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空间两三角形的相交问题 被引量:17
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作者 于海燕 何援军 《图学学报》 CSCD 北大核心 2013年第4期54-62,共9页
重点考虑几何奇异问题,同时兼顾算法的效率。运用"分而治之"的方法从一维解得到二维解,进而得到三维解,将空间问题变为平面问题、线性问题。基于几何代数化依赖于坐标系,引入"计算坐标系",简化了几何的表述与关系... 重点考虑几何奇异问题,同时兼顾算法的效率。运用"分而治之"的方法从一维解得到二维解,进而得到三维解,将空间问题变为平面问题、线性问题。基于几何代数化依赖于坐标系,引入"计算坐标系",简化了几何的表述与关系的类型,使"几何奇异"状态最后归结为平面上线段被三角形裁剪时的共点、共线问题,简单而明晰,从而可从理论上保证算法的鲁棒性,以平面处理的形式给出了两个空间三角形求交的完整解决方案。测试证明,几何关系、几何奇异类型与计算的简化足以弥补因"变换"而增加的额外开销。算法的速度也能达到实用要求——在笔记本电脑上也能达到每秒100万对三角形的相交计算。 展开更多
关键词 几何计算 三角形相交 降维 几何奇异 计算坐标系
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捷联寻北仪方位角误差分析 被引量:11
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作者 徐建华 刘星桥 陈家斌 《兵工学报》 EI CAS CSCD 北大核心 2006年第2期284-287,共4页
应用捷联惯导系统的基本理论研究了动力调谐陀螺寻北仪在有姿态时,由于坐标不一致性和纬度的计算误差引入的寻北误差,为全方位补偿和姿态补偿提供了理论探索。仿真和实际系统结果表明,由方位角引起的方位角误差与纬度及姿态有关。
关键词 自动控制技术 寻北仪 姿态矩阵 计算地理坐标系 动力调谐陀螺
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A new measuring method for maximal length, width and thickness dimensions of coarse aggregates
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作者 段跃华 张肖宁 吴传海 《Journal of Central South University》 SCIE EI CAS 2011年第6期2150-2156,共7页
In order to establish a new method for measuring the dimensions of coarse aggregates, five different-size flat and elongated (F&E) coarse aggregates were glued into two specimens by epoxy resin, respectively, and ... In order to establish a new method for measuring the dimensions of coarse aggregates, five different-size flat and elongated (F&E) coarse aggregates were glued into two specimens by epoxy resin, respectively, and slice images were obtained by X-ray CT, then the aggregates were extracted by the fuzzy c-means clustering algorithm. Attributions of the particle on different cross-sections were determined by the ‘overlap area method’. And unified three-dimensional Cartesian coordinate system was established based on continuous slice images. The coefficient values of spherical harmonics descriptor representing particles surface profile were gained, then each scanned particle was represented by 60×120 discrete points conformably with spherical harmonics descriptor. The chord length and direction angles were determined by the calculation. With the major axis (L) and orthogonal axis (W and T), the calculated results were compared with those measured by caliper. It is concluded that the new L, W, and T dimension measuring method is able to take the place of the present manual measurement. 展开更多
关键词 coarse aggregate flat and elongated (F&E) aggregate X-ray CT digital image processing fuzzy c-means clustering overlap area method spherical harmonics
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