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991.
The synthesis of hemiphasmidic monomers 4‐[(3,4,5‐triethoxy)benzoyloxy]‐4′‐[(p‐allyloxy)benzoyloxy]biphenyl (M1), 4‐[(3,5‐diethoxy)benzoyloxy]‐4′‐[(p‐allyloxy)‐benzoyloxy]biphenyl (M2), and of the corresponding side‐chain liquid‐crystalline polysiloxanes (P1, P2) was carried out. For comparison, rodlike monomer 4‐[(p‐ethoxy)‐benzoyloxy]‐4′‐[(p‐allyloxy)benzoyloxy]biphenyl (M3) and its polysiloxanes (P3) were also prepared. The chemical structures of the monomers and polymers obtained were confirmed by FTIR and 1H‐NMR spectra. Their mesomorphic properties and phase behavior were investigated by differential scanning calorimetry, polarizing optical microscopy, and X‐ray diffraction measurements. The relationship between structures and properties was discussed. It was observed that M1 and M3 were enantiotropic nematic phase, M2 was monotropic mesophase, and their poly(methylsiloxanes) (P1–P3) possessed a broad range enantiotropic nematic phases and high thermal stability. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 946–952, 2005 相似文献
992.
993.
中国公铁两用桥发展至今已有近80年的历史,从早期跨径小、结构受力简单的梁式体系发展到目前大跨径的拱式体系以及大跨径、超大跨径的斜拉、悬索体系等。通过收集中国已建和在建的以上4种结构体系的公铁两用桥相关资料,对中国4种结构体系的公铁两用桥主桥主梁结构、基础以及其他结构部分在结构设计、施工工艺、材料性能上的发展趋势进行了分析。分析发现:4种结构体系公铁两用桥主桥主梁结构设计中的主桁形式、桥面系、联结系在结构上由繁至简、由离散拼装至整体栓焊;主桁桁式在力学特性上与各结构体系公铁两用桥主梁受力特点相辅相成,充分发挥了材料的性能和结构的受力特点,主梁施工工艺趋于系统化、高效化、经济化,其材料性能趋于优质化;基础的类型没有明显变化,但其施工方法实现了自我创新,材料性能趋于优质化;拱式体系公铁两用桥主桥主拱的结构设计趋于新型化,施工工艺趋于复杂化,在材料的选择上趋于科学和经济化;斜拉和悬索体系公铁两用桥除主梁和基础部分外,其他部分结构的设计趋于科学化,施工趋于经济化、智能化,材料性能趋于优质化。 相似文献
994.
995.
针对某公司加工高酸值、重质原油的常减压装置的原油与渣油换热器管板密封槽腐蚀情况进行分析,提出在原油换热过程中存在的一种类似于塔顶系统的低温露点腐蚀的这一新论断。并针对此提出相应的防护措施。 相似文献
996.
Marina M. Silantyeva Anna Ju. Grebennikova Petr A. Kosachev Aleksander A. Kuznetzov 《The International journal of environmental studies》2014,71(5):667-670
This paper contains previously unknown information about the appearance and expansion of a number of adventive species of plants new for the Altai Territory. They were discovered in 2008–2012 during the fieldwork tasks of the herbarium Altai State University, Barnaul. One of the species is invasive (quarantine plant for the Russian Federation) – Acroptilon repens (L.) DC. The range was about 10?ha. One of the species was listed as adventive for the first time – Briza maxima L. The species is sometimes cultivated as an ornamental plant. New locations were identified for three species previously found only in one area of the Altai Territory: (1) Scleranthus annuus L. – an agrophyte, a weed that spreads with cultivated crops; (2) Onopordon acanthium L. – a species that spreads in flood plains, along the highways, railways and pastures; and (3) Xanthium albinum (Widd.) H. Schulz – a plant, often seen along roadsides, wastelands and sandy riverbanks; only one reliable location within the Altai Territory was known for S. annuus and O. acanthium. Based on the classification of adventive elements of flora, A. repens was specified as agrophyte and xenophyte; B. maxima as horthophyte and ergasiofigophyte; S. annuus as agrophyte and xenophyte; O. acanthium; and X. albinum as dromophyte and acolucophyte. 相似文献
997.
Do‐Hyun Kim Young K. Ju Myeong‐Han Kim Sang‐Dae Kim 《The Structural Design of Tall and Special Buildings》2014,23(7):549-562
A buckling‐restrained brace (BRB) is a system with excellent earthquake‐proof performance, but it does not dissipate energies caused by the load from weak earthquakes or winds. A hybrid BRB (H‐BRB), which improved the performance of the BRB, is a type of composite damper system consisting of a BRB and a viscoelastic damper. To explain the wind‐induced vibration control performance of H‐BRB, a 40‐story steel building was designed and used as an analysis model in this study, on the basis of the damping ratio from a structural performance test, using normal steel braces, BRB and H‐BRB. In addition, to evaluate the optimal location of H‐BRB, a time‐history analysis of four models was conducted in the study. For such time‐history analysis, wind‐load data in a 10‐year recurrence interval, which were calculated from the wind tunnel test, were used. The result of the time‐history analysis showed that H‐BRB is effective in improving both the lateral stiffness and serviceability of a building using the existing BRB. It also confirmed that it is most effective to position H‐BRBs mainly on the lower stories. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
998.
随着港口建设规模的不断扩大,深水防波堤建设项目也逐年增多,防波堤在抵御海浪侵袭等方面具有重要的作用。但近年来不断出现的防波堤损坏事件,给港口水工工程建设造成了一定的困扰。本文就港口防波堤的损坏情况及损坏的原因进行了分析。 相似文献
999.
浙江省风土建筑类型多样,成因复杂。文章借助建筑人类学、语言学研究成果,从主匠关系出发,引入分级风土特征图谱的概念,探讨浙江省范围内风土建筑区域的划分方法。 相似文献
1000.