bluuebunny/crossref_metadata_2025 huggingface dataset:
A hybrid prediction model of multivariate chaotic time series based on error correction
Authors: Han Min  , Xu Mei-Ling  ,   Faculty of Electronic Information and Electrical Engineering, Dalian University of Technology, Dalian 116023, China
Published: December 2020

Considering the problem that simply modifying the reservoir algorithm cannot significantly improve the prediction accuracy of chaotic multivariate time series, in this paper we propose a hybrid prediction model based on error correction. The observed data includes both linear and nonlinear features. First, we use autoregressive and moving average model to capture the linear features, then build a regularized echo state network to portray the dynamic nonlinear features. Finally, we add the predicted nonlinear value to the predicted linear value, in order to improve forecasting accuracy achieved by either of the models used separately. The experimental results of Lorenz and Sunspot-Runoff in the Yellow River time series demonstrate the effectiveness and characteristics of the proposed model herein.
Investigation of high power terahertz emission in gap crystal based on collinear difference frequency generation
Authors: Huang Jing-Guo  , Lu Jin-Xing  , Zhou Wei  , Tong Jing-Chao  , Huang Zhi  , Chu Jun-Hao  ,   Key Laboratory of Infrared Physics, Shanghai Institute of Technical Physics, Chinese Academy of Sciences, Shanghai 200083, China
Published: December 2020

Among many terahertz wave generation methods, nonlinear optical collinear difference frequency generation (CDFG) is always regarded as a promising way to achieve the high power, broadband, continual tunable terahertz wave emission. Theoretical analysis shows that a big coherent length (on millimeter scale) in isotropic GaP crystal could be realized by the laser wavelength near 1064 nm in the CDFG process, which meets the condition of high power and broadband terahertz generation. In the experiment, a high power and broadband terahertz wave is achieved from GaP crystal, with its tunable terahertz range 95.9-773.4 μm (0.39-3.13 THz) and the highest terahertz peak power 7 W at 2 THz. The experimental result is generally consistent well with its theoretical calculation.
Study on the performance of a high-gain gas electron multiplier-MicroMegas chamber
Authors: Fan Sheng-Nan  , Wang Bo  , Qi Hui-Rong  , Liu Mei  , Zhang Yu-Lian  , Zhang Jian  , Liu Rong-Guang  , Yi Fu-Ting  , Ouyang Qun  , Chen Yuan-Bo  ,   State Key Laboratory of Particle Detection and Electronics, Beijing 100049, China;,   Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China;,   University of Chinese Academy of Sciences, Beijing 100049, China;,   Lanzhou University, Lanzhou 730000, China
Published: December 2020

With the continuous development of the micro-structure of gas detectors, many different new detection requirements have been proposed. For more stable working time, lower discharge rate with long term and high effective gain, a new structure detector has been designed. Combined with the detection's advantages of MicroMegas and gas electron multiplier (GEM), it is composed of a MicroMagas chamber with one GEM foil as preamplifier. In this paper, the structure of the detector and detection principle are presented in detail. Using a 55Fe X-ray radioactive source in the operation mixtures gas of argon and isobutene (Ar/Iso =95/5), the performances of the detector gain, discharge rate, energy resolution and stable working time are investigated. Compared with standard MicroMegas detectors with no GEM foil, our detector show that a stable working time could reach more than 30 h of continuous work, the gain of the detector could exceed 106 and the discharge rate could be reduced by nearly 100 times at the same gain.
A simple method of extracting multiple-information with diffraction enhanced imaging
Authors: Zhao Xue-Jiao  , Zhang Kai  , Hong You-Li  , Huang Wan-Xia  , Yuan Qing-Xi  , Zhu Pei-Ping  , Wu Zi-Yu  ,   Institute of High Energy Phisics, Beijing 100049, China;,   National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230026, China
Published: December 2020

Sample information-extracting with diffraction enhanced imaging (DEI) has been one of the interesting areas for many years. Using cosine curve to fit rocking curve in DEI, we deduce the equations described by cosine functions for peak-position image, low- and high-angle image. The analytical expressions of absorption image, refractive angle image and scattering image are also developed. Then a simple method is proposed for sample information-extracting with DEI based on those deductions. This method can extract the absorption information, refractive angle information and scattering information of a sample using only three images, i.e. one peak-position, one low-angle image and on high-angle image, resulting in simple experimental process and low radiation dose introduced to sample by imaging process. The experiments are carried out on a standard sample and a real biological sample. For comparison, experiments are also carried out on the same two samples using the common multiple-image radiography (MIR) method, in which at least seven images should be used to extract sample information. Experimental results show that our new method does extract sample information successfully, and the results from our new method are comparable to those from the MIR method.
Simulational study on streamer discharge in transformer oil under positive nanosecond pulse voltage
Authors: Li Yuan  , Mu Hai-Bao  , Deng Jun-Bo  , Zhang Guan-Jun  , Wang Shu-Hong  ,   State Key Laboratory of Electrical Insulation and Power Equipment, School of Electrical Egineering, Xi’an Jiaotong University, Xi’an 710049, China
Published: December 2020

In this paper, we investigate the streamer discharge process in transformer oil under positive nanosecond pulse voltage through developing a two-dimensional axially symmetric fluid model and simulating the physics of discharge inception and propagation. The streamer discharge profile and distributions of electric field and space charge density are obtained under different conditions such as the amplitude of applied voltage, rise time and gap distance. Simulation results show that space charges enhance the front field of streamer head, which is conducive to the longer propagation of discharge channel, therefore "ionization wave" is formed. The magnitude and rise time of applied voltage have evident influences on the average speed of streamer propagation. It can be observed that the higher the applied impulse voltage, the faster the streamer propagates, and the steeper the rise time of applied impulse, when streamer arrives at the same position, the larger the discharging radius will be and the smaller maximal electric field will be. The cases of different gap distances indicate that longer gap distance corresponds to a faster average speed of streamer. It is considered that field-dependent molecular ionization predominates the charge generation mechanism of streamer discharge process in transformer oil, and space charge effect contributes to further developing ionization until the whole gap eventually breakdowns. The study is dedicated to the better understanding of the process from inception to breakdown of discharging in transformer oil, as well as ionization mechanism in liquid dielectric.
Evolution of spiral waves in indirectly coupled excitable medium with time-delayed coupling
Authors: Chen Xing-Ji  , Qiao Cheng-Gong  , Wang Li-Li  , Zhou Zhen-Wei  , Tian Tao-Tao  , Tang Guo-Ning  ,   College of Physical Sicence and Technology, Guangxi Normal University, Guilin 541004, China
Published: December 2020

The interaction between two spiral waves in two-layer excitable medium coupled indirectly through a passive medium and with time-delayed coupling is investigated by using the Bär model. The numerical results show that time-delayed coupling can either facilitate the synchronization of two spiral waves or lead to the transition from spiral wave to collective oscillation, different target waves, spatiotemporal chaos or rest state. Period-2 and period-3 spiral waves and the meander or drift of spiral wave are observed in the coupled excitable medium. The physical mechanism underlying these phenomena is discussed.
Nonlinear intermodulation waves of large-scale shallow water equations
Authors: Mao Jie-Jian  , Yang Jian-Rong  ,   Department of Physics and Electronics, Shangrao Normal University, Shangrao 334001, China
Published: December 2020

According to the general shallow water equations, the nondimensional nonlinear dynamic equations are obtained that can describe large-scale barotropic atmosphere. Using multi-scale method, a nonlinear controlling equation for disturbed height (or pressure) field is deduced. Applying elliptic equation to construct the solutions of the controlling equation, the analytic solutions of the disturbed height field and velocity are obtained, which include the multiply periodic waves and shock (explosive) waves. The solutions of the disturbed height field present periodic waves with different periodicity and wavelength along longitude and latitude, which are modulated by the solitary waves of latitude. The velocity solutions display that in the large-scale air flows exist periodic distribution phenomena of cyclone and anticyclone.
Quantum correlation for a central two-qubit system coupled to Ising chain
Authors: Yang Yang  , Wang An-Min  ,   Department of Modern Physics, University of Science and Technology of China, Hefei 230026, China
Published: December 2020

Studying quantum correlation dynamics of a central two-qubit system coupled to Ising chain model, we obtain that the evolution of quantum discord and geometric measure of quantum discord for the central atoms. We find that quantum correlation exists a sudden transition in the weak coupled interaction near the quantum critical point of Ising chain. Moreover, the evolution of geometric measure of quantum discord in invariant to some extent.
Landau damping and frequency-shift of monopole mode in an elongated-rubidium Bose-Einstein condensate
Authors: Chai Zhao-Liang  , Zhou Yu  , Ma Xiao-Dong  ,   College of Physics and Electronic Engineering, Xinjiang Normal University, Urumchi 830054, China;,   School of Mathematics and Physics, Jiangsu University of Science and Technology, Zhenjiang 212003, China
Published: December 2020

The Landau damping and frequency-shift of monopole mode in an elongated-rubidium Bose-Einstein condensate are investigated by using the time-dependent Hartree-Fock-Bogoliubov approximation. Improving the previous approach, We have taken into account the practical relaxations of elementary excitations and the orthogonal relation among them. With such an approach, we provide a new calculation formula for Landau damping rate and frequency-shift. In addition, our previous method of eliminating the divergence in three-mode coupling matrix elements is also improved by zeroing the kinetic energy at the condensate boundary instead of minimizing the ground-state energy. Based on these improvements, both the Landau damping rate and the frequency-shift of the monopole mode are analytically calculated and their temperature dependences are also discussed. And all the theoretical results are in agree meat with experimental data.
Chaotic control of the Buck converter based on improving the correlation
Authors: Jia Mei-Mei  , Zhang Guo-Shan  , Niu Hong  ,   School of Electrical Engineering and Automation, Tianjin University, Tianjin 300072, China
Published: December 2020

Due to the strong nonlinearity of the Buck converter, it can be in the chaotic state under certain parameters and the chaotic Buck converter does not work normally. In order to suppress the chaotic phenomena in the Buck converter, a chaotic control scheme is demonstrated by establishing the accurate state equation models, and then analyzing the controllable range diagrams, the switching logic diagrams, the phase portrait, the inductor current waveforms and the output voltage waveforms. Also this scheme can be implemented by improving the correlation between the inductor current and the output voltage of the Buck converter. Research results show that this scheme can stabilize the chaotic Buck converter to the period-1, period-2, period-4, period-8 orbits, without determining the desired targeting orbits in advance. Moreover, this scheme does not depend on circuit parameters of the Buck converter, it only depends on an external parameter named the coupling strength, so this scheme can be applied to the other power converters.
Study on the characteristics of cosh-Gaussian vortex beams in the far field
Authors: Tang Bi-Hua  , Luo Ya-Mei  , Jiang Yun-Hai  , Chen Shu-Qiong  ,   Department of Biomedical Engineering, Luzhou Medical College, Luzhou 646000, China
Published: December 2020

Based on the methods of vector angular spectrum of electromagnetic beams and stationary phase, the analytical expressions of TE and TM terms and energy flux distributions of cosh-Gaussian (ChG) vortex beams in the far field are derived, and used to study the phase singularities and energy flux distributions of the ChG vortex beams. It is shown that the density and position of optical vortices will vary by changing decentered parameter or waist width in the ChG vortex beams. The vortex off-axis distance leads to an asymmetric spatial distribution of energy flux. With gradually increasing vortex off-axis distance, dark spots around the origin will move toward the origin center.
Study of the high hydrogen storage capacity on 2D Li+BC3 complex
Authors: Zhao Yin-Chang  , Dai Zhen-Hong  , Sui Peng-Fei  , Zhang Xiao-Ling  ,   Computational Physics Laboratory, Institute of Opto-electronic Information Science and Technology, Yantai University, Yantai 264005, China
Published: December 2020

First principle calculations predicted that Li atoms can be uniformly adsorbed on both sides of BC3 sheet without clustering. After the coverage of adsorbed Li atoms approaches 33.3%, Li+BC3 complex attains a largest hydrogen storage ability of 12.57 wt.%. Thermodynamic analysis confirms that at room temperature (300 K) and pressure in the range of 115–250 atm, Li+BC3 complex can have the hydrogen storage capacity mentioned above. These values satisfy not only the DOE (U.S.) requirement but also the security needs in application.
Analysis and circuit implementation for the fractional-order Lorenz system
Authors: Jia Hong-Yan  , Chen Zeng-Qiang  , Xue Wei  ,   Department of Automation, Tianjin University of Science and Technology, Tianjin 300222, China;,   Department of Automation, Nankai University, Tianjin 300071, China
Published: December 2020

Transfer function approximation in frequency domain is not only one of common numerical analysis methods studying portraits of fractional-order chaotic systems, but also a main method to design their chaotic circuits. According to it, in this paper we first investigate the chaotic characteristics of the fractional-order Lorenz system, find some more complex dynamics by analyzing Lyapunov exponents diagrams, bifurcation diagrams and phase portraits, that is, we display the chaotic characteristics as well as periodic characteristics of the system when changing fractional-order from 0.7 to 0.9 in steps of 0.1, and show that the chaotic motion exists in the a lower-dimensional fractional-order Lorenz system. Then, according to transfer function approximation and the approach to designing integer-order chaotic circuits, we also design an analog circuit to implement the fractional-order system. The resistors and capacitors in the circuit are selected according to the system parameters and transfer function approximation in frequency domain. Some phase portraits including chaotic attractors and periodic attractors are observed by oscilloscope, which are coincident well with numerical simulations, and the chaotic characteristics of the fractional-order Lorenz system are further proved by the physical implementation.
Plasma characterization studies of laser dressing for bronze-bonded diamond wheel by a pulsed fiber laser
Authors: Chen Gen-Yu  , Deng Hui  , Xu Jian-Bo  , Li Zong-Gen  , Zhang Ling  ,   State Key Laboratory of Advanced Design and Manufacturing for Vehicle Body, Hunan University, Changsha 410082, China;,   Laser Research Institute, Hunan University, Changsha 410082, China
Published: December 2020

In this paper, we present the optical emission studies of the spatial evolution of plasma during pulsed fiber laser dressing of bronze-bonded diamond grinding wheel and especially investigate the plasma light emission, which is measured through a high sensible optical spectrometer. Space-resolved spectra in a wavelength range of 500-600 nm are measured at different laser average powers and pulse repetition frequencies, and the intensity of spectral lines achieves a maximum intensity at about 2.4 mm away from the surface of the grinding wheel. The electron temperature is determined by employing the Boltzmann plot method under the assumption of local thermodynamic equilibrium using six Cu (I) lines, and the highest electronic temperature is calculated to be 4380 K at about 3 mm away from the surface of wheel. Finally the effect of the laser parameters on the electron temperature of the plasma is studied, and the results show that there are different variation laws in the electron temperature of the plasma with laser average power and pulse repetition frequency.
Corner-pumped Nd:YAG/YAG composite slab continuous-wave 946 nm laser
Authors: Liu Huan  , Wang Wei  , Gong Ma-Li  ,   State Key Laboratory of Tribology, Center for Photonics and Electronics, Department of Precision Instruments and Mechanology, Tsinghua University, Beijing 100084, China
Published: December 2020

A corner-pumped type is a new pumping type in the diode-pumped solid-state lasers, which has the advantages of high pump efficiency and favorable pump uniformity. Using the single corner-pumped type, an efficient corner-pumped Nd:YAG/YAG composite slab continuous-wave 946 nm laser is demonstrated in this paper. The compact plane-concave linear cavity configuration is adopted and the cavity length is only 20 mm. When the pumping power is 50 W, the maximal output power can reach as high as 5.29 W with an optical-to-optical conversion efficiency of 10.6% and a slope efficiency of 12%. This laser has a compact structure, simple tuning and low cost, which will have a broad application prospect.
Analysis of delay time signature in broadband chaos generated by an optoelectronic oscillator
Authors: Li Kai  , Wang An-Bang  , Zhao Tong  , Wang Yun-Cai  ,   Key Laboratory of Advanced Transducers and Intelligent Control System, Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024, China;,   Institute of Optoelectronic Engineering, College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024, China
Published: December 2020

Chaotic laser characteristics of an optoelectronic oscillator are investigated theoretically and numerically, and the influences of the offset phase and the feedback strength on the time-delay signature of chaos which is generated by an optoelectronic oscillator are studied, based on the method of autocorrelation function. Numerical analyses show that the increase of the feedback strength can further suppress or even conceal the time-delay signature. The closer to the extreme point of the transmission curve the operating point corresponding to the DC offset phase, the weaker the time-delay signature is. The time-delay signature can be suppressed obviously as the offset phase is set to be 0. We also find that the sign of the correlation coefficient corresponding to the time-delay signature is changed when the offset phase and the phase shift caused by the delay feedback produce a phase-shift value of π/2.
Nonlinear focusing of weak beam by another high power laser
Authors: Lin Feng  , Tan Chao  , Zhou Yuan  , Fu Xi-Quan  ,   Key Laboratory for Micro/Nano Optoelectronic Devices of Ministry of Education, College of Information Science and Engineering, Hunan University, Changsha 410082, China
Published: December 2020

In this paper, we theoretically and experimentally investigate the controllable nonlinear focusing of the weak laser beam on the basis of the induced nonlinear effects by another strong pump laser beam. When couple laser beams co-propagate in the Kerr medium, it is possible to change the refractive index by the pump beam, and the locally changing medium in turn modifies the weaker probe beam. Depending on cross-phase modulation theory, we obtain an exact analytical solution to the model under the approximate condition and qualitatively verify it in experiment. The results show that the weaker probe beam can be induced to focus at any position due to induced nonlinear effects from the stronger pump beam under certain conditions.
Propagation of polychromatic partially coherent decentred laser beams propagating in non-Kolmogorov turbulence
Authors: Deng Jin-Ping  , Ji Xiao-Ling  , Lu Lu  ,   Department of Physics, Sichuan Normal University, Chengdu 610068, China
Published: December 2020

In this paper, the analytical expressions for the total intensity, the on-axis spectrum and the degree of coherence of polychromatic partially coherent decentred laser beams propagating in non-Kolmogorov turbulence are derived. The influences of the beam decentred parameter β, the fractal constant α of the atmospheric power spectrum, and the bandwidth Ω of spectrum on propagation property are studied. It is shown that the larger the value of β, the bigger the deviation of centre of beam gravity from the propagation axiis, and the more unsymmetrical the coherence degree is. However, the on-axis spectrum is nearly independent of β. The influence of α on total intensity, on-axis spectrum and coherence degree is non-monotonic. When α=3.1, the propagation properties are most affected by turbulence. It is mentioned that at certain propagation distances, the shifts of on-axis spectrum are the same for different values of α. Furthermore, the on-axis spectral shift disappears at other propagation distances which are independent of Ω, and these propagation distances decrease due to turbulence. The results obtained in this paper will be useful for the applications of polychromatic partially coherent decentred laser beams propagating in non-Kolmogorov turbulence.
Influence of local zero-plane displacement on effective aerodynamic parameters over heterogeneous terrain
Authors: Zhong Shi  , Yang Xiu-Qun  , Guo Wei-Dong  ,   School of Atmospheric Sciences, Nanjing University, Nanjing 210093, China
Published: December 2020

In this paper, we investigate the statistical features of the influences of local zero-plane displacement on effective roughness length and effective zero-plane displacement for three surface categories, with a so-called joint calculation scheme for effective aerodynamic parameters over heterogeneous terrain proposed by Zhong et al. [Zhong Z, Lu W, Song S and Zhang Y 2011 J. Hydrometeor. 12 1610]. The local zero-plane displacement is found to magnify the effective roughness length. However, such a magnification effect tends to decrease as the roughness step increases. On the other hand, the effective zero-plane displacement increases as local zero-plane displacement increasing, though it is always less than the area-weighted linear average of the local zero-plane displacement. However, the effective zero-plane displacement tends to decrease with the roughness step increasing.
Secondary electromagnetic polarimetric scattering from dune surface
Authors: Liu Wei  , Guo Li-Xin  , Meng Xiao  , Zheng Fan  ,   School of Science Xidian University, Xi'an 710071, China
Published: December 2020

Secondary electromagnetic polarimetric scattering from a barchan dune is studied. The secondary polarimetric scattering field from the secondary scattering facet is deduced in the Kirchhoff approximation with the waves reflecting from the first scattering facet based on the Ray-tracing theory. The results show that secondary scattering plays an important role in specific range of angle. The co-polarized backscattering coefficients of the lee slope have a local peak value when the incident angle equals the repose angle. Cross-polarized bistatic coefficient of the lee slope near the backscattering region is enhanced when the incident angle is close to the repose angle. The secondary polarimetric scattering between two dunes in line is especially noticeable. The information about wind field in desert region can be retrieved and analyzed by the results in this paper.
Measurement of end-face reflection property of micro-nano fibers
Authors: Hou Jian-Ping  , Zhao Chen-Yang  , Yang Nan  , Hao Jian-Ping  , Zhao Jian-Lin  ,   Shaanxi Key Laboratory of Optical Information Technology, The Key Laboratory of Space Applied Physics and Chemistry, Ministry of Education, School of Science, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

The end-face reflection property of micro-nano fiber (MNF) is one of its important transmission features, which plays remarkable roles in a variety of practical applications of MNF. In this paper, we propose a novel method to study the MNF end-face reflection property using an optical circulator, which overcomes the deficiencies of the direct measurement relying on a 3 dB coupler. On the basis of this method, we further introduce the aerogel fixing and power compensation techniques to effectively eliminate the errors caused by MNF pigtail floating, the light source output instability and internal loss. Therefore, the whole experimental design improves the measurement accuracy. The MNF end-face reflections with respect to the diameter of MNF and the wavelength of the guided light are investigated. The experimental results are in good agreement with simulation results, showing that this new approach is reliable for measuring the reflectivity of specific MNF. This detailed investigation on the end-face reflection versus various factors will be conducive to the constructions of versatile micro-nano scale devices based on the MNF, such as the MNF lasers, MNF amplifiers, MNF couplers and MNF filters.
The generation of jet and mixing induced by the interaction of shock wave with R22 cylinder
Authors: Sha Sha  , Chen Zhi-Hua  , Xue Da-Wen  ,   Key Laboratory of Transient Physics, Nanjing University of Science and Technology, Nanjing 210094, China
Published: December 2020

Based on the large eddy simulation, combined with the 5th order weighted essentially non-oscillatory scheme and the immersed boundary method, the shock wave interacting with an R22 cylinder is numerically simulated. Our numerical results present clearly the deformation of cylinder induced by the Richtmyer-Meshkov instability due to the interaction of shock wave with R22 cylinder, which accords well with previous experimental results of Haas and Sturtevant [Haas J F and Sturtevant B 1987 J. Fluid Mech. 181 41]. In addition, the numerical results reveal the generation process of a jet induced by the refracted shock focusing near the right interface of the inner cylinder, as well as the roll-up of the secondary vortexes along the slip layer of two main vortexes. The mixing mechanism of R22 gas and air is also expatiated. Furthermore, the evolution of R22 cylinder under reshock condition is numerically simulated with two different end wall distances. For the long distance case, the reflected wave interacts with severely distorted R22 volume, making it further compressed on the x-axis. While for the small case, two Mach reflections occur between the reflected shocks during their propagating upstream within the cylinder. The two high pressure areas behind two triple points can accelerate the boundary of the R22 cylinder while they are passing through it and induce two jets.
The identification and forecasting of chaos for natural circulation flow instabilities under rolling motion
Authors: Zhang Wen-Chao  , Tan Si-Chao  , Gao Pu-Zhen  ,   National Defense Key Subject Laboratory for Nuclear Safety and Simulation Technology, Harbin Engineering University, Harbin 150001, China
Published: December 2020

Chaos identification and forecasting of the irregular complex flow oscillations in a two-phase natural circulation system under the rolling motion are performed. The irregular complex flow oscillation has chaotic characteristics by calculating the geometric invariants such as the correlation dimension, Kolmogorov entropy and the largest Lyapunov exponent. But the reliability of calculation result is liable to be influenced by data length and the interference of measurement noise, false judgment results may exist in the direct method. To avoid misjudgment for chaos flow oscillation, both the geometric invariants and chaos identification need to be calculated by surrogate-data method. The chaos is identified by the iterated-amplitude adjusted Fourier transform method. Chaotic forecasting for the irregular complex flow oscillation is carried out by adding weight one-rank local region method. By surrogate-data method, we can confirm that the irregular complex flow oscillation is chaotic oscillation from the deterministic system. Comparisons between the prediction results and experimental data indicate that the chaos forecasting based on adding weight one-rank local region method is an effective way for two-phase natural circulation flow instabilities, and a way of dynamical forecast to monitor flow oscillation is presented.
Investigation on the relationship between the properties of atomic layer deposition ZnO film and the dose of precursor
Authors: Dong Ya-Bin  , Xia Yang  , Li Chao-Bo  , Lu Wei-Er  , Rao Zhi-Peng  , Zhang Yang  , Zhang Xiang  , Ye Tian-Chun  ,   Key Laboratory of Microelectronics Devices and Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029, China
Published: December 2020

In this paper, we present the properties of new type of material ZnO and the ZnO films prepared on sapphire substrate through atomic layer deposition (ALD). In experiment, we use N2 as the carrier, DEZn and DI-water as the precursors. The deposition temperature is 180℃. The value of Zn/O could be modified through changing the dose of DEZn. Furthermore, we investigate the influences of Zn/O value on the thickness, growth rate, crystalline property, surface morphology, three-dimensional structure and roughness of the ZnO film prepared by the ALD method.
Improvement on the electron transport efficiency of the carbon nanotube field effect transistor device by introducing heterogeneous-dual-metal-gate structure
Authors: Liu Xing-Hui  , Zhao Hong-Liang  , Li Tian-Yu  , Zhang Ren  , Li Song-Jie  , Ge Chun-Hua  ,   College of Physics, Liaoning University, Shenyang 110036, China;,   College of Chemistry, Liaoning University, Shenyang 110036, China
Published: December 2020

To improve the carbon nanotube field effect transistor (CNTFET) device performance and enhance the electron transport efficiency of the device, a heterogeneous-dual-metal-gate (HDMG)-CNTFET is proposed. By appropriately modifying the transport model for single-metal-gate (SMG)-CNTFET, the electron transport properties of the HDMG-CNTFET device are investigated. The results indicate that the work function WGS of the metal gate near the source (S-gate) is fixed such that it is equal to that of the intrinsic CNT, and the work function WGd of the metal gate near the drain (D-gate) is selected to be smaller than WGS within a certain range, the electric field distribution can be optimised and the average electron velocity in the CNTFET channel can be significantly increased; at the same time, due to the electric potential modulation by the D-gate, the device has a lower threshold voltage. When the same operating voltage is applied, HDMG-CNTFET has a larger on-state current than SMG-CNTFT; and due to the shielding effect of the drain voltage variation by D-gate, the HDMG-CNTFET device exhibits good gate-control ability and can suppress the drain-induced barrier lower effect, hot electron effect and ambipolar conduction behavior compared with SMG-CNTFET. This study, by reasonably selecting the gate electrode work function of the HDMG-CNTFET, can effectively overcome the deficiency of existing research on improving the CNTFET performance at the expense of reducing the on-current, more importantly, can improve the electron transport efficiency, thereby improving the characteristic frequency and reducing the delay time of the device, which will be of benefit to CNTFET application in high-speed/high-frequency circuit.
Distributed current source reconstruction of magnetocadiography and its accuracy analysis
Authors: Wang Wei-Yuan  , Zhao Chen  , Lin Yu-Zhang  , Zhang Shu-Lin  , Xie Xiao-Ming  , Jiang Shi-Qin  ,   School of Electronics and Information Engineering, Tongji University, Shanghai 201804, China;,   Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050 China
Published: December 2020

Reconstructing cardiac current source by magnetocardiogram signal is a noninvasive method of revealing cardiac electrical activity. The visualization of spatial and temporal information about cardiac electrical activity will be conducive to the analysis of the heart function and the diagnosis of heart disease. In this paper, the capability of reconstructing distribution of current sources, whose distribution is changed over time, is studied by a reduced time window (RTW) beamformer, and the relationship between source reconstruction results and ventricular excitation propagation is analyzed in simulation. The cellular automaton is used to simulate ventricular excitation propagation and to generate the current sources. Moreover, a heart-torso model is constructed by the boundary element method to simulate the effect of the volume conductor. The simulation results show that the RTW beamformer can provide a good accuracy of reconstructing the distribution of current sources. The RTW beamformer is also used to analyze a normal subject with the lead field of infinite homogeneous medium. The results demonstrate that they reflect the basic characteristic of ventricular excitation propagation.
The magnetism study of N-doped diamond
Authors: Lin Xue-Ling  , Pan Feng-Chun  ,   School of Physics and Electric Information Emgomeeromg, Ningxia University, Yinchuan 750021, China
Published: December 2020

We perform the first-principles calculations to investigate the roles of C vacancy and nitrogen impurity in the magnetic properties of diamond. The coupling is ferromagnetic between the C vacancies in -2e charged state, whereas they prefer to interact antiferromagnetically in -e charged state. Substituting C with N atoms can manipulate the charge states of C vacancies and the magnetic interactions between them. Our work offers a possible route toward high Curie temperature ferromagnetism in metal-free diamond.
Optical detection sensitivity of area light source in optical read-out IR imaging
Authors: Wu Jian-Xiong  , Cheng Teng  , Zhang Qing-Chuan  , Gao Jie  , Wu Xiao-Ping  ,   Key Laboratory of Mechanical Behavior and Design of Materials of Chinese Academy of Sciences, University of Science and Technology of China, Hefei 230027, China
Published: December 2020

In the theoretical analysis of the optical readout IR imaging, the incoherent area light source with a certain size is typically simplified into an ideal point light source, which leads to analytical errors. In this paper an area light source model is established, and using the Fraunhofer diffraction theory the influence of the optical detection sensitivity on area light source is studied. The dependence of the optical detection sensitivity on light source radius and reflector length of the focal plane array is found. And optimized design criteria for the size of light source and the length of the reflector are proposed. According to theoretical analysis, the experimental verification is carried out, and the results are consistent with theoretical analyses.
Experimental study on coherent beam combination of fiber amplifiers using adaptive power-in-the-bucket cost function
Authors: Geng Chao  , Luo Wen  , Tan Yi  , Liu Hong-Mei  , Mu Jin-Bo  , Li Xin-Yang  ,   Key Laboratory on Adaptive Optics, Chinese Academy of Sciences, Chengdu 610209, China;,   Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China
Published: December 2020

Beam combination (BC) of fiber amplifiers based on master-oscillator-power-amplifier configuration is an outstanding way to generate high power and high beam quality laser output, where the tip/tilt aberrations among beamlets are considered as a serious influence factor to BC effects. In this paper, a new tip/tilt control method based on adaptive power-in-the-bucket (PIB) cost function is proposed to solve the problem of restricted tip/tilt correcting value in current BC systems. Experimental setup of coherent BC of two-channel 2 W fiber amplifier array is established. Home-made piezoelectric-ring fiber-optic phase-modulator and adaptive fiber-optics collimator are employed to correct piston-and tip/tilt-type aberrations, respectively. The feasibility of proposed tip/tilt control method using adaptive-PIB is demonstrated and nice effect of coherent BC is achieved.
Study of CO2 spectroscopic parameters at high temperature near 2.0 μm
Authors: Chen Jiu-Ying  , Liu Jian-Guo  , He Ya-Bai  , Wang Liao  , Gang Qiang  , Xu Zhen-Yu  , Yao Lu  , Yuan Song  , Ruan Jun  , He Jun-Feng  , Dai Yun-Hai  , Kan Rui-Feng  ,   Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China;,   Key Laboratory of hypersonic ramjet technology, 31st Research Institute, China Aerospace Science and Industry Corporation, Beijing 100074, China
Published: December 2020

Reliable spectroscopic parameters of probed species at high temperature, such as line strengths, self-broadening coefficients, air-broadening coefficients, and temperature exponents, are important in absorption spectroscopy for accurately studying species properties, such as temperature, concentration, speed, and their corresponding field distributions. However, parameters from widely used database such as HITEMP are mainly theoretical calculation results, and there exist considerable errors compared with the results in actual situations. In order to validate spectroscopic parameters of CO2 lines used in combustion diagnosis, CO2 spectrum is recorded as a function of temperature in a range between 700 K and 1300 K in experiment using a distributed feed-back diode laser. Parameters of each line are deduced, such as line strengths, self-broadening coefficients and temperature exponents. The relative errors between measured and calculated line-strengths are less than 11% at 5006.978 cm-1 and 5007.7874 cm-1. The measured self-broadening coefficients at different temperatures and temperature exponents are conducive to the detection of CO2 concentration in combustion diagnostics.
Electron-LO phonon scattering in Ga1-xInxNyAs1-y/GaAs quantum well
Authors: Chen Qian  , Wang Hai-Long  , Wang Hui  , Gong Qian  , Song Zhi-Tang  ,   Shandong Provincial Key Laboratory of Laser Polarization and Information Technology, Department of Physics, Qufu Normal University, Qufu 273165, China;,   Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201203, China;,   State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China
Published: December 2020

Within the framework of effective mass approximation, the values of energy eigenvalue En in Ga1-xInxNyAs1-y/GaAs quantum well are theoretically calculated using shooting method. In addition, we calculate the electron-LO phonon scattering and mean scattering rate at different temperatures, well width, N concentrations and In concentrations for an electron initially in the second subband and finally in the ground state using Fermi’s golden rule. It is shown that the electron-LO phonon scattering and mean scattering rate increase with the increase of N concentration under the In concentration constant. The electron-LO phonon scattering and mean scattering rate decrease with the increase of In concentration under the In concentration constant. The electron-LO phonon scattering increases monotonically with the increase of temperature. When the temperature is relatively low, the variation of mean scattering rate is not obvious with the increase of temperature When the temperature is relatively high, mean scattering rate increases with the increase of temperature. The scattering and mean scattering rate increase up to their maxima and then begin to decrease as the well width increases. The maximum value is reached when the well width is about 200 Å. Our calculated results are meaningful and can be used for designing the optoelectronic devices based on Ga1-xInxNyAs1-y/GaAs quantum well.
Magnetic properties of multiferroic material DyMnO3 in orthorhombic structure
Authors: Wang Mei-Na  , Li Ying  , Wang Tian-Xing  , Liu Guo-Dong  ,   School of Materials Science and Engineering, Hebei University of Technology, Tianjin 300130, China;,   College of Physics and Electronic Engineering, Henan Normal University, Xinxiang 453007, China
Published: December 2020

The lattice parameters, total energy, magnetism, density of states, and band structure in the multiferroic material DyMnO3 with orthorhombic structure are investigated by using different magnetic models, and the non-collinear magnetism and the collinear magnetism are taken into account by using density functional theory combined with the projector augmented wave method via the software package of VASP. The generalized-gradient approximation (GGA) pseudo potential is used in the calculation, and the local spin density approximation +U method is also adopted to deal with the strong correlation effect of the 3d electrons. The results show that Mn ion in the AAFM magnetic model has the lowest energy and is the most stable, while the weak magnetism of the rare earth ion Dy can be neglected, and that the total energy and the magnetic moment of DyMnO3 in orthorhombic structure increase when the non-collinear magnetic structure of Mn ion is considered and that the DyMnO3 material is an indirect-gap insulator with an energy gap value of 0. 38 eV obtained from GGA or 1.36 eV from GGA+U, and the lattice distortion should be considered to be due to the hybridization between Mn-3d and O-2p electrons, which can be analyzed from the density of state.
Physical process and characteristics for rapid charging events at international space station
Authors: Huang Jian-Guo  , Yi Zhong  , Meng Li-Fei  , Zhao Hua  , Liu Ye-Nan  ,   Beijing Institute of Spacecraft Environment Engineering, Beijing 100094, China;,   Science and Technology on Reliability and Environmental Engineering Laboratory, Beijing 100094, China
Published: December 2020

The rapidly charging event (RCE) is a new category of spacecraft charging, which was first observed at an international space station in 2006. It occurred in the presence of the eclipse, with the floating potential increasing abruptly to tens of volts, well beyond the safety level of –40 V, within a few seconds. The RCE has not yet been understood thoroughly until now. Based on Ferguson and Craven’s theory, we developed a physical model for the rapidly charging events recently and gave satisfactory predictions compared with the observations. In this paper, we investigate the physical process and mechanism in detail, and explain the statistical characteristics and the underlying physics through the model calculations. It is shown that the rapidly charging event is a non-equilibrium charging process and driven by the high voltage solar arrays. The rapid charging is mainly due to the fact that the cover glass blocking effect cannot follow the rapid increasing of the solar voltage when it is abruptly turned on at the exit of eclipse. As the RCE reaches equilibrium it acts as a normal charging event. The rapidly charging amplitudes depend on many factors, such as the switch-on time of the solar arrays, the pattern of switch-on, etc., which play key roles, and so that the floating potential data exhibit a spread to a certain extent. The maximum potential decreases with electron density increasing, which is in good agreement with observations.
Theory of ELF/VLF wave directional radiation by modulated heating of ionosphere
Authors: Hao Shu-Ji  , Li Qing-Liang  , Yang Ju-Tao  , Wu Zhen-Sen  ,   Department of Physics, Xidian University, Xi’an 710071, China;,   China Research Institute of Radiowave Propagation, Qingdao 266107, China
Published: December 2020

ELF/VLF waves are generated via amplitude-modulated heating of the lower ionosphere. Based on the modulated heating theory, the directional radiation models of dual beam amplitude modulation (DAM) and circle geometric modulation (CGM) are established by introducing the phased array ideas, which are validated by comparison with the experimental data. According to the models, differences between the above two directional radiation models and the normal amplitude modulation (AM) are analyzed with parameters of HARRP phased-array HF facility, and the influences of the modulation frequency (fELF/VLF) and elevation of the heating waves on mode are investigated as well. Compared with the AM mode, DAM and CGM can realize the directional radiation, and enhance the radiant intensity by properly setting the initial phase, the modulation frequency (fELF/VLF) and angle of inclination of the heat wave to the vertical direction. The ELF/VLF radiant intensity may be increased by 11.3 dB when replacing AM with CGM.
Study on the gravitational waveform emitted from post-Newtonian eccentric spinning compact binary
Authors: Zhong Shuang-Ying  , Liu Song  , Hu Shu-Juan  ,   School of Sciences, Nanchang University, Nanchang 330031, China
Published: December 2020

This paper mainly deals with the effects of eccentricity on the gravitational waveforms emitted by the non-conservative post-Newtonian (PN) Hamiltonian formulations of the spinning compact binaries. The numerical results show that the change of eccentricity has a slight influence on the time-domain gravitational waveforms from the conservative spinning compact binaries, but the frequency bands of gravitational waveforms is broadened with increasing eccentricity. Owing to the effects of dissipation from the gravitational radiation reaction, the separation and the eccentricity decrease gradually with time, and the gravitational waveforms emitted from the non-conservative PN spinning compact binaries are modulated by the eccentricity, meanwhile the amplitude of the waveforms enhances with the increase of eccentricity; the duration of the waveforms decreases.
Theoretical and experimental study of a novel double-well optical dipole trap for two-species of cold atoms or molecules
Authors: Lu Jun-Fa  , Zhou Qi  , Pan Xiao-Qing  , Yin Jian-Ping  ,   College of Science, East China Institute of Technology, Jiangxi Fuzhou 344000, China;,   State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China;,   College of Science, Jiangxi University of Science and Technology, Jiangxi Ganzhou 341000, China
Published: December 2020

A novel scheme based on light diffraction to generate a double-well optical trap for trapping and controlling two-species samples of cold atoms or molecules is proposed. Specialized phase modulation similar to the binary phase-grating is implemented in a diffraction device of liquid crystal spatial light modulator (LC-SLM). A continuous and reversible evolution between single-well trap and double-well trap is investigated. Corresponding experiments are performed and the results are in agreement with theories. Our results show that the proposed scheme has a controllability advantage, which is beneficial to the loading and controlling two-species samples in cold atoms or molecules experiments.