左半正则纯整群并半群的左半织积结构

作为拟Ｃ－半群的推广,本文定义了左半正则纯整群并群,给出了它的左半织积结构。讨论了两类特殊的右（右）半正则纯整群并半群,得出了左（右）半正则纯整群并半群类与拟Ｃ－半群类之间的关系。     

正规Ehresmann型wrpp半群

众所周知,Clifford半群是正则半群类中的一类重要半群,本文定义正规 Ehresmann型wrpp半群,它是Clifford半群在wrpp半群类中的推广,给出了此类半群的若干刻划.     

Three Constructions of Authentication Codes with Perfect Secrecy

In this paper, we present three algebraic constructions of authentication codes with secrecy. The first and the third class are optimal. Some of the codes in the second class are optimal, and others in the second class are asymptotically optimal. All authentication codes in the three classes provide perfect secrecy.     

On Douglas general (<Emphasis Type="Italic">α</Emphasis>, <Emphasis Type="Italic">β</Emphasis>)-metrics

Douglas metrics are metrics with vanishing Douglas curvature which is an important projective invariant in Finsler geometry. To find more Douglas metrics, in this paper we consider a class of Finsler metrics called general (α, β)-metrics, which are defined by a Riemannian metric \(\alpha = \sqrt {{a_{ij}}\left( x \right){y^i}{y^j}} \) and a 1-form β = b _i (x)y ⁱ . We obtain the differential equations that characterizes these metrics with vanishing Douglas curvature. By solving the equivalent PDEs, the metrics in this class are totally determined. Then many new Douglas metrics are constructed.     

复杂设计下类均值复制与类加权均值复制的比较（英文）

复制数据是处理抽样调查中数据项目缺失的一种常用方法。在两种常见模型及复杂抽样设计下，本文对处理数据项目缺失的类均值复制和类加权均值复制方法进行了对比。     

单调类定理的一个集合论证明

本文利用集合论中的序数理论和超限归纳法,给出概率测度论中一个集族生成的最小σ代数,最小λ类和最小单调类的具体形式,并给出单调类定理一个直接的证明.     

Radical constructions in the presence of two universal classes

Summary The constructions for the lower radical class, the upper radical class, and the smallest semisimple class were introduced in 1953 by KUROSH. Generalizations of the lower radical class and smallest semisimple class constructions were given in 1970 by LEAVITT. Here these constructions are investigated in the presence of two universal classes. The result of KUROSH for the lower radical construction is generalized and similar results are obtained for the other constructions. Entrata in Redazione il 12 ottobre 1970.     

Neighborhood contraction in graphs

Let G be a graph and v be any vertex of G. Then the neighborhood contracted graphG_v of G, with respect to the vertex v, is the graph with vertex set V ? N(v), where two vertices u,w ∈ V ? N(v) are adjacent in G_v if either w = v and u is adjacent to any vertex of N(v) in G or u,w ? N[v] and u,w are adjacent in G. The properties of the neighborhood contracted graphs are discussed in this paper. The neighborhood contraction in some special class of graphs, the domination in a graph and the neighborhood contracted graphs are discussed in the paper.     

An anisotropic geometrical approach for non-relativistic extended dynamics

In this paper we present the distinguished (d-) Riemannian geometry (in the sense of nonlinear connection, Cartan canonical linear connection, together with its d-torsions and d-curvatures) for a possible Lagrangian inspired by optics in non-uniform media. The corresponding equations of motion are also exposed, and some particular solutions are given. For instance, we obtain as geodesic trajectories some circular helices (depending on an angular velocity $\omega $ ), certain circles situated in some planes (ones are parallel with $xOy $ , and other ones are orthogonal on $xOy$ ), or some straight lines which are parallel with the axis $Oz$ . All these geometrical geodesics are very specific because they are completely determined by the non-constant index of refraction $n(x)$ .     

DISCRETE FUNCTORS

Abstract

The concept of a T-discrete object is a generalization of the notion of discrete spaces in concrete categories. In this paper. T-discrete objects are used to define discrete functors. Characterizations of discrete functors are given and their relation to other important functors are studied. A faithful functor T: A → X is discrete iff the full subcategory B of A consisting of all T-discrete objects is (X-iso)-coreflective in A. It follows that the existence of bicoreflective subcategories is equivalent to the existence of suitable discrete functors. Finally, necessary and sufficient conditions are found such that for a given functor T: A → X, the full subcategory B of A consisting of all T-discrete A-objects is monocoreflective in A.     

Prime Ideals in Algebras Determined by Submonoids of Nilpotent Groups

The prime spectrum of the semigroup algebra K[S] of a submonoid S of a finitely generated nilpotent group is studied via the spectra of the monoid S and of the group algebra K[G] of the group G of fractions of S. It is shown that the classical Krull dimension of K[S] is equal to the Hirsch length of the group G provided that G is nilpotent of class two. This uses the fact that prime ideals of S are completely prime. An infinite family of prime ideals of a submonoid of a free nilpotent group of class three with two generators which are not completely prime is constructed. They lead to prime ideals of the corresponding algebra. Prime ideals of the monoid of all upper triangular n × n matrices with non-negative integer entries are described and it follows that they are completely prime and finite in number.     

Integral Modular Categories of Frobenius-Perron Dimension <Emphasis Type="Italic">pq</Emphasis><Superscript><Emphasis Type="Italic">n</Emphasis></Superscript>

Integral modular categories of Frobenius-Perron dimension pq ⁿ , where p and q are primes, are considered. It is already known that such categories are group-theoretical in the cases of 0 ≤ n ≤ 4. In the general case we determine that these categories are either group-theoretical or contain a Tannakian subcategory of dimension q ⁱ for i > 1. We then show that all integral modular categories \(\mathcal {C}\) with \(\text {FPdim}(\mathcal {C})=pq^{5}\) are group-theoretical, and, if in addition p < q, all with \(\text {FPdim}(\mathcal {C})=pq^{6}\) or pq ⁷ are group-theoretical. In the process we generalize an existing criterion for an integral modular category to be group-theoretical.     

Finding a complete set of solutions or proving unsolvability for certain classes of matrix polynomial equations with commuting coefficients

Two classes of matrix polynomial equations with commuting coefficients are examined. It is shown that the equations in one class have complete sets of solutions, whereas the equations in the other class are unsolvable. A method is given for finding the solution set of an equation in the former class.     

On distinct distances among points in general position and other related problems

A set of points in the plane is said to be in general position if no three of them are collinear and no four of them are cocircular. If a point set determines only distinct vectors, it is called parallelogram free. We show that there exist n-element point sets in the plane in general position, and parallelogram free, that determine only O(n ²/√log n) distinct distances. This answers a question of Erd?s, Hickerson and Pach. We then revisit an old problem of Erd?s: given any n points in the plane (or in d dimensions), how many of them can one select so that the distances which are determined are all distinct? — and provide (make explicit) some new bounds in one and two dimensions. Other related distance problems are also discussed.     

The limits of nested subclasses of several classes of infinitely divisible distributions are identical with the closure of the class of stable distributions

It is shown that the limits of the nested subclasses of five classes of infinitely divisible distributions on ${\mathbb{R}^{d}}$ , which are the Jurek class, the Goldie– Steutel–Bondesson class, the class of selfdecomposable distributions, the Thorin class and the class of generalized type G distributions, are identical with the closure of the class of stable distributions. More general results are also given.     

Root n estimates of vectors of integrated density partial derivative functionals

Based on a random sample of size \(n\) from an unknown \(d\) -dimensional density \(f\) , the nonparametric estimations of a single integrated density partial derivative functional as well as a vector of such functionals are considered. These single and vector functionals are important in a number of contexts. The purpose of this paper is to derive the information bounds for such estimations and propose estimates that are asymptotically optimal. The proposed estimates are constructed in the frequency domain using the sample characteristic function. For every \(d\) and sufficiently smooth \(f\) , it is shown that the proposed estimates are asymptotically normal, attain the optimal \(O_p(n^{-1/2})\) convergence rate and achieve the (conjectured) information bounds. In simulation studies the superior performances of the proposed estimates are clearly demonstrated.     

Calculating the branch points of the eigenvalues of the Coulomb spheroidal wave equation

A method for computing the eigenvalues λ _mn (b, c) and the eigenfunctions of the Coulomb spheroidal wave equation is proposed in the case of complex parameters b and c. The solution is represented as a combination of power series expansions that are then matched at a single point. An extensive numerical analysis shows that certain b _s and c _s are second-order branch points for λ _mn (b, c) with different indices n ₁ and n ₂, so that the eigenvalues at these points are double. Padé approximants, quadratic Hermite-Padé approximants, the finite element method, and the generalized Newton method are used to compute the branch points b _s and c _s and the double eigenvalues to high accuracy. A large number of these singular points are calculated.     

Extremal behavior of recurrent random sequences

A process Y _n , n ≥ 1, satisfying the stochastic recurrent equation Y _n = A _n Y _n?1 + B _n , n ≥ 1, Y ₀ ≥ 0, is studied in the paper; here (A _n , B _n ), n ≥ 1, are independent identically distributed pairs of nonnegative random variables. The cases when the values A _n have a lognormal and log-Laplace distributions are considered. The tail index κ (for a stationary distribution) and the extremal index ? are studied. In the lognormal case, κ is determined and some useful properties of ? are established. In the log-Laplace case the both characteristics are obtained in explicit form.     

Convexity,moduli of smoothness and a Jackson-type inequality

For a Banach space B of functions which satisfies for some m>0

$ \max ({\|F+G\|}_B,{\|F-G\|}_B)\geqq ({\|F\|}^s_B+m{\|G\|}^s_B)^{1/s},\quad \forall \,F,G\in B $

(?)

a significant improvement for lower estimates of the moduli of smoothness ω ^r (f,t) _B is achieved. As a result of these estimates, sharp Jackson inequalities which are superior to the classical Jackson type inequality are derived. Our investigation covers Banach spaces of functions on ? ^d or \(\mathbb{T}^{d}\) for which translations are isometries or on S ^d?1 for which rotations are isometries. Results for C ₀ semigroups of contractions are derived. As applications of the technique used in this paper, many new theorems are deduced. An L _p space with 1<p<∞ satisfies (?) where s=max??(p,2), and many Orlicz spaces are shown to satisfy (?) with appropriate s.