bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of the washer-rod structure on high frequency characteristics of wide-gap klystron cavity
Authors: Bai Xian-Chen  , Zhang Jian-De  , Yang Jian-Hua  ,   College of Opto-Electronic Science and Engineering, National University of Defense Technology, Changsha 410073, China
Published: December 2020

Using the HFSS and MAGIC code, influences of the washer/rod structure on the high frequency characteristics and the basic operation of the wide-gap klystron amplifier (WKA) are presented. Generally, the rod structure has a great influence on the space-charge potential depression and the eigenmode resonant frequency of the cavity. Once the rods are employed, the space charge field can be nearly eliminated with only 4 washers. Moreover, the presence of the rods raises the cavity eigenmode resonant frequency by ～ 9.0% due to their comparable lumped inductance to the cavity's inherent inductance. Nevertheless, if only the cavities are tuned to the desired operation frequency, the effect of the rod size on the basic operation of the WKA is expected to be very small.
Study of extended interaction oscillator with folded waveguide in sub-terahertz band
Authors: Zhang Kai-Chun  , Wu Zhen-Hua  ,   THz Research Center, School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

In this paper, a folded waveguide is adopted as a slow wave structure (SWS) of the extended interaction oscillator (EIO). An EIO with frequency 105 GHz in sub-Terahertz band is studied in detail, including the dispersion relation and the impedance of the SWS, and the variation of starting current with the period number, which provides an effective way to reduce starting current. On this basis, from the PIC simulation studies are discussed the EIO beam-wave interaction and output characteristics under the operation modes of low current continuous wave and strong current pulse. Further, the tuning characteristic of the EIO is analyzed, showing that output power reaches 26-50 W and the corresponding frequency range is 105.26-105.31 GHz. By EDM technology two fabrication methods of the SWS are investigated and the transmission properties of the SWS and the window are tested indicating that they are in good agreement with the simulation results.
Decoherence effect of target roughness in synthetic aperture ladar
Authors: Dang Wen-Jia  , Zeng Xiao-Dong  , Feng Zhe-Jun  ,   School of Technical Physics, Xidian University, Xi'an 710071, China
Published: December 2020

Optical heterodyne detection is one of the key techniques for developing synthetic aperture ladar. The decoherence effect caused by the roughness of the target surface is particularly important for the practical use of the synthetic aperture ladar. The effect of the target surface roughness on the echo signal detection is discussed in the paper. One-dimensional and two-dimensional Gaussian random rough surface model are created by the use of the Monte Carlo method. The detection process of the target echo signal is simulated to study the effect of the target surface roughness on the intermediate frequency signal. And two optical heterodyne detection experiments are conducted in which the targets each include a rough surface and a smooth surface to verify the serious decoherence effect of the target roughness on the synthetic aperture laser radar echo signal. Meanwhile, the wavefronts of both the local oscillator and the signal beam are monitored at the position of the detector with a digital wavefront analyzer. The measured phase distribution accords well with the simulation result. It is shown that the phase of the echo signal from a rough surface has a serious distortion. The results obtained could be useful for designing the parameters of the laser source and the receiver, as well as for estimating the detection range of the ladar system.
Three-dimensional thermal effects of the diode-pumped Nd:YVO4 slab
Authors: Zhou Ying  , Dai Yu  , Yao Shu-Na  , Liu Jun  , Chen Jia-Bin  , Chen Shu-Fen  , Xin Jian-Guo  ,   School of Optoelectronics, Beijing Institute of Technology, Beijing 100081, China;,   Department of Foundation, Beijing Union University, Beijing;,   School of Automation, Beijing Institute of Technology, Beijing 100081, China
Published: December 2020

The thermal effects induced by high-power diode pumping in the Nd:YVO4 slab laser crystal are numerically modeled. Using three-dimensional (3D) finite volume method, an accurate numerical solution based on heat transfer equation is achieved. The transient temperature distribution curves and the steady state 3D temperature distributions of the diode double end-pumped, uniformly face-pumped and the periodical face-pumped Nd:YVO4 slab are presented.
Method of designing astigmatic compensation cavity for mode-locked laser based on propagation circle
Authors: Zhang Xiao-Jun  , Yang Fu  , Wang Yong-Gang  , Sun Li-Qun  , Wen Qiao  , Niu Han-Ben  ,   Key Laboratory of Optoelectronic Devices and Systems of Ministry of Education and Guangdong Province, College of Optoelectronic Engineering, Shenzhen University, Shenzhen 518060, China;,   College of Science, HeBei North University, Zhangjiakou 075000, China;,   Department of Applied Physics and Materials Research Center, Polytechnic University, Hong Kong, China;,   State Key Laboratory of Precision Measurement Technology and Instruments, Tsinghua University, Beijing 100084, China
Published: December 2020

The cavities of ultrashort pulsed lasers are mostly based on folded resonators with multi-mirrors. Astigmatism is an important issue to affect the performance of the mode-locked laser. An effective method of astigmatic ally compensating a continuous-wave passively mode-locked laser is presented in this paper. This method, in which the resonator propagation circle graphic theory is used, is easy and intuitive to seek the optimal location of the semiconductor saturable absorber mirror (SESAM), where the astigmatism can be compensated. Theoretical results show that the tangential and the sagittal spot size at the SESAM are equal and that the astigmatism can be compensated, when an SESAM is located at the tangential and the sagittal propagation circle intersection. The mode-locked resonator is insensitive to external perturbation including the vibration and the change of the thermal lens focal length, which leads to the instability of the mode locking operation. The antijamming ability of the resonator is outstanding. The experimental results indicate that the mode-locked laser works in a stabilized continuous-wave mode locking state and operates extremely steadily, when the SESAM is located at the tangential and the sagittal propagation circle intersection. The experimental results of the mode locking lasers show good agreement with the theoretical studies.
Design of tunable optical power splitter based on thermal expansion effect
Authors: Tang Xiong-Gui  , Liao Jin-Kun  , Li He-Ping  , Liu Yong  , Liu Yong-Zhi  ,   School of Opto-Electronic Information, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

The tunable optical power splitter is a key optical component used to dynamically control its optical power at its output ports, which has a wide application in many optical fields. A novel approach to controllable optical power splitter is proposed in this work, which is based on thermal expansion effect resulting in width variation of air gap at the branching point of Y-branch waveguide. The thermal expansion profile and the optical performance are simulated by using the finite element method (FEM). The simulation results show that the tunable optical power splitter can exhibit good performance such as large dynamical range, low dependence of operation wavelength and its optical polarization. In addition, the proposed splitter with a simple structure can be easily designed, fabricated and controlled, which is very useful for potential application in integrated optical system.
Analytical approximations for capillary flow in interior corners of infinite long cylinder under microgravity
Authors: Li Yong-Qiang  , Liu Ling  , Zhang Chen-Hui  , Duan Li  , Kang Qi  ,   Institute of Applied Mechanics, College of Science, Northeastern University, Shenyang 110819, China;,   Institute of Mechanics, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

The capillary flow in interior corners of infinite long cylinder under microgravity environment is investigated by the homotopy analysis method (HAM). Different from other approximate computational method, the HAM totally depends on small physical parameters, and thus it is suitable for most nonlinear problems. The HAM provides us with a great freedom to choose basis functions of solution series, so that a nonlinear problem can be more effectively approximated. The HAM can adjust and control the convergence region and the convergence rate of the series solution through introducing auxiliary parameter and the auxiliary function. The computed result indicates that this method has the advantage of high accuracy.
Lattice Boltzmann modeling of particle inertial migration in a curved channel
Authors: Sun Dong-Ke  , Xiang Nan  , Chen Ke  , Ni Zhong-Hua  ,   School of Mechanical Engineering, Southeast University, Nanjing 211189, China;
Published: December 2020

A three-dimensional coupled model for particle inertial migration in the presence of micro flows is proposed and implemented. In the present model, the kinetic theory based lattice Boltzmann method is used to describe the fluid flows, and the Newton dynamics equation based model is used to describe the translation and rotation of the particle. The fluid and particle model are coupled by the LBM bounceback scheme based moving boundary method. The processes of particle settlement under gravity and particle rotation in the condition of Couette flow take place. The reliability of the present model and algorithm is validated through comparisons between the present simulation and the benchmark tests in the literature. The simulations of particle migration with various radii in an annular curved channel are performed, and the classic velocity distribution of the secondary flow in the channel cross-section is reproduced successfully. The mechanism of the particle radius influencing the particle equilibrium position in the curved channel is discussed. The results show that the particle equilibrium position in the curved channel will approach to the channel inner wall with the increase of radius. The present model is of important value for detailed study of the particle dynamics in micro flows as well as for the design and development of new micro fluidic particle selective chips and devices.
Study on the energy dissipation of macroscopic traffic models
Authors: Liang Jia-Yuan  , Ten Wei-Zhong  , Xue Yu  ,   Institute of Physical Science and Engineering, Guangxi University, Nanning 53004, China
Published: December 2020

In this paper, the energy dissipation formulas of the several typical macroscopic continuum models of traffic flow are derived according to the loss of the kinetic energy of traffic flow on road. The calculation of energy dissipation via two traffic cases: two Riemann initial conditions and the traffic bottleneck on the road indicates the energy dissipation of macroscopic traffic mode is influenced by not only the velocity reduction of the vehicle, but also the velocity gradient of the vehicle and the traffic density along the road, which is different from the result obtained from the CA model.
Research on coupling characteristics of low hybrid wave in the presence of electron cyclotron wave in Tokamak
Authors: Huang Jie  , Bai Xing-Yu  , Zeng Hao  , Tang Chang-Jian  ,   Physics Department of Sichuan university 610064, China;,   Southwestern Institute of Physics 610041, China
Published: December 2020

It is found in the experiments on synergy between low hybrid wave (LHW) and electron cyclotron wave (ECW) that the LHW reflection coefficient decreases with the injection of ECW into plasmas in the presence of LHW. In the present paper, the coupling characteristics of LHW, and the pump-out phenomenon caused by ECW are analyzed theoretically. The analysis shows the law of pump-out and the increase of plasma density in the vicinity of the grill mouth caused by pump-out, there by improving LHW coupling. The conclusion is proved by the experiments. Also, considering the change of the plasma density in the vicinity of the grill mouth caused by pump-out in synergy experiments, the synergy current should be corrected.
Smith fuzzy control of teleoperation rendezvous with variable time delay
Authors: Zhang Bo  , Li Hai-Yang  , Tang Guo-Jin  ,   College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China
Published: December 2020

The control methods of ground-based teleoperation rendezvous with variable time delay are surveyed. With the help of root locus method, the influences of time delay on the stability and performance of the control system are analyzed. Then, a time-delay compensator is designed to transfer the variable delay into a constant. A predictive model is established based on the relative dynamic equations. After that, a multivariable Smith predictor is designed based on the principle of Smith predictor, which makes the control input state variables independent of variable time delay. At the same time, the fuzzy control method is introduced to alleviate the uncertainties in the teleoperation rendezvous system. Finally, semi-physical simulations are carried out to verify the methods presented in this paper. Simulation results show that time-delay compensation and Smith-Fuzzy control are effective in alleviating the variable time delay and model uncertainties in the process of teleoperation rendezvous, and the success probability and control accuracy can be improved.
Partial Bessel electromagnetic wave
Authors: Li Liang-Sheng  , Yan Hua  , Hou Zhao-Guo  , Yin Hong-Cheng  ,   Science and Technology on Electromagnetic Scattering Laboratory, Beijing 100854, China
Published: December 2020

We present the spatially self-bending solutions (the partial Bessel functions) of the Maxwell equations, where the self-bending wave can be produced through launching a group of plane waves that interfere with each other by modulating their initial phases and the emission directions. The self-bending electromagnetic waves accelerating in a circular trajectory preserve the beam shape within a certain propagation distance. Unlike Ariy wave packet, the bending angle of the new self-accelerating wave can be much larger than that of Ariy beam. The Poynting vector of the half Bessel beam shows that the main lobe maintains a propagation-invariant structure and can complete a turn close to 180°. In addition, one pair of half Bessel electromagnetic waves is forbidden to propagate inside a certain area where the designed beam generates the self-shielding region.
Nonsingular terminal sliding-mode observer design for interior permanant magnet synchronous motor drive at very low-speed
Authors: Yuan Lei  , Shen Jian-Qing  , Xiao Fei  , Chen Ming-Liang  ,   National Key Laboratory of Vessel Integrated Power System Technology, Naval University of Engineering, Wuhan 430033, China
Published: December 2020

A nonsingular high-order terminal sliding-mode observer of interior permanent magnet synchronous motor (IPMSM) is presented, of which the state variable is the current of rotor-oriented d-q reference frame, to obtain the accurate information about angular speed and rotor position for high-performance vector control system. A nonsingular terminal sliding-mode observer is used to improve dynamic response of the observer speed and robustness of the current observer, and the high-order sliding mode method is adopted to estimate the chattering phenomenon of the conventional sliding-mode. Meanwhile, to obtain the regulator parameters of speed and current loop, an integral-feedback method of estimating the rotor speed is adopted, and the inner current loop is realized using a decoupling and diagonal internal model control algorithm. Experimental results of 2 MW PMSM drive system show that the proposed method can accurately estimate the position and speed of the rotor, and the system has good dynamic and static performances.
Resonant behavior of a fractional linear oscillator with fluctuating frequency and periodically modulated noise
Authors: Tu Zhe  , Peng Hao  , Wang Fei  , Ma Hong  ,   Department of Mathematics, Sichuan University, Chengdu 610065, China;,   Science and Technology on Electronic Information Control Laboratory, Chengdu 610036, China
Published: December 2020

The resonant behavior of a fractional linear oscillator subjected to both parametric excitation of colored noise and external excitation of periodically modulated noise is considered. Using Laplace transformation technique and Shapiro-Loginov formula, exact expressions of the first moment for the system response and its long-time amplitude are presented. The influence of the system parameters on the long-time behavior of the system response is discussed, such as fractional order, friction coefficient, driving frequency, noise intensity and relevant rate. It is found that the long-time amplitude of the fractional oscillator behaves non-monotonical, that is, there exist stochastic resonances in a wide sense. Moreover, generalized stochastic resonance with two peaks can be found subject to some appropriate parameters.
Feedback compensation control on chaotic system with uncertainty based on radial basis function neural network
Authors: Zeng Zhe-Zhao  ,   College of Electric and Information Engineering, Changsha University of Science and Technology, Changsha 410076, China
Published: December 2020

For the problem of controlling uncertain chaotic systems, a method of feedback compensation control based on the radial basis function neural network (RBFNN) is studied. In the proposed method, dynamic properties of chaotic system is first trained by RBFNN, and then feedback compensation control for chaotic system is implemented using trained good RBFNN model. The characteristics of this method is that this method can quickly track any given reference signal with on requirement for any mathematic model of controlled chaos system. The numerical simulation results show that the proposed control method not only has the fast response speed, high control accuracy, but also has a stronger ability to suppress parameter perturbation and to resist interference to chaos system.
Parameter estimation for chaotic systems based on hybrid biogeography-based optimization
Authors: Lin Jian  , Xu Li  ,   College of Electrical Engineering, Zhejiang University, Hangzhou 310027, China;,   College of Printing Engineering, Hangzhou Dianzi University, Hangzhou 310018, China
Published: December 2020

Parameter estimation for chaotic system is, in fact, a multi-dimensional optimization problem. By combining biogeography-based optimization (BBO) with harmony search (HS) and opposition-based learning (OBL), a hybrid BBO scheme is proposed for solving the chaotic parameter estimation problem. The HS is used to enhance the local search ability of BBO, and OBL is employed to increase the diversity of the initial population, thereby improving the optimizing performance. The effectiveness and robustness of the proposed scheme are verified by numerical simulations on two typical chaotic systems.
Dielectric property of binary phase composite and its interface investigated by electric force microscope
Authors: Sun Zhi  , Wang Xuan  , Han Bai  , Song Wei  , Zhang Dong  , Guo Xiang-Yu  , Lei Qing-Quan  ,   College of Electrical and Electronic Engineer, Harbin University of Science and Technology, State Key Laboratory Breeding Base of Dielectrics Engineering, Key Laboratory of Engineering Dielectrics and Its Application, Ministry of Education, Harbin 150080, China
Published: December 2020

Dielectric property of two-phase stack-up sample is studied by electric force microscopy (EFM). Highly oriented pyrolytic graphite (HOPG)/polyethylene(PE) and mica/PE are fabricated. The phenomenon that phase shift (Δθ) of conducting probe varys with dielectric constant of material is discovered near the interface between the two materials by using phase detection EFM. The characteristic curves of tan(Δθ) versus tip voltage VEFM are of parabolic type. Quadratic coefficient increases with dielectric constant ε increasing. An approach to the qualitative analysis of the dielectric property near the interface between different material at the micro/nanometer scale, is provided in this paper.
Location-free optical microscopic imaging method with high-resolution based on microsphere superlenses
Authors: Wang Shu-Ying  , Zhang Hai-Jun  , Zhang Dong-Xian  ,   State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China
Published: December 2020

In this paper, we propose a novel location-free high-resolution optical microscopic imaging method based on micropipette-microsphere combined probe. According to optical principle, a physical model is established to determine the value of magnification. With SiO2 microspheres of different diameters such as 3.0, 4.4, 5.6, 7.5 and 10.0 μm, microscopic imaging experiments are carried out. The results show that the microstructure of un-etched DVD disk can be significantly magnified and the image contrast is obviously improved, which is consistent well with the theoretical calculation. Microscopic imaging of microstructures based on SiO2 microsphere array is realized by controlling the microspheres with a micropipette. Furthermore, a kind of micropipette-microsphere combined probe is prepared, by which location-free high-resolution optical microscopic imaging has implemented for the first time.
Effects of Ge profile on thermal characteristics of SiGe heterojunction bipolar transistor with non-uniform doping profile in base region
Authors: Zhang Yu-Jie  , Zhang Wan-Rong  , Jin Dong-Yue  , Chen Liang  , Fu Qiang  , Guo Zhen-Jie  , Xing Guang-Hui  , Lu Zhi-Yi  ,   College of Electronic Information and Control Engineering, Beijing University of Technology, Beijing 100124, China
Published: December 2020

As is well known, base region is the design focus of bipolar junction transistor (BJT). Generally, the doping distribution in base is non-uniform. In this paper, the effects of different Gaussian dopings in the base on bulk temperature distribution, temperature dependences of current gain and cut-off frequency are first studied. It is found that current gain and cut-off frequency of BJT have positive temperature coefficients, and the temperature in bulk is high. Then, the effect of Ge composition distribution on these device parameters is investigated. It is found that the SiGe heterojunction bipolar transistors (HBTs) with box Ge composition distribution and trapezoidal Ge composition distribution have negative temperature coefficients of current gain and cut-off frequency, and have good bulk temperature distributions. Furthermore, the SiGe HBT with trapezoidal Ge profile has higher current gain and cut-off frequency, and its temperature insensitivity is kept. The good trade-off is made among the magnitudes of current gain and cut-off frequency, temperature sensitivity and bulk temperature distribution.
Optimization of the longitudinal structure of intrinsic layer in microcrystalline silicon germanium solar cell
Authors: Cao Yu  , Zhang Jian-Jun  , Li Tian-Wei  , Huang Zhen-Hua  , Ma Jun  , Ni Jian  , Geng Xin-Hua  , Zhao Ying  ,   Institute of Photo-electronic 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 of Ministry of Education, Tianjin 300071, China
Published: December 2020

Using radio-frequency plasma enhanced chemical vapor deposition, based on the influences of discharge power on structural and photoelectric properties of μc-SiGe:H thin films, RF power profiling technique is developed during the deposition of μc-SiGe:H intrinsic layer. The optimized μc-SiGe:H intrinsic layer not only maintains homogeneity of the crystalline volume fraction along the depth profile, but also forms a band gap profiling configuration from wide to narrow in the direction of growth. By this method, the fill factor and the short-circuit current density of μc-SiGe:H solar cell are significantly improved, and an efficiency of 9.54% for the a-Si:H/μc-SiGe:H tandem solar cell is achieved.
Twisting effects on energy band structures and transmission behaviors of graphene nanoribbons
Authors: Jin Feng  , Zhang Zhen-Hua  , Wang Cheng-Zhi  , Deng Xiao-Qing  , Fan Zhi-Qiang  ,   School of Physics and Electronic Science, Changsha University of Science and Technology, Changsha 410114, China
Published: December 2020

By using the first-principles method based on the density-functional theory, twisting- deformation-dependent electrical characteristics of graphene nanoribbons (GNRs) are studied systematically. It is shown that the energy gap of the zigzag-edge graphene nanoribbon (ZGNR) is the most insensitive to twisting deformation, and it almost keeps metallicity unchanged, next is the armchair-edge graphene nanoribbons (AGNRs) by width W=3p-1 (p is a positive integer), and its gap has only a small change when twisting deformation occurs. However, the gap of AGNR with width W=3p+1 is extremely sensitive to twisting deformation, and it can display a variation from wide-gap semiconductor to moderate-gap semiconductor, quasi-metal, and metal, next is AGNR with W=3p. In other words, the larger the band gap for GNR in the absence of twisting deformation, the more significant the change (becoming small) of its band gap with twisting deformation. Additionally, for the whole electronic structure and transmission behavior, one can find that there is a much larger influence under twisting deformation in AGNR than in ZGNR. These studies suggest that it is necessary to take the effect of twisting deformation on the electrical characteristics into account in designing GNR-based nanodevices.
Release melting of bismuth
Authors: Tan Ye  , Yu Yu-Ying  , Dai Cheng-Da  , Yu Ji-Dong  , Wang Qing-Song  , Tan Hua  ,   Laboratory for Shockwave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

Reverse-impact experiments are performed on bismuth (Bi) to probe into the release melting from shock pressures in a pressure range of 11-16 GPa. A displacement interferometer system for any reflector (DISAR) is employed to measure the particle velocity history at the impact interface of LiF window with Bi flyer. The obtained experimental data, together with the results from characteristic formulations and one-dimensional hydrodynamic simulations, indicate that bismuth is converted into the body-center-cubic phase under shock loading, and then melted with the releasing of state from the initial shock (Hugoniot). The inflexion on the release wave profiles is attributed to the release melting. The proposed method and extracted results are of importance for developing the phase-change diagnostics and understanding phase-transition behavior of Bi and its analogues.
First-principles study on the effect of high Mn 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;,   Schooe of Chemistry Engineering, 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 three different concentration Mn doped ZnO models, and perform the geomertry optimizations for the three modes. The total density of states, the band structures and the optical absorption are also calculated. The results show that in the case of non-spin state, the smaller the doping concentration of Mn is, the smaller the formation energy of ZnO is and the easier the Mn doping is, thus the stabler the crystal struetuer is; the Mn doping leads to the degenerations of the impurity energy band and the conduction band, and also to the optical absorption blue-shift. These calculation results accord with the experimental results. Moreover, the magnetism exists in the system under the situation of spin polarization, the absorption spectrum has a red-shift, which is consistent with the experimental result.
Comparison between exponential-doping reflection-mode GaAlAs and GaAs photocathodes
Authors: Chen Xin-Long  , Zhao Jing  , Chang Ben-Kang  , Xu Yuan  , Zhang Yi-Jun  , Jin Mu-Chun  , Hao Guang-Hui  ,   Institute of Electronic Engineering and Optoelectronic Technology, University of Science and Technology, Nanjing 210094, China
Published: December 2020

A reflection-mode GaAlAs photocathode and a reflection-mode GaAs photocathode using exponential-doping technique are prepared by metal organic chemical vapor deposition, and the Al content of GaAlAs emission layer is 0.63. The two photocathodes are activated in an ultra-high vacuum system, and the spectral response curves are measured after activation. The quantum efficiency formula for exponential-doping reflection-mode photocathode is used to fit the experimental curves of the two photocathodes respectively, and the effects of some performance parameters on photoemission are analyzed, such as electron diffusion and drift length, back-interface recombination velocity, surface electron escape probability, etc. The results show that the Al content of the GaAlAs photocathode plays a bad role in the photoemission compared with that the GaAs photocathode, but it solves the problem that the GaAs photocathode cannot be well used in the area of detecting the narrow wavelength light due to the broad spectral response. The reflection-mode GaAlAs photocathode prepared is responsive to the blue and green light.
Quantitative analysis on the influences of the precursor and annealing temperature on Nd2O3 film composition
Authors: Zhang Xu-Jie  , Liu Hong-Xia  , Fan Xiao-Jiao  , Fan Ji-Bin  ,   Microelectronics School, Xidian University, Key Laboratory of Wide Bandgap Semiconductor Materials and Devices, Xi'an 710071, China
Published: December 2020

In this paper, ultra-thin Nd2O3 dielectric films are deposited on p-type silicon substrates by advanced atomic layer deposition method. Nd (thd)3 and O3 are used as the reaction precursors separately. The as-grown samples are annealed in N2 atmosphere in a temperature range of 700900 ℃. The samples are investigated at room temperature by X-ray photoelectron spectroscopy and the changes of the film composition at different annealing temperatures are discussed in detail. For a higher precursor temperature of 185 ℃ in the deposition process, the ratio of oxygen to neodymium atoms for the as-grown film is 1.82, which is close to the stoichiometry. Dielectric constant increases from 6.85 to 10.32.
Study on the p-type conductivities and Raman scattering properties of N+ ion-implanted O-rich ZnO thin films
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 p-type N doped ZnO thin films are fabricated using radio-frequency magnetron sputtering technique in O-rich growth condition together with the direct N+ ion-implantation and annealing. The conductivities and Raman scattering properties of the samples are studied by Hall measurements and Raman spectra respectively. Hall measurements indicate that the optimal p-type ZnO film can be obtained when the sample is annealed at 600 ℃ for 120 min in N2 ambience, and its hole concentration is about 2.527×1017 cm-3. N+-implantation induces three additional vibrational modes in ZnO, which are located at 274.2, 506.7 and 640.4 cm-1 respectively. In the process of the annealing, by comparing the electrical properties and Raman speetra of the samples, we find that the competition between intrinsic donor defects and the activation of N acceptors plays a crucial role in the p-type formation of ZnO:N films during annealing.
Preparation and luminescent properties of Sr0.8-xBaxEu0.2WO4 red phosphors for white LED
Authors: Mao Jin-Wei  , Lü Shu-Chen  , Qu Xiu-Rong  , He Dong-Li  , Meng Qing-Yu  ,   Key Laboratory of Photoelectric Bandgap Materials, Ministry of Education, Harbin Normal University, Harbin 150025, China
Published: December 2020

Sr0.8-xBaxEu0.2WO4 red phosphors with different Ba2+ doping concentrations is prepared by the co-precipitation method at different sintering temperatures. We study the influences of the crystal orientation and lattice distortion of the samples on the luminescence property. The results show that the Sr0.8-xBaxEu0.2WO4 synthesized by the process has a phase with tetragonal structure and that the red emission 5D0-7F2 of Eu3+ in the sample can be excited effectively by the near-UV light and blue light. The part of Sr2+ replaced with Ba2+ leads to the increase in emission intensity of Sr0.8-xBaxEu0.2WO4. The doping concentration of Ba2+ has a great influence on the crystal parameter, the crystal symmetry and the luminescent property. The optimized doping concentration of Ba2+ is found to be 30%.
Design and reconfiguration of cognitive engine based on Bayesian network
Authors: Wang Jiao  , Zhou Yun-Hui  , Huang Yu-Qing  , Jiang Hong  ,   School of Information Engineering, Southwest University of Science and Technology, Mianyang 621010, China
Published: December 2020

The past communication behaviors that guide the system communication in the future to satisfy the requirements of users and adapt to the changes of environment are the core part of cognitive radio system. In this paper, a cognitive engine based on Bayesian network is proposed to solve the parameters self-adaptive-adjusting problem of cognitive radio system under the complicated and highly varying radio environment and user requirement. Through structure learning and parameter learning of the sample data from the past communication behaviors, cognitive engine is established. The states of radio environment and requirements of users are made as inference evidences by data preprocessing, and the cognitive engine is used to make decision of the configuration parameters of communication system, and then the reconfiguration system is completed. A mobile wireless network is modeled to finish reconfiguration simulation using OPNET tool in this paper. Simulation results show that the proposed cognitive engine can make the wireless mobile network adapt to environment and effectively improve end-to-end communication performance. The feasibility of the method to model cognitive engine with Bayesian network is validated in this paper.
Influences of deposition rate in second stage on the Cu(In,Ga)Se2 thin film and device prepared by low-temperature process
Authors: Li Zhi-Guo  , Liu Wei  , He Jing-Jing  , Li Zu-Liang  , Han An-Jun  , Zhang Chao  , Zhou Zhi-Qiang  , Zhang Yi  , Sun Yun  ,   Institute of Photo-Electronics Thin Film Devices and Technique, College of Information Technical Science, Nankai University, Tianjin 300071, China
Published: December 2020

Polycrystalline Cu(In,Ga)Se2 (CIGS) thin ?lms are deposited onto soda-lime glass substrates by the low-temperature three-stage process (below substrate temperature of 420℃). The influences of growth rate in the second stage on structural and electrical properties of CIGS thin film and device performance are investigated. With the increase of deposition rate during the second stage, the crystallinity and grain compactness of CIGS thin film are promoted, and the double-peak reflection pattern is reduced obviously,which can reduce the recombination in the grain boundary and help to improve the conversion efficiency of the CIGS solar cell significantly. However, according to the experimental results, higher growth rate during the second stage leads to rough surface and low carrier concentration. The larger surface roughness can be attributed to the larger grain size of secondary-phase Cu2-xSe, and the lower carrier concentration results from the reduction of passivation donor defect effect which is induced by the hindrance of Na diffusion from the glass substrate. High growth rate in the second stage is found to be able to increase the interface recombination and induce shunt paths in the solar cell and then the open circuit voltage and the cell parameters are deteriorated. Finally, a high conversion efficiency of 11.24% is achieved by optimizing the growth rate in the second stage.
Bifurcation control of a cubic symmetry discrete chaotic system
Authors: Zhang Hui  , Chu Yan-Dong  , Ding Wang-Cai  , Li Xian-Feng  ,   School of Mechatronic Engineering, Lanzhou Jiaotong University, Lanzhou 730070, China;,   Department of Mathematics, Lanzhou Jiaotong University, Lanzhou 730070, China;,   Department of Civil and Architectural Engineering, City University of Hong Kong, Hong Kong
Published: December 2020

A direct and effective linear-controller is employed to exactly control the locations of bifurcation points, both the symmetry-breaking bifurcation and the period-doubling bifurcation, in a cubic symmetry discrete system. Moreover, both the sensibility and the symmetry to the initial values of the system are analyzed. The lack of the solution branches due to the symmetry-breaking bifurcation can be reinstated temporarily by selecting the corresponding basins of attraction. The effectiveness of the controller is verified by numerical simulations.
Solution of a class of rotational relativistic rotation dynamic equation using the generalized variational iteration theory
Authors: Shi Lan-Fang  , Mo Jia-Qi  ,   College of Mathematics and Statistics, Nanjing University of Information Science and Technology, Nanjing 210044, China;,   Department of Mathematics, Anhui Normal University, Wuhu 241000, China
Published: December 2020

A class of relational relativistic rotation nonlinear disturbed dynamical equations possessing nonlinear damping force and forcing periodic force is investigated. Firstly, by using the variational principle, the generalized variational iteration is constructed. Then the initial approximate solution is determined. Finally, by using the iteration, the approximation to an arbitray degree for corresponding equation is found.
New hybrid stream cipher based on chaos and neural networks
Authors: Chen Tie-Ming  , Jiang Rong-Rong  ,   College of Computer Science and Technology, Zhejiang University of Technology, Hangzhou 310023, China;,   College of Information and Engineering, Zhejiang Radio and TV University, Hangzhou 310013, China
Published: December 2020

A hybrid stream cipher scheme is proposed based on the novel interacting neural networks and the multiple chaotic systems. At first, random sequences generated by 3 independent logistics functions respectively are taken as dynamic inputs to 3 hidden layers of the interacting neural networks model. Then two inner weights of the two structures of neural networks will be synchronized through some steps of interacting learning, and the random key stream can be finally identified by combining the random sequence extracted from the aforementioned synchronized weight and 3 Logistics sequences. The comparison shows that the generated key stream performs the better randomness than others. As a good example, the proposed novel chaos-based stream cipher works perfectly on digital image encryption.
Semi-analytical recursive convolution algorithm in the finite-difference time domain analysis of anisotropic dispersive medium
Authors: Wang Fei  , Wei Bing  ,   Department of Physics, Xidian University, Xi’an 710071, China
Published: December 2020

The polarizability tensor of magnetized plasma in frequency domain in laboratory coordinate system is gained by using the transfer matrix between the principal and the laboratory system, and then its exponential function form in time domain is derived by inverse Fourier transform. Combined with the semi-analytical recursive convolution (SARC) algorithm in digital signal process techniques, the SARC-finite-difference time-domain method applied to magnetized plasma subjected to an arbitrary direction of external dc magnetic field is derived. The co-polarized and cross-polarized backward radar scattering cross-section for a magnetized plasma sphere are obtained by the presented algorithm. The computed results indicate the correctness and feasibility of the method.
Theory and measurement for mutual coupling effect of ultra high frequency radio-frequency identification in dense environments
Authors: Zuo Lei  , He Yi-Gang  , Li Bing  , Zhu Yan-Qing  , Fang Ge-Feng  ,   College of Electrical and Information Engineering, Hunan University, Changsha 410082, China;,   School of Electrical and Automation Engineering, Hefei University of Technology, Hefei 230009, China;,   The 41st Research Institute of China Electronics Technology Group Corporation, Qingdao 266555, China
Published: December 2020

The close displacement of ultra high frequency radio-frequency identification (UHF RFID) tags can be considered as an electromagnetically interconnected system which causes the mutual coupling effect among antennas of tags, thereby resulting in change in impedance matching condition. Based on the principles of RFID technology and Friis propagation equation, a link budget model of UHF RFID is provided which consists of one reader and one tag. Expressions of mutual impedance in dense environments are derived by using a two-port network. Utilizing the parameters of power transmission coefficient and modulation factor, the variation of system performance is discussed in theory and tested by three experiments which are conducted in open indoor environment. The measurement results show that the change rate of minimum power transmitted by the reader antenna is in a range from -7% to 11.6% for two-tag scene and from -10% to 12.5% for two-plane arrangement.
Design of an ultrathin and wideband metamaterial absorber based on resistance film and fractal frequency selective surface
Authors: Cheng Yong-Zhi  , Nie Yan  , Gong Rong-Zhou  , Wang Xian  ,   School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China
Published: December 2020

An ultrathin, wideband, polarization-insensitive and wide-angle metamaterial absorber is presented, which is based on one order Minkowski fractal double square loop (MFDSL) electric resonator structure and resistance film. The unit cell of this absorber consists of MFDSL, square resistance film, dielectric substrate and metal ground plane. The simulations and analyses of electromagnetic absorbing properties of this composite structure absorber are performed by the finite-difference time-domain method. The simulated reflection and absorption indicate that the absorption of the composed structure absorber is greater than 90% in a frequency range of 7.5-42 GHz. The simulated absorptions under different polarization conditions and incident angles indicate that this composite structure absorber is polarization-insensitive and of wide-angle. The further numerical simulation results indicate that the absorption of this absorber originates mainly from the absorbing mechanism of electromagnetic resonance and circuit resonance, the operation frequency range can also be adjusted by the design of the square resistance.
Three-dimensional simulation for early breast cancer detection by ultra-wideband
Authors: Xiao Xia  , Xu Li  , Liu Bing-Yu  ,   School of Electronic Information Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

Ultra-wideband (UWB) microwave imaging technology can be used as an effective method of detecting early breast cancer, which is based on the difference of the electrical characteristic between normal breast tissues and tumor. The method can provide both the sufficient resolution and the adequate penetration depth in the breast. In this paper, the finite difference time domain method is employed to simulate the microwave propagation in three-dimensional breast tissue. The single pole Debye model is used to approximate the real electrical properties of the breast organism. The antenna arrays made up of 8 emitters and 9 detectors are performed for the detection. The confocal imaging algorithm is employed for the reconstruction of the breast tissue and location. The tumor information displayed in the reconstructed breast image verifies the correctness of the confocal imaging algorithm and the effectiveness of the UWB microwave imaging technique applied to the early breast cancer detection.
Goos-Hänchen shift of self-collimated beam in Kretschmann configuration based on photonic crystal
Authors: Han Kui  , Wang Juan-Juan  , Zhou Fei  , Shen Xiao-Peng  , Shen Yi-Feng  , Wu Yu-Xi  , Tang Gang  ,   College of Science, China University of Mining and Technology, Xuzhou 221116, China
Published: December 2020

We perform the finite-difference time-domain (FDTD) simulations and analyze a dual-beam-reflection phenomenon for a Gaussian beam illuminating a Kretschmann configuration composed of a lossless dielectric waveguide between a photonic-crystal-made prism and air. One reflection beam has a small positive shift and the other has a large negative shift in the dual-beam-reflection phenomenon. The FDTD shows that the specific phenomenon takes place just when the corresponding leaky surface mode supported in the Kretschmann configuration is excited. Field profile of the surface mode demonstrates a strong localized stationary field in the dielectric waveguide. We find that the maximum negative lateral shift is -23.23a, corresponding to 4.99 times of the incident wavelength, which is 1.1615 times of the beam waist.
Methods of analytical mechanics for exact Cosserat elastic rod dynamics
Authors: Xue Yun  , Weng De-Wei  , Chen Li-Qun  ,   School of Mechanical Engineering, Shanghai Institute of Technology, Shanghai 201418, China;,   Shanghai Institute of Applied Mathematics and Mechanics, ShanghaiUniversity, Shanghai 200072, China
Published: December 2020

Thin elastic rod mechanics with background of a kind of single molecule such as DNA and other engineering object has entered into a new developing stage. In this paper the vector method of exact Cosserat elastic rod dynamics is transformed into the form of analytical mechanics with the arc length and time as its independent variables, whose aims are to find new tools for studying rod mechanics and to develop the area of applications of classical analytical mechanics. Based on the plane cross-section assumption, a cross-section of the rod is taken as an object. Basic formulas on deformation and motion of the section are given. After defining virtual displacement of a cross-section and its equivalent variation rule, a differential variational principle such as d’Alembert-Lagrange one is established, from which dynamical equations of thin elastic rod are expressed as Lagrange equations or Nielsen equations under the condition of linear elasticity of the rod. For the rod statics when there exist conserved quantities, Lagrange equation which makes use of these quantities is derived and its first integral is discussed. Finally integral variational principle is derived from differential one, and expressed as Hamilton principle under the condition of linear elasticity. Hamilton canonical equations in phase space with 3×6 dimensions are also derived. All of the results have formed the method of analytical mechanics of dynamics of an exact Cosserat elastic rod, so that the further problems such as symmetry and conserved quantities, and numerical simulation of the rod dynamics may be further studied.