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11.
近期在欧洲建筑保温材料市场出现一种隔热性能优异新型VIP真空隔热板,尤其适用于寒冷地区保温要求较高的节能建筑。本文简要介绍了建筑用VIP真空隔热板的结构和性能;概述了它在节能建筑领域的应用现状;例举了德国VIP板用于节能建筑保温的工程实例;希望能为我国北方区域低能耗建筑的发展提供信息。 相似文献
12.
针对非均质软土地基上吸力式沉箱的抗拔极限承载力,运用大型有限元分析软件ABAQUS进行了三维非线性数值分析。通过一定数量的数值计算与分析,较系统地考察了沉箱承受拉拔荷载过程中主动侧土体与结构接触状态对沉箱极限承载力的影响。由此表明:软土地基的不排水抗剪强度、吸力式沉箱结构的长径比、荷载作用点位置等因素对于主动侧土体与结构的接触状态具有一定影响。通过与有关模型试验结果及极限分析上限解的对比分析,在一定程度上验证了有限元计算模型与数值分析结果的合理性。 相似文献
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对膜结构施工中由裁剪片拼接张拉形成的膜面进行应力松弛分析,考察膜面应力随时间逐渐减小的变化规律。考虑膜材材料和几何双重非线性,采用广义Maxwell黏弹性模型建立积分型本构方程,推导增量本构方程,编制非线性有限元程序实现成形曲面的应力松弛数值分析过程。对聚氯乙烯 (PVC)膜材进行了不同初始应力水平下的单轴应力松弛试验和不同应力比下的双轴应力松弛试验,用5单元的广义Maxwell黏弹性模型对试验数据拟合,确定了膜材本构方程的黏弹性参数。进行十字形膜片的加载及应力松弛试验,对其试验过程进行数值分析,结果表明试验结果与数值分析结果基本一致,验证了成形曲面黏弹性数值分析方法的可行性。对PVC膜材马鞍形曲面算例进行黏弹性分析,结果表明,马鞍形曲面在张拉完成4 d后,膜面平均应力降低了44%。 相似文献
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《Food Control》2015
Chinese red pepper (Zanthoxylum bungeanum Maxim.) leaf (ZML) extract contains high amounts of phenolic compounds possessing high total antioxidant capacity and hydroxyl, 1, 1-dipheny-2-picrylhydrazyl (DPPH) free radical scavenging activity. ZML extract was investigated as a natural antioxidant for the lipid stability of salted silver carp (Hypophthalmichthys molitrix) throughout salting and drying. Both dorsal and ventral muscles were examined for differences in moisture content, salt content, total lipid content, and degree of lipid oxidation. The hexanal content, Thiobarbituric acid reactive substances (TBARS) value, and lipoxygenase (LOX) activity in the ventral muscle were significantly higher than those of the dorsal muscle (p < 0.05). In the treatments with ZML extract, the hexanal content, the TBARS value, and the LOX activity were significantly lower (p < 0.05) during processing both in the dorsal and ventral muscles. The sensory qualities of processed salted fish could be improved with the amount of 0.030% extract in the dorsal muscle and 0.045% extract in the ventral muscle. These results showed that ZML extract can be a source of natural antioxidants and used as a food additive. 相似文献
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Huilong Guo Jingqing Li Jiayi Wang Yanfeng Meng Zhonghua Wu Shichun Jiang 《Polymer Engineering and Science》2020,60(3):581-586
The deformation induced structure evolutions of polyamide 6 (PA6) during uniaxial tension at high tensile temperatures (60 °C and 90°C) were investigated with in situ wide- and small-angle X-ray scattering (WAXS and SAXS) technologies. The obtained data on structure evolutions revealed that they were different from the results measured at low temperature (30 °C). The α-phase got oriented once upon the beginning of deformation. After yielding the γ-phase started to be oriented following the α-phase. While, the breakdown of PA6 crystals along a and c axis overcame partial crystalline orientation at the high tensile temperatures (60 and 90 °C). The competition between stretch of amorphous phase and slippage of lamellae after yielding affected the deformation behavior of PA6. The collapse of lamellae was also confirmed from SAXS analysis and such disrupted lamellar structure resulted in the decrease of long spacing of PA6. The results showed that PA6 materials may show higher ductility at high temperatures. Therefore the crystals could be broken more easily and the formed lamellar fragments of PA6 could be preserved at larger strain at 90 °C. In addition, the yielding of PA6 and γ-phase orientation depended on the lamellar slippage during the deformation. POLYM. ENG. SCI., 60:581–586, 2020. © 2019 Society of Plastics Engineers 相似文献
18.
《International Journal of Hydrogen Energy》2020,45(51):27202-27209
The catalytic mechanism and activity of transition metal atom doped C2N (M-C2N, M = Fe, Co, Ni, and Cu) for the oxygen reduction reaction (ORR) are investigated in detail by density functional theory method. All the screened M-C2N are thermodynamically stable based on the binding energy calculations. The adsorption energy results indicate that the adsorption strength of O2 and ORR intermediates are decreased in the order of Fe-C2N ˃ Co-C2N ˃ Ni-C2N ˃ Cu-C2N, in which the adsorption energy values on Cu-C2N are most close to those on the Pt(111). Based on the relative energy diagram of ORR, the energetically favorable pathway on Fe-C2N and Co-C2N is direct 4e− mechanism, in which the O–O bond is directly dissociated after the second electron transfer. While for Ni-C2N and Cu-C2N, the most favorable pathway is indirect 4e− mechanism, in which the H2O2 is formed as the intermediate product. For all studied M-C2N, the Ni-C2N and Cu-C2N hold better catalytic activity, which could attribute to the contribution of metal atom and part of its activated nitrogen atoms. 相似文献
19.
Iron‐mediated activators generated by electron transfer for atom‐transfer radical polymerization of methyl methacrylate using ionic liquid as ligand and Fe(0) wire as reducing agent 下载免费PDF全文
Liangjiu Bai Suqi Huang Wenxiang Wang Hui Xu Hou Chen Yuzhong Niu Minghua Wang 《Polymer International》2015,64(12):1754-1761
1‐Butyl‐3‐methylimidazolium hexafluorophosphate (BMIMPF6) as a typical ionic liquid (IL) effectively acted as ligand for the control of iron‐mediated activators generated by electron transfer for atom‐transfer radical polymerization of methyl methacrylate (MMA) in the presence of a limited amount of oxygen, using FeCl3.6H2O as the catalyst and Fe(0) wire as the reducing agent. The polymers obtained with BMIMPF6 had controlled molecular weights and low Mw/Mn values (<1.40). Moreover, a well‐defined final product PMMA without additional processing was easily obtained and the reducing agent (iron wire) could be recycled and reused effectively just by washing three times with solvents. 相似文献
20.
带有不匹配干扰的多智能体系统有限时间积分滑模控制 总被引:1,自引:1,他引:0
针对动态多智能体系统协同控制问题,本文研究了带有不匹配干扰的二阶多智能体系统的有限时间包容控制,提出了基于非线性积分滑模控制(Integral sliding-mode control,ISMC)的复合分布式包容控制算法.首先利用Lyapunov稳定性和齐次性定理,分析了未受扰系统的有限时间包容控制问题;然后针对存在不匹配干扰的多智能体动态系统,设计非线性有限时间干扰观测器估算智能体的状态和干扰,提出基于干扰观测器的复合分布式积分滑模控制协议,结合现代控制理论和滑模控制理论,研究了带有不匹配干扰的多智能体系统有限时间包容控制问题.最后数值仿真证明了控制算法的有效性. 相似文献