以环形子孔径扫描法测量大口径非球面的研究

总结非球面常用检验方法在应用中优、缺点的基础上,使用环形子孔径扫描法来测量大口径非球面。这种方法使被测元件相对于参考波前的斜率差减小到干涉仪允许的测量范围内,每次测量仅是被测表面的一部分,通过算法实现数据“拼接”,从而得到整个面形信息。该方法无需辅助光学元件即可实现对大口径、大相对口径非球面的直接测量,为大口径高精度非球面的加工检验提供了有效手段。     

子孔径拼接检验法中倾斜的影响及消除方法

在子孔径拼接检测大口径光学平面时,子孔径检测的数据往往存在倾斜,它将会导致拼接的数据沿着一个方向的倾斜累加,最后引入很大的倾斜误差。由于这种倾斜误差难以手动修正,通过实验,先用最小二乘法编制软件对所测子孔径数据进行消除倾斜处理,然后把去倾斜的子孔径数据进行拼接处理,对比消除倾斜的子孔径拼接结果与全口径直接检测结果,证明了去倾斜处理在子孔径拼接检测处理中的有效性。     

环形子孔径检测技术中测量数据的准确提取方法

环形子孔径拼接测试技术是一种无需辅助元件就能检测旋转对称大口径非球面镜的有效手段。根据该技术的检测原理及基于Zemike多项式的“拼接”算法,提出了一种相应的环形子孔径数据提取方法。该方法基于商用相移干涉仪的CCD成像系统和其数据处理软件提供的Mask编辑功能,利用被测镜面上方的三个可移动的基准标记进行绝对定位,给出了具体的实施方案。对一口径700mm、F2的抛物面主镜进行实验,研究结果表明,该数据提取方法操作简单可行,适合于加工车间的实施,取得了符合“拼接”算法需求的子孔径测试数据和对应环带的内外半径值。     

子孔径拼接干涉检测大口径平面波前

介绍了子孔径拼接检测平面波前的基本原理,提出了基于均化误差和最小二乘法的多个子孔径同时拼接的数据处理方法,有效减小了误差传递和积累.用该方法对Zemax仿真的望远镜光学系统进行了子孔径拼接检测,拼接光学系统波前和直接用Zemax得到的全孔径波前对比,其峰谷值(PV)和均方根(RMS)的偏差分别为0.015 1λ和0.0016λ.并用口径为100 mm的小口径干涉仪对口径为200 mm的平面镜进行了拼接实验,将其全孔径波前与直接检测的结果对比,其峰谷值(PV)和均方根(RMS)的偏差分别为0.055 9λ和0.0004λ.实验结果表明了该算法的有效性,该方法不仅适用于检测光学元件,也适用于对光学系统平面波前检测.     

基于标记点的子孔径全局优化拼接检测法

为实现小口径干涉仪完成较大口径光学平面镜片的测试,得到镜片的完整面形信息,提出了基于标记点的平面Givens变换,实现了子孔径的精确定位.采用Zemike多项式拟合对每个子孔径数据进行了消倾斜量的处理.建立了全局优化拼接数学模型.利用该模型进行了九孔径拼接计算机仿真实验,利用该方法得到的PV值和RMS值的相对误差均在10-6左右.对直径为150 mm的镜片进行九孔径拼接检测实验,对比全口径干涉检测结果,PV值和RMS值的相对误差为0.36%和2.27%.仿真和实验结果证明:该方法稳定可靠,降低了传统的子孔径拼接干涉检测方法中对导轨的高精度要求.     

拼接检测系统平面波前稀疏子孔径排列模型的优化

稀疏子孔径拼接检测是大口径、超大口径光学系统像质检测的主要方法之一,其拼接检测的精度与子孔径排列方式、数目以及大小密切相关。本文通过建立数学模型,推导出子孔径个数k在1到无穷区间取值,子孔径个数k与填充因子M的关系曲线,从而得出在1.5 m以下系统检测的最优的七个稀疏子孔径排列布局图,并通过Φ200 mm自准干涉检验,验证了这种排列布局的合理性。     

基于Shack-Hartmann的子孔径拼接波前检验技术

针对传统的地基大口径望远镜自准直干涉检测受器材限制和环境影响而检测困难的问题,提出了基于Shack-Hartmann波前探测器的子孔径拼接波前检测方法.介绍了子孔径拼接检测理论和拼接算法,研究了Shack-Hartmann下实现子孔径上波前精确测量的方法,设计了具有透射孔的光阑实现自准直光路中子孔径毫米级的定位.实验使...     

大口径光学件误差均化拼接技术

运用子孔径检测及拼接的方法可完成大口径光学件面形的干涉测量。为了能够减少子孔径拼接的误差累积与数据处理算法带来的精度影响,运用子孔径拼接的误差拼接算法,并通过对实验检测数据的处理,得到拼接结果与全孔径检测结果比较,面形波面峰谷值相差0．0842,均方根值相差0．01λ,误差在Veeco光学干涉测量仪器的公差范围内。实验结果验证了误差均化算法可有效减少误差的传递与累积,实现子孔径拼接技术对大口径光学件的正确检测。     

平面子孔径拼接的面旋转误差

在按某一基准面进行拼接的过程中,存在着只与测量误差相关而与子孔径面形无关的误差,将其命名为面旋转误差.本文对比分析了顺序拼接和误差均化拼接中存在的面旋转误差的情况,讨论了面旋转误差对拼接的影响.给出了对抑制面旋转误差的基本想法,并论述了其可行性.     

对比度最优与子孔径相关自聚焦算法的比较

为了选用快速高效的自动聚集算法对机载SAR数据进行聚焦处理，针对两种自聚焦算法--对比度最优法（Contrast Optimization，简称CO）与子孔径相关法（Map Drift，简称MD），利用中科院电子所机载L波段合成孔径雷达(SAR)的实际数据和仿真的点目标对这两种算法进行了对比实验研究。给出了分别用两种算法处理的点目标冲激响应和实际SAR图像。通过对比分析，表明CO算法比MD算法计算速度快、估计效果较好。     

天文观测中快速倾斜镜控制系统的应用

介绍了应用于天文观测中的快速倾斜镜控制系统的结构及其 PI控制算法、剔野值与滤波算法的设计 ,给出了在天文观测中的试验结果。     

改进操作以缩短制氧机排液及启动时间

在马钢 35 0 0 0m3 /h制氧机 2 0 0 2年大修期间 ,改进操作 ,返送液体 ,缩短制氧机排液及启动时间 ,以缩短工期 ,提前出氧 ,提高经济效益。     

Structure,Analysis, and Methods of Investigating and Correcting the Errors of an Extremum Counting-Interpolating System for Displacement Measurements

The errors of an extremum counting-interpolating system are analyzed. The structure of the total error of measurement of this system is given. Methods for investigating and correcting those errors are described. The use of a correction is shown to decrease the interpolator error to 0.01%.     

A subspace iteration algorithm for the eigensolution of large structures subject to non‐classical viscous damping

This paper describes an efficient and numerically stable algorithm for accurately computing the solutions of the quadratic eigenproblem associated to non‐proportionally viscously damped structures characterized by symmetric matrices. Combining the simultaneous inverse iteration with a generalized Rayleigh–Ritz analysis, the proposed procedure is well suited for extracting the subset of the lowest natural frequencies, the corresponding subcritical damping ratios and the mode shapes of large dissipative systems with non‐classical viscous damping. The iterative process exploits the specific nature of non‐proportionally damped structures, takes full advantage of the banded configuration of the structural matrices involved in the eigenproblem, avoids the computation of the left eigenvectors and circumvents the use of complex algebra owing to a unitary transformation strategy. An academic test case and an industrial numerical example are presented to highlight the effectiveness of the algorithm. Copyright © 2000 John Wiley & Sons, Ltd.     

Parameter estimation for load‐sharing system subject to Wiener degradation process using the expectation‐maximization algorithm

In practice, many systems exhibit load‐sharing behavior, where the surviving components share the total load imposed on the system. Different from general systems, the components of load‐sharing systems are interdependent in nature, in such a way that when one component fails, the system load has to be shared by the remaining components, which increases the failure rate or degradation rate of the remaining components. Because of the load‐sharing mechanism among components, parameter estimation and reliability assessment are usually complicated for load‐sharing systems. Although load‐sharing systems with components subject to sudden failures have been intensely studied in literatures with detailed estimation and analysis approaches, those with components subject to degradation are rarely investigated. In this paper, we propose the parameter estimation method for load‐sharing systems subject to continuous degradation with a constant load. Likelihood function based on the degradation data of components is established as a first step. The maximum likelihood estimators for unknown parameters are deduced and obtained via expectation‐maximization (EM) algorithm considering the nonclosed form of the likelihood function. Numerical examples are used to illustrate the effectiveness of the proposed method.     

磁光盘非平衡差分信道信噪比模型的研究

针对磁光存储系统中的非平衡差分信道建立了描述其信道特性的信噪比模型，并就其读出特性与平衡差分信道进行了比较。研究结果表明：非平衡差分信道的读出信噪比仅略低于平衡差分信道。     

Genetic algorithm for informative basis function selection from the wavelet packet decomposition with application to corrosion identification using acoustic emission

Chemical process installations are exposed to aggressive chemicals and conditions leading to corrosion. The damage from corrosion can lead to an unexpected plant shutdown and to the exposure of people and the environment to chemicals. Due to changes within and on the surface of materials subjected to corrosion, energy is released in the form of acoustic waves. This acoustic activity can be captured and used for corrosion monitoring in chemical process installations. Wavelet packet coefficients extracted from the acoustic activity have been considered to determine whether corrosion occurs, and to identify the type of corrosion process, at least for the most important corrosion processes in the chemical process industry. Feature subset selection is then applied to these wavelet coefficients to achieve a much higher accuracy in the identification of different corrosion processes than when no feature subset selection is applied to the acoustic waves. However, due to the statistical dependencies that potentially exist between the wavelet coefficients, the latter should not be selected independently from each other. Local discriminant basis selection algorithms do not take the statistical dependencies between wavelet coefficients into account. In this paper, we have used several mutual information-based approaches that take these dependencies into account and compared them to the wavelet-specific local discriminant basis selection algorithm. Furthermore, a hybrid filter-wrapper genetic algorithm, which uses a relevance-redundancy approach as a local search procedure, was designed. The highest classification accuracies are obtained with the hybrid filter-wrapper genetic algorithm, for all classifiers used in this paper. Furthermore, the proposed algorithm easily outperformed one of the most commonly used classifiers in chemometrics: partial least squares discriminant analysis (PLS-DA). A naïve Bayes classifier that uses the features selected by the hybrid filter-wrapper genetic algorithm was able to identify the absence of corrosion, uniform corrosion, pitting and stress corrosion cracking, with an accuracy of up to 87.20%.     

Hybrid Clustering Algorithms with GRASP to Construct an Initial Solution for the MVPPDP

Mobile commerce (m-commerce) contributes to increasing the popularity of electronic commerce (e-commerce), allowing anybody to sell or buy goods using a mobile device or tablet anywhere and at any time. As demand for e-commerce increasestremendously, the pressure on delivery companies increases to organise theirtransportation plans to achieve profits and customer satisfaction. One important planning problem in this domain is the multi-vehicle profitable pickup and delivery problem(MVPPDP), where a selected set of pickup and delivery customers need to be served within certain allowed trip time. In this paper, we proposed hybrid clustering algorithms with the greedy randomised adaptive search procedure (GRASP) to construct an initial solution for the MVPPDP. Our approaches first cluster the search space in order toreduce its dimensionality, then use GRASP to build routes for each cluster. We compared our results with state-of-the-art construction heuristics that have been used to construct initial solutions to this problem. Experimental results show that our proposed algorithms contribute to achieving excellent performance in terms of both quality of solutions and processing time.