bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical simulation on the thermal deposition of optical surface irradiated by low energy ion beam in ion beam figuring
Authors: Yuan Zheng  , Dai Yi-Fan  , Xie Xu-Hui  , Zhou Lin  ,   School of Mechatronic Engineering and Automation, National University of Defense Technology, Changsha 410073, China
Published: December 2020

Based on energy deposition theory of Sigmund, the model of thickness of energy perturbation layer caused by low energy ion bombarding optical surface is built up. Beam current density on the optical surface is obtained by theory analysis, and the model of thermal deposition caused by low energy ion bombarding optical surface is built up. TRIM program is used to simulate the collision between low energy ions and atoms on the optical surface. And then, contributions to the thermal deposition and energy perturbation layer thickness from parameters such as ion energy, ion type and incidence angle are discussed. Finally, by taking the thermal quantity of deposited workpiece as a heat source in ANSYS, temperature field, thermal gradient field and stress field of the workpiece are obtained. The temperature and thermal gradient of the surface radiated by ion beam each present a Gaussian profile, and decrease along the radius from the center to the edge. The stress on the surface is a compressive stress within the radius of Half Maxim, and it is a tension-tension stress from the radius of Half Maxim to the edge.
Study on the lattice constants and energy band properties of Be and Ca doped wurtzite ZnO
Authors: Zheng Shu-Wen  , Fan Guang-Han  , Zhang Yong  , He Miao  , Li Shu-Ti  , Zhang Tao  ,   Institute of Opto-electronic Materials and Technology, South China Normal University, Guangzhou 510631, China
Published: December 2020

The lattice constants, energy band properties and formation energies of BexZn1-xO, CayZn1-yO and BexCayZn1-x-yO alloys of Be and Ca doped wurtzite ZnO alloys are calculated by the plan-wave pseudopotential method with GGA in density functional theory (DFT). The theoretical results show the lattice constants of BexZn1-xO alloy decrease with Be content increasing, which is contrary to the scenario of CayZn1-yO alloy. For the energy band properties of Be_xZn1-xO and CayZn1-yO alloys, the valence band maxima (VBM) are determined by O 2p states and the conduction band minima (CBM) is occupied by Zn 4s states, and their band gaps are broadened when Be or Ca content is increased. The lattice constant of Be0.125Ca0.125Zn0.75O alloy of Be and Ca co-doped ZnO is matched with that of ZnO and its energy bandgap is greater than that of ZnO, so Be0.125Ca0.125Zn0.75O /ZnO structure is suitable for high-quality ZnO based device. In addition, the stability of Be0.125Ca0.125Zn0.75O alloy is also analysed.
A Monte Carlo simulation study on growth mechanism of horizontal nanowires on crystal surface
Authors: Lan Mu  , Xiang Gang  , Gu Gang-Xu  , Zhang Xi  ,   Department of Physics and Key Laboratory for Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064, China
Published: December 2020

With the kinetic Monte Carlo simulation of smooth (001) surface of symmetry-broken simple cubic crystal in fluid with low supersatuaration rate, the mechanism of nanowire growth based on crystal nuclei on the surface is discovered and the morphology of nanowire is obtained. The dependences of nanowire morphology on thermal roughness in the longitudinal and latitudinal direction and growth time on the anisotropic surface of the crystal are further discussed. The relations of nanowire growth rate with thermal roughness, supersaturation rate, surface size and diffusion rate on the surface are then systematically studied.
Growth and spectral properties of 5 at%Yb:YNbO4 crystal
Authors: Zhou Peng-Yu  , Zhang Qing-Li  , Yang Hua-Jun  , Ning Kai-Jie  , Sun Dun-Lu  , Luo Jian-Qiao  , Yin Shao-Tang  ,   The Key Laboratory of Photonic Devices and Materials, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China;,   Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

5 at%Yb3+:YNbO4 crystal is grown by Czochralski(CZ) method. Its transmission and emission spectra are measured. The absorption peaks are located at 933, 955, 974 and 1003 nm with their corresponding absorbtion cross section values 0.7310-20, 1.8510-20, 0.8610-20 and 0.4410-20 cm2; and the FWHM of 955 nm absorbtion peak is 17 nm. Its emission band centered at 1020 nm with the FWHM is 41 nm, which is over three times that of Yb3+:YAG crystal. The emission cross section values of 955, 974, 1005, 1021 and 1030 nm peaks are calculated to be 0.6910-20, 0.8610-20, 1.8110-20, 1.1110-20 and 0.5710-20 cm2, respectively, and the biggest one is comparable to that of Yb3+:YAG crystal. The laser parameters of 5 at% Yb3+:YNbO4 crystal are evaluated and the results suggest that it is a potential all-solid-state pumped laser crystal in tunable and ultrafast lasers field.
Progress of the improved mobilities of organic field-effect transistors based on dielectric surface modification
Authors: Shi Wei-Wei  , Li-Wen  , Yi Ming-Dong  , Xie Ling-Hai  , Wei-Wei  , Huang Wei  ,   Key Laboratory for Organic Electronics & Information Diaplays and Institute of Advanced Materials, Nanjing 210046, China;,   Institute of Optoelectronics Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210046, China
Published: December 2020

The surface property of the dielectric has a significant influence on growth, morphology, order of the organic semiconductor, and charge carrier transport. The relevant research shows that the mobility of organic field-effect transistor could be effectively improved via ameliorating the surface property of the dielectric. The purpose of this review is to introduce the main factors, including the roughness and the surface energy of dielectric, which exert a tremendous influence on the field effect mobility of OFET, and chiefly describe the progress of the two common methods used for the dielectric modification, viz., the self-assembled monolayer modification and the polymer modification. Finally, the novel applications at present are summarized in this review and some perspectives on the research trend are proposed.
Theoretical analysis on optimal navigation with total energy restriction in a two-dimensional lattice
Authors: Li Yong  , Dou Fei-Ling  , Fan Ying  , Di Zeng-Ru  ,   Department of Systems Science, School of Management and Center for Complexity Research, Beijing Normal University, Beijing 100875, China
Published: December 2020

Recently, a certain total energy constraint =cN was introduced into the Kleinberg's navigation model, where is the total length of the long-range connections, c is a positive constant and N is the network size. The simulation results obtained in the one and two-dimensional cases indicate that with total cost restricted the optimal power-law exponent for adding extra long-range links between any two nodes seems to be =d+1, where d is the dimension of the underlying lattice in this paper. Based on mean field theory, the navigation process on the 2-dimensional cost constrained navigation model can be described by dynamical equations. Based on our theoretical analysis and the numerical results of the dynamical equations, we prove that for large networks and comparatively small total energy, the optimal power-law exponent is =3 for the two-dimensional case. Our results can perfectly correspond to simulations reported previously.
The element-free Galerkin method based on the shifted basis for solving the Kuramoto- Sivashinsky equation
Authors: Feng Zhao  , Wang Xiao-Dong  , Ouyang Jie  ,   Department of Applied Mathematics, Northwestern Polytechnical University, Xi'an 710129, China
Published: December 2020

The Kuramoto-Sivashinsky equation is a kind of high-order nonlinear evolution equation which can describe complicated chaotic nature. Due to the existence of high-order derivatives in the equation, the shape functions violate the consistency conditions when using traditional element-free Galerkin method which adopts high-order polynomial basis functions to construct the shape functions. In order to solve the problems encountered in the traditional element-free Galerkin method, a kind of element-free Galerkin method adopting the shifted polynomial basis functions is presented in this paper. Compared with the traditional element-free Galerkin method, the Galerkin principle is still used to discrete the equation in this method, but the shape functions are constructed by moving least squares based on the shifted polynomial basis functions. Numerical results for the Kuramoto-Sivashinsky equation having traveling wave solution and chaotic nature prove the validity of the presented method.
Electromagnetic scattering study for metal/dielectic coated inlet diffuser
Authors: Wang Long  , Zhong Yi-Cheng  , Zhang Kun-Yuan  ,   College of Energy and Power Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
Published: December 2020

As one of strong scattering sources of planes, assessing accurately the characteristic of radar cross-section (RCS) about inlets is still hot in investigation into computational electromagnetics. An iterative physical optics method, which an impedance boundary condition and forward-backward method are added to, is studied and a box-segmentation method of blanking off is proposed. It can compute accurately the electric magnetic current distribution on the wall and the RCS. What is more, by developing a kind of software which can be verified by the relevant examples, the RCS characteristic of any metal or dielectric cavity can be evaluated. On this basis, using the software, the numerical simulation about the metal/coated medium S-diffuser with rectangular shape is carried out, and the RCS variational regulation of diffuser under an incident wave length in 0.03 m is obtained. The improved iterative physical optics method is applicable to the design of any cavity and the study of coating absorbing materials, therefore the design cycle is shortened.
The analysis of CO2 absorption spectrum characteristics near 1.58 μm at high pressures
Authors: Lü Xiao-Jing  , Weng Chun-Sheng  , Li Ning  ,   National Key Laboratory of Transient Physics, NJUST, Nanjing 210094, China
Published: December 2020

The study of gas spectrum characteristics at high pressure is the foundation for tunable diode absorption spectroscopy technique used in pulsed detonation engines and other high-pressure combustion environments. To understand variations of gas spectrum characteristics with pressure, especially the absorption spectrum characteristics at high pressures, gas absorption spectrum characteristics at high pressure are studied by tunable diode laser absorption spectroscopy in this paper, a method to calculate gas concentration at high pressure is also presented. Within a pressure range of 1-10.13×105 Pa, CO2 absorption spectrum in a near-infrared band of 1.58 μm is simulated. Gas online measurement at high pressure is set up. The CO2 absorption spectrum is measured by a direct absorption method near 1578.0-1579.7 nm. The concentration at high-pressure environment is calculated by linear fitting method and compared with theoretical absorption spectrum. The results show that the absorption spectrum obtained experimentally is in good agreement with simulations result. In high-pressure environment, maximum error of linear fitting method to calculate gas concentration at high pressure is 5.5%, and the average error is 2.6%.
Light propagation characteristics of one-dimensional photonic crystal with double-barrier quantum well
Authors: Su An  , Gao Ying-Jun  ,   Department of Physics and Electronic Engineering, Hechi University, Yizhou 546300, China;,   Department of Physical Science and Engineering, Guangxi University, Nanning 530004, China
Published: December 2020

The light transfer characteristics of one-dimensional photonic crystal with single and double-barrier quantum well are studied by transfer matrix method. The results show that when the refractive index of the barrier layer is high, the transmission peaks in single-barrier quantum well of photonic crystal will be narrower and the inner localized field will be stronger, that the peak in the double-barrier is narrower than the one in the single-barrier, and also the inner localized field is stronger in the double-barrier, that with the number of period layer in the photonic crystal increasing, the inner localized field in the double-barrier well is enhanced, furthermore, the bigger the refractive index ratio between barrier and dielectric layers of well, the stronger the inner localized field in the photonic crystal quantum well is. In addition, when the periodicity of the barrier layer in the photonic crystal with a thicker refractive index increases, the inner localized field will strengthen faster, and accordingly, the transmittance of the transmission peak will decrease more quickly. Both of the strengthening and decreasing will work at the top speed when all periods in different barriers increase at the same time. While the period number of the photonic crystal in well layers increases, the inner localized fields in both single and double-barrier will increase, but their transmittances of the transmission peak will keep the same. The characteristics above can provide guidance for designing new high-quality quantum optical devices.
Radiation from the unsymmetrical modes of the periodical waveguide structure excited by eccentric electron beam
Authors: Liu Wei-Hao  , Zhang Ya-Xin  , Zhou Jun  , Gong Sen  , Liu Sheng-Gang  ,   Terahertz Science and Technology Research Center, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

The special kind of diffraction radiation from the uniformly moving electron beam in a periodical waveguide structure has great potential applications in developing the tunable terahertz radiation sources. Rigorous theoretical analyses and detailed computer simulation on the diffraction radiation from the periodical waveguide structure excited by the eccentric electron beam are carried out. Our results show that the eccentric beam can primarily excite the axial symmetrical modes (TM0 modes) and axial unsymmetrical modes with axial variation numbers of 1 and 2. The energies of the unsymmetrical modes increase with the distance of electron beam to the axis. For each mode, the radiation intensity changes with beam location as the square of modified Bessel function and in direct proportion with the square of the charge quantity. The results of theoretical analyses and computer simulations are in good agreement with each other. These results are of significance for developing this kind of radiation source.
High birefringence and negative dispersion effect of hexagonal honeycomb lattice photonic crystal fiber
Authors: Xu Qiang  , Miao Run-Cai  , Zhang Ya-Ni  ,   College of Physics and Information Technology, Shaanxi Normal University, Xi'an 710062, China;,   Department of Physics and Information Technology, Baoji College of Arts and Science, Baoji 721016, China
Published: December 2020

A novel hexagonal honeycomb lattice photonic crystal fiber is proposed, which is composed of a central defect core, a cladding with elliptical air-hole and small round air-holes. Based on the full vector finite element method with anisotropic perfectly matched layers, its birefringence, dispersion, nonlinearity, leakage loss and mode field are numerically investigated. We compare hexagonal honeycomb lattice photonic crystal fiber and hexagonal elliptical lattice photonic crystal fiber, both of which have the same structure parameters. Numerical results indicate that the proposed fiber shows high birefringence and negative dispersion effect. The birefringence is 1.02× 10-2, both its dispersion and dispersion slope are negative, the dispersion slope values are between -0.132- -0.121 ps·km-1·nm-2 over C band, the leakage loss is close to 102 dB·m-1 and the non-linear coefficient is 45.7 km-1·W-1 at a wavelength of 1.55 μm, if the parameter is selected as Λ =1.15 μm, η =0.5, f=0.48, and d1=0.4 μm. It is found that the hexagonal honeycomb lattice photonic crystal fiber easily obtains high birefringence, large negative dispersion and low non-linear coefficient. It is demonstrated that the hexagonal honeycomb lattice photonic crystal fiber has huge potential in designing dispersion compensation photonic crystal fiber.
Quantitative separation of radiation induced charges for gate controlled later PNP bipolar transistors
Authors: Xi Shan-Bin  , Lu Wu  , Ren Di-Yuan  , Zhou Dong  , Wen Lin  , Sun Jing  , Wu Xue  ,   Xinjiang Technical Institute of Physics & Chemistry CAS, Urumqi 830011, China;,   Xinjiang Key Laboratory of Electronic Information Materials and Devices, Urumqi 830011, China;,   Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

A new test structure of gate controlled lateral PNP bipolar transistors designed and fabricated. An independent gate terminal is patterned on the oxide layer above the active base region of normal lateral PNP bipolar transistors. According to the gate sweep technique, by sweeping the voltage applied to the gate terminal, one can obtain the characteristic of base current versus gate voltage. The quantitative variations of oxide trapped charges and interface traps are analytically estimated and numerically calculated, and the radiation induced defects in the gate controlled lateral PNP bipolar transistors during 60Co-γ irradiation and annealing at room temperature are separated independently. The test structures and measurements of the bipolar transistors used in the experiment are introduced in detail in this paper.
Solitary waves solution in atmospheric inhomogeneous quantum plasma
Authors: Zhou Xian-Chun  , Lin Wan-Tao  , Lin Yi-Hua  , Mo Jia-Qi  ,   Jiangsu Key Laboratory of Meteorological Observation and Information Processing, Nanjing University of Information Science and Technology , Nanjing 210044, China;,   College of Electronic and Information Engineering, Nanjing University of Information Science and Technology, Nanjing 210044, China;,   State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamic, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing 100029, China;,   Department of Mathematics, Anhui Normal University, Wuhu 241003, China
Published: December 2020

For an inhomogeneous quantum magnetoplasma system in the atmospheric environment with density and temperature gradient, a two-dimensional nonlinear fluid dynamic perturbation equation is studied in the case where the collision frequency between ions and neutrals is small. The approximate solution of the potential in the dense astrophysical environment is obtained.
Pseudospin symmetry for a noncentral electric dipole ring-shaped potential in the tridiagonal representation
Authors: Zhang Min-Cang  ,   College of Physics and Information Technology, Shaanxi Normal University, Xi'an 710062, China
Published: December 2020

A noncentral harmonic oscillatory ring-shaped potential is proposed, in which the noncentral electric dipole is included. The pseudospin symmetry for this potential is investigated by working in a complete square integrable basis that supports a tridiagonal matrix representation of the wave operator. The resulting three-term recursion relations for the expansion coefficients of the wavefunctions (both angular and radial) are presented. The angular/radial wavefunction is written in terms of the Jacobi/Laguerre polynomials. The discrete spectrum of the bound state is obtained by diagonalizing the radial recursion relation. The algebraic property of energy equation is also discussed, showing the exact pseudospin symmetry
Spatial correlation properties of focused spatially and spectrally partially coherent Hemite-Gaussian pulsed beams
Authors: Liu Dong-Bing  , Cheng Jin-Ming  , Qi Shuang-Xi  , Wang Wan-Li  , Qian Wei-Xin  ,   Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

Based on the propagation law of partially coherent beams and Fourier transform, the analytical expressions for the spectral intensity and spectral degree of coherence of focused spatially and spectrally partially coherent Hermite-Gaussian (H-G) pulsed beams are derived and used to study the spatial correlation properties in the focal region. It is shown that the spectral degree of coherence depends on the spatial correlation length, temporal coherence length and beam order. As the temporal coherence length decreases, the spectral degree of coherence decreases, whereas the temporal coherence length does not contribute to the spatial distribution of the spectral degree of coherence. An increase of the beam order results in an oscillatory behavior of the spectral degree of coherence, which becomes more prominent with the increase of beam order or the decrease of spatial correlation length.
Two-lane cellular automaton traffic model based on car following behavior
Authors: Jing Ming  , Deng Wei  , Wang Hao  , Ji Yan-Jie  ,   School of Transportation, Southeast University, Nanjing 210096, China
Published: December 2020

With considering the influence of relative motion of vehicles in car following behavior, safe driving conditions and lane changing rules, a two-lane cellular automaton traffic model is proposed based on car following behavior, which is able to illustrate the system's metastable state near the critical point and produce simulation results that accord with observed data. With simulation data on lane changing behavior, a study is conducted on relationship between traffic density and number of vehicles meeting lane changing conditions. Lane changing function is defined to describe lane change process under standard driving behavior. Analytical solution of the function is obtained and used to predict traffic density that stabilizes after lane change process, which contributes to further research on vehicle lane changing behavior.
Ab initio calculation of phase transitions, elastic, and thermodynamic properties of MnPd alloys
Authors: Zhang Wei  , Chen Wen-Zhou  , Wang Jun-Fei  , Zhang Xiao-Dong  , Jiang Zhen-Yi  ,   School of Science, Xi'an University of Posts and Telecommunications, Xi'an 710121, China;,   Institute of Modern Physics, Northwest University, Xi'an 710069, China
Published: December 2020

The phase transitions, elastic and thermodynamic properties of MnPd are investigated using first-principles calculations. The elastic constant calculations indicate that the paramagnetic cubic structure is unstable to external strain and the softening of C11-C12 triggers the paramagnetic cubic phase transformation. The paramagnetic tetragonal structure is mechanically and dynamically stable. When considering the magnetic property, a antiferromagnetic tetragonal structure is lower in energy than the paramagnetic tetragonal structure. So we can conclude that the structural behaviors of MnPd alloys change from paramagnetic cubic to paramagnetic tetragonal, and then to antiferromagnetic tetragonal structure. Moreover, we employ quasiharmonic approximation to calculate the heat capacity and the Debye temperature.
The progress of semiconductor photoelectric devices based on graphene
Authors: Yin Wei-Hong  , Han Qin  , Yang Xiao-Hong  ,   State Key Laboratory of Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Science, Beijing 100083, China
Published: December 2020

Graphene has rich optical and electronic properties, nincluding zero band gap, high mobility and special optical absorption properties, and it has attracted much attention. More and more investigations focus on its fundamental physical properties and electronic devices. However, many researchers believe that its true potential lies in photonics and optoelectronics, such as photodetectors, modulators and transparent conductors used in light-emitting diodes or touch screens. In this review, we summarize its applications in semiconductor photoelectric devices, mainly for telecommunications.
Algrithm for detecting homoclinic orbits of time-continuous dynamical system and its application
Authors: Yang Fang-Yan  , Hu Ming  , Yao Shang-Ping  ,   Key Laboratory of Industrial Internet of Things and Networked Control of Ministry of Education, Chongqing University of Postsand Telecommunications, Chongqing 400065, China;,   Institute for Nonlinear Circuits and Systems, Chongqing University Posts and Telecommunications, Chongqing 400065, China
Published: December 2020

Detecting homoclinic orbits is a key problem in nonlinear dynamical systems, especially in the study of bifurcation and chaos. In this paper, we propose a new method to solve the problem with trajectory optimization. By defining a distance between a saddle point and its near trajectories, the problem becomes a common problem in unconstrained nonlinear optimization to minimize the distance. A subdivision algorithm is also proposed in this paper to improve the integrity of results. By applying the algorithm to the Lorenz system, the Shimizu-Morioka system and the hyperchaotic Lorenz system, we successfully find many homoclinic orbits with the corresponding parameters, which suggests that the method is effective.
Design and error analysis for optical tweezers based on finite conjugate microscope
Authors: Ren Hong-Liang  ,   College of Information Science and Engineering of Huaqiao University, Xiamen 361021, China
Published: December 2020

Optical tweezers are unique tools for studying biophysical properties of single molecules. Design and construction of optical tweezers are very important. The optical path, the radial manipulation equation and axial manipulation equation of optical tweezers based on a finite conjugate microscope system are calculated using matrix optics. The influences of axial position adjustment of the objective, the installation location error of the coupling lens, the installation location error of the laser beam control system, and the installation location error of the confocal system lens' on radial trap position manipulation accuracy and axial trap position manipulation accuracy are analyzed. The results show that axial position adjustment of objective introduces no error in radial and axial trap position manipulation. The misalignment of laser beam control system has no effect on the radial manipulation, nor on axial manipulation when the coupling lens maintains alignment. It is concluded that misalignment of components of optical tweezers based on a finite conjugate microscope system has a greater effect on trap position manipulation error than misalignment of components of optical tweezers based on a infinite conjugate microscope system. The radial trap position manipulation error is less than 5.9% and the axial trap position manipulation error is less than 11.4% when the coupling lens installation location error is less than 10 mm. It is shown that optical tweezers can be modified from a finite conjugate microscope system. The formulations provide the basis for theoretical analysis of experimental alignment and adjustment.
Influence of external electric field on the molecular structure and electronic spectrum of paranitrochlorobenzene
Authors: Li Tao  , Tang Yan-Lin  , Ling Zhi-Gang  , Li Yu-Peng  , Long Zhen-Wen  ,   Department of Phisics, Guizhou University, Guiyang 550025, China
Published: December 2020

In order to achieve the goal of degenerating organic pollutant nitrochlorobenzene, the influence of electric field on molecular structure and electronic spectrum and so on is studied by applying an external parallel electric field. Take paranitrochlorobenzene as a study object, the method B3LYP of the density functional theory at 6-311+g(d, p) level is used to calculate its molecucar structure, dipole moments and total energies of the ground state under different external electric fields (from 0 to 0.025 a.u.) in this paper. On this basis, the time-dependent density functional theory is used to study the influences of external electric field on excited wavelength and oscillator strength of the first six excited states. The results show that bond lengths (C–Cl, C–N) increase rapidly and bond energy decrease rapidly with the increase of field intensity. At the same time, bond length (C–C, C–H) changes of benzene ring are very small, and the increases or decreases are not uniform. This illustrates that molecular degradation may lead to the fractures of bonds (C–Cl, C–N), and the benzene ring is relatively stable. what is more, the molecular total energy first increases then decreases, and the dipole moment first decreases then increases with the increase of the field intensity. In addition , the maximum absorption wavelength first slowly decreases, and then increases rapidly with the increase of the field intensity, which causes the electron transition to be relatively easy, while oscillator strength changes relatively complex in anner.
A polarization-independent transmission absorption metamaterial absorber based on electromagnetic resonance
Authors: Lu Lei  , Qu Shao-Bo  , Ma Hua  , Yu Fei  , Xia Song  , Xu Zhuo  , Bai Peng  ,   Science College, Air Force Engineering University, Xi’an 710051, China;,   Electronic Materials Research Laboratory, Key Laboratory of the Ministry of Education, Xi'an Jiaotong University, Xi'an 710049, China;,   Synthetic Electronic Information System Research Department, Air Force Engineering University, Xi'an 710051, China
Published: December 2020

In this paper, we simulate and experimentally validate a polarization-independent transmission absorption metamaterial absorber based on electromagnetic resonance. The metamaterial absorber can absorb the high-frequency electromagnetic wave, and the low-frequency wave can transmit through the absorber. The tested results indicate that the metamaterial absorber can achieve a narrow bandwidth high absorption with a peak absorption of 83.6% at 6.77 GHz, and a full width at half maximum (FWHM) of 4.3%. To further broaden the absorption bandwidth of the resonant metamaterial absorber, we place two absorbers with different working frequencies together for its low-frequency transmitted characteristic. The measured data show that the composite metamaterial absorber can increase the FWHM to 10.9%, and can enhance the absorption slightly. The metamaterial absorber has some advantages, such as simple design, strong practicability, and important application foreground.
Phase and amplitude-dependent inversionless gain controlled by a three-level closed loop system
Authors: Zhang Zhi-Ying  , Fu Shen-Cheng  , Gou Li-Dan  , Yao Zhi-Hai  ,   School of Science, Changchun University of Science and Technology, Changchun 130022, China
Published: December 2020

We study a four-level atomic system controlled by a three-level closed loop subsystem in order to obtain the phase-sensitive probe gain without population inversion. In the case of three-photon resonance, a large steady-state inversionless probe gain can be obtained. Due to the quantum interference effect, the inversionless gain is sensitive to the relative phase of the three-level closed loop subsystem. Further, the field intensity of the three-level closed loop subsystem is also an important parameter that can affect gain characteristic of the probe field.
Phase field modeling of the influence of interfacial wettability and solid volume fraction on the kinetics of coarsening
Authors: Wang Tao  , Li Jun-Jie  , Wang Jin-Cheng  ,   State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China
Published: December 2020

Coarsening of solid particles in a solid-liquid two-phase system with high solid volume fraction is studied using the multiphase-field model. The influences of interfacial wettability and solid volume fraction on growth exponent, coarsening rate, and particle size distribution (PSD) are analyzed. It is found that the growth exponent is independent of the volume fraction, while the coarsening rate constant and the PSD are closely related to the interfacial wettability and the solid volume fraction. Under the completely wetting condition the coarsening rate constant increases with volume fraction increasing, but this variation is insignificant under the incompletely wetting condition. Moreover, when the wettability is low and volume fraction is high, the coarsening rate may also decrease with volume fraction increasing. The simulation results also show that with the increase of volume fraction, the peak frequency decreases and the PSD becomes broader, but the fall of the peak frequency under the incompletely wetting condition is slower than under the completely wetting condition. The simulation results provide an insight into the discrepancy between different experimental observations.
Effect of the direct correlation function on phase diagram of the two-mode phase field crystal model
Authors: Guo Can  , Wang Zhi-Jun  , Wang Jin-Cheng  , Guo Yao-Lin  , Tang Sai  ,   State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China
Published: December 2020

Effects of the width of direct correlation function peak and the peak at k=0 on the phase diagram for the two-mode phase field crystal model are examined carefully. The results indicate that increasing the width of direct correlation function peak will expand the stability region of the ordered phases; however, increasing the ratio of peak width will significantly increase the fcc phase region but reduce the bcc phase region. Adding a negative Gaussian peak at k=0 to the two-mode approximate direct correlation function will compress the phase diagram and make the two-phase coexisting region narrow.
A simulation technique of X-ray pulsar signals with high timing stability
Authors: Sun Hai-Feng  , Xie Kai  , Li Xiao-Ping  , Fang Hai-Yan  , Liu Xiu-Ping  , Fu Ling-Zhong  , Sun Hai-Jian  , Xue Meng-Fan  ,   School of Electronic Engineering, Xidian University, Xi’an 710071, China;,   School of Mechano-Electronic Engineering, Xidian University, Xi'an 710071, China;,   School of Telecommunication Engineering, Xidian University, Xi'an 710071, China
Published: December 2020

A simulation experiment system is required presently, for the space flight experiment of X-ray pulsar based navigation is very costly. To solve the crucial issues of the timing stability and the profile precision in existing simulation techniques of pulsar signal, a new simulation technique which utilizes visible light is proposed. The simulation experiment system is set up based on the proposed technique. And some experiments are carried out to test the proposed technique. The results demonstrate that the proposed technique can be used to simulate any of known pulsars. The timing stability of simulated X-ray pulsars is raised from 10-4 to 10-9. And the accuracy of pulsar profile simulation is noticeably improved. Within the X-ray band 1-10 keV, when the observation time reaches 1200 s, and the area of the X-ray detector is 1 m2, the Pearson correlation coefficient of pulsar's observation profile with the standard template profile arrives at 0.993. And the simulation experiment system can be realized with high flexibility and low cost. On the basis of the simulation experiment system, the signal characteristic of X-ray pulsar can be investigated. On the other hand, the performances of X-ray pulsar signal processing algorithms and navigation algorithms can be surveyed in detail.
Optical lattice solitons in nonlinear media under the condition of hollow cylinder boundary
Authors: Jiang Xian-Ce  , Xu Bin  , Liang Jian-Chu  , Yi Lin  ,   Department of Mechenical and Aeronautical Engineering,Naval Aeronautical Engeering Institute Qingdao Branch, Qingdao 266041, China;,   Department of Mathematics and Information Sciences, North China Institute of Water Conservancy and Hydroelectric Power, Zhengzhou 450008, China;,   Department of Electronic Science, Huizhou University, Guangdong 516001, China;,   Department of Physics, Huazhong University of Science & Technology, Wuhan 430074, China
Published: December 2020

By using the self-similar method to solve the nonlinear Schrödinger eguation with distributed coefficients, the self-similar solitons in Bessel lattice are studied under the hollow cylinder boundary conditions and the analytical solutions are obtained. Analytical solutions and numerical solutions are found to be identical. The result indicates that optical lattices induced by non-diffractive Bessel beams are possible to support stable self-similar soliton clusters.
Ultracold spin-1 atoms in three-well optical superlattice under a weak magnetic field
Authors: Qin Shuai-Feng  , Zheng Gong-Ping  , Ma Xiao  , Li Hai-Yan  , Tong Jing-Jing  , Yang Bo  ,   Department of Physics, Henan Normal University, Xinxiang 453007, China
Published: December 2020

Ultracold atoms trapped in an optical lattice of double-well potential, the so-called optical superlattice, have received much attention in the field of cold atoms. A protocol generalized to three-well optical superlattice is suggested in this paper. The ground-state diagrams of ultracold spin-1 atoms trapped in a symmetric three-well optical superlattice in a weak magnetic field are studied based on the exact diagonalization. It is shown that the ground-state diagrams are remarkably different for the ferromagnetic and antiferromagnetic atoms. There does not exist the type of ground state for the antiferromagnetic interaction atoms, where the magnetic quantum number of the total spin of the system along the external magnetic field are ±2. But for the ferromagnetic interaction atoms, there do exist. In addition, there exist only the fully polarized ground-states for the ferromagnetic atoms in the negative quadratic-Zeeman-energy region. The physicsal origin of the dependence of the ground states on the controllable parameters are analyzed. These quantum spin-states can be controlled easily and exactly by modulating the external magnetic field and the height of the optical barrier, which may be a tool for the study of spin-entanglement.
Soliton dynamical behavior of the condensates trapped in a square-well potential
Authors: Zhang Bo  , Wang Deng-Long  , She Yan-Chao  , Zhang Wei-Xi  ,   Department of Physics, Xiangtan University, Xiangtan 411105, China;,   Department of Physics and Electronic Science, Tongren University, Tongren 554300, China
Published: December 2020

Using multiple-scale method, we study analytically the soliton dynamical behaviors of the Bose-Einstein condensates trapped in a square-well potential. It is found that the square-well potential has important effects on the soliton dynamics. When the soliton goes into the square-well potential, its movement is accelerated; while it leaves the square-well potential, the soliton is decelerated. With the increase in depth of the square-well potential, the velocity of the soliton increases, and its amplitude becomes larger and its width decreases. This may serve as a reference effect for controlling the dynamical characteristics of the soliton in experiments.
Scattering of the Laguerre-Gaussian beam by a homogeneous spheroid
Authors: Ou Jun  , Jiang Yue-Song  , Shao Yu-Wei  , Qu Xiao-Sheng  , Hua Hou-Qiang  , Wen Dong-Hai  ,   School of Electronic and Information Engineering, BeiHang University, Beijing 100191, China
Published: December 2020

The scattering features of a spheroidal particle illuminated by the Laguerre- Gaussian (LG) beam have been studied based on the generalized Lorenz-Mie theory. By using the localized approximations method, the beam shape coefficients are evaluated and the results obtained agree with the cases of on-axis incidence. Calculations of the far-field scattering intensity are performed to study the LG beam scattered by spheroids, of different size parameters and eccentricities. The simulation results show that when the particle's size parameter is within the range that can be compared to the wavelength of the incident light, the magnitude of the scattering intensity will increase as the particle's size parameter increases, and it will decrease as the ratio of the spheroid's major axis to minor axis increases. Comparisons between LG beams with different topological charges illumination are made and explained physically. It turns out that the magnitude of the scattering intensity decreases as the topological charge increases. The theoretical investigation in this paper may provide a more accurate particle model and reference for applications of LG beams in areas such as particle size measurement, atmospheric laser communication, atmospheric remote sensing and so on.
Fabrication of cylindrical opals and inverse opals and their optical properties
Authors: Chen Wei  , Wang Ming  , Ni Hai-Bin  ,   Key Laboratory on Opto-Electronic Technology of Jiangsu Province, School of Physics Science and Technology, Nanjing Normal University, Nanjing 210046, China
Published: December 2020

Hollow and solid cylindrical opals and inverse opals have been made by the self-assembly method in a capillary. The mechanism as well as the assembly process of monodispersed microspheres self-assembly in a capillary has been investigated. By the vertical self-assembly method, hollow cylindrical polystyrene opals and silica inverse opals of different radii have been made in capillaries; whereas cylindrical solid opals and inverse opals have been prepared under the interactions of gravity sedimentation, evaporation induced micro-flow, liquid surface tension and capillary tension. The growth process of producing solid photonic crystals in capillaries have been described and discussed. By scanning electron microscope, we characterize the internal structure of the samples and with spectrometer we test the reflection spectra of these films. Results show that the substrate curvature radius and microsphere size are the main factors that affect the quality of hollow cylindrical opal and inverse opal films while microsphere size has influence on the internal structure of solid cylindrical opals and inverse opals.
Nonlinear forced oscillations of gaseous bubbles in elastic microtubules
Authors: Wang Cheng-Hui  , Cheng Jian-Chun  ,   Institute of Acoustics, Nanjing University, Nanjing 210093, China;,   Institute of Applied Acoustics, Shaanxi Normal University, Xi'an 710062, China
Published: December 2020

The wall of elastic microtubules can be described as a membrane-type elastic structure. An oscillating system driven by ultrasound consists of liquid columns, a bubble and elastic wall of the tube. The nonlinear properties of this system are explored. Based on the successive approximation method, the nonlinear resonance frequencies, the amplitude response of fundamental and third oscillations to driving acoustic wave, and the mechanism of resonance response related to the driving wave whose frequency is lower than the resonant frequency are analyzed theoretically. The nonlinear system is oscillating in two directions: the axial and radial directions of the bubble in the microtubule. Numerical results show that the resonance responses cannot be present simultaneously. It has been found that the amplitudes of the fundamental and third harmonic oscillation are multivalued, which may lead to instable response. The third harmonic oscillation is stronger in the region of lower frequencies.
Numerical simulation of Trichel pulse characteristics in bar-plate DC negative corona discharge
Authors: Wu Fei-Fei  , Liao Rui-Jin  , Yang Li-Jun  , Liu Xing-Hua  , Wang Ke  , Zhou Zhi  ,   State Key Laboratory of Power Transmission Equipment & System Security and New Technology, Chongqing 400044, China;,   Zibo Power Supply Company, Shandong Electric Power Corporation, Zibo 255000, China
Published: December 2020

An improved multi-component two-dimensional hybrid model is presented for the simulation of Trichel pulse corona discharge. The model is based on the plasma hydrodynamics and chemical models, including 12 species and 27 reactions. In addition, the photoionization and secondary electron emission effects are taken into account. Simulation is carried out on a bar-plate electrode configuration with an inter-electrode gap of 3.3 mm, the positive potential applied to the bar being 5.0 kV, the pressure in air discharge being fixed at 1.0 atm, and the gas temperature assumed to be a constant (300 K). In this paper, some key microscopic characteristics such as electric field distribution, net charge density distribution, electron density distribution at 5 different instants during a Trichel pulse are analyzed emphatically. Further more, the electron generation and disappearing rates, positive and negative ion distribution characteristics along the axis of symmetry are also investigated in detail in the later Trichel pulse cycle. The results can give valuable insights into the physical mechanism of negative corona discharge.
Investigation of light trapping structure and performance in PIN-type and NIP-type thin film silicon solar cells
Authors: Yu Xiao-Ming  , Zhao Jing  , Hou Guo-Fu  , Zhang Jian-Jun  , Zhang Xiao-Dan  , Zhao Ying  ,   Key Laboratory of Photo-Electronics Thin Film Devices and Technique of Tianjin, Key Laboratory of Opto-Electronic Information Science and Technology, Ministry of Education, Institute of Photo-Electronics Thin Film Devices and Technique of Nankai University, Tianjin 300071, China
Published: December 2020

In both PIN-type and NIP-type thin film silicon solar cells, textured light trapping substrates are used to enhance light absorption and improve energy conversion efficiencies. Scalar scattering theory is used to simulate the light trapping performance of textured substrates. The results indicate that in order to get good light trapping performance, the root mean square (RMS) for front reflectors in PIN-type solar cells should be at least 160 nm, while it is only 40 nm for back reflectors in NIP-type solar cells. A series of a-SiGe:H single-junction solar cells is deposited on back reflectors with different RMS values. It is found that a-SiGe:H solar cells deposited on back reflectors with RMS values of 40 and 61.5 nm demonstrate similar short current density values and quantum efficiencies. These results indicate that RMS value of 40 nm is enough to get good light trapping performance, which is consistent with the numerical simulation.
The resonant behavior of a linear harmonic oscillator with fluctuating mass
Authors: Yu Tao  , Zhang Lu  , Luo Mao-Kang  ,   Department of Mathematics, Sichuan University, Chengdu 610064, China
Published: December 2020

The mass of Brownian particle is fluctuant in a viscous medium, because the molecules of surrounding medium may randomly stick on it. This mass fluctuation influence on the system resonant behavior is studied by modeling it as a symmetric dichotomous noise. Using Shapiro-Loginov formula and Laplace transformation, the analytical expression of system steady response amplitude is presented. The corresponding numerical results are used to discuss system resonant behavior. Furthermore, the reliability of theoretical results is tested by simulation experiments. All the research results show that: 1) the system steady response is a simple harmonic vibration which has the same frequency as the driving signal; 2) with the variations of driving frequency, oscillator mass and noise parameters, the system presents real resonance, parameter induced resonance and stochastic resonance phenomenon, respectively; 3) because of the mass fluctuation, some new resonant forms are observed, such as one-peak and one-valley resonance, two-peak resonance, etc.