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Qing Yuan,Shihong Zhai,Li Wu,Peishuai Chen,Yuchun Zhou,Qingjun Zuo 한국자원공학회 2019 Geosystem engineering Vol.22 No.5
In blasting excavation engineering of super-large section underground caverns, blasting vibration velocity prediction accuracy is affected by many factors. In order to improve its accuracy, the key problem is to obtain these affect factors comprehensively. In this paper, we innovatively put forward eight independent factors in the aspect of explosion source conditions, engineering conditions and propagation medium conditions. These factors have complex non-linear relationship with blasting vibration velocity. We consider particle swarm optimization (PSO) algorithm and least squares support vector machine (LS-SVM) method for prediction (PSO-LSSVM). In this way, how to determine the characteristic parameters and calculation rules of PSO-LSSVM method is another key problem, which has been innovatively solved in this paper. Then it is used to predict the blasting vibration velocity of underground water-sealed LPG caverns in Yantai, China, and compared with Sadov’s formula (SA), fuzzy neural network (FNN) and LS-SVM methods. The results indicate that relative errors of PSO-LSSVM are significantly less than LS-SVM, FNN and SA. Whether global root mean square relative error for prediction accuracy, or group number meeting requirement of error threshold value for generalization performance, the PSO-LSSVM method is superior to LS-SVM, FNN and SA with best availability and superiority.
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Lingling Ren,Huimin Gu,Wei Wang,Shuai Wang,Chengde Li,Zhenbiao Wang,Yuchun Zhai,Peihua Ma 대한금속·재료학회 2021 METALS AND MATERIALS International Vol.27 No.1
Despite showing considerable potential, wire arc additive manufacturing (WAAM) has been limited to producing Al–Mgalloys. As the addition of Sc can improve the mechanical properties of Al–Mg alloys, in this study, Al–Mg–Sc alloy depositswith different Sc contents were prepared by a WAAM process. The porosity, microstructure, and mechanical properties ofthe deposits were studied. At Sc contents less than 0.15%, Sc was completely dissolved in the Al matrix without grain refinement,and the mechanical properties were slightly improved. At a Sc content of 0.3%, the primary Al3Scphase precipitatedout of the as-deposited body, resulting in an abrupt change in the microstructure, significant grain refinement, significantlyincreased tensile strength and yield strength, with a tensile strength, yield strength, and elongation of 372 MPa, 270 MPa,and 22.5%, respectively. Following heat treatment at 350 °C for 1 h, the grain boundaries were refined and the secondaryAl3Scphase was precipitated. Furthermore, the tensile strength and yield strength were significantly increased to 415 MPaand 279 MPa, respectively, and elongation decreased to 18.5%. At a Sc content of 0.45%, due to the aggregated precipitatedphase, the coarsened grain boundaries and the limited solid solution amount of Sc in the α(Al) matrix (~ 0.25%), themechanical properties were not further improved compared with the deposit with Sc content of 0.3%. Thus, based on economicconsiderations, the optimal Sc content was 0.3%. Owing to their enhanced mechanical properties, WAAM-producedAl–Mg–Sc alloys are expected to have a wide range of applications in aviation, aerospace.
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Huamei Duan,Yunxia Yang3,Jim Patel,Nick Burke,Yuchun Zhai,Paul A. Webley,Dengfu Chen,Mujun Long 한국탄소학회 2018 Carbon Letters Vol.25 No.-
Activated carbon (AC) was modified by ammonium persulphate or nitric acid, respectively. AC and the modified materials were used as catalyst supports. The oxygen groups were introduced in the supports during the modifications. All the supports were characterized by N2-physisorption, Raman, X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and thermogravimetric analysis. Methanol synthesis catalysts were prepared through wet impregnation of copper nitrate and zinc nitrate on the supports followed by thermal decomposition. These catalysts were measured by the means of N2-physisorption, X-ray diffraction, XPS, temperature programmed reduction and TEM tests. The catalytic performances of the prepared catalysts were compared with a commercial catalyst (CZA) in this work. The results showed that the methanol production rate of AC-CZ (23 mmol-CH3OH/(g-Cu·h)) was higher, on Cu loading basis, than that of CZA (9 mmol-CH3OH/(g-Cu·h)). We also found that the modification methods produced strong metal-support interactions leading to poor catalytic performance. AC without any modification can prompt the catalytic performance of the resulted catalyst.
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