基于四平面全等集合匹配原理的建筑质量监测方法

本文针对建筑物的手工测量人工流程复杂,测量独立误差的问题,提出一种基于建筑信息模型(BuildingInformationModel,BIM)和原始点云的快速匹配方法。首先,提取BIM和原始测量点云的平面模型;然后,分别选择其中的四个平面,采用暴力匹配的方法,求解全等匹配平面集合,实现BIM和原始点云模型的匹配功能。结果表明:该算法能实现BIM模型和建筑点云模型匹配功能,可作为监测建筑过程的辅助手段和监测建筑物健康程度的依据。

单晶硅磨面倒圆专用磨床简介

介绍了一种单晶硅专用磨床的基本布局,对加工单晶硅类零件机床内关键技术及主要部件做了重点说明。通过对单晶硅棒磨削工艺的研究、编辑磨削工艺和实现机床自动磨削等方法,证明了所采用的单晶硅磨面倒角磨床,可用于磨削单晶硅开方后的四平面和圆弧角,可以收到理想的效果。

基于VisualC^(++)的平面四连杆机构的CAI系统

介绍利用VisualC++工具开发平面四连杆机构的计算机辅助教学系统的总体结构、功能和方法。

Late Quaternary sedimentary environmental evolution offshore of the Hangzhou Bay,East China——implications for sea level change and formation of Changjiang alongshore current

This study focuses on sedimentary environmental changes offshore of Hangzhou Bay, East China, since the Late Quaternary. AMS ^14C ages from core CJK10, lithologies, distribution of foraminifera, heavy minerals, and S and C1 elements show a fluvial terrace environment during -23.2-11.0 cal ka BP; a littoral to tidal-flat environment during 11.0-10.2 cal ka BP; and a shallow marine environment with a relatively low sedimentation rate （0.1-0.22 cm/a） since 4.3 cal ka BP. High depositional rates （-1.6 cm/a） from 10.9 to 10.2 cal ka BP resulted from sufficient accommodation space created by rapid sea level rise from -44 m to -33 m, from high sediment delivery by local rivers, and effective trapping of sediments by tidal-flat vegetation. The rate of sea level rise was variable; relatively high from 10.9 to 10.6 cal ka BP （2.1 cm/a）, and lower since 10.6 cal ka BP （1.2 cm/a）. The Changjiang alongshore current crossed the Hangzhou Bay to form the mud wedge on the inner shelf of the East China Sea later than 9.4 cal ka BP. The CJK10 site was a tide-dominated shelf environment and experienced erosion from approximately 9.4-9.2 cal ka BP to 4.3 cal ka BP. The depositional hiatus was caused by the Changjiang alongshore current, which was relatively weak during 9.4-7.5 cal ka BP and increased in strength during -7.5-4 cal ka BP. From -4.3 cal ka BP, a large amount of sediment from the Changjiang River was partly deposited on the continental shelf of Hangzhou Bay with some transported southward. Therefore, this study clarifies the history of Changjiang-derived sediment dispersal and deposition, although a detailed record of the changes in the Chang3iang alongshore current since 4.3 cal ka BP is difficult to obtain because of the scarcity of evidence.

The Analysis of Link Mechanism and Its Programming Realization

This paper introduces realization method of kinematics analysis for the planar four bar mechanism based on the MFC. A mathematicat model is established by a simple and effective method, using the computer simulation technology can the dynamic demonstration mechanism taotion and automatic drawing trajectory curve of arbitrary point on the connecting rod, and can output various motion displacement, speed and acceleration diagram. The paper provides a simple way for motion analysis of planar four link.

The catalytic properties of DNA G‐quadruplexes rely on their structural integrity

The influence of the G‐quartet structural integrity on the catalytic activity of the G‐quadruplex(G4)was investigated by comparing the G4‐DNAzyme performances of a series of G4s with a G‐vacancy site and a G‐triplex(G‐tri).The results presented herein not only confirm that the structural integrity of the 3'‐end G‐quartet is necessary for G4s to be catalytically competent but also show how to remediate G‐vacancy‐mediated catalytic activity losses via the addition of guanine surrogates in an approach referred to as G‐vacancy complementation strategy that is applicable to parallel G4s only.Furthermore,this study demonstrates that the terminal G‐quartet could act as a proximal coordinating group and cooperate with the flanking nucleotide to activate the hemin cofactor.

Reconfigurable parallel mechanisms with planar five-bar metamorphic linkages

This paper presents the idea of constructing reconfigurable limbs by integrating metamorphic linkages as subchains.The planar five-bar metamorphic linkages that have three phases resulting from locking of motors are considered.Under the assumption that the constraint exerted by the reconfigurable limb can switch between no constraint,a constraint force,and a constraint couple,the output motions of the metamorphic linkage in its two planar four-bar linkage phases are identified.By adding an appropriate joint to planar four-bar linkages with translational output,four planar five-bar linkages that can be employed in the construction of reconfigurable limbs are enumerated.Serial chains that can provide a constraint couple and a constraint force are synthesized based on screw theory.Reconfigurable limbs that have three configurations associated with the three distinct phases of the metamorphic linkages are assembled with planar five-bar metamorphic linkages and serial chains with four degrees of freedom.A class of reconfigurable parallel mechanisms are constructed by connecting a moving platform and a base with three identical reconfigurable limbs.The degrees of freedom of the reconfigurable parallel mechanism in different configurations with the metamorphic linkages in different phases are given.Finally,the actuation scheme for this kind of mechanisms is addressed.