中国物理B

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STUDY OF HAWKING EFFECT IN VAIDYA-BONNER BLACK HOLE BY MEANS OF SECOND QUANTIZATION

朱建阳

1995 (4): 241-246. doi: 10.1088/1004-423X/4/4/001

摘要 ( 984 )

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Hawking thermal spectrum of a spherically charged evaporating black hole can be obtained by means of the second quantization and Bogolubov transformation on Klein-Gordon scalar field near the event horizon of Vaidya-Bonner space-time. It is shown that the ingoing vacuum state becomes an outgoing state involving thermal particles after scattering on the surface of horizon. These particles show Planck spectrum whose temperature is T.

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THE AMPLITUDE-N-TH POWERED SQUEEZING OF AN ELECTROMAGNETIC FIELD IN THE MULTIPHOTON JAYNES-CUMMINGS MODEL INTERACTING WITH THE SUPERPOSITION STATE

王继锁, 王传奎, 孙金祚, 贺金玉

1995 (4): 247-253. doi: 10.1088/1004-423X/4/4/002

摘要 ( 1079 )

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We have studied the properties of the amplitude-N-th powered squeezing of an elec-tromagnetic field in the k-photon Jaynes-Cummings model of an atom initially being in the ground state and coupling with the superposition state. The results show that, under the condition of n≥k, where n is the photon number of the superposition state, the field exhibits not only the amplitude-N = n-th powered squeezing but also the amplitude-N = (n/2)-th powered squeezing for even n. The variations of the amplitude-N-th powered squeezing of the field with the powers N and k are discussed.

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CW Nd:YAG THERMO-STABLE RESONATORS OPERATING IN POWER-STEADY STATES

林美荣, 张包铮, 姚和军, 张光寅

1995 (4): 254-258. doi: 10.1088/1004-423X/4/4/003

摘要 ( 1172 )

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There are two dynamical stable zones in the operation of solid laser containing a thermal lens. In this paper, we point out that in the two stable zones two kinds of dynamical stable states can exist in a laser resonator: mode-steady thermo-stable state and power-steady thermo-stable state. They are different from each other in general. The operating conditions for power-steady thermo-stable state are presented. A cw Nd: YAG thermo-stable resonator operating in power-steady states has been designed, and 40 W TEM₀₀ output power in 1.06μm is obtained experimentally.

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EFFECT OF HIGH-ANGLE DIFFRACTION DATA ON RIETVELD STRUCTURE REFINEMENT

陈小龙, 梁敬魁, 王聪

1995 (4): 259-267. doi: 10.1088/1004-423X/4/4/004

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By utilizing the powder X-ray step-scanning diffraction data of PbSO₄, we have studied the effect of the diffraction data (with different high-angle upper-limit: 2θ_m= 160,140,120,100,80, 70 and 60°) on the precision of the Rietveld refined lattice constants, structure parameters, and agreement indices. Tbese refined results are compared with those obtained from the single crystal data. It is revealed that the deviations of the refined lattice constants, atomic positions and isotropic temperature factors decrease, and agreement indices become smaller With the increase of 2θ_m. But when 2θ_m> 120°, the deviations and agreement indices decrease very slowly. Therefore, in general cases, 2θ_m should be taken to be 120°or larger in order to get satisfactory refined results in the Rietveld crystal structure refinement.

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A STUDY OF THE CRYSTALLIZATION OF AMORPHOUS Cu₆₀Zr₄₀ ALLOY

包昌林, 陆华, 薛其坤, 张小军, 崔玉德

1995 (4): 268-277. doi: 10.1088/1004-423X/4/4/005

摘要 ( 1327 )

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The crystallization of the amorphous Cu₆₀Zr₄₀ alloy has been studied by differential scanning calorimetry (DSC), scanning Auger microprobe (SAM) and transmission electron microscopy (TEM). The DSC trace showed that the sample exhibited a glass transition at 750 K and a strong exothermic effect beginning from 782 K. An enrichment of the element Zr and significant oxygen contamination in a zone near the surface to a depth of about 10 nm were revealed by SAM in the analysis of surface competition and depth profiles of the Cu₆₀Zr₄₀ sample. Also, the change of concentration ratio of Ca to Zr in amorphous matrix at the clean Cu₆₀Zr₄₀ surface as a function of annealing temperature was examined in detail, and it was found that the concentration of Zr at the surface is slightly higher than that in the bulk until 780K and that the concentration ratio of Cu to Zr in matrix has an abrupt increase in the temperature range of 780-800K. The observations by high resolution TEM revealed the appearance of cluster-like regions of approximately 1.5-2.0 nm in size just before crystallization and they distributed randomly throughout the sample. This phenomenon is analogous to the results obtained using field ion microscopy (FIM) by the present authors. The microstructural changes of the sample daring heating show the gradual crystallization of the amorphous matrix.

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NON-NEAREST-NEIGHBOR HOPPING IN POLYACETYLENE

童国平, 冯家显, 李鹤年

1995 (4): 278-290. doi: 10.1088/1004-423X/4/4/006

摘要 ( 1085 )

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In this paper, the extended Wannier function suitable for instable lattice is constructed, by employing a linear combination of hydrogenlike-atom wave functions, and used to calculate the non-nearest-neighbor hopping and energy-band structure of trans-polyacetylene. Studies show that the non-nearest-neighbor terms have a considerable influence on the band structure. The computed results agree very well with the experimental results.

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EFFECTS OF ELECTRON-ELECTRON INTERACTION AND ELECTRON-PHONON COUPLING ON THE SPIN-DENSITY-WAVE OF QUASI-ONE-DIMENSIONAL ORGANIC POLYMER FERROMAGNETS

方忠, 刘祖黎, 姚凯伦, 李再光

1995 (4): 291-295. doi: 10.1088/1004-423X/4/4/007

摘要 ( 1129 )

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Based on a theoretical model proposed for quasi-one-dimensional organic polymer ferro-magnet poly-BIPO, the effects of electron-electron interaction and electron-phonon coupling on the spin-density-wave (SDW) state of poly-BIPO system are studied. It is found that the SDW state is the stable ground state of the system, in which the system shows ferromagnetic order. And the larger electron-electron interaction and the smaller electron-phonon coupling will make the SDW state more stable than the nonmagnetic state.

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SURFACE PHASE DECOMPOSITION IN Bi₂Sr₂CaCu₂O_7-y SINGLE CRYSTALS UNDER NITROGEN IONS IRRADIATION

石磊, 汪良斌, 李晓光, 吴文彬, 周贵恩, 张裕恒

1995 (4): 296-300. doi: 10.1088/1004-423X/4/4/008

摘要 ( 1231 )

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The influence of irradiation by 30 keV nitrogen ions with a fluence 1×10¹⁸N⁺·cm^-2 on the crystal structure of single crystal Bi₂Sr₂CaCu₂O_7-y was investigated by means of X-ray photoelectron spectroscopy and X-ray diffraction. The irradiation caused a transformation from Bi₂Sr₂CaCu₂O_7-y (2212 phase) to Bi₂Sr₂CuO_5-x (2201 phase). It was observed that. a small amount of metallic bismuth with an average thickness of about 6.3nm appeared after the irradiation. The possible reaction mechanism under nitrogen-ion irradiation was discussed.

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THE ELECTRON-BEAM IRRADIATION ON THE HIGH TEMPERATURE SUPERCONDUCTING THIN FILMS: A NUMERICAL SIMULATION OF THE LOW TEMPERATURE SCANNING ELECTRON MICROSCOPY

冯一军, 程其恒, 吴培亨

1995 (4): 301-310. doi: 10.1088/1004-423X/4/4/009

摘要 ( 994 )

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Low-temperature scanning electron microscopy (LTSEM) is a promising measuring technique for probing the spatial distribution of the superconducting properties of the high-temperature superconducting (HTS) thin films. A theoretical analysis of the electron-beam irradiation on the HTS thin films in the LTSEM has been carried out. An inhomogeneously distributed grain array model has been applied in the analysis, and some numerical sim-ulations have been carried out on the electron-beam induced voltage (EIV) signals in the LTSEM experiments. The comparisons of our numerical results with the LTSEM experi-mental data indicate that it is quite reasonable to use a two-dimensional Josephson junction array for stimulating the inhomogeneous HTS thin film sample. Our numerical results also show that the EIV signals are influenced by the electron-beam power used in the LTSEM, and a reduction of the electron-beam power is suggested in order to eliminate the errors in estimating the local values of critical temperature T_c and critical current I_c by the sample temperature and the bias current at which the first EIV signal occurs.

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