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GRAPHS WITH ONE HOLE AND COMPETITION NUMBER ONE
KIM SUH-RYUNG Korean Mathematical Society 2005 대한수학회지 Vol.42 No.6
Let D be an acyclic digraph. The competition graph of D has the same set of vertices as D and an edge between vertices u and v if and only if there is a vertex x in D such that (u, x) and (v, x) are arcs of D. The competition number of a graph G, denoted by k(G), is the smallest number k such that G together with k isolated vertices is the competition graph of an acyclic digraph. It is known to be difficult to compute the competition number of a graph in general. Even characterizing the graphs with competition number one looks hard. In this paper, we continue the work done by Cho and Kim[3] to characterize the graphs with one hole and competition number one. We give a sufficient condition for a graph with one hole to have competition number one. This generates a huge class of graphs with one hole and competition number one. Then we completely characterize the graphs with one hole and competition number one that do not have a vertex adjacent to all the vertices of the hole. Also we show that deleting pendant vertices from a connected graph does not change the competition number of the original graph as long as the resulting graph is not trivial, and this allows us to construct infinitely many graph having the same competition number. Finally we pose an interesting open problem.
THE NUMBER OF 4-CYCLES IN A TENSOR PRODUCT OF TWO GRAPHS
Kim, Suh-Ryung,Park, Chang Hoon,Park, In-Sook 慶熙大學校 1997 論文集 Vol.26 No.-
두 그래프 G〓(V(G),E(G))와 H〓(V(H),E(H))의 텐서곱은 기호 G??H로 나타내어지며, V(G)와 V(H)의 cartesian곱을 점들의 집합으로 가지고, x와 y가 G에서 u와 v가 H에서 각각 선으로 맺어지는 것을 두 점 (x,y)와 (u,v)가 선으로 맺어질 필요충분조건으로 가진다. 어떤 그래프가 두 그래프의 텐서곱인 그래프와 같은 꼴일 때 그 그래프는 텐서합성그래프라 불린다. 이 논문은 텐서합성그래프의 구조에 대하여 연구하였다. 논문의 주요 결과들은 다음과 같다. bipartite 그래프 G와 n개의 성분(component)들로 이루어져 있으며 그 성분 각각이 길이가 1인 path인 그래프의 텐서합성그래프는 2n개의 성분들로 이루어져 있으며 각 성분이 G인 그래프임을 보였다. 텐서곱에 대하여 제곱근을 갖는 forest는 동형 하에서는 유일하다는 것을 보였다. 또한 두 그래프 G와 H의 텐서곱인 그래프의 4-cycle의 개수를 G, H 각 그래프에서의 길이가 1인 path의 개수, 길이가 2인 path의 개수, 4-cycle의 개수를 사용하여 세는 공식을 찾았고 이 공식을 여러 특수한 형태를 가지는 텐서합성 그래프의 chordless 4-cycle의 개수를 계산하였다.
Kim, Mi-Ryung,Lee, Hyun-Sun,Choi, Hyeon-Son,Kim, Sun Young,Park, Yooheon,Suh, Hyung Joo Humana Press 2014 Applied biochemistry and biotechnology Vol.173 No.4
<P>UVA is responsible for numerous biological effects on the skin, including premature aging characterized by wrinkles, leathery texture, and mottled pigmentation. The objective of this study was evaluating the protective effect of ginseng leaf extract prepared by Ultraflo L on skin from photodamage. Anti-wrinkle effect of ginseng leaf extract with or without Ultraflo L treatment were tested on human keratinocyte cells (HaCaT) irradiated with ultraviolet (UV) A. Ginseng leaves inhibited ROS generation, GHS depletion, and expression of MMP-2 and MMP-9 induced by UVA irradiation. The glutathione (GSH) content of the cells was significantly increased by over 25?μg?mL(-1) of Ultraflo-treated extract (UTGL) as well as by over 100?μg?mL(-1) of nonenzyme-treated extract (NEGL) compared to control. UTGL and NEGL treatments significantly decreased expression of metalloproteinase (MMP)-2 and 9 compared with control, but inhibitory effects of two groups on expression of MMPs were not significantly different. Overall, ULtraflo L-treated ginseng leaves inhibited ROS generation, GHS depletion, and expression of MMP-2 and MMP-9 in UVA photodamaged HaCat cells. From these results, enzyme-treated ginseng leaf extract has advantages over untreated ginseng leaves and have potential as a skin protective ingredient against UVA-induced photodamage.</P>
Controlling the magnetic properties of layered Cr₂Te₃ ultra-thin film via ex-situ annealing
In Hak Lee,Yeong Gwang Khim,Jae Un Eom,Jung Yun Kee,Hyuk Jin Kim,Byoung Ki Choi,Min Jay Kim,Younghak Kim,Byeong-hyeon Lee,Sung Ok Won,Hoyoung Suh,Hye Jung Chang,Ryung Kim,Minyoung Jung,Kyeong Jun Lee 한국자기학회 2022 한국자기학회 학술연구발표회 논문개요집 Vol.32 No.2
On CCE graphs of doubly partial orders
Kim, Seog-Jin,Kim, Suh-Ryung,Rho, Yoomi Elsevier BV, North-Holland 2007 Discrete Applied Mathematics Vol.155 No.8
<P><B>Abstract</B></P><P>Let <I>D</I> be a digraph. The competition-common enemy graph (CCE graph) of <I>D</I> has the same set of vertices as <I>D</I> and an edge between vertices <I>u</I> and v if and only if there are vertices w and <I>x</I> in <I>D</I> such that (w,u), (w,v), (u,x), and (v,x) are arcs of <I>D</I>. We call a graph a CCE graph if it is the CCE graph of some digraph. In this paper, we show that if the CCE graph of a doubly partial order does not contain <SUB>C4</SUB> as an induced subgraph, it is an interval graph. We also show that any interval graph together with enough isolated vertices is the CCE graph of some doubly partial order.</P>