bluuebunny/crossref_metadata_2025 huggingface dataset:
Stress models relevant to Raman spectrum in uniaxial/biaxial strained Si
Authors: Wang Cheng  , Wang Guan-Yu  , Zhang He-Ming  , Song Jian-Jun  , Yang Chen-Dong  , Mao Yi-Fei  , Li Yong-Mao  , Hu Hui-Yong  , Xuan Rong-Xi  ,   Key Lab of Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi’an 710071, China
Published: December 2020

Performance enhancement of strained Si material originates from the stress on it, which can be measured by Raman spectroscopy. A study of the theoretical model of strain-induced Raman spectrum frequency shift in strained Si material is of profound theoretical and practical significance. The Raman frequency shift of strained Si is significantly correlated with the stress intensity, the stress type and the crystal plane. However, the corresponding reports republished are lacking in integrality and systematization in the process of modeling. In this paper, according to the theory of Raman spectroscopy, based on Secular equation and Raman selection rules, quantitative relationships between strain tensor and Raman frequency shift for uniaxial and biaxial strained Si grown on (001), (101), and (111) SiGe substrates are achieved. On this basis, theoretical models of mechanical stress and Raman spectrum for uniaxial and biaxial strained Si materials grown on (001), (101), and (111) SiGe substrates are obtained using Hooke's law, respectively. The procedure for setling up these models is elaborate and systematic and the results obtained are comprehensive and quantificational, which can provide an important reference for the stress analysis in strained Si material.
Study on the local field enhancement of elliptical gold nanotube
Authors: Cong Chao  , Wu Da-Jian  , Liu Xiao-Jun  ,   School of Physics, Nanjing University, Nanjing 210093, China
Published: December 2020

The local electric field components of the elliptical gold nanotube are calculated based on the finite difference time domain (FDTD) method. It is find that when the wavelength of the incident light is just at a resonant wavelength, the local field enhancement of the gold nanotube reaches a maximum. The increase of the semiminor axis of the ellipse makes the distribution of the local field change from a distribution that is high in both sides and low in the middle part of the nanotube into a distribution that is uniform around the tube. With the increase of the angle between the incident polarization and the semimajor axis, the local electric field components increase rapidly. The increases of the dielectric constants for both the core and the embedding medium cause the local field around the nanotube to decrease.
Molecular dynamics simulation of energy exchanges between single hydrogen and graphite(001)
Authors: Zhang Zhi-Hai  , Sun Ji-Zhong  , Liu Sheng-Guang  , Wang De-Zhen  ,   School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China
Published: December 2020

Molecular dynamics simulation is applied to the investigation of energy exchanges between single hydrogen and graphite (001). In addition to energy transfer efficiency, in this paper we analyse various kinds of possible processes, which are the absorption on the upside graphite surface, reflection, absorption on the downside graphite surface and penetration, during the course of a hydrogen atom bombarding the crystalline graphite containing four graphene sheets. The simulation results show that the interlayer interaction has a big influence on the reflection, especially when the incident energy is larger than 20.0 eV. The reflection coefficient increases evidently compared with that in single graphene sheet case. If the incident hydrogen has a kinetic energy more than 25.0 eV, it can penetrate the four- sheet graphite at some striking locations. When the incident energy is larger than 28.0 eV, the energy transferring to the first graphene sheet is more than to the second graphene sheet. These results will be helpful for understanding the chemical erosion of carbon based materials and the tritium retention occurring in fusion devices.
Meshless local Petrov-Galerkin method with complex variables for elasticity
Authors: Yang Xiu-Li  , Dai Bao-Dong  , Li Zhen-Feng  ,   Department of Engineering Mechanics, Taiyuan University of Science and Technology, Taiyuan 030024, China;,   College of Transportation and Logistics, Taiyuan University of Science and Technology, Taiyuan 030024, China
Published: December 2020

In this paper, the shape functions are obtained by the moving least-squares method with complex variable (MLSCV). The advantages of MLSCV are that the approximation function of a two-dimensional (2D) problem is formed with one-dimensional (1D) basis function, and the number of the undetermined coefficients is reduced, so it effectively improves the computational efficiency. Based on the MLSCV and meshless local Petrov-Galerkin method, the essential boundary conditions are imposed by the penalty method and the corresponding discrete equations are derived, then a meshless local Petrov-Galerkin method with complex variables is presented for 2D elasticity problems. Some examples given in this paper demonstrate the effictiveness of the present method.
Discussion on applying tortoise coordinates to a dynamical Vaidya black hole
Authors: Lu Peng-Ju  , Zhao Zheng  , Liu Wen-Biao  ,   Department of Physics, Beijing Normal University, Beijing 100875, China
Published: December 2020

Applying generalized tortoise coordinates with undetermined parameters to a dynamical Vaidya black hole, we find the interesting condition for reducing the wave function into its standard form without divergence. It is shown that the Damour-Ruffini method with tortoise coordinate can be applied only to the event horizon rather than the apparent horizon in a dynamical space time.
Fabrication and fast photoresponse properties of ZnO nanowires photodetectors
Authors: Song Zhi-Ming  , Zhao Dong-Xu  , Guo Zhen  , Li Bin-Hui  , Zhang Zhen-Zhong  , Shen De-Zhen  ,   Key Laboratory of Excited State Processes, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences,Changchun 130033, China;,   Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

One-dimensional ZnO nanostructure is especially attractive because of its unique properties such as high surface-to-volume ratio and a large exciton binding energy, but how to put it into a device is still a challenge. In this article, we show that a novel lateral metal-semiconductor-metal ultraviolet detector composed of ZnO nanowires is fabricated on glass substrate by a single-step hydrothermal approach. The fabricated photodetector demonstrates that the response to UV illumination in air is fast, the rise time is about 4 s, and the fall time is about 5 s, which could be attributed to the fact that the adsorption and the desorption of water molecules in the air onto oxygen vacancy of the nanowire significantly influence the photoresponse.
Experimental research of target uniform illumination using smoothing by spectral dispersion and continuous phase plate
Authors: Zhang Rui  , Li Ping  , Su Jing-Qin  , Wang Jian-Jun  , Li Hai  , Geng Yuan-Chao  , Liang Yue  , Zhao Run-Chang  , Dong Jun  , Lu Zong-Gui  , Zhou Li-Dan  , Liu Lan-Qin  , Lin Hong-Huan  , Xu Dang-Peng  , Deng Ying  , Zhu Na  , Jing Feng  , Sui Zhan  , Zhang Xiao-Min  ,   Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

To improve laser irradiation uniformity, experimental research on smoothing by spectral dispersion (SSD) and continuous phase plate (CPP) is carried out on the technical integration line (TIL). A bulk phase modulator with 9.2 GHz modulation frequency is adopted. The output spectrum of the phase modulator is stable and the residual amplitude modulation is quite small. The experimental results indicate that when the number of color cycles (Nc) is adopted to be 1, imposing of SSD in this divergence does not lead to pinhole closure in the spatial filters of the preamplifier and main amplifier. The contrast of the focal spot with 95% energy included with SSD and CPP drops to 0.47 compared with 1.71 without SSD and CPP. When the pulse width of the third harmonic wave is 1 ns and its energy is 1115 J, no damage is found in CPP and other final optics. The experiment solves some key techniques by using SSD and CPP on high-power laser facilities, and provides sound basis for the upcoming physics experiment.
Fabrication of mid-infrared hollow-core Bragg fiber and it application in gas sensing
Authors: Shi Li-Chao  , Zhang Wei  , Jin Jie  , Huang Yi-Dong  , Peng Jiang-De  ,   Department of Electronic Engineering, Tsinghua University, Beijing 100084, China
Published: December 2020

In its application of gas sensing, the transmission band of the hollow-core Bragg fiber should match the main absorption peak of the target gas. In this paper, we introduce the design method of the hollow-core Bragg fiber transmission band and develop a fabrication process supporting its transmission band control. Fiber samples with fundamental transmission bands at 10.6 m and 3.3 m are fabricated, whose transmission losses are 5.9 dB/m and 8.8 dB/m, respectively, measured by the cut-back method. Utilizing the fiber sample with a transmission band of 3.3 m, the injection and the expulsion of CH4/N2 gas are realized and observed by the change of fiber transmission spectrum. The detection limit of the experimental system is measured to be 26 ppm for CH4 by exponential dilution method, demonstrating the feasibility of hollow-core Bragg fiber in its application of gas sensing.
Fiber-optical grating sensing based on flextensional member
Authors: Zhang Jing-Hua  , Qiao Xue-Guang  , Feng Zhong-Yao  , Hu Man-Li  , Gao Hong  , Zhou Rui  , Yang Yang  ,   Department of Physics, Northwest University, Xi'an 710069, China
Published: December 2020

Based on the structure health monitoring of civil engineering structure such as bridges, dams, high-rise building, the fiber Bragg grating sensor is used to achieve the real-time monitoring and diagnosis of structural performance, in order to discovery the damage and to evaluate the safety of structure. Fiber-optical grating sensing based on flextensional member is proposed. The measuring of pressure, strain and acceleration can be realized. The strain of camber beam belly is analysed theoretically and verified experimentally. The strain of the camber beam belly is proportional to the pressure and acceleration in the vertical direction. Its biggest advantage is small size under the same sensitivity. The transverse dimensions is limited in well and the longitudinal acceleration needs to be measured, so beam based sensor structure are not likely to be used. Under the condition of measuring longitudinal acceleration sensor structure, beam pumping are not likely to be used. This new type of flextensional member elastic sensitive structure can serve as elastic element for the design of fiber bragg grating strain, weighing and pressure, and acceleration sensor.
Preliminary research on large-size optical polymer image transmitting fiber faceplate
Authors: Wang Jin-Meng  , Kong De-Peng  , Wang Li-Li  ,   State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics, Chinese Academy of Science,Xi'an 710119, China;,   Graduate University of Chinese Academy of Science, Beijing 100049, China
Published: December 2020

Preliminary research on large-size optical polymer image transmitting fiber faceplate is carried out by the stacking-heated fusing method with commercial low-loss optical PMMA fiber which is arranged in a home-made mold by hexagonal packing. A fiber faceplate sample with 2 mm in thickness, 500 μm in pixel diameter and 59052 in pixel number, is manufactured by cutting and stitching the preforms The fiber faceplate sample has a good image transmission capacity. The resulting large-size optical polymer fiber mosaic faceplate screen has the role that cannot be replaced for large-screen LCD protection and elimination of display seam.
All-fiber 177.6 W supercontinuum source
Authors: Song Rui  , Hou Jing  , Chen Sheng-Ping  , Wang Yan-Bin  , Lu Qi-Sheng  ,   College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073, China
Published: December 2020

Supercontinuum has wide and important applications in a range of fields, so it is one of the hot research spots in recent years. In this paper the mechanism and the latest achievements in high power supercontinuum generation under continuous wave laser pump and pulsed laser pump regimes during the past several years are reviewed. The challenges and the problems that need to overcome in scaling the average output power of supercontinuum generation are analyzed. An all-fiber supercontinuum source constructed at the national university of defense technology is demonstrated with 177.6 W average output power which overcomes the problems of low splicing loss, facet damage of the output fiber, the heat treatment and the effective control of the nonlinear effects through the optimization of the whole system. To the best of the author's knowledge, the 177.6 W average output power is the highest value in ever reported ones.
Researches on the interference structure in low-frequency acoustic field based on space-time filter theory
Authors: Yu Yun  , Hui Jun-Ying  , Chen Yang  , Hui Juan  , Yin Jing-Wei  ,   Naral Academy of Armament, Beijing 100161, China;,   Science and Technology on Underwater Acoustic Laboratory, Harbin Engineering University, Harbin 150001, China
Published: December 2020

Compared with the waveguide invariant, the interference structures in low-frequency acoustic field are more comprehensively described by four system functions: coherent function, power response function, spread function and dual-frequency function, from space-time filter theory. A stable interference structure in the low-frequency acoustic field is testified based on theoretical analysis, simulation and sea trial data processing. When the target moves in a uniform rectilinear motion from far to near then from near to far, the interference structure of coherent function (LOFARgram) appears to be a family of quasi hyperbolas; the interference structure obtained by power response function represents the group delay difference and the dispersive characteristic of the normal mode; and the phase slowness difference can be exhibited by dual-frequency function. Each system function owns special characteristics, which can give prominence to certain features of the interference structure.
Numerical simulation of droplet impact on liquid with smoothed particle hydrodynamics method
Authors: Ma Li-Qiang  , Chang Jian-Zhong  , Liu Han-Tao  , Liu Mou-Bin  ,   School of Mechatronice Engineering, North University of China, Taiyuan 030051, China;,   Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

In this paper, we present a modified smoothed particle hydrodynamics (SPH) method. The kernel approximation and the particle approximation are corrected to ensure that polynomial functions are exactly interpolated up to a given degree. Riemann solver is adopted to solve equations of fluid motion. A surface tension calculation program is used for considering the surface tension effects in droplets splashing. The process of droplet impact on liquid surface is numerically simulated by the modified smoothed particle hydrodynamics method. The numerical results clearly demonstrate that the modified SPH method can effectively describe the dynamics of droplet splashing and the variation of the free surface, and that the accuracy of the results can be stable.
Molecular dynamics simulation of energetic hydrogen isotopes bombarding the crystalline graphite(001)
Authors: Sun Ji-Zhong  , Zhang Zhi-Hai  , Liu Sheng-Guang  , Wang De-Zhen  ,   School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China
Published: December 2020

Molecular dynamics simulation is applied to the investigation of the isotopic effects during a hydrogen isotope atom bombarding the crystalline graphite containing four graphene sheets. Both Brenner's reactive empirical bond order potential and Ito's interlayer intermolecular potential are adopted to represent `àBAB" stacking of graphite. The simulation results reveal that the mass of the incident species has a big influence on the absorption on and the reflection from the upside graphite surface, the peaks of which shift toward higher end side of incident energy as the mass increases. The absorption coefficient of the incident tritium is large, compared with that of the incident either hydrogen or deuterium. To penetrate the four- sheet graphite at some striking locations, deuterium and tritium need more kinetic energy. It is found that both the mass and the incident energy of the incident species affect the energy transfer to background substrate. These results would be important for understanding the tritium retention occurring in fusion devices.
The magnetocaloric effect of the Gd-based amorphous composite with Gd nanocrystals
Authors: Wang Yong-Tian  , Liu Zong-De  , Yi Jun  , Xue Zhi-Yong  ,   Key Laboratory of Condition Monitoring and Control for Power Plant Equipment of Ministry of Education, North China Electric Power University, Beijing 102206, China;,   The Suzhou Research Institute of North China Electric Power University, Suzhou 215123, China;,   Institute of Physics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

The Gd-based amorphous/nanocrystal composite is prepared by controlling the cooling rate and the element ratio. The X-ray diffraction, differential scanning calorimeter and atomic force microscope/magnetic force microscope are used to confirm the composite microstructures from different perspectives. The magnetic test shows the great enhancement of magnetocaloric effect in the metallic glassy composite. The large magnetic refrigerant capacity (RC) up to 103 J. kg-1 is more than double the RC values of the Gd-based bulk metallic glass and pure Gd. The full width at half maximum of the magnetic entropy change (Sm) peak almost spreads over the whole low-temperature range, which is five times wider than that of the pure Gd. The maximum Sm approaches a nearly constant value in a wide temperature span (over 80 K). The super paramagnetic nanoclusters of the composite increase the magnetic refrigerant capacity greatly. In combination with the low magnetic hysteresis and large resistance, the metallic glass composite may be a potential candidate for the ideal Ericsson-cycle magnetic refrigeration.
Spectroscopic ellipsometry study of the Ag2O film deposited by radio-frequency reactive magnetron sputtering
Authors: Ma Jiao-Min  , Liang Yan  , Gao Xiao-Yong  , Chen Chao  , Zhao Meng-Ke  , Lu Jing-Xiao  ,   Key Laboratory of Materials Physics of Ministry of Education, School of Physics and Engineering, Zhengzhou University, Zhengzhou 450052, China;,   College of Information Science and Engineering, Henan University of Technology, Zhengzhou 450001, China
Published: December 2020

Ag2O film has a potential application in high-density optical and magneto-optical disks. In this paper, a series of Ag2O films is deposited by radio-frequency reactive magnetron sputtering at different substrate temperatures, a deposition pressure of 0.2 Pa and an oxygen flow ratio of 2:3. The spectroscopic ellipsometry spectra of the films are fitted by using a general oscillator model (including one Tauc-Lorentz oscillator and two Lorentz oscillators). In an energy range between 1.5 eV and 3.5 eV, the refractive index and extinctive coefficient of the film are in ranges between 2.2 and 2.7, and between 0.3 and 0.9, respectively. The film indicates a clear abnormal dispersion in an energy range of 3.5 eV and 4.5 eV, meaning that the plasma oscillator frequency of the film is in this energy range . A redshift of the absorption edge of the film occurs with substrate temperature increasing, which can be attributed to the increased lattice strain. The optical constants of the film clearly show the dielectric properties.
Study on fabrication and optical properties of Ge-Sb-Se thin films
Authors: Zhang Wei  , Chen Yu  , Fu Jing  , Chen Fei-Fei  , Shen Xiang  , Dai Shi-Xun  , Lin Chang-Gui  , Xu Tie-Feng  ,   College of Information Science and Engineering, Ningbo University, Ningbo 315211, China;,   State Key Laboratory of Transient Optics and Photonics, Xi'an Institute of Optics and Precision Mechanics of CAS, Xi'an 710119, China
Published: December 2020

Several methods of fabricating chalcogenide thin films are introduced. In this paper, thermal evaporation and radio frequency methods are used to fabricate Ge-Sb-Se thin films. The thicknesses and roughnesses of the films are measured by surface profile-meter. The film growth rates are calculated. The component difference between film and target material is tested by X-ray photoelectron spectroscopy. The third-order optical nonlinearity and the transmission spectra of films fabricated by thermal evaporation are investigated using femto-second Z-scan method and spectrophotometer, to obtain the values of nonlinear refraction, nonlinear absorption and thickness of films. The results show that the films fabricated by thermal evaporation have excellent physical structures and optical properties, and possess promising potential applications in integrated optical devices.
Study on the piezoresistive effect of the multiwalled carbon nanotube films
Authors: Wang Yong-Tian  , Liu Zong-De  , Yi Jun  , Xue Zhi-Yong  ,   Key Laboratory of Condition Monitoring and Control for Power Plant Equipment of Ministry of Education, North China Electric Power University, Beijing 102206, China;,   The Suzhou Research Institute of North China Electric Power University, Suzhou 215123, China;,   Institute of Physics, Chinese Academy of Sciences, Beijing 100080, China
Published: December 2020

In this paper, the piezoresistive effect of the multiwalled carbon nanotube (MWCNT) film is studied. Carbon nanotubes are synthesized by hot filament chemical vapor deposition. The piezoresistive effect in the MWCNT film is studied by a three-point bending test. The gauge factor of the MWCNT film under 500 microstrain is found to be at most 120 at room temperature, exceeding that of polycrystalline silicon (30) at 35℃. The origin of the piezoresistivity in MWCNT film is also discussed.
Study on the size-dependent magnetic properties of multiferroic BiFeO3 nanoparticles
Authors: Wei Jie  , Chen Yan-Jun  , Xu Zhuo  ,   Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

The pure phase BiFeO3 nanoparticles with different sizes are prepared by an ethylenediaminetetraacetic acid complexing sol-gel process. The structure, the morphology and the magnetic properties of BiFeO3 nanoparticles are characterized by X-ray diffractometry, scanning electron microscopy, superconducting quantum interference device magnetometer and Mossbauer spectra analysis. The results show that the BiFeO3 nanoparticle possesses an weak ferromagnetism at room temperature with a strongly size-dependent property. It reflects that the weak ferromagnetism present in the BiFeO3 nanoparticle should be attributed to the grain size-confinement effect, rather than the existence of the magnetic impurity or Fe2+.
Intercalation assembly, characterization and luminescent properties of novel composite material, Tb(III) complex-montmorillonite
Authors: Nong Lan-Ping  , Jiang Wei  ,   College of Chemistry and Life Sciences, Guangdong University of Petrochemical Technology, Maoming 525000, China
Published: December 2020

Tetrapodal ligand L (2, 2, 2', 2'-tetra[N-benzyl-N-phenyl (acetamide)-2-oxymethyl] n-butyl ether) and complex [TbL] (ClO4)3 are synthesized. The complex ion with tetrapodal ligand L, [TbL]3+ is intercalated into the interlayer space of montmorillonite (MMT) by ion exchanging. The obtained luminescent supramolecular composite material, [TbL]3+-MMT is characterized by elemental analysis, X-ray diffraction, Fourier transform infrared spectroscopy, and ultraviolet-visible spectroseopy. At the same time, the luminescent properties of the material are also studied. The results show that the intercalated material with regular layered structure and the interlayer spacing (d001) approximate to the diameter of the complex ion arranged in the interlayer space of the MMT in the formation of a monolayer emit characteristic green emission of Tb3+ strongly under the excitation of ultraviolet light. It is also found that the relative luminescence intensity, the luminescence monochromatic index and the light stability of the intercalated material are distinctly improved after the [TbL]3+ has been intercalated into the MMT. And the excitation wavelength of the complex is modulated till the red shift occurs in the composite material.
Two-step switching method improved turn-on characteristic in reversely switching dynistor
Authors: Hong Wu  , Liang Lin  , Yu Yue-Hui  ,   Department of Electronic Science and Technology, Huazhong University of Science and Technology, Wuhan 430074, China
Published: December 2020

Due to short of pre-charge, a high power semiconductor switch reversely switching dynistor (RSD) suffers from switching-on locally. Based on the direct pre-charge circuit, a new two-step switching method is introduced. The conditions for the normal turn-on of RSD are analyzed and the model of RSD in a cell structure is built. The model simulation shows that the RSD has better performances: shorter width pre-charge current, and reduced recombination of plasma during the pre-charge. Two-step switching experiment indicates that a proper preliminary turn-on current is important for uniformly switching-on the RSD, and the reverse pre-charge current works mainly for switching preliminary forward current. Simulation and experimental results both show that two-step switching increases RSD uniform turn-on characteristic compared with the direct pre-charge circuit, because the stored charges inside are increased obviously by two-step switching.
Network synchronization of spatiotemporal chaos and parameter identification in complex Ginzburg-Landau equation
Authors: Lü Ling  , Li Gang  , Xu Wen  , Lü Na  , Fan Xin  ,   College of Physics and Electronic Technology, Liaoning Normal University, Dalian 116029, China
Published: December 2020

The synchronization and the parameter identification of a complex network are studied, in which nodes are uncertain spatiotemporal chaos systems. The recognition laws of parameters are designed, and the unknown parameters in spatiotemporal chaos systems at the nodes of the complex network are identified. An appropriate Lyapunov function is constructed, and the conditions of realizing global synchronization of the network are discussed and confirmed based on the stability theory. The uncertain complex Ginzburg-Landau equation having spatiotemporal chaos behavior is taken as nodes in the complex network, and simulation results of spatiotemporal chaos synchronization and parameter identification show the effectiveness of the method.
Charge transport properties of triazole or cyclopentene triphenylene derivative discogen molecules
Authors: Yang Qiong-Fen  , Nie Han  , Chen Zi-Ran  , Li Quan  , Zhao Ke-Qing  ,   Key Laboratory of Advanced Functional Materials, Sichuan Province Higher Education System; College of Chemistry and Material Science, Sichuan Normal University, Chengdu 610066, China;,   Department of Architecture and Environment Engineering, Sichuan Vocational and Technical College, Suining 629000, China
Published: December 2020

Charge transport is one of the most important properties in organic electronic materials. On the basis of Marcus theory, the charge-transfer is the course of electron-electron interaction and electron-phonon interaction, and the greater the electron-phonon interaction coupling strength, the greater the reorganization energy is, which is not conducive to the charge transport. The greater the electron-electron interaction coupling strength, the greater the charge transfer matrix element is, which is beneficial to the charge transport. Charge transport properties of triphenylene derivative discogens molecules with a 1, 2, 3-triazole, 1, 2, 4-triazole or 1, 2, 3-trinitrogen-2, 3- cyclopenten side chain are investigated computationally. The results show that the electronic mobility and the hole mobility of 1, 2, 3-triazole triphenylene derivative are nearly equal, and the rate constant is 21012s-1. The hole transfer rate constant of the 1, 2, 4-triazole triphenylene derivative molecules is 51012s-1, which is ten times higer than the electronic transfer rate constant. Triphenylene containing 4, 5-dihydro-1, 2, 3-triazole has better electronic mobility but smaller hole mobility than triphenylene discogens containing 1, 2, 3-triazole or 1, 2, 4-triazole, and the electronic mobility is 31012s-1, which is equal to ten times of the hole mobility. The hole transfer or electron transfer rate of the target molecules is affected mainly by the transfer matrix element, in other words, electron-electron interaction coupling strength determines the magnitude of mobility rate variation.
Au L X-ray and Xe M X-ray emission following 129Xe30+ ion impact on Au surface
Authors: Li Yao-Zong  , Zhang Xiao-An  , Liang Chang-Hui  , Zhao Yong-Tao  , Cheng Rui  , Zhou Xian-Ming  , Wang Xing  , Lei Yu  , Sun Yuan-Bo  , Xu Ge  ,   Xianyang Normal University and Institute of Modern Physics, Chinese Academy of Sciences Jointly Established: Laboratory of Ion Beam and Photophysics, Xianyang 712000, China;,   Institute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China
Published: December 2020

The X-ray emission due to the impact of 129Xe30+ ions of 1.07.0 MeV kinetic energies on Au surface is detected. The experimental result shows that when ion kinetic energy is larger the incident ion excits not only Au M X-ray but also Xe L X-ray. The X-ray yield and the ion kinetic energy have a strong correlation with each other. The relationship between the X-ray yield with ion kinetic energy is analyzed.
The effect of thermal excitation on the interfacial friction
Authors: Wang Ya-Zhen  , Huang Ping  , Gong Zhong-Liang  ,   School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China;,   Guangdong College of Industry and Commerce, Guangzhou 510510, China
Published: December 2020

In the present paper, by analyzing the microscopic mechanism of forced vibration of interfacial atoms, it is shown that the atomic vibration is actually the superposition of the self-excited vibration and the forced vibration. The phonon excitation and annihilation due to the thermal vibration of the interfacial atoms in a non-equilibrium state are studied based on solid state physics and quantum mechanics. Then, the temperature effect on vibration energy levels of interfacial atoms are investigated, which shows that when the temperature is low, the probability for a quantum harmonic oscillator being in an excited state rises with temperature, causing the friction coefficient to rise with temperature. When the temperature is around 100 K, the probability for a harmonic oscillator being in the excited state reaches the peak, causing a peak friction coefficient at this point. When the temperature is above 100 K, the friction coefficient decreases with temperature. The trends of our analytical results and the experimental results of others are the same, indicating that the proposed theory and method are feasible.
Change of the off-center Laguerre-Gaussian vortex beam while propagation
Authors: Ding Pan-Feng  , Pu Ji-Xiong  ,   College of Information Science and Engineering, Huaqiao University, Xiamen 361021, China
Published: December 2020

The center of the Gaussian beam from solid laser cannot be completely aligned with the center of the spiral phase panel (SPP) while vortex beam is produced by SPP. The projecting beam from the SPP is actually an off-center vortex beam. Based on the diffraction theory, the propagation of off-center vortex beam is investigated. The analytic expressions of the electric field and the intensity are derived in the observation plane while the beam propagates a certain distance. It is shown that the intensity distribution of the beam changes asymmetricly. Besides the spreading, the core of the vortex beam moves while propagating, which is quite different from that of the ideal vortex beam. The magnitude of topological charge determines the spreading of the beam and has no influence on the motion of the vortex core. Furthermore, the sign of the topological charge determines the direction along which the core moves. If the topological charge is positive, the core will move in the tangential direction anticlockwise; if it is negative, the core will move in the tangential direction clockwise, from which the conclusion can provide a guidance for the beam aligning while the vortex beam is detected under the condition of long distance propagation.
A technique for tunable microwave/millimeter-wave generation based on a polarization-stable dual-wavelength polarization maintaining fiber Bragg grating laser
Authors: Pei Li  , Liu Guan-Hui  , Ning Ti-Gang  , Gao Song  , Li Jing  , Zhang Yi-Jun  ,   Institute of Lightwave Technology, Key Laboratory of All Optical Network and Advanced Telecommunication Network, Ministry of Education, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

A technique for tunable microwave/millimeter-wave generation based on a polarization-stable dual-wavelength polarization maintaining fiber Bragg grating (PMFBG) laser is proposed in which the frequency selecting of PMFBG is used to produce two polarization-stable lasing signals, the polarization scrambler is adopted to ensure the consistency of the orthogonal polarization's power, and then the beating frequency in high-speed photodetector is used to generate the microwave/millimeter-wave. Lateral strain loading on the PMFBG allows the frequency of the microwave/millimeter to be controlled. In the experiment, a scheme for tunable microwave/millimeter-wave generation based on a polarization-stable dual-wavelength PMFBG laser is produced, and the microwave signals of 20.407 GHz and 22.050 GHz are generated by different axial pulls loading on PMFBG. In the simulation, the millimeter-wave of 60 GHz is generated and transmission performance of the millimeter-wave in radio-over-fiber downlink is analyzed. The results show that the eye diagrams demodulated in the mobile station are excellent when the optical carrier which is modulated as the millimeter-wave sub-carrier transmits over 80 kilometers from center station to base station. The excellent performance of the system is verified.
Numerical study on power limit of single-mode fiber lasers
Authors: Zhu Jia-Jian  , Du Wen-Bo  , Zhou Pu  , Xu Xiao-Jun  , Liu Ze-Jin  ,   College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073, China
Published: December 2020

Study on power limit of fiber lasers and analysis of their physical limits are helpful to develop high power fiber lasers both in theory and in experiment. In this paper, power limits and physical limits of ytterbium-doped and thulium-doped fiber lasers are analyzed by considering several limits to the power scalability of fiber laser, including thermal effect, optical effect, nonlinear effect and the brightness of pump source. Then combining these considerations with the basic requirement for single-mode fiber, the power limits of single-mode ytterbium-doped and thulium-doped fiber lasers are calculated. It is found that using traditional 976 nm and 793 nm laser diodes, separately, as a pump source, based on current technical conditions, power limits of single-mode ytterbium-doped and thulium-doped fiber lasers are 4.2 kW and 7.8 kW, respectively. It is concluded that the fact that the actual power presented by the single-mode thulium-doped fiber laser is much lower than its limit power is due to the pump brightness limitation. Finally the principal approaches to enhancing power limits of single-mode fiber lasers are summarized, including reducing numerical aperture of fiber core and improving beam quality of few-mode fiber lasers.
Design of angular magnifier based on multiplexed volume holographic grating
Authors: Si Lei  , Zou Yong-Chao  , Tao Ru-Mao  , Jiang Peng-Zhi  , Ma Hao-Tong  , Zhou Pu  ,   College of Optoelectronics Science and Engineering, National University of Defense Technology, Changsha 410073, China
Published: December 2020

In order to design an angular magnifier based on multiplexed volume holographic grating, the physical model of multiplexed angular magnifier (MAM) is established. The design principle is summarized from two aspects, namely, uniform angular distribution and optimum diffraction efficiency. The effect of production error on MAM is studied. The effect of beam divergence on the performance of MAM is investigated. The results show that the desired angular distribution of MAM is achieved by controlling the spatial frequency and the tilted angle of the grating while the optimum diffraction efficiency is achieved by controlling the thickness and the amplitude of refractive index modulation of the gratings. The 10 VHGs can be multiplexed in the MAM at most. The raising of the grating tilted angle or the ratio between the wavelength of recording beam and working beam can weaken the effect of angular error of reference beam on the output angle distribution of MAM, and the reducing of the thickness is beneficial for reducing the effect of error of thickness and refractive index modulation on diffraction efficiency. When the beam divergence is greater than the angular half width, the optimum diffraction efficiency falls down to 50% or lower and the local minimum values disappear. The raising of the spatial frequency or thickness of the gratings can reduce the desired amplitude of refractive index modulation and multiplex more VHGs, but is not beneficial for achieving uniform diffraction efficiency distribution and weakening the effect of divergent beam.
Stimulated Raman scattering in liquid water in a low-frequency region
Authors: Li Zhan-Long  , Wang Yi-Ding  , Zhou Mi  , Men Zhi-Wei  , Sun Cheng-Lin  , Li Zuo-Wei  ,   State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, China;,   College of Electronic Science and Engineering, Key Laboratory on Integrated Optoelectronics, Jilin University, Changchun 130012, China;,   College of Physics, Jilin University, Changchun 130012, China
Published: December 2020

Stimulated Raman scattering is studied in liquid water using pulse laser at a wavelength of 532 nm. At a lower excitation energy, Stokes line and anti-Stokes line 3426 cm-1 can be observed in the forward Raman scattering. When excitation intensity is increased to 140 mJ, the low frequency 313 cm-1 line in the forward Raman scattering can be observed, and the 3389 cm-1 Stokes line and 3268 cm-1 Stokes line in the backward Raman scattering can also be observed. The experimental results demonstrate that the structure of water under the action of the intense excitation energy is similar to that of ice Ⅷ.
Dissipative particle dynamics simulation of flow around a mesoscopic sphere with different Reynolds numbers
Authors: Chang Jian-Zhong  , Liu Han-Tao  , Liu Mou-Bin  , Su Tie-Xiong  ,   School of Mechatronice Engineering of North University of China, Taiyuan 030051, China;,   Key Laboratory for Hydrodynamics and Ocean Engineering, of Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

Dissipative particle dynamics (DPD) is used to investigate the flow passing through a three-dimensional sphere within two parallel plates. The sphere and the plates are composed of frozen DPD particles which are in an equilibrium state. The fluid is driven by a dimensionless external force exerting on each fluid particle. The force on the sphere is computed from the total particles consistituting the sphere. After the flow is fully developed, the obtained results, including the force exerted on the sphere is computed, and then we can calculate the drag coefficient. The accuracy and the reliability are compared with classical results. The results show that the DPD method can predict drag coefficient accurately when Re is less than 100. However, when Re is bigger than 100, the results deviate from analytical values, which is due mainly to the fluid compressibility.
A latent defect degradation model of metal-oxide-semiconductor field effect transistor based on pre-irradiation1/f noise
Authors: Sun Peng  , Du Lei  , Chen Wen-Hao  , He Liang  ,   School of Technical Physics, Xidian University, Xi’an 710071, China
Published: December 2020

Based on metal-oxide-semiconductor field effect transistor (MOSFET) microscopic mechanism of radiation damage, a relation between radiation induced increase in number of oxide hole-traps and post-irradiation threshold voltage drift is proposed. Then, Based on MOSFET microscopic mechanism of1/f noise generation, a quantitative relationship between pre-irradiation1/f noise power spectral amplitude and post-irradiation threshold voltage drift is founded, which accords well with the experimental results. This relationship shows that pre-irradiation1/f noise power spectral amplitude is proportional to post-irradiation threshold voltage drift, which can reflect the degradation of latent defect in MOSFET. So, this modal is helpful to characterize the quantity and severity of latent defect in MOSFET by using1/f noise parameters.
Effect of surface potential barrier on electron escape probability of GaN photocathode
Authors: Yang Yong-Fu  , Fu Rong-Guo  , Zhang Yi-Jun  , Wang Xiao-Hui  , Zou Ji-Jun  ,   Institute of Electronic Engineering and Optoelectronic Technology, Nanjing University of Science and Technology, Nanjing 210094, China
Published: December 2020

Aiming to inverstigate the effect of surface potential barrier on electron escape probability of negative electron affinity GaN photocathode, the electron escape probability is calculated by using the Boltzmann distribution and the method of transfer matrix based on Airy function. It is found that barrier I is a key influencing factor of electron escape probability, while barrier II has a limited influence. The activation photocurrent curve of the transmission-mode GaN photocathode is measured by using our built activation and evaluation experimental system of NEA GaN photocathode. The obvious increase of electron escape probability can be achieved mainly by activating Cs only. The increase of electron escape probability is not large in Cs/O activation process with only Cs activated sufficiently. The theoretical calculations are in good agreement with the photocurrent curves from experimental test. The reason is that the contribution of activating only Cs to the reducing of vacuum level for obtaining NEA state is much larger than that of activating Cs/O.
Lightning discharge process based on short-baseline lightning VHF radiation source locating system
Authors: Cao Dong-Jie  , Qie Xiu-Shu  , Duan Shu  , Xuan Yue-Jian  , Wang Dong-Fang  ,   Key Laboratory of Atmosphere and Global Environment Observation (LAGEO), Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China;,   Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

A lightning VHF radiation source location system based on short-baseline technology is used to study the location of VHF radiation source in the lightning discharge process. The observation was conducted in Daxing'anling during summer of 2009. Positive cloud-to-ground (CG) lightning, negative CG lightning, and intra-cloud (IC) lightning are analyzed based on the locating results and simultaneous electric field changes. The long lasting preliminary breakdown process of CG flash appears as two-level structure of discharge channel in cloud. There are obvious recoil streamers during the final stage of preliminary breakdown process. The preliminary breakdown process propagates at a speed of about 104 m/s. The preliminary breakdown seems to be necessary for the initiation of stepped leader. The stepped leader starts from the source region of preliminary breakdown and propagates downwards. The stepped leader produces intensive VHF radiation. The propagation speed of stepped leader is about 105 m/s. The K process is caused by the streamers propagating backwards and forwards along the electrified channel. Characteristics of discharge processes before and after the return stroke of positive CG flash are different from those of negative CG flash obviously. During long continuing current after the return stroke of positive CG flash, discharges in cloud produce intensive VHF radiation. The energy spectrum of the VHF radiation produced by lightning is studied statistically. It is found that the energy spectrum of VHF radiation decreases quickly with the frequency at a rate of about f-2.9 between 125 and 200 MHz.
Experimental study on phase diversity wavefront sensing technology in piston error detection
Authors: Luo Qun  , Huang Lin-Hai  , Gu Nai-Ting  , Li Fei  , Rao Chang-Hui  ,   College of Opto-Electronics Science and Engineering, National University of Defense Technology, Changsha 410073, China;,   The Laboratory on Adaptive Optics, Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China;,   The Key Laboratory on Adaptive Optics, Chinese Academy of Sciences, Chengdu 610209, China
Published: December 2020

Phase diversity wavefront sensing technology has been implemented successfully in many domains because of its simple and compact optical configuration, lower environment requirement, better measurement accuracy, and so on. In this paper, the co-phasing technique for segment primary mirrors is studied by using the phase diversity wavefront sensing technology, and the corresponding experimental optical system is also set up. The experimental results show that the measurement accuracy of phase diversity wavefront sensing technology for piston error is better than /20 and that it can be used to detect the piston errors of segment mirrors.
A new time-domain estimation method for period of pulsars
Authors: Li Jian-Xun  , Ke Xi-Zheng  , Zhao Bao-Sheng  ,   Automation and Information Engineering School, Xi'an University of Technology, Xi'an 710048, China;,   State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics of CAS, Xi’an 710119, China
Published: December 2020

The estimation of pulsar period is important for pulsar searching, observation and timing. In this paper, the frequency-domain method which is popular in periodicity searches is analyzed, and further more, a novel method in time-domain is proposed to estimate the cyclo-period of pulsars based on the second-order cyclo-stationary model of the radiation signal. Firstly, the discrete-time observing signal is blocked by assumed period which is alterable. Then, the correlation estimations and their sample variances are computed each as a function of blocking operator index, where the largest peaks display a periodic pattern, from which the cyclo-period can be obtained. Using this method, the period of PSR J0437-4715 with single pulse is estimated well based on original signal, and the period of PSR B1821-24 with double pulses is also estimated based on the simulated signal. The same work is done for the observed data from ATNF EPN pulsar database. The simulation results and the experimental results for many pulsars show that compared with the classical Fourier-transform method, this algorithm is non-sensitive to the noise, and it is effective even though in the case of low signal-to-noise ratio. And it is of low computation complexity compared with the bispectrum coherence method. This method possesses higher popularization value in real-time observation and processing for weak pulsar signal, though it does not work well in dealing with noncontinuous observing data.