关于k-消去二分图的一些结果

图 G的一个 k-正则支撑子图称为 G的 k-因子 ,若对 G的任一边 e,图 G- e总存在一个 k-因子 ,则称 G是 k-消去图 .证明了二分图 G=( X,Y) ,且 | X | =| Y|是 k-消去图的充分必要条件是 k| S|≤ r1 + 2 r2 +…+ k( rk+… + rΔ) - ε( S)对所有 S X成立 .并由此给出二分图是 k-消去图的充分度条件 .     

2003年全国攻读硕士学位研究生入学考试数学试题(一)(附答案)

一、填空题 (本题共 6小题 ,每小题 4分 ,满分 2 4分 )( 1 )　 limx→ 0 ( cosx) 1ln( 1+ x2 )　　 =　 1e　。( 2 )　曲面 z=x2 +y2 与平面 2 x+4 y-z=0平行的切平面的方程是　 2 x+4 y-z=5　。( 3 )　设 x2 =∑∞n=0ancosnx( -π≤ x≤π) ,则 a2 =　 1　( 4)　从 R2 的基 α1=10 ,α2 =　 1-1 到基 β1=11 ,β2 =12 的过渡矩阵为 　 2　　　 3-1　　 -2 　。( 5)　设二维随机变量 ( X,Y)的概率密度为f ( x,y) =6x,　　 0≤ x≤ y≤ 1 ,0 ,　　　其他则 P{ X+Y≤ 1 } =　 14 　。( 6)　已知一批零件的长度 X(单位 :cm)服从正态分布 N(…     

Traces on an (AF)-Algebra

Let A= U A_n be an (AF)-algebra with identity e, where A_n = M(p(n)),p(n) = (p~(n)) ∈Z_(++)~(r(n)), A_n→A_(n+1), e∈A_n, n, τ(A) be the space of alltracial states on A,G(A) = lim (Z~(r(n)),φ_n) be the dimension group of A,φ_u(G) bethe state space of G(A), where u =φ_(n∞).(p(n)) is an ordered unit of G(A).     

再探半角余弦和的上界

近期在阅读贵刊 2 0 0 2年第 3期时 ,看到了安徽师范大学的郭老师给出的《半角的余弦和上界的加强》一文 ,觉得证明较繁 .实际上利用柯西不等式结合恒等式 cos A cos B cos C =1 rR证明较为简便 .现证如下 :cos A2 cos B2 cos C2　≤ 3(cos2 A2 cos2 B2 cos2 C2 )　 = 32 (3 cos A cos B cos C)　 = 32 (3 1 rR) =6 3r2 R.另外我还利用均值不等式得到了关于半角余弦和的两个上界的一个隔离 .cos A2 cos B2 cos C2 =23.(32 cos A2 32 cos B2 32 cos C2 )≤ 13(94 cos2 A2 cos2 B2 cos2 C2 )=33 (174 r2 R) ,∵　 …     

二部平衡公平划分的一个下界

设V_1,V_2是图G的一个二部划分.如果一1≤|V_1|-|V_2|≤1,则称V_1,V_2是G的一个二部平衡划分.对于n个顶点m条边的简单图G,本文证明了:(1)若G是k-正则图(k≥3),则G存在一个最小二部平衡划分V_1,V_2,使得max{e(V_1),e(V_2)}≥((k-1)m)/4k;(2)如果r是大于4的实数,且当n是偶数时△(G)≤((3r-4))/(r+4)δ(G)-(2r)/(r+4),当n是奇数时△(G)≤(3r-4)/(r+4)δ(G)-(8r)/(r+4),那么G存在一个二部平衡划分,使得min{e(V_1),e(V_2)}≥m/r,这里e(V_i)表示G中两个顶点都在V_i中的边的数目.     

THE CONVERGENCE OF APPROACH PENALTY FUNCTION METHOD FOR APPROXIMATE BILEVEL PROGRAMMING PROBLEM

' 1 IntroductionWe collsider the fOllowi11g bilevel programndng problen1:max f(x, y),(BP) s.t.x E X = {z E RnIAx = b,x 2 0}, (1)y e Y(x).whereY(x) = {argmaxdTyIDx Gy 5 g, y 2 0}, (2)and b E R", d, y E Rr, g E Rs, A, D.and G are m x n1 s x n aild 8 x r matrices respectively. If itis not very difficult to eva1uate f(and/or Vf) at all iteration points, there are many algorithmeavailable fOr solving problem (BP) (see [1,2,3etc1). However, in some problems (see [4]), f(x, y)is too com…     

C2(4,k) 中的强支撑可迹图

设2≤h≤3,l0,k≥0是整数,C_h(l,k)是由h-边连通简单图组成的集合,图G∈C_h(l,k)当且仅当对图G的任意一个二边割或三边割X,图G-X的每个分支都至少有︱V(G)-k︱/l个点.设e=u_1v_1和e'=u_2v_2是图G的两条边.若e≠e',G(e,e')是将图G中的边e=u_1v_1和e'=u_2v_2分别用路u_1v_ev_1和u_2v_e'v_2替换得到的图(其中,v_e,v_e'是不在V(G)中的两个新的点).若e=e',G(e,e')是将图G中的边e=u_1v_1用路u_1v_ev_1替换得到的图,也记作G(e).若对任意的e,e'∈E(G),G(e,e')都有支撑(v_e,v_e')迹,则称图G是强支撑可迹的.作者证明了,若图G∈C_2(4,k)且|V(G)|5k,则要么图G是强支撑可迹图,要么存在e,e'∈E(G),使得G(e,e')可以收缩成一个有限图类F中的图.当k=4时,F被完全确定了.     

A RECOGNITION OF SIMPLE GROUPS PSL（3, q） BY THEIR ELEMENT ORDERS

For any group G, denote byπe(G) the set of orders of elements in G. Given a finite group G, let h(πe (G)) be the number of isomorphism classes of finite groups with the same set πe(G) of element orders. A group G is called k-recognizable if h(πe(G)) = k <∞, otherwise G is called non-recognizable. Also a 1-recognizable group is called a recognizable (or characterizable) group. In this paper the authors show that the simple groups PSL(3,q), where 3 < q≡±2 (mod 5) and (6, (q-1)/2) = 1, are recognizable.     

On the adjacent vertex-distinguishing equitable edge coloring of graphs

Let G(V, E) be a graph. A k-adjacent vertex-distinguishing equatable edge coloring of G, k-AVEEC for short, is a proper edge coloring f if (1) C(u)≠C(v) for uv ∈ E(G), where C(u) = {f(uv)|uv ∈ E}, and (2) for any i, j = 1, 2,… k, we have ||Ei| |Ej|| ≤ 1, where Ei = {e|e ∈ E(G) and f(e) = i}. χáve (G) = min{k| there exists a k-AVEEC of G} is called the adjacent vertex-distinguishing equitable edge chromatic number of G. In this paper, we obtain the χáve (G) of some special graphs and present a conjecture.     

从L~p(G,A)到L~p(G,X)的L~1(G,A)-模同态和不变算子(1

于树模 《数学年刊A辑(中文版)》1990,(6)