RS联合最佳逼近

1 引言 设X是Hausdorff空间,C(X)表示定义在X上的实连续函数全体组成的空间,λ_i>0(i=1,…,N)(1≤N≤+∞)。且sum from i=1 to n(λ_i)=1,再设X_i是X的紧子集(i=1,…,N),(?)X_i至少含有n+1个点,对f∈C(X_i)令     

不等式研究成果集锦(17)

20 2　设 xi >0 ,i =1,2 ,… ,n,n≥ 2 ,∑ni= 1xi =1,记 Ek(x) =Ek(x1 ,x2 ,… ,xn) =∑1≤ i1 <… 0 )时 ,有Ek(1x1 - m,… ,1xn - m)≥ Ckn(n - m) k.(续铁权 .2 0 0 1,1)2 0 3　设 Ai >0 ,λk>0　 (i =1,2 ,… ,n;k = 1,2 ,… ,n) ,∑ni=1Ai ≤π,n∈ N.(1)若 0≤λ≤ 1,有C2n(1-λ21 λ2 ) 2 (λπ) 2 ≤ (n - 1 cosλπ) .∑nk= 1cos2 λAk - cosλπ(∑ni=1cosλAi) 2 ≤ C2n(λπ) 2 ,等号同时成立当且仅当λ=0 .(2 )若 0≤λ≤ 1,有4λ2 C2ncos2 λ2 π≤ (n - 1 cosλ…     

边界层的奇性分析

设 λ∈[λ_0,∞)(0<λ_0<<1),H_1=H_0~2(Ω)∩H~3(Ω),H_2=H_0~1(Ω)∩H~3(Ω),H_3=H~3(Ω),k_1=1/4,k_2=1/12,k_3=1/36,J_6(λ)=integral d(x,Γ)≥a~λlog(1+a~(-β) |△▽(u_e-u)|~2dx,α(ε)=1/6×log_ε1/C(C>1).我们考虑问题(?)定理.若 u=f∈H_i,对问题(1),有如下三种情形成立:i)正规区域 当 λ_0≤λ≤1/6-α(ε)时,有J_6(λ)≤C‖f‖_(H~3(Ω))~2;ii)奇性增长区域当1/6-α(ε)<λ<1/6+k_i/6时,有J_6(λ)≤Cε~(-6λ+2k_i)‖f‖_(H~3(Ω))~2;iii)奇性稳定区域当 λ≥1/6+(k_i)/6时,有J_6(λ)≤Cε~(-1+k_i)‖f‖_(H~3(Ω))~2;其中 i=1,2,3,β≥(45)/(32),C 为同 ε 无关的常数(见图1).     

有限域上的高斯和与有理点的计算

设f是有限域Fq上的n元m项多项式,D_f∈Z_(≥0)~(n×m)为其次数矩阵,用N(f)表示由超曲面f=0在仿射空间An(Fq)确定的Fq-有理点的个数.若矩阵A∈Z~(n×m)在环Z/(q-1)Z中与Df行等价,则记为D_fr～A.本文利用高斯和给出了当m≤n且0D_fr～diag(λ_1,···,λ_m),其中λi∈{1,3}时N(f)的具体表达式,从而推广了已知结论.     

Mn(C)中的不可约性

对于Mn(C)(所有n×n矩阵的全体)中的不可约矩阵得到以下结果:对于任意A∈Mn(C),设λ1,λ2,…,λm为A的所有特征值,这里m≤n而且当i≠j时,λi≠λj.则A是不可约的当且仅当任意P∈A'(A),P*=P=P2,有σ(P|ker(A-λ1))=σ(P|ker(A-λ2))=…=σ(P|ker(A-λm))为单点集.     

三角域上Bernstein多项式的Lipschitz常数

设T是平面上以T₁,T₂,T₃为顶点的三角形,f(p)为定义在T上的函数,称Bⁿ(f,P):=(?)f(i/n,j/n,k/n)B_i,j,kⁿ(P),为f的n次Bernstein多项式,这儿B_i,j,kⁿ(P):(n!)/(i!j!k!)uⁱv^jω^k是Bernstein基函数,(u,v,w)是P关于T的重心坐标。 B.M.Brown等人对单变量的Bernstein多项式证明了如果f∈Lip_Aλ,0<λ≤1,则对所有的n,都有B^α(f,x)∈Lip_Aλ。本文的目的是对定义在三角域T:{(x,y):x≥0,y≥0,x+y≤1}上的Bernstein多项式证明了类似的结果: 设f(P)∈Lip_Aλ,0<λ≤1,则对所有的n,Bⁿ(f,P)∈Lip_(2^1/2λA)λ,并且,在一定意义上,常数2^1/2λA是最好的。 上述结果对于任意的锐角或直角三角形T,也是成立的。 最后还指出,当T可为钝角三角形时,则不存在同一常数C,使对所有的n和任意三角形T,有Bⁿ(f,P)∈Lip_cλ。     

加权Bloch空间上复合算子的线性组合

设λi(i=1,...,N)是一列非0的数,D是一维复平面C的开单位圆盘,φi(i=1,...,N)是D的解析自映射,本文研究了定义在加权Bloch空间上复合算子线性组合∑i=1NλiCφi、的紧致性.     

求解逆特征值问题的牛顿类方法的收敛判据

<正>1引言多年来,众多数学工作者在推导和分析如下定义的逆特征值问题(IEP)的理论和算法上表现出了相当大的兴趣.以下我们设c=(c_1,c_2,….c_n)~T E R~n,{A_i}_(i=1)~n是n个实对称的n×n矩阵.定义A(c)=∑ni=1c_iA_i.(1)设A(c)的特征值为{λ_i(c)}_(i=1)~n且λ_1(c)≤λ_2(c)≤…≤λ_n(c).设{λ_i~*)_(i=1)~n为任意给定的n个数并且满足λ_1~*≤λ_2~*≤…≤λ_n~*.我们这里考虑的IEP就是寻找向量c~*∈R~n使得λ_i(c~*)=λ_i~*对任意的i=1,2,…,n.(2)     

关于变量个数的几个单调函数

目前 ,人们对比较变量大小之间关系的不等式较为关注 ,但是 ,笔者发现 ,有一些不等式在变量的定义域内 ,经过变量置换 ,可以得到关于变量个数的一些单调函数 .为了讨论方便 ,设实函数 f(x)的定义域为x∈(a ,b) ,实数Pi>0 (1≤i≤n) ,n∈N .记λn=∑ni=1Pi,An=∑ni=1Pixi/λn,Bn=∑ni=1Pif(xi) /λn.定理　若 f(x)在区间 (a ,b)上为凸函数 ,则φ(n) =λn[f(An) -Bn]是n的递增函数 .证　设x′i∈ (a ,b) ,根据凸函数定理有f(A′n)≥B′n (1)A′n=∑ni=1Pix′i/λn,B′n=∑ni=1Pif(x′i) /λn.令x′1=x′2 =… =x′n - 1=An - 1,x′n=xn…     

康托洛维奇不等式的一个简证及其极限形式

线性规划中有一个康托洛维奇不等式 (Канторович) :若ai >0 (i=1 ,2 ,… ,n)　∑ni=1ai =1 ,0<λ1 ≤λ2 ≤… ≤λn,则 :(∑ni=1λiai) (∑ni=1aiλi) ≤(λ1 +λn) 24λ1 λn《中学数学》和《中学教研》杂志先后给出了该不等式的多种证明 ,有些需用高等方法 ,有些初等方法又相当复杂 ,本文给出该不等式一个极简证明和其极限形式。一、简证 :设f(x) =(∑ni=1λiai)x2 + (λ1 +λn)x +λ1 λn(∑ni=1aiλi)∵λi-(λ1 +λn) + λ1 λnλi 　　 (i=1 ,2 ,… ,n)=(λi-λ1 ) (λi-λn)λi≤ 0而ai>0∴λiai-(λ1 +λn)ai+ λ1 λnai…     

对n个函数的最佳同时L_1逼近

1 G.M.Phillips和B.N.Sahney在[1]中讨论了对两个实值函数f_1(x)和f_2(x)的最佳同时L_1逼近问题.接着,A.S.B.Holland,J.H.McCabe,G.M.Phillips和 B.N.Sahney在[2]中把[1]的部分结果推广到了n个实值函数的情形. 按照[2],n个实值函数的最佳同时L_1逼近有三种不同提法,它们可以分别定义如下.     

复赋范空间中复RS集的最佳同时逼近

研究了复赋范空间中具限制系数的广义多项式集G对无穷序列的最佳同时逼近问题,得到了特征定理;当G是复RS集时还得到了惟一性定理．     

On vector valued function approximation using a peak norm

A peak norm is defined for L_p spaces of E-valued Bochner integrable functions, where E is a Banach space, and best approximations from a sun to elements of the space are characterized. Applications are given to some families of simultaneous best approximation problems.     

Characterization of semicontinuity of solutions to abstract optimization problems

Abstract

We develop a theory of best simultaneous approximations for closed downward sets in a conditionally complete lattice Banach space X with a strong unit. We study best simultaneous approximation in X by elements of downward and normal sets, and give necessary and sufficient conditions for any element of best simultaneous approximation by a closed subset of X. We prove that a downward subset of X is strictly downward if and only if each its boundary point is simultaneous Chebyshev.     

Closed convex sets and their best simultaneous approximation properties with applications

We develop a theory of best simultaneous approximation for closed convex sets in a conditionally complete lattice Banach space X with a strong unit. We study best simultaneous approximation in X by elements of closed convex sets, and give necessary and sufficient conditions for the uniqueness of best simultaneous approximation. We give a characterization of simultaneous pseudo-Chebyshev and quasi-Chebyshev closed convex sets in X. Also, we present various characterizations of best simultaneous approximation of elements by closed convex sets in terms of the extremal points of the closed unit ball B _X* of X*.     

关于非线性共同逼近的强唯一性

本文首先指出文献［１］中的一个错误，举例说明弱拟凸集的最佳逼近未必具有广义强唯一性，进而讨论两类共同逼近的强唯一性，在空间是一致凸、逼近集是共同太阳集的条件下，证明了最佳共同逼近具有广义强唯一性     

Best Simultaneous Local Approximation in the Lp Norms

We study the behavior of the best simultaneous approximation to two functions from a convex set in L^p spaces, 2<p<∞, on a finite union of intervals when its measure tends to zero. In particular, we give su?cient conditions over the differentiability of two functions to assure existence of the best simultaneous local approximation from the class of algebraic polynomials of a fixed degree. These conditions are weaker than the ordinary differentiability given in previous works. More precisely, we consider differentiable functions in the sense L^p.     

SimultaneousL 1 approximation of a compact set of real-valued functions

Summary In this paper the uniqueness results found in simultaneous Chebychev approximation are extended to simultaneousL ₁ approximation. In particular a sufficient condition to guarantee uniqueness of a best approximate to aL ₁ compact set is given.This paper is taken in part from a thesis to be submitted by M. P. Carroll in partial fulfillment of the requirements for the Ph. D. degree in the Department of Mathematics at Rensselaer Polytechnic Institute.     

On well posedness of best simultaneous approximation problems in Banach spaces

The well posedness of best simultaneous approximation problems is considered. We establish the generic results on the well posedness of the best simultaneous approximation problems for any closed weakly compact nonempty subset in a strictly convex Kadec Banach space. Further, we prove that the set of all points inE(G) such that the best simultaneous approximation problems are not well posed is a u- porous set inE(G) whenX is a uniformly convex Banach space. In addition, we also investigate the generic property of the ambiguous loci of the best simultaneous approximation.     

Multiple Container Packing: A Case Study of Pipe Packing

While the problem of packing single containers and pallets has been thoroughly investigated very little attention has been given to the efficient packing of multiple container loads. Normally in practice a multiple container load is packed by a single container algorithm used in a greedy fashion. This paper introduces the issues involved in multiple container loading. It lays out three different strategies for solving the problem: sequential packing using a single container heuristic, pre-allocating items to the containers and choosing container loads using simultaneous packing models. The principal simultaneous models are pattern selection IP models. We present an application of packing pipes in shipping containers using two pattern selection IP models, a pattern selection heuristic, a sequential greedy algorithm and a pre-allocation method. The experimental results use randomly generated data sets. We discuss several useful insights into the methods and show that for this application the pattern selection methods perform best.