微分几何观点下二元函数的极值

利用曲面的局部微分性质给出二元函数极值存在的必要条件和充分条件,并将之运用于具有明显几何特征的曲面对应的二元函数极值的判别问题中.     

Dirac Operator in Two Variables from the Viewpoint of Parabolic Geometry

In this paper, we show the existence of a sequence of invariant differential operators on a particular homogeneous model G/P of a Cartan geometry. The first operator in this sequence is locally the Dirac operator in 2 Clifford variables, D = (D ₁, D ₂), where D _i = ∑ _j e _j . ∂ _ij . It follows from the construction that this operator is invariant with respect to the action of the group G. There are 2 other G-invariant differential operators following it so that the sequence of operators is exact. We compute the local expression of these operators and show that it coincides with the operators described in [2, 5, 6] by the tools of Clifford analysis. However, it follows from our approach that the operators are invariant. The work presented here was supported by the grants GAUK 447/2004 and GA ČR 201/05/H005.     

An Exploration of a Quantitative Reasoning Instructional Approach to Linear Equations in Two Variables With Community College Students

In this exploratory study, we examined the effects of a quantitative reasoning instructional approach to linear equations in two variables on community college students’ conceptual understanding, procedural fluency, and reasoning ability. This was done in comparison to the use of a traditional procedural approach for instruction on the same topic. Data were gathered from a common unit assessment that included procedural and conceptual questions. Results demonstrate that small changes in instruction focused on quantitative reasoning can lead to significant differences in students’ ability to demonstrate conceptual understanding compared to a procedural approach. The results also indicate that a quantitative reasoning approach does not appear to diminish students’ procedural skills, but that additional work is needed to understand how to best support students’ understanding of linear relationships.     

二元函数的可微性研究

研究二元函数的可微性,得到两个充分条件,它们与已有的判别二元函数可微性的充分条件相比更为简单,因而使得应用更为简便.     

Homogeneous Nilpotent Matrices in Two Variables

We give a general geometrical procedure to construct nilpotent morphisms Φ : F → F(d), with F a vector bundle on ?¹, obtaining an analog of the Jordan canonical form. We investigate the possible splitting types of F in dependence on the degeneration behavior of Φ. Applications to nilpotent matrices with an arbitrary number of variables are also given.     

Inequalities for Means in Two Variables

We present various new inequalities involving the logarithmic mean L(x,y)=(x-y)/(logx-logy) L(x,y)=(x-y)/(\log{x}-\log{y}) , the identric mean I(x,y)=(1/e)(x^x/y^y)^1/(x-y) I(x,y)=(1/e)(x^x/y^y)^{1/(x-y)} , and the classical arithmetic and geometric means, A(x,y)=(x+y)/2 A(x,y)=(x+y)/2 and G(x,y)=?{xy} G(x,y)=\sqrt{xy} . In particular, we prove the following conjecture, which was published in 1986 in this journal. If M_r(x,y) = (x^r/2+y^r/2)^1/r(r 1 0) M_r(x,y)= (x^r/2+y^r/2)^{1/r}(r\neq{0}) denotes the power mean of order r, then $ M_c(x,y)<\frac{1}{2}(L(x,y)+I(x,y)) {(x,y>0,\, x\neq{y})} $ M_c(x,y)<\frac{1}{2}(L(x,y)+I(x,y)) {(x,y>0,\, x\neq{y})} with the best possible parameter c=(log2)/(1+log2) c=(\log{2})/(1+\log{2}) .     

学习理论中Rademacher随机变量的应用

利用Rademacher随机变量,本文讨论了学习函数f的亏损函数及f的样本误差的估计问题,给出了f的亏损函数及样本误差的估计,同时也给出了f的亏损函数的期望值的估计,这些估计都是O(m-1/2),这里m为样本容量.     

两组变量间相关关系的统计分析方法

研究典型相关分析的原理、典型成分的计算方法及计算步骤.把两组变量X与Y转化为具有最大相关性的若干对典型成分,直到两组变量的相关性被分解.通过典型相关系数及其显著性检验.选择典型成分分析两组变量的相关性.实例表明只有第一个典型相关系数能通过显著性检验,而其它两个典型相关系数显著为零,故应选取第一对典型成分F1和G1做分析...     

An Empirical Investigation of the Adaptive-Filtering Learning Factor

Acceptance of the adaptive-filtering parameter-estimation process has been mixed. Much of the variability between studies may result from the particular learning factor selected and may be further affected by the type of standardization used. The author presents a modification of the Makridakis and Wheelwright adaptive-filtering algorithm. This modified algorithm provides superior performance and simplifies the selection of the learning factor when used with simple autoregressive processes.     

Maximizing the Product of Two Linear Functions In 0-1 Variables

We study both the continuous and discrete problems of maximizing the product of two linear functions subject to all variables being between 0 and 1. We first give linear and low-order polynomial algorithms for the solution of the continuous problem. In addition, we describe penalties that help to fix variables in the discrete problem. Extensive computational tests demonstrate the effectiveness of these results.     

离散几何的两个铺砌问题

利用图论和代数的方法研究离散几何中的两个铺砌问题:1)给出1×2长方形铺砌多米诺骨牌的充分必要条件;2)对高维空间盒子的情形,给出m_1×m_2×…×m_n砖能够铺砌a_1×a_2×…×a_n盒子的一些必要条件和充要条件.     

变量的两种新观念

提出“第一变量”和“弹性变量”的概念 .为了更好地在科学技术上使用数学工具 ,在此给同辈少许解决问题的线索 .     

两个变量的Hardy型积分不等式

建立了两个独立变量函数的新的Hardy型积分不等式.     

The Generalized Dolbeault Complex in Two Clifford Variables

The Penrose transform is used to construct a complex starting with the Dirac operator in two Clifford variables. The corresponding relative BGG complex and its direct image is computed for cohomology with values in line bundles induced by representations in singular infinitesimal character. The limit of the induced spectral sequence is computed in cases connected with the Dirac operator in two Clifford variables. The work presented here is a part of the research project MSM 0021620839 and was supported also by the grants GAUK 447/2004 and GA ČR 201/05/2117.     

The Calculation of Some Rational Approximants in Two Variables

Chisholm has shown how rational approximants may be definedfor functions of two variables, which reduce to diagonal Pad?Approximants when one variable is zero. We extend the idea toallow for different maximum powers in numerator and denominator,and state the relevant theorems. We discuss numerical difficultiesand possible singularities occurring in the construction ofthe approximants; approximants to the Beta function are calculatedand discussed in detail.     

多复变数星形映照的两类子族

本文首先讨论有界星形圆型域上星形映照的一个子族---次星形映照,着重研究其几何性质,包括增长定理与掩盖定理.然后,在有界凸圆型域上讨论星形映照的另一类子族---α次的γ-凸映照.讨论它与星形映照,β次星形映照以及凸映照的关系.     

1-Dependent Stationary Sequences for Some Given Joint Distributions of Two Consecutive Random Variables

We provide a method to construct a 1-dependent stationary sequence provided some mixing condition on the joint distribution of two consecutive random variables. Two illustrations of computational benefits of the method are given. We obtain analytical formulas to compute the expectation and variance of the number of occurrences of a word in a sequence of letters from a finite alphabet generated by the 1-dependent model.We also obtain an approximation formula for the distribution of the longest success run in a Bernoulli sequence generated by our model.     

二元函数四条性质之间的关系

二元函数的连续性,偏导数存在性,偏导数连续性以及可微性是二元函数的四条经典性质,它们之间的关系一直是学生的疑惑点,本文结合严格的证明和典型的反例给出四条性质之间关系的详尽阐释.