全站仪竖直传高法在水电站金结安装施工测量中的应用

在水电站施工过程中，平面基准和高程基准是施工测量中最重要的环节，为了保证施工工序的质量，特别是大型金属结构安装的质量，就必须严格保证平面基准和高程基准的统一性。其中难度较大的就是高程基准，利用全站仪竖直传高方法有效的保证了基准传递精度和提高了作业效率。     

高精度激光功率能量基准的研究

西方介绍了我国光学计量中最新建立的高精度激光功率基准和激光能量基准。该基准是激光功率，能量测量最重要的量值溯源和依据，有着重要的科学和经济意义。在建立高精度激光基准时采用了光陷阱型硅光电二极管绝对光谱响应自基准新技术，因此新基准比传统的用电能校准绝对辐射计基准器具有更高的灵敏度，线性，更快的响应，量值准确，使用方便等优点；     

光辐射计量基准标准的发展现状

本文着重介绍中国计量科学研究院光学处复现，保存和传递的光辐射计量基准标准：光强度基准，乐通量副基准，光谱车速亮度基准，光谱辐照度副基准和全辐射出射度基准的原理，结构和不确定度等，及这结量值的传递链。同时，通过相关的国际比对结果，证实了光辐射底单位的国际一致性。最后简单地指出了正在研究的低温辐射计和同步辐射源的计划。     

量子基准与基本物理常数

从二十世纪六十年代起，计量基准已逐步从“实物基准”过渡到“量子基准”时代，即用一些特定的原子系统中的量子效应来定义单位的量值，其准确度和稳定性均大大超过实物基准。但这样的量子基准还有其局限性，因此从八十年代起，人们又不断探讨另一种更好的方法，即用基本物理常数来作为计量基准，这样不仅有极高的准确度和稳定性，而且普适性极强。但这些工作难度非常大，还需长时间的艰苦实践。     

放射性活度基准

中国计量科学研究院建立我国放射性活度基准的研究工作，始于50年代，建成的第一套国家活度基准4πβ正比计数装置，于1965年通过国家科委主持的技术鉴定并批准使用于全国放射性活度的量传工作。几十年来，进行了活度基准技术的广泛研究。经国家质量技术监督局批准，现行使用的放射性活度基准装置有：4πβ（PC）—γ符合活度基准装置、4πX（PPC）—γ符合活度基准装置、4πβ（LS）活度基准装置、低本底4πα、4。6活度基准装置及27ra、2。p粒子发射率基准装置。各套基准装置通常由相应的探测器装置和核电子学仪器组成。目前，可测量…     

长度计量基础知识讲座（十二）

平面度是长度计量中的一个重要参数，也是机械零件形状误差的一个主要参数。平面度计量器具广泛应用于光学、机械制造业。一、平面度计量基准和计量标准1．平面度计量基 准目前我国平面度国家基准由平面等倾干涉仪、φ150mm基准平晶组、210mm基准长平晶组和310mm基准长平晶组组成。为保证平面度量值的准确传递，国家还设置与基准相同类型的平面度国家副基准。     

激光洛氏及表面洛氏硬度副基准

中国计量科学研究院于1981年研制成功激光洛氏及表面洛氏硬度副基准，并于1986年被批准为副基准。激光洛氏和表面洛氏硬度副基准都是应用激光双光程干涉原理测量压入深度，激光洛氏硬度副基准包括洛氏硬度机和一组基准金刚石压头组，激光表面洛氏硬度副基准包括麦面洛氏硬度机和一组基准金刚石压头组。语氏硬度测量在工业生产和国防建设中应用广泛，是最主要的硬度试验方法之一，如差一个洛氏硬度单位（HR），就会对轴承、刀具、齿轮、武器等的寿命产生较大的影响；表面洛氏硬度测量是检查产品质量、测定材料机械性能以及确定合成T艺的主…     

基准是否应设定公差的思考

基准是用来制造、测量其他元素的参考，通常公差设定为0，但实际任何基准都不可避免地存在误差，当用它作测量基准时，其误差会带入测量值中，实际中我们经常首先来判断基准是否正确，它的误差是否在我们接受的范围，如果认为不可接受，得首先精加工或改进基准，再去加工或测量判断其他要素，那到底多大才可接受，为能够有效的指导实践，本文认为应该给基准明确公差，本文建议取所有测量要素中最小公差值的1／5—1／3作为基准的公差。     

ITS－90（13．8～273．16K）国家温度基准组和工作基准组的建立

本文介绍了ＩＴＳ－９０（１３．８～２７３．１６Ｋ）国家温度基准组和工作基准组的建立、误差传递的研究、以及基准组和工作基准组的非唯一性的实验研究。实验表明，该基准组和工作基准组在全温区（１３．８～２７３．１６Ｋ）的总不确定度为２．７ｍＫ。研究了基准组在全温区的误差分布。     

位置往昔误差测量技术

位置误差分为定向误差、定位误差和跳动误差。根据定义，位置误差是指被测实际要素对一具有确定方向和位置的理想要素的变动量。理想要素的方向和位置由基准和理论正确尺寸确定。根据国家标准规定．由基准实际要素建立基准时，基准为该基准实际要素的理想要素，而理想要素的位置应符合最小条件原则。     

Different finite element formulations of 3D magnetostatic fields

Several finite-element formulations of three-dimensional magnetostatic fields are reviewed. Both nodal and edge elements are considered. The aim is to suggest remedies to some shortcomings of widely used methods. Various formulations are compared based on results for Problem No. 13 of the TEAM Workshops, a nonlinear magnetostatic problem involving thin iron plates     

Reduced modeling of eddy current-driven electromechanical system using conductor segmentation and circuit parameters extracted by FEA

To analyze the mechanical dynamic characteristics of electromechanical system, we present a new and fast method using the reduced modeling technique for the levitated conductor. As of now, to solve this electromechanical system, the finite element method (FEM) or the boundary element method (BEM) employing the finite difference time-stepping scheme is used. These approaches, however, need too much solving time because the system matrix equation should be solved at each time step. Additionally, when the operation condition is changed or it needs more incremental steps, the system should be solved from the beginning again. To reduce the solving time, we use the circuit parameters of self- and mutual inductances which are evaluated using the FEM and the conductor segmentation. The formulated ordinary differential equations are solved using the fourth-order Runge-Kutta method. To show validity and usefulness of this proposed method, the TEAM Workshop Problem 28 model is tested, and the results of the experiment and time-stepping FEM are compared to this new method.     

Comparison of the ${mbi A}^{*}{-}{mbi A}$ and ${mbi T}, Phi{-}Phi$ Formulations for the 2-D Analysis of Solid-Rotor Induction Machines

We present two eddy-current field potential formulations to solve rotating electrical machine problems by applying the finite-element method (FEM) using the motional ${mbi A}^{*}{-}{mbi A}$-potential formulation and the motional ${mbi T}, {bf Phi}{-}{bf Phi}$-potential formulation. We use the single-phase and three-phase solid-rotor induction motors of Problem No. 30a of TEAM Workshops to compare the potential formulations. We have solved both problems in the time domain and the frequency domain.      

Optical tomography by the temporally extrapolated absorbance method

The concept of the temporally extrapolated absorbance method (TEAM) for optical tomography of turbid media has been verified by fundamental experiments and image reconstruction. The TEAM uses the time-resolved spectroscopic data of the reference and object to provide projection data that are processed by conventional backprojection. Optical tomography images of a phantom consisting of axisymmetric double cylinders were experimentally obtained with the TEAM and time-gating and continuous-wave (CW) methods. The reconstructed TEAM images are compared with those obtained with the time-gating and CW methods and are found to have better spatial resolution.     

E4: the Drexel curriculum

Drexel University's College of Engineering has undertaken a pioneering project to enhance the educational experience of engineering students. A new curriculum has been designed for the first two years of the undergraduate engineering programme. This new approach aims to bring engineering education into the 21st century by using integrated syllabi, team teaching and inverted curriculum principles and philosophies     

Nonlinear three-dimensional magnetic field computations usingLagrange finite-element functions and algebraic multigrid

The paper proposes an efficient solution strategy for nonlinear three-dimensional (3-D) magnetic field problems. The spatial discretization of Maxwell's equations uses Lagrange finite-element functions. The paper shows that this discretization is appropriate for the problem class. The nonlinear equation is linearized by the standard fixed-point scheme. The arising sequence of symmetric positive definite matrices is solved by a preconditioned conjugate gradient method, preconditioned by an algebraic multigrid technique. Because of the relatively high setup time of algebraic multigrid, the preconditioner is kept constant as long as possible in order to minimize the overall CPU time. A practical control mechanism keeps the condition number of the overall preconditioned system as small as possible and reduces the total computational costs in terms of CPU time. Numerical studies involving the TEAM 20 and the TEAM 27 problem demonstrate the efficiency of the proposed technique. For comparison, the standard incomplete Cholesky preconditioner is used     

对Flowshop排序问题启发式方法的评价与改进

在对Ｆｌｏｗｓｈｏｐ排序问题的几种主要的启发方式法进行深入剖析的基础上，提出了一种新的启发式方法，这种方法不仅简单适用，工作量小，能迅速求得排序问题的解，而且优度较高，能得到近似最优的排序方案。     

A Heuristic Algorithm for the Mixed Chinese Postman Problem

The Chinese Postman Problem (CPP) is to find a minimum-cost Eulerian tour in a given graph. CPP is efficiently solvable when the original graph is either undirected or directed. For a mixed graph consisting of both edges and arcs, the Mixed Chinese Postman Problem (MCPP) is known to be NP-complete. Many heuristics and optimal algorithms have been devised for solving MCPPs. A new heuristic is proposed. The heuristic finds the initial solution by using a Minimum Cost Flow algorithm; then it repeatedly uses the shortest path algorithm with slightly modified costs of the edges/arcs. The heuristic improves the solution by trying to find the correct direction of unoriented edges and simultaneously it deletes some of the additional edges/arcs. A number of previous heuristics are tested, analyzed, and compared with the proposed approach. Based upon computational results, the proposed heuristic on average outperforms all previous heuristics.     

组织工程学——现代生物生命科学的前沿

组织工程是应用细胞生物学和工程学的原理研究和开发,以达到修复和重建损伤的组织或器官的外形和功能的生物替代物的一门新学科,是继细胞生物学和分子生物学后,人类生命科学发展史上又一新的里程碑,标志着医学将超越组织和器官移植的旧模式,进入制造组织和器官的新时代,将在21世纪中绽露头角。文章简略介绍世界组织工程发展历史及各类组织和器官组织工程的研究现状,并介绍我国组织工程科研工作开展的最新情况。目前组织工程已有了迅猛发展,在不少方面已取得重大突破。由于其孕育的巨大科学价值及广阔的研究和应用前景,因此加快我国组织工程的研究,尽早地投入临床应用,对我国医学科学事业和国民经济的发展具有重大意义。     

Design of unidirectional cyclic layouts

This work is concerned with the unidirectional cyclic layout problem, which is known to be NP-complete. This type of problem arises, for example, in the determination of workstation locations around a closed loop conveyor system, in the allocation of cutting tools on the sites around a turret, in the positioning of stations around a unidirectional single loop AGV path. Although it can be formulated as a Quadratic Assignment Problem, in general there are two special cases satisfying additional assumptions. In the Balanced Unidirectional Cyclic Layout problem, the material flow is conserved at every workstation. In the Equidistant Unidirectional Cyclic Layout Problem, distances between circular candidate locations are all equal. It is known that both problems are equivalent, which makes any valid formulation of the balanced flow problem also valid for the equidistant problem and vice versa. We first analyse and show new features of the existing formulations. Then we discuss and propose new heuristics using ideas originally introduced for two well-known combinatorial optimization problems: the Asymmetric Travelling Salesman Problem and the Linear Ordering Problem. Based on the computational tests we can say they are both accurate and efficient.