Nonvolatile bipolar resistance switching effects in multiferroic BiFeO3 thin films on LaNiO3-electrodized Si substrates

We report on reversible bipolar resistance switching effects in multiferroic BiFeO₃ thin films without electroforming. The BiFeO₃ thin films with (110) preferential orientation were prepared on LaNiO₃-electrodized Si substrates with a Pt/BiFeO₃/LaNiO₃ device configuration. The resistance ratio of high resistance state (HRS) to low resistance state (LRS) of the devices was as high as three orders of magnitude. The dominant conduction mechanisms of LRS and HRS were dominated by ohmic behavior and trap-controlled space charge limited current, respectively. The resistance switching mechanism of the devices was discussed using a modified Schottky-like barrier model taking into account the movement of oxygen vacancies.     

The Hamiltonian structure of general relativistic perfect fluids

We show that the evolution equations for a perfect fluid coupled to general relativity in a general lapse and shift, are Hamiltonian relative to a certain Poisson structure. For the fluid variables, a Lie-Poisson structure associated to the dual of a semi-direct product Lie algebra is used, while the bracket for the gravitational variables has the usual canonical symplectic structure. The evolution is governed by a Hamiltonian which is equivalent to that obtained from a canonical analysis. The relationship of our Hamiltonian structure with other approaches in the literature, such as Clebsch potentials, Lagrangian to Eulerian transformations, and its use in clarifying linearization stability, are discussed.Research supported in part by NSF grant MCS 81-08814(A02)Research supported in part by NSF grant MCS 81-07086     

冷绝缘高温超导电缆电磁特性计算与分析

为了获得超导电缆电磁特性变化规律,针对冷绝缘高温超导电缆本体的基本结构,采用安培定律推导了超导电缆导体层和屏蔽层自感、互感的计算公式.通过110kV冷绝缘超导电缆的实例计算,研究了超导电缆导体层、屏蔽层的内径、绕向角、绕制方向三个结构参数对电磁特性的影响,总结了电感参数变化规律.     

化学计量学方法在三维荧光光谱分析中的应用

随着分析数据日益复杂,传统的用于光谱分析中的数据处理方法已不能满足分析需要,而化学计量学应用数学、统计学以及计算机等科学的方法与手段,设计和选择最优的量测方法,并通过对数据的解析,可最大限度的获取光谱数据中的有用信息.本文首先介绍了几类常用化学计量学方法分析的三维荧光光谱,其次介绍了常用于光谱分析的化学计量学方法,如统...     

两种不锈钢在高压下的状态方程

 测定了两种不锈钢在室温下、4.5 GPa内的p-V关系，并给出了它们的Bridgman方程。根据Bridgman方程的系数a和b，计算了它们的格临爱森参数γ₀、体积模量B₀和B₀的压力导数B₀'。     

摩擦点火Ti-V-Cr阻燃钛合金燃烧产物的组织特征

采用摩擦氧浓度实验方法, 结合原位观察、扫描电镜、能谱仪和X-射线衍射分析, 系统研究Ti-V-Cr 阻燃钛合金燃烧产物的微观组织形貌、燃烧反应过程的合金元素分布规律及微观机理. 结果表明: Ti-V-Cr 阻燃钛合金燃烧过程发出闪亮耀眼的白光, 具有典型金属燃烧的火焰特征. 燃烧产物主要有TiO₂, V₂O₅和Cr₂O₃三种氧化物, 该混合氧化物以分散颗粒和致密连续体存在. 分散颗粒为规则的球形; 致密连续燃烧产物的微观组织具有分区特征, 从合金基体至燃烧表面依次为过渡区、热影响区、熔凝区和燃烧区. 其中, 过渡区存在一些微小的颗粒状凸起, 且有一定方向性; 热影响区中形成大量V基固溶体相和少量的Ti基固溶体相, V基固溶体相上存在Ti的含量远高于基体的针状析出物; 熔凝区中, 大量的Ti基固溶体中存在少量的V基固溶体; 燃烧区主要为Ti, V和Cr的氧化物混合物. 热影响区的V基固溶体相降低了Ti元素向熔凝区的迁移速率, 减慢了燃烧区Ti与O的优先反应; 燃烧区形成的TiO₂, V₂O₅和Cr₂O₃混合氧化物和熔凝区O在Ti中大量固溶共同终止了O向合金基体的继续扩散, 从而使Ti-V-Cr阻燃钛合金表现出优异的阻燃功能性.     

Gap exponents for percolation processes with triangle condition

A study is made of the gap exponents for percolation processes with the triangle condition in the subcritical region. It is show that the gaps are given by _t =2 fort=2, 3,. Scaling theory predicts thatP _p (¦C ₀¦S(p))–(p _c –p) andE _p (1/¦C ₀¦; ¦C ₀¦S(p))–(p _c –p)³, whereS(p) is the typical cluster size. It is found that (p _c –p)P _p (|C ₀S(p) ^1–)(p _c –p)^1–2 and (p _c –p)³E _p (1/|C ₀|;|C ₀|S(p) ^1–))(p _c –p)^3–4.     

面向对象建模语言AML的设计与实现

ＡＭＬ语言吸取了Ａｄａ９５ 基本原理和思想,引进它的基本数据类型、语句等设施,对其作更高层次的抽象和扩充．用３ 种有相同名字不同类型的程序包从不同的侧面描述给定模块的模型,提高了系统的完整性和一致性;同时运用二级并发模型和限制设施,详述了系统的并发性和不确定性的描述问题．     

Benson真有效意义下集值优化的广义最优性条件

本文引入了关于集值映射的α-阶Clarke切导数、α-阶邻接切导数及α-阶 伴随切导数的概念,借此建立了约束向量集值优化Benson真有效解导数型的Kuhn- Tucker条件.     

On the p—Local Rank of Finite Groups

In this paper,we shall mainly study the p-solvable finite group in terms of p-local rank,and a group theoretic characterization will be given of finite p-solvabel groups with p-local rank two.Theorem A Let G be a finite p-solvable group with p-local rank plr(G)=2 and Op(G)=1.If P is a Sylow p-subgrounp of G,then P has a normal subgroup Q such that P/Q is cyclic or a generalized quaternion 2-group and the p-rank of Q is at most two.Theorem B Let G be a finite p-solvable group with Op(G)=1.Then the p-length lp(G)≤plr(G);if in addition plr(G)=lp (G) and p≥5 is odd,then plr(G)=0 or 1.