On Two Dimensional Packing

The paper considerspacking of rectanglesinto an infinite bin. Similar to theTetris game, the rectangles arrive from the top and, once placed, cannot be moved again. The rectangles are moved inside the bin to reach their place. For the case in which rotations are allowed, we design an algorithm whose performance ratio is constant. In contrast, if rotations are not allowed, we show that no algorithm of constant ratio exists. For this case we design an algorithm with performance ratio ofO(log(1/)), where is the minimum width of any rectangle. We also show that no algorithm can achieve a better ratio than for this case.     

Packing Trees with Constraints on the Leaf Degree

If m is a positive integer then we call a tree on at least 2 vertices an m-tree if no vertex is adjacent to more than m leaves. Kaneko proved that a connected, undirected graph G = (V, E) has a spanning m-tree if and only if for every the number of isolated vertices of G − X is at most —unless we have the exceptional case of and m = 1. As an attempt to integrate this result into the theory of graph packings, in this paper we consider the problem of packing a graph with m-trees. We use an approach different from that of Kaneko, and we deduce Gallai–Edmonds and Berge–Tutte type theorems and a matroidal result for the m-tree packing problem. Jácint Szabó: Research is supported by OTKA grants K60802, TS049788 and by European MCRTN Adonet, Contract Grant No.504438.     

Two Dimensional Landau-Lifshitz Equation

In this paper, we consider the Cauchy problem for two dimensional Landau-Lifshitz equation on 2-dimenslonal Riemannian manifold M without boundary. We proved that if u: M × R_+ → S², is a weak solution, then u is unique and smooth on M × R_+ with the exception of finitely many points.     

二维矩形条带装箱问题的改进左下角定位模型

针对不可旋转二维矩形条带装箱问题(2DR-SPP),基于两矩形的左下角单元坐标及其覆盖区域的关系,提出并证明了两矩形在条带箱中发生重叠的充分必要条件,然后根据此充分必要条件得到了禁止矩形重叠的约束条件,建立了问题的线性整数规划模型.增添旋转90~0后所得的矩形数据至原有的矩形数据中,基于更新后的矩形数据,修改不可旋转2DR-SPP的数学模型,得到了可旋转情形下问题的线性整数规划模型.算例结果验证了所建模型的有效性和准确性.     

Two Dimensional Submanifolds in Four Manifolds with Boundary

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两个约束条件下多产品报童问题的求解方法研究

对两个约束条件下多产品报童问题的求解方法进行研究。首先分析了问题的结构特征,利用对偶问题解空间的四个不同区域对应的最优解具有的不同性质,给出了不同解空间区域的求解思路。然后基于两种资源的边际利益的性质,提出一种二分搜索算法对问题进行求解,并证明了该算法能够得到问题的最优解或者近似最优解,且具有多项式复杂度。最后应用算例说明算法计算效率高,可以在较少的迭代步骤内快速求解两个线性约束下产品数较大的多产品报童问题。     

N-d维广义Brownian单的像集一致Packing测度和一致Packing维数

我们获得了Ｎ－ｄ维广义Ｂｒｏｗｎｉａｎ单的像集的一致Ｐａｃｋｉｎｇ测度和一致Ｐａｃｋｉｎｇ维数。     

Two Dimensional Nilpotent Euclidean Nearrings

We find all multiplications on the two dimensional Euclidean group (IR²,+) such that (IR², +, ·) is a nilpotent topological nearring of rank three. We determine the left, right, and two sided ideals of these nearrings and we determine when two of these nearrings are isomorphic. As a consequence, we are able to conclude that there are infinitely many isomorphism classes of such nearrings. This is in considerable contrast to the case for rings. There are only eight isomorphism classes of topological rings with additive group (IR²,+).AMS Subject Classification (2000) 16Y30     

二维整环的刻划

设R是整环,在本文中我们证明了R的弱整体维数不超过2当且仅当每一对w-模是平坦模,当且仅当每一有限型的w-模是投射模．     

On the Indefinite Quadratic Fractional Optimization with Two Quadratic Constraints

In this paper, we consider minimizing the ratio of two indefinite quadratic functions subject to two quadratic constraints. Using the extension of Charnes–Cooper transformation, we transform the problem to a homogenized quadratic problem. Then, we show that, under certain assumptions, it can be solved to global optimality using semidefinite optimization relaxation.     

Three Dimensional Affine Hyperspheres Generated by Two Dimensional Partial Differential Equations

It is well‐known that locally strongly convex affine hyperspheres can be determinedas solutions of differential equations of Monge‐Ampère type. In this paper we study in particular the 3‐dimensional case and we assume that the hypersphere admits a Killing vector field (with respect to the affine metric) whose integral curves are geodesics with respect to both the induced affine connection and the Levi‐Civita connection of the affine metric. We show that besides the already known examples, such hyperspheres can be constructed starting from the 2‐dimensional Poisson equation, the 2‐dimensional sine‐Gordon equation or the 2‐dimensional cosh‐Gordon equation.     

Two Dimensional Indecomp osable Mo dules over Infinite Dimensional Hereditary Path Algebras

Non-isomorphic two dimensional indecomposable modules over infinite dimensional hereditary path algebras are described. We infer that none of them can be determined by their dimension vectors.     

Symmetrical Independence Tests for Two Random Vectors with Arbitrary Dimensional Graphs

Test of independence between random vectors X and Y is an essential task in statistical inference.One type of testing methods is based on the minimal spanning t...     

两个约束条件下允许外购的多产品报童问题

研究在资源和预算约束条件下允许外购的多产品报童问题.为解决因资源有限而引起的缺货问题,允许外购,外购的最大可得到量是给定的.建立了在非零延迟时间外购情况下以求总体花费最小值为目标函数的的优化模型,分析了模型的结构特征,结合最优化理论,利用可行方向方法对模型进行了求解.数值结果表明了模型的合理性和算法的有效性.     

一类只有两个不同非零交换理想的无限维李代数

构造了一类无限维李代数,它是无中心的Virasoro李代数的推广,且只有两个不同的非零交换的理想.还研究了这类李代数的理想、中心和子代数.     

二维不可压缩流的谱方法

本文以二维涡度方程为模型,介绍了谱方法和拟谱方法以及它们与差分方法和有限元法相结合的混合解法．这些方法可推广应用于其它一些类似的非线性问题．本文还给出了这些方法的某些数值例子和误差估计结果     

关于高维单形的两个性质

应用度量几何理论与解析方法,研究了n维欧氏空间En中n维单形的性质,将三角形内心与中线两个性质推广到n维单形,获得n维单形内心与中位面的两个性质.     

Automorphisms of the Two Dimensional Crystallographic Groups

We compute the groups Aut(G) and Out(G) where G is a crystallographic group of rank 2, or so-called wallpaper group.     

关于乘积图的二维带宽问题

给出一般乘积图的二维带宽的界，并解决一类乘积图的二维带宽问题．最后给出完全ｋ部图的二维带宽。