作者机构：
CHINA CTR ADV SCI & TECHNOL,WORLD LAB,BEIJING 100080,PEOPLES R CHINA.;NANJING UNIV SCI & TECHNOL,DEPT APPL PHYS,NANJING 210014,JIANGSU,PEOPLES R CHINA.;CENT CHINA NORMAL UNIV,DEPT PHYS,WUHAN 430070,PEOPLES R CHINA.;[Yang, JL] UNIV SCI & TECHNOL CHINA,CTR FUNDAMENTAL PHYS,HEFEI 230026,ANHUI,PEOPLES R CHINA.
通讯机构：
[Yang, JL] U;UNIV SCI & TECHNOL CHINA,CTR FUNDAMENTAL PHYS,HEFEI 230026,ANHUI,PEOPLES R CHINA.
摘要：
Local spin-density-functional calculations are performed to study the geometric and electronic structure of PbNa6 clusters. Three possible isomeric structures are examined. Both the electronic and the geometric factors are shown to be important to the stabilization of the cluster and the most stable structure is found to be a tricapped tetrahedron. The electronic structure of this cluster indicates that the metallic bonding interaction of delocalized electrons is responsible for the exceptional stability of the cluster.
作者机构：
HUAZHONG NORMAL UNIV, INST PARTICLE PHYS, WUHAN 430070, PEOPLES R CHINA.;CHINA CTR ADV SCI & TECHNOL, WORLD LAB, BEIJING 100080, PEOPLES R CHINA.;[Jia, Y] HUAZHONG NORMAL UNIV, DEPT PHYS, WUHAN 430070, PEOPLES R CHINA.
通讯机构：
[Jia, Y] H;HUAZHONG NORMAL UNIV, DEPT PHYS, WUHAN 430070, PEOPLES R CHINA.
摘要：
In this Letter we discuss a bistable model driven by two white noise sources, when the correlation time of the correlations between two sources τ is nonzero. We find that there is a critical value of the correlation time τc. For τ>τc, the system undergoes a succession of two phase transitions (namely, the reentrance phenomenon) as the strength of the correlations between two noise sources λ is varied. However, for τ<τc, the system undergoes a (single) phase transition as λ is varied.
期刊：
Physica C: Superconductivity and its Applications,1997年282-287(PART3):1611-1612 ISSN：0921-4534
通讯作者：
Li, JQ
作者机构：
SE UNIV,ANAL & TEST CTR,NANJING 210018,PEOPLES R CHINA.;NANJING UNIV,DEPT PHYS,NANJING 210093,PEOPLES R CHINA.;NANJING UNIV,NATL LAB SOLID STATE MICROSTRUCT,NANJING 210093,PEOPLES R CHINA.;CENT CHINA NORMAL UNIV,DEPT PHYS,WUHAN,PEOPLES R CHINA.;[Li, JQ] CITY UNIV HONG KONG,DEPT PHYS & MAT SCI,HONG KONG,HONG KONG.
通讯机构：
[Li, JQ] C;CITY UNIV HONG KONG,DEPT PHYS & MAT SCI,HONG KONG,HONG KONG.
会议名称：
International Conference on Materials and Mechanisms of Superconductivity - High Temperature Superconductors V
会议时间：
FEB 28-MAR 04, 1997
会议地点：
BEIJING, PEOPLES R CHINA
会议主办单位：
SE UNIV,ANAL & TEST CTR,NANJING 210018,PEOPLES R CHINA.^NANJING UNIV,DEPT PHYS,NANJING 210093,PEOPLES R CHINA.^NANJING UNIV,NATL LAB SOLID STATE MICROSTRUCT,NANJING 210093,PEOPLES R CHINA.^CENT CHINA NORMAL UNIV,DEPT PHYS,WUHAN,PEOPLES R CHINA.
摘要：
The effect of hydrogenation on the positron annihilation in different oxygenated YBa2Cu3O7-delta superconductors have been investigated. Experimental results showed that the effect of the hydrogenation process is to affect the concentrations of monovacancy and microvoid in both of intragrain and intergrain of the sample. The hydrogenation effect in the YBCO superconductor can be classified into four stages. In the first stage, i.e. for the initial hydrogen charging, the hydrogen atoms fill into the monovacancies and microvoids. The long lifetime tau(2) for positron annihilation is increased, and reaches the maximum value when monovacancies and microvoids have been fully filled with hydrogen atoms. In the second stage, the further hydrogen charging leads to the formation of new monovacancies. The long lifetime tau(2) decreases and reaches a minimum value at the end of this stage. In the third stage, the further hydrogen charging promotes the formation of microvoids by coalescence of clustered monovacancies and leads to increase tau(2) again. Finally in the fourth stage, zz reaches a steady state which corresponds to the equilibrium concentrations for both monovacancy and microvoid maintained at the temperature of the material.
摘要：
With asymptotic method developed from weak turbulent theory, the kinetic equations for QGP are expanded in fluctuation field potential A(mu)(T). Considering the second-order and third-order currents, we derive the nonlinear permeability tensor function from Yang-Mills field equation, and find that the third-order current is more important in turbulent theory. The nonlinear permeability formulae for longitudinal color oscillations show that the non-Abelian effects are more important than the Abelian-like effects. To compare with other works, we give the numerical result of the damping rate for the modes with zero wave vector. (C) 1997 Elsevier Science B.V.
作者机构：
[Qishan T.] Dept. of Phys, Normal College, Hubei Sanxia College, 443000;[Gaoxiang L.] Dept. of Phys, Huazhong Normal University, Wuhan, 430070, China;[Tangkun L.] Dept. of Phys, Hubei Normal University, Huangshi, 435002, China
通讯机构：
[Qishan, T.] D;Dept. of Phys, Normal College, Hubei Sanxia College,
