材料热传导系数随温度变化函数的反演方法

材料热传导系数的反演是一类典型的热传导逆问题。针对材料热传导系数随温度变化的情况,本文将材料的热传导系数值按温度区间分段离散,建立了通过材料边界点的温度测量来反演各温度区间热传导系数值的遗传算法和伴随方程法。通过典型算例分析和考虑测量噪声、系统噪声的反演计算结果分析表明：所建立的两种反演算法都是可行有效的,受测量随机噪...     

结构电磁有限元分析的网格依赖性研究

分析了基于有限元方法的超材料电磁性能仿真分析结果对有限元网格的依赖性.通过对仿真结果的分析,发现基于S参数的材料性能参数反演结果对S参数的计算准确度的依赖性巨大,特别是处在谐振频域的S参数误差会导致等效电磁参数的性态误差.针对基于求解频率的网格自适应技术对远离求解频率的谐振频域的分析结果的准确度改善不够这个问题,需要确定合适的求解频率来执行网格自适应.提出了一种改进电磁性能仿真分析准确度的方法,其基本思想是首先给定一个初始的求解频率值,根据Kramers-Kronig关系反演等效电磁参数,进而获得谐振频率的近似值,并把此值作为求解频率来实现网格自适应以获得合适的网格剖分,最后经扫频获得S参数并进行等效电磁参数的反演.数值结果表明,该方法可有效提高仿真分析和参数反演的准确度.     

海洋平台水动力系数识别及精度分析

论文利用新动态模型减缩方法对海洋平台结构进行自由度减缩,利用简化后的模型对水动力系数进行反演,改善了反演模型中解的不确定性,并对载荷反演中的病态问题进行了探讨,同时给出了反演结果的评估方法,为反演中测量数据的获取提供了依据,提高了反演结果的可靠性.     

实验数据反演识别分析方法与力学表征

本文给出了两类基于实验(实测)数据的反演识别方法,简述了其在界面力学性能及工程实测数据分析中的应用.在粘接界面力学性能的反演识别实验研究中,基于不同加载速率的实验曲线,结合参数化界面力学模型,通过反演识别给出粘接界面力学性能参数,并对识别结果的适定性进行独立的实验验证;在基于工程实测数据的反演识别与力学建模方面,在分析盾构装备载荷特点的基础上,对海量的实测数据统计分类,提出了力学量纲分析的建模方法,并应用于盾构掘进载荷的反演识别研究.     

基于同伦方法反演非饱和土中镉离子传输参数

依据实验室土柱实验结果，引入同伦方法对镉离子在不同非饱和土样中的传输参数进行了反演计算，得到了相应的反演结果．     

共和干热岩地热井GR2井区三维地应力场反演分析

GR2 地热井位于共和恰卜恰镇，干热岩地热井井深达到4000 米，大深度井区极大增加了反演的难度．井区附近20 千米内无大型构造，附近地应力场的主要影响因素为板块构造应力和自重应力．由于井中未进行三维地应力场测井工作，所以我们以地面地应力调查结果和震源机制解反演结果为依据，基于MIDAS GTS 和大比例尺高清卫星云图建立有限元数值模型，使用改进的边界法进行反演计算，最终预估了井中地应力场分布特征．对于后续的井网布置以及干热岩井场开采具有重要意义．     

平面弹性波传递算子反演方法

讨论了弹性水平层状介质中的反演问题，在平面脉冲波激励和反射模式下利用传递算子方法逐层反演了介质的Ｓ－波速度，Ｐ－波速度，Ｌａｍｅ弹性常数μ和厚度，并且进行了数值模拟，这种逐层反演方法简化了方程的阶数和计算量。     

基于数据驱动的薄板结构多裂纹反演方法

采用比例边界有限元法(scaled boundary finite element methods,SBFEM)模拟薄板结构内Lamb波的传播过程，将SBFEM和最大信息系数相结合，研究了缺陷参数与观测点位置的相关性，为缺陷反演时传感器布置位置的选取提供了依据。在此基础上建立了基于SBFEM数据集和深度学习的结构内部多裂纹反演方法，将多裂纹反演归类为分类和回归预测问题，可在未知裂纹数量的情况下反演出裂纹的数量、位置和大小，并通过数值算例验证了该方法能够较好地进行裂纹状缺陷数量和参数的反演。     

基于无迹卡尔曼滤波的高层建筑风荷载反演

基于无迹卡尔曼滤波提出了一种高层建筑风荷载的反演算法，该方法利用有限测量楼层的风致响应数据，实时识别结构的未知风荷载和风致响应。通过典型高层建筑的风洞试验进行风荷载反演实例分析，验证了该方法的准确性和适用性，评估了模态参数误差、测量噪声水平对风荷载反演的影响。研究结果表明，文中提出的算法对模态参数误差不敏感，在一定噪声水平下反演的结果基本能够满足实际工程需要，该算法为实时评估高层建筑的风荷载和风致响应提供了有效的工具。     

部分输入未知条件下结构动力复合反演的分解算法

在充分利用部分输入已确知而部分输入未知的激励特性的基础上，提出了结构动力复合反演的分解算法，该算法从源头上消除了迭代过程中参数识别与荷载反演的相互影响，降低了问题的计算规模。对于线性参数系统，该算法不经过任何迭代计算即可一次性完成结构参数识别及荷载反演。将其与松弛法结合，可解决非线性参数系统的识别问题，与文献[4]的方法比较，其收敛速度有显著提高。     

Chebyshev spectral method and Chebyshev noise processing procedure for vorticity calculation in PIV post-processing

Chebyshev spectral method and Chebyshev noise processing procedure are proposed for the calculation of vorticity from PIV experimental data. The Chebyshev spectral method offers superior intrinsic accuracy of derivative calculations. To overcome its noise sensitivity, the Chebyshev noise processing procedure can be applied prior to the derivative calculation to remove the high-frequency noise in the Chebyshev transform space. We compare the Chebyshev spectral method against the least-squares approach and test their performance in the calculation of vorticity with an Oseen vortex and with PIV data of the wake of a trapezoidal mixing tab. It is found that for clean velocity data the Chebyshev spectral method is extremely accurate. However, the Chebyshev spectral method alone is found to be more sensitive to noise than the least-squares method. When the Chebyshev noise processing procedure is applied together with the Chebyshev spectral method it greatly reduces the error and makes the Chebyshev spectral method more accurate than the least-squares method for a wide range of vorticity values. A special requirement imposed by the Chebyshev spectral method is that the PIV velocity processing must be carried out on special grids such as Gauss–Lobatto points.     

PIV error correction

 A non-post-interrogation method of reducing subpixel errors and eliminating spurious vectors from particle image velocimetry (PIV) results is presented. Unlike methods that rely on the accuracy or similarity of neighboring vectors, errors are eliminated before correlation information is discarded using available spatial and/or temporal data. Anomalies are removed from the data set through direct element-by-element comparison of the correlation tables calculated from adjacent regions. The result is a processing technique that yields a symmetric correlation profile representing the velocity at the boundary of the combined regions. This correlation based correction (CBC) technique greatly improves subpixel accuracy, and is highly robust to out-of-boundary particle motion, particle overlap, unmatched particle correlations, and electronic and optical imaging noise. Received: 22 June 1999/Accepted: 21 September 1999     

An Improved Weighting Method for Inversely Determining Elastic Constants of Coating Layers from Dispersion Curves of Surface Acoustic Waves

This paper investigates the inversion of elastic constants of a coating layer from measured dispersion curves of a layered half-space sample. A systematic analysis on the sensitivity of dispersion curves is performed and the results provide important information in constructing a better inversion process. Numerical simulation has been given to demonstrate several possibilities for obtaining accurate elastic constants from the measured dispersion data over different frequency domains. Experiments have also been carried out using broadband Poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] focusing transducers and their surface wave measurement system over a wide frequency range of 4?~?120 MHz. Nickel coating layers electroplated on thick glass substrates are tested for the inversion. It is observed that the proposed inversion method, which carefully chooses the dispersion data at specific frequency ranges as well as adding some weightings to them, is indeed significantly improve the accuracy and convergence of the obtained elastic constants of the coated nickel layers. Young’s modulus of the coated nickel layers is also measured by a nano-indentation system and the results show good agreement with the data determined by the proposed inversion method.     

Variation method for acoustic wave imaging of two dimensional targets

IntroductionAcousticwaveimaginghasagreatpotentialtobeappliedtonondestructivetesting ,medicalimaging ,geologicalprospectingandmaterialscienceetc.,andvariousimagingmethods,eachpossessingitsownpeculiarities,havebeenproposed .In 1 992 ,Moghaddam[1]putforwarda…     

Digital Image Correlation Using Stochastic Parallel-Gradient-Descent Algorithm

This article proposes a digital image correlation (DIC) method based on the stochastic parallel gradient descent (SPGD) algorithm. Stochastic parallel perturbations are imposed on deformation parameters to make the correlation coefficients converge to a global extremum; thus, this allows the final measured values of the deformation parameters to be obtained and the DIC measurement to be made. Both simulated and real data processing, including rigid body and strain deformation, show that the proposed method can achieve nearly the same accuracy as the Newton–Raphson (NR) method in most cases and higher accuracy in some cases, such as the simulated experiments of rigid body translation with and without noise. It also has a good noise-robustness. Furthermore, a series of experiments have been designed to evaluate the convergence characteristics of the proposed method, and it has been proved able to process large displacement and have a stable convergence process, good robustness, and a high convergence speed when bilinear interpolation is adopted.     

用同伦方法反演非饱和土中溶质迁移参数

非饱和土中溶质迁移参数反演问题可以归结为非线性算子方程的求解问题. 将同伦方法 引入该问题的求解，通过构造线性同伦将原问题转化为求解同伦函数最小值的无约束优化问 题. 同时在分析了同伦参数正则化效应的基础上，提出一种两段同伦参数修正方法. 即在求 解的初始阶段，根据拟Sigmoid函数调整同伦参数，以追踪同伦路径，保证计算稳定地进行； 在迭代的后期，采用与残差相关的同伦参数修正方法，以抵抗观测噪声对求解的影响. 数值 算例为求解带有平衡及非平衡吸附效应的一维非饱和土中溶质迁移模型参数反演问题，计算 结果表明了该方法的大范围收敛性及较强的抵抗观测噪声的能力.     

基于小波分析法的光纤陀螺系统标定方法

光纤陀螺的随机噪声很大程度地影响系统的标定精度,通常的解决方法是增加平均次数、延长采样时间等,不能从根本上解决问题。利用小波变换阈值滤波对光纤陀螺系统标定的测试数据进行预先处理,采用Allan方差法分析滤波前后的测试数据,发现滤波后陀螺各项随机误差系数均得到明显抑制。用消噪后的陀螺信号进行标定处理,结果表明仅用原数据量的十分之一即可获得相同的标定精度,减少了测试时间,提高了标定效率。     

小波分析在捷联惯导陀螺信号滤波中的应用

介绍了小波变换和多分辨率分析理论。针对捷联惯导系统中光纤陀螺输出信号的特点，对其进行小波变换，去除信号中高频部分的噪声，从而抑制了陀螺的随机漂移。通过仿真实验，肯定了使用小波分析算法对陀螺输出信号进行滤波消噪处理的可行性。在实际用于捷联惯导系统中的实验结果表明，有效地提高了系统的精度。