bluuebunny/crossref_metadata_2025 huggingface dataset:
Design and performanec of a high-gain double-layer GaAs photoconductive switch
Authors: Shi Wei  , Wang Xin-Mei  , Hou Lei  , Xu Ming  , Liu Zheng  ,   西安理工大学应用物理系，西安  710048
Published: December 2020

A new kind of ultra-fast power photoconductive semiconductor switch with double-layer semi-insulating GaAs:EL2 is designed and prepared. Because the distribution of voltage between the triggered double GaAs layers is dynamic, when biased at a high electric field, the double layers go into the high-gain state one after the other but prevent each other from entering the Lock-on state, so the output electric pulse has double peaks and looks like a rectangular wave. This working mode not only has the strong points of the nonlinear mode, such as the required laser energy is far less and the rise time is shorter than that of the linear mode, but also has the merits of the linear mode, such as the repetition frequency is higher and the life is far longer than that of the nonlinear mode. Biased at 6500 V and triggered by an 8 ns, 3 mJ and 1064 nm laser pulse, the rise time of the output electric pulse is 13.2 ns, the fall time is 54.6 ns, the full width at half maximum is 148.4 ns, the first peak is 885 V and the second peak is 897 V. With the bias voltage increasing, the rise time nearly keeps a constant, the width and fall time decrease slightly and the double peaks increase obviously.
Analysis of magnetoimpedance in amorphous wire passing through a magnetic ring
Authors: Pang Hao  , Li Gen  , Wang Zan-Ji  ,   清华大学电机系，电力系统国家重点实验室，北京  100084
Published: December 2020

A unified expression of magnetic susceptibility tensor is presented according to the magnetic-moment motion equation with Landau-Lifshitz damping term and Gilbert damping term. The application of equivalent magnetic permeability enables to transform the anisotropy problem to an isotropy one with the same electromagnetic solution in amorphous wire. By this transformation, the impedance of amorphous wire passing through an insulating or conducting magnetic ring are analyzed. Additionally, the magnetoimpedance effect in amorphous wire through a magnetic ring is simulated by the numerical analysis based on the finite element method. The results of theoretical analysis and numerical simulation, which agree with each other, indicate that the additional impedance caused by extra magnetic objects seriously reduces the magnetoimpedance change of amorphous wire and destroy the giant magnetoimpedance characteristic. Therefore, the return wire structure is proposed to diminish the additional impedance. The simulation results verified the effectiveness of this method.
The effect of thickness on the structure and superconductivity of La1.85Sr0.15CuO4 films
Authors: Zu Min  , Zhang Ying-Zi  , Wen Hai-Hu  ,   中国科学院物理研究所超导国家重点实验室，北京  100190
Published: December 2020

Highly c-oriented La1.85Sr0.15CuO4 (LSCO) films were successfully deposited on SrTiO3 (STO) substrates by on-axis magnetron sputtering. By using the standard four-probe technique and X-ray diffraction (XRD), we investigated the influence of film thickness on the structure and superconductivity of LSCO(x=0.15) films. The experiment results show that the full-width at half maximum (FWHM) of the (006) rocking curve decreases with increasing film thickness, which indicates that the crystal qualities of films are improved. Meanwhile, the superconducting transition temperature is higher for the thicker films.
Influence of bias magnetic field on magnetoelectric effect of magnetostrictive/elastic/piezoelectric laminated composite
Authors: Yang Chang-Hai  , Wen Yu-Mei  , Li Ping  , Bian Lei-Xiang  ,   重庆大学光电工程学院，光电技术及系统教育部重点实验室,重庆  400030
Published: December 2020

The dynamic Young's modulus of elasticity and the dynamic piezomagnetic coefficient of magnetostrictive material are derived based on the nonlinear constitutive model of magnetostrictive material. Based on the equivalent circuit method, the relation between magnetoelectric effect of the laminated composite and the dynamic Young's modulus of elasticity, and the dynamic piezomagnetic coefficient of magnetostrictive material is established. The influences of bias magnetic field on the resonant frequencies and the resonant magnetoelectric voltage coefficients of the laminated composite are discussed. The theoretical analysis and the experimental results indicate that there is an optimal bias magnetic field at which the resonant magnetoelectric voltage coefficient of the laminated composite reaches its maximum.
Study on slim-loop ferroelectric ceramics for high-power pulse capacitors
Authors: Chen Xue-Feng  , Li Hua-Mei  , Li Dong-Jie  , Cao Fei  , Dong Xian-Lin  ,   (1)中国工程物理研究院,绵阳  621900; (2)中国科学院上海硅酸盐研究所,上海  200050
Published: December 2020

A slim-loop ferroelectric ceramic of Pb (Zr0.42Sn0.40Ti0.18)O3(PZST42/40/18) was prepared by partially replacing Pb with Ba and La, and replacing (Zr, Sn, Ti) with Nb in low zirconiumn. The saturation polarization (Ps), the remnant polarization (Pr) and the area of the hysteresis loop (S) were measured to be 20.66 μC/cm2, 0.55 μC/cm2 and 0.0298J/cm3, respectively. Relative permittivity (ε)≈2840 can be reached in this ferroelectric ceramic at room temperature and frequency of 1kHz, but the energy density (w) is 0.319J/cm3. The results of the pulse charge-discharge measurements showed that a single piece of the PZST42/40/18 slim-loop ferroelectric ceramic can carry 2330 A and endures charge-discharge cycle over one thousand times. The released charge decreases with increasing cycle times according to second order exponential decay. These ferroelectric ceramics have potential for pulsed power capacitor applications.
Electrically tunable multiplexed grating with alternate liquid crystal-polymer structure
Authors: Zheng Zhi-Gang  , Li Wen-Cui  , Liu Yong-Gang  , Xuan Li  ,   (1)中国科学院长春光学精密机械与物理研究所，应用光学国家重点实验室，长春  130033; (2)中国科学院长春光学精密机械与物理研究所，应用光学国家重点实验室，长春  130033；中国科学院研究生院,北京  100049
Published: December 2020

In this paper, we report a kind of electrically tunable multiplexed grating which is prepared conveniently with a single step holographic exposure on the mixture of nematic liquid crystals and photosensitive monomers. The periods of two sub-gratings contained in the multiplexed grating are tested with scanning electronic microscopy (SEM), the results show that their periods are 1 μm and 4 μm, respectively. Diffraction properties of this multiplexed grating are tested, and it is found that there are two diffraction peaks when the testing beam incidents at two different incidence angles. The corresponding diffraction efficiencies of the two sub-gratings are 90% (for Λ=1μm) and 60% (for Λ=4μm), which have a good agreement with the theoretical results obtained by coupled wave theory (the theoretical values being 92.57% for Λ=1μm and 63.68% for Λ=1μm). In addition, the electro-optical performance indicates, that the threshold voltage for the sub-gratings are similar with each other, the V90 of Λ=1μm is 7V/μm and 6V/μm for Λ=4μm, respectively. Such results show the good synchronized electrically-tunable property of multiplexed grating.
Ultrafast energy transfer of a porphyrin-polypyridyl ruthenium (Ⅱ) hybrid linked by a butyl chain
Authors: Shen Han  , Liu Jie  , Chen Zhi-Feng  , Huang Jin-Wang  , Shen Yong  , Wang Hui  , Ji Liang-Nian  ,   (1)中山大学光电材料与技术国家重点实验室，广州  510275; (2)中山大学光电材料与技术国家重点实验室，广州  510275；中山大学化学与化工学院/生物无机与合成教育部重点实验室，广州  510275; (3)中山大学化学与化工学院/生物无机与合成教育部重点实验室，广州  510275
Published: December 2020

The ultrafast energy transfer has been investigated in a porphyrin (TPP) and polypyridyl ruthenium (Ⅱ) (Ru) hybrid, which is linked by a butyl chain by using time-resolved fluorescence spectroscopic technique. The experimental result shows that，when the excitation wavelength is at the absorption peak (～453 nm) of the Ru moiety，an ultrafast energy transfer occurs from Ru to porphyrin moiety (～400ps). When the excitation wavelength (～400 nm) is at the absorption peak of the TPP moiety，no energy transfer is detected from TPP to Ru. The origin of the energy transfer has been analyzed by using Frster theory. The theoretical result shows that the energy transfer is attributed to dipole-dipole interaction based on the spectra overlap.
Influence in polarization of cosmic microwave background radiation due to relic gravitational waves
Authors: Lei Zhong-Hua  , Lan Ming-Jian  , Wang Xian-You  , Li Jian-Jie  ,   (1)上海交通大学电子信息与电子工程学院，上海  200240; (2)重庆大学理论物理研究所，重庆  400044; (3)重庆工商大学计算机科学与信息工程学院，重庆  400067
Published: December 2020

According to the prediction of the theory of Big Bang, the universe has gone through from the phase of inflation to the phase of radiation and to the phase of matter at last to the phase of acceleration expansion now. In the radiation phase, the rudimental free photons of decoupling become the Cosmologic Microwave Background Radiation which we observe by now. If there is not any perturbation, the CMB radiation will be isotropy, but in the earlier era of the universe, there exist all kinds of the perturbations, which caused the anisotropy the Cosmic Microwave Background radiation. This research will emphatic depict the influence of the relic gravitational wave for the Cosmic Microwave Background radiation in anisotropy of polarization, especially in E-mode and B-mode polarization.
Homotopic mapping solution of soliton for perturbed KdV equation
Authors: Mo Jia-Qi  , Yao Jing-Sun
Published: December 2020

Using the homotopic mapping method, a class of nonlinear KdV(Korteweg de Vries) equation is considered. Firstly, by introducing a homotopic transform, the problem of solving soliton for the corresponding equation is changed into a problem of mapping transform. Then on account of the property of the homotopic mapping, the approximate solution of soliton for the original equation is obtained.
On the properties and controlling of thermal entanglement in a two-qubit Heisenberg XY model with external magnetic fields
Authors: Du Xiu-Mei  , Man Zhong-Xiao  , Xia Yun-Jie
Published: December 2020

We investigate the thermal entanglement of Heisenberg-type coupled two-qubit system in the presence of two controllable magnetic fields (B+b) and (B-b). We find that under the condition of low temperature and uniform magnetic field, the entanglement between the two qubits exhibits platform-like behavior. By controlling the inhomogeneous magnetic field b and selecting suitable material we can optimize the thermal entanglement and enhance the critical temperature Tc of dead entanglement. We also find that the entanglement switch can be realized in a broader region of temperature by modulating the uniform field B.
Parameters identification and adaptive synchronization of uncertain Chua’s circuit
Authors: Li Jian-Fen  , Li Nong  , Cai Li  , Zhang Bin
Published: December 2020

This paper addresses the adaptive synchronization of two Chua's circuits with uncertain parameters by transmitting one single signal. Based on the Lyapunov stability theory, it is proved that the controller and update rule proposed in this paper can make the states of the driving system and the response system asymptotically synchronized, and with which the uncertain parameters of response system are identified. Numerical simulation results illustrate the effectiveness of proposed method.
The study of stochastic Van der Pol system with delayed state feedback
Authors: Zou Shao-Cun  , Xu Wei  , Jin Yan-Fei
Published: December 2020

In this paper, we studied the amplitude control of the limit cycle in Van der Pol system with time-delay and time-delayed feedback strength. We show the critical stability boundary and the corresponding linearized equation of the Van der Pol system by mean-field approximation method. Mean-field approximate analytical expressions and numerical simulations for the power spectral density and the correlation time were given, and mean-field approximate analytical expressions in dependence upon noise intensity, delay time, and feedback strength are in good agreement with our numerical simulations. The time delayed feedback strength, noise intensity and time delay are taken as variable parameters to investigate their effects on the dynamics of the system, such as the power spectral density and the correlation time.
Two-car following model of traffic flow and numerical simulation
Authors: Peng Guang-Han  , Sun Di-Hua  , He Heng-Pan
Published: December 2020

Based on the full velocity difference (FVD) model, with the consideration of the effect of information about the two leading cars to the following car, an improved two_car following model of traffic flow has been deduced. The linear stable judging condition is obtained to the improved model by its stability analysis, which shows the stability range of the improved model is obviously larger than FVD model by comparing them. Numerical simulation shows that our model can avoid the disadvantage of negative velocity occurring at small reaction coefficient in FVD model by adjusting the information of the next-nearest-neighbor leading car. And there is unavoidable effect to traffic flow from the next-nearest-neighbor leading car’s information.
Numerical calculation of laser-induced collisional energy transfer in Ba-Sr system
Authors: Zhang Hong-Ying  , Chen De-Ying  , Lu Zhen-Zhong  , Fan Rong-Wei  , Xia Yuan-Qin
Published: December 2020

Based on the existing four-level model of laser-induced collisional energy transfer, the collision process in Ba-Sr system in both weak and strong fields is calculated by immediate integration of the equation of motion, and profiles of laser-induced transition probability and collision cross section under both conditions are obtained. Numerical results for the weak field are in fair to good agreement with former analytical results, while the ones for the strong field show that the effect of laser-induced collision is enhanced when the transfer laser intensity increases. Moreover, the peak of the laser-induced collisional energy transfer spectrum shows an evident shift from resonant frequency to the violet side in strong field, and full width at half maximum (i.e. tuning range) of the spectrum becomes obviously narrower compared with that in weak field.
Total cross sections of electron scattering by large molecules C4H8O, C5H10O2, C6H5CH3 and C4H8O2 at 50—5000 eV
Authors: Shi De-Heng  , Sun Jin-Feng  , Liu Yu-Fang  , Zhu Zun-Lue  , Ma Heng
Published: December 2020

Using the modified additivity rule (AR) approach, the total cross sections (TCSs) for electron scattering by large molecules C4H8O, C5H10O2, C6H5CH3 and C4H8O2 are calculated over a wide energy range from 50 to 5000eV by employing the experimental TCS results of electron scattering from atoms C, H and O. Here the atomic TCSs are derived from the experimental TCS results of simple molecules (H2, O2, CO). The quantitative TCSs are compared with those obtained by measurements and other theories wherever available. It is shown that there is excellent accordance between the theories obtained by the modified AR approach and the measurements even at energies of several tens of eV. And it is also shown that the problem that the log_log TCS curves obtained by the original AR approach are steeper than those obtained by the experiments, is introduced by the AR model itself. The intrinsic reason is that the mutual screening effects are not taken into consideration in the original AR approach at lower energies.
Polarization effect and post-collisional interaction in (e, 2e) reaction process for He and Ar in coplanar asymmetric geometry
Authors: Zhou Li-Xia  , Yan You-Guo
Published: December 2020

The (e, 2e) triple differential cross sections for He(1s2)，Ar(3p6)and Ar(2p6)have been calculated using the modified distorted wave Born approximation (DWBA) in coplanar asymmetric geometry. The kinematics employs large energy transfer and is close to minimum momentum transfer. The theoretical results have been compared with those of the experiment, the Brauner, Briggs and Klar (BBK) method and the standard DWBA calculation. It is shown that the polarization and post-collisional interaction effects are very important in coplanar asymmetric (e, 2e)reaction with special kinematics for He(1s2), Ar(3p6) and Ar(2p6).
Structure, electronic properties and magnetism of La-doped Be clusters BenLa
Authors: Ren Feng-Zhu  , Luo You-Hua
Published: December 2020

With many kinds of initial configurations and spin multiplicities taken in full consideration, the first principile method based on density_functional theory (DFT) has been employed to study the equilibrium geometries, electronic properties and magnetism of BenLa (n=1—18). Our results showed that there are many isomers with extremely close energies near the ground state, thus the cluster is very complex, making the ground state seek quite challenging. The BenLa has magnetism and its stability is far higher than that of Ben+1, indicating that one can acquire magnetic clusters with higher stabilities by choosing the proper doping atom. The Be17La is specially stable and its gap between the highest occupied and the lowest unoccupied molecular orbitals is quite the same as that of the host cluster. The magnetic moment in BenLa cluster system comes mainly from the outer layer unpaired valence electrons and the La element's contribution. The magnetic moment of BenLa is 1μB except that of BeLa and Be3La, which is 3μB.
Non-close-packed photonic crystal of TiO2 hollow spheres: Fabrication and photonic bandgap calculation
Authors: Zhu Yong-Zheng  , Yin Ji-Qiu  , Qiu Ming-Hui
Published: December 2020

We have fabricated the non-close-packed photonic crystals of SiO2 microspheres with the help of the modified vertical method, the thermal sintering technology and etching. The face-centered cubic photonic crystals of TiO2 hollow spheres connected by TiO2 cylindrical tubes have been fabricated using silica template. The structure of the non-close-packed opals was characterized by scanning electron microscopy. We performed photonic band-structure calculations of this structure by a plane wave expansion method. The calculations indicate that the photonic bandgaps at all points of the Brillouin zone in non-close-packed structure were opened except point W.
A study on the interval between longitudinal modes of Fabry-Perot cavity composed of fiber Bragg gratings
Authors: Ren Wen-Hua  , Wang Yan-Hua  , Feng Su-Chun  , Tan Zhong-Wei  , Liu Yan  , Jian Shui-Sheng
Published: December 2020

The characteristics of transmission spectrum of the Fabry-Perot (F-P) cavity composed of two fiber Bragg gratings (FBG) are analyzed detailedly in this paper. The influencing factors of the position of the longitudinal mode are pointedout. The relationship and difference between the FBG F-P cavity and normal F-P cavity are discussed. The phase factor of the amplitude reflection coefficient in the range of the FBG main lobe is simulated linearly using the effective mirror surface model. The effective length of the FBG is defined and the expression of the effective length is obtained. Furthermore， the effective length of the FBG is brought into the equivalent cavity length of the FBG F-P cavity. The interval between longitudinal modes of the FBG F-P cavity is calculated using the equivalent cavity length. Both the numerical simulation and experimental results show that the interval calculated using the equivalent cavity length accords well with the true interval between longitudinal modes of the FBG F-P cavity.
Effect of Nb doping on electronic structure of TiO2/NiTi interface: A first-principle study
Authors: Wu Hong-Li  , Zhao Xin-Qing  , Gong Sheng-Kai
Published: December 2020

The electronic structure of pure and Nb doped TiO2/NiTi interface have been calculated with the first-principle ultrasoft pseudopotential approach of the plane wave based on the density functional theory aiming at examining the effect of Nb on the electronic structure of the TiO2/NiTi interface. The formation energy calculation results show that the structure with Ti_terminated NiTi matrix and O_terminated TiO2 layer (Ti/O interface) is the most stable one among the four possible interface structures. Based on the optimized Ti/O interface model, the calculation results of the partial density of states, charge population and bond order suggest that the introduction of Nb on the interface strengthens the atomic interactions on the interface, as well as the interactions between the matrix and the oxidation layer in the neighborhood of the interface, which results in the improvement in the interfacial adhesion and the oxidation resistance of NiTi intermetallic compound.
The electronic structure and optical properties of Co and Mn codoped ZnO from first-principle study
Authors: Bi Yan-Jun  , Guo Zhi-You  , Sun Hui-Qing  , Lin Zhu  , Dong Yu-Cheng
Published: December 2020

The geometrical structures of pure ZnO and Co and Mn codoped 32-atom supercell of ZnO were optimized by using the ultra-soft pseudopotential method of total-energy plane wave based on the density functional theory. Band structure, density of states and optical properties were calculated and discussed in detail. The results revealed that the band gap of Co and Mn codoped ZnO are reduced and the absorption to ultraviolet visible light is obviously enhanced.
High-energy level linear Stark effect in CdS/HgS/CdS spherical nanometric system
Authors: Zheng Rui-Lun  , Wu Qiang
Published: December 2020

The influence of electric field and interlamellar effect on the electronic energy and wave function of spherical nanometric system is studied. Taking CdS/HgS/CdS as example， the influence of interlamellar effect， electric field and sample linear size on high-energy level Stark effect， spectral line frequency and intensity are discussed. The results show that for the spherical nanosystem CdS/HgS/CdS, the external electric field， Stark effect and the law of level effect-split-level resemble that of the hydrogen atom， but with different displacement of energy levels. The displacement of spectral lines is always proportional to the square of intensity in the electric field， and most spectral lines' frequency excursion decreased with the increase of linear sample-size， while some of the frequency excursions are on the opposite. The spectral line frequency excursion caused by interlamellar effect will decrease with the increase of linear size. Except a few spectral lines， most spectral lines will weaken with the increase of the linear size. Interlamellar effect will not change the trend of the relative intensity changing with linear size， but will make the intensities of spectral lines change. When the linear size is small， the influence of interlamellar effect on the intensity of spectral line is obvious.
First principles calculations of structure and the electronic properties of fullerene derivative phenyl-C71-butyric acid methyl ester
Authors: Zhang Zhu-Xia  , Zhao Yan-Liang  , Yan Xin  , Han Pei-De  , Liu Xu-Guang  , Hao Yu-Ying  , Xu Bing-She  ,   (1)太原理工大学新材料界面科学与工程教育部重点实验室，太原  030024；太原理工大学材料科学与工程学院，太原  030024; (2)太原理工大学新材料界面科学与工程教育部重点实验室，太原  030024；太原理工大学化学与化工学院，太原  030024; (3)太原理工大学新材料界面科学与工程教育部重点实验室，太原  030024；太原理工大学理学院，太原  030024
Published: December 2020

Phenyl-C71-butyric acid methyl ester （［70］PCBM） clusters are investigated by using the B3LYP method with 6-31G（d） basis set. The optimized results indicate that the addition of PCBM into the ［6，6］-junction produces a closed methanofullerene which is thermodynamically stable product; and the addition into the ［5，6］-junction results in an enlarged fullerene （an open fulleroid） which is a kinetically controlled product. The first adiabatic electron affinity for ［70］PCBM is similar to that for C70. The energy gaps of ［70］PCBM are reduced compared with those of C70. PCBM derivatives and show increased level of the lowest unoccupied molecular orbital of fullerenes. From the natural charge populations， it is found that adding PCBM unit onto the C70 cages does not change the charge populations remarkably; attaching a PCBM has no effect on the electronic structures of C70. The results of theoretical calculation suggest that PCBM is not involved in the process of photoelectric conversion but it plays a key role in adjusting the level of HOMO-LUMO for increasing photoelectric conversion efficiencies.
Topological research on the molar magnetic susceptibility of alkali metal compounds with support vector regression
Authors: Cai Cong-Zhong  , Zhuang Wei-Ping  , Wen Yu-Feng  , Zhu Xing-Jian  , Pei Jun-Fang  , Xiao Ting-Ting  ,   重庆大学应用物理系，重庆  400044
Published: December 2020

According to the experimental dataset on the molar magnetic susceptibility χm of 45 alkali metal compounds and the topological descriptor?——magnetic connectivity index mF， which is extracted by the magnetic valence gi of simple ion deduced from classical electrodynamics， support vector regression （SVR） combined with particle swarm optimization for its parameter optimization is proposed to establish a model for predicting the molar magnetic susceptibility of alkali metal compound via 0F and 1F. The performance of SVR model is compared with that of multivariate linear regression （MLR） model. The results show that the mean absolute error， the mean absolute percentage error and the root mean square error for 9-fold cross validation test of SVR models are all smaller than those achieved by MLR models. It is revealed that the generalization ability of SVR model is superior to that of MLR model. This study suggests that magnetic connectivity index is an effective descriptor and the SVR is a powerful approach to the prediction of the molar magnetic susceptibility of alkali metal compounds.
The degree distribution of simple generalized collaboration networks
Authors: Zhao Qing-Gui  , Kong Xiang-Xing  , Hou Zhen-Ting  ,   (1)中南大学数学科学与计算技术学院,长沙  410075; (2)中南大学数学科学与计算技术学院,长沙  410075；重庆文理学院数学与统计学院，重庆  402160
Published: December 2020

We study three special cases of simple generalized collaboration networks， namely the preferential attachment, random attachment and mixed attachment networks. Based on Markov chain theory, we provide a rigorous proof for the existence of the steady-state degree distribution of the network generated by this model and obtain its corresponding exact formula. In particular, for mixed attachment, if it has preferential attachment, degree distribution of the network obeys power-law distribution, and it is a scale-free network.
Molecular dynamics study of freezing a molten Cu55 cluster on Cu(010)surface
Authors: Zhang Zong-Ning  , Liu Mei-Lin  , Li Wei  , Geng Chang-Jian  , Zhao Qian  , Zhang Lin  ,   (1)东北大学理学院，沈阳  110004; (2)沈阳工业大学理学院，沈阳  110178
Published: December 2020

Structural change of a molten Cu55 cluster on Cu（010） substrate during freezing at two different cooling rates is investigated by molecular dynamics simulations based on the embedded atom method. The analyses of energy per atom and pair distribution functions show that cooling processes have great influence on the structural changes. A rapid cooling rate results in the lower energy of the atoms in the cluster. At a slow cooling rate， the cluster atoms in the substrate are more likely to move to the substrate surface at high temperature， and then they form face-centred cubic configuration.
Linear prediction of exponential decaying sinusoidal superposition signal
Authors: Gao Xiao-Feng  , Xu Zhi-Hai  , Feng Hua-Jun  , Li Qi  ,   浙江大学现代光学仪器国家重点实验室,杭州  310027
Published: December 2020

In spectral resolution enhancement the linear prediction of exponentially decaying sinusoidal superposition signal is one of the key technologies. In this study, the direct calculating equations of forward and backward linear prediction coefficients, the relationship between forward and backward linear prediction coefficients, and the forward and backward linear predictability conditions are derived. It is shown that, for exponential decaying sinusoidal superposition signal, there is not simple conjugate symmetry between forward and backward linear prediction coefficients, but they are still related. This research provides a theoretical basis for spectral resolution enhancement about decaying interference signals.
Capacity of multiple-input-multiple-output quantum key distribution channels
Authors: Xiao Hai-Lin  , Ouyang Shan  , Nie Zai-Ping  ,   (1)电子科技大学电子工程学院，成都  610054; (2)桂林电子科技大学信息与通信学院，桂林  541004
Published: December 2020

Quantum safety communications is a process of quantum key distribution （QKD）. Current QKD technology restricts transmission to a low bit rate. To improve the QKD bit rate and develope high rate and large capacity, we propose a multiple-input-multiple-output（MIMO） quantum key distribution system. The Wigner operator of multi-photon entangled states in MIMO quantum key distribution channel is presented. As a result, the Wigner function of multi-photon double-model squeezed entangled sates and MIMO quantum key distribution channel capacity are also obtained, which will provide theoretical support and technical basis for developing robust space-time processing algorithm of MIMO quantum safety communications and designing optimum high performance system of MIMO quantum key distribution.
The phonon effect of qubit in quantum ring
Authors: Jiang Fu-Shi  , Zhao Cui-Lan  ,   内蒙古民族大学物理与电子信息学院,通辽  028043
Published: December 2020

Under the condition of electron-LO photon strong coupling, the eigenfunction and the eigenenergy of the ground state and the first excited state of the electron in quantum ring, are obtained by solving precisely the Schrdinger equation. A qubit is formed by overlaying both the ground state and the first excited state of the electron-LO phonon system.Numerical calculations indicate that the distribution of the probability density of electrons in quantum oscillates periodically with time and angle coordinate. The oscillating period decreases with the increase of the electron-LO phonon coupling strength, which shows that the existence of phonon can reduce the coherence of qubit, and that the oscillating period increases with the increasing inner（or outer） radius of quantum ring. Therefore, the coherence of qubit can be improved by choosing proper size of quantum ring.
Generalized synchronization control of multi-scroll chaotic systems
Authors: Wu Zhong-Qiang  , Kuang Yu  ,   燕山大学工业计算机控制工程河北省重点实验室,秦皇岛  066004
Published: December 2020

Based on the adaptive backstepping method, a kind of synchronization controller is proposed for multi-scroll chaotic systems with different initial states and unknown parameters. The synchronization controller can realize complete synchronization, anti-synchronization, and a kind of nonlinear generalized synchronization between two chaotic systems, and it is better for application. Simulations show the effectiveness of the controller.
Frequency-dependent stochastic resonance in a two-dimensional neural map
Authors: Wang Mao-Sheng  ,   安徽师范大学物理系，芜湖  241000
Published: December 2020

The effect of noise on a two-dimensional neural map with stable subthreshold oscillations is investigated by numerical simulation. It is found that noise can induce action potential and stochastic resonance. Furthermore, the influences of control parameter and input signal frequency on the dynamics of the system are also studied. Only when the parameters are chosen in or near to the regime of silence, we can observe the frequency-dependent stochastic resonance phenomenon.
Analytical potential energy functions and spectroscopic properties of the ground and excited states of BH molecule
Authors: Wang Xin-Qiang  , Yang Chuan-Lu  , Su Tao  , Wang Mei-Shan  ,   鲁东大学物理与电子工程学院，烟台  264025
Published: December 2020

The potential energy curves （PECs） for the ground state （X1Σ+） and six excited states （a3П, A1П, B1Σ+, b3Σ-,c3Σ+, and C′1Δ） of BH molecule have been computed using the multireference configuration interaction （MRCI） method and Dunning’s correlation consistent basis sets aug-cc-pV5Z. By employing the Murrell-Sorbie function （MS） and the least-square fitting method, the analytical potential energy functions （APEFs） of these states are obtained. The root means square （RMS） errors between the fitted results and the ab initio values are very small in comparison with the chemical accuracy （349755 cm-1）, which implies that the APEFs can well display the interactions between the two atoms of BH molecule. Based on the APEFs, we have calculated the spectroscopic parameters and compared them with the available theoretical and experimental values. The calculating results are in good agreement with the experimental values, which shows that the present APEFs are accurate. The double-well PEC for the B1Σ+ state has also been fitted accurately with MS function, which provides a sample for more wider application of MS function.
Extraordinary transmission of sub-wavelength apertures in terahertz region
Authors: Wang Yuan-Yuan  , Zhang Cai-Hong  , Ma Jin-Long  , Jin Biao-Bing  , Xu Wei-Wei  , Kang Lin  , Chen Jian  , Wu Pei-Heng  ,   南京大学超导电子学研究所，南京  210093
Published: December 2020

Using terahertz time domain spectroscopy （THz-TDS）, THz transmission spectrum of the array with sub-wavelength apertures on the Nb thin film has been studied in the temperature range of 5—300 K. The extraordinary transmission is observed and the peak positions are in agreement with the computer simulation technology simulation results. The transmission amplitude increases with the decreasing temperature.
Fractal characteristics of surface roughness and its effect on laminar flow in microchannels
Authors: Zhang Cheng-Bin  , Chen Yong-Ping  , Shi Ming-Heng  , Fu Pan-Pan  , Wu Jia-Feng  ,   东南大学能源与环境学院,南京  210096
Published: December 2020

The fractal characteristics of the surface roughness are investigated by using fractal geometry. A three-dimensional model of laminar flow in microchannels with surface roughness characterized by fractal geometry is developed and analyzed numerically. The Weierstrass-Mandelbrot function is introduced to characterize the multiscale self-affine roughness. The effects of Reynolds number Re， relative roughness， and fractal dimension on Poiseuille number are investigated and discussed. The results show that， different from the conventional channels， Poiseuille number in rough microchannels is no longer constant for different Re， but increases approximately linearly with Re， and is larger than the classical value. The flow over roughness features with high relative roughness induces recirculation and flow separation， which plays an important role in flow pressure drop. More specifically， roughness with larger fractal dimension， which yields more frequent variation in the surface profile， also results in a significant increase in pressure loss， even though at the same relative roughness. In addition， the accuracy of Poiseuille number calculated by the present model is verified by the experimental data available in the literature.
Structural， optical and electrical properties of Ga2（1-x）In2xO3 films prepared by metalorganic chemical vapor deposition
Authors: Yang Fan  , Ma Jin  , Kong Ling-Yi  , Luan Cai-Na  , Zhu Zhen  ,   山东大学物理学院，济南  250100
Published: December 2020

Ga2（1-x）In2xO3（x=01—09） thin films were prepared on α-Al2O3 （0001） substrates by metalorganic chemical vapor deposition （MOCVD）. The structure， the optical and electrical properties as well as the effect of annealing on the properties of the films were investigated in detail. The results indicate that the film deposited with composition x=02 was polycrystalline with β-Ga2O3 structure， the film with x=05 was amorphous and transformed into body-centered cubic （bcc） structure of In2O3 with a preferred orientation of （222） after annealing. For x=08， the obtained film showed bcc structure of In2O3 and the crystalinity was improved after annealing treatment. The average transmittance for the films in the visible range was over 85%. The band-gap of the Ga2（1-x）In2xO3 films can be suitably tuned from 376 to 443 eV by controlling the gallium content and it is increased obviously by annealing.
Phase-field modeling of the effect of liquid-solid interface anisotropies on free dendritic growth
Authors: Zhao Da-Wen  , Li Jin-Fu  ,   上海交通大学材料科学与工程学院，金属基复合材料国家重点实验室，上海  200240
Published: December 2020

Based on the adaptive finite element method， the phase-field model has been employed to simulate the free dendritic growth process governed by capillary anisotropy or kinetic anisotropy. It is illustrated that the free dendritic growth depends sensitively on the degree of the capillary anisotropy or kinetic anisotropy of the solid-liquid interface. As the anisotropies are enhanced， the dendrite tip growth velocity increases， but the dendrite tip radius decreases. These two kinds of anisotropies have different effects on the free dendritic growth behaviors. Under the capillary anisotropic condition， there is a power law relationship between the stability parameter and the capillary anisotropy parameter. And under the kinetic anisotropic condition， there is a linear relationship between the stability parameter and the capillary anisotropy parameter.
Effects of Ti ion implantation and post-thermal annealing on the structural and optical properties of ZnS films
Authors: Su Hai-Qiao  , Xue Shu-Wen  , Chen Meng  , Li Zhi-Jie  , Yuan Zhao-Lin  , Fu Yu-Jun  , Zu Xiao-Tao  ,   (1)电子科技大学应用物理系，成都  610054; (2)兰州大学物理科学与技术学院，兰州  730000; (3)湛江师范学院物理系，湛江 524048
Published: December 2020

Ti ions were implanted into ZnS films at a dose of 1×1017ions/cm2 and energy of 80 keV by vacuum evaporation. After ion implantation， the as-implanted sample was annealed in argon ambient at different temperatures from 500 ℃ to 700 ℃. The effects of ion implantation and post-thermal annealing on the structural and optical properties of ZnS films were investigated by x-ray diffraction （XRD）， photoluminescence （PL） and optical absorption. The results showed that the diffraction peak intensity was recovered by annealing at 500 ℃. The optical absorption in the visible region increased after Ti ion implantation and the absorption edge blueshifted with the increasing annealing temperature. The PL emission intensity increased with the increasing annealing temperature.
First-principles study on the effects of the concentration of Al-2N high codoping on the electric conducting performance of ZnO
Authors: Hou Qing-Yu  , Zhao Chun-Wang  , Jin Yong-Jun  ,   内蒙古工业大学理学院物理系，呼和浩特  010051
Published: December 2020

Under the same condition，ZnO models with different sizes are proposed by using the plane wave ultra-soft pseudopotential technique based on the density functional theory （DFT）. Al and N with different concentrations are heavily doped in ZnO semiconductor，and the density of states of Al and N doped ZnO is calculated by DFT mothod under the condition of low temperature. The relative average number of holes and the scattering mobility of holes in the valence band are calculated. We find that heavily doping of Al-2N atoms with low concentration can enhance the conducting of ZnO，which means that the conductivity of ZnO semiconductor is related with not only the concentration of heavy doped Al and N，but also the relative average number of holes and the scattering mobility of holes in the valence band. The calculated results agree with the experimental results.
First-principles study on field emission of C-doped capped single-walled BNNT
Authors: Yang Min  , Wang Liu-Ding  , Chen Guo-Dong  , An Bo  , Wang Yi-Jun  , Liu Guang-Qing  ,   西北工业大学应用物理系，西安  710072
Published: December 2020

The electron field emission properties of C-doped capped single-walled BNNT （C@BNNT） are investigated by first-principles study. The results show that with the increase of the applied electric field, the electronic structure of C@BNNT changes significantly，the density of states （DOS） shifts towards the low energy position，the local density of states （LDOS） at the Fermi level increases dramatically，the energy gap between the lowest unoccupied molecular orbital （LUMO） and the highest occupied molecular orbital （HOMO） decreases drastically and the electrons congregate to the capped side. The investigations of DOS，HOMO/LUMO and Mulliken population analysis indicate that， compared with pristine BNNT, the field emission properties of C@BNNT, especially of C@BNmoreNT， are greatly improved.
Synthesis and luminescence properties of YPO4:Eu3+ nanophosphor
Authors: Zhang Jia  , Wang Yu-Hua  , Wang Dan  ,   兰州大学物理科学与技术学院，兰州  730000
Published: December 2020

A series of nanophosphors of Y1-xPO4:xEu3+（005≤x≤030）were synthesized by a mild hydrothermal method with post heat treatment. The structure and morphology of the samples were characterized by X-ray diffraction （XRD） and scanning electron microscope （SEM）. The results show that these nanophosphors have tetragonal structure with spherical and fine rod-like morphologies in acidic and alkaline condition, respectively, but all are on the nanoscale. The photoluminescence （PL） properties were also investigated under vacuum ultraviolet （VUV） excitation. Compared with samples prepared by solid state reaction, the PO3-4 absorption band located at 142 nm in vacuum ultraviolet region shifts towards high-energy direction. The intensity of 5D0→7F2 （619 nm） emission peak of Eu3+ is higher than that of 5D0→7F1. After heat treatment, the color purity and luminous intensity of the phosphors can be greatly improved. The PL intensity of optimized phosphor is superior to that of samples prepared by solid state reaction. These phenomena can be attributed to the improved crystallinity and reduced defects.
Effect of AlGaN intermediate layer on residual stress control and surface morphology of GaN grown on 6H-SiC substrate by metal organic vapour phase epitaxy
Authors: Jiang Yang  , Luo Yi  , Xi Guang-Yi  , Wang Lai  , Li Hong-Tao  , Zhao Wei  , Han Yan-Jun  ,   清华大学电子工程系，清华信息科学与技术国家实验室（筹），集成光电子学国家重点实验室，北京  100084
Published: December 2020

GaN layers with AlGaN intermediate layers of different Al mole fraction steps were grown on 6H-SiC by metal organic vapour phase epitaxy system. The residual stress and surface morphology of these samples were compared with GaN/AlN/SiC structure in detail. High resolution X-ray diffraction indicates that the c-axis constant increases with the increasing number of AlGaN steps, while low-temperature photoluminescence measurement shows a blue-shift of the GaN peak. These results should be attributed to the decreased residual stress in GaN. Furthermore, surface morphology of samples with AlGaN intermediate layers is improved according to the results of atomic force microscope.
Molecular dynamics simulation of stress-induced martensitic phase transformation in NiAl
Authors: Cao Li-Xia  , Shang Jia-Xiang  , Zhang Yue  ,   北京航空航天大学材料科学与工程学院,空天材料与服役教育部重点实验室,北京  100191
Published: December 2020

Molecular dynamics simulations are utilized to study the deformation process in NiAl under uniaxial tension using embedded atom method （EAM） interatomic potential. Both the tensile stress-strain curve and the atomic configurations are analyzed. The martensitic phase transformation is observed and the initial B2 NiAl transforms to a face-centered cubic ordered phase （L10）. The investigation of atomic configuration evolution indicates that the martensitic phase transformation occurs by the propagation and annihilation of {110} twinning planes. The nucleation mechanism of stress induced martensile has also been discussed.
Characteristics of hydrogen storage studied using homemade apparatus
Authors: Dai Wei  , Tang Yong-Jian  , Wang Chao-Yang  , Sun Wei-Guo  ,   (1)四川大学原子与分子物理研究所,成都  610065; (2)中国工程物理研究院激光聚变研究中心,绵阳  621900; (3)中国工程物理研究院激光聚变研究中心,绵阳  621900；四川大学原子与分子物理研究所,成都  610065
Published: December 2020

To deal with the problem that autosorb analyzer can only work under the condition of pressure below 0.1 MPa, we have designed and fabricated a new apparatus which is used to study the characteristics of adsorption in an extended range of pressure.Ideal gas equation of state and van der Waals equation are used to calculate the capacity of hydrogen storage of the materials of resorcinol-formaldehyde carbonized aerogel with the help of the new apparatus.
Study on the regional characteristics of the temperature changes in China based on complex network
Authors: Zhou Lei  , Gong Zhi-Qiang  , Zhi Rong  , Feng Guo-Lin  ,   (1)扬州大学物理科学与技术学院,扬州  225002；国家气候中心,中国气象局气候研究开放实验室,北京  100081; (2)扬州大学物理科学与技术学院,扬州  225002；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; (3)扬州大学物理科学与技术学院,扬州  225002；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；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

To analyze the regional characteristics of temperature changes in China, by using the daily mean temperature series from 1961 to 2002 of 435 weather stations in China, we set up the temperature fluctuant networks, calculate the topology statistics of every station, and present the special distribution graph of all stations. We find that the degrees of RRD, RDD, DRR, DDR, DrR are extraordinarily high, and the occurrence probability of temperature fluctuation represented by these 5 nodes is greater, which is helpful for forecasting the trend of temperature changes. Then,from the distribution graph of the degrees of these 5 nodes in all the 435 stations, we define them by the symbols as countrywide model, hypo-countrywide model, eastern model, blend model, and western with southern model. The coefficient between the degree distribution in every station and the national average degree distribution has a regional characteristics, which provide us with the feasibility for analyzing the regional characteristics in theory. From the regional characteristics of the national distribution of the average clustering coefficient, we define three kinds of significant regions of temperature changes in China: strong complex regions, weak complex regions and middle complex regions.
The spatio-temporal stochastic resonance of calcium in coupled hepatocytes systems affected by subthreshold stimuli and noise
Authors: Wang Bao-Hua  , Lu Qi-Shao  , Lü Shu-Juan  ,   (1)北京航空航天大学一般力学研究室，北京  100191; (2)北京航空航天大学一般力学研究室，北京  100191；黑龙江大学数学科学学院，哈尔滨  150080
Published: December 2020

The influence of subthreshold periodic stimuli on temporal-spatial resonance of ［Ca2+］ in a stochastic coupled hepatocytes system is studied. When the frequency of stimuli is close to that of the determinate coupled system before the Hopf bifurcation, the eruption rate of ［Ca2+］ is enhanced greatly in the stochastic system. By computing the autocorrelation function of the eruption rate, it is found that the temporal resonance of ［Ca2+］ becomes more ordered by the subthreshold stimuli. Furthermore, for a given coupling strength between cells, there is an optimal noise level to make the ［Ca2+］ resonance reach maximum, and the optimal noise level also increases with the coupling strength increasing. Though the action of subthreshold stimuli promotes the temporal resonance of the system, it strengthens the sensibility to noise and then depresses the spatial ordered calcium waves induced by medium-strength noise only, as shown by the analysis by the spatial Fourier transform and its structure function.
Experimental studies on the statistical functions of speckle fields based on the extraction of the complex amplitudes by use of interference beam
Authors: Song Hong-Sheng  , Cheng Chuan-Fu  , Teng Shu-Yun  , Liu Man  , Liu Gui-Yuan  , Zhang Ning-Yu  ,   (1)山东建筑大学理学院，济南  250101; (2)山东师范大学物理与电子科学学院，济南  250014; (3)山东师范大学物理与电子科学学院，济南  250014；山东建筑大学理学院，济南  250101; (4)山东师范大学物理与电子科学学院，济南  250014；山东轻工业学院数理系，济南  250100
Published: December 2020

Using the interference patterns of speckle fields and the reference beam, we extract digitally the complex amplitudes, phases and intensities of speckles fields and then study experimentally their properties. The influences of noise on the measurement of statistical functions, especially on that of the probability density function, appearing in the conventional method is satisfactorily eliminated. The experimental studies of the statistical properties of the complex amplitude and the phases of the speckle fields were also performed. By the practical measurement of speckle fields scattered at different angles, we find that the speckles are laterally broadened gradually with increase of the scattering angle, and their average widths become anisotropic. Such anisotropy brings about no change in the probability density function of the speckle fields, which remain circularly Gaussian as in the case of the traditional small angle scattering.