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Yulin Feng,Yaoyao Meng,Wenjie Guo,Lizhong Jiang,Wang-Bao Zhou 국제구조공학회 2023 Steel and Composite Structures, An International J Vol.49 No.1
A simplified calculation method of natural vibration characteristics of high-speed railway multi-span bridgelongitudinal ballastless track system is proposed. The rail, track slab, base slab, main beam, bearing, pier, cap and pile foundation are taken into account, and the multi-span longitudinal ballastless track-beam-bearing-pier-cap-pile foundation integrated model (MBTIM) is established. The energy equation of each component of the MBTIM based on Timoshenko beam theory is constructed. Using the improved Fourier series, and the Rayleigh-Ritz method and Hamilton principle are combined to obtain the extremum of the total energy function. The simplified calculation formula of the natural vibration frequency of the MBTIM under the influence of vertical and longitudinal vibration is derived and verified by numerical methods. The influence law of the natural vibration frequency of the MBTIM is analyzed considering and not considering the participation of each component of the MBTIM, the damage of the track interlayer component and the stiffness change of each layer component. The results show that the error between the calculation results of the formula and the numerical method in this paper is less than 3%, which verifies the correctness of the method in this paper. The high-order frequency of the MBTIM is significantly affected considering the track, bridge pier, pile soil and pile cap, while considering the influence of pile cap on the low-order and highorder frequency of the MBTIM is large. The influence of component damage such as void beneath slab, mortar debonding and fastener failure on each order frequency of the MBTIM is basically the same, and the influence of component damage less than 10m on the first fourteen order frequency of the MBTIM is small. The bending stiffness of track slab and rail has no obvious influence on the natural frequency of the MBTIM, and the bending stiffness of main beam has influence on the natural frequency of the MBTIM. The bending stiffness of pier and base slab only has obvious influence on the high-order frequency of the MBTIM. The natural vibration characteristics of the MBTIM play an important guiding role in the safety analysis of highspeed train running, the damage detection of track-bridge structure and the seismic design of railway bridge.
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Luyi Chen,Kunyao Jiang,Yaoyao Zhou,Linjiang Zhu,Xiao-Long Chen 한국생물공학회 2022 Biotechnology and Bioprocess Engineering Vol.27 No.4
The α-glycosidase from Xanthomonas campestris (XgtA) can specifically catalyze the transglycosylation reactions, thus can be applied for the enzymatic synthesis of α-glycosides. However, the low thermal stability of XgtA has been a bottleneck for its industrial application. In this research, a combined semi-rational design strategy was used based on analysis of the α-helices and β-turns of XgtA, FireProt prediction of thermostable mutants and molecular dynamic simulations for improving the thermostability. The key positions with a significant impact on the thermal stability of XgtA were identified and the effect of proline substitution was tested. Five single-point mutants V167P, A177P, A210P, A220P, T345P, and a combined mutant Mut5 were obtained with improved thermal stability. Mut5 displayed a 3.06-fold increase in time of half-life at 45°C without impairing its initial hydrolytic activity. Molecular dynamics simulations revealed that changes in the flexibility of amino acid residues, newly-forming hydrogen bonding networks and hydrophobic interactions were responsible for the improved thermostability. These results suggest that proline substitution of key flexible positions is an effective strategy for improving enzyme thermostability.
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Song Sa,Pan Jian,Zhang Yaoyao,Xu Yuehuan,Zhang Qingmei,Xie Xiaoxun,Zhou Qingniao,Mo Farong,Luo Guorong,Chao Naixia 한국유전학회 2023 Genes & Genomics Vol.45 No.1
Background Hepatocellular carcinoma (HCC) is the most common primary liver malignancy with a high mortality rate. P14.5 is a member of the highly conserved YER057c/YIL051c/YjgF subfamily and is highly expressed in the liver. However, its low expression is associated with carcinogenesis in HCC. Objective This study aimed to investigate the role and prognostic significance of P14.5 in HCC. Methods The clinical significance of P14.5 in HCC was examined using ONCOMINE, UALCAN, Human Protein Atlas, and Kaplan–Meier plotter. The DNA methylation profile of the P14.5 promoter was examined in 103 HCC and paired precancerous tissues; the HCC cell lines HepG2, MHCC-97L, SMMC-7721, SK-Hep-1, and Huh7; and the normal hepatic cell line HL-7702 via MALDI-TOF mass spectrometry. In addition, in vitro experiments were performed to examine the effects of P14.5 overexpression on the proliferation and migration of SMMC-7721 cells. Results Low expression of P14.5 was correlated with shorter overall survival (OS) and disease-free survival (DFS) in HCC. Based on the results of MALDI-TOF mass spectrometry, no difference was observed in the methylation level between HCC cells and normal human hepatic cells and between HCC and paired precancerous tissues. Additionally, P14.5 overexpression promoted the proliferation and inhibited the migration of SMMC7721 cells in vitro. Conclusions P14.5 may serve as a prognostic biomarker in HCC and plays a role in the migration and proliferation of HCC cells. Low expression of P14.5 during hepatocarcinogenesis is not attributed to DNA methylation.
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Xiao Song,Tong Mengyuan,Rao Yang,Li Yuhang,Ye Zhizong,Shen Yixiang,Hou Hao,Gao Guoqiang,Wu Guangning,Jin Yaoyao,Zhou Jie,Liu Jie 대한전기학회 2022 Journal of Electrical Engineering & Technology Vol.17 No.1
Along with the operating velocity and traction power increasing continuously, the issue related to the safety and reliability of the high-voltage traction power system for high-speed trains have gradually been exposed during the practical service process. When the train passes a neutral section settled roughly per 15 km between two neighboring substations, the on-board vacuum circuit breaker (VCB) must to be operated for changing the input powers with diff erent phases. At the moment of switching on or off the VCB, the arc between the contacts in the arc-extinguishing chamber may be triggered, which tends to result in the operational overvoltage. Due to numerous inductances and capacitances existing in the traction power supply system, the overvoltage may lead to high-frequency electromagnetic oscillation spreading along the transmission routes. The on-board high-voltage equipments within the power supply system may suff er from the impulse brought from the VCB operational overvoltage frequently, which is possible to cause the insulation aging or breakdown issue. To investigate the characteristic of the operational overvoltage of VCBs, a ‘train-rail-catenary’ power supply model is built based on the measured impedance parameters, which has been verifi ed by the experimental tests. The generating mechanism with the infl uence factors of the operational overvoltage when switching on or off the VCB has been explored, meanwhile the distribution of the train body overvoltage on each carriage has also been presented.
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