宏微结合的多机械手微装配机器人系统

为解决复杂组件装配中存在的并行操作、空间操作和多操作对象的难题,研制了一套基于显微视觉伺服的多机械手微装配机器人系统.该系统有6个机械手,每个机械手都由宏动模块、微动模块和末端夹持器组成.分别针对5种不同结构类型的零件,设计了5种异形零件夹持器.通过给镜头配置高精度的位移平台,实现了在30 mm×30 mm×30 mm的大操作空间内2μm精度的在线检测,可实现±9μm的装配精度.通过显微视觉反馈和力觉反馈相结合的策略,设计了过盈配合件的装配方法.使用该微装配机器人开展了微装配实验,实验结果表明该微装配机器人系统是可行的,基本能实现既定的装配要求.     

离散元（DEM）仿真技术在料仓散料流的研究进展

散料是介于流体与固体之间的介质,不同物料表现出的性质不同,其运动机理非常复杂。利用离散元仿真技术可以对散料流颗粒运动的微观机理进行分析和了解。文章就离散元技术的发展过程及原理进行阐述。仿真模拟的准确性其根本是在于力学模型建立的准确性,介绍目前离散元法常用的几种力学模型以及利用DEM仿真技术对料仓中散料流运动机理研究的进展,包括其流动形式,速度和接触力的分布,以及散料物性参数的影响。这些研究对实际工程,例如火电行业的煤仓、灰渣仓及石灰石仓等料仓的应用有着重要的指导意义。     

几种常用的粉体粒度测试方法

介绍了几种常用的粉体粒度测试方法,如筛分法、沉降法、显微镜法、电感计数法、激光散射法以及电超声法等的测试原理、适用范围及注意事项,并对各种测试方法的优缺点进行了比较,最后对粉体粒度测试的发展方向进行了展望。     

Fatigue of materials used in microscopic components

This paper discusses the fatigue behaviour of materials used in microscopic components, which are defined as components in which the section size is between one and ten grain diameters. Experimental data were obtained on microscopic and conventional (macroscopic) notched specimens of 316L stainless steel, which is used in many biomedical components including the cardiovascular stent. Microscopic specimens showed unusual behaviour: low threshold values and very flat stress‐life(S‐N) curves. The low threshold values were attributed to the extremely small thickness, which may be preventing closure; a secondary contribution may be coming from a change in the length of non‐propagating cracks. Good predictions could be achieved using the Smith–Miller approach and the theory of critical distances (TCD) if this reduced threshold was taken into account or if, alternatively, the critical distance was made equal to the grain size.     

Thermophysical Properties Necessary for Advanced Casting Simulations

Numerical modelling of casting processes has become an up-to-date standard in industry, aiming at a short term design of modern casting with optimized properties. This paper outlines the present modelling approaches and gives an overview on thermophysical properties (parameters) necessary for such simulations. Mould filling and heat transport simulations, stress and strain predictions, Cellular Automaton and phase-field techniques, and recent multiphase volume average approaches are discussed. The number of necessary material properties is shown to be directly correlated to the amount of complexity considered in the corresponding modelling approach.     

AA‐FVDM: An accident‐avoidance full velocity difference model for animating realistic street‐level traffic in rural scenes

Most of existing traffic simulation efforts focus on urban regions with a coarse two‐dimensional representation; relatively few studies have been conducted to simulate realistic three‐dimensional traffic flows on a large, complex road web in rural scenes. In this paper, we present a novel agent‐based approach called accident‐avoidance full velocity difference model (abbreviated as AA‐FVDM) to simulate realistic street‐level rural traffics, on top of the existing FVDM. The main distinction between FVDM and AA‐FVDM is that FVDM cannot handle a critical real‐world traffic problem while AA‐FVDM settles this problem and retains the essence of FVDM. We also design a novel scheme to animate the lane‐changing maneuvering process (in particular, the execution course). Through numerous simulations, we demonstrate that besides addressing a previously unaddressed real‐world traffic problem, our AA‐FVDM method efficiently (in real time) simulates large‐scale traffic flows (tens of thousands of vehicles) with realistic, smooth effects. Furthermore, we validate our method using real‐world traffic data, and the validation results show that our method measurably outperforms state‐of‐the‐art traffic simulation methods.Copyright © 2013 John Wiley & Sons, Ltd.     

光纤集成化高分辨率无标记差分显微成像系统

得益于荧光标记技术,远场超分辨显微成像技术的不断发展为人们打开了一道微观世界的大门。远场超分辨光学显微镜也成为现代医学、生命科学等领域研究发展的重要工具和设备。但是相比之下,远场无标记显微成像技术发展却相对缓慢。为此,本文提出了一种采用光纤器件的集成化差分显微成像方法。该方法通过特制的光纤模式选择耦合器(MSC)实现了差分成像系统中空心光斑的生成,并解决了空心光斑和实心光斑严格对准困难的问题。搭建了一套结构简单紧凑,高度集成化的无标记显微成像系统。实验中,采用直径为150 nm的金颗粒和最小间距约50 nm的无标记聚合物线对结构对系统进行成像测试,分辨率相较传统扫描共聚焦显微镜大幅提升。

     

1926−2009 年额尔齐斯河流域中游地区气候变化及其对水资源的影响分析

因北疆供水一期工程膨胀土渠坡每年经历通水、停水及冻结、融化过程,导致渠坡多次发生滑动破坏现象。为深入探讨膨胀土渠坡的滑动破坏机理,通过对膨胀土进行裂隙性试验、剪切试验及其微观试验,从宏-细-微三个角度分析了膨胀土的劣化物理机制。研究结果表明：膨胀土经过干湿-冻融循环后,裂隙率、裂隙条数及裂隙总长度等评价指标呈急剧上升的趋势,而后速度变缓最后趋于稳定,因现有指标存在量度单一等问题,在已有裂隙性指标基础上,通过相交点数和裂隙条数提出一种新的裂隙评价指标$ Q $,可全面评价裂隙发育程度,$ Q $随着循环次数的增加而增加,而后变缓最后趋于稳定;膨胀土经过不同次数干湿-冻融循环,黏聚力随循环次数的增加而减小,内摩擦角基本处于稳定值,抗剪强度主要与黏聚力相关联,黏聚力与裂隙参数$ Q $关系曲线呈线性变化,黏聚力随$ Q $的增加而减小;微观机理方面,通过微观电镜扫描,发现土体微观结构受干湿-冻融循环影响显著,土体微观结构逐渐破碎,颗粒总面积减少,孔隙体积增加,微小孔隙不断连接,逐渐形成新的裂隙;裂隙参数$ Q $与各微观参数的灰色关联度均大于0.67,其中颗粒总数及颗粒总面积为主要影响因素;裂隙的产生使土颗粒之间的相互作用力逐渐减小,导致黏聚力变小。

     

搅拌反应釜中微观混和问题的研究——(Ⅰ)—频闪高速显微摄影法研究微观混和过程

本文介绍了作者首次开发成功的、用于观察亚微观及微观混和过程的微流元团变形历程的新型方法——高速频闪显微摄影法。作者用此方法首次拍摄到了无化学反应与伴有化学反应时的湍流场中亚微观及微观混和过程中微流元团的照片,对微观混和过程有了感性认识。并提出此过程由以下三个过程组成:(i)湍流涡旋的产生、死亡和再生,使得大涡团分裂成小涡团;(ii)小涡团内的无规则复杂的层片状伸长变形及(iii)分子扩散过程。所得到的这些结果为微观混和问题的进一步深入研究提供了重要的感性认识和物理基础。