Blind bolted moment connection to sides of hollow section columns

This paper presents the results of an experimental programme for a new blind bolted connection to unfilled hollow section (HS) columns under static loading. In this connection, channels with side plates connect beam flanges to the side face of HS columns. This is a simple alternative connection to typical face connections, i.e. the extended endplate connection or the T-stub connection (with T-stubs connecting the top and bottom flanges of the beam to the face of the column). The channel side plate connection was found to be much stiffer than a typical face connection and has the potential to achieve a rigid connection status for braced frames according to the EC3 classifications. Comparison of the test results and three dimensional finite element (FE) modelling indicates that the FE analyses can be used to predict the connection behaviour with sufficient accuracy. The preliminary investigation for the channel side plate connection shows promising results and forms the basis for the development of other blind bolted side connections for applications in the low rise construction industry.     

偏心荷载下非弹性工字型钢梁的侧向屈曲抗力

承受梯度弯矩的工字型钢梁的侧向—扭转屈曲(LTB)强度取决于弯矩梯度系数Cb。而Cb取决于弯矩图的非均匀性、无支撑长度内所施加的横向荷载的大小和钢梁支座类型。一般地,Cb由规范根据弹性LTB分析理论给出。然而,同样的Cb被用在梁的非弹性屈曲分析中。提出1个三维有限元ANSYS模型用于工字型钢梁的非线弹性弯-扭分析,并用此模型研究了无支撑长度和偏剪心荷载(分别位于中心、上翼缘和下翼缘)对非弹性性能区域弯矩梯度的影响。研究发现AISC-LRFD的钢结构规范(AISC360-05)和结构稳定研究委员会导则给出的Cb对加载点在非弹性屈曲工字型钢梁的中心和下翼缘的情况并不准确。AISC-LRFD的抗弯公式过高评估了梯度弯矩作用下非弹性工字型钢梁的实际抗弯承载力。因此,提出了一个适用于该工况下非弹性区域的简单公式,用于替代规范给出的公式。     

基于小物镜系统的热像差影响因素分析

光机热集成分析是光机结构设计中的重要环节,对光学系统像质的预测与补偿有着重要的参考价值。针对小物镜系统,进行光机热集成分析,结果表明该系统产生的热像差较大,影响系统光学性能,其中温度升高导致折射率变化引入的系统热像差较大;结构热变形引入的系统热像差较小,可以忽略;镜片与支撑结构之间的导热、上下窗口的空气扰动、机械结构外表面的环境对流也会存在一定影响,但影响较小。由此可知系统热像差的主要影响因素是热载的大小,设计过程中减少透镜厚度及材料吸收率,降低系统热载,是减小光学系统热像差最为有效的途径。     

利用相位恢复波前传感技术检测球面镜面形

为了验证相位恢复波前传感器系统波前检测的能力,搭建了基于相位恢复测量方法的波前传感器检测球面镜面形的实验平台。该平台结构简单,抗震动,可以在对光路不进行任何改变的前提下,利用成像系统上已有的相机对整个光学系统进行在位检测。为了验证相位恢复波前传感器测量方法的准确性,将相位恢复波前传感器测量结果与ZYGO干涉仪测量结果进行比较,实验结果表明在面形误差分布及误差的峰谷值(PV)和方均根值(RMS)上,两者具有极大的相似性,所以利用相位恢复波前传感器技术能有效地检测出球面镜的面形误差。     

基于几何特征的圆形标志点亚像素中心定位

视觉测量系统中圆形标志点中心定位的精度易受噪声的影响。为了增强其抗噪性从而提高定位精度,提出了一种利用几何特征以降低噪声干扰的中心定位算法。首先将自适应阈值分割法与质心法相结合,对点目标进行圆心粗定位。利用粗定位的圆心和半径对Canny算子检测到的边缘进行半径约束,以消除孤立点和噪声点。然后根据理想的圆成像后边缘点分布的几何特征和链接规律,采用一种基于分区原理的方法获取点目标的理想边缘。最后,采用Zernike正交矩对像素级边缘点进行亚像素定位,并用最小二乘椭圆拟合法计算得到中心坐标。实验结果表明,该方法的定位精度可以达到0.023 7pixel,算法的运行时间为2~3ms,基本满足测量系统对于圆形标志点中心定位在精度、稳定性和实时性上的要求。     

Performance of Object Classification Using Zernike Moment

Moments have been used in all sorts of object classification systems based on image. There are lots of moments studied by many researchers in the area of object classification and one of the most preference moments is the Zernike moment. In this paper, the performance of object classification using the Zernike moment has been explored. The classifier based on neural networks has been used in this study. The results indicate the best performance in identifying the aggregate is at 91.4% with a ten orders of the Zernike moment. This encouraging result has shown that the Zernike moment is a suitable moment to be used as a feature of object classification systems.     

Exact and fast algorithm for two-dimensional image wavelet moments via the projection transform

Wavelet moments are perfect representations of moments in multiresolution wavelet domain, which integrates the theory of moment invariants into wavelet analysis. However, the calculations of moments are very complicated in terms of computational complexity, so it is difficult to implement them in real time. An exact and fast projection-based algorithm for two-dimensional wavelet moments is presented in this paper. In our approach, the computation of a two-dimensional wavelet moment of order of r is performed in (r+1) different one-dimensional spaces. Since only additions are required to perform the projection transform, the total computational complexity can be greatly reduced.     

Self-Consistent Approximation for Fluids and Lattice Gases

A self-consistent Ornstein–Zernike approximation (SCOZA) for the direct-correlation function, embodying consistency between the compressibility and the internal energy routes to the thermodynamics, has recently been quantitatively evaluated for a nearest-neighbor attractive lattice gas and for a fluid of Yukawa spheres, in which the pair potential has a hard core and an attractive Yukawa tail. For the lattice gas the SCOZA yields remarkably accurate predictions for the thermodynamics, the correlations, the critical point, and the coexistence curve. The critical temperature agrees to within 0.2% of the best estimates based on extrapolation of series expansions. Until the temperature is to within less than 1% of its critical value, the effective critical exponents do not differ appreciably from their estimated exact form, so that the thermodynamics deviates from the correct behavior only in a very narrow neighborhood of the critical point. For the Yukawa fluid accurate results are obtained as well, although a comparison as sharp as in the lattice-gas case has not been possible due to the greater uncertainty affecting the available simulation results, especially with regard to the position of the critical point and the coexistence curve.     

V形缝隙天线的研究

本文利用第二类尖劈并矢格林函数对任意夹角的Ｖ形缝隙天线进行了矩量法计算。Ｖ形缝开在Ｖ形金属板上，并且由双线从中间馈电。文中给出了缝隙口面场分布和天线Ｈ面方向图的理论计算结果和实验结果，两者基本吻合。文中最后给出了三种非Ｖ形弯曲缝隙的实验结果。     

Zernike矩不变性分析及其改进

在分析了Zernike矩不变性后,提出了一种基于图像整个区域形状描述算子的改进Zernike矩。改进的Zernike矩不仅具有旋转不变性,而且还具有改进前不具有的比例不变性。试验结果证明,和改进前的Zernike矩相比,改进后的Zernike矩具有更好的不变特征,可用作基于区域的形状描述算子。