bluuebunny/crossref_metadata_2025 huggingface dataset:
Prediction of chaotic time-series based on online wavelet support vector regression
Authors: Yu Zhen-Hua  , Cai Yuan-Li  ,   西安交通大学电子与信息工程学院，西安  710049
Published: December 2020

Support vector regression (SVR) is an effective method for the predication of chaotic time-series, which is a fundamental topic of nonlinear dynamics. Through analyzing the possible variation of support vector sets after new samples are inserted to the training set, a novel SVR algorithm is proposed; thus an online learning algorithm is set up. In connection with the specific characteristics of chaotic signals, a wavelet kernel satisfying wavelet frames is also presented. The wavelet kernel can approximate arbitrary functions, and is especially suitable for local processing; hence the generalization ability of SVR is improved. To illustrate the good performance of the online wavelet SVR, a benchmark problem, i.e. the online prediction of chaotic Mackey-Glass time-series, is considered. The simulation results indicate that the online wavelet SVR algorithm outperforms the existing algorithms in higher efficiency of learning as well as better accuracy of prediction.
Applying a special kind of two coupled Duffing oscillator system to detect periodic signals under the background of strong colored noise
Authors: Li Yue  , Lu Peng  , Yang Bao-Jun  , Zhao Xue-Ping  ,   (1)吉林大学地球物理系，长春  130026; (2)吉林大学信息工程系，长春  130012
Published: December 2020

The paper shows that the coupled oscillator systems are more complicated in the dynamic behaviors, more stable in periodic phases and stronger in the anti-noise capacity than the same kind of single oscillator systems by analyzing the function of coupled parameters, the complexity of the large-scale periodic phase states of the system and the comparison with the states of the system under the condition of no noise. Moreover, the harmonious wave and square wave signals are detected under the background of colored noise, applying a kind of constructed middle-intensity two coupled Duffing oscillator system including a special resilience force item. The signal-to-noise ratio reaches to -111.0 and -108.45dB, respectively.
Analysis of an open cavity with abrupt changes by S-matrix
Authors: Liu Ying-Hui  , Li Hong-Fu  , Li Hao  , Wang E-Feng  , Xu Yong  , Wang Hui  , Wang Li  ,   电子科技大学高能电子学研究所，成都  610054
Published: December 2020

Based on the modal expansion and field matching technique, the S-matrix of a abrupt change is derived. The open resonator with a series of abrupt changes in radius is studied, and the S-matrix of the open cavity is derived by matrix cascading. A computer program was deueloped to calculate the scattering matrix of the cavity and the result shows good agreement with experiment and HFSS simulation.
New mechanism of reactivity enhancement for advanced fuel fusion
Authors: Chen Zhi  , Deng Bai-Quan  , Feng Kai-Ming  ,   核工业西南物理研究院，成都  610041
Published: December 2020

If electron cyclotron wave is adopted for heating of D-３Ｈe advanced fuel fusion plasma, it makes the latter operate at elevated electron temperature. Under these circumstances, some new physical processes, such as nuclear-nuclear elastic scattering, nuclear plus Coulomb interference scattering, secondary reaction propagation between the fusion products and bulk Maxwellian ions, become relatively more pronounced. However the Coulomb-interactions between fusion produced energetic ions and electrons turn to be weakening, a fraction of bulk Maxwellian fuel ions will be shifted to super-hot tail ions in their distribution functions, hence D-３Ｈe fusion reactivity may be enhanced. The energy transfer of these new mechanisms is highlighted in this paper.
Dissociation of sulfur trimer S3:the nonadiabatic process
Authors: Yan Bing  , Pan Shou-Fu  , Wang Zhi-Gang  , Yu Jun-Hua  ,   (1)哈尔滨工业大学可调谐激光技术国家重点实验室,哈尔滨  150001; (2)吉林大学原子与分子物理研究所,长春  130012
Published: December 2020

The dissociation process of the sulfur trimer S３ in the low-lying excited states is investigated using ab initio method in this work. The dissociation limits of S３ are constructed. The calculation of transition moment between certain states indicates that the nonadiabatic process of conversion between different excited states occurs in the crossing regions of potential surfaces. Thus, we conclude that the nonadiabatic predissociation is important in the dissociation paths of S３ into S２+S.
Study of multi-level run-length limited photo-chromic storage
Authors: Hu Heng  , Pan Long-Fa  , Qi Guo-Sheng  , Hu Hua  , Xu Duan-Yi  ,   清华大学精密仪器与机械学系,光盘国家工程研究中心,北京  100084
Published: December 2020

Multi-level run-length limited (ML-RLL) storage is a novel method to increase the recording density and data transfer rate without making changes on optical pickup head. The storage mechanism and experimental system of ML-RLL photo-chromic storage are presented. The mathematical model of ML-RLL storage using photo-chromic materials is proposed. The nonlinear relation between the reflectivity of marks and the exposure power and time is reflected in this model. Based on the model, a proper write strategy used for 4-level run-length limited (4L-RLL) photo-chromic storage is obtained. Then a 4L-RLL photo-chromic dynamic experiment is carried out on 650nm photo-chromic material. Experimental results show that the 650nm photo-chromic materials used in the experiment can be used for ML-RLL storage and the recording channel can be effectively linearized by using proper write strategy, so the conventional signal processing techniques used for linear system can be used.
Direct acceleration of electrons by a Laguerre-Gaussian laser beam in vacuum
Authors: Zhao Zhi-Guo  , Lü Bai-Da  ,   (1)洛阳师范学院物理系，洛阳  471022;四川大学激光物理与化学研究所，成都  610064; (2)四川大学激光物理与化学研究所，成都  610064
Published: December 2020

The acceleration of electrons by a Laguerre-Gaussian(LG) beam in vacuum is studied. It is shown that only the longitudinal electric field of the LG beam with mode indices p and l=1 can be used to accelerate electrons. The linearly- and circularly-polarized LG beams with mode indices p and l=1 effectively play the role in laser electron acceleration. Some physical characteristics, such as phase and group velocities of the axial optical field, and energy gain of electrons etc., are discussed. The analytical expressions for the phase and group velocities of the axial optical field, accelerating potential and energy gain etc. are derived and are used to make numerical analysis.
Coupling characteristics of electromagnetic waves in parallel three photonic crystal waveguides and its application
Authors: Yu Tian-Bao  , Wang Ming-Hua  , Jiang Xiao-Qing  , Yang Jian-Yi  ,   (1)浙江大学信息与电子工程学系，杭州  310027; (2)浙江大学信息与电子工程学系，杭州  310027;南昌大学物理系，南昌  330047
Published: December 2020

We consider the coupling between three photonic crystal waveguides as a multimode interference system and show that the dispersion curves of the eigenmodes intersect or almost intersect. Degenerate modes appear in the system. Due to the strong coupling between the degenerate modes, the modal patterns of the guided modes are changed obviously. We find that the power distribution of output light waves of different frequencies is different by selecting the coherence length. At the crossing point, the multimode interference is deprived and power is confined to its input direction without observable transferring to other photonic crystal waveguides. On the basis of these, a wavelength de-multiplexer or multiplexer is designed.
The two-dimensional metal photonic band gap structure consisting of a skew lattice in a nonorthogonal coordinate system
Authors: Hao Bao-Liang  , Liu Pu-Kun  , Tang Chang-Jian  ,   (1)四川大学物理科学与技术学院，成都  610065; (2)四川大学物理科学与技术学院，成都  610065;中国科学院电子学研究所，北京  100080; (3)中国科学院电子学研究所，北京  100080
Published: December 2020

The metal photonic band gap structure has potentialities in the areas of high-energy accelerators,microwave vacuum electron devices, and terahertz radiation sources etc. The real space transfer matrix method in a nonorthogonal coordinate system is used to study the two-dimensional metal photonic band gap structure consisting of a skew lattice. A general formula for calculating the complete band gap structure is derived for transverse-electric and transverse magnetic modes, and the influences of the filling fraction, skew angle and cross section of the metal rod on band gap are analyzed. The results are in good agreement with results of other methods in some special cases.
Reentering spin glass behavior and charge ordering in phase separation Nd0.5Ca0.5MnO3 system
Authors: Yu Jian  , Zhang Jin-Cang  , Cao Gui-Xin  , Wang Shi-Peng  , Jing Chao  , Cao Shi-Xun  ,   上海大学物理系，上海  200444
Published: December 2020

Half-doped manganese oxides are very important on clarifying physical mechanism of strong correlation electron system and colossal magnetoresistance (CMR) effec t due to their rich physical content. The structure, electrical and magnetic tra nsport properties of Nd0.5Ca0.5MnO3 manganite w as systemically studied. The results show that Nd0.5Ca0.5 MnO3 compound displays the O′-orthorhombic structure and indicate th e existence of the typical Jahn-Teller distortion under 300 K. The transport pro perties show that the system undergoes paramagnetic insulator-ferromagnetic meta l transition under a magnetic field of 8 T and is accompanied by CMR effect. Mea nwhile, it is found that the temperature of antiferromagnetic transition and cha rge ordering is around 150 and 240K, respectively. There appears a typical reent rant spin glass behavior around 41K and the negative magnetization is also obser ved in the compound. All these phenomena indicate that there exist several comp lex magnetic interactions in the ground state of this half-doped Nd0.5Ca0.5MnO3 compound at low temperature. The present result s provide experimental data for strongly electronic correlated system of manga nites.
Crystallization, mechanical and corrosion properties of Zr-Cu-Ni-Al-Nb bulk glassy alloys
Authors: Liu Lin  , Sun Min  , Chen Qi  , Liu Bing  , Qiu Chun-Lei  ,   华中科技大学塑性成型及模具技术国家重点实验室，武汉  430074
Published: December 2020

Zr65-xCu17.5Al7.5Ni10Nbx bulk metallic glasses (BMGs) with x=0, 2 and 5 were prepared by water-cooled cop per mold casting. X-ray diffraction and differential scanning calorimetry reveal ed that the addition of Nb changes crystallization pathway of the base alloy and promotes an initial formation of icosahedral quasicrystals. The mechanical prop erties of the BMGs prepared were measured with MTS in a mode of quasi-static com pression. It was found that the addition of an appropriate amount of Nb signific antly enhances the compression strength and plastic strain with the maximum valu e of σb =1741MPa and εp= 5.0% for the BMG containing 5at % Nb. In addition, the corrosion behavior of the BMGs was investigated in 3% NaC l aqueous solution by electrochemical measurements. It showed that the BMGs with different compositions are all spontaneously passivated with passive current de nsity of 10-6—10-5 A/cm2, which is three order of magnitude lower than that of 1Cr18Ni9Ti stainless steel. The corrosion resis tance of the BMGs can be further enhanced with the addition of Nb, as indicated by the increase in pitting potential with the increase of Nb content.
Negative-ion element impurities breakdown model
Authors: Wu Shi-Gang  , Shao Jian-Da  , Fan Zheng-Xiu  ,   (1)中国科学院上海光学精密机械研究所，上海  201800; (2)中国科学院上海光学精密机械研究所，上海  201800;中国科学院研究生院，北京  100039
Published: December 2020

Negative-ion element impurities breakdown model of HfO2 optical thin film is reported. We believe the main impurity element in thin film comes from t he coating material. The weak absorption and laser induced damage threshold (LID T) of HfO2 thin film are measured to testify the negative-ion element impurities breakdown model. These results indicate that the LIDT would decrease and the absorption of the films would increase with the increase of the content of negative-ion element. The main reason is the negative-ion elements become th e center of volatile gas source and form defects, which in turn become the cente r of absorption during laser irradiation. So negative-ion elements are harmful i mpurities, their existence will speed up the damage of the thin film.
A finite-temperature Landau theory for multilayered cuprate superconductors
Authors: Wu Jian-Bao  ,   池州师范专科学校物理系，池州  247000
Published: December 2020

A finite-temperature Landau theory is proposed to describe competing orders and interlayer tunneling in multilayered cuprate superconductors. For mono- and do uble-layered superconductors, the zero temperature order parameters and transiti on temperatures are calculated as functions of doping concentration. By comparin g such phase diagrams with relevant experiments, the phenomenolgical parameters in the theory are determined. Then we apply the theory to multilayered supercond uctors and determine the superconducting transition temperature as a function of layer number N in the underdoped, nearly optimally doped and overdoped region, respectively. In a reasonable parameter space the result of optimally doped regi on turns out to be in agreement with experiment, and as theoretical predictions, in the very underdoped and very overdoped case, Tc increases monoton ically with N.
Luminescence and optical constant of ZnSe/SiO2 composite thin films
Authors: Jiang Hai-Qing  , Yao Xi  , Che Jun  , Wang Min-Qiang  ,   西安交通大学电子材料与器件研究所，电子陶瓷与器件教育部重点实验室，西安  710049
Published: December 2020

The ZnSe/SiO2 composite thin films were prepared by sol-gel process a nd in-situ growth technique. X-ray diffraction results showed that the phase str ucture of ZnSe particles embedded in ZnSe/SiO2 composite thin films i s the sphalerite (cubic ZnS). X-ray fluorescence results revealed that the molar ratio ofZn/Se is about 1∶1.01—1∶1.19. Scanning electron microscopy results r evealed that the size of ZnSe crystal particles is about 400nm, while some parti cles are less than 100nm in size. The dependence of ellipsometric angle Ψ, Δ w ith wavelength λ of ZnSe/SiO2 composite thin films was investigated with spectroscopic ellipsometers. The optical constant, thickness, porosity and the concentration of ZnSe in ZnSe/SiO2 composite thin films were fitt ed according to Maxwell-Garnett effective medium theory. The photoluminescence p roperties of ZnSe/SiO2 composite thin films were investigated with fl uorescence spectrometer. The photoluminescence results indicated that the emissi on peak at 487nm under 395nm excitation corresponds to the band-to-band emission of sphalerite ZnSe crystal. The strong free exciton emission and other emission peaks correlated with ZnSe lattice defect were also observed.
Evaporation self-assembly method to fabricate high-quality polystyrene microsphere colloid crystal
Authors: Wang Xiao-Dong  , Dong Peng  , Yi Gui-Yun  ,   中国石油大学重质油国家重点实验室，北京  102249
Published: December 2020

Evaporation self-assembly method, which is used to assemble sub-micrometer polys tyrene microspheres, is presented in this paper. In this process the polystyrene microspheres are effectively assembled at the gas-liquid interface of suspensio n as moisture evaporates at fixed temperature. The scanning electron microscope shows that the three-dimensional colloidal assemblies have regular close-packed face-centered cubic structure. It was shown that the evaporation was blocked by the polystyrene colloid crystals growing at the gas-liquid interface, and the am ount of the polystyrene microspheres transferred to the colloid crystals from th e suspension in unit time increased with the area of the assemblies. High-qualit y polystyrene colloid crystals can be assembled when not changing or decreasing the phase concentration, whose changes can be controlled by adjusting the assemb ly area and the evaporation temperature.
The effect of biexciton, wetting layer leakage and Auger capture on Rabi oscillation damping in quantum dots
Authors: Liu Shao-Ding  , Cheng Mu-Tian  , Zhou Hui-Jun  , Li Yao-Yi  , Wang Qu-Quan  , Xue Qi-Kun  ,   (1)武汉大学物理系，武汉  430072; (2)武汉大学物理系，武汉  430072；中国科学院物理研究所，国际量子结构中心，北京  100080; (3)中国科学院物理研究所，国际量子结构中心，北京  100080
Published: December 2020

The decoherence of Rabi oscillation with multi-level processes in semiconductor quantum dots excited by laser pulses is investigated. By using population dynamic equations of multi-level system, the effect of three kinds of multi-level processes on the damping of Rabi oscillation in quantum dots are numerically simulated and discussed. The effect of biexciton can be neglected when the pulse width is larger than 5ps; the population leakage to wetting layer results in the decreasing of the amplitude and average of the population oscillation on the exciton ground state with the increasing of the excitation intensity; the effect of the two kinds of Auger capture processes on the Rabi oscillation and the spectral width of the photoluminescence from the exciton recombination are also discussed.
Fractional spins and fractional statistics of composite Boson field
Authors: Wang Yong-Long  , Li Zi-Ping  , Xu Chang-Tan  ,   (1)临沂师范学院凝聚态物理研究所，临沂  276005; (2)中国高等科学技术中心，北京  100080；北京工业大学应用数理学院，北京  100022
Published: December 2020

The composite Boson fields are quantizated in FS (Faddeev-Senjanovic) path integral quantizated formalism. The fractional spins and fractional statistics is obtained by using the quantum Noether theorem.
The effect of external electric field on the excited states of plutonium dihydride
Authors: Xie An-Dong  , Meng Da-Qiao  , Luo De-Li  , Ma Mei-Zhong  , Zhu Zheng-He  ,   (1)表面物理与化学国家重点实验室,绵阳919信箱  621900; (2)四川大学原子与分子物理研究所,成都  610065; (3)四川大学原子与分子物理研究所,成都  610065；井冈山学院物理系,吉安  343009
Published: December 2020

The ground states of plutonium dihydride under electric field ranging from -0.005 to 0.005 a.u. have been optimized using density functional theory DFT/B3LYP with SDD for Pu and 6-311++G** for H. The excitation energies and oscillator strengths have been calculated under the same electric field employing the time-dependent DFT method. The results show that the electronic state, total energy,molecular geometry, dipole moment and excitation energy are strongly dependent on the applied field strength. As the electric field changes from -0.005 to 0.005 a.u., the bond length of Pu-H increases whereas the bond angle of H-Pu-H decreases because of the charge transfer induced by the applied electric field. The dipole moment of the ground state increases linearly with the applied field strength. The total energy of the ground state decreases linearly with the applied field strength. The dependence of the calculated excitation energies on the applied electric field strength fits well to the relationship proposed by Grozema. The excitation energies of the first five excited states of plutonium dihydride decrease as the applied electric field increases because the energy gap between the HOMO and LUMO become narrower with the field, which shows that the molecule is apt to be excited under electric field and hence can be easily dissociated.
Theoretical study of the anisotropic interaction potential and partial scattering cross sections for He-HCl system
Authors: Yu Chun-Ri  , Huang Shi-Zhong  , Feng Er-Yin  , Wang Rong-Kai  , Cheng Xin-Lu  , Yang Xiang-Dong  ,   (1)安徽师范大学物理系，芜湖  241000; (2)安庆师范学院物理与电气工程学院，安庆  246011；安徽师范大学物理系，芜湖  241000；四川大学原子与分子物理研究所，成都  610065; (3)四川大学原子与分子物理研究所，成都  610065; (4)四川大学原子与分子物理研究所，成都  610065；贵州师范大学理学院，贵阳  550001
Published: December 2020

In this paper, an anisotropic intermolecular potential of the He-HCl complex has been obtained by utilizing the BFW analytic function to fit the intermolecular energy data, which have been calculated at the theoretical level of the single and double excitation coupled-cluster method with noniteractive perturbation treatment of triple excitation CCSD(T). Then the differential and partial scattering cross sections for collisions between He atoms and HCl molecules have been calculated by using CC(Close-Coupling) approximation method. Finally, the law governing the changes of the partial scattering cross sections has been given. This study shows that the fitted anisotropic intermolecular potential not only possesses the advantage of a simpler function form but also offers a better description of the characteristic of interaction in He-HCl system. At the same time, the difficult problem to determine the intermolecular potential parameters can be solved on the basis of the results of ab initio calculation for the collision systems. Therefore, the result obtained may be helpful for probing collision mechanism of atoms and molecules.
Study of the interface optical property of bubbles in water based on PIV
Authors: Tang Yuan-He  , Xie Guang-Yong  , Liu Han-Chen  , Shao Jian-Bin  , Ma Qi  , Liu Hui-Ping  , Ning Hui  , Yang Yu  , Yan Cheng-Hai  ,   (1)西安工程科技学院理学院,西安  710048; (2)西安理工大学理学院,西安  710048
Published: December 2020

Based on the technique of PIV (particle image velocimetry),We calculated the light intensity of the bubble interface and discovered that the intensities of lighr reflected or refracted twice succeedingly abide by the rules of geometric series, and the light will disappear after reflecting or refracting 4 times by the bubbles. When the angle of incidence of 35° is avoided , the intensity of second refraction out of a bubble is independent of the incident beam width, similar to the case of a narrow light ray falling on the bubble interface. The integral formulas for the intensities of reflection or refraction are given for the planar light beam falling on the bubble interface. The numerical solution of the integral is in agreement with the experiment value.
Entanglement and intrinsic decoherence in the interaction between two-mode field and atom
Authors: Tan Xia  , Zhang Cheng-Qiang  , Xia Yun-Jie  ,   曲阜师范大学物理工程学院，曲阜  273165
Published: December 2020

Considering the interaction between two-mode SU(1,1) coherence states and a two-level atom, we find an exact solution of the Milburn equation for the system. We investigate the time evolution of the entanglement of field-atom and one of two modes of field using the quantum-reduced entropy and quantum relative entropy, respectively. The influences of intrinsic decoherence and two-mode photon number difference on the evolution of the entanglement of field-atom and one of two modes of field are discussed. It is shown that the entanglement of field-atom reduces to a stationary value with time evolution and the entanglement between two modes increases to another stationary value with intrinsic decoherence, and the values only depend on the two-mode photon number and mean photon number.
Investigation on reflection tomography imaging with terahertz wave of nonparallel interfaces inside the sample
Authors: Xi Zai-Jun  , Xiao Ti-Qiao  , Zhang Zeng-Yan  , Chen Min  , Yu Xiao-Han  , Xu Hong-Jie  ,   中国科学院上海应用物理研究所，上海  201800
Published: December 2020

In previous studies on reflection tomography imaging with terahertz wave, only parallel interfaces were considered. In this article we report the numerical simulation on reflection tomography imaging with terahertz wave of nonparallel interfaces inside the sample. The reconstructing algorithm is given according to the physical model and the correlative reconstructing software is compiled. The results show that the reconstructing method of nonparallel interface is feasible. The analysis indicates that the reconstructing errors result from approximate treatment and accumulative error. The approximate treatment method of the curve contour is discussed. If the curvature radii at all points are large, the curve can be treated by cutting it into several line segmeants. The factors affecting longitudinal resolution are analyzed finally. The results show that the longitudinal resolution becomes worse as the pulse width of input pulse becomes larger. The longitudinal resolution can reach sub-millimeter size usually.
The energy deposition and propagation of fast ions in ultra-dense plasmas
Authors: Li Xue-Mei  , Shen Bai-Fei  , Zha Xue-Jun  , Fang Zong-Bao  , Zhang Xiao-Mei  , Jin Zhang-Ying  , Wang Feng-Chao  ,   (1)中国科学院上海光学精密机械研究所强光光学实验室,上海  201800; (2)中国科学院上海光学精密机械研究所强光光学实验室,上海  201800；中国科学院研究生院，北京  100049
Published: December 2020

The collision dynamics of the fast ion population in ultra-dense DT plasmas are investigated and analyzed within the framework of the relativistic Fokker-Planck equation. The Green function expansing on the spherical harmonics is used to express the solution of the equation. With the Green function we can calculate the stopping time, the ion range, the straggling range, and the mean transverse dispersion of different kinds of ions in plasmas. Compared to the previous ways of studying the movement of ions in plasmas, we not only calculate the straggling range without the approximation that the energy loss of the ions is much smaller than the energy of the ions, but we also calculate the stopping time and the mean transverse dispersion. This calculation is important for the experimental study of high energy density plasmas and fast ignition of laser fusion.
The effect of grain boundaries on magnetic and transport properties in colossal magnetoresistance particle film
Authors: Li Pei-Gang  , Lei Ming  , Tang Wei-Hua  , Song Peng-Yun  , Chen Chin-Ping  , Li Ling-Hong  ,   (1)Department of Physics,University of Dayton,Dayton,OH45469,USA; (2)北京大学物理系，北京  100871; (3)浙江理工大学物理系，杭州  310038；中国科学院物理研究所，北京凝聚态物理国家实验室，北京  100080
Published: December 2020

La0.67Ca0.33MnO3 grain films have been grown by pulsed electron beam deposition technology,and their magnetic and electronic transport properties investigated in detail.The influence of grain boundaries on the physical properties of La0.67Ca0.33MnO3 grain films were studied.Grain boundaries weaken the coupling between grains,resulting in a cluster spin glass state.The metal-insulator transition temperature (Tp) was shifted far below the ferromagnetic-paramagnetic transition temperature (Tc).At low temperatures,the electron transportation indicates a weak localization behavior,and under low magnetic fields,the intrinsic magnetoresisance effect is screened by the influence of grain boundaries.
Vacancy of laser field induced by phase reflection in underdense plasmas and its relation to laser-plasma parameters
Authors: Zhang Qiu-Ju  , Sheng Zheng-Ming  , Wang Xing-Hai  , Man Bao-Yuan  , Cang Yu  , Zhang Jie  ,   (1)山东师范大学物理与电子科学学院，济南  250014; (2)中国科学院物理研究所光物理开放实验室，北京  100080
Published: December 2020

It is shown theoretically and by particle- in-cell simulations that the plasma density modulation produced by laser in underdense pre-plasmas can serve as a Bragg reflector, which results in phase reflection occurring at low-density plasma area. The phase reflection can influence the laser propagating in plasmas, such as the vacancy of laser field induced by two laser pulses counter-propagating in plasmas. It is also shown that the period of phase reflection and the reflectivity are related with the plasma density, thickness, intensity and the duration of laser.
Experimental study on the plasma jet attenuation of reflected wave in vacuum environment
Authors: Zhu Bing  , Yang Juan  , Huang Xue-Gang  , Mao Gen-Wang  , Liu Jun-Ping  ,   西北工业大学航天学院，西安  710072
Published: December 2020

The microwave test method of transmission line can be applied to study the characteristics of wave absorption by plasma. With this method, how the parameters of microwave plasma generator, the medium being argon, and the vacuum environment affect the variation trends of plasma return loss, which imply the plasma jet attenuation of reflected electromagnetic wave, is studied in vacuum environment. Experimental results show that when the mass flow rate and output power of plasma generator are 52.5mg/s and 52W, respectively, microwave plasma jet can absorb the energy of reflected electromagnetic wave maximally at the frequency near 5GHz. With the output power increasing and the environment pressure decreasing, the wave attenuation of plasma will be increased. The plasma jet will attenuate reflected wave maximally with appropriate generator parameters.
Real-time visualization system of plasma shape for HL-2A
Authors: Yuan Bao-Shan  , You Tian-Xue  , Liu Li  , Li Fang-Zhu  , Yang Qing-Wei  , Fen Bei-Bin  ,   核工业西南物理研究院，成都  610041
Published: December 2020

The real-time visualization system of plasma shape is developed for studying the divertor plasma in HL-2A. The plasma boundary reconstruction code CF(Current Filaments) are written using the current filaments model and the finit current element model. The information of the magnetic field around plasma is collected with USB data acquisition card UA301, having 100kHz/s, 32 channels with simultaneous sampling. A compatible computer with 3GHz E CPU processes the data. This system collects and stores data in every 4ms, and plots the plasma boundary in every 16ms. After discharge, the mgnetic field at the plasma boundary and some plasma parameters which are deduced from it are calculated.
Composite oscillator model for the energy dissipation mechanism of friction
Authors: Xu Zhong-Ming  , Huang Ping  ,   华南理工大学机械工程学院，广州  510640
Published: December 2020

A composite oscillator model is proposed for studying energy dissipation mechanism of atomic-scale wearless friction. The model consists of the whole macroscopic oscillator and the micro oscillators of interfacial atoms. Different influences of the two oscillators on the energy dissipation process of friction are discussed. It is found that the frequency of the interfacial excitation force is the key to energy conversion in the friction process by analyzing the dynamic characteristics of interfacial atoms. In the equilibrium stage, the interfacial force acts integrally and uniformly on each atom because its frequency is nearly zero. In the non-equilibrium stage, however, the distribution of the energy received by the interfacial atoms is not uniform because the frequency of the interfacial acting force is very high. Therefore, the extra energy may be easily transferred to the adjacent atoms to make the energy dissipate. The results show that the composite oscillator model can more clearly explain the energy dissipation mechanism of friction in detail.
Electronic theoretical study of the influence of impurities on corrosion resistance of magnesium alloy
Authors: Zhang Guo-Ying  , Zhang Hui  , Zhao Zi-Fu  , Li Yu-Cai  ,   沈阳师范大学物理科学与技术学院，沈阳  110034
Published: December 2020

The atomic structure model of symmetric ［0001］ tilt boundary of α phase in magnesium alloy was set up by using the concept of coincidence-site lattice (CSL). The segregation energies of impurities, the interaction energies between impurities and fermi levels of different systems at grain boundary (GB) were calculated by using recursion method. The segregation behaviour of impurities, the relationship between the interaction between impurities and the ordering tendency, as well as the physical nature of the influence of impurities on corrosion resistance of magnesium alloy were discussed. Calculation results show that impurity atoms segregate to GB, and are apt to occupy the sites in the compressed region of GB. Impurity atoms repel each other, therefore form ordered phases in the region of GB. The relationship between the fermi level of a kind of material and its equilibrium potential is: the higher the fermi level is, the lower the equilibrium potential is; and vice versa. The difference of fermi level of regions with different composition in a system leads to the flow of electrons from the region with high fermi level to the region with low fermi level. It is just the difference of fermi levels that forms the electrodynamic force of the electrochemical corrosion in magnesium alloys.
Interactions of CO molecules adsorbed on metallic nanostructured surfaces in an external electric field
Authors: Huang Xiao-Jing  , He Su-Zhen  , Wu Chen-Xu  ,   (1)集美大学理学院物理系,厦门  361021;厦门大学物理系软凝聚态研究室,厦门  361005; (2)厦门大学物理系软凝聚态研究室,厦门  361005
Published: December 2020

A model is proposed to analyze the interaction energy of CO molecules adsorbed on metallic nanostructured surfaces in an external electric field, including the one between effective dipoles and the local electric field as well as the one between effective dipoles . The local fields near the nanoparticles surfaces are also calculated and discussed. Using Monte-Carlo numerical computation and simulation, the configuration of CO molecules adsorbed on nanoparticle surfaces and the interaction energy are given in detail. The results show that the metallic nanostructures cause the CO molecules to agglomerate and the interaction energy increase may explain the abnormal IR effects (AIREs).
Study of radiation damage in Mg+-implanted GaN
Authors: Meng Kang  , Jiang Sen-Lin  , Hou Li-Na  , Li Chan  , Wang Kun  , Ding Zhi-Bo  , Yao Shu-De  ,   北京大学物理学院，北京  100871
Published: December 2020

The GaN films grown on sapphire by metal-organic chemical vapor deposition (MOCVD) have excellent crystalline quality (χmin=2.00%). Combining Rutherford backscattering/channeling (RBS/C) and high-resolution X-ray diffraction (HXRD) measurements, we investigate the radiation damage in GaN films with various doses and angles of Mg+-implantation. The results of experiments reveal that the radiation damage rises with the increasing implantation dose. Under the dose of 1×1015atom/cm2, χmin is less than 4.78%, and when implantation dose exceeds the threshold of 1×1016atom/cm2, χmin will be up to 29.5%. Random implantation causes more serious damage than channeled implantation, and in a definite range the damage level rises with a larger implantation angle. At the implantation angles of 0°,4°,6°and 9°deviating from〈0001〉, χmin(%)is 6.28,8.46,10.06 and 10.85, respectively, at a dose of 4×1015atom/cm2. After annealing at 700℃ for 10min and then 1050℃ for 20s, the damage recovers to some extend. The crystalline quality of the sample with 1×1016atom/cm2 implanted was reduced to 19.08%. In addition, the annealing condition of 1000℃ for 30s is more efficient and the damage recovers better.
The electronic structure of quasi-two-dimensional disordered systems
Authors: Liu Xiao-Liang  , Xu Hui  , Ma Song-Shan  , Song Zhao-Quan  , Deng Chao-Sheng  ,   中南大学物理科学与技术学院，长沙  410083
Published: December 2020

For the quasi-two-dimensional disordered systems of the form of Nt×Nl, only considering the nearest-neighbor hopping integrals and using a special method to code the sites, we write the Hamiltonians of the systems as precisely symmetric matrixes, which can be transformed into three diagonally symmetric matrixes by the Householder transformation. The densities of states, the localization lengths and the conductance of the systems are calculated numerically using the negative eigenvalue theory and the transfer matrix method. We study mainly the quasi-two-dimensional disordered systems with four and five parallel chains. By comparing the results with that of the disordered systems with one chain, two chains and three chains, we find that the energy band of the system extends slightly and the distribution of the density of states changes obviously with the increase of the effective dimensionality. Especially, for the systems with four or five chains, at the energy band center, there exist extended states whose localization lengths are larger than the size of the systems, accordingly, they have greater conductance. With the increasing of the number of the chains, the correlated ranges expand and the systems present the behaviour similar to that with off-diagonal long-range correlation.
Large current out-put of PZT 95/5 ferroelectric ceramics under shock loading
Authors: Du Jin-Mei  , Zhang Yi  , Zhang Fu-Ping  , He Hong-Liang  , Wang Hai-Yan  ,   中国工程物理研究院流体物理研究所冲击波物理与爆轰波物理实验室，绵阳  621900
Published: December 2020

The poled PZT 95/5 ferroelectric ceramic is in ferroelectric (FE) phase, it can be transformed into the antiferroelectric (AFE) phase by shock compression, so the bound charge can be liberated into an external circuit to generate pulses of electrical current. Based on this FE/AFE transition theory, the electrical response of LRC load was discussed, especially for the small resistance (R) and small inductance (L) load in this paper. A set of PZT 95/5 ceramics in parallel connection was devised to generate large pulses of electrical current in two plane-wave tests. The maximum output current reaches above 5 kA, and the corresponding rise time of the front edge is under 500ns.
The domain and domain wall structure of PT/PZT/PT ferroelectric thin film
Authors: Wang Long-Hai  , Yu Jun  , Liu Feng  , Zheng Chao-Dan  , Li Jia  , Wang Yun-Bo  , Gao Jun-Xiong  , Wang Zhi-Hong  , Zeng Hui-Zhong  , Zhao Su-Ling  ,   (1)成都电子科技大学微电子与固体电子学院，成都  610054; (2)华中科技大学电子科学与技术系,武汉  430074; (3)武汉理工大学材料研究与测试中心，武汉  430070
Published: December 2020

The polycrystalline perovskite-phase PT/PZT/PT ferroelectric thin film was prepared by sol-gel method. The domain and domain wall structures were investigated by scanning force microscopy. The out-of-plane polarization(OPP), in-plane polarization(IPP), the OPP amplitude and OPP phase images were obtained. The domain of the film has a complex structure with c-domain and deviated-c-domain the direction of which deviated from the surface normal of the film. The complex domain structure is related to the orientation of the crystal grains in the film. For the［111］oriented films, the 180° domain wall is formed when deviated-c-domains have reverse directions in OPP and IPP. The 90° domain wall is formed when the domains have the same direction in OPP and reverse directions in IPP, or when they have reverse directions in OPP and same direction in IPP.
Spectroscopic properties of Tm3+ ions in heavy metal oxide glasses for S-band optical amplifications
Authors: Yang Gang-Feng  , Zhang Qin-Yuan  , Shi Dong-Mei  , Deng Zai-De  , Jiang Zhong-Hong  ,   华南理工大学特种功能材料及其制备新技术教育部重点实验室，广州  510640
Published: December 2020

The spectroscopic properties of Tm3+ ions in PbO-Bi2O3-Ga2O3-GeO2 glasses were investigated through the absorption, emission, and lifetime measurements. The JO intensity parameters, the spontaneous emission probability, the fluorescence branching ratio, and the radiative lifetime were calculated using the Judd-Ofelt theory. From the measured 1470nm band emission spectra, we found the FWHM was ～122nm and the peak stimulated emission cross-section was ～2.2×10-21cm2, but the measured lifetimes decreased with the Tm3+ ion concentration increasing and the increase of cross relaxation rates was a function of the square of the Tm3+ ion concentration. As a result, PbO-Bi2O3-Ga2O3-GeO2 glasses were still thought to be a promising host material for potential S-band optical fiber amplifiers.
Luminescence intensity of Ag+ doped Y2O3:Eu nanocrystals
Authors: Meng Qing-Yu  , Chen Bao-Jiu  , Zhao Xiao-Xia  , Yan Bin  , Wang Xiao-Jun  , Xu Wu  ,   (1)中国科学院长春光学精密机械与物理研究所 激发态物理重点实验室，长春  130033; (2)中国科学院长春光学精密机械与物理研究所 激发态物理重点实验室，长春  130033；中国科学技术大学，合肥  230026; (3)中国科学院长春光学精密机械与物理研究所 激发态物理重点实验室，长春  130033；中国科学院研究生院，北京  100049
Published: December 2020

Eu3+ doped Y2O3 nanocrystalline and bulk powders with small content of Ag+ were prepared by chemical self-combustion. An interesting phenomenon was observed: with an increase in Ag+ content the luminescent intensity of the nanosized crystal is enhanced at first and then maintains a stable level; however for the bulk powder there is no obvious change in the luminescent intensity when the Ag+ content is varied. The morphology and crystal structure were characterized by transmission electron microscopy (TEM) and X-ray Diffraction (XRD), respectively. Emission spectra were measured for nano- and bulk samples. The fluorescence decay curves for all the samples, including nanosized and bulk ones, either with or without Ag+, were measured. It is found that the lifetime for the nanosized sample with Ag+ is longer than that without Ag+, and the lifetime for the bulk sample has no change. From these experimental results wecome to the conclusion that the Ag+ ion may link with a surfice O2-, which has a free bond, then the surfice unsaturated dangling bonds can be eliminated. The elimination of surfice dangling bonds may cause the increase of luminescence efficiency of Eu3+ doped nanosized Y2O3.
A technique for distinguishing dynamical species in the temperature time series of north China
Authors: Hou Wei  , Feng Guo-Lin  , Dong Wen-Jie  , Li Jian-Ping  ,   (1)扬州大学物理科学与技术学院，扬州  225009;中国科学院大气物理研究所东亚中心，北京  100029; (2)中国科学院大气物理研究所LASG，北京  100029; (3)中国科学院大气物理研究所东亚中心，北京  100029;国家气候中心，中国气象局气候研究开放实验室，北京  100081
Published: December 2020

A new method named “permutation entropy” for detecting dynamical changes in time series was used to analysis the day-to-day temperature time series of north China from 1960a to 2000a. We detected three abrupt climate changes in the mid-1970s and early 1980s. Further analysis using Empirical Mode Decomposition to decompose the permutation entropy shows that the approximate 10a cycle is most important. So we can draw the conclusion that north China suffered three abrupt climate changes in the mid-1970s and early 1980s, and moreover, the the approximate 10a cycle induced the climate changes directly.
Profile comparison between the Raman-induced Kerr effect spectrum and photoacoustic Raman spectrum of methane
Authors: Yu Yuan-Qin  , Zhou Xiao-Guo  , Lin Ke  , Dai Jing-Hua  , Liu Shi-Lin  , Ma Xing-Xiao  ,   合肥微尺度物质科学国家实验室(筹),中国科学技术大学化学物理系,合肥  230026
Published: December 2020

Two kinds of spectrum, the Raman-Induced Kerr Effect Spectrum(RIKES)and the Photoacoustic Raman Spectrum(PARS),were measured simultaneously for the ν1 vibrational band of methane. The difference between the profiles of the two spectra obtained with linearly polarized pump and Stokes laser beams lies in that, the intensity of RIKES spectrum is stronger at the small Raman shift side, and is weaker at the large Raman shift side compared to the PARS spectrum. It was confirmed that this difference is caused by the interference between the resonant and non-resonant parts of the third order non-linear susceptibility.
Propagation of phase modulated Gaussian beam in strongly nonlocal nonlinear media
Authors: Shao Yi-Quan  , Guo Qi  ,   (1)华南师范大学光子信息技术广东省高校重点实验室，广州  510631；华南师范大学信息光电子科技学院传输光学实验室，广州  510631; (2)华南师范大学光子信息技术广东省高校重点实验室，广州  510631；华南师范大学信息光电子科技学院传输光学实验室，广州  510631；内江师范学院物理学与电子信息工程系，四川内江  641112
Published: December 2020

We explore the control of the Gaussian beams propagating in the planar waveguide by use of the (1+1)-dimensional Snyder-Mitchell model and the spatial sinusoidal phase modulation.The steady symmetrical co-propagation of three,five and six beams can be obtained with proper modulation parameters. Their unique interaction has potential application in the optical switch,optical coder and the spectrometer.
Electric field intensity distribution in disordered one-dimensional photonic crystal with omnidirectional reflection band
Authors: Wen Xie-Wen  , Dong Jian-Wen  , Wang He-Zhou  ,   中山大学光电材料与技术国家重点实验室，广州  510275
Published: December 2020

It is theoretically demonstrated that the omnidirectional reflection band in one-dimensional disordered photonic crystals (1D DPCs) can have a width as broad as that in one-dimensional periodic photonic crystals (1D PPCs) with the same layer number. In the band gap, the electric field intensity distributions in a 1D DPC are almost the same as in 1D PPCs. However, near the band edges, the electric field intensity distribution in the 1D PPC is symmetric, remarkably different from the asymmetric field patterns in the 1D DPCs that are designable and controllable. This characteristic in the 1D DPCs should open a new way to design photonic-crystal-based devices.
Band gap characteristics of compound structure composed of lattices with different periodic constants
Authors: Zeng Jun  , Pan Jie-Yong  , Dong Jian-Wen  , Wang He-Zhou  ,   中山大学光电材料与技术国家重点实验室，广州  510275
Published: December 2020

Our numerical simulation results show that if a compound structure is composed of a lattice with a larger periodic constant and a lattice with a small periodic constant, the lattice with larger periodic constant will play the role of defects. The frequencies of defect modes are dependent on the rod radius (r2) of square lattice with a larger periodic constant, and the relationship of the defect modes and r2 is almost independent of a2. The defect mode is dependent on incidence angle when a22. Furthermore, by optimizing the size of the rods (r2) of the larger periodic lattice, single defect mode, multiple defect modes with equal or different frequency spacing, including single polarization or TE and TM overlap defect mode, can be gotten respectively. The transmissivity of the defect modes are inversely proportional to a2.
Study of chirps induced by the higher-order nonlinear effects in the photonic crystal fiber
Authors: Wang Jing  , Shi Yan-Mei  ,   中国海洋大学光学光电子实验室，青岛  266071
Published: December 2020

Based on nonlinear Schrdinger equation, the stimulated Raman scattering (SRS) chirp, self-steepening (SS) chirp and total chirps induced by all nonlinear effects in photonic crystal fiber (PCF) are simulated numerically. The results show that the center of SRS chirp wanders and the chirps of the leading edge and the trailing edge are asymmetrical, the central SS chirp mainly shifts to the trailing edge, and the total chirps increases. Thus, SRS leads to the shift of spectrum to the longer wavelength and the asymmetric broadening of spectrum, and SS is the most important contributor to the asymmetry spectrum broadening. Consequently, asymmetrical red-shift supercontinuum (SC) spectrum is finally resulted due to all nonlinear effects mentioned above.
Collision operator for moderately coupled plasma
Authors: Zha Xue-Jun  , Han Shen-Sheng  , Xu Zhi-Zhan  , Wang Yan  ,   (1)上海大学物理系，上海  200444; (2)中国科学院上海光学精密机械研究所，强场激光物理国家重点实验室，上海  201800
Published: December 2020

A new approach has been developed to treat large-angle and small-angle binary collisions in plasmas when the test particles' distribution function fα is an even function about the test velocity vα. In the approach, the Boltzmann collision operator is derived to be suitable for the plasma considered as weakly coupled (Coulomb logarithm ln Λ≥10) or moderately coupled (2≤lnΛ≤10). The modified collision operator has a direct and practical connection to the Rosenbluth potentials. In addition, with mαmβ(such as electron-ion collision or Lorentz-gas model) and vαvβ, the reduced electron-ion collision operator differs from the original Fokker-Planck operator for Coulomb collisions by terms of order 1/lnΛ.
The effect of interwall coupling interaction on the field emission characteristics of commensurate double-walled carbon nanotubes
Authors: Liu Xing-Hui  , Zhu Chang-Chun  , Zeng Fan-Guang  , He Yong-Ning  , Bao Wen-Xing  ,   (1)辽宁大学物理系,沈阳  110036;西安交通大学电子与信息工程学院，西安  710049; (2)西安交通大学电子与信息工程学院，西安  710049
Published: December 2020

The band structure model of commensurate double-walled carbon nanotube (DWNT) was built by using tight-binding Hamiltonian with curvature effect included. The field emission characteristics of commensurate DWNT were quantitatively investigated basing on its dependence on the band structure. The results indicate that interwall coupling interaction (ICI) can form additional electronic energy level in the band structure of DWNT so as to increase the emitting channel of electrons;and at the same time, it can also increase the energy gap of the metallic DWNT and decrease that of the semiconducting DWNT, which will result in a change in the number of electrons emitted from the valence band. At a given applied electric field, the emission current of DWNT has an obvious increase, compared with that of DWNT when ICI is turn off, and the current increment of semiconducting DWNT is larger than that of the metallic one. At an applied electric field of 5V/μm, the field emission currents of commensurate DWNTs (6,6)&(12,12), (10,0)&(20,0) and (8,2)&(16,4) have an increase of about 3%,10% and 4%, respectively, compared with those when ICI is turn off. The results reveal that ICI contributes to the transport and electron emission of DWNT, which is helpful for understanding the field emission mechanism of DWNT ,and hence that of MWNT.