beams subjected to seismic displacements.     

A recursive approach to prony parameter estimation

The Prony series method of fitting a series of complex exponentials to a time series can be applied to many acoustic and vibration signals. For example, in the analysis of a structure's response to transient excitation the Prony series method can be used to find the natural frequencies, damping ratios, amplitudes and relative phases of the modes of the structure. One of the main problems with this method is the need to calculate and invert matrices. In this paper an algorithm that combines the Prony series method with the recursive least squares algorithm is described. This eliminates the need to invert any matrices and also requires only part of the data to be available at one particular time. The method is applied to analyze a simulated structure's response and also to analyze the response of a beam to transient excitation.     

Vibration testing based on impulse response excited by pulsed-laser ablation: Measurement of frequency response function with detection-free input

We have developed a non-contact vibration-measurement system that is based on impulse excitation by laser ablation (i.e. laser excitation) to measure the high-frequency-vibration characteristics of objects. The proposed method makes it possible to analyse the frequency response function just by measuring the output (acceleration response) of a test object excited by pulsed-laser ablation. This technique does not require detection of the input force. Firstly, using a rigid block, the pulsed-laser-ablation force is calibrated via Newton's second law. Secondly, an experiment is conducted in which an object whose natural frequency lies in the high-frequency domain is excited by pulsed-laser ablation. The complex frequency spectrum obtained by Fourier transform of the measured response is then divided by the estimated pulsed-laser-ablation force. Finally, because of the error involved in the trigger position of the response with respect to the impulse arrival time, the phase of the complex Fourier transform is modified by accounting for the response dead time. The result is the frequency response function of the object. The effectiveness of the proposed method is demonstrated by a vibration test of an aluminium block.     

基于梯度响应面模型的优化设计

本文主要研究一种梯度响应面模型及其在气动优化设计中的应用. 目前应用广泛的多项式响应面模型是连续可导的, 采用梯度信息构造完全二阶多项式响应面模型, 所需样本数与设计参数个数呈线性关系. 首先通过改进实验设计方法, 快速生成满足精度要求的样本并确定梯度响应面模型. 随后通过函数实验验证梯度响应面模型的精度, 及该模型在多极值函数最值搜索中的有效性. 最后由伴随方法快速求解气动优化设计目标函数的梯度信息, 并开展基于梯度响应面模型和复合形法的叶片压力反设计和效率优化设计. 结果表明: 基于梯度响应面模型的优化方法在全局最优及提高优化效率两方面均有出色表现, 基于该优化方法的气动优化设计能够显著改善叶片的气动性能. 关键词： 气动优化设计 响应面模型 伴随方法 复合形法     

Transient vibration analysis of a completely free plate using modes obtained by Gorman's superposition method

This paper shows that the transient response of a plate undergoing flexural vibration can be calculated accurately and efficiently using the natural frequencies and modes obtained from the superposition method. The response of a completely free plate is used to demonstrate this. The case considered is one where all supports of a simply supported thin rectangular plate under self weight are suddenly removed. The resulting motion consists of a combination of the natural modes of a completely free plate. The modal superposition method is used for determining the transient response, and the natural frequencies and mode shapes of the plates used are obtained by Gorman's superposition method. These are compared with corresponding results based on the modes using the Rayleigh-Ritz method using the ordinary and degenerated free-free beam functions. There is an excellent agreement between the results from both approaches but the superposition method has shown faster convergence and the results may serve as benchmarks for the transient response of completely free plates.     

The steady state response of a damped circular plate driven at a diameter

The steady state response of a damped circular plate transversely or rotationally driven at a diameter is determined by the series-type method. With the reaction force or moment acting along a diameter of a circular plate regarded as an unknown harmonic load, the response of the plate to the load is expressed by the Green function. The force or moment distribution along the diameter is expanded into Fourier series with unknown coefficients, and the simultaneous linear equations for the coefficients are derived by the restraint condition on the diameter. The dynamic response of the plate is determined by solving the equations. The method is applied to circular plates driven by a sinusoidally varying transverse deflection or angular rotation at a diameter, and the steady state response of the plates is studied.     

Estimation of structural wave numbers from spatially sparse response measurements

A method is presented for estimating the complex wave numbers and amplitudes of waves that propagate in damped structures, such as beams, plates, and shells. The analytical basis of the method is a wave field that approximates response measurements in an aperture where no excitations are applied. At each frequency, the method iteratively adjusts wave numbers to best approximate response measurements, using wave numbers at neighboring frequencies as initial estimates in the search. In comparison to existing methods, the method generally requires far fewer measurement locations and does not require evenly spaced locations. The number of locations required by the method scales with the number of waves that propagate in the structure, whereas the number of locations required by existing methods scales with the minimum wavelength. In addition, the method allows convenient inclusion of the analytic relationships between wave numbers that exist for flexural vibrations of beams and plates. Advantages of the method are illustrated by an example in which a beam is excited by a transverse force at one end. Using analytic data and experimental measurements, the method produces a wave field that matches response measurements to within 1 percent. One interesting feature of the new method is that, when applied to analytic data, it supplies more robust wave number estimates using responses at unevenly spaced locations.     

The time response of structures with bounded parameters and interval initial conditions

Uncertainty plays an important role in the performance of structures. In this paper, we focus on the dynamic response of structures with bounded parameters and interval initial conditions, and present a new method to determine the supremum and infimum of the time response. The method is based on the vertex solution theorem for the first-order deviation of the dynamic response from its central value and avoids interval extension problems present in current methods, where the length of the interval increases significantly due to the intermediate calculations. The method is more accurate than existing perturbation methods and provides tighter bounds on the response. The approach neglects the second-order terms in the equation of motion, and care should be exercised when the parameter variations are large. The other advantage of this method is its ability to solve problems with uncertainties in the initial conditions.     

Numerical analysis of the 2D acoustic field with epistemic uncertainty

Aiming at the problem that the epistemic uncertain parameters exist in an acoustic field,an evidence theory-based finite element method(ETFEM) is proposed by introducing the evidence theory,in which the focal element and basic probability assignment(BPA) are used to describe the epistemic uncertainty.In order to reduce the computational cost,the interval analysis technique based on perturbation method is adopted to acquire the approximate sound pressure response bounds for each focal element.The corresponding formulations of intervals of expectation and standard deviation of the sound pressure response with epistemic uncertainty are deduced.The sound pressure response of a 2D acoustic tube and a 2D car acoustic cavity with epistemic uncertain parameters are analyzed by the proposed method.The proposed method is verified through the comparison of the analysis results of random acoustic field with that of epistemic uncertain acoustic field.Numerical analysis results show that the proposed method can analyze the 2D acoustic field with epistemic uncertainty effectively,and has good prospect of engineering application.     

Quantifying the synchronizability of externally driven oscillators

This paper is focused on the problem of complete synchronization in arrays of externally driven identical or slightly different oscillators. These oscillators are coupled by common driving which makes an occurrence of generalized synchronization between a driving signal and response oscillators possible. Therefore, the phenomenon of generalized synchronization is also analyzed here. The research is concentrated on the cases of an irregular (chaotic or stochastic) driving signal acting on continuous-time (Duffing systems) and discrete-time (Henon maps) response oscillators. As a tool for quantifying the robustness of the synchronized state, response (conditional) Lyapunov exponents are applied. The most significant result presented in this paper is a novel method of estimation of the largest response Lyapunov exponent. This approach is based on the complete synchronization of two twin response subsystems via additional master-slave coupling between them. Examples of the method application and its comparison with the classical algorithm for calculation of Lyapunov exponents are widely demonstrated. Finally, the idea of effective response Lyapunov exponents, which allows us to quantify the synchronizability in case of slightly different response oscillators, is introduced.     

红外光谱辐射计探测器高阶非线性响应校正方法

针对傅里叶变换红外光谱辐射计辐射定标需要黑体辐射面充满仪器视场的技术特点,分析了由于入射光子流较高导致红外探测器产生非线性响应误差的机理.通过仿真包含非线性误差的黑体辐射数据,研究了非线性误差对光谱产生的影响,并根据卷积和交叉迭代两种校正方法,提出了适合校正高阶非线性响应误差的迭代方法—梯度下降法.利用傅里叶变换红外光谱辐射计进行辐射定标实验,对比卷积、交叉迭代和梯度下降法三种校正方法的效果,结果显示三种校正方法均可有效减小非线性误差,分别使拟合优度提高了0.15%,0.29%和0.39%,梯度下降法校正后的光谱数据更为准确.     

An approximate theory for the sound radiated from a periodic line-supported plate

An approximate method is presented for estimating the sound power radiated by an infinite plate, supported elastically along parallel, equi-spaced lines and subjected to a simple pressure field convecting uniformly over the plate in a direction perpendicular to the supports. Suitable complex modes are assumed for the induced plate flexural wave motion, and an energy method is used to estimate the plate response and the radiated sound power. The effect on the plate response of the acoustic loading is taken into account. The influence of the convection velocity (which may be subsonic) and of certain plate parameters is investigated.