双曲复平面上的类时邻域     

李武明  许宁 《通化师范学院学报》2009,30(10):1-2

利用双曲复平面上M inkowsk i圆的性质,引入双曲复平面上类时邻域（类空邻域,类光邻域）的概念,讨论了类时邻域的性质,得到类时曲线的有限覆盖定理.  相似文献   

关于逆、顺三角形有向面积的一个定理及其推论     

吴跃生  李咏秋 《赣南师范学院学报》2010,31(3):31-34

给出平面三角形有向面积的一个定理及其若干推论.推广拿破仑三角形的一些已知结论.  相似文献   

锦屏电站大坝右岸洞室开挖过程控制及对策     

胡治中  刘涛  刘艳兰 《长江工程职业技术学院学报》2009,26(2):44-45,48

锦屏一级水电站大坝右岸地下洞室具有地质条件复杂、施工条件差、干扰因素多、难度大、工程量大、质量要求高、工期紧等诸多特点,因此施工过程控制极其重要。  相似文献   

A three-dimensional examination of the planar nature of the golf swing     

Simon GS Coleman  Andrew J Rankin 《Journal of sports sciences》2013,31(3):227-234

Previous planar models of the downswing in golf have suggested that upper limb segments (left shoulder girdle and left arm) move in a consistent fixed plane and that the clubhead also moves only in this plane. This study sought to examine these assumptions. Three-dimensional kinematic analysis of seven right-handed golfers of various abilities (handicap 0?–?15) was used to define a plane (named the left-arm plane) containing the 7th cervical vertebra, left shoulder and left wrist. We found that the angles of this plane to the reference horizontal z axis and target line axis (parallel to the reference x axis) were not consistent. The angle to the horizontal z axis varied from a mean of 133° (s = 1°) at the start of the downswing to 102° (s = 4°) at impact, suggesting a “steepening” of the left-arm plane. The angle of the plane to the target line changed from ??9° (s = 16°) to 5° (s = 15°) during the same period, showing anticlockwise (from above) rotation, although there was large inter-individual variation. The distance of the clubhead from the left-arm plane was 0.019?m (s = 0.280?m) at the start at the downswing and 0.291?m (s = 0.077?m) at impact, showing that the clubhead did not lie in the same plane as the body segments. We conclude that the left arm and shoulder girdle do not move in a consistent plane throughout the downswing, and that the clubhead does not move in this plane. Previous models of the downswing in golf may therefore be incorrect, and more complex (but realistic) simulations should be performed.  相似文献   

互成角度的两平面镜成像问题的讨论     

刘克涛 《南阳师范学院学报》2003,2(12):25-28

夹角为θ的平面镜M和N之间放置一物点P,由反射所成的虚像设为K个,这些像均分布在同一个圆周上,像的总数K=[(180°-α)/θ]+[(180°-β)/θ]。当180°/θ为整数时,K个虚像中有两个像重合,故只有K-1个虚像能被看到;当180°/θ不为整数时,K的值既取决于平面镜M和N之间的夹角,还与物点P所放位置有关。  相似文献   

对速度瞬心的动量矩定理及其应用     

陈云信 《文教资料》2005,15(4):176-177

本文从动能定理出发论证了对速度瞬心的动量矩定理,并通过实例阐述了用它求解有瞬心的力学问题更简洁有效。  相似文献   

Stewart formula and some inequalities for a simplex     

杨世国 《重庆大学学报(英文版)》2005,4(1):55-58

1 Stewart formula and inequalities for a simplex Given a triangle ABC, suppose that , ,a bw w and cw are respectively the lengths of the angle bisectors of ?ABC, a, b and c are the lengths of the sides of ?ABC. The well-known Stewart’s formula for a triangle is proved as follows 222222222,( ),( ).( )abca bcw bc b cab cw ac a cabcw ab a b? = ?? +??? = ?? +??? = ? +?? (1) Let 1 2 1n nA A A? += be an n-dimensional simplex in the n-dimensional Euclidean space nE , V be the volume of ;n? kF…  相似文献   

球面和圆柱面相等对应关系的研究     

杨道富  彭明 《商丘师范学院学报》2005,21(5):61-63

建立轴射圆柱面投影方法，研究轴射圆柱面投影下球面向圆柱面投影的理论，解决正投影无法解决的复杂的旋转体投影问题．用轴射圆柱面投影法的投影理论，建立球面和圆柱面的一一对应关系，找出二者之间的某些几何规律，该投影下任意形状的球面投影到圆柱面上是相等的，建立球面的轴射圆柱面投影定理，解决球面不规则计算问题．  相似文献   

有关透镜组合基点基面公式的讨论     

窦超  潘章 《牡丹江教育学院学报》2006,(5)

本文以两个共轴透镜组成的光学系统为例,结合具体的光路图,推导出主点和节点的计算公式,其过程简单,物理意义清晰。  相似文献   

天球坐标系的难点解析     

杨柯金 《南阳师范学院学报》2003,2(9):97-99,124

通过对天球坐标系的两个难点“认识天球坐标系”和“掌握天球坐标系间的联系”的分析，阐述降解难度的切入点和关键点，把抽象的、虚幻的天球坐标系变得具体、真实、便于接受和领会，以求达到学用结合的目的。  相似文献