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International Journal of Minerals,Metallurgy and Materials 2025年第2期32卷 369-379页

作者： mei zhang Wenhao Li Yangfei Chen Yang Jiang Xiaofei Guo Han Dong School of Materials Science and Engineering Shanghai UniversityShanghai 200444China State Key Laboratory of Advanced Special Steel Shanghai UniversityShanghai 200444China

The microstructural evolution of a cold-rolled and intercritical annealed medium-Mn steel(Fe-0.10C-5Mn)was investigated during uniaxial tensile ***-situ observations under scanning electron microscopy,transmission electron microscopy,and X-ray diffraction analysis were conducted to characterize the progressive transformation-induced plasticity process and associated fracture initiation *** findings were discussed with the local strain measurements via digital image *** results indicated that Lüders band formation in the steel was limited to 1.5%strain,which was mainly due to the early-stage martensitic phase transformation of a very small amount of the less stable large-sized retained austenite(RA),which led to localized stress concentrations and strain hardening and further retardation of *** small-sized RA exhibited high stability and progressively transformed into martensite and contributed to a stably extended Portevin-Le Chatelier *** volume fraction of RA gradually decreased from 26.8%to 8.2%prior to *** the late deformation stage,fracture initiation primarily occurred at the austenite/martensite and ferrite/martensite interfaces and the ferrite phase.

关键词： medium-Mn steel retained austenite progressive transformation-induced plasticity effect local strain fracture initiation

Two Weighted Estimates for the Commutators of Multilinear Maximal Singular Integral Operators with Dini-type Kernels

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Acta Mathematica Sinica,English Series 2023年第3期39卷 459-480页

作者： Chun mei zhang School of Mathematical Sciences Beijing Normal UniversityBeijing 100875P.R.China

The main purpose of this paper is to investigate the properties of the higher order commutators of maximal Calderón-Zygmund operators with Dini-type *** weighted estimates have been established for these *** results ... 详细信息

关键词： Commutators sparse domination multlinear maximal singular integral operators Dinitype kenels two weighted boundedness

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Construction of solitonary and periodic solutions to some nonlinear equations using EXP-function method

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第4期8卷 660-664页

作者： zhang mei zhang Wen-jing Department of Applied Physics College of Science Donghua University Shanghai 201620 China

This paper applies the EXP-function method to find exact solutions of various nonlinear equations. Tzitzeica- Dodd-Bullough (TDB) equation was selected to illustrate the effectiveness and convenience of the suggested method. More generalized solitonary solutions with free parameters were obtained by suitable choice of the free parameters, and also the obtained solitonary solutions can be converted into periodic solutions.

关键词： Soliton Periodic solution Nonlinear equation EXP-function method

Moderate Deviation for the Single Point Catalytic Super-Brownian Motion

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Acta Mathematica Sinica,English Series 2012年第9期28卷 1799-1808页

作者： Xu YANG mei zhang School of Mathematical Sciences Beijing Normal University

We establish the moderate deviation for the density process of the single point catalytic super-Brownian motion. The main tools are the abstract Gaertner-Ellis theorem, Dawson-Gaertner the- orem and the contraction principle. The rate function is expressed by the Fenchel-Legendre transform of log-exponential moment generation function.

关键词： Super-Brownian motion catalytic conditional log-Laplace functional locally uniform moderate deviation

Harmonic moments and large deviations for a critical Galton-Watson process with immigration

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Science China Mathematics 2021年第8期64卷 1885-1904页

作者： Doudou Li mei zhang School of Mathematical Sciences Beijing Normal UniversityBeijing 100875China

In this paper,a critical Galton-Watson branching process with immigration Z_(n)is *** first obtain the convergence rate of the harmonic moment of Z_(n).Then the large deviation of S_(Z_(n)):∑_(i=1)^(Z_(n))X_(i)is obtained,where{X_(i)}is a sequence of independent and identically distributed zero-mean random variables with the tail indexα>*** shall see that the converging rate is determined by the immigration mean,the variance of reproducing and the tail index of X_(1)^(+),compared with the previous result for the supercritical case,where the rate depends on the Schroder constant and the tail index.

关键词： harmonic moment large deviation local probability estimate immigration

Biporous nanocarbon foams and the effect of the structure on the capillary performance

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Progress in Natural Science:Materials International 2020年第3期30卷 360-365页

作者： Jiang Li mei zhang High-Performance Materials Institute Florida State University Department of Industrial and Manufacturing Engineering FAMU-FSU College of Engineering

Biporous nanocarbon foams （NC foams） which have both nano-pores and micro-pores,were fabricated and used to explore the liquid transportation in the porous structures formed by *** electron microscopy was utilized to observe the structure of the NC *** rise tests using acetone as the working fluid were conducted by the IR thermal imaging *** results show that the capillary rise height of the NC foam with 65μm micro-pore size was 47%higher than that with 9μm micro-pore size in 50 *** capillary performance of the NC foams was reduced when its density was higher than 60 mg/cm;.A model is built to illustrate the effect of both nano-structure and micro-structure on the transportation of working fluid in the biporous *** data indicates that the nano-structure generated high capillary pressure while the microstructure provided low resistant pathways for fast liquid *** size of micro-pores and the ratio of micro-pores to nano-pores were two important *** is demonstrated that the NC foams had large sorption capacity up to 878 mg/cm;and their capillary performance was further enhanced when using a substrate.

关键词： Biporous wick Micro-pore Nano-structure Carbon nanotube Capillary performance

Lower deviations for supercritical branching processes with immigration

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Frontiers of Mathematics in China 2021年第2期16卷 567-594页

作者： Qi SUN mei zhang School of Mathematics and Statistics Beijing Technology and Business UniversityBeijing 100048China School of Mathematical Sciences Laboratory of Mathematics and Complex SystemsBeijing Normal UniversityBeijing 100875China

For a supercritical branching processes with immigration {Zn};it is known that under suitable conditions on the offspring and immigration distributions, Zn/mn converges almost surely to a finite and strictly positive limit, where m is the offspring mean. We are interested in the limiting properties of P(Zn=kn) with kn=o(mn) as n→∞. We give asymptotic behavior of such lower deviation probabilities in both Schröder and Böttcher cases, unifying and extending the previous results for Galton-Watson processes in literature.

关键词： Supercritical branching processes lower deviations immigration

Approximation for counts of head runs

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Science China Mathematics 2011年第2期54卷 311-324页

作者： zhang mei School of Mathematical Sciences Beijing Normal University Beijing 100875 China

In this paper, we study the count of head runs up to a fixed time in a two-state stationary Markov chain. We prove that in total variance distance, the negative binomial, Poisson and binomial distributions are appropriate approximations according to the relation of the variance and mean of the count, generalizing earlier results in previous literatures. The proof is based on Stein's method and coupling.

关键词： head run negative binomial distribution Poisson distribution binomial distribution Stein's method total variation distance coupling

A Comparison of Co-temporal Vector Magnetograms Obtained with HMI/SDO and SP/Hinode

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Research in Astronomy and Astrophysics 2023年第12期23卷 175-183页

作者： mei zhang Haocheng zhang Chengqing Jiang National Astronomical Observatories Chinese Academy of SciencesBeijing 100101China School of Astronomy and Space Sciences University of Chinese Academy of SciencesBeijing 100049China High Altitude Observatory National Center for Atmospheric Research3080 Center Green DriveBoulderCO 80301USA Jericho High School 99 Cedar Swamp RoadJerichoNY 11753USA School of Space and Environment Beihang UniversityBeijing 100091China

Accurate measurement of magnetic fields is very important for understanding the formation and evolution of solar magnetic ***,there are two types of solar magnetic field measurement instruments:filter-based magnetographs and Stokes *** former gives high temporal resolution magnetograms and the latter provides more accurate measurements of magnetic *** the magnetograms obtained by filter-based magnetographs with those obtained by Stokes polarimeters is a good way to combine the advantages of the two *** previous studies have shown that,compared to the magnetograms obtained by the Spectro-Polarimeter(SP)on board Hinode,those magnetograms obtained by both the filter-based Solar Magnetic Field Telescope(SMFT)of the Huairou Solar Observing Station and by the filter-based Michelson Doppler Imager(MDI)aboard SOHO have underestimated the flux densities in their magnetograms and systematic center-to-limb variations present in the magnetograms of both ***,using a sample of 75 vector magnetograms of stable alpha sunspots,we compare the vector magnetograms obtained by the Helioseismic and Magnetic Imager(HMI)aboard Solar Dynamics Observatory(SDO)with co-temporal vector magnetograms acquired by SP/*** analysis shows that both the longitudinal and transverse flux densities in the HMI/SDO magnetograms are very close to those in the SP/Hinode magnetograms and the systematic center-to-limb variations in the HMI/SDO magnetograms are very *** study suggests that using a filter-based magnetograph to construct a low spectral resolution Stokes profile,as done by HMI/SDO,can largely remove the disadvantages of the filter-type measurements and yet still possess the advantage of high temporal resolution.

关键词： The Sun-Sun magnetic fields-Sun photosphere-(Sun:)sunspots

The influence of the stray-light component in determining coronal temperature structures

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Science China(Physics,Mechanics & Astronomy) 2009年第11期52卷 1728-1736页

作者： HAO Juan zhang mei Key Laboratory of Solar Activity National Astronomical ObservatoriesChinese Academy of SciencesBeijing 100012China

We use a few solar partial eclipse observations made by XRT/Hinode to estimate the influence of stray-light component in determining coronal temperature structures. Our analysis shows that the stray light will largely affect the estimation of coronal temperature and change the estimated temperature structure in one coronal hole region. The stray lights mildly influence the estimated temperatures in one quiet Sun region and do not change the estimated temperature structure. This implies that the influence of stray lights differs from one region to another, and definitely needs to be considered in some regions. Whereas a carefully estimated point-spread-function is needed to remove the stray light component, our study shows that by a simple approach such as subtracting the average intensity of distant (e.g. >1.4 solar radius) points from the data values, the influence of stray light can be largely removed, at least for the two regions we study here.

关键词： Sun: Corona Sun: X-rays