bluuebunny/crossref_metadata_2025 huggingface dataset:
Binary collision approximation for solitary wave in periodic dimer granular chains
Authors: Chen Qiong  , Yang Xian-Qing  , Zhao Xin-Yin  , Wang Zhen-Hui  , Zhao Yue-Min  ,   College of Science, China University of Mining and Technology, Xuzhou 221116, China;,   School of Chemical Engineering & Technology, China University of Mining and Technology, Xuzhou 221116, China
Published: December 2020

We study solitary wave propagation in periodic dimer granular chains of beads with the same material but different sizes by binary collision approximation. This kind of chain which is called N:1 dimer consists of pairs of N big beads and one small bead. First we present a method to map the actual chain into an effective chain, then use the binary collision approximation to obtain the transmitted solitary wave speed, the total time taken by the pulse to pass through the chain, and the frequency of oscillation of the small particle. Frequency of oscillation, which increases with the decrease of the radius of the small particle, is analytically obtained. And the results are in excellent agreement with numerical results. For the total time of the pulse passing through the chain, the results of theoretical analysis is in good agreement with numerical results when N 2. The relative error seems no change with the chain length but becomes larger with the increase of the value of N.
Pressure increase in foam-solid target from X-ray driven shock waves
Authors: Zhang Lu  , Yang Jia-Min  ,   Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China;,   Department of Engineering Physics, Tsinghua University, Beijing 100084, China
Published: December 2020

A strong pressure increase is produced by X-ray heating a foam-solid target in comparison with heating directly the solid target, due to impedance mismatch at the foam-solid interface. We study the pressure increase of CH foam-aluminum target, and find that only by shock present in foam can the ablative pressure in aluminum increase. In this paper an analytical model based on strong wave assumption is developed to study the shock impedance mismatching crossing the interface and the interaction of rarefaction with shock. We evaluate the shock pressure amplified in the aluminum layer as a function of density and adiabatic exponent, and show that the amplified pressure is a short high pressure pulse which is destroyed by rarefactions. This is in agreement with simulation results by MULTI code.
Oxygen adsorption on Nb(110) surface by first-principles calculation
Authors: Fang Cai-Hong  , Shang Jia-Xiang  , Liu Zeng-Hui  ,   School of Materials Science and Engineering, Beihang University, Beijing 100191, China
Published: December 2020

The adsorption of atomic oxygen on the Nb (110) surface is systematically investigated through the first-principles method for oxygen coverage ranging from 0.25 to 1 monolayer (ML)．It is found that the hollow site is the most energetically favorable for the whole coverage range considered and that the long-bridge site takes the second place．The work function increases almost linearly with the increase of oxygen coverage for the long-bridge site adsorption, whereas for the hollow site adsorption the work function decreases when the coverage is 0.25 ML or 0.5 ML and increases when the coverage is 0.75 ML or 1 ML．Using the planar averaged charge density and the dipole moment change we can explain the complicated change of work function induced by atomic oxygen adsorption．In addition, the interaction between O and Nb is analyzed by the surface atomic structure and electronic density of states．
First-prinicples study of Li-N and Li-2N codoped p-type ZnO
Authors: Hu Xiao-Ying  , Tian Hong-Wei  , Song Li-Jun  , Zhu Pin-Wen  , Qiao Liang  ,   College of Science, Changchun University, Changchun 130022, China;,   College of Science and Engineering, Jilin University, Changchun 130012, China;,   State Key Lab of Superhard Materials, Jilin University, Changchun 130012, China
Published: December 2020

Using the density-functional theory, the electronic structures of pure and Li-N, Li-2N codoped wurtzite ZnO systems are explored. It is find that Li-N and Li-2N codoped wurtzite ZnO systems each cause the Fermi level to cross the top of the valence band and to form shallow acceptor level, which indicates that p-type ZnO system can be obtained by codoping Li and N. Moreover, the carrier concentration is enhanced in the Li-2N codoped system and this structure is more favorable for the formation of p-type ZnO.
A semiempirical model for kink effect on the AlGaN/GaN high electron mobility transistor
Authors: Ma Ji-Gang  , Ma Xiao-Hua  , Zhang Hui-Long  , Cao Meng-Yi  , Zhang Kai  , Li Wen-Wen  , Guo Xing  , Liao Xue-Yang  , Chen Wei-Wei  , Hao Yue  ,   School of Technical Physics, Xidian University, Xi’an 710071, China;,   Key Laboratory for Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi’an 710071, China
Published: December 2020

Kink effect is analyzed in AlGaN/GaN devices primarily. A semiempirical model is given by analyzing the kink effect on AlGaN/GaN high electron mobility transistor and by considering the relationship between Vds,kink and gate voltage. Due to a little error between simulation results and measured data, this model can be used to identify the occurrence of kink effect and change in drain current. The analyses of experimental results and model simulation lead to a conclusion that impact ionization plays an important role in generating kink effect.
Experimental study of magnetic quantum-dot cellular automata function arrays
Authors: Yang Xiao-Kuo  , Cai Li  , Wang Jiu-Hong  , Huang Hong-Tu  , Zhao Xiao-Hui  , Li Zheng-Cao  , Liu Bao-Jun  ,   College of Science, Air Force Engineering University, Xi’an 710051, China;,   State Key Laboratory for Manufacturing System Engineering, Xi’an Jiaotong University, Xi’an 710054, China
Published: December 2020

Magnetic quantum-dot cellular automata (MQCA) function arrays are fabricated by electron beam lithography, thermal evaporation and lift-off technologies at room temperature. The effects of exposure dose and exposure time on MQCA function array patterns with three various spacings are experimentally investigated. The results show that the ideal pattern can only be obtained with 100 pA electron beam current and 0.38 μs exposure time. Magnetic force microscopy measurement on the fabricated inverter structure shows that the array demonstrates correct logic operation, which validates the feasibility of fabrication process for MQCA function arrays. Moreover, defect is observed in the experiments, simulations on the defective array show that missing nanomagnet defect in the array leads to signal inversion error.
Theory research of negative dynamic conductivity in electrically pumped multiple graphene layer structures with split gates
Authors: Zhang Yu-Ping  , Zhang Hong-Yan  , Yin Yi-Heng  , Liu Ling-Yu  , Zhang Xiao  , Gao Ying  , Zhang Hui-Yun  ,   Qingdao Key Laboratory of Terahertz Technology, College of Science,Shandong University of Science and Technology, Qingdao 266510, China
Published: December 2020

The negative dynamic conductivity of graphene in THz range makes it to be a promise medium in THz radiation and amplification. This paper proposes electrically pumped multiple graphene layer structures with split gates, sets up the theory model of electrically induced n-i-p junction, calculates the ac conductivity associated with the interband and intraband transitions under the conditions of population inversion, discusses the bias voltage, gate voltage, number of graphene layers and the momentum relaxation time dependences of ac conductivity. It is shown that the real part of dynamic conductivity within terahertz range can be negative in certain conditions, namely, interband radiation is greater than the intraband absorption, which demonstrates the feasibility of taking electrically pumped multiple graphene layer structures with split gates as an active medium in radiating terahertz coherent source.
Mesoscopic picture of fracture in porous brittle material under shock wave compression
Authors: Yu Yin  , Wang Wen-Qiang  , Yang Jia  , Zhang You-Jun  , Jiang Dong-Dong  , He Hong-Liang  ,   Department of Physics and Key Laboratory for Radiation Physics and Technology of Ministry of Education, Sichuan University, Chengdu 610064, China;,   National Key Laboratory of Shock Wave and Detonation Physics , Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

Void is one of the most common type of structure flaws existing in brittle materials, which dramatically affects the shock loading response of brittle materials. A quantitative discrete element method is employed in this work to study the fracture characteristics of porous isotropic brittle material under shock wave compression. Scenarios of isolated void, three types of simple distribution and random distribution of voids are computed, from which we find that shear fracture and local tensile fracture are two type of basic fracture modes for brittle material under shock wave compression. Coalescence of damage bands between voids can induce the collapse of voids at relatively low pressure, while stress relaxation caused by damage can shield fracture evolution in a certain zone. The combination of amplification and shielding effects of damage results in a unique pattern of alternate distribution of severe and mild damage zones. These simulation results present a basic physics picture for the understanding of evolution process and mechanism of fracture in porous brittle material under shock wave compression.
Effects of mechanical alloying process on thermoelectric properties of Bi2S3 Bulk
Authors: Ge Zhen-Hua  , Zhang Bo-Ping  , Yu Zhao-Xin  , Liu Yong  , Li Jing-Feng  ,   Beijing Key Lab of New Energy Materials and Technology, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China;,   State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
Published: December 2020

Bismuth sulfide (Bi2S3) polycrystalline bulks are fabricated by spark plasma sintering (SPS) combined with a mechanical alloying (MA) process. The electrical transport properties are investigated with a special emphasis on dry-milling speed, wet-milling time and mediums in MA process. The phase structure, the microstructure, and the electrical/thermal transport properties for the bulk samples are measured. The results suggest that the second Bi2O3 phase is formed because of the micro-oxidation when the wet medium is fixed to absolute ethyl alcohol, which refines the grain sizes and affects electrical transport properties of the bulk samples. Prolonging the wet-milling time in absolute ethyl alcohol causes the increase of resistivity and the decrease of the power factor. The electrical transport properties degrade due to the porous microstructure in bulk samples even without oxidization as the acetone is used as a milling medium. The largest ZT value 0.25 is obtained at 573 K for the samples dry-milled under 425 r/min for 15 h without wet-milling, which is the highest value in the reported values so far.
Time-delay effect of a stochastic genotype selection model
Authors: Wang Can-Jun  ,   Nonlinear Research Institute, Baoji University of Arts and Sciences, Baoji 721016, China
Published: December 2020

The time-delay effect of a genotype selection model driven by noise is investigated. The approximate delay Fokker-Planck equation is obtained based on the small time delay method and the stochastic equivalent rule. The explicit expression of the steady state probability distribution is derived, and the effect of the time delay on the steady sate properties of the genotype selection model driven by noise is discussed. It is found that the time delay can induce the transition from monostable state to bistable state. The time delay is helpful to select one type of genes from another type of mixing genes. The theoretical predictions are found to be in basic agreement with numerical results.
Cavity design and optimization for a passive hydrogen maser (Retracted Article)
Authors: Zhou Tie-Zhong  , Li Jing  , Gao Lian-Shan  ,   Beijing University of Aeronautics and Astronautics, Beijing 100191, China;,   Beijing Institute of Radio Metrology and Measurement, Beijing 100854, China
Published: December 2020

According to the theory of electromagnetism, we establish the equation of resonance frequency for simplified model of cavity of passive hydrogen maser. We find the optimal dimension of the cavity, which makes the product of the Q value and the filling factor reach a maximal value. The experimental results indicate that the so designed cavity can be utilized undoubtedly for the passive hydrogen maser, and achieve the Q value of 9800 and the filling factor of 1.2. Furthermore, the resulting capacity of storage volume is the biggest is ever reported cavities of passive hydrogen maser.
Research of quantitative remote sensing of natural gas pipeline leakage based on laser absorption spectroscopy
Authors: Zhang Shuai  , Liu Wen-Qing  , Zhang Yu-Jun  , Ruan Jun  , Kan Rui-Feng  , You Kun  , Yu Dian-Qiang  , Dong Jin-Ting  , Han Xiao-Lei  ,   Key Laboratory of Environmental Optics and Technology, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences,Hefei 230031, China;,   Shengli Engineering Design and Consulting Co., Ltd., Dongying 257026, China
Published: December 2020

Quantitative remote sensing of natural gas pipeline leakage based on laser absorption spectroscopy is reported. Key technical issues of mobile laser remote sensing are discussed through simulating leak detection. For quantitative remote sensing of trace leakage, the signals with counter-phase and isovalue of residual amplitude modulation are introduced. Then the offset is compensated, the influence of harmonic signal is reduced and sensitivity is improved. The improved soft-threshold denoising method is proposed by analyzing the characteristics of echo absorption spectrum. The results show that the signal-to-noise ratio is improved two times as great as that by the traditional soft-threshold denoising method and the shape of second harmonic (2f) signal is well preserved. The minimum remote sensitivity will be 80 ppm/m under the mobile remote sensing.
The influence of channel length on total ionizing dose effect in deep submicron technologies
Authors: Hu Zhi-Yuan  , Liu Zhang-Li  , Shao Hua  , Zhang Zheng-Xuan  , Ning Bing-Xu  , Bi Da-Wei  , Chen Ming  , Zou Shi-Chang  ,   The State Key Laboratory of Functional Materials for Informatics, Shanghai Institute of Microsystem and Information Technology, the ChineseAcademy of Sciences, Shanghai 200050, China;,   Graduate University of the Chinese Academy of Sciences, Beijing 100039, China
Published: December 2020

The influence of channel length on total ionizing dose effect in a 180 nm complementary metal-oxide semiconductor technology is studied. When other conditions such as radiation bias, device structure are the same, the overall radiation response is determined by the charges trapped in the oxide. The off-state leakage due to the charges trapped in the shallow trench isolation oxide inverting the parasitic sidewall channel has correlation with the channel length. A shorter channel leads to a larger leakage current. For the first time, we report that the leakage current also exhibits the radiation enhanced channel-length modulation effect, which further degrades the device performance.
Effects of some factors on X-ray spiral micro-computed tomography at synchrotron radiation
Authors: Wang Yu-Dan  , Peng Guan-Yun  , Tong Ya-Jun  , Zhou Guang-Zhao  , Ren Yu-Qi  , Yang Qun  , Xiao Ti-Qiao  ,   Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China;,   Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

It is difficult to obtain low-dose three-dimensional images of a long sample with high spatial resolution in a single scan using conventional X-ray micro-CT technique because the synchrotron X-ray beam is prolate. Spiral scanning is induced into synchrotron X-ray micro-CT (SR -CT) to resolve this problem. We investigate the effects of some factors on imaging quality and scanning speed by simulation and experiment, such as pitch, vertical beam width and projections per 180. When the pitch is not greater than 2, it is found that the relative error and the CT scanning speed decrease while the projections per 180 increases. The scanning speed increases with vertical beam width. Furthermore, as pitch becomes greater, the scanning speed becomes faster. The relative error is minimized by choosing the appropriate parameters to make the ratio between rotation and vertical transfer be an integer. The simulated results are confirmed by the synchrotron-based spiral micro-CT (SRS -CT) experiments performed at the Shanghai Synchrotron Radiation Facility and parameters are optimized. The results presented herein provide a theoretical and experimental basis for future applications of SRS -CT.
Generation of high purity quantum correlated photon pairs based on photonic crystal fiber
Authors: Cui Liang  , Li Xiao-Ying  , Li Lu  ,   Key Laboratory of Opto-electronic Information Technology of Ministry of Education, College of Precision Instruments and OptoelectronicsEngineering, Tianjin University, Tianjin 300072, China
Published: December 2020

A one-meter-long high nonlinear photonic crystal fiber is pumped by laser pulse train at room temperature, and the generated correlated idler and signal photons are centred at 830 nm and 1411 nm, respectively. The full widths at half maximum of the broad band filters of the two channel are 15 nm and 35 nm, respectively. The fitting results of single channel photon counts reveal that almost all the photons originate from spontaneous four wave mixing and the influence of Raman scattering is eliminated. When the production rate is 0.0085 photon per pulse, the ratio between coincidence rate and accidental coincidence rate is measured to be 102, which not only confirms the low noise property of the photon pair, but also shows that the photon pair are naturally narrow band, and the collecting efficiency in our experiment is high. Moreover, these high purity photon pairs connect different optical bands, and have potential applications in quantum information technologies.
Generation of microwave subcarrier phase modulation signal based on optical injection into a semiconductor laser
Authors: Wu Bo  , Yu Jin-Long  , Wang Wen-Rui  , Han Bing-Chen  , Guo Jing-Zhong  , Luo Jun  , Wang Ju  , Zhang Xiao-Yuan  , Liu Yi  , Yang En-Ze  ,   Optical Fiber Communication Laboratory, School of Electronic and Information Engineering, Tianjin University, Tianjin 300072, China;,   School of Physics and Electronic Science, Shanxi Datong University, Datong 037009, China
Published: December 2020

Radio-over-fiber technology has become an important solution for ultra wide band wireless communication, and the convergence of signal processing between optics and microwave/millimeter wave is more crucial. In this paper, microwave subcarrier phase modulation signal generation based on optical injection into a semiconductor Fabry-Perot laser is proposed. According to the period-one(P1) oscillation effect of laser output optical field, one modulation component of the optical phase modulation signal is amplified by sideband of P1 oscillation. The amplified component beats with injection optical carrier to generate microwave subcarrier. The phase shifts lead to the phase shift of subcarrier, thus the phase information is converted into phase information about microwave subcarrier. The optical phase-shift-keying signals at 1.3 Gb/s, 2.7 Gb/s, 2 Gb/s are converted into microwave subcarrier phase modulation signal, and the single sideband phase noise is measured. By logically comparing the demodulated signal with original signal, the feasibility of data information conversion is proved experimentally.
Study on wave plate angles of polarization controller in nonlinear polarization rotation mode-locked fiber laser
Authors: Zuo Lin  , Yang Ai-Ying  , Zhou Da-Wei  , Sun Yu-Nan  ,   School of Optoelectronics, Beijing Institute of Technology, Beijing 100081, China;,   School of Electronics Engineering and Computer Science, Peking University, Beijing 100871, China
Published: December 2020

Based on Jones matrices, a numerical model is proposed for the simulation of nonlinear polarization rotation (NPR) mode-locked fiber lasers with the advantage of a clear physical meaning. Ultra short pulses are derived with symmetric shape, stable amplitude and a square width of 0.28 ps. A self-starting NPR mode-locked fiber laser experimental setup is established and the fundamental repetition of the pulses is 67.35 MHz. Both the numerical simulation and the experimental results indicate that the angle of the half wave plate has a period of 180 while the quarter wave plate has a period of 90. Due to the influence of random birefringence, the tuning range of the angle of the wave plates measured in experiment is smaller than that shown in numerical simulation, which is verified by adding the effect of random birefringence in numerical simulation.
Dynamic wave superposition method for moving sound sources
Authors: Yang Dian-Ge  , Li Bing  , Wang Zi-Teng  , Lian Xiao-Min  ,   Department of Automotive Engineering, State Key Laboratory of Automotive Safety and Energy, Tsinghua University, Beijing 100084, China
Published: December 2020

In order to improve the identification of moving sound sources and solve the ghost source problem, the short-time wave superposition relation for moving sound source is established according to the Doppler frequency shift in short time, the equivalent sound source is pre-estimated by beam-forming, based on the pre-estimation result, the wave superposition equation is developed and the sound source is calculated by solving the equation. Then the dynamic wave superposition method for moving sound source is obtained. This method extends the wave superposition method to the case of the moving sound sources and solves the ghost source problem in moving sound source identification without adding extra microphones or changing the layout of microphone array. This method is used in the experiment to measure the moving sound sources, and satisfactory results prove the effectiveness of the method.
Preparation and properties of graphite-like carbon films fabricated by unbalanced magnetron sputtering
Authors: Wang Yong-Jun  , Li Hong-Xuan  , Ji Li  , Liu Xiao-Hong  , Wu Yan-Xia  , Zhou Hui-Di  , Chen Jian-Min  ,   State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000, China;,   Graduate University of the Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

A series of graphite-like carbon films is fabricated by the middle frequency magnetron sputtering technique. The microstructures and the morphologies of the resulting films are investigated by Raman spectroscopy, high resolution transmission electron microscopy and atomic force microscopy, respectively. The mechanical and the tribological properties of the films are studied by nanoindentation and CSM tribometer. The results show that the deposited carbon film is dominated by sp2 sites, and has an amorphous structure, a moderate hardness, low internal stress, high surface roughness and superior tribological properties. With the increase of the duty ratio, the intensity ratio between D and G peaks first decreases and then increases, while the film hardness first increases and then decreases. Tribological testing in humid atmosphere demonstrates that the present carbon film has a superior wear resistance (～10-11 cm3/N-1.m-1) and high load bearing capacity (～2.5 GPa). Although the duty ratio has no obvious influence on friction coefficient, the wear rate decreases obviously and then increases slightly with the increase of duty ratio. The superior tribological properties of the graphite-like carbon film are attributed mainly to its unique structure, low internal stress and high structure stability.
Preparation and physical properties of (BEDT-TTF)[FeBr4] crystal
Authors: Wu Yong-Sheng  , Wang Bing  ,   Hefei National Laboratory of Physical Sciences at the Microscale, University of Science and Technology of China, Hefei 230026, China
Published: December 2020

(BEDT-TTF)[FeBr4] single crystal is grown with electrochemical crystallization method, and its crystal structure is determined by four-circle single crystal diffraction. From 300 K to 185 K, the crystal resistivity is related to the efficiency of electronic thermal excitation and the strength of the electron scattering by ionized impurities, while from 185 K to 10 K, the conductivity depends mainly on the ionization of the impurities and defects in crystal. Because of electron scattering increased by the effect of Lorentz force, the magnetic reluctance has positive value. The magnetism of the crystal is determined mainly by magnetic ferric ions, and neither ferrromagnetic coupling nor antiferromagnetic coupling between the ferric ions in crystalis induced. The resonance signals of the electrons and the d electrons are found in the electron paramagnetic resonance spectra, and the -d coupling is enhanced as the temperature is decreased. When the crystal rotates along different axes, the resonance signal changed with the angle of rotation, is greatly different.
Electronic structure and optical properties of Cs/GaN(0001) adsorption system
Authors: Du Yu-Jie  , Chang Ben-Kang  , Wang Xiao-Hui  , Zhang Jun-Ju  , Li Biao  , Fu Xiao-Qian  ,   Institute of Electronic Engineering and Opto-Electric Technology, Nanjing University of Science and Technology, Nanjing 210094, China;,   Department of Physics, Institute of Binzhou, Binzhou 256603, China
Published: December 2020

We employ first-principles to calculate the adsorption energy, the band structure, the density of states, the charge populations, the work function and the optical properties of 1/4ML Cs adsorption on (2 2) GaN(0001) surface using the density-functional theory within a plane-wave ultrasoft pseudopotential scheme. The results show that the most stable position of Cs adatom on GaN(0001) surface is at the bridge site of N atoms for 1/4 coverage. The surface of GaN(0001) shows still metallic character after adsorption. Cs adatom affects mainly Ga atoms at surface. The transfer of Cs6s state electrons to Ga atoms at outmost layer leads to the decrease of work function. By analysis of optical properties, we can see imaginary part of dielectric function, absorption spectrum and reflected spectrum shift toward low energy after Cs adsorption.
Room temperature NO2-sensing properties and mechanism of the sensors based on tungsten oxide nanowires/single-wall carbon nanotubes composites
Authors: Qin Yu-Xiang  , Wang Fei  , Shen Wan-Jiang  , Hu Ming  ,   School of Electronic Information Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

One-dimensional tungsten oxide nanowires are synthesized by the solvothermal method. The sensors based on tungsten oxide nanowires/single-wall carbon nanotubes (SWNTs) composites are fabricated by introducing SWNT, and their NO2 sensing properties are evaluated at room temperature. X-ray diffraction and field emission scanning electron microscope characterizations indicate that the as-synthesized nanowires are monoclinic W18O49, and SWNTs are embedded within the nanowire matrix in the prepared tungsten oxide nanowires/SWNT composites. The tungsten oxide nanowires/SWNT composites-based sensors show high sensitivity, good selectivity and super fast response to NO2 gas at room temperature. The NO2 sensing properties of the sensors increase with the decrease of SWNT content. The sensing mechanism of the composites-based sensor is discussed and it is thought that the introduction of SWNT induces the formation of a large number of p-n hetero junctions and cross-linked diffusion channels in the structure of the composites, which are responsible for the good NO2 sensing properties at room temperature.
Hole scattering mechanism in tetragonal strained Si
Authors: Song Jian-Jun  , Zhang He-Ming  , Hu Hui-Yong  , Wang Xiao-Yan  , Wang Guan-Yu  ,   Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices, School of Microelectronics, Xidian University, Xi'an 710071, China
Published: December 2020

Based on Fermi's golden rule and the theory of Boltzmann collision term approximation, hole scattering mechanism in strained Si/(001)Si1-xGex, namely, tetragonal strained Si is studied, including ionized impurity, acoustic phonon, non-polar optical phonon and total scattering rates. It is found that the total scattering rate of hole in strained Si/(001)Si1-xGex decreases obviously with the increase of stress when Ge fraction (x) is less than 0.2 and the values continue to show a constant tendency. The total hole scattering rate of strained Si/(001)Si1-xGex decreases about 66% at most in comparison with one of unstrained Si. The hole mobility enhancement in strained Si material is due to the decrease of hole scattering rate. The result can provide valuable references for the research of hole mobility of strained Si materials and the design of PMOS devices.
Nuclear magnetic resonance and magnetic structure study on Sr doped Eu1-xSrxMnO3 system
Authors: Song Gai-Bei  , Cao Shi-Xun  , Zhang Jia-Jia  , Yuan Shu-Juan  , Shimizu Kenji  , Zhang Jin-Cang  ,   Department of Physics,Shanghai University, Shanghai 200444, China;,   Faculty of Science, University of Toyama, Toyama 930-8555, Japan
Published: December 2020

The magnetic properties of Eu1-xSrxMnO3 (x=0.4, 0.5, 0.6, 0.7) are systematically studied. Nuclear magnetic resonance, magnetization and electrical transport measurements are carried out, and the results indicate that the substitution of Sr for Eu could produce ferromagnetic phase in antiferromagnetic EuSrMnO3 matrix. The competition between ferromagnetic and antiferromagnetic phases induces the spin-glass behavior. In addition, the magnetic properties of Eu0.4Sr0.6MnO3 and Eu0.3Sr0.7MnO3 show more complex features at low temperatures, resulting mainly from the appearance of ferromagnetic clusters and the existence of disordered structure.
Influence of polarization effects on photoelectric response of AlGaN/GaN heterojunction p-i-n photodetectors
Authors: Liu Hong-Xia  , Gao Bo  , Zhuo Qing-Qing  , Wang Yong-Huai  ,   Key Laboratory of Wide Band-Gap Semiconductor Materials and Devices of the Ministry of Education, School of Microelectronics, XidianUniversity, Xi'an 710071, China
Published: December 2020

Based on the simulation of the polarization effect by the sheet charge layer approximately, the energy band structures and electric field distributions of AlGaN/GaN heterostructures with different doping concentrations of p-AlGaN and polarization effects are calculated by self-consistenly solving the Poisson-Schrödinger equations. The corresponding photoelectric response is calculated and discussed by solving the carriers continuity equation. The results show the interaction between the doping concentration and the polarization effect has an important influence on the performance of the p-i-n detector. Specially, under the condition of complete polarization, a high doping concentration in the p-AlGaN layer will result in a narrow depletion region in p-AlGaN layer and the i-GaN layer will be depleted easily, which corresponds to a low photocurrent. Similarly, a strong polarization will result in a wide depletion region in p-AlGaN and high photocurrent for the same doping concentration in p-AlGaN layer. Finally, the effect of temperature on the performance of the detector is calculated and analyzed. It is concluded that AlGaN/GaN heterostructure p-i-n ultraviolet detector can be used in the high temperature environment.
Dual band metamaterial absorber in microwave regime
Authors: Shen Xiao-Peng  , Cui Tie-Jun  , Ye Jian-Xiang  ,   State Key Laboratory of Millimeter Waves, Southeast University, Nanjing 210096, China;,   Department of Physics, China University of Mining and Technology, Xuzhou 221116, China
Published: December 2020

We report on the design, the fabrication and the measurement of a microwave dual band absorber in microwave regime. The single unit cell consists of two closed ring resonators and a metallic ground plane separated by an FR4 layer. Experimental results show that the absorber has two distinctive absorption peaks at frequencies 4.06 GHz and 6.66 GHz with absorptions 99.60% and 95.83%, respectively, and the absorptivity drops in a wide range of incident angle. Fourfold rotational symmetry of the geometry makes the absorber insensitive to transverse electric and transverse magnetic polarization. The dual band absorber is a promising candidate as absorbing elements in multi-frequency imaging and thermal detection, due to its multi-band absorption performance, polarization-insensitivity, and wide angle of incidence.
Study on the thermal conductivity of diamond-like carbon functionally graded material on copper substrate
Authors: Wang Jing  , Liu Gui-Chang  , Li Hong-Ling  , Hou Bao-Rong  ,   Key Lab oratory of Corrosion Science, Shandong Province, Institute of Oceanology, Chinese Academy of Sciences, Qingdao 266071, China;,   Faculty of Chemical, Environmental and Biological Science and Technology, School of Chemical Engineering, Dalian University of Technology,Dalian 116024, China
Published: December 2020

In recent years, with the rapid development of electronic technology and digital network information, copper has increasing applications in micro-electronics, micro-electro-mechanical systems and Hi-tech materials. However copper has its material limitations. In particular, it has relatively low hardness, high oxidation and wear rate, which have severely restricted its widespread applications. In this paper, aiming at difficulties of copper applications, Ti/TiC/DLC has been proposed as functionally graded material to deposit on the copper substrate with plasma depositing method, which intensifies the adhesion between DLC film and copper substrate and improves the properties of copper. The maximal value of thermal conductivity of DLC film with optimized parameter of graded intermediate layer is 3.63 Wm-1.K-1, which enhances the heat transfer effect of copper substrate.
Key issues for high-efficiency silicon thin film solar cells prepared by RF-PECVD under high-pressure-depletion conditions
Authors: Hou Guo-Fu  , Xue Jun-Ming  , Yuan Yu-Jie  , Zhang Xiao-Dan  , Sun Jian  , Chen Xin-Liang  , Geng Xin-Hua  , Zhao Ying  ,   Institute of Photo-electronics Thin Film Devices and Technique of Nankai University, Key Laboratory of Photo-electronics Thin Film Devices andTechnique of Tianjin, Key Laboratory of Photo-electronic Information Science and Technology of Ministry of Education (Nankai University),Tianjin 300071, China
Published: December 2020

Our recent work on deposition and characterization of hydrogenated microcrystalline silicon (μ c-Si:H) thin films and silicon thin film solar cells prepared by RF-PECVD under high-pressure-depletion conditions is summarized in this paper. Several key issues are studied in detail: 1) process windows for device-quality μ c-Si:H thin films, 2) formation mechanism of amorphous silicon incubation layer and the effective methods to reduce the incubation layer thickness, 3) modification of crystalline fraction volume of intrinsic μ c-Si:H layers and its influence on the device performance of μ c-Si:H solar cells, 4) deposition of high conductive p-type μ c-Si:H window layers with high crystalline fraction volume, and the influence of p-layer on the device performance. After solving the above key issues, a high efficiency of 8.16% is obtained for μ c-Si:H sing-junction solar cell with intrinsic layer prepared by RF-PECVD under high-pressure-depletion conditions. When it is used as bottom cell in a-Si:H/μ c-Si:H tandem solar cell, the efficiency of tandem cell reaches 11.61%.
The helix transition of semirigid polymer chains confined in cylinders
Authors: Tong Huan-Ping  , Zhang Lin-Xi  ,   College of Physics and Electronic Information Engineering, Wenzhou University, Wenzhou 325027, China;,   Department of Physics, Zhejiang University, Hangzhou 310027, China
Published: December 2020

In this paper we use an off-lattice bead-spring model to study the behaviors of polymer chain confined in an infinite cylinder by Monte Carlo simulations. Our simulation results show that when the bending energy b increases in the presence of the adsorption energy of the inner-surface of cylinder, the polymer chain is first randomly attracted on the inner surface of cylinder, and then gradually takes on helix structure, and finally is stretched into the rod-like structure. In order to understand the process of structure transition of polymer chain, we calculate the average of number of helical turns per chain Nt, the average percentage Ph of beads of helical structure per chain and the energy fluctuations with different values of bending energy b. The confined semirigid chain can form helical structure with the appropriate bending energy and the proper radius of cylinder. This study can help us understand the conformational behaviors of biopolymers in confined space.
Inplane oscillation analysis of the highline system with 1:2 internal resonance and dominate resonance
Authors: Ren Ai-Di  , He Xue-Jun  , Wang Xiao-Lin  , Zhang Liang-Xin  ,   Department of Logistics Command and Engineering, Navy University of Engineering, Tanggu 300450, China
Published: December 2020

A three-degree-of-freedom nonlinear dynamic model of piecewise highline system during underway replenishment is investigated when the lumped mass swings in which the influences of piecewise characteristic of highline cable's static profile due to cargo deadweight, the incline angle and the horizontal motion of the sending end are considered. Considering 1:2 internal resonance and primary resonance, ordinary differential equations are gained by decoupling the inertial terms. Perturbation analysis and numerical analysis are carried out by adopting the multiple-scale method, which will be the theoretical basis of the further research of nonlinear dynamics.
Projective synchronization of a five-term hyperbolic-type chaotic system with fully uncertain parameters
Authors: Yu Fei  , Wang Chun-Hua  , Hu Yan  , Yin Jin-Wen  ,   College of Information Science and Engineering, Hunan University, Changsha 410082, China
Published: December 2020

A new simple hyperbolic-type three-dimensional autonomous chaotic system is proposed. It is of interest that the chaotic system has only five terms which mainly rely on a nonlinear quadratic hyperbolic sine term and a quadratic cross-product term. Compared with other three-dimensional chaotic systems, the new system has not only less terms, but also a wider range of chaos when the parameter varies. Basic dynamical properties of the system are studied by numerical and theoretical analysis. Moreover the projective synchronization of the five-term hyperbolic-type chaotic system with fully uncertain parameters is also investigated in this paper. Based on Lyapunov stability theory and Barbalat's lemma, a new adaptive controller with parameter update law is designed to projectivly synchronize two chaotic systems asymptotically and globally, including two identical exponential-type chaotic systems and two non-identical chaotic systems. Numerical simulations show the effectiveness and the feasibility of the developed methods.
Numerical study of plasma aerodynamic actuation mechanism
Authors: Cheng Yu-Feng  , Nie Wan-Sheng  , Li Guo-Qiang  ,   Department of Space Equipment, the Academy of Equipment Command and Technology, Beijing 101416, China
Published: December 2020

Based on the physical processes of dielectric barrier discharge (DBD) and quasi-direct-current (quasi-DC) discharge, the plasma aerodynamic actuation mechanism is analyzed, then the numerical model of plasma aerodynamic actuation is founded, finally the DBD and the quasi-DC discharge plasma flow control processes are simulated in the cases of low velocity and high velocity. The results show that the aerodynamic actuation mechanism of DBD plasma is that the discharge changes three kinds of forces in continuum fluent medium, these being shear stress caused by Newton friction, body force caused by electro hydrodynamic and impulsive active force caused by pressure change, and the main aerodynamic actuation mechanism of DBD plasma is body force caused by electro hydrodynamic. The effect of body force is stronger in near space than in the sea level, plasma induced flow velocity increases in near space. The main aerodynamic actuation mechanism of quasi-DC discharge plasma in supersonic air flow is the thermal mechanism of heat plasma, the exploding wires diathermanous model found in this paper is good for the simulation of the process of surface quasi-DC discharge plasma incident shock. The effect of quasi-DC discharge plasma on the supersonic flow field is conform with the effect of protuberance with a bevel to the supersonic flow field, so it can be used to control the shock wave in supersonic aircraft.
-radiation damage of fiber Bragg grating and its effects on reflected spectrum characteristics
Authors: Ma Jing  , Che Chi  , Yu Si-Yuan  , Tan Li-Ying  , Zhou Yan-Ping  , Wang Jian  ,   National Key Laboratory of Tunable Laser Technology, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

The ionizing radiation effects on fiber Bragg grating are theoretically analyzed based on the color center model. And the relationship between the radiation induced refractive index change and dose is deduced. Fiber Bragg grating sample are irradiated by ray with a total dose of 1 106 rad. Under radiation the reflected spectrum peak wavelength of FBG sample is red shifted, but the full width at half maximent and the reflectivity are not changed obviously. The experiment results accord well with our function. With the low level radiation experiment, this expression can screen the FBG samples and predict their performances under high level radiation.
Effect of Doppler broadening on VIC-dependent two-photon absorption in Y-type four-level system
Authors: Jia Ke-Ning  , Liu Zhong-Bo  , Liang Ying  , Tong Dian-Min  , Fan Xi-Jun  ,   College of Physics and Electronics, Shandong Normal University, Jinan 250014, China;,   School of Physics, Shandong University, Jinan 250100, China
Published: December 2020

Using the numerical result, the influence of the Doppler broadening on the two-photon absorption related to vacuum induced coherence is discussed. In the absence of Doppler broadening, when VIC is absent, the absorption curve has a double-peak structure and the electromagnetically induced transparency phenomenon can occur; when VIC is present, the absorption curve has a single-peak structure and EIT phenomenon does not appear. In the presence of Doppler broadening, regardless of VIC being present or not, EIT phenomenon always can occur; when VIC is absent, no matter whether the propagation directions of the probe and driving fields are the same or opposite, with the Doppler broadening width (D) increasing, the absorption first increases and then decreases and the absorption curve changes gradually from a double-peak structure to a single-peak structure; when VIC is present, if propagation directions of the probe and driving fields are the same, with the value of D increasing, the absorption first increases and then decreases and the absorption curve changes gradually from a single-peak structure to a double-peak structure; if propagation directions of the probe and driving fields are opposite, with the value of D increasing, the absorption decreases monotonieally and the absorption curve remains a single-peak structure.
A new diagonal form fast multipole boundary element method for solving acoustic Helmholtz equation
Authors: Li Shan-De  , Huang Qi-Bai  , Li Tian-Yun  ,   State Key Laboratory of Digital Manufacturing Equipment and Technology, Huazhong University of Science and Technology, Wuhan 430074, China;,   Department of Naval Architecture and Ocean Engineering, Huazhong University of Science and Technology, Wuhan 430074, China
Published: December 2020

The conventional exterior acoustic Helmholtz boundary integral equation is prohibitively expensive for solving large-scale engineering problems. In order to effectively overcome this problem, the fast multipole method is introduced to the BIE, and accelerates the iterative solution for the system matrix equation. Due to using the diagonal form multipole expansions of the fundamental solution in the BIE, the computational efficiency of the new fast multipole boundary element method (FMBEM) is improved significantly compared to the conventional BEM. Both the computational complexity and memory requirement of the FMBEM are drastically reduced to O(N), where N is the number of degrees of freedom (DOFs). Numerical examples including a large submarine model with more than 420000 DOFs demonstrate the accuracy and efficiency of the FMBEM, and clearly show the advantage of the new algorithm for solving the large-scale acoustic problems. The developed FMBEM would be potential for engineering applications.
The analytical reduction of the Kirchhoff thin elastic rod model with asymmetric cross section
Authors: Wang Wei  , Zhang Qi-Chang  , Jin Gang  ,   State Key Laboratory of Engines, Department of Mechanics, School of Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

The Kirchhoff thin elastic rod models and related systems are always the important basis to research the topology and stability of the flexible structures in not only the macroscopic but also microscopic scale. Firstly the initial Kirchhoff equations are rebuilt in a complex style to suit the character of obvious asymmetry embodied on the cross section by considering the mathematical background of DNA double helix. Then we introduce a complex form variable solution of the torque, and extend the knowledge of effective bending coefficients as well as its facility in the high dimensional system by using the complicated system. As the result, a simplified second order ordinary differential equation with single variable is obtained. Furthermore the periodically varying bending coefficients of the DNA molecular are considered as the appended components to the effective bending coefficients. The whole reduction process makes the numerical simulation become not solely the exclusively eligible approach, and produces adaptable channel to quantitative analysis.
Size effect on the freezing behavior of aluminum nanowires
Authors: Zhou Guo-Rong  , Teng Xin-Ying  , Wang Yan  , Geng Hao-Ran  , Hur Bo-Young  ,   Shandong Provincial Key Laboratory of Preparation and Mearuement of Building Materials University of Jinan, Jinan 250022, China;,   i-Cube Center, School of Nano and Adcanced Materials Engineering, Gyeongsang National Univeristy, Jinju 660-701, South Korea
Published: December 2020

The freezing behaviors of Al nanowires with different section sizes and cooling rates are studied by using the classic molecular dynamics simulation via embedded atom potentials. In order to invesligate the evolution of the local clusters in the transformation of Al nanowires, the pair analysis technique is employed. The simulation results indicate that the final structure of Al nanowires is strongly affected not only by cooling rate, but also by the size effect during solidification from liquid. At a rapid cooling rate, the final structures are all helical multi-shelled structures. However, at a slower cooling rate, the structure changes from helical multi-shelled to crystalline via near-hexagonal shell structure with the increase of section size except that the thinnest Al nanowires break down.