bluuebunny/crossref_metadata_2025 huggingface dataset:
Germanium-niobate glasses doped with Tm3+ and their infrared spectral properties
Authors: Wang Yong-Chao  , Xia Hai-Ping  , Zhang Jian-Li  , Zhang Qin-Yuan  ,   (1)Key Laboratory of Specially Functional Materials of Ministry of Education and Institute of Optical Communication Materials,South China University of Technology,Guangzhou 510641,China; (2)Laboratory of Photo-electronic Materials,Ningbo University,Ningbo 315211,China
Published: December 2020

Glasses with the compositions of (90-x)GeO2-xNb2O5-10Na2O(x=1,2,4,6,8 molar ratio)doped with Tm2O3 at the same concentration (4wt%) and 86GeO2-4Nb2O5-10Na2O dore at different concentrations were fabricated respectively by conventional melting method.The effects of Nb2O5 content on glass stability,fluorescence strength and J-O strength parameters were studied.According to the Judd-Ofelt theory,the J-O strength parameters (Ω2, Ω4, Ω6) of Tm3+ in different Nb2O5 concentration were calculated,with which the radiative transition probabilities,branching ratios and radiative lifetime were obtained.Meanwhile,according to the McCumber theory,the absorption and emission cross-sections corresponding to the 3F4→3H6 transitions of Tm3+ at 1.8 μm were obtained.The gain cross section was calculated by using the emission cross-section,absorbtion cross section and Tm3+ concentration.The fluorescence features (under 808 nm LD excitation) at ～1.47 and ～1.8 μm of Tm3+-doped glasses of different concentrations were studied.The fluorescence intensity at ～1.8 μm reached to the maximum when the Tm2O3-doping concentration was about 3wt%,and then decreased as the doping concentration increased further.The fluorescence intensity at ～1.8 μm reached to the maximum when the Nb2O5 content in glass composition was about 2 mol%.The effects of Nb2O5 content on the glass structure and the spectra properties were also discussed.
Synthesizing a kind of controllable nanopillar arrays
Authors: Li Qiang  , Wang Kai-Ge  , Dang Wei-Jun  , Hui Dan  , Ren Zhao-Yu  , Bai Jin-Tao  ,   Institute of Photonics and Photonic Technology, Northwest University, Xi'an 710069, China
Published: December 2020

On the basis of the first oxide prepared anodized aluminum oxide template (AAO), the second, third and fourth oxidation preparation are implemented in turn. Then, the surface morphology and current curve changes of the AAO template with multiple oxidation preparation were compared and analyzed systemically. The apertures of nanopore made by the second, third and forth oxidation increase in order, the intervals between neighboring apertures reduce. However, the scale of ordered distribution of nanopores on the whole template surface does not change significantly. Then, carefully controlling the working conditions for the membrane-removed of the one-step oxidation AAO, the nanoporous with regular apertures and highly ordered was obtained after getting rid of the top oxidation layer about 10 minutes. Finally, based on those prepared AAO templates, integrated with the thermal nanoimprint lithography, we achieved the PMMA nano-pillar arrays with controllable lengths and diameters.
The relationship between surface energy balance unclosure and vertical sensible heat advection over the loess plateau
Authors: Li Hong-Yu  , Zhang Qiang  ,   (1)Institute of Arid Meteorology,CMA;Key laboratory of Arid Climatic Change and Reducing Disaster of Gansu Province; Key Open Laboratory of Arid Climatic Change and Disaster Reduction of CMA, Lanzhou 730020, China; (2)Institute of Arid Meteorology,CMA;Key laboratory of Arid Climatic Change and Reducing Disaster of Gansu Province; Key Open Laboratory of Arid Climatic Change and Disaster Reduction of CMA, Lanzhou 730020, China; Gansu Provincial Meteorological Bureau, Lan
Published: December 2020

The surface energy imbalance problem has been an important challenge in the study of surface land process since it was found in the late 1980s. By utilizing the observed data in the land surface process experiment carried out over the Loess Plateau region in the middle part of Gansu, the characteristics of climate unclosure and short-term unclosure of the surface energy balance are analyzed and the relationship between surface energy balance unclosure and vertical velocity is studied in the paper. It is found that there is a good correlation between surface energy balance unclosure and vertical velocity. Furthermore, the paper estimates the values of vertical sensible heat advection in the surface layer. After considering the vertical sensible heat advection, characteristics of the surface energy balance condition are analyzed again and there is a significant improvement in the surface energy balance unclosure.This means vertical velocity plays an important role in the surface energy buget and the vertical sensible heat advection has a significant influence on the surface energy balance unclosure over the Loess Plateau region.
Analysis of precursors and predictability of PDSI extremes in China
Authors: Feng Guo-Lin  , Zhang Lu  , Zhang Da-Quan  ,   College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China;,   College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China; State Key Laboratory of Earth Surface Processes and Resource Ecology, College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, China;,   State Key Laboratory of Earth Surface Processes and Resource Ecology, College of Global Change and Earth System Science, Beijing Normal University, Beijing 100875, China; Laboratory for Climate Studies of China Meteorological Administration, National Clim
Published: December 2020

We investigate precursors and predictability of extreme events of Lorenz system with different percentile. The precursors and predictability of Palmer Drought Severity Index (PDSI) extremes in China are analyzed, and obtained how the quality of the prediction depends on the size of the extreme events and on the correlation strength. Results indicate that for extreme events of Lorenz system and PDSI series, the stronger the extreme, the higher the predictablility. Moreover, we analyzed precursors and predictability of eight regions in China and provide some due scientific basis for flood and drought predictions.
Memoryless state observer-based adaptive control for uncertain nonlinear systems with multiple time delays
Authors: Guo Peng  , Hu Hui  , Liu Guo-Rong  , Hu Jun-Da  ,   Hunan Institute of Engineering,Xiangtan 411101,China
Published: December 2020

In this paper,the problem of adaptive control based on memoryless state observer is considered for uncertain nonlinear systems with multiple time delays. The upper bound of the time-delay state disturbance is unknown. And an adaptive law is proposed to estimate the unknown parameter of the disturbance,and the estimated value is used to design a memoryless state observer and controller,which are both independent of time-delay. Based on the Lyapunov-Krasovskii function,it is shown that the observation error can converge asymtotically to zero. Simulation results illustrate the applicability of this method.
Integral methods for the generalized Birkhoff equations
Authors: Li Yan-Min  , Mei Feng-Xiang  ,   (1)Department of Applied Mechanics,School of Aerospace,Beijing Institute of Technology,Beijing 100081,China; (2)Department of Physics and Information Engineering,Shangqiu Normal University,Shangqiu 476000,China
Published: December 2020

The field method and the last multiplier method are general integral methods for solving the differential equations of motion. The two methods are applied to the generalized Birkhoff system,and the complete integrals of the basic partial differential equation are given. Furthermore,the solutions of the generalized Birkhoff equations are obtained by Jacobi last multiplier theorem. An example is given to illustrate the application of the results.
The study of the two-dimensional position sensitive gas electron multiplier based on strips readout
Authors: Dong Jing  , Lü Xin-Yu  , Liu Ben  , Liu Rong-Guang  , Ma Xiao-Yan  , Wang Lan  , Chen Yuan-Bo  , Ouyang Qun  , Xie Yi-Gang  ,   Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

To meet the need of Beijing Synchrotron Radiation Facility (BSRF) in two-dimensional detectors, a two-dimensional position sensitive X-ray gas electron multiplier(GEM)detector based on PCB strips and anolog readout were designed and constructed. Through the test of two kinds of strip pitchs and based on the system of multi-channel charge sensitive preamplifier and VME buffer-ADC, the spatial resolution of soft X-ray was measured and pretty good spatial resolutions of about 84 μm and 75μm respectively were obtained. The effect of the sum of the voltages applied on the three GEM foils on the spatial resolution was studied and position veracity and linearity of GEM was tested. The principles of GEM based on anode readout and the anolog electronic system were clarified meanwhile.
Theoretical study of autoionization Rydberg series 3d4s(1D2)nf2 D3/2,3d4s(1D2)nf2 F5/2 and 3d4s(1D2</s
Authors: Fan Shi-Lin  , Zhang Xin-Feng  , Xue Ping  , Jia Feng-Dong  , Zhong Zhi-Ping  , Xu Xiang-Yuan  ,   (1)Collage of Physics, Graduate University of Chinese Academy of Sciences, Beijing 100049, China; (2)Department of Physics, The Key Laboratory of Atomic and Molecular Nanosciences of the Ministry of Education, Tsinghua University, Beijing 100084, China; (3)Department of Physics, The Key Laboratory of Atomic and Molecular Nanosciences of the Ministry of Education, Tsinghua University, Beijing 100084, China;Department of Physics, Capital Normal University, Beijing 100037, China
Published: December 2020

In the frame work of multi-channel quantum defect theory, the energy levels of three autoionization Rydberg series converging to Sc+ 3d4s(1D2) with Jπ=(3/2)-,(5/2)- are calculated from first principles by relativistic multi-channel theory at two levels of approximation, i.e., frozen core approximation and that with consideration of dipole polarization. Considering dipole polarization effect, the difference between calculated and experimental quantum defects for the 3d4s(1D2)np2D3/2 and 3d4s(1D2)nf2F5/2 series are smaller than 0.01, thus the dipole polarization effects are important for the two autoionization Rydberg series. While for 3d4s(1D2)nf2D3/2 series, the calculated data by frozen core approximation are close to those by considering dipole polarization effects, and the difference between calculated and experimental quantum defects are generally about 0.04.
Numerical calculation of infrared extinction for carbon nanofibers
Authors: Wang Hong-Xia  , Zhou Zhan-Rong  , Zhang Qing-Hua  , Ma Jin  , Liu Dai-Zhi  ,   Department of Basal Courses, Second Artillery Engineering Institute, Xi'an 710025, China
Published: December 2020

To explore the applications of carbon nanofibers in passive interference by smoke screen, the integral equation of induced current for carbon nanofibers is established based the electromagnetic field theory. The method of moment (MOM) is used to solve the integral equation. The formulae of scattered field and extinction cross section are derived for carbon nanofibers. By comparing with variational method, our proposed method is proved to be valid. The relationships between infrared extinction cross section of carbon nanofiber and the wavelength, the angle of incidence, the fiber length and diameter are analyzed and calculated.The results provide a theoretical basis for the applicatrion of nanocarbon fiber in infrared smoke interference.
One-dimensional photon counting detector with vernier position sensitive anode
Authors: Yan Qiu-Rong  , Zhao Bao-Sheng  , Yang Hao  , Liu Yong-An  , Zhu Xiang-Ping  , Li Mei  ,   (1)State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an 710119, China; (2)State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an 710119, China;Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

One-dimensional photon counting detector with vernier position sensitive anode is reported. The decode principle and design of vernier position sensitive anode are described in detail. An ultraviolet photon counting system was built based on one-dimensional photon counting detector with vernier position sensitive anode. One-dimensional coordinates of single-photon events can be simultaneously measured when the detection system works in photon counting mode. The spatial distribution of pulse counts, which corresponds to one-dimensional spatial distribution of incident light intensity, was obtained. The resolution of this system is better than 100 mμ according to the resolution test. The detector can detect one-dimensional spatial distribution of the intensity of very weak particle flow such as high-energy photons, electrons and ions flow, so it can be used for deep space exploration, spectral measurement, high-energy physics and bio-luminescence detection.
Entanglement between a two-level atom and spontaneous emission field in anisotropic photonic crystal
Authors: Xie Shuang-Yuan  , Hu Xiang  ,   Department of Physics, Tongji University, Shanghai 200092, China
Published: December 2020

By means of Von Neumann entropy and Schmidt number K, we study the time evolution properties of the entanglement between a two-level atom and spontaneous emission field in anisotropic photonic crystal. The evolution properties of the atom-field entanglement are directly related to the relative position of the upper level from the band edge. The atom-field entanglement can keep steady when the atomic upper level is within the band gap. The atom-field entanglement increases to the maximum value firstly and then decay to zero when the atomic upper level is within the transmitting band. The atom-field entanglement also depends on the initial state of the atom. We can control the time evolution properties of the atom-field entanglement by choosing special atomic initial state and the relative position of the upper level from the band edge.
Experimental research on high-energy dissipative solitons in an erbium-doped fiber laser
Authors: Wang Lei-Ran  , Liu Xue-Ming  , Gong Yong-Kang  ,   State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi'an 710119, China
Published: December 2020

We have employed a nonlinear polarization rotation technique to realize the self-starting passive mode-locking in an erbium-doped fiber laser with positive dispersion. The laser can emit high-energy dissipative solitons without wave-breaking. The pulse-shaping mechanism, which is qualitatively distinct from the conservative solitons in negative dispersion cavity, may originate from the laser gain, loss, NPR, cavity dispersion, or other fiber nonlinearity effects. To our best knowledge, it is the first report on the experimental observations for high-energy wave-breaking-free dissipative solitons forming in a fiber laser with ultra-large net-normal cavity dispersion. The spectrum of these strongly chirped pulses covers the wavelength range from 1530 to 1660 nm. The FWHM width of the spectrum can be as large as 42 nm, and the maximal total energy of a single-pulse is estimated to be ~34.4 nJ.
The study of spatiotemporal perturbation in the nonlinear propagation of broadband chirped pulsed laser
Authors: Wang Can-Hua  , Zhang Li-Fu  , Fu Xi-Quan  , Wen Shuang-Chun  ,   Key Laboratory for Micro/Nano Opto-Electronic Devices of Ministry of Education, School of Computer and Communication, Hunan University, Changsha 410082, China
Published: December 2020

In the paper, we extended the propagation equation of the large chirped pulse based on the nonlinear Schrodinger equation, and then analyzed the spatiotemporal instability of chirped pulsed-beam by using the perturbation theory. The influence of the spatiotemporal noise and the effect of chirp on the perturbation modulation of noise of the broadband pulsed-laser with large chirp were investigated theoretically. The results showed that the chirp of pulse has no direct influence on the modulation growth of noise under the same value of γI0(the product of the nonlinear coefficient and the peak intensity). Then the spatial small-scale self-focusing of chirped pulse was measured in experiment using nonlinear medium, and the modulation growth of the temporal noise of the broadband chirped pulse were also simulated numerically, and the result was basically consistent with the analysis of perturbation theory.
Theoretical study of tunable terahertz radiation based on stimulated polariton scattering in zinc blende crystal
Authors: Li Zhong-Yang  , Yao Jian-Quan  , Li Jun  , Bing Pi-Bin  , Xu De-Gang  , Wang Peng  ,   The Institute of Laser & Otpoelectronics,The College of Precision Instruments and Opto-Electronic Engineering,Tianjin University, Key Laboratory of Opto-electronics Information and Technical Science (Ministry of Education),Tianjin 300072, China
Published: December 2020

Based on the theory of stimulated polariton scattering, adopting reported experimental conditions that generate tuning terahertz wave utilizing nonlinear optical parametric oscillation as the theoretical analysis model,and taking GaAs, GaP, InP, ZnTe crystals as representatives, the absorption and gain characteristics in zinc blende crystal are calculated, and the output tuning characteristics of terahertz wave are also analyzed. We give detailed analysis of the cavity structure that efficiently outputs terahertz wave, and compare it with the terahertz parametric oscillator composed of MgO: LiNbO3 crystal.
The relationships study of structure-nonlinear optical property of two-dimensional charge transfer molecules substituted annulenes
Authors: Han Kui  , Li Ming-Xue  , Li Hai-Peng  , Wu Yu-Xi  , Tang Gang  , Wu Qiong-Hua  , Tong Xing  , Zhong Qi  ,   College of Science, China University of Mining and Technology, Xuzhou 221116, China
Published: December 2020

The molecular first hyperpolarizabilities β and ultraviolet spectra of two-dimensional charge transfer (2DCT) substituted annulenes by employing MP2 and TD-DFT approach, respectively. It is found that these 2DCT molecules 2—6 possess larger β values and blue-shifted absorption spectra in comparison with 1DCT molecules 8 and 9. It is helpful to solve the nonlinearity-transparency trade-off. For 2DCT molecules 2—7, values of β depend on the band length alternation (BLA) and when the BLA increases, the values of β decrease. Moreover, there is not a relationship between β and HOMO-LUMO energy gap ΔEHL for 2DCT molecules. The maximum absorption wavelength λmax of 2DCT molecules originates from deeper energy level orbital transition than HOMO→LUMO transition.
Upconversion luminescence of Tm3+/Ho3+/Yb3+ codoped tellurite glass used for white light emission
Authors: Wang Da-Gang  , Zhou Ya-Xun  , Wang Xun-Si  , Dai Shi-Xun  , Shen Xiang  , Chen Fei-Fei  , Wang Sen  ,   College of Information Science and Engineering, Ningbo University, Ningbo 315211, China
Published: December 2020

Tm3+/Ho3+/Yb3+ codoped tellurite glass (TeO2-ZnO-La2O3) was prepared by conventional melt-quenching method. The absorption spectra and upconversion spectra of the glass were measured, and the upconversion luminescence mechanism was analyzed. Intensive red (662 nm), green (546 nm) and blue (480 nm) emissions of the tellurite glass were simultaneously observed at room temperature under 975 nm LD excitation. Upconversion red luminescence are due to the energy transition of Tm3+ ion: 1G4→3F4 and Ho3+ ion: 5F5→5I8, while upconversion green and blue are the results of Ho3+ ion: 5S2→5I8 and Tm3+ ion: 5S2(5F4) →5I8, respectively. With the increasing of Yb3+ content and the pump power, upconversion luminescence are also enhanced. The white light close to the standard white light emission has been obtained by adjusting the concentration of rare earth doping. Our result has practical significance for developing high-quality white LED.
The influence of thermodynamic equilibrium state prior to the phase transition on the alignment of ferroelectric liquid crystal
Authors: Tang Xian-Zhu  , Peng Zeng-Hui  , Liu Yong-Gang  , Lu Xing-Hai  , Xuan Li  ,   (1)State Key Laboratory of Applied Optics , Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China; (2)State Key Laboratory of Applied Optics , Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China;Graduate University of the Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

In this experiment, devices of ferroelectric liquid crystal (FLC) were prepared by selecting ZLI-3654 FLC and SE-3140 alignment material. In order to study the influence of thermodynamic equilibrium state before the phase transition on the alignment of FLC, ten sets of experiments were carried out by changing the cooling rate during phase transition and thermodynamic equilibrium state before the phase transition. From experiments, a conclusion that the thermodynamic equilibrium state prior to chiral nematic-smectic A (N*-SmA) phase transition play an important role in realizing a uniform alignment of FLC devices, was obtained by comparing static contrasts of the devices. The static contrast ratio of our samples reached 620 ∶1 and the thermodynamic equilibrium state before N*-SmA phase transition was conducive to the formation of high contrast ratio FLC devices. The conclusion can provides a theoretical and practical guidance for the fabrication of FLC devices with I←→N*←→SmA←→S*mC←→Cr phase sequence.
Effect of defects outside the centre on dispersive properties of photonic band gap guiding photonic crystal fibers
Authors: Zhao Yan  , Shi Wei-Hua  , Jiang Yue-Jin  ,   Nanjing University of Posts & Telecommunication Optical Communications Research Institute Nanjing 210003, China
Published: December 2020

The dispersion properties of optical wave in photonic band gap guiding photonic crystal fibers (PBG-PCF) were analyzed by the finite differential time domain method. The result demonstrates that: the point defects and the dislocation of air holes make the zero-dispersion-point move to the long-wavelength side, but the change of the shape of the air columm makes it move in the opposite direction. All kinds of defects make the dispersion curves flatten.
Focusing properties of a tapered hollow silver waveguide
Authors: Zeng Xia-Hui  , Fan Dian-Yuan  ,   (1)Department of Physics & Electronic Information Engineering, Minjiang University, Fuzhou 350108,China;Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science, Shanghai 201800, China; (2)Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Science, Shanghai 201800, China
Published: December 2020

We numerically demonstrate a kind of tapered hollow silver waveguide for optically guiding and focusing of light through finite-difference time-domain (FDTD) simulations. The results of numerical simulation reveal that the tapered hollow silver waveguide can efficiently guide and focus a laser light to a tiny, highly localized beam spot of 1 μm diameter. The physical mechanism of the cone-focused laser light is explored. The influence of incident angle and waveguide geometry on the focusing properties is also discussed. The results obtained here might have important reference value for applications in tapered optics, and designing the optimum cone shape for fast ignition and generating high energy charged particles.
Effect of exit Reynolds number on a turbulent round jet
Authors: Du Cheng  , Xu Min-Yi  , Mi Jian-Chun  ,   State Key Laboratory for Turbulence and Complex Systems, College of Engineering, Peking University, Beijing 100871, China
Published: December 2020

The present study systematically investigates by experiment the influence of Reynolds number (Re) on a turbulent jet issuing from a smoothly-contracting round nozzle. Measurements were performed for seven Reynolds numbers varying from Re = 4,050 to Re = 20,100 using single hot-wire anemometry and over an axial distance of 30 nozzle exit diameters. Although all the exit velocity profiles are of "top-hat" shape, these measurements reveal significant dependence on Re of the exit and downstream flows. The effect of Re on both the mean and turbulent fields is substantial for Re ＜ 10,000 and becomes weak beyond Re = 10,000. The length of the jet’s potential core and the far-field rates of decay and spread all depend significantly on Re.
Two-dimensional numerical studies of ablated-plasma dynamics of wire-array Z-pinches
Authors: Huang Jun  , Sun Shun-Kai  , Xiao De-Long  , Ding Ning  , Ning Cheng  , Zhang Yang  , Xue Chuang  ,   Institute of Applied Physics and Computational Mathematics, Beijing 100094, China
Published: December 2020

The dynamics of ablated plasma of wire-array Z-pinches are studied numerically in (r, θ) geometry by using 2D MHD simulation model, in which plausible mass injection boundary conditions are incorporated, and 2D spatio-temporal distribution of plasma parameters and magnetic field are obtained. The ablated-plasma dynamics involves 4 stages: drifting towards the axis, arriving at the axis and forming the precursor column, contraction and expansion of the precursor column, which is essentially reasonable. The relationships between the ablation velocity, the ratio of ablated plasmas to the total wire-array mass and the initial array load parameters are analyzed, and the results are in reasonablly good agreement with the experiment. The effects of the initial inter-wire separation on the structure of magnetic field are investigated and the results can give valuable suggestions to designing the wire array Z-pinch loads.
Molecular dynamical investigation on plastic behavior of Cu(100) twist-grain boundary under shear load
Authors: Zhao Xue-Chuan  , Liu Xiao-Ming  , Gao Yuan  , Zhuang Zhuo  ,   Ministry of Education Key Laboratory of Applied Mechanics, School of Aerospace, Tsinghua University, Beijing 100084, China
Published: December 2020

By using molecular dynamics with EAM potential, yield strength of copper column with (100) twist grain boundary and twist grain boundary effect are investigated under shear load. The results reveal that dislocations nucleate at the misfit dislocation network of low-angle twist grain boundary and dislocations stacking influence the yield strength of copper column. For high-angle twist grain boundary, twist grain boundary sliding decreases the yield stress of copper column. Meanwhile it is found that, with increasing twist angle, copper column yielding strength increases firstly. When twist angle reaches the critical value, the yielding strength decreases with increasing twist angle. It is concluded that different mechanisms mediate the yielding of copper column. Dislocation nucleation controls the yield stress of copper column for low-angle twist grain boundary and yielding of copper column is dominated by grain boundary sliding for high-angle twist grain boundary.
The vacancy defect clusters in polycrystalline pure nickle induced by high-current pulsed electron beam
Authors: Zou Hui  , Jing Hong-Yang  , Wamg Zhi-Ping  , Guan Qing-Feng  ,   (1)College of Material Science and Engineering, Jiangsu University, Zhenjiang 212013, China; (2)College of Material Science and Engineering, Tianjin University,Tianjin 300072, China; (3)College of Material Science and Engineering, Tianjin University,Tianjin 300072, China;College of Science,Civil Aviation University of China, Tianjin 300300, China; (4)College of Science,Civil Aviation University of China, Tianjin 300300, China
Published: December 2020

High-current pulsed electron beam (HCPEB) technique is employed to irradiate the samples of polycrystalline pure nickel. The microstructures of the irradiated surface layers are investigated by using transmission electron microscopy (TEM). After HCPEB irradiation, very high value of residual stress is induced in the irradiated surface layer, which leads to the formation of dense dislocation walls and twins. Furthermore, a larger number of vacancy defect clusters including dislocation loops, stacking fault tetrahedra (SFT) and voids are also formed. Among three vacancy defect clusters, the number of SFT is much more than that of two other vacancy defect clusters. The lower dislocation density near the regions with dense SFT is observed and voids are likely to be present in these regions. It suggests that the stress with very high value and strain rate induced by rapid heating and cooling due to HCPEB irradiation could cause the shifting of the whole atomic plane synchronously.
Variation of graphene Raman G peak splitting with strain
Authors: Chen Dong-Meng  ,   College of Physics Science and Technology, China University of Petroleum, Dongying 257061, China
Published: December 2020

Variation of graphene Raman G peak splitting due to uniaxial strain and absorption of polyaromatic moleculars on both sides are studied by fifth-nearest neighbor force-constant model. The calculation results show that symmetry lowering is responsible for the G peak splitting, where G peak splits into G+ and G- peaks by lifting the energy degeneracy of in-plane longitudinal and transverse optical phonons at Γ point. Under uniaxial strain, the elongation of C—C bonds reduces the force-constant and softens the in-plane optical phonons which induce red shifts of both G+ and G- peaks. The different strains produced by polyaromatic molecules along its long and short edges lead to red shift and blue shift of the two in-plane optical phonons relevant to G- and G+ peaks, which gives a plausible explanation to the different G peak splitting of the recent Raman experiment on graphene with uniaxial strain and graphene sandwiched by the polyaromatic molecules.
Dynamics of two-dimensional interchain delocalized polarons
Authors: Liu Wen  , Liu De-Sheng  , Li Hai-Hong  ,   (1)Department of Physics and Information Engineering,Jining University,Qufu 273155, China; (2)Department of Physics and Information Engineering,Jining University,Qufu 273155, China;School of Physics,Shandong University,Jinan 250100, China
Published: December 2020

Based on the SSH model, polaron dynamics in a system of highly ordered conjugated polymer chains is investigated, including polaron formation and transport in the presence of an external electric field. It is found that, beyond a certain strength of the interchain coupling, the injected electron will induce a two-dimensional delocalized polaron state, expanding over several chains. Dynamical simulations suggest that, under the same electric field, two-dimensional interchain delocalized polarons move faster than intrachain localized polarons, as suggested by earlier experiments.
The effect on electronic density of states and optical properties of ZnO by doping Ga
Authors: Liu Jian-Jun  ,   Department of Physics and Electronic Information, Huaibei Normal University, Huaibei 235000, China
Published: December 2020

The electronic structures and optical properties of pure and Ga-doped wurtzite ZnO are studied by using first-principles plane wave pseudopotential method based on the density functional theory. The bonding of ZnO and changes in density of states are analyzed using of the crystal ligand field theory. Electron concentration is 2.42×1021 cm-3 by calculation, and carrier concentration of ZnO is raised 104 fold by doping Ga. Analysis of dielectric function, refractive index, absorption spectrum and reflectance spectrum of pure and Ga-doped ZnO shows that the optical absorption edge moving to high energy leads optical gap to broaden. In the visible light region, optical absorption coefficient and reflectivity are reduced and optical transmittance is increased significantly. Optical properties of ZnO are improved effectively by Ga doping.
Significant influence of isothermal crystallization conditions on charge stability of fluorinated cellular polypropylene films
Authors: Yao Jun-Lan  , An Zhen-Lian  , Mao Ming-Jun  , Zhang Ye-Wen  , Xia Zhong-Fu  ,   Phoe Institute of Solid State Physics, Tongji University, Shanghai 200092, China
Published: December 2020

On the basis of the measurement of open-circuit thermally stimulated discharge current and isothermal charge decay, the influence of isothermal crystallization conditions on charge stability of fluorinated cellular polypropylene (PP) film was systematically investigated. The results indicate that the time and temperature of isothermal crystallization of the fluorinated PP film have significant influences on its charge trap structure and charge stability. Charge traps and charge stability can be significantly deepened or improved even by isothermal crystallization at 90 ℃ for 0.5 h. And with the increase of crystallization temperature and time, charge traps are deepened further, presenting further improved charge stability, as observed in the case of isothermal crystallization at 130 ℃ for more than 2 h. Attenuated total reflection infrared analysis and wide angle X-ray diffraction measurement indicate that the improvement of charge stability results from the changes in chemical composition and structure of the PP film.
Magnetic hardening of soft phase in nanocomposite permanent magnetic materials by exchange coupling
Authors: Yin Jin-Hua  , Chen Xi-Fang  , Zhang Shuai  , Zhang Hong-Wei  , Chen Jing-Lan  , Jiang Hong-Wei  , Wu Guang-Heng  ,   Department of Physics, Captial Normal University, Beijing 100048, China;,   State Key Laboratory for Magnetism, Institute of Physics and Beijing National Laboratory for Condensed Mater Physics, Chinese Academy of Sciences, Beijing 100190, China;,   State Key Laboratory for Magnetism, Institute of Physics and Beijing National Laboratory for Condensed Mater Physics, Chinese Academy of Sciences, Beijing 100190, China;Department of Physics, Captial Normal University, Beijing 100048, China;,   State Key Laboratory for Magnetism, Institute of Physics and Beijing National Laboratory for Condensed Mater Physics, Chinese Academy of Sciences, Beijing 100190, China;Department of Physics, University of Science and Technology Beijing, Beijing 100086, C
Published: December 2020

In this work, the issue of magentic hardening of soft phase in nanocomposite permanent magnetic materials has been investigated using one-and three-dimensional models. For the same microstructure, it is found that the coercivity is decreased and the low-field demagnetization curve keeps unchanged when the anisotropy constant of magnetic hard phase is decreased in anisotropic one-or three-dimensional samples. Therefore, the drop in anisotropy of magnetic hard phase will not lead to the increase of remanence and maximum energy product (BH)max. According to the simulation results of isotropic three-dimension samples, both the remanence and (BH)max will be obviously decreased by the drop in anisotropy. As a result, enhancing the anisotropy and/or enlarging the grain size of magnetic hard phase is one of the means to improve the hard magnetic properties of nanocomposite permanent magnetic materials.
Effect of MnO2 additive on the piezoelectric and dielectric properties of Ba(Zr, Ti)O3 ceramics
Authors: Ding Nan  , Tang Xin-Gui  , Kuang Shu-Juan  , Wu Jun-Bo  , Liu Qiu-Xiang  , He Qin-Yu  ,   (1)School of Physics & Optoelectric Engineering, Guangdong University of Technology, Guangzhou Higher Education Mega Center, Guangzhou 510006, China; (2)School of Physics & Telecommunication Engineering, South China Normal University, Guangzhou 510006, China
Published: December 2020

Ba(Zr0.06Ti0.94)MnxO3 ceramics were prepared by oxide solid state reaction method. The effects of Mn-doping on the phase structure, piezoelectric and dielectric properties of BZT ceramics were studied. Mn ions preferentially incorporated in the lattice acted as donors when the concentration of Mn ions is below 0.5 mol%, which improves the piezoelectric coefficient and decreases the dielectric loss. When the concentration of MnO2 doping is larger than 0.5 mol%, it accumulated at the grain boundaries and deteriorates the piezoelectric properties of BZT ceramics as a result of domain pinning effect. With the increase of MnO2 contew, the ferroelectric behaves more diffused. The BZT ceramics doped with x=0.3—0.4 mol% MnO2 showed improved properties with d33 value as high as 195—220 pC/N, dielectric permittivity εr of 7500 and loss tanδ of 2%.
The mathematical model and properties of memristor with border constraint
Authors: Zhang Xu  , Zhou Yu-Ze  , Bi Qiang  , Yang Xing-Hua  , Zu Yun-Xiao  ,   School of Electronic Engineering, Beijing University of Posts and Telecommunications, Beijing 100876, China
Published: December 2020

The properties of memristor as the fourth basic circuit element are studied. The mathematical models in integral form for memristors with and without border constraint are developed. The simulation is done for the memristor with border constraint. The influences of the source frequency and model parameters on the memristor’s properties are analyzed and some conclusions are drawn. The model parameters considered include the doping ratio and the initial doping width, and their influnce on the current, voltage-current relation and flux-charge relation of the memrister are investigaled.
Topological analysis of temperature networks using bipartite graph model
Authors: Feng Ai-Xia  , Gong Zhi-Qiang  , Zhi Rong  , Zhou Lei  ,   (1)Department of Physics, Yangzhou University, Yangzhou 225009, China; (2)Department of Physics, Yangzhou University, Yangzhou 225009, China;Laboratory for Climate diagnose and prediction, National Climate Center, China Meteorological Administration, Beijing 100081, China; (3)Laboratory for Climate diagnose and prediction, National Climate Center, China Meteorological Administration, Beijing 100081, China
Published: December 2020

Using the daily main observational temperature data of 435 stations in China from 1961 to 2002, temperature change on 9-day scale has been compiled in network. Research on the connection between nodes and items in bipartite graph temperature (BGT) network, reveals the temperature change on 9-day scale and the topological statistics in the space. The nodes of RRRD, RrDD, eeed, DRRD and DDRR have remarkably high degree, which is helpful to predict the temperature change on 9-day scale. Calculation of the topological parameters of this network, including degree distribution and clustering coefficients, shows the normal school character of the bipartite graph model temperature network. The distribution of nodes’ degree diversity in each item presents quadruple type character, and has similar characteristics as the complex regions defined by the fluctuant temperature network(FT network), displaying the background information of temperature change in the region by this two kind of network respectively. Thus, temperature network modeled by bipartite graph model present a possible and available approach to research the characteristic and rule about temperature change from the combination of the time and space scale.
Dynamics of two-dimensional parabolic discrete map
Authors: Meng Ji-De  , Bao Bo-Cheng  , Xu Qiang  ,   (1)School of Computer and Information Engineering, Changzhou Institute of Technology, Changzhou 213002, China; (2)School of Electrical and Information Engineering, Jiangsu Teachers University of Technology, Changzhou 213001, China
Published: December 2020

By extending and nonlinearly coupling two one-dimensional parabolic discrete maps, a new two-dimensional parabolic discrete map is achieved. By using stability analysis of fixed points and bifurcation analysis of map, the complex dynamical behavior and attractor evolution of the proposed two-dimensional discrete map are investigated, and its peculiar dynamical characteristics, such as the coexisting bifurcation modes and fast-slow periodic oscillation effects, etc., are illustrated. The research results indicate that two-dimensional parabola discrete map has two control parameters with different functions of adjustable dynamical behaviors and adjustable dynamic amplitudes, and there emerge nonlinear physical phenomena of Hopf bifurcation, bifurcation mode coexisting, locked-frequency and periodic oscillation fast-slow effect. Furthermore, the corresponding theoretical analysis and numerical simulation results are verified based on a digital circuit realized by microcontroller.
Time-delayed generalized projective synchronization of piecewise chaotic system with unknown parameters
Authors: Hu Shou-Song  , Tao Hong-Feng  ,   (1)College of Automation Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China; (2)School of Communication and Control Engineering, Jiangnan University, Wuxi 214122, China
Published: December 2020

The time-delayed generalized projective synchronization problem for a class of piecewise modified Lorenz-Stenflo chaotic system with unknown parameters is discussed. The adaptive nonlinear feedback controller and the parameter update rules are designed based on the Lyapunov stability theory, and the feedback gain can be adjusted adaptively according to the error values and the states. The method can make all full states asymptotically generalized projected synchronization and identify the real-time drive system and the time-delayed response system’s unknown parameters. Results of simulation verified the realistic feasibility and effectiveness of the proposed method to the time-delayed generalized projective synchronization of the piecewise chaotic system.
Study on temperature calibration and surface phase transition of GaAs crystal substrate in MBE growth by RHEED real-time monitoring
Authors: Ding Zhao  , Wei Jun  , Yang Zai-Rong  , Luo Zi-Jiang  , He Ye-Quan  , Zhou Xun  , He Hao  , Deng Chao-Yong  ,   (1)School of Physics and Electronics Science, Guizhou Normal University, Guiyang 550001, China; (2)Science college, Guizhou University, Key laboratory of MicroNano Electronies of Guizhou Province, Guiyang 550025, China; (3)Science college, Guizhou University, Key laboratory of MicroNano Electronies of Guizhou Province, Guiyang 550025, China;School of Physics and Electronics Science, Guizhou Normal University, Guiyang 550001, China
Published: December 2020

Using RHEED as a real-time monitoring tool, the MBE temperature measurement system was calibrated according to the relationship between GaAs (100) surface reconstruction phase and the substrate temperature, As4 beam equivalent pressure of the substrate. This approach can also be applied to other MBE systems. It provides an experimental basis of the growth of high-quality epitaxial thin films for studying of the surface roughness of InGaAs, the phase transformation process and the surface morphology.
Influence of sputtering pressure on microstructure and mechanical properties of TiN/SiNx multilayer coatings
Authors: An Tao  , Wang Li-Li  , Wen Mao  , Zheng Wei-Tao  ,   (1)College of Science, Changchun University, Changchun 130022, China; (2)College of Science, Changchun University, Changchun 130022, China;Department of Materials Science, Jilin University, Changchun 130012, China; (3)Department of Materials Science, Jilin University, Changchun 130012, China
Published: December 2020

TiN/SiNx multilayer coatings were deposited at different deposition pressure by reactive magnetron sputtering. The microstructure and mechanical properties of the coatings were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM) and nanoindentation. The results showed that the layer structure became rough and the preferred orientation of TiN transferred from (200) to (111) plane with the increase of deposition pressure. Surface roughness of the coatings increased but the hardness and elastic modulus decreased with increasing deposition pressure. The variation of mechanical properties are attributed to the changes in layer structures and the densities of the coatings.
Geometric structure and electronic transport property of single alkanemonothiol molecule junction: external force effect and terminal group effect
Authors: Hu Wei  , Li Zong-Liang  , Ma Yong  , Li Ying-De  , Wang Chuan-Kui  ,   (1)College of Physics and Electronics, Shandong Normal University, Jinan 250014, China; (2)College of Physics and Electronics, Shandong Normal University, Jinan 250014, China;College of Physics and Electronics, Weifang University, Weifang 261061, China
Published: December 2020

The hybrid density functional theory is used to study formation of the junction of alkanemonothiol molecules with different terminal groups. The relationship between geometric structures of the molecular junction and the external force is obtained. On the basis of the relationship, the electronic transport properties of the molecular junctions under different external forces are investigated using the elastic-scattering Green’s function method. The results show that the C11S molecular junction is broken when the distance of the two electrodes is larger than 2.1 nm. While for C11SOH and C10SCOOH molecular junctions, their critical distances are similarly 2.15 nm. Taking the same external force, we find that the C11S molecule has the largest conducting ability, and the C10SCOOH molecule has the smallest conducting ability. Furthermore, the conductance of the three molecular junctions is monotonically enhanced with the increase of the external force. The numerical results are consistent with the experimental findings qualitatively.
The effect of AlO and C elements addition on magnetic properties and frequency response of FeCo alloy film
Authors: Wang Xuan  , Zheng Fu  , Lu Jia  , Bai Jian-Min  , Wang Ying  , Wei Fu-Lin  ,   Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education Research,Institute of Magnetic Materials, Lanzhou University, Lanzhou 730000, China
Published: December 2020

FeCoAlOC thin films with various C contents were fabricated by magnetron sputtering. The effect of C and Al2O3 addition on magnetic properties and frequency response of FeCo alloy films was studied. The microstructure of FeCo alloy films changed from polycrystalline to nano-crystalline, and became amorphous eventually with the increasing of content of AlO and C. It was found that the soft magnetic properties of FeCo alloy film was improved and resistivity increased from 87 μΩ·cm to 900 μΩ·cm because of C, Al-O addition. Frequency characteristics were improved: the cut-off frequency increased up to 2. 9 GHz, the permeability at low-frequency reached 400.
Theoretical and experimental study on magnetoelectric effect in laminated composites of magnetostrictive and piezoelectric materials with finite input impedance
Authors: Luo Ying  , Bao Bing-Hao  ,   (1)Micro-Nano Science and Technology Research Center, Jiangsu University, Zhenjiang 212013, China; (2)School of Science, Jiangsu University, Zhenjiang 212013, China
Published: December 2020

Combining the motion equation with the constitutive equations of the magnetostrictive and piezoelectric materials and considering the influence of the finite input impedance of the capacitance of coaxial cable and the measuring instrument on output voltage produced by magnetoelectric element, the theoretical formula of magnetoelectric voltage sensitivity was derived. A sandwich structureed magnetoelectric element consisting of one-dimensional terfenol-D thin bars and transversely polarized Pb(Zr1-xTix)O3 piezoelectric materials was developed. The property of the element was tested also. The theoretical results are in better agreement with the experimental after taking account of the finite input impedance. The theoretical results show that the magnetic sensitivity of the magnetoelectric element at lower excitation frequency and with finite input impedance is about 150 mV/Oe, while the magnetic sensitivity in open circuit situation is about 290 mV/Oe.