线性结构的基于市场机制的鲁棒控制

系统建模不可避免地要忽略一些因素从而造成模型误差,因此基于不确定性的非精确模型来设计控制器显得尤为重要.随着各国学者的不断研究,在线性系统H_∞控制方面取得了很大的发展,但仍存在求解过程繁琐、系统的保守性不强、结构复杂和控制器阶数较高等问题.运用计算结构力学与最优控制相模拟的理论来试图完善存在的问题.导引模就是结构力学中的本征值问题,即弹性稳定的欧拉(Euler)临界力或结构振动的本征频率;通过引入区段混合能的概念,采用精细积分和扩展的威廉姆斯(W-W)算法计算导引模,将此方法引入到基于市场机制的控制(market-based control,MBC)理论中,提出了线性结构基于市场机制的鲁棒控制策略.同时给出了在鲁棒控制下,采用李雅普诺夫(Lyapunov)直接法证明了结构基于市场机制的鲁棒控制器的稳定性及参数的确定方法.最后对一高层受控结构进行数值计算与分析,并与H_∞鲁棒算法的控制效果进行了对比.结果表明,导引模不能取到临界值,否则会导致控制输入趋于无穷大.基于市场机制的鲁棒控制效果要好于H_∞鲁棒算法,并且具有较强的应变能力和在线计算时间短等优点,能较好地适用于高层和大跨结构.      

带一致变化尾上负相关随机变量和的精确大偏差

随机变量和尾概率性状的研究是保险精算领域的热门问题,而随机变量和的精确大偏差则精确刻画了其尾概率的极限性态。文章分别研究了一列同分布(但不一定独立)随机变量确定和以及随机和的精确大偏差,得到如下结果:如果这列随机变量带一致变化尾,是上负相关的,并且在左直线无支撑,则它们确定和以及随机和的精确大偏差结果均成立。     

一类风险模型的精细大偏差

考虑一类重尾索赔条件下带干扰项的双险种风险模型,当索赔到达过程为一般非负整值过程,索赔额的分布属于重尾分布C族时,利用分析和概率方法得到了索赔剩余过程的精细大偏差.     

Simultaneous Measurement of Refractive Index and Thickness of Transparent Plates by Low Coherence Interferometry

We demonstrate a novel low coherence Michelson interferometer which can provide simultaneous measurement of the refractive index and thickness of transparent plates used as a measured object. Unlike the existing low coherence interferometers reported so far, either an object or a focusing lens aligned on the signal arm is scanned repeatedly by a precise translation stage in synchronization with movement of a reflection mirror on the reference arm. The so-called object or lens scanning method gives us two measured quantities a movement distance of the stage between two light focusing states on the front and rear planes of an object and the corresponding optical path difference. These two measured quantities, result in desirable values of the index and thickness of the object with a short calculation. The measurement accuracy of ≤0.1% is expected for a thickness of more than 1 mm. In the experiment using the object scanning method, the accuracy of 0.3% or less was successfully attained for nearly 1-mm thick plates of fused quartz, sapphire, LiTaO₃ and slide glass.     

光学触摸式投影机中亚像素边缘检测

针对光学触摸式投影机中,像素级边缘检测不能满足测量精度要求的现状,提出亚像素寻边检测方法.该方法利用二次函数逼近高斯函数,将二次函数极值作为图像亚像素边缘,使边缘定位更加准确.实验结果表明:该亚像素边缘检测方法,能有效提高光学触摸式投影机图像边缘的检测精度.     

Zero-difference and single-difference precise orbit determination for LEO using GPS

Various methods for precise orbit determination (POD) of low earth orbiters (LEO) are briefly intro-duced in this paper. Based on the software named SHORD-Ⅲ developed by our institute,sin-gle-difference (SD) and zero-difference (ZD) dynamic POD based on LEO carrying an on-board GPS receiver is mainly discussed. The approaches are tested using real GRACE data (November 5―25,2002) and independently validated with Satellite Laser Ranging (SLR) measurements over the same 21 days. Comparisons with the scientific orbits provided by GFZ indicate that the SD POD RMS accuracy can achieve 5,10 and 6 cm in radial,along and cross the track,and the ZD POD RMS accuracy can achieve 4,8 and 4 cm in radial,along and cross the track. SLR validation shows that SD POD accuracy is better than 8 cm in distance,and ZD POD accuracy is better than 6 cm.     

Coherent Vibrational Dynamics of [Au25(SR)18]- Nanoclusters?

Coherent vibrational dynamics can be observed in atomically precise gold nanoclusters using femtosecond time-resolved pump-probe spectroscopy. It can not only reveal the coupling between electrons and vibrations, but also reflect the mechanical and electronic properties of metal nanoclusters, which holds potential applications in biological sensing and mass detection. Here, we investigated the coherent vibrational dynamics of [Au₂₅(SR)₁₈]^- nanoclusters by ultrafast spectroscopy and revealed the origins of these coherent vibrations by analyzing their frequency, phase and probe wavelength distributions. Strong coherent oscillations with frequency of 40 cm^-1 and 80 cm^-1 can be reproduced in the excited state dynamics of [Au₂₅(SR)₁₈]^-, which should originate from acoustic vibrations of the Au₁₃ metal core. Phase analysis on the oscillations indicates that the 80 cm^-1 mode should arise from the frequency modulation of the electronic states while the 40 cm^-1 mode should originate from the amplitude modulation of the dynamic spectrum. Moreover, it is found that the vibration frequencies of [Au₂₅(SR)₁₈]^- obtained in pump-probe measurements are independent of the surface ligands so that they are intrinsic properties of the metal core. These results are of great value to understand the electron-vibration coupling of metal nanoclusters.     

β-Laguerre随机矩阵最大特征值精确渐近性的一般结果

利用β-Laguerre随机矩阵最大特征值的中心极限定理、 尾概率不等式及广义β-Tracy-Wisdom分布的性质, 对于相当广泛的边界函数 和拟权函数, 得到了其最大特征值的矩完全收敛性的精确渐近性的一般结果.     

基于Autodesk Map的地理数据组织方法

介绍了基于Autodesk Map的数字地图制图和地理信息数据库解决方案,包括精确地图制图、地理数据整理、属性数据链接、空间分析、与Oracle协作的空间地理数据库管理等,并指出了其存在的不足。