N重亏损状态矩阵广义特征向量灵敏度分析

为了克服具有N重特征值的状态矩阵发生亏损现象后对灵敏度分析的制约,本文基于亏损矩阵的若当标准形理论,引入广义特征向量及其伴随向量系,提出了广义特征向量灵敏度的全模态算法。求解亏损矩阵广义特征向量的灵敏度时,发现除一个灵敏度系数为非精确解外,其余灵敏度系数均为精确解。针对非精确解,通过引入松驰因子获得了较好的近似解。数值算例证实该算法适用于N重亏损状态矩阵的灵敏度分析。     

接近亏损系统模态灵敏度分析的有效算法

为求解振动系统特征问题的灵敏度分析,建立了快速计算状态向量导数的方法。该方法利用广义模态理论,将接近亏损系统的灵敏度分析转化为亏损系统的灵敏度分析问题来处理,并且在组合近似方法的基础上,引入松弛因子保证了系数矩阵的非奇异性,从而提供了接近亏损系统灵敏度分析的理论和方法。数值算例证明了算法的有效性。     

高温热采井水泥环缺陷对套管安全性的影响分析

针对水泥环缺陷导致套管承受非均匀载荷并引起套管失效的问题,建立了套管、含缺陷水泥环和地层耦合系统有限元计算模型。将温度场与应力场耦合,考虑套管强度降低,计算了水泥环缺陷形状、缺陷环向开度、缺陷深度及缺陷数量对套管安全的影响。应用塑性变形、剩余强度和安全系数来评价水泥环含缺陷井筒中套管的安全性,并分析了套管的失效模式。计算结果表明:完整井筒和水泥环含缺陷井筒中套管的屈服温度相差较大,水泥环缺陷环向开度和深度对套管安全的影响比较大。此研究为揭示套管失效机理提供了依据,对预防套损具有指导意义。     

N重亏损系统摄动的原点移位组合近似方法

针对不完全特征向量系的黏性阻尼线性振动系统,提出了基于原点移位组合近似方法求解N重亏损系统重分析问题的快速算法。利用广义模态理论,在组合近似方法的基础上,通过引入原点移位参数求解摄动后的亏损系统,将广义特征向量表示成基向量和系数向量的组合形式,避开求解大规模方程组,简化了复杂的求解运算。数值算例表明,本文提出的算法高效、快速,并且有较好的精确性和稳定性。     

Defective kernel detection using a linear colour CCD

Abstract

This study was aimed at detecting defective wheat (Triticum durum Desf) with a machine vision system of linear colour charge-coupled device. One thousand one hundred and sixty-nine images were captured for sound kernels, 710 for black germ kernels and 627 for broken kernels. A software package was developed to extract various morphological, colour and texture features from the images captured. Then the experimental data were subjected to multivariate analysis. Principal component analysis was employed to differentiate samples from different categories. Partial least square discriminant analysis and venetian blinds cross-validation were used to develop classification models. The best detection accuracies of samples were 92·7, 88·0 and 89·6% for black germ kernels, broken kernels and sound kernels. The results have proved that it is feasible and effective to employ partial least square discriminant analysis for feature selection and defective kernel detection.     

Improved photochromic stability in less deficient cesium tungsten bronze nanoparticles

Hexagonal cesium tungsten bronze (Cs_0.32WO₃) nanoparticles are well known as near-infrared (NIR) shielding materials. However, one of the critical issues for industrial applications involves a photochromic instability, i.e., a blue color change of this material under ultraviolet (UV) irradiation. This color change is attributed to the formation of H_xWO₃ phase through doping of H⁺ ions into Cs-deficient sites present at the surface of Cs_0.32WO₃ nanoparticles. Therefore, a new approach was adopted to prevent the color change by synthesizing a Cs_0.32WO₃ nanoparticle with less Cs-deficient sites using spray pyrolysis followed by heat treatment and short-time milling. The Cs_0.32WO₃ nanoparticles of spray pyrolysis route exhibited an improved photochromic stability under UV irradiation compared to those synthesized through a solid-state-reaction route. Detailed analysis using atomic resolution transmission electron microscopy revealed that the Cs_0.32WO₃ nanoparticles of spray pyrolysis route retain Cs ions up to a depth of less than 1 nm from the surface. This work demonstrates that the less-Cs-deficient Cs_0.32WO₃ nanoparticles are beneficial to improve the photochromic stability.     

冲击荷载下缺陷介质裂纹扩展的DLDC试验

采用数字激光动态焦散线试验系统,利用落锤冲击含预制裂纹(倾斜角度分别为0°,30°,45°)的缺陷介质,研究裂纹扩展的动态行为.结果表明:冲击荷载下,裂纹会于预制裂纹一端起裂,扩展至整个试件,且扩展路径指向重锤落点;主裂纹尖端的动态应力强度因子振荡增大又减小,然后增大至最大值时主裂纹起裂;次裂纹起裂前,KId振荡变化,起裂后迅速增大后振荡减小;主裂纹起裂后,速度迅速减小;次裂纹扩展速度先增大后振荡减小,与KId的变化趋势保持一致;含缺陷的冲击断裂试验中,主裂纹起裂时间较晚.     

A Sequential Scheme for Estimating Average Quality in a Mixed Product Production Process

A production process is assumed to produce k types of items in varying proportions and with varying defect rates. This paper proposes a sequential inspection plan which allows one to optimally allocate inspection resources so that one obtains a good estimate of average quality. The plan is fairly easy to put into practice and allows for easy modification should production characteristics change.     

重级值点对亚纯函数唯一性的影响

用Nevanlinna理论对涉及重值时的亚纯函数唯一性问题进行了讨论,并得出了一系列唯一性定理,其中有些定理是对Nevanlinna R,仪洪勋,杨力,Ozawa M等人的几个定理的推广。这些定理的一个简单推论表明,在不蜕化为常数的情况下,亚纯函数可由其若干个值的重级不超过3的值点唯一确定。从而,使亚纯函数值分布的研究有可能简单化,即仅考虑重级不超过3的值点就夠了。     

由主子阵和缺损特征对构造一类特殊矩阵

本文主要讨论了由给定的主子阵和两个缺损特征对构造一类特殊矩阵的问题．这类矩阵是对称阵,除第一行,第一列及对角元外其它元素都为零,并且第一行的元素从第二个开始都大于零．文中给出了问题有解的充分必要条件,并给出了算法及数值例子．