马中玉
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田源
,
P.Ring
原子核物理评论
在相对论密度泛函理论框架下引入了可分离的对相互作用,它的参数是由拟合核物质中Gogny力对关联性质来确定.在有限核的相对论Hartree-Bogoliubov和相对论准粒子无规位相近似的理论框架下,建立了可分离对相互作用在球形核和变形核中粒子-粒子道矩阵的计算方法.通过Talmi和Moshinsky变换,这种新的对相互作用在坐标空间下可以展开成一系列可分离项,并且很快收敛.它不仅保持了平移不变性,而且作为有限力程的对力,可以避免零程对力在高动量截断的困难.通过对Sn同位素链核基态、E2和E3激发态性质,以及Sm同位素链基态的性质研究,发现可分离对相互作用能够再现用Gogny对力得到的球形核的超流性质,并能够很好地符合已有的实验结果.这种方法还可用来描述任意微观对相互作用,并推广于三轴形变原子核以及转动系统的研究.为考虑角动量投影和粒子数投影的生成坐标(GCM)方法和粒子-振动耦合(PVC)理论提供更加真实的对关联性质描述.
关键词:
可分离有限力程对相互作用
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相对论Hartree-Bogoliubov理论
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相对论准粒子无规位相近似
He YANG
材料科学技术（英文）
Cold ring rolling is an advanced but complex metal forming process under coupled effects with multi-factors, such as geometry sizes of rolls and ring blank, material, forming process parameters and friction, etc. Among these factors, friction between rolls and ring blank plays an important role in keeping the stable forming of cold ring rolling. An analytical method was firstly presented for proximately determining the critical friction coefficient of stable forming and then a method was proposed to determine the critical friction coefficient by combining analytical method with numerical simulation. And the influence of friction coefficient on the quality of end-plane and side spread of ring, rolling force, rolling moment and metal flow characteristic in the cold ring rolling process have been explored using the three dimensional (3D) numerical simulation based on the elastic-plastic dynamic finite element method (FEM) under the ABAQUS software environment, and the results show that increasing the friction on the contact surfaces between rolls and ring blank is useful not only for improving the stability of cold ring rolling but also for improving the geometry and dimension precision of deformed ring.
关键词:
Cold ring rolling
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null
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null
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null
SONG Guangsheng
,
LIU Xianghua
,
WANG Guodong
,
XU Xiangqiu
钢铁研究学报(英文版)
The carburizing process of the gear ring was simulated by taking into account the practical carburizing and quenching techniques of the gear ring and by solving the diffusion equation. The carbon content distribution in the carburized layer was obtained. Based on the results, the quenching process of the gear ring was then simulated using the metallic thermodynamics and FEM; it was found that the carburization remarkably affects the quenching process. Microstructures and stress distributions of the gear ring in the quenching process were simulated, and the results are confirmed by experiments.
关键词:
carburization;FEM;quenching;martensite transformation;residual stress
H.Q.Chen
,
J.S.Liu
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H.G.Guo
金属学报(英文版)
Mn18Cr18N, the high-nitrogen steel, is the 2nd generation material for manufacturing the retaining ring of firepower generators. In this paper, the hot deformation behavior of the material was investigated by thermo-mechanical modeling tests. And the flow stress curves of the steel were obtained for various combinations of the temperature and strain rate.Based on the results of the tests, the complex forming process of a retaining ring including punching, expanding and extrusion with an enclosure was put forward and simulated by means of numerical simulation method. The results indicate that the process is a novel and force-saved practical technology for manufacturing heavy retaining rings.
关键词:
Mn18Cr18N high-nitrogen steel
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null
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null
Journal of Applied Physics
By introducing local Rashba spin-orbit interaction in a three-terminal quantum dot ring, we calculate the currents induced by thermoelectric effect. It shows that, when a temperature bias is applied between the source and drains, there emerge apparent spin currents in the two drains. We find, via adjusting the structure parameters, that an electron from the source will choose its drain according to its spin index. Due to the advances in nanodevice fabrication, this structure can be constructed, and then we believe that it can be a candidate of the spin-manipulating device. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3673594]
关键词:
silicon nanowires;junctions
Physics Letters A
In this work, via introducing local Rashba spin-orbit interaction in a four-terminal quantum-dot (QD) ring, we show that the spin bias in the transverse terminals induces apparent charge currents in the longitudinal terminals, accompanied by the similar magnitude and opposite directions of them. The reason is that the Rashba interaction destroys the space-reversal symmetry of this structure and causes the spin dependence of the quantum interference. Then the opposite-spin currents driven by the spin bias present different magnitudes, which gives rise to the emergence of finite charge currents in the longitudinal terminals. Via these results, we suggest that the spin bias can be measured by observing the longitudinal charge currents, which provides an electrical but practical scheme to detect the spin bias (or spin current). (C) 2011 Elsevier B.V. All rights reserved.
关键词:
Quantum dot;Spin bias;Rashba interaction;Charge current;spintronics;transport
Physics Letters A
By means of the non-equilibrium Green's function technique, the persistent spin and charge currents in a quantum-dot ring are theoretically investigated. We find that by introducing local spin-orbit interaction on an individual quantum dot, a pure persistent spin current can be induced even in the absence of external magnetic flux and magnetic material. Compared with persistent spin current in the quantum ring, the magnitude and direction of the persistent spin current can be controlled experimentally by means of adjusting the energy levels of quantum dots. In addition, a certain spin component of the persistent current can be suppressed by introducing an external magnetic flux. (c) 2009 Elsevier B.V. All rights reserved.
关键词:
Quantum-dot ring;Green's function;Persistent spin current;phase-factors;berrys phase;loop;transport;single
Journal of Applied Physics
The impurity-modulated electron transport properties in a double quantum dot (QD) Aharonov-Bohm ring are theoretically studied, by considering impurities locally and nonlocally coupled to the QDs in the ring arms, respectively. It is found that the impurities influence the electron transport in a nontrivial way: in the case of zero magnetic flux, a single-level impurity leads to the appearance of Fano line shapes in the conductance spectra, and the positions of Fano antiresonances are determined by both the impurity-QD couplings and the QD levels separated from the Fermi level; whereas when a magnetic flux is introduced with the phase factor phi=pi the Breit-Wigner line shapes appear in the conductance curves. Compared with the local-impurity case, nonlocal impurities alter the conductance period versus the magnetic flux. In addition, when many-body effect is considered within the second-order approximation, we find the important role of the Coulomb interaction in modifying the electron transport. (C) 2011 American Institute of Physics. [doi: 10.1063/1.3530842]
关键词:
transport;resonances;amplifiers;coherence;islands;systems
Solid State Communications
By applying a local Rashba spin-orbit interaction to an individual quantum dot of a four-terminal four-quantum-dot ring and introducing a finite bias between the longitudinal terminals, we theoretically investigate the charge and spin currents in the transverse terminals. It is found that when the quantum dot levels are separate from the chemical potentials of the transverse terminals, notable pure spin currents appear in the transverse terminals with the same amplitude but opposite polarization directions. In addition, the polarization directions of such pure spin currents can be inverted by altering the structure parameters, i.e., the magnetic flux, the bias voltage, and the values of quantum dot levels with respect to the chemical potentials of the transverse terminals. (C) 2009 Elsevier Ltd. All rights reserved.
关键词:
Quantum dot;Rashba interaction;Pure spin current;transport
