基于线性矩阵不等式的巡检机器人路径规划

针对现有的巡检机器人路径规划方法对路径约束考虑不足的问题,提出一种对运维任务环境中巡检机器人路径规划的算法.使用Delaunay划分法对机器人工作环境进行三角划分;使用整数规划法对问题中的变量进行定义;将问题转换到求解线性矩阵不等式,以此得到符合航迹规划要求的最优轨迹.这种算法简单、完备,并且不会陷入局部最小点.构建了巡检机器人工作环境并进行仿真;与其他相近方法进行对比,验证了该算法的正确性与高效性.     

基于线性矩阵不等式的巡检机器人路径规划

针对现有的巡检机器人路径规划方法对路径约束考虑不足的问题,提出一种对运维任务环境中巡检机器人路径规划的算法.使用Delaunay划分法对机器人工作环境进行三角划分;使用整数规划法对问题中的变量进行定义;将问题转换到求解线性矩阵不等式,以此得到符合航迹规划要求的最优轨迹.这种算法简单、完备,并且不会陷入局部最小点.构建了巡检机器人工作环境并进行仿真;与其他相近方法进行对比,验证了该算法的正确性与高效性.     

基于等几何分析的薄壳静力学分析

以等几何分析方法的计算过程作为参考,介绍了等几何分析方法壳单元几何模型的构造和在等几何分析方法中坐标系的定义求解;推导了两种RM壳单元IGA位移插补方法,并将其应用于典型的板壳结构静力学分析。分析结果表明,在单元划分较细的情况下,两种位移插补方法的插补精度基本一样,第二种插补模型的计算效率更高。静力学分析结果与ANSYS分析结果一致,验证了两种位移插补方法的正确性。     

齿轮周节偏差的意义和应用

《渐开线圆柱齿轮精度》JB179-83中有一项“周节偏差”(代号△f_pl),其定义为:“在分度圆上*,实际周节**与公称周节之差。用相对法测量时,公称周节是指所有实际周节的平均值”。如图1所示,定义中的*号表示变位     

飞机结构腐蚀疲劳分析中的DFR法

通过分析和试验,说明DFR(detail fatigue rating)法在腐蚀疲劳分析中的适用性及其与常规疲劳分析的DFR法的主要差异;给出腐蚀环境中细节疲劳额定值DFRf(t)的定义及其在典型环境中细节疲劳额定值的表达式;在此基础上,简单说明飞机结构腐蚀疲劳作用下产生工程可检裂纹α0的日历年限分析方法,并通过算例说明分析过程.     

基于离散时间贝叶斯网络的列控中心可靠性分析

针对动车组列控中心在实际工作环境中的故障同时具有多态性和动态性的问题,提出一种依据列控中心各单元的功能逻辑关系来建立离散时间贝叶斯网络的分析方法.归纳部件的多种故障模式并描述列控中心故障的多态特性,采用EM算法优化更新条件概率表;针对列控中心动态失效问题,建立动态贝叶斯网络模型,将一次任务划分为启动、运行、制动三个阶段...     

简单而重要:什么是农业机械化——农业机械化定义泛议

一个问题的出发点往往从定义开始,定义是揭示概念内涵的逻辑方法.一个好的定义,其定义项与被定义项的外延必须相等.对于农业机械化的定义,一直是农机界最明白、似乎又是道不清的问题,然而,却是个非常重要的问题.     

波形曲面弯形加工的处理方法

在本刊2010年第1期《零件加工中波形曲面的处理》一文中讲述了对波形零件曲面的一种定义方法,并最终确定运用“参数化”进行定义。本文将重点论述弯形问题,而弯形问题的难点在于回弹量控制。     

产品设计耦合分析研究进展

为了解决复杂产品设计中耦合分析这一关键问题,介绍了设计耦合的定义及其表达方法,并把耦合分析研究分为直接耦合分析和耦合传播分析两类。按照不同矩阵化的耦合表达方式,阐述了目前常用的直接耦合分析方法及其在产品设计中的应用,总结和归纳出这些方法共有的方法论本质。介绍了耦合传播分析的一般过程和存在的困难;讨论了基于图论的变更传播判断方法和基于设计结构矩阵的变更传播分析方法;总结比较了直接耦合和耦合传播分析方法的研究和目前存在的问题。给出了产品设计耦合分析方法研究中未来值得深入研究的问题和方向。     

弹簧成形机几何误差的完备建模及其补偿方法研究

针对弹簧成形机成形精度低、误差大等问题,以弹簧成形机为研究对象,对弹簧成形机的几何误差进行了定义、识别、测量、建模和补偿方法研究.根据弹簧形状特征划分弹簧成形机多体系统,以多体系统理论与齐次坐标变换为理论基础,建立了包含20项几何误差的完备模型;采用Sobol灵敏度分析方法与蒙特卡洛采样方法识别出了关键误差项为刀具的定...     

Mass spectrometry and natural variations of iron isotopes

Although the processes that govern iron isotope variations in nature are just beginning to be understood, multiple studies attest of the virtue of this system to solve important problems in geosciences and biology. In this article, we review recent advances in the geochemistry, cosmochemistry, and biochemistry of iron isotopes. In Section 2, we briefly address the question of the nucleosynthesis of Fe isotopes. In Section 3, we describe the different methods for purifying Fe and analyzing its isotopic composition. The methods of SIMS, RIMS, and TIMS are presented but more weight is given to measurements by MC-ICPMS. In Section 4, the isotope anomalies measured in extraterrestrial material are briefly discussed. In Section 5, we show how high temperature processes like evaporation, condensation, diffusion, reduction, and phase partitioning can affect Fe isotopic composition. In Section 6, the various low temperature processes causing Fe isotopic fractionation are presented. These involve aqueous and biologic systems.     

Plain bearing materials: The role of tin

The field of plain bearings (excluding dry bearings) is surveyed with emphasis on tin-containing materials and new developments in this area. The characteristics, structures and properties of whitemetals, aluminium-tin alloys, and bronzes are described, and their scope and limitations are defined. Whitemetal bearing design is covered and methods of construction of journal and thrust pad bearings are given special attention. The final section describes commercial manufacture of bearings, including centrifugal and static casting methods for whitemetal linings, methods of bonding aluminium - 20% tin alloys to a steel backing, and centrifugal and continous casting methods for bronze. Overplay plating is briefly discussed.     

实用有限元计算方法的若干进展

概要介绍和综合论述有限元方法的几种先进的新型算法。从较高层次上揭示了结构工程中有限元方法的总体发展。     

pcANYWHERE——异地协同工作的一个有效工具

市场的全球化趋势 ,使制造企业面临日趋激烈的市场竞争。虚拟企业是实现敏捷制造的组织模式 ,是未来企业的理想组织模式。异地联合产品开发是虚拟企业产品设计的主要模式。本文分析了现代企业进行异地协同工作时通常所选用的异地协同工具的特点 ,比较了 pc A NYWHERE与其它异地协同工具在性能上的差异 ,提出了pc ANYWHERE是一种现代一般企业进行联合产品开发的有效工具。     

Pronounced loss of cell nuclei and anisotropic deformation of thick sections

The local deformation and variations in section thickness are studied in 100-μm thick vibratome sections of well-fixed human brain tissue. During processing, including drying on glass slides, the section thickness is reduced to less than half, but close to the edges there is less shrinkage of the section thickness. Close to both surfaces there is a pronounced reduction in the number of neuronal nucleoli. At the scale of the original section, the upper 15 μm and the lower 10 μm are depleted. The loss is most pronounced at the upper surface, which is unprotected during processing. In the central 70% of the section height, where one would ordinarily use an optical disector for sampling, there is no indication of non-uniform shrinkage. The simplest explanation for the observed loss of nucleoli is that all cells opened by the knife may lose their nuclei across an unprotected section surface. The observations do not generalize to other tissues and other preparation techniques, but illustrate the magnitude of some of the problems for uniform sampling and unbiased estimation in very thick sections. The uniform optical disector sampling of nucleoli in thick sections, as opposed to that of cell nuclei, raises a special problem, which is discussed briefly.     

含钪铝合金的现状与开发前景

对国内外Al—Sc合金的发展历史和现状进行了概括。讨论了发展钪及铝钪合金中存在的一些问题，并总结了一些解决方法。简要阐述了钪对铝的很好弥散强化作用，是铝合金强有力的晶粒细化剂和有效的再结晶抑制剂。钪在铝及铝合金中同时具有稀土金属和过渡族金属类金属的有益作用。但其效果却比这2类金属明显得多，铝钪合金的开发有望逐步扩大应用。     

HORIBA公司EMIA-20系列高频红外碳硫仪故障分析与排除

本文简单介绍了HORIBA公司EMIA-20系列高频红外碳硫仪的工作原理，详细介绍一些典型故障的处理过程，总结维修的思路和方法。     

Mobility of the Myard 5R Linkage Involved in ＂Gogu Problem＂

Since the traditional Grübler-Kutzbach criterion fails in many overconstrained mechanisms, developing a general mobility formula is a hot topic lasting for more than 150 years in mechanisms. GOGU systematically investigated various mobility methods, and pointed that the methods were not fit for two kinds of paradoxical overconstrained mechanisms. The mobility on the two kinds of mechanisms in "Gogu problem", and has developed into a systematic mobility methodology. Myard 5R linkage is one of the single-loop mechanisms involved in "Gogu problem", its joint axes are distributed in space with special geometric conditions, which increases the difficulty of mobility analysis. The study is to calculate the global mobility of the Myard 5R linkage using the mobility methodology. Firstly, the mobility methodology based on screw theory is briefly introduced. Secondly, some homogeneous transforms are performed accnrding to the D-H parameters and the invarianee of the linkage plane symmetry is revealed, which provides an idea to judge a plane-symmetric loop. The special geometric features of the axes distribution are discussed as well. Finally, the global mobility of the more paradoxical mechanisms.     

Limitations on optical sectioning in live-cell confocal microscopy

In three-dimensional (3-D) live-cell microscopy, it has been common to treat cells as having a constant refractive index (RI). Although the variations in RI associated with the nucleus and other organelles were recognized from phase- and differential interference contrast (DIC) images, it was assumed that they were small and would not affect 3-D fluorescence images obtained using widefield/deconvolution, confocal of multiphoton imaging. This paper makes clear that this confidence was misplaced. Confocal images made using backscattered light (BSL) to image the flat, glass/water interfaces above and below living microscope specimens should reveal these structures as flat and featureless. That the image of the interface on the far side of the cells is neither flat nor featureless indicates that the "optical section" surface can be profoundly distorted by the RI irregularities associated with the presence of nuclei and other subcellar structures. This observation calls into question the reliability of images made using any of the current methods for performing 3-D light microscopy of living cells.     

应用有限元法(FEM)验证在直齿轮和斜齿轮内采用ISO和AGMA标准的齿根强度的比较分析

在工程界现在普遍的趋势是要求重新研究各不同的标准以确是其在工业内最好的实践.本文介绍采用在ISO和AGMA标准对齿根强度估算方法的比较分析,并用开发的有限元和模型仿真进行证实.本分析(1)介绍了采用齿条和齿轮刀具制造的广大范围的直齿和斜齿轮,而(2)是齿轮主要几何学(齿轮设计),制造(齿条和齿轮刀具)和性能参数的不同组合,以及对每个齿轮进行齿根强度分析的有限元方法(FEM).FEM的结果与用ISO和AGMA标准计算的相比较.对不同的设计、制造和性能参数组合的比较分析用图解说明和简要讨论.该结果将许可在现代工程实际中应用标准所存在的限制有一个很好的了解,并为改进和统一标准提供一个基础.