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Tianzuo Wang,Ruipeng Wang,Fei Xue,Ningbo Tang 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.1
Complex ground conditions or support failures during tunnel construction can lead to high ground loss, which may cause damage to surrounding structures. In this paper, a series model tests are carried out in order to clarify tunnelling-induced ground deformation at high ground loss conditions. The model tunnel in this test is shallowly buried in loose sand and the tunnel volume loss (Vl,t) is set from 4% to 10%. The Vl,t is controlled by a water-filling-drainage system and the ground deformation is monitored by digital image correlation (DIC) system. The results show that the Peck-Gaussian function can be used to fit the settlement data well, and the increase of Vl,t has no significant effect on the width of the settlement trough, while the horizontal displacement can be described by modified empirical method. The width of influence aera caused by tunnelling decreases linearly with depth, and the width near the tunnel crown is about 78% of that on the surface. For loose sand ground, it is the shear band rather than the soil arch that dominates the ground deformation. Furthermore, excavation leads to a volume contraction of the ground, which suggests predictions based on tunnel over-excavation trend to underestimate the ground deformation, and that should be taken seriously in consideration of the safety of the engineering project. This study can provide a better understanding of ground deformation induced by tunnelling.
Remote control system based on the internet and machine vision for tracked vehicles
Shuai Wang,Shubing Zhang,Ruoding Ma,E. Jin,Xinhui Liu,He Tian,Ruipeng Yang 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.3
A remote control system based on the Internet and machine vision is designed in this study for tracked vehicles. The system consists of remote monitoring, remote control, and visual navigation subsystems. The on-board computer receives control commands issued by the monitoring center and controls the speed and steering angle of the tracked vehicles. The front camera collects navigation line information, and the collected image is processed by filtering, gray processing, binarization processing, and interference elimination to obtain the center point coordinates of the navigation line. Proportional-integral-derivative (PID), fuzzy PID, and neural network control algorithms are compared based on the distance and angle deviations of the preview point to control the operation of tracked vehicles through simulation. The Internet remote control system with the fuzzy PID control algorithm is then tested on a tracked vehicle. Experimental results indicate that the trajectory of the tracked vehicle fits the navigation path well.
Phase Transitions of Formamidinium Lead Iodide Perovskite under Pressure
Jiang, Shaojie,Luan, Yiliang,Jang, Joon I.,Baikie, Tom,Huang, Xin,Li, Ruipeng,Saouma, Felix O.,Wang, Zhongwu,White, Timothy J.,Fang, Jiye American Chemical Society 2018 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.140 No.42
<P>The pressure-induced structural evolution of formamidinium-based perovskite FAPbI<SUB>3</SUB> was investigated using <I>in situ</I> synchrotron X-ray diffraction and laser-excited photoluminescence methods. Cubic α-FAPbI<SUB>3</SUB> (<I>Pm</I>3̅<I>m</I>) partially and irreversibly transformed to hexagonal δ-FAPbI<SUB>3</SUB> (<I>P</I>6<SUB>3</SUB><I>mc</I>) at a pressure less than 0.1 GPa. Structural transitions of α-FAPbI<SUB>3</SUB> followed the sequence of <I>Pm</I>3̅<I>m</I> → <I>P</I>4/<I>mbm</I> → <I>Im</I>3̅ → partial amorphous during compression to 6.59 GPa, whereas the δ-phase converted to an orthorhombic <I>Cmc</I>2<SUB>1</SUB> structure between 1.26 and 1.73 GPa. During decompression, FAPbI<SUB>3</SUB> recovered the <I>P</I>6<SUB>3</SUB><I>mc</I> structure of the δ-phase as a minor component (∼18 wt %) from 2.41-1.40 GPa and the <I>Pm</I>3̅<I>m</I> structure of the α-phase becomes dominant (∼82 wt %) at 0.10 GPa but with an increased fraction of δ-FAPbI<SUB>3</SUB>. The photoluminescence behaviors from both the α- and δ-forms were likely controlled by radiative recombination at the defect levels rather than band-edge emission during pressure cycling. FAPbI<SUB>3</SUB> polymorphism is exquisitely sensitive to pressure. While modest pressures can engineer FAPbI<SUB>3</SUB>-based photovoltaic devices, irreversible δ-phase crystallization may be a limiting factor and should be taken into account.</P> [FIG OMISSION]</BR>