bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical calculation of radiation pattern and impedance of column plasma
Authors: Zhao Guo-Wei  , Xu Yue-Min  , Chen Cheng  ,   (1)中国科学院空间科学与应用研究中心，北京  100080; (2)中国科学院空间科学与应用研究中心，北京  100080;中国科学院研究生院，北京  100049
Published: December 2020

When the frequency of the incident electromagnetic wave is lower than that of the plasma, the high-density and low-temperature plasma column is equivalent to a good conductor. However, because of the dispersive relation and the uneven distribution of density, the wave vector propagating along the plasmas is not a real constant, but a complex quantity varying with the change in the space. So, it is hard to calculate the radiation pattern, radiation impedance and gain of the column plasma with the normal methods used with the metallic antenna. In this paper, the space distribution of the wave vectors of the signal along the column plasma is calculated from the dispersive relation of the non-magnetized columnar plasma. And then, according to the antenna equation, the radiation pattern, radiation impedance and gain of the columnar plasma with even or uneven axial density distribution can be derived. The experimental results show that the numerical values calculated by this new method are much more accurate. This method will be of great importance in the application of the plasmas in the antenna transportation.
FDTD analysis of 3-D conducting target coated by anisotropic magnetized plasma
Authors: Xu Li-Jun  , Liu Shao-Bin  , Mo Jin-Jun  , Yuan Nai-Chang  ,   国防科技大学电子科学与工程学院,长沙  410073
Published: December 2020

The JEC finite-difference time-domain (JEC-FDTD) method is extended to three dimensional anisotropic dispersive media—the magnetized plasma. The problem which incorporates both anisotropy and frequency dispersion at the same time is solved for the electromagnetic wave propagation. The three dimensional JEC-FDTD formulations for anisotropic magnetized plasma are derived. The method is applied to the electromagnetic scattering of dihedral corner reflector and sphere-cone coated with anisotropic magnetized plasma. By simulating the interaction of electromagnetic wave with magnetized plasma, some numerical results are obtained, which indicate that an appropriate plasma coating may efficiently reduce the RCS of a metallic target.
Studies of implosion processes of nested tungsten wire-array Z-pinch
Authors: Ning Cheng  , Ding Ning  , Liu Quan  , Yang Zhen-Hua  ,   北京应用物理与计算数学研究所，北京  100088
Published: December 2020

Nested wire-array is a kind of promising structured-load because it can improve the quality of Z-pinch plasma and enhance the radiation power of X-ray source. Based on the zero-dimensional model, the assumption of wire-array collision, and the criterion of optimized load (maximal load kinetic energy), optimization of the typical nested wire-array as a load of Z machine at Sandia Laboratory was carried out. It was shown that the load has been basically optimized. The Z-pinch process of the typical load was numerically studied by means of one-dimensional three-temperature radiation magneto-hydrodynamics (RMHD) code. The obtained results reproduce the dynamic process of the Z-pinch and show the implosion trajectory of nested wire-array and the transfer process of drive current between the inner and outer array. The experimental and computational X-ray pulse was compared, and it was suggested that the assumption of wire-array collision was reasonable in nested wire-array Z-pinch at least for the current level of Z machine.
Numerical simulation of plasma of large-dimensions produced by injecting electron beam into air
Authors: Li Hong  , Su Tie  , Ouyang Liang  , Wang Hui-Hui  , Bai Xiao-Yan  , Chen Zhi-Peng  , Liu Wan-Dong  ,   中国科学院基础等离子体物理重点实验室，中国科学技术大学近代物理系，合肥  230026
Published: December 2020

A four-species 1-D hybrid numerical model was set up to simulate the process of formation of large-dimension plasma produced by injecting electron beams into air. It showed that plasma of the order of 0.5m in length and 1012cm-3 in density can be produced by an electron beam with the energy of 140keV and flux of 50mA/cm2. The effect of space charge associated with the beam on the beam propagation and related process vanishes soon after the plasma is produced. The beam flux is directly relevant to the plasma density, but the beam energy affects both the dimensions and the density of produced plasma.
Effect of adding hydrogen to a nitrogen glow discharge on electron behavior
Authors: Zhang Lian-Zhu  , Gao Shu-Xia  ,   河北师范大学物理科学与信息工程学院，石家庄  050016
Published: December 2020

The effect of adding hydrogen to a nitrogen dc glow discharge is investigated by using Monte Carlo code to simulate the electron behavior in the cathode dark space (CDS). It is shown that when increasing the percentage of H2, the electron mean energy is increased, the electron density and various e-N2 collision rates are decreased, and when adding small amounts of H2 into nitrogen gas, e-N2 dissociation and electron excitation rates can be enhanced under certain discharge conditions, which will contribute to increase the density of significant active nitrogen species (N*2，N+，N) in discharge space. The hydrogen concentration is varied between 0% and 30%. These effects can be explained by the collisions taking place in the discharge. We have also compared our calculated results with experimental data.
Study of 2D metallic photonic band gap structures
Authors: Lu Zhi-Gang  , Gong Yu-Bin  , Wei Yan-Yu  , Wang Wen-Xiang  ,   电子科技大学物理电子学院，成都  610054
Published: December 2020

In order to study 2D metallic photonic crystal, a new plane-wave expansion method was proposed. Based on traditional plane wave expansion method, the “original problem” to be solved was extended to a “new problem”. First, the relation between them were given, second, the “new problem” was transformed to an integral-differential eigen equation through an auxiliary function. The eigen equation was solved to obtain the band gap structures of the “new problem”. The band gap structures of the “original problem” were deduced according to “new problem”. Finally, numerical computations were done for 2D square-lattice square metallic rods photonic crystal, and excellent results were achieved.
GW quasiparticle band structure of BaSe
Authors: Chen De-Yan  , Lü Tie-Yu  , Huang Mei-Chun  ,   厦门大学物理系，福建 厦门  361005
Published: December 2020

The electron structure of barium's VIB compound is not clearly known yet. The main problem is that not only the band gap calculated by using DFT (density functional theory) has a large discrepancy compared with experimental results,but also the theoretical values of band gap are inconsistent for different research groups.In order to resolve these problems, this paper makes the Green function-screened coulomb interaction quasiparticle theory(GW) calculation to get the quasiparticle band structure of BaSe.For the convenience of comparison, it deals with the systematic calculation of the energy band of BaSe by using the methods of local density approximation (LDA) and the generalized gradient approximation(GGA). The result shows that the methods LDA and GGA can not describe the band gap of the material accurately, because the calculation errors are as high as 39.9% and 32.6%, respectively. However, the result of quasiparticle band gap by GW improves the band gap value greatly and give the theoretical result which agrees with the experimental measurement. At variance with the known result, BaSe of quasiparticle band gap in the B1 structure is shown to have a direct gap at the Γ-point in the present paper,which indicates that it is important to take into account the 4d electronic effect in the valence electron configuration of barium.
Optimization design of the band profiles of HgCdTe heterojunctions
Authors: Quan Zhi-Jue  , Sun Li-Zhong  , Ye Zhen-Hua  , Li Zhi-Feng  , Lu Wei  ,   中国科学院上海技术物理研究所红外物理国家重点实验室，上海  200083
Published: December 2020

In this paper, the band profiles of HgCdTe (MCT) heterojunctions with the configuration of wide/narrow gap-p on narrow/wide gap-n are calculated, respectively. In the theoretical model employing a valence band offset, a new simple carrier density approximation is proposed to include the carrier degeneracy and conduction band non-parabolicity in the calculations. The effects of the location of p-n junction (zB) and the interface charge density (Q) on the band profiles of MCT heterojunctions are studied systemically, which is found to be significant and can't be neglected. With the help of the results of above research, the optimal design related to zB and Q is obtained.
Density-functional theory calculations for the carbon-monoxide and hydrogen co-adsorbed on Ni(111) surface
Authors: Zhao Xin-Xin  , Tao Xiang-Ming  , Chen Wen-Bin  , Chen Xin  , Shang Xue-Fu  , Tan Ming-Qiu  ,   浙江大学物理系，杭州  310027
Published: December 2020

In this article a first-principles total energy calculation of the atomic geometry and electronic structure of carbon-monoxide and hydrogen co-adsorbed on Ni(111) p(2×2) surface at a coverage of 0.25 ML is reported. The optimized atomic geometry is in good agreement with the most recently reported LEED experiment on Ni(111) p(2×2)/(CO+H) co-adsorbed system. The carbon-monoxide is predicted to be adsorbed on the hcp site while hydrogen atom occupies the fcc site, and both adsorbates locate on opposite p(1×1) cells within a p(2×2) supercell. The adsorption energy of CO and H in this configuration is 2.81 eV with respect to the CO and H2 molecule and the surface work function is calculated to be 6.28 eV in comparison with 5.23 eV of clean Ni(111) surface. The bond lengths of C—O, C—Ni, and H—Ni are estimated to be 1.19?, 1.96?, and 1.71?, respectively, and the substrate interlayer distance variations, Δd12 and Δd23, are calculated to be +1.6% and +0.4%, respectively. The chemisorptions of CO and H atom on the Ni(111) p(2×2) surface were calculated in the same way and the adsorption heights of CO and H were evaluated to be 1.33? and 0.90?, respectively. The interaction energy between CO and H in the best fit geometry of Ni(111) p(2×2)/(CO+H) system is about 0.60 eV, which could be taken as the essential factor for the realization of Fisher-Tropsch reaction.
Study of the modulated spectra of dilute GaNxAs1－x (x≤0.03) thin films
Authors: Wang Chong  , Chen Ping-Ping  , Liu Zhao-Lin  , Li Tian-Xin  , Xia Chang-Sheng  , Chen Xiao-Shuang  , Lu Wei  ,   中国科学院上海技术物理研究所 红外物理国家重点实验室，上海  200083
Published: December 2020

Dilute GaNxAs1-x thin films with N concentration from 0.0% to 3% have been grown by molecular beam epitaxy. Piezomodulated reflectance (PzR) spectra of these thin films have been measured at room temperature, and optical transitions in PzR spectra have been well resolved. The N-related transition of E1+Δ1+ΔN had been observed in PzR spectrum of GaN0.005As0.995 and GaN0.01As0.99 films. The well resolved split between heavy hole and light hole of Γ valence band is shown in PzR when the N doping level is up to 1%. The N concentration dependence of transition energies supports the model that both E+ and E* originate from the L conductive band at room temperature.
The grating optical coupling of the very long wavelength quantum well infrared photodetectors
Authors: Xiong Da-Yuan  , Zeng Yong  , Li Ning  , Lu Wei  ,   中国科学院上海技术物理研究所红外物理国家重点实验室，上海  200083
Published: December 2020

Because of the isotropic energy band structure of the Γ electrons in the GaAs/AlGaAs quantum well infrared photodetector (QWIP), normal incident radiation absorption is forbidden, so that the optimization of optical grating becomes a key technology. In this work we present a scattering-matrix method based on plane-wave expansion for the two-dimensional QWIP grating. The transmission spectrum of the QWIP grating has been studied theoretically and experimentally. It has been shown that in general, both the propagating wave and the evanescent wave contribute to the optical coupling in n-type QWIP. The grating parameters, like period, depth and filling factor, will strongly affect the optical coupling.
Electric field distribution in charge imbalance super junction
Authors: Fang Jian  , Qiao Ming  , Li Zhao-Ji  ,   电子科技大学微电子与固体电子学院, 成都  610054
Published: December 2020

2D analytic models for the electric field distribution of charge imbalance SJ structures, such as concentration and width imbalance, trapezoid n-/p- regions and lateral linearly graded doping have been presented. The comparison of the 2D analytic model with numerical device simulations shows that the proposed model can accurately predict electric field distribution. Although this solution is in the form of trigonometric series, some most important information also can be obtained from this solution. For example, the peak electric field and breakdown voltage in charge imbalance SJ structure can be obtained from the results of this paper.
Study of high temperature superconduction under pressure
Authors: Liang Fang-Ying  , Liu Hong  , Li Ying-Jun  ,   (1)中国矿业大学(北京),北京  100083; (2)中国矿业大学(北京),北京  100083;烟台大学光电信息科学技术学院,烟台  264005
Published: December 2020

We used a time-dependant Ginzburg-Landau modified model to calculate the model under pressure. We obtained some expressions for the relation between the external pressure and the temperature of superconductivity. In some special cases, the critical temperature decreases with applied pressure. In some other cases, the critical temperature increases with applied pressure.
Magnetic transition and conducting behavior of the Cu-doped LaMn1－xCuxO3 system
Authors: Gao Tian  , Cao Shi-Xun  , Li Wen-Juan  , Kang Bao-Juan  , Yuan Shu-Juan  , Zhang Jin-Cang  ,   上海大学物理系,上海  200444
Published: December 2020

The magnetic transition and conducting behaviors of LaMn1-xCuxO3 (x=0.05, 0.1, 0.2, 0.3, 0.4) system have been systematically studied. The results show that very small amount of Cu-doping (x=0.05) into the anti-ferromagnetic LaMnO3 matrix induces strong ferromagnetic transition below about 157K. The Curie temperature decreases gradually with the increase of Cu-doping content, while the magnetization increases firstly and then decreases. In accordance with the magnetic properties, the electrical resistivity decreases at low dopant (x≤0.10) and then increases with the increase of Cu-doping content. All samples exhibit insulating conducting behavior in the whole temperature range: from a paramagnetic insulator to a ferromagnetic insulator. The conducting behavior of lower doped samples (x≤0.10) is well fitted by the Mott Variable Range Hopping (VRH) model,and then favors to the thermoactivation model when 0.10≤x≤0.40. With the increase of Cu-doping content, the influence of Cu ions on the double exchange interaction among the Mn-O-Mn chains and the magnetic structure results in that the eg electron transport obeys the domination of potential barrier in the VRH model at lower doping and then favors the domination of energy gap in the thermal activation model at higher doping contents.
Influence of irradiation dose on free volume and microstructure of SB biblock copolymer study by PALS and FT-IR
Authors: Jiang Zhong-Ying  , Yu Wei-Zhong  , Zhao Yong-Fu  , Jiang Xi-Qun  , Xia Yuan-Fu  ,   (1)江苏农科院原子能所，南京  210014; (2)南京大学化工学院高分子科学与工程系，南京  210093; (3)南京大学物理系，南京  210093; (4)南京大学物理系，南京  210093;伊犁师范学院物理系，伊宁  835000; (5)清华大学物理系，北京  100084
Published: December 2020

Positron annihilation lifetime spectroscopy and Fourier transform Infrared spectrometer were used to study the effect of γ irradiation dose on free volume and microstructure of polystyrene-block-butadiene diblock copolymer, respectively. Based on the free volume classic model of Eldrup and examonation of the correlation between their results, the model of γ irradiation effect on cross-linking and degradation of SB is established. Thermal gravity analysis was used to study thermal stability of SB at various irradiation doses to reveal the relationship between thermal stability and micro-structure changes.
Diamond-like carbon (DLC) films deposited on copper substrate through preparation of intermediate layers
Authors: Wang Jing  , Liu Gui-Chang  , Ji Da-Peng  , Xu Jun  , Deng Xin-Lu  ,   (1)大连理工大学化工学院，大连  116012; (2)大连理工大学三束改性国家重点实验室，大连  116012
Published: December 2020

Diamond-like carbon (DLC) films were prepared on copper substrate through preparation of intermediate layers by combined plasma enhanced sputtering physical vapor deposition and microwave electron cyclotron resonance plasma enhanced chemical vapor deposition techniques. Raman spectroscopy indicated that the films had amorphous structure and typical characteristic of DLC film. With the increase of deposition bias voltage, D and G band both shifted to high wave-number and ID/IG increased gradually. The morphology was characterized by atomic force microscopy (AFM) and the results indicated that the films were dense and homogeneous , and the roughness of the films decreased with the increase of the deposition bias voltage. Hardness and modulus of DLC were measured by the nanoindentation.
Radiative energy flux of diffusive supersonic wave in a cylinder
Authors: Lan Ke  , He Xian-Tu  , Lai Dong-Xian  , Li Shuang-Gui  ,   北京应用物理与计算数学研究所，北京  100088
Published: December 2020

The calculation of radiative energy flux is very important in the study of diffusive supersonic wave transfer when the radiative thermal conduction approximation is used. In this paper, a formula of radial position-dependent spectral energy flux is given for the diffusive supersonic wave in a low density filled cylinder with a high density wall. A geometrical factor is defined to describe the influence of the radial size of the cylinder on the radiative energy flux. From the formula, the geometrical factor decreases with the radial position from center to edge, due to the much shorter mean free path in the wall than in the fill. This is another important reason in causing a significant curvature in the radiation front, which was observed in recent diffusive supersonic wave experiments. In addition, expressions for calculating the averaged spectral energy flux over the cylinder cross-section and the energy flux in local thermal equalibrium are given. The geometrical factor in the expression of the averaged spectral energy flux is compared with the conventional geometrical factor obtained via geometrical free path which people usually used in their simulation. Finally, to make the simulation easy, approximate expressions are given for the geometrical factors.
The scale-free feature and evolving model of large-scale software systems
Authors: Yan Dong  , Qi Guo-Ning  ,   浙江大学现代制造工程研究所，杭州  310027
Published: December 2020

In software engineering, class diagrams are generally used to describe the relationship of classes. Software systems as networks are studied in this paper. By the demonstration and analysis of the large-scale software systems provided by Sun and IBM, it is found that the degree distribution of software systems written in Java is characterized by the scale-free distribution, and its scaling exponent γ is about 2.5. In the evolving process of software systems, in addition to addition of nodes, there are some other local events as follows: addition of edges, random removal of edges and rewiring edges. The evolving model of software systems is established consequently. As for the network generated by this model, its degree distribution follows the power-law distribution. The actual application and numerical simulations validate this model.
Soliton solutions for variable coefficient nonlinear Schr?dinger equation for optical fiber and their application
Authors: Zong Feng-De  , Dai Chao-Qing  , Yang Qin  , Zhang Jie-Fang  ,   浙江师范大学非线性物理研究所,金华  321004
Published: December 2020

In this paper, the general variable coefficient nonlinear Schrdinger equation for the optical fiber is investigated based on the extended cubic nonlinear Klein-Gordon equation. The soliton solutions under non-chirp case are discussed, and some new exact solutions, including the bright soliton, the dark soliton and the soliton-like solution are obtained. The standard nonlinear Schrdinger equation and four kinds of the variable coefficient nonlinear Schrdinger equation are all corresponding special cases. In addition, some interesting results for the optical fiber system with periodic gain or loss are also obtained.
Concurrence of the mixed state of two non-orthogonal pure states
Authors: Di Yao-Min  , Hu Bao-Lin  , Liu Dong-Dong  , Yan Shi-Ming  ,   徐州师范大学物理系，徐州  221116
Published: December 2020

In this article an obvious expression of concurrence of the mixed state of two non-orthogonal pure states in two qubits is derived. The result reveals that the expression of concurrence of the mixed state of two orthogonal states can be directly generalized to the case of the mixed state of two non-orthogonal states. Then the maximally entangled states mixed by two pure states and the concurrences in some important special cases are discussed.
The synchronization condition of linearly coupled chaotic system
Authors: Liu Zhen-Ze  , Tian Yan-Tao  , Song Yan  ,   吉林大学通信工程学院，长春  130025
Published: December 2020

We describe the problem of chaos synchronization with rigorous mathematical theory, and convert it to the analysis of stability of the differential equations. Chen's system, which belongs to the Lorenz's group, has been introduced as a typical system for discussing the stability of the linear coupled chaotic systems. A theorem on the sufficient conditions for attaining the chaotic synchronization has been proposed and a detailed proot is given. Using the conditions discussed above, a method of identifying the coupled parameter is also developed. Eventually, the results of simulation prove the validity of the theorem, and demonstrate the synchronization phenomenon of coupled systems in different ways and for different systems.
The bifurcation diagram of a wavelet function
Authors: Yu Wan-Bo  , Wei Xiao-Peng  ,   大连理工大学机械工程学院，大连  116024;大连大学信息科学与工程辽宁省重点实验室,大连  116622
Published: December 2020

The bifurcation diagram of a wavelet function is discussed in the paper. The chaotic property of the map is changed with the variations of the constant k. Its μ-y diagram shows specially that there are bifurcations not only from period-2n to chaotic state but also from the chaotic state to period-2n when the parameter μ increases. The Lyapunov exponent diagram of the maps and one of the graphical iteration plot for the map are drawn. The wavelet function is also expanded with polynomial approximation in order to analyze the chaotic process.
Dynamical properties of discontinuous and noninvertible two-dimensional map
Authors: Dai Jun  , Chu Xiang-Sheng  , He Da-Ren  ,   (1)江苏科技大学数理学院，镇江  212003;扬州大学物理科学与技术学院，扬州  225002; (2)扬州大学物理科学与技术学院，扬州  225002
Published: December 2020

This paper reports five different features in piecewise continuous and noninvertible system described by two conservative maps or one conservative map and another dissipative map. The features are as follows: the stochastic web bounded by images of discontinuous borderline is the only chaotic trajectory; phase collapse is caused by the irreversibility which makes some points to have two pre-images; fat fractal forbidden web induced by irreversibility; riddled-like attraction basin in stochastic web and forbidden web, when there are different attractors coexisting; and the impossibility to tell to which attractor an initial condition will approach. In an integrate-and-fire circuit, we find that the features still exist in the circuit system described by two dissipative maps, so they are common features in discontinuous and noninvertible maps.
Interacting herding model: memory and oblivion
Authors: Dong Lin-Rong  ,   温州大学教育科学学院,温州  325035
Published: December 2020

The interacting herding model only includes the affects of the last activity and ignores all the activities before. In real market, agents have a long-range time memory about the past activities which affects actually the current one. But, due to oblivion, the past activities have different influences on the current one depending on the time line. In the paper, a long-range memory is introduced to the interacting herding model in which the past activities affect the current one with exponential decay which reflects the fact that agents have a long-range time memory and mislay along with time about the past activities. The numerical calculation shows that its dynamics behaviors exhibit some characteristics more close to the real markets and can include the previous model as a limit case.
Investigation of conformation transition of poly(N-isopropylacrylamide) by surface stress detection using micro-cantilever
Authors: Li Kai  , Liu Hong  , Zhang Qing-Chuan  , Hou Yi  , Zhang Guang-Zhao  , Wu Xiao-Ping  ,   (1)中国科学技术大学化学物理系，合肥  230026; (2)中国科学技术大学中国科学院材料力学行为和设计重点实验室，合肥  230027
Published: December 2020

A new method based on micro-cantilever sensors was presented and used to investigate conformation transition of macromolecules. Poly(N-isopropylacrylamide)(PNIPAM)were grafted onto one surface of a micro-cantilever by self assemble monolayer method. Then the micro-cantilever was immersed into distilled water in which the temperature can be adjusted in the range of 20—40℃. The deflection of the micro-cantilever induced by conformation transition of PNIPAM chains was measured using optical lever technique. The results show that the micro-cantilever deflects upon heating and opposite deflection occurs upon cooling, which indicates that the surface stress of the micro-cantilever changes when the conformation of PNIPAM changes upon heating and cooling. The surface stress changes continuously over the range of 20—40℃. However, a sharp change appears around the low critical solution temperature (～32℃), at which a coil-globule transition occurs in free aqueous solution of PNIPAM. The whole process is irreversible and shows a clear hysteresis, which can be attributed to hydrogen bonding and the possible chain entanglement formed during the collapse process.
General theory of nonlinear beam-wave interaction in traveling-wave tubes
Authors: Li Jian-Qing  , Mo Yuan-Long  ,   电子科技大学物理电子学院，成都  610054
Published: December 2020

Using the theory of waveguide excited, the full three-dimensional self-consistent working equations of interaction between slow electromagnetic traveling wave and electronic beam have are obtained in traveling-wave tubes, considering multi-signal inputs and relativistic effect. The equations include excited equation, motion equations, energy conversion equation, phase evolving equation etc., which can be applied to simulate most of nonlinear interactions between slow electromagnetic traveling wave and electronic beam in traveling wave tubes (TWT). The crossmodulation in a wide-band helix TWT is simulated using this theory, and is compared with the experimentation results to confirm the theory. The nonlinear beam-wave interaction processes in a relativistic disk-loaded waveguide TWT are also been simulated using the theory.
Threshold and saturation properties of two-dimensional random lasers and mode selection
Authors: Liu Jin-Song  , Liu Hai  , Wang Chun  , Lü Jian-Tao  , Fan Ting  , Wang Xiao-Dong  ,   华中科技大学激光技术国家重点实验室，武汉  430074
Published: December 2020

Based on the time dependent theory of random lasers, which was established via combining Maxwell equations with the rate equations of a four-level atomic system, the output intensity of lasing modes varying with the pump rate and area as well as the medium's size and shape is simulated for two-dimensional random media by use of the finite difference time domain method. Results show that the pump-rate dependence of the output intensity presents not only a threshold property, but also a saturation property, just like that of the lasing modes in conventional lasers. Based on the dependence of mode property on the medium's and pump's parameters, the mode-selection approaches are proposed for two-dimensional random lasers, which are quite different from those performed in conventional lasers.
A semiconductor nanocrystal PbSe quantum dot fiber amplifier
Authors: Cheng Cheng  , Zhang Hang  ,   浙江工业大学应用物理系，杭州  310023
Published: December 2020

A novel kind of fiber amplifier——quantum dot doped fiber amplifier (QDFA) is presented. Using semiconductor nanocrystal PbSe as a dopant, the gain bandwidths of the PbSe-QDFA are simulated by solving the rate equation and the light propagation equation in a two-level system, applying a genetic algorithm combined with an “inversing method”. Comparing with conventional erbium-doped fiber amplifiers available, there is evidence to show that characteristics of the PbSe-QDFA are obviously advantageous in respect of bandwidth and noise, especially on long-waelength band. Furthermore, the ideal emission-absorption cross-sections of the quantum dot are determined by utilizing the genetic algorithm. Under such ideal cross-sections, the QDFA possesses with the performance of ultra-bandwidth and low noise figure near a quantum limit.
Electromagnetically induced absorption in four-level atomic system
Authors: Wang Li  , Song Hai-Zhen  ,   南阳师范学院物理系,南阳  473061
Published: December 2020

A four-level atomic system is employed as an example, in which three transitions are in N configuration and the middle transition is used as a probe transition. We show that electromagnetically induced absorption and electromagnetically induced transparency can appear in the four-level N-type atomic system, which are dependent not only on the spontaneous transfer of atomic coherence, but also on the relaxation of the fourth level, the Rabi frequency of the coupling and the control field.
Spectroscopic characteristics of Cr4+ in transparent polycrystalline Al2O3
Authors: Yang Qiu-Hong  , Zeng Zhi-Jiang  , Xu Jun  , Ding Jun  , Su Liang-Bi  ,   (1)上海大学材料科学与工程学院，上海  200072; (2)中国科学院上海光学精密机械研究所，上海  201800
Published: December 2020

Transparent polycrystalline Cr:Al2O3 ceramics were synthesized by conventional pressureless synthesis processing. The absorption and emission spectra of Cr:Al2O3 ceramics specimens before and after annealing were measured at room temperature. It was discovered that the emission spectra of Cr4+ in Al2O3 octahedral coordination site is in infrared wavelength range of 1100—1600nm. The emission peak of Cr4+ is centered at 1223nm, which is similar to that of Cr4+ in tetrahedral site. Al2O3 has smaller lattice constant, resulting in the larger crystal field strength, so there is a blue shift in the peak of Cr4+:Al2O3 ceramics compared to those of other Cr4+-doped crystals. And the emission band is much narrower with full width at half maximum Δλ 37nm.
Hydrogen storage mechanism of multiwalled carbon nanotube bundles studied by X-ray absorption spectra
Authors: Tang Yuan-Hong  , Lin Liang-Wu  , Guo Chi  ,   湖南大学材料科学与工程学院，长沙  410082
Published: December 2020

Multiwalled carbon nanotube bundles have been investigated with the near-edge X-ray absorption fine structure (NEXAFS) spectra. In the angle-dependent NEXAFS spectra of multiwalled carbon nanotube bundles, a change of the intensity of the C—H σ* with the synchrotron radiation light incident angle has been observed. The presence of the C—H bond at room temperature and ambient pressure may be related to the defects in the carbon nanotubes. Neither the C—C π* nor the C—C σ* is similar to the C—H σ*, which strongly suggests that the hydrogen atoms are adsorbed on the defects on the interior surface of the wall of carbon nanotubes at room temperature and ambient pressure. These results indicate that NEXAFS spectrum is a powerful tool for the investigation of multiwalled carbon nanotube bundles.
Temperature dependence of dynamic yield strength and spall strength for LY12 aluminum alloy under shock loading
Authors: Wang Yong-Gang  , Chen Deng-Ping  , He Hong-Liang  , Wang Li-Li  , Jing Fu-Qian  ,   (1)宁波大学工学院，宁波  315211;中国工程物理研究院流体物理研究所，绵阳  621900; (2)中国工程物理研究院流体物理研究所，绵阳  621900
Published: December 2020

A velocity interferometer system for use with an arbitrary reflector was used to measure the free surface velocity history of LY12 aluminum alloy in a wide range of pre-heating from the room temperature approaching to the melting point, and the dependences of dynamic yield strength and spall strength on the initial sample temperature have been investigated. Experimental results indicate that the dynamic yield strength decreases rapidly with the heating temperature, and only 15% of the initial strength at room temperature is retained when heated up to 847K (86K lower than the melting temperature). The measured yield strength has been compared with the Zerilli-Armstrong (ZA) model and Steinberg-Cochran-Guinan (SCG) model calculation, which points out that the ZA model could describe the dependence of the yield strength on temperature well and the SCG model has overestimated the dynamic yield strength at high temperature significantly. Decrease of the spall strength with the increase of heating temperature for LY12 aluminum alloy was observed also, and nearly 80% loss of spall strength was determined in the present experimental temperature range of 296—847 K. An empirical formula has been proposed to normalize the dependence of spall strength on the heating temperature, and it gives a fairly good fitting for a number of aluminum based materials, including pure aluminum, aluminum alloy and single crystal aluminum, measured in this work and by others in the literature.
Surface growth mechanism of cubic boron nitride thin films prepared by plasma-enhanced chemical vapor deposition
Authors: Yang Hang-Sheng  ,   浙江大学材料与化学工程学院，杭州  310027
Published: December 2020

Chemical species in the low-pressure inductively coupled plasma for cubic boron nitride (cBN) film deposition using B2H6, N2, He and Ar as reactant gases were investigated by quadrupole mass spectrometry. B2H6 was found to be ionized totally, while N2 was only partially ionized. The species in plasma were Ar, He, N2 molecules and Ar+, He+, N+, N+2, B+, BxH+y, H+ and H+2 ions, no H and N radical was detected by appearance potential mass spectrometry. The introduction of H2 and N2 gases into the deposition system was found to produce a large mount of H radicals and excited N*2 molecules, which suppressed the cBN formation by reacting with the growth surface. The etching and sputtering of cBN and turbostraotic boron nitrde (tBN) by H2 and Ar plasmas were also evaluated, and we did not find that the tBN is selectively etched or sputtered. Moreover, high-resolution transmission electron microscopy of as-deposited cBN on the edge of ultrathin silicon flake substrate showed that the surface of as-deposited cBN film was composed of cBN {111} nanofacets, and no thin sp2-bonded boron nitride surface layer was observed. Our results suggest that cBN nucleates and then grows on the top surface in chemical vapor deposition systems, and the processes of cBN surface nucleation and growth in the present system was also discussed simply.
Visualization of domain inversion region characteristics in RuO2:LiNbO3 crystal by digital holographic interferometry
Authors: Qu Wei-Juan  , Liu De-An  , Zhi Ya-Nan  , Luan Zhu  , Liu Li-Ren  ,   (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  100049
Published: December 2020

In order to obtain the two dimensional distribution of the refractive index changes due to the domain inversion in the RuO2:LiNbO3 crystal, we make use of the Mach-Zehnder interferometer and 4f optical lens system to record holograms, with the object light transmitting through the poled RuO2:LiNbO3 crystal, and then filter the spectrum in the frequency domain to get the object light spectrum for numerically reconstructing the object wavefront. The results confirm that the electro-chromic effect region well coincides with the domain inversion region in RuO2:LiNbO3 crystal. Digital holographic interferometry has the merits of being nondestructive and it provides a prospective way to in-situ visualization, monitoring and analysis of the domain inversion in LiNbO3 crystal.
Magnetic polarization currents in parallel-coupled double-quantum-dot devices
Authors: Chen Xiong-Wen  , He Da-Jiang  , Wu Shao-Quan  , Song Ke-Hui  ,   (1)怀化学院物理与电子信息科学系,怀化  418008;怀化学院信息科学研究所,怀化  418008; (2)四川师范大学物理系，成都  610068
Published: December 2020

We theoretically study the properties of the magnetic polarization currents (MPC) in parallel-coupled double-quantum-dot devices by means of the two-impurity Anderson Hamiltonian and Green functions. It is shown that at zero temperature, the Kondo effect of the system becomes weaker with the increase of the coupling strength. At low temperature, by varying some conditions such as temperature and bias voltage, the direction and magnitude of MPC can be changed, which implies that the magnetic states of the device can be mode up-, non- or down-polarized.
Effects of Ce3+ ions on the spectroscopic properties of fluorophosphate glasses codoped with Er3+/Yb3+
Authors: Li Tao  , Zhang Qin-Yuan  , Jiang Zhong-Hong  ,   (1)华南理工大学光通信材料研究所，特种功能材料制备新技术教育部重点实验室，广州  510640; (2)华南理工大学光通信材料研究所，特种功能材料制备新技术教育部重点实验室，广州  510640;华南农业大学理学院，广州  510640
Published: December 2020

This paper reports on the influence of energy acceptors Ce3+ ions on the upconversion and 1.5μm emission properties of fluorophosphate glasses codoped with Er3+/Yb3+. The energy transfer mechanism has been discussed based on the energy matching and the energy level. The Ce3+ ions are excited from the 2F5/2 level to the 2F7/2 level due to the non-radiatively energy transfer process of the Er3+ ions from the 4I11/2 level to the 4I13/2 level. The upconversion luminescence intensities of the Er3+ are decreased quite significantly owing to this energy transfer process. Meanwhile, the luminescence intensities, peak stimulated emission cross sections, and lifetimes of the 4I13/2 level of Er3+/Yb3+-codoped fluorophosphate glasses increase largely with the introduction of the Ce3+ ions at the proper concentration of 1.11×1020cm-3.
Effect of Y co-doping on the photoluminescence and lifetime of Er3+ in silicate glasses
Authors: Miao Zhuang  , Li Shan-Feng  , Zhang Qing-Yu  ,   大连理工大学三束材料改性国家重点实验室，大连  116023
Published: December 2020

0.5at% and 1.0at% Er/Y co-doped silicate glasses with different Y2O3 concen trations were fabricated by means of high-temperature solid-state reaction, with the Y concentration varying from 0.0at%—2.5at% and 0.0at%—5.0at%, respectively. By measuring the absorption spectra, the photoluminescence (PL) and PL decay, we studied the dependence of absorption and emission cross-section at 1530nm and the lifetime and PL features on Y concentration. The results showed that Y co-doping enabled the absorption peak to widen and enhanced the absorption. The lifetime was prolonged considerably, especially for the highly Er-doped silicate glasses. However, considerable enhancement of PL intensity was not detected when the glasses were excited by a 980nm laser.
Preparation and upconversion emission of nanocrystalline ZrO2:Er3+-Yb3+
Authors: Yu Ying  , Lü Shu-Chen  , Zhou Bai-Bin  , Xin Xian-Shuang  ,   哈尔滨师范大学材料物理与化学黑龙江省重点实验室,哈尔滨  150080
Published: December 2020

Er3+, Yb3+ codoped ZrO2 nanocrystalline powders were prepared by chemical co-precipitation. We determined the crystal structures and the room temperature upconversion emission properties of samples with different doping concentrations of Yb3+ and at different sintering temperatures, respectively. It is shown that the monoclinic phase increases with the sintering temperature and the tetragonal phase increases with the increasing of Yb3+ concentration. We found that the green emission intensity and the red emission intensity of the samples sintered at 800℃ were enhanced with the increasing of Yb3+ concentration, but the red emission intensity increased much more. The quadratic dependence of the green and the red emissions on excitation power indicates that a two-photon absorption process occurs under 976nm excitation. The infrared emission properties were also discussed in the present paper.
Photoacoustic tomography imaging based on an acoustic lens imaging system
Authors: Chen Zhan-Xu  , Tang Zhi-Lie  , Wan Wei  , He Yong-Heng  ,   (1)华南师范大学物理与电信工程学院,广州  510631; (2)华南师范大学信息光电子科技学院，广州  510631
Published: December 2020

Photoacoustic tomography is a new type of medical imaging technology based on the measurement of laser-induced ultrasonic waves. It can detect the light absorption distribution of the target hidden inside optically turbid or opaque tissues. When a short laser pulse illuminates the scattering medium, such as biological tissue, the scattering media will generate ultrasound signals which are linearly proportional to the optical absorption of the media. The ultrasound signals are imaged with an acoustic lens. According to the imaging principle of lens, the photoacoustic signals from a plane in scattering media require the same delay time to reach the image plane, and the signals from different planes require different delay time to reach the same detecting plane. A BOXCAR was used to hold on the same delay-time, and a 64-element linear transducer array was one-dimensionally scanned on an imaging plane to acquire the acoustic pressure distribution, and the signals were recorded and reconstructed by a computer. By scanning the sampling gate of BOXCAR, the photoacoustic images of different planes in the media can be obtained. We experimentally obtained photoacoustic tomography images on different planes of the scattering media successfully. The images are vivid and contrast clearly with the background. This method directly provides images of absorbing structures without the need of computational reconstruction.
Sol-gel processing of ZrO2 and polymer doped-ZrO2 monolayer reflective films with high laser damage threshold
Authors: Liang Li-Ping  , Xu Yao  , Zhang Lei  , Wu Dong  , Sun Yu-Han  , Li Zhi-Hong  , Wu Zhong-Hua  ,   (1)中国科学院高能物理研究所,北京  100049; (2)中国科学院山西煤炭化学研究所煤转化国家重点实验室,太原  030001; (3)中国科学院山西煤炭化学研究所煤转化国家重点实验室,太原  030001；太原科技大学材料科学与工程学院,太原  030024；中国科学院研究生院,北京  100049; (4)中国科学院山西煤炭化学研究所煤转化国家重点实验室,太原  030001；中国科学院研究生院,北京  100049;中国工程物理研究院激光聚变研究中心，绵阳  621900
Published: December 2020

A series of ZrO2 and polymer doped-ZrO2 sols have been synthesized by the controlled hydrolysis of zirconium n-propoxide. Acetic acid was used as the chelating agent. Poly(ethylene glycol)(PEG) 200 and polyvinylpyrrolidone(PVP) were introduced to produce the hybrid sols. ZrO2 and the polymer doped-ZrO2 optical thin films were then prepared by spin-coating the stable sols on K9 glass substrates. Effects of various synthetic parameters were studied, on the sol stability, the microstructure of colloidal system, the structural and optical properties of the films, as well as the laser damage resistance. In our reaction systems, both hydrolysis and chelation coexist. The preference for any of the two reactions strongly depends on the system composition and ultimately determines the stability and microstructure of the colloidal system. Besides, the addition of a proper amount of PEG200 and PVP, which probably acts as the competitive ligands, particle surface protective polymers and structure directive agents, can modify the hydrolysis-condensation process, thus producing more stable, uniform sols with mass fractal structure (fm=2.33—2.46) and average particle diameter of 19.1—23.7nm. Benefiting from the precursor sol structure, the polymer doped-films exhibit excellent surface planarity and uniform inner structure, which endows the films with good optical property and excellent laser damage resistance. For instance, the hybrid film with 10% PEG200 and 15% PVP (mass fractions) showed a high laser damage threshold of 24.5J/cm2 (for 1ns pulse duration) and a reflectivity increase of about 2% than that of the substrate at wavelength of about 1000nm.
A new method of dynamical analogue prediction based on multi-reference-state updating and its application
Authors: Ren Hong-Li  , Zhang Pei-Qun  , Li Wei-Jing  , Chou Ji-Fan  ,   (1)国家气候中心中国气象局气候研究开放实验室，北京  100081; (2)兰州大学大气科学学院，兰州  730000; (3)兰州大学大气科学学院，兰州  730000；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 multi-reference-state updating (MRSU) pertaining to the dynamical analogue prediction, is developed on the basis of previous studies on analogue-dynamical models, in order to further effectively utilize the available information of historical observation data. In this scheme, according to a new idea of “updating", it is required that multi-reference states are renewedly selected on the period of analogue updating in the process of the analogue-dynamical model integration, and optimal forecast vectors are estimated from multi-forecasts produced by analogue-dynamical model by employing the hyperplane approximation method. Such “selection-estimation" cycles are repeatedly operated until the whole forecasts are completed. Furthermore, the simplified MRSU is applied to the T63 global spectral model, and the results of monthly forecast experiments show that for the daily and monthly mean circulation, the MRSU can effectively reduce forecast errors and improve forecast skill compared with the control forecasts.
Keyed one-way Hash function construction based on the chaotic dynamic S-Box
Authors: Guo Xian-Feng  , Zhang Jia-Shu  ,   (1)西南交通大学信号与信息处理四川省重点实验室，成都  610031; (2)西南交通大学信号与信息处理四川省重点实验室，成都  610031;西南民族大学计算机科学与技术学院，成都  610041
Published: December 2020

This paper presents a novel keyed one-way Hash function based on a chaotic dynamic S-Box together with traditional one-way Hash function construction. The proposed approach can give a chaotic Hash value by means of the look up table of functions and chaotic dynamic S-Box. Compared with the existing chaotic Hash functions, this method improves computational performance of Hash system by using the chaotic dynamical S-Box substitution in place of iterating the original message directly in chaos system. Theoretical and experimental results show that the proposed method has strong one way property, large key space, sensitivity to initial conditions and chaotic system's parameters.
A novel chaotic system via combining a unified system with R?ssler system
Authors: Gao Bing-Jian  , Lu Jun-An  , Chen Ai-Min  ,   (1)武汉大学数学与统计学院,武汉  430072; (2)武汉大学数学与统计学院,武汉  430072;武汉理工大学理学院,武汉  430070
Published: December 2020

This brief paper designs a novel chaotic system via convex-combining a unified system with Rssler system. The combined system includes a Unified-Rssler system with double parameters, a Lorenz-Rssler system and a Chen-Rssler system with single parameter. The chaotic intervals in Chen-Rssler system are determined by calculating maximum Lyapunov exponent spectrum and numerical simulation.
Study on fractal coagulation characteristics of fire smoke particles
Authors: Shu Xue-Ming  , Fang Jun  , Shen Shi-Fei  , Liu Yong-Jin  , Yuan Hong-Yong  , Fan Wei-Cheng  ,   (1)清华大学工程物理系，公共安全研究中心，北京  100084; (2)清华大学工程物理系，公共安全研究中心，北京  100084;中国科学技术大学火灾科学国家重点实验室，合肥  230026; (3)中国科学技术大学火灾科学国家重点实验室，合肥  230026
Published: December 2020

Primary particles produced in the early fire period evolve into bigger aggregates due to Brown coagulation, which take on fractal properties. In this article, smoke particle images were obtained by a field emission scanning electron microscope (SEM), and the fractal characteristics of the particles were analyzed based on the power law of fractal theory. By using digital image processing technique, more fractal parameters such as the fractal dimension, fractal prefactor, primary particles' size and radius of gyration were obtained. The results can provide a fundamental basis for fire smoke detection research.
Effect of external field on the fidelity of quantum states in the two-atom Tavis-Cummings model
Authors: Wang Zhong-Chun  ,   盐城师范学院物理系,盐城  224002
Published: December 2020

The fidelities of quantum states in the two-atom Tavis-Cummings model where the atoms are driven by an external classical field are derived. The influence of the external field and the dipole-dipole interaction of the atoms in a special initial state on the fidelity is discussd.