bluuebunny/crossref_metadata_2025 huggingface dataset:
First-principle molecular dynamics study of clusters:optimum valence bond scheme
Authors: Yuan Zhe  , He Chun-Long  , Wang Xiao-Lu  , Liu Hai-Tao  , Li Jia-Ming  ,   (1)清华大学物理系原子分子纳米科学研究中心,北京  100084; (2)上海交通大学物理系,上海  200230; (3)上海交通大学物理系,上海  200230;清华大学物理系原子分子纳米科学研究中心,北京  100084
Published: December 2020

We present an optimum valence bond scheme to study stable geometric structures of clusters, by combining the characteristics of valence bonds and the first-prin ciple molecular dynamics simulation. With limited computational effort, we can o btain the properties of cluster Xm with m as large as possible, and th e properties of all clusters Xi (i<m), e.g., their stable geometric struct ures, electronic properties, etc. Consequently we can elucidate the evolution la w of clusters. We illustrate the optimum valence bond scheme with the second_row elements. The properties of three-atom clusters interestingly reflect the evolv ement law with atomic number of macroscopic properties of corresponding elements (melting and boiling points).
V type three-level symmetric second-order coherence theory of attosecond polarization beats
Authors: Gan Chen-Li  , Zhang Yan-Peng  , Feng Yu  , Yu Xiao-Jun  , Wang Jie  , Li Chuang-She  , Song Jian-Ping  , Lu Ke-Qing  , Hou Xun  ,   (1)西安交通大学电子科学与技术系,西安  710049; (2)西安交通大学电子科学与技术系,西安  710049;中国科学院西安光学精密机械研究所瞬态光学技术国家重点实验室,西安 710068; (3)西安市农业学校,西安  710077; (4)中国科学院西安光学精密机械研究所瞬态光学技术国家重点实验室,西安 710068
Published: December 2020

Based on the phaseconjugate polarization interference between two onephoton processes, we have studied theoretically the symmetric sumfrequency polarization beat (SFPB) of V type threelevel system in attosecond scale in the case of arbitrary bandwidth or broadband linewidth laser. The homodyne detected SFPB signal is shown to be particularly sensitive to the statistical properties of the Markovian stochastic light fields with arbitrary bandwidth. We have found that the accuracy in the measurement of the energylevel sum of two excited states which are dipolar forbidden transition to each other is determined by the homogeneous linewidths of the optical transitions and exceeds the laser linewidth. A Dopplerfree precision in the measurement of the energylevel sum can be achieved with an arbitrary bandwidth. The field correlation has weakly influence on the SFPB signal when the laser has a narrow bandwidth. When the laser has a broadband linewidth, the SFPB signal shows resonantnonresonant cross correlation. As an attosecond ultrafast modulation process, SFPB can be extended intrinsically to any sumfrequency of energylevels.
Molecular dynamics study on the energy characteristic of copper nanoclusters at room temperature and during heating
Authors: Yang Quan-Wen  , Zhu Ru-Zeng  , Wen Yu-Hua  ,   (1)厦门大学物理系,厦门  361005; (2)中国科学院力学研究所非线性力学国家重点实验室，北京  100080
Published: December 2020

Molecular dynamic method and Finnis Sinclair potential are used to study the e nergy characteristic of copper nanoclusters at room temperature and its changes during heating, by which we get the surface thickness and surface energy in diff erent cluster sizes at room temperature and get the probability density of energ y distribution of the copper nanoclusters at different temperatures. The differe nce of the energy characteristic during heating between the inner atoms and the surface atoms is given in detail.
Influence of heavy-doping with Dy on the magnetic and electrical properties in La0.7Sr0.3MnO3
Authors: Cai Zhi-Rang  , Liu Ning  , Tong Wei  , Zhang Yu-Heng  ,   (1)宿州学院材料研究室，宿州  234000; (2)宿州学院材料研究室，宿州  234000;中国科学技术大学结构分析开放实验室，合肥  230026; (3)中国科学技术大学结构分析开放实验室，合肥  230026
Published: December 2020

The M_T curves, M_H curves, ρＴ curves and MR_T curves of La0.7-xDyxSr0.3MnO3 (x=000，030，040，050，060 and 070) are studied. Experimental results indicate that with increasing do ping concentration of Dy, the system changes from long_range ferromagnetic order to cluster_spin glass state, then to antiferromagnetic state and to subferromag netic state. For x=03, there appears a peak on the M_T curve near T N,however, it disappears at x=04. For x=05, and zero field cooli ng(ZFC) the curve shows a valley, and then a peak at TN; after the 001 T field cooling process, the initial value of M is negative at low temperatur es. For x=060 and 070, their ZFC and FC M_T curves are both similar to the ZFC one of x=050, and the transport properties at heavy doping beco me abnormal under a magnetic background. The peculiar phenomena shown above can be interpreted in terms of the Nel's double_lattice model combined with the re sultsof M_H hysteresis at the characteristic temperatures.
Fabrication of NiFe2O4 nanowire arrays and its magnetic properties
Authors: Yu Dong-Liang  , Du You-Wei  ,   (1)南京大学物理系,固体微结构国家重点实验室,南京  210093; (2)南京大学物理系,固体微结构国家重点实验室,南京  210093;江苏教育学院物理系,南京  210013
Published: December 2020

Arrays of NiFe2O4 nanowires were prepared by using porous anodic al uminum oxide(AAO) membrane as the template. For the preparation of the ferrite n anowires, Ni_Fe alloy nanowires were electrodeposited into the pores of the AAO membranes. The atomic ratio is about Ni∶Fe=1∶2 which can be detected by engerg y dispersive spectroscopy. X-ray diffraction study showed the pure phase of NiFe 2O4 after anodization. SEM and TEM studies showed the diameters of t he pores and the nanowires are all about 70nm. The vibrating sample magnetometer studies of the nanowire arrays showed the anisotropic magnetic properties befor e and after anodization. Coercivity and squareness ratio have been improved appa rently in the NiFe2O4 nanowires arrays.
Frequency and temperature dependence of the hysteresis loop in PMnN-PZT ceramics
Authors: Li Bao-Shan  , Zhu  Zhi-Gang  , Li Guo-Rong  , Yin Qing-Rui  , Ding Ai-Li  ,   中国科学院上海硅酸盐研究所高性能陶瓷和超微结构国家重点实验室，上海  200050
Published: December 2020

The frequency and temperature dependence of the hysteresis loops in Pb［(Zr0 52Ti048)095(Mn1/3Nb2/3)005］O3 (PM nN_PZT) ceramics have been investigated. It has been demonstrated that the polar ization_field hysteresis curves show “pinched" shapes instead of the normal squ are_like P_E loops when tested at room temperature or higher frequency. While at 200℃ or lower frequency, normal square_like loops are observed. In the meantim e, important ferroelectric features such as coercive field, polarization and int ernal bias field are strongly frequency or temperature dependent. High increase of the remnant polarization (Pr) reveals that there may be defect dipo les that induce the unsaturated hysteresis loop. The close relations between the P_E loops and the applied frequencies or temperatures indicate that there exist s a typical relaxation time associated with reorientation of the defect dipoles.
Electron-spin polarization and its relaxation probed by femtosecond laser absorption
Authors: Lai Tian-Shu  , Liu Lu-Ning  , Lei Liang  , Shou Qian  , Li Xi-Ying  , Wang Jia-Hui  , Lin Wei-Zhu  ,   中山大学光电材料与技术国家重点实验室，物理系，广州  510275
Published: December 2020

Based on the rate equations of a two_level system, the analytical solutions of r elaxation of carrier populations with spin_up and spin_down polarization are obt ained under the condition of incomplete initial spin polarization. In the small signal regime, the saturated absorption_change expression of right_ and left_cir cularly polarized probe beam is given. The parameter, initial degree of spin pol arization of electron population, appears in the expression. Therefore, the init ial degree of spin polarization of electron population, which is a very importan t key parameter in the transport of spin polarization, can be extracted by fitti ng the expression to the saturated absorption trace obtained experimentally. Fin ally, the initial degree of spin polarization of photo_injected electron populat ion and its relaxation time constant in GaAs/AlGaAs multiple quantum wells are a cquired in experiments.
Molecular dynamics simulation on the out-of plane thermal conductivity of argon crystal thin films
Authors: Wu Guo-Qiang  , Kong Xian-Ren  , Sun Zhao-Wei  , Wang Ya-Hui  ,   哈尔滨工业大学卫星技术研究所，哈尔滨  150001
Published: December 2020

Part of results of research on satellite heat control under the Harvest Project of the National 973 Program is reported.In accordance with the “minimized nucleus” requirement of the satellite,the thermal conductivity of the dielectric FCC argon-crystal nano-film in the normal direction is predicted using the equilibrium molecular dynamic (EMD) and non-equilibrium molecular dynamic (NEMD) methods. The calculated results are compared with the experimental value of the bulk cryastal.Our calculation shows that the thermal conductivity of the thin films is much lower than that of its bulk conterpart,and the size-effect is significant;it increses nearly linearly with increasing thickness in the thickness range of 2.124—5.310nm.
Structure and potential energy function of CH, NH and OH free radical ground and low-lying states
Authors: Li Quan  , Zhu Zheng-He  ,   (1)四川大学原子分子物理研究所,成都  610065; (2)四川师范大学化学与材料科学学院,成都  610066
Published: December 2020

Structure and properties of the ground states and low-lying excited electronic states of CH, NH and OH radicals are reported in this paper using CCSD(T) method and aug-cc-pVTZ basis set.Their analytic potential energy functions are in good agreement with the Murrell-Sorbie function, and the ground states are X2Π for CH, X3Σ- for NH and X2Π for OH radicals, and the adiabatic excitation energies of a4Σ- and 6Σ- for CH, a1Δ and 5Σ- for NH, a4Σ- and 6Σ- for OH are 0.705, 7.669, 1.895, 3.492, 4.535 and 14.041eV, respectively.
Study on the delayed feedback control of chaos in chaotic neural networks
Authors: He Guo-Guang  , Zhu Ping  , Chen Hong-Ping  , Cao Zhi-Tong  ,   浙江大学物理学系，杭州  310027
Published: December 2020

Chaotic neural networks consisting of chaotic neurons exhibit rich dynamic behaviors and are expected to be used in information processing. But the output sequence of chaotic neural networks is chaotic, so the networks do not converge to a stable pattern. In order to apply chaotic neural networks to information search or pattern recognition, etc., it is necessary to control chaos in chaotic neural networks. In this paper, we propose an improved delayed feedback control method for chaotic neural networks. By means of the control method, computer simulation shows that controlled chaotic neural networks can converge to period-2 states between one stored pattern and its reverse pattern or various multiple-period states depending on the delay time.
Photoionization and dissociative photoionization study of HFC-152a using synchrotron radiation
Authors: Huang Chao-Qun  , Wei Li-Xia  , Yang Bin  , Yang Rui  , Wang Si-Sheng  , Shan Xiao-Bin  , Qi Fei  , Zhang Yun-Wu  , Sheng Liu-Si  , Hao Li-Qing  , Zhou Shi-Kang  , Wang Zhen-Ya  ,   (1)中国科学技术大学国家同步辐射实验室，合肥  230029; (2)中国科学院安徽光学精密机械研究所环境光谱学实验室，合肥  230031
Published: December 2020

Photoionization and dissociative photoionization of HFC-152a have been studied using synchrotron radiation and a reflectron time-of-flight mass spectrometry (RTOF-MS). The ionization energy of parent molecule (11.94±0.04eV) and appearance potentials of various fragment ions have been determined by measuring their photoionization efficiency curves. Energies, symmetry point groups and ground electronic states of neutrals and cations of parent and its fragments have been calculated using GAUSSIAN-03 program with the G3 method. According to the theoretical and experimental results, some dissociation channels and their dissociation energies of CH3CHF+2 have been analyzed.
Relativistic theoretical study on the KLL dielectronic recombination of helium-like ions
Authors: Zhang Deng-Hong  , Dong Chen-Zhong  , Xie Lu-You  , Ding Xiao-Bin  , Fu Yan-Biao  ,   (1)西北师范大学物理与电子工程学院，兰州  730070; (2)西北师范大学物理与电子工程学院，兰州  730070;兰州重离子加速器国家实验室原子核理论研究中心，兰州  730000
Published: December 2020

Based on the multiconfiguration Dirac-Fock method, a new program was developed for the calculation of cross sections of dielectronic recombination (DR). As an example, the decay rates and the corresponding DR cross sections have been systematically calculated for the doubly excited state 1s2l2l′ of C3+, Ar15+, Kr33+ and U89+ ions. For C4+, Ar16+ and Kr34+ ions, a good agreement has been found between the present calculations and the previous theoretical and experimental results; for U90+ ion, the effect of the Breit interation on the DR cross sections has been emphasized especially.
Influence of energy-transfer up-conversion on upper level lifetime of Tm, Ho:YLF Q-switched laser
Authors: Zhang Xin-Lu  , Wang Yue-Zhu  ,   (1)哈尔滨工业大学光电技术研究所可调谐激光国家重点实验室,哈尔滨  150001; (2)哈尔滨工业大学光电技术研究所可调谐激光国家重点实验室,哈尔滨  150001;哈尔滨工程大学理学院,哈尔滨  150001
Published: December 2020

Based the energy transfer between energy levels and the transition between ions of diode-end-pumped Tm,Ho:YLF laser, with consideration of energy transfer up-conversion, the rate equations of Tm,Ho:YLF Q-switched laser are given, and the analytical formulas of single pulse energy is deduced from the rate-equations. It is shown theoretically that the energy transfer up-conversion reduces not only the single pulse energy but also the upper level lifetime of Tm,Ho:YLF Q-switched laser. An experiment is carefully designed to verify these conclusions.
Three dimensional pondermotive scattering of ultrashort electron beam in the field of focused ultraintense laser pulse
Authors: Liu Yun-Quan  , Zhang Jie  , Wu Hui-Chun  , Sheng Zheng-Ming  ,   中国科学院物理研究所光物理重点实验室，北京  100080
Published: December 2020

Using a three-dimensional test particle simulation code, we study the pondermotive scattering of an ultrashort electron beam subject to a focused ultraintense femtosecond laser pulse. The dependence of the spatial distribution of electron beam and electron energy spectrum on the time delay between laser pulse and electron pulse is discussed in detail. Through the measurement of the spatial distribution of electron beam or electron spectrum, we present a method to measure the duration of an ultrashort electron pulse.
Output characteristics of LD end-pumped Nd:YVO4 solid-state laser with flat-flat cavity
Authors: Wu Ding-Er  , Zhou Rui  , Zhang Xiao-Hua  , Ding Xin  , Yao Jian-Quan  , Yan Cai-Fan  , Zhang Guang-Yin  ,   (1)南开大学物理科学院，天津  300071; (2)南开大学物理科学院，天津  300071;中国民航学院理学院，天津  300300; (3)天津大学精仪学院，天津  300072
Published: December 2020

Internal factors (thermal lens,cavity lengths,enabled aperture etc) restricting the output of the LD end-pumped Nd:YVO4 solid-state laser with flat-flat cavity is studied. A reasonable explaination is given and a way of improving the output is pointed out through the graphic analysis of the transmitting and transforming circle.
Spectroscopic characteristics of transparent Yb:Y2－2xLa2xO3 laser ceramics
Authors: Yang Qiu-Hong  , Xu Jun  , Su Liang-Bi  , Zhang Hong-Wei  ,   (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机密机械研究所，上海  201800
Published: December 2020

It was first reported the spectral properties of a low-temperature sintered transparent Yb:Y2-2xLa2xO3 laser ceramics. Yb:Y2-2xLa2xO3 laser ceramics have broad absorption band and large absorption cross-section of 4.0×10-20cm2 at wavelengths 977nm of the highest absorption peak. Its fluorescence lifetime is 1.1ms, and the emission cross-sections are 1.0×10-20cm2 and 0.7×10-20cm2 at wavelengths 1033nm and 1077nm, respectively. All the optical properties are similar to those of single crystals.
Stimulated Brillouin scattering reflection pumped by broadband KrF laser
Authors: Wang Xiao-Hui  , Lü Zhi-Wei  , Lin Dian-Yang  , Wang Chao  , Tang Xiu-Zhang  , Gong Kun  , Shan Yu-Sheng  ,   (1)哈尔滨工业大学光电子技术研究所,哈尔滨  150001; (2)哈尔滨工业大学光电子技术研究所,哈尔滨  150001;国家卫星海洋应用中心，北京  100081; (3)中国原子能科学研究院,北京  102413
Published: December 2020

Stimulated Brillouin scattering (SBS) reflectivity as a function of pump power density, pressure of medium and focal length for broadband KrF laser pump was investigated experimentally. SBS reflectivity increases nonlinearly, approaches to saturation and decreases with the pump power density increasing. The pressure in the medium makes the SBS reflectivity to increase. SBS saturation has a peak value with the focal length from 10cm to 100cm. Broadband multimode SBS model has been built theoretically. Experimental results agree well with the model.
Electroabsorption-modulated laser light-source module using selective area growth for 10 Gb/s transmission
Authors: Zhao Qian  , Pan Jiao-Qing  , Zhang Jing  , Li Bao-Xia  , Zhou Fan  , Wang Bao-Jun  , Wang Lu-Feng  , Bian Jing  , Zhao Ling-Juan  , Wang Wei  ,   中国科学院半导体研究所国家光电子工艺中心,北京  100083
Published: December 2020

In this work, a novel light source of strained InGaAsP/InGaAsP MQW EAM monolithically integrated with DFB laser is fabricated by ultra-low-pressure (22×102Pa) selective area growth (SAG) MOCVD technique. Superior device performances have been obtained, such as low threshold current of 19 mA, output light power of about 7 mW, and over 16 dB extinction ratio at 5 V applied voltage when coupled into a single mode fiber. Over 10 GHz 3 dB bandwidth in EAM part is developed with a driving voltage of 3 V. After the chip is packaged into a 7-pin butterfly compact module, 10-Gb/s NRZ transmission experiments are successfully performed in standard fiber. A clearly-open eye diagram is achieved in the module output with over 8.3 dB dynamic extinction ratio. Power penalty less than 1.5 dB has been obtained after transmission through 53.3 km of standard fiber, which demonstrates that high-speed, low chirp EAM/DFB integrated light source can be obtained by ultra-low-pressure (22×10\+2Pa) SAG method.
Investigation on holographic algorithm and experiment of combined wave superposition approach
Authors: Li Wei-Bing  , Chen Jian  , Bi Chuan-Xing  , Chen Xin-Zhao  ,   合肥工业大学噪声振动工程研究所,合肥  230009
Published: December 2020

The general nerar-field acoustic holography (NAH) cannot reconstruct the surface acoustic information of each coherent acoustic source in coherent acoustic field,which has more than one acoustic sources with the same frequency, and they cannot realize holographic reconstruction and prediction of the independent acoustic field generated by one coherent acoustic source too.So the holographic reconstruction and prediction of coherent acoustic field has become the foremost problem to be resolved in the application of NAH. On the basis of the proposed combined wave superposition approach, an experiment is carried out to realize the holographic reconstruction and prediction of a coherent acoustic filed generated by two sound boxes.By this experiment,the feasibility and accuracy of combined wave superposition approach are demonstrated,the shortcoming of general wave superposition approach in holographic construction and prediction of coherent acoustic field are also demonstrated.The Tikhonov regularization method is proposed to control the ill-posedness of inverse acoustic problem, and the principle of filter coefficient selection is also studied.The experiment indicates that Tikhonov regularization method with appropriate filter coefficient can improve the precision of the holographic reconstruction and prediction.
Temperature distribution of microstructure fiber preform during fiber drawing
Authors: Zhou Gui-Yao  , Hou Zhi-Yun  , Pan Pu-Feng  , Hou Lan-Tian  , Li Shu-Guang  , Han Ying  ,   (1)燕山大学红外光纤与传感研究所,秦皇岛  066004; (2)燕山大学亚稳材料制备技术与科学重点实验室,秦皇岛  066004;燕山大学红外光纤与传感研究所,秦皇岛  066004
Published: December 2020

Drawing temperature is an important factor affecting the structure of microstructure fibers (MSF) during MSF drawing. According to the Fourier equation of time-dependent heat conduction with, original conditions and boundary conditions of MSF preform, the temperature distribution equation of MSF preform is derived in cylindrical coordinates. It is shown the feeding speed of MSF preform is optimal when the temperature distribution of MSF preform is close to the steady-state heat conduction in high temperature furnace, then the temperature of high temperature furnace can be lowered to the intenerate temperature of MSF preform. In addition, the optimal speed will be increased if the air-filling fraction of MSF preform is high.
Study of soft X-ray energy spectra from gas-puff Z-pinch plasma
Authors: Zou Xiao-Bing  , Wang Xin-Xin  , Zhang Gui-Xin  , Han Min  , Luo Cheng-Mu  ,   清华大学电机工程系，电力系统及发电设备安全控制和仿真国家重点实验室，北京  100084
Published: December 2020

A ROSS-FILTER-PIN spectrometer in the spectral range of 0.28keV —1.56keV was developed to study the soft X-ray radiation emitted from gas-puff Z-pinch plasma. It is composed of five channels covering the energy interval of interest without gaps. Soft X-ray spectral energy cuts were determined by the L absorption edges of selected filter elements (K absorption edges being used for light filter elements), and the optimum thickness of filter material was designed using computer code. To minimize the residual sensitivity outside the sensitivity range of each channel, element of the first filter was added into the second filter of all the Ross pair. To diminish the area of each filter, PIN detector with small sensitive area of 1 mm2 was adopted for the spectrometer. A filter with small area is easy to fabricate and would be helpful to withstand the Z-pinch discharge shock wave. With this ROSS-FILTER-PIN spectrometer, the energy spectra of soft X-ray from a small gas-puff Z-pinch were investigated, and the correlation between the soft X-ray yield and the plasma implosion state was also studied.
Electromagnetic performance of plane delamination media with ITO transparent conductive film
Authors: Zhang Wei-Jia  , Wang Tian-Min  , Cui Min  , Rong Ai-Lun  ,   北京航空航天大学理学院，北京  100083
Published: December 2020

Electromagnetic performances of multilayer plane delamination media with an ITO (indium tin oxide) transparent conductive film have been researched theoretically and the calculated curve well agrees with the measured curve.The research shows that the electromagnetic performances of the multilayer media are related to ITO (with sheet resistance 8Ω) film's interface location,the layer number of the plane delamination media and the thickness of the plane delamination media,and so on.An optimized system of four-layer plane delamination mediums with a thickness of only 7.35mm and very large electromagnetic reflectance within the rauge of 8—18GHz has been designed.The sheet resistance of the ITO film in the multilayer plane delamination media should be less than 30Ω,and the smaller the sheet resistance,the langer the electromagnetic reflectance of the multilayer plane delamination media.
New exact solitary wave solutions for nonlinear wave equation with fifth-order strong nonlinear term constructed by hyperbolic function type of auxiliary equation
Authors: Taogetusang  , Sirendaoerji  ,   内蒙古师范大学数学科学学院，呼和浩特  010022
Published: December 2020

Based on the method of auxiliary equation,the paper uses two auxiliary equations with function-transformation and one auxiliary equation of hyperbolic function type to construct an important model in mechanics,which has solutions of new trigonometric function type of wave equation with fifth-order strong nonlinear term and the exact solitary wave solutions of hyperbolic function type, obtained via the symbolic calculation system of Mathematica.The method has general meanings in searching for other new exact solutions to the nonlinear evolution equation with fifth-order strong nonlinear term.
Simulation on heating of plasma in a magnetic field with electrostatic wave
Authors: Sheng Zheng-Mao  , Wang Yong  , Ma Jian  , Zheng Si-Bo  ,   浙江大学物理系，杭州  310027
Published: December 2020

A uniform nonlinear resonant condition for interaction between electrostatic wave and charged particles in a uniform magnetic field is given by multi-scale expansion.It is verified by numerical simulation.It is shown that resonant heating can be produced by electrostatic wave with sub-harmonic frequency of the cyclotron.Moreover,it is shown that the heating efficiency does not increase with the amplitude of driving wave even if for the same frequency,which means there is an optimum combination of frequency and amplitude to get efficient heating.
Comparison of temperature-dependent dielectric characteristic in two different (Ba,Sr)TiO3 films
Authors: Tang Qiu-Wen  , Shen Ming-Rong  , Fang Liang  ,   苏州大学物理科学与技术学院，薄膜材料江苏省重点实验室，苏州  215006
Published: December 2020

A high dielectric constant of 2500 near room temperature was observed in (Ba０.５Sr０.５)TiO３ (BSTO) film prepared by pulsed-laser deposition (PLD) on Pt/Ti/SiO２/Si (100) substrate at 550℃ in N2 atmosphere. The dielectric constant is weakly temperature dependent above 200 K. The dielectric behavior of this film is different from the BSTO film deposited in the O2 atmosphere, but very similar to that reported for the so-called “colossal” dielectric constant materials, such as CaCu3Ti4O12. The film prepared in O2 atmosphere at 650℃ shows normal ferroelectric phase transition, which are fitted with Curie-Weiss law. However, for the film prepared in N2 atmosphere at 550℃, the temperature dependence of dielectric relaxation can be characterized by a thermally excited relaxation process. Such anomalous dielectric response of the BST films is ascribed to the formation of the Schottky barrier between the metallic electrode and the film surface.
Nucleation-growth and spinodal decomposition of zinc oxide films prepared by sol-gel technique
Authors: Zang Jing-Cun  , Tian Zhan-Kui  , Liu Yan-Hang  , Chi Jing  , Zou Yu-Lin  , Wei Jian-Zhong  , Ye Jian-Ping  ,   (1)北京工业大学材料科学与工程学院,北京  100022; (2)北京工业大学环境与能源工程学院，北京  100022; (3)中国科学院化学研究所光化学重点实验室，北京  100080
Published: December 2020

Transparent zinc oxide (ZnO) films were prepared on ZnWO4 crystal by sol-gel technique. Surface morphology of ZnO films were observed with optical mi croscope. The results of show that ZnO films are formed in three different stage s from nucleation on surface, grain growth to island formation. Because ZnO crys tal nucleus were grown under non_equilibrium condition, it is inevitable that de ndrite growth, fractal growth and spinodal decomposition phenomenon are involved in the growing process.
Characterization of silicon nitride films prepared by MW-ECR magnetron sputtering
Authors: Ding Wan-Yu  , Xu Jun  , Li Yan-Qin  , Piao Yong  , Gao Peng  , Deng Xin-Lü  , Dong Chuang  ,   大连理工大学三束材料表面改性国家重点实验室，大连  116024
Published: December 2020

Hydrogen-free silicon nitride films were deposited at room temperature by microw ave electron cyclotron resonance (ECR) plasma source enhanced unbalanced magnetr on sputtering system. Fourier-transform infrared spectroscopy and X-ray photoele ctron spectroscopy were used to study the bond type, the change of bond structur es, and the stoichiometry of the silicon nitride films. Atomic-force microscopy and nano-indentation were used to study the morphological features and mechanica l characteristics of the films. The results indicate that the structure and char acteristics of the films deposited by this technique depend strongly on the dens ity of sputtered Si in plasma and the films deposited at 4 sccm N2 fl ow show excellent stoichiometry and properties.
Surface reconstructions and the local magnetic moments in Mn/GaAs(001) system
Authors: Zhang Li-Xin  , Wang En-Ge  ,   中国科学院物理研究所表面物理国家重点实验室，北京  100080
Published: December 2020

First principles calculations have been used to study the various surface reconstructions, local density of states of surface atoms, and the local magnetic moments of the Mn constituents in Mn/GaAs(001) surface. It is found that the Mn atoms will act as donors and donate as many electrons as required by the GaAs surface. The local magnetic moment of Mn being an important factor in surface magnetic properties can be deduced directly from the reconstruction by electron counting.
Growth of p-GaN at low temperature and its properties as light emitting diodes
Authors: Liu Nai-Xin  , Wang Huai-Bing  , Liu Jian-Ping  , Niu Nan-Hui  , Han Jun  , Shen Guang-Di  ,   北京工业大学北京市光电子技术实验室，北京  100022
Published: December 2020

The p-type GaN(p-GaN) samples grown at low temperature 870—980℃ on sapphire su bstrate were prepared by the metal organic chemical vapor deposition technique(M OCVD), and their electrical properties were investigated. The p-GaN samples grow n below 900℃ show high-resistivity, and samples grown at above 900℃ have good conductivity. In addition, the electrical properties are also related with the d oping level and the growth condition of p-GaN. The low N-Ga mole ratio leads to poor conductivity, the high ratio leads to rough morphology. At last, we use the optimized p-GaN to fabricate the green-light emitting diodes.We found that when the growth temperature is lower, the luminescence intensity and reverse voltage is higher but the forward voltage increases slightly.
Microstructure of TiNi shape memory alloy films made of sputter-deposited Ni/Ti multilayers
Authors: Wei Xiang-Jun  , Xu Qing  , Wang Tian-Min  , Jia Quan-Jie  , Wang Huan-Hua  , Feng Song-Lin  ,   (1)兰州大学物理科学与技术学院,兰州  730000; (2)兰州大学物理科学与技术学院,兰州  730000;中国科学院高能物理研究所,北京  100049; (3)中国科学院高能物理研究所,北京  100049
Published: December 2020

Phase depth profile in TiNi shape memory alloy films is studied by the combinati on of grazing-incidence X-ray diffraction and X-ray reflectivity measurement. Th e film is made from sputter-deposited Ni/Ti multilayers. At room temperature, bo th the phase depth profile and element depth profile are not uniform, and both h ave multilayer structure. There is a three-phase mixture region consisting of Ti 3Ni4 precipitates, martensite and a little of austenite ne ar the free surface. A uniform martensite phase is formed near the substrate. Di ffusion and reaction take place between film and substrate. The simulation resul t of X-ray reflectivity shows that the results of film microstructure analysis a re reasonable. It is the kinetic factors that mainly cause the ununiformity of p hase depth profile in the film.
Measurement of nitrous acid and retrieval of aerosol parameters with differential optical absorption spectroscopy
Authors: Hao Nan  , Zhou Bin  , Chen Li-Min  ,   复旦大学环境科学与工程系，上海  200433
Published: December 2020

Differential optical absorption spectroscopy (DOAS) is a spectroscopic technique which can be used to monitor many kinds of air pollutants simultaneously. In th is paper, in situ measurement of nitrous acid and retrieval of aerosol parameter s in a fixed wavelength range (307 nm—380 nm) were performed with DOAS system d eveloped by our laboratory. The measurements of HONO concentration were more acc urate using the NO2 standard absorption cross section measured by our selves a nd aerosol parameters were retrieved successfully in a shorter wavelength range.
Polymer anchored fluid membrane
Authors: Guo Kun-Kun  , Qiu Feng  , Zhang Hong-Dong  , Yang Yu-Liang  ,   复旦大学高分子科学系，教育部聚合物分子工程重点实验室，上海  200433
Published: December 2020

By combining the self-consistent field theory for polymers with the Helfrich elasticity theory of membrane, the polymer anchored infinite membrane is investigated. Both the density distribution of the polymer and deformation of the membrane are obtained. Close to the anchoring site,the membrane has the conical shape and bends away from the polymer due to the membrane's impenetrability to the polymer and the confined space for the polymer, which is consistent with previous theoretical results and Monte Carlo simulations. Moreover, the interaction between the membrane and polymer chain length, and the effects of bending rigidity and surface tension on the deformation of the membrane are investigated.
Optimum valence bond scheme: theoretical study of small clusters of elements in the second and third row of periodic table
Authors: He Chun-Long  , Yuan Zhe  , Shen Xu-Yang  , Xu Ya-Ge  , Li Jia-Ming  ,   (1)清华大学物理系，原子分子纳米科学教育部重点实验室，北京  100084;上海交通大学物理系，上海  200030; (2)上海交通大学物理系，上海  200030; (3)上海交通大学物理系，上海  200030;清华大学物理系，原子分子纳米科学教育部重点实验室，北京  100084
Published: December 2020

Using optimum valence bond scheme which reduces the computation effort, we study systematically the properties of the critical structures (critical points) of small clusters (up to four atoms) of elements in the second and third row of the periodic table. We also show the evolution process of the clusters from two atoms to four atoms. By examining the electronic structures of all clusters, we can understand why the four-atom clusters for specific elements can have three-dimensional structures with Td symmetry. More interestingly, comparing the variation of the binding energy of such small clusters with the melting points and boiling points of corresponding pure element materials, we can understand the effect of the critical structures in the melting and boiling processes.
The influence of weak interaction on thermodynamic properties and the stability of imperfect Bose gas
Authors: Yuan Du-Qi  ,   宝鸡文理学院物理系，宝鸡  721007
Published: December 2020

Using the free energy and the equation of state for an imperfect Bose gas, the analytical expression between the critical temperature and the length of dispersion wave and the pressure for the imperfect Bose gas is derived. The unusual properties of the specific heat at constant pressure and the expansion coefficient at constant pressure and isothermal compressibility by the attractive force for the imperfect Bose gas are revealed. The instability arising from the attractive force is pointed out, and the temperature criterion and particle density criterion of instability is given for the imperfect Bose gas under the action of attraction.
Negative effective refraction index in guided wave mode for periodic layered ferrite-dielectric/metallic film composites
Authors: Zhao Tian-En  , Wu Rui-Xin  , Yang Fan  , Chen Ping  ,   南京大学电子科学与工程系，南京  210093
Published: December 2020

We have studied the effective refraction index of the guided wave mode in periodic layered ferrite-dielectric/metal film composites. Using the equivalent transmission line approach we have analyzed and calculated the dispersion characters and then the effective refraction index of the composites. We have found that the effective refraction index of the composites will be negative within a certain frequencies only when the wave is in TE mode. The loss of the composite is closely related to the dielectric layers, which can be effectively reduced by decrease the dielectric loss. However, too small dielectric loss results in disappearing of the negative refraction index.
Properties of the propagation of negatively chirped femtosecond pulses in normally dispersive media
Authors: Liu Jun  , Chen Xiao-Wei  , Liu Jian-Sheng  , Leng Yu-Xin  , Zhu Yi  , Dai Jun  , Li Ru-Xin  , Xu Zhi-Zhan  ,   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

We experimentally studied the temporal and spectral characteristics of the output pulses after the negatively chirped pulses passed through normally dispersive media. The spectrum of the pulse is narrowed and reshaped due to strong self-actions. The pulse is self-compressed, instead of broadening, accompanied with the spectrum narrowing in the experiment. For the same spectral bandwidth, shorter than sech2 transform-limited self-compressed femtosecond pulses are obtained. The simulation result is in agreement with the experiment.
Preparation of ZnMnO by ion implantation and its spectral characterization
Authors: Zhong Hong-Mei  , Chen Xiao-Shuang  , Wang Jin-Bin  , Xia Chang-Sheng  , Wang Shao-Wei  , Li Zhi-Feng  , Xu Wen-Lan  , 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

This paper reports the fabrication of ZnMnO semiconductor by high-dose Mn impla ntion. We studied the influence of implantation dose and annealing on its optica l properties. The broad band at 575cm-1 in Raman spectrum is attribut ed to defects related to high-dose Mn implantion. The vibration modes at 528cm-1 are considered to be associated with Mn impurities. Room temperature photoluminescence spectra show that the high-dose Mn implantion can enhance the intensity in visible band.
Electrical properties of alpha-particle detectors based on CVD diamond films
Authors: Wang Lin-Jun  , Liu Jian-Min  , Su Qing-Feng  , Shi Wei-Min  , Xia Yi-Ben  ,   上海大学材料科学与工程学院，上海  200072
Published: December 2020

The influences of the applied bias voltage and the pre-irradiation treatment by alpha particles on the electrical properties of sandwich structural diamond film detectors under 5.5 MeV 241Am alpha-particle irradiation were investigated. Results of current- voltage(I-V) and pulse height distribution measurements showed that the dark current of the diamond film detector would increase due to the pre-irradiation by alpha particles. Under the alpha irradiation, the detector under negative bias voltage had a higher response current and a better signal-to-noise ratio than that under a positive bias. Raman scattering studies directly demonstrated that the above phenomenon resulted mainly from the different structural imperfection distributions along the thickness direction. An energy resolution of about 25.0% was obtained for the detector under a negative bias voltage and 38.4% under a positive bias voltage. With increasing alpha-particle irradiation time, both the response current and the charge collection efficiency increased obviously.
10 GHz optical short pulse generation using tandem electroabsorption modulators monolithically integrated with distributed feedback laser by ultra-low-pressure selective area growth
Authors: Zhao Qian  , Pan Jiao-Qing  , Zhang Jing  , Zhou Guang-Tao  , Wu Jian  , Zhou Fan  , Wang Bao-Jun  , Wang Lu-Feng  , Wang Wei  ,   (1)北京邮电大学光通信与光波技术教育部重点实验室,北京  100876; (2)中国科学院半导体研究所国家光电子工艺中心,北京  100083
Published: December 2020

In this work, a novel light source of tandem InGaAsP/InGaAsP multiple quantum well electroabsoption modulator(EAM) monolithically integrated with distributed feedback laser is fabricated by ultra-low-pressure (22×１０２Pa) selective area growth metal-organic chemical vapor diposition technique. Superior device performances have been obtained, such as low threshold current of 19 mA, output light power of 4.5 mW, and over 20 dB extinction ratio at 5 V applied voltage when coupled into a single mode fiber. Over 10 GHz 3dB bandwidth in EAM part is developed with a driving voltage of 2 V. Using this sinusoidal voltage driven integrated device, 10GHz repetition rate pulse with an actual width of 13.7 ps without any compression elements is obtained due to the gate operation effect of tandem EAMs.
The effect of wires in negative refractive index material
Authors: Feng Yu  , Wu Jian  , Song Jian-Ping  ,   (1)西安交通大学,电子科学系,西安  710049; (2)中国电波传播研究所，电波环境及模化技术国家重点实验室,北京  102206
Published: December 2020

Two structures of left handed metamaterials were proposed. Using numerical simulation, the S parameters for the two structures were calculated. Because the electromagnetic fields in conducting metamaterials can be localized to regions much smaller than the incident wavelength, it can be difficult to perform accurate numerical simulations. To obtain greater numerical accuracy， finite integration technique (FIT) was used. The results show that the wire symmetry breaking affects the resonant frequency and passband for SRR owing to the coupling between wires and SRR.
High-order harmonic generation of hydrogen molecule irradiated by ultra-strong femto-second laser pulse——a simulation via TDDFT
Authors: Gu Bin  , Cui Lei  , Zeng Xiang-Hua  , Zhang Feng-Shou  ,   (1)北京师范大学低能核物理研究所，北京市辐射中心，北京  100875; (2)扬州大学物理科学与技术学院,复杂性科学中心,扬州  225002; (3)扬州大学物理科学与技术学院,复杂性科学中心,扬州  225002;北京师范大学低能核物理研究所，北京市辐射中心，北京  100875
Published: December 2020

The high order harmonic generation (HHG) of hydrogen molecule irradiated by ultra-strong femto-second laser pulse is simulated by the TTDFT method with the classical and quantum combination technique. The results indicate that the HHG spectra of H2 have a “decrease-plateau-cutoff” structure. A kind of “odd allowed, even forbidden” selective phenomenon of the order number of HHG is observed. Change in polarization direction of laser beam may change the cut-off order and spectrum intensity of HHG simultaneously.
Influence of under-dense plasma on laser conical target interaction
Authors: Liu Zhan-Jun  , Zheng Chun-Yang  , Cao Li-Hua  , Li Bin  , Zhu Shao-Ping  ,   北京应用物理与计算数学研究所，北京8009信箱，100088
Published: December 2020

The laser light propagation inside the conical target has been studied by three-dimensional particle-in-cell simulations. It is found that the existence of under-dense plasma significantly affects the light propagation and the generation of relativistic electrons. The laser light can be focused at the tip of the cone and the intensity increases up to tens of times in the focal spot. With the under-dense plasma the laser light focused intensity is decreased. The existence of under-dense plasmas favors the relativistic electron generation in the laser conical target interaction in enhancing the number and energy of relativistic electrons.
Characteristics of the electronic structure of DNA sequence
Authors: Ma Song-Shan  , Xu Hui  , Liu Xiao-Liang  , Guo Ai-Min  ,   中南大学物理科学与技术学院，长沙  410083
Published: December 2020

Based on a tight-binding disordered model describing a single electron band, we establish a one-dimensional disordered binary DNA model, and calculate the density of electronic states，the localization property of electronic wave-function and the localization length of a DNA sequence with 2×104 nucleotide base pairs. We also investigate the effect of composition of nucleotide base pairs, the degree of disorder of the energy base pairs on the localization length. The results indicate that the electronic states of DNA sequence are localized due to the compositional disorder of nucleotide base pairs and the energy disorder of the lattices, and the localization length is dependent on the composition of nucleotide base pairs and the disorder degree of lattices energy.
Synchronization of a class of chaotic systems using nonlinear observers
Authors: Yao Li-Na  , Gao Jin-Feng  , Liao Ni-Huan  ,   (1)华北水利水电学院，郑州  450008; (2)郑州大学电气工程学院，郑州  450002; (3)中国科学院自动化研究所，北京  100080
Published: December 2020

This paper investigates the synchronization design for a class of chaotic systems with uncertainties in which all state variables are not measured. The design makes use of an observer with a controller. Assuming the boundedness of chaotic attractors and limited cycles, the approach, which is both global and not relying on complete knowledge of the systems involved, is rigorously proved by means of Lyapunov theory. Computer simulation results illustrate the validity of the method.
Two-dimension numerical research on the ablation of target irradiated by intense pulsed ion beam
Authors: Wu Di  , Gong Ye  , Liu Jin-Yuan  , Wang Xiao-Gang  , Liu Yue  , Ma Teng-Cai  ,   (1)大连理工大学三束材料改性国家重点实验室，大连  116024; (2)大连理工大学三束材料改性国家重点实验室，大连  116024;大连轻工业学院数理系，大连  116034
Published: December 2020

Two-dimension numerical research has been carried out on the ablation of metal Ti target irradiated by intense pulsed ion beam(IPIB) produced by TEMP Ⅱ accelerator. Spatial and temporal evolution of the ablation process of the target during the pulse time has been obtained. Melting and evaporation processes begin from the surface of the target and the ablation process of target is layer by layer while the target is irradiated by IPIB. Meanwhile, we have also obtained the result that the average ablation velocity in center region of the target is about 10m/s, which is far lower than the ejection velocity of the plume plasma formed during the pulse time. The effects have been compared for different ratios of two kinds of ions in the pulsed beams produced by using different kinds of materials as the anode of magneto-isolated diosts during the irradiation time.
A novel LD pumped Yb:GSO laser operating at 1090 nm with low threshold
Authors: Xue Ying-Hong  , Wang Qing-Yue  , Chai Lu  , Liu Qing-Wen  , Zhao Guang-Jun  , Su Liang-Bi  , Xu Xiao-Dong  , Xu Jun  ,   (1)天津大学精密仪器与光电子工程学院，光电信息技术科学教育部重点实验室，天津  300072; (2)中国科学院上海光学精密机械研究所，上海  201800
Published: December 2020

We report what we believe to be the first demonstration of laser operation with a novel laser material of Yb3+-doped Gd2SiO2(Yb:GSO)pumped by a laser diode at 940 nm. We obtained a low lasing threshold of 1.27 kW/cm2 with the center wavelength of 1090 nm, which is lower than the value of 1.53 kW/cm2 predicted for Yb:YAG. The maximal output power of 360 mW was obtained with a 2% output, which corresponds to a slope efficiency up to 19%.
Characteristic crisis in a system with distinguishable strong and weak dissipation functions
Authors: Chao Xiao-Gang  , Dai Jun  , Wang Wen-Xiu  , He Da-Ren  ,   (1)江苏工业学院信息科学系,常州  213016;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 article reports a crisis in a system described by a concatenation of a conservative and a dissipative mapping. The special feature of the crisis lies in its special escaping hole. A fat fractal forbidden net, induced by interaction between discontinuous and noninvertible properties, introduces rippled-like attraction basins of two periodic attractors, which appear after the crisis when a chaotic attractor suddenly loses stability. There are small areas, which serve as escaping holes and are dominated by strong dissipation as well as confined by the boundary of forbidden region only in the vicinity of each periodic point. To our knowledge, the crisis has not been reported before.
Analysis of features of climate change of Huabei area and the global climate change based on heuristic segmentation algorithm
Authors: Gong Zhi-Qiang  , Feng Guo-Lin  , Wan Shi-Quan  , Li Jian-Ping  ,   (1)国家气候中心气候研究开放实验室，北京  100081;中国科学院大气物理研究所东亚区域气候-环境重点实验室，北京  100029; (2)扬州大学物理科学与技术学院，扬州  225009; (3)中国科学院大气物理研究所大气科学和地球流体力学数值模拟国家重点实验室，北京 100029
Published: December 2020

Global change science is a new research field, and one of the most important topics of which is the climate change study, to which great importance is attached by all governments of the world, and climatic abrupt change is one of manifestations of climate changes. Nowadays, research of climate change is mainly based on climatic proxy using traditional statistical method. However, climatic system is nonlinear, non-stationary and hierarchical, which makes even harder to detect and analyze abrupt climate changes. As well known, climatic system is made up of several sub-systems, and there may be inherent connections between them; however, there is only a few research methods and theories in this field. This article introduces a new detecting method, the heuristic segmentation algorithm, which is well fitted to nonlinear and non-stationary time series. Then, dealing with northern hemisphere tree rings and Beijing stalagmite based on high and low frequency series, we try to distinguish abrupt changes in different sles and disclose its physial mechanism. Defining a new physical quantity, the abrupt density, and analyzing the distribution characteristics of abrupt changes before and after 1000 a, We take Huabei area's climatic change as an example to explore the inherent connections between local and global areas.
General solution for multi-dimensional coupled and forced quantum oscillator
Authors: Xu Xiu-Wei  , Ren Ting-Qi  , Liu Shu-Yan  , Dong Yong-Mian  , Zhao Ji-De  ,   烟台师范学院物理系，烟台  264025
Published: December 2020

Utilizing the general linear quantum transformation theory, we give the exact expressions of evolutionary operator's matrix elements, wave function, expectation value of an observable and partition function, for multi-dimensional coupled and forced quantum oscillator.
Dynamical properties of an asymmetric Josephson junction in Bose-Einstein condensates
Authors: Xiao Yu-Fei  , Wang Deng-Long  , Wang Feng-Jiao  , Yan Xiao-Hong  ,   (1)湘潭大学物理系和现代物理研究所，湘潭  411105; (2)湘潭大学物理系和现代物理研究所，湘潭  411105;南京航天航空大学理学院,南京  210016
Published: December 2020

Based on the semiclassical quantum theory, we study the dynamical behaviors of Bose-Einstein condensate in an asymmetric Josephson junction. It is shown that the Josephson effect appears in the system when the ratio χ　of the difference of two ground state energies to the interaction energies is zero. When χ≠0, the dynamical behavior of the system shows both the macroscopic quantum tunneling and the macroscopic quantum localization.