bluuebunny/crossref_metadata_2025 huggingface dataset:
First-principles study of low-compressibility of transition-metal Tc and its nitrides TcN,TcN2,TcN3 and TcN4
Authors: Xu Hong-Bin  , Wang Yuan-Xu  ,   河南大学物理与电子学院计算材料科学研究所，开封  475004
Published: December 2020

Tc and its nitrides TcN, TcN2, TcN3 and TcN4 are studied using the projector augmented wave method based on the density functional theory. The elastic properties, electronic structure and atomic populations, theoretical hardness of Tc nitrides are calculated and analyzed. The calculation results show that with increasing N content by incorporated into transition-metal Tc, the solid structures of the material change into laminar, and its elastic moduli do not monotonically increase. It reveals that TcN with solid structure has the largest bulk modulus and the smallest shear modulus, while TcN3 with layered structure has the largest shear modulus and the smallest bulk modulus, and TcN4 is found to have the largest theoretical hardness by means of chemical bonding analysis. It can be seen that the bulk modulus depends mainly on electrons per atomic volume and mass density, while covalent structure of chemical bonding and N content make more contribution to theoretical hardness, and appropriate content N—N covalent bonding in the same direction tends to increase the shear modulus of nitrides.
The dynamic exponent of two-dimensional fully frustrated XY model
Authors: Lei Xiao-Wei  , Zhao Xiao-Yu  ,   重庆文理学院物理系，重庆  402160
Published: December 2020

With a large-scale Monte Carlo simulation, non-equilibrium dynamics of the two-dimensional fully frustrated XY model is investigated. We tackle the Kosterlitz-Thouless phase transition. Starting from an ordered initial state, we study the dynamic evolution of the magnetization as well as a specifically defined Binder cumulant. From the dynamic scaling ansatz, we extract the correlating time of the dynamics and the spatial correlation length of the equilibrium state. The dynamic exponent z is determined with relatively high accuracy. Especially, we suggest and demonstrate how one may directly measure the dynamic exponent z above TKT from the scaling fit of the Binder cumulant. These results indicate that the dynamic exponent z fluctuates around z=2, and this is consistent with that observed at temperatures below the transition temperature TKT.
Molecular dynamics study on the plastic behavior of monocrystalline copper under shock loading and unloading
Authors: He An-Min  , Shao Jian-Li  , Qin Cheng-Sen  , Wang Pei  ,   北京应用物理与计算数学研究所，北京  100088
Published: December 2020

Molecular dynamics simulations were used to study the plastic behavior of copper monocrystal under shock loading and unloading. We obtained the Hugoniot relation for both ［001］ and ［111］ orientations and the melting pressure, which turns out to be in agreement with experiment. The results showed that higher initial temperature increases the possibility for the dislocation loop generate and expansion. The release behavior after the shock wave reaching the back of the sample was also analyzed. We found that the release behavior was quasi-elastic and most of the stacking-fault networks disappear behind the release wave along ［001］ orientation while few stacking faults disappear along ［111］ orientation.
Nonequilibrium properties of Sherrington-Kirkpatric spin glass model
Authors: Zhang Kai-Cheng  ,   中国科学院物理研究所，北京  100190
Published: December 2020

Using Sherrington-Kirkpatric （SK） model we investigated the nonequilibrum properties of spin glass by dynamical Monte Carlo simulation. Our results revealed that the susceptibility in the weak field shows a cusp near the glass transition, while the specific heat shows a more broad transition. The aging and zero-field colding memory effect is also reproduced in our simulation, and the phenomena can be explained by energy relaxation. Our simulation also reveals that homogeneous SK model can not reproduce the exchange bias effect observed in the experiment.
Growth behavior of ZnO nanoparticles formed on Zn implanted Si(001) combined with thermal oxidation
Authors: Fu Wei-Jia  , Liu Zhi-Wen  , Liu Ming  , Mu Zong-Xin  , Zhang Qing-Yu  , Guan Qing-Feng  , Chen Kang-Min  ,   (1)大连理工大学三束材料改性国家重点实验室，大连  116024; (2)江苏大学材料科学与工程学院，镇江  212013
Published: December 2020

Si（001） chips were implanted by Zn ions of 40 keV with different ion dosages and are annealed in air at different temperatures. Atomic force microcopy， transmission electron microcopy， X-ray diffraction and electron probe are applied to study the microstructure， morphology and chemical composition of the chips, either as-implanted or annealed at different temperatures. It was found that the as-implanted Zn atoms aggregate into clusters scattering about 35 nm beneath the surface of the chips. During the annealing process， Zn atoms are found to migrate towards the surface of the chips and aggregate into nanoparticles at the interface between the amorphous SiO2 layer and polycrystal line Si layer. Annealing temperature was found to be the crucial factor controlling the formation of ZnO nanoparticles. ZnO nanoparticles begin to appear at about 400 ℃ and the diffraction intensity of ZnO becomes strong while the diffraction intensity of metallic Zn weakens with increasing annealing temperature. At the annealing temperature of 800 ℃， Zn2SiO4 phase was observed due to the reaction between ZnO and SiO2 or Si.
Analysis of degradation mechanism of GaN blue light emitting diode by the characteristics of capacitance and conductance
Authors: Chen Huan-Ting  , Lü Yi-Jun  , Chen Zhong  , Zhang Hai-Bing  , Gao Yu-Lin  , Chen Guo-Long  ,   厦门大学物理系，福建省半导体照明工程技术研究中心，厦门  361005
Published: December 2020

A study of the capacitance-voltage characteristics of GaN light emitting diode（LED） with a view to reveal its degradation mechanism is presented in this article by forward alternating current small-signal method. Combined with series resistance， ideality factor and tunneling current measurement， the properties of negative capacitance and conductance are discussed. The threshold voltage of negative capacitance during degradation is qualitatively analysed. The decreased negative capacitance during aging may be due to the decrease in the effective acceptor concentration and radiative recombination rate， and the increase of defects and non-radiative recombination centers resulting in the enhanced capture effect of carriers. The tunneling effect leads to the obvious increase of conductance under reversed and low-forward bias voltage. The decreased conductance during aging may be due to the series resistance. On the basis of the capacitance-voltage characteristic， light output， current-voltage curves with the degradation mechanism of LED， the characteristics of negative capacitance and conductance can be used as important evidence for the degradation analysis of LED as proved by experiment and theory.
First-principles investigations on the electron transport of a TaSi3 cluster
Authors: Zheng Xin-Liang  , Zheng Ji-Ming  , Ren Zhao-Yu  , Guo Ping  , Tian Jin-Shou  , Bai Jin-Tao  ,   (1)西北大学光子学与光子技术研究所，西安  710069; (2)西北大学物理系，西安  710069; (3)西北大学物理系，西安  710069；西北大学光子学与光子技术研究所，西安  710069; (4)中国科学院西安光学精密机械研究所瞬态光学与光子技术国家重点实验室，西安  710119
Published: December 2020

The electron transport properties of a TaSi3 cluster sandwiched between two Al electrodes are investigated by using the first-principle-analysis. The results show that transport properties under low bias are determined by the 8th and 9th state of MPSH. Equilibrium conductance of TaSi3 cluster is very sensitive to the cluster-electrode distance. The oscillation form of conductance becomes obviously when the distance is greater than 0.35 nm. While the equilibrium conductance decreases quickly when the distance is less than 0.35 nm. The asymmetric current-voltage characteristics occur when the bias is in the range of -1 to 1 V and negative differential resistance is observed when the bias changes from 0.3 to 0.4 V.
Photoluminescence of as-grown and annealed ZnO films on Ti-buffered Si(111) substrates
Authors: Wei Wei  , Liu Ming  , Qu Sheng-Wei  , Zhang Qing-Yu  ,   大连理工大学三束材料改性国家重点实验室，大连  116024
Published: December 2020

ZnO thin films with strong c-axis preferred orientation have been deposited on Ti buffered Si （111） substrate by reactive ratio-frequency magnetron sputtering. With X-ray diffraction analysis and photoluminescence （PL） measurement， the structure， residual stress and PL emission properties of Ti-buffered ZnO films are studied and effects of Ti-layer thickness and annealing temperature are discussed. It is found that the PL properties of the films are improved after the introduction of Ti buffer layer and an optimized thickness of Ti buffer layer is given. Annealing treatment can improve the properties of Si（111）/Ti-buffer/ZnO films further. The residual stress is found to be an important factor influencing the emission properties of ultraviolet light. It is helpful for the emission of ultraviolet light if the films have a small residual stress. The residual stress can also change the transition energy of excitons. With the increase of annealing temperature， the increase of tension strain in films reduces the band gap of ZnO， hence results in the shift of the excitonic peak to lower energy.
Detection of nuclear magnetic resonance in the microtesla range using a high Tc dc-superconducting quantum interference device
Authors: Li Shao  , Ren Yu-Feng  , Wang Ning  , Tian Ye  , Chu Hai-Feng  , Li Song-Lin  , Chen Ying-Fei  , Li Jie  , Chen Geng-Hua  , Zheng Dong-Ning  ,   (1)中国科学院物理研究所北京凝聚态物理国家实验室,北京  100190; (2)中国科学院物理研究所北京凝聚态物理国家实验室,北京  100190；长春理工大学物理系，长春  130022
Published: December 2020

We have carried out nuclear magnetic resonance experiments in microtesla range.The free induction signal was recorded using a high Tc dc-superconducting quahtum interference device.The measurement was performed in a home-made magnetic shield room.Resonance spectra of 1H from a sample of 15 ml tap water was obtained in the field range from 7—70 μT，corresponding to resonance frequency of 300—3000 Hz，The signal to noise ratio in a single-shot measurement is around 4，which could be increased to about 40 after 100 times averaging.The effect of residual magnetic field in the shield room， prepolarization time and data acquisition time was investigated.
Magnetic-field-induced phase transition of vortex glass states in disordered Josephson junction arrays
Authors: Zhao Zhi-Gang  , Xu Zi-Wei  , Li Bin  , Liu Mei  ,   (1)东南大学物理系，南京  211189; (2)东南大学物理系，南京  211189；南京农业大学工学院，南京  210031
Published: December 2020

Using the resistively shunted junction model，we study magnetic-field-induced phase transitions of the vortex glass states in a disordered two-dimensional Josephson junction array. From calculated results of the vorticity of the vortex system and the voltage noise generated by current-driven vortices as a function of the magnetic field， the following conclusions can be drawn. 1） With decreasing the magnetic field， the vortex system exhibits a reentrant transition from a vortex glass phase to a pinned dilute vortex liquid. 2） There is a peak of voltage noise driven by the current in the vortex glass state. It follows that the system is in a sub-stable state as a result of the competition between ordered and disordered interactions， which results in peak effects of the critical current. The calculated results are consistent with recent experimental reports by Okuma and Kamada on disordered and superconducting MoxSi1-x films.
Activation of room-temperature ferromagnetism in Mn doped ZnO thin films by N codoping
Authors: Zou Wen-Qin  , Lu Zhong-Lin  , Wang Shen  , Liu Yuan  , Lu Lu  , Li　Li  , Zhang Feng-Ming  , Du You-Wei  ,   (1)东南大学物理系，南京  210096; (2)南京大学物理系，固体微结构物理国家实验室，南京  210093
Published: December 2020

Mn doped ZnO films with and without N codoping have been fabricated by oxidative annealing of sputtered Zn:Mn and Zn2N3:Mn films on silicon substrates in flowing O2 ambient. It was found that the ZnO:Mn films show very weak ferromagnetic behavior, while for those with N codoping, significant ferromagnetism with a moderate saturation magnetization of about 0.23—0.61 μB per Mn2+ ion was observed at room temperature. It suggests that significant ferromagnetism in ZnO:Mn films could be activated by N codoping. The results indicate that holes are favorable for ferromagnetic ordering of the doped Mn2+ ions in ZnO, in agreement with the recent theoretical studies.
Effects of substitutions of Nd3+ for Sr2+ on the properties of SrBi2Nb2O9 ceramics and their mechanism
Authors: Sun Lin  , Chu Jun-Hao  , Yang Ping-Xiong  , Feng Chu-De  ,   (1)华东师范大学信息科学技术学院，极化材料与器件教育部重点实验室，上海  200241; (2)中国科学院上海硅酸盐研究所，上海  200050
Published: December 2020

（Sr1-3x/2Ax/2Ndx）Bi2Nb2O9 （x=0，0.05，0.1 and 0.2） ceramics are prepared by traditional solid-reaction method， and effects of substitutions of Nd3+ for Sr2+ on the properties of SrBi2Nb2O9 ceramics and their mechanism are investigated. The results show that the temperature spectra of dielectric constant and loss for these Nd-doped samples are obviously characteristic of ion relaxor polarization. The partial substitution of Nd3+ for Sr2+ leads to the slight reduction in remanent polarization （Pr） and the increase in piezoelectric coefficient d33， which can be attributed to the increase in dielectric constant of samples according to ferroelectric thermodynamics theory. Raman spectrum shows that no change in the Curie temperature （TC） of （Sr1-3x/2Ax/2Ndx） Bi2Nb2O9 samples is observed， which might result from no appreciable variation in NbO6 octahedron distortion. For （Sr1-3x/2Ax/2Ndx） Bi2Nb2O9 ceramics， the substitution of Nd3+ for Sr2+ increases permittivity εr， piezoelectric coefficient d33，and electromechanical coupling coefficient Kp and reduces mechanical quality factor Qm, but it does not change temperature coefficient of harmonic frequency value.
Investigation of transient thermally induced nonlinear refraction in metal cluster polymer ［Tp*W(μ3-S)3Cu3Py3(μ3-Br)］(PF6)/DMF solution using the phase ob
Authors: Liu Jin-Shan  , Yang Jun-Yi  , Song Ying-Lin  , Hou Deng-Ke  ,   苏州大学物理科学与技术学院，苏州  215006
Published: December 2020

The transient thermally induced nonlinearity of a novel metal cluster polymer solution was investigated by using the phase object （PO） Z-scan technique which can distinguish the transient thermal effect from the third-order nonlinear refraction easily in the nanosecond regime. We studied the optical nonlinearity of the ［Tp*W（μ3-S）3Cu3Py3（μ3-Br）］（PF6）/DMF solution using both PO Z-scan and conventional Z-scan techniques with the laser pulse width of 8 ns under different input pulses energe. Results of numerical simulations and solution of simultaneously acoustic wave equation and the diffusion equation of conduction of heat agree well with the experimental results，which shows that the nonlinear refraction of the sample is due to transient thermally induced nonlinear refraction.
The effect of Eu2+ doping concentration on luminescence properties of BaAl2Si2O8：Eu2+ blue phosphor
Authors: Ma Ming-Xing  , Zhu Da-Chuan  , Tu Ming-Jing  ,   四川大学材料科学与工程学院，成都  610065
Published: December 2020

The BaAl2Si2O8：Eu2+ blue phosphor was synthesized by one-step calcination of the precursor prepared by chemical coprecipitation. X-ray diffraction and fluorescence spectrophotometry were used to investigate the structural and luminescent properties of the BaAl2Si2O8：Eu2+ blue phosphor. The result showed the BaAl2Si2O8：Eu2+ synthesized by the process was pure. The excitation spectrum of the BaAl2Si2O8：Eu2+ blue phosphor extended from 240 to 410 nm， and the peak appeared around 320 nm，thus the phosphor can be excited effectively by InGaN chip in the range of 350—410 nm. The emission spectrum excited by 365 nm showed a characteristic wide band with the peak at about 465 nm. The emission spectrum intensity firstly increased with Eu2+ doping concentration increasing，then decreased. The strongest emission intensity was obtained when Eu2+ doping concentration reached 3.5mol%. The concentration quenching mechanism was caused by the exchange interaction of Eu2+ ions according to the Dexter theory.
Luminescence characteristics and crystallographic sites of Ce3+ in LiBaBO3
Authors: Li Pan-Lai  , Wang Zhi-Jun  , Wang Ying  , Yang Zhi-Ping  , Guo Qing-Lin  , Li Xu  , Yang Yan-Min  , Fu Guang-Sheng  ,   河北大学物理科学与技术学院，保定  071002
Published: December 2020

LiBaBO3：Ce3+ phosphor was prepared by solid-state method，and its luminescence characteristics were investigated. LiBaBO3：Ce3+ phosphor shows one asymmetrical band at 440 nm. Monitored at 440 nm，the excitation spectrum has a broad band at 370 nm. The crystallographic sites of Ce3+ in LiBaBO3 were calculated by van Uitert formula，the results show that the emission band centered at 438 nm originates from the Ce3+ center of the nine compounds，and at 469 nm originates from the Ce3+ center of the eight compounds. The effect of Ce3+ concentration on luminescent intensity of LiBaBO3：Ce3+ phosphor was investigated，the result shows that the luminescent intensity firstly increases with increasing Ce3+ concentration，and reaches the maximal value at 3mol% Ce3+, then decreases. The concentration quenching mechanism is the dipole-dipole interaction by Dexter theory. Under the condition of doping charge compensator Li+，Na+ or K+，the emission intensity of LiBaBO3：Ce3+ was all heightened. The relative emission spectrum of the InGaN-based LiBaBO3：Ce3+ light emitting diode（LED） was investigated，and the CIE chromaticity of InGaN-based LiBaBO3：Ce3+ LED is （x=0.291，y=0.297），and shows the blue white emission.
Photoluminescence characteristics of Zn1-xMgxO films
Authors: Fang Qing-Qing  , Wang Wei-Na  , Zhou Jun  , Wang Sheng-Nan  , Yan Fang-Liang  , Liu Yan-Mei  , Li Yan  , Lü Qing-Rong  ,   安徽大学物理与材料科学学院，光电信息获取与控制教育部重点实验室，合肥  230039
Published: December 2020

Single-crystalline Zn1-xMgxO thin films with c-axis orientation have been deposited on Si（100） substrates by pulsed laser deposition. The photoluminescence characteristics of the films are studied by fluorescence spectrometer. The results show that the ultraviolet emission peak has a blue shift and the intensity weakens with the increasing content of Mg. At the same time，the intensity of defect emission increases with increasing content of Mg. Some local bound states were introduced by Mg-doping. For the samples grown in oxygen atmosphere，the results show that both the ultraviolet emission peak and green emission peak are enhanced，but the value of R reduced and the ultraviolet emission peak has a red shift. The study of green-emitting mechanism indicated that the green emission band mainly depends on zinc vacancy，substitutional O on the zinc site （OZn） and interstitial oxygen vacancies （Oi）. Green emission band is composed of many defect-peaks，and its movement as a whole mobile is due to the change of relative intensities of individual defect-peaks.
The flux profile of granular gas in compartmentalized system
Authors: Li Yin-Chang  , Zhang Zhao-Bu  , Tu Hong-En  , Liu Rui  , Hu Hai-Yun  , Hou Mei-Ying  ,   (1)北京理工大学应用物理系，北京  100081; (2)中国科学院物理研究所北京凝聚态物理国家实验室，北京  100190; (3)中国科学院物理研究所北京凝聚态物理国家实验室，北京  100190；北京理工大学应用物理系，北京  100081
Published: December 2020

Vibration driven compartmentalized granular gas is capable of clustering in one of the compartments，which is an effect called Maxwell demon phenomenon. One of the keys for understanding the Maxwell demon phenomenon is establishing a flux model. Based on granular hydrodynamics，Eggers deduced a simplified flux model which has been successfully used in describing the spontaneous symmetry breaking of granular gas in the compartmentalized system，but so far has not been able to predict the oscillation phenomenon of bidisperse granular gas. Experimentally studying the flux of mono-disperse granular gas in one compartment，we modify the flux model of Eggers to fit the experimental results. The modified flux model can be extended to the bidisperse granular case，and the oscillatory state can be well obtained by this modified flux model.
Numerical simulation of the formation of artificial radiation belt caused by high altitude nuclear detonation
Authors: Gu Xu-Dong  , Zhao Zheng-Yu  , Ni Bin-Bin  , Wang Feng  ,   武汉大学电子信息学院，武汉  430079
Published: December 2020

According to the previous theory of the motion of charged particles in the Earths magnetic field， we derive the spatial region to which energetic particles around the Earth can extend. Using an empirical model for radiative debris produced by the high altitude nuclear detonation （HAND），we investigate the primary region where HAND-induced artificial radiation belt can form.Finally，in terms of the fission property of HAND and the characteristic features of energetic electron distributions in the natural belts，the electron flux within the artificial radiation belt is calculated and the preliminary study of its dependences on explosion latitude，altitude，and equivalence are carried out quantitatively. The numerical results show that，under certain circumstances，the HAND with 0.1—1 Mt TNT explosion equivalence can be expected to produce an artificial radiation belt near the Earth with the flux 3—4 orders of magnitude higher than the natural ones. The central location of the artificial belt largely relies on the magnetic latitude where the detonation takes place while the thickness and electron flux of the artificial radiation belt are affected by the explosion altitude and equivalence.
Constructing new exact solutions to nonlinear difference-differential equations by Riccati 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

A method for combining Riccati equation with function transformation is applied to seek exact solutions to the nonlinear difference-differential equations. And new exact solitary wave solutions and triangular function solutions to modified Volterra equation and general lattice equations are obtained with the help of symbolic computation system Mathematica.
Research of malware propagation in complex networks based on 1-D cellular automata
Authors: Song Yu-Rong  , Jiang Guo-Ping  ,   (1)南京邮电大学控制与智能技术研究中心,南京  210003; (2)南京邮电大学控制与智能技术研究中心,南京  210003；南京邮电大学自动化学院,南京  210003
Published: December 2020

In this paper, based on 1-D cellular automata, the probabilistic behaviors of malware propagation in complex networks are investigated. Neighborhood and state transition functions with integrated expression are established and two models of malware propagation are proposed to evaluate the probabilistic behavior of malware propagation in various networks. We run the proposed models on nearest-neighbor coupled network （NC） and Erdos-Renyi （ER） random graph network and Watts-Strogatz（WS） small world network and Barabasi-Albert （BA） power law network respectively. Analysis and simulations show that, the proposed models describe perfectly the dynamic behaviors of propagation in the above networks. Furthermore, the proposed models describe not only the average tendency of malware propagation but also the rare events such as saturation and extinction of malware, and overcome the limitation occurring in a deterministic model based on mean-field method that describes only the average tendency of malware propagation and neglects the probabilistic event. Meanwhile, the result of simulations shows that the heterogeneity of degree distribution and local spatial interaction are key factors affecting the malware propagation and immunization.
Micro continuum analysis of Wigner-Seitz model
Authors: Tian Wen-Chao  , Jia Jian-Yuan  ,   西安电子科技大学机电工程学院,西安  710071
Published: December 2020

There is a continuum contradiction between the Wigner-Seitz model and the volume infinitesimal. By analyzing the attractive force and the repulsive force of the bcc and fcc double Wigner-Seitz model with the classical Lennard-Jones potential, the conclusion that the relative error satisfies the engineering analysis is established even if double Wigner-Seitz models superpose. By comparing the single atom Al sphere-surface force of the Wigner-Seitz model with the discrete simulation, a satisfactory result is obtained. Based on the Wigner-Seitz model, the dynamic equation of the digital micro-mirror device （DMD）, including the sticking effect, is found. The DMD simulation result is compared with the measurement result. The conclusion that the Wigner-Seitz model satisfies the micro-continuum requirement of the micro- and nano-engineering is arrivedat.
Establishment of multi-user quantum channel of entangled multi-atom based on cavity QED
Authors: Zhao Han  , Zhou Xiao-Qing  , Yang Xiao-Lin  ,   吉首大学物理科学与信息工程学院,吉首  416000
Published: December 2020

We present a scheme for establishing a multi-user quantum channel of multi-atom entangled W states and GHZ states based on cavity QED. Each user has shared EPR pairs with quantum switch during the leisure time of quantum network. An entangled W state is prepared base on two EPR pairs in cavity field by quantum switch at first，and entanglement swapping and direct measurement is operated on the other EPR pairs to establish a quantum channel of W states between three users. In the same way, we can establish a quantum channel of four atoms entangled W state. Three atoms of quantum switch simultaneously interact with cavity field to establish a quantum channel of entangled GHZ states between three users after direct measurement, and we also establish an N users’ quantum channel of entangled GHZ states.
Local higher-order Volterra filter multi-step prediction model of chaotic time series
Authors: Du Jie  , Cao Yi-Jia  , Liu Zhi-Jian  , Xu Li-Zhong  , Jiang Quan-Yuan  , Guo Chuang-Xin  , Lu Jin-Gui  ,   (1)南京工业大学自动化学院，南京  210009; (2)南京信息工程大学计算机软件学院，南京  210044；浙江大学电气工程学院，杭州  310027; (3)浙江大学电气工程学院，杭州  310027; (4)浙江大学电气工程学院，杭州  310027；湖南大学电气工程学院，长沙  410082
Published: December 2020

In general, the prediction modeling of chaotic time series is conducted by Volterra filters through constructing nonlinear fitting functions according to the methodology of pattern training. Since the proposed approach is consistent with the nonlinear characteristics of chaotic systems, the corresponding model turns to be more effective than conventional models. However, something abnormal is likely to occur, such as inadequate trainingor, over training, and the training data set size is not easy to choose, because the existing Volterra filters are trained point by point along the chaotic orbit. Based on the similarity of the evolving tendency of neighbor orbits in phase space, the chaotic time series multi-step-prediction model （MSP-HONFIR） employing the adaptive higher-order nonlinear Volterra filter （HONFIR） is constructed in this paper. A new method of choosing neighbor orbits in phase space is presented by considering the Euclidean distance and the evolving tendency. In addition, the criterion for the choice of the training data set size is discussed. Numerical experiments demonstrate that the performances of multi-step-prediction are improved compared to the original HONFIR method.
Chaos characteristics of the semiconductor laser with double external cavity optical feedback
Authors: Zhao Yan-Feng  ,   黄淮学院电子科学与工程系，驻马店  463000
Published: December 2020

The chaos characteristics of a DFB semiconductor laser subjected to single and double external cavity optical feedback are analyzed experimentally. The results show that the correlation dimension, bandwidth of the chaos generated by one external cavity optical feedback can be expanded by using double external cavity optical feedback. When the laser is subjected to double external cavity optical feedback, the bandwidth with one external cavity feedback is increased from 5.5 GHz to 11 GHz. Correspondingly, the correlation dimension is increased from 2.8 to 3.6. The information of the external cavity length of the chaos generated by double external cavity optical feedback can be masked in the autocorrelation function.
A systematic study on nuclear pairing energy under the relativistic mean-field model
Authors: Ding Bin-Gang  , Zhang Da-Li  , Lu Ding-Hui  ,   (1)浙江大学近代物理中心，杭州  310027; (2)浙江湖州师范学院理学院，湖州  313000
Published: December 2020

Nuclear pairing energy of dozens of atomic nuclei in nuclear period chart are calculated along the stable line by extracting the swatch at a proton or neutron number interval of 4. Especially, we have studied the rule of pairing energy of the even-even nuclei of O isotopes changing with nucleon number under the relativistic mean-field model, and found, when energy gap Δ is fixed, the magnitude of nuclear pairing energy is related to nuclear shell structure. Thereof we propose a simple method to test closed shell, and further, we conclude that the neutron number N=6 is a new magic number not only in neutron-rich region, but also in proton-rich region of light nuclei.
The potential energy function for a1Δg and b1Σ+g states of O2 molecule
Authors: Huang Duo-Hui  , Wang Fan-Hou  ,   (1)宜宾学院计算物理重点实验室，宜宾  644007; (2)宜宾学院计算物理重点实验室，宜宾  644007；宜宾学院物理与电子工程系，宜宾  644007
Published: December 2020

The equilibrium structure, harmonic frequency and potential energy curves for two of the excited states a1Δg and b1Σ+g of O2 molecule were calculated by using MRCI method with aug-cc-pVQZ, cc-pV5Z, 6-311++g（d,p）and 6-311++g（3df,3pd） basis sets. The analytical potential energy functions for a1Δg and b1Σ+g of O2 was fitted by Murrell-Sorbie theory . The force constants and spectrum data were obtained according to fitted parameters. Results show that our results are good agreed with the experimental value.
Improvement on the up-conversion fluorescence emission in Tm3+ doped optical materials by adjusting phonon distribution
Authors: Gao Dang-Li  , Zhang Xiang-Yu  , Zhang Zheng-Long  , Xu Liang-Min  , Lei Yu  , Zheng Hai-Rong  ,   (1)陕西师范大学物理学与信息技术学院，西安  710062; (2)陕西师范大学物理学与信息技术学院，西安  710062；青海民族学院电子工程与信息科学系，西宁  810007
Published: December 2020

The influence of phonon distribution on the frequency upconverted fluorescence emission is studied with laser spectroscopy in different matrices and at different ambient temperatures. The spectrum of phonon energy can be adjusted by varying the content of SiO2 in the oxyfluoride glass and glass ceramics, which affects the upconverted fluorescence emission of doped ions. Since the phonon energy depends on the sample temperature, the variation of the temperature can also influence the population rate of 3H4 level in Tm3+ doped low-phonon-energy LaF3 crystal, resulting in a change of the fluorescence upconversion.
Density functional theory study of the geometry, stability and electronic properties of ScnO(n=1—9) clusters
Authors: Li Xi-Bo  , Wang Hong-Yan  , Luo Jiang-Shan  , Wu Wei-Dong  , Tang Yong-Jian  ,   (1)西南交通大学物理科学与技术学院，成都  610031; (2)中国工程物理研究院激光聚变研究中心，绵阳  621900
Published: December 2020

The geometric structures, relative stability, electronic structure and their size dependence of scandium monoxide（ScnO, n=1—9） clusters are investigated by using density functional theory （DFT） at the BP86/CEP-121G level （the O atom treated with 6-311G** basis sets）. With the cluster size increasing, the geometries of the lowest energy clusters show that the oxygen atom situated on the surface turn to be embed in the interior. The doped O atom enhances the stability, increases the energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital and changes the trends of stability and electronic properties with the cluster size increasing. Results on even-odd oscillation in cluster stability and electronic properties predicted that the oxide clusters with even number of Sc atoms are more stable than the neighboring clusters with odd number of Sc atoms. The calculated vertical ionization energy values agreed especially well with the experimental values. The trend of electron affinities shows an obvious oscillatorg increasing behavior as the cluster size increasing. The stability and electronic structure of ScnO clusters are also characterized by the maximum hardness principle of chemical reactivity.
A novel FDTD method for multi-conductor transmission lines terminating in frequency-dependent loads
Authors: Wu Zhen-Jun  , Wang Li-Fang  , Liao Cheng-Lin  ,   (1)中国科学院电工研究所，北京  100190; (2)中国科学院电工研究所，北京  100190；郑州轻工业学院电气工程学院，郑州  450002
Published: December 2020

A novel finite difference time domain （FDTD） method has been introduced to analyze multi-conductor transmission lines terminated with frequency-dependent loads. The admittance of frequency-dependent loads can be modeled by rational functions by using vector-fitting, then converting these functions into time-domain by inverse Fourier transform （IFT）. Based on the piecewise linear recursive convolution （PLRC） method, the relation between voltage and current of admittance parameters are deduced. Incorporating the formula into multiconductor transmission lines （MTL） FDTD equations, we get the general formula of MTL FDTD dealing with frequency-dependent loads. In simulating a typical circuit, the results agreed well with the results obtained by using the state-variable transmission model. It shows the method is valid in dealing with frequency-dependent loads.
A finite difference time domain absorbing boundary condition for general frequency-dispersive media
Authors: Wei Bing  , Li Xiao-Yong  , Wang Fei  , Ge De-Biao  ,   西安电子科技大学物理系，西安  710071
Published: December 2020

The dispersion relations and the reflectionless conditions are obtained by the Maxwell’s curl equations in a uniaxial anisotropic medium and the phase-matching. Using the shift operator finite difference time domain （SO-FDTD） method and the transform relationship of frequency domain to time domain （jω replaced by /t）, an FDTD absorbing boundary condition for three kinds of general dispersive media model, i.e. the Debye model, Lorentz model and Drude model, is given. The characteristics of our absorbing boundary condition are tested. The computed results illustrated the generality and the feasibility of the scheme.
Propagation of a Lorentz beam through an apertured misaligned paraxial optical system
Authors: Zhou Guo-Quan  ,   浙江林学院理学院，临安  311300
Published: December 2020

Based on the generalized integral formula and the complex Gaussian expansion of the aperture function, an approximate analytical propagation formula for a Lorentz beam passing through a circular-apertured misaligned paraxial optical system is derived. The analytical propagation formula of a Lorentz beam through a unapertured misaligned paraxial optical system is treated as the special case of the general formula. As a numerical example, the propagation properties of a Lorentz beam through an apertured misaligned thin lens are investigated numerically. The results show that diffraction of different intensity, in other words, the radius of the circular aperture apparently influences on the distribution of the normalized light intensity of the diffracted beam and its propagation law.
Influences of misaligned optical beam carrying orbital angular momentum on the information transfer
Authors: Li Fang  , Jiang Yue-Song  , Tang Hua  , Wang Hai-Yang  ,   北京航空航天大学电子信息工程学院，北京  100191
Published: December 2020

An analysis of the orbital angular momentum of an optical beam misaligned with respect to a receiver during propagation in the information transfer is investigated. The analytical expressions of Laguerre-Gaussian beams laterally displaced， angularly deflected and simultaneously misaligned in both ways are derived, and the features of the spiral spectrum in these cases are studied. It is shown that both parallel displacement and angular tilt will lead to the spread of the spiral spectrum, which is independent of the misalign direction. The larger the misalign, the more serious the spectrum spread. However, with the increasing of the propagation distance, the degree of the spread for the laterally displacement is decreasing gradually, while that for the angular tilt is increasing. In the angular tilt case, the spread of the spiral spectrum always keeps symmetric during propagation, while in the case of lateral displacement, the spiral spectrum is asymmetric, and goes to a stable state. The spiral spectrum is also investigated for the case with simulataneous lateral misalignment and angular tilt, and we conclude that the effects of both misaligns on the spectrum are related with one another.
Research of LED light extraction efficiency of photonic crystal with square and hexagonal lattice
Authors: Chen Jian  , Li Xiao-Li  , Li Hai-Hua  , Wang Qing-Kang  ,   (1)薄膜与微细技术教育部重点实验室、微米/纳米加工技术国家级重点实验室，上海交通大学微纳科学技术研究院，上海  200240; (2)薄膜与微细技术教育部重点实验室、微米/纳米加工技术国家级重点实验室，上海交通大学微纳科学技术研究院，上海  200240；上海市纳米科技与产业发展促进中心，上海  200237
Published: December 2020

Using finite-difference time-domain （FDTD） method, we found the relationship between filling factor and band gap of square and hexagonal array of circular photonic crystal, and obtained the geometric parameters of the 2D photonic crystal, for which the number of bandgaps are the greater. Using FDTD method to calculate the extraction efficiency of the photonic crystals with the parameters, we verified the enhancement in extraction efficency of the GaN-based blue light-emitting diode based on the square and hexagonal array of circular photonic crystals with the the parameters, and the hexagonal arrangement is better than the square arrangement. By using the bang gap theory and equivalent medium theory was analyzed the mechanism of antireflection.
Design and optimization of phase regenerator with photonic crystal fiber
Authors: Xi Li-Xia  , Tang Xian-Feng  , Wang Shao-Kang  , Zhang Xiao-Guang  ,   北京邮电大学信息光子学与光通信教育部重点实验室, 北京邮电大学信息光子学与光通信研究院，北京  100876
Published: December 2020

Amplification and simultaneous phase regeneration of differential phase-shift keying （DPSK） signals is demonstrated using a phase regenerator. Phase regeneration is achieved in a Sagnac fiber interferometer comprised of photonic crystal fiber operating in an un-depleted pump regime. The formula of signal after phase regenerator is derived. For different incident power of signal, the relations between signal-pump phase difference and signal gain are discussed, as well as the influence of fiber length on signal output intensity. The optimum parameters of the phase regenerator are given. The distributions of phase and intensities for both the non-regenerated and regenerated signals are simulated. Simulations show that nearly ideal regeneration can be achieved for the DPSK signals.
Depth measurement in the direction of optical axis based on defocused micro-manipulation system
Authors: Sun Ming-Zhu  , Zhao Xin  , Lu Gui-Zhang  ,   南开大学机器人与信息自动化研究所，天津  300071
Published: December 2020

After analyzing the principle of imaging of the objective, a method of depth measurement in the direction of optical axis in micro-manipulation system is put forward. To measure depth, the relationship between defocus and blur of microscopic images is established based on optical transfer function （OTF）. This method has high precision and good linearity, since lens parameters and diffraction effect have been taken into account. Meanwhile, the fast identification algorithm of bar objects is utilized to simplify the original method, then depth can be measured online. In addition, the method is applied to micro-manipulation system, and an experiment to insert one needle into another automatically in defocused status is designed and carried out to show the effectiveness of the method. Thus, the operation range of the micro-manipulation system has been extended.
Calculating the threshold of random laser by using Monte Carlo method
Authors: Fu Fang-Zheng  , Li Ming  ,   南昌大学物理学系,南昌  330031
Published: December 2020

We put forward a model of calculating the threshold gain of random laser, a method for obtaining the distribution function and the relevant random variables according to the mean free path and scattering intensity distribution. The distribution functions are derived for isotropic scattering of light, and then we get the random variables according with the distribution at every scattering. Simulating the random walk of photons in random media by using Monte Carlo method, the threshold of random laser is got. The relationship of the threshold gain to the photon mean free path, the radius of gain zone, the depth of gain zone and light absorption coefficient of non-gain zone is discussed. We make some suggestions to lower the threshold. The theoretical results agree with the experimental data.
Passively mode-locked Nd:Gd0.1Y0.9VO4 laser with a semiconductor saturable absorber mirror
Authors: Cao Shi-Ying  , Zhu Yue  , Chai Lu  , Wang Qing-Yue  , Zhang Zhi-Gang  ,   (1)北京大学信息科学技术学院量子电子学研究所，北京  100871; (2)北京大学信息科学技术学院量子电子学研究所，北京  100871；天津大学精密仪器与光电子工程学院超快激光研究室，信息技术科学教育部重点实验室，天津  300072; (3)天津大学精密仪器与光电子工程学院超快激光研究室，信息技术科学教育部重点实验室，天津  300072
Published: December 2020

A home-made semiconductor saturable absorber mirror （SESAM） with or without high reflectivity coating is incorporated in the cavity of a laser with an Nd∶Gd0.1Y0.9VO4 crystal as the laser material and a Z-type cavity. In this paper, we explore the effect of the SESAM on the mode-locking property of the laser. The threshold value of the mode locking was found to decreased from 1.69W to 1.45W and the mode locking was more stable with the high reflectivity coating SESAM. At a pump power of 2 W, stable continuous-wave mode locking was obtained with an average output power of 250mW at an optical conversion efficiency of 12.5% at the central wavelength of 1064nm and a repetition rate of 142.25MHz.
High stability mono-wavelength output optical fiber laser based on polarization-maintaining erbium-doped fiber
Authors: Yan Feng-Ping  , Mao Xiang-Qiao  , Wang Lin  , Fu Yong-Jun  , Wei Huai  , Zheng Kai  , Gong Tao-Rong  , Liu Peng  , Tao Pei-Lin  , Jian Shui-Sheng  ,   全光网络与现代通信网教育部重点实验室； 北京交通大学光波技术研究所,北京  100044
Published: December 2020

A photosensitive polarization-maintaining erbium-doped fiber was fabricated experimentally and a high efficiency resonance cavity was set up by writing three fiber Bragg gratings on this fiber using UV laser. The mono-wavelength laser with mean output power of 9.20dBm and mean wavelength of 1554.554nm was produced by pumping at a power of 23.617dBm and wavelength of 976nm. The fluctuations of output power and wavelength were less then ±0.05dB and ±0.0015nm for a test time of 800min, respectively, at room temperature.
High performance resonant cavity light emitting diodes for POF application
Authors: Li Jian-Jun  , Yang Zhen  , Han Jun  , Deng Jun  , Zou De-Shu  , Kang Yu-Zhu  , Ding Liang  , Shen Guang-Di  ,   北京工业大学北京光电子技术实验室,北京  100124
Published: December 2020

A device structure of resonant cavity light emitting diodes （RCLED） at 650nm wavelength was proposed by using AlGaAs as the n-type bottom DBR, AlGaInP as the p-type top DBR, and GaInP/AlGaInP MQW as the active region. The device was designed according to the transfer matrix method, and both RCLED and normal LED were fabricated for comparison. Results showed that the efficiency of RCLED is 30% higher than the normal LED, and the peak wavelength of RCLED changed only 1nm when the driving current increased from 3mA to 30mA, compared with that of 7nm for the normal LED. Meanwhile, RCLED has a narrower spectrum and a smaller far field divergence angle.
Control of the fabrication parameters during the fabrication of photonic crystal fibers
Authors: Guo Tie-Ying  , Lou Shu-Qin  , Li Hong-Lei  , Jian Shui-Sheng  ,   全光网络与现代通信网教育部重点实验室,北京  100044；北京交通大学光波技术研究所, 北京  100044
Published: December 2020

The interplay between the fabrication parameters during the fabrication of photonic crystal fibers（PCF） are numerically analyzed. Relation between these parameters and the final fiber’s geometry is identified. With the cooperative control of drawing temperature and feed speed, the final hole structure can be effectively controlled by tuning the applied pressure. A single-mode PCF with its d/Λ approaching 0.45, and a PCF with high air-filling fraction, whose d/Λ equals 0.8, are successfully fabricated. For fabrication of PCFs with uneven-sized holes, parameter control alone is sometimes inadequate in achieving the desired geometry. Taking a single-polarization single-mode（SPSM） PCF structure as example, the preform’s geometry is redesigned for optimization by inverse calculation. And the required SPSM PCF can thus be fabricated.
Numerical simulation of laser-generated Rayleigh wave by finite element method on viscoelastic materials
Authors: Sun Hong-Xiang  , Xu Bai-Qiang  , Wang Ji-Jun  , Xu Gui-Dong  , Xu Chen-Guang  , Wang Feng  ,   江苏大学理学院,镇江  212013
Published: December 2020

The propagation of laser-generated Rayleigh wave in the viscoelastic material are studied theoretically. Taking account of the viscosity characteristic of the viscoelastic material, a numerical model for simulating laser-generated Rayleigh wave in the viscoelastic material is developed in the frequency domain. Based on the correctness of the finite element numerical model in the frequency domain, the laser generation of Rayleigh wave in the viscoelastic material is simulated. And then, the propagation characteristics of laser-generated Rayleigh wave are discussed and the difference of Rayleigh waves in the viscoelastic material and the elastic material are compared. The effect of different viscosity modulus to the characteristic of Rayleigh wave is analyzed in detail.
Audible sound metamaterial
Authors: Ding Chang-Lin  , Zhao Xiao-Peng  ,   西北工业大学应用物理系，西安  710129
Published: December 2020

We fabricated a kind of 1D metamaterial which consists of periodic array of Helmholtz resonators and tested its acoustic transmission at audible sound frequency in air. The experimental results show that a transmission dip appears at the frequency range of 2.1—3.5 kHz. The transmission ratio simulated by acoustic transmission line method （ATLM） is in accordance with the experimental results. From the effective impedance calculated by ATLM, the transmission dip is ascribed to the backward wave reflection of HRsresonance. Furthermore, the transmission pressure distribution measurement of the inner sample clearly demonstrates the resonance effect in the metamaterial, in which there is an out-of-phase response to the driving field. The value of effective modulus is calculated to be negative based on the resonant model mentioned before.
Propagation of water wave over a periodically perforated bottom and the band structure
Authors: Zhong Lan-Hua  , Wu Fu-Gen  ,   (1)广东工业大学实验教学部，广州  510090; (2)湛江师范学院物理科学与技术学院，湛江  524048
Published: December 2020

The band structures of shallow water surface wave propagating over a periodically perforated bottom are calculated by the plane wave expansion method，and complete band gaps appear. Through considering three drilling patterns （square holes arrayed in square lattice，circular holes arrayed in square and hexagonal lattices），we find that the number，width，frequency and location of band gaps are related to the area，shape，orientation of drilled holes and the lattice. These rules are similar to those in photonic/ phononic crystals.
Microstructure and DC conduction properties of CaCu3Ti4O12
Authors: Yang Yan  , Li Sheng-Tao  ,   西安交通大学电力设备电气绝缘国家重点实验室，西安  710049
Published: December 2020

CaCu3Ti4O12were prepared using conventional solid state reaction processing techniques of ceramic. The CaCu3Ti4O12crystalline phase was verified by XRD patterns. From SEM micrographs, obvious grain and grain boundary structures were observed, and the grain boundary region was comprised of small grains, which were found to be CuO, by EDS, the dielectric constant almost remains at a constant value of 105 in a wide temperature range, but drops dramatically at the frequency of 103 Hz when temperature is below 150 K. The relationship between conductance and temperature of CaCu3Ti4O12 was obtained through the I-V characteristics measured in the temperature range from 93 K to 373 K. It can be separated into three parts with the corresponding activation energies of 0.681, 0.155 and 0.009 eV, which are consistent with the activation energy of CuO ceramics. It was concluded that the small CuO grains in the grain boundary region dominated the DC conductance in CaCu3Ti4O12 ceramics. Thus a new approach for explaining the extraordinary dielectric properties was provided.