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Effect of cooling rate on the phase transformation and stability of the mushy zone during the solidification of Waspaloy

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International Journal of Minerals,Metallurgy and Materials 2010年第4期17卷 464-469页

作者： Ling Wang Yi-jun Yao Bin Liu Bo-ying Zhong jian-xin dong College of Mathematics and Physics Nanjing University of Information Science and Technology Nanjing 210044 China School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China

Scanning electron microscopy（SEM） and energy dispersive X-ray analysis（EDAX） were used to study the microstructure,microsegregation, and fluid flow tendency of the superalloy Waspaloy in the mushy zone,which had been solidified at different cooling rates. The investigation was accompanied with the calculation of Rayleigh *** is found that Ti is the main segregating element and the content of Ti is the highest in the final liquid at the cooling rates of 3-6℃/*** eta phase（η） precipitate presented in the residual liquid at the cooling rates higher than 6℃/min is responsible for the fluctuations in the curves of Ti *** dendrite arm spacing is found to markedly decrease with the increase of cooling *** maximum relative Rayleigh number occurs at 10-20℃below the liquidus temperature at a cooling rate of 1℃/min,where the mushy zone is most unstable and fluid flow is most prone to occur.

关键词： Waspaloy cooling rate solidification segregation stability mushy zone

Exponential Decay in Time of Density of One-dimensional Quantum Navier-Stokes Equations

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Acta Mathematicae Applicatae Sinica 2018年第4期34卷 792-797页

作者： jian-wei dong Guang-pu LOU Jun-hui ZHU Yong YANG School of Mathematics and Physics Zhengzhou University of Aeronautics

The long-time behavior of the particle density of the compressible quantum Navier-Stokes equations in one space dimension is studied. It is shown that the particle density converges exponentially fast to the constant thermal equilibrium state as the time tends to infinity, the decay rate is also obtained. The results hold regardless of either the bigger of the scaled Planck constant or the viscosity constant. This improves the decay results of [5] by removing the crucial assumption that the scaled Planck constant is bigger than the viscosity constant. The proof is based on the entropy dissipation method and the Bresch-Desjardins type of entropy.

关键词： quantum Navier-Stokes equations exponential decay entropy dissipation method

Tensor Effect on Bubble Nuclei

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Chinese Physics Letters 2011年第10期28卷 62-65页

作者： WANG Yan-Zhao GU jian-Zhong ZHANG Xi-Zhen dong jian-Min China Institute of Atomic Energy P.O.Box 275(10)Beijing 102413 Center of Theoretical Nuclear Physics National Laboratory of Heavy Ion Accelerator of LanzhouLanzhou 730000 School of Nuclear Science and Technology Lanzhou UniversityLanzhou 730000

In the framework of the Hartree–Fock–Bogoliubov(HFB)approach with Skyrme interactions SLy5+T,SLy5+Tw and several sets of TIJ parametrizations,*** Skyrme interaction parametrizations including the tensor terms,the proton density distribution in ^(34)Si and ^(46)Ar nuclei is calculated with and without the tensor *** is shown that the bubble effect in ^(34)Si does not depend a great deal on the Skyrme parametrization and the proton density distribution in ^(34)Si is hardly influenced by the tensor *** to ^(46)Ar,the SLy5+Tw parametrization favors the formation of the bubble structure due to the inversion between the 2s_(1/2) and 1d_(3/2) orbits(2s_(1/2)–1d_(3/2) inversion).The inversion mechanism induced by the SLy5+Tw interaction is analyzed based on the proton single−particle spectra obtained from the SLy5 and SLy5+Tw interactions as well as the wave functions of the 2s_(1/2) and 1d_(3/2) states.

关键词： force tensor bubble

Relationship Between Grain Boundary Segregation of Antimony and Temper Embrittlement in Titanium-Doped Nickel-Chromium Steel

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Journal of Iron and Steel Research International 2011年第1期18卷 68-72页

作者： ZHENG Lei ZHANG Mai cang dong jian-xin MENG Ye School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083China

The antimony segregation at grain boundary was observed and the temper embrittlement in titanium-doped nickel-chromium steel was analyzed. It is concluded that the antimony segregation at grain boundary is nonequilibium and the kinetics of temper embrittlement agrees well with those of nonequilibrium antimony segregation at grain boundary. Besides, the mechanism of nonequilibrium antimony segregation at grain boundary proved to be the most satisfactory one among the existing mechanisms to interpret the antimony induced embrittlement kinetics in the nick- el-chromiunl steel. Based on these, the activation energy and frequency factor of diffusion of antimony vacancy complexes were obtained according to the concept of critical time in nonequilibrium grain boundary segregation theory.

关键词： grain boundary segregation temper embrittlement critical time diffusion activation energy

Ionized gas clouds near the Sagittarius Arm tangent

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Research in Astronomy and Astrophysics 2017年第5期17卷 91-106页

作者： Li-Gang Hou jian dong Xu-Yang Gao Jin-Lin Han National Astronomical Observatories Chinese Academy of Sciences Shanghai Astronomical Observatory Chinese Academy of Sciences

Radio recombination lines（RRLs） are the best tracers of ionized gas. Simultaneous observations of multi-transitions of RRLs can significantly improve survey sensitivity. We conducted pilot RRL observations near the Sagittarius Arm tangent by using the 65-m Shanghai Tian Ma Radio Telescope（TMRT） equipped with broadband feeds and a digital backend. Six hydrogen RRLs（H96α-H101α）at C band（6289 MHz-7319 MHz） were observed simultaneously toward a sky area of 2°× 1.2° by using on-the-fly mapping mode. These transitions were then stacked together for detection of ionized gas. Star forming complexes G48.6＋0.1 and G49.5-0.3 were detected in the integrated intensity *** found agreements between our measured centroid velocities and previous results for the 21 known HII regions in the mapped area. For more than 80 cataloged HII region candidates without previous RRL measurements, we obtained new RRL spectra at 30 targeted positions. In addition, we detected 25 new discrete RRL sources with spectral S/N 〉 5σ, and they were not listed in the catalogs of previously known HII regions. The distances for 44 out of these 55 new RRL sources were estimated.

关键词： tangent recombination listed transitions positions targeted pilot complexes toward FWHM

Microstructure and homogenization process of as-cast GH4169D alloy for novel turbine disk

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International Journal of Minerals,Metallurgy and Materials 2019年第7期26卷 889-900页

作者： Kai Chen Shu-yuan Rui Fa Wang jian-xin dong Zhi-hao Yao School of Materials Science and Engineering University of Science and Technology Beijing

To investigate the microstructure, segregation, and suitable homogenization process of as-cast GH4169D alloy, the microstructure, elements segregation, and precipitates of cast GH4169D ingots prepared by vacuum induction melting (VIM) and vacuum arc remelting (VAR) were observed by optical microscopy (OM), scanning electron microscopy, and energy-dispersive X-ray spectroscopy (EDS). According to the residual segregation model and simulation results of DICTRA thermodynamic software, the homogenization temperature and time range were set as 1120–1170°C and 5–20 h, respectively. The experimental results showed that microscopic dendrite and element segregation occurred in the interior of ingots and the main segregation elements were Nb and Ti. In addition, the precipitates were mainly distributed in interdendritic regions and were composed of NbC, Laves,γ′, and δ phases. The homogenization process suggested that the interdendritic detrimental precipitated Laves phase can be eliminated or redissolved after homogenization at 1150°C for 20 h, suggesting it was the most suitable homogenization treatment. Thermal compression test results showed that the GH4169D alloys after homogenization treatment had no cracks and dynamic recrystallization occurred, with recrystallization volume fraction increasing with temperature, indicating a good working plasticity at temperatures from 1050 to 1200°C.

关键词： GH4169D superalloy as-cast microstructure segregation homogenization thermal deformation

Reflection and transmission at the surface of a chiral negative refractive medium

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Optoelectronics Letters 2007年第6期3卷 462-465页

作者： LIU Bln dong jian-feng Institute of optical fiber communication and network technology Ningbo University Ningbo 315211 China

Electromagnetic fields at the surface of a chiral negative refraction medium (the chirality parameter is larger than the refractive index) are analyzed theoretically. For obtaining chirality parameter,the normalized reflected and transmitted powers as a function of the incident angle are given for the perpendicular (TE) and parallel (TM) polarized incident wave. Brewster angle and total internal reflection angle are discussed. Due to the negative refraction of one eigen-wave in the chiral medium, the reflection, transmission and Brewster angle characteristics are very different from those in the normal chiral medium.

关键词：特种结构材料手性折射反射

An Equivalent Condition for the Self Similar Sets on the Real Line to Have Best Coverings

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数学学报（中文版） 2013年第6期56卷 I0001-I0004页

作者： jian dong YIN Zuo Ling ZHOU

Antenna selection based on large-scale fading for distributed MIMO systems

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High Technology Letters 2016年第3期22卷 233-240页

作者：施荣华 Yuan Zexi dong jian Lei Wentai Peng Chunhua School of Information Science and Engineering Central South University

An antenna selection algorithm based on large-scale fading between the transmitter and receiver is proposed for the uplink receive antenna selection in distributed multiple-input multiple-output(D-MIMO) systems. By utilizing the radio access units(RAU) selection based on large-scale fading,the proposed algorithm decreases enormously the computational complexity. Based on the characteristics of distributed systems,an improved particle swarm optimization(PSO) has been proposed for the antenna selection after the RAU selection. In order to apply the improved PSO algorithm better in antenna selection,a general form of channel capacity was transformed into a binary expression by analyzing the formula of channel capacity. The proposed algorithm can make full use of the advantages of D-MIMO systems,and achieve near-optimal performance in terms of channel capacity with low computational complexity.

关键词： distributed MIMO systems antenna selection particle swarm optimization large-scale fading