30 Most Down Articles
Published in last 1 year | In last 2 years| In last 3 years| All| Most Downloaded in Recent Month | Most Downloaded in Recent Year|

Most Downloaded in Recent Year
Please wait a minute...
For Selected: View Abstracts Toggle Thumbnails
Fusion Reaction Rate Coefficient for Different Beam and Target Scenarios
OU Wei, ZENG Xian-Jun, DENG Bai-Quan, GOU Fu-Jun
Chin. Phys. Lett.    2015, 32 (02): 022801.   DOI: 10.1088/0256-307X/32/2/022801
Abstract   PDF (567KB)
Fusion power output is proportional not only to the fuel particle number densities participating in reaction but also to the fusion reaction rate coefficient (or reactivity), which is dependent on reactant velocity distribution functions. They are usually assumed to be dual Maxwellian distribution functions with the same temperature for thermal nuclear fusion circumstances. However, if high power neutral beam injection and minority ion species ICRF plasma heating, or multi-pinched plasma beam head-on collision, in a converging region are required and investigated in future large scale fusion reactors, then the fractions of the injected energetic fast ion tail resulting from ionization or charge exchange will be large enough and their contribution to the non-Maxwellian distribution functions is not negligible, hence to the fusion reaction rate coefficient or calculation of fusion power. In such cases, beam-target, and beam-beam reaction enhancement effect contributions should play very important roles. In this paper, several useful formulae to calculate the fusion reaction rate coefficient for different beam and target combination scenarios are derived in detail.
High Power Er/Yb Codoped Double Clad Fiber Pulsed Amplifier Based on an All-Fiber Configuration
ZHOU Lei, NING Ji-Ping, CHEN Cheng, HAN Qun, ZHANG Wei-Yi, WANG Jun-Tao
Chin. Phys. Lett.    2009, 26 (6): 064215.   DOI: 10.1088/0256-307X/26/6/064215
Abstract   PDF (543KB)
We report an all-fiber two-stage high power pulsed amplifier, seeded with a 1550nm, 1kHz repetition rate rectangular pulse, and based on Er/Yb co-doped double clad fiber. All the characteristics are measured in the experiment. The maximal slope efficiency is 22.56%, which is the highest we know of at such a low repetition rate, and the maximal output signal power is 1W. The various factors that affect the pulsed amplifier performance are analyzed. A high output power while keeping high power conversion efficiency can be obtained with careful selection of the input power, pump power and repetition rate. The experimental results show that the crucial parameters should be optimized when designing all-fiber pulsed amplifiers.
X-Ray Diffraction Pattern of Graphite Oxide
MU Shi-Jia, SU Yu-Chang, XIAO Li-Hua, LIU Si-Dong, HU Te, TANG Hong-Bo
Chin. Phys. Lett.    2013, 30 (9): 096101.   DOI: 10.1088/0256-307X/30/9/096101
Abstract   PDF (633KB)
X-ray diffraction patterns of graphite oxide (GO) are theoretically simulated as a function of the displacements of carbon atoms using the Debye–Waller factor in terms of the Warren–Bodenstein equation. The results demonstrate that GO has the turbostratically stacked structure. The high order (00l) peaks gradually disappear with the increase in atomic thermal vibrations along c-axis while the (hk0) ones weaken for the vibrations along a-axis. When the displacement deviation ua=0.015 nm and uc=0.100 nm the computed result is consistent with the experimental measurements.
Experimental Realization of an Intrinsic Magnetic Topological Insulator
Yan Gong, Jingwen Guo, Jiaheng Li, Kejing Zhu, Menghan Liao, Xiaozhi Liu, Qinghua Zhang, Lin Gu, Lin Tang, Xiao Feng, Ding Zhang, Wei Li, Canli Song, Lili Wang, Pu Yu, Xi Chen, Yayu Wang, Hong Yao, Wenhui Duan, Yong Xu, Shou-Cheng Zhang, Xucun Ma, Qi-Kun Xue, Ke He
Chin. Phys. Lett.    2019, 36 (7): 076801.   DOI: 10.1088/0256-307X/36/7/076801
Abstract   HTML   PDF (7918KB)
An intrinsic magnetic topological insulator (TI) is a stoichiometric magnetic compound possessing both inherent magnetic order and topological electronic states. Such a material can provide a shortcut to various novel topological quantum effects but remained elusive experimentally for a long time. Here we report the experimental realization of thin films of an intrinsic magnetic TI, MnBi$_{2}$Te$_{4}$, by alternate growth of a Bi$_{2}$Te$_{3}$ quintuple layer and a MnTe bilayer with molecular beam epitaxy. The material shows the archetypical Dirac surface states in angle-resolved photoemission spectroscopy and is demonstrated to be an antiferromagnetic topological insulator with ferromagnetic surfaces by magnetic and transport measurements as well as first-principles calculations. The unique magnetic and topological electronic structures and their interplays enable the material to embody rich quantum phases such as quantum anomalous Hall insulators and axion insulators at higher temperature and in a well-controlled way.
A Universal Formula for the Secondary Electron Yield of Metals at an Incident Angle of θ
XIE Ai-Gen**, ZHANG Jian, WANG Tie-Bang
Chin. Phys. Lett.    2011, 28 (9): 097901.   DOI: 10.1088/0256-307X/28/9/097901
Abstract   PDF (679KB)
Based on the main physical processes, we deduce the relationships among the incident energy Wp0 of the primary electron, the number of released secondary electrons (i.e. δPEθ) per primary electron entering the metal at incident angle θ and the angle θ itself. In addition, the relationship of δ PEθ at θ = 0°, i.e. δPE0, with Wp0 is determined. From the experimental results, the relationship of the ratio at θ = 0°, i.e. β0 which is the ratio of the average number of released secondary electrons generated by a single primary electron backscattered at the metal surface to that generated by a single primary electron entering the metal, with Wp0 is determined. Moreover, the relationships among the ratio βθ , Wp0 and θ are obtained. Based on the relationships among the secondary electron yield at θ (i.e. δθ), the yield at θ = 0° (i.e. δ0), the backscattering coefficient at θ (i.e. ηθ), the coefficient at θ = 0° (i.e. η0), δPEθ and δPE0, we deduce the universal formula for δθ0, ηθ, η0, and Wp0 for the primary electrons at an incident energy of 2–10 keV. The secondary electron yields calculated from the universal formula and the experimental yields of some metals are compared, and the results suggest that the proposed formula is universal for estimation of secondary electron yields at θ=0°−80°.
Characterization and Magnetic Properties of Nickel Ferrite Nanoparticles Prepared by Ball Milling Technique
G. Nabiyouni**, M. Jafari Fesharaki, M. Mozafari, J. Amighian
Chin. Phys. Lett.    2010, 27 (12): 126401.   DOI: 10.1088/0256-307X/27/12/126401
Abstract   PDF (676KB)
Nickel ferrite nanoparicles with various grain sizes are synthesized using annealing treatment followed by ball milling of its bulk component materials. Commercially available nickel and iron oxide powders are first mixed, and then annealed at 1100°C in an oxygen environment furnace and for 3 h. The samples are then milled for different times in an SPEX mill. X-ray diffraction pattern indicates that in this stage the sample is single phase. The average grain size is estimated by scanning electron microscopy (SEM) and x-ray diffraction techniques. Magnetic behavior of the sample at room temperature is studied using a superconducting quantum interference device (SQUID). The Curie temperature of the powders is measured by an LCR–meter unit. The x-ray diffraction patterns clearly indicate that increasing the milling time leads to a decrease in the grain size and consequently leads to a decrease in the saturation magnetization as well as the Curie temperatures. This result is attributed to the spin-glass-like surface layer on the nanocrystalline nickel ferrite with a ferrimagnetically aligned core.
Pressure-Induced Metallization Accompanied by Elongated S–S Dimer in Charge Transfer Insulator NiS$_{2}$
Hao Wu, Yong-Hui Zhou, Yi-Fang Yuan, Chun-Hua Chen, Ying Zhou, Bo-Wen Zhang, Xu-Liang Chen, Chuan-Chuan Gu, Chao An, Shu-Yang Wang, Meng-Yao Qi, Ran-Ran Zhang, Li-Li Zhang, Xin-Jian Li, Zhao-Rong Yang
Chin. Phys. Lett.    2019, 36 (10): .   DOI: 10.1088/0256-307X/36/10/107101
Abstract   HTML   PDF (1071KB)
The insulator-metal transition triggered by pressure in charge transfer insulator NiS$_{2}$ is investigated by combining high-pressure electrical transport, synchrotron x-ray diffraction and Raman spectroscopy measurements up to 40–50 GPa. Upon compression, we show that the metallization firstly appears in the low temperature region at $\sim$3.2 GPa and then extends to room temperature at $\sim $8.0 GPa. During the insulator-metal transition, the bond length of S–S dimer extracted from the synchrotron x-ray diffraction increases with pressure, which is supported by the observation of abnormal red-shift of the Raman modes between 3.2 and 7.1 GPa. Considering the decreasing bonding-antibonding splitting due to the expansion of S–S dimer, the charge gap between the S-$pp\pi^*$ band and the upper Hubbard band of Ni-3$d$ $e_{\rm g}$ state is remarkably decreased. These results consistently indicate that the elongated S–S dimer plays a predominant role in the insulator-metal transition under high pressure, even though the $p$-$d$ hybridization is enhanced simultaneously, in accordance with a scenario of charge-gap-controlled type.
Generalized Second Law of Thermodynamics in Wormhole Geometry with Logarithmic Correction
Faiz-ur-Rahman, Salahuddin, M. Akbar**
Chin. Phys. Lett.    2011, 28 (7): 070403.   DOI: 10.1088/0256-307X/28/7/070403
Abstract   PDF (444KB)
We construct various cases for validity of the generalized second law (GSL) of thermodynamics by assuming the logarithmic correction to the horizon entropy of an evolving wormhole. It is shown that the GSL is always respected for α0 ≤0, whereas for α0>0 the GSL is respected only if πr2A+/ℏ<α.
Pulse-Width Jitter Measurement for Laser Diode Pulses
TANG Jun-Hua, WANG Yun-Cai
Chin. Phys. Lett.    2006, 23 (10): 2756-2758.  
Abstract   PDF (346KB)
Theoretical analysis and experimental measurement of pulse-width jitter of diode laser pulses are presented. The expression of pulse power spectra with all amplitude jitter, timing jitter and pulse-width jitter is deduced. The power spectra with and without pulse-width jitter are numerically simulated. The simulation results indicate that the pulse-width jitter will contribute considerably noise to the pulse power spectrum while the product of pulse width and angular frequency is larger than 1. The experimental measurement of pulse-width jitter of a gain-switched Fabry--Perot laser diode with 2.4GHz repetition rate is also reported. In comparison of the noise power spectra of the first, fourth and seventh harmonics of the pulse repetition rate, 2.3ps pulse-width jitter is obtained.
Schlieren Visualization of Acoustic Propagation Characteristics in a One-Dimensional Phononic Crystal
JIANG Xue-Ping, QIAN Meng-Lu, CHENG Qian
Chin. Phys. Lett.    2013, 30 (8): 084302.   DOI: 10.1088/0256-307X/30/8/084302
Abstract   PDF (1136KB)
The acoustic propagation characteristics of a finite one-dimensional water-glass phononic crystal (PC) are studied using the Schlieren visualization method, which is fast and non-invasive. The band structures of this PC are measured experimentally with continuous acoustic waves incident on it using the Schlieren method, and the results are highly consistent with the theoretical calculations. The dynamic acoustic field in the PC at different frequencies is imaged and the resonance phenomena in the components of the PC are observed. The results show that the Schlieren method is an effective means of studying the interactions between acoustic waves and PCs.
An Isotropic Electric-Field Sensing System Using Optical Probe
YANG Yong-Jun, CHEN Fu-Shen, SUN Bao
Chin. Phys. Lett.    2007, 24 (4): 965-967.  
Abstract   PDF (482KB)
We design an isotropic electric-field sensing system using an optical probe. The optical probe consists of three electric-field sensors based on a Mach--Zehnder interferometer with the structure of segmented electrodes, which are perpendicular to each other. The measured results show that the ±5dB baseband can reach 3GHz, the linear dynamics range is 70dB, and the minimum detectable electric field is lower than 90dBμV/m (the spectrum analyser resolution is 100Hz). The directional characteristics are almost isotropic within deviations of ±1.5dB. Therefore this sensing system can be used in the electromagnetic compatibility measurements.
Analysis and Simulation of Quantum Radar Cross Section
LIU Kang, XIAO Huai-Tie, FAN Hong-Qi
Chin. Phys. Lett.    2014, 31 (03): 034202.   DOI: 10.1088/0256-307X/31/3/034202
Abstract   PDF (675KB)
We derive a modified analytical expression of a quantum radar cross section (QRCS). Subsequently, we present a comparison between the QRCS and a classical radar cross section (RCS) and analyze the factors that can affect the intensity of the peak and side lobes. Simulation results on a flat rectangular plate demonstrate that QRCS has a similar structure to that of RCS. The analysis of side-lobe structure can benefit the design of quantum stealth platforms as well as the research on quantum radars.
Erbium-Doped Zirconia-Alumina Silica Glass-Based Fiber as a Saturable Absorber for High Repetition Rate Q-Switched All-Fiber Laser Generation
P. Harshavardhan Reddy, N. A. A. Kadir, M. C. Paul, S. Das, A. Dhar, E. I. Ismail, A. A. Latiff, S. W. Harun
Chin. Phys. Lett.    2017, 34 (8): .   DOI: 10.1088/0256-307X/34/8/084203
Abstract   HTML   PDF (2477KB)
We propose and demonstrate a Q-switched erbium-doped fiber laser (EDFL) using an erbium-doped zirconia-alumina silica glass-based fiber (Zr-EDF) as a saturable absorber. As a 16-cm-long Zr-EDF is incorporated into a ring EDFL cavity, a stable Q-switching pulse train operating at 1565 nm wavelength is successfully obtained. The repetition rate is tunable from 33.97 kHz to 71.23 kHz by increasing the pump power from the threshold of 26 mW to the maximum of 74 mW. The highest pulse energy of 26.67 nJ is obtained at the maximum pump power.
Rear-Surface Deformation of a Water Drop in Aero-Breakup of Shear Mode
Xiang-Yu Yi, Yu-Jian Zhu, Ji-Ming Yang, Tun Wang, Ming-Yu Sun
Chin. Phys. Lett.    2017, 34 (8): .   DOI: 10.1088/0256-307X/34/8/084701
Abstract   HTML   PDF (1990KB)
Deformation of water drops in shock-induced high-speed flows is investigated with a focus to the influence of primitive flow parameters on the rear-surface deformation features. Two typical deformation patterns are discovered through high-speed photography. A simple equation to evaluate the radial acceleration of the drop surface is derived. The combined use of this equation and outer flow simulation makes it possible for us to reconstruct the profiles of the early deformed drops. The results agree well with the experiments. Further analysis shows that the duration of flow establishment with respect to the overall breakup time shapes the rear side profile of the drop. Thereby the ratio of the two times, expressed as the square root of the density ratio, appears to be an effective indicator of the deformation features.
Dilepton Production in a Chemically Equilibrating Quark--Gluon Matter
HE Ze-Jun, JIANG Wei-Zhou, ZHANG Jia-Ju, ZHANG Wei, LIU Bo
Chin. Phys. Lett.    2002, 19 (7): 923-925.  
Abstract   PDF (293KB)
We have studied dilepton production in a chemically equilibrating quark-gluon matter produced at RHIC energies. We find that the dilepton yield is no longer a monotonously decreasing function of the initial quark chemical potential. therefore, the dilepton suppression may not be useful as a signature for quark-gluon matter formation.
High Current Operation of a Semi-insulating Gallium Arsenide Photoconductive Semiconductor Switch Triggering a Spark Gap
XU Ming, SHI Wei, HOU Lei, XUE Hong, WU Shen-Jiang, DAI Hui-Ying
Chin. Phys. Lett.    2010, 27 (2): 024212.   DOI: 10.1088/0256-307X/27/2/024212
Abstract   PDF (340KB)
A transient peak current as high as 5.6 kA is obtained by a GaAs photoconductive semiconductor switch (PCSS) in series with a spark gap. Based on the characteristics of the GaAs PCSS, mechanisms of discharge between the PCSS and the spark gap are discussed. It is implied that a hybrid operation mode of photo-activated charge domain occurs due to the superposition of the bias voltage and the instantaneous radio frequency voltage.
Ultrafast and Broadband Terahertz Switching Based on Photo-Induced Phase Transition in Vanadium Dioxide Films
CHEN Zhi, WEN Qi-Ye, DONG Kai, SUN Dan-Dan, QIU Dong-Hong, ZHANG Huai-Wu
Chin. Phys. Lett.    2013, 30 (1): 017102.   DOI: 10.1088/0256-307X/30/1/017102
Abstract   PDF (638KB)
Single-phase VO2 thin films are sputtering deposited on BK7 substrates, and sharp insulator-to-metal phase transition is obtained with a resistivity change of four orders of magnitude. Terahertz (THz) pump-probe measurements reveal that by illuminating the films with a low pumping power of 143 μJ/cm2, VO2 films exhibit an ultrafast optical switching to THz transmission within 8 ps. Furthermore, the THz switching ratio reaches over 80% in a wide frequency range from 0.3 to 2.5 THz. All these outstanding features indicate a strong potential of VO2 films for broadband terahertz wave switching and modulation applications.
In-Situ Resistivity Measurement of ZnS in Diamond Anvil Cell under High Pressure
HAN Yong-Hao, LUO Ji-Feng, HAO Ai-Min, GAO Chun-Xiao, XIE Hong-Sen, QU Sheng-Chun, LIU Hong-Wu, ZOU Guang-Tian
Chin. Phys. Lett.    2005, 22 (4): 927-930.  
Abstract   PDF (383KB)
An effective method is developed to fabricate metallic microcircuits in diamond anvil cell (DAC) for resistivity measurement under high pressure. The resistivity of nanocrystal ZnS is measured under high pressure up to 36.4GPa by using designed DAC. The reversibility and hysteresis of the phase transition are observed. The experimental data is confirmed by an electric current field analysis accurately. The method used here can also be used under both ultrahigh pressure and high temperature conditions.
Investigation of Oxygen Vacancy and Interstitial Oxygen Defects in ZnO Films by Photoluminescence and X-Ray Photoelectron Spectroscopy
FAN Hai-Bo, YANG Shao-Yan, ZHANG Pan-Feng, WEI Hong-Yuan, LIU Xiang-Lin, JIAO Chun-Mei, ZHU Qin-Sheng, CHEN Yong-Hai, WANG Zhan-Guo
Chin. Phys. Lett.    2007, 24 (7): 2108-2111.  
Abstract   PDF (341KB)
ZnO films prepared at different temperatures and annealed at 900°C in
oxygen are studied by photoluminescence (PL) and x-ray photoelectron
spectroscopy (XPS). It is observed that in the PL of the as-grown films the green luminescence (GL) and the yellow luminescence (YL) are related, and after annealing the GL is restrained and the YL is enhanced. The O 1s XPS results also show the coexistence of oxygen vacancy (VO) and interstitial oxygen (Oi) before annealing and the quenching of the VO after annealing. By combining the two results it is deduced that the GL and YL are related to the VO and Oi defects, respectively.
Reflection of Electromagnetic Waves by a Nonuniform Plasma Layer Covering a Metal Surface
GAO Hong-Mei, FA Peng-Ting
Chin. Phys. Lett.    2008, 25 (7): 2562-2565.  
Abstract   PDF (343KB)

Reflection coefficients of electromagnetic waves in a nonuniform plasma layer with electrons, positive ions and negative ions, covering a metal surface are
investigated by using the finite-difference-time-domain method. It is shown that the reflection coefficients are influenced greatly by the density gradient on the layer edge, layer thickness and electron proportion, i.e., the effect of the negative ions. It is also found that low reflection or high attenuation can be reached by properly choosing high electron proportion, thick plasma layer, and smooth density gradient in the low frequency regime, but sharp density gradient in the high frequency regime.

A New 3D Four-Wing Chaotic System with Cubic Nonlinearity and Its Circuit Implementation
LIU Xing-Yun
Chin. Phys. Lett.    2009, 26 (9): 090504.   DOI: 10.1088/0256-307X/26/9/090504
Abstract   PDF (1461KB)
A new 3D four-wing smooth autonomous chaotic system in which each equation contains a cubic product term is presented and physically implemented. Spectral analysis shows that the four-wing chaotic attractor has extremely wide frequency bandwidth compared with that of the Lorenz system and other four-wing chaotic systems, which is important in some relevant engineering applications such as secure communications.
The Effect of Gas Leaks on Underground Gas Storage Performance During Development and Operation
SHI Lei**,XIONG Wei,GAO Shu-Sheng
Chin. Phys. Lett.    2012, 29 (4): 044602.   DOI: 10.1088/0256-307X/29/4/044602
Abstract   PDF (614KB)
Underground gas storage is an efficient tool for matching the constant supply of gas to the variable demands of the market. Gas escaping from a storage field may cause environmental and safety problems. We present a physical simulation together with actual field data to evaluate the caprock of underground gas storage in the Jing-Bian area. The effect of gas leaks on the performance of gas storage is analyzed by using the type curves of the injection-withdrawal cycle.
Structural Design of a Compact in-Plane Nano-Grating Accelerometer
YAO Bao-Yin, ZHOU Zhen, FENG Li-Shuang, WANG Wen-Pu, WANG Xiao
Chin. Phys. Lett.    2012, 29 (11): 118502.   DOI: 10.1088/0256-307X/29/11/118502
Abstract   PDF (2318KB)
A combination of large mass, weak spring and nano-grating is the key for a nano-grating accelerometer to measure nano-G acceleration. A novel compact nano-grating accelerometer integrating a large mass with nano-grating is proposed. First, the numbers of diffraction orders are calculated. Then, structure parameters are optimized by finite element analysis to achieve a high sensitivity in an ideal vibration mode. Finally, we design the fabrication method to form such a compact nano-grating accelerometer and successfully fabricate the uniform and well-designed nano-gratings with a period of 847 nm, crater of 451 nm by an FIB/SEM dual beam system. Based on the ANSYS simulation, a nano-grating accelerometer is predicted to work in the first modal and enables the accelerometer to have displacement sensitivity at 197 nm/G with a measurement range of ±1 G, corresponding to zeroth diffraction beam optical sensitivity 1%/mG. The nano-gratings fabricated are very close to those designed ones within experimental error to lay the foundation for the sequent fabrication. These results provide a theoretical basis for the design and fabrication of nano-grating accelerometers.
Anti-Synchronization of Chaotic Systems via Adaptive Sliding Mode Control
Wafaa Jawaada, M. S. M. Noorani, M. Mossa Al-sawalha
Chin. Phys. Lett.    2012, 29 (12): 120505.   DOI: 10.1088/0256-307X/29/12/120505
Abstract   PDF (437KB)
An anti-synchronization scheme is proposed to achieve the anti-synchronization behavior between chaotic systems with fully unknown parameters. A sliding surface and an adaptive sliding mode controller are designed to gain the anti-synchronization. The stability of the error dynamics is proven theoretically using the Lyapunov stability theory. Finally numerical results are presented to justify the theoretical analysis.
Magnetic Sensing inside a Diamond Anvil Cell via Nitrogen-Vacancy Center Spins
Yan-Xing Shang, Fang Hong, Jian-Hong Dai, Hui-Yu, Ya-Nan Lu, En-Ke Liu, Xiao-Hui Yu, Gang-Qin Liu, Xin-Yu Pan
Chin. Phys. Lett.    2019, 36 (8): 086201.   DOI: 10.1088/0256-307X/36/8/086201
Abstract   HTML   PDF (1001KB)
The diamond anvil cell-based high-pressure technique is a unique tool for creating new states of matter and for understanding the physics underlying some exotic phenomena. In situ sensing of spin and charge properties under high pressure is crucially important but remains technically challenging. While the nitrogen-vacancy (NV) center in diamond is a promising quantum sensor under extreme conditions, its spin dynamics and the quantum control of its spin states under high pressure remain elusive. In this study, we demonstrate coherent control, spin relaxation, and spin dephasing measurements for ensemble NV centers up to 32.8 GPa. With this in situ quantum sensor, we investigate the pressure-induced magnetic phase transition of a micron-size permanent magnet Nd$_{2}$Fe$_{14}$B sample in a diamond anvil cell, with a spatial resolution of $\sim$2 μm, and sensitivity of $\sim$20 $\mu$T/Hz$^{1/2}$. This scheme could be generalized to measure other parameters such as temperature, pressure and their gradients under extreme conditions. This will be beneficial for frontier research of condensed matter physics and geophysics.
Lorentz Force Electrical Impedance Detection Using Step Frequency Technique
Zhi-Shen Sun, Guo-Qiang Liu, Hui Xia
Chin. Phys. Lett.    2018, 35 (1): .   DOI: 10.1088/0256-307X/35/1/014301
Abstract   HTML   PDF (520KB)
Lorentz force electrical impedance tomography (LFEIT) inherits the merit of high resolution by ultrasound stimulation and the merit of high contrast through electromagnetic field detection. To reduce the instantaneous peak power of the stimulating signal to the transducer, the sinusoidal pulse and step-frequency technique is investigated in LFEIT. The theory of application of step-frequency technique in LFEIT is formulated with the direct demodulation method and the in-phase quadrature demodulation method. Compared with the in-phase quadrature demodulation method, the direct demodulation method has simple experimental setup but could only detect half of the range. Experiments carried out with copper foils confirmed that LFEIT using the step-frequency technique could detect the electrical conductivity variations precisely, which suggests an alternative method of realization of LFEIT.
Superconducting Single-Layer T-Graphene and Novel Synthesis Routes
Qinyan Gu, Dingyu Xing, Jian Sun
Chin. Phys. Lett.    2019, 36 (9): 097401.   DOI: 10.1088/0256-307X/36/9/097401
Abstract   HTML   PDF (15832KB)
Single-layer superconductors are ideal materials for fabricating superconducting nano devices. However, up to date, very few single-layer elemental superconductors have been predicted and especially no one has been successfully synthesized yet. Here, using crystal structure search techniques and ab initio calculations, we predict that a single-layer planar carbon sheet with 4- and 8-membered rings called T-graphene is a new intrinsic elemental superconductor with superconducting critical temperature ($T_{\rm c}$) up to around 20.8 K. More importantly, we propose a synthesis route to obtain such a single-layer T-graphene, that is, a T-graphene potassium intercalation compound (C$_4$K with $P4/mmm$ symmetry) is firstly synthesized at high pressure ($>$11.5 GPa) and then quenched to ambient condition; and finally, the single-layer T-graphene can be either exfoliated using the electrochemical method from the bulk C$_4$K, or peeled off from bulk T-graphite C$_4$, where C$_4$ can be obtained from C$_4$K by evaporating the K atoms. Interestingly, we find that the calculated $T_{\rm c}$ of C$_4$K is about 30.4 K at 0 GPa, which sets a new record for layered carbon-based superconductors. The present findings add a new class of carbon-based superconductors. In particular, once the single-layer T-graphene is synthesized, it can pave the way for fabricating superconducting devices together with other 2D materials using the layer-by-layer growth techniques.
Exact Solutions to the Two-Dimensional Spatially Inhomogeneous Cubic-Quintic Nonlinear Schrödinger Equation with an External Potential
CHEN Jun-Chao, ZHANG Xiao-Fei, LI Biao, CHEN Yong
Chin. Phys. Lett.    2012, 29 (7): 070303.   DOI: 10.1088/0256-307X/29/7/070303
Abstract   PDF (2076KB)

We investigate the two-dimensional spatially inhomogeneous cubic-quintic nonlinear Schrödinger equation with different external potentials. In the absence of external potential or in the presence of harmonic potential, the number of localized nonlinear waves is associated not only with the boundary condition but also with the singularity of inhomogeneous cubic-quintic nonlinearities; while in the presence of periodic external potential, the periodic inhomogeneous cubic-quintic nonlinearities, together with the boundary condition, support the periodic solutions with an arbitrary number of circular rings in every unit. Our results may stimulate new matter waves in high-dimensional Schrödinger equations with spatially modulated nonlinearities.

A 526 W Diode-Pumped Nd:YAG Ceramic Slab Laser
CHEN Yan-Zhong, LIU Wen-Bin, BO Yong**, JIANG Ben-Xue, XU Jian, KOU Hua-Min, XU Yi-Ting, PAN Yu-Bai, XU Jia-Lin, GUO Ya-Ding, YANG Feng-Tu, PENG Qin-Jun, CUI Da-Fu, JIANG Dong-Liang, XU Zu-Yan
Chin. Phys. Lett.    2011, 28 (9): 094208.   DOI: 10.1088/0256-307X/28/9/094208
Abstract   PDF (519KB)
A diode-side-pumped Nd:YAG ceramic slab laser with a high power output is presented. An average power of 526 W is achieved at 1064 nm with a repetition rate of 120 Hz and a pulse width of 180 µs from a 93mm×52mm×8mm ceramic slab at a pump power of 1928 W, corresponding to an optical-to-optical efficiency of 27.3%.
Fabrication and Characterization of a GaN-Based 320$\times$256 Micro-LED Array
Xiao-Fan Mo, Wei-Zong Xu, Hai Lu, Dong Zhou, Fang-Fang Ren, Dun-Jun Chen, Rong Zhang, You-Dou Zheng
Chin. Phys. Lett.    2017, 34 (11): .   DOI: 10.1088/0256-307X/34/11/118102
Abstract   HTML   PDF (884KB)
Design, fabrication and characterizations of GaN-based blue micro light emitting diode (LED) arrays are reported. The GaN micro-LED array consists of $320\times256$ pixels with a pitch size of 30 μm. Each pixel is $25\times25$ μm$^{2}$ in size, which is designed for backside emission and high density flip-chip packaging. The selected LED pixels being tested exhibit good uniformity in terms of turn-on voltage and reverse leakage current. The efficiency droop behavior and reliability behavior under high forward current stress are also studied. The micro-LED pixel shows improved reliability, which is likely caused by enhanced heat dissipation.