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Journal of Thermal Analysis and Calorimetry - The bio-based semi-aromatic high-temperature polyamide PA5T/56 was successfully synthesized by one-step method, which shortened the reaction time... 相似文献
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分析我国现行《钢结构设计规范》GB50017-2003,对比美、欧规范,针对钢结构常用受力构件设计的强度问题和稳定问题涉及到的弹塑性理论应用,通过课堂教学环节,讲授钢结构构件设计原理和弹塑性设计方法,让学生深刻体会弹性设计理论和弹塑性设计理论的差异,认识弹塑性理论在钢结构设计中应用的必要性. 同时也让学生学习正确运用力学知识解决工程问题的思维方法,激发学生学习力学理论的兴趣,培养学生综合应用知识解决工程问题的能力. 相似文献
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Copolymerization of acrylic acid and p‐chloromethylstyrene (p‐CMS) in dioxane initiated with α,α′‐azobisisobutyronitrile was carried out to produce macroinitiator P(AA‐co‐CMS) containing PhCH2Cl group at 65°C. Then methyl methacrylate was grafted onto P(AA‐co‐CMS) backbone using PhCH2Cl group as an initiation site and FeCl2/triphenyl phosphine complex as a catalyst. The resulted copolymer (AA‐co‐CMS)‐g‐PMMA with a comb‐like branched structure has a hydrophilic backbone (PAA) and hydrophobic side chains (PMMA). Compositions and structures of macroinitiator and the grafted product of P(AA‐co‐CMS)‐g‐PMMA were determined by 1H‐NMR, infrared (IR), and gel permeation chromatography (GPC). The average graft number, the average length of branch chains, the graft ratio, and the graft efficiency were investigated. The swelling behavior of the comb‐like branched polymer was also investigated. The gradual increase of swelling ratios was accompanied by an increase of pH and temperature. The kinetic exponents indicated that the swelling transport mechanisms transformed from Fickian diffusion to non‐Fickian transport as the decreasing pH. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
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A new stochastic method of reconstructing porous media 总被引:1,自引:0,他引:1
We present a new stochastic method of reconstructing porous medium from limited morphological information obtained from two-dimensional
micro- images of real porous medium. The method is similar to simulated annealing method in the capability of reconstructing
both isotropic and anisotropic structures of multi-phase but differs from the latter in that voxels for exchange are not selected
completely randomly as their neighborhood will also be checked and this new method is much simpler to implement and program.
We applied it to reconstruct real sandstone utilizing morphological information contained in porosity, two-point probability
function and linear-path function. Good agreement of those references verifies our developed method’s powerful capability.
The existing isolated regions of both pore phase and matrix phase do quite minor harm to their good connectivity. The lattice
Boltzmann method (LBM) is used to compute the permeability of the reconstructed system and the results show its good isotropy
and conductivity. However, due to the disadvantage of this method that the connectivity of the reconstructed system’s pore
space will decrease when porosity becomes small, we suggest the porosity of the system to be reconstructed be no less than
0.2 to ensure its connectivity and conductivity. 相似文献
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Ying Feng Rui Zhou Peng Zhang Qian Sang Xiucai Dong Jiruo Zhao 《Journal of Macromolecular Science: Physics》2013,52(1):57-65
Composites of chlorinated polyethylene with various Cl-contents and carbon nanotubes (CNT) were produced and their rheological behaviors were characterized by capillary viscometry. For polyethylene (PE)/CNT composites with CNT loadings of 3 wt% and 5 wt%, the melt viscosity was higher than that of PE alone. However, the PE/CNT composite with CNT loading of 2 wt% gave a much lower melt viscosity than that of PE alone. The melt viscosity of chlorinated polyethylene (PECl)/CNT composites prepared also depended on the amount of added CNT and chlorine content. PECl/CNT composites with higher chlorine content displayed lower melt viscosities than that of PECl alone. A mechanism was proposed. 相似文献
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Haixiao Hu Bin Chang Xiucai Sun Dr. Qin Huo Dr. Baoguo Zhang Dr. Yanlu Li Yongliang Shao Dr. Lei Zhang Prof. Yongzhong Wu Prof. Xiaopeng Hao 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(44):10420-10426
The anisotropy of crystalline materials results in different physical and chemical properties on different facets, which warrants an in-depth investigation. Macroscopically facet-tuned, high-purity gallium nitride (GaN) single crystals were synthesised and machined, and the electrocatalytic hydrogen evolution reaction (HER) was used as the model reaction to show the differences among the facets. DFT calculations revealed that the Ga and N sites of GaN (100) had a considerably smaller ΔGH* value than those of the metal Ga site of GaN (001) or N site of GaN (00−1), thereby indicating that GaN (100) should be more catalytically active for the HER on account of its nonpolar facet. Subsequent experiments testified that the electrocatalytic performance of GaN (100) was considerably more efficient than that of other facets for both acidic and alkaline HERs. Moreover, the GaN crystal with a preferentially (100) active facet had an excellently durable alkaline electrocatalytic HER for more than 10 days. This work provides fundamental insights into the exploration of the intrinsic properties of materials and designing advanced materials for physicochemical applications. 相似文献
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