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Radio-Frequency Spectra of Ultracold Fermi Gases Including a Generalized GMB Approximation at Unitarity
RUAN Xiao-Xia, GONG Hao, DU Long, JIANG Yu, SUN Wei-Min, ZONG Hong-Shi
Chin. Phys. Lett. 2013, 30 (11):
110303
.
DOI: 10.1088/0256-307X/30/11/110303
Taking into account the effect of the generalized Gor'kov and Melik–Barkhudarov (GMB) approximation, we calculate the radio-frequency spectra of balanced and homogeneous ultracold Fermi gases within the framework of the non-self-consistent T-matrix approximation at unitarity in the normal phase. The corresponding equations are numerically calculated on the real frequency axis directly. It is found that our results agree well with the experimental result of the radio-frequency spectroscopy [ Phys. Rev. Lett. 101 (2008) 140403].
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Semi-physical Simulation Platform of a Parafoil Nonlinear Dynamic System
GAO Hai-Tao, YANG Sheng-Bo, ZHU Er-Lin, SUN Qing-Lin, CHEN Zeng-Qiang, KANG Xiao-Feng
Chin. Phys. Lett. 2013, 30 (11):
110503
.
DOI: 10.1088/0256-307X/30/11/110503
Focusing on the problems in the process of simulation and experiment on a parafoil nonlinear dynamic system, such as limited methods, high cost and low efficiency, we present a semi-physical simulation platform. It is designed by connecting parts of physical objects to a computer, and remedies the defect that a computer simulation is divorced from a real environment absolutely. The main components of the platform and its functions, as well as simulation flows, are introduced. The feasibility and validity are verified through a simulation experiment. The experimental results show that the platform has significance for improving the quality of the parafoil fixed-point airdrop system, shortening the development cycle and saving cost.
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Dynamical Behaviors of a TiO2 Memristor Oscillator
WANG Guang-Yi, HE Jie-Ling, YUAN Fang, PENG Cun-Jian
Chin. Phys. Lett. 2013, 30 (11):
110506
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DOI: 10.1088/0256-307X/30/11/110506
We design a new chaotic oscillator based on the realistic model of the HP TiO2 memristor and Chua's circuit. Some basic dynamical behaviors of the oscillator, including equilibrium set, Lyapunov exponent spectrum and bifurcations with respect to various circuit parameters, are investigated theoretically and numerically. Chaotic attractors generated by the proposed oscillator are described with simulations and experiments, showing a good agreement. The main finding by analysis is that the proposed oscillator has no transient chaos and weak hyperchaos appears. Furthermore, its stability is insensitive to its initial values, thereby generating continuous and stable chaotic oscillation signals for chaos-based applications.
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Lifetime Measurement of the Low Lying Yrast States in 189Pt
HE Chuang-Ye, WU Xiao-Guang, WANG Jin-Long, WU Yi-Heng, ZHENG Yun, LI Guang-Sheng, LI Cong-Bo, HU Shi-Peng, LI Hong-Wei, LIU Jia-Jian, LUO Peng-Wei, YAO Shun-He
Chin. Phys. Lett. 2013, 30 (11):
112101
.
DOI: 10.1088/0256-307X/30/11/112101
High-spin states in 189Pt are populated through the heavy-ion fusion-evaporation reaction176Yb (18O, 5n)189Pt at 87 MeV beam energy. An array consisting of 13 HPGe detectors is used in conjunction with the plunger device in CIAE. The lifetimes of two levels in the yrast band are determined by using the recoil distance Doppler shift method. The transition quadrupole moments Qt are extracted. The results show that the 17/2+ state has a much larger Qt value than that of the ground state, whereas the value deceases quickly with spin increasing. This may contribute to the shape driving effect of the quasi-neutron from the em13/2 orbital.
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Theoretical Study of the H+ClO Reaction
LI Ya-Min, CHE Ru-Xin, LI Ying, DONG Bin
Chin. Phys. Lett. 2013, 30 (11):
113101
.
DOI: 10.1088/0256-307X/30/11/113101
We present a theoretical study of the H+OCl system on an accurate ab initio potential energy surface (PES) investigated by Peterson et al. [ J. Chem. Phys. 113 (2000) 6186]. Both the exact time-dependent quantum wave packet (TDWP) and quasi-classical trajectory (QCT) methods are employed. The results of reaction probabilities for total angular momentum J=0 and the integral cross section calculated by the TDWP are in good agreement with the QCT ones. Additionally, the nearly forward-backward symmetric product scattering angular distributions and the weak products' rotational alignment effect obtained by the QCT calculations are attributed to a long-lived intermediate reaction process.
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Molecular Dynamics Simulation of Damage to Coiled Carbon Nanotubes under C Ion Irradiation
ZHOU Bin, ZHANG Wei, GONG Wen-Bin, WANG Song, REN Cui-Lan, WANG Cheng-Bin, ZHU Zhi-Yuan, HUAI Ping
Chin. Phys. Lett. 2013, 30 (11):
113402
.
DOI: 10.1088/0256-307X/30/11/113402
The stability of coiled carbon nanotubes under C ion irradiation is investigated by molecular dynamics simulations. The defect statistics shows that small curvature coiled carbon nanotubes have better radiation tolerance than normal straight carbon nanotubes. To understand the effect of the curvature on defect production, the threshold displacement energies for the upper and lower walls, as well as those for the side parts, are calculated. The results show that the lower wall has better radiation tolerance than the upper wall. For the upper wall, a small increase in the curvature of nanotube axis gives rise to an increase in the radiation tolerance and then a decrease with the curvature becomes larger. However, for the lower wall, as the curvature of the nanotube axis increases, the radiation tolerance increases as the bonds compressed slightly in our simulation.
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Quantum Random Number Generation Based on Quantum Phase Noise
TANG Guang-Zhao, JIANG Mu-Sheng, SUN Shi-Hai, MA Xiang-Chun, LI Chun-Yan, LIANG Lin-Mei
Chin. Phys. Lett. 2013, 30 (11):
114207
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DOI: 10.1088/0256-307X/30/11/114207
We experimentally demonstrate a kind of high-quantum correlated, practical quantum random generation based on the quantum phase noise of a laser, which uniformly distributes in the range of (?π,π] by driving the laser with a stream of narrow electrical pulses. We propose a working mode to further suppress the impact of phase drift after we use the passive measures (thermal and mechanical isolation) to slow it down. Moreover, a new method which ensures random numbers to be true representations of quantum characteristics is presented to quantify the quantum randomness. This scheme has an inherent advantage for multiplex generation.
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Three-Dimensional Sound Propagation and Scattering in Two-Dimensional Waveguides
QIN Ji-Xing, LUO Wen-Yu, ZHANG Ren-He, YANG Chun-Mei
Chin. Phys. Lett. 2013, 30 (11):
114301
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DOI: 10.1088/0256-307X/30/11/114301
A coupled-mode method for three-dimensional acoustic propagation and scattering in two-dimensional waveguides is presented. This method synthesizes the three-dimensional field solution by using Fourier transform techniques based on a sequence of two-dimensional problems, each of which is solved by a numerical model recently developed by Luo et al. [ Chin. Phys. Lett. 29 (2012) 014302]. Numerical results indicate that the present model is remarkably accurate, and thus can serve as benchmark against other numerical models. In addition, this model can be applied to realistic problems, and can also be used to analyze horizontal refraction in some range-dependent waveguides in reality, such as the continental shelf environment, ridge-like bathymetry, and underwater trenches.
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Path Integral Monte Carlo Study of X@C50 [X=H2, He, Ne, Ar]
PENG Chun, ZHANG Hong, CHENG Xin-Lu
Chin. Phys. Lett. 2013, 30 (11):
116501
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DOI: 10.1088/0256-307X/30/11/116501
Path integral Monte Carlo (PIMC) method is employed to study the thermal properties of the X@C50 [X=H2, He, Ne, Ar] system at temperatures from 5 K to 300 K. The interaction energies and probability distribution functions of one noble gas atom or H2 inside D5h-symmetry C50 are obtained. A rough sphere model is used in calculating interaction energies, as a comparison. This model gives much lower interaction energy than PIMC calculations on all X@C50, except He@C50. The PIMC method and the sphere model get nearly the same values of interaction energies on He@C50. The spatial distributions are enlarged by the increase in temperature, while the interaction energies change slowly in a wide range of temperature. Temperature is not the major reason for the stability of the system. It is impossible to trap an X atom into C50, except H2 because only the H2@C50 has positive interaction energies from the PIMC calculations.
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Unintentional Doping Mechanisms in GaAs/Si Films Grown by Metalorganic Chemical Vapor Deposition
WANG Jun, DENG Can, JIA Zhi-Gang, WANG Yi-Fan, WANG Qi, HUANG Yong-Qing, REN Xiao-Min
Chin. Phys. Lett. 2013, 30 (11):
116801
.
DOI: 10.1088/0256-307X/30/11/116801
To explain different doping effects in a buffer layer, thermally annealed interface, and upper epilayers of GaAs/Si films grown by Metalorganic Chemical Vapor Deposition (MOCVD), the behaviors of unintentional doping in GaAs/Si films are investigated in detail. A third doping mechanism of arsine impurity incorporation during the growth process of GaAs/Si films, apart from conventional mechanisms of gas phase reaction and diffusion from the silicon substrate, is proposed. The experimental results reveal that the doping behavior in the buffer layer studied is determined by the three types of doping mechanisms together. However in the thermally annealed interface and upper epilayers, the third doping mechanism is dominant. According to the third mechanism, the background carrier concentration in GaAs/Si films grown by MOCVD could be properly controlled through the arsine flow rate.
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First Principles Study on the Stability and Mechanical Properties of MB (M=V, Nb and Ta) Compounds
QI Chen-Jin, FENG Jing, ZHOU Rong-Feng, JIANG Ye-Hua, ZHOU Rong
Chin. Phys. Lett. 2013, 30 (11):
117101
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DOI: 10.1088/0256-307X/30/11/117101
The first principles calculations based on density functional theory are performed to investigate the stability, chemical bonding, elastic constants, hardness and Debye temperature of MB (M=V, Nb and Ta) compounds. The structures of these borides are optimized, and the lattice parameters are in good agreement with the experimental data. The calculated cohesive energy and formation enthalpy indicate that they are of a thermodynamically stable structure. The mechanical properties, including elastic constants Cij, bulk modulus, Young's modulus, shear modulus and Poisson's ratio, are calculated. The bulk moduli of them ranging from 263.0 to 278.4 GPa are larger than many common Laves phases and TaB with 278.4 GPa being the largest bulk modulus value among them. The population analysis is used to analyze the chemical bonds in these compounds. The hardness of the compounds is also evaluated, and the result reveals that TaB is the hardest compound among them. The Debye temperature of MB is calculated. The results show that the values of MB compounds range from 419.3 to 794.3 K.
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Electronic States of IC60BA and PC71BM
SHENG Chun-Qi, WANG Peng, SHEN Ying, LI Wen-Jie, ZHANG Wen-Hua, ZHU Jun-Fa, LAI Guo-Qiao, LI Hong-Nian
Chin. Phys. Lett. 2013, 30 (11):
117103
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DOI: 10.1088/0256-307X/30/11/117103
We investigate the electronic states of IC60BA and PC71BM using first-principles calculations and photoelectron spectroscopy (PES) measurements. The energy level structures for all possible isomers are reported and compared with those of C60, C70 and PC61BM. The attachment of the side chains can raise the LUMO energies and decrease the HOMO-LUMO gaps, and thus helps to increase the power-conversion efficiency of bulk heterojunction solar cells. In the PES studies, we prepared IC60BA and PC71BM films on Si:H(111) substrates to construct adsorbate/substrate interfaces describable with the integer charge-transfer (ICT) model. Successful measurements then revealed that one of the most important material properties for an electron acceptor, the energy of the negative integer charge-transfer state (EICT?), is 4.31 eV below the vacuum level for PC71BM. The EICT? of IC60BA is smaller than 4.14 eV.
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Electrical Characterization in the Phase Transition between Cubic PbCrO3 Perovskites at High Pressures
WANG Wen-Dan, HE Duan-Wei, XIAO Wan-Sheng, WANG Shan-Min, XU Ji-An
Chin. Phys. Lett. 2013, 30 (11):
117201
.
DOI: 10.1088/0256-307X/30/11/117201
By in situ x-ray diffraction, an isostructural phase transition between two kinds of the cubic PbCrOperovskites at around 1.6 GPa and room temperature with a 9.8% volume change is discovered. Recently, we have synthesized this cubic PbCrO3perovskite successfully. Here we report our high-pressure in situ electrical resistance measurements up to 4.1 GPa for this perovskite sample. At room temperature, the resistance shows special changes at 1.2 and 2.7 GPa. They may indicate the starting and ending points of this transformation. At 4.1 GPa, the negative temperature resistance coefficient is observed, which means that phase II could be considered as a semiconductor according to our present measurement.
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Vacuum Violet Photo-Response of AlGaN-Based Metal-Semiconductor-Metal Photodetectors
ZHOU Dong, LU Hai, CHEN Dun-Jun, REN Fang-Fang, ZHANG Rong, ZHENG You-Dou, LI Liang
Chin. Phys. Lett. 2013, 30 (11):
117301
.
DOI: 10.1088/0256-307X/30/11/117301
Al0.5Ga0.5N-based metal-semiconductor-metal photodetectors (PDs) with a large device area of 5×5 mm2 are fabricated on a sapphire substrate, which are tested for vacuum ultraviolet light detection by using a synchrotron radiation source. The PD exhibits low dark current of less than 1 pA under 30 V bias and a spectral cutoff around 260 nm, corresponding to the energy bandgap of Al0.5Ga0.5N. A peak photo-responsivity of 14.68 mA/W at 250 nm with a rejection ratio (250/360 nm) of more than four orders of magnitude is obtained under 30 V bias. For wavelength less than 170 nm, the photoresponsivity of the PD is found to increase as wavelength decreases, which is likely caused by the enhanced photoemission effect.
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Raman Gain Coefficients of Nd:LuxY1?xVO4 Crystals
ZHANG Fang, WANG Zheng-Ping, ZHAO Yong-Guang, XU Xin-Guang
Chin. Phys. Lett. 2013, 30 (11):
117802
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DOI: 10.1088/0256-307X/30/11/117802
By using a pulse laser at 532.36 nm as the incident light, stimulated Raman scattering (SRS) of a series of a-cut and c-cut Nd:LuxY1?xVO4 (x=0, 0.10, 0.26, 0.41, 0.61, 0.67, 0.80) crystals is investigated. For the π-polarization (E||c), the gain coefficient reduced as x value increased. For the σ-polarization (E||a), the Raman gain of all of the mixed crystals is larger than the pure Nd:YVO4, and the maximum value is obtained from the Nd:Lu0.1Y0.9VO4 crystal. Such results are also supported by the measurement of spontaneous Raman scattering spectra.
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Broadband Light Emission from Chirped Multiple InAs Quantum Dot Structure
LV Xue-Qin, JIN Peng, CHEN Hong-Mei, WU Yan-Hua, WANG Fei-Fei, WANG Zhan-Guo
Chin. Phys. Lett. 2013, 30 (11):
118102
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DOI: 10.1088/0256-307X/30/11/118102
Broadband light emission is obtained from a chirped multiple InAs/InGaAs/GaAs quantum dot (QD) structure. The thickness of the InGaAs strain-reducing layer (SRL) is used as the tuning parameter to adjust the light emission property of each QD layer in the chirped structure. It is shown from the photoluminescence (PL) measurement that the SRL thickness has a strong influence on the PL peak position, linewidth, and intensity. By constructing the chirped QD structure comprising five groups of QD layers with different SRL thicknesses, a broadband electroluminescence emission with the full width at half maximum of 202 nm is realized, indicating the feasibility of chirped multiple InAs QD layers on broadening the emission spectrum.
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Upconversion Properties of the Er-Doped Y2O3, Bi2O3 and Sb2O3 Nanoparticles Fabricated by Pulsed Laser Ablation in Liquid Media
Reza Zamiri, Hamid-Reza Bahari-Poor, Azmi Zakaria, Raheleh Jorfi, Golnoush Zamiri, Avito Rebelo, Akrajas Ali Omar
Chin. Phys. Lett. 2013, 30 (11):
118103
.
DOI: 10.1088/0256-307X/30/11/118103
Er-doped Y2O3, Bi2O3 and Sb2O3 nanoparticles are synthesized using pulsed laser ablation in a liquid. Ceramic targets of Y2O3:Er3+, Bi2O3:Er3+ and Sb2O3:Er3+ for ablation process are prepared by standard solid-state reaction technique and ablation is carried out in 5-ml distilled water using nanosecond Q-switched Nd:YAG laser. The morphology and size of the fabricated nanoparticles are evaluated by transmission electron microscopy and the luminescence emission properties of the prepared samples are investigated under different excitation wavelengths.
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Measurement of ZnO/Al2O3 Heterojunction Band Offsets by in situ X-Ray Photoelectron Spectroscopy
LEI Hong-Wen, ZHANG Hong, WANG Xue-Min, ZHAO Yan, YAN Da-Wei, JIANG Zhong-Qian, YAO Gang, ZENG Ti-Xian, WU Wei-Dong
Chin. Phys. Lett. 2013, 30 (11):
118201
.
DOI: 10.1088/0256-307X/30/11/118201
ZnO films are grown on c-sapphire substrates by laser molecular beam epitaxy. The band offsets of the ZnO/Al2O3 heterojunction are studied by in situ x-ray photoelectron spectroscopy. The valence band of Al2O3 is found to be 3.59±0.05 eV below that of ZnO. Together with the resulting conduction band offset of 2.04±0.05 eV, this indicates that a type-I staggered band line exists at the ZnO/Al2O3 heterojunction.
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Quantifying the Attractive Force Exerted on the Pinned Calcium Spiral Waves by Using the Adventive Field
QIU Kang, TANG Jun, LUO Jin-Ming, MA Jun
Chin. Phys. Lett. 2013, 30 (11):
118701
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DOI: 10.1088/0256-307X/30/11/118701
The cytosolic calcium system is inhomogenous because of the discrete and random distribution of ion channels on the ER membrane. It is well known that the spiral tip can be pinned by the heterogenous area, and the field can detach the spiral from the heterogeneity. We use the adventive field to counteract the attractive force exerting on the calcium spiral wave by the heterogeneity, then the strength of the adventive field is used to quantify the attractive force indirectly. Two factors determining the attractive force are studied. It is found that: (1) the attractive force sharply increases with size of the heterogeneity for small-size heterogeneity, whereas the force increases to a saturated value for large-size heterogeneity; (2) for large-size heterogeneity, the force almost remains constant unless the level of the heterogeneity vanishes, the force decreases to zero linearly and sharply, and for small-size heterogeneity, the force decreases successively with the level of the heterogeneity. Furthermore, it is found that the forces exist only when the spiral tip is very close to the heterogenous area. Our study may shed some light on the control or suppression of the calcium spiral wave.
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Effect of Low-Pass Filtering in Force Calibration of Magnetic Tweezers
ZHENG Hai-Zi, NONG Da-Guan, LI Ming
Chin. Phys. Lett. 2013, 30 (11):
118702
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DOI: 10.1088/0256-307X/30/11/118702
In typical experiments where magnetic tweezers are involved, precise measurement of the magnetic forces is of crucial importance. To achieve this, a widely applied method is to track the bead's Brownian motion trajectory and to calculate the force from its mean-squared-displacement. However, this method does not take into account the fact that the bead-tracking device always has a finite bandwidth, acting effectively as a low-pass filter. The result could be subjected to significant system errors, which overestimates the magnetic force. We analyze the power spectrum of the bead's Brownian motion, and provide a corrected formula to calculate the magnetic force, which is free of system errors induced by limited detection bandwidth. A dsDNA force-extension curve is experimentally measured. The curve is consistent with the WLC model, exhibiting correctness of the new formula. On the other hand, the force given by the traditional method shows significant deviation from the WLC model, which is 3 times larger at most.
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Efficient Natural Dye-Sensitized Solar Cells Based on Spin-Coated TiO2 Anode Materials
YU Xiao-Hong, SUN Zhao-Zong, LIAN Jie, LI Yi-Tan, CHEN Yan-Xue, GAO Shang, WANG Xiao, WANG Ying-Shun, ZHAO Ming-Lin
Chin. Phys. Lett. 2013, 30 (11):
118801
.
DOI: 10.1088/0256-307X/30/11/118801
TiO2 anode materials are prepared on ITO glass by spin-coated method. Dye-sensitized solar cells are assembled with these anodes and natural dyes extracted from radix ophiopogonis by different solvents. The formation and characterization of anode materials are confirmed by field-emission scanning electron microscopy, x-ray diffraction, UV-visible absorption spectroscopy. Photovoltaic testing results show that energy conversion efficiency could reach 1.67% with fill factor of 0.51, open-circuit voltage of 457 mV, and short-circuit photocurrent density of 7.2 mA/cm2. The short-circuit photocurrent density can reach 7.6 mA/cm2 with efficiency of 1.33.
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57 articles
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