bluuebunny/crossref_metadata_2025 huggingface dataset:
LD pumped Nd:YAG ceramic/KTP green laser
Authors: Lan Rui-Jun  , Liu Hong  , Wang Zheng-Ping  , Ren Quan  , Zhang Huai-Jin  , Wang Ji-Yang  , Yu Hao-Hai  , Lü Yao-Hui  , Sang Yuan-Hua  , Xu Xin-Guang  ,   (1)山东大学晶体材料国家重点实验室,济南  250100; (2)山东大学晶体材料国家重点实验室,济南  250100；山东大学信息科学与工程学院,济南  250100; (3)山东大学信息科学与工程学院,济南  250100
Published: December 2020

A CW green laser was reported with ceramic Nd:YAG as gain material and KTP crystal as frequency doubler. When the pump power was 21.6 W， the 1064 nm fundamental output was 11.3 W， corresponding to an optical conversion efficiency of 52.3%. When a type-II cut KTP crystal was inserted in the straight cavity as a frequency doubler， the maximum 532 nm green output was 1.86 W， and the optical conversion efficiency was 7%. The one-dimensional intensity distribution of the green facula was of Gaussian type， and the M2 factor was measured to be 1.7 when the output power was 1 W.
Properties of MgB2 films fabricated under different conditions by ex-situ annealing of Mg/B multilayer precursor
Authors: Liu Liang  , Ma Xiao-Bai  , Nie Rui-Juan  , Yao Dan  , Wang Fu-Ren  ,   (1)北京大学物理学院,人工微结构和介观物理国家重点实验室,北京  100871; (2)空军航空大学,长春  130022
Published: December 2020

The effects of annealing temperature, annealing time and film thickness on the properties of MgB2 thin films prepared by ex-situ annealing of Mg/B multilayer have been studied. The films with the thickness of 250 nm annealed at temperatures as low as 400 ℃ exhibited a superconducting transition. The optimal annealing condition of 250 nm thick MgB2 films regarding to the transition temperature, Ｔc, was 750 ℃ for 20—30 min. Ｔc became lower as the film thickness decreased and the Ｔc of thinner MgB2 films was influenced more greatly by the annealing temperature. With reducing the thickness of each single layer, we were able to fabricate the 20 nm thick MgB2 superconducting film with a Tonsetc of 31K.
Study on the compound film of diamond for absorbing radiation
Authors: Liang Zhong-Zhu  , Liang Jing-Qiu  , Zheng Na  , Jiang Zhi-Gang  , Wang Wei-Biao  , Fang Wei  ,   (1)吉林大学超硬材料国家重点实验室，长春  130012; (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; (3)中国科学院东北地理与农业生态研究所，长春  130012
Published: December 2020

The solar radiation has significant impact on the earth climate and environment, so it’s important to detect it. High thermal conductivity and high absorptivity material for absorbing radiation is highly needed to improve the performance of the radiation detector. The compound diamond films were deposited using microwave plasma chemical vapor deposition （MW-PCVD） and hot cathode direct current plasma chemical vapor deposition （DC-PCVD） methods. The absorptivity of the compound diamond film is 99%—99.2%. With the increase of the thickness of black diamond layer, the thermal conductivity of the compound diamond film decreases a little, but the thermal conductivity is always larger than 16 W/K·cm when the thickness of black diamond layer is less than 15 μm and so it is still a high thermal conductivity material. The black diamond layer deposited on high purity diamond film by hot cathode DC-PCVD method has apparent wide Raman peaks at 1500—1600 cm-1and 1350 cm-1 which correspond to non-diamond carbon phase. With the increase of methane, this non-diamond carbon phase also increases. As the non-diamond carbon phase, like graphite, increases, the transmissivity of the compound diamond films decreases. The black diamond layer deposited on the high purity diamond acts as the heat sink and has high surface adhesion property, and high thermal conductivity.
Effect of rotating cavities on the group velocities of the coupled-resonater optical waveguides
Authors: Zhang Jian-Xin  , Qu Dao-Kuan  , Feng Shuai  , Wang Yi-Quan  , Wang Chuan-Kui  ,   (1)山东师范大学物理与电子科学学院，济南  250014; (2)中国矿业大学理学院，北京  100083; (3)中央民族大学理学院，北京  100081
Published: December 2020

In this article，the influence of cavity rotation on the group velocities of the coupled-resonator optical waveguides，which consists of the two-dimensional square-lattice photonic crystal，is studied theoretically by the multiple-scattering method and the finite-difference time-domain method. Simulation results show that the original single propagation mode becomes two modes when the cavities within the waveguide are rotated alternately，and the group velocities of the modes is reduced greatly. When the rotated angle of the selected cavities is 45°，the group velocities of the propagating modes can be reduced by one order of magnitude. Compared with that of the coupled-resonator optical waveguide without rotation of selected cavities，the two velocities get their minimum value，which are 0.0016c and 0.0009c respectively. The difference between them is determined by the symmetry of the propagating modes.
Flexural vibration property of periodic pipe system conveying fluid based on Timoshenko beam equation
Authors: Shen Hui-Jie  , Wen Ji-Hong  , Yu Dian-Long  , Wen Xi-Sen  ,   国防科学技术大学机电工程与自动化学院，长沙  410073；国防科学技术大学光子/声子晶体教育部重点实验室,长沙  410073
Published: December 2020

Fluid and structure interaction induced vibration in pipe system conveying fluid occurs in many fields, and the flexural vibration control is very important. The idea of phononic crystals is introduced into the design of pipe system conveying fluid. Basing on Timoshenko beam equation, and using the transfer matrix method, we study the band gap properties of the vibration and its transmission properties. The effect of the material damping ratio and spring support stiffness on the band gap is analyzed. The existence of band gaps in the periodic pipe system conveying fluid lends new insight into vibration control of pipes.
Approximate Lie symmetries and approximate invariants of the orbit differential equation for perturbed Kepler system
Authors: Lou Zhi-Mei  ,   Department of Physics, Shaoxing College of Arts and Sciences, Shaoxing 312000, China
Published: December 2020

We obtained the orbit differential equation of Kepler system when the θ is the independent variable. The Lie symmetries and invariants of the orbit differential equation for Kepler system , the exact Lie symmetries and exact invariants of the orbit differential equation for perturbed Kepler system are discussed firstly. Then we discuss the approximate Lie symmetries and approximate invariants of the orbit differential equation for perturbed Kepler system. Nine first order approximate Lie symmetries and six first order approximate invariants are obtained, one of them is a exact invariant in fact, and the other five of them are equivalent to the corresponding invariants of Kepler system multiplyied by the perturbation coefficient ε.
Acquisition method of precise periodic signal and uniqueness of periodic solutions of Duffing oscillator system
Authors: Wang Kun  , Guan Xin-Ping  , Ding Xi-Feng  , Qiao Jie-Min  ,   College of Science, Yanshan University, Qinhuangdao 066004, China
Published: December 2020

The acquisition method of precise periodic signal and uniqueness of periodic solutions of Duffing oscillator system is investigated. The necessary condition of uniqueness of periodic solutions of a kind of Duffing oscillator system is presented and the uniqueness of periodic solutions of some extensive nonlinear periodic system is simultaneously obtained by using qualitative analysis method .The acquisition method of precise periodic signal Duffing oscillator system is given under certain conditions.
Dynamic range of X-ray streak camera affected by space charge effect
Authors: Yuan Yong-Teng  , Hao Yi-Dan  , Zhao Zong-Qing  , Hou Li-Fei  , Miao Wen-Yong  ,   Research Center of Laser Fusion, China Academy of Engineerning Physics, Mianyang 621900, China
Published: December 2020

x ray streak camera is an important equipment for time resolved measurement in the field of inertial confinement fusion. Its dynamic range indicates the ability that effectively measuring the intensity of incidence x ray. The photoelectron pulse will be broaden in passing through the photocathode-to-mesh region because of space charge effect. This limits the dynamic range of the streak camera. This paper adopts a fluid model, making use of particle conservation, momentum conservation, and Poisson equations to deduce the widening of the electron pulse and derive the change in the electron density distribution. The results can be used to evaluate the dynamic range of the streak camera.
Hyper-spectral imaging system with harmonic diffraction element in medium and far infrared
Authors: Liu Ying  , Sun Qiang  , Lu Zhen-Wu  , Qu Feng  , Wu Hong-Sheng  , Li Chun  ,   (1)Opto-electronic Technology Research Center, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China; (2)Opto-electronic Technology Research Center, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China, Graduate School of the Chinese Academy of Sciences, Beijing 100049,China
Published: December 2020

In order to obtain enough information about the target and make full use of medium- and long-wave infrared spectral data, this article describes a harmonic diffractive/refractive (HDE) optical imaging system. Taking advantage of its special dispersion capability, the application of HDE in the infrared dual-band provides hundreds of spectral images in infrared band, medium-wave infrared band of 3.7—4.8 μm and long-wave infrared band of 8—12 μm. The design results show that: at 18 lines/mm, the optical modulation transfer function is greater than 0.55 in medium-wave infrared band, at 13 lines/mm the optical modulation transfer is greater than 0.5 in long-wave infrared band, in the circle of 30 μm radius, the encircled energy is greater than 85% in medium-wave infrared band, in the circle of 38 μm radius, the encircle energy is great than 80% in long-wave infrared band, the spectral resolution is 0.039 μm at 4.25 μm and 0.072 μm at 8.5 μm respectively. So the optical modulation transfer function in infrared dual-band is close to the diffraction limit, and the encircled energy meets the energy requirement of one pixel of existing domestic detectors.
Prediction of transport properties of O2-CO2 mixtures based on the inversion method
Authors: Wang Xiao-Po  , Song Bo  , Wu Jiang-Tao  , Liu Zhi-Gang  ,   State Key Laboratory of Multiphase Flow in Power Engineering, Xi'an Jiaotong University, Xi'an 710049, China
Published: December 2020

A new potential energy surface of O2-CO2 mixtures was obtained by means of inversion method. According to the kinetic theory of gas,the transport properties of O2-CO2 mixtures,including viscosity coefficient,thermal diffusion coefficient and thermal diffusion factor, were caluclated in the temperature range between 273.15 K and 3273.15 K at zero-density.
Numerical simulation of femtosecond laser heating of metal films using electron thermal emission
Authors: Chen An-Min  , Gao Xun  , Jiang Yuan-Fei  , Ding Da-Jun  , Liu Hang  , Jin Ming-Xing  ,   Institute of Atomic and Molecular Physics, Jilin University, Changchun 130012, China
Published: December 2020

The whole process of the electron thermal emission by ultrafast pulsed laser is studied in the paper. When an ultra-short laser pulse interaction with the target film, first of all, the incident laser excites free electrons within the absorption depth, next, electron energy is transferred to nearby lattice through the heat transfer systems of the free electron and lattice, and by the thermal coupling between the electron and the lattice, the energy is delivered to the internal material. Therefore, in a short period of ps and shorter, the energy coupling of the electron and lattice can not be established. So that the electron temperature is much higher than the lattice temperature, the electron thermal emission becomes apparent. The characteristics of thermionic emission of the films during ultrashort pulse laser ablation are investigated using two-temperature model coupled with the Richardson-Dushman equation. It is found that electron thermal emission can significantly change the development of electron and lattice temperatures, meanwhile, the film thickness and laser fluence directly affect electron thermal emission.
Orbital ordering driven spin dimer state in double-layered antiferromagnet K3Cu2O7
Authors: Liu Da-Yong  , Chen Dong-Meng  ,   (1)College of Physical Science and Technology, China University of Petroleum, Dongying 257061, China; (2)Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

Magnetic, orbital and lattice structures of K3Cu2F7 are determined by cluster self-consistent field approach based on the spin-orbital-lattice Hamiltonian. Symmetry breaking and Jahn-Teller distortion of approximately isolated bilayer cause Cu2+ ions alternatively to occupy  z2-x2〉/ z2-y2〉 orbitals in each layer. This orbital ordering occupation leads to the dominant intrabilayer antiferromagnetic coupling, which favors spin dimerization, and the weak intralayer ferromagnetic coupling. Due to absence of spin frustration resulting from the intralayer orbital arrangement and the weak ferromagnetic coupling satisfing Goodenough-Kanamori-Anderson (GKA)rule, the ground state is a stable spin dimer state. The spin singlet-triplet excitation gap obtained by bond-operator mean field method is about 326 K, which is close to the experimental value of 400 K. The present theory is also applicable to explaining the formation of spin dimer state in Cs3Cu2Cl4Br3.
Comparative study on fractal model and spherical model of fire smoke particles for light scattering
Authors: Zhang Qing  , Deng Xiao-Jiu  , Zhang Qi-Xing  , Li Yao-Dong  , Zhang Yong-Ming  ,   (1)Optical Engineering, School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei 230009, China; (2)Optical Engineering, School of Electronic Science and Applied Physics, Hefei University of Technology, Hefei 230009, China, State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei 230027, China; (3)State Key Laboratory of Fire Science, University of Science and Technology of China, Hefei 230027, China
Published: December 2020

It is important to research light scattering from fire smoke particles by numerical calculation. Traditionally, spherical or spheroid models were used to approximate the shape of smoke particles for light scattering calculations. But actually, smoke particles have a similar fractal structure, which is different from spherical structure. Using the discrete-dipole approximation method, the light scattering Muller matrices were computed for the randomly oriented fractal aggregate, as well as the spherical particle with the same aggregate volume, and then their normalized Muller matrix elements were compared. The results indicate that the angular distributions of the normalized matrix elements F11(θ)/F11(0), F22(θ)/F11(θ) and F34(θ)/F11(θ) have significant differences between the fractal model and spherical model. We can discriminate spherical non-fire aerosols from smoke particles, using the difference of F22(θ)/F11(θ) between fractal model and spherical model.
Adaptive image interpolation algorithm based on the fuzzy logic
Authors: Xu Yan  , Dong Jiang-Tao  , Wang Shao-Hua  ,   (1)Optical and Electronic Engeering Department, Ordnance Engineering College, Shijiazhuang 050003, China; (2)The 54th Research Institute of China Electronics Technology Group Corporation, Shijiazhuang 050081, China
Published: December 2020

Conventional image interpolation algorithm always introduces the the blur and jagged edges. To solve this problem, an improved adaptive image interpolation algorithm with using membership function is proposed in this paper. Fuzzy logic is used to obtain the membership function with the local characteristics of the gradient and phase angle. The first step is to correct the special distance of interpolated pixels along one dimension in the basis of local asymmetry features and the membership function, and then to convert the corrected distance of one dimension into two dimensions, applying the corrected distance to conventional image interpolation algorithm. Experimental results demonstrate that the improved algorithm can produce better results in regard to the signal-to-nosie ratio and succeed in preserving interpolation image edges in various directions.
The ground state solutions of superfluid Fermi gas in optical lattices
Authors: Bai Xiao-Dong  , Liu Rui-Han  , Liu Lu  , Tang Rong-An  , Xue Ju-Kui  ,   College of Physics and Electronic Engineering, Northwest Normal University, Lanzhou 730070, China
Published: December 2020

The ground state solutions of superfluid Fermi gas in optical lattices are studied by means of the balance condition between the lattices potential and inter-atomic interaction energy. We derive the atoms density distribution, the atoms number and the energy of the ground state along the entire BEC-BCS crossover. It is shown that, the properties of the ground state present very different characters as the system transits from the BEC side to the BCS side.
Effect of vibrational quantum number on stereodynamics of reaction O+HCl→OH+Cl
Authors: Xu Xue-Song  , Zhang Wen-Qin  , Jin Kun  , Yin Shu-Hui  ,   (1)Department of Physics,Dalian Martime University,Dalian 116026,China; (2)Department of Physics,Dalian Martime University,Dalian 116026,China;School of Physics and Optoelectronic,Dalian University of Technology,Dalian 116024, China; (3)School of Physics and Optoelectronic,Dalian University of Technology,Dalian 116024, China
Published: December 2020

The stereodynamical properties of O+HCl→OH+Cl reaction are studied by using the quasi-classical trajectory (QCT) method on Peterson ab initio potential energy surface. The vibrational level and the rotational level of the reactant molecule are taken as v=0—4 and j=0 respectively. The calculation results show that the vibrational quantum number has a considerable influence on the distribution of the k-j'vector correlation. The effects of vibrational quantum number on k-k' -j' three-vector correlation and on generalized polarization dependent differential cross section are minor. The effect of initial vibrational excited state of reactant molecule on the rotational alignment of product molecule is stronger than that on the P(r) distribution of product molecule.
Calculation of geometrically active atomic state
Authors: Li Zun-Mao  , Xiong Zhuang  , Dai Li-Li  ,   AMS Research Center, Southeast University, Nanjing 210096,China
Published: December 2020

We develop a computer code to calculate ab-initio variational configuration interaction of electronic structure of atoms via generalised Lagurre type orbitals. Treating the orbital effective charges as variational parameters and computing the absolute minimum of energy, yield its optimal wave function.Then utilizing the one-electron density and the probability distribution of the angular two-electron density according to the optimal wave function, we investigate the geometrically active atomic states (GAASs) of Be, B, C, N, O and Ne atoms that are in the first excited states with configurations sαpβ. These results reveal that as an intrinsic property of the wave function of atoms, the angle of the most probabl angular distribution of two-electron density is approximately equal to the bond angle of the molecule, which usually can be explained by the hybridization theory.
Mid-IR multiwavelength difference frequency generation laser source based on fiber lasers
Authors: Jiang Jian  , Chang Jian-Hua  , Feng Su-Juan  , Mao Qing-He  ,   Anhui provincial Key Lab of Photonics Devices and Materials, Anhui Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

The quasi-phase-matched (QPM) wavelength acceptation bandwidth for a difference frequency generation (DFG)mid-IR laser source with fiber lasers as the fundamental sources is effectively broadened by using the dispersion relations and its temperature characteristic of periodically poled MgO-doped LiNbO3 (PPMgLN). Our simulation results show that, with an erbium-doped fiber laser (EDFL) and a ytterbium-doped fiber laser (YDFL) respectively operating near 1550 and 1060 nm wave-bands as the signal source and pump source, for the same mid-IR wavelength regions, the allowable wavelength range given by the QPM condition for the pump wave is much larger than that for the signal wave. When the wavelength of the signal wave is fixed at 1560 nm, for a given optimized crystal temperature, the acceptance bandwidth for the pump wave is over 17 nm, corresponding to the acceptance bandwidth for the idler wave of about 180 nm. Based on it, by using a multiwavelength YDFL and a single wavelength EDFL cascaded by an erbium-doped fiber amplifier (EDFA) respectively as the pump source and the signal source, 14-wavelength mid-IR laser lines, with a spacing of about 14 nm in between, are obtained simultaneously with our QPM-DFG laser system when both the temperature and the grating period of the PPMgLN used being kept unchanged at 73.5 ℃ and 30 μm respectively. Moreover, the mid-IR multiwavelength laser lines may be tuned synchronously by varying the signal wavelength.
Anelastic relaxation and phase transition internal friction properties of La2-x NdxCuO4+δ(0.1≤x≤1.2) compounds
Authors: He Qing  , Yang Chun-Li  , Wu Xiu-Sheng  , Chen Zhi-Jun  , Chen Chu-Sheng  , Liu Wei  ,   (1)Department of Materials Science and Engineering, Anhui Institute of Archtecture and Indusstry, Hefei 230026, China; (2)Laboratory of Advanced Functional Materials and Devices, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei 230022,China
Published: December 2020

The low-frequency internal frictions of La2-xNdi>xCuO4+δ(0.1≤x≤1.2) compounds are measured. The results show that the relaxation internal friction peak related to the excess oxygen atoms appears around 250K with 0.1≤x≤1.0.And the peak becomes higher with the value of x increasing for 0.1≤x≤0.4 and all these compounds have orthorhombic structures. When 0.5≤x≤1.0, the compounds have all tetragonal structures on a macro scale and the peak reduces as the value of x increases. However, the sample with x=1.2 exhibits tetragonal structure but the relaxation internal friction peak is not found. Further more, when 0.1≤x≤0.8, there exists a phase transition internal friction peak around 550K. The transition temperature shifts toward high temperature zone as the value of x increases and relative shear modulus M is enlarged. But for x=1.0 and 1.2, there appears no phase transition internal friction peak in the measurement range. We find that all these phase transition internal friction peaks are related to the transition between the orthorhombic structure and the tetragonal structure.
Thermal stability of glow discharge polymer coatings on glass microspheres
Authors: Yan Jian-Cheng  , He Zhi-Bing  , Yang Zhi-Lin  , Chen Zhi-Mei  , Tang Yong-Jian  , Wei Jian-Jun  ,   (1)Sichuan University, Institute of Atomic and Molecular Physics, Chengdu 610065, China; (2)Sichuan University, Institute of Atomic and Molecular Physics, Chengdu 610065, China;The Centre of Laser Fusion Research, China Academy of Engineering Physics, Mianyang 621900, China; (3)The Centre of Laser Fusion Research, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

Using trans-2-butene and hydrogen as the precursor, the glow discharge polymer (GDP) films are successfully coated on glass microspheres with diameters of 350—400 μm and thicknesses of 2.5—3 μm by the glow discharge polymerization technology. Glass/GDP microsphere is heated to test its thermal stability, whose process is the same as the D2 gas charge procedure. The chemical structures, the thermal stabilities of the GDP films, the morphologies of glass/GDP microspheres are characterized by the FT-IR, TG, stereoscopic microscope and X-radiography technology. The Results show that the C/H and C C in GDP films decrease as pressure increases. Their thermal stabilities are better, and the adhesion between GDP film and glass microsphere is enhanced when the GDP coatings are fabricated at lower pressures.
Influence of well structure on efficiency of organic light-emitting diodes
Authors: Zhu Hai-Na  , Xu Zheng  , Zhao Su-Ling  , Zhang Fu-Jun  , Kong Chao  , Yan Guang  , Gong Wei  ,   Key Laboratory of Luminescence and Optical Information,Ministry of Education,Institute of Optoelectronic Technology,Beijing Jiaotong University,Beijing 100044,China
Published: December 2020

Five kinds of organic quantum well structured light-emitting devices are fabricated, and their electrical characteristics are studied. The effects of quantum well period number and barrier thickness on device performance are analyzed. Experimental results show that appropriate cycle quantum well structured devices have higher brightness and current efficiency than the traditional three-layer devices. That is because of the limitation effect of quantum well structure on electrons and holes,and the structure of this kind could improve the composite probability of excitons in the light-emitting layer,thereby increasing brightness and efficiency of OLED. There is also an effect on brightness and efficiency when the potential well layer thickness of quantum well structured device is changed. Consequently,the adoption of appropriate potential well layer thickness can also improve the brightness and the efficiency of the device.
Electronic transport properties of single-walled carbon nanotubes under a low bias
Authors: Zhao Qi-Di  , Zhang Zhen-Hua  ,   School of Physics and Electronic Science,Changsha University of Science and Technology,Changsha 410114,China
Published: December 2020

In this paper,changing patterns of electronic velocity and effective mass of the lowest conduction band for various carbon nanotubes are calculated systematically. Based on these calculation results,low-bias transport properties of single-walled carbon nanotubes (SWCNTs) and deduced thoroughly. It is found that under a low bias,chiral metallic SWCNTs belonging to the same series ( i.e,having the same chiral angles) have the entirely identical transport properties and are independent of diameter of the SWCNT. But those that belong to different series have obviously distinguishable transport properties. While for chiral semi-conducting SWCNTs belonging to the same series,they have some different transport properties. But those that belong to different series have greatly different transport properties. Our findings suggest that low-bias transport properties of SWCNTs are intimately related to the series and the chiral angle is the most important geometry parameter for the determination of different low-bias transport properties of various SWCNTs.
Performance optimization of carbon nanotube field effect transistors based on stair-case doping strategy
Authors: Zhou Hai-Liang  , Chi Ya-Qing  , Zhang Min-Xuan  , Fang Liang  ,   Key Laboratory of Parallel and Distribution Processing, School of Computer,National University of Defense Technology,Changsha 410073,China
Published: December 2020

The ambipolar transporting characteristic is one of the most important factors that prevent the performance of Carbon Nanotube Field Effect Transistors (CNFETs) from further being improved. In order to reduce the ambipolar conductance and increase the ON-OFF current ratio of the device,a stair-case doping strategy in drain lead,which is suitable for not only the Conventional MOS-like CNFETs (C-CNFETs) but also Tunneling CNFET (T-CNFETs),is proposed in this paper. The non-equilibrium Greens function based simulation results show that this strategy can reduce the ambipolar conductance and increase the ON-OFF current ratio of the device effectively. Further study shows that many differences exist with using this stair-case doping strategy applied in C-CNFETs and T-CNFETs. First,the potential band pinning in stair-case doped C-CNFETs would weaken the ON-state performance of the device,while no band pinning exists in stair-case doped T-CNFETs. Second,applying such a stair-case doping strategy to both source and drain leads can further increase the device performances in C-CNFETs but not T-CNFEts. Third,the transporte property of T-CNFETs is dependent more strongly on the width of lightly doped drain region than that of C-CNFETs. However,certain device area would be costly because of using this stair-case doping strategy. So,much attention should be paid to the choice of device structure,doping concentration and lightly doped drain region width,to obtain a best tradeoff among speed,power and device area,in application.
Research on least-squares fitting calculation of the field-effect mobility
Authors: Chen Yue-Ning  , Xu Zheng  , Zhao Su-Ling  , Sun Qin-Jun  , Yin Fei-Fei  , Dong Yu-Hang  ,   Institute of Optoelectronics Technology,Beijing Jiaotong University,Key Laboratory of Luminescence and Optical Information(Beijing Jiaotong University),Ministry of Education,Beijing 100044,China;,   Institute of Optoelectronics Technology,Beijing Jiaotong University,Key Laboratory of Luminescence and Optical Information(Beijing Jiaotong University),Ministry of Education,Beijing 100044,China;Physics Department,Liaoning University,Shenyang 110036,China;,   Physics Department,Liaoning University,Shenyang 110036,China
Published: December 2020

In this article,organic thin-film transistors (OTFTs) with top-gate and bottom contact geometry based on pentacene as active layer were fabricated. The experimental data of the I-V were obtained from the organic thin-film transistors. The field-effect mobility of the OTFT was calculated by fitting of theoretical calculation to the experimental data. We find that field-effect mobility values have great difference by different fitting methods. We calculate the field-effect mobility by least-squares fitting method to the experimental data of the I-V away from the center of the linear region of the transfer characteristics curves 1/2 range. The inherent inaccuracy of other fitting method can be reduced. The results is the nearest field-effect mobility obtained with other methods.
Hamiltonization of Whittaker equations
Authors: Ding Guang-Tao  ,   College of Physics and Electronic Information, Anhui Normal University, Wuhu 241000, China
Published: December 2020

A Birkhoffian representation of Whittaker equations is introduced. A Hamiltonian corresponding to the Birkhoffian representation is constructed. The Whittaker equations are solved by using the Hamilton-Poisson method. The difference between the above Hamiltonian and the Hamiltonians of traditional analytical mechanics is pointed.
Momentum image of emission electrons in transfer ionization process of slow He2+ colliding on He
Authors: Feng Wen-Tian  , Ma Xin-Wen  , Zhu Xiao-Long  , Zhang Shao-Feng  , Liu Hui-Ping  , Xu Shen-Yue  , Qian Dong-Bin  , Li Bin  , Yan Shun-Cheng  , Zhang Da-Cheng  , Meng Ling-Jie  , Zhang Peng-Ju  ,   (1)Insititute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China; (2)Insititute of Modern Physics, Chinese Academy of Sciences, Lanzhou 730000, China;Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

The velocity distribution of emission electrons in the transfer ionization process of 70keV He2+ colliding on He has been studied with a reaction microscope. These distributions show that the electrons lie mainly in the scattering plane which are observed to be emitted preferentially in the forward direction, lying between 0 and projectile velocity Vp. The distributions also display a typical two-fingered structure with a local minimum on internuclear axis. This characteristic can be qualitatively explained as being due to the interference between σ amplitude and π amplitude of electrons final wavefunction. It depends also on the impact parameters; the π amplitude contribution is dominant at small impact parameters, which leads to a symmetric velocity distribution around the internuclear axis. However, at large impact parameters the σ amplitude contribution increases relatively obviously, resulting in an asymmetric electrons velocity distribution around the internuclear axis.
Influence of nonlinearity on focused acoustic field of array in atmosphere
Authors: Lü Jun  , Zhao Zheng-Yu  , Zhang Yuan-Nong  , Zhou Chen  ,   School of Electronic Information, Wuhan University, Wuhan 430079, China
Published: December 2020

The difference wave equation is obtained by the discretization of nonlinear acoustic wave equation in atmosphere with in the second-order miniterm approximation based on the finite-difference time-domain method. And the two-dimensional field distribution of continuous sinusoidal wave vertically or obliquely radiated by a linear array of five monopole sound sources is numerically simulated at the different initial acoustic pressures. A comparison between nonlinear simulation and linear one show that weak nonlinearity has definite and apparent effects on the distribution of acoustic field and focused gain of array, leading the distribution of waveform to be closer to the array and the focusing gain to deteriorate, and that the strong nonlinearity has a strong waveform aberration, because the other waves of non-fundamental frequency appear. No evident distinction is found in the effect between the oblique propagation and the vertical propagation, though less focusing gain and influence caused by strong nonlinearity produced by the acoustic geometric spreading result in more attenuation of axial pressure in the case of oblique propagation.
Analyses of buckling failure mode for porous materials under compression
Authors: Liu Pei-Sheng  ,   Key Laboratory of Beam Technology and Material Modification of Ministry of Education, College of Nuclear Science and Technology, Beijing Normal University, Beijing 100875, China
Published: December 2020

The compressive behavior is one of most basic mechanical properties for engineering materials, and the struts of porous materials under compression may display the buckling phenomena when the porous bodies are under compressive loadings. In the present paper, a failure model of simplified structures is established for isotropic three-dimensional reticulated porous materials, and the failure modes resulting from the strut bucklings are analyzed for these materials under compressive loadings. The mathematical relationships between nominal main stresses and porosities are systemically derived for this buckling failures of these materials under uniaxial compression, biaxial compression and triaxial compression. Based on these results, the relevant loading conditions resulting in the strut buckling are further obtained for these materials under compressive loadings.
Analysis of variation in geomagnetic field of Chinese mainland based on comprehensive model CM4
Authors: Feng Yan  , An Zhen-Chang  , Mao Fei  , Sun Han  ,   (1)Chinese Academy of Meteorological Sciences, Beijing 100081, China; (2)College of Resources and Environmental Science, Nanjing Agricultural University, Nanjing 210095, China; (3)Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing 100029, China; (4)Remote Sensing Application and Experiment Station of National Satellite Meteorological Center, Guangxi Meteorological Disaster Mitigation Institute, Nanning 530022, China
Published: December 2020

The fourth generation of comprehensive model of geomagnetic field CM4 is a numerical model in which earths magnetic field can completely be divided into internal and external parts. In this paper we have calculated and plotted the grid values of internal and external fields of Chinese mainland in every 10 a from 1960 to 2000 by combining CM4 with Taylor polynomial model based on all survey data during 1960—2000, and made more efforts to analyze the whole distribution of crustal anomaly field. Results show that internal field value of northern component X decreased with time. The amplitude was about 750 nT in the period from 1960 to 2000, the trend of external field variation increased in 1960, then gradually decreased about 32 nT until 2000. The internal field value of eastern component Y decreased first, then continuously increased, and its intensities decreased about 40 nT from 1960 to 2000. The trend of external field variation was increased, decreased and increased as time went on, and the external field increased up to about 3.8 nT since 1960. The internal field value of vertical component Z was similar to that of Y, its intensities totally increased about 600 nT. The trend of external field variation decreased and then increased with time, amplitude of which was about 4.6 nT. As for anomalous field, the distributions of components X and Z, total intensity F, and horizontal component H were all negative, the intensities of X and H decreased with longitude while those of Z and F increased. The distributions of Y and declination D were very similar and both of them had positive values in west-central region of China. Their intensities decreased with longitude. The distribution of inclination I was mainly negative, and its intensity increased with longitude.
Design of a quasi-optical mode converter for 94 GHz gyrotron
Authors: Liu Jian-Wei  , Zhao Qing  , Li Hong-Fu  ,   Institute of the Energy Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

Based on geometry optics theory and vector diffraction theory, mode converter is studied to convert the gyrotron and other high-power microwave oscillator output mode into quasi-optical Gaussian beam, using Vlasov launcher and two quasi-optical reflector achieved quasi-Gaussian mode TEM00 transverse output.The working mechanism of Vlasov launcher in analyzed, the radiation field is calculated by using vector diffraction theory, and the surface radiation field is also calculated by using the surface current distribution method. A built-in quasi-optical mode converter is designed to convert the 94GHz, TE62 model millimeter wave into quasi-optical Gaussian beam through programming.
Output intensity of Ne-like Ge soft X-ray laser with double-pass amplification
Authors: An Hong-Hai  , Wang Chen  , Fang Zhi-Heng  , Xiong Jun  , Sun Jin-Ren  , Wang Wei  , Fu Si-Zu  , Qiao Xiu-Mei  , Zheng Wu-Di  , Zhang Guo-Ping  ,   Shanghai Institute of Laser Plasma, Shanghai 201800, China;,   Institute of Applied Physics and Computational Mathematics, Beijing 100080, China
Published: December 2020

Ne-like germanium soft X-ray lasers driven by nanosecond laser have very good applications, due to their stable output and strong intensity. The double-pass amplification mode, with a multi-layer reflective mirror added is investigated. The estimate and the experiment show that the output intensity of Ne-like germanium soft X-ray laser is enhanced by double-pass amplification. For 24mm length of double-pass amplification, the total output intensity is enhanced by 2.3 times as against that with no mirror added. Meanwhile, this mode results in quality decline of soft X-ray laser beam. So this mode is not entirely beneficial to the applied study.
Propagation properties of light in multimode photonic crystal waveguides with triangular lattices based on total internal reflection
Authors: Zhang Jun  , Yu Tian-Bao  , Liu Nian-Hua  , Liao Qing-Hua  , He Ling-Juan  ,   Department of Physics, Nanchang University, Nanchang 330031, China;,   State Key Laboratory on Integrated Optoelectronics, Institute of Semiconductors, CAS, Beijing 100083, China;,   Institute for Advanced Study, Nanchang University, Nanchang 330031, China 
Published: December 2020

The properties of the propagating field in multimode photonic crystal waveguides exhibiting no photonic band gaps with triangular lattices are investigated. By the effective refractive index method, these structures are regarded as three layer planar dielectric waveguides. And the multimode interference effect is numerically analyzed and simulated based on the self-imaging principle. The results show that the field can propagates effectively and resembles index-guided mode due to the combination of total internal reflection and distribution Bragg reflection. High transmission region shifts toward the shorter wavelength region, the bandwidth and the transmissivity increase with the increase of filling ratio, which provides a theoretical reference for selecting an appropriate filling ratio in practical applications.
Qualitative analysis of excess noise in nanoscale MOSFET
Authors: Tang Dong-He  , Du Lei  , Wang Ting-Lan  , Chen Hua  , Chen Wen-Hao  ,   School of Technical Physics, Xidian University, Xi'an 710071, China
Published: December 2020

Recent experiment indicates that shot noise is the dominant excess noise in nanoscale MOSFET. However the early research reported that no shot noise was observed in MOSFET, and thermal noise was the excess noise in short channel MOSFET. Based on the device current model, we derive the conversion conditions for the dominant component of excess noise shifting from thermal noise to shot noise. According to the conversion conditions, the prediction of the noise performance of nanoscale MOSFET is given, and the results coincide with experimental phenomena, simulation data and conclusion of mesoscopic shot noise, which has been reported in the article.
Investigation of the response mechanism of photovoltaic semiconductor with sub-bandgap photons
Authors: Jiang Tian  , Cheng Xiang-Ai  , Jiang Hou-Man  , Lu Qi-Sheng  ,   College of Optoelectric Science and Engineering, National University of Defense Technology, Changsha 410073, China;,   95844 Unit of PLA, Jiuquan 735018, China
Published: December 2020

The photovoltaic HgCdTe detectors with band gaps 0.91 and 0.33 eV are irradiated by 10.6 m laser (0.12 eV photon energy), separately. It is found that output voltage of detector (0.91 eV band gap) is positive, while the response voltage of detector (0.33 eV band gap) is opposite to it. To investigate this phenomenon, the detector with a band gap of 0.91 eV is irradiated by a given power 10.6 m laser under different initial open-circuit voltags. It is experimentally demonstrated that the phenomenon is caused by the initial open-circuit voltage. With further investigation, the open-circuit voltage of the photovoltaic detector is determined by both the thermovoltage caused by thermoexcited carrier and the crystal thermal effect produced by free carrier absorption under sub-bandgap laser irradiation.
Chaotic time series prediction based on robust echo state network
Authors: Li De-Cai  , Han Min  ,   Faculty of Electronic Information and Electrical Engineering Dalian University of Technology, Dalian 116023, China
Published: December 2020

Focusing on the problem that the echo state network is easily influenced by outliers, in this paper we propose a robust model based on the Laplace prior distribution. This is achieved by replacing the Gaussian distribution with the Laplace distribution as the prior of the model output, the Laplace prior is less sensitive to the outliers and can enhance the capbility of the model to restrict outliers. Furthermoer, to solve the problem arising from the introduction of the Laplace distribution, which makes the solving process of the method difficlut, the bound optimization algorithm is employed and a suitable surrogate function is established. Based on the bound optimization algorithm, the Laplace prior can be equivalently transformed into the form of Gaussian prior, which is easily computed, and it can also be use to estimate the model parameters adaptively. Simulation results illustrate that the proposed method can be robust when outliers exist, while remaining acceptable prediction accuracy.
Extension characteristics of the depth of field for wavefront coding system
Authors: Zhang Rong-Fu  , Wang Tao  , Pan Chao  , Wang Liang-Liang  , Zhuang Song-Lin  ,   School of Optical-Electrical and Computer Engineering,University of Shanghai for Science and Technology,Shanghai 200093, China;,   School of Electric and Electronic Information Engineering,Huangshi Institute of Technology,Huangshi 435003, China
Published: December 2020

The wavefront coding extension of the depth of field (DOE) for an imaging system is achieved by inserting a third order phase plate into the pupil plane of a spatially incoherent imaging system. The encoded image can be digitally restored to produce a final image with improved depth-dependent details. The characteristics of the system are studied, and the modulation transfer function (MTF) varying with defocus and modulation coefficient,, of the third order phase mask is analyzed, the results about the effects of value on the extension of DOE and the bandwidth are obtained. The results are conducible to the design of wavefront coding optical system and the choice of an appropriate velue.
Effect of interface contacts between TiO2 particles on electron transport in dye-sensitized solar cells
Authors: Xu Shuang-Ying  , Hu Lin-Hua  , Li Wen-Xin  , Dai Song-Yuan  ,   Key Laboratory of Novel Thin Film Solar Cells, Institute of Plasma Physics, Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

Based on sol-gel and screen-printed method, nanoporous TiO2 thin films obtained under different sintering temperatures and times are adopted in dye-sensitized solar cells. According to FESEM, TiO2 particles tend to compact through touch contact under low sintering temperature, but touch contact is substituted by surface contact when the temperature is up to 510 ℃, which results in larger particle coordination number. Moreover, the influence of different contact ways between TiO2 particles on the electron transport is investigated by IMPS/IMVS technology. The results indicate that with the sintering temperature increasing from 420 ℃ to 510 ℃, the electron transport time ( d) decreases while the electron effective diffusion length (L n) increases, owing to the increased contact surface between TiO2 particles. However, when the sintering temperature increases up to 550 ℃, the porous structure of the TiO2 electrode collapses and new surface state appears on the TiO2 surface, leading to the increase of d. It is suggested that the larger short-circuit current density (Jsc) and efficiency () can be obtained when the sintering temperature of nanoporous TiO2 film is in a range of 480-510 ℃.
Electrochemical property of Si-O-C composite anode materials prepared by pyrolyzing polysiloxane containing phenyl under different atmospheres
Authors: Liu Xiang  , Xie Kai  , Zheng Chun-Man  , Wang Jun  ,   Department of Material Science and Applied Chemistry, National University of Defence Technology, Changsha 410073, China;,   Key Laboratory of New Ceramic Fibers and Composites, National University of Defence Technology, Changsha 410073, China
Published: December 2020

Silicon Oxycarbide (Si-O-C) composite anode materials are prepared by pyrolysis of polysiloxane containing phenyl under argon and hydrogen atmospheres, separately. They are characterized by element analysis, wide-angle powder X-ray diffraction, Raman spectroscopy for comparison with each other. It is found that the silicon oxycarbide composite anode pyrolyzed under a hydrogen atmosphere demonstrates lower irreversible capacity and larger reversible capacity which increases with temperature rising. The one pyrolyzed at 1000 ℃ shows a reversible capacity of 622 mAh/g, and first coulombic efficiency of 59%.The magnitude of the irreversible capacity is correlated with the content of oxygen, and the reversible capacity is related to the content and structure of free carbon, and also the structure of Si-O-C. It is believed that Si-O-C composite materials pyrolyzed under a hydrogen atmosphere could be promising anode materials for lithium ion batteries.