摘要：The special electronic characteristics and high atom usage efficiency of metal-nitrogen-carbon(M-N-C)materials have made them extremely attractive for oxygen reduction reactions(ORRs).However,it is inevitable that hydrogen peroxide(H_(2)O_(2))will be formed via the two-electron pathway in ***,the Cu nanoparticles(NPs)have been encapsulated into Ni doped hollow mesoporous carbon spheres(Ni-HMCS)to reduce the generation of H_(2)O_(2)in *** tests confirm that the introduction of Cu NPs improves the ORR performance *** obtained Cu/Ni-HMCS exhibits a half-wave potential of 0.82 V *** hydrogen electrode and a limited current density of 5.5 mA cm^(-2),which is comparable with the commercial Pt/***,Cu/Ni-HMCS has been used in Zn-air battery,demonstrating a high power density of 161 mW cm^(-2)and a long-term recharge capability(50 h at 5 mA cm^(-2)).The theoretical calculation proposes a tandem catalysis pathway for Cu/Ni multi-sites catalysis,that is,H_(2)O_(2)released from the Ni-N_(4)and Cu-N_(4)sites migrates to the Cu(111)face,on which the captive H_(2)O_(2)is further reduced to H_(2)*** work demonstrates an interesting tandem catalytic pathway of dual-metal multi-sites for ORR,which provides an insight into the development of effective fuel cell electrocatalysts.

摘要：Both of planar and mesoporous architectures prevail for perovskite solar cells(PSCs).However,it is still an open question how the architecture affects the performance of *** inconsistent results in the references often create *** particular,the specific roles of mesoporous frameworks are yet to be well elaborated and require further *** this study,we carefully compared the properties of perovskite films and the device performances for both architectures to unravel the roles of mesoporous TiO2 framworks in CH3NH3PbI3 *** detailed characterizations of structural,microscopic,optical and electrical properties revealed that the presence of mesoporous TiO2 framework contributed to enlarged perovskite crystal sizes,enhanced light harvesting,efficient electron extration and suppressed charge *** a result,compared with the planar device,the mesoporous device yielded an improved power conversion efficiency of 18.18%,coupled with a reduced *** study reveals the benefits of mesoporous TiO2 framework in PSCs and provides the guidance for the design and optimization of architectures for high-performance devices.

摘要：Single gimbal control moment gyroscope(SGCMG)with high precision and fast response is an important attitude control system for high precision docking,rapid maneuvering navigation and guidance system in the aerospace *** this paper,considering the influence of multi-source disturbance,a data-based feedback relearning(FR)algorithm is designed for the robust control of SGCMG gimbal servo *** on adaptive dynamic programming and least-square principle,the FR algorithm is used to obtain the servo control strategy by collecting the online operation data of SGCMG *** is a model-free learning strategy in which no prior knowledge of the SGCMG model is ***,combining the reinforcement learning mechanism,the servo control strategy is interacted with system dynamic of *** adaptive evaluation and improvement of servo control strategy against the multi-source disturbance are ***,a data redistribution method based on experience replay is designed to reduce data correlation to improve algorithm stability and data utilization ***,by comparing with other methods on the simulation model of SGCMG,the effectiveness of the proposed servo control strategy is verified.

摘要：A kind of surface instability,basin-like depression defect companied by mixed grain structure at the bottom of large-scale valve during electric upsetting process,would significantly influence the microstructures and mechanical properties of *** order to analyze the forming process of the basin-like depression defect,a finite element model for the electric upsetting process of Ni80A superalloy was developed using multi-field and multi-scale coupling analysis ***,a series of parameters loading path schemes for force and current were designed by varying the initial value,peak value and value level,and their effects on basin-like depression and mixed grain structure were simulated and *** is concluded that the changes of heating speed and pressurization speed result in the different flow velocities between the inner and outer layers of billet,thus exerting the basin-like *** results also indicate that these defects can be optimized through the parameter coordination between force and ***,the validity and reliability of the finite element model were verified by physical experiments in electric upsetting process.

摘要：通讯技术不断升级以及移动设备的快速发展极大改善了人们生活,但也带来了电磁干扰和信息安全问题.因此,亟需开发高性能电磁屏蔽材料来抑制电磁辐射和阻止信息泄露.研究发现,在外力作用下填料的自取向行为有助于实现聚合物基复合材料电磁屏蔽性能的提升,因此如何在聚合物基体中构筑有效的填料取向结构正成为电磁屏蔽材料研究的热点.本文首先关注外场诱导复合材料内导电网络的构建策略.随后,梳理了利用外场诱导无机填料取向制备聚合物基电磁屏蔽复合材料的研究进展,其中外场包括温度场、静电场、重力场、机械力场和磁场.值得注意的是,基于外场诱导制备的独特结构与电磁波之间的特殊响应关系通过精选的案例被进一步剖析.最后,提出外场辅助制备聚合物基电磁屏蔽复合材料各自亟待解决的关键科学和技术问题,并对未来的发展方向进行了理性预测.本文讨论的方法和提出的策略有望为高性能聚合物基电磁屏蔽复合材料的创新设计提供一些指导意见.

摘要：The friction and wear tests were performed using Nitinol 60 alloy pin sliding over GCr15 steel disk in a pin-on-disk tribometer system under PAO oil lubrication conditions. It was found that Nitinol 60 alloy can be lubricated well and has shown remarkable tribological performance. Average coefficient of friction （COF） of Nitinol 60 is 0.6 under dry friction; however, average COF decreases to 0.1 under PAO oil lubrication. SEM image of the worn surface shows that Nitinol 60 exhibits excellent wear resistance and the wear mechanism is mainly adhesive wear. Flow pattern of oil-air flow in oil pipe was simulated by FLUENT software with VOF model for acquiring working performance of oil-air lubrication. The optimum velocity of oil and air at the inlet was achieved, which provides the great proposal for the design of experiment of oil-air lubrication of Nitinol 60 alloy. The simulation results showed that the optimum annular flow of flow pattern was obtained when air velocity is 10 m/s and oil velocity is 0.05 m/s. The formation mechanism of annular flow was also discussed in the present study.

摘要：Radon is a polluting and radioactive gas released by rock fracture. Shear fracture is widely developed in surrounding rock mass of deep engineering. Nevertheless, the correlation between radon release and the shear fracture is undefined. In this study, the intact Jinping marble and Baihetan basalt were adopted as samples. Based on radionuclide content analysis, the intrinsic characteristics of radon emission were analyzed. Then a direct shear testing system was designed to synchronously measure radon release during rock fracture. The direct shear tests were carried out under different normal stresses. The relationship between shear fracture process and cumulative radon concentration was explored. The results indicated that radon release varied with the increase of shear displacement under the same normal stress. The general pattern showed a slight increase and fell in the initial loading phase, then increased rapidly to the peak release approximately corresponding to the peak of shear stress, and finally decreased to a stable level with the development of shear displacement after sample failure. The initial and peak radon concentrations increased linearly with the increase of normal stress. The same trend was found in shear failure surface area and cumulative radon concentration according to the rise angle(RA) value-average frequency(AF) distribution.

摘要：In piled and geosynthetic-reinforced(PGR) embankment, the arching behavior determines the overburden load on piles and subsoils. Placement of geosynthetic is effective in reducing the relative displacement between pile and subsoil. When the mobilized shear stress is less than the shear strength, partially developed arching will occur. Consequently, existing analytical methods, adopting the ultimate shear strength failure criterion, need to be improved. This study developed a simplified 2 D analytical method, which is based on the developing arching effect, to evaluate the load redistribution of the PGR embankment. Then, the influences of embankment height and internal friction angle, subsoil depth, ratio of pile cap width to pile clear spacing(RPC) and geosynthetic tensile stiffness on the critical height ratio, stress concentration ratio, soil arching ratio, geosynthetic tension and axial strain were investigated. This study suggests that a RPC of 1:1.0 and a one-way of single-layer geosynthetic tensile stiffness of 2000 kN/m should be considered as the sensitivity thresholds for the PGR embankment.

摘要：The development of a high-performing pseudocapacitor requires a comprehensive understanding of electrode materials from the aspects of electron transfer and electrolyte ion adsorption and ***,these factors are considered over the prototype TiO_(2),and a high pseudocapacitance is achieved via the introduction of various defects,i.e.,oxygen defect(V_(O))and co-doped defect(V_(O)+N_(O)).The study is based on joint explorations of first-principle calculations and the transfer matrix *** to pristine TiO_(2)(300 F g^(-1)),defective TiO_(2) produces pseudocapacitance as high as 1700 F g^(-1).Moreover,defects induce small barriers for electron transmission caused by surface band *** climbing image nudged elastic band diffusion of H ions displays a much higher barrier in TiO_(2)-V_(O) than in TiO_(2)-V_(O)+N_(O).Such a result indicates easy H diffusion in the co-doped *** work provides insights into the adsorption and diffusion of electrolyte ions and the influence of defects on electron *** results are also significant for the design and optimization of electrode materials for the next generation of supercapacitors.

摘要：Trap-mediated energy loss in the buried interface with non-exposed feature constitutes one of the serious challenges for achieving high-performance perovskite solar cells(PSCs).Inspired by the adhesion mechanism of mussels,herein,three catechol derivatives with functional Lewis base groups,namely 3,4-Dihydroxyphenylalanine(DOPA),3,4-Dihydroxyphenethylamine(DA)and 3-(3,4-Dihydroxyphenyl)propionic acid(DPPA),were strategically *** molecules as interfacial linkers are incorporated into the buried interface between perovskite and SnO_(2) surface,achieving bilateral synergetic passivation *** crosslinking can produce secondary bonding with the undercoordinated Pb^(2+) and Sn^(4+) *** PSCs treated with DOPA exhibited the best performance and operational *** the DOPA passivation,a stabilized power conversion efficiency(PCE)of 21.5%was demonstrated for the planar *** 55 days of room-temperature storage,the unencapsulated devices with the DOPA crosslinker could still maintain 85%of their initial performance in air under relative humidity of-15%.This work opens up a new strategy for passivating the buried interfaces of perovskite photovoltaics and also provides important insights into designing defect passivation agents for other perovskite optoelectronic devices,such as light-emitting diodes,photodetectors,and lasers.