两圆相交的两条性质及应用

两圆相交为圆周角定理、圆内接四边形性质定理提供了用武之地.由此我们也获得了两相交圆的一系列重要性质.本文介绍其中的两条性质及应用的几个例子。下面的性质1及其推论也就是贵刊88年第5期中的《相交圆内接三角形的性质及应用》一文的三条性质.以一交点为一顶点,过另一交点的割线为对边的三角形叫两相交圆的内接三角形。性质1 相交两圆的内接三角形的三个内角均为定值.(如图1,△AEC为其内接三角形) 推论1 在相交两圆中,内接三角形都相似。推论2 在相交两圆中,若内接三角形的一边与公共弦垂直,则另两边必分别为两圆直     

相交圆内接三角形的性质及应用

两圆相交于 A、D,过 D 任作割线分别交两圆于 B,C,我们称△ABC 为相交圆内接三角形.(见图1),相交圆内接三角形有下述三条性质.性质一相交圆内接三角形的三个内角均为定值.(证明略)这个性质揭示了相交圆内接三角形三内角的角度不变性,它对解决某类定值问题常常会有所启发.     

无穷级数中高斯判别法的进一步讨论

经过计算和逻辑推理,提出两种判别范围较大的正项级数判敛法,即广义高斯判别法及广义拟对数判别法,并对这两个判别法进行了比较.     

反常积分敛散性的两个新的判别法

根据反常积分的比较判别法,给出了反常积分的两个新的对数判别法.     

快速求解三角形面积最小值

在平面解析几何的学习和教学中 ,我们经常会遇到如下类型的题目 :1 求过点Ｐ(2 ,1 )的直线与ｘ、ｙ轴的正半轴相交所成三角形的最小面积 .2 已知直线ｌ∶ｙ=4ｘ和定点Ｍ(6,4) ,在ｌ上求一点Ｎ ,Ｎ在第一象限 ,使直线ＭＮ、ｌ及ｘ轴正半轴所围成的三角形的面积最小 .以上类型的题目关键是确定三角形在什么情况下面积最小 ,通常的解法是把面积的表达式写出来 ,最后应用重要不等式或二次函数等知识确定出最小值 ,从而相应地求出直线方程或点的坐标等 .以上思路很容易想到 ,但计算过于繁琐 ,这就需要我们另辟蹊径 .请看如下定理 :定理　过角内…     

对现行高中数学教学参考书的几点意见

笔者在教学中发现 ,与人教版现行高中课本《立体几何》、《平面解析几何》相配套的教学参考书有不妥之处 ,现对其提出几点意见 ,供商榷 .1　高中《立体几何教学参考书》1 高中《立体几何》(必修 )课本第 33页上的第 9题 :“求证 :两条平行线和同一个平面所成的角相等 .”本题应分两种情况论证 :(1 )两条平行线与同一平面平行 ;(2 )两条平行线与同一平面相交 ,这又分为垂直相交和斜交两种情形 .教学参考书中的答案只证明了第 (2 )种情况中的斜交情形 .2 同一课本第 48页上前 2题的第 (1 )小题 :“求证 :每两条都相交且不共点的四条直线共面…     

解答梯形问题的几种常用辅助线

在解答有关梯形的题目时 ,常常要添加辅助线 ,把梯形问题转化成三角形、平行四边形的问题来解 .解答梯形问题时 ,常引辅助线的方法有以下几种 :一、延长两腰 (使其相交 )得到两个相似三角形 ,如图 (一 ) .例 1　已知 ,梯形ＡＢＣＤ中 ,ＡＢ∥ＣＤ ,∠Ａ =∠Ｂ ,求证 :ＡＤ =ＢＣ .分析 :结论要证两条线段相等 ,由题意知 ,此题不能用证两个三角形全等的方法来证明 .因此可考虑将结论中的两条线段集中到一个三角形中 .如图 ,延长ＡＤ与ＢＣ相交于点Ｅ ,由∠Ａ =∠Ｂ知△ＥＡＢ是等腰三角形 ,又因为ＤＣ∥ＡＢ ,所以△ＥＤＣ也是等腰三角形 ,从…     

非锐角三角形个数的估计的改进

文[1]定理1证明：平面上任何三点不共线的n(n≥4)个点所组成的三角形中，非锐角三角形个数不少于1/4Gn^2，即至少有三角形总数的25％是非锐角三角形．令f(n)表示平面上任何三点不共线的n(n≥4)个点所组成的三角形中，非锐角三角形个数的极小值．下面对这一结果进行改进，并作进一步的探讨。     

利用面积法求有关线段的长

面积法就是通过面积的相互转化或面积与边、角关系的互相转化,而使问题得到解决的方法.对三角形而言,就是指利用三角形的面积自身相等的性质,或根据等高(底)的两个三角形的面积之比等于对应底边(对应高)的比的性质等进行解题的一种方法.利用面积法解题具有便捷、快速的特点,它是中学数学中一种常见的解题方法.现举例如下.一、利用三角形的面积自身相等的性质求线段的长问题1:已知等腰△ABC中,AB=AC=10,底边BC上     

抛物线的外切三角形和内接三角形的另外两个性质

文[1]给出了抛物线的外切三角形和内接三角形的两个性质:性质1抛物线y2=2px(p>0)上不同的三点A,B,C处的切线两两相交于P1,P2,P3,设△ABC和△P1P2P3的重心分别为G1,G2,则G1,G2的纵坐标相同.性质2抛物线y2=2px(p>0)上不同的三点A,B,C处的切线两两相交于P1,P2,P3,设抛物线的焦点为F,则     

Finding Shortest Paths in a Sequence of Triangles in 3D by the Planar Unfolding

We present an efficient algorithm for finding the shortest path joining two points in a sequence of triangles in three-dimensional space using the concept of funnels associated with common edges along the sequence of triangles and the planar unfolding for each funnel. We show that the unfolded image of a funnel is a simple polygon, it thus is non-overlapping. Therefore, such funnels are determined iteratively to their associated common edges by the planar unfolding and the shortest path joining two points is determined by cusps of these funnels.     

A generalization of Williams’ results on Fourier coefficients of eta quotients

Recently, combining a product-to-sum formula and conditions for the non-representability of integers by certain ternary quadratic forms, Williams gave ten eta quotients such that their Fourier coefficients vanish for all positive integers n in each of infinitely many non-overlapping arithmetic progressions. In this paper, we generalize Williams’ results by utilizing theta function identities.     

Non-overlapping Common Substrings Allowing Mutations

This paper studies several combinatorial problems arising from finding the conserved genes of two genomes (i.e., the entire DNA of two species). The input is a collection of n maximal common substrings of the two genomes. The problem is to find, based on different criteria, a subset of such common substrings with maximum total length. The most basic criterion requires that the common substrings selected have the same ordering in the two genomes and they do not overlap among themselves in either genome. To capture mutations (transpositions and reversals) between the genomes, we do not insist the substrings selected to have the same ordering. Conceptually, we allow one ordering to go through some mutations to become the other ordering. If arbitrary mutations are allowed, the problem of finding a maximum-length, non-overlapping subset of substrings is found to be NP-hard. However, arbitrary mutations probably overmodel the problem and are likely to find more noise than conserved genes. We consider two criteria that attempt to model sparse and non-overlapping mutations. We show that both can be solved in polynomial time using dynamic programming.      

A solution for cyclic scheduling of multi-hoists without overlapping

In this paper, we study the cyclic scheduling problem for electroplating lines where products are loaded into the system at one end and unloaded at the other end. The electroplating jobs must be processed within a given time window in each tank. There is no buffer between tanks. Two hoists sharing a common track are used to move products between the tanks in the production line. The objective is to minimize the production cycle time through scheduling hoist moves. A solution procedure is proposed in this study. The production line is first divided into two non-overlapping zones with a hoist assigned to each zone. Then a mixed integer linear programming model is developed for scheduling hoist moves. Computational results on a benchmark example problem are given in the paper to demonstrate the application of the proposed method.     

无重叠区的双抓钩周期性排序问题的求解

在当今的自动化制造系统中，计算机控制的抓钩的排序直接影响系统的生产率。本文研究了产品在系统的一边装载、而在另一边卸载的电镀线周期性排序问题。工件在每个工作站的处理时间在给定时间范围内，工作站之间没有缓冲槽，相同轨道上的两个抓钩用于工作站之间工件的运送，目标是对运送进行排序以极小化生产周期。为了求解这个问题，本文提出一个求解方法，所提出的方法首先将生产线分为两个无重叠的区域，并且为每个区域分配一个抓钩，然后，提出了一个给定抓钩分配下的混合整数线性规划模型。通过求解不同抓钩分配下模型的最优解，并且选择这些解中最好的一个，以便得到最优解，一个标杆示例被运行，以表明该方法的应用。另外，给出有多重处理槽工序问题的模型和求解方法。     

CONVERGENCE RESULTS FOR NON-OVERLAP SCHWARZ WAVEFORM RELAXATION ALGORITHM WITH CHANGING TRANSMISSION CONDITIONS

In this paper,we establish a new algorithm to the non-overlapping Schwarz domain decomposition methods with changing transmission conditions for solving one dimensional advection reaction diffusion problem.More precisely,we first describe the new algorithm and prove the convergence results under several natural assumptions on the sequences of parameters which determine the transmission conditions.Then we give a simple method to estimate the new value of parameters in each iteration.The interesti...     

Cover-based combinatorial bounds on probability of overfitting

The paper improves existing combinatorial bounds on probability of overfitting. A new bound is based on partitioning of a set of classifiers into non-overlapping clusters, and then embedding each cluster into a superset with known exact formula for the probability of overfitting. Such approach makes the bound sharper because it accounts for similarities between classifiers within each cluster.     

A time-stepping scheme for inelastic collisions

We propose here a numerical scheme to compute the motion of rigid bodies with a non-elastic impact law. The method is based on a global computation of the reaction forces between bodies. Those forces, whose direction is known since we neglect friction effects, are identified at the discrete level with a scalar which plays the role of a Kuhn-Tucker multiplier associated to a first-order approximation of the non-overlapping constraint, expressed in terms of velocities. Since our original motivation is the handling of the non-overlapping constraint in fluid-particle direct simulations, we paid a special attention to stability and robustness. The scheme is proved to be stable and robust. As regards its asymptotic behaviour, a convergence result is established in the case of a single contact. Some numerical tests are presented to illustrate the properties of the algorithm. Firstly, we investigate its asymptotic behaviour in a situation of non-uniqueness, for a single particle. The two other sets of results show the good behaviour of the scheme for large time steps.     

HAUSDORFF DIMENSION OF GENERALIZED STATISTICALLY SELF-AFFINE FRACTALS

The authors consider generalized statistically self-affine recursive fractals K with random numbers of subsets on each level. They obtain the Hausdorff dimensions of K without considering whether the subsets on each level are non-overlapping or not. They also give some examples to show that many important sets are the special cases of their models.     

Momentum Operators in Two Intervals: Spectra and Phase Transition

We study the momentum operator defined on the disjoint union of two intervals. Even in one dimension, the question of two non-empty open and non-overlapping intervals has not been worked out in a way that extends the cases of a single interval and gives a list of the selfadjoint extensions. Starting with zero boundary conditions at the four endpoints, we characterize the selfadjoint extensions and undertake a systematic and complete study of the spectral theory of the selfadjoint extensions. In an application of our extension theory to harmonic analysis, we offer a new family of spectral pairs. Compared to earlier studies, it yields a more direct link between spectrum and geometry.