bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of electrostatic discharge on the I-V and low frequency noise characterization of Schottky barrier diodes
Authors: Liu Yu-Dong  , Du Lei  , Sun Peng  , Chen Wen-Hao  ,   School of Technology Physics, Xi dian University, Xi'an 710071, China
Published: December 2020

Based on the analysis of thermal electron emission, the model of the carrier mobility fluctuation and the white noise theory, the effect of electrostatic discharge (ESD) on the I-V and low frequency noise of Schottky barrier diode (SBD) is discussed in this paper. The different Human Body Model(HBM) ESD injected times with the same voltage peaks are applied to the cathode and anode separately. It is found that the diode subjected to the cathode stress shows greater degradation than subjected to the anode stress, and the magnitude of noise shows significant change. With the increase of ESD injected times, the forward characteristic has no change, while reverse current almost increases at each time. The magnitudes of forward and reverse 1/f noise increase all the time. In view of the relationship between defects and damage, and the noise sensibility, the low frequency noise can serve as a tool for researching the sensitivity to the electrostatic discharge damage of SBD.
The effect of ITO annealing on electrical characteristic of GaN based LED
Authors: Liu Jian-Peng  , Zhu Yan-Xu  , Guo Wei-Ling  , Yan Wei-Wei  , Wu Guo-Qing  ,   Beijing Optoelectronic Technology Laboratory, Beijing University of Technology, Beijing 100124, China
Published: December 2020

In the recent years，more and more light-emitting diodes use indium tin oxide (ITO) as the current spreading layer. But if there is not any treatment, the electrical properties of light emitting diode are very poor. So to get excellent electrical properties of light emitting diode, annealing is an effective method to improve the electrical properties of light emitting diode using indium tin oxide as the current spreading layer. However, the annealing time and temperature can affect the electrical property of light emitting diode individually. In order to investigate this problem，we measured the series resistance and ideality factor of the light emitting diode got under different annealing time and annealing temperature. According to the model proposed by Jay M. Shah，we can inferred the characteristics of indium tin oxide and P-type GaN contact. The results showed that: the electrical properties of the light-emitting diode can reach an excellent value with increasing annealing temperature and time, and if continuing to increase in temperature or time, it can lead to a decline in light-emitting diode electrical properties. It is very helpful to optimize the annealing temperature and time and manufacture excellent electrical properties of devices.
The effects of magnetization methods with additional permanent magnet on the magnetic field distribution and levitation force of single domain GdBCO bulk superconductor
Authors: Ma Jun  , Yang Wan-Min  , Li Jia-Wei  , Wang Miao  , Chen Sen-Lin  ,   College of Physics and Information Technology, Shaanxi Normal University, Xi'an 710062, China;,   Department of Physics, Qinghai Normal University, Xining 810008, China
Published: December 2020

The effects of magnetization methods with additional permanent magnet on the magnetic field distribution and the levitation force of single domain GdBCO bulk superconductor are investigated with a cubic permanent magnet in their coaxial configuration in zero field cooled state at liquid nitrogen temperature in three different ways. It is found that when the N pole of the cubic permanent magnet, for the levitation force measurement, is placed above the GdBCO bulk superconductor and in the downward direction, the maximal levitation force can be improved to 31.8 N, and that when the N pole of the additional cubic permanent magnet points to upward and sticks to the bottom of the GdBCO bulk, the maximal levitation force is increased up to about 222% of the levitation force of 14.3 N for the system without additional permanent magnet. The maximal levitation force can be improved to 21.6 N (or reduced to 8.6 N), when the GdBCO bulk superconductor is closely placed below and magnetized by the additional cubic permanent magnet with N pole in the upward (or downward) direction, and the additional permanent magnet is removed away after the magnetization, the maximal levitation force is about 151% (or 60%) of 14.3 N for the system without the additional permanent magnet. The results indicate that the levitation force of high temperature bulk superconductors can be effectively improved by introducing additional permanent magnet based on the scientific and reasonable designing of the system configurations, which is very important for the practical design and application of superconducting magnetic levitation system.
Influence of annealing ambience on the magnetic properties of doped ZnO films
Authors: Li Zhi-Wen  , Qi Yun-Kai  , Gu Jian-Jun  , Sun Hui-Yuan  ,   Department of Physics, Hebei Normal University for Nationalities, Chengde 067000, China;,   College of Physics Science & Information Engineering, Hebei Normal University, Shijiazhuang 050016, China;,   Key Laboratory of Advanced Films of Hebei Province, Shijiazhuang 050016, China
Published: December 2020

The non-magnetic element Al and magnetic element Co doped ZnO films are prepared by dc magnetron sputtering The films were annealed first in vacuum and then in air. The crystal structures are analyzed by x-ray diffraction (XRD) and magnetic properties are measured by Physical Properties Measurement System (PPMS). The results show that annealing ambience has a great influence on structure and magnetic property of sample Al doped ZnO films annealed in vacuum show no room temperature ferromagnetism, but the ones annealed in air show room temperature ferromagnetism. The room temperature ferromagnetism may be associated with enhanced charge transfer between Al and ZnO films annealed in air. And for Co doped ZnO films annealed in air annealed, the ferromagnetism is weakened. The change of magnetism may be related to the competition between enhanced magnetism resulting from charge transfer between Al and ZnO and reduced magnetism resulting from interstitial Co atoms oxygenated.
Theoretical and experimental investigation of W doped ZnO
Authors: Wang Yan-Feng  , Huang Qian  , Song Qing-Gong  , Liu Yang  , Wei Chang-Chun  , Zhao Ying  , Zhang Xiao-Dan  ,   Institute of Photo-electronic Thin Film Devices and Technology of Nankai University, Key Laboratory of Photo-Electronic Thin Film Devices and Technology of Tianjin, Key Laboratory of Opto-electronic Information Science and Technology, Ministry of Education, Tianjin 300071, China;,   College of Science, Civil Aviation University of China, Tianjin 300300, China
Published: December 2020

The properties of high valence difference W doped ZnO films (WZO) are investigated by means of plane wave pseudo-potential method based on the density-functional theory (DFT) and pulsed DC magnetron sputtering technique. The theoretical result shows after incorporation of W the Fermi level enters into the conduction band, showing that a typical n-type metallic characteristic and the optical band gap Eg* increase significantly. The carriers originate from the orbits of W 5d, O 2p and Zn 3d. Moreover, the increase of the lattice constant is due to the longer bond length of W-O and lattice distortion. The experimental results demonstrate that the deposited WZO film grows preferentially in the (002) crystallographic direction but the lattice constant increases. The resistivity decreases from 1.35 10-2 cm to 1.55 10-3 cm and the optical bandgap extends from 3.27 eV to 3.48 eV compared with those of ZnO. The average transmittance is over 83 % in a wavelength range from 400 to 1100 nm. The experimental results are in good agreement with the theoretical results, showing that the WZO thin film has a great potential application as transparent conductive oxide.
Solvothermal recrystallized synthesis of one-dimensional CdS nanorods self-assembled from nanoparticles
Authors: Zhang Bao-Hua  , Guo Fu-Qiang  , Sun Yi  , Wang Jun-Jun  , Li Yan-Qing  , Zhi Li-Li  ,   Department of Physics, Changji College, Changji 831100, China
Published: December 2020

Two different solvothermal synthesis routines are used to fabricate CdS nanocrystals with different morphologies and sizes. Anhydrous ethylenediamine (en) is chosen as solvent, CdCl2. 2.5H2O and thiourea (H2NCSH2N) as the cadmium source and sulfur source respectively in the first method. CdS Nanocrystals are prepared at different reaction temperatures (160 ℃-220 ℃) and the influence of the reaction temperature on the growth of CdS nanocrystals is discussed. In the other routine, anhydrous ethylenediamine (en) is also chosen as solvent. The synthesized products at 160 ℃ are recrystallized under 200 ℃ for 2-8 h. The influence of the recrystallisation time on the growth of CdS Nanocrystal is discussed. The in-situ analysis of effect of the growth time on the growth of CdS nanocrystals is performed. The phase, morphology and crystallographic structure of CdS nanocrystals are investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) respectively. The results show that both products exhibit pure hexagonal structures, the morphology of the product is nanoparticles at the temperatures below 160 ℃, when the temperature is rasied to higher than 160 ℃, the products are CdS nanorods. Meanwhile, the morphologies of the recrystallisation products under 200 ℃ for different times are found to convert from nanoparticles into nanorods gradually. The nanorods are composed of zero-dimensional particles through self-assembly process which could be demonstrated by field emission scanning electron microscopy (HRTEM) analysis. Finally, the factors that influence the morphology changes of CdS nanocrystals and the mechanism of the growth of nanorods are discussed.
Influence of surface fluorination temperature on space charge accumulation in polyethylene
Authors: Chen Xuan  , An Zhen-Lian  , Liu Chen-Xia  , Zhang Ye-Wen  , Zheng Fei-Hu  ,   Ministry of Education Key Laboratory of Advanced Microstructure Materials, Department of Physics, Tongji University, Shanghai 200092, China;,   State Key Laboratory of Electrical Insulation and Power Equipment, Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

Polyethylene (PE) discs prepared by hot-pressing, each with a thickness of 0.8 mm, are surface fluorinated in a laboratory vessel by an F2/N2 mixture containing 12.5% F2 by volume at different temperatures of 35, 55, and 70 ℃ for the same time of 2 h. The influence of fluorination temperature on space charge accumulation in PE is investigated by the pressure wave propagation method. The results show an obvious decrease in space charge accumulation in the fluorinated sample subject to a direct current high voltage with the increase of fluorination temperature, and there exists almost no charge accumulation in the sample fluorinated at 70 ℃. Attenuated total reflection infrared analyses indicate a substantial change in chemical composition of the sample surface layers by the fluorinations and an obvious increase in degree of fluorination with fluorination temperature increasing. Contact angle measurements and surface energy calculations indirectly indicate a significant increase in permittivity of the fluorinated layers by the fluorinations. Open-circuit thermally stimulated discharge current measurements further reveal different charge trapping properties of the fluorinated layers and the improved barrier properties of the fluorinated layer to the diffusion of the chemical species from the semi-conductive electrode to the PE with increase of fluorination temperature, thus indicating a corresponding decrease in free volume of the surface layer. The decrease in the free volume plays a more important role in suppressing the space charge accumulation, compared with the increase in permittivity and the change in charge trap.
High-speed and high-power uni-traveling-carrier photodetector
Authors: Zhang Ling-Zi  , Zuo Yu-Hua  , Cao Quan  , Xue Chun-Lai  , Cheng Bu-Wen  , Zhang Wan-Chang  , Cao Xue-Lei  , Wang Qi-Ming  ,   Key Laboratory of Particle Astrophysics, Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China;,   State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
Published: December 2020

The drift-diffusion theory is adopted to simulate the bandwidth and the saturation characteristics of InGaAs/InP uni-traveling-carrier (UTC) photodetector. According to the experiment results, we analyze the physical mechanisms in high speed and high power UTC photodetector. It is shown that introducing the cliff layer and the gradually doped absorption layer can enhance the saturation characteristic obviously. Electric field collapse in the absorption layer leads to the saturation, and RC constant is still a limitation factor for device with diameter larger than 20 μm. In this paper we point out the effective methods to improve device performance.
Optimization of quantum dot solar cells based on structures of GaAs/InAs-GaAs/ZnSe
Authors: Jiang Bing-Yi  , Zheng Jian-Bang  , Wang Chun-Feng  , Hao Juan  , Cao Chong-De  ,   Shaanxi Key Laboratory of Optical Information Technology, School of Science, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

Based on the structures of GaAs/InAs-GaAs/ZnSe P-i-N quantum dot solar cells, according to the optical principle and diffusion theory, mathematic model describing the relationship between photogenerated electron current density and thickness of layer is proposed, and the effect of the quantum dot layer on the characteristics of solar cell is analyzed quantitatively for improving the power conversion efficiency of quantum dot solar cells. Simulations show that the optimal thicknesses of P(GaAs) and N(ZnSe) are 1541 nm and 78 nm respectively when the i layer thickness is 3000 nm, and the power conversion efficiency of solar cell is 20.1% at a single wavelength; At the same time, the volume of quantum dot and the temperature affect I-V property of quantum dot solar cell, and the value of open voltage reduces with the increase of the volume of quantum dot and temperature, so that the power conversion efficiency will be reduced.
The analysis of the influence of globe SST anomalies on 500 hPa temperature field based on Bayesian
Authors: Yan Peng-Cheng  , Hou Wei  , Qian Zhong-Hua  , He Wen-Ping  , Sun Jian-An  ,   College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China;,   National Climate Center, China Meteorological Administration, Beijing 100081, China;,   Department of Physics, Yangzhou University, Yangzhou 225002, China
Published: December 2020

In this paper, we break down sea surface temperature(SST) anomaly field by using the empirical orthogonal function (EOF) to obtain a rebuilding space made up of different patterns which are orthogonal to each other, then we unfold 500 hPa temperature field in this space. Furthermore, with the method of Bayesian analysis, we define the impact index of different patterns on 500 hPa air temperature field and research the variation characteristic of index with the change of spatial pattern of SST. It is found that SST field has a great effect on 500 hPa temperature field between April to June. Besides, after the abrupt climate change, different patterns of SST have different effects on temperature field.
Eigen-vector expansion theorem of a class of operator matrices appearing in elasticity and applications
Authors: Zhang Guo-Ting  , Huang Jun-Jie  , Alatancang  ,   School of Mathematical Sciences, Inner Mongolia University, Hohhot 010021, China
Published: December 2020

For a class of operator matrices appearing in elasticity, the eigen-vector expansion theorem is considered. It is shown that the eigen-vectors possess the symplectic orthogonality. And a necessary and sufficient condition for the completeness of the eigen-vector system is further given. As concrete applications, the obtained results are tested for the plate bending equation and the buckling deflection problem of rectangular thin plates.
Quantum behaviors of the particles affected by the linear-damping and time-dependent external force
Authors: Qin Yue-Kai  , Xu Xiu-Wei  , Qu Jian-Tao  ,   College of Physics, Ludong University, Yantai 264025, China
Published: December 2020

In this paper, we handle the Hamiltonian of the particles that are affected by the linear-damping and time-dependent external force given by two different canonical transformations by using the theory of generalized quantum linear transformation. We give the rigorous solution of evolution operator, and the expectation values of coordinate and momentum of the particles quantum fluctuations. Results show that 1) the two regular translations are equivalent; 2) linear damping has a squeezing effect on the momentum of particle, and the deviation of the momentum attenuates with time t according to the rule of negative exponent, and the bigger the damping coefficient, the faster the attenuation is; 3) the expectation values of coordinate and momentum of the particle are equal to their classical values correspondingly.
Measurement of atmospheric water vapor using infrared differential optical absorption spectroscopy
Authors: Sun You-Wen  , Liu Wen-Qing  , Xie Pin-Hua  , Chan Ka-Lok  , Zeng Yi  , Xu Jin  , Li Ang  , Si Fu-Qi  , Li Xian-Xin  ,   Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China;,   School of Energy and Environment, City University of Hong Kong, Hong Kong, China
Published: December 2020

In this paper, we present a method of measuring atmospheric water vapor concentration by using infrared differential optical absorption spectroscopy (DOAS). The experimental setup is converted from a self-made non-dispersive infrared multi-gas analyzer. In the process of DOAS retrieval, the reference absorption cross section is calculated by applying the Voigt broadening method to the absorption lines from HITRAN database. The influences of temperature, pressure and instrument function are also taken into account in the calculation. A validation study of the water vapor measurement is performed by comparing the results measured by a non-dispersive infrared analyzer. The results show good agreement with each other (correlation coefficient = 0.93347). It indicates that the infrared DOAS technique has the potential applications to other gases measurements which have no or weak absorption within the UV region, e.g. CO2, CH4, CO, N2O, etc.
Conformal invariance, Noether symmetry and Lie symmetry for systems with unilateral Chetaev non-holonomic constraints
Authors: Chen Rong  , Xu Xue-Jun  ,   Department of Physics, Zhejiang Normal University, Jinhua 321004, China
Published: December 2020

The conformal invariance of a system with unilateral Chetaev non-holonomic is studied, and its definition is given. The relation between the conformal invariance and the Noether symmetry is discussed. Finally, the relation between the conformal invariance and the Lie symmetry is discussed, and the Hojman conserved quantity due to the conformal invariance of the systems is obtained. In the paper, an example is given to illustrate the application of the results.
Isospin-dependent nucleon-nucleon cross section and the collective flow of nucleons in heavy-ion collision at intermediate energy
Authors: Zhu Yu-Lan  , Wang Yan-Yan  , Xing Yong-Zhong  ,   College of Physics and Information Technology, Shaanxi Normal University, Xi'an 710062, China;,   Department of Physics, Tianshui Normal University, Tianshui 741000, China
Published: December 2020

In this paper, the influences of the different forms of nucleon-nucleon (NN) cross sections on the rapidity distributions and the in-plane flows of nucleons in reactions 60Ca+60Ca and 60Ni+60Ni are studied by using IBUU04 transport model with the moment-dependent symmetry potential. The calculation results indicate that (1) the discrepancies of the rapidity distributions and in-plane flows corresponding to different forms of NN cross sections are large, (2) the sensitivity of the in-plane flow to the NN cross section still holds when the new form of moment-dependent symmetry energy is adopted, and (3) the influence of the N/P ratio of reaction systems on the transverse flow calculated with a certain NN cross section is more obvious when the incident energy is near the balance energy.
Generation of isolated attosecond pulse from two-color pulse with duration of 60 fs
Authors: Liu Sheng-Nan  , Chen Gao  , Meng Jian  ,   College of Science, Changchun University of Science and Technology, Changchun 130022, China
Published: December 2020

We theoretically investigate the high-order harmonic and attosecond pulse generation by numerically solving the one-dimensional time-dependent Schrödinger equation from a hydrogen atom in a two-color laser field, which is synthesized by adding a suitable multicycle infrared pulse to a multicycle 800 nm fundamental pulse. Our results clearly show that when there are 12 Ti: sapphire optical cycles in the pulse envelope, by adding a suitable second optical field, the electric field of the synthesized pulse presents three-segments, and only amplitude of the electric field in middle segment makes a major contribution to the plateau and cutoff region of the harmonic spectrum. By analyzing the compression mechanism of two-color electric field, we further enlarge the duration of the synthesized pulse to 60 fs, and obtain a single 160 as short pulse. This has been the longest pulse duration used for obtaining single attosecond pulse so far. Here the effect of synthesized pulses is similar to the effect of single 5 fs ultrashort pulse. This scheme greatly reduces the requirements for the pump laser system used traditionally for generating an isolated attosecond pulse, and it allows us to use a well-established conventional high-power pumping laser.
Anisotropic explosions of hydrogen clusters in intense femtosecond laser field
Authors: Zhang Chun-Yan  , Zhao Qing  , Fu Li-Bin  , Liu Jie  ,   Department of Physics School of Science, Beijing Institute of Technology, Beijing 100081, China;,   Institute of Applied Physics and Computational Mathematics, Beijing 100088, China
Published: December 2020

In this paper, a simulation discussing the cause inducing the anisotropy of hydrogen cluster expansion is implemented by using LAMMPS tool for the molecule dynamics simulations. Through analyzing the behavior of electrons contained in the cluster and the variations of distance between outermost protons of all directions and cluster center with time, we clearly find that the expansion of hydrogen cluster is anisotropic, which is due mainly to the anisotropies of the quiver and escaping of electrons. Then we study the evolutions of proton energy component and anisotropic degree, and find that the anisotropic degree first increases with laser electric field increasing, then decreases gradually to a stable value greater than one. Additionally, we analyze the relationship between observation angle and average proton energy from hydrogen cluster irradiated by ultreshort laser pulse, and find that our simulation results accord with the experimental results qualitatively.
Quantitative infrared prediction method for defect depth in carbon fiber reinforced plastics composite
Authors: Huo Yan  , Zhang Cun-Lin  ,   School of Material Science and Engineering, Beihang University, Beijing 100191, China;,   Beijing Key Laboratory for Terahertz Spectroscopy and Imaging, Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Department of Physics, Capital Normal University, Beijing 100048, China
Published: December 2020

In this work, we present a quantitative method of predicting defect depth within carbon fiber reinforced plastics (CFRP) composite with unknown thermal property of specimen. The method discussed in this paper is derived from theoretical model of ideal one-dimensional heat conduction in a flat plate sample. The principle of depth prediction using pulsed infrared thermography is presented; the time based on the peak second-derivative of the temperature difference in the logarithmic scale is selected as the characteristic time; the calibration curve based on data of single defect depth can be easily affected by random error. The calibration curve is put forward in the paper and obtained by designing a stepped reference sample, and it can be obtained by a curve fit of different depths and corresponding characteristic time using polynomial function. The polyfitting curve is used as the calibration curve for depth prediction when the relative error square is minimum. The experimental results show that the depth measured by the calibration curve based on many reference defect depths is more accurate than by single reference defect depth. Defect depth in CFRP composite can be measured by the method without knowing thermal property of specimen.
The propagation characteristics of a Gaussian beam passing through the thick nonlinear medium with defects
Authors: Su Qian-Qian  , Zhang Guo-Wen  , Pu Ji-Xiong  ,   Department of Information Science and Engineering, Huaqiao University, Xiamen 361021, China;,   National Laboratory on High Power Laser and Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800, China
Published: December 2020

The defects unavoidably existing on the optical component will modulate the phase and the amplitude of the beam propagation in the system. Based on the Fresnel diffractiond and split-step Fourier method, the two-dimensional intensity distributions of the Gaussion beam propagation in the nonlinear medium and the free space are simulated. And the intensity distributions of the beam propagation in the medium and the free space are also studied in the case where there exist defects on the front surface of thick medium. It is shown that the thicker the medium and the lager the nonlinear index of refraction, the stronger the beam focus and the closer to the medium surface the focal position is. The defects on the medium surface will lead to a strong beam intensity near the rear surface of the medium. And the intensity generated by the phase modulated defects is stronger than by the amplitude modulated defects.
The influences of Sr or Ba substitution on the structure and luminescence properties for Ca2.955Si2O7: 0.045Eu2+ phosphor
Authors: Lu Fang  , Zhang Xing-Hua  , Lu Zun-Ming  , Xu Xue-Wen  , Tang Cheng-Chun  ,   School of Material Science and Engineering, Hebei University of Technology, Tianjin 300130, China
Published: December 2020

A series of Ca2.955-xMxSi2O7: 0.045Eu2+ (M= Sr, Ba, x= 0.10.5) phosphors is prepared by solid-state reaction method. The influences of Sr or Ba with larger radius substitution on the structure and luminescence properties for Ca2.955Si2O7: 0.045Eu2 + phosphor are investigated. The XRD results show that a small quantity of Sr or Ba substitution of Ca does not change the structure of Ca3Si2O7 host which has a monoclinic crystal structure. Before the substitution, the emission peak is at about 574 nm. If the Ca2+ ions are substituted by Sr2+ or Ba2+ ions, the emission peak is blue shifted when the Sr or Ba concentration is 0.5. In addition, for the same doping contents of Sr and Ba, the Ba doped phosphors have stronger emission intensity.
Behaviors of ion and electron temperatures on EAST with lower hybrid current drive and lithium wall coating
Authors: Xu Jing-Cui  , Wang Fu-Di  , L� Bo  , Shen Yong-Cai  , Li Ying-Ying  , Fu Jia  , Shi Yue-Jiang  , Sanggon Lee  , M. Bitter  , K. Hill  ,   Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China;,   National Fusion Research Institute, 52 Eoeun-Dong, Yusung-Gu, Daejeon 305-333, Korea;,   Princeton Plasma Physics Laboratory, P.O. Box 451, Princeton, NJ 08543-0451, USA
Published: December 2020

It is observed that the profiles of ion and electron temperatures become broader within a region of r/a 0.6 on experimental advanced superconducting tokamak with high-power lower hybrid wave heating and lithium wall coating. It is found that the above phenomena are related to the low recycling at the first wall as a result of the lithium wall coating. The lithium wall coating affects the plasma particles coming from the plasma boundary to the first wall, thereby causing a reduction in recycling. The low recycling causes the temperature profiles to change. It is also found that the electron and ion temperatures approach to each other as a result of high collision rate between electrons and ions when the plasma density increases.
Molecular dynamics simulation of isothermal crystallization dynamics in Cu nanocluster
Authors: Chen Qing  , Wang Shu-Ying  , Sun Min-Hua  ,   Key Laboratory of Semiconductor Nanocomposite Materials, Ministry of Education, School of Physics and Electronic Engineering, Harbin Normal University, Harbin 150025, China
Published: December 2020

We investigate the structural and dynamic properties of isothermal crystallization of Cu nanocluster which contains 500 Cu atoms (Cu500), according to the embedded atom model, using molecular dynamics simulations. We calculate the Honeycutt-Anderson bond-type index, the inherent structure (IS) and the revisionary mean-square displacement of Cu nanocluster in crystallization process. All analyses suggest that the crystallization time of Cu500 is dependent on temperature. At high temperature, the crystallization time is well represented by a Gaussian distribution, which is not observed at low temperature. Cu500 displays multi-step crystallization at low temperature. On the other hand, we note that the influence of initial configuration on isothermal crystallization is significant. For the same thermodynamic state, especially at low temperature, the lower the IS of initial configuration, the longer the crystallization time is.
Steered molecular dynamics simulation of peeling a carbon nanotube on silicon substrate
Authors: Peng De-Feng  , Jiang Wu-Gui  , Peng Chuan  ,   School of Aircraft Engineering, Nanchang Hangkong University, Nanchang 330063, China;,   School of Aeronautical Manufacturing Engineering, Nanchang Hangkong University, Nanchang 330063, China
Published: December 2020

Steered molecular dynamics (SMD) simulations are performed to study the peeling of a single wall carbon nanotube (8, 8) from a silicon surface at room temperature. There is a regular relationship between the average force probed by the ideal spring and the peeling distance when the carbon nanotube (CNT) is peeled from the silicon substrate. A large positive and a large negative peak value can be found in the peeling process. The average force for varying peeling velocities is investigated and their peak values are fitted to a function of the peeling velocity. The SMD simulation results show that there is a linear relationship between the peak value and the peeling velocity, which is consistent well with some biophysics peeling experiments. Compared with macromolecules, the CNT has a strong adhesion to the silicon surface. The influences of both radius and length as well as the defects of the CNT on the peeling process are also examined. The numerical results indicate that the peak value of the peeling force is independent of the length of the CNT but increases linearly with the radius of the CNT increasing. The peak value of the peeling force is almost independent of the 5-7-7-5 defect in the CNT but critically weakened by the radius defect of the CNT. The suggested method provides a theoretical prediction for the future experiment at atomic scale, which is helpful for the potential application of the CNT in the silicon-based microelectronics industry.
First principles investigations of the structural stability and thermal dynamical properties of metal Ba under high pressure
Authors: Zhou Da-Wei  , Lu Cheng  , Li Gen-Quan  , Song Jin-Fan  , Song Yu-Ling  , Bao Gang  ,   College of Physics and Electronic Engineering, Nanyang Normal University, Nanyang 473061, China;,   College of Physics and Electronic Information, Inner Mongolia University for Nationalities, Tongliao 028043, China
Published: December 2020

The stabilities and the thermal dynamical properties of the three high-pressure phases of Ba (Ba-I, Ba-Ⅱ and Ba-V ) are investigated systemically by first principles method. Our results show that all the three phase meet the criteria of mechanical and dynamical stabilities at 0 K. With pressure increasing, the phonon frequencies in Ba-I and Ba-Ⅱ phases become softened, whereas the Ba-V phase exhibits the hardening of phonon frequencies. Although both Ba-Ⅱ and Ba-V phase are the same hcp structures, they show different elastic anisotropies under high pressure. We also find that Ba-Ⅱ phase at higher pressure still meets the mechanical stability criterion, but does not meet the dynamical stability criterion. The absence of dynamical stability may be the reason for the transition from Ba-Ⅱ phase to Ba-I!V phase. We also calculate and make comparisons of sound velocity, Debye temperature, bulk modulus and shear modulus etc between Ba-Ⅱ and Ba-V phases, showing that Ba possesses the thermal dynamical properties under high pressure.
Resistively detected nuclear magnetic resonance: recent developments
Authors: Liu Hong-Wu  , Yang Kai-Feng  , Tetsuya D. Mishima  , Michael B. Santos  , Katsumi Nagase  , Yoshiro Hirayama  ,   State Key Laboratory of Superhard Materials and Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China;,   ERATO Nuclear Spin Electronics Project-JST, Sendai, Miyagi 980-8578, Japan;,   Homer L. Dodge Department of Physics and Astronomy, University of Oklahoma, Norman, Oklahoma 73019-2061, USA;,   Department of Physics, Tohoku University, Sendai, Miyagi 980-8578, Japan
Published: December 2020

The resistively detected nuclear magnetic resonance (RDNMR), a high-sensitivity NMR technique developed by Klaus von Klitzing's group in 1988, is used to investigate exotic electron and nuclear spin properties in GaAs two-dimensional electron gases (2DEGs). Because the dynamic nuclear polarization (DNP) approach required for the RDNMR demonstration is strongly dependent on unique material properties of GaAs, this highly-sensitive technique has not yet been applied to 2DEGs confined in other host semiconductors. More recently, we have developed a novel DNP method for demonstration of RDNMR in a 2DEG within the typical narrow-gap semiconductor InSb. In this article, we focus on the discussion of our newly-developed DNP method, experimental details and results as well as future prospects after some preliminary remarks on the principles of RDNMR and DNP.
The calculation model of space-charge field based on the Galerkin series
Authors: Huang Chuan-Lu  , Ding Yao-Gen  , Wang Yong  , Xie Xing-Juan  , Gao Dong-Ping  ,   Key Laboratory of High Power Microwave Sources and Technologies, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China;,   Graduate University of Chinese Academy of Science, Beijing 100049, China
Published: December 2020

In this paper, we present a model of calculating the electron beam space-charge field using the partial Galerkin moments method. The space-charge field can be expanded as a series of different modes and thus using the Galerkin series. So, the space-charge field can be obtained finally through the solving the Galerkin coefficient equations set. A 2.5-dimensinal computer program of the beam-wave interaction in a klystron is compiled based on this model. Using the results from the program, the characteristic of the beam space-charge field is analyzed and the effects of the parameter in the simulation on the calculation result of the space-charge field are studied. This model uses the particle in cell method and it can be used in the 2- or 3-dimensional calculation model of the beam-wave interaction in a klystron.
Parameter adaptation in green cognitive radio
Authors: Zheng Shi-Lian  , Yang Xiao-Niu  ,   School of Communications Engineering, Xidian University, Xi'an 710071, China;,   Science and Technology on Communication Information Security Control Laboratory, Jiaxing 314033, China
Published: December 2020

The model for parameter adaptation problem in green cognitive radio and a particle swarm optimization based solution are proposed. Simulations are conducted to show the performance of the proposed method. Results show that given different quality of service (QoS) requirements, the proposed method can reduce the total transmit power of the system while maintaining the QoS requirements. Thus the goal of reducing energy consumption is reached.
Viscoelastic relaxation attenuation property for saturated sandstones and corresponding investigation of micro-scale mechanism
Authors: Xi Dao-Ying  , Xu Song-Lin  , Liu Yong-Gui  , Du Yun  ,   Mengcheng National Geophysical Observatory, School of Earth and Space Science, University of Science and Technology of China, Hefei 230026, China;,   CAS Key Laboratory for Mechanical Behavior and Design of Materials, University of Science and Technology of China, Hefei 230027, China
Published: December 2020

Attenuation experiments are performed by Metravib dynamic mechanical analyzer with sine wave loading style to study the viscoelastic relaxation property of pump-oil saturated and glycerol saturated Pengshan sandstone and Zigong arkoses with three kinds of porosities. Based on the thermal relaxation regularities, the activation energies and the atomic vibration frequencies of relaxation attenuation peaks for three kinds of saturated sandstones are evaluated. The results show that activation energies and atomic vibrations frequencies of sandstone samples are lower than those of interstitial atoms. The overall vibration behavior of atomic cluster with defects can be used to explain why vibration frequencies are low in samples. Besides the solid atoms, the gas and liquid atoms filled in defects contribute greatly to overall vibration of sample. Saturated sandstone, cemented by a combination of mineral crystals, is a polycrystalline, multiphase solid with internal complex structure and widespread defects, and it easily takes on thermal relaxation property under sine wave loading. Such flaws and defects as point defects, dislocation and grain boundary in samples and their interaction interaction can produce relaxation attenuation peak. To explain the relaxation mechanism by saturated liquid and internal structure of the sandstone, it is natural to relate the attenuation characteristics to its macro-meso-structure. It is notable that when taking the defects, multiple phase boundary into consideration, a new interesting phenomenon appears, there produces multi relaxation with broader peak and more widely distributed parameter. This investigation is helpful to study theoretical model and seismic data interpretation.
Study of weak constraint 4dvar with model error forcing control variable
Authors: Zhong Jian  , Fei Jian-Fang  , Huang Si-Xun  , Du Hua-Dong  ,   Institute of Meteorology, PLA University of Science and Technology, Nanjing 211101, China
Published: December 2020

In the traditional implementations of four-dimensional variational data assimilation (4dvar for short), it is assumed that the model used is perfect. However the model error in the model can directly affect the accuracy of data assimilation. The weak constraint 4dvar is an effective way of correcting and estimating the model error in 4dvar. In this paper, an approach to weak constraint 4dvar with model error forcing control variable is studied and implemented in the one-dimensional shallow water equations. The results show that when the model error cannot be ignored, the prediction error with the weak constraint 4dvar is smaller than with the traditional 4dvar in both the assimilation window and the prediction period, and the improvement with weak constraint 4dvar is more obvious in the condition with large model error. Also, the weak constraint 4dvar approach to estimating model error captures some basic features of model error including the magnitude and the characteristic of distribution.
Sudden birth and control of entanglement between two atoms successively passing through a bimodal cavity
Authors: Liao Qing-Hong  , Liu Ye  ,   Department of Electronic Information Engineering, Nanchang University, Nanchang 330031, China
Published: December 2020

The dynamics of entanglement of two atoms passing through a bimodal cavity one after another are investigated by employing the concurrence. The effects of the atomic coherence of the first atom and the initial entanglement of the cavity field on the time evolution of atom-atom entanglement are analyzed. The results show that the phenomenon of sudden birth of entanglement between two atoms occurs under some conditions and the maximum for the creation of the entanglement is dependent on the initial entanglement of the cavity field. Moreover, the threshold time and maximum for the creation of the entanglement can be controlled by changing the amplitude of atom. We find that the proposal may provide us with a theoretical way to control and manipulate the entanglement.
Modeling of dendritic growth and bubble formation
Authors: Wu Wei  , Sun Dong-Ke  , Dai Ting  , Zhu Ming-Fang  ,   Jiangsu Key Laboratory for Advanced Metallic Materials, Southeast University, Nanjing 211189, China
Published: December 2020

A two-dimensional (2D) lattice Boltzmann method (LBM)-cellular automaton (CA) coupled model is developed for the simulation of dendritic growth and bubble formation during solidification. In the model, the dendritic growth is simulated by a CA approach. The driving force of dendritic growth is determined by a local solute equilibrium approach. The LBM based on the Shan-Chen multiphase flow scheme is adopted to simulate the growth and the motion of bubbles in liquid. The interaction mechanism between dendrites and bubbles is embedded in the model. Model validation is carried out by comparing the simulations with the Laplace law, and by simulating the wettability of a bubble on a smooth solid surface. The proposed model is used to study the effect of gas-liquid interaction coefficient on single bubble growth. It is found that the growth velocity and the equilibrium radius of bubble increase with the gas-liquid interaction coefficient. The simulations of the dendritic growth and bubble formation during directional solidification reproduce the physical phenomena, including dendritic competitive growth, the preferential nucleation locations of bubbles, and bubble growth, coalescence, deformation due to the squeeze of neighboring dendrites, as well as bubble motion in the liquid channels. The simulation results are compared reasonably well with the experimental results. In addition, gas pore volume fraction increases with the initial gas content. The simulations of the present LBM-CA model provide an insight into the physical mechanism of bubble nucleation, growth, and motion, as well as the interaction between the dendritic growth and bubble formation during solidification.
The characteristics of the chaotic parameters for a loss type of modified coupled dynamic system
Authors: Hao Jian-Hong  , Sun Na-Yan  ,   School of Electric and Electronic Engineering, North China Electric Power University, Beijing 102206, China
Published: December 2020

A coupled dynamos model considering two loss characteristics is proposed, which can characterize the practical situation well compared with the previous one. By numerical calculation, the Lyapunov exponential spectrum, bifurcation diagram and Poincaré mapping are given. Then the dynamic characteristics of the parameters space are analyzed. From these results, it can be found that the novel coupled dynamo model with the consideration of mechanical damping loss, has double attractors. The mechanical damping loss can suppress the chaotic occurrence and leads to more complex bifurcation characteristic appearing in the parameter space. The two kinds of the loss characteristic parameters have significant influence on the dynamic behavior of the system.
Design of parameter identification law and studies on projective synchronization of spatiotemporal chaotic system
Authors: Zhang Xin  , Lü Ling  , Fan Xin  , Lü Na  ,   College of Physics and Electronic Technology, Liaoning Normal University, Dalian 116029, China
Published: December 2020

The parameter identification and the projective synchronization between spatiotemporal chaotic systems are studied. The parameter identification law and the adaptive law of undetermined function representing the coupling strength are designed based on Lyapunov theorem. Not only the unknown parameters in responses system are identified, but also projective synchronization between spatiotemporal chaotic systems is realized. The Burgers equation with spatiotemporal chaos behavior is further taken as an example of simulation analysis.
Phase and chemical stability of simulated waste forms Gd2Zr2-xCexO7(0≤ x≤ 2.0)
Authors: Lu Xi-Rui  , Dong Fa-Qin  , Hu Song  , Wang Xiao-Li  , Wu Yan-Lin  ,   Institute of Nuclear Science and Technology, SU, Chengdu 610064, China;,   National Defense Key Discipline Lab of Nuclear Waste and Environmental Safety, SWUST, Mianyang 621010, China;,   Institute of Nuclear Physics and Chemistry, CAEP, Mianyang 621900, China;,   Graduate University for Advanced Studies, Hayama 240-0193, Japan
Published: December 2020

In order to investigate phase change and chemical stability of pyrochlore Gd2Zr2O7 used for immobilizing Pu(Ⅳ), tetravalent cerium is used as the simulacrums for plutonium with tetravalence, and Gd2Zr2-xCexO7(0≤ x≤ 2.0) series samples are successfully synthesized by high temperature solid reaction and using Gd2O3 and ZrO2 powders as starting materials. The experiments of long-term chemical stability are conducted in synthetic seawater at 40 °C and 70 °C separately. The XRD diffractive data and extraction ratio of as-gained samples are collected by the help of X-ray diffraction (XRD) instrument and inductively coupled plasma mass spectrometry. The results indicate that the phases of compounds change from pyrochlore to fluorite-type phase when the value of x is more than 0.08. Extraction ratios of Gd3+, Zr4+ and Ce4+ in waste forms increase with the increase of immersion time in synthetic seawater. The extraction ratio of waste form at 70 °C is higher than at 40 °C. The highest extraction ratios of Gd3+, Zr4+ and Ce4+ for 42 days are no more than 0.032, 0.003 and 0.032 μg·ml-1 respectively.
MBPT calculation for the fine-structure intervals of principal series np(n=39) for Na
Authors: Chen Sun  , Zhu Yun-Xia  , Ge Zi-Ming  , He Li-Ming  ,   Department of Physics, East China University of Science and Technology, Shanghai 200237, China
Published: December 2020

The fine-structure intervals of Na principal series np(n=39) are calculated by the many-body perturbation theory (MBPT) within the framework of relativity. To deal with the problem that a large set of continuum states is required in the MBPT calculation, an exponential potential is employed to generate a discrete, finite and nearly complete set of numerical basis functions. The zeroth-order wavefunctions and eignvalues are obtained by solving the relativistic Hartree-Fock (RHF) equation and the RHF equation with the action of a potential barrier. The basis set used in this work contains intermediate orbitals with the angular momentum l 6 and in an appropriate energy range, and most of them are the so called contracted orbitals. Encouraging results are obtained using this technique to calculate the second-order correlation corrections, combining the Breit effects in a first-order perturbation approach. Compared with other theoretical calculations, the present results are much close to the experimental results.