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Relationship between martensite microstructure and ductility of H13 steel from aspect of crystallography

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Journal of Iron and Steel Research International 2021年第10期28卷 1268-1281页

作者： jian Zhu Zhi-hao Zhang jian-xin Xie Institute for Advanced Materials and Technology University of Science and Technology BeijingBeijing100083China Key Laboratory for Advanced Materials Processing(MOE) University of Science and Technology BeijingBeijing100083China

Based on the parent austenite orientation reconstruction method,it is aimed to reveal the origination of high angle grain boundaries(HAGBs)and its relationship with ductility of H13 *** orientation relationship between martensite and parent austenite of quenched H13 samples was(123.5°,9.3°,192.5°),which agreed with the Kurdumov–Sachs *** variant distribution of quenched samples was dominated by close-packed plane group,and its high length fraction of V1/V2 inter-variant boundaries of calculated 62.6%was mainly contributed to HAGBs(>45°).When the quenched H13 samples underwent the pre-tempering treatment,their density of HAGBs(>45°)notably increased from 1.33 to 2.39μm^(−1),which improved its total elongation from 8.3%to 11.5%.Compared with the quenched H13 samples,the length fraction of V1/V2 inter-variant boundaries of H13 samples with pre-tempering for 5,10 and 60 min was reduced by 6.7%,7.0%and 7.5%,*** pre-tempering treatment,V1/V3&V5 variant pairs,etc.,merged V1/V2 variant pair by strain-induced grain boundary migration,which decreased the length fraction of V1/V2 inter-variant boundaries by 7.0%.The pre-tempering treatment significantly increased HAGBs(>45°)of H13 samples by sub-grains coarsening and strain-induced grain boundary migration mechanism.

关键词： H13 steel Pre-tempering treatment Variant selection Parent austenite orientation reconstruction High angle grain boundary

Stability of Fullerene Cages:C_(30) to C_(70) and Their Dependence on Shared Pentagon Bonds

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Chinese Journal of Structural Chemistry 2006年第9期25卷 1051-1056页

作者： WU Hai-Shun TIAN xin-xin jian jian-Feng FENG Rui-Juan Chemistry and Material Science Institute Shanxi Normal University Linfen 041004 China

The topological characters of all fullerene isomers from C30 to C70 with respect to their number of shared pentagon bonds have been investigated. Systematic calculations were also carried out at the B3LYP/6-31G^＊ level. It is found that the most stable structure has the smallest number of shared pentagon bonds, and the relative energies of a given size show an increasing tendency to rise with Nss number which denotes the number of C-C bonds shared by pentagon. The topological criterion that has extremely low computational cost can be used as filtering principle to prescreen the thermodynamically viable fullerenes and predict the relative stability of isomers.

关键词： fullerene density functional theory most stable isomer topology Nss

THE EIGENVALUE PERTURBATION BOUND FOR ARBITRARY MATRICES

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Journal of Computational Mathematics 2006年第2期24卷 141-148页

作者： Wen Li jian-xin Chen School of Mathematical Sciences South China Normal University Guangzhou 510631 China College of Applied Mathematics Guangdong University of Technology Guangzhou 510090 China

In this paper we present some new absolute and relative perturbation bounds for the eigenvalue for arbitrary matrices, which improves some recent results. The eigenvalue inclusion region is also discussed.

关键词： Eigenvalue perturbation bound Jordan canonical form Frobenius norm Spectral norm Inclusion region.

Mathematical treatment of wave propagation in acoustic waveguides with n curved interfaces

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2008年第10期9卷 1463-1472页

作者： jian-xin ZHU Peng LI Department of Mathematics Zhejiang University Hangzhou 310027 China

There are some curved interfaces in ocean acoustic waveguides. To compute wave propagation along the range with some marching methods, a flattening of the internal interfaces and a transforming equation are needed. In this paper a local orthogonal coordinate transform and an equation transformation are constructed to flatten interfaces and change the Helmholtz equation as a solvable form. For a waveguide with a flat top, a fiat bottom and n curved interfaces, the coefficients of the transformed Helmholtz equation are given in a closed formulation which can be thought of as an extension of the formal work related to the equation transformation with two curved internal interfaces. In the transformed horizontally stratified waveguide, the one-way reformulation based on the Dirichlet-to-Neumann （DtN） map is then used to reduce the boundary value problem to an initial value problem. Numerical implementation of the resulting operator Riccati equation uses a large range step method to discretize the range variable and a truncated local eigenfunction expansion to approximate the operators. This method is particularly useful for solving long range wave propagation problems in slowly varying waveguides. Furthermore, the method can also be applied to wave propagation problems in acoustic waveguides associated with varied density.

关键词： Helmholtz equation Local orthogonal transform Dirichlet-to-Neumarm (DtN) reformulation Marching method Curved interface Multilayer medium

Microstructure and mechanical properties of BFe10 cupronickel alloy tubes fabricated by a horizontal continuous casting with heating-cooling combined mold technology

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International Journal of Minerals,Metallurgy and Materials 2012年第4期19卷 339-347页

作者： Jun Mei xin-hua Liu jian-xin Xie Key Laboratory for Advanced Materials Processing (Ministry of Education) University of Science and Technology Beijing Beijing 100083 China Institute for Advanced Materials and Technology University of Science and Technology Beijing Beijing 100083 China

A new horizontal continuous casting method with heating-cooling combined mold （HCCM） technology was explored for fabri- cating high-quality thin-wall cupronickel alloy tubes used for heat exchange pipes. The microstructure and mechanical properties of BFe 10 cupronickel alloy tubes fabricated by HCCM and traditional continuous casting （cooling mold casting） were comparatively investigated. The results show that the tube fabricated by HCCM has smooth internal and external surfaces without any defects, and its internal and external surface roughnesses are 0.64 μm and 0.85 μm, respectively. The tube could be used for subsequent cold processing without other treatments such as surface planning, milling and acid-washing. This indicates that HCCM can effectively reduce the process flow and improve the pro- duction efficiency of a BFel0 cupronickel alloy tube. The tube has columnar grains along its axial direction with a major casting texture of {012}〈 621 〉. Compared with cooling mold casting （6 = 36.5%）, HCCM can improve elongation （3 = 46.3%） by 10% with a slight loss of strength, which indicates that HCCM remarkably improves the cold extension performance of a BFe 10 cupronickel alloy tube.

关键词： cupronickel alloys thin-wall tubes continuous casting microstructure mechanical properties

Dynamical brane creation and annihilation via a background flux

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Science China(Physics,Mechanics & Astronomy) 2022年第2期65卷 24-29页

作者： Yi-Fei Chen jian-xin Lu Interdisciplinary Center for Theoretical Study University of Science and Technology of ChinaPeng Huanwu Center for Fundamental TheoryHefei 230026China

We study the dynamical Myers effect by allowing the fuzzy(or the dynamical dielectric brane)coordinates to be time *** find three novel kinds of the dynamical spherical dielectric branes depending on their respective excess *** first represents a dynamical spherical brane carrying a negative excess energy(having a lower bound)with its radius oscillating periodically between two given non-zero *** second is the one with zero excess energy and whose time dependence can be expressed in terms of a simple *** particular dynamical spherical configuration represents the dielectric brane creation and/or annihilation like a photon in the presence of a background creating an electron-position pair and then annihilating back to a *** third is the one carrying positive excess energy and the radius can also oscillate periodically between two non-zero values but,unlike the first kind,it passes zero twice for each *** of the above can also be interpreted as the time evolution of a semi-spherical D-brane–anti semi-spherical D-brane system.

关键词： dynamical Myers effect D-branes string/M-theory

The role of Debye mass in the chiral crossover in a strong magnetic field

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Communications in Theoretical Physics 2022年第10期74卷 68-75页

作者： Jia Zhang xin-jian Wen Institute of Theoretical Physics State Key Laboratory of Quantum Optics and Quantum Optics DevicesShanxi UniversityTaiyuanShanxi 030006China

In this paper,the Debye mass of quarks is investigated in the Nambu–Jona-Lasinio model at zero and nonzero chemical *** a uniform plasma,the Debye mass usually behaves as a monotonous increasing function of the temperature,the chemical potential and the magnetic *** the fixed coupling interaction G,we find that the magnetic catalysis(MC)on the occurrence of the chiral restoration could be revealed by the susceptibility of the Debye mass dmD/dT at low chemical potential and by the quantity TdmD/dT in the region of moderate ***,the inverse MC is realized under a thermomagnetic coupling constant G(B,T)by the behavior of the Debye mass at both zero and nonzero chemical potentials.

关键词： chiral restoration strong magnetic field Debye mass Nambu-Jona-Lasinio

Effect of strain rate on the compressive deformation behaviors of lotus-type porous copper

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International Journal of Minerals,Metallurgy and Materials 2014年第7期21卷 687-695页

作者： xin-hua Liu Hai-you Huang jian-xin Xie Institute for advanced Materials and Technology University of Science and Technology Beijing Key Laboratory for Advanced Materials Processing(MOE) University of Science and Technology Beijing

Lotus-type porous copper was fabricated by unidirectional solidification, and compressive experiments were subsequently conducted in the strain rate range of 10-3-2400 s-1 with the compressive direction parallel to the pores. A GLEEBLE-1500 thermal-mechanical simulation system and a split Hopkinson pressure bar （SHPB） were used to investigate the effect of strain rate on the compressive deforma-tion behaviors of lotus-type porous copper. The influence mechanism of strain rate was also analyzed by the strain-controlling method and by high-speed photography. The results indicated that the stress-strain curves of lotus-typed porous copper consist of a linear elastic stage, a plateau stage, and a densification stage at various strain rates. At low strain rate （〈1.0 s^-1）, the strain rate had little influence on the stress-strain curves; but when the strain rate exceeded 1.0 s^-1, it was observed to strongly affect the plateau stage, showing obvious strain-rate-hardening characteristics. Strain rate also influenced the densification initial strain. The densification initial strain at high strain rate was less than that at low strain rate. No visible inhomogeneous deformation caused by shockwaves was observed in lotus-type porous copper during high-strain-rate deformation. However, at high strain rate, the bending deformation characteristics of the pore walls obviously differed from those at low strain rate, which was the main mechanism by which the plateau stress exhibited strain-rate sensitivity when the strain rate exceeded a certain value and exhibited less densification initial strain at high strain rate.

关键词： porous materials copper directional solidification strain rate sensitivity deformation modes stress-strain curves

A practical iterative two-view metric reconstruction with uncalibrated cameras

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第10期8卷 1614-1623页

作者： ZHOU Yong-jun KOU xin-jian School of Naval Architecture. Ocean and Civil Engineering Shanghai Jiao Tong University Shanghai 200240 China

This paper presents a practical iterative algorithm for two-view metric reconstruction without any prior knowledge about the scene and motion in a nonsingular geometry configuration. The principal point is assumed to locate at the image center with zero skew and the same aspect ratio, and the interior parameters are fixed, so the self-calibration becomes focal-length cali- bration. Existing focal length calibration methods are direct solutions of a quadric composed of fundamental matrix, which are sensitive to noise. A quaternion-based linear iterative Least-Square Method is proposed in this paper, and one-dimensional searching for optimal focal length in a constrained region instead of solving optimization problems with inequality constraints is applied to simplify the computation complexity, then unique rotational matrix and translate vector are recovered. Experiments with simulation data and real images are given to verify the algorithm.

关键词： Close-range photogrammetry Computer vision General relative orientation Unit quaternion Metric reconstruction