|
Mechanisms for Oscillations in Volume of Single Spherical Bubble Due to Sound Excitation in Water
REN Sheng, ZHANG Jia-Zhong, LI Kai-Lun
Chin. Phys. Lett. 2012, 29 (2):
020504
.
DOI: 10.1088/0256-307X/29/2/020504
Mechanisms for the evolution of a single spherical bubble subjected to sound excitation in water are studied from the viewpoint of nonlinear dynamics. First, the shooting method is combined with a Poincaré map to obtain the fixed point for the case of forced oscillation in volume. Then, the stabilities are judged by Floquet theory and the bifurcation theorem. Moreover, the transitions of bubble oscillation in volume due to sound excitation in water are explained from the viewpoint of nonlinear dynamics in detail. The results show that with an increase in sound frequency, the period-1 oscillation becomes unstable, and oscillation behaves in a double-periodic manner, then a quasi-periodic manner, and finally chaotically. Additionally, with an increase of the amplitude of the sound pressure, the bubble eventually oscillates with chaos via a series of period-doubling bifurcations.
|
|
Fabrication and Performance of Micro-sensors for Methane Detection Based on In-Pd-Co-SnO2 Composite Nanofibers
QIAO Ji-Ping, ZHU Zi-Peng, YAN Xiao-Yan, QIN Jian-Min
Chin. Phys. Lett. 2012, 29 (2):
020701
.
DOI: 10.1088/0256-307X/29/2/020701
In-Pd-Co-SnO2 composite nanofibers have been synthesized by an electrospinning method and characterized by x−ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). Micro-sensors with a tiny area of 1×1 mm2 are fabricated by spinning the nanofibers on sensor substrates. Excellent CH4 sensing properties are found based on the micro−sensors. The sensitivity is up to 13 when the sensors are exposed to 10 ppm CH4 at 140°C, and the response and recovery times are about 8 and 14 s, respectively. High selectivity, good stability, and low power-consumption are also observed in the investigation.
|
|
Analyses of β−Bands of 230,232Th and 232,234U by the Projected Shell Model
CUI Ji-Wei, ZHOU Xian-Rong, CHEN Fang-Qi, SUN Yang, WU Cheng-Li
Chin. Phys. Lett. 2012, 29 (2):
022101
.
DOI: 10.1088/0256-307X/29/2/022101
The ground bands and β−bands of four nuclei 230,232Th and 232,234U in the actinide region are investigated by introducing a collective D0 pair into the projected shell model. We discuss the collectivity of the D0 pair. The calculated energy schemes agree well with experimental data, and so do the E2 transition rates.
|
|
Identification of a New Four-Quasiparticle State in Odd-Odd 186Au
LI Shi-Cheng, SHI Yue, ZHANG Yu-Hu, ZHOU Xiao-Hong, XU Fu-Rong, FANG Yong-De, LIU Min-Liang, DING Bing, GUO Song, LI Guang-Shun, ZHOU Hou-Bing, M. Oshima, Y. Toh, M. Koizumi, A. Osa, A. Kimura, Y. Hatsukawa, H. Hayakawa, T. Shizuma, J. Katakura, M. Matsuda, T. Morikawa, M. Sugawara, H. Kusakari
Chin. Phys. Lett. 2012, 29 (2):
022102
.
DOI: 10.1088/0256-307X/29/2/022102
The high-spin level structure of 186Au is re−investigated by means of in-beam γ−ray spectroscopy via the 172Yb(19F, 5nγ)186Au reaction. The oblate bands previously reported are revised and extended to higher−spin states. A new Iπ=(20+) excited state has been identified and assigned to the πh11/2−1 ⊗νi13/2-2h9/2-1 configuration. The total Routhian surface and cranked shell model calculations suggest that the πh11/2−1 ⊗νi13/2-2h9/2-1 band in 186Au has a non-axial deformation.
|
|
Measurement of Spatial Distribution of Cold Atoms in an Integrating Sphere
WANG Xu-Cheng, CHENG Hua-Dong, XIAO Ling, ZHENG Ben-Chang, MENG Yan-Ling, LIU Liang, WANG Yu-Zhu
Chin. Phys. Lett. 2012, 29 (2):
023701
.
DOI: 10.1088/0256-307X/29/2/023701
We present an experiment on the measurement of the spatial distribution of cold atoms in a ceramic cell. The atoms are first cooled by diffusing light produced by multiple scattering of laser light at the inner surface of the cell. An inhomogeneous magnetic field is applied after the atoms are cooled by using a pair of anti-Helmholtz coils, and thus the shift of atomic magnetic sub-levels is position-dependent. We move the anti-Helmholtz coils point by point while keeping the probe laser beam resonant with the cold atoms at zero magnetic field. The number of cold atoms at different positions can be extracted by detecting the absorption to the probe beam. The density of the cold atoms in the cell is measured in two dimensions perpendicular and parallel to the tube connecting to the vacuum system, respectively. The results show that at the center of the cell, fewer atoms exist due to the leakage of diffuse light into the hole connecting to the vacuum pump. The method we developed is used to detect cold atoms in a region where imaging is impossible.
|
|
Three-Dimensional Thermal Analysis of 18-Core Photonic Crystal Fiber Lasers
ZHENG Yi-Bo, YAO Jian-Quan, ZHANG Lei, WANG Yuan, WEN Wu-Qi, JING Lei, DI Zhi-Gang
Chin. Phys. Lett. 2012, 29 (2):
024203
.
DOI: 10.1088/0256-307X/29/2/024203
The three-dimensional thermal properties of 18-core photonic crystal fiber lasers operated under natural convection are investigated. The temperature sensing technique based on a fiber Bragg grating sensor array is proposed to measure the longitudinal temperature distribution of a 1.6-m-long ytterbium-doped 18-core photonic crystal fiber. The results show that the temperature decreases from the pump end to the launch end exponentially. Moreover, the radial temperature distribution of the fiber end is investigated by using the full-vector finite-element method. The numerical results match well with the experimental data and the coating temperature reaches 422.7 K, approaching the critical value of polymer cladding, when the pumping power is 40 W. Therefore the fiber end cooling is necessary to achieve power scaling. Compared with natural convection methods, the copper cooling scheme is found to be an effective method to reduce the fiber temperature.
|
|
A 200 kHz Q-Switched Adhesive-Free Bond Composite Nd:YVO4 Laser using a Double-Crystal RTP Electro-optic Modulator
YU Yong-Ji, CHEN Xin-Yu, WANG Chao, WU Chun-Ting, LIU Rui, JIN Guang-Yong
Chin. Phys. Lett. 2012, 29 (2):
024206
.
DOI: 10.1088/0256-307X/29/2/024206
A diode-end-pumped electro-optic (EO) Q-switched adhesive-free bond composite Nd:YVO4 laser operating at a repetition rate of 200 kHz is reported. A pair of RbTiOPO4 (RTP) crystals are used as a high repetition EO Q-switch. At the repetition rate of 200 kHz, the maximum average output power of 11.8 W at wavelength 1064 nm and full width at half maximum of pulses of 16.65 ns are achieved at an incident pump power of 27 W, corresponding to an optical conversion efficiency of 43.7% and a slope efficiency of 44.6%, respectively. To the best of our knowledge, this is the highest repetition rate reported on the EO Q-switched laser by using RTP crystals.
|
|
Surface Acoustic Wave Propagation in Relaxor-Based Ferroelectric Single Crystals 0.93Pb(Zn1/3Nb2/3)O3−0.07PbTiO3 Poled along [011]c
LI Xiu-Ming, ZHANG Rui, HUANG Nai-Xing, LÜ, Tian-Quan, CAO Wen-Wu
Chin. Phys. Lett. 2012, 29 (2):
024302
.
DOI: 10.1088/0256-307X/29/2/024302
Surface acoustic wave (SAW) propagation in relaxor-based ferroelectric single crystals 0.93Pb(Zn1/3Nb2/3)O3−0.07PbTiO3 (PZN−7%PT ) poled along [011]c has been analyzed theoretically. The results show that PZN−7%PT single crystals have excellent SAW properties, such as low phase velocities, very high electromechanical coupling coefficients and small power flow angles. It is also found that the SAW properties strongly depend on the propagation direction and the characteristic curves of SAW phase velocity, and the electromechanical coupling coefficients are symmetric with respect to θ=90°. Considering all related factors, the X−cut PZN-7%PT single crystal has the best performance. Based on our results, the X−cut PZN-7%PT single crystals poled along [011]c are an excellent candidate for ultra-wide bandwidth low-frequency SAW devices.
|
|
Comparison of Dust Lattice Waves in Three-Dimensional Cubic Configurations
B. Farokhi, A. Hameditabar
Chin. Phys. Lett. 2012, 29 (2):
025204
.
DOI: 10.1088/0256-307X/29/2/025204
A three-dimensional (3D) dusty plasma crystalline with cubic configurations is considered. We calculate the interaction between particles up to distance √2a, implying the second−neighbor interactions for the simple cubic structure, the third-neighbor interactions for the body-centered cubic structure, and the forth-neighbor interactions the for face-centered cubic structure. Longitudinal and transverse dispersion relations are derived in arbitrary directions. The dispersion relations are studied in special directions, i.e. (1,0,0), (1,1,0)/√2, and (1,1,1)/√2. Study of dispersion relations with more neighbor interactions show that in some cases the results change physically.
|
|
Dislocation and Elastic Strain in an InN Film Characterized by Synchrotron Radiation X-Ray Diffraction and Rutherford Backscattering/Channeling
CHENG Feng-Feng , FA Tao, WANG Xin-Qiang, YAO Shu-De
Chin. Phys. Lett. 2012, 29 (2):
026101
.
DOI: 10.1088/0256-307X/29/2/026101
Dislocation information and strain-related tetragonal distortion as well as crystalline qualities of a 2-µm −thick InN film grown by molecular beam epitaxy (MBE) are characterized by Rutherford backscattering/channeling (RBS/C) and synchrotron radiation x-ray diffraction (SR-XRD). The minimum yield χmin=2.5% deduced from the RBS/C results indicates a fairly good crystalline quality. From the SR−XRD results, we obtain the values of the screw and edge densities to be ρscrew=7.0027×109 and ρedge=8.6115×109 cm−2, respectively. The tetragonal distortion of the sample is found to be −0.27% by angular scans, which is close to the −0.28% derived by SR-XRD. The value of |e⊥/e|| |=0.6742 implies that the InN layer is much stiffer along the a axis than that along the c axis, where e|| is the parallel elastic strain, and e⊥ is the perpendicular elastic strain. Photoluminescence results reveal a main peak of 0.653 eV with the linewidth of 60 meV, additional shoulder band could be due to impurities and related defects.
|
|
Microscopic Phase-Field Study of the Occupancy Probability of α Sublattices Involving Coordination Environmental Difference for D022−Ni3V
ZHANG Jing, CHEN Zheng, ZHUANG Hou-Chuan, LU Yan-Li
Chin. Phys. Lett. 2012, 29 (2):
026103
.
DOI: 10.1088/0256-307X/29/2/026103
The nickel sites of a D022−Ni3V phase are subdivided into Ni1 and Ni2 sublattices according to their coordination sphere difference. The occupancy probability (OP) differences influenced by the coordination sphere are interpreted using the microscopic phase field model. The OP of regular atoms (NiNi1, NiNi2), antisite defects (VNi1, VNi2), and substitutional defects (AlNi2, AlNi1) have strong site preferences, as well as temperature−dependence features, on both sublattices. These features involve both redistribution of components, and phase transition from D022 to L12.
|
|
A Temperature Sensor Based on a Symmetrical Metal-Cladding Optical Waveguide
ZHOU Guo-Rui, FENG Guo-Ying, ZHANG Yi, MA Zi, WANG Jian-Jun
Chin. Phys. Lett. 2012, 29 (2):
026501
.
DOI: 10.1088/0256-307X/29/2/026501
A compact temperature sensor based on a symmetrical metal-cladding optical waveguide using free-space coupling is proposed and demonstrated theoretically and experimentally. The symmetrical Au-cladding optical waveguide is based on a thin LiNbO3 slab sandwiched between two metal films, which serve as the coupling layer and reflecting panel, respectively. The sensitivity of this sensor of 9.08×10−2 deg/°C, 6.6×10−2 deg/°C and 4.8×10−2 deg/°C corresponding to 3238−order, 3237-order and 3236-order modes, respectively, are obtained. Higher resolution is predicted with a larger linear expansion coefficient material and a higher resolution θ/2θ goniometer.
|
|
Morphological Evolution of a-GaN on r-Sapphire by Metalorganic Chemical Vapor Deposition
SANG Ling, LIU Jian-Ming, XU Xiao-Qing, WANG Jun, ZHAO Gui-Juan, LIU Chang-Bo, GU Cheng-Yan, LIU Gui-Peng, WEI Hong-Yuan, LIU Xiang-Lin, YANG Shao-Yan, ZHU Qin-Sheng, WANG Zhan-Guo
Chin. Phys. Lett. 2012, 29 (2):
026801
.
DOI: 10.1088/0256-307X/29/2/026801
The morphological evolution of a-GaN deposited by metalorganic chemical vapor deposition (MOCVD) on r-sapphire is studied. The influences of V/III ratio and growth temperature on surface morphology are investigated. V−pits and stripes are observed on the surface of a-GaN grown at 1050°C and 1100°C, respectively. The overall orientation and geometry of V−pits are uniform and independent on the V/III molar ratio in the samples grown at 1050°C, while in the samples grown at 1100°C, the areas of stripes decrease with the adding of V/III ratio. We deduce the origin of V−pits and stripes by annealing the buffer layers at different temperatures. Because of the existence of inclined (1011) facets, V−pits are formed at 1050°C. The (1011) plane is an N terminated surface, which is metastable at higher temperature, so stripes instead of V−pits are observed at 1100°C. Raman spectra suggest that the growth temperature of the first layer in the two-step process greatly affects the strain of the films. Hence, to improve the growth temperature of the first layer in the two-step method may be an effective way to obtain high quality a-GaN film on r-sapphire.
|
|
Wetting Behavior between Droplets and Dust
YU Yang, WU Qun, WANG Xue-Wei, YANG Xiao-Bin
Chin. Phys. Lett. 2012, 29 (2):
026802
.
DOI: 10.1088/0256-307X/29/2/026802
The wetting behavior of dust by droplets is investigated by experiments and numerical simulation methods. Experimental observation reveals that the surface of a coal slice is hydrophilic in nature, while surfaces of coal dust stacks are hydrophobic. We show that water droplets settle on these surfaces following the Cassie–Baxter wetting model, as supported by theoretical, numerical analyses and experimental observations, i.e. water droplets only wet the first layer of coal dust. Our numerical simulation results also show that a water droplet could not enclose any coal dust inside it and many coal dust particles are adhered with a hexagonal close packing on a large water droplet. Based on these results, we conclude that the surface area of water droplets is an important factor on their wetting and capturing coal dust, and producing smaller water droplets can improve the efficiency of settling dust.
|
|
Resonant Tunneling States of a Pairing Ladder with Random Dimer Chains
HU Dong-Sheng, ZHANG Yan-Ling, YIN Xiao-Gang, ZHU Chen-Ping, ZHANG Yong-Mei
Chin. Phys. Lett. 2012, 29 (2):
027101
.
DOI: 10.1088/0256-307X/29/2/027101
We propose three models of pairing ladders, in which two types of atoms, A and B, exist, and the corresponding atoms in different chains are pairng, i.e. if atom A is in a site of one chain, the atom in the corresponding site of another chain should be atom B. It is found that there are three resonant states in the ladder when the two types of atoms are both random dimers (RD) in the same chain. No extended state exists in the ladder when only one type of atom is RD distributed or two types of atoms both are random distributed in the same chain.
|
|
Raman Scattering Study of InxGa1−xN Alloys with Low Indium Compositions
TENG Long, ZHANG Rong, XIE Zi-Li, TAO Tao, ZHANG Zhao, LI Ye-Cao, LIU Bin, CHEN Peng, HAN Ping, ZHENG You-Dou
Chin. Phys. Lett. 2012, 29 (2):
027803
.
DOI: 10.1088/0256-307X/29/2/027803
InxGa1−xN alloys with low indium composition x in the range 0.13≤x≤0.23 are systematically studied mainly based on a Raman scattering technique. Scanning electron microscopy and x−ray diffraction results show that our samples can be divided into two groups: pseudomorphic (0.13≤x≤0.16) and relaxed (0.18≤x≤0.23). The prominent enhancement of A1 longitudinal−optical (LO) mode is found with 325 nm laser excitation. For pseudomorphic samples, the frequencies of A1 (LO) phonons agree well with the theoretical predictions, which verifies that the samples are fully strained. For relaxed InxGa1−xN samples, a linear dependence of the A1 (LO) mode frequency is obtained: Ω0 (x)=(740.8±3.3)−(143.1±16.0)x, which is the evidence of one-mode behavior in InxGa1−xN ternary alloys. Residual strains in these partially relaxed samples are also evaluated.
|
|
AlGaN/GaN Metal-Insulator-Semiconductor High Electron-Mobility Transistor Using a NbAlO/Al2O3 Laminated Dielectric by Atomic Layer Deposition
BI Zhi-Wei, HAO Yue, FENG Qian, GAO Zhi-Yuan, ZHANG Jin-Cheng, MAO Wei, ZHANG Kai, MA Xiao-Hua, LIU Hong-Xia, YANG Lin-An, MEI Nan, CHANG Yong-Ming
Chin. Phys. Lett. 2012, 29 (2):
028501
.
DOI: 10.1088/0256-307X/29/2/028501
We investigate the characteristics of AlGaN/GaN metal-insulator-semiconductor high-electron-mobility transistors (MIS-HEMTs) with a NbAlO/Al2O3 lamination dielectric deposited by atomic layer deposition (ALD) as the gate insulator. A large gate voltage swing (GVS) of 3.96 V and a high breakdown voltage of −150 V for the MIS-HEMT were obtained. We present the gate leakage current mechanisms and analyze the reason for the reduction of the leakage current. Compared with traditional HEMTs, the maximum drain current is improved to 960 mA/mm, indicating that NbAlO layers could reduce the surface-related depletion of the channel layer and increase the sheet carrier concentration. In addition, the maximum oscillation frequency of 38.8 GHz shows that the NbAlO high-k dielectric can be considered as a potential gate oxide comparable with other dielectric insulators.
|
|
Reconfigurable Threshold Logic Element with SET and MOS Transistors
WEI Rong-Shan, CHEN Jin-Feng, CHEN Shou-Chang, HE Ming-Hua
Chin. Phys. Lett. 2012, 29 (2):
028502
.
DOI: 10.1088/0256-307X/29/2/028502
A novel reconfigurable threshold logic element (TLE) using single-electron transistors (SETs) and metal-oxide-semiconductor (MOS) transistors is proposed. The proposed TLE is highly reconfigurable, which can perform all two-variable logic functions directly or indirectly, including OR, NOR, AND, NAND, XOR and XNOR. The reconfiguration of the TLE is realized by simply configuring the input bits without changing the device parameters. The design methodology can also be applied in the design of a multi-variable TLE. The reconfigurable TLE demonstrates good performance at room temperature with a compact structure and ultralow power dissipation. The reconfigurable TLE can be useful in high-density high-performance reconfigurable systems and artificial neural networks.
|
|
Principle Fluctuation Modes of the Global Stock Market
YAN Yan, LIU Mao-Xin, ZHU Xiao-Wu, CHEN Xiao-Song
Chin. Phys. Lett. 2012, 29 (2):
028901
.
DOI: 10.1088/0256-307X/29/2/028901
The purpose of this work is to study the principle fluctuation modes of the global stock market, which is regarded as a complex system. It is proposed that the systematic risk can be reflected by the trace calculated from the cross-correlation matrix, and the integrity can be classified into clusters according to the plus-minus signs of the elements of the eigenvectors corresponding to several top largest eigenvalues whose total value accounts for more than 60 percent of the trace. The principle fluctuation modes of 30 stock markets are in the same direction in each year of 2005–2010. According to the classification criteria proposed here, the stock markets of the Americas, Europe and Asia & Oceania are automatically classified into different clusters, while Brazil, Russia and China are separated.
|
64 articles
|