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Synchronization of Colored Networks via Discrete Control
SUN Mei, LI Dan-Dan, HAN Dun, JIA Qiang
Chin. Phys. Lett. 2013, 30 (9):
090202
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DOI: 10.1088/0256-307X/30/9/090202
We investigate the synchronization problem of two colored networks via discrete control based on the Lyapunov stability theory. First, intermittent control is adopted to synchronize two edge-colored networks, and the sufficient condition connecting the control width, control period and the network topology is established for reaching synchronization. Then, an impulsive controller is designed to ensure two general colored networks in synchronization, and the relation among the impulsive interval, impulsive gain and the network topology for synchronization is also discovered. Finally, two numerical examples are provided to demonstrate and verify the theoretical results.
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The Thermodynamical Behaviors of Kerr–Newman AdS Black Holes
A. Belhaj, M. Chabab, H. El Moumni, L. Medari, M. B. Sedra
Chin. Phys. Lett. 2013, 30 (9):
090402
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DOI: 10.1088/0256-307X/30/9/090402
We reconsider the study of critical behaviors of Kerr–Newman Anti-de Sitter (AdS) black holes in four dimensions. The study is made in terms of the moduli space parameterized by the charge Q and the rotation parameter a, relating the mass M of the black hole and its angular momentum J via the relation a =J/M. Specifically, we discuss such thermodynamical behaviors in the presence of a positive cosmological constant considered as a thermodynamic pressure and its conjugate quantity as a thermodynamic volume. The equation of state for a charged Reissner–Nordstrom AdS black hole predicts a critical universal number depending on the (Q,a) moduli space. In the vanishing limit of the a parameter, this prediction recovers the usual universal number in four dimensions. Then, we find the bounded region of the moduli space allowing the consistency of the model with real thermodynamical variables.
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Multi-Scale Permutation Entropy: A Complexity Measure for Discriminating Two-Phase Flow Dynamics
FAN Chun-Ling, JIN Ning-De, CHEN Xiu-Ting, GAO Zhong-Ke
Chin. Phys. Lett. 2013, 30 (9):
090501
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DOI: 10.1088/0256-307X/30/9/090501
We propose an improved permutation entropy method, i.e., multi-scale permutation entropy (MSPE), for discriminating two-phase flow dynamics. We first take the signals from different typical dynamical systems as examples to demonstrate the effectiveness of the methods. In particular, we compute the MSPE values of sinusoidal signal, logistic, Lorenz and Chen chaotic signals and their signals with white Gaussian noise added. We find that the MSPE method can be an effective tool for analyzing the time series with distinct dynamics. We finally calculate the multi-scale permutation entropy and rate of MSPE from 66 groups of conductance fluctuating signals and find that these two measures can be used to identify different flow patterns and further explore dynamical characteristics of gas-liquid flow patterns. These results suggest that the MSPE can potentially be a useful tool for revealing the dynamical complexity of two-phase flow on different scales.
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Self-Starting Harmonic Mode-Locked Thulium-Doped Fiber Laser with Carbon Nanotubes Saturable Absorber
S. W. Harun, N. Saidin, D. I. M. Zen, N. M. Ali, H. Ahmad, F. Ahmad, K. Dimyati
Chin. Phys. Lett. 2013, 30 (9):
094204
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DOI: 10.1088/0256-307X/30/9/094204
We report a ring cavity passively harmonic mode-locked thulium-doped fiber laser (TDFL) using a newly developed single-wall carbon nanotube-based saturable absorber. The TDFL generates the 25th harmonic mode-locked stretched pulse train with a high repetition rate of 213 MHz and a pulse duration of 710 fs. The laser operates at 1901.6 nm with an average power of 1.89 mW, which corresponds to the pulse energy of 0.008 nJ, at 1552 nm pump power of 719 mW. The peak-to-background ratio is measured to be 60 dB, which indicates the stability of the laser.
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Experimental Investigation of the Induced Airflow of Corona Discharge
HUANG Yong, ZHANG Xin, WANG Xun-Nian, WANG Wan-Bo, HUANG Zong-Bo, LI Hua-Xing
Chin. Phys. Lett. 2013, 30 (9):
094702
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DOI: 10.1088/0256-307X/30/9/094702
In order to improve the acceleration effect of corona discharge acting on air, we present an experimental study on the induced airflow produced by corona discharge between two parallel electrodes. The parameters investigated are the type of electrodes, actuation voltage and the distance in the absence of free airflow. The induced flow velocity is measured directly in the accelerated region using the particle image velocimetry technology. The results show that if corona discharge is not developed into arc discharge, the induced airflow velocity increases nearly linearly with the applied voltage and the maximum induced airflow velocity near the needle electrode reaches 36 m/s. It is expected that in the future, the result can be referred to in the research about effect of active flow control to reach much higher induced airflow speed.
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Wake Effects in Ion Transport through Carbon Nanotubes
ZHANG Ying-Ying, ZHAO Dan, YOU Shu-Yan, SONG Yuan-Hong, WANG You-Nian
Chin. Phys. Lett. 2013, 30 (9):
096103
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DOI: 10.1088/0256-307X/30/9/096103
A semiclassical kinetic model is explored to investigate the wake effects in the transport of charged particles through single-walled (SWCNT) and double-walled (2WCNTs) carbon nanotubes, with the introduction of electron band structure effect. The analytical expressions of the induced electron density at nanotube surface and the induced potential around the nanotube walls are obtained. The simulation results indicate that a bell-like distribution appears for the induced electron density when the incident particle speed is below a threshold value, otherwise wake-like oscillation can be seen behind the particle in the axial distribution. Dependencies of the amplitude and frequency of oscillations on the incident particle speed are also discussed. Meanwhile, we notice that the valence electrons on the outer wall of 2WCNTs tend to be easily excited by the polarized electrons on the inner wall, compared with that by the incident particle without the inner wall in SWCNTs. Finally, the induced potential trailing the incident particle also exhibits remarkable oscillations, not only along the axial direction but also in the lateral region, with evident extrema at the nanotube walls.
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Characterization of Obtuse Triangular Defects on 4H-SiC 4° off-Axis Epitaxial Wafers
DONG Lin, SUN Guo-Sheng, YU Jun, ZHENG Liu, LIU Xing-Fang, ZHANG Feng, YAN Guo-Guo, LI Xi-Guang, WANG Zhan-Guo, YANG Fei
Chin. Phys. Lett. 2013, 30 (9):
096105
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DOI: 10.1088/0256-307X/30/9/096105
We investigate the triangular defects with different structural features on 4H-SiC epilayers by a Nomarski microscope, a Candela optical surface analyzer and ultraviolet photoluminescence (UV-PL) imaging. Both the foreign particles and the substrate scratches can cause the formation of the obtuse triangular defects. The central area of some obtuse triangular defects can have the spatially confined core, in which the in-grown stacking faults can be observed under the UV-PL imaging. In contrast, the obtuse triangular defects induced by the scratches appear in the form of band-like defects, of which the width depends on the scratch direction and reaches the maximum when the scratch direction is parallel to the step flow direction. The formation mechanisms of these obtuse triangular defects are discussed.
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Influence of Temperature and Stress on Near-Surface Cascades in Alpha-Zirconium Revealed by Molecular Dynamics Simulation
WU Tian-Yu, PENG Meng-Meng, LUO Xiao-Feng, LAI Wen-Sheng
Chin. Phys. Lett. 2013, 30 (9):
096106
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DOI: 10.1088/0256-307X/30/9/096106
Molecular dynamics simulations are used to study cascades near the surface in hcp Zr. The influences of several factors, namely the primary knock-on atom (PKA) in different layers, angle of incidence, temperature and stress, on the number and type of defects are considered. Compared to bulk cascades, near-surface cascades show different characteristics in defect type and quantity when the PKA is in different layers. Low angle incidences create surface sputtering while the effects of high angle incidences are similar to those of bulk cascades. The effect of temperature is mainly focused on the number of sputtered atoms, with little influence on the total number of surviving defects. Stress helps to create more defects and the influence of compressive stress is more prominent than tensile stress.
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First Principle Calculations of the Ground and Excited State Properties of RbPbF3
Hayatullah, G. Murtaza, R. Khenata, S. Naeem, M. N. Khalid, S. Mohammad
Chin. Phys. Lett. 2013, 30 (9):
097101
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DOI: 10.1088/0256-307X/30/9/097101
Structural, elastic, electronic, chemical bonding and optical properties of the cubic RbPbF3 compound under pressure are studied using a highly accurate state-of-the-art full potential linearized augmented plane wave method. The exchange correlation effects are included through the generalized gradient and modified Becke–Johnson exchange potential. The lattice constant and band gap of the cubic RbPbF3 decreases with enhanced pressure. RbPbF3 is brittle, elastically anisotropic, and a direct bandgap material. Its optical properties such as refractive index n(ω), extinction coefficient k(ω), reflectivity R(ω), and optical conductivity σ(ω) are predicted.
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An All-Optical Diode Based on Plasmonic Attenuation and Nonlinear Frequency Conversion
REN Ming-Liang, ZHONG Xiao-Lan, CHEN Bao-Qin, LI Zhi-Yuan
Chin. Phys. Lett. 2013, 30 (9):
097301
.
DOI: 10.1088/0256-307X/30/9/097301
We present the design of an all-optical diode in a metal-dielectric structure where plasmonic attenuation and quasi-phase-matching are harnessed to greatly improve its performance. Due to the asymmetric design of the second-order nonlinear coefficient, different incident directions will ignite different plasmonic nonlinear processes, which compensate or accelerate plasmonic attenuation. As a result, a unidirectional output of plasmonic signal is achieved. This designed all-optical diode shows advantages of low power consumption, short sample length, high isolation contrast, wide acceptance of structural and initial conditions, and tunable unidirectionality, and becomes of practical interest.
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The Application of a New Simulation Approach to Ferrimagnetic Nanowires
LIU Zhao-Sen, YANG Cui-Hong, GU Bin, MA Rong, LI Qing-Fang
Chin. Phys. Lett. 2013, 30 (9):
097302
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DOI: 10.1088/0256-307X/30/9/097302
The quantum simulation model and the self-consistent computational algorithm we proposed two years ago are utilized to investigate the physical properties of a magnetic nanowire consisting of 3d ions which are coupled antiferromagnetically. In the absence of the external magnetic field, all simulations are started from a spin configuration with all moments in the nanosample randomly oriented and performed from a temperature above the magnetic transition temperature TM down to very low temperature as carried out by previous researchers using the Monte Carlo method, and such obtained results are all physically reasonable, verifying the correctness of the simulation model and computing algorithm. In addition, our calculated results suggest that increasing the surface anisotropy enables an increase in the magnetic transition temperature, although less effectively than by enhancing the Heisenberg exchange strength directly.
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The Impact Induced Demagnetization Mechanism in NdFeB Permanent Magnets
LI Yan-Feng, ZHU Ming-Gang, LI Wei, ZHOU Dong, LU Feng, CHEN Lang, WU Jun-Ying, QI Yan, DU An
Chin. Phys. Lett. 2013, 30 (9):
097501
.
DOI: 10.1088/0256-307X/30/9/097501
Compression of unmagnetized Nd2Fe14B permanent magnets is executed by using shock waves with different pressures in a one-stage light gas gun system. The microstructure, crystal structure, and magnetic properties of the magnets are examined with scanning electronic microscopy, x-ray diffraction, hysteresis loop instruments, and a vibrating sample magnetometer, respectively. The NdFeB magnets display a demagnetization phenomenon after shock wave compression. The coercivity dropped from about 21.4 kOe to 3.2 kOe. The critical pressure of irreversible demagnetization of NdFeB magnets should be less than 4.92 GPa. The coercivity of the NdFeB magnets compressed by shock waves could be recovered after annealing at 900°C and 520°C for 2 h, sequentially. The chaotic orientation of Nd2Fe14B grains in the compressed magnets is the source of demagnetization.
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Strain Distributions in Non-Polar a-Plane InxGa1?xN Epitaxial Layers on r-Plane Sapphire Extracted from X-Ray Diffraction
ZHAO Gui-Juan, YANG Shao-Yan, LIU Gui-Peng, LIU Chang-Bo, SANG Ling, GU Cheng-Yan, LIU Xiang-Lin, WEI Hong-Yuan, ZHU Qin-Sheng, WANG Zhan-Guo
Chin. Phys. Lett. 2013, 30 (9):
098102
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DOI: 10.1088/0256-307X/30/9/098102
By using x-ray diffraction analysis, we investigate the major structural parameters such as strain state and crystal quality of non-polar a-plane InxGa1?xN thin films grown on r-sapphire substrates by metalorganic chemical vapour deposition. The results of the inplane grazing incidence diffraction technique are analyzed and compared with a complementary out-of-plane high resolution x-ray diffraction technique. When the indium composition is low, the a-plane InxGa1?xN layer is tensile strain in the growth direction (a-axis) and compressive strain in the two in-plane directions (m-axis and c-axis). The strain status becomes contrary when the indium composition is high. The stress in the m-axis direction σyy is larger than that in the c-axis direction σzz. Furthermore, strain in the two in-plane directions decrease and the crystal quality becomes better with the growing of the InxGa1?xN film.
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Efficient Green Organic Light-Emitting Devices Based on a Solution-Processable Starburst Molecule
ZHANG Xin-Wen, WANG Jian-Yun, ZHAO Ling-Ling, GUO Xin, LAI Wen-Yong, HUANG Wei
Chin. Phys. Lett. 2013, 30 (9):
098501
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DOI: 10.1088/0256-307X/30/9/098501
We develop high efficiency solution-processed pure green organic light-emitting devices using a starburst molecule 7,7',7"-(5,5,10,10,15,15-hexahexyl-10, 15-dihydro-5H-diindeno[1, 2-a:1', 2'-c]fluorene-2,7,12-triyl)tris(4-(4-(9H-carbazol-9-yl)phenyl)benzo[c][1,2,5]thiadiazole) (TRcz) doped 2-methyl-9,10-di(2-naphthyl)anthracene (MADN) as the emitting layers. The electroluminescence properties of the devices with different doping concentrations are investigated. With the increasing doping concentration from 0.5wt% to 5wt%, the maximum efficiency changes from 4.8 cd/A to 8.4 cd/A. Under the optimal concentration of 4wt%, the device shows pure green emission at 516 nm with a chromaticity coordinate of (0.30, 0.59) as well as a high brightness of 19900 cd/m2 and a high efficiency of 10.1 cd/A, which are better than 11490 cd/m2 and 4.2 cd/A obtained in the undoped device.
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Stochastic Resonance of a General Relativistic Accretion Disk
WANG Zhi-Yun, CHEN Pei-Jie, ZHANG Liang-Ying
Chin. Phys. Lett. 2013, 30 (9):
099801
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DOI: 10.1088/0256-307X/30/9/099801
Based on a generalized Langevin equation, we consider a full general relativistic model to describe the vertical oscillations of particles in accretion disks around compact astrophysical objects, and calculate oscillating luminosity and power spectral density (PSD) of an accretion disk. The influences of the friction parameter ζ, spin parameter a? and mass M of the center compact object on the stochastic resonance (SR) in PSD curves are discussed. The results show that a large spin parameter a? can enhance the SR phenomenon, but the larger the ζ or M is, the weaker the SR phenomenon becomes. In addition, our simulated PSD curves of the output luminosity of stochastically oscillating disk have the same profile as the observed PSD of x-ray binaries, and the resonance peak in the PSD curve can interpret the quasi-periodic oscillations at the same time.
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51 articles
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