Table of contents

20 March 2007, Volume 16 Issue 3 Previous issue    Next issue

GENERAL

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Multifractal analysis of the Yellow River flows Zang Bao-Jiang(臧保将) and Shang Peng-Jian(商朋见) Chinese Physics, 2007, 16 (3):  565-569.  DOI: 10.1088/1009-1963/16/3/001 Abstract ( 1941 )   PDF (152KB) ( 1008 )   This paper deals with time series of the Yellow River daily flows at Tongguan hydrological station, from the year 2000 to 2005. Power spectrum analysis and statistical moment scaling function on a range of scales revealed scaling qualities of the data. The partition function, which displayed a convex curvature, and the generalized dimension function showed that multifractality is presented. The singularity spectrum, which is single-humped, has shown strong multifractality degree.

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Discrete variational principle and first integrals for Lagrange--Maxwell mechanico-electrical systems Fu Jing-Li(傅景礼), Dai Gui-Dong(戴桂冬), Salvador Jimènez(萨尔瓦多·希梅尼斯), and Tang Yi-Fa(唐贻发) Chinese Physics, 2007, 16 (3):  570-577.  DOI: 10.1088/1009-1963/16/3/002 Abstract ( 1585 )   PDF (162KB) ( 798 )   This paper presents a discrete variational principle and a method to build first-integrals for finite dimensional Lagrange--Maxwell mechanico-electrical systems with nonconservative forces and a dissipation function. The discrete variational principle and the corresponding Euler--Lagrange equations are derived from a discrete action associated to these systems. The first-integrals are obtained by introducing the infinitesimal transformation with respect to the generalized coordinates and electric quantities of the systems. This work also extends discrete Noether symmetries to mechanico-electrical dynamical systems. A practical example is presented to illustrate the results.

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Asymptotic solution of a sea--air oscillator for ENSO mechanism Mo Jia-Qi(莫嘉琪), Lin Wan-Tao(林万涛), and Wang Hui(王辉) Chinese Physics, 2007, 16 (3):  578-581.  DOI: 10.1088/1009-1963/16/3/003 Abstract ( 1444 )   PDF (95KB) ( 707 )   The EI Niño/La Niña--Southern Oscillation (ENSO) is an interannual phenomenon involved in the tropical Pacific ocean--atmosphere interactions. In this paper, a class of coupled system of the ENSO mechanism is considered. Based on a class of oscillator of ENSO model, the asymptotic solution of a corresponding problem is studied by employing the approximate method. It is proved from the results that the perturbation method can be used for analysing the sea surface temperature anomaly in the equatorial eastern Pacific and the thermocline depth anomaly of the atmosphere--ocean oscillation for the ENSO model.

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The discrete variational principle and the first integrals of Birkhoff systems Zhang Hong-Bin(张宏彬), Chen Li-Qun(陈立群), Gu Shu-Long(顾书龙), and Liu Chuan-Zhang(柳传长) Chinese Physics, 2007, 16 (3):  582-587.  DOI: 10.1088/1009-1963/16/3/004 Abstract ( 1568 )   PDF (117KB) ( 668 )   This paper shows that first integrals of discrete equation of motion for Birkhoff systems can be determined explicitly by investigating the invariance properties of the discrete Pfaffian. The result obtained is a discrete analogue of theorem of Noether in the calculus of variations. An example is given to illustrate the application of the results.

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Two types of loop algebras and their expanding Lax integrable models Yue Chao(岳超), Zhang Yu-Feng(张玉峰), and Wei Yuan(魏媛) Chinese Physics, 2007, 16 (3):  588-594.  DOI: 10.1088/1009-1963/16/3/005 Abstract ( 1474 )   PDF (116KB) ( 519 )   Though various integrable hierarchies of evolution equations were obtained by choosing proper U in zero-curvature equation $U _{t}-V_  {x}+[U,V]=0$, but in this paper, a new integrable hierarchy possessing bi-Hamiltonian structure is worked out by selecting V with spectral potentials. Then its expanding Lax integrable model of the hierarchy possessing a simple Hamiltonian operator $\widetilde{J}$ is presented by constructing a subalgebra $\widetilde{G}$ of the loop algebra $\widetilde{A}_{2}$. As linear expansions of the above-mentioned integrable hierarchy and its expanding Lax integrable model with respect to their dimensional numbers, their (2+1)-dimensional forms are derived from a (2+1)-dimensional zero-curvature equation.

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The Liouville integrable coupling system of the m-AKNS hierarchy and its Hamiltonian structure Yue Chao(岳超), Yang Geng-Wen(杨耕文), and Xu Yue-Cai(许曰才) Chinese Physics, 2007, 16 (3):  595-598.  DOI: 10.1088/1009-1963/16/3/006 Abstract ( 1472 )   PDF (93KB) ( 502 )   In this paper a type of 9-dimensional vector loop algebra $\tilde{F}$ is constructed, which is devoted to establish an isospectral problem. It follows that a Liouville integrable coupling system of the m-AKNS hierarchy is obtained by employing the Tu scheme, whose Hamiltonian structure is worked out by making use of constructed quadratic identity. The method given in the paper can be used to obtain many other integrable couplings and their Hamiltonian structures.

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A series of non-Noether conservative quantities and Mei symmetries of nonconservative systems Liu Hong-Ji(刘鸿基), Fu Jing-Li(傅景礼), and Tang Yi-Fa(唐贻发) Chinese Physics, 2007, 16 (3):  599-604.  DOI: 10.1088/1009-1963/16/3/007 Abstract ( 1586 )   PDF (119KB) ( 658 )   In this paper Mei symmetry is introduced for a nonconservative system. The necessary and sufficient condition for a Mei symmetry to be also a Lie symmetry is derived. It is proved that the Mei symmetry leads to a non-Noether conservative quantity via a Lie symmetry, and deduces a Lutzky conservative quantity via a Lie point symmetry.

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Multi-component Dirac equation hierarchy and its multi-component integrable couplings system Xia Tie-Cheng(夏铁成) and You Fu-Cai(尤福财) Chinese Physics, 2007, 16 (3):  605-610.  DOI: 10.1088/1009-1963/16/3/008 Abstract ( 1507 )   PDF (116KB) ( 876 )   A general scheme for generating a multi-component integrable equation hierarchy is proposed. A simple 3M-dimensional loop algebra $\tilde{X}$ is produced. By taking advantage of $\tilde{X}$, a new isospectral problem is established and then by making use of the Tu scheme the multi-component Dirac equation hierarchy is obtained. Finally, an expanding loop algebra $\tilde{F}$M of the loop algebra $\tilde{X}$ is presented. Based on the $\tilde{F}$M, the multi-component integrable coupling system of the multi-component Dirac equation hierarchy is investigated. The method in this paper can be applied to other nonlinear evolution equation hierarchies.

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The extended trace identity and its application Yao Yu-Qin(姚玉芹) and Chen Deng-Yuan(陈登远) Chinese Physics, 2007, 16 (3):  611-620.  DOI: 10.1088/1009-1963/16/3/009 Abstract ( 1392 )   PDF (144KB) ( 554 )   The trace identity is extended to the general loop algebra. The Hamiltonian structures of the integrable systems concerning vector spectral problems and the multi-component integrable hierarchy can be worked out by using the extended trace identity. As its application, we have obtained the Hamiltonian structures of the Yang hierarchy, the Korteweg-de--Vries (KdV) hierarchy, the multi-component Ablowitz--Kaup--Newell--Segur (M-AKNS) hierarchy, the multi-component Ablowitz--Kaup--Newell--Segur Kaup--Newell (M-AKNS--KN) hierarchy and a new multi-component integrable hierarchy separately.

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Quantum secure direct communication protocol with blind polarization bases and particles' transmitting order Song Jie(宋杰), Zhu Ai-Dong(朱爱东), and Zhang Shou(张寿) Chinese Physics, 2007, 16 (3):  621-623.  DOI: 10.1088/1009-1963/16/3/010 Abstract ( 1641 )   PDF (82KB) ( 605 )   This paper presents a modified secure direct communication protocol by using the blind polarization bases and particles' random transmitting order. In our protocol, a sender (Alice) encodes secret messages by rotating a random polarization angle of particle and then the receiver (Bob) sends back these particles as a random sequence. This ensures the security of communication.

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Probabilistic teleportation of an unknown N-atom state using a two-atom nonmaximally entangled state in cavity QED Lin Xiu (林秀), Li Hong-Cai(李洪才), and Yang Rong-Can(杨榕灿) Chinese Physics, 2007, 16 (3):  624-629.  DOI: 10.1088/1009-1963/16/3/011 Abstract ( 1714 )   PDF (129KB) ( 687 )   We present a scheme for realizing probabilistic teleportation of an unknown $N$-atom state via cavity QED. This scheme requires only a nonmaximally entangled pair to be used as a quantum channel, so the requirement of entanglement is reduced. In addition, our scheme does not involve the Bell-state measurement and is insensitive to the cavity decay, which is important from the experimental point of view. If the quantum channel is a two-atom maximally entangled state, teleportation of an unknown $N$-atom state can be realized by a simpler scheme via cavity QED.

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Trigger and control entanglement by atoms with different interaction times Hot! Ren Jie(任杰), Hao Xiang(郝翔), and Zhu Shi-Qun(朱士群) Chinese Physics, 2007, 16 (3):  630-634.  DOI: 10.1088/1009-1963/16/3/012 Abstract ( 1502 )   PDF (208KB) ( 587 )   The generation of the entanglement between two two-level atoms interacting with the third atom driven by white noise is investigated when the coupling between atoms is modulated by a pulse function. This paper finds that the initial triggering time and the width of the pulse can generate a peak in the entanglement. There is an optimal width of the pulse for which the entanglement can reach a maximum. The asymmetry of the coupling between atoms can generate different entanglement in the system. The multiple triggers can generate multiple peaks in the entanglement. The separation between two peaks is increased as the width of the pulse is increased.

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Remarks on interpretations of the Eötvös experiment and misinterpretation of E=mc2 C. Y. Lo (Lu Zhong-Xian)(鲁重贤) Chinese Physics, 2007, 16 (3):  635-639.  DOI: 10.1088/1009-1963/16/3/013 Abstract ( 1505 )   PDF (110KB) ( 585 )   The Eötvös experiment on the verification of equivalence between inertial mass and gravitational mass of a body is famous for its accuracy. A question is, however, can these experimental results be applied to the case of a physical space in general relativity, where the space coordinates could be arbitrary? It is pointed out that it can be validly applied because it has been proven that Einstein's equivalence principle for a physical space must have a frame of reference with the Euclidean-like structure. Will claimed further that such an overall accuracy can be translated into an accuracy of the equivalence between inertial mass and each type of energy. It is shown that, according to general relativity, such a claim is incorrect. The root of this problem is due to an inadequate understanding of special relativity that produced the famous equation $E=mc^2$, which must be understood in terms of energy conservation. Concurrently, it is pointed out that this error is a problem in Will's book, `Theory and Experiment in Gravitational Physics'.

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Scheme for entanglement concentration of unknown W class states via linear optics Zhang Li-Hua(章礼华), Dong Ping(董萍), and Cao Zhuo-Liang(曹卓良) Chinese Physics, 2007, 16 (3):  640-643.  DOI: 10.1088/1009-1963/16/3/014 Abstract ( 1615 )   PDF (241KB) ( 694 )   This paper proposes a scheme for entanglement concentration of unknown triparticle $W$ class states with a certain probability. This protocol is mainly based on the coincidences of single-photon detectors and requires single-photon detectors and linear optical elements. The scheme is feasible within current technology.

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The solution of the time-dependent Fokker--Planck equation of non-degenerate optical parametric amplification and its application to the optimum realization of EPR paradox Zhao Chao-Ying(赵超樱) and Tan Wei-Han(谭维翰) Chinese Physics, 2007, 16 (3):  644-649.  DOI: 10.1088/1009-1963/16/3/015 Abstract ( 1518 )   PDF (143KB) ( 546 )   In this paper, the solution of the time-dependent Fokker--Planck equation of non-degenerate optical parametric amplification is used to deduce the condition demonstrating the Einstein--Podolsky--Rosen (EPR) paradox. The analytics and numerical calculation show the influence of pump depletion on the error in the measurement of continuous variables. The optimum realization of EPR paradox can be achieved by adjusting the parameter of squeezing. This result is of practical importance when the realistic experimental conditions are taken into consideration.

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Atomic population oscillations between two coupled Bose--Einstein condensates with time-dependent nonlinear interaction Li Fei(李飞), Shu Wei-Xing(舒维星), Luo Hai-Lu(罗海陆), and Ren Zhong-Zhou(任中洲) Chinese Physics, 2007, 16 (3):  650-659.  DOI: 10.1088/1009-1963/16/3/016 Abstract ( 1598 )   PDF (1058KB) ( 588 )   The atomic population oscillations between two Bose--Einstein condensates with time-dependent nonlinear interaction in a double-well potential are studied. We first analyse the stabilities of the system's steady-state solutions. And then in the perturbative regime, the Melnikov chaotic oscillation of atomic population imbalance is investigated and the Melnikov chaotic criterion is obtained. When the system is out of the perturbative regime, numerical calculations reveal that regulating the nonlinear parameter can lead the system to step into chaos via period doubling bifurcations. It is also numerically found that adjusting the nonlinear parameter and asymmetric trap potential can result in the running-phase macroscopic quantum self-trapping (MQST). In the presence of a weak asymmetric trap potential, there exists the parametric resonance in the system.

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Chaos synchronization between two different 4D hyperchaotic Chen systems Liu Yang-Zheng(刘扬正), Jiang Chang-Sheng(姜长生), Lin Chang-Sheng(林长圣), and Jiang Yao-Mei(蒋耀妹) Chinese Physics, 2007, 16 (3):  660-665.  DOI: 10.1088/1009-1963/16/3/017 Abstract ( 1757 )   PDF (310KB) ( 1043 )   This paper presents chaos synchronization between two different four-dimensional (4D) hyperchaotic Chen systems by nonlinear feedback control laws. A modified 4D hyperchaotic Chen system is obtained by changing the nonlinear function of the 4D hyperchaotic Chen system, furthermore, an electronic circuit to realize two different 4D hyperchaotic Chen systems is designed. With nonlinear feedback control method, chaos synchronization between two different 4D hyperchaotic Chen systems is achieved. Based on the stability theory, the functions of the nonlinear feedback control for synchronization of two different 4D hyperchaotic Chen systems is derived, the range of feedback gains is determined. Numerical simulations are shown to verify the theoretical results.

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Adaptive synchronization of hyperchaotic Lü system with uncertainty Gao Bing-Jian(高秉建) and Lu Jun-An(陆君安) Chinese Physics, 2007, 16 (3):  666-670.  DOI: 10.1088/1009-1963/16/3/018 Abstract ( 1443 )   PDF (470KB) ( 742 )   This paper presents a novel adaptive control scheme for synchronization of the latest hyperchaotic Lü system. Based on the Lyapunov stability theory, a feedback controller and a parameter update law are designed for the synchronization of hyperchaotic Lü systems with uncertainty. Numerical simulations are given to demonstrate the validity of the synchronization technique.

ATOMIC AND MOLECULAR PHYSICS

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Photodetachment cross section of S- in electric and magnetic fields Wang De-Hua(王德华) and Ding Shi-Liang(丁世良) Chinese Physics, 2007, 16 (3):  671-674.  DOI: 10.1088/1009-1963/16/3/019 Abstract ( 1374 )   PDF (148KB) ( 614 )   In this paper, the quantum-mechanical photodetachment cross section of S- in uniform electric and magnetic fields at arbitrary angles is presented. It compares the quantum-mechanical cross section with the quantum source formalism cross section. The results show that at large angle, the two results have good agreements, however, with the decrease of the angles, they deviate obviously from each other. The reasons for this discrepancy are also discussed.

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High-order harmonic generation spectrum of an excited one-dimensional Coulomb atom in an intense laser field Zhou Zhao-Yan(周兆姸） and Yuan Jian-Min(袁建民) Chinese Physics, 2007, 16 (3):  675-679.  DOI: 10.1088/1009-1963/16/3/020 Abstract ( 1763 )   PDF (641KB) ( 774 )   Response of the wave packet of a one-dimensional Coulomb atom to an intense laser field is calculated using the symmetrized split operator fast Fourier method. The high-order harmonic generation (HHG) of the initial state separately being the ground and excited states is presented. When the hardness parameter $\alpha$ in the soft Coulomb potential $V(x)=-1/\sqrt{x^2+\alpha}$ is chosen to be small enough, the so-called hard Coulomb potential $V(x)=-1/|x|$ can be obtained. It is well known that the hard one-dimensional Coulomb atom has an unstable ground state with an energy eigenvalue of $\sim0.5$ and it has no states corresponding to physical states in the true atoms, and has the first and second excited states being degenerate. The parity effects on the HHG can be seen from the first and second excited states of the hard one-dimensional Coulomb atom. The HHG spectra of the excited states from both the soft and hard Coulomb atom models are shown to have more complex structures and to be much stronger than the corresponding HHG spectrum of the ground state of the soft Coulomb model with $\alpha=2$ in the same laser field. Laser-induced non-resonant one-photon emission is also observed.

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Ab initio calculations on the spectroscopic constants, vibrational levels and classical turning points for the 21$\Pi$u state of dimer 7Li2 Liu Yu-Fang(刘玉芳), Sun Jin-Feng(孙金锋), Ma Heng(马恒), and Zhu Zun-Lue(朱遵略) Chinese Physics, 2007, 16 (3):  680-685.  DOI: 10.1088/1009-1963/16/3/021 Abstract ( 1598 )   PDF (210KB) ( 641 )   The accurate dissociation energy and harmonic frequency for the highly excited 21$\Pi$u state of dimer 7Li2 have been calculated using a symmetry-adapted-cluster configuration-interaction method in complete active space. The calculated results are in excellent agreement with experimental measurements. The potential energy curves at numerous basis sets for this state are obtained over a wide internuclear separation range from about 2.4a0 to 37.0a0. And the conclusion is gained that the basis set 6-311++G(d,p) is a most suitable one. The calculated spectroscopic constants De, Re, $\omega$e,  $\omega$e$\chi$e, $\alpha$e and Be at 6-311++G(d,p) are 0.9670 eV, 0.3125 nm, 238.6 cm-1, 1.3705 cm-1, 0.0039 cm-1 and 0.4921 cm-1, respectively. The vibrational levels are calculated by solving the radial Schr?dinger equation of nuclear motion. A total of 53 vibrational levels are found and reported for the first time. The classical turning points have been computed. Comparing with the measurements, in which only the first nine vibrational levels have been obtained so far, the present calculations are very encouraging. A careful comparison of the present results of the parameters De and $\omega$e with those obtained from previous theories clearly shows that the present calculations are much closer to the measurements than previous theoretical results, thus representing an improvement on the accuracy of the ab initio calculations of the potentials for this state.

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Spin polarization effect for Mn2 molecule Yan Shi-Ying(阎世英) and Xu Guo-Liang(徐国亮) Chinese Physics, 2007, 16 (3):  686-691.  DOI: 10.1088/1009-1963/16/3/022 Abstract ( 1549 )   PDF (367KB) ( 694 )   The density functional theory method (DFT) (b3p86) of Gaussian 03 has been used to optimize the structure of the Mn2 molecule. The result shows that the ground state of the Mn2 molecule is an 11-multiple state, indicating a spin polarization effect in the Mn2 molecule, a transition metal element molecule. Meanwhile, we have not found any spin pollution because the wavefunction of the ground state does not mingle with wavefunctions of higher-energy states. So the ground state for Mn2 molecule being of an 11-multiple state is the indicative of spin polarization effect of the Mn2 molecule among those in the transition metal elements: that is, there are 10 parallel spin electrons in a Mn2 molecule. The number of non-conjugated electrons is the greatest. These electrons occupy different spacious orbitals so that the energy of the Mn2 molecule is minimized. It can be concluded that the effect of parallel spin in the Mn2 molecule is larger than the effect of the conjugated molecule, which is obviously related to the effect of electron d delocalization. In addition, the Murrell--Sorbie potential functions with the parameters for the ground state and other states of the Mn2 molecule are derived. The dissociation energy De for the ground state of the Mn2 molecule is 1.4477eV, equilibrium bond length Re is 0.2506nm, vibration frequency $\omega$e is 211.51cm-1. Its force constants f2, f3, and f4 are 0.7240aJ$\cdot$nm-2, -3.35574aJ$\cdot$nm-3, 11.4813aJ$\cdot$nm-4 respectively. The other spectroscopic data for the ground state of the Mn2 molecule $\omega$e$\chi$e, Be, $\alpha$e are 1.5301 cm-1, 0.0978 cm-1, 7.7825$\times$ 10-4cm-1 respectively.

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The closed-orbit and the photoabsorption spectra of the Rydberg hydrogen atom between two parallel metallic surfaces Wang De-Hua(王德华) Chinese Physics, 2007, 16 (3):  692-699.  DOI: 10.1088/1009-1963/16/3/023 Abstract ( 1354 )   PDF (293KB) ( 658 )   Using the closed orbit theory, we study the classical motion and calculate the photoabsorption spectra of Rydberg hydrogen atom between two parallel metallic surfaces. The results show that the metallic surfaces have a significant effect on the photoabsorption process. When the distances between the hydrogen atom and the two metallic surfaces are close to a critical value dc, the number of the closed orbits is the greatest. When the distance larger or smaller than dc, the number of the closed orbits decreases and the absorption spectra are shown to exhibit a damping oscillation. This work is an interesting new application of closed-orbit theory and is of potential experimental interest.

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Ab initio calculations for the absorption spectra and polarizabilities of small sulfur clusters Bai Yu-Lin(白玉林), Chen Xiang-Rong(陈向荣), Cheng Xiao-Hong(程晓洪), and Yang Xiang-Dong(杨向东) Chinese Physics, 2007, 16 (3):  700-706.  DOI: 10.1088/1009-1963/16/3/024 Abstract ( 1818 )   PDF (180KB) ( 832 )   Absorption spectra for Sn clusters ($n=2\ldots8$) are calculated using an adiabatic time-dependent density functional formalism within the local density approximation (LDA). We compare the calculated spectra with those computed using a simple LDA approach. The time-dependent LDA (TDLDA) spectra display a significant blue shift with respect to the LDA spectra. The calculated spectra present a variety of features that can be used for comparison with future experimental investigations. We also obtain a significant threshold absorption, which can distinguish between different ground states of the sulfur clusters. In addition, the polarizabilities of the clusters are calculated by using the higher-order finite-difference pseudopotential density functional method in real space. We find that the polarizabilities of the clusters considered are higher than the value estimated from the `hard sphere' model using the bulk static dielectric constant. The computed polarizabilities per atom tend to decrease with increasing cluster size. The polarizabilities are closely related to the HOMO--LUMO gaps and the geometrical configurations.

CLASSICAL AREAS OF PHENOMENOLOGY

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Electrostatic surface guiding of cold polar molecules with a single charged wire Deng Lian-Zhong(邓联忠), Xia Yong(夏勇), and Yin Jian-Ping(印建平) Chinese Physics, 2007, 16 (3):  707-717.  DOI: 10.1088/1009-1963/16/3/025 Abstract ( 1552 )   PDF (1390KB) ( 641 )   This paper proposes a scheme to guide cold polar molecules by using a single charged wire half embanked in an insulating substrate and a homogeneous bias electric field, which is generated by a plate capacitor composed of two infinite parallel metal plates. The spatial distributions of the electrostatic field produced by the combination of the charged wire and the plate capacitor and the corresponding Stark potentials (including dipole forces) for metastable CO molecules are calculated, the relationships between the electric field and the parameters of our charged-wire layout are analysed. It also studies the influences of the insulator on the electric field distribution and the discharge effect. This study shows that the proposed scheme can be used to guide cold polar molecules in the weak-field -- seeking states, and to form various molecule-optical elements, such as molecular funnel, molecular beam-splitters and molecule interferometer, even to construct a variety of integrated molecule-optical elements and their molecule chips.

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Phase control in an open $\varLambda$-type system with spontaneously generated coherence Cui Ni(崔妮), Fan Xi-Jun(樊锡君), Li Ai-Yun(李爱云), Liu Cheng-Pu(刘呈普), Gong Shang-Qing(龚尚庆), and Xu Zhi-Zhan(徐至展) Chinese Physics, 2007, 16 (3):  718-724.  DOI: 10.1088/1009-1963/16/3/026 Abstract ( 1755 )   PDF (192KB) ( 573 )   This paper investigates the control role of the relative phase between the probe and driving fields on the gain, dispersion and populations in an open $\varLambda$ system with spontaneously generated coherence (SGC). It shows that by adjusting the value of the relative phase, a change from lasing with inversion to lasing without inversion can be realized; the values and frequency spectrum regions of the inversionless gain and dispersion can be obviously varied; high refractive index with zero absorption and electromagnetically induced transparency can be achieved. It is also found that when the driving field is resonant, the shapes of the dispersion and the gain curves versus the probe detuning are very similar if the relative phase of the dispersion lags $\pi/2$  than that of the gain, however for the off-resonant driving field the similarity will disappear; the gain, dispersion and populations are periodical functions of the relative phase, the modulation period is always $2\pi$; the contribution of SGC to the inversionless gain and dispersion is much larger than that of the dynamically induced coherence.

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Low-dimensional structures formed by irradiation of laser Huang Wei-Qi(黄伟其), Liu Shi-Rong(刘世荣), Xu Li(许丽), Wu Ke-Yue(吴克跃), Qin Cao-Jian(秦朝建), and Cai Sao-Hong(蔡绍洪) Chinese Physics, 2007, 16 (3):  725-729.  DOI: 10.1088/1009-1963/16/3/027 Abstract ( 1536 )   PDF (2028KB) ( 811 )   Some kinds of low-dimensional nanostructures can be formed by irradiation of laser on the pure silicon sample and the SiGe alloy sample. This paper has studied the photoluminescence (PL) of the hole-net structure of silicon and the porous structure of SiGe where the PL intensity at 706nm and 725nm wavelength increases obviously. The effect of intensity-enhancing in the PL peaks cannot be explained within the quantum confinement alone. A mechanism for increasing PL emission in the above structures is proposed, in which the trap states of the interface between SiO2 and nanocrystal play an important role.

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Significant improvement of OLED efficiency and stability by doping both HTL and ETL with different dopant in heterojunction of polymer/small-molecules Nie Hai(聂海), Zhang Bo(张波), and Tang Xian-Zhong(唐先忠) Chinese Physics, 2007, 16 (3):  730-734.  DOI: 10.1088/1009-1963/16/3/028 Abstract ( 1927 )   PDF (158KB) ( 2568 )   This paper reports that the polymer/organic heterojunction doped light-emitting diodes using a novel poly-TPD as hole transport material and doping both hole transport layer and emitter layer with the highly fluorescent rubrene and DCJTB has been successfully fabricated. The basic structure of the heterostructure is PTPD/Alq3. When hole transport layer and electron transport layer are doped simultaneously with different dopant, the electroluminescence quantum efficiencies are about 3 times greater than that of the undoped device. Compared with undoped device and conventional TPD/Alq3 diode, the stability of the doping device is significantly improved. The process of emission for doped device may include carrier trapping as well as F?rster energy transfer.

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Phenomena of optic-bound effect on fibre optic gyro Song Ning-Fang(宋凝芳), Zhang Chun-Xi(张春熹), and Jin Jing(金靖) Chinese Physics, 2007, 16 (3):  735-739.  DOI: 10.1088/1009-1963/16/3/029 Abstract ( 1446 )   PDF (173KB) ( 756 )   The optic-bound effect on fibre optic gyro (FOG) precision is analysed theoretically, and formulas describing the change of FOG light power under the action of optic-bound effect are given. It is confirmed that optic-bound effect is a main instantaneous non-reciprocity effect of FOG in addition to the Sagnac effect and can lead to a dynamic error of FOG in practical environments. An approach to suppressing or eliminating the error due to the optic-bound effect is presented and verified experimentally. The result shows that the approach is valid and the precision of FOG is improved observably.

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Steering light into logic patterns with two-dimensional cascaded multimode waveguide Zhou Hai-Feng(周海峰), Yang Jian-Yi(杨建义), Wang Ming-Hua(王明华), and Jiang Xiao-Qing(江晓清) Chinese Physics, 2007, 16 (3):  740-745.  DOI: 10.1088/1009-1963/16/3/030 Abstract ( 1526 )   PDF (571KB) ( 719 )   Steering light into logic patterns with two-dimensional cascaded multimode waveguide is demonstrated. By employing the imaging properties of 2D multimode interference (MMI) and partial phase modulation method, the design ideas and the implementing methods of the 2(2×2) bits type spatial logic steering are discussed; therefore the structure of logical pattern is proposed. Numerical simulation is carried out to verify the design in detail by using the beam propagation method. It is expected to realize logic coders by using the integrated optical methods and exploit their potential applications in the field of optical logic.

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Acousto-electric well logging by eccentric source and extraction of shear wave Cui Zhi-Wen(崔志文), Wang Ke-Xie(王克协), Hu Heng-Shan(胡恒山), and Sun Jian-Guo(孙建国) Chinese Physics, 2007, 16 (3):  746-752.  DOI: 10.1088/1009-1963/16/3/031 Abstract ( 1732 )   PDF (204KB) ( 715 )   The nonaxisymmetric acousto-electric field excited by an eccentric acoustic source in the borehole based on Pride seismoelectric theory is considered. It is shown that the acoustic field inside the borehole, converted electric and magnetic fields and coupled fields outside the borehole are composed of an infinitude of multipole fields with different orders. The numerical results show that both the electromagnetic waves and the seismoelectric field in the borehole, and the three components of both electric field and magnetic field can be detected. Measurements on the borehole axis will be of advantage to determining shear velocity information. The components of the symmetric and nonsymmetric acoustic and electromagnetic fields can be strengthened or weakened by adding or subtracting the two full waveforms logged in some azimuths. It may be a new method of directly measuring the shear wave velocity by using the borehole seismoelectric effect.

PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

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Statistical analysis of aggregation in freeway traffic Li Jun-Wei(李俊卫), Lin Bo-Liang(林柏梁), and Huang Yong-Chang(黄永畅) Chinese Physics, 2007, 16 (3):  753-757.  DOI: 10.1088/1009-1963/16/3/032 Abstract ( 1682 )   PDF (129KB) ( 658 )   We restudy the master-equation approach to aggregation in freeway traffic based on the theory of birth--death process, in which the clustering behaviour in one-lane freeway traffic model is investigated. The transition probabilities for the jump processes are reconstructed by using Greenshields' model, and the equation of the mean size of the cluster at any time t is derived from the birth--death equation. Numerical experiments show the clustering behaviours varying with time very well.

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Review of relaxation oscillations in plasma processing discharges Zhou Zhu-Wen(周筑文), M. A. Lieberman, and Sungjin Kim Chinese Physics, 2007, 16 (3):  758-765.  DOI: 10.1088/1009-1963/16/3/033 Abstract ( 1510 )   PDF (620KB) ( 819 )   Relaxation oscillations due to plasma instabilities at frequencies ranging from a few Hz to tens of kHz have been observed in various types of plasma processing discharges. Relaxation oscillations have been observed in electropositive capacitive discharges between a powered anode and a metallic chamber whose periphery is grounded through a slot with dielectric spacers. The oscillations of time-varying optical emission from the main discharge chamber show, for example, a high-frequency ($\sim$  40 kHz) relaxation oscillation at 13.33Pa, with an absorbed power being nearly the peripheral breakdown power, and a low-frequency ($\sim$  3 Hz) oscillation, with an even higher absorbed power. The high-frequency oscillation is found to ignite plasma in the slot, but usually not in the peripheral chamber. The kilohertz oscillations are modelled using an electromagnetic model of the slot impedance, coupled to a circuit analysis of the system including the matching network. The model results are in general agreement with the experimental observations, and indicate a variety of behaviours dependent on the matching conditions. In low-pressure inductive discharges, oscillations appear in the transition between low-density capacitively driven and high-density inductively driven discharges when attaching gases such as SF6 and Ar/SF6 mixtures are used. Oscillations of charged particles, plasma potential, and light, at frequencies ranging from a few Hz to tens of kHz, are seen for gas pressures between 0.133 Pa and 13.33 Pa and discharge powers in a range of 75--1200 W. The region of instability increases as the plasma becomes more electronegative, and the frequency of plasma oscillation increases as the power, pressure, and gas flow rate increase. A volume-averaged (global) model of the kilohertz instability has been developed; the results obtained from the model agree well with the experimental observations.

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Theoretical analysis of a relativistic travelling wave tube filled with plasma Xie Hong-Quan(谢鸿全) and Liu Pu-Kun(刘濮鲲) Chinese Physics, 2007, 16 (3):  766-771.  DOI: 10.1088/1009-1963/16/3/034 Abstract ( 1579 )   PDF (864KB) ( 914 )   A cold and uniform plasma-filled travelling wave tube with sinusoidally corrugated slow wave structure is driven by a finite thick annular intense relativistic electron beam with the entire system immersed in a strong longitudinal magnetic field. By means of the linear field theory, the dispersion relation for the relativistic travelling wave tube (RTWT) is derived. By numerical computation, the dispersion characteristics of the RTWT are analysed in different cases of various geometric parameters of the slow wave structure and plasma densities. Also the gain versus frequency for three different plasma densities and the peak gain of the tube versus plasma density are analysed. Some useful results are obtained on the basis of the discussion.

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Experimental study on imploding characteristics of wire-array Z pinches on Qiangguang-1 facility Wang Zhen(王真), Xu Rong-Kun(徐荣昆), Yang Jian-Lun(杨建伦), Hua Xin-Sheng(华欣生), Li Lin-Bo(李林波), Xu Ze-Ping(许泽平), Ning Jia-Min(宁家敏), and Song Feng-Jun(宋凤军) Chinese Physics, 2007, 16 (3):  772-777.  DOI: 10.1088/1009-1963/16/3/035 Abstract ( 1565 )   PDF (481KB) ( 717 )   To investigate the imploding characteristics of cylindrical wire array, experiments with load current varying from 1.5 MA to 1.7 MA were carried out on the Qiangguang-1 facility. The complicated temporal-spatial distribution of x-ray radiation was measured by the one-dimensional (1D) x-ray imaging system. Other diagnostic equipments including the x-ray power meter (XRPM) and the time-integrated pinhole camera were used to record time-resolved x-ray power pulse and pinhole x-ray images. Analysis shows that the fast leading edge of the local x-ray radiation pulse is of primary importance in sharpening x-ray power pulse rather than the temporal synchrony and the spatial uniformity of implosion. Experimental results indicated that the better axial imploding synchrony, the faster the increase of x-ray power for an array consisting of 32 tungsten wires of 5$\mu$m diameter than for the others, and the higher the x-ray radiation power with maximal convergence ratio ($r_0/r_1$) of 10.5. A `zipper-like' effect of x-ray radiation extending from the anode to the cathode was also observed.

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Experimental study of polarity dependence in repetitive nanosecond-pulse breakdown Shao Tao(邵涛), Sun Guang-Sheng(孙广生), Yan Ping(严萍), Wang Jue(王珏), Yuan Wei-Qun(袁伟群), and Zhang Shi-Chang(张适昌) Chinese Physics, 2007, 16 (3):  778-783.  DOI: 10.1088/1009-1963/16/3/036 Abstract ( 1575 )   PDF (658KB) ( 741 )   Pulsed breakdown of dry air at ambient pressure has been investigated in the point-plane geometry, using repetitive nanosecond pulses with 10 ns risetime, 20--30 ns duration, and up to 100 kV amplitude. A major concern in this paper is to study the dependence of breakdown strength on the point-electrode polarity. Applied voltage, breakdown current and repetitive stressing time are measured under the experimental conditions of some variables including pulse voltage peak, gap spacing and repetition rate. The results show that increasing the E-field strength can decrease breakdown time lag, repetitive stressing time and the number of applied pulses as expected. However, compared with the traditional polarity dependence it is weakened and not significant in the repetitive nanosecond-pulse breakdown. The ambiguous polarity dependence in the experimental study is involved with an accumulation effect of residual charges and metastable states. Moreover, it is suggested that the reactions associated with the detachment of negative ions and impact deactivation of metastable species could provide a source of primary initiating electrons for breakdown.

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES

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Determination of the sites of Fe atoms in Fe-substituted Mn12 Cao Hui-Bo(曹慧波), Chen Dong-Liang(陈栋梁), He Lun-Hua(何伦华), Zhang Jun-Rong(张俊荣), Wang Fang-Wei(王芳卫), Wu Zi-Yu(吴自玉), and Yan Qi-Wei(严启伟) Chinese Physics, 2007, 16 (3):  784-787.  DOI: 10.1088/1009-1963/16/3/037 Abstract ( 1473 )   PDF (410KB) ( 680 )   In this paper neutron diffraction experiments were performed for Fe-substituted Mn12 in order to determine the sites of Fe atoms. The results of structure refinements for the sample with our accessed highest Fe content showed that all Fe atoms occupied Mn(3) sites in the Mn12 skeleton. The x-ray absorption fine structure experiments as well as multiple scattering simulations gave the same result. Thus we concluded that Fe atoms only occupied Mn(3) sites. This conclusion also means that Fe-substituted Mn12 series only includes the four single-molecule magnets of [Mn12-xFexO12(CH3COO)16(H2O)4]$\cdot$ 2CH3COOH$\cdot$ 4H2O (x = 1, 2, 3, and 4), denoted by Mn11Fe1, Mn10Fe2, Mn9Fe3, and Mn8Fe4, respectively.

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Composition-induced structural modifications in the quaternary CuIn1-xGaxSe2 thin films:bond properties versus Ga content Xu Chuan-Ming(徐传明), Sun Yun(孙云), Li Feng-Yan(李凤岩), Zhang Li(张力), Xue Yu-Ming(薛玉明), He Qing(何青), and Liu Hong-Tu(刘洪图) Chinese Physics, 2007, 16 (3):  788-794.  DOI: 10.1088/1009-1963/16/3/038 Abstract ( 1668 )   PDF (220KB) ( 1348 )   In this paper the dependence of structural properties of the quaternary CuIn1-xGaxSe2 films with tetragonal structure on the Ga content has been systematically investigated by Raman scattering and x-ray diffraction spectra. The shift of the dominant A1 mode, unlike the lattice constants, does not follow the linear Vegard law with increasing Ga content x, whereas exhibits approximately polynomial change from 174 cm-1 for CuInSe2 to 185cm-1 for CuGaSe2. Such behaviour should be indicative of presence of the asymmetric distribution of Ga and In on a microscopic scale in the films, due to Ga addition. The changes in the tetragonal distortion $\eta$ lead to a significant variation in the anion displacement parameter $U$, which should be responsible for the evolution of bond parameters and resultant Raman bands with $x$.

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Charge storage characteristics of hydrogenated nanocrystalline silicon film prepared by rapid thermal annealing Li Zhi-Gang(李志刚), Long Shi-Bing(龙世兵), Liu Ming(刘明), Wang Cong-Shun(王丛舜), Jia Rui(贾锐), Lv Jin(闾锦), and Shi Yi(施毅) Chinese Physics, 2007, 16 (3):  795-798.  DOI: 10.1088/1009-1963/16/3/039 Abstract ( 1854 )   PDF (760KB) ( 665 )   The early stages of hydrogenated nanocrystalline silicon (nc-Si:H) films deposited by plasma-enhanced chemical vapour deposition were characterized by atomic force microscopy. To increase the density of nanocrystals in the nc-Si:H films, the films were annealed by rapid thermal annealing (RTA) at different temperatures and then analysed by Raman spectroscopy. It was found that the recrystallization process of the film was optimal at around 1000℃. The effects of different RTA conditions on charge storage were characterized by capacitance--voltage measurement. Experimental results show that nc-Si:H films obtained by RTA have good charge storage characteristics for nonvolatile memory.

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The microwave response of MgB2/Al2O3 superconducting thin films Shi Li-Bin(史力斌), Wang Yun-Fei(王云飞), Ke Yu-Yang(柯于洋), Zhang Guo-Hua(张国华), Luo Sheng(罗胜), Zhang Xue-Qiang(张雪强), Li Chun-Guang(李春光), Li Hong(黎红), He Yu-Sheng(何豫生), Yu Zeng-Qiang(于增强), and Wang Fu-Ren(王福仁) Chinese Physics, 2007, 16 (3):  799-804.  DOI: 10.1088/1009-1963/16/3/040 Abstract ( 1778 )   PDF (579KB) ( 728 )   Microwave characteristics of MgB2/2O3 superconducting thin films were investigated by coplanar resonator technique. The thin films studied have different grain sizes resulting from different growth techniques. The experimental results can be described very well by a grain-size model which combines coplanar resonator theory and Josephson junction network model. It was found that the penetration depth and surface resistance of thin films with smaller grain sizes are larger than those of thin films with larger grain sizes.

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Investigation on stability of directionally solidified CBr4--C2Cl6 lamellar eutectic by using multiphase field simulation Zhu Yao-Chan(朱耀产), Wang Jin-Cheng(王锦程), Yang Gen-Cang(杨根仓), and Zhao Da-Wen(赵达文) Chinese Physics, 2007, 16 (3):  805-811.  DOI: 10.1088/1009-1963/16/3/041 Abstract ( 1508 )   PDF (1161KB) ( 840 )   With the multiphase field method, the stability of lamellar basic state is investigated during the directional solidification of eutectic alloy CBr4--C2Cl6. A great number of lamellar patterns observed in experiments are simulated, and a stability diagram for lamellar pattern selections is presented. The simulated growth behaviours of these patterns are found to be qualitatively consistent with Karma et al's numerical calculations and experimental results. The formation of the primary instability is attributed to the destabilization of solute boundary layer.

CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

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Corner effects in double-gate/gate-all-around MOSFETs Hou Xiao-Yu(侯晓宇), Zhou Fa-Long(周发龙), Huang Ru(黄如), and Zhang Xing(张兴) Chinese Physics, 2007, 16 (3):  812-816.  DOI: 10.1088/1009-1963/16/3/042 Abstract ( 1660 )   PDF (652KB) ( 808 )   Two kinds of corner effects existing in double-gate (DG) and gate-all-around (GAA) MOSFETs have been investigated by three-dimensional (3D) and two-dimensional (2D) simulations. It is found that the corner effect caused by conterminous gates, which is usually deemed to deteriorate the transistor performance, does not always play a negative role in GAA transistors. It can suppress the leakage current of transistors with low channel doping, though it will enhance the leakage current at high channel doping. The study of another kind of corner effect, which exists in the corner at the bottom of the silicon pillar of DG/GAA vertical MOSFETs, indicates that the D-top structure with drain on the top of the device pillar of vertical transistor shows great advantage due to lower leakage current and better DIBL (drain induced barrier lowering) effect immunity than the S-top structure with source on the top of the device pillar. Therefore the D-top structure is more suitable when the requirement in leakage current and short channel character is critical.

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Comparison of two kinds of active layers for high-power narrow-stripe distributed feedback laser diodes Fu Sheng-Hui(付生辉), Song Guo-Feng(宋国峰), and Chen Liang-Hui(陈良惠) Chinese Physics, 2007, 16 (3):  817-820.  DOI: 10.1088/1009-1963/16/3/043 Abstract ( 1697 )   PDF (148KB) ( 824 )   Usually GaAs/AlGaAs is utilized as an active layer material in laser diodes operating in the spectral range of 800--850 nm. In this work, in addition to a traditional unstrained GaAs/AlGaAs distributed feedback (DFB) laser diode, a compressively strained InGaAlAs/AlGaAs DFB laser diode is numerically investigated in characteristic. The simulation results show that the compressively strained DFB laser diode has a lower transparency carrier density, higher gain, lower Auger recombination rate, and higher stimulated recombination rate, which lead to better a device performance, than the traditional unstrained GaAs/AlGaAs DFB laser diode.

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Hot-carrier degradation for 90nm gate length LDD-NMOSFET with ultra-thin gate oxide under low gate voltage stress Chen Hai-Feng(陈海峰), Hao Yue(郝跃), Ma Xiao-Hua(马晓华), Li Kang(李康), and Ni Jin-Yu(倪金玉) Chinese Physics, 2007, 16 (3):  821-825.  DOI: 10.1088/1009-1963/16/3/044 Abstract ( 1697 )   PDF (489KB) ( 757 )   The hot-carrier degradation for 90~nm gate length lightly-doped drain (LDD) NMOSFET with ultra-thin (1.4 nm) gate oxide under the low gate voltage (LGV) (at Vg=Vth, where Vth is the threshold voltage) stress has been investigated. It is found that the drain current decreases and the threshold voltage increases after the LGV (Vg=Vth stress. The results are opposite to the degradation phenomena of conventional NMOSFET for the case of this stress. By analysing the gate-induced drain leakage (GIDL) current before and after stresses, it is confirmed that under the LGV stress in ultra-short gate LDD-NMOSFET with ultra-thin gate oxide, the hot holes are trapped at interface in the LDD region and cannot shorten the channel to mask the influence of interface states as those in conventional NMOSFET do, which leads to the different degradation phenomena from those of the conventional NMOS devices. This paper also discusses the degradation in the 90 nm gate length LDD-NMOSFET with 1.4 nm gate oxide under the LGV stress at Vg=Vth with various drain biases. Experimental results show that the degradation slopes (n) range from 0.21 to 0.41. The value of n is less than that of conventional MOSFET (0.5-0.6) and also that of the long gate length LDD MOSFET ($\sim$0.8).

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The upper critical field in two-band layered superconductors Liu Min-Xia(刘敏霞) and Gan Zi-Zhao(甘子钊) Chinese Physics, 2007, 16 (3):  826-833.  DOI: 10.1088/1009-1963/16/3/045 Abstract ( 1861 )   PDF (196KB) ( 703 )   The upper critical field of clean MgB2 is investigated using the two-band layered Ginzburg--Landau (GL) theory. The calculated results are fitted to the experimental data of clean MgB2 crystal very well in a broad temperature range. Based on the GL theory for clean superconductors, a phenomenological theory for dirty superconductor is proposed. Selecting appropriate parameters, two-band layered GL theory is successfully applied to the crystal of Mg(B1-xCx)2 and the neutron irradiation samples of MgB2.

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Energy spectrum and entanglement of two tunnel- coupled Bose--Einstein condensates Cheng Rong(程茸) and Liang Jiu-Qing(梁九卿) Chinese Physics, 2007, 16 (3):  834-839.  DOI: 10.1088/1009-1963/16/3/046 Abstract ( 1653 )   PDF (123KB) ( 647 )   This paper obtains the energy-spectrum and eigenstate corrections of two-mode Bose--Einstein condensates (BECs) coupled by quantum tunnelling by perturbation method in both strong and weak tunnelling regions. The population imbalance between two BECs are then studied in terms of the low-lying eigenstates which also characterize the intrinsic entanglement between the two-mode BECs. The strong parity effect in the weak tunnelling region is also investigated.

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Reversal transient laser-induced voltages in La2/3Ca1/3MnO3 films Zhao Kun(赵昆), He Meng(何萌), and LüHui-Bin(吕惠宾) Chinese Physics, 2007, 16 (3):  840-842.  DOI: 10.1088/1009-1963/16/3/047 Abstract ( 1672 )   PDF (448KB) ( 631 )   This paper reports that the transient laser-induced voltages have been observed in La2/3Ca1/3MnO3 thin films on MgO (001) in the absence of an applied current. A peak voltage of $\sim$ 0.15 V was detected in response to 0.015 J pulse of 308 nm laser. It is demonstrated that the signal polarity is reversed when the films are irradiated through the substrate rather than at the air/film interface. Off-diagonal thermoelectricity may support the inversion of the signal when the irradiation direction is reversed.

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Electron emission degradation of nano-structured sp2-bonded amorphous carbon films Lu Zhan-Ling(鲁占灵), Wang Chang-Qing(王昶清), Jia Yu(贾瑜), Zhang Bing-Lin(张兵临), and Yao Ning(姚宁) Chinese Physics, 2007, 16 (3):  843-847.  DOI: 10.1088/1009-1963/16/3/048 Abstract ( 1591 )   PDF (371KB) ( 715 )   The initial field electron emission degradation behaviour of original nano-structured sp2-bonded amorphous carbon films has been observed, which can be attributed to the increase of the work function of the film in the field emission process analysed using a Fowler--Nordheim plot. The possible reason for the change of work function is suggested to be the desorption of hydrogen from the original hydrogen termination film surface due to field emission current-induced local heating.For the explanation of the emission degradation behaviour of the nano-structured sp2-bonded amorphous carbon film, a cluster model with a series of graphite (0001) basal surfaces has been presented, and the theoretical calculations have been performed to investigate work functions of graphite (0001) surfaces with different hydrogen atom and ion chemisorption sites by using first principles method based on density functional theory-local density approximation.

CROSS DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

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Characterization of doped hydrogenated nanocrystalline silicon films prepared by plasma enhanced chemical vapour deposition Wang Jin-Liang(王金良) and Wu Er-Xing(毋二省) Chinese Physics, 2007, 16 (3):  848-853.  DOI: 10.1088/1009-1963/16/3/049 Abstract ( 1669 )   PDF (378KB) ( 602 )   The B- and P-doped hydrogenated nanocrystalline silicon films (nc-Si:H) are prepared by plasma-enhanced chemical vapour deposition (PECVD). The microstructures of doped nc-Si:H films are carefully and systematically characterized by using high resolution electron microscopy (HREM), Raman scattering, x-ray diffraction (XRD), Auger electron spectroscopy (AES), and resonant nucleus reaction (RNR). The results show that as the doping concentration of PH3 increases, the average grain size (d) tends to decrease and the crystalline volume percentage (Xc) increases simultaneously. For the B-doped samples, as the doping concentration of B2H6 increases, no obvious change in the value of d is observed, but the value of Xc is found to decrease. This is especially apparent in the case of heavy B2H2 doped samples, where the films change from nanocrystalline to amorphous.

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Dynamic scaling behaviour of late-stage phase separation in Ni75AlxV25-x alloys Li Yong-Sheng(李永胜), Chen Zheng(陈铮), Lu Yan-Li(卢艳丽), and Xu Guo-Dong(徐国栋) Chinese Physics, 2007, 16 (3):  854-861.  DOI: 10.1088/1009-1963/16/3/050 Abstract ( 1395 )   PDF (974KB) ( 571 )   The dynamic scaling behaviour of late-stage phase separation and coarsening mechanisms of L12 and D022 in Ni75AlxV25-x ($3 \leq x \leq 10$, at.%) alloys are studied using the microscopic phase-field dynamic model. The microelasticity field is incorporated into the diffusion dynamic model. The results show the morphology and coarsening dynamics being greatly changed by the elastic interactions among different precipitates, the particles aligning along the dominant directions, the average domain size (ADS) of L12 and D022 deviating from the exponent of temporal power-law, and the growth slowing down due to the increasing of elastic interactions. The dynamic scaling regime of late-stage coarsening of the precipitates is attained. Thus the scaling behaviour of structure function is also applicable for elastic interaction systems. It is also found that the variations of ADS and scaling function depend on the volume fraction of precipitates.

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Direct current hopping conductance along DNA chain Ma Song-Shan(马松山), Xu Hui(徐慧), Liu Xiao-Liang(刘小良), and Li Ming-Jun(李明君) Chinese Physics, 2007, 16 (3):  862-867.  DOI: 10.1088/1009-1963/16/3/051 Abstract ( 1269 )   PDF (151KB) ( 601 )   This paper proposes a model of direct current (DC) electron hopping transport in DNA, in which DNA is considered as a binary one-dimensional disordered system. To quantitatively study the DC conductivity in DNA, it numerically calculates the DC conductivity of DNA chains with different parameter values. The result shows that the DC conductivity of DNA chain increases with the increase of temperature. And the conductivity of DNA chain is depended on the probability $p$, which represents the degree of compositional disorder in a DNA sequence to some extent. For $p<0.5$, the conductivity of DNA chain decreases with the increase of $p$, while for $p\geq0.5$, the conductivity increases with the increase of $p$. The DC conductivity in DNA chain also varies with the change of the electric field, it presents non-Ohm's law conductivity characteristics.

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The preferences of orientations between the pairs of amino acids Chen Ying(陈颖), Wang Jun(王骏), and Wang Wei(王炜) Chinese Physics, 2007, 16 (3):  868-875.  DOI: 10.1088/1009-1963/16/3/052 Abstract ( 1199 )   PDF (936KB) ( 391 )   In this work, we make an investigation on the preferences of orientations between amino acids using the orientation defined based on the local geometry of the amino acids concerned. It is found that there are common preferences of orientations (70°, 30°, 140°) and (110°, 340°, 100°) for various pairs of amino acids. Different side chains may strengthen or weaken the common preferences, which is related to the effect of packing. Some amino acids having specific local flexibility may possess some preferences of orientations besides the common ones, such as (10°, 280°, 210°). Another analysis on the pairs of the amino acids with different secondary-structure preferences shows that the directional interaction may affect the distribution of orientation more effectively than the packing or local flexibility. All these results provide us some insight of the organization of amino acids in protein, and their relation with some related interactions.

GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS

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The parameters of binary black hole system in PKS 1510-089 Li Juan(李娟) Fan Jun-Hui(樊军辉), and Yuan Yu-Hai(袁聿海) Chinese Physics, 2007, 16 (3):  876-880.  DOI: 10.1088/1009-1963/16/3/053 Abstract ( 1553 )   PDF (321KB) ( 671 )   Observations of PKS 1510-089 indicate the existence of a deep flux minimum with a timescale of  $\sim$35 min and an interval of about 336±14 d. A binary black hole system is proposed to be at the nucleus of this object. The secondary black hole orbits around the primary black hole. The minimum is caused by the periodic eclipse of the primary black hole by the secondary black hole. Based on the observations of PKS 1510-089, we estimate the parameters of the binary black hole system. The masses for the primary and secondary black holes are 1. 37×109$M_{\odot}$ ($M_{\odot}$ is the solar mass) and 1. 37 $\times $107$M_{\odot}$, and the major axis for this pair being about 0.1 parsec(pc).