bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis and evaluation on the noise of novel polarization interference imaging spectrometer
Authors: Zhang Chun-Min  , Huang Wei-Jian  , Zhao Bao-Chang  ,   School of Science, Xi'an Jiaotong University, Non-equilibrium Condensed Matter and Quantum Engineering Laboratory, Xi'an 710049, China
Published: December 2020

The principle of home-designed novel polarization interference imaging spectrometer is discussed. The noise of novel polarization interference imaging spectrometer is analyzed, and the expression of total noise related to system throughput is deduced. The noise induced by imaging spectrometer system and CCD image sensor is extracted from spectrometer image. The signal-to-noise ratio of novel polarization interference imaging spectrometer based on such noise analyses is discussed, which proves that though luminous throughput of imaging spectrometer system has a crucial effect on the total noise, it does not affect the trend of variation in signal-to-noise ratio. A new practical guidance is thereby provided for the accurate calculation of the signal-to-noise ratio of imaging interference and the application of denoising method effectively.
Image thresholding based on θ-division of 2-D histogram and maximum Shannon entropy
Authors: Wu Yi-Quan  , Zhang Jin-Kuang  ,   College of Information Science and Technology, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China
Published: December 2020

In view of the obvious wrong segmentation in commonly used region division of 2-D histogram and the non- universality of oblique segmentation method for image thresholding proposed recently, in this paper a much more widely suitable thresholding method is proposed based on the θ-division of 2-D histogram and the maximum Shannon entropy criterion. Firstly, the θ-division method of 2-D histogram is given. The region is divided by four parallel oblique lines and a line, where the angle between its normal line and gray level axis is θ degrees. Image thresholding is performed according to pixel's weighted average value of gray level and neighbour average gray level. The oblique segmentation method can be regarded as a special case of the proposed method at θ=45°. Then the formulae and its fast recursive algorithm of the method are deduced. Finally the segmented results and the running time at different values of θ are listed, which show that the segmented images achieve more accurate borders at smaller values of θ and the anti-noise is better at larger values of θ. The value of θ can be selected according to the real image characteristics and the requirements of segmented results. Compared with the algorithm of conventional 2-D maximum Shannon entropy method, the proposed method not only achieves more accurate segmentation results and more robust anti-noise, but also reduces the running time and memory space significantly.
Influence of the field with varying frequency modulation on atomic population inversion in non-ratating-wave approximation
Authors: Liao Xu  , Cong Hong-Lu  , Jiang Dao-Lai  , Ren Xue-Zao  ,   College of Science, Southwest University of Science and Technology, Mianyang 621010, China
Published: December 2020

By the method of coherent-state orthogonalization expansion, the evolution of atomic population inversion is investigated in the non-rotating-wave approximation. The numerical results indicate that, when field frequency and coupling do not change with time, the collapse-revival period of population inversion increases with the mean photon number of the field increasing, and the quick oscillation due to virtual photon process increases with couplings strengthening. When the frequency changes with time in the sine form, amplitude α and angle frequency β of the field both have a great influence on atomic population inversion. The sudden jumping of the field frequency can lead to some new collapses and rebibals in the evolution of atomic population inversion. Both of the field frequency forms can have an influence on quick oscillation due to virtual photon process.
Brillouin optical time domain analyzer based on bi-directional Raman amplification
Authors: Zhang Chao  , Rao Yun-Jiang  , Jia Xin-Hong  , Chang Liang  , Ran Zeng-Ling  ,   (1)Key Laboratory of Optical Fiber Sensing and Communications, Ministry of Education, School of Communication and Information Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China; (2)Key Laboratory of Optical Fiber Sensing and Communications, Ministry of Education, School of Communication and Information Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China; Key Laboratory of Optoelectronic Techn
Published: December 2020

We report a Brillouin optical time domain analyzer (BOTDA) based on bi-directional Raman amplification in this paper. With the bi-directional Raman amplification, the loss of the optical fiber and the depletion of Brillouin pump light can be compensated for efficiently, hence the measurement resolution is improved at the end of the optical fiber significantly. The detected signal is stable along the whole length of the sensing fiber, free from the spectral broadening caused by the modulation instability and the problem of uneven ness of detected signals of the conventional BOTDA. The Raman amplification is very useful for enhancing the measurement accuracy. With the bi-directional Raman pump, a temperature resolution of 0.6 ℃ was achieved over a sensing distance of 50 km with a 50 m spatial resolution. The signal-to-noise ratio and the optical signal power distribution characteristics of the system have been studied by experiment.
Periodically poled lithium niobate investigated by micro-Raman spectroscopy and luminescence
Authors: Zhang Yun  ,   School of physical science and technology, Southwest university, Chong qing 400715, China
Published: December 2020

Periodically poled lithium niobate (PPLN) is investigated by micro-Raman spectrum and luminescence in a confocale microscopy configuration. It is observed that there exists a different in fluorescence strength between reversed domain and non reversed domain. And the Raman result shows that a Raman forbidden line occurs in the interface between the two domains. Results suggests a new non-destructive method to image polarisation gratings and provide important information about the mechanism involved in the polarisation reversal process.
Design of novel polarization beam splitter in two-dimensional photonic crystal
Authors: Guo Hao  , Wu Ping  , Yu Tian-Bao  , Liao Qing-Hua  , Liu Nian-Hua  , Huang Yong-Zhen  ,   (1)Department of Physics, Nanchang University, Nanchang 330047, China; (2)The State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
Published: December 2020

We present the design and the simulation of an ultracompact high efficiency polarization beam splitter(PBS) based on the properties of the light waves propagating in straight waveguide and composite structure photonic crystal. The splitting properties of the PBS are numerically simulated and analyzed by using the plane wave expansion (PWE)method and finite difference time domain(FDTD) method. The PBS consists of three parts, namely, input waveguide, beam structure and output waveguide. It is shown that a high efficiency and a large separating angle for TE mode and TM mode can be achieved. Owing to these excellent features, including small size and high rate, the PBS makes a promising candidate in the future photonic integrated circuits.
Numerical study on 2-D photonic crystal with negative refractive index at multiple frequency bands
Authors: Tong Yuan-Wei  , Mao Yu  , Zhuang Song-Lin  ,   (1)College of Optical and Electronics Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China; (2)College of Science,University of Shanghai for Science and Technology, Shanghai 200093, China; (3)College of Science,University of Shanghai for Science and Technology, Shanghai 200093, China; College of Optical and Electronics Engineering, University of Shanghai for Science and Technology, Shanghai 200093, China
Published: December 2020

In this paper, a 2D photonic crystal (PC) with negative refractive index at multi-band is designed. Plane wave expansion method (PWEM) is used to obtain the band diagram and the equal-frequency surface (EFS). And the finite difference time domain (FDTD) simulation method is also used to analyze the equivalent refractive index of the PC. The results from both methods show that the equivalent refractive index of the PC at specifical band is negative.
Resolution enhancement of nearfield acoustic holography by the wave superposition approach
Authors: Zhang Xiao-Zheng  , Bi Chuan-Xing  , Xu Liang  , Chen Xin-Zhao  ,   Institute of Sound and Vibration Research, Hefei University of Technology, Hefei 230009, China
Published: December 2020

By the wave superposition approach a method of enhancing the spatial resolution of the nearfield acoustic holography is proposed. According to wave superposition approach, the source strengths of fictitious sources placed on the fictitious surface which is near the hologram surface are obtained by measuring the hologram pressure signal, then these fictitious sources are used to realize the interpolation of acoustic pressure, finally, the reconstruction can be done by the interpolated hologram pressure. By this method the spatial resolution of the reconstructed image can be improved, the measurement workload is reduced, and the measurement process is simplified. The parameters affecting the interpolated result are reasonably chosen by numerical simulations and the availability of this method is proved by numerical simulations and experimental resuets.
Investigation on the microscopic structure of bubble in dense particle system
Authors: Rong Liang-Wan  , Zhan Jie-Min  ,   (1)Department of Applied Mechanics and Engineering, Sun Yet-sen University, Guangzhou 510275, China; (2)Department of Applied Mechanics and Engineering, Sun Yet-sen University, Guangzhou 510275, China; Guangdong Province Key Laboratory of Coastal Ocean Engineering, Sun Yet-sen University, Guangzhou 510275, China
Published: December 2020

An efficient approach for discrete particles coupled with the continuous fluid based on unstructured meshes is developed by reorganizing gas phase governing equations. The bubble formation caused by a single central jet pulse in a two-dimensional Pulsed Fluidized Bed (PFB) is simulated. The calculation results show good agreement with the experimental observations. Then our work concentrates on the study of the microscopic structures of two PFBs with different width. Pressure drop pulse and force chain breaks to overcome the inter-particle locking are found just as the jet starts. The simulations show that the gas flows in the bed experience from two-main-vortices to multi-vortices then to two-secondary-vortices. Particles in the bed demonstrate three types of characterized behaviors, i.e., raising, downslide along the bubble's boundary, and creeping motion in the corner.
Convection and crystallization in vertically vibrated granular “capillary” systems
Authors: Jiang Ze-Hui  , Zhang Feng  , Guo Bo  , Zhao Hai-Fa  , Zheng Rui-Hua  ,   Department of Physics, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

The packing structure of identical spheres poured into a narrow cylindrical container will be influenced by the curvature of the container wall. This has been known as the wall effect. Our experiments reveal that under the action of vertical vibration, the wall effect can be enhanced, that the spheres, initially in a random packed state, can be organized through convection into a stable ordered packing consisting of a concentric array of cylindrical "shells" of spheres. In each shell the spheres are hexagonally arrayed. During such a structure transition, the packing density distribution, initially with a damped oscillatory variation along the radial direction, turns into an undamped one. The effects of interstitial air and inhomogeneity in the packing on the convection of particles, and thereby on the dynamics for the formation of "shell" structure, are analyzed. In addition, some discussions on the stability of the "shell" structure are made.
Investigation of slide-away discharges in HT-7 tokamak
Authors: Lu Hong-Wei  , Hu Li-Qun  , Lin Shi-Yao  , Zhong Guo-Qiang  , Zhou Rui-Jie  , Zhang Ji-Zong  ,   Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

In tokamak plasmas, the discharge will turn into "runaway" discharge if the density decays to a critical one. The discharge will enter into "slide-away" discharge if the density reaches a lower level. The slide-away discharge is characterized by high confinement of superthermal electrons which constitute a large part of plasma current. In HT-7 Tokamak, the slide-away discharge is achieved by reducing the plasma density. The relationship between plasma current and critical density of slide-away discharge is investigated. It is also find that the increase of density in slide-away discharge can make the confinement of superthermal electrons poor and lots of superthermal electrons lost from the vacuum chamber.
Single crystal growth and magnetic properties of spinel structure and spin ordering compound CaTi2O4
Authors: Liu Yong  , Zhou Rui  , Li Jing  , Zhang Yue  , Xiong Rui  , Yin Di  , Tang Wu-Feng  , Shi Jing  ,   Key Laboratory of Acoustic and Photonic Material and Device of Ministry of Education, Department of Physics,Wuhan University, Wuhan 430072, China
Published: December 2020

High quality and large-size single crystals of CaTi2O4 were prepared by the molten salt flux method. The X-ray diffraction and the EDS results showed that all the CaTi2O4 crystals have the rom temperature lattice parameters a=9.781 ?,b=9.966 ? and c=3.148 ?, and all the samples have perfect stoichiometric composition. Through the magnetic susceptibility measurement, we first obtained the Van-Vleck paramagnetic parameter of CaTi2O4 of 6.85×10－5cm3/mol, and Cure-Weiss temperature of -0.44 K, revealing that CaTi2O4 is a weak ferromagnetic compound. Further more, the existence of Ti-Ti dimer was confirmed by anisotropy measurement, the structure and direction of the antiferromagnetic dimer chains were also determined.
Shock induced polymorphism phase transitions in high density glass
Authors: Liu Xun  , Zhou Xian-Ming  , Li Jun  , Li Jia-Bo  , Cao Xiu-Xia  ,   (1)College of Physical and Technology, Sichuan University, Chengdu 610065,China; (2)College of Physical and Technology, Sichuan University, Chengdu 610065,China; Laboratory for Shockwave and Detonation Physics, Institute of Fluid Physics ,China Academy of Engineering Physics, Mianyang 621900,China; (3)Laboratory for Shockwave and Detonation Physics, Institute of Fluid Physics ,China Academy of Engineering Physics, Mianyang 621900,China
Published: December 2020

Plate impact experiments are conducted on high density glass (HDG) with an initial density of ～4.817g/cm3 (Brand ZF6) at a two-stage light gas gun facility. A copper flyer plate is used as a standard sample. Experimental shock pressure is between 52.1GPa and 167.8GPa. A multi-wavelength pyrometer and optical analyzer technique are used to determine the Hugoniot curve, sound velocity and shock temperature of HDG. The experiment results reveal that polymorphism phase transitions occur in HDG under compression, and the onset pressures are ～23, ～78 and ～120GPa, respectively. The measured sound velocity first increases and arrives at about 78GPa, then decreases rapidly, and increases again with pressure increasing. Beyond ～120 GPa, the longitudinal sound velocity turns in to bulk sound velocity, indicating the melting of HDG. Measured shock temperatures also show discontinuities at ～78 and ～120GPa, after which its increase rate becomes small and consistent with the calculated Lindemann melting line, confirming the above HDG phase transformation behaviors. Our Hugoniot data are consistent well with LASL shock Hugoniot data of HDG, which shows discontinuity only at about 23GPa, indicating that the phase transitions at 78 and 120GPa are not first-order ones. Our shock data and the gained knowledge of dynamic response behavior of HDG are valuable for improving the accuracies in sound velocity measurements for metals and non-metals at pressures over a megabar range.
Study on the influence of temperature on interfacial micro-friction
Authors: Wang Ya-Zhen  , Huang Ping  , Gong Zhong-Liang  ,   (1)School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China; (2)School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640, China; Guangdong College of Industry and Commerce, Guangzhou 510510, China
Published: December 2020

The influence of temperature on micro-friction at point contact was studied on the basis of analysis of micro interfacial friction. Based on Towle's experimental relationship between sheer strength and temperature and the theory of thermal effect on mechanical properties of material, the relationship between the friction force and temperature is deduced. Theoretical analysis shows that the friction decreases as the temperature increases when the interfacial temperature is lower than the material's Debye temperature. Theoretical calculation and experimental results of atomic force microscopy show the same trend, indicating that the theory and the method presented in this paper is feasible.
First-principles calculation of structure, electronic and elastic properties of MAlH4(M=Na, K)
Authors: Hou Yu-Qing  , Zhang Xiao-Dong  , Jiang Zhen-Yi  ,   (1)Department of Electronic, Northwest University, Xi'an 710069,China; (2)Department of Electronic, Northwest University, Xi'an 710069,China; Institute of Modern Physics, Northwest University, Xi'an 710069,China; (3)Institute of Modern Physics, Northwest University, Xi'an 710069,China
Published: December 2020

We have calculated the structure, electronic and elastic properties of MAlH4(M=Na,K) based on density functional theory. We found both NaAlH4 and KAlH4 are insulators and are characterized by Al—H covalent bond and M—AlH4 ionic bond. The elastic constants are small compared with those of other compounds (e.g MgH2) and decrease in the MAlH4(M=Li,Na,K,Rb,Cs) series. We explain this phenomenon according to the volume change of MAlH4(M=Li,Na,K,Rb,Cs) .
A study of radiative properties of randomly distributed soot aggregates
Authors: Lei Cheng-Xin  , Wu Zhen-Sen  ,   (1)School of Science, Shandong University of Technology, Zibo 255049, China; (2)School of Science, Xidian University, Xi'an 710071, China
Published: December 2020

Based on fractal theory, the Monte Carlo method is used to simulate the structures of fractal soot aggegates in random distribution. The radiative properties of randomly distributed soot aggregates are studied using the discrete dipole approximation (DDA), and the effects of the fractal dimension ,the monomer diameters , the number of monomers in the soot aggregates and the refractive index on the radiative properties of aggregated soot particles are analyzed. The results show that the radiative properties of randomly distributed soot aggregates of a given fractal dimension are complex functions of the monomer diameters, the number of monomers in the aggregates,and the refractive index. For small values of the monomer diameters, the absorption cross section of soot aggregates tends to be relatively constant when the fractal dimension is small, but increases rapidly when the fractal dimension exceeds two. However, a monotonical reduction in light absorption with the increase of the fractal dimension is observed for soot aggregates with sufficiently large monomer diameters, number of monomers,and refractive index. The scattering cross section , extinction cross section and single-scattering albedo increase monotonically with the increase of the fractal dimension. In a word, the results for soot aggregates differ profoundly from those calculated for the equivalent spherical particles, and the discrepancies between them change litte with the increase of the fractal dimension.This research is of scientific value in studying the radiative properties of aerosols and their climatic effects.
Transient thermal effect of semi-insulating GaAs photoconductive switch
Authors: Shi Wei  , Ma Xiang-Rong  , Xue Hong  ,   (1)Department of Applied Physics, Xi' an University of Technology, Xi'an 710054, China; (2)Department of Applied Physics, Xi' an University of Technology, Xi'an 710054, China; State key Laboratory of Electrical Insulation for Power Equipment, Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

Results of experiments of the 4 mm gap semi-insulating(SI) GaAs photoconductive switch triggered by 1064 nm, 1.0 mJ pulse laser showed the nonlinear mode when the bias field was 3800 V. Under the same bias electric field and trigger light energy conditions, the switch outputs stably nonlinear electrical pulses, and the switch surface injury mark is caused by filamentation after 1500 times triggering. Analysis shows that under given conditions of trigger energy and electric field, two transient thermal effects occur in the switch chip, namely the thermal relaxation and photoactivated charge domain-phonon drag, respectively. Thermal relaxation time is shortened to the order of picoseconds or subpicoseconds, thermal relaxation process leads to the thermal conduction relaxation. When photoactivated charge domain moves at 107cm/s speed from cathode to anode, switch chip transient temperature makes relaxation oscillations owing to these effects, and the rapid increase of temperature in the chip is constrained. Photoactivated charge domain-phonon drag effect transmits in the direction of the dislocation movement, the temperature in mobile region increases when the flow of thermal energy carried by the phonons was concentrated in the movement plane, the injury of filamentation is produced by superposition and cumulation of mobile tracks.
N-polar n-type ohmic contact of GaN-based LED on Si substrate
Authors: Wang Guang-Xu  , Jiang Feng-Yi  , Feng Fei-Fei  , Liu Jun-Lin  , Qiu Chong  ,   (1)Education Ministry Engineering Research Center for Luminescence Materials and Devices, Nanchang University, Nanchang 330047, China; (2)Education Ministry Engineering Research Center for Luminescence Materials and Devices, Nanchang University, Nanchang 330047, China; Latticepower (jiangxi) Corporation, Nanchang 330096, China; (3)Latticepower (jiangxi) Corporation, Nanchang 330096, China
Published: December 2020

Ti/Al contacts have been deposited by electron beam Evaporation onto N-polar n-type surfaces of GaN-based vertical structure LED on Si substrate. The effect of AlN buffer layer on ohmic contact of these chips has been investigated through I-V characteristic. The results shown Ti/Al contacts prepared on N-polar n-type surface without AlN buffer layer became ohmic contact after annealing in the temperature range of 500—600℃. The as-deposited Ti/Al contacts on N-polar n-type surface with AlN buffer layer shown ohmic behaviors with a specific contact resistivity of 2×10-5 Ωcm2 and maintained ohmic contact characteristics until anneal at 600℃. Therefore, The exsiting of AlN buffer layer is the key to forming highthermal stability ohmic contact for GaN-based vertical structure LED on Si substrate.
Conduction mechanisms in (La0.7Sr0.3MnO3)m(BiFeO3)n superlattice
Authors: Jiang Ping  , Wang Shun-Li  , Tang Wei-Hua  , Zhu Hui-Wen  , Mao Ling-Feng  ,   (1)Department of physics, Center for Optoelectronics Materials and Devices, Zhejiang Sci-Tech University, Hangzhou 310018, China; (2)School of Electronics and Information Engineering, Soochow University, Suzhou 215021, China
Published: December 2020

(La0.7Sr0.3MnO3)m(BiFeO3)n superlattices were grown in situ on SrTiO3(001) substrates by rf magnetron sputtering. The current-voltage measurements were performed under the temperature of 50—150℃ for the superlattices specimens. The analysis showed that the leakage current increased with increasing the temperature or decreasing the BFO thickness in the samples. And the conduction mechanisms of the prepared (La0.7Sr0.3MnO3)m(BiFeO3)n superlattices were analyzed according to common insulator conduction models. It exhibited that the space-charge-limited current were dominated in the as fabricated (La0.7Sr0.3MnO3)m(BiFeO3)n superlattices in high temperature or high electrical field.
Study on the simulation and measurement of ring structures metamaterial absorber
Authors: Xiao Ting  , Yang He-Lin  , Xiao Bo-Xun  , Cheng Yong-Zhi  ,   (1)College of Physical Science and Technology, Huazhong Normal University, Wuhan 430079,China; (2)Engineering Geophysical Research Center, Yangtze University, Jingzhou 434023,China
Published: December 2020

In this paper, two kinds of ring-type microwave electric resonant structures were proposed, which were appropriately assembled with metal wires to form electromagnetic coupling units. The coupled structures have resonance response to the incident electromagnetic wave, and absorb the electric and magnetic fields strongly. We simulated these two kinds of coupled structures, and then optimized the simulation results to achieve the best absorption properties. The electromagnetic properties (the reflection coefficients S11 and the transmission coefficients S21) of metamaterial absorber sample were measured using free space method in microwave frequency from 8 to 12 GHz. At 10.7 GHz and 10.07 GHz, the absorptivity reaches 95% and 98%, respectively.
Two-color quantum well infrared photodetector simultaneously working at 10—14 μm
Authors: Liu Xiao-Yu  , Ma Wen-Quan  , Zhang Yan-Hua  , Huo Yong-Heng  , Chong Ming  , Chen Liang-Hui  ,   Laboratory of Nano-Optoelectronics, Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
Published: December 2020

We have demonstrated a two-color quantum well infrared photodetector (QWIP) exhibiting simultaneous photoresponse with cutoff wavelengths at 11.8 and 14.5 μm, respectively. Strong photocurrent signals are observed at temperature of 77 K. The simultaneous two-color photoresponse is achieved by utilizing a simple design by broadening the width of the quantum well and selecting an appropriate doping density. The two peaks are attributed to the intersubband transitions from the ground state to the first excited state (bound state) and to the fifth excited state (continuum state), respectively.
Effect of different cap layers on the structure and optical properties of InAs/GaAs self-assembled quantum dot
Authors: Tian Peng  , Huang Li-Rong  , Fei Shu-Ping  , Yu Yi  , Pan Bin  , Xu Wei  , Huang De-Xiu  ,   Wuhan National Laboratory for Optoelectronics,College of Optoelectronic Science and Engineering,Huazhong University of Science and Technology,Wuhan 430074,China
Published: December 2020

Self-assembled InAs/GaAs quantum dot structures with different cap layers are grown by metal-organic chemical vapor deposition.The structure and optical properties of quantum dots are investigated using atomic force microscopy and photoluminescence.The cap layers sandwiched between quantum dots are composed of a low-temperature layer and a high-temperature layer.The comparative studies on low-temperature cap layer show that In graded InGaAs layer structure improves the uniformity of quantum dots,decreases coalescent islands and enhances photoluminescence intensity.Emission wavelength shifts from 1256.0 nm to 1314.4 nm when the thickness of graded InGaAs low-temperature cap layer increases form 6.8 nm to 12 nm.The research on high-temperature cap layer structure indicates that In graded InGaAs layer can increase photoluminescence intensity.
Strain relaxation mechanism of pseudomorphic SiGe using low-temperature technology
Authors: Yang Hong-Dong  , Yu Qi  , Wang Xiang-Zhan  , Li Jing-Chun  , Ning Ning  , Yang Mo-Hua  ,   The State Key Laboratory of Electronic Thin Films and Integrated Devices,University of Electronic Science and Technology of China,Chengdu 610054,China
Published: December 2020

In the light of energy balance and screw dislocation formation model,a detailed analysis is presented on strain relaxation mechanism of pseudomorphic SiGe based on the experimental result that shear modulus of low-temperature Si (LT-Si) is less than that of SiGe.The mechanism shows that strain is relaxed by dislocation formed in LT-Si buffer layer when the thickness of pseudomorphic SiGe film is smaller than the critical thickness, and dislocations prefecentially form in LT-Si layer then the thickness of the film is equal or exceeds the critical thickness,which agrees with the experimental results reported in the literature.At the same time,an experiment was carried out to grow relaxed Si0.8Ge0.2 virtual substrate using LT-Si technology.The results indicated that dislocations were resmicted to the LT-Si layer and the relaxation degree was 85.09% without threading dislocations in Si0.8Ge0.2.The experimental results proved that the strain of pseudomorphic Si0.8Ge0.2 is relaxed by dislocations formed in the LT-Si buffer layer.
Study of ZnS thin films prepared by RF magnetron sputtering technique
Authors: Xie Jing  , Li Bing  , Li Yuan-Jie  , Yan Pu  , Feng Liang-Huan  , Cai Ya-Ping  , Zheng Jia-Gui  , Zhang Jing-Quan  , Li Wei  , Wu Li-Li  , Lei Zhi  , Zeng Guang-Gen  ,   College of Materials Science and Engineering ,Sichuan University ,Chengdu 610064 ,China
Published: December 2020

ZnS thin films were prepared on glass substrate by RF magnetron sputtering technique.The quality of ZnS films formed at different deposition pressures,annealing temperatures and substrate temperatures were studied.The change of the film microstructure was analyzed by XRD and the lattice stress was evaluated.The spectral transmittance was measured by a spectrometer.From the spectrum,the band gap and Urbach energy were calculated.Scanning electron microscopy (SEM) was used to study the morphology of the surface of the sample.The result showed that there is big stress in the lattice when the substrate is at room temperature,and the value of stress increases with the pressure.After annealing at 300 ℃,the stress is minimal.When the substrate temperature is 350 ℃,the stress decreases,at the same time,ZnS films have good transmittance,and annealing at 300 ℃ improves the film quality.
The resonance behaviour and dynamic stabilities of strained superlattice
Authors: Luo Shi-Yu  , Li Hong-Tao  , Wu Mu-Ying  , Wang Shan-Jin  , Ling Dong-Xiong  , Zhang Wei-Feng  , Shao Ming-Zhu  ,   College of Electronic Engineering,Dongguan University of Technology,Dongguan 523106, China
Published: December 2020

The dynamic behaviour in the vicinity of the interface for the strained superlattice is discussed in the classical mechanics frame based on the Seeger equation. We found that the motion and the accumulation of the dislocations by the non-linear resonance may give rise to the lamination or the fracture of the superlattice. At first, byintroducing the damping term,the Seeger equation describing the dislocation motion is reduced to the generalized Duffing equation describing superlattice in the small amplitude aproximation. Secondly,the main resonance, the super-harmonic resonance and the sub-harmonic resonance of the system are analysed by the multiscale method. The critical condition for the system to enter into resonance is found. It shows that the critical condition is related to the parameters of the system,by adeguately regulating the parameters of the system,the resonance can be avoided in principle,then the stability and the perfection of the superlattice materials may be bellev ensured.
Preparation of multiferroic of Bi0.85Nd0.15FeO3 thin films prepared by sol-gel method
Authors: Guo Dong-Yun  , Li Chao  , Wang Chuan-Bin  , Shen Qiang  , Zhang Lian-Meng  , Tu Rong  , Goto Takashi  ,   Institute for Materials Research,Tohoku University,Sendai 980-8577,Japan;,   State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, and School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, China;,   State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, and School of Materials Science and Engineering, Wuhan University of Technology, Wuhan 430070, China; Institute for Materials Research,Tohoku University,Sendai 980-8577,Ja
Published: December 2020

The Bi0.85Nd0.15FeO3 thin films were prepared on the Pt/Ti/SiO2/Si substrates by Sol-gel method.The effect of annealing temperature on formation of Bi0.85Nd0.15FeO3 phase was investigated. It was found that the Bi0.85Nd0.15FeO3 phase was formed and coexisted with the impurity phase when the films annealed at 450 ℃. The single-phase Bi0.85Nd0.15FeO3 films were obtained,when they were annealed at 500—600 ℃. Bi0.85Nd0.15FeO3 films annealed at 600 ℃ had saturated magnetization about 44.8 emu/cm3, remnant polarization (2Pr) about 16.6 μC/cm2,dielectric constant 145 and dielectric loss 0.032(1 MHz), respectively.
Preparation and characterization of homogeneity and fine pyramids on the textured single silicon crystal
Authors: Zhou Chun-Lan  , Wang Wen-Jing  , Zhao Lei  , Li Hai-Ling  , Diao Hong-Wei  , Cao Xiao-Ning  ,   Institute of Electrical Engineering,Key Laboratory of Solar Thermal Energy and Photovoltaic System of Chinese Academy of Sciences, Beijing 100190, China
Published: December 2020

Texturing of silicon surface is a major way to increase short circuit current and then improve the efficiency of silicon solar cells by effective light trapping.The anisotropic texturing of a (100) silicon surface was performed using tetramethyl ammonium hydroxide (TMAH) solution and NaClO additive in combination with continual ultrasonic wave treatment.The effect of ultrasonic wave and NaClO on the nucleation and growth of finc pyramids during the anisotropic texturing, and the effect of size of pyramids on the minority carrier lifetime of textured silicon wafer after the high temperature process were investigated.The enhancement of homogeneity of the smaller pyramids in the textured structure of silicon crystalline is obtained by adding continnal ultrasonic wave treatment to control the time of H2 bubble staying on the silicon surface and the speed of H2 detaching from the surface.The weighted mean reflectance for the solar spectrum AM 1.5G is 12.4% for the silicon surface with the optimal size of pyramids.After high temperature oxidation, the size of pyramid has an obvious exponential relation with the minority carrier lifetime of textured silicon wafer.
Light transmission in thermal stress-induced birefringent medium
Authors: Cen Zhao-Feng  , Li Xiao-Tong  ,   State Key Laboratory of Modern Optical Instrumentation, Zhejiang University, Hangzhou 310027, China
Published: December 2020

In this paper the temperature and thermal stress distribution in a simplified-mode transparent slab is calculated and then variation of refractive index is acquired based on the photo-elastic theory. Using the vector differential algorithm the refractive behavior of rays in such media is simulated, and luminous intensity distribution and shape of fringes at the receiving plane is predicted. The output of the program is in coincidence with the check experiment based on photo-elasticity technique, which indicates the correctness of our analysis method and light transmission calculation method. This research provides a practical means for improving the imaging quality of optical instruments.
Optoelectronic properties of ZnO nanorods fabricated by hydrothermal decomposition and its applications in organic/inorganic electroluminescence heterostructure
Authors: Huang Jin-Zhao  , Li Shi-Shuai  , Feng Xiu-Peng  ,   School of Science, University of Jinan, Jinan 250022, China
Published: December 2020

The ZnO nanorods, primarily aligned perpendicular to the substrate, have been fabricated by hydrothermal decomposition. The scanning electron microscopy and photoluminescence method were used to characterize their morphology and optical properties, respectively. The field emission properties were also studied. The results indicate that the ZnO nanorods present good morphology, structure and good field emission property. The on-set field is 2.8 V/μm at a current density of 1 μA/cm2. The emission current density can reach 0.67 mA/cm2 at 6.4 V/μm. The field emission enhancement factor is 3660. Fluctuation of the current density is less than 25% at 4.5 V/μm for 5 hours. In the organic/inorganic electroluminescence heterostructure, with the ZnO nanorods as the electron transport layer and the m-MTDATA(4,4',4″-tris{N,(3-methylphenyl)-N-phenylamino}-triphenylamine) as the hole transport layer, the ultra-violet emission of ZnO nanorods was obtained with a 40 nm blue-shift compared with the photoluminescence of the ZnO nanorods.
Study of the resolution of limited-view photoacoustic tomography
Authors: Wu Dan  , Tao Chao  , Liu Xiao-Jun  ,   Key Laboratory of Acoustics of Ministry of Education and Institute of Acoustics, Nanjing University, Nanjing 210093, China
Published: December 2020

In this study, numerical experiments are carried out to quantitatively investigate the effects of limited-view scanning on the resolution of photoacoustic tomography. An empirical formula is provided to approach our numerical results.The results of the study are helpful for the design of scanning trajectory and the evaluation of reconstruction.
The investigation on the mechanism of enhanced performance of dye-sensitized solar cells after anode modified
Authors: Kou Dong-Xing  , Liu Wei-Qing  , Hu Lin-Hua  , Huang Yang  , Dai Song-Yuan  , Jiang Nian-Quan  ,   (1)College of physics and electronic information engineering, Wenzhou University, Wenzhou 325035, China; (2)Key Laboratory of Novel Thin Film Solar Cells, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

IMPS(intensity-modulated photocurrent spectroscopy) and IMVS(intensity–modulated photovoltage spectroscopy) measurements are utilized to analyse different mechanisms for enhancing the performance of dye-sensitized solar cells(DSC) based on modified anode. Electron transport and back reaction in DSC are investigated under different illumination intensities. The modifications of anode, blocking layer and modified TiO2films, are performed by electrodeposition. It is found that short-current density Jsc and efficiency η of DSC are improved, but different mechanisms are obtained: the optimization of TCO by coating a blocking layer can effectively extend electron lifetime τ n, but it has little influence on electron transport. On the other hand, the optimization of TiO2 film can enhance electron transport, finally shorten transit time τ d and extend τ n.
Influence of surface effect to the performance of LiMn2O4 cathode material for lithium ion batteries
Authors: Ouyang Chu-Ying  , Hu Guo-Jin  ,   (1)Department of Physics, Jiangxi Normal University, Nanchang 330022, China; (2)Jiangxi Institute of Education, Nanchang 330029, China;Department of Physics, Jiangxi Normal University, Nanchang 330022, China
Published: December 2020

The surface geometrical and electronic structure of LiMn2O4 (001) are investigated via a density functional approach within the spin-dependent generalized gradient approximation (GGA). Large relaxations perpendicular to the (001) plane of surface and subsurface atoms are observed, which is partly responsible for the Mn dissolution problem of the material when used as cathode material for lithium ion batteries. Because of the surface effect, only Mn3+ ions are observed at the LiMn2O4 (001) surfaces, which is very active for the disproportionation reaction occurs at the electrode/electrolyte interface. The calculated results are also in good agreements with experimental observations.
Evaluation model for robustness of digital watermarking
Authors: Zeng Gao-Rong  , Qiu Zheng-Ding  ,   Institute of Information Science, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

Robustness is one of the most important requirements when digital watermarking is applied. Different from the StirMark test and various simulation tests, a mutual information function is defined as a criterion to measure the robustness of watermarking algorithm. Taking the additive spread spectrum watermarking scheme and quantization index modulation (QIM) watermarking scheme as two examples, the calculation formulas of mutual information function are derived to evaluate the robustness of the algorithms. Numerical computation of mutual information is performed with change of watermark noise rate (WNR). In the experiment, spread spectrum watermarking is implemented in discrete cosine transform (DCT) and QIM watermarking is implemented in discrete wavelet transform (DWT). The statistic bit error rate (BER) is derived against Gaussian distribution noise and JPEG compression. Experiment results show that the evaluation conclusion of mutual information method is in accordance with the empirical BER. Mutual information can be selected as a cost function to predict the BER.
Nonlinear characteristics extraction from electrical signals of dorsal spinal nerve root evoked by acupuncture at Zusanli point
Authors: Guo Yi  , Guo Yong-Ming  , Liu Yang-Yang  , Han Chun-Xiao  , Wang Jiang  , Che Yan-Qiu  , Deng Bin  ,   (1)College of Acupuncture, Tianjin University of Traditional Chinese Medicine, Tianjin 300193, China; (2)School of Electrical and Automation Eng., Tianjin University, Tianjin 300072, China
Published: December 2020

Neural system generates various kinds of fire patterns when stimulated by external or internal inputs. Acupuncture, as a mechanical action, is equivalent to an external stimulus to the neural system. When stimulated by the acupuncture, the neural system can evoke irregular electrical signals. Neural system is a complex nonlinear dynamic system that possesses strong nonlinear characteristic, so it is necessary to introduce the nonlinear time series analysis method to study the neural electrical signal. In this paper, an experiment is designed in which acupuncture is made at Zusanli with four different acupuncture manipulations to obtain action potentials on dorsal spinal nerve root. The concept of the interspike interval (ISI) is used for the study of the acupuncture electrical signals. Several nonlinear characteristic parameters are extracted, such as the Lyapunov exponent, correlation dimension and Lempel-Ziv complexity, and the neural coding of the electrical signal evoked by different acupuncture manipulations is obtained. It is also shown that under the effect of the acupuncture, the electrical signals of dorsal spinal nerve root based on acupuncture at Zusanli point has distinguished chaotic features.
The detection error analysis of Hartmann-Shack wavefront sensor based on electron multiplying charge-coupled devices
Authors: Zhang Yan-Yan  , Rao Chang-Hui  , Li Mei  , Ma Xiao-Yu  ,   (1)Institute of Optics and Electronics, the Chinese academy of sciences, Chengdu 610029, China; (2)Institute of Optics and Electronics, the Chinese academy of sciences, Chengdu 610029, China; Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

The detection error of Hartmann-Shack (H-S) wavefront sensor is one of the main errors in adaptive optical systems. In this paper, the detection error of H-S wavefront sensor based on the electron multiplying charge-coupled devices (EMCCD) is firstly analyzed and the detection error formula is established. Furthermore, the numerical simulation and experimental results show that the centroid detection error is related to the gain of EMCCD. The centroid detection error decreases with gain increasing when the gain is lower than Pmax/(Q·Nmean). When the gain is higher than Pmax/(Q·Nmean), the centroid detection error increases with the gain increasing, where Pmax is the peak electric charge value of EMCCD, Q is quantum efficiency, Nmean is the mean number of incident photons.
Phase synchronization between two adjacent nodes in amplitude coupled dynamical networks
Authors: Lu Jing  , Zhang Rong  , Xu Zhen-Yuan  ,   School of Scienc,Jiangnan University,Wuxi 214122,China
Published: December 2020

The present paper aims to investigate the phase synchronization in chaotic oscillator networks by using quantitative indexes. We define two new quantitative indexes, namely the mean phase locking value and mean frequency difference of two adjacent nodes of the network. Lorenz chaotic oscillators with several rotational centers are chosen as networks nodes. We convert the original Lorenz system into the dynamics of amplitude and phase. The chaotic oscillator networks are formed via amplitude coupling. We find that for star-coupled network and small-world network the adjacent oscillation phases are locked. Moreover, phase synchronization definitely comes along with the transition of the mean phase locking value and mean frequency difference by increasing the coupling strength.
Anti-synchronization of uncertain chaotic system and parameters identification
Authors: Li Nong  , Li Jian-Fen  , Liu Yu-Ping  ,   (1)The Engineering Institute,Air Force Engineering University,Xian 710038,China; (2)The Science Institute,Air Force Engineering University,Xian 710051,China
Published: December 2020

We present a systematic design procedure to anti-synchronize a class of chaotic systems. An adaptive control method for anti-synchronization of uncertain chaotic system is proposed based on the scheme,by which the uncertain parameters of response system are identified. Numerical simulations show the effectiveness of the developed approache.
Grid-scroll hyperchaotic system based on microcontroller digital hardware implementation
Authors: Xu Yu-Ming  , Bao Bo-Cheng  , Xu Qiang  ,   (1)School of Computer and Information Engineering, Changzhou Institute of Technology, Changzhou 213002, China; (2)School of Electrical and Information Engineering, Jiangsu Teachers University of Technology, Changzhou 213001, China
Published: December 2020

Based on the microcontroller (MCU), a universal digital hardware experimental circuit for four-dimensional chaotic system is designed, from which 9×7-grids scroll chaotic and hyperchaotic attractors are generated. Reference [1] has presented a four-dimensional multi-scroll hyperchaotic system extended from Colpitts oscillator model. In this paper, a new four-dimensional grid-scroll hyperchaotic system is constructed by introducing a unit sawtooth wave function to replace the triangular function in the original system, which is realized by utilizing MCU digital hardware implementation easily. Analysis and numerical simulations are performed for the formation mechanism of grid-scroll attractor in the new system. By using Euler algorithm to discretize the proposed grid-scroll hyperchaotic system, an attractor with more grid-scroll number than that of the original system can be generated in the effective dynamic range of the experimental circuit. Experimental results verified the feasibility of grid-scroll hyperchaotic system based on MCU implementation.
The synchronization of spatiotemporal chaos of nearest-neighbor coupled network
Authors: Lü Ling  , Li Gang  , Shang Jin-Yu  , Shen Na  , Zhang Xin  , Liu Shuang  , Zhu Jia-Bo  ,   College of Physics and Electronic Technology,Liaoning Normal University,Dalian 116029,China
Published: December 2020

The synchronization of spatiotemporal chaos in a nearest-neighbor coupled network is studied. Spatiotemporal chaos systems are taken as the nodes of the network,and the condition to realize global synchronization of the network is obtained by identifying the maximum Lyapunov exponent of the network according to Lyapunov stability theory. The nearest-neighbor coupled network with nodes of Fisher-Kolmogorov spatiotemporal chaos systems is taken as an example for simulation,the synchronization of spatiotemporal chaos for the network is checked. The synchronizing function of the network under bounded noise is further studied,and the results show that the method has good capability of anti-jamming.