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Super-harmonic resonance of gear transmission system under stick-slip vibration in high-speed train

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Journal of Central South University 2017年第3期24卷 726-735页

作者： HUANG guan-hua XU si-si ZHANG Wei-hua YANG Cai-jin State Key Laboratory of Traction Power （Southwest Jiaotong University） Chengdu 61003 I China Beijing Haidongqing Electrical and Mechanical Equipment Co. Ltd Beijing 101300 China CRRC Institute Co. Ltd Beiiing 100070 China

This work deals with super-harmonic responses and the stabilities of a gear transmission system of a high-speed train under the stick-slip oscillation of the *** dynamic model of the system is developed with consideration on the factors including the time-varying system stiffness,the transmission error,the tooth backlash and the self-excited excitation of the *** frequency-response equation of the system at super-harmonic resonance is obtained by the multiple scales method,and the stabilities of the system are analyzed using the perturbation *** nonlinear behaviors of the system including multi-valued solutions,jump phenomenon,hardening stiffness are *** effects of the equivalent damping and the loads of the system under the stick-slip oscillation are *** shows that the change of the load can obviously influence the resonance frequency of the system and have little effect on the steady-state response amplitude of the *** damping of the system has a negative effect,opposite to the *** synthetic damping of the system composed of meshing damping and equivalent damping may be less than zero when the wheel-set has a large slippage,and the system loses its stability owing to the Hopf *** results are validated by numerical simulations.

关键词： stick-slip vibration super-harmonic resonance Hopf bifurcation gear transmission system high-speed train

Indoor massive multiple-input multiple-output channel characterization and performance evaluation

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Frontiers of Information Technology & Electronic Engineering 2017年第6期18卷 773-787页

作者： Jian-zhi LI Bo AI Rui-si HE Qi WANG Mi YANG Bei ZHANG Ke guan Dan-ping HE Zhang-dui ZHONG Ting ZHOU nan LI State Key Laboratory of Rail Traffic Control and Safety Beijing Jiaotong UniversityBeijing 100044China Engineering University of Armed Police Force Telecommunication Engineering DepartmentXi'an 710086China Key Laboratory of Wireless Sensor Network and Communication Shanghai Institute of Microsystem and Information TechnologyChinese Academy of SciencesShanghai 200050China ZTE Corporation Beijing 100191China

We present a measurement campaign to characterize an indoor massive multiple-input multiple-output (MIMO) channel system, using a 64-element virtual linear array, a 64-element virtual planar array, and a 128-element virtual planar array. The array topologies are generated using a 3D mechanical turntable. The measurements are conducted at 2, 4, 6, 11, 15, and 22 GHz, with a large bandwidth of 200 MHz. Both line-of-sight (LOS) and non-LOS (NLOS) propagation scenarios are considered. The typical channel parameters are extracted, including path loss,shadow fading, power delay profile, and root mean square (RMS) delay spread. The frequency dependence of these channel parameters is analyzed. The correlation between shadow fading and RMS delay spread is discussed. In addition, the performance of the standard linear precoder—the matched filter, which can be used for intersymbol interference (Isi) mitigation by shortening the RMS delay spread, is investigated. Other performance measures,such as entropy capacity, Demmel condition number, and channel ellipticity, are analyzed. The measured channels,which are in a rich-scattering indoor environment, are found to achieve a performance close to that in independent and identically distributed Rayleigh channels even in an LOS scenario.

关键词： Massive MIMO Channel modeling 5G Shadow fading Delay spread Matched filter Entropy capacity Condition number Channel ellipticity

Microbial mediated arsenic biotransformation in wetlands

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Frontiers of Environmental Science & Engineering 2017年第1期11卷 5-15页

作者： si-Yu Zhang Paul N. Williams Jinming Luo Yong-guan Zhu State Key Laboratory of Urban and Regional Ecology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China State Key Joint Laboratory of Environment simulation and Pollution Control School of Environment Beijing Normal University Beijing 100875 China Institute for Global Food Security School of Biological Sciences Queen's University Belfast Belfast BT9 7BN UK Key Laboratory of Drinking Water Science and Technology Research Center for Eco-Environmental Sciences Chinese Academy of Sciences Beijing 100085 China Key Laboratory of Urban Environment and Health Institute of Urban Environment Chinese Academy of Sciences Xiamen 361021 China

Arsenic （As） is a pervasive environmental toxin and carcinogenic metalloid. It ranks at the top of the US priority List of Hazardous Substances and causes worldwide human health problems. Wetlands, including natural and artificial ecosystems （i.e. paddy soils） are highly susceptible to As enrichment; acting not only as repositories for water but a host of other elemental/chemical moieties. While macroscale processes （physical and geological） supply As to wetlands, it is the micro-scale biogeochemistry that regulates the fluxes of As and other trace elements from the semi-terrestrial to neighboring plant/ aquatic/atmospheric compartments. Among these fine-scale events, microbial mediated As biotransformations contribute most to the element＇s changing forms, acting as the ＇switch＇ in defining a wetland as either a source or sink of As. Much of our understanding of these important microbial catalyzed reactions follows relatively recent scientific discoveries. Here we document some of these key advances, with focuses on the implications that wetlands and their microbial mediated transformation pathways have on the global As cycle, the chemistries of microbial mediated As oxidation, reduction and methylation, and future research priorities areas.

关键词： Arsenic Wetland Microbes Switch

Neuromorphic terahertz imaging based on carbon nanotube circuits

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Science China(Information Sciences) 2023年第6期66卷 303-304页

作者： nan YANG Zhizhong si Xinhe WANG Xiaoyang LIN Weisheng ZHAO School of Integrated Circuit Science and Engineering Beihang University Fert Beijing Institute MIIT Key Laboratory of SpintronicsSchool of Integrated Circuit Science and EngineeringBeihang University

We propose a neuromorphic THz imaging system based on the integration of carbon nanotubes(CNTs) circuits and the spin-transfer torque magnetic tunnel junctions(STTMTJs). Utilizing the photothermoelectric effect of CNT...

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Influence of borehole quantity and distribution on lithology field simulation

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Journal of Groundwater Science and Engineering 2019年第4期7卷 295-308页

作者： nan Tian GUO si-jia Institute of Hydrogeology and Environmental Geology Chinese academy of Geological Sciences

This paper aims to study the influence of the number and distribution of drill samples on the simulation accuracy of the lithology field. This research mainly applies the variation function method in geo-statistics, and determines important indicators such as the variation, and then the lithology field is simulated by sequence index simulation. It is shown that(1) simulation error decreases with the increase of sampling density;(2) at the scale and complexity of this study, when the sampling density reaches 40/km^2, the average error of the lithology field simulation can be less than 2.0%;(3) in the study mode of examples, the simulation results of random sampling in the whole region are the most ideal, with an average error of 5.4%. The average error of the simulation results of the centralized sampling is about 10 times that of the random sampling method;(4) known from the influence analysis of the degree of study sample unevenness influence on the imitation results, under the same sample size, the simulation error decreases with the increase of the most adjacent index. When the nearest index reaches 1, the simulation error will be less than 6%, and the error variable range is within 3%.

关键词： Variation function Lithology field simulation Nearest index Sequence indicator simulation Sampling method

nanotribological properties and scratch resistance of MoS_(2)bilayerona siO_(2)/si substrate

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Friction 2023年第1期11卷 154-164页

作者： si-hwan KIM Hyo-sok AHN Department of Transdisciplinary Studies Seoul National UniversitySeoul 08826Republic of Korea Department of Manufacturing Systems and Design Engineering Seoul National University of Science and TechnologySeoul 08826 Republic of Korea

The tribological properties and scratch resistance of MoS_(2)bilayer deposited on siO_(2)/si substrates prepared via chemical vapor deposition are *** force microscopy(FFM)is employed to investigate the friction and wear properties of the MoS_(2)bilayer at the nanoscale by applying a normal load ranging from 200 to 1,000 *** resistance is measured using the scratch mode in FFM based on a linearly increasing load from 100 to 1,000 *** probe force microscopy(KPFM)is performed to locally measure the surface potential in the tested surface to qualitatively measure the wear/removal of Mos,layers and identify critical loads associated with the individual failures of the top and bottom *** analysis of the contact potential difference values as well as that of KPFM,friction,and height images show that the wear/removal of the top and bottom layers in the MoS_(2)bilayer system occurred *** FFM and KPFM results show that the top MoS_(2)layer begins to degrade at the end of the low friction stage,followed by the bottom layer,thereby resulting in a transitional friction stage owing to the direct contact between the diamond tip and siO_(2)*** the stable third stage,the transfer of lubricious MoS_(2)debris to the tip apex results in contact between the MoS_(2)-transferred tip and siO_(2).nanoscratch test results show two ranges of critical loads,which correspond to the sequential removal of the top and bottom layers.

关键词： chemical vapor deposition(CVD)-grown MoS,bilayer friction force microscopy(FFM) nanoscratch test Kelvin probe force microscopy(KPFM) scratch resistance

Peri-centrosomal localization of small interfering RNAs in C. elegans

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Science China Life Sciences 2025年

作者： Qile Jin Xuezhu Feng Minjie Hong Ke Wang Xiangyang Chen Jiewei Cheng Yan Kuang Xiaoyue si Mingjing Xu Xinya Huang Shouhong guang Chengming Zhu Department of Obstetrics and Gynecology The First Affiliated Hospital of USTC The USTC RNA Institute Hefei National Research Center for Physical Sciences at the Microscale School of Life Sciences Division of Life Sciences and Medicine Biomedical Sciences and Health Laboratory of Anhui Province University of Science and Technology of China School of Basic Medicine Anhui Medical University

The centrosome is the microtubule-organizing center and a crucial part of cell division. Centrosomal RNAs(cnRNAs) have been reported to enable precise spatiotemporal control of gene expression during cell division in many species. Whether and how cnRNAs exist in C. elegans are unclear. Here, using the nuclear RNAi Argonaute protein NRDE-3 as a reporter, we observed potential peri-centrosome localized small interfering(si)RNAs in C. elegans. NRDE-3 was previously shown to associate with pre-mRNAs and pre-rRNAs via a process involving the presence of complementary siRNAs. We generated a GFP-NRDE-3 knock-in transgene through CRISPR/Cas9 technology and observed that NRDE-3 formed peri-centrosomal foci neighboring the tubulin protein TBB-2, other centriole proteins and pericentriolar material(PCM)components in C. elegans embryos. The peri-centrosomal accumulation of NRDE-3 depends on RNA-dependent RNA polymerase(RdRP)-synthesized 22G siRNAs and the PAZ domain of NRDE-3, which is essential for siRNA binding. Mutation of eri-1, ergo-1, or drh-3 significantly increased the percentage of pericentrosome-enriched NRDE-3. At the metaphase of the cell cycle, NRDE-3 was enriched in both the peri-centrosomal region and the spindle. Moreover, the integrity of centriole proteins and pericentriolar material(PCM) components is also required for the peri-centrosomal accumulation of NRDE-3. Therefore, we concluded that siRNAs could accumulate in the pericentrosomal region in C. elegans and suggested that the peri-centrosomal region may also be a platform for RNAi-mediated gene regulation.

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Generation of simultaneous H^(+)and He^(+)band EMIC waves in the nightside radiation belt

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Science China(Technological Sciences) 2020年第11期63卷 2369-2374页

作者： guan ChunYi SHANG XiongJun XIE YanQiong YANG Chang ZHANG Sai LIU si XIAO FuLiang School of Physics and Electronic Sciences Changsha University of Science and TechnologyChangsha 410114China College of Meteorology and Oceanography National University of Defense TechnologyNanjing 211101China State Key Laboratory of Space Weather Chinese Academy of SciencesBeijing 100190China

Previous studies have shown that EMIC waves occur preferentially in the afternoon sector of the *** we report obliquely propagating H^(+)and He^(+)band EMIC waves detected by Van Allen Probe B in the region of MLT=22.7–23.5 during the June 20,2013 *** the correlated energetic proton data,we present continuous calculations on EMIC wave growth rates along the inward orbit in the region L=5.5–*** modeled growth rate shows remarkable agreement with the observed double band EMIC waves in both temporal and spatial *** current results demonstrate that H^(+)and He^(+)band EMIC waves can be simultaneously excited in the midnight sector under appropriate conditions.

关键词： EMIC waves instability nightside radiation belt Van Allen Probes coordinated observations

Homologous CoS2 interface with directed electron transfer and strong chloridion repulsion for efficient seawater oxidation

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Science China Chemistry 2025年

作者： Yuan Tian Jiang-Bo Chen Jie Ying Ge Tian Yu-Xuan Xiao Yi Lu si-Ming Wu Wei Geng Ling Shen Xiao-Yu Yang State Key Laboratory of Advanced Technology for Materials Synthesis and Processing and School of Materials Science and Engineering and Shenzhen Research Institute & Laoshan Laboratory Wuhan University of Technology School of Chemical Engineering and Technology Sun Yat-Sen University National Energy Key Laboratory for New Hydrogen-Ammonia Energy Technologies Foshan Xianhu Laboratory

Seawater electrolysis is a highly promising method to produce high energy density hydrogen,especially in dry areas that have scarce freshwater ***,application of seawater electrolysis is confronted by two major problems associated with catalysts employed for the anodic oxygen evolution reaction （OER） including the competitive hypochlorite evolution reaction（HCER） and strong chloridion （Cl–） triggered *** studies aimed at overcoming these problems,a facile method has been developed to synthesize a homologous CoS2heterojunction as an OER *** to a difference in work functions at the interface and increased electron density,this material has directed electron transfer and strong chloridion repulsion properties,*** have shown that CoS2achieves low overpotentials of 289 and 322 mV at 10 mA cm-2current density in respective alkaline （1 M KOH） and alkaline simulated seawater ***,the outstanding stability of CoS2is reflected in a negligible decline in activity during promotion of the OER for 100 *** of density functional theory calculations reveal that the homologous CoS2heterojunction promotes directed electron transport for optimizing adsorption/desorption of reactive species and heightens the Cl-adsorption energy for strongly repulsing Cl-,phenomena that enhance OER performance in alkaline simulated seawater.

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