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61.
62.
YEH Yeong-Nan 《中国科学A辑(英文版)》2006,49(10):1383-1391
Let G be a simple graph. Define R(G) to be the graph obtained from G by adding a new vertex e* corresponding to each edge e = (a,b) of G and by joining each new vertex e* to the end vertices a and b of the edge e corresponding to it. In this paper, we prove that the number of matchings of R(G) is completely determined by the degree sequence of vertices of G. 相似文献
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One way of defining an oriented colouring of a directed graph is as a homomorphism from to a target directed graph , and an injective oriented colouring of can be defined as a homomorphism from to a target directed graph such that no two in-neighbours of a vertex of have the same image. Oriented colourings may be constructed using target directed graphs that are nice, as defined by Hell et al. (2001). We extend the work of Hell et al. by considering target graphs that are tournaments, characterizing nice tournaments, and proving that every nice tournament on vertices is -nice for some . We also give a characterization of tournaments that are nice but not injective-nice. 相似文献
66.
《Journal of Graph Theory》2018,87(3):285-304
We initiate a general study of what we call orientation completion problems. For a fixed class of oriented graphs, the orientation completion problem asks whether a given partially oriented graph P can be completed to an oriented graph in by orienting the (nonoriented) edges in P. Orientation completion problems commonly generalize several existing problems including recognition of certain classes of graphs and digraphs as well as extending representations of certain geometrically representable graphs. We study orientation completion problems for various classes of oriented graphs, including k‐arc‐strong oriented graphs, k‐strong oriented graphs, quasi‐transitive‐oriented graphs, local tournaments, acyclic local tournaments, locally transitive tournaments, locally transitive local tournaments, in‐tournaments, and oriented graphs that have directed cycle factors. We show that the orientation completion problem for each of these classes is either polynomial time solvable or NP‐complete. We also show that some of the NP‐complete problems become polynomial time solvable when the input‐oriented graphs satisfy certain extra conditions. Our results imply that the representation extension problems for proper interval graphs and for proper circular arc graphs are polynomial time solvable. The latter generalizes a previous result. 相似文献
67.
融合就业是残疾人可持续发展的关键途径。基于演化博弈理论和残疾人就业促进政策,建立残疾人与用人单位(企业)行为交互过程的动态演化模型,用数值实验展示了初始条件改变和决策变量不同取值对系统演化结果的影响。研究发现,残疾人就业行为路径演化系统收敛于良好状态和“锁定”状态两种模式;调控模型中的参数收敛于不同模式的概率发生显著变化或变化不明显,揭示了现实中残疾人就业治理效果不理想的深层次原因;通过提高残疾人的工资待遇、心理收益、为企业创造的价值,减少残疾人的社会补助与就业付出的人力和社会资本,增加残疾人就业法定比例、企业雇佣残疾人的声誉收益、增值税退税优惠(企业符合退税条件)与雇佣残疾人数量,减少企业支持残疾人的就业投入等均能使系统演化到良好状态的概率增加。这为制定灵活有效的残疾人就业制度、政策与措施提供了较大的操作空间,多元主体协同治理,利益共享,良性互动,以跳出不良“锁定”状态,实现残疾人就业行为良序发展,破解就业难题。 相似文献
68.
H. Janeschitz‐Kriegl 《Journal of Macromolecular Science: Physics》2013,52(3):591-601
Thread‐like nuclei for the crystallization of polymers which are formed at high deformation rates in a temperature range close to the equilibrium melting point appear to be practically stable at temperatures where spherulites are melting. However, the fact that the great majority of experiments on flow induced crystallization have been carried out at temperatures below the melting temperature of the spherulites leads to the conclusion that the precursors for elongated structures, as formed under those conditions, are practically stable from the moment of their creation. In other words: their relaxation times are much longer than any deformation time applied. As a consequence, deformation times as independent parameters lose their importance in these experiments. Long lasting deformations under low stresses can yield the same precursors as short term deformations under high loads. Apparently the only condition is that the applied specific work is the same. 相似文献
69.
Ruihua Lv Bing Na Zhujun Li Shufen Zou Nana Tian Feng Chen 《Journal of Macromolecular Science: Physics》2013,52(10):2042-2049
The oriented crystallization in stretched rubbery poly(L-lactide) has been studied with the aid of in-situ rheo-Fourier transform infrared spectroscopy (FTIR) measurements and morphological observations. The oriented segments that survived after stretching are first transformed into shish structure composed of helical sequences via intra-chain conformational ordering and propagation, followed by the transverse growth of kebabs from the coiled chains in the surrounding matrix. Moreover, the formation of shish structure and kebabs shows different dependences on the stretching temperature as a result of different controlling molecular processes. 相似文献
70.
W.D. Lakin J. Yu P.L. Penar 《Mathematical and Computer Modelling of Dynamical Systems: Methods, Tools and Applications in Engineering and Related Sciences》2013,19(1):55-73
Lumped parameter, compartmental models provide a promising Method for mathematically studying the dynamics of human intracranial pressure. In this modeling approach, a system of fully time-dependent differential equations for interacting compartmental pressures is obtained by considering the intracranial system to be confined within the almost-rigid skull and developing continuity equations associated with conservation of mass. Intracranial volumes and flows are related to compartmental pressure differences through compliance and resistance parameters. In the nonlinear case where compliances are not constant, there is a lack of physical information about these parameters. Consequently, it is vital that any mathematical model with an assumed pressure-dependent compliance be validated through comparison with experimental data. The present work develops a logistic representation for the compliance between the cerebrospinal fluid and brain matter compartments. The nonlinear mathematical model involving this logistic compliance is validated here by comparing its predicted response for bolus injections of cerebrospinal fluid to laboratory data generated in an animal model. Comparison with the animal studies fully supports the validity of the mathematical model with the logistic compliance. 相似文献