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通过对42CrMo4风机主轴结构尺寸、性能要求、材质特点等方面进行分析,对原有锻后热处理工艺进行优化,制定出既能达到锻后热处理效果又经济节能的工艺参数。 相似文献
95.
《Ceramics International》2022,48(2):1889-1897
SiC fiber reinforced ceramic matrix composites (SiCf-CMCs) are considered to be one of the most promising materials in the electromagnetic (EM) stealth of aero-engines, which is expected to achieve strong absorption and broad-band performance. Multiscale structural design was applied to SiCf/Si3N4–SiOC composites by construction of micro/nanoscale heterogeneous interfaces and macro double-layer impedance matching structure. SiCf/Si3N4–SiOC composites were fabricated by using SiC fibers with different conductivities and SiOC–Si3N4 matrices with gradient impedance structures to improve impedance matching effectively. Owing to its unique structure, SiCf/Si3N4–SiOC composites (A3-composites) achieved excellent EM wave absorption performance with a minimum reflection coefficient (RCmin) of ?25.1 dB at 2.45 mm and an effective absorption bandwidth (EAB) of 4.0 GHz at 2.85 mm in X-band. Moreover, double-layer SiCf/Si3N4–SiOC with an improved impedance matching structure obtained an RCmin of ?56.9 dB and an EAB of 4.2 GHz at 3.00 mm, which means it can absorb more than 90% of the EM waves in the whole X-band. The RC is less than ?8 dB at 2.6–2.8 mm from RT to 600 °C in the whole X-band, displaying excellent high-temperature absorption performance. The results provide a new design opinion for broad-band EM absorbing SiCf-CMCs at high temperatures. 相似文献
96.
Longbang Qing Yuehua Cheng Ru Mu 《Fatigue & Fracture of Engineering Materials & Structures》2019,42(11):2533-2543
Based on theoretical analysis and numerical simulation, the impact of steel fibres on the stress intensity factor (SIF) at the crack tip for cementitious composite was studied. The enhanced toughness of steel fibre reinforced cementitious composite (SFRC) in resisting cracks was explained by the decrement of SIF caused by steel fibre inclusions at the crack tip of the composite. The equivalent initial fracture toughness was used to characterize the crack initiation of SFRC. A simplified method for determining the of SFRC was proposed based on a linear regression method. Fracture tests were conducted on three‐point bending notched beams with different steel fibre volume fractions and specimen sizes to study the crack initiation behaviour of aligned steel fibre reinforced cementitious composite (ASFRC). of ASFRC was calculated, and the size effect of was analysed. The results showed that slightly increased with the steel fibre volume fraction and gradually became stable. For the tested specimens, whose heights varied between 40 and 100 mm, the specimen size had little impact on the . 相似文献
97.
The purpose of feature construction is to create new higher-level features from original ones. Genetic Programming (GP) was usually employed to perform feature construction tasks due to its flexible representation. Filter-based approach and wrapper-based approach are two commonly used feature construction approaches according to their different evaluation functions. In this paper, we propose a hybrid feature construction approach using genetic programming (Hybrid-GPFC) that combines filter’s fitness function and wrapper’s fitness function, and propose a multiple feature construction method that stores top excellent individuals during a single GP run. Experiments on ten datasets show that our proposed multiple feature construction method (Fcm) can achieve better (or equivalent) classification performance than the single feature construction method (Fcs), and our Hybrid-GPFC can obtain better classification performance than filter-based feature construction approaches (Filter-GPFC) and wrapper-based feature construction approaches (Wrapper-GPFC) in most cases. Further investigations on combinations of constructed features and original features show that constructed features augmented with original features do not improve the classification performance comparing with constructed features only. The comparisons with three state-of-art methods show that in majority of cases, our proposed hybrid multiple feature construction approach can achieve better classification performance. 相似文献
98.
Electrochemical impedance spectroscopy (EIS), anodic polarization and scanning electron microscopy techniques were used to investigate the damage mechanism in the transpassive potential region of AISI ... 相似文献
99.
为提高矿山工程建设项目造价管理水平,设计了矿山工程建设项目造价管理系统。通过分析矿山工程项目的造价组成,并采用三层B/S架构设计系统硬件框架,运用Web服务器传输矿山工程项目各项数据,划分系统功能子系统,并对矿山工程建设项目造价额与价差预备费进行计算,完成系统软件设计。结果表明,该系统能够有效管理矿山工程建设项目造价,并对外部的恶意攻击进行及时报警,系统具有有效性与安全性。 相似文献
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