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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

The study of perfectly matched layer absorbing boundaries for SH wave fields

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Applied Geophysics 2009年第3期6卷 267-274,300,301页

作者： Liu Jiong Ma jian-wei yang Hui-zhu Institute of Seismic Exploration School of Aerospace Tsinghua University Beijing 100084China

When modeling wave propagation in infinite space, it is necessary to have stable absorbing boundaries to effectively eliminate spurious reflections from the truncation boundaries. The SH wave equations for Perfectly Matched Layers （PML） are deduced and their Crank-Nicolson scheme are presented in this paper. We use the second-, sixth-, and tenth-order finite difference and pseudo-spectral algorithms to compute the spatial derivatives. Two numerical models, a homogeneous isotropic medium and a multi-layer model with a cave, are designed to investigate how the absorbing boundary width and the algorithms determine PML effects. Numerical results show that, for PML, the low-order finite difference algorithms have fairly good absorbing effects when the absorbing boundary is thin, whereas, high-order algorithms always have good absorption when the boundary is thick. Finally, we discuss the reflection coefficient and point out its shortcomings, which is why we use the SNR to quantitatively scale the PML effects,

关键词： absorbing boundary PML SH wave fields

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

Immune Tolerance Therapy： A New Method for Treatment of Traumatic Brain Injury

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Chinese Medical Journal 2018年第16期131卷 1990-1998页

作者： Ruo-yang Feng Qian Chen wei-jian yang Xiao-Guang Tong Zhi-Ming Sun Hua Yan Department of Neurosurgery Tianjin Medical University Tianjin 300070 China Tianjin Key Laboratory of Cerebral Vascular and Neurodegenerative Diseases Tianjin 300350 China Department of Neurosurgery Tianjin Huanhu Hospital Tianjin 300350 China Department of Spine Surgery Tianjin Huanhu Hospital Tianjin 300350 China

Objective： Due to the special anatomical structure and pathophysiological mechanism of the central nervous system （CNS）, there is a big difference between the repair of brain injury and other systems of the body. More and more evidence shows that targetedly reducing the autoimmune response of brain tissue without affecting the immune function in other parts of the body will be the best optimized treatment for brain injury. Data Sources： This review was based on data in articles published in PubMed up to June 5,2017, with the following keywords：＂immune tolerance＂, ＂traumatic brain injury＂, and ＂central nervous system＂. Study Selection： Original articles and critical reviews on immune tolerance and brain damage were selected for this review. References of the retrieved articles were also screened to search for potentially relevant papers. Results： The CNS is isolated from the immune system through the blood-brain barrier. After brain injury, brain antigens are released into the systemic circulation to induce damaging immune responses. Immune tolerance can effectively reduce the brain edema and neurological inflammatory response after brain injury, which is beneficial to the recovery of neurological function. The clinical application prospect and theoretical research value of the treatment of immune tolerance on traumatic brain inj ury （TBi） is worth attention. Conclusions： The establishment of immune tolerance mechanism has a high clinical value in the treatment of TBI. It opens up new opportunities for the treatment of brain damage.

关键词： Central Nervous System Immune Tolerance Traumatic Brain Injury

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