车载站三轴天线座测角精度分析

从AZ-EL 第三轴天线座的坐标变换公式出发,推导出第三轴角度对地平系AZ,EL角影响的数学模型,从而对AZ-EL型天线座在引入第三轴后对测角精度的影响进行了计算。计算证明:三轴天线座用于测角系统,只要第三轴编码器精度足够高,并对其加以精确标定,其对天线测角精度的影响很小。     

Damage in edge cracking of rolled metal slabs

Materials get damaged under shear deformations. Edge cracking is one of the most serious damage to the metal rolling industry, which is caused by the shear damage process and the evolution of anisotropy. To investigate the physics of the edge cracking process, simulations of a shear deformation for an orthotropic plastic material are performed. To perform the simulation, this paper proposes an elasto-aniso-plastic constitutive model that takes into account the evolution of the orthotropic axes by using a bases rotation formula, which is based upon the slip process in the plastic deformation. It is found through the shear simulation that the void can grow in shear deformations due to the evolution of anisotropy and that stress triaxiality in shear deformations of (induced) anisotropic metals can develop as high as in the uniaxial tension deformation of isotropic materials, which increases void volume. This echoes the same physics found through a crystal plasticity based damage model that porosity evolves due to the grain-to-grain interaction. The evolution of stress components, stress triaxiality and the direction of the orthotropic axes in shear deformations are discussed.     

A Lagrangian Mixed Subgrid-Scale Model in Generalized Coordinates

This paper presents the formulation of a mixed dynamic subgrid-scale model in non-Cartesian geometries suitable for the study of complex flows. Following the approach developed by Jordan [J. Comput. Phys. 148, 322 (1999)], the variables are first transformed into a contravariant form and then filtered in the computational space. A dynamic localized mixed model, previously developed within the Cartesian framework has been entirely re-formulated for non-orthogonal meshes. The model performance was evaluated by carrying out two tests. First, a plane channel flow at Re_τ = 395 was simulated using both Cartesian and curvilinear grids; the results show that the model formulation is consistent and insensitive to grid distortion, and compares well with the reference data. Then, computations of the turbulent flow over a two-dimensional channel with a wavy wall were performed. Accurate first- and second-order statistics were obtained using relatively coarse grids. This revised version was published online in July 2006 with corrections to the Cover Date.     

Influence of the Direction of the Principal Anisotropy Axes in a Rectilinearly Orthotropic Material on the Stress State of a Compound Solid of Revolution Subject to Nonaxisymmetric Heating

A technique for analysis of the temperature fields and the stress state of isotropic and orthotropic laminated bodies of revolution under nonaxisymmetric loading is described. The influence of the direction of the principal anisotropy axes in a rectilinearly orthotropic material on the stress state of a three-layer body of revolution under nonaxisymmetric loading is studied     

NONLINEAR MICRO－MECHANICAL MODEL FOR PLAIN WOVEN FABRIC

The warp yarns and weft yarns of plain woven fabric which, being the principal axes of material of fabric, are orthogonal in the original configuration, but are obliquely crossed in the deformed configuration in general. The orthotropic constitutive model is unsuitable for fabric. In the oblique principal axes system the relations between loaded stress vectors and stress tensor are investigated, the stress fields of micro-weaving structures of fabric due to pure shear are carefully studied and, finally, a nonlinear micro-mechanical model for plain woven fabric is proposed. This model can accurately describe the nonlinear mechanical behavior of fabric observed in experiments. Under the assumption of small deformation and linearity of mechanical properties of fabric the model will degenerate into the existing linear model.     

对轴误差对光纤陀螺输出的影响

理论分析并试验研究了Y波导保偏尾纤与保偏光纤线圈之间熔接点的对轴误差对光纤陀螺输出的影响.根据简化的光纤陀螺光路误差模型,对光纤陀螺的输出相位误差与光路中主要耦合点的对轴误差的关系进行了理论推导和仿真分析,并利用一个实际的闭环光纤陀螺试验研究了主要熔接点的对轴误差变化对光纤陀螺零偏和零偏稳定性的影响.结果表明,Y波导保偏尾纤与保偏光纤线圈之间的对轴误差是引起光纤陀螺输出误差的重要因素,必须尽量减小.     

被动多轴DOAS技术污染气体垂直柱浓度反演方法研究

介绍了基于太阳散射光的多轴被动差分吸收光谱技术与系统及其在大气污染气体垂直柱浓度监测中的应用．实验中利用夫琅和费光谱作为参考光谱,同时将Ring光谱作为一种吸收结构参与拟合去除太阳光谱中的夫琅和费结构和Ring效应对测量结果的影响,并结合辐射传输模型将污染气体斜柱浓度转换为垂直柱浓度,通过“好运北京”奥运限车期间与OMI卫星的对比实验一致得出限车期间NO2有约20％的下降,证实了本方法的可行性．     

基于光轴垂直双目立体视觉系统的物体运行姿态研究

提出了一种采用光轴垂直的双目视觉测量技术获得运动物体运行姿态角的方法。首先,对光轴垂直立体视觉系统进行了建模;然后,采用光轴垂直原理求取被测物体在某时刻的中轴矢量;最后,通过建立中轴矢量与姿态角间的数学关系得到被测物运行时的姿态角。实验结果表明,该测量方法具有较高的精度和速度,能满足远距离运动的被测物体运动参数的测量要求。     

Influence of polarization extinction ratio on distributed polarization coupling detection

Distributed polarization coupling in polarization-maintaining fibers can be detected by using a white light Michelson interferometer. This technique usually requires that only one polarization mode is excited. However, in practical measurement, the injection polarization direction could not be exactly aligned to one of the principal axes of the PMF, so the influence of the polarization extinction ratio should be considered. Based on the polarization coupling theory, the influence of the incident polarization extinction on the measurement result is evaluated and analyzed, and a method for distributed polarization coupling detection is developed when both two orthogonal eigenmodes are excited.     

Null Riemannian cubics in tension in SO(3)

^** Email: lyle{at}maths.uwa.edu.au^*** Email: popiet01{at}maths.uwa.edu.au Riemannian cubics in tension in the rotation group SO(3) arevariational curves with applications to interpolation problemsin computer graphics and rigid-body trajectory planning. Theyare related by a linking equation to Lie quadratics in tension(LQT) in the Lie algebra so(3). This paper provides a qualitativeanalysis of the null case of LQT in so(3).