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Study on the two and three-parameter working stability regions of 3Y-TZP suspension

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Science China(Technological Sciences) 2006年第5期49卷 547-568页

作者： CHEN Youqiang1, 2. ZHANG Xinni3, CHEN Sha’ou3 & QI Ping3 1. department of Chemistry, Qingdao University, Qingdao 2.6071, China 2. department of Chemistry, Tsinghua University, Beijing 100084, China 3. department of physics, Qingdao University, Qingdao 2.6071, China 1. department of Chemistry Qingdao University Qingdao 266071 China 2. department of Chemistry Tsinghua University Beijing 100084 China 3. department of physics Qingdao University Qingdao 266071 China

We determined the variation tendency of viscosity (η) at various solids load- ing (α) for 3Y-TZP suspension as a function of dispersant concentration (Cw) using vis- cosity measurement, measured the diameter of particles as a function of Cw in very dilute suspension using light scattering method, and obtained the surface features of the sedi- ment of suspension with different Cw using SEM. We also discussed the influence of the microstructure of adsorbed polymer layers on particles and their interactions in the dis- persing medium on the stability of suspension. Then two different stable states and two different unstable states for 3Y-TZP suspension were given. Accordingly, the (Cw, η), (Cw, α), and (α, η) two-parameter, and (Cw, α, η) three-parameter stability maps were con- structed. Based on the DLVO theory calculations, the dispersant concentration, particle distance (r), and interparticle potential energy (VT) maps with various solids loading for 3Y-TZP aqueous suspension were also constructed. In (Cw, r) two-parameter coordinate system, the stable motion region map for particles was established. The Cw, α, and VT,max (the highest potential energy) surface of the potential barrier map was obtained through calculation and simulation on the basis of the surfaces of Cw, r, VT maps introduced above. The (Cw, α) two-parameter stability map was then obtained from the Cw, α, VT,max map. The results showed that this theoretical map can qualitatively prove the experimentally obtained results—the existence of different dispersed states of particles in suspension system and the variation tendency of suspension stability with changing each parame- ter—were reasonable.

关键词： 3Y-TZP, suspension, stability, DLVO theory, interparticle potential energy.

Density-functional formula for strongly correlated systems

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Progress in Natural Science:Materials International 2005年第5期15卷 395-401页

作者： WANG Huaiyu1*, HAN Rushan2.and CHEN Nanxian1(1. department of physics, Tsinghua University, Beijing 100084, China 2. department of physics, Peking University, Beijing 100871, China) department of physics Tsinghua University Beijing 100084 China department of physics Peking University Beijing 100871 China

Density functional method is applied for strongly correlated systems. Based on the assumption that the systems are composed of electrons in singly-occupied orbitals and those in doubly-occupied orbitals, a set of self-consistent equations are obtained by standard variation procedure. The equations consist of two parts. One part is to solve the wave functions of the electrons in singly-occupied orbitals and the other is to solve the wave functions of the electrons in doubly-occupied orbitals. The physical meanings of the terms appearing in the equations are discussed.

关键词： density-functional theory strongly correlated systems doubly-occupied orbital two-particle wave function self-consistent equations.

Superconductivity of small metal grains

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Science China(physics,Mechanics & Astronomy) 2005年第4期48卷 431-441页

作者： ZHENG Renrong1 CHEN Zhiqian2.& ZHU Shunquan1,3 1. department of physics, Shanghai Normal University, Shanghai 2.02.4, China 2. department of physics, Southwest Normal University, Chongqing 400715, China 3. department of Computer and Electric Technology, Shanghai Business School, Shanghai 2.1400, China 1. department of physics Shanghai Normal University 200234 Shanghai China 2. department of physics Southwest Normal University 400715 Chongqing China 3. department of Computer and Electric Technology Shanghai Business School 201400 Shanghai China

The formulas of the energy gap and superconducting critical temperature appropriate for systems with both odd and even number of electrons are derived; the bases of the derivations are BCS theory and energy level statistics. Numerical results qualitatively agree with the experimental phenomena. i.e., the superconductivity of small metallic grains will first enhance then decrease to zero when the grain are getting smaller and smaller. The calculations indicate that the above phenomena happen in the metallic grains belonging to Gaussian Orthogonal Ensemble (GOE) and Gaussian Unitary ensemble (GUE) with zero spin; The superconductivity of small metallic grains in Gaussian Symplectic Ensemble (GSE) will monotonically decrease to zero with the decreasing of the grain size. The analyses suggest that the superconductivity enhancements come from pairing and the balance of the strengths between spin-orbital coupling and external magnetic field. In order to take the latter into account, it is necessary to include the level statistics given by Random Matrix Theory (RMT) in describing small metallic grains.

关键词： size effect, superconductivity enhancements, small metallic grains.

Electronic structure and magnetism of R(Fe,Si)_(12. (R=Y,Nd)

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Science China(physics,Mechanics & Astronomy) 2006年第2期49卷 195-202页

作者： SUN Guang’ai1, CHEN Bo1, DU Honglin2. FAN Zhijian1, GAO Tao3 & QI Xinhua31. Institute of Nuclear physics and Chemistry, China Academy of Engineering physics, Mianyang 62.900, China 2. {2. of physics, Peking university, Beijing 100871, China 3. Institute of Atomic and Molecular physics, Sichuan University, Chengdu 610065, China 1. Institute of Nuclear physics and Chemistry China Academy of Engineering Physics Mianyang 621900 China 2. department of physics Peking university Beijing 100871 China 3. Institute of Atomic and Molecular physics Sichuan University Chengdu 610065 China

The newly developed full-potential linearized augmented plane wave (LAPW) and local orbitals (lo) based on standard APW methods are briefly introduced, and the structure and magnetic properties of R(Fe, Si)12.compounds (R = Y, Nd) are calculated using the method. The distribution of Si at different sites is analyzed based on total energy of one crystal unit with structure having been optimized. The characters of magnetic mo-ments, total density of states (TDOS) and partial density of states (PDOS) for different crystal sites Si occupies are obtained and analyzed. The results show that the total mag-netic moments of RFe10Si2.(R = Y, Nd) are larger than those of RFe10M2.(M = Ti, V, Cr, Mn, Mo and W) and the hybridization mechanism is seen as follows. Si(8j) reduce the mag-netic moments of Fe at three sites, however, Si(8f) mainly reduce the magnetic moments of Fe(8i) and Fe(8j) atoms. The Curie temperature is markedly enhanced by the introduc-tion of Si atoms according to spin fluctuation of DOS at Fermi level.

关键词： (L)APW+lo method R(Fe Si)12.R = Y Nd) magnetic moment Density of state.

Approaches to improving critical current density of YBCO superconducting thick films deposited by electrophoresis

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Science China(physics,Mechanics & Astronomy) 2004年第2期47卷 165-172页

作者： ZHU Yabin1,2. ZHOU Yueliang2. LIU Zhen2. WANG Shufang2. CHEN Zhenghao2. L?Huibin2. YANG Guozhen2. XIAO Ling3, REN Hongtao3, JIAO Yulei3 & ZHENG Minghui3 1. department of physics, College of Science, Beijing Jiaotong University, Beijing 100044, China 2. Laboratory of Optical physics, Institute of physics and Center for Condensed Matter physics, Chinese Academy of Sciences, Beijing 100080, China 3. General Research Institute for Nonferrous Metals, Beijing 100088, China Correspondence should be addressed to Zhu Yabin (email: ybzhu@***) 1. department of physics College of Science Beijing Jiaotong University 100044 Beijing China 2. Laboratory of Optical physics Institute of physics and Center for Condensed Matter physics Chinese Academy of Sciences 100080 Beijing China 3. General Research Institute for Nonferrous Metals 100088 Beijing China

Fabrication of YBCO superconducting thick films by electrophoresis has been widely reported. However, the value of critical current density (J c) is far from what the practical application requires. The superconducting thick films are obtained using top-seeded melt growth method with different proportional Y2.aCuO5 (Y2.1) addition. High-pressure oxygen has been used in the annealing process to improve the uniformity of the oxygen content in the superconducting thick films. When 40mol% Y2.1 powder is added to the YBa2.u3O7–5 (Y12.) powder,J c for the superconducting thick film by approaches described above reaches 7.008×103 A/cm2.(77 K, 0 T), which is greater than the value ever reported.

关键词： YBCO thick films, electrophoretic deposition, melt-textured.

Langevin Treatment of Atomic Coherence Effect on Hybrid Erbium doped Fiber Amplification

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Chinese Journal of Lasers 1999年第6期8卷 3-5页

作者： LIU Fangxin 1,3 GUO Yang 2.MING Hai 2.( 1 Structure Research Laboratory, 2.department of physics, 3 department of Astronomy and Applied physics, University of Science and Technology of China, Hefei 2.002., China) 中国科学技术大学结构研究实验室结构分析开放实验室安徽合肥 230026 中国科学技术大学物理系安徽合肥

The effects of atomic coherence on hybrid erbium doped fiber amplifier (HEDFA) pumped simultaneously by two diode lasers with different frequencies are studied by using Langevin quantum theory. The expressions of coherence and incoherence gain are derived. The theoretical results show that HEDFA has a near flat bandwidth response from 1531 to 1568 nm and large coherence gain under the conditions of low temperature and small detuning.

关键词： atomic coherence hybrid erbium doped fiber amplifier LD pump

Effect of an impurity on 3-electron quantum dots in magnetic fields

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Science China(physics,Mechanics & Astronomy) 2004年第5期47卷 521-530页

作者： LIU Yimin1,2. HUANG Gangming1 & BAO Chengguang1 1. department of physics, Zhongshan University, Guangzhou 5102.5, China 2. department of physics, Shaoguan University, Shaoguan 512.05, China 1. department of physics Zhongshan University 510275 Guangzhou China 2. department of physics Shaoguan University 512005 Shaoguan China

The ground-state property of a 2.dimensional 3-electron quantum dot (QD) subjected to an external magnetic fieldB and affected by an impurity is studied. The impurity is located at thez-axis by a distanced from the plane of the dot. The evolution of the angular momentumL o and the spinS o of the ground state in accordance withB andd has been calculated, and the results are summarized and plotted in a (L o,S o) diagram. The spatial distribution of the electrons (the size and the geometric features) and the optical absorption have also been investigated. The (L o S o) diagram indicates thatL o andS o may jump whend and/orB vary. It was found that, due to the constraints arising from symmetry, each symmetric geometry is accessible only to a specific group of states having specificL o andS o.

关键词： quantum dot, ground state, charged impurity, magnetic field.

X-ray spectra induced in highly charged 40Ar^q+ interacting with Au surface

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Science China(physics,Mechanics & Astronomy) 2006年第2期49卷 203-212页

作者： ZHANG Xiao’an1,2. XIAO Guoqing1, YANG Zhihu1, CHEN Ximeng3, ZHAO Yongtao1, LI Fuli4, ZHANG Yinping1, CUI Ying3, ZHANG Hongqiang3, XU Xu3, SHAO Jianxiong3 & ZHAN Wenlong11. Institute of Modern physics, Chinese Academy of Sciences, Lanzhou 730000, China 2. department of physics, Xianyang Normal University, Xianyang 712.00, China 3. department of Modern physics, Lanzhou University, Lanzhou 730000, China 4. department of Applied physics, Xi’an Jiaotong University, Xi’an 710049, China 1. Institute of Modern physics Chinese Academy of Sciences Lanzhou 730000 China 2. department of physics Xianyang Normal University Xianyang 712000 China 3. department of Modern physics Lanzhou University Lanzhou 730000 China 4. department of Applied physics Xi’an Jiaotong University Xi’an 710049 China

By use of optical spectrum technology, the spectra of X-ray induced by highly charged 40Arq+ ions interacting with Au surface have been studied. The results show that the argon Kα X-ray were emitted from the hollow atoms formed below the surface. There is a process of multi-electron exciting in neutralization of the Ar16+ion, with electronic con-figuration 1s2.in its ground state below the solid surface. The yield of the projectile Kα X-ray is related to its initial electronic configuration, and the yield of the target X-ray is related to the projectile kinetic energy.

关键词： highly charged ion hollow multi-electron excitation X- ray.

Silicon nanoporous pillar array and its surface copper deposition

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Chinese Science Bulletin 2005年第14期50卷 1424-1428页

作者： FU Xiaonan1,2.3, CHAI Huadou1,2.& LI Xinjian1,2.1. department of physics, Zhengzhou University, Zhengzhou 450052. China 2. Key Laboratory of Material physics (Zhengzhou University), Ministry of Education, Zhengzhou 450052. China 3. department of Mathematics and physics, Henan University of Tech- nology, Zhengzhou 450052. China department of physics Zhengzhou University Zhengzhou 450052 China Key Laboratory of Material physics (Zhengzhou University) Ministry of Education Zhengzhou 450052 China department of Mathematics and physics Henan University of Technology Zhengzhou 450052 China

Silicon nanoporous pillar array (Si-NPA) has been prepared by a hydrothermal etching technique. Using Si-NPA as substrate, a Cu/Si-NPA nanocomposite thin film has been obtained with immersion plating method. Morpho- logical and structural analysis indicates that Si-NPA is a typical structural composite system characterized by a triple hierarchical structure, i. e. the array of micron-sized silicon pillars, the nanopores densely distributed on the surface of the pillars, and the silicon nanocrystallites that constitute the pore walls. Cu/Si-NPA inherits the morphological character- istics of Si-NPA. The compactability of the deposited copper nanoparticles varies alternatively with the local geometrical features of Si-NPA and forms a quasi-periodical pattern. Such an experimental phenomenon is attributed to the veloc- ity dependence of the copper deposition upon the local geo- metrical features of Si-NPA. These results indicate that Si-NPA might be used as an ideal template for preparing specially patterned, structured or functionalized metal/ sili- con nanocomposite systems.

关键词：硅元素薄膜蚀刻技术电镀技术