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点构法构建下颌骨正中矢状平面的初步探究 被引量:2
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作者 张鑫 刘洋 +3 位作者 周建萍 吴艳 郑雷蕾 戴红卫 《上海交通大学学报(医学版)》 CAS CSCD 北大核心 2019年第1期52-59,共8页
目的·应用点构法将下颌骨多个区域骨性标志点组合构建不同平面,从中筛选出对称性最佳者作为下颌骨正中矢状平面。方法·随机选取40例成年患者,依据颏部偏斜程度分为偏斜组(MA组,20例)和非偏斜组(MS组,20例),应用Mimics 19.0软... 目的·应用点构法将下颌骨多个区域骨性标志点组合构建不同平面,从中筛选出对称性最佳者作为下颌骨正中矢状平面。方法·随机选取40例成年患者,依据颏部偏斜程度分为偏斜组(MA组,20例)和非偏斜组(MS组,20例),应用Mimics 19.0软件重建下颌骨3D模型并描记10组同名标志点,通过点构法构建出120个待定平面。以迭代最近点(iterative closest point,ICP)算法所构平面作为参考标准,在MS组中依据角度、点距、面积等几何偏差指标进行排序初筛,在MA组、MS组中通过对应点点距、表面积及体积差值、3D偏差定值区间比率等临床对称性分析指标进行细筛,找出待定平面中对称性最佳者作为下颌骨正中矢状平面。结果·以正中联合前部、下颌角、喙突等区域标志点共同构建的平面排序位居总体前5%。其中由下牙槽座点(supramentale,B)、喙突顶点(coronoid superius,Cor)、下颌角外侧凸点(gonion lateralis,Golat)所构平面(B-Cor-Golat)与ICP平面间各项指标差值最小,且差异无统计学意义(P>0.05),其余平面与参考平面间差异具有统计学意义(P<0.05)。结论·B-Cor-Golat平面能较好地反映下颌骨对称程度,在临床中可作为下颌骨正中矢状平面。 展开更多
关键词 下颌骨 正中矢状平面 点构平面 下颌偏斜
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The Brillouin zones and band gaps of a two-dimensional phononic crystal with parallelogram lattice structure
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作者 HU JiaGuang XU Wen 《Science China(Physics,Mechanics & Astronomy)》 SCIE EI CAS 2014年第6期1013-1019,共7页
We present a detailed theoretical study on the acoustic band structure of two-dimensional (2D) phononic crystal. The 2D pho- nonic crystal with parallelogram lattice structure is considered to be formed by rigid sol... We present a detailed theoretical study on the acoustic band structure of two-dimensional (2D) phononic crystal. The 2D pho- nonic crystal with parallelogram lattice structure is considered to be formed by rigid solid rods embedded in air. For the circu- lar rods, some of the extrema of the acoustic bands appear in the usual high-symmetry points and, in contrast, we find that some of them are located in other specific lines. For the case of elliptic rods, our results indicate that it is necessary to study the whole first Brillouin zone to obtain rightly the band structure and corresponding band gaps. Furthermore, we evaluate the first and second band gaps using the plane wave expansion method and find that these gaps can be tuned by adjusting the side lengths ratio R, inclined angle 0 and filling fraction F of the parallelogram lattice with circular rods. The results show that the largest value of the first band gap appears at θ=90° and F--0.7854. In contrast, the largest value of the second band gap is at θ=60° and F=0.9068. Our results indicate that the improvement of matching degree between scatterers and lattice pattern, ra- ther than the reduction of structural symmetry, is mainly responsible for the enhancement of the band gaps in the 2D phononic crystal. 展开更多
关键词 phononic crystal band gap lattice basis vectors plane wave expansion method
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