基于车载原子干涉仪的野外流动重力测量

移动重力测量在计量学、地球科学及国防军事等领域有着广泛的应用需求。原子干涉重力仪在可移动高精度重力测量上具有良好的技术潜力,但目前仍很难兼具高集成度与高灵敏度。针对此问题,本文研制了一套基于原子干涉仪的车载重力测量系统,基于小型化、高度集成的仪器设计,实现了高精度的野外重力测量,室外测量灵敏度为■、测量重复性优于20μGal。在长10 km、高程变化100 m的野外测线上开展了单点调试时间小于5 min、有效测量时间小于15 min的快速重力测量,并与LG-1相对重力仪进行比对。在一般性的野外测试环境下,2种重力仪的测量残差小于100μGal,车载绝对重力仪自身测量残差小于15μGal。因此,该车载重力测量系统极大地提高了野外重力测量效率,方便运输、随停随测、测量准确,为可移动重力测量领域提供了可靠的技术解决方案。     

Use of 3D field simulators in the synthesis of waveguide capacitive iris coupled lowpass filters

This paper presents the generalized lowpass filter design method of Levy based on three‐dimensional electromagnetic analysis and discontinuity modeling using commercially available full‐wave electromagnetic simulators. It shows how to use Levy's method for very accurate theoretical design of a waveguide capacitive iris lowpass filter, using modern 3D EM field‐solvers based on the finite element method (FEM), the mode matching method (MM), and the transmission line matrix (TLM) analysis method. This is the first time that design curves and equations, based on full electromagnetic modeling, have been presented for constant thickness capacitive iris filters. We will demonstrate our approach by designing a number of waveguide capacitive iris filters. This paper also demonstrates the generality of the method. This method can be applied to many other types of waveguide lowpass and bandpass filters. © 2000 John Wiley & Sons, Inc. Int J RF and Microwave CAE 10: 190–198, 2000.     

电磁固体非均匀载荷作用下的裂纹分析

根据广义Crouch基本解和广义不连续位移边界元方法,研究电磁固体中的裂纹在非均匀载荷下的广义应力强度因子和裂纹腔内的电位移和磁感应强度,以及电磁均不可穿透和电磁均可穿透边界条件对解的影响.以线性分布的力载荷为例,给出三维电磁固体方形裂纹问题的解.运用迭代方法,求解在非均匀载荷作用下裂纹张开模型的解.作为特例,给出抛物线型载荷作用下二维裂纹问题的数值解.     

CIEDE 2000色差公式的研究

CIEDE 2000色差公式是迄今为止最为先进的色差计算公式.但是,此公式在色彩工作的使用过程中发现其在某些数据点的计算上出现间断,即数学中常提到的不连续性.本文使用数学不连续性的方法旨在从理论上证明公式中存在的小的数学不连续性.计算结果表明,此公式存在三方面的不连续性,即平均色相角的计算、色相差的计算和色相角在经过360°时均存在不连续性.最后,简单的介绍了公式中不连续性的应用.     

预应力梁桥齿板锚固区配筋设计新方法

预应力混凝土梁桥的齿板锚固区,由于存在着几何形体上的突变,集中锚固力的作用以及预应力钢束局部弯曲引起的径向力作用,易产生开裂甚至剥落破坏,因此齿板锚固区的抗裂配筋设计十分重要。以7种典型局部作用效应刻画齿板锚固区内拉应力的集中分布特征,并在此基础上形成了齿板锚固区拉压杆模型,初步形成预应力混凝土梁桥的抗裂钢筋设计新方法。     

Numerical approach for the description of different fracture modes for Zr/ZrO2 system — Deterministic and probabilistic aspects

In the context of the prediction of materials durability in multiphysics aggressive environments, we present a numerical model which is able to describe the phenomenon of the oxide layer fracture after the formation of the oxide for Zr/ZrO₂ system. In order to evaluate the characteristic distance of the periodic crack pattern in the oxide layer and the debonding of the oxide/metal interface, we use a finite element model combining strong discontinuity approach and interface elements. The influence of all the parameters: the metal/oxide decohesion, the oxide layer thickness, Young's modulus ratio of the oxide to the metal, the oxide limit stress and the interface limit stress for sliding is evaluated in terms of the inter-crack distance. To take the initial defects in the material into account, we consider the randomly distributed limit stress in the oxide layer. A statistical analysis is performed to evaluate the inter-crack distance. Finally, the parameters of the numerical models will be identified from the results of experimental tests.     

Fatigue growth prediction of center slant crack in rectangular plate

This paper presents a numerical prediction model of mixed‐mode crack fatigue growth in a plane elastic plate. It involves a formulations of fatigue growth of multiple crack tips under mixed‐mode loading and a displacement discontinuity method with crack‐tip elements (a boundary element method) proposed recently by Yan is extended to analyse the fatigue growth process of multiple crack tips. Due to an intrinsic feature of the boundary element method, a general growth problem of multiple cracks can be solved in a single‐region formulation. In the numerical simulation, for each increment of crack extension, remeshing of existing boundaries is not necessary. Crack extension is conveniently modelled by adding new boundary elements on the incremental crack extension to the previous crack boundaries. At the same time, the element characters of some related elements are adjusted according to the manner in which the boundary element method is implemented. As an example, the present numerical approach is used to analyse the fatigue growth of a centre slant crack in a rectangular plate. The numerical results illustrate the validation of the numerical prediction model and can reveal the effect of the geometry of the cracked plate on the fatigue growth.     

螺栓连接单搭接件疲劳特性试验与全寿命估算方法研究

飞机搭接件结构在疲劳载荷下会产生裂纹并扩展,而目前对搭接件结构参数与其疲劳寿命的关系研究还不够系统,且寿命估算模型只考虑了全寿命的一部分。对不同结构参数的三螺栓单搭接件的疲劳特性进行了试验研究,并以现有工程方法为基础,构建了基于材料初始不连续状态的搭接件全寿命估算模型。结果表明,搭接件的疲劳破坏具有一定的隐蔽性,在一定条件下,采用直孔形式、增大孔间距和螺栓预紧力、减小孔直径等都可以改善搭接件的疲劳特性。数值估算结果与试验结果的对比表明,所建寿命模型具有一定的精度,能满足工程需要,计算结果和结论可作为该类结构损伤容限设计的参考依据。     

裂隙化岩体不连续面密度的分形研究

 不连续面密度是表征岩体内部不连续面分布特征的重要参数之一,但是岩体内不连续面的分布是随机的、不规则的,要想准确获得岩体不连续面密度的真实值是不可能的。基于现场调查的岩体露头不连续面特征,借助计算机模拟技术建立岩体不连续面分布的二维、三维随机裂隙网格模型,从数理统计学的角度计算岩体不连续面密度数值。并基于分形理论计算岩体不连续面分布的二维、三维分布特征,尝试建立岩体不连续面密度与分维数的数学关系。计算结果表明,岩体不连续面密度与分维数具有相同的变化趋势,随着不连续面分维数的增大,不连续面密度增大,不连续面密度与分维数之间存在线性关系。研究结果表明,不连续面分布的体密度和三维分形维数,可以更加综合地反映岩体内部不连续面的分布特征和空间信息及对岩体强度参数的影响,对工程应用具有更好的实际作用。且在此基础上,提出基于不连续面分布的体密度和三维分形维数的岩体等效抗剪强度指标的折减计算。     

三维送电线路GIS系统在电力线路勘测路径选择中的应用

GIS系统可提供在高精度的三维真实地形地貌虚拟环境下漫游、查询设备台帐、沿线路飞行、选择线路路径、优化塔型及塔位和输出设计结果等功能。借助于该系统,可以将部分路径优化工作提前到规划可研阶段进行,能够使路径走向更加合理。由于GIS系统采用高分辨率的卫星影像图,在设计线路时可以很好地避开房屋以及其它特殊地物,择优出一个比较经济合理的方案来,从而减少后续勘测设计返工,加快设计进度,为线路顺利施工、投产运营奠定良好的基础。