Source localization using a non-cocentered orthogonal loop and dipole （NCOLD） array

A uniform array of scalar-sensors with intersensor spacings over a large aperture size generally offers enhanced resolution and source localization accuracy,but it may also lead to cyclic ambiguity.By exploiting the polarization information of impinging waves,an electromagnetic vector-sensor array outperforms the unpolarized scalar-sensor array in resolving this cyclic ambiguity.However,the electromagnetic vector-sensor array usually consists of cocentered orthogonal loops and dipoles（COLD）,which is easily subjected to mutual coupling across these cocentered dipoles/loops.As a result,the source localization performance of the COLD array may substantially degrade rather than being improved.This paper proposes a new source localization method with a non-cocentered orthogonal loop and dipole（NCOLD）array.The NCOLD array contains only one dipole or loop on each array grid,and the intersensor spacings are larger than a half-wavelength.Therefore,unlike the COLD array,these well separated dipoles/loops minimize the mutual coupling effects and extend the spatial aperture as well.With the NCOLD array,the proposed method can effciently exploit the polarization information to offer high localization precision.     

Bezier曲线在生产设计中的应用

根据解析函数和Bezier曲线的相关性质,提出一种两者相互转化的新算法,既保证了曲线与实际的一致,又减少了计算的维数。     

给定任意拓扑控制多面体的分片光滑样条曲面拟合

张量积B样条曲面在CAD领域具有重要意义，但是普通张量积B样条曲面的控制顶点必须呈拓扑矩形阵列形式排列，不能满足任意拓扑控制网格的要求。本文基于双四次广义B样条基函数和G1连续条件，推导出线性混合矩阵。利用这些混合矩阵，非规则控制多面体中的控制顶点被转换成分片B样条曲面的控制顶点，相邻曲面片间满足G1连续条件。即利用混合矩阵，可以用与张量积B样条曲面相同的概念框架处理具有非四边界及多于或少于4个四边界面汇聚于一点的非规则控制多面体的曲面拟合。文中还包括应用实例以表明文中方法的正确性。     

中华世纪坛旋转圆坛旋转平稳性测试

介绍了两种旋转平稳性的测试方法。角速率均匀性的经纬仪测量法和水平跳动的水平仪测量法,精确度高,简单方便,亦可作为其它相似建筑的旋转平稳性的测试方法。     

读者园地——有问有答

从本期开始，我刊将在“探索俱乐部”中开设一个“有问有答”的新栏目，不定期地回答一些比较有代表性的问题。希望大家积极支持这个栏目，踊跃提问．也许下一个被选中的就是你。     

未来超声速飞机的关键技术

空气动力学新进展结合了最优化技术的现代计算流体动力学，可以对机翼、机身、短舱和尾部的几何形状进行布局调整，使超声速飞行的阻力减少10％以上，从而增加了飞机的最大航程。此外。预测受载荷模型的气动弹性效应的方法，已经在NASA的兰利研究中心和阿姆斯研究中心的超声速和高雷诺数亚声速风洞中得到了试验验证。可以     

IONOSPHERIC CORRECTION METHOD FOR PRECISE POSITIONING WITH GPS ACTIVE NETWORK

The ionospheric delay error is a major error source which degrades the positioning accuracy in network real time kinematic (RTK) positioning over a long distance. Different approaches are proposed to estimate GPS errors based on GPS reference network, such as virtual reference stations (VRSs) and network corrections. A new method is used to model the ionospheric total electronic content (TEC) distribution in space. Unlike most ionospheric models, only the ionospheric delays along the satellite tracks are modelled. Therefore, the models are of high precise resolution of the ionospheric TEC distribution in both spatial and temporal scales. A new algorithm is used to solve the equation singularity problem. Experiments demonstrate that the new ionospheric correction method can be used to describe the ionospheric variation at a low latitude area where ionospheric activities are strong. Also, the accuracy of the ionospheric model is enough to support centimeter-level positioning within the network. As ionospheric models are satellite-based models (each satellite has one model), the model parameters can be easily incorporated with the existing differential GPS Radio Technical Commission for Maritime Service (DGPS RTCM) 104 format.     

美法联合研制的Jason－1海洋卫星简介

Jason-1是2001年12月7日发射的海洋地形卫星,由法国宇航局(CNES)和美国宇航局(NASA)下属的JPL联合研制。Jason-1卫星是Topex-Poseidon卫星的后继星。Jason-1和Topex-Poseidon的技术参数对比见表1。     

带有突起物防热结构件的再入加热模拟试验

载人飞船防热层表面的突起部件会使周围流动分离，引起较大的局部加热，因此，需要进行地面模拟加热试验，验证这种带有突起物防热结构的性能。对模拟参数和各种加热模拟装置作了分析和评估后，确定试验在大尺度的等离子电弧烧蚀风洞里进行。模拟的参数为：热流密度、总加热量、来流马赫数、流动状态和几何形状。地面试验的结果与飞行结果相当符合。     

机载合成孔径雷达几何校准技术探讨

几何校准是合成孔径雷达(SAR)成像的关键技术之一。对几种能将失真的图象进行重新采样，使其投影到某一新的投影图，成为高质量且易于判读图象的几何校正算法作了介绍，并对其应用前景进行了探讨。