Jun 2006, Volume 1 Issue 2

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  • WU Xue-bing
    The determination of the mass of black holes in our universe is crucial to understand their physics nature but is a great challenge to scientists. In this paper I briefly review some methods that are currently used to estimate the mass of black holes, especially those in X-ray binary systems and in galactic nuclei. Our recent progress in improving the mass estimates of supermasssive black holes in active galactic nuclei by involving some empirical relations is presented. Finally I point out the similarities and common physics in Galactic black hole X-ray binaries and active galactic nuclei, and demonstrate that the black hole mass estimation is very much helpful to understand the accretion physics around black holes.
  • MA Yong-ge
    Unifying general relativity and quantum mechanics is a great challenge left to us by Einstein. To face this challenge, considerable progress has been made in non-perturbative canonical (loop) quantum gravity during the past 20 years. The kinematical Hilbert space of the quantum theory is constructed rigorously. However, the semiclassical analysis of the theory is still a crucial and open issue. In this review, we first introduce our work on constructing a semiclassical weave state, using the Q[ω] operator on the kinematical Hilbert space of loop quantum gravity. Then we give an introduction to the two different approaches currently investigated for constructing coherent states in the kinematical Hilbert space. The current status of semiclassical analysis in loop quantum gravity is then summarized.
  • ZHI Qi-jun, Mao Ying-chen, REN Zhong-zhou
    We systematically calculate the ground state properties of superheavy even-even nuclei with proton number Z=94-118. The calculations are based on the liquid drop macroscopic model and the microscopic model with the modified single-particle oscillator potential. The calculated binding energies and ?-decay energies agree well with the experimental data. The reliability of the macroscopic-microscopic(MM)model for superheavy nuclei is confirmed by the good agreement between calculated results and experimental ones. Detailed comparisons between our calculations and Möller s are made. It is found that the calculated results also agree with Möller s results and that the MM model is insensitive to the microscopic single-particle potential. Calculated results are also compared with results from relativistic mean-field (RMF) model and from Skyrme-Hatree-Fock(SHF) model. In addition, half-lives, deformations and shape coexistence are also investigated. The properties of some unknown nuclei are predicted and they will be useful for future experimental researches of superheavy nuclei.
  • LI Yan-feng, HU Ming-lie, CHAI Lu, WANG Ching-yue
    Photonic crystal fibers are a new class of single-material optical fibers with wavelength-scale air holes running down the entire fiber length. Photonic crystal fibers were first developed in 1996 and have subsequently been the focus of increasing scientific and technological interest in the field of fiber optics. The manufacturing, principles, basic properties, and some applications of photonic crystal fibers are briefly described in this paper. A review of our recent work on the nonlinear effects in photonic crystal fibers is presented, and special emphasis is placed on such effects as supercontinuum generation, frequency conversion, and solitons observed when femtosecond light pulses propagate in these fibers.
  • GONG Qi-huang, HU Xiao-yong
    Photonic crystal, a novel and artificial photonic material with periodic dielectric distribution, possesses photonic bandgap and can control the propagation states of photons. Photonic crystal has been considered to be a promising candidate for the future integrated photonic devices. The properties and the fabrication method of photonic crystal are expounded. The progresses of the study of ultrafast photonic crystal optical switching are discussed in detail.
  • DAI Zhong-ling, WANG You-nian
    The characteristics of radio-frequency(RF) plasma sheaths have been topics of much scientific study for decades, and have also been of great importance in the manufacture of integrated circuits and fabricating microelectromechanical systems (MEMS), as well as in the study of physical phenomena in dusty plasmas. The sheaths behave special properties under various situations where they can be treated as collisionless or collisional, single- or dual-RF, one- or two-dimensional (1D or 2D) sheaths, etc. This paper reviews our recent progress on the dynamics of RF plasma sheaths using a fluid method that includes the fluid equations and Poission s equation coupled with an equivalent circuit model and a hybrid method in which the fluid model is combined with the Monte-Carlo (MC) method. The structures of RF sheaths behave differently in various situations and plasma parameters such as the ion density, electron temperature, as well as the external parameters such as the applied frequency, power, gas pressure, magnetic field, are crucial for determining the characteristics of plasma sheaths.
  • ZHANG Hai-yan, MA Hong-ru
    This article offers a survey on our current knowledge of the dynamics of the colloidal suspension, where each particle experiences the friction force with solvent, hydrodynamic interaction, and potential force from surrounding particles and thermodynamic force. It further contains a summary of the basic concepts about microstructures and equilibrium properties, and of analytical and numerical methods, which are relevant for the theoretical description of the suspensions. The description of the dynamics of colloidal particles, based on the generalized Smoluchowski equation, is justified for the time scale accessible in DLS experiments. The combined influence of hard sphere or electrostatic potential and solvent-mediated hydrodynamic interaction on the short-time dynamics of monodisperse suspensions is investigated in detail. A thorough study of tracer-diffusion in hard sphere and charge-stabilized suspensions is presented. Mean-square displacements and long-time tracer-diffusion coefficients are calculated with two alternative approximations, i.e., a mode-coupling scheme and a single relaxation time ansatz.
  • XIAO Jing-hua, LI Hai-hong, YANG Jun-zhong, HU Gang
    The problem of Turing pattern formation has attracted much attention in nonlinear science as well as physics, chemistry and biology. So far spatially ordered Turing patterns have been observed in stationary and oscillatory media only. In this paper we find that spatially ordered Turing patterns exist in chaotic extended systems. And chaotic Turing patterns are strikingly rich and surprisingly beautiful with their space structures. These findings are in sharp contrast with the intuition of pseudo-randomness of chaos. The richness and beauty of the chaotic Turing patterns are attributed to a large variety of symmetry properties realized by various types of self-organizations of partial chaos synchronizations.
  • WANG Zhi-wen, ZHANG Nan, HU Mu-hong
    The transition energies of the 1s23d-1s2nf (4"dn"d9) transitions and fine structure splittings of 1s2nf (n"d9) states for Sc18+ ion are calculated with the full-core plus correlation method. The quantum defect of 1s2nf series is determined by the single-channel quantum defect theory. The energies of any highly excited states with n"e10 for this series can be reliably predicted using the quantum defect as function of energy. Three alternative forms of the dipole oscillator strengths for the 1s23d-1s2nf (n"d9) transitions of Sc18+ ion are calculated with the transition energies and wave functions obtained above. Combining the quantum defect theory with the discrete oscillator strengths, the discrete oscillator strengths for 1s23d-1s2nf (n > 9) transitions and the oscillator strengths densities corresponding to the bound-free transitions are obtained.
  • LIU Yi-ding, SUN Wei-guo, REN Wei-yi
    The first accurate studies on the vibrational spectroscopic constants and the corresponding full vibrational energy spectra of some electronic states of diatomic molecular ions XY+ were performed using algebraic method(AM). The AM is applied on the X1?+ state of BeH+, the X2?+ state of CO+ ? the X2?g state of F2+ , the A2?u state of O2+ and the X2?g+ state of Li2+. The results show that AM can generate accurate vibrational spectroscopic constants as well as accurate full vibrational energy spectra by using some accurate experimental vibrational energies, and that the AM vibrational energies are better than other theoretical data.
  • CAI Yang-jian, ZHU Shi-yao
    we present a theoretical study of coincidence imaging and interference with coherent Gaussian beams. The equations for the coincidence image formation and interference fringes are derived?from which it is clear that the imaging is due to the corresponding focusing in the two paths. The quality and visibility of the images and fringes can be high simultaneously. The nature of the coincidence imaging and interference between quantum entangled photon pairs and coherent Gaussian beams are different. The coincidence image with coherent Gaussian beams is due to intensity-intensity correspondence?a classical nature? while that with entangled photon pairs is due to the amplitude correlation a quantum nature.
  • YAO Jian-quan, XU De-gang, WANG Yu-ye
    In the high power frequency-doubled Nd:YAG Laser, the temperature inside a nonlinear crystal will become non-uniform due to the absorbtion of the fundamental and second harmonic waves, leading to phase mismatch, conversion efficiency reduction and output power instability. This phenomenon appears severe in the high-power high-repetition rate laser system. In this paper, temperature distribution inside a KTP crystal was analyzed by solving the thermal conductivity equation. According to the temperature distribution of the KTP, we have theoretically calculated the optimal phase matching angles, tolerance angles and walk-off angles of type II KTP crystal as a function of temperature.
  • YANG Jing, CUI Lian-jun, XU Jian, CHENG Jian-chun
    An inverse method is presented to determine the elastic constants of an experimental sample, a titanium graphite unidirectional fiber-reinforced composite plate, using wavelet transform and neural networks. Optimal algorithms of wavelet transform and neural networks are given here in order to improve the accuracy of inversion results. Coherent results were shown in both fiber direction and cross fiber direction, proving the feasibility of this method. Neither the group velocity of the Lamb wave modes are needed, as in the conventional method?and no direct least-square fitting of the experimental waveforms is necessary.
  • LIU Can-de, LIU Wen, SU Xi-yu, LI Feng-ling, WU Da-peng
    Dynamical behaviors of an exciton in an asymmetric double coupled quantum dot and an alternatingcurrent (ac) electric field have been analyzed based on the two-level approximation theory, and the conditions under which dynamical localization occurs are obtained. It shows that when the amplitude of the ac electric field is small, the Coulomb interaction plays an important role. The dynamical behaviors of the exciton are mainly confined in the low-level subspace. When the ratio of the field intensity to frequency is the root of Bessel function, electron and hole are localized in one dot, and they can be divided with the increasing amplitude of the ac electric field.
  • CHEN Chun-xia, LI Guang, LI Xiao-guang
    The dependences of critical current density Jc on the interlayer coupling strength and magnetic field in Bi2212 crystals were obtained by measuring the magnetic loop of the crystals with different interlayer coupling strengths. It was revealed that Jc decreases with the decrease in the interlayer coupling of the crystals. The relation of Jc ∝ exp(-Hβ) was also found in the crystals, and further analysis indicated that it was the result of Zeldov pinning potential model.
  • ZHUANG Cheng-gang, CHEN Li-ping, DING Li-li, ZHANG Kai-cheng, CHEN Chin-ping, FENG Qing-rong, GAN Zi-zhao, AN Ling, XU Jun
    We fabricated several superconducting MgB2 thick films on stainless steel (SS) substrates by using hybrid physical-chemical vapor deposition (HPCVD) technique. The thickness was in the 10 m μ to 20 m μ range, and the onset critical transition temperature Tc (onset) and the width of the superconducting transition (?T) were about 37.8 and 1.2 K. They were dense and textured along (101) direction with high tenacity, despite the existence of a little amount of MgO and Mg. We bent the films at different degrees and studied the ductility and transport properties of these MgB2 thick films under applied force. The results demonstrated that the superconducting properties of these thick films, prepared by HPCVD, stay almost unaffected even with the films bent to a large degree with a curvature of 0.5 mm. This indicated that the superconducting wires or tapes of MgB2 with a core of SS had the advantages of avoiding rigidity and brittleness in industrial handling. The technique of HPCVD has, therefore, a high application potential.