In order to reveal the complex network characteristics and evolution principle of China aviation network, the probability distribution and evolution trace of average degree of edge vertices of China aviation network w...In order to reveal the complex network characteristics and evolution principle of China aviation network, the probability distribution and evolution trace of average degree of edge vertices of China aviation network were studied based on the statistics data of China civil aviation network in 1988, 1994, 2001, 2008 and 2015. According to the theory and method of complex network, the network system was constructed with the city where the airport was located as the network node and the route between cities as the edge of the network. Based on the statistical data, the average degrees of edge vertices in China aviation network in 1988, 1994, 2001, 2008 and 2015 were calculated. Using the probability statistical analysis method and regression analysis approach, it was found that the average degree of edge vertices had the probability distribution of normal function and the position parameters and scale parameters of the probability distribution had linear evolution trace.展开更多
In order to reveal the complex network characteristics and evolution principle of China aviation network, the relationship between the node degree and the nearest neighbor average degree and its evolution trace of Chi...In order to reveal the complex network characteristics and evolution principle of China aviation network, the relationship between the node degree and the nearest neighbor average degree and its evolution trace of China aviation network in 1988, 1994, 2001, 2008 and 2015 were studied. According to the theory and method of complex network, the network system was constructed with the city where the airport was located as the network node and the airline as the edge of the network. According to the statistical data, the node nearest neighbor average degree of China aviation network in 1988, 1994, 2001, 2008 and 2015 was calculated. Through regression analysis, it was found that the node degree had a negative exponential relationship with the nearest neighbor average degree, and the two parameters of the negative exponential relationship had linear evolution trace.展开更多
In order to reveal the complex network characteristics and evolution principle of China aviation network,the probability distribution and evolution trace of node nearest neighbor average degree of China aviation netwo...In order to reveal the complex network characteristics and evolution principle of China aviation network,the probability distribution and evolution trace of node nearest neighbor average degree of China aviation network were studied based on the statistics data of China civil aviation network in 1988,1994,2001,2008 and 2015.According to the theory and method of complex network,the network system was constructed with the city where the airport was located as the network node and the route between cities as the edge of the network.Based on the statistical data,the nearest neighbor average degrees of nodes in China aviation network in 1988,1994,2001,2008 and 2015 were calculated.Using the probability statistical analysis method,it was found that the nearest neighbor average degree had the probability distribution of normal function and the position parameters and scale parameters of the probability distribution had linear evolution trace.展开更多
A proper <em>k</em>-edge coloring of a graph <em>G</em> = (<em>V</em>(<em>G</em>), <em>E</em>(<em>G</em>)) is an assignment <em>c</em>...A proper <em>k</em>-edge coloring of a graph <em>G</em> = (<em>V</em>(<em>G</em>), <em>E</em>(<em>G</em>)) is an assignment <em>c</em>: <em>E</em>(<em>G</em>) → {1, 2, …, <em>k</em>} such that no two adjacent edges receive the same color. A neighbor sum distinguishing <em>k</em>-edge coloring of <em>G</em> is a proper <em>k</em>-edge coloring of <em>G</em> such that <img src="Edit_28f0a24c-7d3f-4bdc-b58c-46dfa2add4b4.bmp" alt="" /> for each edge <em>uv</em> ∈ <em>E</em>(<em>G</em>). The neighbor sum distinguishing index of a graph <em>G</em> is the least integer <em>k</em> such that <em>G </em>has such a coloring, denoted by <em>χ’</em><sub>Σ</sub>(<em>G</em>). Let <img src="Edit_7525056f-b99d-4e38-b940-618d16c061e2.bmp" alt="" /> be the maximum average degree of <em>G</em>. In this paper, we prove <em>χ</em>’<sub>Σ</sub>(<em>G</em>) ≤ max{9, Δ(<em>G</em>) +1} for any normal graph <em>G</em> with <img src="Edit_e28e38d5-9b6d-46da-bfce-2aae47cc36f3.bmp" alt="" />. Our approach is based on the discharging method and Combinatorial Nullstellensatz.展开更多
The establishment of effective null models can provide reference networks to accurately describe statistical properties of real-life signed networks.At present,two classical null models of signed networks(i.e.,sign an...The establishment of effective null models can provide reference networks to accurately describe statistical properties of real-life signed networks.At present,two classical null models of signed networks(i.e.,sign and full-edge randomized models)shuffle both positive and negative topologies at the same time,so it is difficult to distinguish the effect on network topology of positive edges,negative edges,and the correlation between them.In this study,we construct three re-fined edge-randomized null models by only randomizing link relationships without changing positive and negative degree distributions.The results of nontrivial statistical indicators of signed networks,such as average degree connectivity and clustering coefficient,show that the position of positive edges has a stronger effect on positive-edge topology,while the signs of negative edges have a greater influence on negative-edge topology.For some specific statistics(e.g.,embeddedness),the results indicate that the proposed null models can more accurately describe real-life networks compared with the two existing ones,which can be selected to facilitate a better understanding of complex structures,functions,and dynamical behaviors on signed networks.展开更多
Given a graph G=(V,E)and a positive integer k,a k-total-coloring of G is a mappingφ:V⋃E→{1,2,⋯,k}such that no two adjacent or incident elements receive the same color.The central problem of the total-colorings is th...Given a graph G=(V,E)and a positive integer k,a k-total-coloring of G is a mappingφ:V⋃E→{1,2,⋯,k}such that no two adjacent or incident elements receive the same color.The central problem of the total-colorings is the Total Coloring Conjecture,which asserts that every graph of maximum degreeΔadmits a(Δ+2)-total-coloring.More precisely,this conjecture has been verified forΔ≤5,and it is still open whenΔ=6,even for planar graphs.Let mad(G)denote the maximum average degree of the graph G.In this paper,we prove that every graph G withΔ(G)=6 and mad(G)<23/5 admits an 8-total-coloring.展开更多
A star k-edge-coloring is a proper k-edge-coloring such that every connected bicolored subgraph is a path of length at most 3.The star chromatic indexχ'_(st)(G)of a graph G is the smallest integer k such that G h...A star k-edge-coloring is a proper k-edge-coloring such that every connected bicolored subgraph is a path of length at most 3.The star chromatic indexχ'_(st)(G)of a graph G is the smallest integer k such that G has a star k-edge-coloring.The list star chromatic index ch'st(G)is defined analogously.The star edge coloring problem is known to be NP-complete,and it is even hard to obtain tight upper bound as it is unknown whether the star chromatic index for complete graph is linear or super linear.In this paper,we study,in contrast,the best linear upper bound for sparse graph classes.We show that for everyε>0 there exists a constant c(ε)such that if mad(G)<8/3-ε,then■and the coefficient 3/2 ofΔis the best possible.The proof applies a newly developed coloring extension method by assigning color sets with different sizes.展开更多
A proper k-edge coloring of a graph G is an assignment of one of k colors to each edge of G such that there are no two edges with the same color incident to a common vertex.Let f(v)denote the sum of colors of the edge...A proper k-edge coloring of a graph G is an assignment of one of k colors to each edge of G such that there are no two edges with the same color incident to a common vertex.Let f(v)denote the sum of colors of the edges incident to v.A k-neighbor sum distinguishing edge coloring of G is a proper k-edge coloring of G such that for each edge uv∈E(G),f(u)≠f(v).Byχ’_∑(G),we denote the smallest value k in such a coloring of G.Let mad(G)denote the maximum average degree of a graph G.In this paper,we prove that every normal graph with mad(G)<10/3 andΔ(G)≥8 admits a(Δ(G)+2)-neighbor sum distinguishing edge coloring.Our approach is based on the Combinatorial Nullstellensatz and discharging method.展开更多
It is a common practice to simulate some historical or test systems to validate the efficiency of new methods or concepts. However, there are only a small number of existing power system test cases, and validation and...It is a common practice to simulate some historical or test systems to validate the efficiency of new methods or concepts. However, there are only a small number of existing power system test cases, and validation and evaluation results, obtained using such a limited number of test cases, may not be deemed sufficient or convincing. In order to provide more available test cases, a new random graph generation algorithm, named ‘‘dualstage constructed random graph’’ algorithm, is proposed to effectively model the power grid topology. The algorithm generates a spanning tree to guarantee the connectivity of random graphs and is capable of controlling the number of lines precisely. No matter how much the average degree is,whether sparse or not, random graphs can be quickly formed to satisfy the requirements. An approach is developed to generate random graphs with prescribed numbers of connected components, in order to simulate the power grid topology under fault conditions. Our experimental study on several realistic power grid topologies proves that the proposed algorithm can quickly generate a large number of random graphs with the topology characteristics of real-world power grid.展开更多
The proposal and innovation of inclusive finance provide a very valuable pathway to realize social equity and eliminate poverty,which has attracted extensive attention,especially from developing countries.Based on the...The proposal and innovation of inclusive finance provide a very valuable pathway to realize social equity and eliminate poverty,which has attracted extensive attention,especially from developing countries.Based on the papers on inclusive finance published in the Chinese journal database CNKI from 2014 to 2018,we constructed an undirected weighted coauthor network 2154 authors.By employing social network analysis,we found that the number of authors in the field of inclusive finance increased rapidly.Although the cooperation between them was still very low and the cooperation authors were relatively fixed,the scale of cooperation was rapidly expanding.Although no scholar could always be at the center position in the coauthor network,the knowledge transfer path was significantly reduced.Financial universities and some financial institutions were the most important promoters of inclusive finance.Knowledge discovery in this field was promoted alternately by several center authors and cooperation by many scholars 2014-2018.We believe these discoveries are of great significance to promote knowledge sharing and innovation in the academic community of inclusive finance.展开更多
文摘In order to reveal the complex network characteristics and evolution principle of China aviation network, the probability distribution and evolution trace of average degree of edge vertices of China aviation network were studied based on the statistics data of China civil aviation network in 1988, 1994, 2001, 2008 and 2015. According to the theory and method of complex network, the network system was constructed with the city where the airport was located as the network node and the route between cities as the edge of the network. Based on the statistical data, the average degrees of edge vertices in China aviation network in 1988, 1994, 2001, 2008 and 2015 were calculated. Using the probability statistical analysis method and regression analysis approach, it was found that the average degree of edge vertices had the probability distribution of normal function and the position parameters and scale parameters of the probability distribution had linear evolution trace.
文摘In order to reveal the complex network characteristics and evolution principle of China aviation network, the relationship between the node degree and the nearest neighbor average degree and its evolution trace of China aviation network in 1988, 1994, 2001, 2008 and 2015 were studied. According to the theory and method of complex network, the network system was constructed with the city where the airport was located as the network node and the airline as the edge of the network. According to the statistical data, the node nearest neighbor average degree of China aviation network in 1988, 1994, 2001, 2008 and 2015 was calculated. Through regression analysis, it was found that the node degree had a negative exponential relationship with the nearest neighbor average degree, and the two parameters of the negative exponential relationship had linear evolution trace.
文摘In order to reveal the complex network characteristics and evolution principle of China aviation network,the probability distribution and evolution trace of node nearest neighbor average degree of China aviation network were studied based on the statistics data of China civil aviation network in 1988,1994,2001,2008 and 2015.According to the theory and method of complex network,the network system was constructed with the city where the airport was located as the network node and the route between cities as the edge of the network.Based on the statistical data,the nearest neighbor average degrees of nodes in China aviation network in 1988,1994,2001,2008 and 2015 were calculated.Using the probability statistical analysis method,it was found that the nearest neighbor average degree had the probability distribution of normal function and the position parameters and scale parameters of the probability distribution had linear evolution trace.
文摘A proper <em>k</em>-edge coloring of a graph <em>G</em> = (<em>V</em>(<em>G</em>), <em>E</em>(<em>G</em>)) is an assignment <em>c</em>: <em>E</em>(<em>G</em>) → {1, 2, …, <em>k</em>} such that no two adjacent edges receive the same color. A neighbor sum distinguishing <em>k</em>-edge coloring of <em>G</em> is a proper <em>k</em>-edge coloring of <em>G</em> such that <img src="Edit_28f0a24c-7d3f-4bdc-b58c-46dfa2add4b4.bmp" alt="" /> for each edge <em>uv</em> ∈ <em>E</em>(<em>G</em>). The neighbor sum distinguishing index of a graph <em>G</em> is the least integer <em>k</em> such that <em>G </em>has such a coloring, denoted by <em>χ’</em><sub>Σ</sub>(<em>G</em>). Let <img src="Edit_7525056f-b99d-4e38-b940-618d16c061e2.bmp" alt="" /> be the maximum average degree of <em>G</em>. In this paper, we prove <em>χ</em>’<sub>Σ</sub>(<em>G</em>) ≤ max{9, Δ(<em>G</em>) +1} for any normal graph <em>G</em> with <img src="Edit_e28e38d5-9b6d-46da-bfce-2aae47cc36f3.bmp" alt="" />. Our approach is based on the discharging method and Combinatorial Nullstellensatz.
基金supported by the National Natural Science Foundation of China(Grant No.11571258)the National Natural Science Foundation of Shandong Province(Grant No.ZR2016AM01)Scientific Research Foundation of University of Jinan(Grant Nos.XKY1414 and XKY1613)
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61773091 and 61603073)the LiaoNing Revitalization Talents Program(Grant No.XLYC1807106)the Natural Science Foundation of Liaoning Province,China(Grant No.2020-MZLH-22).
文摘The establishment of effective null models can provide reference networks to accurately describe statistical properties of real-life signed networks.At present,two classical null models of signed networks(i.e.,sign and full-edge randomized models)shuffle both positive and negative topologies at the same time,so it is difficult to distinguish the effect on network topology of positive edges,negative edges,and the correlation between them.In this study,we construct three re-fined edge-randomized null models by only randomizing link relationships without changing positive and negative degree distributions.The results of nontrivial statistical indicators of signed networks,such as average degree connectivity and clustering coefficient,show that the position of positive edges has a stronger effect on positive-edge topology,while the signs of negative edges have a greater influence on negative-edge topology.For some specific statistics(e.g.,embeddedness),the results indicate that the proposed null models can more accurately describe real-life networks compared with the two existing ones,which can be selected to facilitate a better understanding of complex structures,functions,and dynamical behaviors on signed networks.
基金This work was supported by the National Natural Science Foundation of China(11471193,11631014)the Foundation for Distinguished Young Scholars of Shandong Province(JQ201501)the Fundamental Research Funds of Shandong University and Independent Innovation Foundation of Shandong University(IFYT14012).
文摘Given a graph G=(V,E)and a positive integer k,a k-total-coloring of G is a mappingφ:V⋃E→{1,2,⋯,k}such that no two adjacent or incident elements receive the same color.The central problem of the total-colorings is the Total Coloring Conjecture,which asserts that every graph of maximum degreeΔadmits a(Δ+2)-total-coloring.More precisely,this conjecture has been verified forΔ≤5,and it is still open whenΔ=6,even for planar graphs.Let mad(G)denote the maximum average degree of the graph G.In this paper,we prove that every graph G withΔ(G)=6 and mad(G)<23/5 admits an 8-total-coloring.
基金Supported by the National Natural Science Foundation of China(11471193,11631014)the Foundation for Distinguished Young Scholars of Shandong Province(JQ201501)+1 种基金the Fundamental Research Funds of Shandong UniversityIndependent Innovation Foundation of Shandong University(IFYT14012)
基金supported by National Natural Science Foundation of China(Grant No.11901318)the Fundamental Research Funds for the Central Universities,Nankai University(Grant No.63191425)supported by National Natural Science Foundation of China(Grant Nos.11571149 and 11971205)
文摘A star k-edge-coloring is a proper k-edge-coloring such that every connected bicolored subgraph is a path of length at most 3.The star chromatic indexχ'_(st)(G)of a graph G is the smallest integer k such that G has a star k-edge-coloring.The list star chromatic index ch'st(G)is defined analogously.The star edge coloring problem is known to be NP-complete,and it is even hard to obtain tight upper bound as it is unknown whether the star chromatic index for complete graph is linear or super linear.In this paper,we study,in contrast,the best linear upper bound for sparse graph classes.We show that for everyε>0 there exists a constant c(ε)such that if mad(G)<8/3-ε,then■and the coefficient 3/2 ofΔis the best possible.The proof applies a newly developed coloring extension method by assigning color sets with different sizes.
基金Supported by the Natural Science Foundation of Shandong Provence(Grant Nos.ZR2018BA010,ZR2016AM01)the National Natural Science Foundation of China(Grant No.11571258)。
文摘A proper k-edge coloring of a graph G is an assignment of one of k colors to each edge of G such that there are no two edges with the same color incident to a common vertex.Let f(v)denote the sum of colors of the edges incident to v.A k-neighbor sum distinguishing edge coloring of G is a proper k-edge coloring of G such that for each edge uv∈E(G),f(u)≠f(v).Byχ’_∑(G),we denote the smallest value k in such a coloring of G.Let mad(G)denote the maximum average degree of a graph G.In this paper,we prove that every normal graph with mad(G)<10/3 andΔ(G)≥8 admits a(Δ(G)+2)-neighbor sum distinguishing edge coloring.Our approach is based on the Combinatorial Nullstellensatz and discharging method.
文摘It is a common practice to simulate some historical or test systems to validate the efficiency of new methods or concepts. However, there are only a small number of existing power system test cases, and validation and evaluation results, obtained using such a limited number of test cases, may not be deemed sufficient or convincing. In order to provide more available test cases, a new random graph generation algorithm, named ‘‘dualstage constructed random graph’’ algorithm, is proposed to effectively model the power grid topology. The algorithm generates a spanning tree to guarantee the connectivity of random graphs and is capable of controlling the number of lines precisely. No matter how much the average degree is,whether sparse or not, random graphs can be quickly formed to satisfy the requirements. An approach is developed to generate random graphs with prescribed numbers of connected components, in order to simulate the power grid topology under fault conditions. Our experimental study on several realistic power grid topologies proves that the proposed algorithm can quickly generate a large number of random graphs with the topology characteristics of real-world power grid.
基金supported by the Natural Science and Technology Foundation of Guizhou Province,China (QKHJC[2019]1045)the Scientific Research Fund of GUFE (2019XJC02)the Plan Project for Guizhou Provincial Science and Technology (No.QKH−PTRC[2018]5803).
文摘The proposal and innovation of inclusive finance provide a very valuable pathway to realize social equity and eliminate poverty,which has attracted extensive attention,especially from developing countries.Based on the papers on inclusive finance published in the Chinese journal database CNKI from 2014 to 2018,we constructed an undirected weighted coauthor network 2154 authors.By employing social network analysis,we found that the number of authors in the field of inclusive finance increased rapidly.Although the cooperation between them was still very low and the cooperation authors were relatively fixed,the scale of cooperation was rapidly expanding.Although no scholar could always be at the center position in the coauthor network,the knowledge transfer path was significantly reduced.Financial universities and some financial institutions were the most important promoters of inclusive finance.Knowledge discovery in this field was promoted alternately by several center authors and cooperation by many scholars 2014-2018.We believe these discoveries are of great significance to promote knowledge sharing and innovation in the academic community of inclusive finance.
