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一种MSC.NASTRAN中偏心梁有限元计算结果修正方法 被引量:2
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作者 杨刚 《科学技术与工程》 2011年第33期8383-8390,共8页
讨论了MSC.NASTRAN中偏心梁有限元计算结果的弯矩偏差现象,并给出了一种简便、准确的修正方法,能够有效地消除计算结果中偏心梁元的弯矩偏差,并得到较为理想的梁元内力。此修正方法通过插值得到计算部位的梁元轴力,带入修正公式得到偏... 讨论了MSC.NASTRAN中偏心梁有限元计算结果的弯矩偏差现象,并给出了一种简便、准确的修正方法,能够有效地消除计算结果中偏心梁元的弯矩偏差,并得到较为理想的梁元内力。此修正方法通过插值得到计算部位的梁元轴力,带入修正公式得到偏心梁的修正弯矩。将此法与通常的有限元网格细化方法进行了比较,证实了此方法的精确性。 展开更多
关键词 有限元 偏心梁 弯矩偏差 修正方法
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Transformation Method of Exterior Orientation Angular Elements Obtained via Position and Orientation System Under Gauss-Kruger Projection Coordinate System
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作者 YUAN Xiuxiao ZHANG Xueping FU Jianhong 《Geo-Spatial Information Science》 2010年第3期157-165,共9页
Data obtained via airborne position and orientation system (POS) is in WGS 84 global geocentric reference frame, while the national coordinate reference system for topographic mapping in China is generally Gauss-Kru... Data obtained via airborne position and orientation system (POS) is in WGS 84 global geocentric reference frame, while the national coordinate reference system for topographic mapping in China is generally Gauss-Kruger projection coordinate system. Therefore, data obtained via a POS must be transformed to national coordinate system. Owing to the effects of earth curvature and me- ridian deviation, there are some errors in the process of angle transformation from roll, pitch, and heading (φ,θ,ψ) obtained directly via a POS to the attitude angles of images (φ,ω,κ) needed in photogrammetry. On the basis of effect theories of earth curvature and meridian deviation on exterior orientation angular elements of images, a method using a compensation matrix to correct the transformation errors from attitude angles obtained via the POS to exterior orientation angular elements of images is proposed in this paper. Moreover, the rigorous formula of the compensation matrix is deduced. Two sets of actual data obtained via a POS AV 510, which are different in scale and terrain, are selected and used to perform experiments. The empirical results not only indicate that the compensation matrix proposed in this paper is correct and practical but also show that transformation accuracy of exterior orientation angular elements obtained via the POS based on compensation matrix is relevant to the selection of vertical axis (a projection of central meridian) of Gauss-Kruger projection coordinate system; the proper vertical axis should be the Gauss-Kruger projection of the central meridian of projection zone in which the survey area locates. However, the transformation accuracy of exterior orientation angular elements is irrelevant to the choice of origin of coordinate system; it is appropriate that the origin of coordinate system locates at the center point of the survey area. Moreover, transformation accuracy of exterior orientation angular elements achieved based on the compensa- tion matrix deduced in this paper is higher than that obtained via the existing POS processing software. 展开更多
关键词 position and orientation system (POS) exterior orientation elements of image earth curvature meridian deviation compensation matrix
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