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Phase field modeling for the morphological and microstructural evolution of metallic materials under environmental attack

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npj Computational Materials 2021年第1期7卷 1299-1319页

作者： Talha Qasim Ansari Haitao Huang san-qiang shi Department of Applied Physics and Research Institute of Smart Energy the Hong Kong Polytechnic UniversityHung HomKowloonHong Kong SAR Department of Mechanical Engineering the Hong Kong Polytechnic UniversityHung HomKowloonHong Kong SAR

The complex degradation of metallic materials in aggressive environments can result in morphological and microstructural *** phase-field(PF)method is an effective computational approach to understanding and predicting the morphology,phase change and/or transformation of *** models are based on conserved and non-conserved field variables that represent each phase as a function of space and time coupled with time-dependent equations that describe the *** report summarizes progress in the PF modeling of degradation of metallic materials in aqueous corrosion,hydrogen-assisted cracking,high-temperature metal oxidation in the gas phase and porous structure evolution with insights to future applications.

关键词： corrosion cracking metallic

Phase-field model of pitting corrosion kinetics in metallic materials

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npj Computational Materials 2018年第1期4卷 330-338页

作者： Talha Qasim Ansari Zhihua Xiao Shenyang Hu Yulan Li Jing-Li Luo san-qiang shi Department of Mechanical Engineering The Hong Kong Polytechnic University11 Yuk Choi RoadHung HomKowloonHong Kong Pacific Northwest National Laboratory RichlandWA 99352USA Department of Chemical and Materials Engineering University of AlbertaEdmontonAB T6G 2R3Canada

Pitting corrosion is one of the most destructive forms of corrosion that can lead to catastrophic failure of *** study presents a thermodynamically consistent phase field model for the quantitative prediction of the pitting corrosion kinetics in metallic *** order parameter is introduced to represent the local physical state of the metal within a metal-electrolyte *** free energy of the system is described in terms of its metal ion concentration and the order *** the ion transport in the electrolyte and the electrochemical reactions at the electrolyte/metal interface are explicitly taken into *** temporal evolution of ion concentration profile and the order parameter field is driven by the reduction in the total free energy of the system and is obtained by numerically solving the governing equations.A calibration study is performed to couple the kinetic interface parameter with the corrosion current density to obtain a direct relationship between overpotential and the kinetic interface *** phase field model is validated against the experimental results,and several examples are presented for applications of the phase-field model to understand the corrosion behavior of closely located pits,stressed material,ceramic particles-reinforced steel,and their crystallographic orientation dependence.

关键词： corrosion pitting steel

Predicting surface deformation during mechanical attrition of metallic alloys

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npj Computational Materials 2019年第1期5卷 843-857页

作者： Shan Cecilia Cao Xiaochun Zhang Jian Lu Yongli Wang san-qiang shi Robert O.Ritchie Department of Materials Science&Engineering University of CaliforniaBerkeleyCA 94720USA Shanghai Institute of Applied Physics Chinese Academy of SciencesShanghai 201800China Department of Mechanical Engineering City University of Hong KongHong KongChina Department of Mechanical Engineering The Hong Kong Polytechnic UniversityHung HomHong Kong Materials Sciences Division Lawrence Berkeley National LaboratoryBerkeleyCA 94720USA

Extensive efforts have been devoted in both the engineering and scientific domains to seek new designs and processing techniques capable of making stronger and tougher *** such method for enhancing such damage-tolerance in metallic alloys is a surface nano-crystallization technology that involves the use of hundreds of small hard balls which are vibrated using high-power ultrasound so that they impact onto the surface of a material at high speed(termed Surface Mechanical Attrition Treatment or SMAT).However,few studies have been devoted to the precise underlying mechanical mechanisms associated with this technology and the effect of processing *** SMAT is dynamic plastic deformation process,here we use random impact deformation as a means to investigate the relationship between impact deformation and the parameters involved in the processing,specifically ball size,impact velocity,ball density and kinetic *** analytical and numerical solutions,we examine the size of the indents and the depths of the associated plastic zones induced by random impacts,with results verified by experiment in austenitic stainless *** addition,global random impact and local impact frequency models are developed to analyze the statistical characteristics of random impact coverage,together with a description of the effect of random multiple impacts,which are more reflective of *** believe that these models will serve as a necessary foundation for further,and more energy-efficient,development of such surface nano-crystalline processing technologies for the strengthening of metallic materials.

关键词： deformation alloys metallic

Combining gradient structure and supersaturated solid solution to achieve superior mechanical properties in WE43 magnesium alloy

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Journal of Materials Science & Technology 2022年第4期99卷 223-238页

作者： Wanting Sun Bo Wu Hui Fu Xu-Sheng Yang Xiaoguang Qiao Mingyi Zheng Yang He Jian Lu san-qiang shi State Key Laboratory of Ultra-precision Machining Technology Department of Industrial and Systems EngineeringThe Hong Kong Polytechnic UniversityHung HomHong KongChina Hong Kong Polytechnic University Shenzhen Research Institute ShenzhenChina Department of Mechanical Engineering The Hong Kong Polytechnic UniversityHung HomHong KongChina School of Materials Science and Engineering Harbin Institute of TechnologyHarbin 150001China Centre for Composite Materials and Structures Harbin Institute of TechnologyHarbin 150080China Department of Mechanical Engineering City University of Hong KongKowloonHong KongChina

In this study,surface mechanical attrition treatment was employed to sucessfully produce a gradient nanostructured layer on WE43 magnesium alloy.X-ray diffraction,energy dispersive X-ray spectrometer,and high-resolution transmission electron microscope observations were mainly performed to uncover the microstructure evolution responsible for the refinement *** reveals that the grain refinement process consists of three transition stages along the depth direction from the core matrix to the topmost surface layer,i.e.,dislocation cells and pile-ups,ultrafine subgrains,and randomly orientated nanograins with the grain size of~40 ***,the original Mg;RE second phase is also experienced refinement and then re-dissolved into the α-Mg matrix phase,forming a supersaturated solid solution nanostructuredα-Mg phase in the gradient refined *** to the cooperative effects of grain refinement hardening,dislocation hardening,and supersaturated solid-solution hardening,the gradient nanostructured WE43 alloy contributes to the ultimate tensile strength of~435 MPa and ductility of~11.0%,showing an extraordinary strain hardening and mechanical properties among the reported severe plastic deformation-processed Mg *** work provides a new strategy for the optimization of mechanical properties of Mg alloys via combining the gradient structure and supersaturated solid solution.

关键词： Mg-RE alloy Surface mechanical attrition treatment Gradient nanostructure Supersaturated solid solution High strength and ductility Strengthening mechanisms

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德州市主要地质灾害及防治对策

山东地质 2000年第2期16卷 31-35页

作者：孟庆峰董三强颜世强德州市地质矿产局山东德州253012

德州市地质灾害与环境地质问题主要有地下水降落漏斗、地面沉降、地面塌陷、地下水污染和地方病等 ,其发育除受地质、水文地质条件制约外 ,还与人为因素有关。本文对地质灾害的分布、危害程度和致灾因素做了分析 ,并提出了相应的防治对策。

关键词：地质灾害防治对策山东德州地面沉降

Spectrum-effect relationship between HPLC fingerprints and bioactive components of Radix Hedysari on increasing the peak bone mass of rat

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Journal of Pharmaceutical Analysis 2019年第4期9卷 266-273页

作者： Xin-Yue Chen san-Hu Gou Zhi-qiang shi Zhi-Yuan Xue shi-Lan Feng School of Pharmacy Lanzhou University

The traditional Chinese medicine of Radix Hedysari plays an important role in invigorating gas for ascending, benefiting blood for promoting production of fluid, and promoting circulation for removing obstruction in collaterals, which is consistent with the principle of treatment for osteoporosis. This study is designed to investigate the bioactive components on increasing peak bone mass (PBM) by exploring the spectrum-effect relationship between chromatography fingerprints and effect. Multiple indicators are selected to evaluate the pharmacological activity. In fingerprints, 21 common peaks are obtained, five of which are identified. Furthermore, gray relational analysis (GRA) is a quantitative method of gray system theory and is used to describe the correlation degree of common peaks and pharmacological activities with relational value. 21 components are then divided into three different regions, of which ononin and calycosin play an extremely significant role in increasing PBM. In addition, factor analysis and hierarchical cluster analysis (HCA) are used to screen the optimal producing area for Radix Hedysari. This provides a comprehensive and efficient method to improve the quality evaluation of Radix Hedysari, confirming the bioactive components for PBM-enhancement and further develop its medicinal value.

关键词： Factor analysis Gray relational analysis Hierarchical cluster analysis Peak bone mass Radix Hedysari Spectrum-effect relationship

On the Equation n1n2= n3n4 Restricted to Factor Closed Sets

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Acta Mathematica Sinica,English Series 2018年第10期34卷 1517-1530页

作者： san Ying shi Michel WEBER School of Mathematics Hefei University of Technology Hefei 230009 P. R. China IRMA UMR 7501 7 rue Rend Descartes 67084 Strasbourg Cedex France

We study the number of solutions N（B,F） of the diophantine equation n1n2 = n3n4,where 1 ≤ n1≤B, 1≤ n3 ≤B, n2, n4 ∈ F and F C [1, B] is a factor closed set. We study more particularly the case when F = {m = p1^... 详细信息

关键词： Diophantine equation arithmetical functions factor closed set

Aerodynamic design on high-speed trains

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Acta Mechanica Sinica 2016年第2期32卷 215-232页

作者： san-san Ding qiang Li Ai-Qin Tian Jian Du Jia-Li Liu School of Mechanical Electronic and Control EngineeringBeijing Jiaotong University CSR Qingdao Sifang Locomotive & Rolling Stock Co. Ltd.

Compared with the traditional train,the operational speed of the high-speed train has largely improved,and thedynamicenvironmentofthetrainhaschangedfromoneof mechanical domination to one of aerodynamic *** aerodynamic problem has become the key technological challenge of high-speed trains and significantl affects the economy,environment,safety,and *** this paper,the relationships among the aerodynamic design principle,aerodynamic performance indexes,and design variables are firs studied,and the research methods of train aerodynamics are proposed,including numerical simulation,a reducedscale test,and a full-scale *** schemes of train aerodynamics involve the optimization design of the streamlined head and the smooth design of the body *** design of the streamlined head includes conception design,project design,numerical simulation,and a reduced-scale *** design of the body surface is mainly used for the key parts,such as electric-current collecting system,wheel truck compartment,and *** aerodynamic design method established in this paper has been successfully applied to various high-speed trains（CRH380A,CRH380 AM,CRH6,CRH2 G,and the Standard electric multiple unit（EMU）） that have met expected design *** research results can provide an effective guideline for the aerodynamic design of high-speed trains.

关键词： High-speed train Aerodynamic design Optimization design Smooth design

Research of Helicobacter pylori infection in precancerous gastric lesions

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World Journal of Gastroenterology 2000年第3期6卷 428-429页

作者： Xiao qiang Zhuang san Ren Lin Department of Gastroenterology General Hospitalof Guangzhou Command AreaGuangzhou 510010Guangdong ProvinceChina Department of Gastroenterology The Third Hospital of Beijing Medical UniversityBeijing 100083China

INTRODUCTION Helicobacter pylori(Hp)infection has beenconsidered to play significant roles in pathogenesisof peptic *** Hp is associated withthe development of gastric epithelial hyperplasiaand lymphoid *** InternationalAgency for Research on Cancer has classified lip asa class Ⅰ carcinogen and a definite cause of gastriccancer in *** infection first causes chronicactive gastritis and may slowly lead to infection ofwhole *** the late stages of infection,mucosal atrophy and intestinal metaplasia(IM),

关键词： Helicobacter pylori precancerous gastric lesions