bluuebunny/crossref_metadata_2025 huggingface dataset:
A modified electromechanical model with one-dimensional abalation model for numerical analysis of the pulsed plasma thruster
Authors: Zhang Hua  , Wu Jian-Jun  , Zhang Dai-Xian  , Zhang Rui  , He Zhen  ,   College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China
Published: December 2020

The electromechanical model is used widely in simulating the operation process of pulsed plasma thrusters, because of its simplicity. Considering the limitation of the model that the late time ablation mass is assumed to be constant and the ablation process is ignored, we propose a modified mechanical model to serve a one-dimensional ablation model, and then the operation process of LES-6 PPT was simulated by this modified electromechanical model. Simulation results show excellent agreement with experimental data from the LES-6 PPT. This modified model can simulate the ablation process which cannot be completed by using the original electromechanical model. So, this modified model can better reflect the real operation mechanism than the electromechanical model. Besides, this modified model is as simple as the original model, it is of great significance for PPT design.
Study on bifurcation and chaos in single-phase H-bridge inverter modulated by unipolar sinusoidal pulse width modulation
Authors: Liu Hong-Chen  , Yang Shuang  ,   School of Electrical Engineering and Automation, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

The unipolar SPWM has been widely used in H-bridge inverter because of its superiority for lower switching loss and less electromagnetic interference as compared with bipolar SPWM. However, the nonlinear phenomena in it have not been reported. In this paper, the bifurcation and chaos in the H-bridge inverter modulated by unipolar SPWM is studied. The one-dimensional discrete iterated mapping model under proportional control is established. Effects of the proportional coefficient k on the system performance are analyzed by using bifurcation diagram, folded diagram, and Lyapunov index spectrum. The time-domain waveforms with different proportional coefficients are obtained by Matlab/Simulink, which verify the correctness of theoretical analysis. Finally, the nonlinear behavior in the inverter caused by the variation of other circuit parameters like input voltage E, load resistance R, and inductance L is investigated through bifurcation diagrams. This paper turns the chaotic research of single-phase H-bridge inverter from bipolar SPWM to unipolar SPWM, So that the proposed approach is more practical. The results have important guiding significance and application value for designing and debugging the single-phase H-bridge inverter correctly.
Hydrogen storage of Mg-decorated closo-hexaborate B6H62-
Authors: Lu Qi-Liang  , Huang Shou-Guo  , Li Yi-De  ,   School of Physics and Material Science, Anhui University, Hefei 230601, China
Published: December 2020

Hydrogen storage capacity of Mg-decorated closo-hexaborate B6H62- has been studied using density functional theory. The binding strength of Mg atom is sufficiently large to ensure the stability of MgB6H62-. Each Mg atom can adsorb six H2 molecules. Moreover, the larger dipole moment combined with enhanced electrostatic field around the Mg atom originates from the charge transfer from B6H62- to Mg, accounting for the higher adsorption capacity of MgB6H62- than that of MgB6H6. Hydrogen storage capacity of MgB6H62- can be up to 11.1 wt% with an average binding energy between 0.23 eV and 0.34 eV. The electrostatic field around the Mg atom can be enhanced by controlling the charge state of the metal-organic complex, thereby significantly improving the hydrogen adsorption capacity.
In-fiber Mach-Zehnder interferometer based on fiber core etched air-bubble and core diameter mismatch for liquid refractive index sensing
Authors: Li Hui-Dong  , Fu Hai-Wei  , Shao Min  , Zhao Na  , Qiao Xue-Guang  , Liu Ying-Gang  , Li Yan  , Yan Xu  ,   Ministry of Education Key Laboratory on Photoelectric oil-gas Logging and detecting, School of Science, Xi’an Shiyou University, Xi’an 710065, China;,   Department of Physics, Northwest University, Xi’an 710069, China
Published: December 2020

A kind of optical fiber liquid refractive index sensor is proposed based on fiber core etched air-bubble and core diameter mismatched in-fiber Mach-Zehnder interferometer. A core etched standard single-mode fiber is spliced to another core etched standard single-mode fiber (SMF) to form an air bubble at the connecting point, and a 20 mm thinned fiber is cascaded (TCF) by fusion splicing method, which is 20 mm apart from the bubble, then a leading-mode fiber is spliced to the thinned fiber to form a structure of SMF-(air-bubble)-SMF-TCF-SMF in-fiber Mach-Zehnder interferometer liquid refractive index sensor. The air-bubble and the two fiber core diameter mismatched points serve as optical couplers for modes conversion. The transmission spectrum of sensor is studied by experiment. Results shows that the peak power changes with respect to surrounding refractive index with good linearity. The sensitivity of the sensor is 142.537 dB/RIU in the range of 1.3511.402 with linearity of 0.996, making it a good candidate for bio-chemical measurements.
Supercontinuum experimental study of V-type photonic crystal fiber with high birefringence
Authors: Zhao Yuan-Yuan  , Zhou Gui-Yao  , Li Jian-She  , Han Ying  , Wang Chao  , Wang Wei  ,   College of Information Science and Engineering, Yanshan University, Qinhuangdao 066004, China;,   College of Science, Yanshan University, Qinhuangdao 066004, China;,   Key Laboratory of Metastable Material Science and Technology, Yanshan University, Qinhuangdao 066004, China
Published: December 2020

High nonlinear and high birefringent photonic crystal fiber is one of the most effective medium for supercontinuum generation, therefore we select the V-type photonic crystal fiber as the research object. Through the numerical simulation results of multipole theory, we determined that the V-type optical fiber has high birefringent and high nonlinear characteristics. Through experiments, we found that the birefringence of the fiber and the central wavelength of the incident light have great influence on the generation of supercontinuum: when the central wavelength of incident light in the anomalous dispersion region of the fiber, its spectrum is quite wide relatively, and the supercontinuum of the long axis is flat tar than that of the short exis and has more abundant spectral components; at the same wavelength of light, the polarization direction of the former is closer to 45°, the supercontinuum spectrum range is larger. With the increase of the incident pulse power, supercontinuum will spread wider, but will reach a saturation when the power is large enough.
Study on tapered chirped fiber grating filter
Authors: Yin Bin  , Bai Yun-Long  , Qi Yan-Hui  , Feng Su-Chun  , Jian Shui-Sheng  ,   Institute of Lightwave Technology, Key Lab of All Optical Network & Advanced Telecommunication Network of EMC, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

Tapered chirped fiber grating filter is analyzed from the detailed theoretical and experimental studies. The transmission spectrum of tapered chirped fiber grating filter is influenced by the parameters and loss of chirped fiber grating (length, refractive index modulation, chirp coefficient) and taper after examined by the transfer matrix method and resonance theory combined with coupled-mode theory. We study the influence of the chirped fiber grating wavelength reflectivity by tapering, and make the corresponding numerical simulation and experimental verification based on the above theories. Numerical simulation result is consistent with the experimental data.
Identification of plastics by laser-induced breakdown spectroscopy combined with support vector machine algorithm
Authors: Yu Yang  , Hao Zhong-Qi  , Li Chang-Mao  , Guo Lian-Bo  , Li Kuo-Hu  , Zeng Qing-Dong  , Li Xiang-You  , Ren Zhao  , Zeng Xiao-Yan  ,   Wuhan National Laboratory for Optoelectronics, Laser and Tera-Hertz Technology Division, Huazhong University of Science and Technology, Wuhan 430074, China;,   Wuhan New Research and Development Laser Engineering Co., Ltd, Wuhan 430074, China
Published: December 2020

Laser-induced breakdown spectroscopy (LIBS) combined with support vector machine (SVM) algorithm was used to identify 11 kinds of plastics. For each plastic, 100 spectra recorded by the spectrometer system were divided equally into training set and test set, and the former was used to train SVM model while the latter was used to validate SVM model created by the training set. Result shows that 543 of 550 test set spectra are identified correctly with the average correct identification rate 98.73%. However, there are six spectra of PU misidentified as PMMA. This is because the difference of nitrogen content in 11 plastics cannot be reflected by the intensities of N I 746.87 nm and C-N (0,0) 388.3 nm due to the influence of ambient air. Methods and reference data are provided for further study of plastics identification by laser-induced breakdown spectroscopy technique.
Lamellarrod transition mechanism under high growth velocity condition
Authors: Wang Lei  , Wang Nan  , Ji Lin  , Yao Wen-Jing  ,   Key Laboratory of Space Applied Physics and Chemisty, Ministry of Education, School of Science, Northwestern Polytechnical University, Xi’an 710072, China
Published: December 2020

At a low velocity, the lamellarrod eutectic transition can be controlled by the volume fraction of one eutectic phase only. The factors which affect this kind of transition at high growth velocities are not clear. Based on the competitive growth rule, the criterion for lamellarrod transition is obtained by combining the models of lamellar and rod eutectic growth under rapid solidification conditions. It is shown that for a certain volume fraction, if its value fluctuates around the critical point predicted by the JH Jackson and Hunt model, the increase of the growth velocity or the partition coefficient will lead to the rodlamellar transition. Otherwise, no transition will take place. The lamellarrod eutectic transition at high growth velocity is controlled by the volume fraction variation, which is caused by the increase of the growth velocity.
Study on the electronic structures of Iridium-doped SmOFeAs under the strongly correlated electrons effects
Authors: Pan Min  , Huang Zheng  , Zhao Yong  ,   Superconductivity and New Energy R&D Center, Key Laboratory of Advanced Technology of Materials (Ministry of Education), Southwest Jiaotong University, Chengdu 610031, China;,   School of Materials Science and Engineering, University of New South Wales, Sydney 2052, NSW, Australia
Published: December 2020

Based on the consideration of strong correlation of electrons, we have used density functional theory generalized gradient approximation method SGGA+U to calculate SmFeAsO and Ir doping effects on the lattices and electronic properties. It is found that iridium doping at the Fe site enhances the interaction between FeAs and SmO layers and results in a modification of the FeAs4 tetrahedron. The electronic density of states (DOS) of SmOFe1-xIrxAs is studied by comparing the calculations with the X-ray photoemission spectroscopy experiments (XPS). It is revealed that the Fe 3d and As 4p hybridization orbits dominate the electric properties for SmOFe1-xIrxAs. Ir doping makes the five orbitals of Fe3d all filled. Superconductivity is sensitive to the peak position shifting away from Fermi level. Our VASP SGGA+U calculation provides a better agreement with the experimental results when we use an on-site coulomb energy of U on Fe 3d shell, which is sharply contrasted to the GGA process.
Study on cryogenic remanence measurement technology for chunk permanent magnet
Authors: He Yong-Zhou  ,   Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China
Published: December 2020

Through improvement of Hall probe cryogenic calibration system, a cryogenic remanence measurement system(CRMS) for chunk permanent magnet was built. With a rectangular NdFeB(N50M) permanent magnet (its size is 40 mm×40 mm×10 mm) as example, cryogenic remanence measurement technology for chunk permanent magnet was studied. Results show that main factors affecting cryogenic remanence measurement reliability are Hall probe cryogenic calibration, Hall probe location, temperature drift, and thermal expansion of the material and so on. If the same methods are used for measurement, then the cryogenic remanence measurement repeatability of a permanent magnet is less than 0.1%. The experimental study creates conditions for measurements and research of cryogenic remanence of chunk permanent magnet of high-precision permanent magnet devices, such as cryogenic undulators.
Study on preparation and characteristics of Fe- and Mn-doped AlN thin films
Authors: Lan Lei-Lei  , Hu Xin-Yu  , Gu Guang-Rui  , Jiang Li-Na  , Wu Bao-Jia  ,   Department of Physics, College of Science, Yanbian University, Yanji 133002, China;,   State Key Laboratory for Superhard Materials, Jilin University, Changchun 130012, China
Published: December 2020

Fe- and Mn-doped AlN thin films were prepared on Si substrates by direct current (DC) magnetron co-sputtering method in the atmospher of Ar and N2 mixture. The influences of sputtering currents and the target to substrate distance on the structure of the films were investigated by X-ray diffraction and Raman spectroscopy, respectively. Surface morphology and composition were studied by scanning electron microscope (SEM) with an energy dispersive X-ray spectroscopy (EDS) attachment. The magnetism of Mn- and Fe-doped AlN films was measured by vibrating sample magnetometer (VSM) at room temperature (RT). Processing of the Mn-doped AlN films produces Mn clusters in the samples. Due to the presence of the antiferromagnetism Mn clusters, ferromagnetism is either suppressed or disappears. The Fe-doped AlN films show ferromagnetism at RT, which should arise from the AlFeN ternary alloy. With the increase of the Fe target sputtering current, the Fe concentration is increased from 6.81 at.% to 16.17at.%; the saturation magnetization Ms is reduced from 0.27 emu·cm-3 to 0.20 emu·cm-3, and the coercive force Hc is increased from 57 Oe to 115 Oe, this is because the separation of Fe ions get shorter and the antiferromagnetic coupling is enhanced.
Mechanism of instability behaviors and stabilization on V2 controlled buck converter
Authors: Zhang Fang-Ying  , Yang Ru  , Long Xiao-Li  , Xie Chen-Yue  , Chen Hong  ,   Labcenter, Guangzhou University, Guangzhou 510006, China;,   School of Physics and Electronic Engineering, Guangzhou University, Guangzhou 510006, China
Published: December 2020

Along with the variation of the feedback amplify coefficient, V2 controlled Buck converter exhibits abundant nonlinear dynamical behaviors. By establishing the discrete-time model of the system, this paper has studied the instability phenomena based on the monodromy matrix method. With increasing feedback factor, the analysis indicated that the converter entered from a stable period-one statue into a period-doubling statue. Finally, it showed chaos. Mechanism of the bifurcation generated by the system was fully analyzed based on the monodromy matrix, which showed that as the increase of the feedback coefficient, an eigenvalue of the monodromy matrix went out of the unit circle; this was the reason why the system generated period-doubling bifurcation. Also presented was the sinusoidal voltage compensation method to extend the stability margin based on the monodromy matrix theory, by which the instability behavior was effectively handled. Simulation and experimental results confirmed the analytical method.
Noise characterization of quantum dot infrared photodetectors
Authors: Liu Hong-Mei  , Yang Chun-Hua  , Liu Xin  , Zhang Jian-Qi  , Shi Yun-Long  ,   Institute of Solid State Physics, Shanxi Datong University, Datong 037009, China;,   School of Technical Physics, Xidian Univiversity, Xi’an 710071, China
Published: December 2020

A theoretical model for the noise is derived in this paper to characterize the influence of the noise on quantum dot infrared photodetectors. In this model, the noise current is estimated with the consideration of the common influence of the nanoscale electron transport and microscale electron transport on the activation energy and the contribution of the noise gain. The obtained results show a good agreement with the published experimental values, which illustrates the validity of the model.
Micromagnetic analysis of the maghemite platelet chains in the iron-mineral-based magnetoreceptor of birds
Authors: Zhang Xi-Chao  , Zhao Guo-Ping  , Xia Jing  ,   College of Physics and Electronic Engineering, Sichuan Normal University, Chengdu 610068, China
Published: December 2020

Experiments demonstrate that large varieties of animals have the ability to sense the magnetic field. Especially, some birds can use the geomagnetic field for navigation. According to the avian magnetoreception mechanisms, birds can build magnetic map for orientation and navigation by sensing the intensity and incline of geomagnetic field. However, researches on the magnetoreceptor of birds are still at the stage of discovery and identification, and it is necessary to study the iron-mineral-based structures to know whether they have the physical and magnetic properties to act as magnetoreceptor in living system. In this paper, the maghemite platelet chains in the iron-mineral-based magnetoreceptor have been studied with three-dimensional simulation based on the theories of micromagnetics. The reaction of the maghemite platelet chains with geomagnetic field has been investigated. Result indicates that the maghemite platelet chains with vortex domain can response to the change of the orientation of geomagnetic field.
Analysis of voluntary vaccination model based on the node degree information
Authors: Hu Zhao-Long  , Liu Jian-Guo  , Ren Zhuo-Ming  ,   Research Center of Complex Systems Science, University of Shanghai for Science and Technology, Shanghai 200093, China
Published: December 2020

The widespread of epidemics bring tremendous losses to the mankind, thus it is very important to prevent the spread of epidemics. In this paper, the differences between individual tendency of vaccination is taken into account to propose a voluntary vaccination model based on the node degree information. Further, the theoretical analysis result shows that if propagation rate exceed a threshold value, the effectiveness of epidemic spreading (the number of infectious nodes) of the model above and the classical model ignoring the difference between the individual vaccination willingness [Zhang et al 2010 New J. Phys. 12 023015] will be the same. Both the permanent vaccination and the temporary vaccination are considered to analyze the process of epidemic spreading for the Barabási-Albert network by using the SIS model. The numerical simulation results are consistent with the empirical ones very well. Experiments prove that when the infection cost and vaccine cost is the same, the model can prevent the spread of the epidemic more effective as compared with the classical one, and the proportion of the infections decreases over 65% than the classical one. In addition, the longer the live of vaccine, the more effective the prevention of the spread of the epidemic using this model (compared with the classical model ignoring the difference between the individual vaccination willingness).
Coloring the complex networks and its application for immunization strategy
Authors: Huang Bin  , Zhao Xiang-Yu  , Qi Kai  , Tang Ming  , Do Younghae  ,   School of Mathematics, Chengdu University of Information Technology, Chengdu 610225, China;,   Web Science Center, University of Electronic Science and Technology of China, Chengdu 610054, China;,   Department of Mathematics, Kyungpook National University, Daegu 702-701, South Korea
Published: December 2020

Structural analysis of complex networks has gained more and more concerns, but not enough attention has been paid to the coloring problem in complex networks. In order to understand the relationship between network structure and coloring problem, we investigate the effects of WS, BA networks and different macro-scale parameters on the K-proper coloring. We find that the maximum clique number can generally reflect the trend of K value change, the average degree and the degree correlation have a greater impact on the K value than the heterogeneity and the clustering coefficient. These results are verified on some real-world networks. After coloring the complex networks properly, the independent sets of networks can be obtained. According to the characteristic that any two vertices are not connected in an independent set, we propose a random immunization strategy based on the independent set. Compared with the random immunization, the proposed strategy can make the network more vulnerable, and thus effectively mitigate epidemic spreading. This immunization strategy is simple and practical, which helps to design more efficient immunization strategy.
The first order approximate Lie symmetries and approximate conserved quantities of the weak nonlinear coupled two-dimensional system
Authors: Lou Zhi-Mei  ,   Department of Physics, Shaoxing University, Shaoxing 312000, China
Published: December 2020

A real weak nonlinear coupled two-dimensional system is constructed first by using coupling spring with variable force constant. The first-order approximate Lie symmetries and approximate conserved quantities of the system are studied. The system possesses six first-order approximate Lie symmetries and approximate conserved quantities, of which one is an exact conserved quantity, four are trivial conserved quantities, and only one is a stable conserved quantity.
Mechanism of bursting oscillations in non-smooth generalized Chua’s circuit with two time scales
Authors: Li Xu  , Zhang Zheng-Di  , Bi Qin-Sheng  ,   Facuity of Science, Jiangsu University, Zhenjiang 212013, China
Published: December 2020

By introducing periodically alternate current source as well as suitable values for the parameters to ensure that there exists order gap between the natural frequency and the exited frequency, a two-time scale namely, a fast-slow coupled non-smooth generalized Chua’s circuit model is established. Based on the corresponding generalized autonomous system, the stabilities of the equilibrium points in different regions are investigated, from which the critical conditions related to different types of bifurcation forms are obtained. At the same time, combining the theory of Clarke derivative, different types of non-conventional bifurcation models which may occur when the trajectory passes across the non-smooth boundaries are explored. Furthermore, with the combination of the generalized phase portraits, two typical periodic bursting phenomena namely, the Fold/Fold and Fold/Hopf periodic bursters, and their associated bifurcation mechanisms are analysed in detail.
Shielding property calculation of B4C/Al composites for spent fuel transportation and storge
Authors: Dai Long-Ze  , Liu Xi-Qin  , Liu Zi-Li  , Ding Ding  ,   Institute of Material Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
Published: December 2020

MCNP program is used to calculate the neutron transmission coefficient of 3–9 cm-thick neutron absorber material B4C/Al composite with 5%–15% B4C content in air, water, 200–1400 ppm (1 ppm=10-6) H3BO3 solution, irradiated by 0.5–20 MeV neutrons and 235U thermal neutron fission source. The results show that the transmission coefficient of B4C/Al composite decreases with the increase of the content of B4C and the thickness of material, but increases with the increase of neutron energy, and has little influence from the variation in H3BO3 solution concentration. A better shielding effect of B4C/Al composite is displayed in water than in H3BO3 solution, and a “reversal” phenomenon of the shielding effect occurs in air. The neutron transmission coefficient is almost unchanged with neutron energy when neutron energy is higher than the 5–15 MeV. The neutron transmission coefficient of B4C/Al composite irradiated under a fission source is lower than under a steady 20 MeV neutron source. Ranking the shielding performances of media, the sequence is H3BO3 solution > water > air, and the exponential decay relationships between neutron transmission coefficient and thickness of medium can be expressed as e-0.71x and e-0.669x, where x is thickness of medium in cm.
Molecular structure and electronic spectrum of 2, 2, 5, 5-tetrachlorobiphenyl under the extenal electric field
Authors: Ling Zhi-Gang  , Tang Yan-Lin  , Li Tao  , Li Yu-Peng  , Wei Xiao-Nan  ,   Department of Physics, Guizhou University, Guiyang 550025, China
Published: December 2020

Polychlorinated biphenyls (PCBs) are persistent organic pollutant, and 2, 2, 5, 5-tetrachlorobiphenyl is generally used as a model molecule of PCBs in some studies. PCB52 molecule is degraded under external electric fields. The molecular structure of PCB ground state is optimized by density functional theory (B3LYP) method with 6-311+g(d) basis sets. The effects of electric fields ranging from-0.04 a.u. to 0.04 a.u. are investigated on structural parameters, total energy, dipole moment and charges distribution. The transition wavelengths, oscillator strengths and excitation energies of the first six excited states under external electric fields are calculated by the time dependent density functional theory method. The result shows that the bond lengths of 1C21Cl and 14C20Cl increase with external electric field increasing. The dihedral angle of two benzene rings of PCB52 molecule increases under the electric fields, and the PCB52 molecule reduces toxicity. PCB52 molecule energy gaps decrease, leading to the fact that the molecule is susceptible to excitation to an excited state and reductive dechlorination reaction. As the increase of the applied electric field, the excitation energies rapidly decrease, absorption wavelengths are red-shifted toward longer wavelength and oscillator strength is no longer zero, which indicates that the PCB52 molecule is easily excited and dissociated.
A study of dynamic properties of exchange reaction H(D)+SH/SD by quasi-classical trajectory method
Authors: Xu Guo-Liang  , Liu Pei  , Liu Yan-Lei  , Zhang Lin  , Liu Yu-Fang  ,   College of Physics and Electronic Engineering, Henan Normal University, Xinxiang 453007, China
Published: December 2020

Sulfur in hydrogen combustion reaction chemistry, which plays an important role in meteorology, combustion reactions, and atmospheric pollution, has been extensively investigated recently. And its reverse reaction has also been a research object gradually. The research in this paper is based on the exact potential energy surface (L S J, Zhang P Y, Han K L, He G Z 2012 J. Chem. Phys. 136 094308), with using the method of quasi-classical trajectory on the exchange reaction of H (D)+SH/SD dynamic properties. In this paper, the scalar properties are calculated, including the cross section, rate constant, opacity function, product vibrational, rotational distributions, product scattering direction, rotational angular momentum orientation, and alignment properties. In this paper, how the collision energy and the isotope affect the reaction H (D)+SH/SD kinetic properties is analyzed in detail. The results show that as collision energy increases, the reaction cross section increases, product backscatter weakens gradually while the product rotational angular momentum alignment and orientation nature strengthen gradually. In addition, the isotope effect has a significant influence on the reaction kinetics. The reaction mechanism which is shown in the title and based on the reaction kinetics and the potential energy surface, is also discussed in this paper.
Investigation on coherence characteristics of Gauss-Schell model beam propagating in atmospheric turbulence
Authors: Li Cheng-Qiang  , Zhang He-Yong  , Wang Ting-Feng  , Liu Li-Sheng  , Guo Jin  ,   State Key Laboratory of Laser Interaction with Matter, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Science, Changchun 130033, China;,   Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

The change in coherence length of Gauss-Schell model beam propagating in atmospheric turbulence is studied by comparing with propagation in free space. The coherence length change only depends on source parameters in free space while its change in turbulence is governed by source parameters and turbulence. Beam spreading results in an increase in the coherence length in vacuum. For propagation in turbulence, the coherence length increases due to beam spreading over relatively short distance while decreases on account of the enhancement of turbulence over a sufficiently long distance. Thus, the simple analysis of the influence of turbulence on the coherence length is not mature enough. In order to exclude the effect of beam spreading, the ratio of coherence length to beam size is employed. It is found that atmospheric turbulence always leads to the decline of ratio. The explanations, based on numerical simulation, of above-mentioned results are given in this paper.
Electromagnetically induced grating based on the coherent population trapping
Authors: Yu Song  , Liao Ping  , Yang Zhan-Yu  , Gu Wan-Yi  ,   State Key Laboratory of Information Photonics and Optical Communications, Beijing University of Posts and Telecommunications, Beijing 100876, China
Published: December 2020

Based on the coherent population trapping theory, a new physical model of the electromagnetically induced grating (EIG) is proposed. Analytical expression of the dielectric susceptibility is derived using this model. Owing to the atomic coherence, introduced by the coherent population trapping, three regions of dielectric susceptibility, i.e., a gain region, a region with no absorption and high-refraction index, and a dark region, are formed. Based on this model and the energy level of 87Rb, a novel scheme to implement the diffraction grating is proposed. Moreover, theoretical analysis and calculation of this grating are carried out. The results show that in the region with no absorption and high refractive index, the grating presents a pure phase grating and the first-order diffraction intensity can reach 0.4. In the gain region, however, the grating is a combination of phase grating and amplitude grating, and at its largest-gain point, the maximum of the first-order diffraction efficiency arrives at 1.26, and the second-order diffraction efficiency can also increase to 0.31.
Study of cascaded raman scattering laser in silica microsphere pumped by 976 nm laser
Authors: Zhang Pei-Jin  , Huang Yu  , Guo Chang-Lei  , Huang Yan-Tang  ,   College of Physics and Information Engineering, Fuzhou University, Fuzhou 350018, China
Published: December 2020

High-quality-factor microspheres with smooth surface are fabricated through surface tension by heating and fusing a single tapered fiber using arc of electrodes discharge. Stimulated Raman scattering of the third order nonlinear phenomena of microspheres with high power density whispering gallery modes was studied by coupling 976 nm laser into microspheres through tapered fiber as evanescent wave. The total six cascaded Raman lasers were observed in the experiment. At each order, single longitudinal mode and multi longitudinal mode Raman lasers were observed. The Raman laser at around 1200 nm was measured with pump power less than 582.6 μW. The sixth-order Raman laser at around 1287.04 nm was observed when pump power is 3.014 mW.
Influences of correlated colored-noises on logistic model for tree growth
Authors: Wang Guo-Wei  , Xu Da-Hai  , Cheng Qing-Hua  ,   College of Physics Sinence and Technology, Yangtze University, Jingzhou 434023, China
Published: December 2020

By virtue of Liouville Theorem and unified colored-noise approximation approach, an approximate Fokker-Planck equation for a tree growth Logistic model subjected to cross-correlated colored noises is derived, and the steady-state probability distribution (SPD) function is obtained. The steady-state properties of the Logistic model are analyzed. We find the following: (1) the position of peak of SPD moves toward left side as D increases while the position of the peak moves toward the contrary direction with Q increasing; (2) the peak of SPD becomes narrow and grows in height as |λ| increases, and for the case of λ >0, the position of peak moves toward right as D increases, but it is opposite for the case of λQ increases.
Theoretical and visualization study of laserinduced surface acoustic wave on annular stator
Authors: Li Fang-Hao  , Zhang Hai-Jun  , Zhang Dong-Xian  ,   State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China
Published: December 2020

The mechanism of laser-induced surface acoustic wave (SAW) on annular stator is theoretically and experimentally studied. An annular stator with groove arrays is specifically designed. The physical model of laser-induced SAW on the stator is established, and the key factors influencing the wave amplitude are disclosed. We introduce a new kind of visualization method to detect laser-induced SAW on the copper-made annular stator, under a pulsed laser of 1053 nm wavelength, 30 ns pulse width and 1 mJ pulse energy. The results show that when the location of the irradiating laser spot is near the groove arrays, the SAW propagating towards the groove will be attenuated and absorbed immediately by the groove arrays, while the SAW away from the groove can keep propagating along the stator surface. In this way, the one-way propagation of laser-induced SAW is successfully acquired. In the contrast experiments, the laser-induced SAW travels in both directions on a copper ring without groove arrays, resulting in a chaotic state of the surface acoustic wave. The one-way SAW induced by pulsed laser on the annular stator will be used in the laser-driven SAW motor in the future.
Study on the emission spectrum of AlO radical B2+X2+ transition using laser-induced breakdown spectroscopy
Authors: Guo Lian-Bo  , Hao Rong-Fei  , Hao Zhong-Qi  , Li Kuo-Hu  , Shen Meng  , Ren Zhao  , Li Xiang-You  , Zeng Xiao-Yan  ,   Wuhan National Laboratory for Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China;,   Wuhan New Research and Development Laser Engineering Co., Ltd, Wuhan 430074, China
Published: December 2020

Based on laser-induced breakdown spectroscopy, a short pulse laser is used to excite Al2O3 (content of 99%) ceramic to produce ceramic plasma. The plasma emission spectrum is collected, and 33 spectral lines of AlO radical B2+X2+ transition are obtained. The time-resolved AlO radical spectrum and its relationship with laser pulse energy are investigated. The results show that the emission spectrum of AlO radical appears later and lasts longer than those of Al atom and Al ion. With the increase of the laser pulse energy, the spectral intensity of AlO radical decreases and the time when the maximum spectral intensity appears moves backward. Finally, the ceramic plasma produced in air is compared with that produced in Ar environment. The results prove that the formation of AlO radical spectrum has an important relationship with O2 in air.
Research on bionic underwater acoustic communication technology based on differential Pattern time delay shift coding and dolphin whistles
Authors: Han Xiao  , Yin Jing-Wei  , Guo Long-Xiang  , Zhang Xiao  ,   Science and Technology on Underwater Acoustic Laboratory, Harbin Engineering University, Harbin 150001, China
Published: December 2020

Regarding the performance degradation caused by the traditional method of covert underwater acoustic communication, in this paper we propose a bionic underwater acoustic communication technology on the basis of differential Pattern time delay shift coding system and dolphin whistles. The signal band of dolphin whistles is narrow and the intervals between information signals are different, and the cross-correlation is very weak. Dolphin whistles are used for synchronization and Patterns, for the time interval between dolphin whistles conveys the information bits. The mimicked version of communication signal is not easy to detect and intercept, and the special encoding method of differential Pattern time delay shift also makes the information not easy to decipher, so this bionic underwater acoustic communication technology has strong covert and confidential nature and it also has an excellent performance in anti inter-symbol interference and anti Doppler effect. A tank experiment is conducted for this system. At SNR 0 dB and relative movement, the user message is recovered at an effective data rate of 67 bit/s with low bit error. It is proved that the system has an effectiveness, robustness and covert nature.
Experimental study of the spatial discontinuity of dynamic damage evolution
Authors: Peng Hui  , Li Ping  , Pei Xiao-Yang  , He Hong-Liang  , Cheng He-Ping  , Qi Mei-Lan  ,   State Key Laboratory of Explosion and Technology, Beijing Institute of Technology, Beijing 100081, China;,   Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China;,   School of Science, Wuhan University of Technology, Wuhan 430070, China
Published: December 2020

In this paper, the damage evolution of high purity aluminum under shock loading is investigated experimentally. The surface profile measurement technique based on white light axial chromatic aberration is used to measure the cross-section of sample which is soft-recovered from dynamic impact experiments. Then, the cross-section image and 3-D surface topography are obtained by reconstruction of the data, the quantified damage is also calculated based on the data. The results show that in the early stage of damage evolution the spatial distribution of relative void volume is not continuous, which results from nucleation affect, size affect and stress relaxation. The damage curves show not only the maximum damage but also a second peak. In the late stage of damage evolution, the spatial distribution of damage increment is discontinuous, which results from the coalescence of voids. The damage of the coalescence region rapidly increases and the secondary peak of the damage curve disappears.
Properties in vanadium dioxide thin film synthesized from V2O5 annealed in H2/Ar ambience
Authors: Yang Xin-Xin  , Wei Xiao-Xu  , Wang Jun-Zhuan  , Shi Yi  , Zheng You-Liao  ,   Jiangsu Provincial Key Laboratory of Photonic and Electronic Materials Sciences and Technology, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China
Published: December 2020

Owning to its sharp metal-insulator transition at ～340 K, VO2 is becoming an attractive candidate for the electrical and optical material. Here we report on the fabrication and characterization of VO2 thin film obtained from the V2O5 thin film annealed in Ar/H2 ambience. V2O5 thin film is fabricated by using the pulsed laser deposition system on the R-sapphire substrate under several different conditions by varying the substrate temperature and the pressure of the growth atmosphere to optimize the growth condition. Then we carry out the annealing treatment on the V2O5 thin film in different annealing conditions. The VO2 thin films are characterized using X-ray diffraction, X-ray photoelectron spectroscopy and R-T measurement. When annealed in a temperature range of 500–525 ℃ for 3 h in H2(5%)/Ar ambience, the V2O5 thin film can be converted into the mixed-structures of metastable monoclinic structure (B) and the monoclinic rutile structure (M) which is responsible for the phase-change property. And under the same conditions, when the annealing time reaches 4.5 h, the pure VO2(B) is obtained. Further we anneal the VO2(B) in pure Ar ambience and tentatively realize the resistivity reduced by nearly four orders with the temperature increasing from 25 ℃ to 105 ℃. The transition temperature is nearly 350 K. And the transition between VO2 (B) and VO2 (M) is realized.
Effects of high magnetic field on the microstructure and magnetic properties of Fe80Ni20 thin films with different thickness values
Authors: Cao Yong-Ze  , Li Guo-Jian  , Wang Qiang  , Ma Yong-Hui  , Wang Hui-Min  , He Ji-Cheng  ,   Key Laboratory of Electromagnetic Processing of Materials (Ministry of Education), Northeastern University, Shenyang 110819, China
Published: December 2020

Fe80Ni20 thin films with different thickness values are prepared by the molecular beam vapor deposition technique, respectively, in the cases with applying no magnetic field and with applying a 6 T magnetic field perpendicular to the surface of substrates. Film property studies show that as film thickness value increases, the coercive force in-plane decreases, which is in accordance with Neel theory, and that the squareness ratio first quickly increases, and then slowly decreases. The 6 T magnetic field restrains coalescence and abnormal growth of grains, and reduces surface roughness. Therefore, with 6 T magnetic field applied during the film preparation, the coercive force of thin film is less and the squareness ratio is larger than that with no magnetic field applied. The thin films are anisotropic in-plane with applying no magnetic field, but isotropic with applying a 6 T magnetic field.
Transmission and application of electron spin wave function in alternating ferromagnetic and nonmagnetic layers
Authors: Zheng Yong-Lin  , Wang Xiao-Xi  , Ge Ze-Ling  , Guo Hong-Li  , Yan Gang-Feng  , Dai Song-Hui  , Zhu Xiao-Ling  , Tian Xiao-Bin  ,   Institute of Electronics and Information Engineering, Chengdu University, Chengdu 610106, China;,   Institute of Condensed Matter Physics, Yangtze Normal University, Chongqing 408100, China
Published: December 2020

We establish a general model of a finite periodic system by n pairs of alternating ferromagnetic and nonmagnetic (FNF) layers. Using Bloch spin wave quantum theory, the basic properties of alternating FNF layers and the dependence of property of electron wave scattering in alternating layers on the number of layers are investigated. It is found that an electron wavefunction in the system can be expressed as the superposition of eigenvectors of a transfer matrix or Bloch-like functions in an infinite periodic system. Form this function we can obtain an exact solution for monochromatic wave scattering of a system with an arbitrary number of layers. On this basis, the dependences of reflection and transmission coefficients on energy for the electron wavefunction in a periodic system are determined. The calculation of spectral window shows that its energy position and width are the same as those of almost full reflection region. The system can be used as spin filter due to high-energy dispersion and dependence of exchange energy on electron spin direction.
Molecular dynamics simulation of low-energy hydrogen atoms bombarding tungsten (001) surface at different angles and their depth distribution
Authors: Guo Long-Ting  , Sun Ji-Zhong  , Huang Yan  , Liu Sheng-Guang  , Wang De-Zhen  ,   School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China
Published: December 2020

Molecular dynamics simulations are performed to study the diffusion behavior of low-energy hydrogen atoms in bcc tungsten (001). The simulation results show that when the energy of vertically incident hydrogen atoms is in a range of 0–20.0 eV, their retention probability increases rapidly; in the whole incident energy range 0.5–50.0 eV, the reflection probability gradually drops, but still exceeds 60%. By varying the incident angle, the retention probability may increase in some energy ranges compared with those in the case of vertical incidence, but the reflection probability still dominates. In this paper, we also obtain the depth distribution of energy deposition of incident hydrogen and its isotopes. It is found that tritium deposits more energies in the surface region than hydrogen.
Uni-traveling-carrier double heterojunction phototransistor photodetector
Authors: Huo Wen-Juan  , Xie Hong-Yun  , Liang Song  , Zhang Wan-Rong  , Jiang Zhi-Yun  , Chen Xiang  , Lu Dong  ,   College of Electronic Information and Control Engineering, Beijing University of Technology, Beijing 100124, China;,   Key Laboratory of Semiconductor Materials Science, Institute of Semiconductor, Chinese Academy of Sciences, Beijing 100083, China
Published: December 2020

An InP/InGaAsP uni-traveling-carrier double heterojunction phototransistor (UTC-DHPT) photodetector is simulated and analyzed in a two-dimensional (2D) model utilizing a numerical device simulator (Atlas). The effects of device structure parameters on operational performance, such as responsivity and characteristic frequency, are studied in detail. Simulation results indicate that the UTC-DHPT can ease the contradiction between detection efficiency and working speed, which exists in traditional heterojun-ction phototransistor and achieve both high responsivity (≥17.93 A/W) and high characteristic frequency (≥121.68 GHz) simultaneously.
The classification of winter regional extreme low temperature events in China and their corresponding relationship to climatic indices extreme anomaly
Authors: Wang Xiao-Juan  , Shen Bai-Zhu  , Gong Zhi-Qiang  , Feng Guo-Lin  ,   Department of Atmospheric and Sciences, Lanzhou University, Lanzhou 730000, China;,   College of Physics and Electronic Project, Changshu Institute of Technology, Changshu 215500, China;,   Laboratory for Climate Monitoring and Diagnose, National Climate Center, China Meteorological Administration, Beijing 100081, China;,   Laboratory for Climate Studies, National Climate Center, China Meteorological Administration, Beijing 100081, China
Published: December 2020

We identify China regional low temperature extreme events (RELTEs) in winter during the periods from 1951 to 2010 using objective identification technique for regional low temperature extreme events (OITRELTEs). The 559 RELTEs are identified and classified into 6 types, i.e., nationwide style, east style, northeast-north China style, north-south China style, south style, and northwest-south China style, according to the spatial distribution of these events. The circulation backgrounds of different styles of low temperature events are also analyzed. In addition, taking the classical event that began from January 21st in 1971 for example, anomaly characteristics of sea surface temperature, geopotential height and winds vectors are investigated specifically. Based on these analyses, the corresponding relationships between different types of events and anomalies of climatic indices are further studied, and the relations between mainly influencing index and event are obtained for different types of events. On the whole, when the NINO3.4, the Pacific decadal oscillation, and the Arctic oscillation are small and the winter wind index is strong, the probability with which the RELTE happens is high; in the years in which the winter average values of the four indices reach 15% of extreme threshold, the percentages of occurrence of RELTE reach up to 80.0%, 77.8%, 60.0% and 62.5%, respectively. Therefore, certain signals can be offered for diagnosing and predicting the RELTE from the index anomalies.
Research of small space debris impact induced discharge
Authors: Li Hong-Wei  , Han Jian-Wei  , Cai Ming-Hui  , Wu Feng-Shi  ,   Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

Small space debris impact the surface of spacecraft frequently at a velocity of about 10 km/s, thereby creating plasma cloud clusters during the impact. If the impact happens in the area with high voltage, then the plasma can induce discharge. This mechanism of spacecraft discharging has been widely accepted but research about it is rare. In this paper we present the experimental results of 200 micron glass ball particles impact induced discharge carried out on a plasma drag small space debris accelerator. The experimental results and characteristics of the discharging signals are also analyzed in this paper.