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- 저자 : Changjian Yan (검색결과 2 건)
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Pengcheng Qin,Jie He,Changjian Zhang,Yuntao Ye,Hao Zhang,Mingnian Wang,Tao Yan 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.9
Extra-long tunnels have adverse effects on driving performance since drivers will be affected by the enclosed, dimly lit, and monotonous environment for a longer time. In the context of the increasing number of extra-long tunnels, this study aims to investigate the effects of extra-long freeway tunnels with a length of 20 km on driving performance using driving simulation tests. Factors including the tunnel environment, driving time, traffic flow, and gender were considered as influencing factors. Performance indicators including the brake reaction time, standard deviation of driving speed, and standard deviation of lateral position were collected. A total of 60 drivers were recruited for the driving simulation study, and the relationships between the driving performance indicators and influencing factors were analyzed by establishing linear mixed models with random intercept. The results demonstrate that driving performance significantly degraded after 5 − 6 min of driving in the extra-long tunnel although drivers were more cautious and presented a better performance when just entering the tunnel. Moderately higher traffic flow could improve driving performance in the extra-long tunnel but not on the open road. Meanwhile, female drivers had better lateral and longitudinal stability in the extra-long tunnel, while no significant difference was witnessed in reaction ability and driving performance on the open road.
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Effect of Li Content on the Surface Film Formed on the Binary Mg–Li Alloys in NaCl Solution
Chuanqiang Li,Dahui Liang,Yejia Lin,Yong Dong,Binqing Shi,Changjian Yan,Zhengrong Zhang 대한금속·재료학회 2024 METALS AND MATERIALS International Vol.30 No.1
The surface film formed on the Mg–Li alloys with different Li content in 0.1 M NaCl solution were investigated via electrochemicaltesting, morphologies observation and chemical composition analysis in this work. The results revealed that thesurface film of Mg–14Li alloy (L14: body centred cubic (BCC)) possessed higher electrical resistivity and remained a highertolerating over-potential (0.1 V vs. open circuit potential) than those of Mg–4Li (L4: hexagonal closed-packed (HCP)) andMg–7.5Li (L7: HCP+BCC), resulting in a better corrosion performance. After 24 h immersion in NaCl solution, the wholesurface film of L14 remained undamaged and displayed weave-like and dense characteristic, while both L4 and L7 present aseverely damaged film. The cross-sectional details illustrated typical two layers of surface film formed on L14 with the outerlayer of ~ 1.5 μm and inner layer of ~ 2.5 μm in thickness, whilst only one layer of film with less than 2.5 μm in thicknesswas observed on L4 and L7. At last, combining analysis of X-ray diffraction, energy dispersive X-ray spectrometry, X-rayphotoelectron spectroscopy and transmission electron microscope confirmed the composition of outer layer of surface filmon the L14 contains much more Mg(OH)2 and Li-containing compounds, and the porous Mg(OH)2 film can be sealed by theLi-containing compounds, which is very different the single Mg(OH)2 film on the traditional magnesium and L4/L7 alloys. As a result, the best protective function of the surface film on the L14 alloy contribute to its high corrosion resistance.
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