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Simultaneous refinement of α-Mg grains and β-Mg_(17)Al_(12) in Mg-Al based alloys via heterogeneous nucleation on Al_(8)Mn_(4)Sm

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Journal of Magnesium and Alloys 2023年第1期11卷 348-360页

作者： Jun-Chen Chen Mei-Xuan Li zhi-Yang Yu Zhao-yuan Meng Cheng Wang zhi-Zheng Yang Hui-yuan Wang State Key Laboratory of Automotive Simulation and Control Jilin UniversityChangchun 130012PR China Key Laboratory of Automobile Materials of Ministry of Education&School of Materials Science and Engineering Jilin UniversityNanling CampusNo.5988 Renmin StreetChangchun 130025PR China International Center of Future Science Jilin UniversityChangchun 130012PR China

Due to the significant differences in the formation temperature and crystal structure between the primaryα-Mg and eutecticβ-Mg_(17)Al_(12),it is a great challenge to achieve simultaneous refinement of the primary and eutectic phases in Mg-Al based alloys via heterogeneous ***,we found that theα-Mg andβ-Mg_(17)Al_(12) in the AZ80 alloy can be simultaneously refined after 0.2 wt.%Sm addition,with the grain size decreasing from∼217±15μm to∼170±10μm and theβ-Mg_(17)Al_(12) morphology changing from a typical continuous network to a nod-like or spherical *** simultaneous refinement mechanism is investigated through solidification simulation,transmission electron microscopy(TEM),and differential thermal analysis(DTA).In the AZ80-0.2Sm alloy,many Al8Mn4Sm particles can be observed near the center of theα-Mg grains or inside theβ-Mg_(17)Al_(12).Crystallographic calculations further reveal that the Al8Mn4Sm has good crystallographic matching with both theα-Mg andβ-Mg_(17)Al_(12),so it possesses the potency to serve as heterogeneous nucleation sites for both *** promoted heterogeneous nucleation on the Al8Mn4Sm decreases the undercooling required by the nucleation of the primary and eutectic phases,which enhances the heterogeneous nucleation rate,thus causing the simultaneous refinement of theα-Mg andβ-Mg_(17)Al_(12).The orientation relationships between the Al8Mn4Sm and Mg/Mg_(17)Al_(12) are identified,which are[1210]_(Mg)//[010]_(Al8Mn4Sm),(1010)_(Mg)//(301)_(Al8Mn4Sm) and[112]_(Mg_(17)Al_(12))//[010]_(Al8Mn4Sm),(110)_(Mg_(17)Al_(12))//(301)_(Al8Mn4Sm),***,the refinement of theβ-Mg_(17)Al_(12) accelerates its dissolution during the solution treatment,which is beneficial for cost saving in industrial *** Al8Mn4RE compounds such as Al8Mn4Y might have the same positive effect on the simultaneous refinement due to the similar physicochemical properties of rare earth *** work not only proves the po

关键词： Magnesium alloys Microstructure refinement Primaryα-Mg Eutecticβ-Mg_(17)Al_(12) Rare earth Heterogeneous nucleation

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High-temperature corrosion of Sn-Bi-Zn-Ga alloys as heat transfer fluid

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Rare Metals 2021年第8期40卷 2221-2229页

作者： Qing-Meng Wang Xiao-Min Cheng yuan-yuan Li Guo-Ming Yu zhi Liu School of Materials Science and Engineering Wuhan University of TechnologyWuhan430070China School of Mechanical and Electrical Engineering Huanggang Normal UniversityHuanggang438000China

The new heat transfer alloy is highly reactive at high temperatures,and the corrosion of the container material determines the service life of the heat transfer *** high-temperature corrosion of Sn-Bi-Zn-Ga alloys as heat transfer fluid was *** microstructure and elemental distribution were studied by field emission scanning electron microscopy(FESEM)and energy dispersive spectroscopy(EDS).The thermal properties before and after corrosion were studied by differential scanning calorimetry(DSC).The results show that the corrosion kinetics of the studied materials follows the parabolic law and the thermal properties after corrosion are *** significantly improves the thermal conductivity.316 stainless steel exhibits excellent corrosion resistance due to its high Cr and Ni *** mechanism analysis shows that the oxidation of Ga has a smaller Gibbs free energy,and an oxide forms at the corrosion interface to prevent dissolution corrosion and oxidative corrosion of the container material.

关键词： Sn-Bi-Zn-Ga Heat transfer fluids Thermophysical properties High-temperature corrosion

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Using shapes correlation for active contour segmentation of uterine fibroid ultrasound images in computer-aided therapy

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Applied Mathematics(A Journal of Chinese Universities) 2016年第1期31卷 37-52页

作者： NI Bo HE Fa-zhi PAN Yi-teng yuan zhi-yong School of Computer Science Wuhan University School of Computer Science Hubei Polytechnic University

Segmenting the lesion regions from the ultrasound （US） images is an important step in the intra-operative planning of some computer-aided therapies. High-Intensity Focused Ultrasound （HIFU）, as a popular computer-aided therapy, has been widely used in the treatment of uterine fibroids. However, such segmentation in HIFU remains challenge for two reasons：（1） the blurry or missing boundaries of lesion regions in the HIFU images and （2） the deformation of uterine fibroids caused by the patient＇s breathing or an external force during the US imaging process, which can lead to complex shapes of lesion regions. These factors have prevented classical active contour-based segmentation methods from yielding desired results for uterine fibroids in US images. In this paper, a novel active contour-based segmentation method is proposed, which utilizes the correlation information of target shapes among a sequence of images as prior knowledge to aid the existing active contour method. This prior knowledge can be interpreted as a unsupervised clustering of shapes prior modeling. Meanwhile, it is also proved that the shapes correlation has the low-rank property in a linear space, and the theory of matrix recovery is used as an effective tool to impose the proposed prior on an existing active contour model. Finally, an accurate method is developed to solve the proposed model by using the Augmented Lagrange Multiplier （ALM）. Experimental results from both synthetic and clinical uterine fibroids US image sequences demonstrate that the proposed method can consistently improve the performance of active contour models and increase the robustness against missing or misleading boundaries, and can greatly improve the efficiency of HIFU therapy.

关键词： Active contour shapes correlation ultrasound image segmentation matrix recovery computer-aided therapy.

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Grain boundary segregation of minor arsenic and nitrogen at elevated temperatures in a microalloyed steel

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International Journal of Minerals,Metallurgy and Materials 2012年第5期19卷 399-403页

作者： yuan-zhi Zhu Zhe Zhu Jian-ping Xu The Key Laboratory of the Ministry of Education of China for Ferrous Metallurgy and Resources Utilization Wulaan University of Science and Technology Wuhan430081 China School of Materials and Metallurgy Wuhan University of Science and Technology Wuhan 430081 China

Auger electron spectroscopy （AES） was used to investigate the grain boundary segregation of arsenic and nitrogen in a kind of microalloyed steel produced by a compact strip production （CSP） technology at 950 to 1100℃, which are similar to the hot working temperature of the steel on a CSP production line. It was discovered that arsenic segregated on grain boundaries when the steel was annealed at 950℃ for 2 h. When the annealing temperature increased to 1100℃, arsenic was also found to have segregated on grain boundaries in the early annealing stage, for instance, within the first 5 min annealing time. However, if the holding time of the steel at this temperature increased to 2 h, arsenic diffused away from grain boundaries into the matrix again. Nitrogen was not found to have segregated on grain boundaries when the steel was annealed at a relatively low temperature, such as 950℃. But when the annealing temperature increased to 1100℃, nitrogen was detected to have segregated at grain boundaries in the steel.

关键词： alloy steel arsenic nitrogen segregation grain boundaries

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Effects of creep characteristics of natural gas hydrate-bearing sediments on wellbore stability

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Petroleum Science 2022年第1期19卷 220-233页

作者： Yang Li yuan-Fang Cheng Chuan-Liang Yan zhi-yuan Wang Li-Fang Song School of Petroleum Engineering China University of Petroleum(East China)66 West Changjiang RoadHuangdao DistrictQingdao 266000China

Natural gas hydrate(NGH)reservoirs consist of the types of sediments with weak cementation,low strength,high plasticity,and high *** on the kinetics and thermodynamic characteristics of NGH decomposition,herein a heat-fluid-solid coupling model was established for studying the wellbore stability in an NGH-bearing formation to analyze the effects of the creep characteristics of NGH-bearing sediments during long-term *** results demonstrated that the creep characteristics of sediments resulted in larger plastic yield range,thus aggravating the plastic strain accumulation around the ***,the creep characteristics of NGH-bearing sediments could enhance the effects induced by the difference in horizontal in situ stress,as a result,the plastic strain in the formation around the wellbore increased nonlinearly with increasing difference in in situ *** lower the pore pressure,the greater the stress concentration effects and the higher the plastic strain at the ***,the lower the initial NGH saturation,the greater the initial plastic strain and yield range and the higher the equivalent creep *** plastic strain at the wellbore increased nonlinearly with decreasing initial saturation.

关键词： Natural gas hydrates Wellbore stability Creep Plastic yield

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Non-Gaussian and Clustering Behavior in One-Dimensional Polydisperse Granular Gas System

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Communications in Theoretical Physics 2007年第6期47卷 1135-1142页

作者： CHEN zhi-yuan ZHANG Duan-Ming ZHONG zhi-Cheng LI Rui department of Physics Huazhong University of Science and Technology Wuhan 430074 China department of Physics Xianning College Xianning 437005 China department of Physics Xiangfan University Xiangfan 441053 China

We present a one-dimensional dynamic model of polydisperse granular mixture with the fractal characteristic of the particle size distribution, in which the particles are subject to inelastic mutual collisions and are driven by Gaussian white noise. The inhomogeneity of the particle size distribution is described by a fractal dimension D. The stationary state that the mixture reaches is the result of the balance between energy dissipation and energy injection. By molecular dynamics simulations, we have mainly studied how the inhomogeneity of the particle size distribution and the inelasticity of collisions influence the velocity distribution and distribution of interparticle spacing in the steady-state. The simulation results indicate that, in the inelasticity case, the velocity distribution strongly deviates from the Gaussian one and the system has a strong spatial clustering. Thus the inhomogeneity and the inelasticity have great effacts on the velocity distribution and distribution of interparticle spacing. The quantitative information of the non-Gaussian velocity distribution and that of clustering are respectively represented.

关键词： inelasticity restitution coefficient e inhomogeneity fractal dimension D polydisperse granulax gases

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Wavefronts of a Nonlocal State-dependent Time delay Model

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Acta Mathematica Sinica,English Series 2020年第1期36卷 77-92页

作者： Rui Jun XIE Rong yuan zhi Hui YANG School of Statistics and Applied Mathematics Anhui University of Finance and EconomicsBengbu 233030P.R.China School of Mathematical Sciences Beijing Normal UniversityBeijing 100875P.R.China

This paper is concerned with the travelling wavefronts of a nonlocal dispersal cooperation model with harvesting and state-dependent delay,which is assumed to be an increasing function of the population density with lower and upper ***,state-dependent delay is introduced into a nonlocal reaction-diffusion *** conditions of Schauder's fixed point theorem are proved by constructing a reasonable set of functionsΓ(see Section 2)and a pair of upper-lower solutions,so the existence of traveling wavefronts is *** present study is continuation of a previous work that highlights the Laplacian diffusion.

关键词： Nonlocality state-dependent delay cooperation traveling wavefronts

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Review:Research progress on Fabry-Perot resonator antenna

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2009年第4期10卷 583-588页

作者： Zhen-guo LIU zhi-chen GE Xi-yuan CHEN State Key Lab of Millimeter Waves Southeast University Nanjing 210096 China Zhenjiang Entry-Exit Inspection and Quarantine Bureau Zhenjiang 212003 China department of lnstrument Science and Engineering Southeast University Nanjing 210096 China

The Fabry-Perot resonator (FPR) antenna has found wide applications in microwave and millimeter waves and recently attracted considerable interest. In this paper, a summary of planar and cylindrical structures, analytic models and research development is presented, and a comparison between these structures and analytic models is made, showing that such analytic models as the FP cavity mode, electromagnetic band gap (EBG) defect mode, transmission line mode, and leaky-wave mode are consistent when applied to analyze this type of resonator antenna. Some interesting topics under recent research, including dual or multi-band, improvement of gain bandwidth, low profile and beam control, are surveyed.

关键词： Fabry-Perot resonator (FPR) antenna Electromagnetic band gap (EBG) resonator antenna Leaky-wave antenna defect mode Artificial magnetic conductor (AMC) Frequency selective surface (FSS)

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Low-thermal-conductivity thermal barrier coatings with a multi-scale pore design and sintering resistance following thermal exposure

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Rare Metals 2020年第4期39卷 352-367页

作者： Wei-Wei Zhang zhi-yuan Wei Li-yuan Zhang Ya-Zhe Xing Qiang Zhang School of Materials Science and Engineering Chang'an UniversityXi'an 710064China State Key Laboratory for Mechanical Behavior of Materials School of Materials Science and EngineeringXi’an Jiaotong UniversityXi'an 710049China College of Chemistry and Chemical Engineering Neijiang Normal UniversityNeijiang 641112China AECC Beijing Institute of Aeronautical Material Beijing 100095China

High-insulation,long-life thermal barrier coatings(TBCs)decrease the service temperature of superalloys and improve the service life of gas *** in the thermal insulation properties of the coating mainly depends on the optimization of the TBC *** important challenge for TBCs is maintaining a high performance during thermal exposure without degradation,as the pore-rich structure of the topcoat would inevitably be transformed by sintering.A low-thermalconductivity anti-sintering coating can overcome the tradeoff between thermal insulation and sinter *** this review,the design,preparation,and serviceability evaluation of a low-thermal-conductivity anti-sintering coating will be ***,directions for potential development are *** paper provides a comprehensive understanding of the structured tailoring of TBCs for better thermal insulation and anti-sintering performance.

关键词： Thermal barrier coatings Multi-scale pore Sintering resistance Low thermal conductivity

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Frequency and Correlation of Nearest Neighboring Nucleotides in Human Genome

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Chinese Journal of Chemical Physics 2009年第1期22卷 27-33页

作者： Neng-zhi Jin Zi-xian Liu Wen-yuan Qiu department of Chemistry State Key Laboratory of Applied Organic Chemistry Lanzhou Universiry. Lanzhou 730000 China

Zipf＇s approach in linguistics is utilized to analyze the statistical features of frequency and correlation of 16 nearest neighboring nucleotides （AA, AC, AG, …, TT） in 12 human chro- mosomes （Y, 22, 21, 20, 19, 18, 17, 16, 15, 14, 13, and 12）. It is found that these statistical features of nearest neighboring nucleotides in human genome：（i） the frequency distribution is a linear function, and （ii） the correlation distribution is an inverse function. The coefficients of the linear function and inverse function depend on the GC content. It proposes the correlation distribution of nearest neighboring nucleotides for the first time and extends the descriptor about nearest neighboring nueleotides.

关键词： Zipf's law Nearest neighboring nucleotide Frequency distribution Correlation distribution

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