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81.
Synthesis,characterization, and properties of acrylate‐modified tung‐oil waterborne insulation varnish
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Qing Ge Hualin Wang Yi She Suwei Jiang Mengye Cao Linfeng Zhai Shaotong Jiang 《应用聚合物科学杂志》2015,132(10)
An acrylate‐modified tung‐oil waterborne insulation varnish was synthesized from tung oil, maleic anhydride, and acrylates via a Diels–Alder reaction and free‐radical polymerization, and the varnish could be solidified at a relatively low temperature with blocked hexamethylene diisocyanate as a curing agent. The resulting films were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, and differential scanning calorimetry. The insulation properties (electrical insulation strength, volume resistivity, and surface resistivity) of the varnish films were tested, and the resistances of films to salted water were evaluated. With an increase in the maleic anhydride content, the thermal stability of the film was improved, whereas the electrical insulation strength, volume resistivity, and surface resistivity decreased. The electrical insulation strength of the film after it was immersed in the NaCl solution was lower than that in dry state, and it decreased as the immersed time was prolonged. In particular, the electrical insulation strength loss of the film increased significantly at maleic anhydride contents beyond 25 wt %. Furthermore, the hardness of the film increased with increasing methyl methacrylate/N‐butyl acrylate ratio, whereas the flexibility and adhesion of film decreased to a certain degree at the same time. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41608. 相似文献
82.
Characteristics of hemicelluloses obtained from sweet sorghum based on successive extractions
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Hemicelluloses were successively extracted from sweet sorghum by hot water, dioxane, DMSO, and different concentrations of NaOH between 0.5% and 6.0%. The yields of the seven fractions together accounted for 88.6% of the original hemicelluloses. The obtained hemicellulosic subfractions were comprehensively investigated by both destructive methods such as alkaline nitrobenzene oxidation and acid hydrolysis and nondestructive techniques such as gel permeation chromatography, Fourier‐transform infrared, 13C‐nuclear magnetic resonance, and 2D‐heteronuclear singular quantum correlation. Sugar composition studies showed that the water‐soluble polysaccharides consisted mainly of glucose, while xylose, arabinose, and glucuronic acid were the major sugars in other hemicellulosic fractions. It was found that the hemicelluloses from sweet sorghum were l‐ arabino‐(4‐O‐methyl‐d‐ glucurono)‐xylans. Comparison with the hemicellulosic fractions dissolved by the alkali treatment, the hemicellulosic fraction extracted by DMSO had lower molecular weight. In addition, it was also found that the hemicelluloses prepared by dioxane and DMSO were more branched since that they had higher nonxylose/xylose ratios than those extracted by the alkali treatment, which were more linear and contained higher amounts xylose. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42790. 相似文献
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针对某直升机主减机匣的振动噪声问题,对主减传动系统模型进行动力学仿真分析,求解了弧齿锥齿轮副高速传动时产生的动态啮合冲击力;以主减机匣为研究对象,基于阻尼减振机理,分析了轴承座添加泡沫铝阻尼材料对机匣振动的影响.求解机匣振动响应,研究轴承座不同厚度的泡沫铝材料对机匣固有频率、模态阻尼比的影响;分析了阻尼层不同安装位置对轴承座阻尼结构减振效果的影响.结果表明,主减速器啮合频率处机匣的振动加速度值减小14.89%;在轴承座处添加阻尼材料可以增大机匣模态阻尼比,有效地抑制机匣的振动. 相似文献
85.
从本体论的视角而言,中西方园林是两种性质完全不同的空间.二者服务于不同的目的,乃至于发展出不同的技术方法和表现形式.因此,造园目的是理解园林形式、园林创作的艺术与技术手段以及园林审美的基础,也是通达园林本质的起点.该文基于中国传统园林的发展脉络,辅以适当的文献资料,分析中国传统造园目的的变迁.并以此为线索,揭示中国传统园林的空间本质和园林空间演变的文化逻辑.最后,对中国传统园林的当代价值提出讨论. 相似文献
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Lim Swee Su Chong Poh She Jong Bor Chyan Abu Bakar Mimi Hani Wan Daud Wan Ramli Md. Jahim Jamaliah Salehmin Mohd Nur Ikhmal 《Journal of Applied Electrochemistry》2022,52(9):1327-1342
Journal of Applied Electrochemistry - A microbial fuel cell (MFC) is an electricity-generating device utilising electrochemically active microorganisms as biocatalysts. Using MFC as a biosensor to... 相似文献
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89.
Zhengshen Wang Huaiji Zheng Juan Yang Xingang Xie Xuegong She 《Advanced Synthesis \u0026amp; Catalysis》2015,357(9):2082-2088
An effective synthesis of structurally diverse pyrroline derivatives has been accomplished by a gold(I)‐catalyzed tandem 1,3‐acyloxy rearrangement/intramolecular azacylization reaction of γ‐amino‐substituted propargylic esters in good to excellent chemical yields (52–98%). The reaction proceeds under extremely mild conditions and has also demonstrated its potential in a concise formal synthesis of (±)‐aphanorphine with a catalyst loading as low as 0.5 mol% to provide the key intermediate 5‐(4‐methoxybenzyl)‐1‐tosyl‐2,5‐dihydro‐1H‐pyrrol‐3‐yl pivalate on a gram scale.
90.
提出了一种自适应阻抗匹配系统.该系统给出了新的阻抗测量算法,并通过选择补偿电感值和变压器变比的方式使电力线阻抗维持在恒定的值上.实验表明,阻抗测量算法准确性很高,匹配方法可行,从而解决了因电力线载波通信中电力线阻抗实时变化带来的各种问题. 相似文献