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61.
针对拟使用充填法将深部矿产资源采出的某矿山,为研究充填性能,取其尾砂进行试验,通过探索充填料浆性能在灰砂比和质量浓度有差异时的变化情况,判断灰砂比和质量浓度对充填料浆性能的影响。采用极差分析法获取两者影响充填料浆性能的主次关系,明确充填料浆配比的适合范畴,随之建立代表料浆性能参数和两因素之间的回归方程。由试验可得:在灰砂比1∶4~1∶12、料浆浓度66%~74%的情况下,料浆流动性能受质量浓度的影响较灰砂比大,但影响充填体强度的关键要素还是灰砂比。根据该矿山的生产需要及室内试验,再联系灰砂比、浓度与充填料浆性能参数间的回归方程,推荐选择最佳参数,灰砂比1∶8,料浆浓度72%。 相似文献
62.
63.
在构建双层无线传感器网络中,汇聚层覆盖需要考虑无重复覆盖面积、汇聚节点连通性和能耗平衡这3个关键问题。该文将上述3个问题统筹为多目标优化难题(MOP),提出一种面向汇聚节点覆盖的量子狼群进化算法(QWPEA),选择出候选头狼(CLW)群体,以滑模交叉、量子旋转门、非门变异等方法产生寻优高效的下一代量子编码人工狼。仿真结果表明,该文所提算法能够有效减少汇聚节点数,提高汇聚层结构稳定性,并平衡网络能耗,适于大范围,大规模传感器节点网络部署环境。在800 m800 m面积部署传感器节点达到1000个时,汇聚有效覆盖率较MOPSO, NSGA-II算法分别高29.55%和25.93%,汇聚通信能耗率分别高15.27%和18.63%,汇聚占通率分别低14.01%和15.46%。 相似文献
64.
The aluminized coating on type 310 stainless steel prepared by high-activity Al pack cementation method has been annealed at 900 °C for 12 h to transform the brittle δ-Fe2Al5 phase into the more ductile β-FeAl phase. The microstructure is studied in detail with transmission electron microscopy. The thick outer layer has β-(Fe, Ni)Al as matrix with cube-like Cr2Al precipitates. The interfacial layer has a thin layer of metastable FCC phase (layer I) and then mixed β-(Fe, Ni)Al grains and α-(Fe, Cr) grains (layers II and III). The Cr2Al precipitates are present in the β-(Fe, Ni)Al grains in layer II but not in those in layer III, while β-FeAl precipitates are present in the α-(Fe, Cr) grains in both layers. The orientation relationships between various phases, the formation of the layers, and the precipitation of Cr2Al in β-(Fe, Ni)Al are discussed. 相似文献
65.
《Ceramics International》2021,47(23):32505-32513
A ZrC–SiC/TiC–SiC/SiC sandwich-structured coating is prepared on a C/C composite by pack cementation methods. The microstructures of this coating are characterized by using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM), and the oxidation resistance is investigated by performing an oxidation test at 1773 K and a cyclic oxidation test. The results show that the mass losses are 7.4% and 3.8% after oxidation for 144 h and 40 cycles, respectively. The sandwich structure relaxes, releases the thermal stress caused by the mismatch in the coefficients of thermal expansion, and absorbs energy to prevent the initiation and propagation of cracks. The ZrC–SiC/TiC–SiC/SiC coating exhibits good isothermal oxidation resistance and excellent cyclic oxidation protection properties. 相似文献
66.
《Ceramics International》2022,48(4):5187-5196
To investigate the silicon/graphite ratio and temperature on preparation and properties of ZrB2–SiC coatings, ZrB2, silicon, and graphite powders were used as pack powders to prepare ZrB2–SiC coatings on SiC coated graphite samples at different temperatures by pack cementation method. The composition, microstructure, thermal shock, and oxidation resistance of these coatings were characterized and assessed. High silicon/graphite ratio (in this case, 2) did not guarantee higher coating density, instead could be harmful to coating formation and led to the lump of pack powders, especially at temperatures of 2100 and 2200 °C. But residual silicon in the coating is beneficial for high density and oxidation protection ability. The SiC/ZrB2–SiC (ZS50-2) coating prepared at 2000 °C showed excellent oxidation protective ability, owing to the residual silicon in the coating and dense coating structure. The weight loss of ZS50-2 after 15 thermal shocks between 1500 °C and room temperature, and oxidation for 19 h at 1500 °C are 6.5% and 2.9%, respectively. 相似文献
67.
68.
提出了实用的型钢垛型CAD系统总体方案,建立了由型钢垛型库,型钢标准数据库,规格库和设计方法库,组成了系统数据库和型钢垛型优化模型。描述了系统功能在AutoCAD R12环境下的实现方法。 相似文献
69.
HUANG Zhi-rong MA Liu-bao LI Pei-ning XU Hong School of Mechanical Engineering East China University of Science Technology Shanghai China 《材料热处理学报》2004,25(5)
IRON ALUMINIDES exhibit excellent corrosionresistance in aggressive atmospheres at elevatedtemperature'1"41,which enables steels or alloys to beprotected by Fe-Al intermetallic coatings.However,itshould be borne in mind that aluminides with a highaluminum content—FeAl3,Fe2Al5—tend to embrittlethe coated layer and reduce its oxidation resistance.Bycontract,iron-rich iron aluminides possess excellentmechanical properties and oxidation resistance15"61.Aluminum diffusion coatings are oft… 相似文献
70.
《Journal of the European Ceramic Society》2022,42(14):6425-6434
New method to prepare Si-SiC coating on C/C composites by laser cladding (LC-Si-SiC) was established to improve the laser ablation resistance of the coating. Results showed that the LC-Si-SiC coating had lower roughness, better mechanical properties and superior laser-ablation resistance compared with the Si-SiC coating fabricated by the traditional coating preparation process: pack cementation (PC-Si-SiC). Due to the shorter heat treatment and less Si infiltration, the flexural strength of the LC-Si-SiC coated sample was 111.32 MPa, which was 144% higher than that of the PC-Si-SiC coated sample. Confirmed by finite element simulation, the LC-Si-SiC coating exhibited better laser-ablation resistance because of the “sweating cooling” mechanism. Under 23.89 MW?m?2 ablation for 7 s, the surface temperature of the LC-Si-SiC coated sample was 3046 K, which was 157 K lower than that of the PC-Si-SiC, causing the mass loss rate of the LC-Si-SiC coating (0.10%) was only 45.45% of the PC-Si-SiC coating. 相似文献