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1.
Eddie Cheng 《Information Sciences》2007,177(22):4877-4882
We prove that when linearly many vertices are deleted in a Cayley graph generated by a transposition tree, the resulting graph has a large connected component containing almost all remaining vertices. 相似文献
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李广智 《气象水文海洋仪器》2005,(Z1)
找星仪是卫星地面站安装、调试、维修所必不可少的设备。旧的找星仪笨重、由于必须两人操作,很不方便。针对这些问题开发了便携式多功能找星仪。本文主要介绍了该设备的构成及其电路原理。 相似文献
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回顾重钢七厂连铸板坯星状裂纹导致轧制钢板表面产生龟裂缺陷、以及对钢坯产生星裂的机理的认识过程,借助国外在这方面的研究成果进行对比分析,认为控制板坯星裂的最重要技术措施是采用"结晶器软冷却”工艺、以及控制钢的铁素体势和铜当量。 相似文献
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p-(Iodomethyl)styrene was polymerized under the action of a radical initiator (AIBN). The polymerization proceeds with degenerative chain transfer and leads to well defined branched polymers with functional primary and secondary iodomethyl groups as revealed by NMR studies. The obtained polymer can be further used as macroinitiator for radical polymerization of styrene. This polymerization proceeds in controlled way to polystyrene star polymers with reactive groups at the end of their arms. The characterization of branched and star structures was performed by NMR and GPC with absolute molar mass detection (MALLS). 相似文献
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The quality of plane layout design of the disc cutters for the full-face rock tunnel boring machine (TBM) directly affects the balance of force distribution on the cutter head during the excavating. Various layout patterns have been adopted in practice during the layout design of the disc cutters. Considering the engineering technical requirements and the corresponding structure design requirements of the cutter head, this study formulates a nonlinear multi-objective mathematical model with multiple constraints for the disc cutters plane layout design, and analyses the characteristics of a multi-spiral layout pattern, a dynamic star layout pattern and a stochastic layout pattern. And then a genetic algorithm is employed to solve a disc cutters’ multi-spiral layout problem, and a cooperative co-evolutionary genetic algorithm (CCGA) is utilized to solve a disc cutters’ star or stochastic layout problems. The emphasis was put on the study of superiority of three different layout patterns. Finally, an instance of the disc cutters’ plane layout design was solved by the proposed methods using three different kinds of layout patterns. Experimental results showed the effectiveness of the method of combining the mathematical model with the algorithms, and the pros and cons of the three layout patterns. 相似文献
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文章从研究“集群设计”的兴起与定位,历史渊源及其发展异化入手,进而探讨中国当代建筑集群设计的现象与概况, 并重点评述中国集群设计的特征、价值、意义与误区,以及与“明星建筑师”的关系 相似文献
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The synthesis of 3-arm star polymers from reversible addition-fragmentation chain transfer (RAFT)-prepared precursor homopolymers in combination with thiol-ene click chemistry is described. Homopolymers of n-butyl acrylate and N,N-diethylacrylamide were prepared with 1-cyano-1-methylethyl dithiobenzoate and 2,2′-azobis(2-methylpropionitrile) yielding materials with polydispersity indices (Mw/Mn) ≤ 1.18 and controlled molecular weights as determined by a combination of NMR spectroscopy, size exclusion chromatography (SEC), and matrix assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS). Subsequent one-pot reaction of homopolymer, hexylamine (HexAM), dimethylphenylphosphine (DMPP), and trimethylolpropane triacrylate (TMPTA) results in cleavage of the thiocarbonylthiol end-group (by HexAM) of the homopolymer yielding a macromolecular thiol that undergoes DMPP-initiated thiol-Michael addition to TMPTA yielding 3-arm star polymers. The presence of DMPP is demonstrated to serve an important second role in effectively suppressing the presence of any polymeric disulfide as determined by SEC. Such phosphine-mediated thiol-ene reactions are shown to be extremely rapid, as verified by a combination of FTIR and NMR spectroscopies, with complete consumption of the CC bonds occurring in a matter of min. MALDI-TOF MS and SEC were used to verify the formation of 3-arm stars. A broadening in the molecular weight distribution (Mw/Mn ∼ 1.35) was observed by SEC that was attributed to the presence of residual homopolymer and possibly 2-arm stars formed from trimethylolpropane diacrylate impurity. Interestingly, the MALDI analysis also indicated the presence of 1- and 2-arm species most likely formed from the fragmentation of the parent 3-arm star during analysis. Finally, a control experiment verified that the consumption of CC bonds does not occur via a radical pathway. 相似文献