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81.
关于结构刚度方程病态问题的疑难分析 总被引：1，自引：0，他引：1
本文围绕矩阵位移法求解结构位移的误差,讨论了结构刚度矩阵的病态问题,指出了计算上的病态常常是结构刚度分布和结构拓扑的不合理,而不一定是计算本身的问题.首先,文章依据误差界的概念和范数的性质推导了衡量结构刚度矩阵病态程度的条件数的公式.然后,阐明了基于不同范数的条件数在衡量矩阵病态程度上的等价性.最后,通过两个具有代表性的算例,分别从结构构件的刚度差异和结构几何拓扑两方面,计算和分析了结构刚度矩阵的病态程度随结构本身性质的改变而改变的规律.在特定的算例中,还有使结构刚度矩阵的病态程度降到最低的最佳刚度分布. 相似文献
82.
通过直接求解轴向受载的单对称均匀Bernoulli-Euler薄壁梁单元弯扭耦合振动的运动微分方程,推导了其动态传递矩阵.讨论了轴向载荷的变化对薄壁梁弯扭耦合振动固有频率的影响,并由此得到零频率振动(弹性屈曲)发生时相应的轴向载荷.数值结果表明本文方法在其适用范围内是精确有效的. 相似文献
83.
84.
刚架结构中瞬态波的传播 总被引：7，自引：0，他引：7
在改进回传矩阵法的基础上 ,引入节点质量阻尼模型 ,结合射线展开技术 ,研究刚架结构中的弹性瞬态波的传播。根据分析结果可以看出 ,节点质量对弹性波的传播影响不大 ,节点阻尼对弹性波的传播影响很大。如果选取合适的节点 ,就可以阻碍波在结构局部中的传播 ,达到结构局部控制的目的。刚架结构中的弹性瞬态波的传播 ,可以对大型刚架结构的无损检测提供一定的帮助。 相似文献
85.
86.
多指标决策与评价的新方法--主成份投影法 总被引：22，自引：0，他引：22
本文介绍了主成份投影法的原理和实施步骤 ,并对全国 31个省、自治区和直辖市的 1998年经济效益指标进行综合分析和排序 相似文献
87.
离子液体作为一种新兴的绿色溶剂,具有低蒸气压、高热稳定性、良好的可设计性和非燃烧性等优点,在各个领域得到了广泛的应用.随着人们对消防安全的日益关注,研究和开发无(低)毒、低烟、绿色环保的阻燃材料逐渐成为阻燃领域的发展方向.本文简要综述了近几年来离子液体在阻燃领域的最新研究进展,重点介绍了离子液体在高分子基体中的阻燃机理... 相似文献
88.
ZHAO Zuyang;CUI Haihua;DU Kunpeng;QU Yiming;QUAN Dong;MU Zhiguo 《光子学报》2022,51(11):304-313
As a branch of augmented reality technology, 3D laser projection positioning technology can accurately present the contour information of the digital 3D model of the product and part of the manufacturing information at the required place on the product assembly site. The 2D galvanometer system is an optical reflection system that can precisely control the optical path of the laser beam. The calibration technology of the 2D galvanometer is the key to achieving high-precision 3D laser projection. As the application of two-dimensional scanning galvanometers expands from two-dimensional plane scanning to three-dimensional space scanning, the difficulty of galvanometer system calibration is also increasing, and the continuous expansion of galvanometer system applications promotes the development of galvanometer system calibration technology. However, the calibration process of the existing laser projection technology has the problems of complicated process operation, low efficiency and the need to use high-cost equipment such as laser trackers, resulting in the inability of 3D laser projection to be widely used in the field of view of assembly manufacturing. Vision measurement technology is a typical non-contact auxiliary measurement technologies with high measurement accuracy. It can not only collect a large amount of high-precision data for the calibration of the galvanometer, but also can be used as a basic coordinate system to realize the alignment of the coordinate system of the projected object and the galvanometer coordinate system. In addition, visual measurement has the advantages of mature development and low hardware requirements. The study of the 3D laser projection system based on visual assistance can lower the threshold for the realization of this technology and promote the promotion and application of 3D laser projection. Aiming at the problems of complicated operation and low efficiency in the existing 3D laser projection system calibration, a 3D laser projection calibration method based on a homography matrix is proposed. Firstly, the monocular vision was introduced as an auxiliary means to establish a model of the 3D laser projection system; secondly, the pose of the projected target was solved by using the 2D homography of the image, and the conversion relationship between the galvanometer and the camera was calibrated. The performance of the proposed calibration method is analyzed from three angles of error, stability and error distribution, and the reliability of the 3D laser projection calibration method based on the homography matrix is verified. By independently building a 3D laser projection system based on visual aids, and conducting specific experiments with standard parts as the projected parts, it is proved that the proposed calibration method can solve the above problems. The experimental results show that when the distance between the projected part and the galvanometer is within 3 m, the calibration time is less than 5 min, and the projection accuracy can reach 0.3 mm. The calibration method of the homography matrix is limited to the plane object, and it is suitable for the case where the projected part is a plane. Compared with the domestic conventional calibration method, the method in this paper avoids the complicated pre-calibration process and improves the calibration efficiency. Such a positioning device reduces the cost and solves the problem of low operation efficiency of the entire 3D laser projection system at present. 相似文献
89.
XIE Jun-shan 《高校应用数学学报(英文版)》2012,27(2):181-191
In this paper,we consider the limiting spectral distribution of the information-plusnoise type sample covariance matrices Cn =1/N (Rn + σXn) (Rn + σXn)*,under the assumption that the entries of Xn are ... 相似文献
90.