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161.
《Journal of the European Ceramic Society》2021,41(14):6859-6868
Electrospun unidirectional SiC fibers reinforced SiCf/SiC composites (e-SiCf/SiC) were prepared with ∼10% volume fraction by polymer infiltration and pyrolysis (PIP) process. Pyrolysis temperature was varied to investigate the changes in microstructures, mechanical, thermal, and dielectric properties of e-SiCf/SiC composites. The composites prepared at 1100 °C exhibit the highest flexural strength of 286.0 ± 33.9 MPa, then reduced at 1300 °C, mainly due to the degradation of electrospun SiC fibers, increased porosity, and reaction-controlled interfacial bonding. The thermal conductivity of e-SiCf/SiC prepared at 1300 °C reached 2.663 W/(m∙K). The dielectric properties of e-SiCf/SiC composites were also investigated and the complex permittivities increase with raising pyrolysis temperature. The e-SiCf/SiC composites prepared at 1300 °C exhibited EMI shielding effectiveness exceeding 24 dB over the whole X band. The electrospun SiC fibers reinforced SiCf/SiC composites can serve as a potential material for structural components and EMI shielding applications in the future. 相似文献
162.
《Journal of the European Ceramic Society》2021,41(13):6196-6206
Creep properties of 2D woven CVI and PIP SiC/SiC composites with Sylramic™-iBN SiC fibers were measured at temperatures to 1650 °C in air and the data was compared with the literature. Batch-to-batch variations in the tensile and creep properties, and thermal treatment effects on creep, creep parameters, damage mechanisms, and failure modes for these composites were studied. Under the test conditions, the CVI SiC/SiC composites exhibited both matrix and fiber-dominated creep depending on stress, whereas the PIP SiC/SiC composites displayed only fiber-dominated creep. Creep durability in both composite systems is controlled by the most creep resistant phase as well as oxidation of the fibers via cracking matrix. Specimen-to- specimen variations in porosity and stress raisers caused significant differences in creep behavior and durability. The Larson-Miller parameter and Monkman-Grant relationship were used wherever applicable for analyzing and predicting creep durability. 相似文献
163.
对低碳钢表面进行等离子弧堆焊时外加间歇交变纵向磁场,研究了电磁搅拌对堆焊层金属组织及性能的影响,并利用光学金相、X射线衍射、显微硬度和湿砂橡胶轮磨损试验等手段对试样进行测试分析.研究发现,随着磁场参数的增强,堆焊层中硬质相的数目随之增加,且均匀分布于堆焊层的表面,堆焊层金属的耐磨性也随之增强;当磁场电流为3 A,磁场频率为10Hz时,堆焊层金属的性能达到最佳状态.结果表明,在适当的电磁参数作用下,堆焊层金属才能获得最佳的细化效果;而且电磁搅拌可以控制堆焊层表面中硬质相的形态,使其由长条状和六方块状的混合形态逐渐转变为较规则、均匀的六方块状,从而进一步提高堆焊层金属的硬度和耐磨性. 相似文献
164.
In order to enhance the dimension precision of bent part, advanced bending technologies is requested recently. Rotary stretch bending(RSB) is a suitable technology to realize high precision of bent part. The effect of processing parameters, namely the side pressure and the stretching force, on the dimension precision of aluminium profile RSB part was studied by finite element method. The numerical simulation of the U-shaped aluminium profile RSB was carried out, and the validity of the simulation was checked. Parametric analysis shows that the section distortion of the U-shaped profile LY 12M bent part decreases with the increasing of the side pressure, whereas the springback of curvature increases, and that both of the section distortion and the springback of curvature decrease with the increasing of the stretching force, moreover, the uniformity of curvature of the bent part is clearly enhanced with the increasing of the stretching force. The results above prove that RSB technology can better improve the dimension precision of aluminium profile bent part. 相似文献
165.
This study aims to add to the discussion about the applicability of the classical deindividuation theory and social identity model of deindividuation effects (SIDE) in explaining online behaviours. It explores the effect of anonymity in facilitating social influence of group identity in online game cheating. A nationally representative survey was conducted face to face. Results from the survey administered in Singapore confirm predictions derived from the SIDE and challenge the classical deindividuation theory. Specifically, it was concluded that the frequency of gaming with online strangers (anonymous gaming) significantly predicted the frequency of cheating in online games. The effect of anonymity on game cheating was found to be significantly mediated by the group identification with online gaming communities/groups. Gender differences were found. Male gamers cheated more frequently than female gamers. Female gamers are more likely to cheat as a consequence of group identification than male gamers. Implications and future research are discussed. 相似文献
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基于接纳控制的智能电网需求响应 总被引:1,自引:0,他引:1
采用效用函数刻画用户的用电满意度, 将需求响应问题建模为一类凸优化问题. 针对电力供应商的供电量不能满足用户最小用电需求的问题, 结合分布式用电量调度和实定价, 设计两类接纳控制算法. 仿真结果表明, 通过接纳控制, 满足了购电用户的最小用电需求, 保证了用户的用电质量, 能够实现电网的供需平衡. 相似文献