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81.
新城金矿竖井保安矿柱的三维圈定与模拟回采 总被引:1,自引:0,他引:1
竖井周边矿体的开采对竖井的稳定性有重要影响。新城金矿Ⅺ#矿体在主竖井下部,首先应用三维软件圈定了竖井保安矿柱并统计压矿量。统计结果显示,依据规范圈定的竖井保安矿柱导致Ⅺ#矿体大部分资源不能被回采。针对这一问题,在Ⅺ#矿体与竖井三维模型的基础上,建立了FLAC3D数值计算模型,并按2种方案进行了模拟回采。数值模拟结果表明:Ⅺ#矿体保安矿柱内部矿石回采具有可行性,回采造成的塑性区主要集中在采空区周围以及充填体内部;回采将导致竖井底部变形较大、应力集中较突出,是关注的重点区域。研究结果为竖井周边矿体的开采提供了理论指导,具有重要的实践意义。 相似文献
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Yuchang Qing Wancheng Zhou Shu Jia Fa Luo Dongmei Zhu State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi an China 《材料科学技术学报》2010,26(11):1011-1015
Microwave absorbing properties of the carbonyl iron particles filled epoxy-silicone resin coatings showed visible degression when the coatings were heat treated at 300 ℃ with different time.The complex permittivity and permeability of the coatings before and after heat treatment were measured.After heat treatment at 300 ℃,the real part of permittivity of the coatings increased with increasing treatment time and showed frequency dependence dielectric response.The complex permeability showed remarkable variat... 相似文献
85.
Su Xiaolei Zhou Wancheng Li Zhimin Luo Fa Du Hongliang Zhu Dongmei 《Materials Research Bulletin》2009,44(4):880-883
The SiC(B) solid solution powders were synthesized via combustion reaction of Si/C system in Ar atmosphere, using boron powder as the dopant and polytetrafluoroethylene as the chemical activator, which were investigated by X-ray diffraction (XRD), scanning electronic microscope (SEM) and Raman spectra. Results show that the prepared powders are C-enriched SiC with C antisites and sp2 carbon defects in which the sp2 carbon is transformed to the sp3 carbon due to boron doping. The electric permittivities of the prepared powders were determined in the frequency range of 8.2-12.4 GHz. The dielectric real part ?′ and dielectric loss tan δ of undoped powder have maximum values (?′ = 5.5-5.3, tan δ = 0.23-0.20), and decrease with increasing boron content. The mechanism of dielectric loss by doping has been discussed. 相似文献
86.
Xiaolei Su ) Wancheng Zhou) Zhimin Li) Fa Luo) Dongmei Zhu) ) State Key Laboratory of Solidification Processing Northwestern Polytechnical University Xi an China ) College of Mechanical & Electronic Engineering Xi an Polytechnic University Xi an China ) School of Technical Physics Xidian University Xi an China 《材料科学技术学报》2009,25(3)
The nonstoichiometric β-SiC powders were synthesized via combustion reaction of Si and C system in a 0.1 MPa nitrogen atmosphere, using Teflon as the chemical activator. The prepared powders were invistigated by XRD and Raman spectra. The results indicates that the cell parameters of all the prepared β-SiC powder are smaller than the standard value of β-SiC because of generation of CSi defects. The complex permittivity of prepared products was carried out in the frequency range of 8.2-12.4 GHz. It shows tha... 相似文献
87.
Effect of composition and annealing on the dielectric properties of ZnO/mullite composite coatings 总被引:1,自引:0,他引:1
ZnO/mullite composite coatings were fabricated by atmosphere plasma spraying technology (APS). Scanning electron microscopy (SEM) and X-ray diffraction (XRD) were employed to investigate the microstructures and compositions of the feedstock and coatings. The permittivity-frequency properties were determined in the microwave frequency range of 8.2-12.4 GHz by network analysis. Our results show that both the real and imaginary part of permittivity increase greatly with increasing ZnO content over the frequency range of 8.2-12.4 GHz, which can be ascribed to interfacial polarization and orientation polarization. However, the composite coatings after 900 °C annealing for 5 h show much lower permittivity, due to the decrease of ZnO content resulting from the further reactions between the ZnO and mullite. Results indicate that the composite coating has excellent permittivity in room temperature, while for high temperature application, more investigation should be done. 相似文献
88.
Influence of the coupling agent on the mechanical properties of SiCf/poly(phenylene benzobisoxazole) composites 下载免费PDF全文
Poly(phenylene benzobisoxazole) (PBO) was first used as matrix to fabricate the two‐dimensional SiCf/PBO composites by a lamination method. Different amounts of coupling agent were introduced to improve the bonding between silicon carbide (SiC) fibers and the PBO matrix during the fabrication of the SiCf/PBO composites. The surface structure and composition of the as‐received PBO and PBO treated with the coupling agent were analyzed, and the morphology and flexural strength of the composites were characterized. The Fourier transform infrared analysis indicated that the hydroxyl groups from the coupling agent were successfully introduced to PBO. The flexural strength of the composites increased at first with increasing content of the coupling agent but decreased with excessive addition of the coupling agent. The flexural strength of the composites was improved from 15 to 89 MPa. The test results suggested that the interaction between the SiC fiber and the treated PBO with the coupling agent was intensified. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39805. 相似文献
89.
采用热压烧结法制备出致密的短切SiC_f增强LAS玻璃陶瓷复合材料,并讨论保温时间与热压压力对复合材料介电性能的影响.结果表明,测试频率在8~12 GHz之间,复合材料复介电常数实部ε′由基体的7.6上升到10~100,虚部ε″由基体的0.34上升到40~160,介电损耗tgδ由基体的0.04上升到1~20,并具有明显的频散效应.随保温时间的延长或热压压力的提高,复合材料ε′增大,ε″与tgδ减小.此外,断口形貌的SEM观察表明,随保温时间的延长或热压压力的提高,复合材料界面层变厚. 相似文献
90.
以硅粉和炭黑为原料,利用燃烧合成法,在0.1MPa 的N_2气氛下合成了β-SiC粉体.对其进行拉曼光谱和SEM表征,结果表明:合成的SiC为含有C反位缺陷C_(si)和石墨态sp~2C的富C β-SiC固溶体.添加剂聚四氟乙烯(PTFE)含量为10%时合成的SiC粉体为等轴状团聚颗粒,粒径约为0.2μm,随着PTFE添加量的增加,SiC粉体颗粒的平均粒径增大.在8.2~12.4 GHz频率范围对所合成SiC的介电常数进行测试,发现15%PTFE时合成的SiC粉体具有较好的介电常数实部ε'、虚部ε"和介电损耗tanδ,对其微波损耗机理进行了讨论. 相似文献