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81.
An equivalence graph is a disjoint union of cliques, and the equivalence number of a graph G is the minimum number of equivalence subgraphs needed to cover the edges of G. We consider the equivalence number of a line graph, giving improved upper and lower bounds: . This disproves a recent conjecture that is at most three for triangle-free G; indeed it can be arbitrarily large.To bound we bound the closely related invariant σ(G), which is the minimum number of orientations of G such that for any two edges e,f incident to some vertex v, both e and f are oriented out of v in some orientation. When G is triangle-free, . We prove that even when G is triangle-free, it is NP-complete to decide whether or not σ(G)≤3. 相似文献
82.
《Journal of Macromolecular Science: Physics》2013,52(4-6):1205-1229
Many normally ductile semi-crystalline polymers, such as polyamide-6 (or 6,6) (Nylon), high density polyethylene (HDPE), and isotactic polypropylene (iPP) are known to be brittle under impact loading. Some general principles for improvement of toughness of semi-crystalline polymers that rely on the reduction of plastic resistance of the cavitated matrix are presented. As typical cases, the mechanisms of the dramatic toughness jumps achievable in both Nylon and HDPE through the incorporation of either flexible rubbery particles or rigid CaCO3 particles are discussed. In both cases these result in the establishment of a material component of reduced plastic resistance in the form of a layer of oriented crystallization of well-defined thickness around the particles. The toughness jumps occur when the average interparticle ligament thickness is reduced below a critical value, specific to the particular polymer, and the component of reduced plastic resistance percolates through the structure. 相似文献
83.
The effect of octupole deformation, β3, and the higher multipole deformations, β6 and β8, on the distribution of barriers in orientation degrees of freedom, is studied. Coulomb barriers are derived in the frame work of the double folding model with the realistic M3Y nucleon–nucleon interaction and its density dependent version. 48Ca + 244Pu spherical-deformed nuclear interacting pair is considered, as an example, to study the effect of deformation parameters on the height and position of the Coulomb barrier. Although the dependence of the Coulomb barrier parameters on the higher deformations is complicated, numerically, if it is treated in microscopic way, we found a simple linear variation of barrier parameters with the different orders of deformation. We found that the variation of the barrier parameters with deformation exactly follows the change of the half density radius of the deformed nucleus in the direction of the separation vector between the centers of mass of the interacting nuclei. This suggests a simple and straightforward way to predict the behavior of the barrier parameters with different orders of deformations. We compared the results of present work with a similar recent study of the same quantities based on simple expression derived by Wong for the Coulomb part and proximity approach for the nuclear part of heavy ion potential, respectively. 相似文献
84.
利用相干受激Raman抽运,选择性地激发C2H2分子(X~1Σg v2=1,J")单一振转态.在Ra-man泵浦与探测激光不同偏振条件下,获得紫外探测激光诱导的A1Au(v3=1)-(X~1Σg v2=1,J")荧光增益光谱,从而研究了C2H2分子单一振转态的光学ACStark效应和mj的定向分布A0(1),利用stark线型加宽数值模型,从理论上计算得到的Rarnan线型与实验结果进行比较,二者符合程度相当好. 相似文献
85.
含微裂纹材料的损伤理论 总被引:5,自引:1,他引:5
本文从含微裂纹材料的变形能出发引出了裂纹的方位张量。在考虑裂纹受压闭合与滑动摩擦的基础上,给出了损伤张量、损伤应变及有效弹性常数。文中给出了损伤机构离散化的方法,并对方位密度给出了演化方程。最后给出一个单向拉压的应力应变关系例子,并揭示了裂纹扩展时的应力突跌现象。 相似文献
86.
M. E. Ahmed 《Monatshefte für Chemie / Chemical Monthly》1997,128(8-9):827-836
Summary A systematic investigation on the adsorption and association of inosine at a hanging mercury drop electrode by phase-sensitive ac voltammetry has been performed. The adsorption equilibrium bas been determined as a function of various parameters such aspH, adsorption potential, adsorption time, and bulk concentration of inosine. It was found that the association of the adsorbed species depends predominantly on the stacking interactions of neutral inosine molecules. Over a wide potential range, inosine exhibits a dilute adsorption characteristic where it is adsorbed with the base flat on the electrode surface. Above a certain threshold value, inosine appears to undergo a surface reorientation and adopts a perpendicular position. The nucleation and growth mechanism is analyzed applying theAvrami equation. Characteristic properties and adsorption parameters of dilute and compact layers of inosine were evaluated from the two-stepFrumkin isotherm and from the potential dependence of adsorption.
Oberflächenaktivität und Orientierung von Inosin an einer Quecksilber/Lösungs-Grenzfläche
Zusammenfassung Die Adsorption und Assoziation von Inosin an einer Quecksilbertropfelektrode wurde mittels phasensensitiver AC-Voltammetrie systematisch untersucht. Die Abhängigkeit des Adsorptionsgleichgewichts von Parametern wiepH-Wert, Adsorptionspotential, Adsorptionszeit und Inosinkonzentration wurde gemessen. Dabei zeigte sich, daß die Assoziation der adsorbierten Spezies vorwiegend von der Anordnung und den Wechselwirkungen der neutralen Inosinmoleküle abhängt. Inosin bildet über einen weiten Potentialbereich eine dünne Adsorptionsschicht aus, wobei die Base flach auf der Elektrodenoberfläche aufliegt. Ab einem bestimmten Grenzwert der Konzentration tritt eine Reorientierung zu einer senkrechten Anordnung ein. Keimbildung und Wachstumsmechanismus wurden mittels derAvrami-Gleichung analysiert. Eigenschaften und Adsorptionsparameter der verdünnten und der kompakten Inosinschicht konnten aus der zweistufigenFrumkin-Isotherme und aus der Potentialabhängigkeit der Adsorption bestimmt werden.相似文献
87.
The hierarchical structure and interfacial morphology of injection-molded bars of polypropylene (PP) based blends and composites have been investigated in detail from the skin to the core. For preparation of injection-molded bars with high-level orientation and good interfacial adhesion, a dynamic packing injection molding technology was applied to exert oscillatory shear on the melts during solidification stage. Depending on incorporated component, interfacial adhesion and processing conditions, various oriented structure and morphology could be obtained. First, we will elucidate the epitaxial behavior between PP and high-density polyethylene occurring in practical molded processing. Then, the shear-induced transcrystalline structure will be the main focus for PP/fiber composites. At last, various oriented clay structures have been ascertained unambiguously in PP/organoclay nanocomposites along the thickness of molded bars. 相似文献
88.
The isotropy or anisotropy in some physical properties of the ammorphous poly(ethyleneterephthalate) films uniaxially drawn at temperatures above its T_g and then quenched toroom temperature have been studied. Experimental results here presented show that thisamorphous state of high global chain orientation but nearly random segmental orientation,the GOLR state, is nearly isotropic in refractive indices and Young's modulus for smalldeformation, while it is very probably anisotropic in thermal conduction and microwavedielectric properties. 相似文献
89.
C2H2分子(X1∑g+,ν2”=1,J”)态mj定向布居及光学AC Stark效应 总被引:2,自引:1,他引:1
利用相干受激Raman抽运,选择性地激发C2H2分子单一振转态。在Raman泵浦与探测激光不同偏振条件下,获得紫外探测激光诱导的A^ ̄^1J(V′3=1)←-^ ̄Z^2Σ^+g,v′2=1,j″)荧光增益光谱,从而研究了C2H2分子单一振转态的光学AC Stark效应和mj的定向分布A0^(1),利用Stark线型加宽数值模型,从理论上计算得到的Raman线型与实验结果进行比较。 相似文献
90.
LI Xiao-ling ZHAO Bing WU Yu-qing XU Wei-qing LI Guo-wen WU Ying BAI Fang CUI Shu-wen 《高等学校化学研究》1998,14(4):395-398
IntroductionInrecentyears,Langmuir-Blodget(LB)filmshaveatractedmuchatentionbecauseoftheirposibilitiesasfunctionalmoleculardev... 相似文献