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Linear fractional composition operators on the Dirichlet space in the unit ball

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Science China Mathematics 2009年第8期52卷 1661-1670页

作者： zhou zehua YUAN Cheng Department of Mathematics Tianjin UniversityTianjin 300072China

We investigate the adjoints of linear fractional composition operators C ? acting on classical Dirichlet space D(B N ) in the unit ball B N of ? N , and characterize the normality and essential normality of C ? on D(B N ) and the Dirichlet space modulo constant function D 0(B N ), where ? is a linear fractional map ? of B N . In addition, we also show that for any non-elliptic linear fractional map ? of B N , the composition maps σ o ? and ? o σ are elliptic or parabolic linear fractional maps of B N .

关键词： linear fractional composition operators Dirichlet space adjoints essential normality 47B38 46E15 32A37

实对称矩阵与Hermite矩阵符号分类的特征多项式法

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大学数学 2024年第1期40卷 96-98页

作者：田代军周泽华天津大学数学学院天津300354

给出了直接用特征多项式判别实对称矩阵与Hermite矩阵的符号分类的方法.

关键词：实对称矩阵 Hermite矩阵符号分类惯性指数特征多项式

Order Bounded Weighted Composition Operators Mapping into the Dirichlet Type Spaces

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Chinese Annals of Mathematics,Series B 2016年第4期37卷 585-594页

作者： Yongxin GAO Sanjay KUMAR zehua zhou Department of Mathematics Tianjin UniversityTianjin 300072China. Department of Mathematics Central University of JammuINDIA. Center for Applied Mathematics Tianjin UniversityTianjin 300072China.

The authors characterize the order boundedness of weighted composition operators acting between Dirichlet type spaces.

关键词： Weighted composition operator Order boundedness Dirichlet typespaces Positive Borel measure

The Combined Impact of Magnetic Field and Chloride Ion Concentration on Corrosion Behavior of Al-Mg Alloys

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Journal of Wuhan University of Technology(Materials Science) 2022年第6期37卷 1192-1203页

作者： ZHANG Xin HUANG Lianpeng TAO Jiahao WANG zehua zhou zehua CAI Xin WEN Tao College of Mechanics and Materials Hohai UniversityNanjing 210098China Beijing Yubing Water Hydraulic Survey Planning Design Co.Ltd.Jiangsu Branch Nanjing 211111China

The impact of magnetic field on the corrosion behavior of Al-Mg-xR_(E)/Fe alloys in NaCl solutions with concentrations of 1.5wt%,3.5wt%,and 5.5wt%were studied by microstructure observation,immersion test,and electrochemical *** combined impacts of magnetic field and chloride ion concentration on the corrosion behavior of Al-Mg alloys with various electrode potential phases were *** results indicate that Al-3.0Mg-xR_(E)/Fe alloys corrode faster and have a higher pitting corrosion potential in the NaCl solution with a higher *** addition,a magnetic field can lower the pitting sensitivity and corrosion rate of Al-3.0Mg and Al-3.0Mg-0.2R_(E)/Fe alloys in NaCl solution with different ***,at a higher concentration of NaCl solution,the magnetic field has a weaker inhibiting effect on corrosion rate and pitting *** NaCl solutions with concentrations of 1.5wt%and 3.5wt%,the corrosion rate and pitting sensitivity of Al-3.0Mg-1.0R_(E)/Fe alloys can be reduced by a magnetic ***,in NaCl solution with the concentration of 5.5wt%,the corrosion rate of the alloys is increased by a magnetic field.

关键词： magnetic field corrosion behavior chloride ion concentration different electrode potential phases

Influence of Rare Earth(Ce and La) Addition on the Performance of Al-3.0 wt%Mg Alloy

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Journal of Wuhan University of Technology(Materials Science) 2017年第3期32卷 611-618页

作者：张欣王泽华 zhou zehua XU Jianming College of Mechanics and Materials Hohai University Nanjing 210098 China Zhangjiagang Hongji Aluminum Co. Ltd. Suzhou 215600 China

The influences of rare earth elements（cerium and lanthanum） on the microstructure and phases of Al-3.0 wt%Mg alloys used for electromagnetic shielding wire were characterized by scanning electron microscopy（SEM）, energy-dispersive spectroscopy（EDS）, X-ray diffraction（XRD） and differential scanning calorimetry（DSC）. The mechanical properties and electrical resistivity were also investigated. The results indicated that a certain content of rare earth could improve the purification of the aluminum molten, enhance the strength, and reduce the electrical resistivity of Al-3.0 wt%Mg alloys. The strength reached the top value when RE content was 0.3 wt% while the alloy with 0.2 wt% RE addition had the smallest electrical resistivity. The elongation varied little when RE addition was no more than 0.2 wt%. But the excessive addition of rare earth would be harmful to the microstructure and properties of Al-3.0 wt%Mg alloys.

关键词： Al-3.0 wt%Mg alloy Ce and La additions microstructure mechanical property electrical resistivity

Effect of shrinkage porosity on mechanical properties of ferritic ductile iron

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China Foundry 2013年第3期10卷 141-147页

作者： Wang zehua Zhao Weihua zhou zehua Jiang Shaoqun Yu Xuru Wang Qiuxin College of Mechanics and Materials Hohai University Suzhou Nuclear Power Research Institute Co. Ltd. Jiangsu First Automotive Foundry Co. Ltd.

Casting defects could largely affect the mechanical properties of casting products. A number of test pieces made of ductile iron (EN-GJS-400-18-LT) with different levels of shrinkage porosity were prepared and then tensile and fatigue tests were performed to investigate the impact of shrinkage porosity on their mechanical properties. The results showed that the tensile strength decreases linearly with increasing of the shrinkage porosity. The tensile elongation decreases sharply with the increase of the shrinkage porosity mainly due to the non-uniform plastic deformation. The fatigue life also dramatically declines with increasing of the porosity and follows a power law relationship with the area percentage of porosity. The existence of the shrinkage porosity made the fatigue fracture complex. The shrinkage pores, especially those close to the surface usually became the crack initiation sites. For test pieces with less porosity, the fatigue fracture was clearly composed of crack initiation, propagation, and overloading. While for samples with high level of porosity, multiple crack initiation sites were observed.

关键词： ferritic ductile iron shrinkage porosity mechanical properties

Characteristics of Fe-based WC Composite Coatings Prepared by Double-pass Plasma Cladding Process

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稀有金属材料与工程 2012年第S1期41卷 195-198页

作者： Jiang Shaoqun Ren Qingwen Ying, Ding Gang, Wang Yu, Yi Wang zehua zhou zehua Hohai Univ Coll Mech & Mat Nanjing 210098 Jiangsu Peoples R China

The Fe-based WC composite coatings were clad on Q235 steel by double-pass plasma cladding method,in which the WC-Co(WC covered with cobalt:78wt%WC,12wt%Co)doping was about 10wt%,20wt%and 40wt%,*** microstructure and wear performance of the composite coatings were investigated by X-ray diffraction(XRD),scanning electron microscope(SEM),energy dispersive spectrometer(EDS)and ball-disc wear *** results show that the clad coatings contain mainly?-Fe,WC and carbides(Cr23C6,Fe3W3C-Fe4W2C)phases and the precipitation of carbides increases with the increase of WC-Co doping *** WC-Co doping content has an obvious effect on the microstructure of the clad *** the clad coatings with low WC-Co doping,the microstructure gradually transforms from planar crystal at the interface of substrate/coating to cell/dendritic crystal at the middle and the upper portion of the *** there are a number of fishbone-like structure at the middle and the upper portion of clad coating with 40wt%WC-Co *** microstructure at the top is smaller than that at the bottom for all the *** maximum of hardness of the clad coatings is 72.3HRC which is about 6.9 as much as the hardness of Q235 steel *** composite coatings have good wear resistance due to the reinforcement of carbide particles and the strong bonding between carbide particles and *** suitable increase of WC-Co doping content can improve the wear resistance of the composite coatings.

关键词： plasma cladding Fe-based WC wear resistance metal matrix composite

中药干预幽门螺杆菌阴性慢性萎缩性胃炎相关信号通路研究进展

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中华中医药学刊 2024年第5期42卷 82-88,I0021,I0022页

作者：周泽华梁琨崔波尤丽莎安叡王新宏上海中医药大学上海201203

慢性萎缩性胃炎(chronic atrophic gastritis,CAG)是炎瘤转换过程的关键阶段,遏制其进一步发展对预防胃癌意义重大。目前,以根除幽门螺杆菌(Helicobacter pylori,Hp)为主的有关机制研究已有不少报道,但对于Hp阴性CAG的发病机制研究及其... 详细信息

慢性萎缩性胃炎(chronic atrophic gastritis,CAG)是炎瘤转换过程的关键阶段,遏制其进一步发展对预防胃癌意义重大。目前,以根除幽门螺杆菌(Helicobacter pylori,Hp)为主的有关机制研究已有不少报道,但对于Hp阴性CAG的发病机制研究及其治疗药物仍有待补充。鉴于信号通路的异常激活或抑制,对CAG的进程有重要影响,以信号转导分子为靶点进行研究,对防治CAG有重大意义。近年来众多学者开展了大量研究,发现Hp阴性CAG发生发展与磷脂酰肌醇-3-激酶(phosphatidylin-ositol-3-kinase,PI3K)/蛋白激酶B(protein kinase B,Akt)通路、Janus激酶(janus ki⁃nase,JAK)/信号转导和转录激活因子(signal transducers and activators of transcription,STAT)通路、Wnt/β-catenin通路和Toll样受体(toll-like receptor,TLRs)/核因子κB(nuclear factor kappa-B,NF-κB)通路的相关报道较多。而中药可通过调控相关信号通路的方式,改善免疫功能和炎性反应,最终影响Hp阴性CAG的发病进程,起到干预作用。以信号通路为基础,对近些年中药干预Hp阴性CAG的国内外研究现状进行总结,旨在为今后中药的深入研究及临床治疗提供新思路。

关键词： Hp阴性慢性萎缩性胃炎信号通路中药综述

Construction of Self-Assembly Based Tunable Absorber:Lightweight,Hydrophobic and Self-Cleaning Properties

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Nano-Micro Letters 2023年第9期15卷 148-163页

作者： zehua zhou Qianqian Zhu Yue Liu Yan Zhang Zirui Jia Guanglei Wu Institute of Materials for Energy and Environment State Key Laboratory of Bio-fibers and Eco-textilesCollege of Materials Science and EngineeringQingdao UniversityQingdao 266071People’s Republic of China College of Chemistry and Chemical Engineering Qingdao UniversityQingdao 266071People’s Republic of China

Although multifunctional aerogels are expected to be used in applications such as portable electronic devices,it is still a great challenge to confer multifunctionality to aerogels while maintaining their inherent ***,a simple method is proposed to prepare multifunctional NiCo/C aerogels with excellent electromagnetic wave absorption properties,superhydrophobicity,and self-cleaning by water-induced NiCo-MOF ***,the impedance matching of the three-dimensional(3D)structure and the interfacial polarization provided by CoNi/C as well as the defect-induced dipole polarization are the primary contributors to the broadband *** a result,the prepared NiCo/C aerogels have a broadband width of 6.22 GHz at 1.9 *** to the presence of hydrophobic functional groups,CoNi/C aerogels improve the stability in humid environments and obtain hydrophobicity with large contact angles>140°.This multifunctional aerogel has promising applications in electromagnetic wave absorption,resistance to water or humid environments.

关键词： MOF aerogel Self-cleaning Electromagnetic wave absorption Hydrophobic