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823 results on '"Hu, Yanan"'

4. Graphs with many independent vertex cuts

Author

Hu, Yanan, Zhan, Xingzhi, and Zhang, Leilei

Subjects
Mathematics - Combinatorics, 05C40, 05C69
Abstract

The cycles are the only $2$-connected graphs in which any two nonadjacent vertices form a vertex cut. We generalize this fact by proving that for every integer $k\ge 3$ there exists a unique graph $G$ satisfying the following conditions: (1) $G$ is $k$-connected; (2) the independence number of $G$ is greater than $k;$ (3) any independent set of cardinality $k$ is a vertex cut of $G.$ The edge version of this result does not hold. We also consider the problem when replacing independent sets by the periphery.

Published
2022

9. On the metric subgraphs of a graph

Author

Hu, Yanan and Zhan, Xingzhi

Subjects
Mathematics - Combinatorics
Abstract

The three subgraphs of a connected graph induced by the center, annulus and periphery are called its metric subgraphs. The main results are as follows. (1) There exists a graph of order $n$ whose metric subgraphs are all paths if and only if $n\ge 13$ and the smallest size of such a graph of order $13$ is $22;$ (2) there exists a graph of order $n$ whose metric subgraphs are all cycles if and only if $n\ge 15,$ and there are exactly three such graphs of order $15;$ (3) for every integer $k\ge 3,$ we determine the possible orders for the existence of a graph whose metric subgraphs are all connected $k$-regular graphs; (4) there exists a graph of order $n$ whose metric subgraphs are connected and pairwise isomorphic if and only if $n\ge 24$ and $n$ is divisible by $3.$ An unsolved problem is posed., Comment: 15 pages, 3 figures

Published
2021

19. Regular homogeneously traceable nonhamiltonian graphs

Author

Hu, Yanan and Zhan, Xingzhi

Subjects
Mathematics - Combinatorics, 05C38, 05C45, 05C76
Abstract

A graph is called homogeneously traceable if every vertex is an endpoint of a Hamilton path. In 1979 Chartrand, Gould and Kapoor proved that for every integer $n\ge 9,$ there exists a homogeneously traceable nonhamiltonian graph of order $n.$ The graphs they constructed are irregular. Thus it is natural to consider the existence problem of regular homogeneously traceable nonhamiltonian graphs. We prove two results: (1) For every even integer $n\ge 10,$ there exists a cubic homogeneously traceable nonhamiltonian graph of order $n;$ (2) for every integer $p\ge 18,$ there exists a $4$-regular homogeneously traceable graph of order $p$ and circumference $p-4.$ Unsolved problems are posed., Comment: 8 pages, 7 figures

Published
2021

20. On almost self-centered graphs and almost peripheral graphs

Author

Hu, Yanan and Zhan, Xingzhi

Subjects
Mathematics - Combinatorics, 05C35, 05C07, 05C69
Abstract

An almost self-centered graph is a connected graph of order $n$ with exactly $n-2$ central vertices, and an almost peripheral graph is a connected graph of order $n$ with exactly $n-1$ peripheral vertices. We determine (1) the maximum girth of an almost self-centered graph of order $n;$ (2) the maximum independence number of an almost self-centered graph of order $n$ and radius $r;$ (3) the minimum order of a $k$-regular almost self-centered graph and (4) the maximum size of an almost peripheral graph of order $n;$ (5) which numbers are possible for the maximum degree of an almost peripheral graph of order $n;$ (6) the maximum number of vertices of maximum degree in an almost peripheral graph of order $n$ whose maximum degree is the second largest possible. Whenever the extremal graphs have a neat form, we also describe them., Comment: 16 pages, 6 figures

Published
2021

29. Deep Survival Analysis in Multiple Sclerosis

Author

Zhang, Xin, Mehta, Deval, Zhu, Chao, Merlo, Daniel, Hu, Yanan, Gresle, Melissa, Darby, David, van der Walt, Anneke, Butzkueven, Helmut, Ge, Zongyuan, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Rekik, Islem, editor, Adeli, Ehsan, editor, Park, Sang Hyun, editor, Cintas, Celia, editor, and Zamzmi, Ghada, editor

Published
2023
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30. Research on the Public Value of Government Social Media Content and Communication Strategies Under 'Infodemic'

Author

Wu, Lianren, Hu, Yanan, Li, Jinjir, Xiang, Panwei, Qi, Jiayin, Filipe, Joaquim, Editorial Board Member, Ghosh, Ashish, Editorial Board Member, Prates, Raquel Oliveira, Editorial Board Member, Zhou, Lizhu, Editorial Board Member, Meng, Xiaofeng, editor, Chen, Yang, editor, Suo, Liming, editor, Xuan, Qi, editor, and Zhang, Zi-Ke, editor

Published
2023
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40. Possible cardinalities of the center of a graph

Author

Hu, Yanan and Zhan, Xingzhi

Subjects
Mathematics - Combinatorics, 05C12, 05C30
Abstract

A central vertex of a graph is a vertex whose eccentricity equals the radius. The center of a graph is the set of all central vertices. The central ratio of a graph is the ratio of the cardinality of its center to its order. In 1982, Buckley proved that every positive rational number not exceeding one is the central ratio of some graph. In this paper, we obtain more detailed information by determining which cardinalities are possible for the center of a graph with given order and radius. There are unexpected phenomena in the results. For example, there exists a graph of order $14$ and radius $6$ whose center has cardinality $s$ if and only if $s\in \{ 1, 2, 3, 4, 9,10,11,12,14\}.$ We also prove a related uniqueness result., Comment: 9 pages, 6 figures

Published
2020

49. The Crisis in Oases: Research on Ecological Security and Sustainable Development in Arid Regions

Author

Chen, Yaning, primary, Fang, Gonghuan, additional, Li, Zhi, additional, Zhang, Xueqi, additional, Gao, Lei, additional, Elbeltagi, Ahmed, additional, Shaer, Hassan El, additional, Duan, Weili, additional, Wassif, Omnia Mohamed Abdou, additional, Li, Yupeng, additional, Luo, Pingping, additional, Selmi, Aida, additional, Yu, Ruide, additional, Yang, Jinhua, additional, Hu, Yanan, additional, Liu, Chuanxiu, additional, Long, Yunxia, additional, Malik, Ireneusz, additional, Fu, Aihong, additional, Wistuba, Małgorzata, additional, Yang, Yuhai, additional, Zhu, Chenggang, additional, and Gao, Yuting, additional

Published
2024
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