一种通过条纹方向图提取散斑条纹中心线的方法

在光测力学中,如何从单幅散斑干涉条纹图中消除散斑噪声,高精度自动提取相位信息,是一项较困难的工作。本文提出了一种计算条纹方向的简单算法,以及通过条纹方向图提取散斑条纹中心线的方法。实验表明此方法对高噪声的散斑条纹图非常有效。     

非线性相位误差补偿的反相条纹投影法

在理论分析伽马非线性引起相位误差的基础上,本文提出一种新的反相条纹投影形貌测量方法,能补偿条纹投影法中非线性误差的影响。若相机和投影仪存在二阶和三阶伽马非线性残余,会造成四步相移法产生四倍频的非线性相位误差。通过预先引入偏移相位π/4到四步相移法中,使其对应的非线性相位误差发生变号,这样偏移前后的测量相位相加即可补偿非线性误差的影响。针对四步相移法,仿真模拟和实验结果显示出非线性相位误差的频率始终是条纹频率四倍,验证了反相条纹投影方法的可行性和适用性,与常规方法相比,具有更高的测量精度。     

用曲线大窗口平滑散斑条纹图的方法研究

提出一种计算条纹方向的简单算法,以及通过条纹方向图获得沿条纹方向的曲线窗口并对散斑条纹图进行曲线大窗口滤波的方法．实验表明此方法较好地消除了散斑条纹图的噪声,同时尽量减小了对条纹结构的损害．为从单幅散斑条纹图中应用条纹中心线法或全灰度法进一步提取相位场的后处理,奠定了良好的基础．     

扫描云纹法中的光载波解调问题研究

本文提出一种新型的光载波技术,扫描云纹被使用为空间相位的探测器,可以用来实时地复原原始条纹.全场条纹级数可以得到快速而精确地自动识别.文中对调制度的概念及应用的充要条件进行了讨论.     

用双频栅测三维物体的形状

本文介绍了一种新的相位测量轮廓术，通过使用不同栅距的栅获得两幅包裹相位图，然后比较这两幅包裹相位图，求得物体上任一像素点的绝对相位值，从而确定物体上任一点的高度。这种方法的优点是实验过程简单，精度高，相位的求解在整个过程中是单独进行的，不需借助相邻点，所以求得的相位值是各点的绝对相位，而且它可测量高度上中跳跃的物体的面形。     

基于多通道滤波技术的散斑条纹图正则化方法

在光测力学中,条纹图正则化是进一步提取条纹位相信息的重要基础。对于散斑条纹图来说,正则化的过程还需能够有效地抑制散斑噪声。本文提出一种基于多通道滤波技术的散斑条纹图正则化方法。通过使用多个Gabor滤波通道对散斑条纹图进行滤波,并且引入与条纹对比度有关的权重因子把各个滤波通道的滤波结果叠加起来,最终得到滤除了散斑噪声的正则化条纹图。数值模拟和实验结果表明,该方法在将散斑条纹图正则化的同时能够有效地滤除条纹图中的散斑噪声,为进一步提取条纹位相奠定了良好的基础。     

一种通过改进Canny算子提取光弹条纹骨架线的方法

光弹性法是确定应力集中系数的有效手段，在实际工程中应力参数都是通过分析光弹干涉条纹图获得的，由于光弹干涉条纹图的复杂性，且影响成像质量的因素较多，因此如何从光弹干涉条纹图中撇开其复杂性，较高精度的提取骨架线，是一项较困难的工作，本文提出一种由改进的Canny算子对条纹方位图进行直接运算提取光弹条纹骨架线的算法，实验表明此方法对光弹条纹图很有效。     

全息干涉条纹图的计算机自动处理与识别

本文应用数字图象处理与识别技术在IBM-PC/AT微处理计算机图象处理系统上对复杂的全息干涉条纹图进行了自动分析,文中采用二维灰度值检测的方法获取条纹的准峰或谷值二值图形,然后通过细化得到条纹中心,提出了用记忆跟踪算法自动去除毛刺和噪声线段.在用光标进行人机对话标定零级条纹后,可自动识别出其它整数条纹级数.分数级条纹级数可在整数级条纹数据之间进行线性或非线性插值得到.最后给出了全息条纹图分析的实例.     

光干涉条纹图的中心线提取算法

本文针对光干涉条纹图的特点,以近年来采用的多种方法为基础,找出了提取条纹中心线的“探索数”算法。分析和实验表明,该算法实现速度快,处理精度好,自动化程度高。本文介绍了该算法处理云纹图和全息图的实例。     

DCM 相位梯度提取技术在光力学图像信息识别中的应用

为解决相位去包裹对光力学图像处理的影响问题,本文将一种直接从数字编码傅立叶变换或相移条纹图中逐相素提取相位梯度的方法应用于光力学图像信息识别中。该方法是一个广泛应用于光纤传感器中的微分正交乘法器(DCM)的正、余弦相位检波技术。这一技术算法简单,不需计算反正切,不受相位去包裹方法标准的限制,非常适于应用在以相位梯度作为最终所需识别的信息的光力学图像处理中。本文以载波等达因条纹图应力场计算及四幅图相移等达因法求板的接触应力为例,对该技术在光力学图像信息识别中的应用进行了论证。     

Equations of heterophase equilibrium of a biomembrane

Summary Phase transitions in a shell are considered within the frame example work of a biomembrane of a general shape divided into parts containing different phases. The configuration of a boundary separating these phases is determined by the condition of minimum of the total membrane free energy with respect to its position. Equations of equilibrium for both the membrane phases and the phase boundary are deduced. They allow to describe the heterophase state of the biomembrane. Received 11 December 1997; accepted for publication 31 July 1998     

Algorithm for phase contrast X-ray tomography based on nonlinear phase retrieval

A new algorithm for phase contrast X-ray tomography under holographic measurement was proposed in this paper. The main idea of the algorithm was to solve the nonlinear phase retrieval problem using the Newton iterative method. The linear equations for the Newton directions were proved to be ill-posed and the regularized solutions were obtained by the conjugate gradient method. Some numerical experiments with computer simulated data were presented. The efficiency, feasibility and the numerical stability of the algorithm were illustrated by the numerical experiments. Compared with the results produced by the linearized phase retrieval algorithm, we can see that the new algorithm is not limited to be only efficient for the data measured in the near-field of the Fresnel region and thus it has a broader validity range.     

区域相关位相去包络技术

本文提出区域相关位相去包络新方法,配合非相容点标记方法,实现了快速、准确的位相去包络,为了验证该技术的可靠性,本文用数值模拟的方法对一个典型的位相结果进行去包络和误差分析,并对相移干涉云纹实验中取得的位图进行了去包络处理,最后讨论了区域相关去包络的优点。     

Rheo-dielectric behavior of low molecular weight liquid crystal 2. Behavior of 8CB in nematic and smectic states

Rheo-dielectric behavior was examined for 4−4^′−n-octyl-cyanobiphenyl (8CB) having large dipoles parallel to its principal axis (in the direction of the C≡N bond). In the quiescent state at all temperatures (T) examined, orientational fluctuation of the 8CB molecules was observed as dielectric dispersions at characteristic frequencies ω_c>10⁶ s⁻¹. In the isotropic state at high T, no detectable changes of the complex dielectric constant ɛ^*(ω) were found under slow flow at shear rates ˙γ≫ω_c. In the nematic state at intermediate T, the terminal relaxation intensity of ɛ^*(ω) was decreased under such slow flow. In the smectic state at lower T, the flow effect became much less significant. These results were related to the flow-induced changes of the liquid crystalline textures in the nematic and smectic states, and the differences of the rheo-dielectric behavior in these states are discussed in relation to a difference of the symmetry of molecular arrangements in the nematic and smectic textures. Received: 1 October 1998 Accepted: 13 January 1999     

基于广义优先搜索的位相展开算法

二维位相展开（phase unwrapping)是位相检测技术中的一个重要组成部分和技术难点。本文设计了一种基于广度优先搜索（breadth-first search)遍历位相图策略的位相展开算法。算法的一个显著优点在于能够自动地绕过可疑的非相容点,避免对这些点进行位相展开时产生的误差影响以后的区域,因此尤其适用于处理包含空洞和环状噪声区域的相位图。文中还用该算法对实际的位相图进行了处理,得到了比较理想的结果。     

多烷基环戊烷/有机硅烷双层膜的制备及摩擦学性能研究

分别在羟基化硅片表面制备了多烷基环戊烷单组分润滑膜(MACs)、(3-胺丙基)三乙氧基硅烷自组装膜(APS-SAMs)和多烷基环戊烷/(3-胺丙基)三乙氧基硅烷双层润滑膜(MACs-APS),对比研究了不同润滑防护涂层的摩擦磨损性能.结果表明:在载荷0.1N、频率1Hz下,与APS-SAMs和MACs单组分膜相比,MACs-APS双层膜在保持较低摩擦系数的基础上,其耐磨性能显著提高,在失效前未发生明显磨损.在所制备的这种双层润滑薄膜体系中,流动性较好的MACs分子镶嵌在固定相APS-SAMs的网络中,因而产生较好的复合摩擦学性能.     

铈γ→α相变的室温动态特性

通过试样组件尺寸匹配设计的被动围压SHPB实验,获得了99.8%纯铈在1.7GPa静水压内的、包含γ?α相变和逆相变过渡区的室温动态静水压-体应变连续曲线。研究显示:室温铈γ→α相变是具有明显滞后现象的一级相变,而非以往研究认为的体积跃变的一级相变;相变过渡区的静水压范围是0.8~1.3GPa。逆相变过渡区的静水压范围是0.6~1.1GPa;逆相变过渡区的静水压-体应变曲线滞后于相变过渡区的静水压-体应变曲线0.15GPa静水压;在相变和逆相变过渡区内,静水压-体应变曲线按照约4.2GPa体积模量的线性关系演化;演化机制为γ和α两相均匀混合、静水压驱动两相组份转化。基于该演化机制,构建了描述相变前后和相变过程的静水压-体应变响应的三段线性模型。     

Galileo/GPS组合接收机载波相位定位方法

鉴于载波相位观测量可提供高精度定位信息的特点，采用扩展卡尔曼滤波和载波相位组合观测值相结合的方法，提出了一种适合Galileo／GPS组合接收机的载波相位定位方法。通过扩展卡尔曼滤波给出精确的载波相位不足整周的相位值，并且在模糊度保持为整数的前提下，根据一定的组合标准论述了具有相应特性的组合观测值，给出一些典型的组合，通过这些组合后的观测值可以容易地解算整周模糊度。最后对结果进行了分析。     

GIANT ANHYSTERETIC RESPONSE OF FERROELECTRIC SOLID SOLUTIONS WITH MORPHOTROPIC BOUNDARIES: THE ROLE OF POLAR ANISOTROPY

Computer modeling and simulation for the Pb(Zr 1 x Ti x )O 3 (PZT) system reveal the role of polar anisotropy on the giant anhysteretic response and structural properties of morphotropic phase boundary (MPB) ferroelectrics. It is shown that a drastic reduction of the composition- dependent polar anisotropy near the MPB flattens energy surfaces and thus facilitates reversible polarization rotation. It is further shown that the polar anisotropy favors formation of polar domains, promotes phase decomposition and results in a two-phase multidomain state, which response to applied electric field is anhysteretic when the polar domain reorientation is only caused by polarization rotation other than polar domain wall movement. This is the case for the decomposing ferroelectrics under a poling electric field with the formation of a two-phase multidomain microstructure, wherein most domain walls are pinned at the two-phase boundaries. Indication of the microstructure dependence of the anhysteretic strain response opens new avenues to improve the piezoelectric properties of these materials through the microstructure engineering.