bluuebunny/crossref_metadata_2025 huggingface dataset:
Density-functional theory study of ConCm (n=15, m=1,2) clusters
Authors: Zhang Bei  , Bao An  , Chen Chu  , Zhang Jun  ,   College of Science, Xi'an Jiaotong University, Xi'an 710049, China;,   Department of Physices, Xinjiang University, Urumchi 830046, China;,   College of Science, Neimenggu science and technology University, Baotou 014010, China
Published: December 2020

The geometrical and electronic structures of ConCm (n=15, m=1,2) clusters are investigated using spin-polarized DFT calculations. ConC (n=25) and ConC2 (n=14) clusters of their ground-state structures different. From n=3, two C atoms are located apart from each other, we think, it is an important reason for Co catalyze C in to single walled carbon nanotubes effectively. The total magnetic moment of ConC2 (n=25) are lower than those of ConC (n=25) clusters, and they both alternated with odd and even numbers. By comparing the fragmentation energies of neutral and charged ConC and ConC2 (n=15) clusters, we conclude that the single walled carbon nanotubes obtained in experiment is electropositive. This conclusion is in good agreement with that from expersimental model
Two-dimensional performance of uniform irradiation with the use of a concentricity deviation lens array and partially coherent light
Authors: Zheng Jian-Zhou  , Yu Qing-Xu  , Guan Shou-Hua  , Dong Bin  , Cao Xiao-Jun  , Lu Yong-Jun  , Wu Yun-Feng  ,   College of Physics and material Engineering, Dalian Nationalities University, Dalian 116600, China;,   School of Physics and Optoelectronic Technology, Dalian University of Technology, Dalian 116024, China
Published: December 2020

A method of employing a lens array (LA) and partially coherent light (PCL) is presented for uniform irradiation on targets in inertial confinement fusion. Quasi-near field spots with a profile of sharp edge and flat top can be obtained with an LA, while the spatial coherence of the incidence beam is reduced by PCL. An appropriate concentricity deviation (CD) of LA results in the superposition of beamlets at the focus dislocated by a small amount each other and the CD and PCL reduce the fringe separations, thus the interference fringes become denser and the small-scale intensity non-uniformity of intensity distribution is suppressed. Based on the generalized diffraction integral theory, the intensity distribution of a Gaussian Schell Beam (GSB), point focused by an LA and a spherical lens is investigated in detail by two-dimensional simulation. And irradiation uniformity effects are compared with coherent light and partially coherent light after the LA. Numerical results indicate that using an appropriate CD and moving the target slightly from the exact focal plane of the principal focusing, a well-irradiated laser spot and great energy efficiency can be obtained.
Continuous-variable quantum deterministic key distribution protocol based on quantum teleportation
Authors: Song Han-Chong  , Gong Li-Hua  , Zhou Nan-Run  ,   Department of Electronic Information Engineering, Nanchang University, Nanchang 330031, China
Published: December 2020

By exploiting quantum teleportation, we propose a continuous-variable quantum deterministic key distribution (CVQDKD) protocol using two-mode squeezed vacuum state and coherent state. The efficiency is 100% under the homodyne detection. The security of CVQDKD is analyzed in detail from information theory, and the result shows that the proposed protocol can securely hand over the pre-deterministic key. By contrast with the quantum random key distribution, the quantum deterministic key distribution plays an irreplaceable role in the field of key management. Furthermore, the CVQDKD can obtain a higher rate and better efficiency than the quantum deterministic key distribution protocols with discrete variables, and the quantum states used in the protocol are also easy to produce and manipulate, which i suitable for long-distance transmission. Therefore, the CVQDKD protocol is more practical.
Research on the V-shape folded rectangular groove slow-wave structure
Authors: Liu Yang  , Xu Jin  , Xu Xiong  , Shen Fei  , Wei Yan-Yu  , Huang Min-Zhi  , Tang Tao  , Wang Wen-Xiang  , Gong Yu-Bin  ,   National Key Laboratory of Science and Technology on Vacuum Electronics, School of Physical Electronics University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

A novel slow-wave structure called V-shape folded rectangular groove waveguide is proposed. This structure evolves from a conventional rectangular groove waveguide bending the groove with V-shape along its longitudinal direction, and the gap between metal plates forms a sheet electron beam channel naturally. Compared with the traditional U-shape structure, it can increase the interaction area without changing good high-frequency properties, which can adopt the sheet electron beam with a larger area to acquire more output power. In this paper, the high-frequency properties of this structure are analyzed, the interaction circuit for the V-band TWT is designed and the PIC simulation is performed to predict the operating characteristics. From our calculations, this tube can produce average saturation output power over 1000 Watts in a frequency range from 58 GHz to 64 GHz when the cathode voltage and beam current are set to be 12.8 kV and 600 mA respectively. The corresponding saturation gain and electron efficiency can reach over 33 dB and 13.2% respectively.
Research of dielectric photonic crystal on red LED to increase luminous flux
Authors: Xu Xin-Wei  , Cui Bi-Feng  , Zhu Yan-Xu  , Guo Wei-Ling  , Li Wei-Guo  ,   Key Laboratory of Opto-Electronics Technology, Beijing University of Technology, Beijing 100124, China
Published: December 2020

According to the photon grating diffraction principle, the extraction efficiency of LED with photonic crystal can be improved. In this paper, the dielectric photonic crystal is introduced into the SiO2 layer of the red LED to improve the extraction efficiency. The theoretical analyses and experimental results show that the LED with dielectric photonic crystal can well achieve the extraction efficiency. The luminous flux of new type LED is improved by 26% compared with the normal red LED.
Progress of electromagnetically induced transparency based on superconducting qubits
Authors: Zhao Hu  , Li Tie-Fu  , Liu Jian-She  , Chen Wei  ,   Institute of Microelectronics, Tsinghua University, Tsinghua National Laboratory for Information Science and Technology (TNList), Tsinghua University, Beijing 100084, China
Published: December 2020

Superconducting quantum computing is currently considered as one of the most promising options to realize a quantum computer. Superconducting qubit is the core component of the superconducting quantum computer. To increase the decoherence time of superconducting qubits as far as possible, the large-scale integration of superconducting qubits have become the main research topic of superconducting quantum computing. As a macroscopic artificial atom, lots of quantum optical phenomena can be observed in the superconducting qubits. Electromagnetically induced transparency based on superconducting qubits can provide a new method to study the superconducting qubit decoherence mechanism, and can also arouse new ideas to study the nonlinear optics, optical storage, ultra-slow optical transmission and quantum optics. In this paper, we introduce a theoretical basis of electromagnetically induced transparency, review the current research of electromagnetically induced transparency based on superconducting qubits, compare the difference between electromagnetically induced transparencies based on gas atoms and superconducting qubits, and evaluat the prospect applications for its development.
DFT calculations on the adsorption of component SF6 decomposed under partial discharge onto carbon nanotubes modified by -OH
Authors: Zhang Xiao-Xing  , Meng Fan-Sheng  , Tang Ju  , Yang Bing  ,   State Key Laboratory of Power Transmission Equipment and System Security and New Technology, Chongqing University, Chongqing 400044, China;,   Shaoxing Power Bureau Zhejiand Electric Power Company, Shaoxing 312000, China
Published: December 2020

Partial discharge (PD) in gas insulated switchgear (GIS) is one of important factors causing accidents. The PD can lead to the decomposition of SF6, generating different gas components. To detect and analyze the decomposed characteristic components of SF6 under PD is significant for fault diagnosis of GIS. However, how to detect the characteristic components from mixed gas components is a main puzzler. In this paper, the molecular dynamics simulation software of MS is used to calculate accurately the process of single-wall carbon nannobutes modified by hydroxide radical (SWNT-OH) adsorbing the main components of SF6 decomposed under PD. The main components contain SOF2, SO2F2, SO2 and CF4. By analyzing the frontier orbital of gas molecules and SWNT-OH, as well as adsorption energy, charge transfer and the electronic density of states in the adsorption process, and the values of energy gap after SWNT-OH adsorbing the gas molecules, the sensitivity and the selectivity of SWNT-OH on gas molecules are evaluated and the theoretical basis on whether the SWNTOH can be prepared as gas sensors to detect the components of SF6 decomposed under PD is presented.
Research on tritium and helium-3 content distributions in steel wall of spherical pressure vessel under general boundary condition
Authors: Liu Yuan-Dong  , Yin Yi-Hui  , Tan Yun  ,   Institute of Structural Mechanics, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

In order to understand the changes of mechanical properties of the wall materials and the carrying capacity of vessel which contains high pressure tritium, the spatiotemporal changes of tritium and helium-3 content in the wall should be studied during tritium storage. Taking into consideration the case that the outer surface of the vessel is with general mass transfer boundary condition and the tritium inside the vessel is van der Waals gas, and also taking into account both decay and permeation of tritium inside the vessel and decay and diffusion of tritium in the wall material, the analytical theoretical models of tritium and helium-3 content in the wall are developed and solved, and relevant theoretical formulas are deduced. Through analytical calculations, the curves of tritium and helium-3 content in the wall versus mass transfer coefficient of the outer surface, storage time and the spatial positions are plotted. Through analysis, a law called 21+2/2 time law of helium-3 content is put forward, where 1 and 2 are the coefficients which are related to van der Waals constant of tritium. The law is proposed: helium-3 content in the wall of the spherical high pressure vessel storing tritium which is in an open space rises along the radius from outer to inner, and the content radial gradient increases with storage time. If storage time is long enough, the helium-3 content at any point will approach to its final value, that is, a maximal value at a relevant point. The ratio of the maximum helium-3 content to the related initial tritium content is 21 + 2/2 at the inner surface. The obtained formulas and understandings can be used as a premise of the safety assessment of tritium stored vessel.
Optical Bi-stability in one-dimensional antiferromagnetic photonic crystal
Authors: Zhang Qiang  , Zhou Sheng  , Li Qiang-Hua  , Wang Xuan-Zhang  , Fu Shu-Fang  ,   Key Laboratory for Photonic and Electric Bandgap Materials, Ministry of Education, Key Laboratory for Advanced Functional Materials and Excited State Processes, School of Physics and Electronic Engineering, Harbin Normal University, Harbin 150025, Cinina
Published: December 2020

Based on the transfer matrix method and the principle of light localization, the optical bi stability (OB) changing with magnetic field strength, incident angle and dielectric layer are investigated in an one-dimensional antiferromagnetic photonic crystal near the resonant frequencies. We find that the OBs can be observed near the two resonant frequencies at a smaller incident angle, but they disappear near the higher resonant frequencies at a bigger incident angle when the magnetic field strength is 1.0 kG. However, once the external magnetic field strength increases up to 2.0 kG, the lost OB will be induced due to the the two resonant frequencies shifting towards two sides. In addition, the dielectric layers also have a greater influence on OB near the lower resonant frequencies at a smaller incident angle.
Nonlinear phenomenon of surface enhanced Raman scattering caused by surface plasmon
Authors: Huang Qian  , Xiong Shao-Zhen  , Zhao Ying  , Zhang Xiao-Dan  ,   Institute of Photo Electronics thin Film Devices and Technique of Nankai University, Key Laboratory of Photo Electronics thin Film Devices and Technique of Tianjin, Key Laboratory of Opto Electronic Information Science and Technology, Ministry of Education, Tianjin 300071, China
Published: December 2020

Silver nanoparticles are synthesized through thermal evaporation for molecular detection using surface enhanced Raman scattering microscopy. The optical properties of silver nanoparticles are obtained by ultraviolet-visible spectrometry, which show the resonance wavelength near the detecting wavelength of Raman scattering (488 nm). Using rhodamine 6G as a test molecule, the results in this paper show that the detected Raman peak intensity has a nonlinear relationship with the incident power density when surface plasmon of silver nanoparticles was excitated by incident photon. This nonlinear phenomenon of surface enhanced Raman scattering caused by "hot spot" with high electromagnetic field strength provides an effective way to obtain high scattering intensity without high incident power density, which may expand the scope of Raman scattering application.
Effects of thermal treatments on the formation of nanocrystalline Si embedded in Si-rich oxide films
Authors: Cai Ya-Nan  , Cui Can  , Shen Hong-Lei  , Liang Da-Yu  , Li Pei-Gang  , Tang Wei-Hua  ,   Center for Optoelectronics Materials and Devices, Department of Physics, Zhejiang Sci-Tech University, Hangzhou 310018, China;,   School of Science, Beijing University Posts and Telecommunications, Beijing 100876, China
Published: December 2020

Silicon oxide films containing nanocrystalline Si (nc-Si) are fabricated by magnetron sputtering method followed by one-step-annealing, two-step-annealing and rapid thermal annealing (RTA), separately. In silicon-rich oxide films containing ～ 42.63 at.% of Si, dense nc-Si in a magnitude of 1012/cm-2 are obtained in all of the samples subjected to three different thermal treatments. In the two-step-annealing sample, the density of nc-Si reachs a maximum (2.2× 1012/cm-2), and the nc-Si is well crystallized and uniform in size distribution. In the one-step-annealing sample, the density of nc-Si is silightly lower than in the two-step-annealing sample, and large deficiently crystallized nc-Si is observed in the sample. The RTA leads to the lowest density of nc-Si with the largest size distribution among the three samples. Moreover, large nc-Si formed by coalescence of small ones and twin crystals are also discovered in the RTA sample. It is believed that nucleation at the early stage of nanocrystal growth influences the density and the micostructure of nc-Si. The annealing at low temperature in the two-step-annealing facilitates the formation of new nulcei, which is beneficial to improving the quality and density of nc-Si.
Study on effect of wind waves on radar echoes in atmosphere duct oversea
Authors: Shao Xuan  , Chu Xiao-Liang  , Wang Jian  , Xu Jin-Ju  ,   College of Physical and Environmental Oceanography, Ocean University of China, Qingdao 266100, China;,   College of Information Science and Engineering, Ocean University of China, Qingdao 266100, China
Published: December 2020

The Wen's wave spectrum model is adopted to describe the rough sea surface, and the relation between wind and ocean waves using sea wave spectrum theory is derived. The improved discrete mixed Fourier transform algorithm and the modified rader scattering coefficient model are used to calculate radio propagation loss and radar cross section respectively. On this basis, the influence of wind waves on radar echoes in the environment of atmosphere ducts is analysed by using numerical calculations. The results show that the influences of wind on propagation loss at different heights are different; wich respect to the propagation loss, rader scattering coefficient influenced by waves of factors is large, which results in large change in the radar echo power.
Experimental study of X-ray phase contrast imaging without absorbing grating
Authors: Yang Qiang  , Liu Xin  , Guo Jin-Chuan  , Lei Yao-Hu  , Huang Jian-Heng  , Niu Han-Ben  ,   Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China
Published: December 2020

According to the theoretical analysis of X-ray differential phase-contrast imaging system based on one-dimensional spatial-coherence X-ray source with multi-line structured anode, a scintillator functioning as an absorption grating, and a phase grating fabricated by photo-assisted electrochemical etching technique developed by us, we construct a non-absorption grating X-ray differential phase-contrast imaging system, conduct the experiments on some biological samples prepared with the above system, and finally obtain some phase-contrast images with more structural information than the ones obtained by conventional X-ray absorption method. Consequently, out system can be considered as a feasible imaging system and can have potential applications in hospitals and laboratories.
Measurement and theoretical calculation for Stark energy and electric dipole moment of Cs Rydberg state
Authors: Li Chang-Yong  , Zhang Lin-Jie  , Zhao Jian-Ming  , Jia Suo-Tang  ,   State Key Laboratory of Quantum Optics and Quantum Optics Devices, Laser Spectroscopy Laboratory, Shanxi University, Taiyuan 030006, China
Published: December 2020

Rydberg atoms has been one of the hot current research subjects in the field of physics becasue of its large volume, long life, easy polarization and energy levels easily controlled by external electric field. In this paper, the Stark energies and electric dipole moments of 15P3/2 and 16P3/2 of atomic cesium are measured experimentally. The empirical analytic equations of dipole moments and Stark energies for these two states are presented. We also numerically solve the Schrdinger equation and obtain Stark energies, dipole moments, and electron probability density distributions. The probability density distribution accords with the calculated dipole moments. The Stark energies and dipole moments are consistent with our experimental results. To the best of our knowledge, the measurement and calculation methods for dipole moments presented in this paper are reported for the first time.
Simulation and experimental confirmation on the reconstruction of Bessel beams
Authors: Fan Dan-Dan  , Zhang Qian-An  , Cheng Zhi-Ming  , Zheng Wei-Tao  , Wu Feng-Tie  ,   College of Information Science and Engineering, Huaqiao University, Quanzhou 362021, China
Published: December 2020

The reconstruction property of the Bessel beam plays a significant role in the application of multi-plane micro-manipulation. We analyze the principle of the generation and the reconstruction of Bessel beam according to the Hankel wave theory; we also discuss the reconstructions of circular and square obstacles on-axial and off-axial of system in detail respectively. The generation of Bessel by axicon and the self-reconstruction property of Bessel beam after different kinds of obstacles are simulated by optical design software ZEMAX. Experimental result is used to confirm the simulation model, and it accords with the simulation very well. Therefore, we obtain a conclusion that the software ZEMAX can quickly and intuitively simulate the reconstruction of Bessel beam generated by axicon with high veracity.
Theoretical analysis of coherent perfect absorption in one-dimensional anti-laser
Authors: Shen Yun  , Yu Guo-Ping  , Fu Ji-Wu  ,   Department of Physics, Nanchang University, Nanchang 330031, China;,   Department of Physics, Wuhan University, Wuhan 430072, China
Published: December 2020

Detailed analyses and the correlations of coherent perfect absorption (CPA) in single-channel and two-channel structures are performed by the transfer matrix and scattering matrix method. The results show that there are many possibilities for single-channel and two-channel structures to satisfy the occurring of CPA. Moreover, with the same incident wavelength and refractive index of dielectric, the length of dielectric for two-channel CPA is twice that for single-channel. For instance, it is 3.701 m/7.402 m for single-/two-channel CPA as 756 nm wavelength is incident on Si material. Our results facilitate the application of CPA in optical modulator, switches, detector, etc., and they are also of significance for Si-based integration of optical circuits in optical communication and computer.
Effects of envelope modulation rate and carrier frequency on auditory temporal modulation detection
Authors: Meng Qing-Lin  , Yuan Meng  , Mou Hong-Yu  , Chen You-Yuan  , Feng Hai-Hong  ,   Shanghai Acoustics Laboratory, Chinese Academy of Sciences, Shanghai 200032, China
Published: December 2020

The effects of envelope modulation rate (below 300 Hz) and pure-tone carrier frequency (below 8 kHz) on auditory temporal modulation detection ability (TMDA) are investigated through psychophysical experiments. The stimuli are sinusoidal amplitude-modulated signals with pure tone carriers. Two-alternative-forced-choice procedure with adaptive step is used. The temporal modulation transfer functions with different carrier frequencies are measured. Twenty-two normal-hearing subjects (22 to 29 years old) are recruited for this study. Experimental results show that both envelope modulation rate and carrier frequency have significant effects on TMDA. When carrier frequency is below 2 kHz, TMDA improves with the increase of modulation rate. When carrier frequency is above about 3.5 kHz, TMDA is influenced by the variation of carrier frequency, but without significant monotonic trend. When modulation rate is between 10 and 100 Hz, carrier frequency does not affect TMDA. When the modulation rate is between 150 and 300 Hz, TMDA decreases with the increase of carrier frequency until the carrier frequency is above 3.5 kHz.
Computer simulation of the glow discharge characteristics in magnetron sputtering
Authors: Shen Xiang-Qian  , Xie Quan  , Xiao Qing-Quan  , Chen Qian  , Feng Yun  ,   Institute of Advanced Optoelectronic Materials and Technology, College of Science, Guizhou University, Guiyang 550025, China
Published: December 2020

In this paper, the process of glow discharge in magnetron sputtering is studied by the particle-in-cell with Monte Carlo collision method. The proposed model is a two-dimensional and self-consistent approach. The results show that the discharge mode transits from the negative space-charge-dominated mode to positive space-charge-dominated mode with working pressure increasing or magnetic field weakening. At the transition state, working pressure and magnetic field are 0.67 Pa and 0.05 T, respectively. Discharge current increases as the cathode voltage increases. When pressure increases, discharge current first increases and then tends to balance. When the pressure is higher than 2.5 Pa, current begins to decreases with the increase of the pressure.
The study on the mechanism of liquid surface in interior corner and the applicability of Surface Evolver
Authors: Xu Sheng-Hua  , Wang Lin-Wei  , Sun Zhi-Wei  , Wang Cai-Xia  ,   Key Laboratory of Microgravity, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

The study on the fluid behavior under microgravity condition is of great importance for the investigation of the fluid behavior caused by surface tension, the prediction and control of the liquid location at microgravity, the fluid management in space, etc. In this study, we analyze the relationship between the contact angle and the direction of the contact line in interior corner of container, and compare it with the Concus-Finn theory. The mechanism of mutual correlation among the direction of contact line, the contact angle and the geometric shape of container, and the physical meaning of relevant theory by Concus and Finn etc. are also analyzed. By comparing the theoretical results with the numerical results calculated by Surface Evolver, we find that the Surface Evolver program can predict the contact line and the liquid surface in interior corner with angle smaller than 180°, simply by the automatically partitioned grid. However, when the angle of the interior corner is larger than 180°, the results given by Surface Evolver can have a remarkable error with the automatically partitioned grid. In order to reduce the error, it is necessary to manually partition the surface to reduce the singularity of grid. And the results from Surface Evolver should be tested quantitatively at the interior corners for complicated containers. The theoretical analysis and the numerical results calculated by Surface Evolver in this study will be helpful for understanding the characteristics and mechanism of liquid surface in interior corner, choosing the applicable parameters for Surface Evolver program, and the future study on the behavior of liquid in interior corner, especially under microgravity condition.
Investigation of the electronic and mechanical properties of Al2O3-AlN solid solution by virtual crystal approximation
Authors: Wang Ying  , Lu Tie-Cheng  , Wang Yue-Zhong  , Yue Shun-Li  , Qi Jian-Qi  , Pan Lei  ,   Key Laboratory of Radiation Physics and Technology of Ministry of Education, Department of Physics, Sichuan University, Chengdu 610064, China;,   International Center for Material Physics, Chinese Academy of Sciences, Shenyang 110015, China;,   Key Laboratory for High Energy Density Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064, China
Published: December 2020

Based on the density functional theory within plane-wave pesudopotential method, the band structure and elastic properties of spinel Al(64 + x)/3(8-x)/3O(32-x)Nx (x=2, 5, 8) and -Al2O3, AlN are calculated. The spinel Al(64 + x)/3(8-x)/3O(32-x)Nx (x=2, 5, 8) are calculated by using the 'virtual crystal approximation'. The results prove it possible to study the Al(64 + x)/3(8-x)/3O(32-x)Nx (x=2, 5, 8) by this approximation. The calculated elastic constants and hardness features accord well with the experimental results. The five structures in the Al2O3-AlN solid solution region all show brittle features and the Al23O27N5 shows the lowest brittleness. High hardness and low brittleness reflect that Al23O27N5 has a great flexural strength. Elastic property analysis confirms the mechanical stability, it also reveals that AlON has highly elastic anisotropy. Band structure analysis shows that the spinel AlON and -Al2O3, AlN are both direct bandgap materials. Hybridizations take place between Al-3p, 3s and O, N-2p orbitals near the Fermi level in the AlON. The calculated results are consistent with relevant experimental results, which provides a theoretical method and reference for the further study.
First-principles study on the effects of high Al doped on the band gap and absorption spectrum of ZnO
Authors: Hou Qing-Yu  , Dong Hong-Ying  , Ying Chun  , Ma Wen  ,   College of Sciences, Inner Mongolia University of Technology, Hohhot 010051, China;,   School of Chemical Engineering, Inner Mongolia University of Technology, Hohhot 010051, China;,   Material Science, Inner Mongolia University of Technology, Hohhot 010051, China
Published: December 2020

According to the density functional theory, using first-principles plane-wave ultrasoft pseudopotential method, we set two different kinds of Zn1-xAlxO supercell models of substituting Zn atom with Al atom and optimige the geomertries for the two models. The total density of states and the band structures are also calculated. The results show that in a range of high doping concentration, when the doping concentration of Al atoms increases, the band gap will be decrease, blue shift will decrease, which accords with the experimental results.
Influence of sintering temperature on thermoelectric properties of La0.1Sr0.9TiO3 ceramics
Authors: Sun Yi  , Wang Chun-Lei  , Wang Hong-Chao  , Su Wen-Bin  , Liu Jian  , Peng Hua  , Mei Liang-Mo  ,   State Key Laboratory of Crystal Materials, School of Physics, Shandong University, Jinan 250100, China;,   Dpartment of Physics, Changji University, Changji 830100, China
Published: December 2020

Ceramic samples of La0.1Sr0.9TiO3 are synthesized by conventional solid state reaction technique at 1440℃, 1460℃, 1480℃ and 1500℃, respectively. Their thermoelectric properties are investigated. X-ray diffraction characterization confirms that the main crystal structure is of perovskite. Scanning electron microscope images indicate that all ceramic samples are dense and compact, and that the average grain size increases with the increase of sintering temperature. Electrical resistivity and Seebeck coefficient of samples are measured in the temperature range between room temperature and 800℃. In general, with the increase of sintering temperature, the electrical resistivity first increases, and then decreases. With the increase of sintering temperature, the absolute Seebeck coefficient first increases, and then decreases. A maximal power factor 21 μW·K-2·cm-1 is obtained at 165℃ for the sample sintered at 1480℃ because of its reletivly high absolute Seebeck coefficient and reletively low electrical resistivity.
Effects of the annealing temperature on microstructure and room-temperature ferromagnetism of N+ ion-implanted ZnO: Mn thin film
Authors: Yang Tian-Yong  , Kong Chun-Yang  , Ruan Hai-Bo  , Qin Guo-Ping  , Li Wan-Jun  , Liang Wei-Wei  , Meng Xiang-Dan  , Zhao Yong-Hong  , Fang Liang  , Cui Yu-Ting  ,   Key Laboratory of Optoelectronic Functional Materials of Chongqing, Chongqing 400047, China;,   College of Physics, Chongqing University, Chongqing 400030, China
Published: December 2020

The Mn-N codoped ZnO thin films are fabricated on quartz glass substrates using the radio-frequency magnetron sputtering technique together with the direct N+ ion-implantation. The effects of annealing temperature on microstructure and room-temperature ferromagnetism of the thin films are investigated. The results indicate that both divalent Mn2+ and trivalent N3- ions are incorporated into ZnO lattice. As the annealing temperature increases, the lattice distortion induced by N+ ion-implantation can decrease, and the N3- may escape from the film, which results in the reducing of acceptor (NO) concentration. Ferromagnetism is observed in the (Mn,N)-codoped ZnO thin film at 300 K and found to be the sensitive to the acceptor concentration. The mechanism of room-temperature ferromagnetism in the ZnO:(Mn, N) is discussed based on the bound magnetic polaron model.
The development and dissemination characteristic of disturbance in weak tropical cyclones
Authors: Tao Jian-Jun  , Hu Xiang-Hui  ,   Department of Geography, Hunan University of Science and Technology, Xiangtan 411201, China
Published: December 2020

The cyclone disturbance in tropical lower atmosphere is the necessary condition of typhoon forming. Satellite cloud imagery and diagnostic analysis both show that the convection represents separate cloud cluster or mesoscale systems in the disturbance. Whether these disturbances can become the typhoon depends on the strength of the convection heating in the mesoscale systems and close degree of the cloud area. This paper deals with the development and mobile of wave driven by conditional instability of second kind (CISK) mechanism through discussing frequency equation and using numerical method. The results show that the mesoscale CISK wave can occur in the tropics weak cyclone. Vertical shear of basic vortex circulation can significantly strengthen unstable effect of this wave to make fluctuation quickly develop. Vertical shear of basic vortex circulation can also make the wave move toward the center of basic vortex circulation and its group velocity points to the center too. The numerical calculation and the examples show that the disturbance will develop rapidly and move towards the center too.
Research on non-linear beam-wave interaction of W-band gyro-TWT with helical waveguide
Authors: Xue Zhi-Hao  , Liu Pu-Kun  , Du Chao-Hai  , Li Zheng-Di  ,   Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China;,   Graduate University of the Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

Gyro-TWT is one of the most promising candidates for the application of the transmitter microwave source of the next-generation imaging radar; meanwhile, it plays an important role in national security. Gyro-TWT with helical waveguide is capable of generating broad-bandwidth radiation, as well as high stable ability. In this paper, we derive the dispersion equation of helical waveguide and the non-linear theory of calculating the beam-wave interaction. Numerical stimulation results accord with the experimental results. We design a W-band gyro-TWT operating at a 80 keV, 5 A electron beam, which can produce an output power of 142 kW, with 3 dB bandwidth 4.5%, cantral frequency 95 GHz and saturation gain 52 dB. Finally, we calculate the effect of variation of voltage and current on the output performance of gyro-TWT with helical waveguide.
Stabilities and bifurcations of sine dynamic equations on time scale
Authors: Hu Wen  , Zhao Guang-Hao  , Zhang Gong  , Zhang Jing-Qiao  , Liu Xian-Long  ,   College of Electronic and Information Engineering, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China;,   Nanjing Changjiang Electronics Group CO., LTD, Nanjing 210037, China
Published: December 2020

A time scale is a nonempty closed subset of the real numbers R. Recently, the dynamic equations on time scale have received much attention, which have the generalized forms of differential and differential dynamic equations. In this paper, we study the stabilities of fixed points and bifurcations of the sine dynamic equations on time scale. The results show that the solutions of the sine dynamic equations become different with the time scale parameter changing. And n-period-doubling bifurcations and splits of fixed points are observed. Moreover, the chaotic parameter spaces of the dynamic equations are expanded by the increase of complexity of time scale but without increasing the system parameter, thus providing a potential advantage for chaos encryption, radar waveform design and other application areas.
Study on period doubling bifurcation in current-mode SEPIC converter
Authors: Li Guan-Lin  , Li Chun-Yang  , Chen Xi-You  , Mu Xian-Min  ,   Department of Electrical Engineering, Dalian University of Technology, Dalian 116023, China
Published: December 2020

Choosing the current of the front inductor as control object, the discrete time model of single-ended primary-inductor converter (SEPIC) converter working in the discontinuous conduction mode (DCM) is established in this paper, and the stability of the fixed point is analyzed. By studying the phase portrait, power spectrum and bifurcation diagram of the circuitry, a special period-doubling bifurcation phenomenon is found in this circuitry. The circuit experiences period, double period, quadruple period and then double period, quadruple period, finally enters into chaotic condition. The experimental results accord with the simulation results, which confirms that the special period-doubling bifurcation exists in the SEPIC converter working in the DCM.
A novel method of estimating parameter and its application to blind separation of chaotic signals
Authors: Wang Shi-Yuan  , Feng Jiu-Chao  ,   School of Electronic and Information Engineering, Southwest University, Chongqing 400715, China;,   School of Electronic and Information Engineering, South China University of Technology, Guangzhou 510641, China
Published: December 2020

To estimate effectively parameters of nonlinear mapping, a cubature rule is used to approximate the weighted integral of this mapping. In this paper, based on these parameters modeled by a state-space model, a novel parameter estimation is proposed. Blind separation of chaotic signals is a challenging problem. The proposed method is used to solve this problem to achieve the effective reconstruction of chaotic signals. Simulation results indicate that the proposed method has a faster convergence speed and a higher numerical accuracy, and can effectively separate original chaotic signals.
The beam propagation factor and the kurtosis parameter of a Gaussian vortex beam
Authors: Zhou Guo-Quan  ,   School of Sciences, Zhejiang A & F University, Lin'an 311300, China
Published: December 2020

Based on the definition of the second-order moment of intensity, the analytical expression for the beam propagation factor, namely the M2 factor, of a Gaussian vortex beam is derived, which is uniquely determined by the topological charge n. The numerical result indicates that the M2 factor of a Gaussian vortex beam increases with the increase of topological charge n. By means of the higher-order moment of intensity, the analytical expression for the kurtosis parameter of a Gaussian vortex beam passing through a paraxial ABCD optical system is also presented, which depends on topological charge n, parameter δ, transfer matrix elements A and D. When propagating in free space, the kurtosis parameter of a Gaussian vortex beam is determined by topological charge n and parameter δ. With the increase of parameter δ, the kurtosis parameter of a Gaussian vortex beam in free space first decreases and finally tends to a minimal value. Moreover, the kurtosis parameter of a Gaussian vortex beam in free space decreases with the increase of topological charge n. This research is helpful for the practical application of the Gaussian vortex beam.
Analysis of the facula of partially coherent vortex beam in propagation
Authors: Ding Pan-Feng  , Pu Ji-Xiong  ,   College of Information Science and Engineering, Huaqiao University, Xiamen 361021, China
Published: December 2020

The propagation law of the cross spectrum density is employed to derive the analytical expression of the elements of the cross spectrum density matrix in the observation plane for partially coherent vortex beam after propagation under the condition of paraxial approximation. Based on the derived result, the intensity distribution in the observation plane is analyzed. It is shown that different from the completely coherent vortex beam, the partially coherent votex beam has an intensity of the center-point in the observation plane, which gradually becomes prominent after propagation, and the intensity distribution in the observation plane tends to the distribution of Gaussian-like type with the increase of propagation length. The evolution of intensity distribution depends on the topological charge and correlation length of the source beam. On the condition that other parameters of the source beam are invariable, the beam will evolve fast if the topological charge is small and the correlation length is short. Finally, for the first-order partially coherent vortex beam, the detail of the evolution of the beam shape is investigated by studying the extremum of the intensity in the observation plane. And the theoretical proof is presented for the rule of the evolution of the beam.
Experimental study of 8-bits information transmission system based on orbital angular momentum of light beams
Authors: Qi Xiao-Qing  , Gao Chun-Qing  , Xin Jing-Tao  , Zhang Ge  ,   School of Optical-Electronics, Beijing Institute of Technology, Beijing 100081, China
Published: December 2020

An experimental setup is built to realize 8-bits information transmission based on orbital angular momentum (OAM) of light beams. In the modulation section, a controllable laser diode array and a stable phase modulator are used to superpose and encode the OAM states. A binary amplitude grating is used to detect the OAM states in the demodulation part. This system transmits 8-bits data successfully.
Off-focus generation of strong super-continuum emission in fused silica using high power femtosecond laser pulses
Authors: Feng Liu-Bin  , Lu Xin  , Liu Xiao-Long  , Ge Xu-Lei  , Ma Jing-Long  , Li Yu-Tong  , Chen Li-Ming  , Dong Quan-Li  , Wang Wei-Min  , Teng Hao  , Wang Zhao-Hua  , Sheng Zheng-Ming  , Wei Zhi-Yi  , He Duan-Wei  , Zhang Jie  ,   Department of Physics and Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610064, China;,   Beijing National Laboratory for Condensed Matter Physics, Institute of Physics, Chines Academy of Sciences, Beijing 100190, China;,   Key Laboratory for Laser Plasmas of the Ministry of Education of China and Department of Physics, Shanghai Jiaotong University, Shanghai 200240, China
Published: December 2020

We report on the generation of millijoules supercontinuum, which covers waveband from ～ 400 nm to ～ 900 nm wavelength, by intense femtosecond laser pulse propagating in 3 mm thick fused silica. The fused silica is placed in front of the geometric focus of incident laser pulse to prevent the breakdown. The dependences of supercontinuum spectrum on incident pulse energy and off-focus distance of medium are investigated in detail. Our work demonstrates that strong supercontinuum can be generated using off-focus pump of solid transparent medium with energetic incident pulses.
The study of meteorological effects and time variations of the fair weather atmospheric electric field near ground in YBJ, Tibet
Authors: Xu Bin  , He Hua  , Yang Xiao-Yan  , Bie Ye-Guang  ,   College of Science, Hubei University of Technology, Wuhan 430068, China
Published: December 2020

Based on the fair weather atmospheric electric field recorded by YBJ Cosmic Ray Station located at the YBJ High Altitude Cosmic Ray Laboratory (90° 31'50" E, 30° 06'38" N, 4300 m a.s.l., 606 g/cm2), Tibet, China, its meteorological effects and time variations are studied. The analysis in this paper is to look into how the factors like atmospheric pressure, temperature and relative humidity in the presence of the meteorological factors in four seasons govern the fair weather atmospheric electric field at the site of measurement. The results of meteorological effects show that there is a strong positive correlation between the fair weather atmospheric electric field and temperature, while a moderate positive correlation is seen between the fair weather atmospheric electric field and the atmospheric pressure, also the relative humidity. The long-term variations of the fair weather atmospheric electric field are affected by seasons. The mean value is higher in summer and fall, but lower in winter and spring. The daily variation of the fair weather atmospheric electric field is modulated by solar diurnal, semi-solar diurnal, and its third and fourth harmonic component. The higher the harmonic frequency, the lower the modulate amplitude is. The daily variation curves show bimodal variation with evening peak and sunrise peak. Two minima can also be seen in early morning and evening. Sunrise peak value is highest during summer and fall, but lowest in spring and winter morning. Sunrise peak occurs at around noon, and evening peak is modulated by the season effects.
Helicities and thermostabilities of Ni nanowires in the carbon nanotubes
Authors: Du Yu-Guang  , Zhang Kai-Wang  , Peng Xiang-Yang  , Jin Fu-Bao  , Zhong Jian-Xin  ,   Faculty of Materials, Optoelectronics and Physics, Institute for Quantum Engineering and Micro-Nano Energy Technology, Xiangtan University, Xiangtan 411105, China
Published: December 2020

Molecular dynamics calculations are performed to study the structures of armchair carbon nanotubes (CNTs) encapsulating Ni nanowires and their helicities and thermal stabilities are discussed. It is found that Ni nanowires are of multiple helical tubular structure and each layer is composed of several Ni atom chains. Different layers of Ni nanowires have different helicities and the helicities of Ni nanowires in the inner layer are greater than those of the outer one. What is more, the helicity will be greatest when the number of the Ni atom chains is an integer multiple of three. As the increases of the diameters of the CNTs, the helicities of Ni nanowires change periodically. The structure and helicity only have tiny variations even at high temperature as the CNTs can protect the Ni nanowire.
First-principles study of p-type ZnO by Te-N codoping
Authors: Yao Guang-Rui  , Fan Guang-Han  , Zheng Shu-Wen  , Ma Jia-Hong  , Chen Jun  , Zhang Yong  , Li Shu-Ti  , Su Shi-Chen  , Zhang Tao  ,   Institute of Opto-Electronic Materials and Technology, South China Normal University, Guangzhou 510631, China;,   Experimental Teaching Center, Guangdong University of Technology, Guangzhou 510006, China
Published: December 2020

The crystal structure, density of states and electronic structures of Te-N doped ZnO are investigated from the first-principles pseudo-potential approach based on density functional theory. It is found that the incorporation of N into ZnO induces contraction of lattice, while Te incorporation will cause expansion of lattice. Thus, the co-doping of both Te and N is conducible to the incorporation of N with minimum lattice strain. Besides, Te atoms is positively charged because the electronegativity of Te is smaller than that of O. Consequently, Te atom is expected to act as an isoelectronic donor in ZnO. Moreover, the acceptor level of N doped ZnO is narrow and deep. While in the Te-N doped ZnO system, N-impurity bandwidth at the top of valence band becomes larger, while tends to delocalize the hole. Meantime, the system obtains shallower acceptor levels and lighter mass of acceptors. The results suggest that the codoping of Te-N is an effective p-type doping method in ZnO.
Study on the electronic structures and energy band properties of Cd-doped wurtzite BeO
Authors: Zheng Shu-Wen  , Fan Guang-Han  , He Miao  , Yao Guang-Rui  , Chen Jun  , He Long-Fei  ,   Institute of Opto-electronic Materials and Technology, South China Normal University, Guangzhou 510631, China;,   Experimental Teaching Center, Guangdong University of Technology, Guangzhou 510006, China
Published: December 2020

The electronic structures and energy band properties of the Cd-doped wurtzite BeO are investigated by plan-wave pseudopotential method with the generalized gradient approximation in the frame of density functional theory. The theoretical results show that the valence band maximum is determined by O 2p states and the conduction band minimum is occupied by Cd 5s and Be 2s orbitals based on the total density of states and partial density of states of Be1-xCdxO alloy. With the Cd content x of Be1-xCdxO increasing, the repulsion effect between Cd 4d and O 2p states is more enhanced and the bandgap of Be1-xCdxO is reduced. At the same time, the bandgap undergoes the direct-indirect-direct transition. In order to obtain the theoretical values in accord with the experimental results, the bandgaps of Be1-xCdxO are corrected. Moreover, the relations among energy bandgap, bowing parameter and lattice constant of the wurtzite BeO-ZnO-CdO ternary alloy are analyzed.
Study of stability of persistent spin helix in two-dimensional electron gases with spin-orbit coupling
Authors: Zhang Lei  , Li Hui-Wu  , Hu Liang-Bin  ,   Laboratory of Quantum Information Technology, School of Physics and Telecommunication Engineering, South China Normal University, Guangzhou 510631, China
Published: December 2020

We study theoretically the stability of persistent spin helix in two-dimensional electron gases with spin-orbit coupling by a semi-classical spin density matrix method. The possible influences of disordering scattering, temperature, spin-orbit coupling strength and external electric field on the lifetime of persistent spin helix state are investigated. The theoretical results are found to be in agreement with some recent relevant experimental results.