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Qiang Feng,Shenggang Fu,Chengxiang Wang,Weiwei Liu,Ying Wang,Weiguo Qiao 대한토목학회 2019 KSCE Journal of Civil Engineering Vol.23 No.9
There is an increasing trend of tunnel infrastructure construction in cold regions due to the advance of a western development strategy. To reduce the frost damage sustained by a tunnel, it is important to consider the mechanical properties of frost heave in the surrounding rock by analyzing the anisotropic frost heave of a cold-region tunnel. This paper elaborates on the behavior of anisotropic frost heave in the rock surrounding a cold-region tunnel, and the coefficient of displacement relief is adopted to indirectly quantify the influence of the tunnel construction process. The analytical elasto-plastic solutions of the stress and deformation in the surrounding rock are derived with Drucker-Prager criteria (hereinafter referred to as the D-P criteria) by modifying the constitutive equation for the frozen surrounding rock. Finally, an example is given to obtain the influence law of the distribution of stress and deformation in the surrounding rock. The results indicate that the plastic radius and frost force calculated by considering isotropic frost heave are greater than those obtained by considering anisotropic frost heave. The influence of the related parameters also analyzed. Some useful insights are provided for future numerical simulations and the design and construction of cold-region tunnels.
Detecting Taxi Travel Patterns using GPS Trajectory Data: A Case Study of Beijing
Hui Zhang,Baiying Shi,Chengxiang Zhuge,Wei Wang 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.4
GPS trajectory is a valuable source to understand the operational status of taxicabs and identify the traffic demand and congestions. This study attempts to use 24-hour taxi trajectory data to investigate the attributes of taxicabs such as the distance of occupied distance, number of active taxicabs in different hours, average trip speed in different hour, coverage area of a taxicab, average radius of a taxicab, occupied rate and service times. The results show that the highest speed of taxicabs occur in the 3:00 am when there is the smallest number of active taxicabs running on the road. Moreover, the average occupied rate is 0.59 and the average service times are 19.8 in a day. Finally, a latent class analysis model is used to make the segment of taxicabs by their attributes. Four operational patterns have been found including ‘downtown preference type’, ‘long-distance preference type’, ‘suburbs preference type’ and ‘free preference type’. This study can shed light on understanding the operational status of taxicabs and gives suggestions for operators and passengers for better managing and using taxicabs.
Mechanism of Ce promoting SO2 resistance of MnOx/γ-Al2O3: An experimental and DFT study
Xiaopeng Zhang,Zhuofeng Li,Jijun Zhao,Yuezong Cui,Bojian Tan,Jinxin Wang,Chengxiang Zhang,Gaohong He 한국화학공학회 2017 Korean Journal of Chemical Engineering Vol.34 No.7
Various physico-chemical techniques and theoretical chemistry computations are used to obtain a deep insight into the mechanism of Ce improving SO2 resistance of the catalyst Mn0.4Cex/Al2O3 (x stands for the molar ratio of Ce : Al). Theoretical computation with density functional theory (DFT) shows that Ce modification enhances the adsorption energy of SO2 adsorbed on Ce surrounding, resulting in the preferential adsorption of SO2 on Ce surrounding. It protects the surface Mn from SO2 poisoning, leading to a better SO2 resistance. FT-IR and TG results are in good accordance with DFT results. FT-IR results suggest that absorption peaks related to SO4 2− cannot be detected in Mn0.4Ce0.12/Al2O3. Moreover, TG results show that weight loss peaks due to sulfated MnOx decomposition disappears after Ce addition. Therefore, Ce modification inhibits sulfates formation on active components lead to a better resistance to SO2 of Mn0.4Ce0.12/Al2O3.