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Solidification Structure of Continuous Casting Large Round Billets under Mold Electromagnetic Stirring

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Journal of Iron and Steel Research international 2016年第4期23卷 329-337页

作者： Tao SUN Feng YUE Hua-jie WU Chun GUO Ying LI Zhong-cun MA Metallurgical Engineering Research institute University of Science and Technology Beijing Collaborative Innovation Center of Steel Technology University of Science and Technology Beijing Beiman Special Steel Co. Ltd.

The solidification structure of a continuous casting large round billet was analyzed by a cellular-automaton-finite-element coupling model using the ProCAST software. The actual and simulated solidification structures were compared under mold electromagnetic stirring （MEMS） conditions （current of 300 A and frequency of 3 Hz）. Thereafter, the solidification structures of the large round billet were investigated under different superheats, casting speeds, and secondary cooling intensities. Finally, the effect of the MEMS current on the solidification structures was obtained under fixed superheat, casting speed, secondary cooling intensity, and MEMS frequency. The model accurately simulated the actual solidification structures of any steel, regardless of its size and the parameters used in the continuous casting process. The ratio of the central equiaxed grain zone was found to increase with decreasing superheat, increasing casting speed, decreasing secondary cooling intensity, and increasing MEMS current. The grain size obviously decreased with decreasing superheat and increasing MEMS current but was less sensitive to the casting speed and secondary cooling intensity.

关键词： continuous casting large round billet solidification structure cellular-automaton-finite-element method mold electromagnetic stirring central equiaxed grain zone grain size

Microwave absorption properties of SiC@SiO2@Fe3O4 hybrids in the 2–18 GHz range

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international Journal of Minerals,Metallurgy and Materials 2017年第7期24卷 804-813页

作者： Peng Zhou Jun-hong Chen Meng Liu Peng Jiang Bin Li Xin-mei Hou National Engineering Research Center for Advanced Rolling Technology University of Science and Technology Beijing Beijing 100083 China School of Material science and Engineering University of Science and Technology Beijing Beijing 100083 China Collaborative Innovation Center of Steel Technology University of Science and Technology Beijing Beijing 100083 China

To enhance the microwave absorption performance of silicon carbide nanowires（SiCNWs）, SiO_2 nanoshells with a thickness of approximately 2 nm and Fe_3O_4 nanoparticles were grown on the surface of SiCNWs to form SiC@SiO_2@Fe_3O_4 hybrids. The microwave absorption performance of the SiC@SiO_2@Fe_3O_4 hybrids with different thicknesses was investigated in the frequency range from 2 to 18 GHz using a free-space antenna-based system. The results indicate that SiC@SiO_2@Fe_3O_4 hybrids exhibit improved microwave absorption. In particular, in the case of an SiC@SiO_2 to iron（III） acetylacetonate mass ratio of 1：3, the microwave absorption with an absorber of 2-mm thickness exhibited a minimum reflection loss of-39.58 d B at 12.24 GHz. With respect to the enhanced microwave absorption mechanism, the Fe_3O_4 nanoparticles coated on SiC@SiO_2 nanowires are proposed to balance the permeability and permittivity of the materials, contributing to the microwave attenuation.

关键词： silicon carbide nanowires hybrids microwave absorption mechanism impedance match

Dynamic behavior of tunneling triboelectric charges in two-dimensional materials

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international Journal of Minerals,Metallurgy and Materials 2023年第9期30卷 1801-1808页

作者： Xuan Zhao Liangxu Xu Xiaochen Xun Fangfang Gao Qingliang Liao Yue Zhang Academy for Advanced Interdisciplinary science and Technology School of Materials Science and EngineeringUniversity of Science and Technology BeijingBeijing 100083China beijing Advanced Innovation Center for Materials Genome Engineering Beijing Key Laboratory for Advanced Energy Materials and TechnologiesUniversity of Science and Technology BeijingBeijing 100083China

Although the research history of triboelectrification has been more than 2000 years, there are still many problems to be solved so *** use of scanning probe microscopy provides an important way to quantitatively study the transfer, accumulation, and dissipation of triboelectric charges in the process of triboelectrification. Two-dimensional materials are considered to be key materials for new electronic devices in the post-Moore era due to their atomic-scale size advantages. If the electrostatic field generated by triboelectrification can be used to replace the traditional gate electrostatic field, it is expected to simplify the structure of two-dimensional electronic devices and reconfigure them at any time according to actual needs. Here, we investigate the triboelectrification process of various two-dimensional materials such as MoS_(2), WSe_(2),and ZnO. Different from traditional bulk materials, after two-dimensional materials are rubbed, the triboelectric charges generated may tunnel through the two-dimensional materials to the underlying substrate surface. Because the tunneling triboelectric charge is protected by the twodimensional material, its stable residence time on the substrate surface can reach more than 7 days, which is more than tens of minutes for the traditional triboelectric charge. In addition, the electrostatic field generated by the tunneling triboelectric charge can effectively regulate the carrier transport performance of two-dimensional materials, and the source–drain current of the field effect device regulated by the triboelectric floating gate is increased by nearly 60 times. The triboelectric charge tunneling phenomenon in two-dimensional materials is expected to be applied in the fields of new two-dimensional electronic devices and reconfigurable functional circuits.

关键词： two-dimensional materials triboelectric charge dynamic behavior reconfigurable electronics

A CASCADIC MULTIGRID METHOD FOR EIGENVALUE PROBLEM

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Journal of Computational Mathematics 2017年第1期35卷 74-90页

作者： Xiaole Han Hehu Xie Fei Xu IAPCM Institute of Applied Physics and Computational Mathematics Beijing 100093 China LSEC NCMIS Institute of Computational Mathematics Academy of Mathematics and Systems Science Chinese Academy of Sciences Beijing 100190 China beijing institute for Scientific and Engineering Computing Beijing University of Technology Beijing 100124 China

A cascadic multigrid method is proposed for eigenvalue problems based on the multilevel correction scheme. With this new scheme, an eigenvalue problem on the finest space can be solved by linear smoothing steps on a series of multilevel finite element spaces and nonlinear correcting steps on special coarsest spaces. Once the sequence of finite element spaces and the number of smoothing steps are appropriately chosen, the optimal convergence rate with the optimal computational work can be obtained. Some numerical experiments are presented to validate our theoretical analysis.

关键词： Eigenvalue problem Cascadic multigrid Multilevel correction scheme Finiteelement method.

Research on Quantitative Identification of Three-Dimensional Connectivity of Fractured-Vuggy Reservoirs

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Energy Engineering 2024年第5期121卷 1195-1207页

作者： Xingliang Deng Peng Cao Yintao Zhang Yuhui Zhou Xiao Luo Liang Wang Exploration and Development Research institute PetroChina Tarim Oilfield CompanyKorla841000China PetroChina Hangzhou Research institute of Geology Hangzhou310023China School of Petroleum Engineering Yangtze UniversityWuhan430100China

The fractured-vuggy carbonate oil resources in the western basin of China are extremely *** connectivity of carbonate reservoirs is complex,and there is still a lack of clear understanding of the development and topological structure of the pore space in fractured-vuggy ***,effective prediction of fractured-vuggy reservoirs is *** view of this,this work employs adaptive point cloud technology to reproduce the shape and capture the characteristics of a fractured-vuggy *** identify the complex connectivity among pores,fractures,and vugs,a simplified one-dimensional connectivity model is established by using the meshless connection element method(CEM).Considering that different types of connection units have different flow characteristics,a sequential coupling calculation method that can efficiently calculate reservoir pressure and saturation is *** automatic history matching,the dynamic production data is fitted in real-time,and the characteristic parameters of the connection unit are *** results show that the three-dimensional connectivity model of the fractured-vuggy reservoir built in this work is as close as 90%of the fine grid model,while the dynamic simulation efficiency is much higher with good accuracy.

关键词： Fractured-vuggy reservoir three-dimensional connectivity connection unit dynamic prediction automatic history matching

A Review of the Ionospheric Investigations in China:Progress During 2008-2010

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空间科学学报 2010年第4期30卷 362-381页

作者： Wan Weixing beijing National Observatory of space Environment Institute of Geology and Geophysics Chinese Academy of Sciences Beijing 100029 China

In the ionospheric research,various progresses have been made during the last two *** paper reviews the recent works of Chinese *** convenience,the contents include:ionospheric storms and space weather;ionospheric irregularities and scintillation;ionospheric variability;ionospheric disturbances;ionospheric response to solar eclipses;ionospheric coupling with atmosphere and lithosphere;ionospheric climatology;ionospheric modeling;and ionospheric prediction and application.

关键词：电离层暴中国科学家综述电离层扰动电离层耦合电离层预报电离层模型空间天气

A regional ionospheric TEC mapping technique over China and adjacent areas: GNSS data processing and DINEOF analysis

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science China(Information sciences) 2015年第10期58卷 168-178页

作者： A Ercha HUANG WenGeng LIU SiQing SHI LiQin GONG JianCun CHEN YanHong SHEN Hua National space science Center Chinese Academy of Sciences

A technique is developed to derive two-dimensional maps of total electron content(TEC) over China and adjacent areas using Global Navigation Satellite System(GNSS) data from the Crustal Movement Observation Network of China(CMONOC) and the international Global Navigation Satellite System Service(IGS). A revised self-calibration of pseudo-range errors(SCORE) algorithm is used to derive the TEC and to determine the Differential Code Biases(DCBs) simultaneously. The accuracy and validity of this technique is verified in two ways. Firstly, the estimated TEC is compared with the results derived using DCBs from Center for Orbit Determination of Europe(CODE) under different solar activity conditions and seasons; secondly, sample TEC along the receiver-to-satellite ray paths are simulated by Ne Quick model and are reprocessed by this TEC derivation technique to make the accuracy test. Two-dimensional maps of vertical TEC of ionospheric pierce points(IPPs) are obtained accordingly with a time resolution of 30 s. The data interpolating empirical orthogonal functions(DINEOF) technique is then used to make the extrapolation for the unknown or missing data points. The optimal EOF modes for data reconstruction are specified via cross-validation method. The regional TEC distribution over China and adjacent areas is scaled into grid size of 1? × 1? for each 5 min, which can well reflect the characteristic of large-scale regional variations and temporal evolution as well as the small-scale local features of ionosphere.

关键词： TEC mapping GNSS processing SCORE algorithm DINEOF technique Ne Quick

Electrochemical corrosion failure mechanism of M152 steel under a salt-spray environment

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international Journal of Minerals,Metallurgy and Materials 2015年第11期22卷 1183-1189页

作者： Pan Yi Kui Xiao Kang-kang Ding Xu Wang Li-dan Yan Cheng-liang Mao Chao-fang Dong Xiao-gang Li Corrosion and Protection Center University of Science and Technology Beijing institute of Advanced Materials and Technology University of Science and Technology Beijing State Key Laboratory for Marine Corrosion and Protection Luoyang Ship Material Research Institute Ningbo institute of Material Technology & Engineering Chinese Academy of Sciences

The corrosion failure mechanism of M152 was studied using the neutral salt-spray test to better understand the corrosion behavior of 1Cr12Ni3Mo2VN（M152）, provide a basis for the optimization of material selection, and prevent the occurrence of failure. Moreover, the mechanism was investigated using the mass loss method, polarization curves, electrochemical impedance spectroscopy（EIS）, stereology microscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy（EDS）. The results show that M152 steel suffers severe corrosion, especially pitting corrosion, in a high-salt-spray environment. In the early stage of the experiment, the color of the corrosion products was mainly orange. The products then gradually evolved into a dense, brown substance, which coincided with a decrease of corrosion rate. Correspondingly, the EIS spectrum of M152 in the late test also exhibited three time constants and presented Warburg impedance at low frequencies.

关键词： heat-resistant steel electrochemical corrosion failure mechanism salt spray test

Modeling the 2017 September 10 solar energetic particle event using the iPATH model

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Research in Astronomy and Astrophysics 2020年第9期20卷 241-252页

作者： Zhe-Yi Ding Gang Li Jun-Xiang Hu Shuai Fu School of Geophysics and Information Technology China University of Geosciences(Beijing)Beijing 100083China Department of space science and CSPAR University of Alabama in HuntsvilleHuntsvilleAL 35899USA Lunar and Planetary science Laboratory Macao University of Science and TechnologyMacao 519020China

On 2017 September 10,a fast coronal mass ejection(CME)erupted from the active region(AR)12673,leading to a ground level enhancement(GLE)event at *** the 2D improved Particle Acceleration and Transport in the Heliosphere(iPATH)model,we model the large solar energetic particle(SEP)event of 2017 September 10 observed at Earth,Mars and *** on observational evidence,we assume that the CME-driven shock experienced a large lateral expansion shortly after the eruption,which is modeled by a double Gaussian velocity profile in this *** apply the in-situ shock arrival times and the observed CME speeds at multiple spacecraft near Earth and Mars as constraints to adjust the input model *** modeled time intensity profiles and fluence for energetic protons are then compared with *** agreements with observations at Mars and STEREO-A are *** simulated results at Earth differ from observations of ***,the simulated results at a heliocentric longitude 20°west to Earth fit reasonably well with the GOES *** can be explained if the pre-event solar wind magnetic field at Earth is not described by a nominal Parker *** results suggest that a large lateral expansion of the CME-driven shock and a distorted interplanetary magnetic field due to previous events can be important in understanding this GLE event.

关键词： Sun:coronal mass ejections(CMEs) Sun:magnetic fields Sun:particle emission