掺杂Y2O3和BaCeO3提高MOD-YBCO超导性能的研究

本文通过在前驱液中添加过量钇盐和铈的有机盐,采用三氟乙酸盐-金属有机沉积法(TFA-MOD) 在铝酸镧单晶基体上制备了含有纳米氧化钇和纳米铈酸钡的YBCO薄膜. 与纯YBCO薄膜相比,掺杂Y₂O₃/BaCeO₃的YBCO膜的临界转变温度几乎保持不变,为91 K左右. 而掺杂Y₂O₃/BaCeO₃的YBCO膜的临界电流密度达到5.0 MA/cm² (77 K, 0T), 是纯YBCO膜临界电流密度的1.5倍.薄膜中的Y₂O₃和BaCeO₃可能在YBCO内部起到了 有效的钉扎磁通作用. 关键词： 钇钡铜氧薄膜 2O₃和纳米BaCeO₃')" href="#">纳米Y₂O₃和纳米BaCeO₃ 磁通钉扎 三氟乙酸盐-金属有机沉积     

PRIMITIVITY IN NEAR-RINGS WITH LOCALIZED DISTRIBUTIVITY CONDITIONS

Abstract

Let K, S, T be subsets of a near-ring R. Then K is (S, T)-distributive if: s(k ₁ + k ₂)t = sk ₁ t + sk ₂ t, for each k ₁, k ₂ ε K, s ε S, t ε T; and K is (S, T)-d.g. on X if K is (S, X)-distributive and T is contained in the additive subgroup generated by X. This paper considers υ-primitivity and the associated ?_υ radicals under various such conditions, particularly where S, T, and K are powers of R. Natural examples which illustrate and delimit the theory are given.     

HOMOGENEOUS FUNCTIONS DETERMINED BY CYCLIC SUBMODULES

Abstract

For a unital module V over a commutative ring R, let C denote the collection of cyclic submodules. The ring ?_R(V;C) = {f ε End_R V |f(C) ?C, ?C ε_R (V;C) has been the object of several recent studies in which the structure of ?_R(V;C) is related to the triple (V, R,C). Here we introduce a new ring H_R(V;C) containing ?(V;C) and investigate its structure in terms of the parameters (V, R, C).     

ON RADICAL THEORY OF NON-ZEROSYMMETRIC NEAR-RINGS

Abstract

This paper is based on an expository talk given at the International Conference on Radicals and Rings ICOR 97. Our aim is not to give a comprehensive survey of the subject. We rather wish to present some selected results and on their basis to analyze the development of radical theory of near-rings, emphasizing the role of non-zerosymmetric near-rings. Besides we present some new results on Jacobson type radicals of non-zerosymmetric near-rings.     

POLARITIES FOR NEARRINGS

Abstract

We show that the left and right polar sets of a nearring N form complete bounded lattices P_R(N) and P_L(N). We consider properties of P_L(N) and its elements, which are ideals, when N is 3-semiprime. If in addition N is zero-symmetric we strengthen these results and use them to describe a class in which 3-semiprime nearrings are strongly 3-semiprime.     

Parallel and bootstrapped stochastic approximation

Parallelization of stochastic approximation procedures can reduce computation and total observation time of a system. Concerning the number of all observations used by the pure sequential and the suggested parallel method a weak invariance principle implies the asymptotic equivalence of both methods. A loglog invariance principle and a rate of a.s. convergence result describe the pathwise properties. Due to the parallel design asymptotic confidence regions can readily be constructed either by computing the bootstrap distribution or the Gaussian limit distribution determined by the empirical covariance     

Identities for the Ramanujan zeta function

We prove formulas for special values of the Ramanujan tau zeta function. Our formulas show that L(Δ,k)$L(\mathrm{\Delta },k)$ is a period in the sense of Kontsevich and Zagier when k?12$k?12$. As an illustration, we reduce L(Δ,k)$L(\mathrm{\Delta },k)$ to explicit integrals of hypergeometric and algebraic functions when k∈{12,13,14,15}$k\in \{12,13,14,15\}$.     

Posner and herstein theorems for derivations of 3-prime near-rings

The analog of Posner's theorem on the composition of two derivations in prime rings is proved for 3-prime near-rings. It is shown that if d is a nonzero derivation of a 2-torsionfree 3-prime near-ring N and an element a ? N is such that ax^d = x^da for all x ? N, then a is a central element. As a consequence it is shown that if d\ and d₂ are nonzero derivations of a 2-torsionfree 3-prime near-ring N and x^d1y^d2 = y^d2x^d1 for all x, y ? N, then N is a commutative ring. Thus two theorems of Herstein are generalized