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Phase diagram,correlations,and quantum critical point in the periodic Anderson model

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Chinese Physics B 2018年第3期27卷 362-367页

作者： jian-wei yang Qiao-Ni Chen Department of Physics Beijing Normal University Beijing 100875 China

Periodic Anderson model is one of the most important models in the field of strongly correlated electrons. With the recent developed numerical method density matriX embedding theory, we study the ground state properties of the periodic Anderson model on a two-dimensional square lattice. We systematically investigate the phase diagram away from half filling. We find three different phases in this region, which are distinguished by the local moment and the spin-spin correlation functions. The phase transition between the two antiferromagnetic phases is of first order. It is the so-called Lifshitz transition accompanied by a reconstruction of the Fermi surface. As the filling is close to half filling, there is no difference between the two antiferromagnetic phases. From the results of the spin-spin correlation, we find that the Kondo singlet is formed even in the antiferromagnetic phase.

关键词： periodic Anderson model Kondo singlet states density matrix embedding theory

Characteristics of Welding Crack Defects and Failure Mode in Resistance Spot Welding of DP780 Steel

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Journal of Iron and Steel Research International 2016年第10期23卷 1104-1110页

作者： Xiao-pei WANG Yong-qiang ZHANG jian-bin JU jian-qiang ZHANG jian-wei yang Shougang Research Institute of Technology Beijing 100043 China College of Science China University of Petroleum (Beijing) Beijing 102249 China

The mechanical properties of welded joints in resistance spot welding of DP780 steel were tested,and three different types of welding cracks in welded joints were investigated by optical microscopy,scanning electron microscopy and electron back-scattered ***,the failure mode of the welded joints in shear tensile test was *** is found the shear tensile strength of welded joints can be greatly improved by adding preheating current or tempering *** surface crack in welded joint is intergranular fracture,while the inner crack in welded joint is transgranular fracture,and the surface crack on the edge of the electrode imprint can be improved by adding preheating current or tempering *** traditional failure mode criterion advised by American Welding Society is no longer suitable for DP780 spot welds and the critical nugget size suggested by Pouranvari is overestimated.

关键词： resistance spot welding mechanical property crack defect failure mode DP780 steel

Evaluation of increasing service life of epoxy zinc-rich coating on 3 wt.%Ni-advanced low-alloy steel in marine atmospheric environment

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Journal of Iron and Steel Research International 2022年第4期29卷 698-706页

作者： Sheng-rong Wang jian-wei yang jian-ping Cao Shan jiang Fei-fan Xu Shougang Research Institute of Technology of Shougang Group Co. Ltd.Beijing 100043China Beijing Key Laboratory of Green Recyclable Process for Iron&Steel Production Technology Beijing 100043China

The addition of Ni element into steel to prolong the service life of coated steel was investigated in marine atmospheric environment by laboratory simulated accelerated *** scanning electron microscope and electron probe microanalysis combined with electrochemical impedance spectroscopy were used to characterize coated steel properties and examined the anti-corrosion *** results showed that 3 wt.%Ni-advanced steel(3Ni steel)substrate obviously delayed the failure time of coating compared to carbon steel,therefore prolonging the service life of coating on the steel.X-ray diffraction patterns for the corrosion products under the scratched coating on 3Ni steel exhibited that FeNi_(2)O_(4) and Fe_(2)O_(3) occurred in the corrosion product of 3Ni *** was also found that Ni element enriched in the product layer through analyzing the appearance and composition of corrosion products by electron probe *** ions were blocked out of product by the enrichment of Ni element in rust layer.

关键词： 3wt.% Ni-advanced low-alloy steel Coating failure Service life Corrosion product Marine atmosphere

Reliability Assessment for the Solenoid Valve of a High-Speed Train Braking System under Small Sample Size

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Chinese Journal of Mechanical Engineering 2018年第3期31卷 189-199页

作者： jian-wei yang Jin-Hai Wang Qiang Huang Ming Zhou Beijing Key Laboratory of Performance Guarantee on Urban Rail Transit Vehicles Beijing University of Civil Engineering Architecture School of Mechanical Electronic and Control EngineeringBeijing Jiaotong University Locomotive and Car Research Institute China Academy of Railway Science

Reliability assessment of the braking system in a high?speed train under small sample size and zero?failure data is veryimportant for safe operation. Traditional reliability assessment methods are only performed well under conditions of large sample size and complete failure data,which lead to large deviation under conditions of small sample size and zero?failure data. To improve this problem,a new Bayesian method is proposed. Based on the characteristics of the solenoid valve in the braking system of a high?speed train,the modified weibull distribution is selected to describe the failure rate over the entire lifetime. Based on the assumption of a binomial distribution for the failure probability at censored time,a concave method is employed to obtain the relationships between accumulation failure prob?abilities. A numerical simulation is performed to compare the results of the proposed method with those obtained from maximum likelihood estimation,and to illustrate that the proposed Bayesian model exhibits a better accuracy for the expectation value when the sample size is less than 12. Finally,the robustness of the model is demonstrated by obtaining the reliability indicators for a numerical case involving the solenoid valve of the braking system,which shows that the change in the reliability and failure rate among the di erent hyperparameters is small. The method is provided to avoid misleading of subjective information and improve accuracy of reliability assessment under condi?tions of small sample size and zero?failure data.

关键词： Zero?failure data Modified weibull distribution Small sample size Bayesian method

Automated flare prediction using the AdaBoost algorithm

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Research in Astronomy and Astrophysics 2012年第9期12卷 1191-1196页

作者： Ru-Shi Lan Yong jiang Liu-Guan Ding jian-wei yang School of Math and Statistics Nanjing University of Information Science and TechnologyNanjing 210044 China lrsOlO6@*** jiang@*** School of Physics and Optoelectronic Engineering Nanjing University of Information Scienceand Technology Nanjing 210044 China

We propose a flare prediction method based on the AdaBoost algorithm, which constructs a strong prediction model from a combination of several basic models. Three predictors, extracted from the photospheric magnetograms, are applied as features to predict the occurrence of flares with a certain level over 24 hours following the time when the magnetogram is recorded. To demonstrate the effectiveness of the proposed method, comparisons of experimental results with respect to some existing methods are given. The results show that an improvement is achieved in predicting the occurrences of large flares.

关键词： Sun: flares — Sun: magnetic fields

Corrosion behavior of low alloy steels in a wet–dry acid humid environment

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International Journal of Minerals,Metallurgy and Materials 2016年第9期23卷 1076-1086页

作者： Qing-he Zhao wei Liu jian-wei yang Yi-chun Zhu Bin-li Zhang Min-xu Lu Institute for Advanced Materials and Technology University of Science and Technology BeijingBeijing 100083China Shougang Research Institute of Technology Beijing 100043China

The corrosion behavior of corrosion resistant steel（CRS） in a simulated wet–dry acid humid environment was investigated and compared with carbon steel（CS） using corrosion loss, polarization curves, X-ray diffraction（XRD）, scanning electron microscopy（SEM）, electron probe micro-analysis（EPMA）, N2 adsorption, and X-ray photoelectron spectroscopy（XPS）. The results show that the corrosion kinetics of both steels were closely related to the composition and compactness of the rust, and the electrochemical properties of rusted steel. Small amounts of Cu, Cr, and Ni in CRS increased the amount of amorphous phases and decreased the content of γ-Fe OOH in the rust, resulting in higher compactness and electrochemical stability of the CRS rust. The elements Cu, Cr, and Ni were uniformly distributed in the CRS rust and formed CuFeO2, Cu2O, CrOOH, NiFe2O4, and Ni2O3, which enhanced the corrosion resistance of CRS in the wet–dry acid humid environment.

关键词： low alloy steel steel corrosion rust polarization curves corrosion resistance

Effect of H_2S concentration on the corrosion behavior of pipeline steel under the coexistence of H_2S and CO_2

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International Journal of Minerals,Metallurgy and Materials 2014年第4期21卷 388-394页

作者： Da-peng Li Lei Zhang jian-wei yang Min-xu Lu Jin-hui Ding Ming-liang Liu Institute of Advanced Materials and Technology University of Science and Technology Beijing Shougang Research Institute of Technology

The effect of H2S concentration on H2S/CO2 corrosion of API-X60 steel was studied by scanning electron microscopy, a weight-loss method, potentiodynamic polarization tests, and the electrochemical impedance spectroscopy technique. It is found that the cor-rosion process of the steel in an environment where H2S and CO2 coexist at different H2S concentrations is related to the morphological structure and stability of the corrosion product film. With the addition of a small amount of H2S, the size of the anode reaction region is de-creased due to constant adsorption and separation of more FeS sediment or more FeHS＋ions on the surface of the steel. Meanwhile, the dou-ble-layer capacitance is diminished with increasing anion adsorption capacity. Therefore, the corrosion process is inhibited. The general cor-rosion rate of the steel rapidly decreases after the addition of a small amount of H2S under the coexistence of H2S and CO2. With a further increase in H2S concentration, certain parts of the corrosion product film become loose and even fall off. Thus, the protection provided by the corrosion product film worsens, and the corrosion rate tends to increase.

关键词： pipeline steel hydrogen sulfide carbon dioxide corrosion corrosion rate electrochemical properties

Environmental boundary and formation mechanism of different types of H2S corrosion products on pipeline steel

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International Journal of Minerals,Metallurgy and Materials 2017年第4期24卷 401-409页

作者： Lei Zhang Hui-xin Li Feng-xian Shi jian-wei yang Li-hua Hu Min-xu Lu Institute for Advanced Materials and Technology University of Science and Technology Beijing Beijing 100083 China Aircraft Engine Corporation of China Shanghai Commercial Aircraft Engine Manufacturing Co. Ltd. Shanghai 201306 China Shougang Research Institute of Technology Beijing 100043 China China National Offshore Oil Corporation Research Institute Beijing 100027 China

To establish an adequate thermodynamic model for the mechanism of formation of hydrogen sulfide (H2S) corrosion products, theoretical and experimental studies were combined in this work. The corrosion products of API X60 pipeline steel formed under different H2S corrosion conditions were analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. A thermodynamic model was developed to clarify the environmental boundaries for the formation and transformation of different products. Presumably, a dividing line with a negative slope existed between mackinawite and pyrrhotite. Using experimental data presented in this study combined with previously published results, we validated the model to predict the formation of mackinawite and pyrrhotite on the basis of the laws of thermodynamics. The established relationship is expected to support the investigation of the H2S corrosion mechanism in the oil and gas industry. © 2017, University of Science and Technology Beijing and Springer-Verlag Berlin Heidelberg.

关键词： Energy dispersive spectroscopy Forecasting Gas industry Iron ores Pipelines Scanning electron microscopy Steel corrosion Steel pipe Thermodynamic properties Thermodynamics X ray diffraction X ray spectroscopy

A Simple-Prepared and Multi-Reusable Adhesive Based on Epoxy Vitrimer

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Chinese Journal of Polymer Science 2024年第10期42卷 1589-1594,I0015页

作者： Yu-Ting Wang Huan Liang Yen wei jian-Long Wang Xiang-Ming He yang yang Institute of Nuclear and New Energy Technology Tsinghua UniversityBeijing100084China The Key Laboratory of Bioorganic Phosphorus Chemistry&Chemical Biology(Ministry of Education) Department of ChemistryTsinghua UniversityBeijing100084China

Adhesives play an important role in modern society's production and daily *** robust and sustainable adhesives remains a great *** we report a sustainable epoxy-vitrimer adhesive with high adhesive strength(about 10 MPa)and reusability(82%strength after 3 times).This adhesive can be fabricated from commercially available products through a straightforward hot-pressing method without the need of *** adhesive process is also simple,requiring only 30 min at 180℃.In addition,the vitrimer adhesive has the advantages of both erasability for reuse and excellent water *** work provides a facile strategy to fabricate high-strength adhesive that ensures reusability,recyclability,low cost of raw materials,and simple processing ***,it expands the range of potential applications for epoxy vitrimers.

关键词： Epoxy Vitrimer Adhesive Reusable Sustainable