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Chin. Phys. Lett.  
  Chin. Phys. Lett.--2014, 31 (8)   Published: 28 July 2014
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GENERAL

Corrected Stefan–Boltzmann Law and Lifespan of a Black Hole

HE Tang-Mei, YANG Jin-Bo, ZHANG Jing-Yi
Chin. Phys. Lett. 2014, 31 (8): 080401 doi: 10.1088/0256-307X/31/8/080401
Full Text: [PDF 414 KB] (235)
Show Abstract
The corrected Stefan–Boltzmann law of black holes in the frame of a generalized uncertainty principle is derived through the Planck equation of thermal radiation. The result is different from the flat spacetime: a corrected T6 term induced by the generalized uncertainty principle emerges; the coefficient of the T4 term is no longer a constant while related with the spacetime in the vicinity of the event horizon and the thin film model. Applying this corrected law to black hole radiation, the highest temperature in the final time of the radiation and the corresponding remnant with a mass of order of Planck mass are obtained. The lifespan of black holes is also corrected, however, the correction is extremely small.

Quantum Heat Transfer in a Harmonic Chain with a Dephasing Reservoir

MING Yi, DING Xing
Chin. Phys. Lett. 2014, 31 (8): 080501 doi: 10.1088/0256-307X/31/8/080501
Full Text: [PDF 477 KB] (118)
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The quantum heat transfer in a harmonic chain with a dephasing reservoir is investigated based on the master equation method. The incoming phonons from the thermal reservoir will be scattered back partially into the reservoir at the contact site, leading to the contact resistance. Dephasing in the harmonic chain suppresses the transmitting of scattered phonons into the harmonic chain. Then the heat flux in the chain is reduced by dephasing. However, the heat flux is symmetric to interchanging the reservoirs temperatures even with the dephasing. Therefore, the thermal rectification cannot be realized with pure dephasing only.

Time-Delay Enhanced Coherence Resonance in a Discrete Neuron with Noises

WANG Can-Jun, YANG Ke-Li, QU Shi-Xian
Chin. Phys. Lett. 2014, 31 (8): 080502 doi: 10.1088/0256-307X/31/8/080502
Full Text: [PDF 1436 KB] (75)
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Coherence resonance in a discrete excitable neuronal model with noises and time delays is investigated. The effects of the time delays on coherence resonance are revealed in two cases: Gaussian white and Gaussian color noises, respectively. The coefficient of variation of interspike intervals is calculated by numerical simulation. The results show that the coherence resonance is enhanced with the time delay increasing in the weak noises intensity cases, while there is no effect in the large noise intensity. Moreover, the coherence resonance can be held back by the self-correlation time, when the system is driven by a color noise.

Dynamics of the Kuramoto Model with Bimodal Frequency Distribution on Complex Networks

FENG Yue-E, LI Hai-Hong, YANG Jun-Zhong
Chin. Phys. Lett. 2014, 31 (8): 080503 doi: 10.1088/0256-307X/31/8/080503
Full Text: [PDF 1346 KB] (61)
Show Abstract
We introduce a piecewise uniform frequency distribution to model a symmetrical bimodal natural frequency distribution and investigate the dynamics in the Kuramoto model on complex networks. We find that the scenario of the synchronization transition depends on the network topology. For an ER network, the incoherent state, standing wave states and stationary synchronous states are encountered successively with the increase of the coupling strength. However, for an SF network, there exists another type of synchronous states, traveling wave states, between the standing wave states and the stationary synchronous states.

Random Walks on Deterministic Weighted Scale-Free Small-World Networks with a Perfect Trap

JING Xing-Li, LING Xiang, HU Mao-Bin, SHI Qing
Chin. Phys. Lett. 2014, 31 (8): 080504 doi: 10.1088/0256-307X/31/8/080504
Full Text: [PDF 524 KB] (60)
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Random walks are the most fundamental process among various dynamical processes, and most previous works focused on binary networks. This work studies random walks on deterministic weighted scale-free small-world networks with a perfect trap. We derive an explicit expression of the mean first passage time on the network with a trap. Meanwhile, we present the evolutionary rule for the first passage time when the network grows. The study can be useful for understanding the random walks on weighted networks.

The Stability Analysis for an Extended Car Following Model Based on Control Theory

GE Hong-Xia, MENG Xiang-Pei, ZHU Ke-Qiang, CHENG Rong-Jun
Chin. Phys. Lett. 2014, 31 (8): 080505 doi: 10.1088/0256-307X/31/8/080505
Full Text: [PDF 590 KB] (50)
Show Abstract
A new method is proposed to study the stability of the car-following model considering traffic interruption probability. The stability condition for the extended car-following model is obtained by using the Lyapunov function and the condition for no traffic jam is also given based on the control theory. Numerical simulations are conducted to demonstrate and verify the analytical results. Moreover, numerical simulations show that the traffic interruption probability has an influence on driving behavior and confirm the effectiveness of the method on the stability of traffic flow.

On a New Class of Self-Referencing, 1/τ Atomic Clocks

WANG Li-Jun
Chin. Phys. Lett. 2014, 31 (8): 080601 doi: 10.1088/0256-307X/31/8/080601
Full Text: [PDF 429 KB] (42)
Show Abstract
The merit of a modern atomic clock is measured by its phase stability. A clock's absolute time-keeping uncertainty typically worsens over its operating time τ as Δτ∝√τ, with an Allan deviation of σy (τ)=Δτ/τ∝τ−1/2. Here we analyze a new class of self-referencing clocks, whose phase is locked to itself after a certain time delay. We show that the Allan deviation of such clocks decreases as 1/τ over a long and controllable operating time. This class of clocks can maintain synchronization over a prolonged period with only a fixed, almost non-increasing, absolute uncertainty, forming an ideal time-piece.
THE PHYSICS OF ELEMENTARY PARTICLES AND FIELDS

Quark and Gluon Condensates at Finite Temperatures by the Linear Sigma Model Approach

DING Jing-Zhi, JIN Hong-Ying
Chin. Phys. Lett. 2014, 31 (8): 081201 doi: 10.1088/0256-307X/31/8/081201
Full Text: [PDF 412 KB] (42)
Show Abstract
Based on a linear sigma model, we discuss the mixing between a quark condensate and a gluon condensate. It is shown that the linear sigma model will not be self-consistent if we switch off the mixing coupling between glueball and chiral fields. By introducing a proper mixing coupling, we realize the second-order phase transitions of chiral symmetry restoration and deconfinement. We further show that the critical temperature of chiral symmetry restoration could not be larger than the temperature of deconfinement phase transition in all possible parameter spaces of our model.
NUCLEAR PHYSICS

Medium Suppression of In medium Nucleon-Nucleon Cross Sections Predicted with Various Microscopic Calculations

XING Yong-Zhong, LU Fei-Ping, WEI Xiao-Ping, ZHENG Yu-Ming
Chin. Phys. Lett. 2014, 31 (8): 082101 doi: 10.1088/0256-307X/31/8/082101
Full Text: [PDF 620 KB] (31)
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The nucleon-nucleon cross sections in the dense nuclear matter are microscopically calculated by using Dirac–Brueckner–Hartree–Fock (DBHF) approximation with different covariant representations of the T-matrix, i.e., complete pseudo-vector (CPV), pseudoscalar (PS) and pseudo-vector (PV) choices. Special attention is paid to the discrepancies among the cross sections calculated with these different T-matrix project choices. The results show that the medium suppression of the cross section given by DBHF in the CPV choice is not only smaller than those obtained in both PS and PV choices, but also smaller than the predictions with a nonrelativistic Brueckner–Hartree–Fock (BHF) method including three body force (3BF). The further analysis reveals that the influence of the different choices on the cross section in the DBHF approximation is mainly determined by the state of smaller total angular momentum due to the medium effect being strongly suppressed in the higher angular momentum.

Ab Initio MCSM Calculation for Reduced Matrix Elements of E2 Operator for A=10 Nuclei

LIU Lang
Chin. Phys. Lett. 2014, 31 (8): 082102 doi: 10.1088/0256-307X/31/8/082102
Full Text: [PDF 600 KB] (18)
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The reduced matrix elements of Ê2 operator for 10Be low-lying states are evaluated with the no-core Monte Carlo shell model, which has been used to investigate the structure of light nuclei in an ab initio sense recently. The MCSM calculation converges within 20 MCSM dimensions. These MCSM results show good agreement with new experimental data and other ab initio calculations. The reduced matrix elements are investigated in terms of single-particle orbits contribution. It is found that the transition among p-shell orbits is dominant. The triaxial deformation of 10Be, as well as its mirror nucleus 10C, is also discussed. Meanwhile, the importance of p-shell orbits to the triaxiality is addressed.

Light Hadron Production in Proton–Proton Collisions at Different LHC Energies: Measured Data versus a Model

P. Guptaroy, S. Guptaroy
Chin. Phys. Lett. 2014, 31 (8): 082501 doi: 10.1088/0256-307X/31/8/082501
Full Text: [PDF 544 KB] (21)
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Experiments involving proton–proton collisions at energies √sNN=0.9, 2.76 and 7 TeV in the large hadron collider produce a vast amount of high-precision data. In this work, we analyze two aspects of the measured data, viz., (i) the pT-spectra of pions, kaons, proton-antiproton at the above-mentioned energies, and (ii) some of their very important ratio behaviors, in the light of a version of the sequential chain model. The agreements between the measured data and the model-based results are generally found to be modestly satisfactory.

A Module Test of CCDA: an Array to Select the Centrality of Collisions in Heavy Ion Collisions

FU Fen, LIN Wei-Ping, LIU Xing-Quan, HUANG Mei-Rong, WADA Roy, ZHANG Su-Ya-La-Tu, SHI Fu-Dong, HAN Rui, JIN Zeng-Xue, LIU Jian-Li, REN Pei-Pei, ZHAO Ming-Hui, CHEN Zhi-Qiang, WANG Jian-Song
Chin. Phys. Lett. 2014, 31 (8): 082502 doi: 10.1088/0256-307X/31/8/082502
Full Text: [PDF 803 KB] (24)
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A test result of a module for the collision centrality detector array (CCDA), a simple detector array for the event classification of the centrality, is presented. The CsI(Tl) module has PMTs on both ends to read out signals. The beam test results indicate that it provides a good light charged particles (LCP) identification and a reasonable energy resolution. The energy spectra of LCPs are compared with the GEANT simulation.
ATOMIC AND MOLECULAR PHYSICS

Velocity Transfer Spectroscopy of Rb 420 nm Transition

ZHANG Li-Guo, LIU Zhong-Zheng, TAO Zhi-Ming, LING Li, CHEN Jing-Biao
Chin. Phys. Lett. 2014, 31 (8): 083101 doi: 10.1088/0256-307X/31/8/083101
Full Text: [PDF 478 KB] (44)
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We propose and demonstrate the velocity transfer spectroscopy of a V-type energy structure with Rb atoms at 420 nm transition. The weak oscillator strength of a lower excited state for V-type energy structure atoms limits the high signal-to-noise ratio of atomic laser spectroscopy, which can be usually realized by optical-optical double-resonance or double-resonance optical pumping for cascade-type energy structure atoms. For 87Rb atoms, the weak 420 nm transition spectrum between the energy level of 52S1/2 and 62P3/2 is transferred to the spectrum on lower excited states at 780 nm with strong oscillator strength, which is recorded by a 780 nm probe laser. This method, which is similar to the electron-shelving detection method, at a certain degree can indirectly measure a higher excited state transition with weak oscillator strength for any V-type energy structure of atoms by transferring the transition spectrum information of the very weak oscillator strength to the strong oscillator strength in an optical-optical double-resonance configuration.

Absolute Cross Sections for Near-Threshold Electron-Impact Excitation of the 2s 2S→2p 2P Transition of Li-Like C3+, N4+, and O5+ Ions

YANG Ning-Xuan, ZHANG Jian-Jun, DONG Chen-Zhong
Chin. Phys. Lett. 2014, 31 (8): 083401 doi: 10.1088/0256-307X/31/8/083401
Full Text: [PDF 647 KB] (25)
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Excitation cross sections of 1s22s 2S1/2→1s22p 2P1/2, 3/2 transition among the fine-structure levels in Li-like C3+, N4+, and O5+ ions are calculated for energies of the near-threshold by using the relativistic distorted-wave program REIE06. The target state wavefunctions are calculated by using the Grasp92 code. The continuum orbitals are studied in the distorted-wave approximation, in which the direct and exchange potentials among all the electrons are included. The results of the Li-like C3+ ion settle the discrepancy between several previous experiments by using the crossed-beams fluorescence method, in good agreement with the measurements of Savin et al. Moreover, the results in Li-like N4+, and O5+ ions are compared with the previous experiments, and a good agreement is obtained.

Impact Excitations of Hydrogen Atoms in Collisions with Protons and Antiprotons

Reda S. Tantawi, T. E. I. Nassar
Chin. Phys. Lett. 2014, 31 (8): 083402 doi: 10.1088/0256-307X/31/8/083402
Full Text: [PDF 1873 KB] (26)
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The direct impact excitations of ground-state hydrogen atoms by protons and antiprotons are investigated by using an impact parameter treatment. The calculations are performed within the solution of the coupled differential equations arising from the one-center atomic-orbital close-coupling approach as well as the impact parameter version of the first and second Born approximations. We have considered calculations that allow couplings to the n=1–5 states (up to g sub-levels) of the target atom as well as others, which neglect the effect of all states other than the initial and final states of the target atom. The sensitivity of the cross sections to the charge of the projectile is studied. The calculated cross sections are compared with those obtained by previous theoretical and experimental results.
FUNDAMENTAL AREAS OF PHENOMENOLOGY(INCLUDING APPLICATIONS)

Application of Ultra-Compact Single Negative Waveguide Metamaterials for a Low Mutual Coupling Patch Antenna Array Design

CAI Tong, WANG Guang-Ming, LIANG Jian-Gang, ZHUANG Ya-Qiang
Chin. Phys. Lett. 2014, 31 (8): 084101 doi: 10.1088/0256-307X/31/8/084101
Full Text: [PDF 1129 KB] (16)
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A novel ultra-compact single-negative waveguide metamaterial (WG-MTM) based on a complementary anti-parallel-spiral line (CAPAL) is proposed and investigated by circuit model analysis, electromagnetic simulation and extraction of the effective parameters. The cell is ultra-compact with dimensions of λ0/22.08×λ0/22.08, which advances a step further toward homogenized concept. Two band-gaps attributing to the negative permeability and negative permittivity appear when the CAPAL-WG-MTM cells response to the time-varying perpendicular E-field and parallel H-field, and thus a high decoupling efficiency is obtained. Mutual coupling reduction of about 8.27 dB is realized by inserting 7×1 CAPSL-WG-MTM cells between two closely placed antenna elements with an edge-to-edge separation of only λ0/19.23. Moreover, the radiation characteristics are improved for both the patch element and the antenna array. A higher front-to-back ratio is obtained for the patch element and an increase of 0.64 dB for the gain of the antenna array by using the CAPAL-WG-MTM structure.

Stability and Group Index Switching in a Four-Level Atomic System

Jafarzadeh Hossein, Ahmadi Sangachin Elnaz, Asadpour Seyyed Hossein
Chin. Phys. Lett. 2014, 31 (8): 084201 doi: 10.1088/0256-307X/31/8/084201
Full Text: [PDF 546 KB] (25)
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A four-level atomic system is proposed for stability and group index switching in the presence of spontaneously generated coherence. It is found that the transition from optical bistability (OB) to optical multistability (OM) and subluminal to superluminal can be obtained simultaneously. It is shown that the relative phase between applied fields can affect the stability and group index behaviors of weak probe light in the medium. Our proposed model provides a new scheme for simultaneous switching from OB to OM and (sub-to-super) luminal light propagation in an atomic system.

Experimental Demonstration of a Displacement Measurement of an Optical Beam beyond the Quantum Noise Limit

SUN Heng-Xin, LIU Zun-Long, LIU Kui, YANG Rong-Guo, ZHANG Jun-Xiang, GAO Jiang-Rui
Chin. Phys. Lett. 2014, 31 (8): 084202 doi: 10.1088/0256-307X/31/8/084202
Full Text: [PDF 647 KB] (26)
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We experimentally generate a spatially squeezed light beam and realize a small−displacement measurement beyond the quantum noise limit with this squeezed light. Moreover, we measure about -2.2±0.2 dB spatial squeezing and reduce the minimum measurable displacement from 1.17 Å to 0.99 Å with the signal-to-noise ratio normalized to 1.

A Stable 2012.1 nm Single-Longitudinal-Mode Tm:YAG Ceramic Laser with Volume Bragg Grating and Fabry–Perot Etalon

DAI Tong-Yu, DENG Yun, JU You-Lun, DUAN Xiao-Ming, YAO Bao-Quan, WANG Yue-Zhu
Chin. Phys. Lett. 2014, 31 (8): 084203 doi: 10.1088/0256-307X/31/8/084203
Full Text: [PDF 633 KB] (19)
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We demonstrate a stable single longitudinal mode Tm:YAG ceramic laser operating at a single wavelength of 2012.1 nm. The single-longitudinal-mode Tm:YAG ceramic laser is obtained by employing volume Bragg grating as one cavity mirror and inserting a Fabry–Perot etalon into the laser cavity. A maximum single longitudinal mode output power of 165 mW with a slope efficiency of 6.6% is achieved under the pump power of 5.02 W. The laser has a beam quality of M2=1.18 at the maximum single longitudinal mode output power.

Long-Term Stabilization of Carrier-Envelope Phase for Few Cycles Ti:Sapphire Laser Amplifier

ZHANG Wei, TENG Hao, YUN Chen-Xia, YE Peng, ZHAN Min-Jie, ZHONG Shi-Yang, HE Xin-Kui, WANG Li-Feng, WEI Zhi-Yi
Chin. Phys. Lett. 2014, 31 (8): 084204 doi: 10.1088/0256-307X/31/8/084204
Full Text: [PDF 901 KB] (21)
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We realize a long-term carrier-envelope phase (CEP) stabilization for a chirped pulse amplified Ti:sapphire laser by locking the oscillator and amplifier independently. Based on the measurement of CEP by employing f-to-2f interference technique between the octave-spanning spectrum which is generated from a rare gas filled hollow fiber, continuous locking time up to 7.2 h with 85 mrad fluctuation is demonstrated. Finely compensating the dispersion by a set of chirped mirrors, quasi-mono cycle pulses as shorter as 3.8 fs are obtained. Further experimental research on high harmonic generation dependence on CEP shown the waveform of laser pulses has been successfully controlled.

Spontaneous-Emission Coupling from an Excited Atom into a Symmetrical Metal-Cladding Optical Waveguide

TAN Rong, HUANG He
Chin. Phys. Lett. 2014, 31 (8): 084205 doi: 10.1088/0256-307X/31/8/084205
Full Text: [PDF 615 KB] (22)
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We consider the coupling behavior which transfers the energy of the spontaneous emission from an atom embedded in free space into a symmetrical metal-cladding optical waveguide. The ratio for spontaneous emission into the waveguide modes is derived by using a compact form of Green's function for a multilayer. Up to 90% of the spontaneous emission energy fed into the waveguide is demonstrated when the atom is positioned above the waveguide in a limited space range.

Passive Phase Locking of Three Nanosecond Fiber Amplifiers Using a Dammann Grating Spatial Filter

YANG Yi-Feng, ZHENG Ye, HE Bing, ZHOU Jun, LIU Hou-Kang, HU Man, WEI Yun-Rong, LOU Qi-Hong
Chin. Phys. Lett. 2014, 31 (8): 084206 doi: 10.1088/0256-307X/31/8/084206
Full Text: [PDF 641 KB] (19)
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A passive coherent beam combination of three nanosecond Yb-doped fiber amplifiers by an all-optical feedback loop is realized by a Dammann grating intracavity spatial filter. By using this diffractive-optics-based spatial filtering technique, three tile-aperture laser beams are phase-locked with a peak power of 1.02 kW. The width of the combined pulses is 9.6 ns, and the repetition frequency is 2.208 MHz. The visibility of the far-field interference pattern is up to 82.9%. The results show that this approach can scale to larger arrays and higher powers.

S0 Lamb Wave Scattering from a Cylindrical Inhomogeneity in a Transversely Isotropic Composite Plate

ZHANG Hai-Yan, YAO Jie-Cong, WANG Rui, MA Shi-Wei
Chin. Phys. Lett. 2014, 31 (8): 084301 doi: 10.1088/0256-307X/31/8/084301
Full Text: [PDF 711 KB] (9)
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An analytical model using the Poisson theory is proposed to predict the S0 Lamb wave scattering from a cylindrical inhomogeneity in a transversely isotropic composite plate. Due to the anisotropic elastic properties of the plate, the suitability of the model is first examined by the dispersion curve of an S0 wave by using approximate Poisson theory compared to the exact Lamb solution. It is found that the Poisson theory can accurately describe the behavior of the S0 wave at low frequency when the incident S0 wave is parallel or perpendicular to the fiber direction of the transversely isotropic composite plate. On this basis, making use of the wave function expansion technique and coupling conditions at the inhomogeneity defect boundary, the far field scattered patterns of various inhomogeneity sizes and properties are then explored. The present results reveal that the scattering patterns are strongly dependent on the size and stiffness of the cylindrical inhomogeneity.
PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES

Anode and Cathode Spots in High-Voltage Nanosecond-Pulse Discharge Initiated by Runaway Electrons in Air

SHAO Tao, Victor F. Tarasenko, YANG Wen-jin, Dmitry V. Beloplotov, ZHANG Cheng, Mikhail I. Lomaev, YAN Ping, Dmitry A. Sorokin
Chin. Phys. Lett. 2014, 31 (8): 085201 doi: 10.1088/0256-307X/31/8/085201
Full Text: [PDF 654 KB] (38)
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We report the experimental results with nanosecond-pulse discharges formed in the air gap between a flat electrode and a sharp electrode. The appearance of anode and cathode spots on the electrodes is studied experimentally. It is considered that bright spots on the flat cathode with positive polarity of the sharp electrode are formed due to the explosive electron emission on the cathode and the dynamic displacement current in the gap. It is also shown that with negative polarity of the sharp electrode, bright spots on the flat anode are formed after changing the polarity of the flat electrode due to the discharge oscillatory mode. Under these conditions, the explosive electron emission firstly forms on the sharp cathode. With negative polarity of the sharp electrode of the subnanosecond-pulse pulser, the runaway electron beam current is measured behind the anode foil with a time resolution of no more than 100 ps.
CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES

Engineering Double-Walled Carbon Nanotubes by Ar Plasma

ZHANG Yu-Chun, YAN Jing, ZHAO Shang-Qian, WANG Wen-Long, LIANG Wen-Jie
Chin. Phys. Lett. 2014, 31 (8): 086101 doi: 10.1088/0256-307X/31/8/086101
Full Text: [PDF 800 KB] (24)
Show Abstract
Double-walled carbon nanotubes (DWCNTs) have been found to be promising nano-materials for nano-mechanical and nano-electrical devices due to their double-walled structures. Modifying DWCNTs would be one of the key technologies for device construction. We demonstrate engineering the geometry of DWCNTs by etching with Ar plasma. The characterization by atomic force microscopy indicates that single atomic carbon layers could be removed from DWCNTs by Ar plasma. The etching effect is further investigated by electrical measurements on DWCNT field-effect transistors, which allow us to study the interwall screen effect as well.

Radiation Induced Optical Absorption of Cubic Lead Fluoride Crystals and the Effect of Annealing

REN Guo-Hao, CHEN Xiao-Feng, LI Huan-Ying, WU Yun-Tao, SHI Hong-Sheng, QIN Lai-Shun
Chin. Phys. Lett. 2014, 31 (8): 086102 doi: 10.1088/0256-307X/31/8/086102
Full Text: [PDF 588 KB] (18)
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Transparent and colorless lead fluoride crystals with sizes of 20×20×20 (mm3) are irradiated with several doses of γ-rays from a 60Co source. Their transmittance spectra before and after irradiation are measured, and a new parameter ΔT=Tb−Ta is defined to evaluate the irradiation damage. Three optical absorption bands peaking at 270 nm, 370 nm and 500 nm are found in the plots of ΔT versus wavelength, and their intensities increase with the irradiation dose. These optical absorption bands, except the one at 270 nm, can recover spontaneously with time. Thermal annealing treatment can enhance this recovery of the transmittance, while the optimum annealing temperature for different samples depends on the irradiation dose.

Effects of 1.0–11.5 MeV Electron Irradiation on GaInP/GaAs/Ge Triple-junction Solar Cells for Space Applications

WANG Rong, LU Ming, YI Tian-Cheng, YANG Kui, JI Xiao-Xia
Chin. Phys. Lett. 2014, 31 (8): 086103 doi: 10.1088/0256-307X/31/8/086103
Full Text: [PDF 540 KB] (12)
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GaInP/GaAs/Ge triple-junction solar cells are irradiated with 1.0, 1.8, and 11.5 MeV electrons with fluence ranging up to 3×1015, 3×1015, and 3×1014 cm−2, respectively. Their performance degradation effects are analyzed by using current-voltage characteristics, spectral response measurements, and electron irradiation-induced displacements. The degradation rates of the maximum power and the spectral response of the solar cells increase with the electron fluence, and also increase with the increasing electron energy. It is observed that the spectral response of the GaAs middle cell degrades more significantly than that of the GaInP top cell.

Mechanical Properties of Sialic Foamed Ceramic and Applications in Defense Structure

LI Xu-Yang, LI Yong-Chi, ZHAO Kai, GAO Guang-Fa
Chin. Phys. Lett. 2014, 31 (8): 086201 doi: 10.1088/0256-307X/31/8/086201
Full Text: [PDF 1382 KB] (19)
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Mechanical properties of a closed-cellular sialic foamed ceramic are investigated by compressive tests. The sialic foamed ceramic under uniaxial stress compression shows brittleness and the flow stress increases with the strain rate. The engineering stress-engineering strain curve under uniaxial strain compression could be divided into three stages: linear elasticity, collapsed plateau and densification. The unloading elastic modulus, Poisson ratio and energy absorption ability are discussed. Shelly cellular material made by sialic foamed ceramic is applied into the stress distribution layer in the defense structure. Field explosion experiments are performed for the sand based stress distribution layer and shelly cellular material based layer. Compared with sand, the shelly cellular material reduces the peak stress of the blast wave.

Mechanical and Electronic Properties of Iridium Nitride

LIU Qiang, PENG Wei-Min, PENG Feng
Chin. Phys. Lett. 2014, 31 (8): 086202 doi: 10.1088/0256-307X/31/8/086202
Full Text: [PDF 547 KB] (20)
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Based on the structures of known transition metal compounds, the phase stabilities and mechanical properties of iridium nitride (IrN) in nine structures are explored by using ab initio calculations. The calculation results show that MnP-structured IrN (MnP–IrN) is not only the most energetically stable, but also mechanically and dynamically stable at the ground state. The hardness is estimated to be 12 GPa.

Cavitation Simulation with Consideration of the Viscous Effect at Large Liquid Temperature Variation

YU An, LUO Xian-Wu, JI Bin, HUANG Ren-Fang, HIDALGO Victor, KIM Song Hak
Chin. Phys. Lett. 2014, 31 (8): 086401 doi: 10.1088/0256-307X/31/8/086401
Full Text: [PDF 674 KB] (11)
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The phase change due to cavitation is not only driven by the pressure difference between the local pressure and vapor saturated pressure, but also affected by the physical property changes in the case of large liquid temperature variation. The present work simulates cavitation with consideration of the viscous effect as well as the local variation of vapor saturated pressure, density, etc. A new cavitation model is developed based on the bubble dynamics, and is applied to analyze the cavitating flow around an NACA0015 hydrofoil at different liquid temperatures from 25°C to 150°C. The results by the proposed model, such as the pressure distribution along the hydrofoil wall surface, vapor volume fraction, and source term of the mass transfer rate due to cavitation, are compared with the available experimental data and the numerical results by an existing thermodynamic model. It is noted that the numerical results by the proposed cavitation model have a slight discrepancy from the experimental results at room temperature, and the accuracy is better than the existing thermodynamic cavitation model. Thus the proposed cavitation model is acceptable for the simulation of cavitating flows at different liquid temperatures.

Thermal Conduction in a Single Polyethylene Chain Using Molecular Dynamics Simulations

HU Guo-Jie, CAO Bing-Yang, LI Yuan-Wei
Chin. Phys. Lett. 2014, 31 (8): 086501 doi: 10.1088/0256-307X/31/8/086501
Full Text: [PDF 546 KB] (18)
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Research on the thermal conduction in a single polymer chain is significant for the improvement of the thermal property of bulk polymer materials. We calculate the thermal conductivity of a single polyethylene (PE) chain by using both the Green–Kubo approach and a nonequilibrium molecular dynamics simulation method. The results suggest that the thermal conductivity of an individual polymer chain is very high although bulk PE is a thermal insulator, even divergent in our case. Moreover, the thermal conductivity of PE chains is observed to increase with the chain length.

Creation of 174Yb Bose–Einstein Condensates in a Crossed FORT

ZHANG Meng-Jiao, ZHANG Xi, LIU Hui, XIONG Zhuan-Xian, LV Bao-Long, HE Ling-Xiang
Chin. Phys. Lett. 2014, 31 (8): 086701 doi: 10.1088/0256-307X/31/8/086701
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Quantum degenerate gases of alkaline-earth-like atoms are unique systems used for quantum simulation, quantum computing and studies of quantum phase transitions. We report an all-optical formation of Bose–Einstein condensates of ytterbium atoms. About 106 atoms of 174Yb are transferred to a far-off-resonance optical trap (FORT) and then cooled by evaporative cooling. Phase transition occurs at the critical temperature of 520 nK. A pure condensate containing approximately 2×104 atoms has been obtained in the crossed FORT, with an atomic peak density of ∼8×1014 cm−3. The condensate lifetime exceeds 1 s.

Aggregation Behaviors of Cr Atoms Sputtering Deposited on Flat and Curved Liquid Surfaces

CHEN Qi-Xiang, FENG Yu-Fei, SUN Ya-Dong, YU Sen-Jiang
Chin. Phys. Lett. 2014, 31 (8): 086801 doi: 10.1088/0256-307X/31/8/086801
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We report on the aggregation behaviors of Cr atoms deposited on flat and curved silicone oil substrates by the sputtering technique. It is found that the Cr atoms are prone to form quasi-circular clusters first and then these clusters connect with each other to form ramified or network-shaped aggregates. In the case of a flat liquid surface, large quasi-circular clusters are frequently observed and their sizes increase with the deposition time. In the case of a curved surface with a larger curvature, the Cr atoms and clusters tend to move toward to the oil drop edge, and ramified aggregates with small widths are shaped. In the case of a curved surface with smaller curvature, large quasi-circular clusters and ramified aggregations can coexist. Based on the motion features of the Cr atoms and clusters on different liquid surfaces, various distinct film morphologies are discussed in detail.
CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES

Comparative Studies of Rare-Earth Element Y-Doped In2O3 by First-Principles Calculations

BAI Li-Na, FENG Li-Feng, WANG Rui, JIANG Qing, LIAN Jian-She
Chin. Phys. Lett. 2014, 31 (8): 087101 doi: 10.1088/0256-307X/31/8/087101
Full Text: [PDF 793 KB] (19)
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In2O3 doped with rare-earth element yttrium shows improved optoelectronic efficiency. Here the structural properties and electronic structures of Y-doped In2O3 are investigated by using a first-principles approximation. For In1.9375Y0.0625O3, the d site is the more stable site. The Yi3+ interstitial has a low formation energy and is a possible interstitial defect, which would lead to shallow and abundant donors without sacrificing optical transparency. Since defects are universally distributed in In2O3 or doped In2O3, complex defect configurations are also calculated.

Pairing Symmetry of Heavy Fermion Superconductivity in the Two-Dimensional Kondo–Heisenberg Lattice Model

LIU Yu, ZHANG Guang-Ming, YU Lu
Chin. Phys. Lett. 2014, 31 (8): 087102 doi: 10.1088/0256-307X/31/8/087102
Full Text: [PDF 764 KB] (14)
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In the two-dimensional Kondo–Heisenberg lattice model away from half-filled, the local antiferromagnetic exchange coupling can provide the pairing mechanism of quasiparticles via the Kondo screening effect, leading to the heavy fermion superconductivity. We find that the pairing symmetry strongly depends on the Fermi surface (FS) structure in the normal metallic state. When JH/JK is very small, the FS is a small hole-like circle around the corner of the Brillouin zone, and the s-wave pairing symmetry has a lower ground state energy. For the intermediate coupling values of JH/JK, the extended s-wave pairing symmetry gives the favored ground state. However, when JH/JK is larger than a critical value, the FS transforms into four small hole pockets crossing the boundary of the magnetic Brillouin zone, and the d-wave pairing symmetry becomes more favorable. In that regime, the resulting superconducting state is characterized by either a nodal d-wave or nodeless d-wave state, depending on the conduction electron filling factor as well. A continuous phase transition exists between these two states. This result may be related to the phase transition of the nodal d-wave state to a fully gapped state, which has recently been observed in Yb-doped CeCoIn5.

Analysis of a Graphane p–n Junction Using the Green Function Method

Ashkan Horri, Seyedeh Zahra Mirmoeini
Chin. Phys. Lett. 2014, 31 (8): 087301 doi: 10.1088/0256-307X/31/8/087301
Full Text: [PDF 368 KB] (20)
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We analyze the graphane p-n junction performance. The analysis method is based on solving Poisson and current equations by using the Green function method. The Green function method gives a simple and fast tool for solving the Poisson equation. Our analysis method is different compared to earlier reports about the analysis of the graphane p-n junction. By using the presented method, the electrical field, electrical potential, and carrier concentration in devices are calculated. Our results are in agreement with numerical and experimental results reported by other researchers. Due to taking into account the carrier concentration in the space charge region, the precision of our results is better than former ones.

Fano-Like Resonance in Cylinders Including Nonlocal Effects

LI Liang-Sheng, YIN Hong-Cheng
Chin. Phys. Lett. 2014, 31 (8): 087302 doi: 10.1088/0256-307X/31/8/087302
Full Text: [PDF 871 KB] (16)
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We investigate the optical response of a metallic wire calculated from the classical electromagnetic theory. The Drude (local) approach is compared with the semi-classical hydrodynamical theory calculations that reveal the Fano-like resonances of subsidiary peaks originated from the nonlocality. The bulk plasma resonances containing the nonlocal effects could be depressed by increasing the dissipation, while the blue shift of the surface localized plasma resonances could be enhanced by increasing the Fermi velocity.

Thermodynamics of the CaLi2 Superconductor in the Vicinity of Structural Phase Transition

D. Szczęśniak, R. Szczęśniak
Chin. Phys. Lett. 2014, 31 (8): 087401 doi: 10.1088/0256-307X/31/8/087401
Full Text: [PDF 777 KB] (15)
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Eliashberg formalism is used to investigate the thermodynamic properties of the high-pressure superconducting phase of the CaLi2 compound. In particular, our calculations are conducted in the vicinity of the C2/c →P21/c pressure-induced structural phase transition. We show that, in the considered case, the value of the Coulomb pseudopotential is high and equals 0.26. Moreover, we give the analysis of the thermodynamic parameters such as the superconducting transition temperature (TC), the energy gap at the Fermi level (2Δ(0)), the thermodynamic critical field (HC), and the specific heat of superconducting (CS) and normal (CN) states. We emphasize that the characteristic dimensionless ratios RΔ ≡2Δ(0)/kBTC, RH≡TCCN(TC)/HC2(0), and RC≡ΔC(TC)/CN(TC), have values that are beyond the predictions of the BCS theory in the case of the considered material. In particular, RΔ=3.85, RH=0.161, and RC=1.86. Furthermore, it is proved that the effective electron mass is high and equals 2.02me, where me denotes the bare electron mass.

Abnormal Visible Luminescence Mechanism of Tb3+-Yb3+ Codoped SiO2-Al2O3-CaF2 Glass Studied by Time-Resolved Spectra

DUAN Qian-Qian, ZHAO Hua, ZHANG Zhi-Guo, JIAN Ao-Qun, SANG Sheng-Bo, ZHANG Wen-Dong
Chin. Phys. Lett. 2014, 31 (8): 087801 doi: 10.1088/0256-307X/31/8/087801
Full Text: [PDF 689 KB] (10)
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The upconversion energy transfer mechanism in Tb3+-Yb3+ co-doped SiO2-Al2O3-CaF2 glass is investigated by time-resolved spectra. The effect of donor ion Yb3+ is involved in the dynamic decay behavior of acceptor ion Tb3+, which provides direct proof for the energy transfer from Yb3+ to Tb3+. The pump power dependence curves show that the upconversion luminescence is a two-photon process. The measured decay curves of the 5D4 state (Tb3+) contain two parts: a slow decay process corresponding to its radiation, and a fast one with a decay parameter approximately twice the lifetime of the 2F5/2 state (Yb3+). The fast decay process is contradictory to the generally accepted cooperative sensitization upconversion rate equation model. Since the effect of the host environmental is excluded by comparative experiments, we believe that there should be another energy transfer mechanism in Tb3+-Yb3+ co-doped SiO2-Al2O3-CaF2 glass in addition to the cooperative sensitization process.
CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY

The Phase Stability, Thermodynamics Properties and Electronic Structures of L12-Type Al3Sc and Al3Y under High Pressures

DUAN Yong-Hua, HUANG Bo, SUN Yong, PENG Ming-Jun, ZHOU Sheng-Gang
Chin. Phys. Lett. 2014, 31 (8): 088101 doi: 10.1088/0256-307X/31/8/088101
Full Text: [PDF 970 KB] (21)
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The phase stability, thermodynamics properties and electronic structures of L12-Al3Sc and Al3Y compounds under pressure up to 40 GPa are investigated by using first-principles within a local density approximation. The results of formation energies show that Al3Sc is more stable than Al3Y and the stability of Al3Sc will be better with the increasing pressure. The Gibbs free energy, heat capacity, Debye temperature and thermal expansion coefficient are also investigated. The decreasing density of states at the Fermi level and the strengthening Sc/Y-d orbital hybridization with Al (s, p) under high pressure lead to the observed increase of the structural stability for L12-Al3Sc and Al3Y under pressures.

Enhanced Depth of Lift-off Pattern Defined with Soft Mold Ultraviolet Nanoimprint by Multi-Layer Masks

WANG Zhi-Hao, LIU Wen, ZUO Qiang, WANG Lei, ZHAO Yan-Li, XU Zhi-Mou
Chin. Phys. Lett. 2014, 31 (8): 088102 doi: 10.1088/0256-307X/31/8/088102
Full Text: [PDF 1256 KB] (13)
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The traditional lift-off process can hardly be carried out in ultraviolet nanoimprint defined patterns due to the poor solubility of the ultraviolet resist. Moreover, the depth of lift-off pattern defined by an ultraviolet nanoimprint is limited by that of the soft mold. In this work, a modified nanoimprint process by a multi-layer mask method is introduced to enhance the depth of the final lift-off pattern. Pillar photonic crystal is fabricated from the hole pattern defined by NIL to prove the pattern-reversal capability. On its basis, combining the features of overetching technology and the lateral diffusion phenomenon in the metal depositing process, pillar-shaped photonic crystal stamps with different duty cycles have been fabricated by adjusting the etching time of the lift-off layer. Based on this process, a 50-nm line width metal grating is fabricated from a soft stamp with an aspect ratio as low as 1.

Photoluminescence of Nanoporous GaN Films Prepared by Electrochemical Etching

WANG Qiang, JI Zi-Wu, XIAO Hong-Di, LV Hai-Yan, LI Jian-Fei, XU Xian-Gang, LV Yuan-Jie, FENG Zhi-Hong
Chin. Phys. Lett. 2014, 31 (8): 088103 doi: 10.1088/0256-307X/31/8/088103
Full Text: [PDF 572 KB] (17)
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Nanoporous (NP) GaN is prepared by electrochemical etching on a GaN epilayer grown on a sapphire substrate by metal-organic chemical vapor deposition. Scanning electron microscopy reveals that the average pore diameter and inter-pore spacing are approximately 25 and 45 nm, respectively. The photoluminescence (PL) spectra show that in contrast to the initial as-grown GaN epilayer, the NP GaN exhibits a high near-band-edge UV intensity, significant relaxation of compressive strain, and a lower yellow luminescence intensity. Both the line shape and line width of the PL spectra are almost the same for these two samples. The high quality of the NP GaN can be explained by the enhancement of the PL extraction efficiency and the decrease of impurity and defect density after etching.

Nano-Crystalline Diamond Films with Pineapple-Like Morphology Grown by the DC Arcjet vapor Deposition Method

LI Bin, ZHANG Qin-Jian, SHI Yan-Chao, LI Jia-Jun, LI Hong, LU Fan-Xiu, CHEN Guang-Chao
Chin. Phys. Lett. 2014, 31 (8): 088104 doi: 10.1088/0256-307X/31/8/088104
Full Text: [PDF 801 KB] (17)
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A nano-crystlline diamond film is grown by the dc arcjet chemical vapor deposition method. The film is characterized by scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD) and Raman spectra, respectively. The nanocrystalline grains are averagely with 80 nm in the size measured by XRD, and further proven by Raman and HRTEM. The observed novel morphology of the growth surface, pineapple-like morphology, is constructed by cubo-octahedral growth zones with a smooth faceted top surface and coarse side surfaces. The as-grown film possesses (100) dominant surface containing a little amorphous sp2 component, which is far different from the nano-crystalline film with the usual cauliflower-like morphology.

Hydrogen Sulfide Detection Using a Gold Nanoparticle/Metalloprotein Based Probe

Meisam Omidi, Gh. Amoabediny, F. Yazdian, M. Habibi-Rezaei
Chin. Phys. Lett. 2014, 31 (8): 088701 doi: 10.1088/0256-307X/31/8/088701
Full Text: [PDF 554 KB] (23)
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We present a simple method for direct detection of hydrogen sulfide (H2S) in an aqueous solution. This method represents a novel biosensor based on metalloprotein cytochrome c (cyt c) with the localized surface plasmon resonance of gold nanoparticles (AuNPs). For this purpose, we develop a new approach based on attaching chemically-modified cyt c onto AuNPs. Here, by reacting H2S with protein heme center, its conformation changes in the locality of the heme moiety. The conformational changes occurring in the protein alter the spectral characteristics by changing the dielectric properties of AuNPs. The conformational changes of cyt c induced by the H2S interaction are characterized by the UV-visible absorption spectroscopy and the circular dichroism technique. The limit of the detection and sensitivity of the AuNPs/cyt c biosensor are evaluated by using UV-visible spectroscopy. According to the experiments, it is revealed that H2S can be detected at a concentration of 4.0 μM (1.3 ppb) by the fabricated AuNPs/cyt c biosensor. In addition, the sensor retains activity and gives reproducible results after storage in 4°C for 60 d. This simple and cost-effective sensing platform provides a rapid and convenient detection for H2S at concentrations far below the hazardous limit.

Denaturation of DNA Double-Helix Characterized by Thermal Conductance

YANG Ming-Ming, ZHONG Wei-Rong
Chin. Phys. Lett. 2014, 31 (8): 088702 doi: 10.1088/0256-307X/31/8/088702
Full Text: [PDF 477 KB] (41)
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We deal with the thermal conductance and the denaturation of a three-dimensional DNA double helix based on the Peyrard–Bishop–Dauxois model by using non-equilibrium molecular dynamics simulations. It is reported that the thermal conductance of DNA has a substantial decrease near the denaturation where the DNA double helix separates into two single chains. We explain this phenomenon through the phonon spectra at different temperatures. It is suggested that the denaturation of DNA can also be characterized by the change of the thermal conductance.

GEOPHYSICS, ASTRONOMY, AND ASTROPHYSICS

Jet Magnetically Accelerated from Advection Dominated Accretion Flow

GONG Xiao-Long, JIANG Zhi-Xiong
Chin. Phys. Lett. 2014, 31 (8): 089801 doi: 10.1088/0256-307X/31/8/089801
Full Text: [PDF 455 KB] (28)
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A jet model for the jet power arising from a steady, optically thin, advection dominated accretion flow (ADAF) around a Kerr black hole (BH) is proposed. We investigate the typical numerical solutions of ADAF, and calculate the jet power from an ADAF using a general relativistic version of electronic circuit theory. It is shown that the jet power concentrates in the inner region of the accretion flow, and the higher the degree to which the flow advection-dominated is, the lower the jet power from the ADAF is.

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