bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical approximation study on the helix structure of ferroelectric liquid crystal
Authors: Tang Xian-Zhu  , Lu Xing-Hai  , Peng Zeng-Hui  , Liu Yong-Gang  , Xuan Li  ,   (1)中国科学院长春光学精密机械与物理研究所应用光学国家重点实验室,长春  130033; (2)中国科学院长春光学精密机械与物理研究所应用光学国家重点实验室,长春  130033；中国科学院研究生院,北京  100049
Published: December 2020

The expressions of average refractive index in a helix pitch of ferroelectric liquid crystal（FLC） were derived by theoretical approximation computation of the helix structure at chiral smectic C phase of FLC. A conclusion that FLC molecules in a helix pitch as a whole can be considered as a model of nematic liquid crystal in terms of the expressions of average refractive index was obtained. When the thickness of FLC with a vertical alignment along the helical axis is integer times long as the helix pitch, FLC molecules can be considered as a group composed of nematic liquid crystal models. The comparisons of experiment results of ZLI-3654 FLC with 5CB nematic liquid crystal confirmed the above conclusion. The theory and experiment are in good agreement. Theoretical guidance and a deeper understanding can be provided by this theory for preparation of deformed helix FLC and vertical alignment deformed helix FLC devices, as well as application of ferroelectric liquid crystal.
Effects of the concentration of Ga high doping on electric conductivity and red shift of ZnO from frist-principles
Authors: Hou Qing-Yu  , Zhao Chun-Wang  , Jin Yong-Jun  , Guan Yu-Qin  , Lin Lin  , Li Ji-Jun  ,   内蒙古工业大学理学院，呼和浩特  010051
Published: December 2020

We present the band structures and densities of states and calculation of absorption spectrum as well as the relative number of electrons and mobility ratio of electrons scattering from Zn1-xGaxO with different concentration of Ga，　and in the condition of high concentration of Ga heavily doped in ZnO semiconductor at low temperature，　by adopting the ab-initio plane wave ultra-soft pseudo potential technique based on the density functional theory. It was found that the relative number of electrons increases with the concenteation of Ga increasing，　but the mobility ratio of electrons of Zn1-xGaxO decreases. The conductivity and minimum band gaps of the doped and undoped ZnO have been compared respectively，from which　we draw the conclusion that the conductivity of Zn1-xGaxO semiconductor decreases with the concentration of Ga increasing. When the concentration of Ga reaches a certain value，　the minimum band gap dreases with the concentration of Ga increasing，　and the phenomenon of red shift happens in the high energy zone. Calculations is in agreement with the experimental results obtained in Zn1-xGaxO with atomic Ga doping in excess of x=004.
Influence of Zr catalyst on reversible hydrogen storage characteristics of NaAlH4 and Na3AlH6
Authors: Ye Jia-Yu  , Liu Ya-Li  , Wang Jing-Lin  , He Yao  ,   云南大学物理系，昆明 650091
Published: December 2020

The cell parameters, electron localization function and density of states of pure and Zr-doped NaAlH4 and Na3AlH6 are investigated using plane-wave pseudo-potential method based on density functional theory. The results show that NaAlH4 and Na3AlH6 are insulators characterized by a band gap of 46 and 31 eV, respectively. The Al and H atoms form covalent bonds and the Na and H atoms form ionic bonds in NaAlH4 and Na3AlH6 When Zr replaces Na, the interaction between Zr and H is stronger than the primary Na—H bond, and the interaction between Al and H becomes weaker; when Zr replaces Al, the bond between Zr and H is weaker than the primary Al—H bond. Our calculations indicate that Zr-doped NaAlH4 and Na3AlH6 are more stable than that of the pure alanates, and the energy to remove H atom is significantly decreased.
Boron/nitrogen pairs doping in armchair single-walled carbon nanotubes
Authors: Xu Hui  , Xiao Jin  , Ouyang Fang-Ping  ,   中南大学物理科学与技术学院,长沙 410083
Published: December 2020

By performing first principles electronic structure calculations, we have revealed the effect of boron/nitrogen pairs doping in armchair single-walled carbon nanotubes (SWCNT). It is shown that for two kinds of sites in the armchair SWCNT, the doping of B/N pairs can more easily happen on the P1 site which is at 30° angle to the tube axis. An energy gap is opened in metallic SWCNT by doping B/N pairs, and the energy gap increases with raising the axial concentration of the B/N pairs. Moreover, when two couples of B/N pairs are doped in SWCNT, the electronic structure is sensitive to the relative positions of B/N pairs in the couple along the circumference of tubes. It’s due to that the original charge distribution is changed by B/N pairs doping, and the effect of B/N pairs is localized. When the distance between B/N pairs increases, the extent of the effect is increased. This result may contribute to preparing pure semiconductor and effectively controlling the electronic structure.
Experimental study of the effect of fabrication condition on absorbing property of nano-absorbent
Authors: Zhang Shuan-Qin  , Shi Yun-Long  ,   (1)山西大同大学固体物理研究所，大同 037009; (2)山西大同大学固体物理研究所，大同 037009；总装备部工程兵技术装备研究所，无锡 214035
Published: December 2020

Co-doped nano-absorbent is prepared by the sol-gel method. The effect of the fabrication condition on physical property and absorbing property are analyzed. The optimum fabrication condition is found. The influence of particle size on absorbing property is compared with that of the conventional absorbent. Radar absorbing measurement shows that nano-absorbent has a good absorbing property.
Influence of aggregation structure and traps on surface flashover of XLPE in vacuum
Authors: Li Sheng-Tao  , Huang Qi-Feng  , Sun Jian  , Zhang Tuo  , Li Jian-Ying  ,   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

In the paper, the influence of aggregation structure and traps on both DC and impulse flashover voltage of semi-crystalline cross-linked polyethylene (XLPE) in vacuum are investigated. After heat treatment at 135 ℃ for 10 min, the XLPE samples were quenched to -56 ℃ or -25 ℃, cooled normally, cooled at a rate of 1 ℃/min or 05 ℃/min to room temperature, respectively. The electrical properties, microstructure and trap distribution of heat-treated samples were studied. Compared with untreated samples, it is found that the dc and impulse flashover voltages of heat treated samples are raised by 76% and 19%, respectively. It is proposed that the aggregation structure and trap level is changed by heat treatment, leading to the improvement of surface flashover properties in vacuum. It is suggested that the vacuum flashover characteristics can be improved by controlling the aggregation structure and trap levels of semi-crystalline polymers.
Study on the microstructures and electrical properties of Bi0.5Ba0.5Fe0.5Ti0.49Nb0.01O3 thermistor ceramic
Authors: Yuan Chang-Lai  , Liu Xin-Yu  , Ma Jia-Feng  , Zhou Chang-Rong  ,   桂林电子科技大学广西信息材料重点实验室,桂林 541004
Published: December 2020

The Bi0.5Ba0.5Fe0.5Ti0.49Nb0.01O3 thermistor has been prepared by the standard solid-state reaction method, and the microstructures, direct current resistivity, dielectric property, impedance and electric modulus were investigated by the X-ray diffraction, scanning electron microscopy, resistivity-temperature measurement and alternating current impedance spectroscopy. The results show that the material, with an average grain size of about 10 μm, still has cubic perovskite structure, and the lattice constant of the material becomes larger compared with that of the BaTiO3. The resistivity and thermistor contant B value of the material are about 107 Ω·cm and 7690 K, respectively, and the phase transition occurs twice (at 403 and 523 K), which are confirmed by the dielectric spectrum as a function of temperature. The complex impedance spectroscopy shows the non-ideal Debye type with two incomplete overlapping Cole-Cole semicircles corresponding to the grain and grain boundary resistance. The imaginary part of alternating current resistance as a function of frequency indicates there are two relaxation effects observable in the grain and grain boundary. The phase transition has little effect on the conduction property of bulk grain, but a great impact on that of the grain boundary.
Tuning photoluminescence of single InAs quantum dot by electric field
Authors: Chang Xiu-Ying  , Dou Xiu-Ming  , Sun Bao-Quan  , Xiong Yong-Hua  , Ni Hai-Qiao  , Niu Zhi-Chuan  ,   中国科学院半导体研究所超晶格与微结构国家重点实验室,北京 100083
Published: December 2020

By using photoluminescence (PL) and time-resolved PL spectra， the optical properties of single InAs quantum dot (QD) embedded in the p-i-n structure have been studied under an applied electric field. With the increasing of electric field， the exciton lifetime increases due to the Stark effect. We noticed that the decrease or quenching of PL intensity with increasing the electric field is mainly due to the decrease of the carriers captured by QD.
Extracting human gait series based on the wavelet transform
Authors: Fu Mao-Jing  , Zhuang Jian-Jun  , Hou Feng-Zhen  , Ning Xin-Bao  , Zhan Qing-Bo  , Shao Yi  ,   (1)南京大学电子科学与工程系，生物医学电子工程研究所，近代声学教育部重点实验室，南京  210093; (2)南京大学电子科学与工程系，生物医学电子工程研究所，近代声学教育部重点实验室，南京  210093；中国药科大学基础科学部，南京  210009
Published: December 2020

The wavelet transform was applied to process the accelerometer signals derived from human walking. The accelerometer signals were first decomposed at different levels utilizing the multi-scale and multi-resolution characteristics of the discrete wavelet transform. After the determination of both the mother wavelet and the optimal decomposition level, human gait series can thus be extracted from the eigen scale of the accelerometer signal. Compared with the method that detects peak values directly from accelerometer signals by thresholding, the wavelet transform gives higher detection rate of peak values on the eigen scale of the accelerometer signals. Even when the accelerometer signals are exposed to serious noise, experimental results still demonstrate that the wavelet approach can guarantee the precision of the extracted gait series, which is of vital importance for the subsequent analyses. It can be concluded that wavelet transform is an effective tool for the extraction of gait rhythmicity. The wavelet transform will be helpful in identifying the characteristics of other physiological signals.
Effective thermodynamic properties of Kerr-Newman-anti-de Sitter black hole
Authors: Wei Yi-Huan  ,   渤海大学物理系,锦州 121000
Published: December 2020

We study thermodynamic properties of the effective right and left systems of Reissner-Nordstrm-anti-de Sitter black hole. Then, we analyze the case of Kerr-Newman-anti-de Sitter(KN-AdS) black hole and calculate the corresponding thermodynamic quantities of the right and the left systems. For the nearly extremal case, it can be seen that the effective right system of KN-AdS black hole satisfies the Nernst theorem and the effective left system has a finite temperature.
Holographic entropy of Gibbons-Maeda dilaton black hole
Authors: Xie Zhi-Kun  , Yu Guo-Xiang  , Liu Cheng-Zhou  ,   绍兴文理学院物理与电子信息系，绍兴  312000
Published: December 2020

In accordance with the holographic principle， by calculating the entropy of the quantum field just on the event horizon of the Gibbons-Maeda dilaton black hole， the holographic entropy and the Bekenstein-Hawking entropy of the black hole are obtained. By using the non-commutative quantum field theory， the divergence of the state density near the event horizon in usual quantum field theory is removed and the ultraviolet cutoff in the heat gas method of black hole entropy is avoided.Using the residue theorem, the integral difficulty in the calculation is overcome and the results here are obtained quantitatively. The results show that black hole entropy is identical with the statistical entropy of the quantum states at the horizon. Black hole entropy may be obtained by calculating the quantum states only at the event horizon, and in the calculation the influences of quantum states outside the horizon should be avoided.
The disturbance energy of Rossby wave in barotropic atmosphere
Authors: Zhang Liang  , Zhang Li-Feng  , Wu Hai-Yan  , Li Gang  ,   (1)94855部队，衢州  324001; (2)解放军理工大学气象学院应用地球物理研究室,南京  211101; (3)解放军理工大学气象学院应用地球物理研究室,南京  211101；96165部队，乐平  333300
Published: December 2020

Fourier-transformed method is used to investigate the problem of the rapid growth and decay of the disturbance energy of Rossby wave in barotropic atmosphere on the assumption that this kind of atmosphere is adiabatic, non-frictional, unforced, non-dissipative and quasigeostrophic on a beta plane. The analytical solution of linear barotropic potential vorticity equation is obtained for the first time and we go a step further to discuss the relations between the disturbance energy and the initial perturbation flow wave numbers, shear of basic flow and viscid coefficient by using the above analytical solution.
Singularly perturbed nonlinear reaction diffusion problem with two parameters
Authors: Chen Huai-Jun  , Mo Jia-Qi  ,   Department of Mathematics, Anhui Normal University, Wuhu 241000, China
Published: December 2020

A class of singularly perturbed initial boundary value problems for nonlinear reaction diffusion equations with two parameters are considered. Under suitable conditions, the asymptotic expansion of the solution is constructed and the asymptotic behaviors of the solution are discussed.
Third-order theory for bichromatic bidirectional water waves partially reflected from vertical breakwaters
Authors: Yang Li  , Huang Hu  ,   Shanghai Institute of Applied Mathematics and Mechanics, Shanghai University, Shanghai 200072, China
Published: December 2020

To overcome the internal limitation of standing wave forces on vertical breakwaters and describe multichromatic multidirectional water waves in front of the breakwaters, a third-order theory, including the classical solutions of two-dimensional long-crested waves and monochromatic unidirectional short-crested waves, for bichromatic bidirectional water waves partially reflected from the breakwaters is developed. A universal law applicable to a higher-order multichromatic multidirectional wave system is proposed, that is, the even-order frequencies are zero, the numbers of the odd-order frequencies constitute a geometric progression.
Real-time novelty detector of chaotic time series based on retina neural network
Authors: Feng Jian  , Liu Jin-Hai  , Zhang Hua-Guang  ,   (1)Key Laboratory of Integrated Automation of Process Industry of Ministry of Education, Northeastern University, Shenyang 110004, China; School of Information Science and Engineering, Northeastem University, Shenyang 110004, China; (2)Key Laboratory of Integrated Automation of Process Industry of Ministry of Education,Northeastern University, Shenyang 110004,China
Published: December 2020

A kind of novelty detection method based on retina neural network is proposed, which could find the novelty in chaotic time series. To demonstrate the capability of the novelty detection method, we designed three novelty detectors,namely the neural network novelty detector (RNNND), back-propagation(BP) novelty detector (BPND) and radial base function(RBF) novelty detector (RBFND), which are based on retina neural network, BP neural network and RBF neural network, respectively. Using Lorenz time series and oil pipeline pressure time series, we tested the performance of the three novelty detectors, including performances of anti-jamming, micro-novelty detection and the computing speed. The results show that the three novelty detectors have good precision and fast computing speed. Finally, the merits and shortcomings of the proposed novelty detection method are analyzed based on retina neural network, BP and RBF neural network, and their applicabilities are given.
Dynamic analysis on the topological properties of the complex network of international oil prices
Authors: Chen Wei-Dong  , Xu Hua  , Guo Qi  ,   Department of Management and Economics, Tianjin University, Tianjin 300072, China
Published: December 2020

To analyze the dynamic of crude oil price data using homogenous partition of coarse graining process,OK WTI Spot Price FOB from January 1986 to November 2009 was transformed into symbolic sequences consisting of three characters (R,e,D). The vertices of the oil price fluctuation network were 5-symbol strings in the number of 102(i.e.102 fluctuation patterns in durations of 5 days) linked in the network's topology by time sequence. It contained integrated information about interconnections and interactions between fluctuation patterns of oil price in network topology. The dynamical statistics of the degree, degree distribution, clustering coefficient and the shortest path length were calculated. The results indicated that the degree of the oil price sequence fluctuation network and the accumulated degree distribution show a power-law distribution, so did the node degree and the rank. The degree of the former 32 nodes was larger, and most oil price fluctuation models had the character with the escalating trend. Some nodes of the oil price fluctuation network had stronger ability in between centrality, and 24.5 percent of the nodes took part in the 80.97 percent of Between Centrality function. The average path length was 2.285, and the paths with length 2—3 were 86.8 percent, which verified the complex characteristics of the oil price fluctuation in network topology. This paper had guiding significance in identifying the topological importance of the node model and understanding the inherent law and information of the oil price fluctuation.
Structure and potential energy function of MgB and MgB2(1A1)
Authors: Han Xiao-Qin  , Jiang Li-Juan  , Liu Yu-Fang  ,   (1)College of Physics and Information Engineering, Henan Normal University, Xinxiang 453007,China; (2)College of Physics and Information Engineering, Henan Normal University, Xinxiang 453007,China; Department of Physics and Information Engineering, Shangqiu Normal University, Shangqiu 476000, China; (3)Department of Physics, Xinxiang University, Xinxiang 453003,China
Published: December 2020

Quadratic configuration interaction (QCISD) method has been used to optimize the possible ground state structures of MgB and MgB2 by the 6-311G and 6-311++G(df) basis sets. The potential energy functions of MgB2 have been derived from the many-body expansion theory. The potential energy functions describe correctly the configurations and the dissociation energies of the two ground-state molecules. Molecular reaction kinetics of B+MgB and Mg+BB based on the potential energy functions is discussed briefly, which is successfully used for describing molecular reaction dynamics.
Multi-reference configuration interaction of the ground and low-lying excited states of LiC
Authors: Wang Quan-Wu  , Chen Heng-Jie  , Cheng Xin-Lu  , Su Xin-Fang  , Tang Hai-Yan  ,   (1)Department of Mathematics and Physics, Chongqing University of Science and Technology, Chongqing 401331, China; (2)Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China
Published: December 2020

The potential energy curves (PECs) for the ground electronic state X4Σ-and five low-lying excited electronic states (a2Π, b2Δ, c2Σ-, d2Σ+, A4Π) of LiC have been calculated using the multiconfiguration reference configuration interaction method including Davidson correction (MRCI+Q). And PECs were fitted to analytical Murrell-Sorbie potential function to deduce the spectroscopic parameters of equilibrium bond length Re, rotation coupling constant ωe, anharmonic constant ωeχe, equilibrium rotation constant Be and vibration-rotation coupling constant αe. Those values were also compared with the other results currently available. By solving the radial Schrdinger equation of nuclear motion, the vibration levels, inertial rotation constant and six centrifugal distortion constants (Dν, Hν, Lν, Mν,Nν,and Oν) are reported for the first time.
X-ray photoelectron spectroscopy study on GaN crystal irradiated by slow highly charged ions
Authors: Han Lu-Hui  , Zhang Chong-Hong  , Zhang Li-Qing  , Yang Yi-Tao  , Song Yin  , Sun You-Mei  ,   (1)Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China; (2)Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China; Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

We utilize slow highly charged ions of Xeq+ and Pbq+ to irradiate GaN crystal films grown on sapphire substrate, and use X-ray photoelectron spectroscopy to analyze its surface chemical composition and chemical state of the elements. The results show that highly charged ions can etch the sample surface obviously, and the GaN sample irradiated by highly charged ions has N depletion or is Ga rich on its surface. Besides,the relative content of Ga—Ga bond increases as the dose and charge state of the incident ions increase. In addition, the binding energy of Ga 3d5/2 electrons corresponding to Ga—Ga bond of the irradiated GaN sample is smaller compared with that of the Ga bulk material. This can be attributed to the lattice damage, which shifts the binding energy of inner orbital electrons to the lower end.
Density functional theory study of silica clusters (SiO2)n-(n≤7)
Authors: Chen Xue-Feng  , Qi Kai-Tian  , Li Bing  , Sheng Yong  , Zhang Yan  , Yang Chuan-Lu  ,   (1)College of Material Science and Engineering,Sichuan University, Chengdu 610065, China; (2)College of Physics and Electronics,Ludong University, Yantai 264025, China
Published: December 2020

Geometric structures of (SiO2)n-(n≤7)anion clusters are optimized by using the generalized gradient approximation density functional theory. The energy and vibrational frequency have been calculated. The lowest energy (SiO2)4- cluster is found to be more thermodynamically favored compared with other neighboring sized cluster isomers. Additionally,the lowest energy (SiO2)n-(n≥4)clusters grow up regularly based on the lowest energy (SiO2)4- cluster.
Propagation of the intense relativistic sheet electron beam with a quasi-rectangular cross section
Authors: Du Guang-Xing  , Qian Bao-Liang  ,   College of Opto-electric Science and Engineering, National University of Defense Technology, Changsha 410073,China
Published: December 2020

The sheet electron beam with a quasi-rectangular cross section has been proposed to carry intense current. Obviously different from the elliptical sheet electron beam with the same high aspect ratio, this kind of beam is almost uniform in thickness, and can be generated by the cold metal cathode. Besides, the uniform thickness leads to uniform beam power in the horizontal direction, implying less modes but better counteraction between the beam and microwave. In addition, the uniform thickness make the width of the propagation system,including the cold cathode, the microwave cavities and the focusing magnets,easily changed. Firstly,the space-charge electric field of the sheet electron beam was analyzed numerically, then the focusing magnets, including the periodic cusped magnets and quadrupole magnets, were designed according to the space-charge electric field for beam matching. To validate the above theoretical analysis, particle-in-cell simulation was performed, which shows that the 300 keV, 3 kA sheet electron beam can be well focused by the 0.163 T periodic cusped magnetic fields with the 0.064 T quadrupole magnetic fields. More than 98% of the total current has been propagated through the distance of 300 mm.
Thermal capacity of nanocrystalline copper at low temperatures
Authors: Zhang Hong-Liang  , Lei Hai-Le  , Tang Yong-Jian  , Luo Jiang-Shan  , Li Kai  , Deng Xiao-Chen  ,   (1)西南科技大学材料科学与工程学院，绵阳  621010；中国工程物理研究院激光聚变研究中心，绵阳  621900; (2)中国工程物理研究院激光聚变研究中心，绵阳  621900
Published: December 2020

Copper nanoparticles with average diameter of about 45 nm were compressed in a high-strength mold under different pressures at 523 K to produce nanocrystalline copper. The X-ray diffraction (XRD)， scanning electron microscopy (SEM)，and physics-property-measurement system (PPMS) were used to study the thermal capacity of nanocrystalline Cu as a function of temperature and the mass density at low temperatures. The experimental results indicate that the thermal capacity at low temperatures increases with decreasing density. The thermal capacity of nanocrystalline Cu is higher than that of the coarsed Cu and the increase ratio reaches maximum at around 10 K. The physical mechanism of the phenomenon is explored in this paper.
Miniaturized electric resonance metamaterial
Authors: Tang Ming-Chun  , Xiao Shao-Qiu  , Deng Tian-Wei  , Bai Yan-Ying  , Guan Jian  , Wang Bing-Zhong  ,   Institute of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

The principle of electric resonance metamaterial design is analyzed in detail, and the designed metamaterial (H-shaped metamaterial) is significantly miniaturized due to the lowering in the operating frequency from 12.21 to 5.46 GHz while keeping the dimensions unchanged, which was achieved by means of equivalent inductance and capacitance loading and grounding based on the equivalent circuit model. Our work not only provides a reference for miniaturizing different metamaterial configurations, but also points out specific research directions and effective ways in the design of metameterials with different characteristics and different operating frequencies.
Comparison and analysis of the basic characteristics of photonic crystal fiber with three typical structures
Authors: Jiang Ling-Hong  , Hou Lan-Tian  , Yang Qian-Qian  ,   (1)Institute of Infrared Optical Fibers and Sensers, Yanshan University, Qinhuangdao 066004, China; (2)Institute of Infrared Optical Fibers and Sensers, Yanshan University, Qinhuangdao 066004, China; State Key Laboratory of Metastable Material Science & Technology, Yanshan University, Qinhuangdao 066004, China
Published: December 2020

The multi-pole method is used to analyse and compare the dispersion coefficient, dispersion slope, nonlinear coefficient, confinement loss of photonic crystal fibers of hexagonal, octagonal and decagonal structures with the same structure parameters. The photonic crystal fiber with hexagonal structure is more suited for study of dispersion compensation and high nonlinearity. The nonlinear coefficient of photonic crystal fiber with hexagonal structure is 0.37 m-1·W-1 at 0.8 μm. The photonic crystal fiber with decagonal structure is more suited for study of flat dispersion curve and low confinement loss.The confinement loss of photonic crystal fiber with decagonal structure is about 3000 orders of magnitude less than that with hexagonal structure around 0.8 μm.The dispersion of photonic crystal fibre with decagonal structure is less than 0.17 and larger than -0.07 ps/(km·nm) from 1.4 to 1.65 μm, resulting in nearly zero dispersion of photonic crystal fiber around 1.55 μm. The cladding structure of photonic crystal fiber is closer to the circular structure, the dispersion of which is much flatter, the nonlinear coefficient and the confinement loss of which are much lower.
Forced solitary Rossby wave with beta effect and topography effect in barotropic flows
Authors: Song Jian  , Lai Jun-Feng  ,   Department of Mathematics, College of Sciences, Inner Mongolia University of Technology, Hohhot 010051, China
Published: December 2020

For the barotropic fluid, based on the quasi-geostrophic potential vorticity equation, an inhomogeneous Boussinesq equation including topographic forcing and an external source is derived by employing the perturbation method and stretching transform of time and space. Through inspection of the evolution of the amplitude of the Rossby wave, it is found that Coridis effect, topography effect and an external source are the key inducing factors of the solitary Rossby wave if the basic stream function has a shear flow. Assuming that there is a balance between nonlinear and topography effects, an inhomogeneous Boussinesq equation is derived. The results show that the topography and the Rossby wave interact in the barotropic flow. The inhomogeneous Boussinesq equation describing the evolution of the amplitude of solitary Rossby waves with the change of Rossby parameter β(y) with latitude β, topographic forcing and the external source is obtained.
Construction of metallic nanocrystalline samples by molecular dynamics simulation
Authors: Ma Wen  , Zhu Wen-Jun  , Zhang Ya-Lin  , Chen Kai-Guo  , Deng Xiao-Liang  , Jing Fu-Qian  ,   (1)Department of Physics, National University of Defense Technology, Changsha 410073, China; National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China; (2)Institute of Computer Application, China Academy of Engineering Physics, Mianyang 621900, China; (3)National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

The construction of metallic nanocrystalline (NC) samples by molecular dynamics simulation is investigated. Firstly, the initial NC aluminum and copper samples are assembled by Voronoi geometrical construction method, then the local minimized energy states of the samples are obtained by quenching (or conjugate gradient method). Finally, the simulated annealing method in normal pressure and temperature condition ensembles at zero pressure is used to approximate the global minimized energy states of the samples. The residual internal stress is employed to signify the difference between the simulated and the experimentally synthesized samples for the first time. The structure of grain boundaries, the descending process and the local distribution of the average internal stress and the energy of the samples, as well as the elastic constants of the final samples are observed during these two relaxation procedures. It is found that the energy and the residual internal stress of the samples are close to the experimental data after relaxation. It is enough to obtain the global minimum energy states through Voronoi geometrical construction to investigate the static and dynamic mechanical properties of NC metals with a 5—10 ps local energy minimization and a 40—100 ps of simulated annealing with annealing temperature between the room temperature and 65% of melting point. The annealing time and temperature are of little importantce to the mechanical properties within the parameter windows properly selected.
Luminescence characteristics of lead tungstate (PbWO4) scintillation crystal doped with fluorine anions
Authors: Ren Guo-Hao  , Chen Xiao-Feng  , Mao Ri-Hua  , Shen Ding-Zhong  ,   Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 201800, China
Published: December 2020

Lead tungstate (PbWO4, shorten as PWO) crystal has attracted much interest as a very dense, fast and radiation hard scintillator. However, its application is strongly hampered by its poor light output. At present, great efforts have been devoted to improve the scintillating efficiency of PWO crystals. In this paper, fluorine anions were used as dopant to improve the light output of PWO crystals. The crystals were grown by modified Bridgman method. The charge was obtained from PbO and WO3 powder with purity of 99.99% and 99.999% respectively. The transmittance spectra measured with a spectrophotometer Shimadzu UV-2501PC reveal that the transmission of PWO:F is much higher than that of undoped PWO, especially in the short wavelength region (330—500 nm). The most significant characteristic of the F-doped PWO is that two emission components can be identified in their photoluminescence spectra, a fast component related to the blue emission (419 nm) and a slow component related to the green emission (553 nm). The measured light yield of PWO:F, based on the pulse height spectra stimulated by 137Cs, is as high as 2 to 3 times of the undoped PWO and meanwhile will be increased with the integration of time gate. This means that the significant contribution to the light yield of PWO may come from the green luminescence. The decay constants excited by 22Na gamma ray can be fitted into three components, they are τ1=2.68[57.5%] , τ2=47.6[31.0%] and τ3=183[11.5%]. 88.5% of total scintillating light decays within 50 ns. However, the distribution of light yield along the crystal axis is not uniform, i.e. higher at the tail end than that in the seed end. It is suggested that the blue emission is ascribed to the regular lattice centers, namely [WO4]2- and the green one to a defect [WO3+F] cluster. The significant defects in PWO lattice induced by F-anion should be responsible for the increase of the light yield.
Path integral Monte Carlo simulations for pair correlation function for liquid 4He systems
Authors: Zhao Xing-Wen  , Cheng Xin-Lu  , Zhang Hong  ,   (1)四川大学物理科学与技术学院，成都  610064; (2)四川大学原子与分子物理研究所，成都  610065
Published: December 2020

Path integral Monte Carlo (PIMC) simulation is a powerful tool in studying the interacting quantum systems at finite temperatures. In this article, we use PIMC to study the pair correlation function g(r) of the system consisting of 124 4He atoms in different conditions. At saturated-vapor-pressure (SVP), we calculated the pair correlation function g(r) at four different temperatures respectively, that is, T=138 K, 167 K, 250 K and 424 K. We also determined the changes in g(r) when either temperature or density is changed while the other remaines fixed, and found that for different densities and the same temperature, the change in g(r) is remarkable, while for different temperatures but same density, the change is not obvious. We used the microcosmic point of view for g(r) to explain the above phenomenon. Although finite size effects exist in the PIMC method, when comparing the pair correlation function belonging to systems consisted of 128 and 256 4He atoms respectively, differences between them are small. And we can conclude that as the increasing of the simulated system size, differences between simulated system and the real one becomes smaller and smaller. So in this particle, the properties educed from the simulated system consisted of 256 4He atoms can represent those of the real liquid system.
Molecular dynamic simulation of ethanol from ambient temperature and pressure to supercritical conditions
Authors: Yang Xiang-Dong  , Lu Peng-Fei  , Li Yong  , Liu Jin-Chao  ,   (1)Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China; (2)Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China; Chengdu Dr.King Technology Co.Ltd, Chengdu 610065, China; (3)Institute of Optical Communication and Optoelectronics, Beijing University of Posts and Telecommunications, Beijing 100876, China
Published: December 2020

The thermodynamic properties, structure, and dynamic properties of ethanol from ambient conditions to supercritical states were investigated by molecular dynamics simulation (MD). With the increase of temperature, the enthalpy and self-diffusion coefficients increase, while the hydrogen bonding interaction between ethanol molecules weakens. With the increase of pressure, the self-diffusion coefficients decrease, while the hydrogen bonding interaction increases. The self-diffusion coefficient of ethanol in supercritical region is 10 times greater than that in the liquid region. It changes slightly with temperature in the liquid region, while decreases rapidly with pressure in the gas region. The influence of density on self-diffusion coefficient could be manifested by the influence of temperature and pressure. Under supercritical conditions, the ethanol system shows aggregation phenomenon which is even more evident in the low-density region due to density fluctuations. The hydrogen bond of ethanol molecules significantly weakens, the structure becomes loose and the molecular polarity is greatly reduced in supercritical conditions compared with that in ambient conditions. Our results are in good agreement with the experimental data.
First-principles study on electronic structure of In-doped wurtzite ZnO
Authors: Liu Xiao-Cun  , Ji Yan-Ju  , Zhao Jun-Qing  , Liu Li-Qiang  , Sun Zhao-Peng  , Dong He-Lei  ,   (1)School of Science, Shandong Jianzhu University, Jinan 250101, China; (2)College of Materials Science and Engineering , Shandong Jianzhu University, Jinan 250101, China (3)School of Physics, Shandong University, Jinan 250100, China; (4)College of Physics and Electronics, Shandong Normal University, Jinan 250014, China
Published: December 2020

The band structure, total density of states and partial density of states of pure and In-doped wurtzite ZnO have been investigated by using the first-principles ultrasoft pseudo potential approach of the plane wave. The calculation indicates that the band gap of ZnO is reduced by In doping. The energies of both the conduction band minimum and the valence band maximum decrease with increasing In-doping concentration, but the decrease of the conduction band minimum is much more pronounced than that of the valence band maximum, which leads to narrowing of the band gap. Moreover, it was found that In-doping can cause increase of the lattice constant, which also reduces the band gap.
Electronic theory study on high temperature oxidation mechanism of Nb-Ti-Al alloy
Authors: Liu Gui-Li  , Yang Jie  ,   School of Constructional Engineering, Shenyang University of Technology, Shenyang 110023, China
Published: December 2020

The electronic structure parameters of density of electronic states, atoms embedding energy, affinity energy and cluster energy of Nb alloy have been calculated using the recursive method. The high-temperature oxidation mechanism of Nb alloy was investigated. Studies show that the oxygen adsorption on Nb alloy surface can lower the adsorption energy, so oxygen is easily adsorbed on the alloy surface, and gradually diffuses into the Nb alloy matrix. Oxygen has a high solubility in the Nb alloy matrix because of the negative atom embedding energy, and it has similar density of states to Nb. Because the atom embedding energies of Ti and Al in the alloy matrix are higher than that on the alloy surface, Ti and Al atoms diffuse from the alloy matrix to the alloy surface and segregate on the alloy surface, ultimately making the Nb surface rich in Ti and Al. The clustering energy calculation shows that Ti and Al atom tend to gather on their own area, forming Ti and Al atom clusters respectively. Oxygen can interact with Nb, Ti and Al because of the negative affinity energy with Nb, Ti and Al on Nb alloy surface, to generate the Nb2O5, TiO2 and Al2O3 mixed oxide film which has protective effect on Nb alloy.
An electronic theoretical study of the high-temperature oxidation behavior of Fe-Cr-Al alloy
Authors: Liu Gui-Li  ,   沈阳工业大学建筑工程学院，沈阳  110023
Published: December 2020

The formation mechanism of the oxide film on Fe-Cr-Al alloy, the effects of sulfur on the adhesion of the oxide film, and the role of RE element Y on the improvement of the oxide film adhesion were systematically studied on an electronic level, so that the physical nature of oxidation of the alloy was revealed. The results show that Al atom (compared with Cr or Fe atom ) has the lowest environment-sensitive embedding energy when O atoms are present on the alloy surface, thus leading to an outward diffusion of Al atoms from the interior of the alloy, and hence to the segregation of Al atoms on the alloy surface. Oxygen atoms are easy to combine with Al atoms to form Al2O3 oxide films on the alloy surface due to its high affinity with Al atoms. The impurity S has a lower environment-sensitive embedding energy on the interface between the Al2O3 oxide film and the alloy matrix than within the alloy matrix, suggesting that S can diffuse (segregate) to the interface. S atoms segregated on the interface weakens the cohesion of Al2O3 oxide film with the alloy matrix. Y is easy to combine with sulfur to form a stable sulfide within the interior of the alloy matrix, which inhibits the diffusion of sulfur to the Al2O3 oxide film /matrix interface. Y added into the alloy can thus markedly increase the adhesion of the oxide film with the alloy matrix, and significantly improve the high-temperature oxidation resistance of the alloy.
First-principles study of the electronic structure and optical properties of UO2
Authors: Chen Qiu-Yun  , Lai Xin-Chun  , Wang Xiao-Ying  , Zhang Yong-Bin  , Tan Shi-Yong  ,   National Key Laboratory for Surface Physics and Chemistry, Mianyang 621907, China
Published: December 2020

The electronic structure and optical properties of UO2 are investigated using the first principles density functional method within local-spin density approximation (LSDA), and the Coulomb correlation energy (U) is used to calculate the lattice constant, energy band structure and optical properties of UO2. The calculated lattice constant is 5.40 ?, and the band gap is 1.82 eV. We succeeded in predicting the correct anti-ferromagnetic insulating ground state of uranium dioxide. By analyzing the energy structure and dielectric function, we find that in uranium ions the 6d band splits into two sub-bands, which is in agreement with experimental results.
Structural stability and field emission properties of carbon nanotubes doped by a boron atom and adsorbed with several H2O molecules
Authors: Wang Yi-Jun  , Wang Liu-Ding  , Yang Min  , Liu Guang-Qing  , Yan Cheng  ,   (1)North Night Vision Technology Co., Ltd, Xi'an 710065, China; (2)School of Science, Northwestern Polytechnical University, Xi'an 710129 , China; (3)School of Science, Northwestern Polytechnical University, Xi'an 710129 , China; School of Physics and Electronic Engineering, Xianyang Normal University, Xianyang 712000, China
Published: December 2020

The structural stability and electronic field emission properties of carbon nanotubes doped with a boron atom in different layers and adsorbed with several H2O molecules, as well as located in the applied electric field, are analyzed by means of the density functional theory based on the first-principles. The results show that the structure of B3CNT+5H2O doped by a boron atom in the third layer and adsorbed with five H2O molecules is most stable, the distribution of Mulliken charge on the tube cap is most dense. In particular, compared with the B3CNT doped by a boron atom and CNT+5H2O adsorbed with five H2O molecules solely, the density of states at the Fermi energy level for B3CNT+5H2O increases by 20% and 33% respectively. Therefore, the latter has the best field emission property.
High temperature oxidation mechanism of Nb-Al alloys
Authors: Liu Gui-Li  ,   沈阳工业大学建筑工程学院，沈阳  110023
Published: December 2020

The atomic cluster model of the interface between aluminum oxide film and the niobium matrix has been set up with our self-programmed software. By using recursion method, the atom embedding energy, the atomic binding energy and other electronic parameters have been calculated. The high temperature oxidation mechanism of niobium alloys is analysis from the electron levels. Our study shows that， aluminum segregates on the alloy surface through the grain boundary diffusion and combines with oxygen to form dense Al2O3 oxide film which blocks oxygen to diffuse into the niobium matrix. Grain boundary and rare earth elements can increase binding energy between the oxide film and the matrix and increase the bonding strength of the interface to enhance the adhesion between the oxide film and the niobium matrix. Thus, by adding rare earth elements in the alloy or refining the alloy grains, the performance of high temperature oxidation resistance of niobium alloys can be improved.
Numerical simulation of charge packet behavior in low-density polyethylene based on Gunn effect-like model
Authors: Xia Jun-Feng  , Zhang Ye-Wen  , Zheng Fei-Hu  , Lei Qing-Quan  ,   (1)哈尔滨理工大学，哈尔滨  150080; (2)同济大学波尔固体物理研究所，上海  200092
Published: December 2020

Packet-like space charge behavior usually induces the electric field distortion and strongly affects the electrical performance of low-density polyethylene. In this paper, we analyze the influence of charge injection, carriers migration and interaction between the free charge and trap in polyethylene on packet-like space charge behavior and introduce the mechanism of Gunn effect to describe the generating process of space charge packet. Based on this, we simulated two kinds of packet-like space charge behaviors with different variation trends and in different applied fields reported by different research groups. The simulated space charge packet shows very good fitting with the experiment data in both packet amplitude and migration velocity. The simulation results also indicate that the injection conditions and trap level depth play an important role in the diversity of packet-like space charge behavior.
Micro-structure of growth solid-liquid boundary layer of KTa1-xNbxO3 crystal
Authors: Zhang Qing-Li  , Yin Shao-Tang  , You Jing-Lin  , Wang Yuan-Yuan  , Zhou Wen-Ping  , Wan Song-Ming  ,   (1)Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China; (2)Shanghai Enhanced Laboratory of Ferro-metallurgy, Shanghai University, Shanghai 200072, China
Published: December 2020

Raman spectra of KTa1－xNbxO3(KTN) single crystal,its melt, and the solid-liquid boundary layer in the growing process at different temperatures were measured in-situ. The structure transformation in KTN crystal growth process was investigated. The results showed that the [Ta/NbO3] entities came into solid-liquid boundary layer from KTN melt, and they were transformed to [Ta/NbO6] octahedron entities. And the structure of [Ta/NbO6] octahedron entity was just like that of KTN single cell. Regarding [Ta/NbO6] octahedron as growth units, the growth habit of KTN crystal in which the (100), (1-00), (010) and (01-0) faces are easily revealed was discussed. The thickness of the growth solid-liquid boundary layer of KTN crystal was about 80—90 μm.
Defects in proton-irradiated Zn-doped GaSb studied by positron annihilation and photoluminescence
Authors: Zhou Kai  , Li Hui  , Wang Zhu  ,   Department of Physics, Wuhan University, Wuhan 430072,China
Published: December 2020

Positron annihilation spectroscopy(PAS)and photoluminescence (PL) have been adopted to study defects in proton-irradiatied Zn-doped GaSb. A monovacancy VGa having a lifetime of 293 ps was observed in the non-irradiated sampls and a divacancy VGaVSb with a tifetime of 333 ps was identified in the proton-irradiated samples when the fluence reached 3×1015 cm-2.The PL results reveal that the acceptor Zn is not related with proton irradiation-induced defects, which act as non-radiation recombination centers in the samples. The acceptor level of Zn in GaSb has been calculated from the PL spectra. After proton irradiation, interstitial monatomic hydrogen in a negative charge state (Hi-) in GaSb has been found, which acts as a shallow-acceptor. Annealing experiments indicated that the as-grown and proton-irradiated samples have different annealing behaviors, the reason for which was attributed to the existence of monatomic hydrogen interstitials in the proton-irradiated samples.
Measurement of volatile organic compounds in the smog chamber using a Chernin multipass cell
Authors: Yang Xi-Bin  , Zhao Wei-Xiong  , Tao Ling  , Gao Xiao-Ming  , Zhang Wei-Jun  ,   Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

A newly developed Chernin cell was combined with the smog chamber for the volatile organic compounds(VOCs) detection using ultraviolet-visible spectroscopy. The principle, design and application of the Chernin cell were introduced in this paper. The Chernin cell has good vibrostability and is easily adjusted. The optical pathlength can be adjusted from 3 to 330 m. The system precision, stability and reliability were proved with NO2 detection. With 37 m absorption pathlength, the NO2 detection limit was 19.1 μg/m3. For the application of this system for VOCs detection, the concentrations of o, m, p-xylene and toluene in the smog chamber were measured with 36 m absorption pathlength, and the corresponding detection limits were 42.6, 15.1, 9.9 and 19.7 μg/m3 respectively.