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Volume 14 Issue 12
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Original Articles
Metric of the Superposition of a Schwarzschild Black Hole and a Semi-infinite Rod: Vacuum C Metric
WANG Yong-cheng
Chin. Phys. Lett. 1997, 14 (12): 881-884 .  
Abstract   PDF(pc) (149KB) ( 391 )
By using a coordinate origin translation and a scale transformation, of which both are constants, the metric of the superposition of a Schwarzschild black hole (SBH) and a semi-infinite rod (SIR) is transformed to the standard form of a vacuum C metric (VCM) in Weyl coordinate system, and for this reason the metric is a VCM exactly. Expressions of mass and acceleration parameters in the VCM are obtained. The expressions show, as a result of the superposition, both the mass of the SBH and the acceleration parameter of the SIR take very great and complex changes.
Kerr-NUT-de Sitter Metric and Step-by-step Extension Method
XU Dian-yan, QIU Zong-yan
Chin. Phys. Lett. 1997, 14 (12): 885-888 .  
Abstract   PDF(pc) (144KB) ( 500 )
The Kerr-NUT-de sitter metric in quasi-Boyer-Lindquest coordinate is derived by using the step-by-step extension method. The extension may be realized in several different paths. For example, one of these paths may be chosen as from Schwarzschild-NUT metric to Schwarzschild- NUT-de Sitter metric and from Schwarzschild-NUT-de Sitter metric to Kerr-NUT-de Sitter metric.
Bosonization and Random-Phase Approximation of the Interacting Fermions in High Dimensions
XU Tie-feng, LI Wen-zhu
Chin. Phys. Lett. 1997, 14 (12): 889-892 .  
Abstract   PDF(pc) (133KB) ( 347 )
The random-phase approximation (RPA) of interacting fermions is recast into a bosonized form and the RPA results are rederived by the standard bosonization method, which shows that there is a natural connection between bosonization and RPA.
Collision Direction Dependence of React ion Channels and Reaction Products in Molecular Collisions Between Two C60 Molecules
ZHANG Zhao-lin, LIANG Qi-min, MU Yu-guang, XIA Yue-yuan
Chin. Phys. Lett. 1997, 14 (12): 893-896 .  
Abstract   PDF(pc) (251KB) ( 366 )
The reaction channels and the reaction products in the collisional reactions between two C60 molecules are found to be sensitively dependent on the relative orientation between the colliding partners. The detailed collision processes and the stable structures of the products are studied by using a molecular dynamics simulation method combined with a Langevin molecular dynamics scheme. The defects of the reaction products are also analyzed.
Role of Cluster Geometry in Evolution of Electronic Structures of Small Aluminum Clusters
ZHAI Hua-jin, ZHAO Ji-jun, NI Guo-quan, ZHOU Ru-fang, WANG Guang-hou, WANG Yu-zhu
Chin. Phys. Lett. 1997, 14 (12): 897-900 .  
Abstract   PDF(pc) (230KB) ( 376 )
The electronic structures of small aluminum clusters, Aln (n = 5 - 24), are investigated by a localized-orbital theory based on the tight-binding approximation. Magic-numbered clusters each exhibit a HOMO-LUMO gap maximum, and simultaneously an s-p gap minimum, but not necessarily an ionization potential maximum, where HOMO-LUMO gap denotes the energy gap between the highest occupied orbital and the lowest unoccupied orbital of the cluster. Also revealed is an irregular odd-even alternation in HOMO-LUMO gaps for Aln (n = 7-24). Cluster geometry either contributes to or dominates these findings.
Photoionization Mass Spectrometric Study of Neutral Bare Aluminum Clusters and Aluminum-Carbon Mixed Clusters
NI Guo-quan, ZHOU Ru-fang, ZHAI Hua-jin, WANG Yu-zhu
Chin. Phys. Lett. 1997, 14 (12): 901-904 .  
Abstract   PDF(pc) (263KB) ( 389 )
Photoionization time of flight mass spectra of bare aluminum and aluminum-carbon mixed clusters as well as a variety of oxygen- and oxygen-carbon-adducted aluminum clusters are recorded and assigned. The discontinuities in the mass abundance spectra at AI7, AI13, AI23 ,AI7C, AI13C, and AI24C are revealed. The findings are interpreted in terms of the electronic and geometric structures of these species.
Collapse and Revival of Supercurrent in Mesoscopic Josephson Junctions in the Presence of Nonclassical Electromagnetic Field
SHAO Bin, ZOU Jian, XING Xiu-san
Chin. Phys. Lett. 1997, 14 (12): 905-907 .  
Abstract   PDF(pc) (174KB) ( 473 )
Dynamic behavior of the supercurrent in a mesoscopic Josephson junction in the presence of a nonclassical electromagnetic field is investigated. It is shown that for the squeezed state the time evolution of the supercurrent can exhibit quantum collapse and revival phenomenon, while for the coherent state the phenomenon does not occur.
Photorefractive Image Amplification and Beam Fanning with Inclusion of Random Volume Scattering
XIE Ping, WANG Peng-ye, DAI Jiari-hua, ZHANG Hong-jun
Chin. Phys. Lett. 1997, 14 (12): 908-911 .  
Abstract   PDF(pc) (207KB) ( 339 )
Photorefractive effects, such as the image amplification and the beam fanning, can be described by a set of multivariable Langevin equations with inclusion of the random-phased volume scattering due to the inhomogeneities and/or defects in the crystal. The image amplification by two-wave-coupling configuration was studied analytically in the undepleted-pump approximation and numerically. It was found that the volume scattering can generate the beam fanning, as the surface scattering does.
A Lattice Boltzmann Boundary Condition at Impermeable Boundaries
FANG Hai-ping, LIN Zhi-fang, TAO Rui-bao
Chin. Phys. Lett. 1997, 14 (12): 912-915 .  
Abstract   PDF(pc) (197KB) ( 778 )
A hydrodynamic boundary condition for the lattice Boltzmann model at impermeable boundaries is developed. This boundary condition satisfies both the no-slip condition and the fluid conservation at boundary nodes. Poiseuille flow and Couette flow are calculated with this technique to demonstrate the accuracy of the present boundary condition.
A New Wall Conditioning Technique Developed on the HT-7 Superconducting Tokamak with a Permanent Magnetic Field
ZHAO Yan-ping, LI Jian-gang, XIE Ji-kang, MENG Yue-dong, WU Xin-chao, HE Ye-xi, XUE Di-ye, DENG Xu, SHAO Yu-gui
Chin. Phys. Lett. 1997, 14 (12): 916-919 .  
Abstract   PDF(pc) (249KB) ( 395 )
A new technique for wall conditioning with a permanent magnetic field has been tested and developed on the HT-7 superconducting tokamak by ion cyclotron range frequency wave injection. The operation ranges for conditioning and recycling was investigated with different working gas (D2, He), toroidal field (0.1-2.5 T) and rf powers. The experimental results show that its cleaning efficiency is about three times higher than that of glow discharge cleaning. This new technique has been used daily during experiments.
Elastic Behaviors of Bulk Metallic Glass Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 Investigated by Using Ultrasonic Technique
WANG Ru-ju, QIN Zhi-cheng, LI Feng-ying, XIE Hong-sen
Chin. Phys. Lett. 1997, 14 (12): 920-923 .  
Abstract   PDF(pc) (217KB) ( 404 )
The acoustic velocity, attenuation, and their pressure dependence of a bulk metallic glass Zr41.2Ti13.8Cu12.5Ni10.0Be22.5 have been measured under pressures up to 0.5 GPa at room temperature using the pulse echo overlap method. The sample was prepared from melt by quenching into liquid nitrogen. Bulk modulus, Young’s modulus, shear modulus, and Poisson’s ratio were derived, other elastic properties and vibrational anharmonicity were also discussed.
Intrinsic Localization of Bloch Electrons in dc-ac Electric Fields
LIU Wu-ming, ZHAO Xian-geng, LIU Ke
Chin. Phys. Lett. 1997, 14 (12): 924-927 .  
Abstract   PDF(pc) (194KB) ( 414 )
Exact soliton solutions describing nonlinear dynamical behavior of Bloch electrons under action of dc-ac electric fields are obtained, from which it is found that the evolution behavior of Bloch electrons is always oscillatory in time, with oscillatory frequencies depending on electric fields. A number of phenomena associated with the translational symmetry of the system, the staggered localized states, as well as the relationship between intrinsic localized states and solitons are addressed. The corresponding energy, momentum, and norm are also studied.
Temperature Characteristics Studies of Nanocrystallite SrTiO3 Grain Boundaries by X-Ray Photoelectron Spectroscopy
LIU Zhen-xiang, GUO Jun, XIE Kan
Chin. Phys. Lett. 1997, 14 (12): 928-931 .  
Abstract   PDF(pc) (223KB) ( 518 )
Strontium titanate (SrTiO3) nanocrystallite thin films have been studied by x-ray photoelectron spectroscopy at different temperature. The surface oxygen concentration and Ti/Sr ratio increase with temperature rising up to 700K, and then decrease. New O1s and Ti 3d peaks appear at the low binding energy side of the corresponding main peaks, these new peaks have some different features from the corresponding main peaks, this phenomenon was not observed in single crystal SrTiO3. A model is proposed to explain this interesting phenomenon.
Optical Anisotropy of InAs Monolayer in (311)-Oriented GaAs Matrix
Y.H.Chen, Z.Yang, XU Bo, WANG Zhan-guo, LIANG Ji-ben
Chin. Phys. Lett. 1997, 14 (12): 932-935 .  
Abstract   PDF(pc) (227KB) ( 374 )
In-plane optical anisotropy which comes from the heavy hole and the light hole transitions in an InAs monolayer inserted in (311)-oriented GaAs matrix is observed by reflectance difference spectroscopy. The observed steplike density of states demonstrates that the InAs layer behaves like a two-dimensional quantum well rather than isolated quantum dots. The magnitude of the anisotropy is in good agreement with the intrinsic anisotropy of (311) orientation quantum wells, indicating that there is little structural or strain anisotropy of the InAs layer grown on (311)-oriented GaAs surface.
Oxygen-Diffusion and Structural Modification in Air-Annealed Superconducting Bi2Sr2CaCu2Oy Single Crystals
ZHAO Xiao-ru, WU Wen-bin, SUN Xue-feng, WANG Liang-bin, ZHOU Gui-en, LI Xiao-Guang, ZHANG Yu-heng, Koichi Kitazawa
Chin. Phys. Lett. 1997, 14 (12): 936-939 .  
Abstract   PDF(pc) (216KB) ( 439 )
Bi2Sr2CaCu2Oy single crystals were air-annealed at 300, 400, 600 and 750°C for 20h in consequence. Measurements of ac susceptibility and x-ray diffraction showed that at annealing temperature below 400°C, the change of Tc was dominated by oxygen-diffusion involved in pervoskite unit and was strongly sample-dependent. This diffusion from pervoskite unit occurred earlier than that from Bi-O layers. At annealing temperature over 400°C, with the intercalation of excess oxygen into Bi-O layers, the hole concentration in the crystal was redistributed so that Bi-O reservoir fully determined superconductivity. From the changes of non-uniform strain in annealing process, it was found that structural modification was also closely correlated to superconductivity.
Local Magnetic Relaxation in High-Temperature Superconductors
WEI Chong-de
Chin. Phys. Lett. 1997, 14 (12): 940-942 .  
Abstract   PDF(pc) (181KB) ( 477 )
The local magnetic relaxation in superconducting slab is investigated numerically for Anderson-Kim model, U(j)=Uc(l - j / jc ) , and periodic pinning potential. The relaxation of B(x,t) depends on the starting profile and the position x. It is important to note that the relaxation of B(x,t) exhibits approximate scaling law for some initial condition, showing that the relaxation rate is roughly uniform over the sample. For long time, B(x,t) is towards an asymptotic behavior independent of x.
Low Coercivity of Amorphous La-Co Films
ZHAO Tong-yun, ZHAO Jian-gao, SHEN Bao-gen, SHAN Zheng-sheng, D. J. Sellmyer
Chin. Phys. Lett. 1997, 14 (12): 943-945 .  
Abstract   PDF(pc) (179KB) ( 441 )
The structure and magnetic properties of sputtered La-Co alloy films have been studied. Less than 10A/m (100mOe) coercivity can be obtained in amorphous La100-xCox films around x = 80 and the coercivity of amorphous La20Co80 film depends on the thickness of the film. The magnetization behaviour has been examined for the films with different compositions through magnetic hysteresis loops. An excellent rectangular magnetic hysteresis loop was obtained for films with thickness less than 60nm.
Organic Light Emitting Diode Using Inorganic Material as Electron Transport Layer
YANG Xiao-hui, HUA Yu-lin, TENG Feng, HOU Yan-bing, XU Xu-rong, HUANG Zhong-hao
Chin. Phys. Lett. 1997, 14 (12): 946-948 .  
Abstract   PDF(pc) (128KB) ( 475 )
In this letter we report a new kind of organic light emitting diode in which an inorganic material was used as electron transport layer. The incorporation of this inorganic material layer increased the brightness in one order.
Low Field-Induced Electron Emission Phenomenon Observed from the Carbon Containing Thin Films
CHEN Jun, WEI Ai-xiang, ZHANG Hai-yan, LU Yong, ZHENG Xin-guo, MO Dang, PENG Shao-qi, XU Ning-sheng
Chin. Phys. Lett. 1997, 14 (12): 949-952 .  
Abstract   PDF(pc) (210KB) ( 428 )
Stable cold-cathode electron emission at fields as low as 3 MV/m has been observed from two types of carbon-containing thin film of thickness in submicron scale, i. e., non-doped fullerene C60 and amorphous diamond films. A transparent anode imaging technique was used to record the spatial distribution of individual sites and the total emission current-voltage characteristic of the films. It is found that supplemental measurements of optical spectra and electrical conductivity of the films can provide important evidence useful for understanding the differences in emission behaviour between two types of film.
A Novel Application of the Pulsed Nitrogen Discharge in the Synthesis of Aluminum Nitride Powder by Laser Ablation
WANG Pei-nan, Pan Qi, Cheung Nai-Ho, Chen Shu-Chi
Chin. Phys. Lett. 1997, 14 (12): 953-956 .  
Abstract   PDF(pc) (238KB) ( 577 )
Pulsed discharge of nitrogen was applied in the laser ablation synthesis of aluminum nitride powder to provide more atomic nitrogen. Very high concentration of aluminum nitride was then achieved. The nitrogen discharge plasma was studied by optical emission spectroscopy. Temporal behaviors of the emissions from various species were observed and discussed.
Propagation of Localized Excitations in Desoxyribonucleic Acid
YANG Xian-jun, ZHUO Yi-zhong, WU Xi-zhen
Chin. Phys. Lett. 1997, 14 (12): 957-960 .  
Abstract   PDF(pc) (188KB) ( 322 )
The result that the process by which the pulses, initially distributed in desoxyribonucleic acid(DNA) molecules can resume its form to localize the large amplitude excitations is proposed. This process may play an important role in the dynamics of localized thermal bubble for the transcription of DNA molecules..
21 articles