高温超导体Josephson阵列在磁场中的微波响应与磁通涡旋激发

本文从分析相变电阻率 ρP 和磁通蠕动电阻率 ρF 出发 ,指出当T小于某一温度T0 时 ,ρF>ρP,而当T >T0 时 ,ρF 远小于 ρP,并进一步分析了 ρF 与 ρP 随温度的变化率分布图 ,得出磁通蠕动电阻率 ρF 随温度的变化率分布图跟微波响应曲线具有相似的分布特征 ,结果表明 :高温超导体的非平衡微波响应机制可能与磁通涡旋的激发有关 .     

凸体的曲率映象与仿射表面积

本文研究了一些特殊凸体与其极体的曲率仿射表面积乘积的下界.对任意两个凸体,建立了它们的投影体的混合体积与其仿射表面积的一个不等式（见文[1-15]）.     

A note on balance vertices in trees

The notion of balanced bipartitions of the vertices in a tree T was introduced and studied by Reid (Networks 34 (1999) 264). Reid proved that the set of balance vertices of a tree T consists of a single vertex or two adjacent vertices. In this note, we give a simple proof of that result.     

Comment on “A Hierarchy of Integrable Nonlinear Lattice Equations and New Integrable Symplectic Map“

Comment on a recent paper on Commun. Theor. Phys. (Beijing, China) 38 (2002) pp. 523-528.     

Discrete global descent method for discrete global optimization and nonlinear integer programming

A novel method, entitled the discrete global descent method, is developed in this paper to solve discrete global optimization problems and nonlinear integer programming problems. This method moves from one discrete minimizer of the objective function f to another better one at each iteration with the help of an auxiliary function, entitled the discrete global descent function. The discrete global descent function guarantees that its discrete minimizers coincide with the better discrete minimizers of f under some standard assumptions. This property also ensures that a better discrete minimizer of f can be found by some classical local search methods. Numerical experiments on several test problems with up to 100 integer variables and up to 1.38 × 10¹⁰⁴ feasible points have demonstrated the applicability and efficiency of the proposed method.     

一类含有非线性传染率的传染病模型的全局稳定性

讨论了一类带有非线性传染率的SIRS型传染病模型,得到了无病平衡点和地方病平衡点存在的阈值条件,借助构造Dulac函数和Liapunov函数,找到了两类平衡点全局渐近稳定的充要条件.     

A NUMERICAL EMBEDDING METHOD FOR SOLVING THE NONLINEAR COMPLEMENTARITY PROBLEM(Ⅱ)-ALGORITHM AND ITS CONVERGENCE

In this paper,based on the results presented in part Ⅰ of this paper[18],we present a numerical embedding algorithm for solving the nonlinear complementarityproblem, and prove its convergence carefully. Numerical experiments show that thealgorithm is successful.     

Winograd矩阵乘法算法用于任意阶矩阵时的一种新处理方法

摘要t矩阵乘法StraSsen算法及其变形winograd算法用分而治之的方法把矩阵乘法时间复杂性由传统的D(n。)改进到0(佗kg。n.但是对于奇数阶矩阵,在划分子矩阵时,要作特殊处理才能继续使用此算法.本文提出了一种非等阶“十”字架划分方法,可以最少化填零,最大化性能,使得奇数阶矩阵乘法的时间复杂性更加接近偶数阶矩阵乘法的效果.计算实例显示该方法是有效的.     

A Facile Synthesis of Ethyl 2,4-Dimethoxy-6-perfluoroalkyl-benzoates via Acyclic Precursors

Introduction Polysubstituted arenes are important intermediates in synthetic medicines and dyestuffs, and the fluorinated analogues are more attractive as a result of their lipo-philicity and the increment of activity.1,2 Therefore, to study the convenient and efficient synthesis of polysub-stituted arenes is valuable in organic synthetic method-ology. We have designed a simple synthesis of fluori-nated polysubstituted arenes through the intramolecular Wittig reaction of a new phosphorous ylid…     

凝胶-燃烧法合成YAG∶Eu3+纳米荧光材料的结构和发光性能

Y₃Al₅O₁₂∶Eu nanophosphors were synthesized by a gel combustion method. The structure of phosphors was characterized by XRD and FTIR. YAG phase came to occur when YAG∶Eu precursors were sintered at 800 ℃, although the phase was mainly amorphous. The organic groups pyrolyzed completely and pure YAG phase was obtained in the samples sintered at 900 ℃. In the formation of YAG phase, no intermediate phases such as YAP and YAM were detected. Both ⁵D₀ → ⁷F₁ orange and ⁵D₀ → ⁷F₂ red emission could be observed for all the sintered samples. However, the emission of amorphous samples was greatly different from that of crystalline ones. The former was mainly ⁵D₀→ ⁷F₂ red emission, but the latter was ⁵D₀ → ⁷F₁ orange emission. As sintering temperature rises, the ratio of orange to red for phosphors increases. Eu could be doped up to 8% in YAG host lattice, and fluorescence quenching was absent. It indicated that the gel combustion synthesis method can increase emission intensity and quenching concentration due to a good distribution of Eu³⁺ activators in Y₃Al₅O₁₂ matrix.