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After reporting the structure of a new polymorph of 1,3,5‐trifluoro‐2,4,6‐triiodobenzene (denoted BzF3I3 ), C6F3I3, (I), which crystallized in the space group P 21/c , we perform a comparative analysis with the already reported P 21/n polymorph, (II) [Reddy et al. (2006). Chem. Eur. J. 12 , 2222–2234]. In polymorph (II), type‐II I…I halogen bonds and I…π interactions connect molecules in such a way that a three‐dimensional structure is formed; however, the way in which molecules are connected in polymorph (I), through type‐II I…I halogen bonds and π–π interactions, gives rise to an exfoldable lamellar structure, which looks less tightly bound than that of (II). In agreement with this structural observation, both the melting point and the melting enthalpy of (I) are lower than those of (II).  相似文献   
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李黎  唐家祥 《实验力学》1999,14(3):316-322
通过对 11 组 19 个角钢插入式基础试件的抗拔试验,得到了角钢在不同埋置长度、不同锚固形式下的抗拔承载力、角钢与混凝土间的粘结应力分布、平均粘结应力以及角钢插入式基础的破坏形式、最大试验荷载等。为工程设计提供了基础数据。  相似文献   
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A finite element method is used to study the cavity nucleation and growth in an elastic-plastic medium. The critical cohesion strength, c at IPM (interface between second phase particle and matrix) is employed as the criterion of cavity formation. Three different values of c are taken to examine their influence on the overall mechanical behaviour and process of cavity formation.  相似文献   
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利用第一性原理中的DFT理论研究了Fe/A1界面的能量学和电子结构,讨论了替位型掺杂的元素Zn、Mn、Ni在Fe/A1界面处的作用.结果表明:元素Zn、Mn、Ni都会优先替换界面处的Fe原子,使得界面结合能增加,体系更稳定,有利于界面的结合;跨界面的Fe原子与Al原子之间的电荷布居、键长以及差分电荷密度图的计算表明:掺杂后有利于跨界面的Fe-Al间成键,从而加强了Al层与Fe基体的结合,且结合强度由强到弱依次为:掺Zn〉掺Mn〉掺Ni;与实验比较吻合.最后对掺杂Zn的增韧机理加以解释.  相似文献   
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油墨用聚氨酯树脂的研究   总被引:6,自引:0,他引:6  
研究用于印刷油墨的单组分溶剂型聚氨酯树脂,考查聚合物多元醇和异氰酸酯对树脂微观形态、机械性能以及印刷适应性和附着性等性能的影响。结果表明:聚酯型树脂的附着性较好,4,4-二甲苯甲烷二异氰酸酯(MDI)基树脂的附着性较佳。  相似文献   
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A single-surface yield function for geomaterials   总被引:6,自引:0,他引:6  
Summary The article outlines a seven-parametric yield function for geomaterials such as soils and rocks. Proceeding from a geometric representation in the principal stress space, the yield surface exhibits a closed shape, thus reflecting the sensitivity of the plastic response of this type of media to hydrostatic stresses. The yield function is able to describe the effects of primary yielding, as well as of isotropic and kinematic hardening. In addition the failure envelope contains an open cone when the number of material parameters is reduced from seven to five.Dedicated to F. G. Kollmann on the occasion of his 60th birthday  相似文献   
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Social action is situated in fields that are simultaneously composed of interpersonal ties and relations among organizations, which are both usefully characterized as social networks. We introduce a novel approach to distinguishing different network macro-structures in terms of cohesive subsets and their overlaps. We develop a vocabulary that relates different forms of network cohesion to field properties as opposed to organizational constraints on ties and structures. We illustrate differences in probabilistic attachment processes in network evolution that link on the one hand to organizational constraints versus field properties and to cohesive network topologies on the other. This allows us to identify a set of important new micro-macro linkages between local behavior in networks and global network properties. The analytic strategy thus puts in place a methodology for Predictive Social Cohesion theory to be developed and tested in the context of informal and formal organizations and organizational fields. We also show how organizations and fields combine at different scales of cohesive depth and cohesive breadth. Operational measures and results are illustrated for three organizational examples, and analysis of these cases suggests that different structures of cohesive subsets and overlaps may be predictive in organizational contexts and similarly for the larger fields in which they are embedded. Useful predictions may also be based on feedback from level of cohesion in the larger field back to organizations, conditioned on the level of multiconnectivity to the field.  相似文献   
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The question about the definition of the “internal pressure” concept is being discussed. It is shown that the previously found differential relation between the cohesion energy density and the internal pressure is one of the examples of an absolutely general interrelation between definitely connected differential functions. It is ascertained that the ratio (the internal pressure divided by the cohesion energy density) is a structuresensitive parameter inherent to the calorific (thermal) equation of a liquid state.  相似文献   
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