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本文探寻到正交各向异性体平面问题应力函数与各向同性体平面问题应力函数间的对应关系,以及横观各向同性体空间问题位移函数,应力函数与各向同性体空间问题位移函数、应力函数间的对应关系,据此,若已知各向民性体应力函数或位移函数的函数形式,即可构造出各向异性体相应问题的应力函数或位移函数。 相似文献
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传统的阵形估计算法都基于这样一个假设,即声传播为平面波或球面波模型,在浅海应用条件下,多途效应显著,该假设失效,造成此类算法的性能下降。提出了一种基于匹配场反演的阵形估计算法,采用简正波模型对声场建模,将多途建模为不同号数的简正波,从而消除了多途效应的影响;并且通过合理地选择目标函数,使算法对环境参数的扰动具有一定的宽容性;利用柔性阵的线性约束,将阵形畸变用弧线建模,使问题简化,在缺少声源精确位置等先验知识的前提下,仍能实现阵形的准确估计。理论仿真和试验结果表明,该算法是有效的。 相似文献
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采用平面弹性理论的复变函数方法,推导了具有小孔的无限介质在无限远处受到剪应力时的水平位移,得出有小孔时和无小孔时的位移关系,可以应用在基于土层位移差的反应位移法的土层位移的求解。为了验证该方法的适用性,设定某地质条件下的典型的圆形盾构隧道和矩形地下车站为基准模型,使用不同的方法求解土层位移,再用反应位移法计算土体刚度变化时的结构内力。结果表明:基于土层位移差的反应位移法适用于埋深较大的地下结构,不适用硬土的情况,对地基弹簧刚度的求解精度要求较高。 相似文献
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为提供一种能够全场测量整个焊接过程动态位移场的工具,建立了激光电子散斑法测量系统.应用于实际TIG焊接过程中,获得了焊接位移场的散斑原始图像.利用自开发软件,对图像进行灰度变换和直方图均衡化处理后,采用频域同态滤波的方法对图像进行降噪滤波处理.经降噪、二值化、细化、平整、拟合、标定等一系列处理后,即可自动生成相对动态位移场.结果表明,激光电子散斑法能够胜任焊接动态位移场的测量,且具有非接触、测量精度高、对环境的防震要求低、可在明光下操作、能进行全场测量的特点. 相似文献
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冠状动脉造影图像序列中估计二维运动及变形的弹性配准算法 总被引:3,自引:1,他引:3
提出一种由单面血管造影图像序列分析心脏冠状动脉运动和变形的方法,即利用弹性配准算法,将动脉运动的估计简化为对连续两帧图像的骨架像素的匹配.采用动态规划的方法进行配准,同时引入自回归建模,二者结合起来互相作用:动态规划为自回归模型参数的估计提供样本值;自回归模型为动态规划提供适当的成本函数。采用临床得到的单面冠状动脉造影图像序列对该算法进行了验证。实验结果表明应用该方法计算血管骨架图像中各点的光滑移动向量场,能够得到精确的结果。 相似文献
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A two-core transducer assembly using a Fe73.5Nb3Cu1Si13.5B9 ribbon to detect a change of magnetic field is proposed and tested for displacement (linear and angular) and current sensor. Two identical inductors, with the ribbon as core, are part of a two-series resonance network, and are in a high impedance state when excited by a small AC field of 1 MHz in the absence of a DC biasing field (Hdc). When the magnetic state of one inductor is altered by the biasing field, produced by a bar magnet or current carrying coil, an AC signal proportional to Hdc is generated by the transducer. The results for the sensitivity and linearity with displacement (linear and angular) of a magnet and with field from the current carrying coil are presented for two particular configurations of the transducer. High sensitivities of voltage response as much as 12 µV/µm and 3 mV/degree have been obtained for the transducer as a linear and angular displacement sensor, respectively, in the transverse configuration of exciting AC and biasing DC fields. 相似文献
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Abstract: A linear digital image correlation algorithm is proposed to eliminate noise‐induced bias in one‐dimensional translation estimation using noisy images. The algorithm uses linear interpolation for both initial and current images at off‐pixel positions and solves directly the displacement parameter by minimizing a sum‐of‐squared‐differences coefficient. Both analytical results and numerical simulations using synthetic image sets show that there is indeed no noise‐induced bias in the displacement estimation using the proposed algorithm if the off‐pixel positions in both images are chosen properly according to the relative displacement between two images. When the displacement is only known initially within a range of ±0.5 pixels from the actual displacement, an iterative procedure using the algorithm is able to obtain the displacement estimation with a residual bias that converges to the noiseless subpixel approximation bias. A further refinement of the off‐pixel analysis algorithm will be needed so the remaining residual bias due to subpixel approximation can also be significantly reduced. 相似文献
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为了提高视频的压缩效率,在传统菱形搜索算法基础上提出一种改进菱形搜索算法.该算法通过引入动态阈值,在起始搜索点预测、菱形搜索模式和搜索中止算法方面进行了优化,减少了SAD计算的内部冗余和搜索区域中不相关的块匹配计算,同时采用自适应搜索模式选择技术减少运输复杂度.实验结果表明:提出的改进菱形搜索算法适合各种运动类型的视频序列,特别适用于运动变化剧烈的序列,相比于FS算法,能够在PSNR值和码率值极其接近于FS算法的情况下对所有序列的MET减少约95%,大大减少运动估计时间. 相似文献
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Abstract: The use of full‐field displacement measurements in mechanical testing provides detailed response information that can be used, in conjunction with modelling and optimisation, for precise material property identification. One limitation of this technique is that the collection of response data and the sectioning of a specimen to reveal the material microstructure are both destructive tests and mutually exclusive, as the displacement measurement occurs only on the exposed surface. Therefore, modelling of an experiment to interpret a full‐field experiment requires assumptions about the structure of the material below the visible surface. This study evaluates the effects of several possible modelling assumptions on the errors in model‐predicted response and on the resulting material property estimates. A 3‐D microstructural model, for which the subsurface grain geometry and orientations are known, provides the basis for comparison of several common modelling assumptions based on the grain geometry and orientations on the visible surface of a specimen. 相似文献
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为在低端计算平台上实现实时的虚拟人运动仿真,提出了一种基于限时梯度投影法的虚拟人运动生成方法。不同于传统的基于Jacobian 矩阵广义逆的逆向运动学方法,该方法在合成末端效应器运动轨迹的基础上,通过将逆向运动学问题转变为约束非线性规划问题,有效克服了计算Jacobian 矩阵广义逆所导致的计算复杂度高、多解及奇异性等问题。同时,通过动态调整系统每帧的规划时间,可同时达到非线性函数局部线性化和限时求解的双重目的。文章最后以人体行走运动为例,在PC 平台上实现了一个虚拟人的行走运动仿真系统。 相似文献
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为了从细观角度分析沥青混合料内部颗粒在荷载作用下所形成的接触力力链和位移场,利用离散元方法生成5种排列形式的沥青混合料细观模型,并对5种细观结构施加0.35kN荷载,追踪了颗粒间接触力力链的分布和大小,以及颗粒所产生的位移。结果表明,3种交叉排列的结构形成各向异性的拉、压力力链,以压力力链为主,最大接触力分别为5598N、17680N、9680N,产生的X向和Y向位移基本呈左右对称分布,随深度的增加位移减小;2种非交叉排列的结构仅产生压力力链,最大接触力分别为385.6N、334.5N,产生的X向和Y向位移变化趋势与交叉排列结构类似,但位移较小。 相似文献