Atomically Precise Nanocluster Assemblies Encapsulating Plasmonic Gold Nanorods

The self‐assembled structures of atomically precise, ligand‐protected noble metal nanoclusters leading to encapsulation of plasmonic gold nanorods (GNRs) is presented. Unlike highly sophisticated DNA nanotechnology, this strategically simple hydrogen bonding‐directed self‐assembly of nanoclusters leads to octahedral nanocrystals encapsulating GNRs. Specifically, the p‐mercaptobenzoic acid (pMBA)‐protected atomically precise silver nanocluster, Na₄[Ag₄₄(pMBA)₃₀], and pMBA‐functionalized GNRs were used. High‐resolution transmission and scanning transmission electron tomographic reconstructions suggest that the geometry of the GNR surface is responsible for directing the assembly of silver nanoclusters via H‐bonding, leading to octahedral symmetry. The use of water‐dispersible gold nanoclusters, Au_≈250(pMBA)_n and Au₁₀₂(pMBA)₄₄, also formed layered shells encapsulating GNRs. Such cluster assemblies on colloidal particles are a new category of precision hybrids with diverse possibilities.     

THE PRECISE AND NEW ANALYSIS FOR A MODE Ⅲ GROWING CRACK IN AN ELASTIC-PERFECTLY PLASTIC SOLID

The near crack line field analysis method has been used to investigate into ModeⅢ quasistatically propagating crack in an elastic-perfectly plastic material.Thesignificance of this paper is that the usual small scale yielding theory has been brokenthrough.By obtaining the general solutions of the stresses and the displacement rate ofthe near crack line plastic region,and by matching the general solutions with theprecise elastic fields(not the usual elastic K-dominant fields)at the elastic-plasticboundary,the precise and new solutions of the stress and deformation fields,the sizeof the plastic region and the unit normal vector of the elastic-plastic boundary havebeen obtained near the crack line.The solutions of this paper are sufficiently precisenear the crack line region because the roughly qualitative assumptions of the smallscale yielding theory have not been used and no other roughly qualitative assumptionshave been taken,either.The analysis of this paper shows that the assumingly“steady-state cas     

求解二点边值问题打靶法的一种改进方法

本文讨论两点边值问题的数值解法,利用最小二乘法修正打靶法所需初始参数,将边值问题转化为相应的初值问题与左梯度控制方程合并,引入精细积分法进行求解。通过数值算例表明,该方法是一种求解两点边值问题的有效方法。     

The distribution of the specific pressure in rolling strips

The principle of the distribution of the specific pressure in rolling strips is used not only for calculating the total rolling pressure but also for providing the basis in calculating the widening and in designing the rational roll profile. Hitherto, the results of analysis on this subject in the references are expressed as a function of one dimension, and they cannot reflect the variation of the specific pressure along the width of the contact surface. This paper deals with the two-dimensional expression of the principle of the distribution of the specific pressure with the help of the calculus of variations.     

Precise orbit determination of a maneuvered GEO satellite using CAPS ranging data

Wheel-off-loadings and orbital maneuvers of the GEO satellite result in additional accelerations to the satellite itself. Complex and difficult to model, these time varying accelerations are an important error source of precise orbit determination (POD). In most POD practices, only non-maneuver orbital arcs are treated. However, for some applications such as satellite navigation RDSS services, uninterrupted orbital ephemeris is demanded, requiring the development of POD strategies to be processed both during and after an orbital maneuver. We in this paper study the POD for a maneuvered GEO satellite, using high precision and high sampling rate ranging data obtained with Chinese Area Positioning System (CAPS). The strategy of long arc POD including maneuver arcs is studied by using telemetry data to model the maneuver thrust process. Combining the thrust and other orbital perturbations, a long arc of 6 days’ CAPS ranging data is analyzed. If the telemetry data are not available or contain significant errors, attempts are made to estimate thrusting parameters using CAPS ranging data in the POD as an alternative to properly account for the maneuver. Two strategies achieve reasonably good data fitting level in the tested arc with the maximal position difference being about 20 m. Supported by the National Natural Science Foundation of China (Grant No. 10703011) and the Science & Technology Commission of Shanghai Municipality of China (Grant No. 06DZ22101)     

地球重力场空间探测: 回顾与展望

地球重力场的科学数据在地球测绘学、冰川学、陆地水循环、固体地球物理、灾害监控及国防军事等领域具有重要应用价值. 美、德合作研制的地球重力场反演与气候实验(gravity recovery and climate experiment, GRACE)卫星, 有力地推动了地球重力场测量、反演和应用. 为进一步提高重力卫星科学数据的时、空分辨率, 扩展应用领域, 中国及欧美等国都考虑发射升级的重力卫星, 即后GRACE 计划(GRACE-follow-on). 本文将简单回顾重力卫星的发展历程, 介绍重力卫星的数据采集技术和反演方法, 亦着重阐述后GRACE计划的测量方法学、关键技术及预期结果.      

A PRECISE INTEGRATION APPROACH FOR THE DYNAMIC-STIFFNESS MATRIX OF STRIP FOOTINGS ON A LAYERED MEDIUM 1）

提出应用精细积分算法计算多层地基的动力刚度问题.精细积分是计算层状介质中波传播的高效而精确的数值方法.利用傅里叶积分变换将层状地基的波动方程转换为频率-波数域内的两点边值问题的常微分方程组,运用精细积分方法求解格林函数,最后再将得到的频率-波数域内地基表面的动力刚度矩阵转换到频率-空间域内,进而得到刚性条带基础频率域的动力柔度或刚度矩阵.所建议的精细积分算法,可以避免一般传递矩阵计算中的指数溢出问题,对各种情况有广泛的适应性,计算稳定,在高频段可以保障收敛性,并能达到较高的计算精度.     

基于二阶系统解耦的精细积分格式下动载荷时域识别

基于模态分析法的载荷识别方法利用模态矩阵获得系统的非耦合形式,推导单自由度系统的载荷识别公式,但要求系统为比例阻尼。在模态模型基础上,对一般系统建立基于二阶系统解耦的动载荷时域识别模型。首先,利用基于Lancaster结构的二阶系统解耦方法推导出系统的非耦合形式;然后,采用精细逐步积分方法,在载荷为阶跃力的假设下,推导出载荷识别数学公式;最后,由系统实时响应反求结构载荷的时间历程。数值算例验证了本文方法针对比例阻尼系统较模态模型具有更高的精度,而且对非比例阻尼系统也有效可行。     

啁啾相移光纤光栅分布式应变与应变点精确定位传感研究

利用啁啾相移光纤光栅狭缝的中心波长对应变点和应变量的波长敏感性,实现应变与应变点精确定位的传感.当啁啾光纤光栅上的某一位置产生微应变时,该应变点会产生相移,其频谱则会出现一个与之对应的狭缝,且狭缝的深度和中心波长与应变的大小和位置相关.当串接不同中心波长的啁啾光纤光栅后,即可实现一定范围内的分布式应变与应变点精确定位检测.本文通过V-I传输矩阵法建立了狭缝深度和中心波长关于应变量和应变位置的理论模型,分析结果表明理论上可以实现微米量级的精确定位.搭建了级联啁啾相移光纤光栅的分布式应变传感装置,实验获得的最大应变灵敏度为0.19 pm/με.该精确定位传感装置在先进制造、精密加工、航空航天、铁路系统等高新技术领域具有重要的应用前景.     

黏塑性本构计算的稳定性分析

提出本构方程计算方法的稳定性问题,针对黏塑性本构计算的显式精确算法的稳定性进行分析,发现该算法并非无条件稳定,使用小扰动方法给出了其计算稳定的必要条件,稳定性条件对数值计算中的时间步长提出限制要求。通过有限元算例验证了分析的正确性,计算结果也表明理论推导得到的稳定性公式能够准确预测满足计算稳定性条件要求的最大时间步长与各参数之间关系。