细分图的零维数

设A(G)为简单图G的邻接矩阵。图G的零维数定义为A(G)中0特征值的重数,记为η(G)。S(G)表示非平凡图G的细分图。本文讨论细分图的零维数并分别给出树、单圈图和双圈图的细分图的零维数。     

导出匹配可扩图的韧度

如果图G的每一个导出匹配都包含在图G的一个完美匹配中,则称图G是导出匹配可扩的.用T(G)表示图G的韧度,文章的主要结论是:设G是有2n(n≥3)个顶点的非完全图,如果G是导出匹配可扩的,则2/(n-1) ≤T (G) ≤n-1;对于任意满足2/(n-1) ≤p/q≤n-1,p+q≤2n,1≤q≤n-1的数p/q,都有韧度为p/q的导出匹配可扩图.     

完全图的边带宽的另一证明

图G的边的一个标号f是指边集E（G）到自然数的子集的一个一一映射。图G的边带宽为B’（G）=minB＇f（G）,B＇f（G）是G的所有邻边的标号f的差的绝对值的最大者。本文确定完全图Kn的边带宽：当n=3,4时，B＇（Kn）=2n-4；当n≥5时，B＇（Kn）=n（n-5）/2＋7。     

包含两个三角形的秩为6的双圈图的刻画

图G的秩r(G)定义为其邻接矩阵的秩,图G的特征值定义为其邻接矩阵的特征值,图G的零维数η(G)定义为其邻接矩阵的零特征值的重数。本文主要刻画包含两个三角形的秩为6的双圈图。     

两类序列的连通实现

所有满足di≤n-1（i=1,2,…,n）的n项非负整数序列π=（d1,d2,…dn）的集合记为NSn．任意π∈NSn,如果π是某一n阶简单连通图G的度序列,则称π是连通可图的,相应地,称G为π的一个连通实现．本文将就序列π中整数di相互之间的大小关系来刻划π的实现,主要研究所有序列数均相等的序列π=（d,d,…,d）和仅有一对序列数相等的序列π=（1,2,3,…,i-1,i,i,i＋1,…,n-1）两类序列的连通实现．     

一个五阶图与n个孤立点及路的联图的交叉数

摘要：目前已经确定的两个图的联图的交叉数结果比较少,为此讨论了五阶图G18分别与nK1,Pn的联图的交叉数,得到了cr（G18＋nK1）=Z（5,n）＋n＋[n/2],n≥i;cr（G18＋Pn）=Z（5,n）＋n＋[n＋2,n≥2．其中nK1是n个孤立点构成的图,只是Pn个点的路．     

直径为n-2的图的最小特征值

对于一个图的集合Ψ,若图G是Ψ中所有图的最小特征值达到最小的那个图,则称G是集合Ψ中最小特征值的极小图.文章刻画了直径为n-2的n阶连通图最小特征值及其极小图.     

关于有限可换群的自同态

对于Abel群G,用End G表示G之自同态集。已知结论表明,对于η、ξ∈End G,用（ξη）（x）=ξ（η（x））和（η+ξ）（x）=η（x）+ξ（x）来定义ξη和η+ξ,用1X=X和0X=0来定义1和0,则（End G,+,、,0,1）一个环。简称End G为Abel群G之自同态环。关于有限Abel群G之End G,已经有了一些结论,比如“P~n阶初等Abel群G的自同态环E（G）是具有p~（n~2）个元的有限环,它与有限域K_p上n阶全阵环同构”等。本文用初等因子定理讨论了n阶Abel群自同态的个数范围及特殊情况下这些自同态的构造并做为例题给出了Klein四元群的所有自同态。     

k-路的零度

图G的零度,记为η(G),是指图的邻接谱中零特征值的重数.若一个图既是k-树也是区间图,则称这个图为k-路,记n个顶点的k-路为Pnk.通过对Pkn奇异性的研究证明了Pn2是拟非奇异图.     

关于图的笛卡积尔的DOMINATION数

本文证明了:设H是任意图,G是n阶图,若G满足下列条件之一1)△(G)=n-1;2)G是γ-generalized comb;3)△(G)=n-2且(G)>2,则γ(G×H)≥γ(G)·γ(H),即V.G.Vizing猜想成立。     

卡思卡特城堡

It is worthy of noting that, whilst Crookston Castle witnessed the earlier and happier portion of Mary's variegated life,     

不同的吃喝玩乐

一、吃和喝吃苹果 eat an apple, 吃药 take medicine,吃糖 have some sweets,吃饭 have one's meals,吃馆子 dine out,吃惊 be surprised/     

漏洞百出的教育

Many college freshmen arrive woefully unprepared to do college work, and as disadvantaged populations continue to grow, the share of the American work force that has made it through college is expected to plummet. Many experts blame that educational failure not just on high schools but also on colleges. School & College, a special report by The Chronicle, looks at efforts to fix the system. What reforms would better prepare students for college? What should schools and colleges be doing differently? How should state and federal officials help?     

只要努力,不要后悔

There are numbers of crossroads on our long and unpredictable life journey where we totally have no idea about which direction to choose. No matter what our decision is, we should not turn back, but face the music and go ahead instead. I am this kind of girl who always does try without regretting, one example is how I dealt with my love.     

浅谈移民问题

Migration occurs behind a variety of reasons and has a great effect on the whole world. People may migrate in order to improve their economic situation, or in order to escape civil strife, persecution, and environmental disasters. The impact of migration is complex, bringing both benefits anddisadvantages. This paper briefly talks about the causes of migration, the allocation of benefits, and the ways in which individual countries and the international community deal with this important subject.     

Sister Carrie, an Adherent of Desires

Sister Carrie is one of the most controversial characters in American literature.Thought as a "fallen woman" firstly,she was defined as a "new woman" by some critics later. However, by digging into the motivaton behind the whole process of Carrie's "success", the relationship between Carrie and her creator (the author), the social conditions of then American, it can be found that Carrie has never been free-standing on her thought and she has never found her real-sdf even after becoming a famous actress. In a society dominated by mass consumerism Carrie is only an adherent of her own desires. She also is a representative of all those country girls flooded into cities, a symbol and a sacrifice of the urbanization of America in a time countryside was overcome by cities.     

Improvement of one-cycle controller by use of proportional integral differential controller

1.IntroductionOne-cyclecontrolmethod,whichwasproposedaboutonedecadeago[1],hasbecomeanattractivemethodinspecialfieldssuchaspowerfactorcorrection[2-6],switchingamplifiers[7,8],etc.Themainideaofthiscontrollerisbasedonintegrationofdiodevoltageinone-cycleandforcesittobeexactlyequaltothereferencevalue.Themainadvantageofthiscontrollerisitsrealtimeabilitytorejectthevariationofinputvoltage[1].Despitethisgreatability,ithasnogoodperformancesinrejectingofloaddisturbanceandfollowingreferencecommands.Espec…     

库克斯顿城堡

城堡, 是欧洲典型的建筑之一, 每个城堡都有一个美丽的传说或是一段历史。从本期开始, 我们将推出“城堡之旅”, 带各位读者去浏览、观赏欧洲各地的城堡, 开始一段文化与历史的旅途!     

胡主席在印度,我却在中国

Today, Sunday morning, I sit thinking and typing at my computer. My thoughts are in my homeland, India and my body is in China. The body is here and mind there for a good reason. Mr. Hu is president and I am resident and both are in each other's countries (what a difference the absence of one small letter makes!). Mr. Hu will return in a few days and I will stay on longer.