bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of doping on the photoluminescence of multilayer Ge quantum dots deposited on Si(001) substrate
Authors: Liu Zhi  , Li Ya-Ming  , Xue Chun-Lai  , Cheng Bu-Wen  , Wang Qi-Ming  ,   State Key Laboratory of Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
Published: December 2020

Four-bilayer Ge quantum dots (QDs) with Si spacers were epitaxially grown on Si(001) substrates by means of ultrahigh vacuum chemical vapor deposition. In two samples, Ge QDs were in situ doped with phosphorus or boron, separately. Surface morphology and room temperature photoluminescence (PL) of multilayer Ge/Si QDs wer studied. Compared with the undoped Ge QDs, phosphorus-doping did not change the morphology of Ge QDs, enhanced PL wer observed from the phosphorus-doped Ge QDs. But reduction of Ge QDs density and PL intensity wer observed from the boron-doped Ge QDs. The intensity enhancement of PL could be attributed to the sufficient supply of electrons in Ge QDs for radiative recombination.
First principles calculation of adsorption for H2S on Fe(100) surface
Authors: Luo Qiang  , Tang Bin  , Zhang Zhi  , Ran Zeng-Ling  ,   State Key Laboratory of Oil and Gas Reservoir Geology and Exploitation, Southwest Petroleum University, Chengdu 610500, China;,   College of Science, Southwest Petroleum University, Chengdu 610500, China;,   Key Laboratory of Optical Fiber Sensing & Communication of the Ministry of Education, University of Electronics Science & Technology of China, Chengdu 611731, China
Published: December 2020

In contrast to the results of sulfur atom adsorption, the adsorption of hydrogen sulfide on the Fe(100) surface has been studied using first principles method, which is based on the density functional theory (DFT). The structures, electronic properties were calculated by the generalized gradient approximation (GGA) for the coverage of 0.25 monolayer (ML). The results show that the H2S adsorbed on B2 site is stable and the adsorption energy is -1.23 eV and the structure of H2S is little changed. While the density of states (DOS) for the adsorption of hydrogen sulfide in the most unstable state after the adsorption at B1 and most stable adsorption at the site of B2 are analyzed. We have compared, under same conditions, the electronic properties of the sulfur atoms of the adsorbed hydrogen sulfide and a single sulfur atom adsorbed on Fe(100) surface. The adsorption effect is very weak for sulfur atoms in adsorbed hydrogen sulfide. At the same time, the density of states for the adsorption of Fe(100) surface was studied comparatively, and we found that the sulfur atom adsorption on Fe(100) showed a series of peaks that have discrete distributions generated by ferrous sulfide. It shows that the adsorption is given by sulfur atoms instead of molecules of hydrogen sulfide.
Physical compact modeling for threshold voltage of strained Si NMOSFET
Authors: Zhou Chun-Yu  , Zhang He-Ming  , Hu Hui-Yong  , Zhuang Yi-Qi  , Su Bin  , Wang Bin  , Wang Guan-Yu  ,   Key Laboratory for Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi’an 710071, China;,   School of Electronic and Information Engineering, Liaoning Technical University, Huludao 125105, China
Published: December 2020

The development of strained-Si physical compact threshold voltage model is based on Poisson's equation, using the gradual channel approximation (GCA) and coherent quasi-two-dimensional (2D) analysis, as well as taking into account the effects of short channel effect (SCE), narrow channel effect (NCE), non-uniform doping effect, and drain-induced barrier lowering (DIBL) effect. Moreover, the threshold voltage parameters are extracted from the experimental results by software. Finally, the validity of our model is derived from the comparison of our simulation results. The proposed model may be useful for the design and simulation of very large scale integrated circuits (VLSI) made of strained-Si.
The phase transformation of Cu(In,Ga)Se2 film prepared by three-stage process of co-evaporation
Authors: Liu Fang-Fang  , Zhang Li  , He Qing  ,   Institute of Photoelectronic Thin Film Devices and Technique, Nankai University, Tianjin 300071, China
Published: December 2020

The Cu(In, Ga)Se2 (CIGS) phase transformation during the "three-stage" evaporation is the key problem for obtaining high-quality absorber. Cu(In, Ga)Se2 (CIGS) thin film has been prepared via co-evaporation "three-stage process". The phase transformation was studied by means of XRD, XRF (X-ray fluoroscopy) and SEM. And the efficiency above 15% of CIGS film solar cell was obtained succossfully.
Analytical I-V model and numerical analysis of single electron transistor
Authors: Su Li-Na  , Gu Xiao-Feng  , Qin Hua  , Yan Da-Wei  ,   Key Laboratory of Advanced Process Control for Light Industry (Ministry of Education), Department of Electronic Engineering, Jiangnan University, Wuxi 214122, China;,   Key Laboratory of Nanodevices, Suzhou Institute of Nano-tech and Nano-bionics, Chinese Academy of Sciences, Suzhou 215123, China
Published: December 2020

The analytical I-V model of single electron transistor has been established and simulated by combining the Monte Carlo method with the Master Equation method. Effects of gate voltage, drain voltage, temperature, and tunneling junction resistance on electrical characteristics of a single electron transistor are analyzed. Simulation results indicate that for the device with symmetrical tunneling junction structure, the Coulomb staircases shift with increasing gate voltage, and the Coulomb oscillation amplitude increases with increasing drain voltage, while the Coulomb gaps decrease. The Coulomb staircases and the Coulomb oscillation disappear gradually with increasing temperature. The Coulomb blockade effects become more significant when the resistance ratio of the two asymmetrical tunneling junctions increases.
The preparation and characteristics research of high mobility amorphous indium gallium zinc oxide thin-film transistors
Authors: Li Shuai-Shuai  , Liang Chao-Xu  , Wang Xue-Xia  , Li Yan-Hui  , Song Shu-Mei  , Xin Yan-Qing  , Yang Tian-Lin  ,   Department of Space Science and Physics, Shandong University at Weihai, Weihai 264209, China
Published: December 2020

Indium gallium zinc oxide (IGZO) is widely used in thin-film transistors (TFT) as an active layer due to its high mobility and transmittance. The amorphous n-type indium gallium zinc oxide thin-film transistors (IGZO-TFT) of bottom gate with high mobility were prepared, the active layer, source and drain electrode of the TFT were prepared by using magnetron sputtering method, and a low cost mask was used to control the size of the channel. The diffraction pattern and transmittance spectrum were measured by using X-ray diffraction and ultraviolet-visible spectrophotometer, respectively. The structural and optical properties of the IGZO thin film were studied. The dependence of active layer thickness on the performance was analyzed by testing the output characteristics and transfer property of IGZO-TFT. The field effect mobility of the IGZO-TFT reaches 15.6 cm2·V-1·s-1, and the on/off ratio is higher than 107.
Influence of liquid flow on cellular and dendritic spacings
Authors: Wang Xian-Bin  , Lin Xin  , Wang Li-Lin  , Yu Hong-Lei  , Wang Meng  , Huang Wei-Dong  ,   State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China
Published: December 2020

The cellular and dendritic formations are two kinds of typical morphology in the solidification, and there are many theoretical models and experimental researches on them. Most models and researches are based on purely diffusive transport mechanism. However, convection effects are of importance in the evolution of cellular and dendritic growth. Since the metal materials are not transparency and the researches on microstructure only after quenching, it is difficult to observe the dynamic microstructure evolution in real time. In this paper, the effect of liquid flow on the cellular and dendritic growth was investigated by the in-situ observation of SCN-1.8 wt% Ace transparent alloy during the directional solidification under the liquid flow. The cellular tip splitting is found in the presence of liquid flow and the cellular microstructure is smaller after the cellular tip splitting. The cellular spacing decreases as the flow rate becomes larger, but the spacing will become steady ultimately. At high growth rate the dendritic spacing increases with the increase of the flow rate, because the upstream side branches, which are accelerated by liquid flow, will suppress adjacent branches. But, at low growth rate the dendritic spacing decreases with the increase of the flow rate, because the lateral branches will exceed the tip of dendrite to form new dendrite by liquid flow.
Antenna cross-polarization correction for spaceborne polarimetric microwave correlation radiometer (I): Derivation of the antenna temperature equation
Authors: Shi Jian-Kang  , Lu Wen  , Yan Wei  , Ai Wei-Hua  ,   Unit 63655 of PLA, Urumchi 841700, China;,   College of Meteorology and Oceanography, PLA University of Science & Technology, Nanjing 211101, China;,   CMA Key Laboratory for Atmospheric Physics and Environment, Nanjing University of Information Science and Technology, Nanjing 210044, China
Published: December 2020

Spaceborne polarimetric microwave correlation radiometer is a new type of instrument for the passive microwave remote sensing from space, which can provide an important way for remote sensing of sea surface wind vector and other ocean atmosphere environmental parameters. Antenna cross-polarization correction is an important part of the data pre-processing algorithm. In this paper, for the demand of antenna cross-polarization correction in spaceborne polarimetric microwave correlation radiometer, we have independently derived the full polarization antenna temperature equation based on the polarization coherent detection theory and the definition of Stokes parameters. The equation for the four parameters of Stokes antenna temperature introduced the cross polarization amplitude and phase between the Stokes parameters. Besides, the influence of the polarization rotation angle on the antenna pattern computation was considered. Finally, we established a geometric correspondence between the antenna scanning beam and the earth scene. The principle for determining the parameters of the antenna temperature equation was also discussed. Stokes antenna temperature equation laid the foundation for antenna cross-polarization correction for spaceborne polarimetric microwave correlation radiometer in the future.
Antenna cross-polarization correction for spaceborne polarimetric microwave correlation radiometer (II): Correction experiment
Authors: Lu Wen  , Yan Wei  , Ai Wei-Hua  , Shi Jian-Kang  ,   College of Meteorology and Oceanography, PLA University of Science & Technology, Nanjing 211101, China;,   CMA Key Laboratory for Atmospheric Physics and Environment, Nanjing University of Information Science and Technology, Nanjing 210044, China;,   Unit 63655 of PLA, Urumchi 841700, China
Published: December 2020

In this paper, we simulated the earth scene brightness temperature by creating the earth scene data sets and using polarimetric microwave radiative transfer model. On the basis of the fully polarized antenna temperature equation we have derived, the radiometer antenna temperature was also simulated by generating antenna pattern through GRASP9 software. Then by using multiple linear regression method, the M matrix was calculated and the antenna cross-polarization correction for spaceborne polarimetric microwave correlation radiometer was realized. The correction results show that the antenna temperature and earth scene brightness temperature have a linear relationship. Antenna cross-polarization influences the orthogonal channels brightness temperature seriously, especially the vertical polarization brightness temperature. The antenna cross-polarization for each channel has been effectively reduced. Residual cross-polarization is better than -23 dB and the polarization purity is greater than 99.5%. Correction of using M matrix to eliminate the antenna cross-polarization is feasible. It has been proved that this technique is most appropriate for the final correction of antenna cross-polarization for the spaceborne polarimetric microwave correlation radiometer on orbit.
Swarm initialization of shuffled frog leaping algorithm for cooperative spectrum sensing in cognitive radio
Authors: Zheng Shi-Lian  , Yang Xiao-Niu  ,   School of Telecommunications Engineering, Xidian University, Xi’an 710071, China;,   Science and Technology on Communication Information Security Control Laboratory, Jiaxing 314033
Published: December 2020

A swarm initialization method is proposed for modified shuffled frog leaping algorithm (SFLA) for linear combination cooperative spectrum sensing in cognitive radio. The solution obtained by modified deflection coefficient optimization is included in the initial swarm of SFLA, thus improving the performance of the algorithm at the early stage of the search. Simulations show that compared with the traditional swarm initialization technique, the proposed swarm initialization can obtain expected solutions faster, which means that the proposed technique can save computation time and is more suitable for real time applications.
A method of abrupt change process analysis based on Logistic model and its applications
Authors: Yan Guan-Hua  , Yan Peng-Cheng  , Hou Wei  , Wu Hao  ,   Nanjing University of Information Science & Technology, School of Atmospheric Sciences, Nanjing 210044, China;,   Training Center, China Meteorological Administration, Beijing 100081, China;,   College of physics and electronic engineering, Northwest Normal University, Lanzhou 730070, China;,   National Climate Center, China Meteorological Administration, Beijing 100081, China;,   Department of Physics, Yangzhou University, Yangzhou 225002, China
Published: December 2020

The traditional detection method of abrupt change may pay more attention on the "point of abrupt change" and neglect the process of its onset, development and extinction. This paper has proposed a new detection method to obtain the abrupt change process (ACP); it can extract suitable parameters from real time series by using a piecewise function which is based on a logistic model that reflects the ACP. With the help of parameters' physical meaning, we researched and analyzed the whole ACP, deepened the understanding and awareness of ACP, to lay the scientific foundation for further study on the formation mechanism, affecting factors and trends of the abrupt change. Besides, by detecting the PDO time series' ACP, we also find that the time series began to change in 1940/1942, 1977, 1987, and the duration of abrupt change is locked in some fixed values; furthesmore, the phase graph of the system showed that a normal system world have 3 basic states.
Stochastic resonance of over-damped bistable system driven by chirp signal and Gaussian white noise
Authors: Peng Hao  , Zhong Su-Chuan  , Tu Zhe  , Ma Hong  ,   College of Mathematics, Sichuan University, Chengdu 610065, China
Published: December 2020

It is improper to use frequency domain signal-to-noise ratio as a measure to judge whether stochastic resonance happens with chirp signal which is common in engineering. As a result, there is little literature on this subject. Using the energy aggregation in an optimal fractional Fourier transform domain of chirp signal, in this paper we propose a new signal-to-noise ratio defined in an optimal fractional domain to study the stochastic resonance of over-damped bistable system driven by chirp signal and Gaussian white noise. A new phenomenon is found, that is, the stochastic resonance phenomenon weakens gradually as the frequency of chirp signal increases. And it is reasonably explained in this paper. The consistency of simulation results with theoretical analysis verifies the effectiveness of the method proposed in this paper.
Traffic dynamics of the complex networks with the heterogeneous bandwidth allocation
Authors: Yu Hao  , Zhou Yu-Cheng  , Jing Yuan-Wei  , Xu Jia-He  , Zhang Xing-Mei  , Ma Yan  ,   School of Information Science and Engineering, Northeastern University, Shenyang 110004, China;,   Research Institute of Wood Industry, Chinese Academy of Forestry, Beijing 100091, China;,   School of Economy and Tradition, Qingdao University of Technology, Qingdao 266520, China
Published: December 2020

How to improve the network traffic capacity (load), in complex networks with the connection edge by which the transmission capacity (bandwidth) is limited, is the main subject of the research in this paper. We propose a heterogeneous bandwidth allocation scheme under the condition of the fixed total bandwidth resource of the network. With an appropriate proportion of 'controlled edge', the bandwidth resource is reallocated in the network. According to the data flow model, with congestion awareness routing strategy, bandwidth allocation we proposed can adjust the data flow and improve the efficiency of bandwidth utilization. Finally, the network traffic capacity is significantly improved compared with the one in the homogeneous bandwidth allocation. Meanwhile, it does not destroy the premise of the network topology by using our bandwidth allocation. In this paper, we make a series of simulation using the heterogeneous bandwidth allocation in the Barabsi-Albert scale-free network and the Watts-Strogats (WS) small world network, and find that there is a strong correlation between the network traffic capacity and the bandwidth of vertex in the WS network.
Energy carriers investigation in the Fermi-Pasta-Ulam β lattice
Authors: Yuan Zong-Qiang  , Chu Min  , Zheng Zhi-Gang  ,   Beijing-Hong Kong-Singapore Joint Center for Nonlinear and Complex Studies, Department of Physics, Beijing Normal University, Beijing 100875, China
Published: December 2020

Recently, heat conduction in low-dimensional materials has attracted much attention. The energy carriers responsible for the heat conduction in the Fermi-Pasta-Ulam (FPU) β lattice is still in debate. To the best of our knowledge, the sound velocity of energy transfer has been measured to examine the properties of the energy carriers, by using both nonequilibrium and equilibrium approaches. Nevertheless, the uncertainty of the computational data is too large to distinguish between the two predictions based on soliton theory and effective-phonon theory. In this paper, the spatiotemporal propagation of a momentum excitation traveling along the FPU-β lattice is investigated. The harmonic and anharmonic couplings induce the dispersion and localization of a energy packet on the lattice, respectively. The bifurcation of a solitary wave takes place as the energy of the packet exceeds a threshold. Based on the "acoustic vacuum" phenomenon in the pure quartic lattice, a two-segment lattice composed of the FPU-β chain and the pure quartic chain is constructed. The heat flux in the two-segment lattice is studied to compare with that in the FPU-β lattice. The ratio of the heat flux of the two-segment lattice to the FPU-β lattice increases monotonically as temperature rises. We conclude that phonons are the majority energy carriers in the low temperature regime, while solitons become dominant carriers as the temperature increases. The spatiotemporal propagation of a momentum excitation traveling along the two-segment lattice is also investigated. Phonon packets excited in the FPU-β part are reflected at the interface while solitary waves can pass through the interface. This supports microscopically our conclusion on the energy carriers in the FPU-β lattice.
Chaotic behaviors and fractal self-similar analysis of particles transport properties in RIKEN mesoscopic devices
Authors: Yang Qin-Nan  , Zhang Yan-Hui  , Cai Xiang-Ji  , Jiang Guo-Hui  , Xu Xue-You  ,   College of Physics and Electronics, Shandong Normal University, Jinan 250014, China;,   Information Research Institute, Shandong Academy of Sciences, Jinan 250014, China
Published: December 2020

The theoretical model of RIKEN mesoscopic device in our study is one kind of the two-dimensional Sinai billiards, which is an ideal model to investigate the chaotic and fractal behaviors in particle escape curves. In the analysis of the escape curves, we use two methods:qualitative comparison and quantitative calculation of the fractal dimensions. Then we obtain the influence of the distribution of chaotic areas caused by the opening width, cavity length, corner positions, arc radius, etc. In the results, we find the fractal self-similar structure of the escape curves in which the similarity is very good, and they display the chaotic property of the transmission in the RIKEN device. Moreover, we use the eye-style structure analysis and the comparation between similar ratios to investagate the fractal self-similar structure.
Parameter estimation of nonlinear map based on second-order discrete variational method
Authors: Cao Xiao-Qun  ,   School of Computer Science, National University of Defense Technology, Changsha 410073, China
Published: December 2020

In this paper a method is proposed to estimate the unknown parameters of nonlinear map based on the second-order discrete variational method. On the basis of adjoint equations and gradient expressions of cost functional derived from variational method, the second-order adjoint equations and the exact formulas for the Hessian-vector product are educed using the second-order discrete variational method. A new algorithm is given for estimating the unknown parameters of nonlinear maps. The numerical simulations show that all unknown physical parameters of Hyperhenón map and two-dimensional parabolic map are estimated successfully and precisely. Simulation results also demonstrate the validity and advantages of second-order discrete variational method of estimating the parameters of the discrete chaotic systems.
The synchronization of fractional order chaotic systems with different orders based on adaptive sliding mode control
Authors: Huang Li-Lian  , Qi Xue  ,   College of Information and Communication Engineering, Harbin Engineering University,Harbin 150001, China
Published: December 2020

In this paper, based on sliding mode control and adaptive control theory, the synchronization of two different fractional order chaotic systems is investigated. First, a fractional sliding surface with strong robustness is designed and a suitable adaptive sliding controller is constructed, then the error states of the systems are controlled to the sliding surface via the method to guarantee the synchronized behaviors between two fractional chaotic systems. Numerical simulations on the hyper Chen chaotic systems and Chen chaotic system are also carried out respectively. Simulation results show that the generalized errors tend to zero after a short time, and the effectiveness and feasibility of this method are well verified.
First-principles calculations of h-BN monolayers by doping with oxygen and sulfur
Authors: Zhang Zhao-Fu  , Zhou Tie-Ge  , Zuo Xu  ,   College of Information Technical Science, Nankai University, Tianjin 300071, China
Published: December 2020

Using first-principles calculations based on density functional theory and projector augmented wave method, we investigate the geometric structures, magnetic properties and electronic structures of h-BN monolayer with nitrogen vacancy (VN), nitrogen substituted by oxygen (ON) or sulfur (SN). The results show that the h-BN monolayer with SN presents a larger geometric distortion than with ON and VN. Although the pure h-BN is non-magnetic, all the systems with defects are magnetic with the magnetization value of 1 μB per cell. Spin polarized density of states and energy band structures are presented. By using symmetrical analyses and molecular orbit theory, the formations of impurity energy levels and local magnetic moment are well explained.
Analysis of refractive index characteristics for magnetoelectric metamaterials
Authors: Xu Xin-He  , Wu Xia  , Xiao Shao-Qiu  , Gan Yue-Hong  , Wang Bing-Zhong  ,   Nanchang Hangkong University, Nanchang 330063, China;,   Institute of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

Based on Maxwell's curl equations, the electric component and the magnetic component in magnetoelectric metamaterial plate are equivalent to the surface electric current and the surface magnetic current respectively. By calculating the total electric field and the total magnetic field in a magnetoelectric metamaterial plate generated by these periodic surface electric currents and magnetic currents, we obtain two equations about the surface current density and the surface magnetic current density, and thus deduce the analytical formulas for relationship between the refractive index of periodic magnetoelectric metamaterial and permeability of the magnetic component, and that between permittivity of the electric component and spatial dispersion. Unlike traditional index formula, the analytical formulas fully consider the spatial dispersion and the interaction of the electrical component and the magnetic component. The theoretical curves for refractive index are found to be in good agreement with the retrieval curves from simulation data, which shows that the analytical formulas for the refractive index can correctly describe the negative refraction characteristics of the magnetoelectric metamaterials. Our work will provide important theoretical reference for researchers to analyze interaction between electromagnetic components and to design magnetoelectric metamaterials with negative refractive indexes which meet certain requirements.
Mode selection in surface wave oscillator with overmoded structure
Authors: Li Xiao-Ze  , Teng Yan  , Wang Jian-Guo  , Song Zhi-Min  , Zhang Li-Jun  , Zhang Yu-Chuan  , Ye Hu  ,   Northwest Institute of Nuclear Technology, Xi’an 710024, China;,   Science and Technology on High Power Microwave Laboratory, Xi'an 710024, China
Published: December 2020

More and more overmoded structures have been adopted in electronic vacuum devices because they can increase the power capacity and the frequency of the output signals. Overmoded structure device can more easily work in a low magnetic field. Overmoded structure may cause mode competition, which will reduce the output power. Mode selection in overmoded structure is studied in this article. Dispersion relation is obtained and solved numerically. The results show that the appropriate selection of working point that ensures the device working in a traveling wave state can realize transverse mode selection and appropriation selection of parameter of electron beam and the structure can realize the axial mode selection. The calculation results are verified by particle simulation.
Comparative study of relativistic electron motion stability in a Raman free-electron laser
Authors: Xu Yong-Gen  , Wang Shi-Jian  , Ji Yu-Pin  , Xu Jing-Yue  , Lu Hong  , Liu Xiao-Xu  , Zhang Shi-Chang  ,   Department of Physics, School of Physics and Chemistry, Xihua University, Chengdu 610039, China;,   Institute of Photoelectronics, Southwest Jiaotong University, Chengdu 610031, China
Published: December 2020

In the Raman free-electron laser as a high-power radiation source with megawatt in millimeter and terahertz wave ranges, the stability of relativistic electron motion is of importance for the performance of the device. By making use of the reported MIT experimental data and Kolmogorov entropy, comparative study is carried out on the stability of the relativistic electron motion in a Raman free-electron laser with positive/reversed guide magnetic field. Results show that the wiggler adiabatic field has trivial influence on the stability of electron motion but substantially affects the electron motion itself in both positive and reversed guide magnetic field cases; the self-field of the electron beam deteriorates the motion stability in the case of a positive guide magnetic field, but favors the motion stability in the case of a reversed guide magnetic field.
Inhomogeneity of external magnetic field for permanent magnet
Authors: He Yong-Zhou  ,   Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China
Published: December 2020

From molecular current viewpoint, demagnetizing field and process of permanent magnet, taking rectangular permanent magnets for example, the various factors that affect inhomogeneity of external magnetic field for permanent magnet are analyzed. The results indicate that the macroscopic inhomogeneity of external magnetic field for permanent magnet is closely related to space distance and shape of permanent magnet design. Demagnetizing field of permanent magnet has a complex influence on micro-inhomogeneity of external magnetic field. Technology of permanent magnet such as powder particles, orientation degree, sintering solidification, mechanical processing will affect inhomogeneity of external magnetic field of permanent magnet such as magnetic degree, symmetry, smoothness, etc.
Z-transform algorithm in the finite-difference time domain analysis of ferrite subject to an arbitrary direction of external magnetic field
Authors: Wang Fei  , Wei Bing  ,   Department of Physics, Xidian University, Xi’an 710071, China
Published: December 2020

The susceptibility tensor of saturated magnetized ferrite in frequency domain in laboratory coordinate system is gained by using the transfer matrix between the principal and the laboratory system, and then its form in Z-domain is derived by Z-transform (ZT). The ZT-finite-difference time domain method applied to the ferrite subject to an arbitrary direction of external dc magnetic field is obtained. The co-polarized and cross-polarized backward radar scattering cross-section for a saturated magnetized ferrite sphere are obtained by the presented algorithm. The computed results indicate the correctness and feasibility of the method.
Local spatial frequency of Airy accelerating beams and its applications in the beam design
Authors: Guo Cheng-Shan  , Wang Shu-Zhen  , Rong Zhen-Yu  , Sha Bei  ,   College of Physics and Electronics, Shandong Normal University, Jinan 250014, China
Published: December 2020

Airy accelerating beams have aroused a great deal of interest because of their non-diffracting and self-accelerating properties, which have many potential applications such as in optical micromanipulations, nonlinear optics and vacuum electron acceleration. A key issue in research of the acceleration beam and its applications is how to generate this specific type of beams with high energy efficiency. In this paper, the spatial oscillation properties of the complex amplitude of an accelerating beam are analyzed and a theory describing the accelerating properties of the beam based on its local spatial frequency is proposed. The local spatial frequency of a general Airy beam is calculated through the zero-point coordinates of the Airy function, and an analytical formula accurately describing the local spatial frequency distribution is given. The relationship between the local spatial frequency and the accelerating trajectory of the beam is also given, based on which a simple algorithm for finding the pure-phase expression of an acceleration beam from its given accelerating trajectory is presented. Finally an analytical expression of the pure-phase function of an acceleration beam for generating a circle-arced trajectory is found out, based on which a pure-phase diffractive optical element is designed and demonstrated successfully.
Design of a novel single-mode large mode area infrared chalcogenide glass photonic crystal fibers
Authors: Yi Chang-Shen  , Dai Shi-Xun  , Zhang Pei-Qing  , Wang Xun-Si  , Shen Xiang  , Xu Tie-Feng  , Nie Qiu-Hua  ,   Laboratory of Infrared Materials and Devices, College of Information Science and Engineering, Ningbo University, Ningbo 315211, China
Published: December 2020

Large mode area photonic crystal fibers (PCFs) have attracted much attention, owing to their applications in such as high power delivery, high power fibre amplifiers and fiber lasers. As an ideal candidate for fabricating mid-infrared fibers, chalcogenide glass possesses some unique advantages, such as high refractive indices (2.0-3.5), low photon energies (lower than 350 cm-1), tailorable compositions, and large infrared transmission window(from 1.0 to 20 μm). In this paper, we present a novel type of effectively single-mode chalcogenide glass Ge20Sb15Se65PCF with utra-large mode area as well as small confinement loss (lower than 0.1 dB/m for the fundamental mode, high confinement loss exceeding 2 dB/m for the higher-order mode at 10.6 μm).
Design and fabrication of a novel side-leakage photonic crystal fiber and its propagation properties
Authors: Lou Shu-Qin  , Wang Xin  , Lu Wen-Liang  ,   School of Electronic and Information Engineer, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

A novel side-leakage photonic crystal fiber (SLPCF) is proposed and fabricated by introducing a central elliptical Ge-doped core and side-leakage channel. The propagation properties of the ideal and actual structure are modeled by using full-vectorial finite element method for the rebuilt structure. This SLPCF exhibits good compatibility with the standard single mode fiber (SMF) due to its modal diameter of 9.275 μm which is very close to that of SMF at a wavelength of 1550 nm. Modal birefringence of 0.837× 10-4 and the group birefringence of 1.508× 10-4 are obtained at a wavelength of 1550 nm. Based on the side-leakage PCF, a Sagnac interferometer is constituted for evaluating the properties of the actual SLPCF. Experimental results demonstrate that the second order mode can be efficiently confined and thus single mode operation can be realized in a wavelength range from 1450 nm to 1750 nm when this fiber reaches a certain length. In addition, the average measuring value of group birefringence accords with the numerical result. The proposed SLPCF has a number of potential applications in fiber sensor and fiber components with high performance since the introduction of the side-leakage channel enhances its sensitivity, the environmental parameters such as torsion, curve and strain and so on.
A high-speed fiber polarization controller with high accuracy
Authors: Ma Hai-Qiang  , Li Quan-Yue  , Wang Long  , Wei Ke-Jin  , Zhang Yong  , Jiao Rong-Zhen  ,   School of Science, Beijing University of Posts and Telecommunications, Beijing 100876, China
Published: December 2020

An all-fiber polarizing controller scheme with high speed and high accuracy is proposed. The stability is tested in detail and the system can compensate for the birefringence effects induced by the deformation of the fiber automatically. The system is simple and has high accuracy and efficiency. A preliminary experiment demonstrates that it reaches an high extinction ratio of 31 dB. The experimental results show that this system has prospects for practical applications.
High temperature probe sensor with high sensitivity based on Michelson interferometer
Authors: Yang Shen  , Rong Qiang-Zhou  , Sun Hao  , Zhang Jing  , Liang Lei  , Xu Qin-Fang  , Zhan Su-Chang  , Du Yan-Ying  , Feng Ding-Yi  , Qiao Xue-Guang  , Hu Man-Li  ,   Departmen of Physics, Northwest University, Xi’an 710069, China
Published: December 2020

We propose a high sensitivity fiber optical temperature sensor with simple structure. The sensor is composed of a multimode fiber (MMF) and a short single mode fiber (SMF) whose end is coated with silver film as a reflective mirror. Due to the mismatch between the MMF core and the SMF core, part of guided mode is coupled with the cladding modes of downstream SMF cladding. The mode index difference between the fiber core and cladding is attributed to the phase difference, resulting in interference. When ambient temperature increases, the interference spectrum presents red-drift because of the difference in thermo-dependence. A high temperature sensitivity of 120 pm/℃ is achieved, and the linearity is 99.5%. The configuration is simple and has a compact size, making it a good candidate for distant temperature sensing and oil prospecting.
Sound field separation technique based on equivalent source method and double-layer particle velocity measurements
Authors: Bi Chuan-Xing  , Hu Ding-Yu  , Zhang Yong-Bin  , Xu Liang  ,   Institute of Sound and Vibration Research, Hefei University of Technology, Hefei 230009, China
Published: December 2020

Two sound field separation techniques based on equivalent source method are proposed:one is based on the double-layer pressure measurements and the other is based on the single-layer pressure-velocity measurements. In this paper, a sound field separation technique based on equivalent source method but using the double-layer velocity measurements is proposed. First, the theoretical description of this technique is given, and then numerical simulations and experiments are conducted to demonstrate the validity of this technique. By comparison with the technique based on double-layer pressure measurements, the superiority of the proposed technique in separating particle velocity field is shown. And also, in the numerical simulations, the influences of the strength of disturbing source and the distance between two measurement planes on separation accuracy are investigated.
Thunder acoustic spectrum obtained by using digital signal processing and propagation effects
Authors: Ouyang Yu-Hua  , Yuan Ping  , Jia Xiang-Dong  , Wang Xiao-Yun  , Xue Si-Min  ,   School of Mathematics and Physics, Lanzhou Jiaotong University, Lanzhou 730070, China;,   College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China;,   College of Computer Science and Engineering, Northwest Normal University, Lanzhou 730070, China
Published: December 2020

There are a few references on thunder at present, moreover they are all about thunder frequency spectrum at observation location. However, thunder frequency spectrum in observation location is a distorted signal because of noises and sound attenuation effects. In this paper, thunder signal from lightning discharge channels is obtained in Lanzhou of China. By using digital filter and Fourier transform, thunder frequency spectrum at the observation location is gained. Then, thunder frequency spectrum near lightning discharge channel is computed with the theory of sound propagation effects.
Lattice Boltzmann simulation of the sedimentation of particles with thermal convection
Authors: Mao Wei  , Guo Zhao-Li  , Wang Liang  ,   State Key Laboratory of Coal Combustion, Huazhong University of Science and Technology, Wuhan 430074, China
Published: December 2020

We investigate numerically the sedimentations of solid particles in a fluid with different temperatures using a lattice Boltzmann method. The sedimentation processes of a single particle in an isothermal, hot, or cool fluid are first simulated, and then the sedimentations of two particles with different temperatures are carefully studied. It is found that the dynamics of the two particles with the same temperature is closely related to the Reynolds number and the Grashof number, while the process of two particles with different temperatures are different from that of two particles with the same temperature. The cold particle will eventually descend under the hot particle, and the drafting and kissing phenomenon occurs as Re is large, while the cold particle falls far from the hot one as Re is small.
An experimental study of rectangular under-expanded supersonic jets collision
Authors: Zhang Qiang  , Chen Xin  , He Li-Ming  , Rong Kang  ,   Aeronautics and Astronautics Engineering Institute of Air Force Engineering University, Xi’an 710038, China
Published: December 2020

Rectangular under-expanded supersonic jet collision experiment is carried out under different nozzle distances and jet pressures and compared with that in the case of free jet. Experiments indicate that there are four screech tone modes of supersonic jet collision, switched from one mode to another depending on the nozzle distance and jet pressure. Two normal shock waves are present between nozzles as jet pressure is more than 0.5 MPa and nozzle distance is less than 50 mm, radiating a stable screech tone with a frequency of about 3 kHz. With nozzle distance increasing or jet pressure decreasing, a bow shock is present at one nozzle exit and a normal shock wave appears at the other exit with the collision surface oscillating between them. Collision surface might be kept balanced in the centre of two nozzles with a 9 kHz frequency screech tone, however, it is vulnerable to disturbance and would return to the equilibrium position near nozzle exit or oscillate between nozzles with large amplitude. When jet pressure is less than 0.36 MPa and nozzle distance greater than 70 mm, the collision surface substantially oscillates between the nozzles, radiating a screech tone with a frequency of about 1 kHz which decreases with jet pressure decreasing and nozzle distance increasing.
Special phenomena of droplet impact on an inclined wetted surface with experimental observation
Authors: Liang Gang-Tao  , Shen Sheng-Qiang  , Guo Ya-Li  , Chen Jue-Xian  , Yu Huan  , Li Yi-Qiao  ,   School of Energy and Power Engineering, Dalian University of Technology, Key Laboratory for Desalination of Liaoning Province, Dalian 116024, China
Published: December 2020

The phenomena of droplet impact on an inclined solid surface covered with a pre-existing liquid film are observed using high speed camera at 10000 frames per second. The processes of droplet spreading, liquid sheet formation, splashing and droplet oscillation are observed and analyzed. From the results the relationship between spreading velocity and time is discussed quantitatively. Besides, the effects of impact velocity and impact angle on front and back spreading factors and initiatory spreading velocity are also revealed. At the impact angles ranging from 28.0° to 74.7°, it is found that with the decrease of impact angle, the deformation degree of the droplet oscillation on the film surface increases. The results also indicate that the front spreading factor can increases by increasing impact velocity or by reducing the impact angle, whereas the back spreading factor increases with impact angle increasing. The impact velocity almost has no influence on it. The initial spreading velocity can increase by increasing the impact velocity and the impact angle.
Viscosities and wetting behaviors of Sn-Cu solders
Authors: Zhao Ning  , Huang Ming-Liang  , Ma Hai-Tao  , Pan Xue-Min  , Liu Xiao-Ying  ,   Key Laboratory of Liaoning Advanced Welding and Joining Technology, Dalian University of Technology, Dalian 116024, China;,   School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China
Published: December 2020

The viscosity and surface tension of metal melt are all sensitive physical properties that relate to the liquid structure and also have a certain correlation between them. For electronic packaging materials, both viscosities and surface tensions are very important parameters affecting the processing properties. In this study, the viscosities of Sn-xCu (x = 0.7, 1.5, 2) solder melts are measured by using a torsional oscillation high-temperature viscometer. Abrupt change in viscosity occurrs in a certain range of temperature. The temperature range can accordingly be divided into a low temperature zone and a high temperature zone. The relationship between viscosity and temperature can fit to the Arrhenius equation very well in each temperature zone. The structure characteristics and evolutions of the liquid solders are then discussed. Meanwhile, the surface tensions of the Sn-xCu solders are calculated according to the viscosity values at the corresponding temperatures. The test results of the wetting angle and the spreading rate are in good agreement with the calculations, indicating that the method of using the viscosity values to calculate the surface tensions of binary lead-free solder alloys and evaluate their wettabilities is feasible.
Occupancy sites of uranium atom in goethite by first-principles calculation
Authors: Jin Bao  , Cai Jun  , Chen Yi-Xue  ,   School of Nuclear Science and Engineering, North China Electric Power University, Beijing 102206, China
Published: December 2020

Occupancy sites of uranium atom in goethite are studied by first principles calculations. It is found that the formation energies of substitution (S), octahedral (O), and tetrahedral (T) sites of uranium in goethite are -13.49, -3.86, and -1.60 eV, respectively. The formation energies of dual uranium in S and O sites in goethite are -27.392 and -16.214 eV, respectively, and corresponding binding energies are -0.417 and 1.131 eV, respectively. It is concluded that dual uranium atoms can aggregate together in S site formation in goethite, but not in O site formation.
Quantum path interferences of high-order harmonic generation in two-color Gaussian beams
Authors: Li Xiao-Gang  , Li Fang  , He Zhi-Cong  ,   School of Science, Wuhan Institute of Technology, Wuhan 430073, China
Published: December 2020

The phase matching of the quantum paths in high-order harmonic generation is investigated in two-color laser fields. The results show that the spatial distribution of the laser field is optimized by adjusting the laser beam waist, the phase-matching properties of the long trajectories can be modulated effectively, and then good phase matching for both the two paths can be achieved from on-axis region to off-axis region. A radial clear interference fringe induced by the well phase-matching of two paths can be observed by placing a near-field filter, which has great potential for distinguishing clearly different interference effects and observing higher order trajectories with improved detection sensitivity.
Electronic state of the limited graphene
Authors: Deng Wei-Yin  , Zhu Rui  , Deng Wen-Ji  ,   Department of Physics, South China University of Technology, Guangzhou 510641, China
Published: December 2020

The limited graphene means that two directions of graphene are limited, one is zigzag type boundary and the other is armchair type boundary. Based on the tight-binding model, the electronic state and band of the limited graphene are given analytically. The results show that there are only two kinds of electronic states, i.e., the standing wave state and edge state. For the standing wave state, the wave function is in the form of sine function in two directions; for the edge state, the wave function is in the form of hyperbolic sine function in the direction of armchair boundary and in the form of sine function in the direction of zigzag boundary. The band is composited of total carbon atom number N discrete eigenvalues. The expression of quantitativly calculating the number of eigenvalues of edge state is deduced. Through the density of states of the limited graphene we analyze the existence of the edge state and the consistency in the infinity case. The results from the analitical method are the same as the numerical resullts. When the width of two restricted boundary goes into infinity, the result of the limited graphene tends to that in the infinity case.