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Volume 27 Issue 6
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Numerical Solution of the Three-Dimensional Helmholtz Equation
Syed Tauseef Mohyud-Din**, Ahmet Yιldιrιm
Chin. Phys. Lett. 2010, 27 (6): 060201 .   DOI: 10.1088/0256-307X/27/6/060201
Abstract   PDF(pc) (1049KB) ( 1130 )

We apply the homotopy analysis method to solve the nonhomogeneous multidimensional partial differential equation model problem. The analytic solutions are calculated in terms of convergent series with easily computable components. The nonhomogeneous problem is quickly solved by observing the self-canceling “noise” terms whose sum vanishes in the limit. Numerical results clearly reveal the complete reliability and efficiency of the proposed algorithm.

A Controlled Phase Gate with Nitrogen-Vacancy Centers in Nanocrystal Coupled to a Silica Microsphere Cavity
XUE Peng
Chin. Phys. Lett. 2010, 27 (6): 060301 .   DOI: 10.1088/0256-307X/27/6/060301
Abstract   PDF(pc) (328KB) ( 510 )

We show how a controlled phase gate, induced by adiabatic passage of dark states, can be implemented with the nitrogen-vacancy defects in nanocrystal coupled to the optical whispering gallery mode in a silica microsphere cavity. The gate presented is robust to the fluctuations of the experimental parameters compared to the dynamical and geometric phases gates. The feasibility of this scheme is characterized by exact numerical simulations that incorporate various sources of experiment noise. The results demonstrate the practicality by way of current experimental technologies.

Late-Time Evolution of the Phantom Scalar Perturbation in the Background of a Spherically Symmetric Static Black Hole
PAN Qi-Yuan, JING Ji-Liang
Chin. Phys. Lett. 2010, 27 (6): 060302 .   DOI: 10.1088/0256-307X/27/6/060302
Abstract   PDF(pc) (275KB) ( 462 )

The late-time evolution of the phantom scalar perturbation is investigated in the spacetime of a four-dimensional spherically symmetric static black hole. It is revealed that the asymptotic tail of the phantom scalar field is dominated by the growth behavior t-(l+3/2)eμt, which depends on the multipole moment l and the field massμ but is independent of the mass M and charge Q of the black hole. This growth behavior is in strong contrast to the decaying tail of the usual massive scalar perturbation and shows that the external phantom scalar perturbation is unstable in the spherically symmetric static black hole spacetime.

Cryptanalysis and Improvement of a Quantum Secret Sharing Protocol between Multiparty and Multiparty with Single Photons and Unitary Transformations
ZHU Zhen-Chao, ZHANG Yu-Qing
Chin. Phys. Lett. 2010, 27 (6): 060303 .   DOI: 10.1088/0256-307X/27/6/060303
Abstract   PDF(pc) (275KB) ( 538 )

In a recent paper [Chin. Phys. Lett 25(2008)1187], a quantum secret sharing scheme between multiparty and multiparty was presented. We show that the protocol is not secure because the last member in Alice's group can illegally obtain most secret messages without introducing any error. Finally, a possible way to avoid the security flaw is suggested.

Network Traffic Anomaly Detection Method Based on a Feature of Catastrophe Theory
YANG Yue, HU Han-Ping, XIONG Wei, CHEN Jiang-Hang
Chin. Phys. Lett. 2010, 27 (6): 060501 .   DOI: 10.1088/0256-307X/27/6/060501
Abstract   PDF(pc) (296KB) ( 622 )

For the existing problems of current network traffic anomaly detection, the behavior of the network traffic anomaly will show nonlinearity, non-stationarity and complexity according to the network traffic often driven by the control of multiple factors. Owing to the characteristic that the internal evolution equation will lead to dynamical structure catastrophe, the phase space reconstruction method and the statistical physics method can be used to compute the macro feature values of the network traffic. By choosing some of the feature values which can obviously reflect the unusual change in the network traffic volume as control variables, a network traffic anomaly detection method based on the catastrophe series theory model is developed. Many experimental results show that the proposed network traffic anomaly detection method has a low false alarm rate under the same condition of detection rate.

Discrete Capability of the Lempel-Ziv Complexity Algorithm on a Vibration Sequence
LI Jian-Kang, SONG Xiang-Rong, YIN Ke
Chin. Phys. Lett. 2010, 27 (6): 060502 .   DOI: 10.1088/0256-307X/27/6/060502
Abstract   PDF(pc) (522KB) ( 488 )

The Lempel-Ziv complexity (LZC) method is used to analyze the acceleration response of the T-shaped plate. The response is converted into symbolic sequences with the multi-segmented coarse-grained method. The LZC of the response of 240 points located in different areas near the center is calculated. The results show that LZC arithmetic applied to elastomer vibration can satisfy the discreteness condition.

Spiking Behavior in Chua's Circuit
JI Ying, BI Qin-Sheng
Chin. Phys. Lett. 2010, 27 (6): 060503 .   DOI: 10.1088/0256-307X/27/6/060503
Abstract   PDF(pc) (454KB) ( 685 )

Chua's circuit with a slow-fast effect is established under certain parameter conditions. The dynamics of this slow-fast system is investigated. A spiking phenomenon can be observed in the numerical simulation. By introducing slow-fast analysis and a generalized Jacobian matrix at the non-smooth boundaries, the bifurcation mechanism for the periodic spiking solution, different from the smooth case, is discussed.

Effect of Correlated Noises in a Genetic Model
Chin. Phys. Lett. 2010, 27 (6): 060504 .   DOI: 10.1088/0256-307X/27/6/060504
Abstract   PDF(pc) (440KB) ( 500 )

The Stratonovich stochastic differential equation is used to analyze genotype selection in the presence of correlated Gaussian white noises. We study the steady state properties of the genotype selection and discuss the effects of the correlated noises. It is found that the degree of correlation of the noises can be used to select one type of genes from another type of mixing genes. The strong selection of genes caused by a large value of multiplicative noise intensity can be weakened by the intensive negative correlation.

Investigation of a Unified Chaotic System and Its Synchronization by Simulations*
WU Qing-Chu, FU Xin-Chu, Michael Small
Chin. Phys. Lett. 2010, 27 (6): 060505 .   DOI: 10.1088/0256-307X/27/6/060505
Abstract   PDF(pc) (369KB) ( 451 )

We investigate a unified chaotic system and its synchronization including feedback synchronization and adaptive synchronization by numerical simulations. We propose a new dynamical quantity denoted by K, which connects adaptive synchronization and feedback synchronization, to analyze synchronization schemes. We find that K can estimate the smallest coupling strength for a unified chaotic system whether it is complete feedback or one-sided feedback. Based on the previous work, we also give a new dynamical method to compute the leading Lyapunov exponent.

Exact Bosonic Solutions of the Truncated Skyrme Model
SHI Chang-Guang, HIRAYAMA Minoru,
Chin. Phys. Lett. 2010, 27 (6): 061101 .   DOI: 10.1088/0256-307X/27/6/061101
Abstract   PDF(pc) (508KB) ( 399 )

A model defined by half the Lagrangian (the highly nonlinear part) of the Skyrme model is investigated. Two classes of bosonic solutions are obtained. It is shown that, although the field configurations of these two classes are different, the energy densities for the two classes take the same form.

Light Flavor Vector and Pseudo Vector Mesons from a Light-Cone QCD Inspired Effective Hamiltonian Model with SU(3) Flavor Mixing Interactions
GUO Xiao-Bo, TAO Jun, LI Lei, WANG Shun-Jin,
Chin. Phys. Lett. 2010, 27 (6): 061201 .   DOI: 10.1088/0256-307X/27/6/061201
Abstract   PDF(pc) (345KB) ( 557 )

Based on the light-cone effective Hamiltonian with confining potential and SU(3) flavor mixing interactions, the flavor mixing mesons on the u, d, and s quark sectors are investigated. The mass eigen equations of the flavor mixing vector and pseudo vector mesons are solved. The calculated masses are in good agreement with the experimental data.

Ideal Mixing of Scalar Mesons and Hyperon-Nucleon Interaction
DAI Lian-Rong
Chin. Phys. Lett. 2010, 27 (6): 061301 .   DOI: 10.1088/0256-307X/27/6/061301
Abstract   PDF(pc) (462KB) ( 424 )

The mixing of scalar mesons is an open problem since their structure is unclear and controversial. By introducing the ideal mixing of scalar mesons, we dynamically investigate the hyperon-nucleon interaction in the chiral SU(3) quark model by solving the resonating group method (RGM) equation. The results show that when the ideal mixing of scalar mesons is considered and the mass of a κ meson is reduced to near 780 MeV, then the hyperon-nucleon scattering data can be reasonably described in the chiral SU(3) quark model. Hence we find that the experimental mass of the κ meson is around 780 MeV, and f0(600) and f0(980) mesons are the ideal mixing of scalar singlet and octet mesons.

Experimental Prospects of the B_c Studies of the LHCb Experiment
GAO Yuan-Ning, , HE Ji-Bo, , Patrick Robbe, Marie-HéléneSchune, YANG Zhen-Wei,
Chin. Phys. Lett. 2010, 27 (6): 061302 .   DOI: 10.1088/0256-307X/27/6/061302
Abstract   PDF(pc) (387KB) ( 596 )

The experimental prospects of the Bc studies of the LHCb experiment are discussed. Production rates of Bc mesons at different center-of-mass energies are estimated with the dedicated generator BCVEGPY. Theoretical estimates and experimental measurements of the inclusive production cross section at =1.96 TeV are compared. The possibilities of studying Bc production, Bc spectroscopy, Bc decays and CP violation in Bc decays in the LHCb experiment are evaluated.

Description of the Triaxial Strongly Deformed Bands in 160,161Tm and 163Tm
ZHANG Da-Li, DING Bin-Gang
Chin. Phys. Lett. 2010, 27 (6): 062101 .   DOI: 10.1088/0256-307X/27/6/062101
Abstract   PDF(pc) (394KB) ( 468 )

Properties of the triaxial strongly deformed (TSD) bands of 160,161Tm and 163Tm are investigated systematically within the supersymmetry scheme including many-body interactions and a perturbation possessing SO(5)(or SU(5)) symmetry on the rotational symmetry. Quantitatively good results of the γ-ray energies, the dynamical moments of inertia and the spin of the TSD bands in 160,161Tm and 163Tm are obtained. The calculation shows that competition between the pairing and anti-pairing effects exist in these TSD bands. Meanwhile, the SU(3) symmetry in TSD bands is broken more seriously than that in superdeformed bands.

Relativistic Mean Field Study of the Z=117 Isotopic Chain
GAO Yuan, ZHANG Hong-Fei, ZHANG Lei, CHEN Xi-Meng, LI Jun-Qing, GUO Wen-Jun
Chin. Phys. Lett. 2010, 27 (6): 062102 .   DOI: 10.1088/0256-307X/27/6/062102
Abstract   PDF(pc) (489KB) ( 523 )

The properties of the Z=117 isotopic chain are studied within the framework of the axially deformed relativistic mean field theory (RMFT) in the blocked BCS approximation. The ground-state properties, such as binging energies, deformations as well as the possible α decay energies and lifetimes are calculated with the parameter set of NL-Z2 and compared with results from the finite range droplet model. The analysis by RMFT shows that the isotopes in the range of mass number A=291~300 exhibit higher stability, which suggests that they may be promising nuclei to be hopefully synthesized in the lab among the nuclei Z=117.

Improvement of a Fission-Like Model for Nuclear α Decay
WANG Yong-Jia, ZHANG Hong-Fei, ZUO Wei, LI Jun-Qing,
Chin. Phys. Lett. 2010, 27 (6): 062103 .   DOI: 10.1088/0256-307X/27/6/062103
Abstract   PDF(pc) (390KB) ( 537 )

The α decay constant is the product of the penetrability P and assault frequencyν0 in the fission-like model. An effective assault frequency Pν replacing the previous assault frequency ν0 is introduced for improvement of a fission-like model named the generalized liquid drop model (GLDM) to describe the nuclear α decay process more accurately. Two analytical formulae are proposed for the effective assault frequency due to experimental data within the GLDM. The improved model can be used to give accurate calculations for α decay half-lives.

Properties of the β-Delayed Proton Decay of 147Er
MA Fei, ZHOU Xiao-Hong, ZHENG Yong, XU Shu-Wei, XIE Yuan-Xiang, CHEN Liang, ZHANG Yu-Hu, LI Zhan-Kui, QIANG Yun-Hua, LEI Xiang-Guo, GUO Ying-Xiang, GUO Song, DING Bing, WANG Hai-Xia, LI Guang-Shun, ZHOU Hou-Bing,
Chin. Phys. Lett. 2010, 27 (6): 062104 .   DOI: 10.1088/0256-307X/27/6/062104
Abstract   PDF(pc) (370KB) ( 421 )

The β-delayed proton decay of 147Er is studied experimentally using the 58Ni+92Mo reaction at a beam energy of 383 MeV. Based on a He-jet apparatus coupled with a tape transport system, theβ-delayed proton radioactivities both from the νs1/2 ground state and the νh11/2 isomer in 147Er are identified by proton-γ coincidence measurements. By analyzing the time distribution of the 4+ 2+γ transition in the grand-daughter nucleus 146Dy, a half-life of 1.6±0.2 s is determined for the νh11/2 isomer in 147Er. The half-life for the ground state of 147Er is estimated to be 3.2±1.2 s.

Collective Band Structures and Identification of One-Phonon and Two-Phonon γ-Vibrational Bands in 109Tc
GU Long, ZHU Sheng-Jiang, J. H. Hamilton, A. V. Ramayya, J. K. Hwang, S. H. Liu, WANG Jian-Guo, Y. X. Luo, J. O. Rasmussen, I. Y. Lee, XU Qiang, E. Y. Yeoh, W. C. Ma
Chin. Phys. Lett. 2010, 27 (6): 062501 .   DOI: 10.1088/0256-307X/27/6/062501
Abstract   PDF(pc) (500KB) ( 417 )

The high spin states of the neutron-rich 109Tc nucleus are reinvestigated by observing prompt γ-rays from the spontaneous fission of 252Cf. The previously known yrast band based on the 7/2+ state is updated. A side band built on the 11/2+ state is expanded and a new band based on the 15/2+ state is identified. Band crossing in the yrast band occurs around ≈0.36 MeV. This band crossing is associated with the alignment of two h11/2 neutrons according to the cranked shell model calculations. The band based on the 11/2+ state is proposed as a candidate for the one-phonon γ-vibrational band, and the band built on the 15/2+ state is proposed as a candidate for the two-phonon γ-vibrational band. Other characteristics for the observed bands are discussed.

Nuclear Hexadecapole Deformation Effects on the Production of Super-Heavy Elements
WANG Nan, DOU Liang, ZHAO En-Guang, Werner Scheid
Chin. Phys. Lett. 2010, 27 (6): 062502 .   DOI: 10.1088/0256-307X/27/6/062502
Abstract   PDF(pc) (479KB) ( 783 )

We investigate the effects of the nuclear hexadecapole deformations on the interaction potentials between nuclei, the driving potentials and the fusion probabilities for some cold fusion reactions leading to super-heavy elements. It is found that nuclear hexadecapole deformations change significantly the structure of the driving potentials and the fusion probabilities for some reaction channels.

Finding a Probe for Extracting Information on the Momentum Dependent-Interaction in Heavy Ion Collisions
LIU Jian-Ye, , GUO Wen-Jun
Chin. Phys. Lett. 2010, 27 (6): 062503 .   DOI: 10.1088/0256-307X/27/6/062503
Abstract   PDF(pc) (424KB) ( 479 )

The effect of momentum-dependent interaction on the kinetic energy spectrum of the neutron-proton ratio < (n/p)gas>b(Ek) for 64Zn+64Zn is studied. It is found that < (n/p)gas>b(Ek) sensitively depends on the momentum-dependent interaction and weakly on the in-medium nucleon-nucleon cross section and symmetry potential. Therefore<(n/p)gas>b(Ek) is a possible probe for extracting information on the momentum-dependent interaction in heavy ion collisions.

Systematic Study on System Size Dependence of Global Stopping: Role of Momentum-Dependent Interactions and Symmetry Energy
Sanjeev Kumar, Suneel Kumar
Chin. Phys. Lett. 2010, 27 (6): 062504 .   DOI: 10.1088/0256-307X/27/6/062504
Abstract   PDF(pc) (637KB) ( 424 )

Using the isospin-dependent quantum molecular dynamical model, we systematically study the role of symmetry energy with and without momentum-dependent interactions on the global nuclear stopping. We simulate the reactions by varying the total mass of the system from 80 to 394 at different beam energies from 30 to 1000 MeV/nucleon over central and semi-central geometries. The nuclear stopping is found to be sensitive towards the momentum-dependent interactions and symmetry energy at low incident energies. The momentum-dependent interactions are found to weaken the finite size effects in nuclear stopping.

Precision Calculations of Atomic Polarizabilities: A Relevant Physical Quantity in Modern Atomic Frequency Standard
GAO Xiang, LI Jia-Ming,
Chin. Phys. Lett. 2010, 27 (6): 063101 .   DOI: 10.1088/0256-307X/27/6/063101
Abstract   PDF(pc) (311KB) ( 393 )

Electric dipole polarizabilities of atoms are very important in many different physical applications, such as the precision atomic frequency standard. Calculations of these properties are very important and challenging. We propose a calculation strategy to calculate the frequency dependent dipole polarizabilities with high precision variationally by using a set of high quality orbital bases where the electron correlations can be taken into account adequately. The static polarizabilities of the ground state of Na are calculated accurately by such a method and can be compared with precision experiment measurement directly. The calculation result is in excellent agreement with the available experimental measurements within about 0.1%, which demonstrates the validity of our strategy. Our calculation strategy has a wide usage, not only in polarizibilies, but also in other fields such as theoretical treatment of electron-atom scattering processes. Using the same orbital bases, we carry out precision calculation of Na- affinities. Our calculated affinity is in excellent agreement with precision laser spectroscopy measurements within 0.1%.

Kinetic Energy of Trapped Ions Cooled by Buffer Gas
CHEN Liang, , SHE Lei, LI Jiao-Mei, GAO Ke-Lin,
Chin. Phys. Lett. 2010, 27 (6): 063201 .   DOI: 10.1088/0256-307X/27/6/063201
Abstract   PDF(pc) (416KB) ( 1036 )

The average kinetic energy of 40Ca+ ions is measured by the method of evaporating ions in an rf ion trap. The kinetic energy of the ion 40Ca+ varies from 0.5 eV to 0.2 eV with changing buffer gas pressure from 10-7 mbar to 10-5 mbar. The Brownian motion model is also introduced to calculate the average kinetic energy of the trapped ions.

Influence of Laser Wavelength on Laser-induced Breakdown Spectroscopy Applied to Semi-Quantitative Analysis of Trace-Elements in a Plant Sample
ZHANG Da-Cheng, MA Xin-Wen, WEN Wei-Qiang, ZHANG Peng-Ju, ZHU Xiao-Long, LI Bin, LIU Hui-Ping
Chin. Phys. Lett. 2010, 27 (6): 063202 .   DOI: 10.1088/0256-307X/27/6/063202
Abstract   PDF(pc) (598KB) ( 608 )

Laser-induced breakdown spectroscopy (LIBS) as a powerful analytical technique is applied to analyze trace-elements in fresh plant samples. We investigate the LIBS spectra of fresh holly leaves and observe more than 430 lines emitted from 25 elements and molecules in the region 230-438 nm. The influence of laser wavelength on LIBS applied to semi-quantitative analysis of trace-element contents in plant samples is studied. The results show that the UV laser has lower relative standard deviations and better repeatability for semi-quantitative analysis of trace-element contents in plant samples. This work may be helpful for improving the quantitative analysis power of LIBS applied to plant samples.

Effects of Bounding Potential on High-Order Harmonic Generation with H2+
ZHAO Jing, ZHAO Zeng-Xiu
Chin. Phys. Lett. 2010, 27 (6): 063301 .   DOI: 10.1088/0256-307X/27/6/063301
Abstract   PDF(pc) (420KB) ( 503 )

We present harmonic spectra from hydrogen molecular ions with different ionization energy Ip. By comparing the recombination matrix element from helium ions and hydrogen molecular ions, we verify that the interference effect in high-order harmonic generation originates from the recombination interference. A numerical study on recombination matrix elements in 1D shows that ω=Ek+Ip holds only when an exact continuum wavefunction is used, and the positions of extrema in harmonic spectra can be predicted accurately. We demonstrate that the positions of extrema in harmonic spectra are mainly affected by bounding potential dependence of the recombination interference.

Transmission Properties of One-Dimensional Photonic Crystals Containing Anisotropic Metamaterials
ZHANG Li-Wei, YAN Ling-Ling, ZHAO Yu-Huan, LIU Li
Chin. Phys. Lett. 2010, 27 (6): 064101 .   DOI: 10.1088/0256-307X/27/6/064101
Abstract   PDF(pc) (776KB) ( 551 )

The transmission properties of one-dimensional photonic crystals (1DPCs) containing anisotropic metamaterials are theoretically studied. It is shown that the 1DPCs can possess a similar zero average index (zero-n)gaps, the edges of zero-n gap are weakly dependent on the incident angles, scale length and the polarization of the electromagnetic wave. When an impurity is introduced, a defect mode appears inside the zero-n gap with a very weak dependence on incident angles and scaling. It is found that in such photonic crystals, a transmitted Gaussian pulse with its carrier frequency lying in the lower gap edge, in the defect mode and in the bandgap, can experience a positive or negative group delay and hence a subluminal, ultraslow or superluminal propagation with small distortions. These properties of the photonic crystals have potential applications in the transfer of information.

A Zone Plate as a Tunable Terahertz Filter
Chin. Phys. Lett. 2010, 27 (6): 064201 .   DOI: 10.1088/0256-307X/27/6/064201
Abstract   PDF(pc) (548KB) ( 461 )

A broadband tunable terahertz filter based on a zone plate is demonstrated in our terahertz time domain spectrometer. The central bandpass frequency covers the whole spectral range of the terahertz wave emitted from a ZnTe emitter, from 0.5 THz to 2.5 THz, and can be tuned continuously by simply moving the zone plate along the terahertz beam path. The peak transmission is about 40% and the bandwidth varies from 0.16 THz to 0.25 THz at different bandpass frequencies when the aperture size is kept constant.

Threshold Analysis of a THz-Wave Parametric Oscillator
LI Zhong-Yang, YAO Jian-Quan, ZHU Neng-Nian, WANG Yu-Ye, XU De-Gang,
Chin. Phys. Lett. 2010, 27 (6): 064202 .   DOI: 10.1088/0256-307X/27/6/064202
Abstract   PDF(pc) (794KB) ( 519 )

The parametric gain of a terahertz wave parametric oscillator (TPO) is analyzed. Meanwhile the expression of TPO threshold pump intensity is derived and theoretically analyzed with different factors. The effective interaction length between the pump wave and Stokes wave is calculated, and particular attention is paid to the coupling efficiency of the pump wave and Stokes wave. Such an analysis is useful for the experiments of TPO.

New Expressions for Dark-Hollow Light Beams
LI Jian-Long
Chin. Phys. Lett. 2010, 27 (6): 064203 .   DOI: 10.1088/0256-307X/27/6/064203
Abstract   PDF(pc) (455KB) ( 511 )

A class of new light beams of dark-hollow beams, named sinusoidal dark-hollow beams, is introduced. The propagation formula for a sinusoidal dark-hollow beam through a paraxial ABCD optical system is derived. The propagation properties of the sinusoidal dark-hollow beam are comparatively studied and illustrated with numerical examples.

Optical Properties of Plasmon Resonances with Ag/SiO2/Ag Multi-Layer Composite Nanoparticles
MA Ye-Wan, ZHANG Li-Hua, WU Zhao-Wang, ZHANG Jie
Chin. Phys. Lett. 2010, 27 (6): 064204 .   DOI: 10.1088/0256-307X/27/6/064204
Abstract   PDF(pc) (682KB) ( 732 )

Optical properties of plasmon resonance with Ag/SiO2/Ag multi-layer nanoparticles are studied by numerical simulation based on Green's function theory. The results show that compared with single-layer Ag nanoparticles, the multi-layer nanoparticles exhibit several distinctive optical properties, e.g. with increasing the numbers of the multi-layer nanoparticles, the scattering efficiency red shifts, and the intensity of scattering enhances accordingly. It is interesting to find out that slicing an Ag-layer into multi-layers leads to stronger scattering intensity and more ``hot spots'' or regions of stronger field enhancement. This property of plasmon resonance of surface Raman scattering has greatly broadened the application scope of Raman spectroscopy. The study of metal surface plasmon resonance characteristics is critical to the further understanding of surface enhanced Raman scattering as well as its applications.

Broadband Source Ranging in Shallow Water Using the Ω-Interference Spectrum
ZHAO Zhen-Dong, WANG Ning, GAO Da-Zhi, WANG Hao-Zhong
Chin. Phys. Lett. 2010, 27 (6): 064301 .   DOI: 10.1088/0256-307X/27/6/064301
Abstract   PDF(pc) (750KB) ( 642 )

The concept of the waveguide invariant is revisited and a simple relationship between the range of source and the quasi-period of the acoustic interference spectrum in the frequency domain (Ω-interference spectrum) is derived. Then a method for a broadband source ranging in shallow water using a single receiver and a broadband guide source, requiring no modeling and no knowledge about the ocean environment, is proposed. The method is validated by simulation and verified with the experimental data.

Asymmetric Oscillation and Acoustic Response from an Encapsulated Microbubble Bound within a Small Vessel
Chin. Phys. Lett. 2010, 27 (6): 064302 .   DOI: 10.1088/0256-307X/27/6/064302
Abstract   PDF(pc) (449KB) ( 451 )

Understanding the dynamics of ultrasonic excited microbubbles bound within microvessels is of significance for novel ultrasonic imaging, drug delivery and therapeutic biomedical applications. A finite element model (FEM) considering acoustic nonlinearity is developed to describe the asymmetric oscillation and acoustic response from an encapsulated microbubble bound within a small vessel. Numerical simulation is performed for a 2 μm encapsulated microbubble bound within 8-20 μm vessels using 2 MHz ultrasound excitation. The oscillation of the bound microbubble becomes more asymmetric under larger ultrasound pressure or within the smaller vessel. The normalized difference between the major and minor axes of epllipse is estimated to be 2.16% for the 8 μm vessel at an acoustic pressure of 0.5 MPa. In addition, the fundamental component of the acoustic scattering from the bound microbubble is enhanced by 6 dB while the second harmonic component is decreased by approximately 29 dB compared with the free microbubble.

Bonding Interface Imaging and Shear Strength Prediction by Ultrasound
LI Yong-An, MAO Jie, WANG Xiao-Min, LI Ming-Xuan, AN Zhi-Wu, ZHUANG Qiao
Chin. Phys. Lett. 2010, 27 (6): 064303 .   DOI: 10.1088/0256-307X/27/6/064303
Abstract   PDF(pc) (440KB) ( 593 )

The propagation of a longitudinal ultrasonic wave normally incident upon an adhesively bonded structure is studied. The structure consists of adherend and adhesive layers with finite thickness. Interfaces between adherend and adhesive are regarded as distributed springs. Theoretical and experimental results show that resonant frequencies of the bonded structure vary sensitively with the interface stiffness constants and adhesive thickness, and these interface characteristics are inversed by the simulation annealing (SA) method. Furthermore, the distribution image of interface stiffnesses is compared with the state of fracture interface, and quantitative prediction of shear strength is achieved based on the distribution of interface stiffnesses and adhesive thicknesses by using a back-propagation neutral network. The average relative error of the shear strength from prediction to real value is 10.7%.

Temperature-Dependent Viscosity Effects on Non-Darcy Hydrodynamic Free Convection Heat Transfer from a Vertical Wedge in Porous Media
A. M. Salem
Chin. Phys. Lett. 2010, 27 (6): 064401 .   DOI: 10.1088/0256-307X/27/6/064401
Abstract   PDF(pc) (421KB) ( 499 )

An analysis is presented to investigate the effect of temperature-dependent viscosity on free convection flow along a vertical wedge adjacent to a porous medium in the presence of heat generation or absorption. The governing fundamental equations are transformed into the system of ordinary differential equations using scaling group of transformations and are solved numerically by using the fifth-order Rung-Kutta method with shooting technique for various values of the physical parameters. The effects of variable viscosity parameter on the velocity, temperature and concentration are discussed. Numerical results for the problem considered are given and illustrated graphically.

Flutter of Finite-Span Flexible Plates in Uniform Flow
BAO Chun-Yu, TANG Chao, YIN Xie-Zhen, LU Xi-Yun
Chin. Phys. Lett. 2010, 27 (6): 064601 .   DOI: 10.1088/0256-307X/27/6/064601
Abstract   PDF(pc) (525KB) ( 615 )

The flutter instability and response of finite-span flexible plates in uniform flow are investigated experimentally. The effects of the plate aspect ratio on its dynamic responses are mainly analyzed. A hysteretic phenomenon is observed and can be described such that the plate flutters spontaneously as the flow velocity is greater than a critical value U*C and the plate returns to its stable state as the flow velocity is slowly decreased to another critical one U*D. We find that the aspect ratio has a greater effect on U*C than on U*D. The flutter frequency decreases and the amplitude increases with the increase in the flow velocity. When the flutter instability of the plate occurs, three typical flutter modes are identified and are associated with the aspect ratio and the flow velocity.

Turbulence Modulations in the Boundary Layer of a Horizontal Particle-Laden Channel Flow
LI Jing, LIU Zhao-Hui, WANG Han-Feng, CHEN Sheng, LIU Ya-Ming, HAN Hai-Feng, ZHENG Chu-Guang
Chin. Phys. Lett. 2010, 27 (6): 064701 .   DOI: 10.1088/0256-307X/27/6/064701
Abstract   PDF(pc) (507KB) ( 503 )

Turbulence modulations are experimentally investigated using particle image velocimetry (PIV) in the lower boundary layer of a fully developed horizontal channel flow. A simultaneous two-phase PIV measurement technique is adopted to acquire the turbulent statistics quantities and to examine the coherent structures in the near-wall region. Polythene beads with diameters of 60μm are used as dispersed phases, and the PIV measurements have been performed at three mass loadings varying from 2.5×10-4 to 5× 10-3. All the experiments are performed at a wall shear Reynolds number of ReΤ=430. The results show that the presence of the particles suppresses the coherent structures, with shorter streamwise extent of the quasistreamwise structures, and then, the wall-normal velocity fluctuations and shear Reynolds stresses are both decreased in the near-core region. In addition, as a result of the particle wake, the turbulence intensity and shear Reynolds stress both increase in the vicinity of the wall. Due to the drag effects of the particles on the gas, the streamwise velocity gradients decrease in the outer region and increase in the viscous sublayer, meanwhile the thickness of the viscous sublayer also decreases. These results cause the peak values of the streamwise velocity fluctuations adjacent to the wall to increase, and the peak positions shift to the wall. This is the reason for decreasing the near-wall region and increasing the near-core region of the streamwise velocity fluctuations in appearance.

Transition of Discharge Mode of a Local Hollow Cathode Discharge
LI Shang, OUYANG Ji-Ting, HE Feng
Chin. Phys. Lett. 2010, 27 (6): 065201 .   DOI: 10.1088/0256-307X/27/6/065201
Abstract   PDF(pc) (666KB) ( 721 )

The discharge characteristics of hollow cathode discharge in argon in a cylindrical cavity are investigated experimentally. The voltage-current (V-I) characteristics and the light emission are measured. It is found that the discharge plasma is localized inside the hollow cavity, with an extensive Faraday dark space between the cathode and the anode. The discharge develops from predischarge to abnormal glow discharge, the hollow cathode effect (HCE) and a hybrid mode as the discharge current increases. The onset of the HCE is found for the first time by the transition from abnormal glow discharge together with a significant decrease in the slope of the V-I curve which shows a positive differential resistivity. The voltage increases proportionally with the current when the HCE is reached.

First Observation of Neoclassical Tearing Modes in the HL-2A Tokamak
JI Xiao-Quan, YANG Qing-Wei, LIU Yi, ZHOU Jun, FENG Bei-Bin, YUAN Bao-Shan
Chin. Phys. Lett. 2010, 27 (6): 065202 .   DOI: 10.1088/0256-307X/27/6/065202
Abstract   PDF(pc) (727KB) ( 575 )

The m/n=2/1 neoclassical tearing modes are first observed in HL-2A low density, low beta plasma with central electron cyclotron resonance heating. The neoclassical tearing modes (NTMs) are triggered by a sawtooth crash with m/n=1/1 precursors, which are toroidal coupled with a small scale m/n=2/1 mode. The time history of the island width is compared with the prediction of the NTM theory, showing a good agreement between theory and experiment.

Structural Investigation of Solid Methane at High Pressure
ZHAO Juan, FENG Wan-Xiang, LIU Zhi-Ming, MA Yan-Ming, HE Zhi, CUI Tian, ZOU Guang-Tian
Chin. Phys. Lett. 2010, 27 (6): 066101 .   DOI: 10.1088/0256-307X/27/6/066101
Abstract   PDF(pc) (724KB) ( 1007 )

High pressure studies of solid methane are performed using both classical simulated annealing and first-principles methods. A series of simulated annealing and geometry optimization reveal a monoclinic P21/b structure with the unit cell containing four methane molecules. The phonon dispersion curves and vibrational density of states indicate that this structure is stable in the pressure range 10-90 GPa. The electronic band structure and density of states show that this structure has not metalized until 90 GPa.

Dynamic Tensile Behavior and Fracture Mechanism of Polymer Composites Embedded with Tetraneedle-Shaped ZnO Nanowhiskers
RONG Ji-Li, WANG Xi, CAO Mao-Sheng, WANG Da-Wei, ZHOU Wei, XU Tian-Fu
Chin. Phys. Lett. 2010, 27 (6): 066201 .   DOI: 10.1088/0256-307X/27/6/066201
Abstract   PDF(pc) (1089KB) ( 676 )

Dynamic tensile properties of glass-fiber polymer composites embedded with ZnO nanowhiskers are investigated by a split Hopkinson tensile bar. The stress-strain curves, ultimate strength, failure strain and elastic modulus are obtained and the failure mechanism of the composites is investigated by the macroscopic and microscopic observation of fractured specimens. The strain rate effect on the mechanical behavior is discussed and a constitutive model is derived by simulating the experimental data. The experimental results show that the materials have an obvious non-linear constitutive relation and strain rate strengthening effect. The composites with ZnO nanowhiskers under dynamic loading have various failure modes and better mechanical properties.

Fabrication of Anodic Aluminum Oxide Templates with Small Interpore Distances
WANG Na, ZHANG Wen-Di, XU Ji-Peng, MA Bin, ZHANG Zong-Zhi, JIN Qing-Yuan, E. Bunte, J. Hüpkes, H. P. Bochem
Chin. Phys. Lett. 2010, 27 (6): 066801 .   DOI: 10.1088/0256-307X/27/6/066801
Abstract   PDF(pc) (662KB) ( 1664 )

The influence of the electropolishing and anodization voltage on surface morphology has been carefully studied for fabrication of ordered anodic aluminum oxide (AAO) templates. In accordance with that in the anodization experiment, the size of small patterns on the foil surface formed from the electropolishing treatment increases with voltage. Using a combined method of small-voltage electropolishing and anodization, we have fabricated well-ordered templates with much smaller interpore distances compared with that under normal-voltage fabrication conditions. The Ni nanowire arrays with two small diameters are electrodeposited through the above templates, exhibiting different magnetic properties. This also helps us to clarify the inner structure of this kind of templates.

Molecular-Dynamics Simulations of Droplets on a Solid Surface
GAO Yu-Feng, SUN De-Yan
Chin. Phys. Lett. 2010, 27 (6): 066802 .   DOI: 10.1088/0256-307X/27/6/066802
Abstract   PDF(pc) (355KB) ( 596 )

By using a semi-empirical Lennard-Jones embedded-atom-method potential, we study the influence of many-body forces and atomic size mismatch on the wetting behavior of nano droplets on a solid surface. With molecular dynamics simulations, we find that the contact angle decreases with increasing many-body forces. The increase of atomic size mismatch between solid and liquid results in the decrease of contact angles. Our calculation also shows that the interface structure is strongly affected by the interaction between liquid and solid as well as the atomic size mismatch. For weak solid-liquid interaction, the interface layer of the droplet nearest to the solid exhibits a typical simple liquid structure regardless of the size mismatch. For strong solid-liquid interaction, evident ordering in the interface layer is observed for well matched cases.

Edge Effects on Growth of Ordered Stress Relief Patterns in Free Sustained Aluminum Films
YU Sen-Jiang, ZHANG Yong-Ju, CHEN Miao-Gen,
Chin. Phys. Lett. 2010, 27 (6): 066803 .   DOI: 10.1088/0256-307X/27/6/066803
Abstract   PDF(pc) (4219KB) ( 393 )

An unusual form of ordered stress relief patterns is observed in a nearly free sustained aluminum film system deposited on liquid substrates by the thermal evaporation method. The edge effects on the growth of the ordered patterns are systematically studied. It is found that the patterns initiate from the film edges, preexisting ordered patterns, or other imperfections of the film. When the patterns extend in the film regions, they decay gradually and finally disappear. If they develop along the boundaries, however, the sizes are almost unchanged over several millimeters. The stress relief patterns look like rectangular waves in appearance, which are proven to evolve from sinusoidal to triangular waves gradually. The morphological evolution can be well explained by the general theory of buckling of plates.

Modifying Quantum Well States of Pb Thin Films via Interface Engineering
FU Ying-Shuang, JI Shuai-Hua, ZHANG Tong, CHEN Xi, JIA Jin-Feng, XUE Qi-Kun, MA Xu-Cun
Chin. Phys. Lett. 2010, 27 (6): 066804 .   DOI: 10.1088/0256-307X/27/6/066804
Abstract   PDF(pc) (2689KB) ( 830 )

We demonstrate the importance of interface modification on improving electron confinement by preparing Pb quantum islands on Si(111) substrates with two different surface reconstructions, i.e., Si(111)-7× 7 and Si(111)-Root3×Root3-Pb (hereafter, 7× 7 and R3). Characterization with scanning tunneling microscopy/spectroscopy shows that growing Pb films directly on a 7×7 surface will generate many interface defects, which makes the lifetime of quantum well states (QWSs) strongly dependent on surface locations. On the other hand, QWSs in Pb films on an R3 surface are well defined with small variations in linewidth on different surface locations and are much sharper than those on the 7×7 surface. We show that the enhancement in quantum confinement is primarily due to the reduced electron-defect scattering at the interface.

Improved Programming Efficiency through Additional Boron Implantation at the Active Area Edge in 90nm Localized Charge-Trapping Non-volatile Memory
XU Yue, YAN Feng, CHEN Dun-Jun, SHI Yi, WANG Yong-Gang, LI Zhi-Guo, YANG Fan, WANG Jos-Hua, LIN Peter, CHANG Jian-Guang
Chin. Phys. Lett. 2010, 27 (6): 067201 .   DOI: 10.1088/0256-307X/27/6/067201
Abstract   PDF(pc) (465KB) ( 374 )

As the scaling-down of non-volatile memory (NVM) cells continues, the impact of shallow trench isolation (STI) on NVM cells becomes more severe. It has been observed in the 90 nm localized charge-trapping non-volatile memory (NROMTM) that the programming efficiency of edge cells adjacent to STI is remarkably lower than that of other cells when channel hot electron injection is applied. Boron segregation is found to be mainly responsible for the low programming efficiency of edge cells. Meanwhile, an additional boron implantation of 10\circ tilt at the active area edge as a new solution to solve this problem is developed.

Spin Transport in a Magnetic Superlattice with Broken Two-Fold Symmetry
HUO Qiu-Hong, WANG Ru-Zhi, CHEN Si-Ying, XUE Kun, YAN Hui
Chin. Phys. Lett. 2010, 27 (6): 067202 .   DOI: 10.1088/0256-307X/27/6/067202
Abstract   PDF(pc) (545KB) ( 429 )

We theoretically investigate the spin-dependent electron transport properties in a magnetic superlattice (MSL) with broken two-fold symmetry. An abnormal barrier in the MSL can break the two-fold symmetry of the system when it is not located at the two-fold symmetry center. A two-fold symmetry breaking factor is introduced to describe the two-fold symmetry breaking degree. Our numerical calculations show that the transmission, the conductance and the spin polarization are non-trivially dependent on the two-fold symmetry breaking factor. When the factor is large enough, the polarization almost approaches 100% in a proper Fermi energy range. However, for two mutually mirror-symmetric MSLs with the same factor, their polarizations may be either similar or distinct. These features provide some clues to the design and applications of MSL-based spin filters or spin-dependent tunneling electron devices.

Van der Pauw Hall Measurement on Intended Doped ZnO Films for p-Type Conductivity
GUO Yang, LIU Yao-Ping, LI Jun-Qiang, ZHANG Sheng-Li, MEI Zeng-Xia, DU Xiao-Long
Chin. Phys. Lett. 2010, 27 (6): 067203 .   DOI: 10.1088/0256-307X/27/6/067203
Abstract   PDF(pc) (355KB) ( 921 )

A Van der Pauw Hall measurement is performed on the intended doped ZnO films (Na doped ZnO) grown by using the molecular beam epitaxial method. All as-grown samples show n-type conductivity, whereas the annealed samples (annealing temperature 900°C) show ambiguous carrier conductivity type (n- and p-type) in the automatic Van der Pauw Hall measurement. A similar result has been observed in Li doped ZnO and in as-doped ZnO films by other groups before. However, by tracing the Hall voltage in the Van der Pauw Hall measurement, it is found that this alternative appearance of both n- and p-type conductivity is not intrinsic behavior of the intended doped ZnO films, but is due to the persistent photoconductivity effect in ZnO. The persistent photoconductivity effect would strongly affect the accurate determination of the carrier conductivity type of a highly resistive intended doped ZnO sample.

Capacitance of Organic Schottky Diodes Based on Copper Phthalocyanine (CuPc)
LI Zhong-Liang, WU Zhao-Xin, JIAO Bo, MAO Gui-Lin, HOU Xun
Chin. Phys. Lett. 2010, 27 (6): 067204 .   DOI: 10.1088/0256-307X/27/6/067204
Abstract   PDF(pc) (446KB) ( 928 )

The capacitance of an organic Schottky diode based on copper phthalocyanine (CuPc) is investigated. Based on the organic small-signal equivalent model established, we calculate the reverse capacitance CMetal of the organic Schottky diode with different kinds of metal cathodes (Mg, Al, Au). It is found that the reverse capacitance of the organic Schottky diode shows behavior as C Mg >C Al >C Au at the same frequency, and according to our analysis, the reverse Schottky junction capacitance Cj is expected to have little effect on the reverse capacitance of the organic Schottky diode, and the space-charge limited current capacitance CS is considered to dominate the reverse capacitance, which limits the improvement of frequency characteristics of organic Schottky diodes.

A High Performance Silicon-on-Insulator LDMOSTT Using Linearly Increasing Thickness Techniques
GUO Yu-Feng, WANG Zhi-Gong, SHEU Gene, CHENG Jian-Bing
Chin. Phys. Lett. 2010, 27 (6): 067301 .   DOI: 10.1088/0256-307X/27/6/067301
Abstract   PDF(pc) (580KB) ( 558 )

We present a new technique to achieve uniform lateral electric field and maximum breakdown voltage in lateral double-diffused metal-oxide-semiconductor transistors fabricated on silicon-on-insulator substrates. A linearly increasing drift-region thickness from the source to the drain is employed to improve the electric field distribution in the devices. Compared to the lateral linear doping technique and the reduced surface field technique, two-dimensional numerical simulations show that the new device exhibits reduced specific on-resistance, maximum off- and on-state breakdown voltages, superior quasi-saturation characteristics and improved safe operating area.

Measurement of GaN/Ge(001) Heterojunction Valence Band Offset by X-Ray Photoelectron Spectroscopy
GUO Yan, LIU Xiang-Lin, SONG Hua-Ping, YANG An-Li, ZHENG Gao-Lin, WEI Hong-Yuan, YANG Shao-Yan, ZHU Qin-Sheng, WANG Zhan-Guo
Chin. Phys. Lett. 2010, 27 (6): 067302 .   DOI: 10.1088/0256-307X/27/6/067302
Abstract   PDF(pc) (531KB) ( 841 )

X-ray photoelectron spectroscopy has been used to measure the valence band offset (VBO) at the GaN/Ge heterostructure interface. The VBO is directly determined to be 1.13±0.19 eV, according to the relationship between the conduction band offset ΔEC and the valence band offset ΔEV: Δ EC=EgGaN-EgGe-Δ EV, and taking the room-temperature band-gaps as 3.4 and 0.67 eV for GaN and Ge, respectively. The conduction band offset is deduced to be 1.6\pm 0.19 eV, which indicates a type-I band alignment for GaN/Ge. Accurate determination of the valence and conduction band offsets is important for the use of GaN/Ge based devices.

Self-Consistent Study of Conjugated Aromatic Molecular Transistors
WANG Jing, LIANG Yun-Ye, CHEN Hao, WANG Peng, R. Note, H. Mizuseki, Y. Kawazoe
Chin. Phys. Lett. 2010, 27 (6): 067303 .   DOI: 10.1088/0256-307X/27/6/067303
Abstract   PDF(pc) (437KB) ( 536 )

We study the current through conjugated aromatic molecular transistors modulated by a transverse field. The self-consistent calculation is realized with density function theory through the standard quantum chemistry software Gaussian03 and the non-equilibrium Green's function formalism. The calculated I-V curves controlled by the transverse field present the characteristics of different organic molecular transistors, the transverse field effect of which is improved by the substitutions of nitrogen atoms or fluorine atoms. On the other hand, the asymmetry of molecular configurations to the axis connecting two sulfur atoms is in favor of realizing the transverse field modulation. Suitably designed conjugated aromatic molecular transistors possess different I-V characteristics, some of them are similar to those of metal-oxide-semiconductor field-effect transistors (MOSFET). Some of the calculated molecular devices may work as elements in graphene electronics. Our results present the richness and flexibility of molecular transistors, which describe the colorful prospect of next generation devices.

Noncommutative Chern-Simons Description of the Fractional Quantum Hall Edge
HUANG Wei, WANG Zhao-Long, YAN Mu-Lin
Chin. Phys. Lett. 2010, 27 (6): 067304 .   DOI: 10.1088/0256-307X/27/6/067304
Abstract   PDF(pc) (318KB) ( 489 )

Noncommutative Chern-Simons (NCCS) theory is a workable description for the fractional quantum Hall fluid. We apply and generalize the NCCS theory to the physically important case with an edge. From relabeling symmetry of electrons and incompressibility of the fluid, we obtain a constraint and reduce the two-dimensional NCCS theory to a one-dimensional chiral Tomonaga-Luttinger liquid theory, which contains additional interaction terms. Further, we calculate one-loop corrections to the boson and electron propagators and obtain a new tunneling exponent, which agrees with experiments.

Spin-charge Separation of the Luttinger Model after an Interaction Quench
ZHOU Zong-Li, ZHANG Guo-Shun, LOU Ping,
Chin. Phys. Lett. 2010, 27 (6): 067305 .   DOI: 10.1088/0256-307X/27/6/067305
Abstract   PDF(pc) (335KB) ( 409 )

A Luttinger model of spin-½ fermions is considered after the interaction is suddenly switched on at time t=0. By means of the bosonization technique, we evaluate analytically the one-particle correlation functions in detail, mainly involving equal-time correlations and propagators. The critical exponent which governs the power-law behavior of equal-time correlations for this spinful non-equilibrium system is obtained. In comparison with the published results, the difference between critical exponents of correlations in spinful and spinless non-equilibrium systems is found and explained. Furthermore, it is found that the propagator exhibits different power-law behavior from other equal-time correlations in this non-equilibrium system.

Shot Noise in Aharonov-Casher Rings
LIN Liang-Zhong, ZHU Rui, DENG Wen-Ji
Chin. Phys. Lett. 2010, 27 (6): 067306 .   DOI: 10.1088/0256-307X/27/6/067306
Abstract   PDF(pc) (927KB) ( 423 )

We investigate the shot noise of electron transport through an Aharonov-Casher ring subject to the Rashba spin-orbit coupling (SOC). Analytic expressions for the coefficients of reflection and transmission are derived by using the Griffith boundary conditions. For this kind of SOC, the ballistic transport of electrons can be analyzed as two independent spin channels, and both of them have the same transmission and reflection coefficients. The dependences of shot noise and Landauer-Büttiker conductance on controllable factors, including the strength of Rashba SOC, the asymmetrical angle of lead-connection positions, the radius of the rings, and the wave vector (or energy) of the incident Fermi electrons, are explicitly described by some new combined parameters. The ways that the shot noise and conductance vary with Rashba SOC and with asymmetrical angle are demonstrated by numerical simulations, respectively. It is revealed that the shot noise reaches its maximum for the particular situation of half transmission and half reflection and zero shot noise occurs at conductance maxima.

Synthesis and Characteristics of Electrodeposited CoxZn1-x Nanorods
LIU Li-Hu, GU Jian-Jun, , LI Hai-Tao, , CAI Ning, SUN Hui-Yuan,
Chin. Phys. Lett. 2010, 27 (6): 067501 .   DOI: 10.1088/0256-307X/27/6/067501
Abstract   PDF(pc) (778KB) ( 728 )

CoxZn1-x nanorod arrays were fabricated by electrodeposition in porous anodic aluminum oxide templates at different electric potentials. X-ray diffraction and transmission electron microscopy indicate that highly-ordered and uniform nanorods have been fabricated. The amounts of Co and Zn contents are investigated using energy dispersive spectroscopy, which demonstrates that the atom ratio of the alloy nanorods changes with the deposition potential. In addition, magnetic measurements show that the magnetic isotropy Co-rich CoZn nanorods will change to magnetic anisotropy nanorods with the easy axis parallel to the rod long axis with decreasing Co content.

Soft Magnetism and High Frequency Properties of Fe65Co35-MgF2 Granular Thin Films
YAO Dong-Sheng, GE Shi-Hui, ZHOU Xue-Yun, ZHANG Bang-Min, ZUO Hua-Ping
Chin. Phys. Lett. 2010, 27 (6): 067502 .   DOI: 10.1088/0256-307X/27/6/067502
Abstract   PDF(pc) (1104KB) ( 522 )

(Fe65Co35)x(MgF2)1-x films with different metal volume fraction x are fabricated by magnetron sputtering. The results reveal that good soft magnetic properties can be obtained in a very wide x range (0.9> x >0.55) with Hc not exceeding 10 Oe, and high resistivity is also realized for the samples. Especially for the sample with x= 0.75, the coercivity in hard and easy axes is 1.6 Oe and 8.5 Oe, respectively, 4π Ms=14.1 kG and ρ reaches 1.16 mΩcdotcm. The dependence of complex permeability μ =μ- jμ'' on frequency shows that the real part μ' is more than 190 below 2.0 GHz and ferromagnetic resonance frequency fr reaches 2.43 GHz, implying that the film is promising for high frequency applications. High resolution transmission electron micrographs show that the films consists of bcc Fe65Co35 particles embedded uniformly in an amorphous insulating MgF2 matrix with particle size around a few nanometers. The excellent soft magnetic properties and high frequency properties are ascribed to exchange of coupling among magnetic granules, and the exchange coupling variation in a wide x range (0.9> x >0.55) is studied systematically byΔ M plots.

Permanent Magnetic Properties of Melt-Spun YCo5Cx Ribbons
WANG Fei, YAN Yu, YUAN Zhou, BAI Xue, DU Xiao-Bo, WANG Wen-Quan, SU Feng, JIN Han-Min
Chin. Phys. Lett. 2010, 27 (6): 067503 .   DOI: 10.1088/0256-307X/27/6/067503
Abstract   PDF(pc) (759KB) ( 466 )

Ribbons of nominal compositions YCo5Cx (x = 0, 0.2, 0.4, 0.6) are prepared by melt spinning at surface velocities v=5, 10, 15, 20, 25, 30 and 35 m/s. YCo5 ribbon is crystallized in a single YCo5 phase of hexagonal CaCu5 structure. A small quantity of YCoC2 phase appears in the ribbons with C addition besides the YCo5 phase. With the increase of x the lattice constant c increases and a along with the unit cell volume decreases. The largest values of iHc=888 kA/m and (BH)max =58.4 kJ/m3 at present for the YCo5 ribbon system were obtained with x=0.4 and v=20 m/s. The improvement of the permanent magnetic properties is rooted in the refinement of the microstructure and the appearance of the YCoC2 phase which can act as domain wall pinning centers.

Elastic Modulus of Fe72.5Ga27.5 Magnetostrictive Alloy
ZHU Xiao-Xi, LIU Jing-Hua, JIANG Cheng-Bao
Chin. Phys. Lett. 2010, 27 (6): 067504 .   DOI: 10.1088/0256-307X/27/6/067504
Abstract   PDF(pc) (523KB) ( 403 )

The elastic modulus of Fe72.5Ga27.5 magnetostrictive alloy is determined by testing ac impedance resonance frequency and first-principle calculations. The observed elastic modulus is 90.2 GPa for a directionally solidified sample and 103.4 GPa for a water-quenched sample tested in a dc magnetic field of 32.7 mT without compressive pre-stress. The bulk modulus by first-principles calculation is 179.3 GPa which is basically consistent with the experimental result. The elastic modulus first increases and then decreases with increasing dc magnetic field, attributed to magnetostriction occurrence in the Fe72.5Ga27.5 alloy. The elastic modulus increases with increasing compressive pre-stress, resulting from the initial magnetic states change under the applied compressive pre-stress. The elastic modulus increases match well with the improved magnetostriction after quenching.

Effect of Media on the Electric Field of a Rhombic Nanostructure Array
ZHU Shao-Li, ZHOU Wei
Chin. Phys. Lett. 2010, 27 (6): 067801 .   DOI: 10.1088/0256-307X/27/6/067801
Abstract   PDF(pc) (2547KB) ( 447 )

Electric field distribution is an important parameter for nanostructure arrays in nanobiosensing applications. It can influence the sensitivity and the resolution of nanobiosensors. We focus on the effect of media on the electric field distribution of a rhombic silver nanostructure array. The finite-difference time-domain algorithm-based numerical calculation method is used to monitor the electric field distribution of the silver nanostructures when the refractive index of the medium around the nanostructure array is changed. The calculated results show that tuning the refractive index of the medium around silver can have a considerable influence on the electric field distribution in the reflection and transmission directions. This effect can be used to increase the extinction efficiency and to improve the resolution of the spectra for nanobiosensing.

Waveform Distortions in Femtosecond Laser Pulses Transmitting through Coated Optical Fiber Probes
LIU Gui-Yuan, HAN Jun-Ling, LIU Man, TENG Shu-Yun, CHENG Chuan-Fu
Chin. Phys. Lett. 2010, 27 (6): 067802 .   DOI: 10.1088/0256-307X/27/6/067802
Abstract   PDF(pc) (580KB) ( 414 )

We calculate the light field in metal-coated optical fiber probes under illumination of femtosecond laser pulses with the three-dimensional finite-difference time-domain method. By choosing the maximum of the calculated light field data in the time period of one light wave cycle at each spatial point, we obtain the amplitude distributions instead of the conventional light field distribution of a time instant. It is found that with an incident plane wave pulse of y-polarization, the output amplitude distributions of y-polarization have roughly a circled-cross-like pattern with two arc-like zero-amplitude zones. By analyzing the y-polarized waveforms versus time at the points near the arc-like zero-amplitude zones, we find that waveform distortions appear at points in the neighborhood of the zero amplitude lines and in the time intervals when two wave-packets overlap.

Magneto-Optic Fiber Gratings Useful for Dynamic Dispersion Management and Tunable Comb Filtering
WU Bao-Jian, LU Xin, QIU Kun
Chin. Phys. Lett. 2010, 27 (6): 067803 .   DOI: 10.1088/0256-307X/27/6/067803
Abstract   PDF(pc) (403KB) ( 631 )

Intelligent control of dispersion management and tunable comb filtering in optical network applications can be performed by using magneto-optic fiber Bragg gratings (MFBGs). When a nonuniform magnetic field is applied to the MFBG with a constant grating period, the resulting grating response is equivalent to that of a conventional chirped grating. Under a linearly nonuniform magnetic field along the grating, a linear dispersion is achieved in the grating bandgap and the maximal dispersion slope can come to 1260 ps/nm2 for a 10-mm-long fiber grating at 1550 nm window. Similarly, a Gaussian-apodizing sampled MFBG is also useful for magnetically tunable comb filtering, with potential application to clock recovery from return-to-zero optical signals and optical carrier tracking.

Upconversion Luminescence of Er3+ Ions in Transparent Germanate Glass Ceramics Containing CaF2 Nanocrystals
WU Dong, TANG Bin, Laurent Calvez, ZHANG Xiang-Hua, ZHANG Long
Chin. Phys. Lett. 2010, 27 (6): 067804 .   DOI: 10.1088/0256-307X/27/6/067804
Abstract   PDF(pc) (723KB) ( 876 )

The visible upconversion and near-infrared luminescence of Er3+ ions in germanate glass ceramics containing CaF2 nanocrystals are investigated. The nanocrystals are characterized by x-ray diffraction (XRD) and transmission electron microscopy, showing their mean sizes less than 20 nm. High transmittance of the glass ceramics is displayed by absorption spectra. The upconversion luminescence intensity in the glass ceramics increases significantly with increasing temperature. Both the shifts of the XRD peaks and the Stark-split shown in the luminescence spectra indicate the entrance of the Er3+ ions into the CaF2 nanocrystals, which is confirmed by a Judd-Ofelt analysis. Possible mechanisms of the upconversion luminescence are analyzed.

High Quality AlN with a Thin Interlayer Grown on a Sapphire Substrate by Plasma-Assisted Molecular Beam Epitaxy
REN Fan, HAO Zhi-Biao, ZHANG Chen, HU Jian-Nan, LUO Yi
Chin. Phys. Lett. 2010, 27 (6): 068101 .   DOI: 10.1088/0256-307X/27/6/068101
Abstract   PDF(pc) (509KB) ( 761 )

We report an AlN epi-layer grown on sapphire by plasma-assisted molecular beam epitaxy with a thin interlayer structure. The effects of growth mode on threading dislocations (TDs) and surface morphology are studied. Then an interlayer structure grown under a V/Ⅲ ratio of 1 is adopted to improve the AlN crystalline quality. By optimizing the thickness of the interlayer, the TD density and surface roughness can be reduced simultaneously.

Elevation of the Power Factor of Co4Sb12 Skutterudite with Sm-Doping in High-Pressure High-Temperature Synthesis
JIANG Yi-Ping, JIA Xiao-Peng, GUO Wei, XU Hui-Wen, DENG Le, ZHENG Shi-Zhao, MA Hong-An
Chin. Phys. Lett. 2010, 27 (6): 068102 .   DOI: 10.1088/0256-307X/27/6/068102
Abstract   PDF(pc) (584KB) ( 655 )

A thermoelectric material SmxCo4Sb12 (0<x≤1.0)compounds exhibits n-type conduction. The absolute value of the Seebeck coefficient decreases with increasing Sm fraction. The resistivity increases with samarium content x from 0.1 to 0.2, but decreases dramatically when x changes from 0.2 to 1.0. The maximum power factor reaches 13.1 μ at x=1.0, which is larger than the data previously reported for the La-doped CoSb3 prepared at room pressure.

Methods for Thickness Determination of SiC Homoepilayers by Using Infrared Reflectance Spectroscopy
LI Zhi-Yun, SUN Ji-Wei, ZHANG Yu-Ming, ZHANG Yi-Men, TANG Xiao-Yan
Chin. Phys. Lett. 2010, 27 (6): 068103 .   DOI: 10.1088/0256-307X/27/6/068103
Abstract   PDF(pc) (473KB) ( 705 )

Infrared reflectance spectra have been widely used to measure layer thickness based either on calculation or on curve fitting, and two traditional methods for thickness determination have been studied. Considering the disadvantages of those two methods, we propose a new fitting model based on the fitting of the fringe order difference. In comparison with the measured results, the new fitting model shows its superiority not only for its stable and accurate results which have great agreement with the results from SEM, but also for its simple and quick fitting process.

Fe Nanoparticle Production by an Atmospheric Cold Plasma Jet
ZHANG Yu-Tao, GUO Ying, WANG Da-Wang, FENG Yan, MA Teng-Cai
Chin. Phys. Lett. 2010, 27 (6): 068201 .   DOI: 10.1088/0256-307X/27/6/068201
Abstract   PDF(pc) (677KB) ( 1418 )

We present a simple method of producing Fe nanoparticles based on the dissociation of ferrocene by a simple single electrode atmospheric cold argon plasma jet. The system is driven by a sinusoidal ac-supply with a peak voltage of 0-30 kV and a frequency of 50 kHz. The average size of iron nanoparticles analyzed by scanning electron microscopy is about 10-30 nm for the gas phase samples, and 30-100 nm for the liquid phase samples. The method should be competitive due to its simplicity and low cost.

Static and Ultrafast Transient Photophysics of Mono- and Dual-Branched Triarylamines
LI Feng-Ming, MENG Fan-Shun, FENG Wen-Ke, WANG Shu-Feng**, TIAN He, GONG Qi-Huang
Chin. Phys. Lett. 2010, 27 (6): 068202 .   DOI: 10.1088/0256-307X/27/6/068202
Abstract   PDF(pc) (495KB) ( 401 )

Mono- and dual-branched molecules, {4-[2-(4-benzothiazol-2-yl-phenyl)-vinyl]-phenyl}-(4-methoxy-phenyl)-phenyl-amine (BS1) and bis-{4-[2- (4-benzothiazol-2-yl-phenyl)-vinyl]-phenyl}-(4-methoxy-phenyl)-phenyl-amine (BS2), are investigated with one- and two-photon static spectroscopy, and the femtosecond fluorescence up-conversion technique. The molecules show branch-based fluorescence emission at low quantum yield. Ultrafast non-radiative decay on a picosecond time scale is found and is attributed to intramolecular charge-transfer bridged by the central triphenylamine. The two-photon absorption cross-sections of BS1 and BS2 are 19.1 and 19.4 GM, respectively.

Simulation of Voltage SET Operation in Phase-Change Random Access Memories with Heater Addition and Ring-Type Contactor for Low-Power Consumption by Finite Element Modeling
GONG Yue-Feng, SONG Zhi-Tang, LING Yun, LIU Yan, LI Yi-Jin
Chin. Phys. Lett. 2010, 27 (6): 068501 .   DOI: 10.1088/0256-307X/27/6/068501
Abstract   PDF(pc) (611KB) ( 739 )

A three-dimensional finite element model for phase change random access memory is established to simulate electric, thermal and phase state distribution during (SET) operation. The model is applied to simulate the SET behaviors of the heater addition structure (HS) and the ring-type contact in the bottom electrode (RIB) structure. The simulation results indicate that the small bottom electrode contactor (BEC) is beneficial for heat efficiency and reliability in the HS cell, and the bottom electrode contactor with size Fx =80 nm is a good choice for the RIB cell. Also shown is that the appropriate SET pulse time is 100 ns for the low power consumption and fast operation.

A Charge-Trap Memory Device with a Composition-Modulated Zr-Silicate High-k Dielectric Multilayer Structure
LV Shi-Cheng, GE Zhong-Yang, ZHOU Yue, XU Bo, GAO Li-Gang, YIN Jiang, XIA Yi-Dong, LIU Zhi-Guo
Chin. Phys. Lett. 2010, 27 (6): 068502 .   DOI: 10.1088/0256-307X/27/6/068502
Abstract   PDF(pc) (845KB) ( 447 )

We report a novel charge-trap memory device with a composition-modulated Zr-silicate high-k dielectric multilayer structure prepared by using the pulsed laser deposition technique. The device employs amorphous (ZrO2)0.5(SiO2)0.5 as the tunneling and blocking oxide layers, and ZrO2 nanocrystals as the trapping storage layer. ZrO2 nanocrystals are precipitated from the phase separation of (ZrO2)0.8(SiO2)0.2 films annealed at 800\circC, and isolated from each other within the amorphous (ZrO2)0.5(SiO2)0.5 matrix. Our charge trapping device shows a memory window of 2.6 V and a stored electron density of 1×1013/cm2.

Heat Assisted Magnetic Recording with Matching Media and Recording Head Field
LIAO Jia-Lin, WEI Shen-Jin, LI Jing, JIN Qing-Yuan, CHE Xiao-Dong
Chin. Phys. Lett. 2010, 27 (6): 068503 .   DOI: 10.1088/0256-307X/27/6/068503
Abstract   PDF(pc) (1027KB) ( 611 )

The dynamic performance of heat assisted magnetic recording (HAMR) on different media is investigated. Signal and signal-to-noise ratio enhancement are achieved in high coercivity perpendicular media with the aid of laser heating. Linear recording density is increased while saturation write current is lowered. Trailing field partial erasure is observed in lower coercivity media with a ring head, which causes signal reduction with increasing write current or application of a laser. Precautions should be taken against partial erasure in overall recording system optimization of HAMR in order to achieve ultrahigh recording density.

Enhanced Field Emission from Large-Area Arrays of W18O49 Pencil-Like Nanostructure
LI Zheng-Lin, DENG Shao-Zhi, XU Ning-Sheng, LIU Fei, CHEN Jun
Chin. Phys. Lett. 2010, 27 (6): 068504 .   DOI: 10.1088/0256-307X/27/6/068504
Abstract   PDF(pc) (838KB) ( 413 )

Field enhancement and field screening are two major factors affecting field emission performance of arrays of quasi one-dimensional nanostructures. We have observed enhanced field emission from large-area arrays of W18O49 pencil-like nanostructure due to both the effects of high aspect ratio and enlarged spacing between neighboring nanostructures. These arrays may be grown on silicon substrates by the multi-step thermal evaporation process. The spacing of nanotip-to-nanotip between neighboring nanostructures may be increased by adjusting the growth temperature. The arrays are observed to have a typical turn-on field as low as about 1.26 MV/m and a threshold field as low as about 3.39 MV/m, resulting in increasing field enhancement and decreasing field screening effect.

Simulation of the Second Grade Fluid Model for Blood Flow through a Tapered Artery with a Stenosis
S. Nadeem, Noreen Sher Akbar
Chin. Phys. Lett. 2010, 27 (6): 068701 .   DOI: 10.1088/0256-307X/27/6/068701
Abstract   PDF(pc) (414KB) ( 703 )

We analyze the blood flow through a tapered artery, assuming the blood to be a second order fluid model. The resulting nonlinear implicit system of partial differential equations is solved by the perturbation method. The expressions for shear stress, velocity, flow rate, wall shear stress and longitudinal impedance are obtained. The physical behavior of different parameters is also discussed, as are trapping phenomena.

Effect of Eliminating Edges on Robustness of Scale-Free Networks under Intentional Attack
LI Yong, WU Jun, ZOU An-Quan
Chin. Phys. Lett. 2010, 27 (6): 068901 .   DOI: 10.1088/0256-307X/27/6/068901
Abstract   PDF(pc) (345KB) ( 456 )

We study the robustness of complex networks under edge elimination. We propose three different edge elimination strategies and investigate their effects on the robustness of scale-free networks under intentional attack. We show that deleting a proper fraction of edges connecting hub nodes and hub nodes can enhance the robustness of scale-free networks under intentional attack.

Statistical Property and Model for the Inter-Event Time of Terrorism Attacks
ZHU Jun-Fang, HAN Xiao-Pu, WANG Bing-Hong,
Chin. Phys. Lett. 2010, 27 (6): 068902 .   DOI: 10.1088/0256-307X/27/6/068902
Abstract   PDF(pc) (750KB) ( 604 )

The inter-event time of terrorism attack events is investigated by empirical data and model analysis. Empirical evidence shows that it follows a scale-free property. In order to understand the dynamic mechanism of such a statistical feature, an opinion dynamic model with a memory effect is proposed on a two-dimensional lattice network. The model mainly highlights the role of individual social conformity and self-affirmation psychology. An attack event occurs when the order parameter indicating the strength of public opposition opinion is smaller than a critical value. Ultimately, the model can reproduce the same statistical property as the empirical data and gives a good understanding for the possible dynamic mechanism of terrorism attacks.

Information Filtering via Improved Similarity Definition
PAN Xin, DENG Gui-Shi, LIU Jian-Guo,
Chin. Phys. Lett. 2010, 27 (6): 068903 .   DOI: 10.1088/0256-307X/27/6/068903
Abstract   PDF(pc) (364KB) ( 545 )

Based on a new definition of user similarity, we introduce an improved collaborative filtering (ICF) algorithm, which could improve the algorithmic accuracy and diversity simultaneously. In the ICF, instead of the standard Pearson coefficient, the user-user similarities are obtained by integrating the heat conduction and mass diffusion processes. The simulation results on a benchmark data set indicate that the corresponding algorithmic accuracy, measured by the ranking score, is improved by 6.7% in the optimal case compared to the standard collaborative filtering (CF) algorithm. More importantly, the diversity of the recommendation lists is also improved by 63.6%. Since the user similarity is crucial for the CF algorithm, this work may shed some light on how to improve the algorithmic performance by giving accurate similarity measurement.

Addendum and Corrigendum: “Heavy Quarkonium Spectra in a Quark Potential Model”
Chin. Phys. Lett. 2010, 27 (6): 069901 .   DOI: 10.1088/0256-307X/27/6/069901
Abstract   PDF(pc) (147KB) ( 412 )
76 articles