bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of macroscopic dipoles on the charge storage and charge dynamics of polypropylene ferroelectret films
Authors: Wang Fei-Peng  , Xia Zhong-Fu  , Zhang Xiao-Qing  , Huang Jin-Feng  , Shen Jun  ,   同济大学波耳固体物理研究所，上海 200092
Published: December 2020

In this work, influence of the formation of macroscopic dipoles with space charges enclosed in a void (electric domain) and their polarization enhancement on the charging current characteristic and the conductivity of cellular polypropylene (PP) film were studied by the corona charging with a grid in combination with the reverse-polarity corona charging compensation method. By measuring the isothermal surface potential decay and analyses of open-circuit and short-circuit thermally stimulated discharging current spectra, the charge stability and charge dynamics of PP ferroelectrets in relation to the formation and density variety of macroscopy dipoles were also discussed. The experimental results indicate that the decrease of charge stability of cellular PP film with high polarization should be attributed to the increase of the conductivity induced by the self-field of macroscopic dipoles. For cellular electret film with weak polarization, macroscopic dipoles formed by space charges should only be trapped at two sharp ends of lens-like void and, therefore, detrapped charges will transport along the side surfaces at both ends of the void. When the sample has high polarization, the trapped charges are distributed in the whole surface layer of the void. Most of the detrapped charges excited by the electret field drift through the solid dielectric layer between adjacent voids, which leads to their decay.
Study of electroluminescence and electron injection on novel red polyelectrolytes copolymer
Authors: Hou Lin-Tao  , Huang Fei  , Peng Jun-Biao  , Cao Yong  ,   (1)华南理工大学高分子光电材料与器件研究所，华南理工大学特种功能材料及其制备新技术教育部重点实验室，广州 510640; (2)华南理工大学高分子光电材料与器件研究所，华南理工大学特种功能材料及其制备新技术教育部重点实验室，广州 510640；暨南大学物理系,广州 510632
Published: December 2020

Single-layer polymer light-emitting diodes with high work function gold cathode were fabricated using a series of novel conjugated polyelectrolytes and their neutral precursors: aminoalkyl-substituted polyfluorenes with different 4,7-di-2-thienyl-2,1,3-benzothiadiazole contents. At the current density of 38.7mA/cm2, the external efficiency reaches 0.42% with the Commission Internationale de I'Eclairage coordinates x=0.67 and y=0.33 for PFN-DBT10. It has been shown that these polymers also can be used as electron injection layer in double-layer devices with high work function gold cathode, which favors the manufacture of solution processing multilayer devices. Based on single-layer and double-layer device structures, it was found that the improvement of device performance is attributed to the interface effect between gold cathode and polyelectrolytes layer.
Stability of GaAs photocathodes under different intensities of illumination
Authors: Zou Ji-Jun  , Chang Ben-Kang  , Yang Zhi  , Gao Pin  , Qiao Jian-Liang  , Zeng Yi-Ping  ,   (1)南京理工大学电子工程与光电技术学院，南京 210094; (2)南京理工大学电子工程与光电技术学院，南京 210094；东华理工大学电子工程系，抚州 344000; (3)中国科学院半导体研究所，北京 100083
Published: December 2020

The photocurrent curves of reflection-mode GaAs photocathodes as a function of time, when were illuminated by white light with an intensity of 0, 33 and 100lx, respectively, were measured using a multi-information measurement system. The calculated lifetimes of cathodes are 320, 160 and 75min, respectively, showing that the stability of cathodes degraded with the increase of light intensity. The lifetime of cathode, illuminated by white light with an intensity of 100lx, while no photocurrent was being drawn during the illumination, was 100min. Through comparison, we found that the influence of illumination on cathodes stability is greater than that of photocurrent. The quantum-yield curves of cathodes as a functions of time, when illuminated by white light with an intensity of 33lx, were measured also. The measured results show that the shape of the yield curves changes with increasing illumination time due to the faster quantum-yield degradation rate of low energy photons. Based on the revised quantum-efficiency equations for the reflection-mode cathodes, the variation of yield curves are analyzed to be due to the intervalley diffusion of photoelectrons and the evolution of the surface potential barrier profile of the photocathodes during degradation process.
Field emission of carbon nanotubes
Authors: Guo Da-Bo  , Yuan Guang  , Song Cui-Hua  , Gu Chang-Zhi  , Wang Qiang  ,   (1)中国海洋大学物理系,青岛 266100; (2)中国科学院物理研究所微加工实验室，北京 100080
Published: December 2020

The temperature dependence of field emission from multiwalled carbon nanotubes deposited on a W tip was studied. It is found that the emission current increases with increase of temperature, while the stability of the emission current did not change. The field emission characteristic deviates from classic Fowler-Nordheim theory. This may result from a dispersion in the field enhancement factor of the carbon nanotubes.
Retrieving of aerosol size distribution based on the measurement of aerosol optical depth
Authors: Zuo Hao-Yi  , Yang Jing-Guo  ,   四川大学物理系,成都 610064
Published: December 2020

A new method for retrieving aerosol size distribution from measurement of aerosol optical depth is reported. Depending on the rigorous Mie scattering theory and the measured optical depth, dispersing the aerosol size distribution, by using linear-regression method, the aerosol size distribution can be calculated directly. And also the suitable wavelength band to retrieve the aerosol size distribution is obtained by analyzing the multi-collinearity.
Secure multiparty quantum summation
Authors: Du Jian-Zhong  , Chen Xiu-Bo  , Wen Qiao-Yan  , Zhu Fu-Chen  ,   (1)北京邮电大学理学院,北京 100876; (2)北京邮电大学理学院,北京 100876；北京科技大学信息工程学院，北京 100083；西安电子科技大学综合业务网国家重点实验室,西安 710071; (3)现代通信国家重点实验室,成都 610041
Published: December 2020

A novel scheme of secure quantum addition module n+1(n≥2) is proposed, based on non-orthogonal states, which allows a number to be added to an unknown number secretly. A proposed protocol for secure n-parity quantum summation is quasisecure to Eve. The collusive attack performed by n-1 legitimate participators cannot eavesdrop all the input information of the other participator in the protocol.
Study on chaotic control of Colpitts oscillator based on Washout filter technique
Authors: Zhao Yi-Bo  , Luo Xiao-Shu  ,   (1)安徽师范大学物理与电子信息学院,芜湖 241000; (2)广西师范大学物理与信息工程学院,桂林 541004
Published: December 2020

Control of chaos in Colpitts oscillator by using Washout filter is studied. Firstly, normalization of the circuit and controlling equations are derived based on Washout filter technique. Then by adjusting the control parameters, chaos in Colpitts oscillator is controlled to stable equilibrium point or periodic state. Finally, the controlling result is analyzed simulation is done and the effectiveness of this control method is verified.
A delay-combining reception scheme for DCSK communications system over a multipath fading channel
Authors: Chen Hong-Bin  , Feng Jiu-Chao  , Hu Zhi-Hui  ,   华南理工大学电子与信息学院,广州 510641
Published: December 2020

A delay-combining reception scheme for DCSK communications system over a multipath fading channel is proposed. BER performance of the scheme is analyzed theoretically and simulated. The results indicate that in comparison with the original DCSK communication system, the one with delay-combining reception has better BER performance. When the delays of reception paths are different, the BER performance are almost the same. When equal gain combining is adopted for the reception paths, the scheme achieves the best BER performance. The theoretical upper bound of the BER performance decreases with the increase of the number of reception paths.
Chaotic characteristic interperted by 250 step chaometry and its applying to the heart rate
Authors: Luo Chuan-Wen  ,   东北林业大学林学院，哈尔滨 150040
Published: December 2020

A discrete orbit is seperated into m pieces, eaoh constituted of k near points. The monopolized sphere capacity of a point is the extent seperating this one from the others. Instantaneous chaometry, which represents the total capacity of the k monopolized spheres, showes the total seperating extent of a orbital piece.The k step chaometry is the mean of the instantaneous chaometries of the m orbital pieces. The convergent property of k step chaometry is proved for the asymptotic periodic orbit. Althongh the convergence of k step chaometry has not been proved mathematically for the chaotic orbit, it is verified by numerical analysis. Lorenz attractor is interpreted by the 250 step chaometry. The powerful interpreting capability is shown by the 250 step chaometry of 3_dimensional and x component of the Lorenz system. The regression equation between the 250 step chaometry and the age of the 71 normal sinus heart rate time series is y=6.4623 -0.0496x with the correlation coefficient r=-0.669, which supports the view point of Goldberger, and means that the 250 step chaometry will decrease to zero before 130 years of age.
The model of capacitively coupled intrinsic Josephson junction array and its chaotic behavior
Authors: Zhou Tie-Ge  , Song Feng-Bin  , Zuo Tao  , Gu Jing  , Xia Hou-Hai  , Hu Ya-Ting  , Zhao Xin-Jie  , Fang Lan  , Yan Shao-Lin  ,   南开大学信息技术科学学院，天津 300071
Published: December 2020

The model of capacitively coupled intrinsic Josephson junction array was constructed with the software PSpice. Taking advantage of this new model, we investigated the behavior of capacitively coupled intrinsic Josephson junction array driven by constant current. The time domain wave, freguency spectrum, fractal dimension and phase portrait were obtained. Compared with the uncoupled array, chaotic behaviors were found firstly in the capacitively coupled intrinsic Josephson junction array. The results are valuable for the research and application of intrinsic Josephson junction arrays.
Multi-agent simulation on day-to-day route choice behavior
Authors: Liu Tian-Liang  , Huang Hai-Jun  ,   北京航空航天大学经济管理学院，北京 100083
Published: December 2020

The day-to-day route choice is a non-cooperative game process with many participants during a long time period. We use the multi-agent simulation system SeSAm to investigate two different route update rules designed for traffic information release and unrelease respectively. Simulation results on a small grid network show that the rule under information release can make route flow evolve to the logit stochastic user equilibrium faster than that under information unrelease. However, the flow pattern may be unstable if travelers put undue compliance on the released information. A stable flow pattern can also be achieved only relying on travelers' perceived experience and learning ability, but the evolution is rather slow. It is thus suggested that the traffic information should be timely released to public meanwhile utilized properly.
Near-field detected photoluminescence spectra of CdS0.65Se0.35 nanoribbon at room temperature
Authors: Wang Xiao  , Pan An-Lian  , Liu Dan  , Bai Yong-Qiang  , Zhang Zhao-Hui  , Zou Bing-Suo  , Zhu Xing  ,   (1)北京大学物理学院，人工微结构与介观物理国家重点实验室，北京 100871; (2)北京大学物理学院，人工微结构与介观物理国家重点实验室，北京 100871；国家纳米科学中心，北京 100080; (3)湖南大学微纳技术研究中心,长沙 410082
Published: December 2020

Ternary alloy CdS0.65Se0.35 nanoribbons were successfully grown by a one-step thermal evaporation. The nanoribbons obtained have high-quality single-crystalline nature. To understand the whole picture of waveguide behavior in CdS0.65Se0.35 nanoribbons, we quantitatively studied the guided photoluminescence (PL) through individual CdS0.65Se0.35 nanoribbon by using scanning near-field optical microscopy (SNOM) at room temperature. The results show significant sustained red shift of PL spectra of the CdS0.65Se0.35 nanoribbons optical waveguide with the increase of the light propagation distance. According to our analysis, the red shift is attributed to the absorption of band-tail of states in nanoribbons. This finding may be extended to other ternary nanosyotems and be useful for fabricating new subwavelength photonic components.
Analysis of ridged elliptical waveguide by polynomial representation
Authors: Xu Jin  , Wang Wen-Xiang  , Yue Ling-Na  , Gong Yu-Bin  , Wei Yan-Yu  ,   电子科技大学物理电子学院，成都 610054
Published: December 2020

Application of ridged rectangular and circular waveguides has been found in many areas. In this paper，with the Rayleigh-Ritz method and polynomial representation，the wave propagation characteristics in the ridged elliptical waveguide are analyzed. The numerical results are in good agreement with calculation using electromagnetic field simulation software. The variation of bandwidth with physical dimensions has been studied. It is helpful for optimizing this kind of structure.
Influence of negative refractive material on Casimir effect
Authors: Zeng Ran  , Xu Jing-Ping  , Yang Ya-Ping  , Liu Shu-Tian  ,   (1)哈尔滨工业大学应用物理系，哈尔滨 150001; (2)哈尔滨工业大学应用物理系，哈尔滨 150001；同济大学物理系，上海 200092; (3)同济大学物理系，上海 200092
Published: December 2020

Three-dimensional Casimir force between two negative-refractive-material slabs is calculated. For the negative-refractive material characterized by dispersive permittivity and permeability of Drude-Lorentz type，the structure of negative refraction frequency band is determined by characteristic frequencies. The different width and depth of the negative refraction frequency bands correspond to reflection properties of different medium，and thus influences the magnitude of Casimir effect between the slabs.
Formation and propagation of dark solitons in metamaterials
Authors: Liu Hai-Lan  , Wen Shuang-Chun  , Xiong Min  , Dai Xiao-Yu  ,   湖南大学计算机与通信学院，长沙 410082
Published: December 2020

We use an extended Tanh-function expansion method to solve the nonlinear equation for ultrashort pulse propagation in matamaterial，and obtain dark solitary solutions in various cases. Further，we study the influence of the controllable self-steepening effect and the second-order nonlinear dispersion on the formation and propagation of dark solitons in metamaterials. It is found that the negative self-steepening effect in metamaterial makes the soliton center move to the leading side，opposite to the moving direction of soliton in ordinary materials in which the self-steepening effect is always positive. Most importantly，due to the role of the second-order nonlinear dispersion，dark solitons can be formed in the medium without linear dispersion or with an anomalous linear dispersion.
Analysis of the shrinkage in size of air holes in different sections during the fabrication of microstructured fibre
Authors: Zhou Gui-Yao  , Hou Zhi-Yun  , Li Shu-Guang  , Han Ying  , Hou Lan-Tian  ,   (1)燕山大学红外光纤与传感研究所，秦皇岛 066004; (2)燕山大学亚稳材料制备技术与科学重点实验室，秦皇岛 066004；燕山大学红外光纤与传感研究所，秦皇岛 066004
Published: December 2020

According to the heat conduction theory，different sections of the cladding of microstructured fibres (MSF) have different temperature in the high temperature zone during drawing MSF. The temperature decreases gradually from the surface to the central in MSF preform，and the temperature gradient will increase with either the increase of feed speed of MSF preform or decrease of the air-filling fraction. Because both the surface tension and the coefficient of viscosity are functions of temperature，when the MSF preform is thinned to MSF，the actual structure of MSF is not a simple down-sealing of the perform. The shrink size of the air holes will increase as the temperature rises. In order to obtain the MSF as expected，we must design the size of air holes of the MSF preform to vary corectly with the temperature variations，so as to effectively eliminate the effects of uneven heating temperature on the air holes in the cladding of MSF.
Annealing of Cd0.9Zn0.1Te in cadmium vapor
Authors: Li Wan-Wan  , Sun Kang  ,   上海交通大学金属基复合材料国家重点实验室,上海 200030
Published: December 2020

Cd0.9Zn0.1Te wafers grown by vertical Bridgman method were annealed in cadmium vapor at different temperatures. The formerly established model correlating resistivity and conduction type of CdZnTe with the main diffusion parameter-diffusion coefficient is used in combination with the analysis of our experimental data (DCd=1.464×10-10, 1.085×10-11 and 4.167×10-13cm2/s), and the values of Cd self-diffusion coefficient in Cd0.9Zn0.1Te at 1073K, 973K and 873K have been obtained, which coincide closely with the Cd self-diffusion coefficient in CdTe provided by different authors. With the data, the effect of annealing time on the resistivity and change of conduction type of Cd0.9Zn0.1 Te wafers annealed in saturated Cd vapor at 1073K, 973K and 873K were simulated, and good agreement was found.
Morphology and structure of the diamond film synthesized from carbon monoxide gas
Authors: Liu Yan-Yan  , Bauer-Grosse E.  , Zhang Qing-Yu  ,   (1)Laboratoire de Science et Génie des Surfaces,Ecole des Mines,Nancy 54042,France; (2)大连理工大学三束材料改性国家重点实验室，大连 116024; (3)大连理工大学三束材料改性国家重点实验室，大连 116024；Laboratoire de Science et Génie des Surfaces,Ecole des Mines,Nancy 54042,France
Published: December 2020

Diamond film was deposited in CO and H2 gas mixture by microwave plasma assisted chemical vapor deposition (MPCVD). Bias enhanced nucleation and two-step growth method were employed. Scanning electron microscopy (SEM), Raman spectroscopy and transmission electron microscopy (TEM) were used to characterize the film. It was found that twins and stacking faults were mainly produced at the stages of nucleation and growth. In the second growth stage, the production of defects in the film was reduced considerably, resulting in the final smooth-faceted diamond grains with five-fold symmetry or parallel twins with a small amount of stacking faults. At the edge of the sample, there was a region with low nucleation density, which might be the result of non-uniform plasma existing there. Meanwhile, a non-diamond structure of carbon was found in the edge region.
Analysis of laser intensification by nodular defects in mid-infrared high reflectance coatings
Authors: Wang Ying  , Zhang Yue-Guang  , Liu Xu  , Chen Wei-Lan  , Li Yi-Yu  ,   浙江大学现代光学仪器国家重点实验室，杭州 310027
Published: December 2020

Electric field modeling of nodular defects is performed to investigate the interaction between defective multilayer coatings and Gaussian profile laser beam. Light intensity is significantly enhanced as large as 6 times within the nodular defects. Different geometries of defects irradiated by laser beams at 0 to 40 deg incident laser angles are analyzed. Nodules with large but shallow seeds, or irradiation of 40 deg p-polarized laser beam, tends to produce the greatest enhancement effect.
First-principles study of 3d transition metal-doped anatase
Authors: Zhao Zong-Yan  , Liu Qing-Ju  , Zhang Jin  , Zhu Zhong-Qi  ,   云南省高校纳米材料与技术重点实验室，云南大学，昆明 650091
Published: December 2020

The geometry, electronic structure and optical properties of pure and 3d transition metals-doped anatase-phase TiO2 were studied by using the plane-wave ultrasoft pseudopotential method based on the density functional theory. The calculations show that the formation of impurity energy level is mainly contributed by 3d orbital of the transition metal doped in TiO2, and the position of impurity energy levels in the band gap is the dominating factor that decides whether the absorption threshold wavelength has a red-shift or not. The doping of Cr, Mn, Fe, Ni, Co and Cu causes the absorption wavelength to red-shift, and the absorption coefficient in the visible light region is increased; whereas the doping of Sc, Zn causes the absorption wavelength to blue-shift, but leads to higher absorption coefficients in the visible region. The doping of V not only causes the absorption wavelength to red-shift and strengthens the absorption in the ultraviolet light region, but also gives rise to extremely big absorption coefficient in the visible region.
Study on field enhancement of a normal-gated field emission nanowire cold cathode
Authors: Lei Da  , Zeng Le-Yong  , Xia Yu-Xue  , Chen Song  , Liang Jing-Qiu  , Wang Wei-Biao  ,   (1)中国科学院长春光学精密机械与物理研究所激发态重点实验室，长春 130033; (2)中国科学院长春光学精密机械与物理研究所激发态重点实验室，长春 130033；中国科学院研究生院，北京 100049; (3)中国科学院长春光学精密机械与物理研究所应用光学国家重点实验室，长春 130033
Published: December 2020

The field enhancement is one of the important factors that indicate the performance of field emission cold cathode devices. It is intimately related to the field emission current density and the threshold voltage of the device. In our paper, the field enhancement factor of a normal-gated field emission nanowire cold cathode model was analytically deduced on the basis of classical electrostatic theory, and it is given by the equation. β=k1{N2·(L-d1)2+［1/k1+(L-d1)］2}1/2. The effect of geometrical parameters of the device on the field enhancement factor was explored. The theoretical analysis showed that the larger the length (L-d1) of nanowire above the gate and the gate hole radius, the larger the enhancement factor is; but the larger the nanowire radius, the smaller the enhancement factor is. When the L is much larger thand1, the enhancement factor satisfies the relation. β∝Ｌ／r0, for which N=N1(k1r0)/N0(k1r0), N0(k1r0) and N1(k1r0) are both Neumann functions and k1=0.8936/R. R, L, r0 and d1 are the gate hole radius, the nanowire length, the nanowire radius and the gate-cathode distance, respectively.
Investigating the effect of doping amorphous silicon nitride on retention characteristics of SONOS device by DFT calculation
Authors: Fang Shao-Hua  , Cheng Xiu-Lan  , Huang Ye  , Gu Huai-Huai  ,   上海交通大学微电子学院,上海 200030
Published: December 2020

Retention characteristics of SONOS non-volatile memory (NVM) device is expected to be improved by doping silicon nitride to change the type and number of defects which traps charge. Firstly, cluster models of defects in amorphous silicon nitride with and without doping special element, such as oxygen, sulfur, phosphorus, fluorine or chlorine, are built. By density functional theory (DFT) of first-principles, positions of all atoms of the cluster are optimized, and energiesof these clusters are calculated. Energy changes of charge capturing processes for various defects are obtained. The calculational data can provide references for investigating discharge mechanism and improving charge retention on nonvolatile memory device. The capability of capturing electrons for all defects is usually better than capability of capturing holes. The electron discharge process should be sensitive to temperature, but the hole discharge process may be mainly controlled by tunneling mechanism. Like silicon oxynitride, silicon nitride doped with sulfur or phosphorus is promising for improving charge retention characteristics of SONOS device, due to more defects having better capability of capturing electrons.
Metal sphere array for long wavelength quantum well infrared photodetectors optical coupling
Authors: Xiong Da-Yuan  , Li Zhi-Feng  , Chen Xiao-Shuang  , Li Ning  , Zhen Hong-Lou  , Lu Wei  ,   中国科学院上海技术物理研究所红外物理国家重点实验室，上海 200083
Published: December 2020

A two-dimensional (2D) metal (Copper) sphere array is designed for the optical coupling of 9.5μm long-wavelength quantum well infrared photodetectors (LW-QWIPs). The optical coupling is studied based on Huygens' principle. It was shown that a metal sphere array with 3μm period and 0.9μm radius can reach optimal optical coupling for the 9.5μm LW-QWIPs. The maximal quantum efficiency hits 66%, which is highly superior to the conventional 45° angle coupling. The theoretical results provide detailed guidelines for 2D metal sphere array optical coupling for 9.5μm LW-QWIPs.
Low temperature growth of carbon nanotubes by chemical vapor deposition for field emission cathodes
Authors: Guo Ping-Sheng  , Chen Ting  , Cao Zhang-Yi  , Zhang Zhe-Juan  , Chen Yi-Wei  , Sun Zhuo  ,   华东师范大学纳光电集成与先进装备教育部工程研究中心，纳米功能材料和应用研究中心，物理系，上海 200062
Published: December 2020

Carbon nanotubes/nanofibers (CNTs) were grown on sodalime glass by low temperature chemical vapor deposition. The catalytic films were pre-patterned using screen-printing method, combined with filtered cathodic vacuum arc or ion beam sputtering. The effect of different catalysts on the CNT growth and field emission were investigated. For samples catalyzed with a-C:Co, Ni-Cu or Cu, no CNTs are formed, and they show no field emission below the applied field of 4.4V/μm. For samples catalyzed with Ni-Fe or Ni-Cr, large amounts of entangled CNTs are successfully obtained and exhibit good electron emission, having a turn-on field as low as 2.5V/μm. The process, due to its simplicity and relatively low growth temperature, is promising for practical application in field emission display.
Fractal shape simulation and light scattering calculation of fire smoke particles
Authors: Qiao Li-Feng  , Zhang Yong-Ming  , Xie Qi-Yuan  , Fang Jun  , Wang Jin-Jun  ,   中国科学技术大学火灾科学国家重点实验室,合肥 230027
Published: December 2020

A fractal shape model was used to simulate the morphology of fire smoke particles, as the aggregated spherical particles have intrinsical fractal structures. The shape model, whose parameters, including the total number of primary spherical particles in an aggregate, the fractal dimension and the radius of the primary particles, were obtained from a sequence of SEM images, was considered to be compatible with the smoke particle shape. The shape model was then used to compute the light scattering of smoke particles, and the results showed that, compared with the spherical particle with the same volume and other optical parameters, the fractal-like aggregate has smaller forward scattering and larger backward scattering.
Error estimates of element-free Galerkin method for potential problems
Authors: Cheng Rong-Jun  , Cheng Yu-Min  ,   (1)上海大学上海市应用数学和力学研究所，上海  200072; (2)上海大学上海市应用数学和力学研究所，上海  200072；浙江大学宁波理工学院，宁波  315100
Published: December 2020

The error estimates for moving least-square approximation, which is the method for obtaining the shape function in element-free Galerkin method, are presented in Sobolev space Wk,p(Ω) for high dimensional problems. Then on the basis of element-free Galerkin method for potential problems, the error estimates for element-free Galerkin method for potential problems, in which the essential boundary conditions are enforced by penalty methods, are obtained. The error estimates we present in this paper have optimal order when the nodes and shape functions satisfy certain conditions. From the error analysis, it is shown that the error bound of the potential problem is directly related to the radii of the weight functions. Two numerical examples are also given to verify the conclusions in this paper.
Prediction of chaotic time series based on EMD method
Authors: Yang Yong-Feng  , Ren Xing-Min  , Qin Wei-Yang  , Wu Ya-Feng  , Zhi Xi-Zhe  ,   西北工业大学，西安  710072
Published: December 2020

In order to improve the nonlinear response prediction precision in a long period, the empirical mode decomposition (EMD) method is introduced in the nonlinear prediction. Here, the EMD method is used to decompose the signal, the rosenstein method is used to calculate the largest Lyapunov exponent (LLE), and then the prediction results are obtained on the basis of the LLE. The simulation results of Duffing equation, Lorenz system and cracked rotor system show that the EMD's signals have smaller LLE than the original signal. In this way, the maximum prediction time of a nonlinear signal can be obtained.
Study of chaos based on single electron device
Authors: Feng Chao-Wen  , Cai Li  , Kang Qiang  ,   (1)空军工程大学科研部，西安  710051; (2)空军工程大学理学院，西安  710051
Published: December 2020

Chua′s circuit in structure of cellular neural networks is realized by the hybrid device of single electron transistor and metal oxide semiconductor, named SETMOS. Then single scroll and double scrolls are obtained. SETMOS transconductance amplifier and SETMOS voltage comparator are designed, and the double-scroll-like chaotic circuit built of SETMOS is proposed. The double-scroll-like chaos attractor is verified by simulation. All the simulation results show that the designed circuits have the characteristics of simple structure and low power dissipation, and they can further improve the density of integrated circuits. It also provides a new method for the chaos to be used in engineering.
Molecular structure and electronic spectrum of styrene under the external electric field
Authors: Ruan Wen  , Luo Wen-Lang  , Zhang Li  , Zhu Zheng-He  ,   (1)四川大学原子与分子物理研究所，成都  610065; (2)四川大学原子与分子物理研究所，成都  610065；井冈山大学数理学院，吉安  343009
Published: December 2020

The ground states of styrene under different intense electric fields ranging from 0 to 0.05a.u. are optimized using density functional theory DFT/B3P86 at 6-311G basis set level. The excitation energies and oscillator strengths under the applied electric fields are calculated employing the revised hybrid CIS-DFT method. The results show that the electronic state，molecular geometry，total energy，dipole moment，and excitation energy are strongly dependent on the applied electric field. As the electric field changes from 0 to 0.02a.u.，many of the bond lengths of C—H increase，while some of the bond lengths of C—H decrease. However，further increase of the electric field strength results in a increase of them both due to the charge transfer induced by the applied electric field. As to the bond lengths of C—C，some of them increase，some of them decrease and some of them remain unchanged as the electric field changes from 0 to 0.05a.u.. The dipole moment of the ground state increases sharply with the applied field strength. With the electric field increasing，the total energy of the molecule decreases. The excitation energies of the first six excited states of styrene decrease with the increase of the applied electric field，indicating that the molecule is easy to be excited and dissociated under the electric field.
Influence of rotating magnetic field on the formation of solidification microstructure
Authors: Chen Zhao  , Chen Chang-Le  , Wen Xiao-Li  , Wen Jun  ,   西北工业大学理学院，陕西省凝聚态结构与性质重点实验室，西安  710072
Published: December 2020

The solidification microstructures of Pb-45%Sn hypoeutectic alloy in rotating magnetic field (RMF) were investigated. When the rotating frequency keeps constant，the grain size reduces linearly with the increase of magnetic intensity，and structure of the primary phase changes from the dendrite to spherical crystals. X-ray diffraction (XRD) measurement indicates that the RMF causes the lattice expansion of primary phase (Pb)，and the lattice parameter increases at first and then decreases with the increase of RMF intensity. Therefore，there is a critical value of magnetic intensity. Moreover，the Sn content in primary phase (Pb)reduces gradually with the increase of magnetic intensity. The results are analyzed theoretically based on electromagnetism field theory and scattering law. It is revealed that RMF causes severe fluid flow，and accelerates the diffusion of solute atom and heats the melt，which results in the increase of nucleation rate and the decrease of growth velocity of crystal.
X-ray microscopic imaging of low Z material wrapped by strongly absorbing medium
Authors: Shi Shao-Meng  , Chen Rong-Chang  , Xue Yan-Ling  , Ren Yu-Qi  , Du Guo-Hao  , Deng Biao  , Xie Hong-Lan  , Xiao Ti-Qiao  ,   中国科学院上海应用物理研究所，上海  201800
Published: December 2020

It is difficult for the nondestructive detection of inertial fusion capsule. Based on this requirement we constructed a physical model of low Z material wrapped by strongly absorbing medium. By simulation and experiments，we investigate the effect of some factors on phase contrast imaging quality，such as X-ray energy，distance of object to detector, thickness of strongly absorbing materials and so on. We find it feasible to realize the high resolution and nondestructive detection of inertial fusion capsule by X-ray phase contrast imaging.
Change of reflectivity of Mo/Si multilayer irradiated by proton
Authors: Fan Xian-Hong  , Li Min  , Ni Qi-Liang  , Liu Shi-Jie  , Wang Xiao-Guang  , Chen Bo  ,   (1)中国科学院长春光学精密机械与物理研究所应用光学国家重点实验室,长春  130033; (2)中国科学院长春光学精密机械与物理研究所应用光学国家重点实验室,长春  130033；中国科学院研究生院，北京  100049
Published: December 2020

In this paper, we simulated part of the low-Earth orbits space radiation environment to investigate its influence on the reflectivity change of Mo/Si multilayer mirror used in the space solar telescope. The reflectivity was investigated before and after irradiation with proton of different energies and fluences. The results show that the reflectivity decreases when irradiated by proton because of the radiation-induced damage in the multilayer mirror, and it drops more when the energy of the proton decreases while their fluence increases. When the energy of proton E=160keV with fluence　=6×1011/mm2，E=100keV with fluence　=6×1011/mm2 and E=50keV with fluence =8×1012/mm2，the reflectivity drops about 4.1%, 5.7% and 10.4%， respectively. The roughness measured by atomic force microscopy increases after irradiation, which results in more scattering of incident ray so that the reflectivity of multilayer is reduced.
Effect of optical phonon-magnon interaction on the magnon life-time at finite temperature
Authors: Cheng Tai-Min  , Luo Hong-Chao  , Li Lin  ,   (1)东北大学理学院,沈阳  110004; (2)沈阳航空工业学院理学系，沈阳  110136; (3)沈阳化工学院数理系,沈阳  110142；沈阳化工学院材料科学与工程学院,沈阳  110142
Published: December 2020

A magnon-phonon interaction model is set up in a two-dimensional ferromagnetic double square-lattice system. By using the Matsubara Green function theory we have studied the magnon life-time of the system, calculated the magnon damping curves on the main symmetric line in the Brillouin zone, compared the influences of magnetic ion optical-mode phonon and non-magnetic ion optical-mode phonon on the magnon damping of the system, and discussed the influences of the parameter variations and temperature on the magnon damping. The results show that the coupling of the optical-mode phonon and magnon plays the main role in the magnon damping, especially, the longitudinal optical-mode phonon contributes the most for the magnon damping. It is also found that the effect of the nonmagnetic ion on magnon damping is more significant than that of the magnetic ion. According to the expression -ImΣ*(1)(k)=/(2τ), the magnon life-time is discussed.
Electroluminescence of an iridium complex phosphorescent material doped polymeric system
Authors: Tang Xiao-Qing  , Yu Jun-Sheng  , Li Lu  , Wang Jun  , Jiang Ya-Dong  ,   电子科技大学光电信息学院,电子薄膜与集成器件国家重点实验室,成都  610054
Published: December 2020

With a novel iridium complex (pbi)2Ir(acac) doped into carbazole copolymer, polymer doped electrophosphorescent organic light-emitting diodes with the structure of indium-tin oxide(ITO)/poly(N-vinylcarbazole) (PVK):(pbi)2Ir(acac) (x)/2,9-dimethyl-4,7-diphenyl-1,10-phenan throline (BCP) (20nm)/8-Hydroxyquinoline aluminum(Alq3) (10nm)/Mg:Ag were fabricated. The photoluminescent (PL) and electroluminescent (EL) characteristics of the polymer doped system were investigated at the low doping concentrations of 0.1% and 0.5%, respectively. The results demonstrate that the luminescent spectra with different intensities of PVK and (pbi)2Ir (acac) co-existed in the PL and EL spectra of blend system, which was ascribed to an incomplete energy transfer process and direct charge trapping in the electroluminescence process. The 0.1% (pbi)2Ir(acac) doped device achieved a white light emission with the commissions internationale de 1'eclairage (CIE) coordinates of (0.32, 0.38) when the bias voltage was 19V; the 0.5% (pbi)2Ir(acac) doped device had a maximum luminance of 11827 cd·m-2 and a maximum luminance efficiency of 4.13 cd·A-1 corresponding to a bias of 20.6V and 13.4V, respectively.
Nitrogen doped 4H-SiC homoepitaxial layers grown by CVD
Authors: Jia Ren-Xu  , Zhang Yi-Men  , Zhang Yu-Ming  , Wang Yue-Hu  ,   西安电子科技大学微电子学院，宽禁带半导体材料与器件教育部重点实验室，西安  710071
Published: December 2020

Homoepitaxial growth of 4H-SiC on off-oriented Si-face (0001) 4H-SiC substrates is performed at 1550℃, under the pressure of 100 mbar using the mbar step-controlled technique with rotation in the horizontal low-pressure hot-wall CVD (LP-HW-CVD) system to obtain high quality 4H-SiC epilayers. The surface morphology, structure and optical properties of the epilayers are characterized by SEM, AFM, FTIR and C-V measurement. The 4H-SiC epitaxial layer has a good crystalline structure and mirror-like surface with few surface defects. N type 4H-SiC epilayers are obtained by in-situ doping of N2.The uniformities of thickness are 1.74%, 1.99%, and 1.32%, and the uniformities of doping concentration are tested to be 3.37%, 2.39%, and 2.01%, respectively. The deviations in thickness and concentration between different samples are 1.54% and 3.63% under the same processing conditions, which shows that the process is repeatable and reliable.
Study of the spread of the energy gap in nanostructure systems
Authors: Liu Yi-Xing  , Yu Ya-Bin  , Zhang Li  , Quan Jun  ,   湖南大学物理与微电子科学学院，长沙  410082
Published: December 2020

In recent years considerable attention is being paid to the blue-shift of photoluminescence due to quantum confinement in the nanostructure. By employing two simple models of one-dimensional crystal potential，we study the electronic energy spectra and confinement energies by solving the Schrdinger equation for the models. Based on the calculation of the confinement energies in the nanostructures，the size- and potential-dependence of the confinement energy and the blue shift are investigated. The results suggest that: with creasing size of the system the energy of electrons at the bottom of the conduction band decreases，but increases at the top of the valence band. Therefore，the confinement energies increased abruptly as the size of nano-particle (or nanostructures) decreases. Meanwhile，our results for the confinement energies show obvious difference from the ones calculated by the effective-mass approximation of ten used in the literature. Moreover，we also find that the band gap and blue shift depend on the crystal potential in the systems，and the confinement energies decrease as the potential increases.
A new three-dimensional chaotic system
Authors: Zhang Jian-Xiong  , Tang Wan-Sheng  , Xu Yong  ,   天津大学系统工程研究所，天津  300072
Published: December 2020

This paper presents a new three-dimensional continuous autonomous chaotic system. The new system has two system parameters and a nonlinear term which takes the form of arc tangent function. The stability of the new system is investigated based on linear matrix inequality (LMI) method. And the complex dynamic properties are studied by theoretical analysis，numerical simulation，Lyapunov exponents spectrum，bifurcation diagrams and Poincaré section diagrams.
Spiral wave in an inhomogeneous excitable medium
Authors: Zhang Guo-Yong  , Ma Jun  , Gan Zheng-Ning  , Chen Yong  ,   (1)兰州大学理论物理研究所，兰州  730000; (2)兰州大学理论物理研究所，兰州  730000；湖北师范学院计算机系，黄石  435002; (3)兰州大学理论物理研究所，兰州  730000；兰州大学磁学与磁性材料教育部重点实验室，兰州  730000; (4)兰州理工大学物理系，兰州  730050
Published: December 2020

Using a Barkley model as an example，the pattern formation of spiral waves in inhomogeneous excitable medium is investigated. The normal distribution of parameters fluctuations is introduced to depict the inhomogeneous medium. It is found that the parameter fluctuations play an important role in the formation of spiral pattern. For a larger variance of the parameter fluctuations，the spiral waves are rough. In the case of the uniform distribution of fluctuations in two parameters，spiral wave cannot be observed for fluctuations beyond a certain range. It is conjectured that these results are induced by the rotating frequency of spiral wave for different parameters. For the larg rotating frequency，the spiral wave pattern is finely crowded，while it is sparse for small frequencies.
Effect of noise in controlling strong turbulence by external periodic signal
Authors: Sang Hai-Bo  , He Kai-Fen  ,   北京师范大学低能核物理研究所，北京  100875；北京市辐射中心，北京  100875
Published: December 2020

Strong turbulence in the driven drift-wave equation of plasma can be suppressed successfully to a laminar flow by an external periodic signal with proper frequency and strength. In the driving wave coordinates，by transforming the wave system to a set of coupled oscillators (modes) moving in a periodic potential，generalized phase synchronization between these modes is regarded as one of the control mechanisms. In this paper，the effect of noise is studied in the course of the turbulence control. It is found that the laminar flow becomes disordered again with fairly weak bias noise，at the same time the generalized phase synchronization between the modes is lost. However，when the bias noise is quite strong，the quasi-period laminar state can be maintained and the modes can also reach generalized phase synchronization with each other.
A novel fifth-order hyperchaotic circuit and its research
Authors: Yu Si-Min  , Yu Zhi-Ding  ,   (1)广东工业大学自动化学院，广州  510006; (2)华南理工大学电子与信息学院，广州  510640
Published: December 2020

A novel fifth-order hyperchaotic circuit is proposed. This circuit is composed by three linear inductors, two linear capacitors, one negative resistor, and two nonlinear elements, and has the π type circuit configuration. By switching the time constant of the circuit by the action of nonlinear element, the voltage and current is rapidly changed, and by using negative resistors, the condition for local divergence in the circuit is satisfied. The rapid change of voltage and current and local divergence are two primary conditions for generating chaos and hyperchaos in the circuit. Bifurcation and Lyapnuov exponent calculations demonstrate that the oscillation mechanism of the circuit evolves into chaos and hyperchaos from periodic with the change of bifurcation parameters. Furthermore, the fifth-order hyperchaotic circuit has been designed and the result of hardware experiment is reported.
Control of chaos in an external cavity delay feedback semiconductor laser via modulating the polarizing light
Authors: Yan Sen-Lin  ,   南京晓庄学院物理系，南京  210017
Published: December 2020

Control of chaos in an external cavity delay feedback semiconductor laser via modulating the feedback polarizing light is studied. The laser dynamic physical models of the delayed feedback of dual beams with orthogonal polarizating, with parallel polarizations, or with synchronous or arbitrary polarizing directions are presented, respectively. The delay time and feedback quantity of the feedback light can be adjusted by adjusting the mirror and the optical attenuator in the external optical path, or by adjusting the polarization plane of one beam of polarized light with respect to the polarization direction of the other beam, or at an arbitrary polarization direction to the other beam of polarizing light. In all these cases, the chaotic laser can be controlled. Numerical results show that the laser can be conducted to the single cycle or the multi-cycle, and at the same time be in the polarizing oscillation, polarizing anti-oscillation or stable states.
Generation of squeezed vacuum states by PPKTP crystal and its Wigner quasi-probability distribution function reconstruction
Authors: Ye Chen-Guang  , Zhang Jing  ,   山西大学光电研究所量子光学与光量子器件国家重点实验室，太原  030006
Published: December 2020

We demonstrated experimentally the generation of squeezed vacuum by a periodically poled KTP crystal in a continuous-wave optical parametric oscillator，which was pumped with 532nm field. The squeezed vacuum of 3.41 dB at 1064 nm was detected by a homodyne detection system. Moreover，the Wigner quasi-probability distribution function of the squeezed vacuum was reconstructed using quantum tomography technique.
Acoustic characteristics of underwater cylindrical Helmholtz resonator
Authors: Wang Ze-Feng  , Hu Yong-Ming  , Meng Zhou  , Ni Ming  ,   国防科技大学光电科学与工程学院，长沙  410073
Published: December 2020

The acoustic characteristics of underwater cylindrical Helmholtz resonator are analyzed theoretically. Based on the theories of electro-acoustic analogy, a low frequency lumped-parameter model of the Helmholtz resonator is constructed with due consideration of the effects of the elasticity and the radiation impedance of the resonator. To our knowledge, this is the first time such a complete model is constructed. The input impedance and the transfer function of the system are given by circuit analysis. The effects of parameter values of the resonator on the acoustic characteristics are studied by numerical method. Some useful conclusions are drawn. A small aluminum cylindrical Helmholtz resonator is measured in a standing-wave tube filled with water. Error analysis is made in detail. The experimental results are in agreement with the simulation results considering the effect of the piezoelectric hydrophone. The validity of the theoretical analysis is testified. This paper supplies a theoretical and experimental basis for the design of underwater cylindrical Helmholtz resonators, and is useful for the estimation of underwater acoustic performance of Helmholtz resonators of other shapes.
Study on crystallization mechanism of hydrogenated silicon film
Authors: Li Shi-Bin  , Wu Zhi-Ming  , Li Wei  , Yu Jun-Sheng  , Jiang Ya-Dong  , Liao Nai-Man  ,   电子科技大学光电信息学院电子薄膜与集成器件国家重点实验室，成都  610054
Published: December 2020

In this paper, amorphous, microcrystalline and polymorphous silicon films were prepared by plasma enhanced chemical deposition. Crystalline volume fraction of microcrystalline silicon was deduced from the Raman spectrum, and this fraction was validated using Bruggeman effective medium approximation (BEMA) model in spectroscopic ellipsometry measurement. The influence of thermal gradient on the deposition mechanism of microcrystalline and polymorphous silicon was investigated using a theoretical model. The dependence of crystalline volume fraction on film thickness shows there is a crystalline gradient between bottom and surface of microcrystalline film, and there is not such a gradient in polymorphous silicon film. Polymorphous and microcrystalline silicon have similar ordered state and density, which are signifieantly higher than those of amorphous silicon.
Thickness measurement of GaN films by X-ray diffraction
Authors: Li Hong-Tao  , Luo Yi  , Xi Guang-Yi  , Wang Lai  , Jiang Yang  , Zhao Wei  , Han Yan-Jun  , Hao Zhi-Biao  , Sun Chang-Zheng  ,   清华信息科学与技术国家实验室(筹)/集成光电子学国家重点实验室，清华大学电子工程系，北京  100084
Published: December 2020

Precise measurement and control of GaN-film thickness is very important for GaN-based material epitaxy and device fabrication. However, GaN-films heteroepitaxially grown on large-mismatch substrates, such as sapphire, SiC and Si, etc., usually show a mosaic structure, which causes great difficulty to the GaN-film thickness measurement. Combining the advantages of Williamson-Hall plot method and diffraction profile shape analysis method, a new strategy was presented to effectively distinguish the X-ray diffraction broadening factors of finite crystallite size and inhomogeneous strain, which can be used to precisely and reliably determine the thickness of epitaxial films. The thickness of a series of GaN films grown on sapphire substrates in the range of 0.7—4.2 μm were measured by this method. Comparing with the thickness obtained from spectroscopic ellipsometry measurements, the difference was found to be within 4%, which shows the excellent performance of this method.
Extraordinary magnetoresistance in nonmagnetic semiconductors: The effective-medium approximation
Authors: Song Ya-Wu  , Sun Hua  ,   苏州大学物理科学与技术学院，江苏省薄膜材料重点实验室，苏州  215006
Published: December 2020

The self-consistent effective-medium approximation is used to study the extraordinary magnetoresistance effect observed in nonmagnetic semiconductors. The inhomogeneous materials are treated as a three-dimensional resistor network of binary disorder, where the receptivity of each component is a tensor describing both the zero-field resistance and the Hall effect. The effective conductivity tensor of the total system is calculated with applied magnetic field. The resulting transversal magnetoresistance, longitudinal magnetoresistance and effective Hall coefficient are shown for different component concentrations and magnetic fields. When the components have two different types of charge carriers, and the mismatch between the zero-resistivity is enlarged, the macroscopic magnetoresisance exhibits complex behaviors which are related closely with the formation of the percolation structure in the inhomogeneous system.