平行四边形的弦长分布

本文研究了凸体的弦长分布问题.利用广义支撑函数、限弦函数和积分几何方法,得到了平行四边形的弦长分布函数.     

一个几何命题的证法与延伸

《数学通报》2 0 0 0年第 1 2期 1 2号数学问题中给出了这样一道题目 :1 2 86　直三棱柱ＡＢＣ -Ａ1 Ｂ1 Ｃ1 中 ,ＡＢ1 ⊥ＢＣ1 、ＢＣ1 ⊥ＣＡ1 、ＣＡ1 ⊥ＡＢ1 (如右图 ) .求证 :该棱柱是正棱柱 .题中简捷的条件 ,直观的结论颇耐人寻味 ,《数学通报》2 0 0 1年第 1期给出的证法图形复杂 ,处理起来有一定的难度 ,今将自己的所得整理成下文 ,供同行参考 .1　关于命题的证明图 11 1　割补法证法一　如图 1在直三棱柱ＡＢＣ-Ａ1 Ｂ1 Ｃ1 的下面补上一个与之完全相同的直三棱柱 ,并设ＡＢ、ＢＣ、ＣＡ的长分别为ｃ、ａ、ｂ,设原直三棱柱的高…     

凸域的外平行集的包含测度

本文研究了凸域内定长线段的包含测度问题,利用广义支持函数和限弦函数,得到了一类特殊凸域的包含测度.     

正n棱柱体积函数的导函数与表面积函数

文[1]否定了司本志老师的猜想，指出“存在正三棱柱和正四棱柱，使其体积函数的导函数等于表面积函数．”笔者进一步发现：     

半圆区域的包含测度

本文研究了半圆区域内定长线段的包含测度问题.利用广义支撑函数和限弦函数,得到了这类区域的包含测度.关于非多边形凸域的包含测度的现有结果不多,本文的结果丰富了凸体包含测度的具体结果.     

随机弦长矩与弦幂积分

本文研究了凸体的五种类型的随机弦长分布.利用限弦投影原理和运动测度积分的方法,揭示了凸体的弦幂积分与随机弦长的矩之间的本质联系.     

一个猜想的解决

司志本老师在文[1]中提出的猜想是： 猜想：对于任意的正三棱柱和正四棱柱，其体积函数的导数都不可能等于表面积函数．笔者对该猜想进行了研究，得出的结论是：     

《几何画板》教学实例

利用《几何画板》可以绘制动态直观的立体图形 ,通过图表的动静结合的交互演示 ,可以使枯燥生硬的图形变得生动形象 ,吸引学生的注意与兴趣 ,帮助学生实现从平面图形向立体图形 ,从二维平面向三维空间的过渡 ,培养学生的空间想象力 .本文通过用《几何画板》制作空间图形旋转时的直观图的教学实例 ,说明《几何画板》对优化教学环境 ,提高教学质量的促进作用 .1　旋转正棱柱的制作 (以正三棱柱为例) (如图 1 )1 )作一水平线段ＯＸ ,并在其上取一点Ｍ ,以图 1Ｏ为圆心 ,Ｍ、Ｘ分别为圆周上的点作小圆ｂ和大圆ａ ,过Ｏ作ＯＸ的垂线交大圆于点Ｐ …     

多面体和球

1．本单元重、难点分析 本单元的重点：1）了解多面体和凸多面体、正多面体、棱柱、棱锥、球等几何概念；2）掌握一般棱柱、直棱柱、正棱柱的区别和联系，正棱锥和球的性质，球的表面积和体积公式；3）会解决棱柱的对角面以及平行于底面的截面的有关问题．     

第八届北京高中数学知识应用竞赛决赛

试题 1.(满分16分)三视图是从主视、左视、俯视 三个方向观察物体,得到的平面图形.如图1所示 的物体是由一个六棱柱和圆柱组合而成的,主视 图显示出正六棱柱的三个侧面和圆柱侧面,左视 图显示出正六棱柱的两个侧面和圆柱侧面,俯视 图显示出一个正六边形和一个圆(中心重合),图1 还给出了三个视图的位置关系.     

RECENT PROGRESS ON SPHERICAL HARMONIC APPROXIMATION MADE BY BNU RESEARCH GROUP ——In memory of Professor Sun Yongsheng

As early as in 1990, Professor Sun Yongsheng, suggested his students at Beijing Normal University to consider research problems on the unit sphere. Under his guidance and encouragement his students started the research on spherical harmonic analysis and approximation. In this paper, we incompletely introduce the main achievements in this area obtained by our group and relative researchers during recent 5 years （2001-2005）. The main topics are： convergence of Cesaro summability, a.e. and strong summability of Fourier-Laplace series; smoothness and K-functionals; Kolmogorov and linear widths.     

Instructions for Authors

<正>Submission Authors must use LaTeX for typewriting,and visit our website www.actamath.com to submit your paper.Our address is Editorial Office of Acta Mathematica Sinica,Academy of Mathematics and Systems Science,Chinese Academy of Sciences,Beijing 100190,P.R.China.     

THE 8~(th) INTERNATIONAL CONGRESS ON INDUSTRIAL AND APPLIED MATHEMATICS

正August 10-14,2015Beijin,China The International Congress on Industrial and Applied Mathematics(ICIAM)is the premier international congress in the field of applied mathematics held every four years under the auspices of the International Council for Industrial and Applied Mathematics.From August 10 to 14,2015,mathematicians,scientists     

Boundedness for commutators of multipliers on Hardy type spaces

In this paper, we study the commutators generalized by multipliers and a BMO function. Under some assumptions, we establish its boundedness properties from certain atomic Hardy space Hb^p（R^n） into the Lebesgue space L^p with p 〈 1.     

A unified approach to certain problems of best local approximation

In this paper we study best local quasi-rational approximation and best local approximation from finite dimensional subspaces of vectorial functions of several variables. Our approach extends and unifies several problems concerning best local multi-point approximation in different norms.     

Towards Excellence in Science Chinese Academy of Sciences

<正>May 26,2014,Beijing Science is a human enterprise in the pursuit of knowledge.The scientific revolution that occurred in the 17th Century initiated the advances of modern science.The scientific knowledge system created by     

THE 8~(th) INTERNATIONAL CONGRESS ON INDUSTRIAL AND APPLIED MATHEMATICS

<正>August 10-14,2015Beijing,ChinaThe International Congress on Industrial and Applied Mathematics(ICIAM)is the premier international congress in the field of applied mathematics held every four years under the auspices of the International Council for Industrial and Applied Mathematics.From August 10 to 14,2015,mathematicians,scientists     

Bounds for the zeros of polynomials

Let P(z)=∑↓j=0↑n ajx^j be a polynomial of degree n. In this paper we prove a more general result which interalia improves upon the bounds of a class of polynomials. We also prove a result which includes some extensions and generalizations of Enestrǒm-Kakeya theorem.