bluuebunny/crossref_metadata_2025 huggingface dataset:
Measurement of NO2 total vertical columns by direct-sun differential optical absorption spectroscopy in Hefei city
Authors: Wang Yang  , Xie Pin-Hua  , Li Ang  , Zeng Yi  , Xu Jin  , Si Fu-Qi  ,   Key Laboratory of Environmental Optical and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

Direct-sun DOAS(DS-DOAS) technique is successfully applied to the measurement of atmospheric trace gas vertical column density(VCD). The DS-DOAS technique for continuously measuring NO2 total vertical column density is investigated based on the passive DOAS. The composition of system is introduced. The statistical method minimum-amount Langley-extrapolation is utilized to reduce the errors from the selected reference spectrum. The VCD measuring error is estimated and the error source is discussed. The NO2 total VCD is measured based on the system in Hefei city in a consecutive period of 11 days. And the results are analyzed. The experiment has verified the feasibility of the algorithm and proved that the technique can be used to continuously measure NO2 total vertical column density.
Simulation of field intensification induced by pit-shaped crack on fused silica rear-surface
Authors: Zhang Chun-Lai  , Wang Zhi-Guo  , Xiang Xia  , Liu Chun-Ming  , Li Li  , Yuan Xiao-Dong  , He Shao-Bo  , Zu Xiao-Tao  ,   School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China;,   Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

Rotating paraboloid model is establishd, and three-dimensional finite-difference time-domain method is used to simulate pit-shaped cracks on fused silica rear-surface. The light intensification with its depth, width, gap distance and etch value are investigated under 355 nm laser incident. Results show that the strongest modulation is located at the connection area between pit and pit, and the modulation become strong with approaching to the surface. The maximum light intensity enhancement factor (LIEF) is 11.53 when the breadth depth ratio ranges from 2.0 to 3.5 and gap distance close to 1/2 width. As gap distance greater than the width, the modulation reduces greatly, which is equal to a single pit. For 60-width, 30-depth and 30-gap distance cracks, the maximum LIEF is 11.0 during the acid etching. As the gap distance is less than 300 nm, the diffraction of the light field makes the neighbor pits connective.
Density distribution of large planar plasma sheet
Authors: Ding Liang  , Huo Wen-Qing  , Yang Xin-Jie  , Xu Yue-Min  ,   Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

A large plasma sheet with a size of 60 cm60 cm2 cm is generated in an apparatus with a hollow cathode. The electron density distribution of the large area plasma sheet is measured. Since the duration of high voltage pulse is short, we change measurement methods. Besides, modification is used for electron saturation current to get the real density. The two-dimensional electron density and electrical field distribution are calculated at discharge currents ranging from 1 to 6 A. Meanwhile we discuss other parameters related to density distribution. The electron density distribution is important for plasma sheet to steer microwave. It is encouraging that the large area plasma sheet generated by the hollow cathode is uniform and has sufficient electron density to reflect X-band (812 GHz) microwaves.
Experimental investigation on the formation of stripe pattern in flowing argon discharge system
Authors: Li Xue-Chen  , Liu Run-Fu  , Jia Peng-Ying  , Kong Liu-Qing  ,   Key Laboratory of Photo-Electronics Information Materials of Hebei Province, College of Physics Science and Technology, Hebei University, Baoding 071002, China
Published: December 2020

Stable stripe pattern is observed in flowing argon at atmospheric pressure by using a dielectric barrier discharge device with two transparent water electrodes. Based on the photography and the electrical measurement, the formation mechanism of stripe is investigated. Results show that a stripe pattern can be obtained at a lower peak value of the applied voltage in flowing argon, and the discharge turns homogeneous at a higher voltage. Results show that the formation of stripe pattern results from the movement of discharge filament in the direction of gas flow. The moving velocity of filaments almost keeps constant during the voltage varying. However, the moving velocity increases with the increase of gas flow rate. The memory effect of active particles in the discharge space is very important for the formation of stripe pattern. Furthermore, the electric characteristics of discharge are studied in flowing gas in this paper. It is found that both the discharge current and the gas inception voltage decrease with the increase of the gas flow rate. A qualitative explanation is given for this experimental phenomenon. These results are of great importance for the research of pattern formation dynamics and industrial applications of dielectric barrier discharge.
Study on synergy of electron-cyclotron and lower-hybrid current drive in Tokamak
Authors: Hong Bin-Bin  , Chen Shao-Yong  , Tang Chang-Jian  , Zhang Xin-Jun  , Hu You-Jun  ,   College of Physical Science and Technology, Sichuan University, Chengdu 610065, China;,   Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

The mechanisms of the synergy effects between electron-cyclotron and lower-hybrid current drive and the synergy current are revealed. The matching relationships required by synergy effect in phase space and on current profile are explained. The non-linear relationship between synergy current and wave power is shown by computer simulation, and its physical explanation is given. This work provides physical support for the design and analysis of relevant experiment.
Gamma radiation effects on absorption and emission properties of erbium-doped silicate glasses
Authors: Sheng Yu-Bang  , Yang Lü-Yun  , Luan Huai-Xun  , Liu Zi-Jun  , Li Jin-Yan  , Dai Neng-Li  ,   College of Optoelectronic Science and Engineering, Huazhong University of Science and Technology, Wuhan National Laboratory for Optoelectronics, Wuhan 430074, China
Published: December 2020

A series of Er-doped silicate glasses is prepared by a conventional melting method under normal processing conditions, and the effects of gamma-ray radiation on absorption and emission properties of all samples are investigated. The radiation-induced darkening causes a strong broad optical absorption band that has a maximum around 400 nm and extends to the near infrared region. The point defects generated in the silicate matrix by irradiation around the Er3+ ion favor the activation of non-radiative relaxation channels thus modifying the photoluminescence quantum efficiency from specific excited levels, such as those emitting at 520 and 650 nm. Photobleaching effects are observed in Er-doped silicate glasses pumped by 980 nm LD at room temperature.
Research on softening of longitudinal mode under high pressure and equation of state of -Ce
Authors: Li Feng-Jiao  , He Duan-Wei  , Liu Lei  , Zhang Yi  , Jing Qiu-Min  , Liu Sheng-Gang  , Chen Hai-Hua  , Bi Yan  , Xu Ji-An  ,   Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China;,   National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, Chinese Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

Angle dispersive X-ray diffraction measurements of -Ce are performed in a diamond anvil cell under up to 0.74 GPa at room temperature. The accurate high pressure bulk modulus data obtained from ultrasonic measurements are used to calculate the parameters of various equations of states (EOSs). We find that the three order Murnaghan EOS and three order Xu EOS are fitted best to the relationships of the pressure vs. volume and the pressure vs. bulk modulus for -Ce.
First-principles study of (InAs)1/(GaSb)1 superlattice atomic chains
Authors: Sun Wei-Feng  ,   Key Laboratory of Engineering Dielectrics and Its Application, Ministry of Education, Heilongjiang Provincial Key Laboratory of Dielectric Engineering, School of Electrical and Electronic Engineering, Harbin University of Science and Technology, Harbin 150080, China
Published: December 2020

The atomic structure, the mechanical properties, the electronic band structure, and the phonon structure of (InAs)1/(GaSb)1 superlattice atomic chain are investigated by first-principles pseudopotential plane wave method, and the quantum transport properties are also calculated by the density functional theory numerical atomic orbit pseudopotential method in combination with nonequilibrium Green's function formalism. Compared with two-dimensional layer structural (InAs)1/(GaSb)1 superlattice, the (InAs)1/(GaSb)1 superlattice atomic chains have obviously different band structures, and represent metal energy band characteristics in certain conditions. The calculated mechanical strength of (InAs)1/(GaSb)1 superlattice atomic chains indicates that such structures can sustain the strain as high as =0.19. The structural stability of (InAs)1/(GaSb)1 superlattice atomic chains is investigated by full Brillouin zone analysis for phonon structure. The electron transport calculations for (InAs)1/(GaSb)1 superlattice atomic chain segments in between Al electrodes show that the conductance exhibits nontrivial features as the chain length or strain is varied. The calculated optical absorption spectra represent precipitous cutoff absorptions in infrared regime, and the cutoff wavelength varies with chain structure. InAs/GaSb superlattice atomic chains are predicted to be applied to infrared optoelectronic nanodevices, modifying optoelectronic response wavelength range by changing the structures of superlattice atomic chains.
Electronic properties on the point vacancy of armchair edged graphene quantum dots
Authors: Yao Zhi-Dong  , Li Wei  , Gao Xian-Long  ,   Department of Physics, Zhejiang Normal University, Jinhua 321004, China;,   Department of Physics, Fudan University, Shanghai 200433, China
Published: December 2020

Based on the numerically solved Dirac equations, we study the electronic properties of the point vacancy of the graphene quantum dots with armchair boundary conditions under magnetic field. The size effect on the gap is analyzed. Without magnetic fields, quantum dot has finite energy gap which is proportional to the inverse of the radius of the dot. In the presence of the magnetic field, there appear Landau levels. The lowest Landau level has zero energy and is irrelevant to the magnetic field. With the increase of the magnetic field, the degeneracy of the Landau levels will increase. We further analyze the relationship between the lowest Landau level in the presence of magnetic field and the size of the quantum dot. The result shows that the degeneracy is linearly dependent on the magnetic field and the square of the radius. Our calculation will be possibly helpful in designing the device based on the graphene quantum dots.
Phase field modeling of the growth and competition behavior of tilted dendrites in directional solidification
Authors: Wang Ya-Qin  , Wang Jin-Cheng  , Li Jun-Jie  ,   State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi'an 710072, China
Published: December 2020

The multi-phase field model is employed to simulate the growth of tilted dendrites during directional solidification. In this simulation, the evolution of a single oriented dendritic array and the overgrowth behavior between two converging grains with different orientations are studied. The simulated results show that the dendritic tip undercooling increases with the tilt angle, which means that the tip position of tilted dendrite is always lower than that of the non-tilted in the same condition. The favorably oriented grain always blocks the unfavorably oriented one in the case of converging growth. However, when the pulling velocity is low, the growth of the preferred crystalline orientation dendrites at the grain boundary is lagged by the immediate unfavorably ones because of the solutal interaction, which may result in the fact that the unfavorably oriented grain overgrows the favorably oriented one.
Study on stereo photography for ocean wave measurements in no sea control points
Authors: Jiang Wen-Zheng  , Yuan Ye-Li  , Wang Ying-Xia  ,   Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;,   The First Institute of Oceanography, State Oceanic Administration, Qingdao 266061, China;,   Graduate University of Chinese Academy of Sciences, Beijing 100039, China
Published: December 2020

A novel stereo photography method is developed for ocean wave measurement, and the mathematical model and algorithm are also developed. A new exterior calibration technique is built by the least square method in combination with the sea wave theory. Compared with the conventional calibration technique, the present method does not need the sea control points are not needed. Thus, this novel stereo photography method can easily be extended to the measurement the sea waves on a mobile platform. The laboratory experiments show that the stereo photography system proposed in the present paper is accurate and can be used to measure Gravity-Capillary waves. Meanwhile, from the outfield experiments we can also find that our method is feasible to measure large-scale ocean wave and the measured area (overlay) is up to 104 m2.
Dynamical modeling and border collision bifurcation in pulse train controlled discontinuous conduction mode buck converter
Authors: Sha Jin  , Bao Bo-Cheng  , Xu Jian-Ping  , Gao Yu  ,   School of Electrical Engineering, Southwest Jiaotong University, Chengdu 610031, China;,   School of Information Science and Engineering, Changzhou University, Changzhou 213164, China
Published: December 2020

According to the charge variation of output capacitor in a switching cycle, the output voltage variation in a switching cycle can be obtained, from which an approximate discrete-time model of pulse train (PT) controlled buck converter operating in discontinuous conduction mode (DCM) is established. Based on the model, the border-collision bifurcations of the PT controlled DCM buck converter with the variations of the load resistance and the input voltage are studied. By constructing the corresponding iterative map curves, the stabilities of the fixed points, formed by the orbits of period-1, period-2, period-3 and so on, are analyzed, and the mechanisms of border-collision bifurcations of the converter under different operation states are revealed. The analysis results indicate that with the variation of parameters, the PT controlled DCM buck converter always operates in different periodic states, in which the change of the operation mode with periodic state is caused by the border-collision bifurcation and the lyapunov exponent is always less than zero. By using PSIM circuit simulation software, the time domain waveforms and phase portraits under different load resistances are obtained. Experimental results are provided to verify the correctnesses of theoretical analyses and circuit simulations and the feasibility of dynamical modelling.
Investigation of blind detection mechanism for chaotic UWB system based on generalized negentrogy
Authors: Gong Yun-Rui  , He Di  , He Chen  ,   Information Transmission and Processing Lab, Shanghai Jiao Tong University, Shanghai 20040, China
Published: December 2020

A non-coherent blind detection method based on the generalized negative entropy mechanism for chaotic ultra-wideband system is proposed in this paper. In the case without knowing the transmission channel information, the chaotic impulse signals can be detected. The proposed method can overcome the practical application problem existing in the direct chaotic communication (DCC) scheme for impulse radio ultra-wideband (IR-UWB) communication system. Also, this method can overcome the complicated and unknown multipath channel effect. Analysis of simulation results show that the proposed approach has a good separating and detection performance in the case without the channel information. A new way for the noncoherent blind detection of chaotic UWB system under non-ideal unknown channel is established.
Cryptanalysis and improvement of a class of hyperchaos based image encryption algorithms
Authors: Zhu Cong-Xu  , Sun Ke-Hui  ,   School of Information Science and Engineering, Central South University, Changsha 410083, China
Published: December 2020

The security of a class of hyperchaotic image encryption algorithms is analysed. The results show that the shuffling process can be separated from the confusion process, and the formulas of encryption are simple, which makes the ciphertext cannot resist the attacks from chosen plaintext and ciphertext. Then we propose an improved and enhanced algorithm based on hyperchaos. The improved algorithm includes two rounds of encryption operation. The theoretical analyses and the experimental results indicate that the improved algorithm can overcome these flaws and has better cryptographic performances in resisting differential attacks and speed of encryption.
Relay node placement and addition algorithms in wireless sensor networks
Authors: Wang Zhu  , Wang Qi  , Wei De-bao  , Wang Ling  ,   School of Information Science and Engineering, Harbin Institute of Technology at WeiHai, Weihai 264209, China;,   School of Electrical Engineering and Automation, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

The node placement is the foundation of network operation in wireless sensor networks. In many applications, the positions of gateway node and sensor node are relatively fixed. To guarantee network connectivity and reliability, some relay nodes must be reasonably placed between the gateway node and the sensor node. In the context of the above applications, we introduce many constraint conditions into the existing placement model, and adopt a hybrid placement method based on enumeration and greedy optimization algorithms to determine relay node positions from their candidate location sets, and we finally achieve the relay node initial placement and follow-up adjustment strategies, owing to new sensor nodes joining the current network. The simulation results demonstrate that our operable and optimized relay node placement algorithm can ensure multi-restricted fault-tolerant relay node placement, and the presented new evaluation standard based on the minimum distance factor can significantly improve the energy-efficiency of relay node placement algorithm.
Solving the spheroidal wave equation with s=3/2 by super-symmetric quantum mechanic
Authors: Guo Wei-Qi  , Tian Gui-Hua  , Dong Kun  ,   School of Science, Beijing University of Posts And Telecommunications, Beijing 100876, China
Published: December 2020

In the paper, we use the method of super-symmetric quantum mechanics to study the spin-weighted spheroidal wave equation in the case of s=3/2. We first change the equation into Schrdinger's form, then calculate and derive the first four terms concerning E and super-potential W. we summarize the general formula of super-potential Wn and use mathematical induction to prove its correctness. In turn, this completely gives all the information about the ground eigenvalue and eigenfunction.
Simulation studies on W-band traveling-wave tube with double rectangular comb slow-wave structure
Authors: Liu Qing-Lun  , Wang Zi-Cheng  , Liu Pu-Kun  ,   Key Laboratory of High Power Microwave sources and Technologies, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China;,   Space Traveling Wave Tube Research and Development Center, Institute of Electronics, Chinese Academy of Sciences, Beijing 100190, China;,   Graduate University of Chinese Academy of Sciences, Beijing 100039, China
Published: December 2020

A double rectangular comb slow-wave structure with a round beam channel is proposed as the slow-wave structure (SWS) circuit of a broad bandwidth traveling-wave tube at W-band. The "cold" characteristic of the SWS and the transmission of the input/output structure are simulated and optimized in this paper. The results show that this circuit has a very broad bandwidth, and that the impedance of the structure with round beam channel can be the same as that of sheet beam by modifying the distance between the double vanes and the radius of the beam channel. Moreover, the transmission of the whole tube is so good that the VSWR can be kept at below 2 in a very broad bandwidth after optimization. The output performance is investigated by both the big signal theory MTSS and the PIC code MAFIA, and they have the same results that in 10 GHz bandwidth the output power is over 40 W and the gain is above 29 dB under a driven power of 50 mW.
Smoothing of small on-target spots produced by frequency-tripled beams using lens array and spectral dispersion
Authors: Jiang Xiu-Juan  , Li Jing-Hui  , Li Hua-Gang  , Zhou Shen-Lei  , Li Yang  , Lin Zun-Qi  ,   School of Information Engineering, Guangdong University of Technology, Guangzhou 510006, China;,   Key Laboratory for High Power laser Physics, Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, P.O. Box 800-211, Shanghai 201800, China;,   Department of Physics, Guangdong Institute of Education, Guangzhou 510303, China
Published: December 2020

The performances of the smoothing of small target spots with a lens array (LA) and two-dimensional smoothing by spectral dispersion (2D SSD) in frequency-tripled high-power laser driver are numerically studied. Intensity distributions and spatial power spectra of the spots are analyzed. Simulative results show that LA can reduce the near-field nonuniformity of the beam and control the envelope of on-target intensity distribution. The 2D SSD has obvious effects in eliminating high-contrast intensity modulation, even in the case that the spots are very small. The results indicate that SSD mainly smoothes the intensity modulation at low-to-middle spatial frequency for small spots, and this would lead to the modifying of the spot profile, while for large spots, SSD sweeps the fine speckle structure to reduce nonuniformity at middle-to-high frequency. These results are valuable for choosing the suitable beam smoothing method in indirect-drive experiment.
Study on the polarization mismatch in micro/millimeter-wave generation employing optical self-heterodyning technology
Authors: Gao Song  , Pei Li  , Ning Ti-Gang  , Qi Chun-Hui  , Liu Guan-Hui  , Li Jing  ,   Key Lab of All Optical Network & Advanced Telecommunication Network of EMC, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

In this paper, we study the effect of polarization mismatch (POM) in micro/millimeter-wave (mm-wave) generation employing optical self-heterodyning technology. The calculation formula of POM-induced mm-wave power penalty is derived for the first time. Utilizing a mm-wave generator based on a homemade dual-wavelength polarization maintaining fiber grating laster, several-mm-wave with frequency around 30 GHz is generated. The experimental results accord well with the theoretical ones, which can prove that the theoretical analysis is correct. Finally the simulation of effect of POM on 60 GHz is performed. Under different conditions, the bit error rates (BERs) and the eye diagrams are obtained. BER below 10-9 and clear eye diagrams can be obtained if the POM is under control. So it is very important to control the POM in fiber-optic wireless link.
Investigation on Doppler spectra of microwave scattering from sea surface
Authors: Jiang Wen-Zheng  , Yuan Ye-Li  , Wang Yun-Hua  , Zhang Yan-Min  ,   Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;,   The First Institute of Oceanography, SOA, Qingdao 266061, China;,   Graduate School, Chinese Academy of Sciences, Beijing 100049, China;,   College of Information Science.& Engineering, Ocean University of China, Qingdao 266003, China
Published: December 2020

Based on the composite surface scattering model, the analytical formulas for Doppler shift and bandwidth of radar echoes return from time-varying sea surface are derived. In our derivations, the influences of the tilt modulation, the shadow and the curvature of large-scale undulating waves are all taken into account for achieving more reasonable results. Comparisons between the theoretical results and direct numerical simulations demonstrate that the analytical formulas can significantly improve the simulated results. And the effects of the tilt modulation, the shadow and the curvature on Doppler spectral properties are discussed in detail. From the simulated results, it is found that the predicted Doppler shifts are always larger in HH-polarization than in VV-polarization due to the tilt modulation of large-scale waves. In addition, at low-grazing angles, the shadow of large-scale waves results in a rapid increase of the predicted Doppler shift, and on the contrary maks the bandwidth narrower.
Full-vectorial analysis of the directional couplers in horizontal multiple-slotted silicon wires with trapezoidal cross-section
Authors: Xiao Jin-Biao  , Li Wen-Liang  , Xia Sai-Sai  , Sun Xiao-Han  ,   Department of Electronic Engineering, Southeast University, Nanjing 210096, China
Published: December 2020

Directional couplers are basic components for forming various kinds of photonic devices. In this paper, a directional coupler composed of two horizontal multiple-slotted waveguide structures with slanted sidewalls is characterized by using a full-vectorial finite element method in terms of the electric fields. The effective indexes of the even and the odd modes and the corresponding coupling lengths, both in quasi-TE and quasi-TM modes, are presented, where the strongly-hybrid nature of the guided-mode is effectively demonstrated. The results show that the coupling lengths in quasi-TE and quasi-TM modes exponentially increase with the increase of the gap between the coupled waveguides, where the value in quasi-TE mode is more sensitive to the variation of the angle of the sidewall, while the value in quasi-TM mode is more sensitive to variation of the height and the index of the slot. Properly choosing the structure and material parameters, polarization-independent directional couplers can be realized.
Experimental research on cylindrical focused beamforming localization method of moving sound sources based on vector sensor array
Authors: Shi Jie  , Yang De-Sen  , Shi Sheng-Guo  ,   Science and Technology on Underwater Acoustic Laboratory, Harbin Engineering University, Harbin 150001, China
Published: December 2020

Based on the passive synthetic aperture principle, a new cylindrically focused beamforming localization method of moving sound sources based on vector sensor array suited for both narrowband and broadband signal is proposed in this paper. By establishing the measurement model of moving sound sources, calculating the localization accuracy versus error, and analyzing the experimental results of cabin model, the performance of this new method can be verified. A comparison between the focused beamforming localization results and the shell vibration measurement results proveds that the proposed method not only can obtain the localization results, but also can reflect the relative contribution of each coherent source.
SO-FDTD method of analyzing the reflection and transmission coefficient of weakly ionized dusty plasma layer
Authors: Li Lin-Qian  , Shi Yan-Xiang  , Wang Fei  , Wei Bing  ,   Department of Electronics and Information Engineering, Yili Normal University, Yining 835000, China;,   Department of Physics, Xidian University, Xi'an 710071, China
Published: December 2020

The complex permittivity of weakly ionized dusty plasma is presented as a fractional polynomial in j. A frequency-domain constitutive relation of weakly ionized dusty plasma is given by shift operator finite-difference time-domain (SO-FDTD) method in time domain. Also the recurrence relation on the electromagnetic properties of weakly ionized dusty plasma is deduced by the SO-FDTD. The reflection and transmission coefficients of the weakly ionized dusty plasma layer are calculated, and the influences which is caused by the change of the dust particle concentration and radius on reflection and transmission coefficients are also analyzed by the SO-FDTD method. The result shows that the reflection coefficient in the presence of dust particles is smaller than in the absence of dust particles, while the transmission coefficient in the former case is larger than in the latter case. Besides, it is found that the reflection coefficient decreases as the concentration or radius of dust particle increases.
Lithium-doped tris (8-hydroxyquinoline) aluminum studied by density functional theory
Authors: Xie Xiao-Dong  , Hao Yu-Ying  , Zhang Ri-Guang  , Wang Bao-Jun  ,   College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024, China;,   Key Laboratory of Coal Science and Technology of Ministry of Education and Shanxi Province, Taiyuan University of Technology, Taiyuan 030024, China
Published: December 2020

The geometry, the frontier molecular orbital and the charge transfer property of lithium (Li) doped tris (8-hydroxyquinoline) aluminum (Alq3) are investigated by the density functional theory (DFT) method. The calculated results show that in the Li-doped Alq3 system, Li-N and Li-O bonds are formed and Li-Alq3 electron transfer complexes are obtained. The incomplete electron transfer from Li atoms to the pyridine side of Alq3 results in donor level in the band gap of Alq3, a typical n-type doping formation, which can improve efficiently the electron transport efficiency. However heavy Li doping can induce the dissociation of Alq3, which leads to the decline of electron transport ability. When the Li:Alq3 doping ratio is about 2:1, the Li-doped Alq3 layer will have a maximal electron transport efficiency.
Research on shot noise suppression in quasi-ballistic transport nano-mOSFET
Authors: Jia Xiao-Fei  , Du Lei  , Tang Dong-He  , Wang Ting-Lan  , Chen Wen-Hao  ,   School of Technical Physics, Xidian University, Xi’an 710071, China;,   Department of Electronic and Information Engineering, Ankang University, Ankang 725000, China
Published: December 2020

Previous studies of shot noise suppression in nano-MOSFET either ignored its suppression or emphasized only its existence but gave no deeper research. In this paper, based on the Navid model, the expressions of shot noise suppression factor (Fano) in quasi-ballistic transport nano-MOSFETs are derived with separately considering Fermi effect, Coulomb interaction and the combination of the two effects. The variations of suppression-factors with source-drain voltage, gate voltage, temperature and source-drain doping are investigated. The results we obtained with considering the combination of the two effects are consistent with those from experiments, and the theoretical explanation is given.
Analysis of influencing factors on current spreading of flip-chip light-emitting diodes (LEDs)
Authors: Zhong Guang-Ming  , Du Xiao-Qing  , Tang Jie-Ling  , Dong Xiang-Kun  , Lei Xiao-Hua  , Chen Wei-Min  ,   Key Laboratory of Optoelectronic Technology and Systems of the Education Ministry of China, College of Optoelectronic Engineering, Chongqing University, Chongqing 400044, China
Published: December 2020

In order to research the factors that affect the current uniformity of Flip-chip LEDs, the three-dimensional model of LED chip is established by the finite-element analysis software COMSOL4.0. The influences of chip size, electrode structure and current injection bump on the electrical property of the LED are investigated. The simulation results show that the non-uniform current distribution of LED chip changes exponentially with the increase of the chip size. Interdigitated electrode structure can reduce the lateral resistance effectively by shorting the channel that current flows through. The reasonable design of the bump on the block electrode can also make current even by reducing the lateral resistance.
Analysis and design of X-band coaxial multi-beam relativistic klystron amplifier
Authors: Liu Zhen-Bang  , Jin Xiao  , Huang Hua  , Chen Huai-Bi  ,   Department of Engineering Physics, Tsinghua University, Beijing 100084, China;,   Institute of Applied Electronics, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

The space charge limiting current in cylinder drifting tube and coaxial drifting tube and the energy that could be obtained and also the restrict magnetic field are analyzed, and the results show that it is propitious to change the energy of electron beam into microwave power in the coaxial conduit. The advantages of the tri-axial relativistic klystron amplifier and the multi-beam klystron amplifier are analyzed, then an x-band coaxial multi-beam relativistic klystron amplifier is designed by using a three-dimensional particle simulation software, and the transmition and the bunching of electron beam are analyzed. A 1.23 GW averaged microwave power over the oscillator period is generated by simulation with 600 kV electron beam voltage, 5 kA current and 0.8 T leading magnetic field density, the frequency is 9.37 GHz and the efficiency is 41%.
Comparison of the performance for InAlAs/GaSbAs/InP DHBT and InP/GaSbAs/InP DHBT
Authors: Zhou Shou-Li  , Yang Wan-Chun  , Ren Hong-Liang  , Li Jia  ,   College of Information Engineering, Zhejiang University of Technology, Hangzhou 310023, China;,   State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, China;,   College of Information Engineering, Xiangtan University, Xiangtan 411105, China
Published: December 2020

The characteristics of a double heterojunction bipolar transistor(DHBT) depend closely on the type of band alignment structure at the hetero-interface between emitter-base(E-B) heterojunction and base-collector(B-C) heterojunction. Based on thermionic-field-diffusion model, the comparisons are made of the DC and the RF characteristics between two novel HBTs, that is, InAlAs/GaSbAs/InP DHBT and InP/GaSbAs/InP DHBT, of which the former has a type-I E-B junction and a type-II B-C junction and the later has a type-II E-B junction and a type-II B-C junction. The simulation results show that DHBT with a type-I E-B junction and a type-II B-C junction has much better current driving capability, DC gain and RF performance, although it has a slightly high turn-on voltage.
Failure mechanism of FC-PBGA devices under external stress
Authors: Lin Xiao-Ling  , Xiao Qing-Zhong  , En Yun-Fei  , Yao Ruo-He  ,   School of Electronic and Information Engineering, South China University of Technology, Guangzhou 510640, China;,   Science and Technology on Reliability Physics and Application of Electronic Component Laboratory, China Electronic Product Reliability and Environmental Testing Research Institute, Guangzhou 510610, China
Published: December 2020

Flip chip plastic ball grid array (FC-PBGA) is unique and has been widely used. During FC-PBGA's practical application, the analysis of its failure mechanisms under high temperature, electricity, water vapor and other comprehensive environmental stress conditions is very important for improving its application reliability. In this paper, with 0.13-μm m/6-level copper-based FPGA with FC-PBGA package, failure mode of the device is exposed under external stress, which is dominated with thermal-mechanical stress generated by high temperature thermal reflow process. And the failure mechanism corresponding to the failure mode is analyzed. Results show that the basic cause of the failure is the thermal-mechanical stress, which is induced by the combination of internal and external reflow temperature difference and high temperature reflow process when assembled. The thermal-mechanical stress makes the solder bumps on the flip chip melt again and bridges the adjacent solder bumps to lead to the device short failure. It also induces crack or delamination in the underfill, crack in solder bump or solder bump fallen off to lead to device open failure. The residual stress on Cu/low-k interconnect structures damages the structure integrity and affects the reliability of FC-PBGA packages.
Effect of noises on moving cut data-approximate entropy
Authors: Jin Hong-Mei  , He Wen-Ping  , Zhang Wen  , Feng Ai-Xia  , Hou Wei  ,   Department of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China;,   National Climate Center, China Meteorological Administration, Beijing 100081, China
Published: December 2020

Affected by some factors such as external forcing and the measurement errors of instrument itself, observational data often contain noises, disturbances and some other false information. To solve this problem, the effects of different noises on moving cut data-approximate entropy (MC-ApEn) are investigated in this paper. The results indicate that MC-ApEn is little affected by random spikes and Gaussian white noise, which means that the MC-ApEn method has strong anti-noise ability. The results provide an essential experimental basis for the wide applications of the present method to observational data.
A method for temperature inversion in middle-upper atmosphere using FPI without laser calibration and its observational data preliminary analysis
Authors: Zhao Jiang-Nan  , Ai Yong  , Wang Jing-Fang  ,   School of Electronic Information, Wunan University, Wunan 430079, China
Published: December 2020

In this paper we present a method, by which the temperature inversion is carried our without the calibration of the laser under the FPI observations. On the basis of 630 nm and 557.7 nm observational data are obtained by Wuhan University FPI atmospheric temperature measurement system, using the above method. The results of temperature inversion show that the method doesnot require the calibration of the laser, and can be used for FPI temperature inversion with different wavelengths.
Modal prediction for open-loop liquid-crystal adaptive optics systems
Authors: Liu Chao  , Hu Li-Fa  , Mu Quan-Quan  , Cao Zhao-Liang  , Hu Hong-Bin  , Zhang Xing-Yun  , Lu Yong-Jun  , Xuan Li  ,   State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China;,   Graduate school of the Chinese Academy of Sciences, Beijing 100039, China;,   Optoelectronic Institute of Dalian Nationalities University, Dalian 116600, China
Published: December 2020

In order to reduce the time delay of the liquid-crystal (LC) adaptive optics system (AOS) which reduces the image resolution of the observed objects, we present a new technique for the first time which is called recursive least square (RLS) modal prediction of turbulent wavefront. First, we introduce the structure of the open-loop LC AOS with RLS predictor. Second, we present the RLS modal prediction algorithm in detail. Third, an actual open-loop LC AOS is designed and built, and the RLS prediction is carried out on it. It is shown that under a pure time delay system and the turbulent condition with Greenwood frequency of 35Hz and Fried parameter of 6 cm, after prediction the residual wavefront error reduce to 0.15 wave (wave=785 nm) from 0.26 wave that is obtained through the direct open loop correction. The prediction gain reaches 42%. Finally, the images obtained by the open-loop AOS with and without prediction are demonstrated. With direct correction without prediction, the image resolution reache 25.4 cycles/mm. After the correction with RLS prediction, the image resolution reaches 32.0 cycles/mm which is equal to 0.9 of the diffraction limit resolution of the system. Therefore, with respect to correction without prediction, a relative gain of 26% in image resolution is achieved with RLS prediction. In conclusion, the RLS modal prediction can improve the image resolution of the open-loop LC AOS effectively.
A method of constructing infinite sequence soliton-like solutions of nonlinear evolution equations
Authors: Taogetusang  , Bai Yu-Mei  ,   The College of Mathematical, Inner Mongolia University for Nationalities, Tongliao 028043, China;,   The College of Mathematical Science, Inner Mongolia Normal University, Huhhot 010022, China
Published: December 2020

The auxiliary equation method is used to construct the finite new exact solutions of nonlinear evolution equations. To search for infinite sequence soliton-like exact solutions of nonlinear evolution equations, characteristics of constructivity and mechanization of auxiliary equation method are analyzed and summarized. Therefore, the quasi-Bcklund transformation between new solutions of a kind of auxiliary equation with Riccati equation is presented, then (2+1)-dimensional modified dispersive water-wave system is taken as an applicable example to find infinite sequence soliton-like new exact solutions by choosing two kinds of formal solutions of nonlinear evolution equations with the help of symbolic computation system Mathematica, where included are the infinite sequence smooth soliton-like solutions, compact soliton solutions and peak soliton-like solutions.
Stochastic resonance in an over-damped linear oscillator driven by multiplicative quadratic noise
Authors: Zhang Lu  , Zhong Su-Chuan  , Peng Hao  , Luo Mao-Kang  ,   College of Mathematics, Sichuan University, Chengdu 610065, China;,   Science and Technology on Electronic Information Control Laboratory, Chengdu 610036, China
Published: December 2020

For an over-damped linear oscillator driven by multiplicative quadratic noise and periodic modulated noise, the exact analytical expressions of the first two moments, the amplitude and variance of the system steady-state response are obtained. We find that this system has richer dynamic behaviors than the traditional linear systems driven by linear noise; when the coefficients of the quadratic noise satisfy certain conditions, both the amplitude and the variance of the system steady-state response present stochastic resonance.
Control of fast-scale bifurcation in single-phase SPWM inverter and its stability analysis
Authors: Hu Nai-Hong  , Zhou Yu-Fei  , Chen Jun-Ning  ,   School of Electronics and Information Engineering, Anhui University, Hefei 230039, China
Published: December 2020

H bridge inverter is a basic nonlinear topology in power electronic circuits. However it is prone to the generation of fast-scale instability phenomenon due to the variation of some parameters in the operation process, which can be eliminated with the slope compensation simply and effectively. Experience plays the leading role and common engineering design is lacking in necessary design criteria. Accrording to the bifurcation control theory of nonlinear system, in this paper we analyze the implementation of slope compensation on H bridge inverter under peak current mode control in detail, thereby obtaining the accurate amplitude requirements of the compensated slope signal and realize the optimization. The results of the analysis are consistent with those of simulation experiment, and the inverter circuit under appropriate slope compensation can operate in stable regime especially with the performances being enhanced remarkably. The research method is also applicable for the stability analysis of other power electronic circuits.
Design of a thin wide-band absorber based on metamaterials and resistance frequency selective surface
Authors: Cheng Yong-Zhi  , Nie Yan  , Gong Rong-Zhou  , Zheng Dong-Hao  , Fan Yue-Nong  , Xiong Xuan  , Wang Xian  ,   Department of Electronic Science & Technology, Huazhong University of Science and Technology, Wuhan 430074, China
Published: December 2020

Three kinds of absorbers, based on square metal patch structure(SMP) metamaterials, resistance frequency selective surface (RFSS), and the combined SMP with RFSS structures, are designed, respectively. The absorptivities of these absorbers are simulated and analyzed by FDTD method. The simulation results indicate that in a frequency range of 230 GHz, SMP absorber can achieve stronger multi-bands absorption by the proper design of geometrical parameters of unit cell; RFSS absorber can achieve stronger high-frequency broadband absorption by the proper design of the square resistance of unit cell. However, the bandwidth of stronger absorption is limited; the absorption of the composite absorber combined with SMP and RFSS structure is greater than 90% in a frequency range of 325 GHz, which has a characteristic of better impedance matching to the free space in a wide frequency range.
Electromagnetic coupling and shielding effectiveness of apertured rectangular cavity under plane wave illumination
Authors: Jiao Chong-Qing  , Qi Lei  ,   School of Electrical and Electronic Engineering, North China Electric Power University, Beijing 102206, China;,   State Key Laboratory of Alternate Electrical Power System with Renewable Energy Sources, North China Electric Power University, Beijing 102206, China
Published: December 2020

Based on the Bethe's theory for small aperture coupling and the eigen-mode expansion method, an approximate analytic model for the field distribution inside a rectangular cavity with apertures under plane wave illumination is presented. The effects of aperture shape, dimensions, number, position, and the wave incidence and polarization angles on cavity mode excitation can be taken into consideration in this model with clear physical explanation. The calculation results from this model are in better agreement with experimental data than those from the equivalent circuit model. The effects of various factors on the shielding effectiveness of the cavity are analyzed, and the obtained results are useful for guiding the design of electromagnetic shielding enclosures.
Precise frequency control of an Er-doped fiber comb
Authors: Cao Shi-Ying  , Meng Fei  , Lin Bai-Ke  , Fang Zhan-Jun  , Li Tian-Chu  ,   Center for Time and Frequency Metrology, National Institute of Metrology, Beijing 100013, China
Published: December 2020

The repetition rate and the carrier-envolope offset frequency of a home-made Er-doped fiber comb are precisely phase-locked. The residual fluctuations of the stabilized repetition rate and the carrier-envolope offset frequency are 0.515 mHz and 93.13 mHz respectively
Properties of photonic quantum well structures containing left-handed materials
Authors: Liu Li-Xiang  , Dong Li-Juan  , Liu Yan-Hong  , Yang Cheng-Quan  , Shi Yun-Long  ,   Institute of Solid State Physics, Shanxi Datong University, Datong 037009, China
Published: December 2020

According to the technology of LC-load transmission lines photonic quantum well structures are fabricated. Two kinds of structures are act as quantum well. While the left-handed materials works as well, the number of resonance modes increase with the thickness of left-handed materials. Compared with the condition of photonic crystals work as well, the left-handed materials act as well has the advantage of smaller size and adjusting. Experimental results are consistent with theory.