高斯拟合算法在光谱建模中的应用研究

采用高斯拟合算法对光谱进行特征提取,利用拟合得到的特征参量表征光谱信息,并结合多元校正方法对光谱模型进行优化和解释,建立了样品快速准确的测定方法。实验以玉米活体叶片为研究对象,建立叶片光谱与叶绿素含量之间的关系模型,采用三个高斯峰对原始光谱的1 551个数据拟合后,光谱数据转换为9个高斯特征量(约为整个波段的0.58%),进而利用该高斯特征量来预测叶绿素含量。实验结果显示,采用高斯拟合分别与偏最小二乘法和主成分回归结合建模,其预测集相关系数分别为0.960和0.962;不采用高斯拟合算法而直接采用偏最小二乘法和主成分回归对全光谱建模,其预测集相关系数分别为0.957和0.919。可见,将高斯拟合算法运用到定量分析模型中是可行的,该方法不仅简化了模型参数,而且提高了模型的可解释性。     

激光辐照下转动柱壳平均温度与破坏时间的工程估算

 推导了激光辐照下转动壳体平均温度沿壳体母线方向分布的解析公式。由于对高斯功率密度分布光束无法得到工程上实用的结果,对公式进行了解析拟合,仅由一个具有实际物理意义的拟合系数——分布因子确定了解析拟合公式的形式,明确了温度估算公式中各项的物理意义。解析拟合公式计算结果与数值模拟结果较为一致。作为温升估算方法的一个应用实例,推导了转动充压柱壳在激光辐照下破坏时间的解析公式,与数值计算结果吻合得较好。     

插值法在低温温度测量中的应用

依托建立的低温精馏装置,针对低温环境中温度测量问题,提出一种基于LabVIEW的低温温度测量方法。该方法将插值法引入到数据分析中,通过软件编程实现数据处理、显示、存储等功能。经过理论分析与实验对比,该方法准确度提高到0.01 K,可移植性强,是低温环境中温度测量的可行方法。     

基于裂纹附加模态Timoshenko梁的裂纹损伤识别

将梁中横向裂纹等效为无质量扭转弹簧，并忽略其对梁剪切变形的影响，得到的具有任意裂纹数目Timoshenko 梁自振模态的统一显示解析表达式．将裂纹梁的自振模态分为基本模态和裂纹附加模态，利用最小二乘拟合，建立了利用裂纹附加模态函数的梁裂纹损伤识别方法．通过数值模拟开展了简支单裂纹梁以及悬臂和固支双裂纹梁等的裂纹损伤识别，考察了测量误差对损伤识别的影响，数值结果表明本文所提出的裂纹损伤识别方法对裂纹位置的识别精度高于对裂纹损伤程度的识别精度；随着测量误差的增加，裂纹位置及裂纹损伤程度的识别误差增加，但仍在可接受的范围内，故该裂纹损伤识别方法在实际工程中具有一定的应用价值．     

基于图像处理的零件二维尺寸检测方法

为了提高零件二维尺寸测量精度和效率,提出一种基于图像处理的非接触式检测方法。对零件图像进行灰度化、采用自适应中值滤波算法来减小图像数据量以及除去噪声;通过最大类间方差法自动确定阈值获得二值图像;采用形态学梯度算子提取图像边缘,并用最小二乘法拟合像素尺寸;通过标准件法对系统进行标定获得零件尺寸。以6204-Z型深沟球轴承作为实验对象,获得轴承内、外径的尺寸。与游标卡尺测量结果比较,所提出的图像处理方法获得的内、外径平均误差达到9.6μm和0.7μm。通过实验对比与分析,方法快速有效,具有较高的准确性和良好的鲁棒性。     

An efficient quasi-Newton method for two-dimensional steady free surface flow

Steady free surface flows are of interest in the fields of marine and hydraulic engineering. Fitting methods are generally used to represent the free surface position with a deforming grid. Existing fitting methods tend to use time-stepping schemes, which is inefficient for steady flows. There also exists a steady iterative method, but that one needs to be implemented with a dedicated solver. Therefore a new method is proposed to efficiently simulate two-dimensional (2D) steady free surface flows, suitable for use in conjunction with black-box flow solvers. The free surface position is calculated with a quasi-Newton method, where the approximate Jacobian is constructed in a novel way by combining data from past iterations with an analytical model based on a perturbation analysis of a potential flow. The method is tested on two 2D cases: the flow over a bottom topography and the flow over a hydrofoil. For all simulations the new method converges exponentially and in few iterations. Furthermore, convergence is independent of the free surface mesh size for all tests.     

基于基样条局部逼近散乱数据拟合中的Shepard方法

本文针对散乱数据拟合的shepard方法,提出了一种局部逼近的新方法.该方法以局部三次基样条函数作为Shepard公式中的权函数,新的权函数具有良好的衰减性和二阶连续性,从而改进了传统方法的不足之处,使实际应用效果更好.     

Coherent convergent beam electron diffraction for analysis of lattice fitting in PbTe/MgO bi-crystals

Coherent convergent beam electron diffraction is for the first time applied to the analysis of lattice fitting between vacuum-deposited PbTe and MgO thin crystals in the plan-view mode. The possibility of determination of the rigid-body shift is discussed on the basis of simulated diffraction patterns from the bi-crystals as well as the preliminary experimental results obtained by a 200 kV transmission electron microscope with a field emission electron gun. In the analysis, the importance of the position of interference fringes at overlaps of PbTe 200 and MgO 200 diffraction disks and that of the corresponding mirror symmetry in the whole pattern are emphasized in order to determine the rigid-body shift and the probe-position.     

Inverse doubly periodic problem of the theory of bending of a plate with elastic inclusions

Based on the balanced strength principle, a problem of determining the optimal interference for fitting elastic inclusions into holes of an isotropic elastic plate weakened by a doubly periodic system of circular holes is solved. A closed system of algebraic equations is derived, which allows solving this problem. The resultant interference increases the load-carrying capacity of the composite plate being bent. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 4, pp. 153–161, July–August, 2006.     

关于误差大小的比较

在实验数据处理过程中 ,经常涉及测量误差比较 ,笔者针对在误差比较中经常存在的模糊认识 ,阐明了几点已有的观点 .