空间l1(Xn)中的弱紧性

本文首先讨论空间l₁(X_n)中的弱收敛性，然后给出了l₁(X_n)中弱紧性的几种等价刻画，同时对l_p(X_n)（１＜ｐ＜∞）中的弱紧性也得到了类似的结果．     

空间l∞(Xn)中的弱紧性

本文首先得到了以l_∞(X_n)为值域的有界线性算子为弱紧算子的一个充要条件和一个充分条件，讨论了l_∞(X_n)中的弱收敛，然后给出了l_∞(X_n)中弱紧性的几种等价刻画．     

LPE GaxIn1-xAs1-ySby/InP和GaxIn1-xAs1-ySby/InAs的生长及其估价

将电负性差法估算的Ga_xIn_1-xAs_1-ySb_y/InP和Ga_xIn_1-xAs_1-ySb_y/InAs的固相和液相组份数据应用于液相外延生长,均获得了晶格匹配的材料,并首次获得了波长λ>3.5μm的Ga_xIn_1-xAs_1-ySb_y/InAs异质外延材料。Ga_xIn_1-xAs_1-ySb_y/InP的固体组份为...     

BaB2O4-Na2B2O4-K2B2O4三元系的研究

本文用实验测定和理论计算相结合的方法,研究了BaB₂O₄-Na₂B₂O₄-K₂B₂O₄三元系.在对该三元系3个侧边二元系相图热力学分析的基础上,用非对称的Toop模型将二元系热力学数据延拓到三元系,计算了BaB₂O₄-Na₂B₂O₄-K₂B₂O₄三元相图,计算结果与该三元系的一个典型垂直截面的测定结果吻合很好.     

范畴 RMRl上的一个函子及范畴A Grn0

本文定义了一个由范畴 _RM_R^l到范畴Ａ G_rn⁰ 的函子Ｇ，并证明了函子Ｇ保持分量正合及全正合，关于范畴ＡＧG_rn⁰ 证明了定理：     

Y1-xNdxSr2Cu2.7Mo0.3O7-δ体系的声子振动谱和输运性质

研究了Y_1-xNd_xSr₂Cu_2.7Mo_0.3O_7-δ(x =0 ,0 .1 ,0 .2 ,0 .5 ,0 .8和 1 .0 )的Ra-man光谱、红外光谱,指出RSr₂Cu_2.7Mo_0.3 O_7-δ结构上与RBa₂Cu₃O_7-δ有显著的差异,而伴随着Nd的掺入,晶体的微结构发生了变化 .结合电阻率和热电势的测量结果 ,我们讨论了这种微结构变化对载流子分布的影响和NdSr₂Cu_2.7Mo_0.3O_7-δ不超导的原因,进而指出在高温超导体中广泛存在的稀土离子尺寸效应也是大稀土离子替代产生的晶体微结构变化的结果     

外延生长YBa2Cu3O7-x超导薄膜的TEM和SEM研究

本文利用高分辨率透射电子显微镜(TEM)和扫描电子显微镜(SEM)对高J_c外延生长YBa₂Cu₃O_7-x超导薄膜的微观结构进行了观察分析.研究发现,薄膜外延程度的好坏与生长工艺和衬底表面的完整性有直接的关系.实验结果表明(100)SrTiO₃单晶衬底上外延生长YBa₂Cu₃O_7-x超导薄膜中影响临界电流密度J_c的因素主要有界面过渡区、缺陷和不同的外延取代等.     

LPL3层膜的结构、磁性和磁电阻效应的研究

采用直流溅射法在 ( 1 0 0 )LaAlO3 单晶基片上制备了La_0.67Sr_0.33MnO_3+δ/Pr_0.7Ca_0.3MnO_3+δ/La_0.67Sr_0.33MnO_3+δ(简称为LPL) 3层膜 .用X射线粉末衍射法(XRD)研究了系列样品的摇摆曲线和衍射全图 ,结果表明所有的样品均为高度取向的外延膜 .SQUID磁强计的测量结果证实了 3层膜中磁耦合的存在 .用常规的四端引线法测量了LSMO、PCMO和LPL 3层膜的电阻 ,分析了logρ 1 /T曲线 .由此可以得出如下结论 :具有铁磁性的PCMO中间层在 3层膜中可能起到了内磁场的作用 ,使得LSMO膜的顺磁性被削弱 ,这个作用与外加磁场的作用一样 ,降低了 ρ_max,增大了由金属到半导体的转变温度T_p;PCMO中间层还诱发了LSMO的能隙中的态密度的变化 .以上两个原因使得在零场中样品的电阻率和T_p 随着中间层PCMO的厚度变化而明显变化 .     

Bi2Sr2Ca1-xYxCu2Oy系超导—绝缘转变中的结构效应

研究了Bi₂Sr₂Ca_1-xY_xCu₂O_y.(BSCYCO)体系中Y替代Ca后材料从超导体向绝缘体的转变过程.研究结果表明,在替代量X=0.4附近发生的从四方到正交的结构转变是BSCYCO超导性消失的直接原因,并发现结构参数c/0.5(a+b)的变化与材料的超导—绝缘—反铁磁这一性能的转变过程有较明显的对应关系.     

新概念下的Sn掺杂(La1-xSrx)2Cu1-xSnxO4超导体的MÖssbauer谱研究 *

对新概念指导下而设计的 (La_1-xSr_x)2Cu_1-xSn_xO₄超导体进行了¹¹⁹Sn M_Össbauer谱研究 .对不同掺杂量样品的系统研究表明 ,M_Össbauer谱实验结果进一步证实了Sn以Sn⁴⁺价态存在并占据Cu晶位 ,不存在占据La晶位的Sn^{2 +}离子 .Sn⁴⁺离子附近的局域晶格畸变较小 ,但是随Sn掺杂量有增加趋势 .在对La₂ CuO₄母体进行Sr和Sn同时掺杂所引入的载流子对超导电性的影响存在新的机制 .在新的额外氧机制下 ,讨论了Sn掺杂所导致的额外氧对超导电性的影响 .     

Dealing with the multiplicity of solutions of the ℓ1 and ℓ∞ regression models

It is well known that the least absolute value (?_∞) and the least sum of absolute deviations (?₁) algorithms produce estimators that are not necessarily unique. In this paper it is shown how the set of all solutions of the ?₁ and ?_∞ regression problems for moderately large sample sizes can be obtained. In addition, if the multiplicity of solutions wants to be avoided, two new methods giving the same optimal ?₁ and ?_∞ values, but supplying unique solutions, are proposed. The idea consists of using two steps: in the first step the optimal values of the ?₁ and ?_∞ errors are calculated, and in the second step, in case of non-uniqueness of solutions, one of the multiple solutions is selected according to a different criterion. For the ?_∞ the procedure is used sequentially but removing, in each iteration, the data points with maximum absolute residual and adding the corresponding constraints for keeping these residuals, and this process is repeated until no change in the solution is obtained. In this way not only the maximum absolute residual values are minimized in the modified method, but also the maximum absolute residual values of the remaining points sequentially, until no further improvement is possible. In the ?₁ case a least squares criterion is used but restricted to the ?₁ residual condition. Thus, in the modified ?₁ method not only the ?₁ residual is minimized, but also the sum of squared residuals subject to the ?₁ residual. The methods are illustrated by their application to some well known examples and their performances are tested by some simulations, which show that the lack of uniqueness problem cannot be corrected for some experimental designs by increasing the sample size.     

一类二阶哈密尔顿系统的周期解

在(CPS)_C及(PS)_C条件下,利用Ambrosetti-Rabinowitz对称形式的山路引理,研究了一类二阶哈密尔顿保守系统在给定能量面上的无穷多个周期解的存在性问题.     

Fibrous Filler-Matrix Interaction in Oxide Composites

The interaction between a fibrous alumina filler and a hydrated zirconia matrix during the fabrication of ceramic composites is studied. The influence of the crystal structure and porosity of the filler on the properties of the ZrO₂-Al₂O₃ composite material is investigated. It is found that, as a result of addition of alumina fibers of cubic and monoclinic structures (- and -phases), the ZrO₂ hydrogel interacts with fibers and solid ZrO₂ solutions of tetragonal structure are formed. These solutions exist over the range of 600 to 1200°C and, at annealing above 1200°C, due to crystallographic transitions the of - and -phases, they break down, namely Al₂O₃ transforms into -corundum and ZrO₂ into a monoclinic modification. However, the material does not fail and a stable porous ceramic composite is formed. To manufacture a composite with improved mechanical characteristics, fibrous alumina fillers with the structure of -corundum must be used.     

Existence of subharmonic solutions and homoclinic orbits for a class of even higher order differential equations

Using the variational structure and the Z ₂ group index theory we establish the existence of subharmonic solutions and homoclinic solutions for a class of even higher order differential equation.     

解在QK 型及Dirichlet 型空间中的线性微分方程

对于单位圆盘上系数函数是解析函数的复微分方程
f⁽ⁿ⁾+A_n-1(z)f^(n-1)+…+A₁(z)f''+A₀(z)f=0,
给出了方程的系数函数和解函数之间的关系, 即当系数函数A_j 满足给定的条件时, 方程的所有解属于Q_K型空间和Dirichlet 型空间.     

L p c -concentration of blow-up solutions for the biharmonic nonlinear Schrödinger equation

This article is concerned with the blow-up solutions of the biharmonic Schrödinger equation with L ²-super critical nonlinearity. We obtain the nonexistence of strong limit of L ^{p _c} -norm and L ^{p _c} -concentration properties of the radially symmetric blow-up solutions, where L ^{p _c} is the invariant Lebesgue space.     

Exponential Behavior of Solutions to Stochastic Integrodifferential Equations with Distributed Delays

In this work, we study the existence, uniqueness, and exponential asymptotic behavior of mild solutions to stochastic integrodifferential delay evolution equations. We assume that the non-delay part generates a C₀-semigroup.     

Efficiency and Solution Approaches to Bicriteria Nonconvex Programs

A new nonlinear scalarization specially designed for bicriteria nonconvexprogramming problems is presented. The scalarization is based on generalizedLagrangian duality theory and uses an augmented Lagrange function. The newconcepts, q _i-approachable points and augmented duality gap, are introducedin order to determine the location of nondominated solutions with respect to aduality gap as well as the connectedness of the nondominated set.     

Epimorphisms and cowellpoweredness for separated metrically generated theories

For metrically generated constructs X we give an internal characterization of the regular closure operator on X, determined by the subconstruct X ₀, consisting of its T ₀ objects. This allows us to describe the epimorphisms in X ₀ and to show that all the constructs of that type are cowellpowered. We capture many known results but our method also gives solutions in cases where the epimorphism problem was still open. The third author is “research assistant” at the FWO-Vlaanderen.