bluuebunny/crossref_metadata_2025 huggingface dataset:
Modulation of nonlinear coupling on the synchronization induced by linear coupling
Authors: Zhao Long  , Yang Ji-Ping  , Zheng Yan-Hong  ,   School of Automation Science and Electrical Engineering, Beihang University, Beijing 100191, China;,   School of Economics and Management, Beihang University, Beijing 100191, China
Published: December 2020

The experimental results confirmin that spiral wave can be observed in the cortex of brain and the electric signals in neurons can proprgate with spiral wave. The mechanism for the formation of spiral wave is investiaged in the regular network of Hodgkin-Huxley, which can measure the effect of ion channels, and the sprial waves with different periods are developed to occupy the network by blocking the travelling wave with defects. The basic condition for inducing spiral wave and the effect of the couling intensity are analyzed. The potential mechanism for developing spiral wave is discussed.
Distribution characteristics of lightning electromagnetic pulsed fields under the ground
Authors: Zhang Shao-Qing  , Wu Qun  ,   School of Electronic and Information Engineering, Harbin Institute of Technology, Harbin 150001, China
Published: December 2020

In order to repeat the propagation and its distribution characteristics, the lightning electromagnetic field (LEMP) in the entire space is calculated by a modified finite difference time-domain (FDTD) approach in this paper. Different from issued results, in which the electromagnetic field operates only at some discrete points near the ground, the LEMP and its time derivatives, power density and energy density at each unit in the whole space under the ground are calculated and expressed as groups of pictures. We find LEMPs attenuate exponentially in the horizontal and vertical direction, in the area near the ground and far from the discharge channel. The peak values of horizontal electric field and azimuthal magnetic field each have an unaltered polarity and their contours are similar to double exponential functions in the entire space under the ground. However the peak values of vertical electric field can be divided into two opposite-polarity parts in the whole area under the ground, and the contours in the area near the strike channel are spherical in shape. The other components have similar features. We also calculate the LEMPs with different values of ground conductivity, ground permittivity, return model and base current, and the characteristics of distribution are not changed, although the values are enhanced integrally in some cases. And in the layered earth, the LEMP has similar contours inside the layers. Even in the case of striking to the lightning rod, the characteristics of distribution are not changed. These patterns and distribution characteristics of LEMP can provide support and reference in shielding design and route planning under the ground.
A study of seasonal fctors impact on climate networks
Authors: Yang Jin-Hui  , Song Jun-Qiang  , Cao Xiao-Qun  ,   School of computer, National University of Defense Technology, Changsha 410073, China
Published: December 2020

Climate network is a new interesting field in the earth sciences. It has advantage in exploring the properties and associated structures of climate fields. In the past researches, only climate dataset for winter month of the years were used to construct climate networks, and the effect of other seasons was ignored. In this paper, how seasonal factors impact on climate networks is investigated. It is find that some of the global properties of climate networks keep stable regardless of season, on the contrary, the community structures of network and local topologies change significantly in different seasons. With this conclusion, the variation of global teleconnection patterns and local area climate in different seasons can be investigated on climate network.
Carbon isotope ratio analysis in CO2 based on Fourier transform infrared spectroscopy
Authors: Li Xiang-Xian  , Gao Min-Guang  , Xu Liang  , Tong Jing-Jing  , Wei Xiu-Li  , Feng Ming-Chun  , Jin Ling  , Wang Ya-Ping  , Shi Jian-Guo  ,   Key Laboratory of Environment Optics and Technology, Anhui Institute of Optics and Fine Mechanics,Chinese Academy of Sciences, Hefei 230031, China
Published: December 2020

A new method to detect carbon isotope ratio of carbon dioxide is presented, which is developed based on Fourier transform infrared spectroscopy (FTIR)technique. The method to obtain the absorption coefficient from HITRAN is introduced in detail. The nonlinear least square algorithm to determine δ13CO2 value is studied. The total system and experimental procedure are shown in the paper. The temperature and pressure effect on δ13CO2 value determination are analyzed from both theory and experiment analysis. For the same CO2 standard gas, the δ13CO2 value is detected by both FTIR and IRMS technology, and the results are also comparatively analyzed and discussed. The difference in mean between both methods is only 0.25%. The experimental results show that the FTIR technique to detect carbon isotope ratio of carbon dioxide is viable.
Feynman's ratchet and pawl heat engine in a one-dimensional lattice
Authors: Cheng Hai-Tao  , He Ji-Zhou  ,   Department of Physics, Nanchang University, Nanchang 330031, China
Published: December 2020

In this paper, we studiy the Feynman's ratchet and pawl heat engine in a one-dimensional lattice. The dynamics of the particle is described by a master equation. The expressions of the current, efficiency and power output of the heat engine are derived analytically. The influences of the height of barrier, external load force and the temperature ratio of the heat reservoirs on the efficiency of heat engine are discussed. When the steady-state current is zero, there is a nonzero heat flux transterred from the hot bath to the cold bath, which is similar to the heat leak of the irreversible Carnot model. The curve of the power output versus the efficiency is a loop-shaped one. The heat engine is irreversible and the efficiency is less than the Carnot efficiency. The heat engine can work in optimal operation by optimizing the performance parameters of the heat engine.
Finite difference time domain analysis on electromagnetic scattering characteristic of plasma thin layer based on surface impedance boundary condition method
Authors: Yang Li-Xia  , Ma Hui  , Shi Wei-Dong  , Shi Li-Juan  , Yu Ping-Ping  ,   Department of Communication Enginerring, Jiangsu University, Zhenjiang 212013, China;,   Research Center of Fluid Machinery Engineering and Technology, Jiangsu University, Zhenjiang 212013, China;,   Department of Physics, Jiangsu University, Zhenjiang 212013, China
Published: December 2020

Using the surface impedance boundary condition (SIBC)-finite difference time domain (FDTD) method, the electromagnetic scattering characteristic of non-magnetized plasma coating on metal material is obtained, under the one-dimensional (1D) oblique incident wave condition. The SIBC method can greatly reduce computational memory by ignoring the mesh division of the background material. Firstly, the expression of frequency domain surface impedance is derived, and substituted into boundary condition equation. Then the equation is transformed to time domain via Fourier inverse transformation method, and the formula is quantized to obtain the update equation by piecewise linear recursive convolution (PLRC) method. The algorithm is used to calculate the reflection coefficients of parallel and vertical polarization waves at oblique incident angels. The comparison of the SIBC-FDTD results with analytic solutions shows the validation and effectiveness of proposed method. Finally, the effect of incident angle on reflection coefficient is analyzed by this method.
Distributed-feedback laser based on low-scattering and high-gain holographic polymer dispersed liquid crystal grating
Authors: Diao Zhi-Hui  , Huang Wen-Bin  , Deng Shu-Peng  , Liu Yong-Gang  , Peng Zeng-Hui  , Yao Li-Shuang  , Xuan Li  ,   State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Science, Changchun 130033, China;,   University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

In this paper, we utilize the acrylate monomer of low functionality to fabricate a holographic polymer dispersed liquid crystal grating with polymer-scaffolding morphology. It is effective to reduce the scattering loss in the grating which acts as a resonator in distributed-feedback laser since there is no droplet of liquid crystal. Moreover, the use of the monomer with high refractive index (RI) ensures the formation of grating with high RI modulation and, correspondingly, high feedback gain. For these two factors mentioned above, an excellent laser property is obtained from the dye-doped laser pumped by Nd:YAG pulse laser at 532 nm. A spectral linewidth of 0.3 nm is observed at pump energy threshold 0.8 μJ/pulse and a conversion efficiency of 1.2% is achieved at operating wavelength 635 nm. The laser performance is improved in some aspects such as threshold energy, linewidth and conversion efficiency to some extent compared with those reports proeviously.
Surface waves formed at the interface between a metal and a photorefractive crystal
Authors: Sun Tong-Tong  , Lu Ke-Qing  , Chen Wei-Jun  , Yao Feng-Xue  , Niu Ping-Juan  , Yu Li-Yuan  ,   Institute of Electronics and Information Engineering, Tianjin Polytechnic University, Tianjin 300387, China
Published: December 2020

The formation conditions and the energy variation of surface waves at the interface between a metal and a photorefractive crystal are investigated by using the particle oscillator model and numerical techniques. Our analysis indicates that the positive and negative values of the propagation constant affect the type of surface waves and the energy distribution: formation surface waves are nonlocal surface waves for negative values of the propagation constant and are oscillating surface waves and localized surface waves for positive values of the propagation constant, and the energy of localized surface waves in photorefractive medium increases monotonically with the propagation constant value increasing. In a given physical system, one can control the different orders and the waveforms of localized surface waves by regulating the variable parameter determining the strength of nonlinear effects.
Breather for weak beam induced by strong beam in strongly nonlocal nonlinear medium
Authors: Lu Da-Quan  , Hu Wei  ,   Laboratory of Nanophotonic Functional Materials and Devices, School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510631, China
Published: December 2020

Breather for weak beam induced by strong beam in a strongly nonlocal nonlinear medium is investigated. Although the nonlinearity induced by the weak beam is weak enough to be negligible, the nonlinearity induced by the strong beam can balance the diffraction of the weak beam, thus the breather for weak beam comes into being. The analytical solution of the breather for weak beam is obtained. Based on the analytical solution, the evolution of the beam width is analysed, and the form as well as the direction of helix for the trajectory of the breather is systematically investigated.
Characteristics of the fiber Bragg grating based all-fiber acousto-optic modulator
Authors: Liu Chao  , Pei Li  , Li Zhuo-Xuan  , Ning Ti-Gang  , Gao Song  , Kang Ze-Xin  , Sun Jiang  ,   Key Laboratory of All Optical Network and Advanced Telecommunication Network of Ministry of Education, Institute of Lightwave Technology, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

The Fourier mode coupling theory is applied to the analysis of the fiber Bragg grating based all-fiber acousto-optic modulator for the first time. Compared with the existing analysis methods, the algorithm of this model is simple and easy, and transmission characteristics of the modulator can be acquired effectively and efficiently. Based on the theory, the performances of the modulator, related to ultrasonic frequency and amplitude of acoustically induced strain, are investigated. Simulation results show that in reflection spectra of the modulator, the wavelength interval between the primary relection peak and the secondary relection peak is proportional to ultrasonic frequency, and the reflectivity of the reflection peak varies periodically with intensity change of the amplitude of acoustically induced strain. In addition, with the same amplitude of acoustically induced strain, more secondary reflections exist in the low-frequency ultrasonic modulated fiber Bragg grating, and the periodic variation of the energy reflected by fiber Bragg graing is more obvious. In the experiment, the fiber Bragg graing is modulated by an ultrasonic wave with a frequency of 885.5 KHz. The experimental results accord well with the simulation results.
Application research of symplectic Runge-Kutta method of solving Lagrange-Maxwell equation
Authors: Liu Shi-Xing  , Song Duan  , Jia Lin  , Liu Chang  , Guo Yong-Xin  ,   College of Physics, Liaoning University, Shenyang 110036, China;,   Physics of Medical Imaging Department, Eastern Liaoning University, Dandong 118001, China
Published: December 2020

In this paper, we show the numerical integration method of solving Lagrange-Maxwell equation by using the symplectic Runge-Kutta (R-K) method, and numerically study the motion of the plate in an RLC circuit spring coupled system and the current changes. Its result is consistent with that obtained by the traditional R-K method, which demonstrates symplectic integration algorithm is reasonable and effective in studying the electro-mechanical systems. And on this basis, the form invariance of Noether sense is studied by using the symplectic Runge-Kutta method.
Microstructures and mechanical properties of (Ti, N)/Al nanocomposite films by magnetron sputtering
Authors: Yang Duo  , Zhong Ning  , Shang Hai-Long  , Sun Shi-Yang  , Li Ge-Yang  ,   State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China;,   Institute of Marine Materials Science and Engineering, Shanghai Maritime University, Shanghai 201306, China
Published: December 2020

A series of aluminum matrix nanocomposite films are synthesized by magnetron sputtering of Al and TiN targets. The composition, microstructure and mechanical property of the composite film are characterized by energy dispersive spectroscopic, X-ray diffraction, transmission electron microscope and nanoindenter. The influences of (Ti, N) content of supersaturated solute Ti,N atoms on the microstructure and mechanical property of the composite films are investigated. The results reveal that the composite film with adding Ti,N atoms together forms a dual-supersaturated solid solution exhibiting both features of substitutional and interstitial solid solution. Higher solute content induced gradual evolutions of nanocrystallization and amorphization of grains in film and solute enrichment occured at the grain boundaries. Correspondingly, the composite film containing 1.8 at.% (Ti, N) can rapidly reach a hardness of 3.9 GPa, and further increasing TiN content to 17.1 at% (Ti, N) the film hardness achieves 8.8 GPa demonstrating the significant strengthening effect of dual-supersaturation of Ti and N on aluminum film.
The DFT analyses of effect of chromium and nickel additions on the mechanical properties of Fe3Al based alloys
Authors: Niu Xue-Lian  , Wang Li-Jiu  , Sun Dan  ,   Institute of Building Materials, Faculty of Infrastructure Engineering, Dalian University of Technology, Dalian 116024, China
Published: December 2020

Site preference behaviors of transition metal (TM) Cr and Ni in Fe3Al alloy and alloying effect are studied by using first-principles. Computational results show that the addition of TM is beneficial to the improvement of the stability of Fe3Al alloy; Cr atoms prefer to stay at FeI sites, while Ni atoms occupy FeII sites. Our investigations reveal that Fe2NiAl has lower bulk modulus B, shear modulus G and B/G than other (Fe3-yXy)Al (X=Cr, Ni; y=0,1,2) alloys, which turns out to be a brittle alloy. The analyses of density of states and electronic charge density indicate that additional TM improves the interaction between TM and neighboring host atoms of Fe3Al but weakens the interaction between Al and Fe.
Optical properties of GaN:Tb nanoparticles synthesized by simple ammonification method
Authors: Pan Xiao-Jun  , An Xiu-Yun  , Zhang Hai-Jun  , Zhang Zhen-Xing  , Xie Er-Qing  ,   School of Physical Science and Technology, Lanzhou University, Lanzhou 730000, China
Published: December 2020

GaN:Tb nanoparticles are synthesized by simple ammonification of a mixture of Ga(NO3)3 and Tb(NO3)3. The XRD result shows that the sample predominantly presents hexagonal phase of GaN and its average grain size is 22.1 nm. TEM images show that the sizes of the particles are almost uniform. Besides conventional GaN Raman shifts, two extra peaks at 251 and 414 cm-1 observed in the Raman spectra can be attributed to the phonons activated by surface disorders or finite-size effects and vibration mode of N-rich octahedral Ga-N6 bonds, respectively. From photoluminescence spectra, four characteristic peaks of Tb3+ions are clearly observed: 5D4 →7F6(493.9 nm), 5D4 →7F5(551.2 nm), 5D4 →7F4(594.4 nm), 5D4 →7F3(630.1 nm).
Investigation of anti-reflection properties of crystalline silicon solar cell surface silicon nanowire arrays
Authors: Liang Lei  , Xu Qin-Fang  , Hu Man-Li  , Sun Hao  , Xiang Guang-Hua  , Zhou Li-Bin  ,   Departmen of Physics, Northwest University, Xi'an 710069, China
Published: December 2020

In order to trap more sunlight onto the crystalline silicon solar cell and improve the photo-electric conversion efficiency, it is very important to study the optical scattering properties of silicon nanowire arrays on silicon wafer. The rigorous coupled wave analysis method is used for optical simulation, and the Taguchi method is used for efficient optimization. The simulation results show that at the above-mentioned wavelengths the reflectance of the optimized structure is less than 2%, and also able to achieve the wide-angle antireflection. At room temperature and ambient pressure, the silicon nanowire arrays each with a period of 50 nm, duty ratio of 0.6 and height of 1000 nm are successfully prepared on mono-crystalline Si wafers using a novel metal-catalyzed chemical etching technique, the reflectance test results are consistent with simulation values. The average reflectance of the optimized structure over the above-mentioned wavelength range is 4%-5%, showing that the antireflection effect is obvious compared with the reflectivity of about 35% of the single crystal silicon. The minus reflection microstructures reduce the sun battery microstructure costs, at the same time, reduce the monocrystalline silicon surface light reflecting loss, improve the photoelectric conversion efficiency.
One-step synthesis of a carbon nano sheet-scarbon nanotubes composite and its field emission properties
Authors: Hu Xiao-Ying  , Wang Shu-Min  , Pei Yan-Hui  , Tian Hong-Wei  , Zhu Pin-Wen  ,   College of Materials Science and Engineering, Jilin University, Changchun 130012, China;,   College of Science, Changchun University, Changchun 130022, China;,   State Key Laboratory of Superhard Materials, Jilin University, Changchun 130012, China
Published: December 2020

One-step synthesis of a carbon nano sheets-carbon nanotubes composite by plasma enhanced chemical vapor deposition and its field emission properties are investigated. We obtain the carbon nano sheets-carbon nanotube composite on the Co thin film with 20 nm Ti interlayer. We gain carbon nano sheets only on the Co thin films without Ti interlayer in the same growth conditions. The carbon nano sheets are distributed on the side wall and the top of carbon nanotubes. The Ti interlayer hinders the diffusion of Co into the silicon substrate and improves the catalytic capability of Co, thus it will help the growth of carbon nanotubes. When the thickness of Co film is 11 nm, the carbon nanotubes are vertically aligned on the flat Co film surface. Most of the carbon nano sheets are distributed on the top of the carbon nanotubes under this condition, which increases the number of emitters and enhances the field emission properties of the composites.
Modified symbolic relative entropy based electroencephalogram time irreversibility analysis
Authors: Zhang Mei  , Wang Jun  ,   Image Processing and Image Communications Key Laboratory, Nanjing University of Posts and Telecomm., Nanjing 210003, China
Published: December 2020

In this letter, we show that the trajectory of electroencephalogram (EEG) possesses the character of time reversal asymmetry, which can provide information about the entropy production of EEG. We develop a kind of new method to estimate symbolic relative entropy and entropy production using forward and backward trajectories. Finally, we use this method to dispose and analyse the EEGs of younger and elder people, and is turned out that this method works and the average energy dissipation can be used as a parameter to detect nonequilibrium.
The grand canonical Monte Carlo simulation of hydrogen physisorption on single-walled carbon nanotubes at the low and normal temperatures
Authors: Shen Chao  , Hu Ya-Ting  , Zhou Shuo  , Ma Xiao-Lan  , Li Hua  ,   Department of Physics, Jinan University, Guangzhou 510632, China
Published: December 2020

In this article, the grand canonical Monte Carlo (GCMC) method included in GULP software system is adopted to study the hydrogen storage properties of armchair-type single-walled carbon nanotubes (SWNT) with at the low and normal temperatures. The adsorption isotherms with five different radii of SWNT at T=77 K and T=280 K are obtained. The manifold configuration diagrams of hydrogen molecule in the carbon nanotubes with the same caliber at different temperatures and pressures are also given. A further study on hydrogen physisorption is carried out under different pressures and different diameters of carbon nanotubes, separately, at temperatures of 77 K and 280 K, and the results are compared with each other. Finally, we put forward some constructive suggestions about how to improve the adsorption capacity of SWNT according to the results of our GCMC simulation. This may be useful for further investigation.
Dynamic modification of the shallow water equation on the slowly changing underlying surface condition
Authors: Da Chao-Jiu  , Feng Ai-Xia  , Gong Zhi-Qiang  , Song Jian  ,   School of Mathematics and Computer Science Institute, Northwest University for Nationalities, Lanzhou 730030, China;,   College of Atmospheric Sciences, Lanzhou University, Lanzhou 730000, China;,   Laboratory for Climate Studies, National Climate Center, China Meteorological Administration, Beijing 100081, China;,   College of Science, Inner Mongolia University of Technology, Hohhot 010062, China
Published: December 2020

In this paper, the shallow water equation is discussed, when the underlying surface is slowly changing. From the continuity equation and the equation of motion controlling the movement of the atmosphere, the slowly changing of the underlying surface is superimposed on the topography function as a small quantity, using the upper and lower boundary conditions of the atmosphere, the modified shallow water equation is obtained. In the modified shallow water equation, the slowly changing local horizontal divergence modifies the equilibrium between the local horizontal divergence and the local change of the thickness of the atmosphere. On the basis of this, the vorticity equation is obtained, which contains the slowly changing underlying surface.
Analysis of partial oscillation phenomenon in a digital-controlled three-phase inverter
Authors: Lei Bo  , Xiao Guo-Chun  , Wu Xuan-L  ,   State Key Laboratory of Electrical Insulation and Power Equipment, School of Electrical Engineering, Xi’an Jiaotong University, Xi’an 710049, China
Published: December 2020

A partial oscillation phenomenon in a digital-controlled three-phase inverter system, which is controlled by proportional controller in synchronous rotating reference frame, is analyzed in this paper. First, the discrete-time model of the system is derived. Then, a dynamics analysis scheme for this type of system is proposed. In addition, the underlying mechanism of the partial oscillation phenomenon occurring in this system is analyzed. The factors, which will cause the partial oscillation, are exactly predicted by analytical expressions. Finally, the theoretical results are verified by both simulations and experiments. These conclusions can provide an insight into the dynamics of the system.
Infrared image segmentation based on clustering combined with sparse coding and spatial constraints
Authors: Song Chang-Xin  , Ma Ke  , Qin Chuan  , Xiao Peng  ,   Department of Computer, Qinghai Normal University, Xining 810008, China
Published: December 2020

A new algorithm for infrared image segmentation is proposed based on clustering combined with sparse coding and spatial constraints. The clustering algorithm is fused on the basis of sparse coding. The traditional image segmentation method based on K-means clustering is extended. The clustering algorithm combined with sparse coding can fuse the local information of image. The inner relationships between pixels are used. However, the problem of over-segmentation and difficulty in pixels classification for segmentation arise. The clustering method is introduced for atoms into dictionary learning. The class number of atoms in dictionary is reduced in order to avoid over-segmentation. The spatial class property information is also introduced by considering the property of the pixel, and the pixels in the neighbor region should have class coherent constraints. An alternate optimization algorithm is proposed to learn the dictionary, sparse coefficients, cluster center and degrees of membership jointly. Then the classes of pixels are estimated by constructing pixel ownership degrees, combining the sparse coefficients and the degrees of membership with the atoms to cluster center. The experimental results show that the important area can be separated well, and the proposed method has good robustness.
MRCI+Q study on spectroscopic parameters and molecular constants of X1Σ+ and A1Π electronic states of the SiSe molecule
Authors: Xing Wei  , Liu Hui  , Shi De-Heng  , Sun Jin-Feng  , Zhu Zun-Lüe  ,   College of Physics and Electronic Engineering, Xinyang NormalUniversity, Xinyang 464000, China;,   College of Physics and Information Engineering, Henan Normal University, Xinxiang 453007, China
Published: December 2020

The potential energy curves (PECs) of X1Σ+ and A1Π electronic states of the SiSe molecule are calculated using the internally contracted multireference configuration interaction approach with the Davidson modification (MRCI+Q) with the correlation-consistent basis sets, aug-cc-pV5Z and aug-cc-pVQZ. In order to improve the quality of the PEC, the PEC is extrapolated to the complete basis set limit by the two-point total-energy extrapolation scheme; and the scalar relativistic correction is included. Scalar relativistic correction calculations are carried out using the third-order Douglas-Kroll Hamiltonian approximation at the level of a cc-pV5Z basis set. The spectroscopic parameters (Te, De, Re, ωe, ωexe, ωeye, Be and αe) of two states are calculated. The spectroscopic results are compared in detail with those reported in the previous literature. Excellent agreement is found between the present spectroscopic results and the experimental ones. Using the PECs obtained by the MRCI+Q/Q5+DK calculations, the Bυ and Dυ are calculated for each vibrational state of each electronic state, and their values of the first 30 vibrational states are reported for X1Σ+ and A1Π states of 28Si80Se molecule when J=0. Comparison with the measurements demonstrates that the present vibrational manifolds are both reliable and accurate. They should be good predictions for the future experimental or theoretical research.
First-principles calculations of P-doped anatase TiO2
Authors: Zheng Shu-Kai  , Wu Guo-Hao  , Liu Lei  ,   Research Center for Computational Materials, College of Electronic and Informational Engineering, Hebei University, Baoding 071002, China
Published: December 2020

The lattice parameters, charge populations, band structures, density of states and absorption spectra of P-doped anatase TiO2 are calculated using the first-principles based on the density functional theory. The results indicate that when the Ti atom is substituted for P atom, the volume of TiO2 decreases. When P atom substitutes for O atom or exists as interstitial atom, the volume of TiO2 increases. The substitutional P at Ti site and interstitial P are oxidized to different degrees, and the substitutional P at O site is reduced a little. The different three sites of P doping result in the increase of anatase TiO2 forbidden gap width and the introduction of local doping energy levels. The band gap increasing of P-doped anatase TiO2 is in the following sequence: interstitial P>substitutional P at Ti site>substitutional P at O site. The absorption spectra indicate that the substitutional P at Ti site cannot enhance the visible light absorption ability of the anatase TiO2, whereas the interstitial P strongly enhances the visible light absorption ability of the anatase TiO2. The interstitial P is probably an important reason for the experimental enhancement of the photocatalytic activity of P-doped anatase TiO2.
A novel bend-resistant large-mode-area photonic crystal fiber
Authors: Lou Shu-Qin  , Lu Wen-Liang  , Wang Xin  ,   School of Electronic and Information Engineer, Beijing JiaotongUniversity, Beijing 100044, China
Published: December 2020

A novel bend-resistant large-mode-area silica photonic crystal fiber (PCF) is proposed and fabricated. With the advantage of flexible design on the PCF configuration, the properties of large-mode-area, single mode propagation and low bend loss can be simultaneously achieved by intentionally designing the position of defect and the size of air holes. Modal properties and bending loss of the actual PCF can be evaluated with previous model for assessing the properties of the actual fiber. Numerical results demonstrate that this fiber has an extremely large mode area of 2812 μm2, low confine loss of 0.00024 dB/m of the fundamental mode and high confine loss of over 1.248 dB/m of higher order mode at a wavelength of 1064 nm when the optical fibre is kept straight. The large difference in propagation loss levels between fundamental mode and higher order modes ensures the efficient single-mode propagation in the fiber core. Furthermore, the effects of bend radius and bend direction angle on bend loss are investigated when the fiber is bent. Even if bend radius is as small as 5 cm, bend loss of this fiber is still below 10-3 dB/m. It is found that the proposed fiber has the negligible bending loss at a bending radius of 30 cm with the bending angle ranging from -60° to 60°. These results illustrate that the fabricated fiber possesses the better bend resistant properties and can overcome the sensitivity to bend direction angle caused by the asymmetric structure. The fabricated fiber will play an important role in developing high power fiber laser, fiber amplifier and high power delivery application.
Research on diffraction and self-acceleration of Airy beam
Authors: Yue Yang-Yang  , Xiao Han  , Wang Zi-Xiao  , Wu Min  ,   Colllege of Engineering and Applied Sciences, Nanjing University, Nanjing 210093, China
Published: December 2020

In 1979, Berry and Balazs [M V Berry and N L Balazs 1979 Am. J. Phys. 47 264] obtained a strict solution of the Schrödinger equation with Airy function used as the initial condition, and described the wave function represented by such solution as the Airy wave-packets. They discovered that infinite Airy wave-packet has unique properties such as non-spreading and free acceleration, proving that it is the only nontrivial non-spreading solution of the time-dependent Schrödinger equation in one dimension. However, the observing of the finite Airy beam seems to be more meaningful since wave-packets in reality is inevitably band limited. A certain form of finite Airy beam was investigated by Siviloglou et al. in 2007 [Siviloglou G A, Broky J, Dogariu A, Christodoulides D N 2007 Phys. Rev. Lett. 99 213901; Siviloglou G A, Christodoulides D N 2007 Opt. Lett. 32 979]. They noted that the Airy wave packet still exhibits its most exotic feature, i.e., its trend toward free acceleration. While in the present paper we discuss the properties of Airy beam in a few steps further and propose several conclusions. On the one hand, a theoretic explanation is given to solve the matter of the centre of mass of infinite Airy beam. On the other hand, deeper research is conducted on the unique properties of finite Airy beam. Another form of finite Airy beam is discussed by reduction to absurdity, and its field distribution is put forward by numerical simulation. We find that the trajectory of the centroid holds its position, which means that the beam cannot accelerate freely as a whole. Ultimately, we have the conclusion that finite Airy beam can neither freely accelerate nor be non-diffractive.
Raman effect on parametric amplification gain spectra of different frequency propagation regimes in polarization maintaining fibers
Authors: Chai Hong-Yu  , Jia Wei-Guo  , Han Feng  , Men-Ke-Nei-Mu-Le  , Yang Jun  , Zhang Jun-Ping  ,   Department of Physics, Inner Mongolia University, Hohhot 010021, China
Published: December 2020

The expression of gain is derived from nonlinear Schrödinger equation with consideration of raman effect when two laser pulses with different wavelengths are emitted into birefringence fiber along two polarization axes. The gain characteristic input laser pulses of different frequencies are revealed by comparing the laser pulses of identical frequency. The result show that the gain spectra will apparently differ when input laser pulses have different frequencies in normal dispersion regime and anomalous dispersion regime. The intensities of outboard gain peak about stokes part and anti-stokes part increase and frequency deviates from central frequency as group velocity mismatch increases. Therefore, the THz pulse can be extracted. The gain spectrum will be apparently different from that with no Raman effect taken into account, when the two polarization modes, are in different dispersion regimes. The symmetry of gain spectrum will be damaged. The intensity of gain peak of stokes is apparently stronger than the peak of anti-stoke.
Higher-order intensity moments of optical beams in atmospheric turbulence
Authors: Li Xiao-Qing  , Ji Xiao-Ling  , Zhu Jian-Hua  ,   College of Physical Science and Technology, Sichuan University, Chengdu 610064, China;,   Department of Physics, Sichuan Normal University, Chengdu 610068, China
Published: December 2020

The higher-order intensity moments of optical beams propagating through atmospheric turbulence are studied in the paper. The method to derive higher-order intensity moments in atmospheric turbulence is proposed, and the simple expressions for intensity moments up to the fourth-order are derived. The results obtained in this paper are general, which can reduce to higher-order intensity moments of an arbitrary optical beam propagating in both free space and turbulence. Taking the Gaussian beam for example, the propagation of the kurtosis parameter in atmospheric turbulence is studied. It is shown that the kurtosis parameter of Gaussian beams is not a propagation invariant in atmospheric turbulence, which depends on propagation distance, waist width, inner and outer scales of turbulence and refraction index structure constant. This result is different from that obtained by using the quadratic approximation of Rytov’s phase structure function or the strong fluctuation condition of turbulence. The reasonable explanations for the differences are given in this paper.
Investigation of the laser action in a dye-doped cholesteric liquid crystal wedge cell
Authors: Dai Qin  , Li Yong  , Wu Ri-Na  , Geng Yue  , Quan Wei  , Li Ye-Qiu  , Peng Zeng-Hui  , Yao Li-Shuang  ,   College of Mathematics and Physics, Shenyang Ligong University, Shenyang 110159, China;,   State Key Laboratory of Applied Optics, Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences, Changchun 130033, China
Published: December 2020

The wedge cell of cholesteric liquid crystal device is designed and fabricated, and doping PM580 (exciton) in the cholesteric liquid crystal, the laser emission action is studied. There appear a series of parallel wedge edges of dislocation lines and different shapes of domain in the wedge cell. The planar state of alignment is confirmed. A second harmonic Nd:YAG 532 nm laser is adopted as a pump light beam, and then one-dimensional tunable laser radiation is obtained and its wavelength interval is approximately 1 nm and tuning range is about 17 nm. In the processs of interaction between the torques of LC and the surface anchoring of direction film, the pitch elongation takes place. The positon of photonic band gap is changed, so the laser radiation wavelength can be tuned in the band edge.
A design for all-optical switch and arbitrary proportion of energy output beam splitter
Authors: Liao Qing-Hua  , Zhang Xuan  , Xia Quan  , Yu Tian-Bao  , Chen Shu-Wen  , Liu Nian-Hua  ,   Department of Physics, Nanchang University, Nanchang 330031, China
Published: December 2020

According to the nonlinear Kerr effect of photonic crystal, we design a simple structure with arbitrary proportion of energy output, which can be controlled by the pump intensity. At the same time, the structure can also realize the dynamic control of optical switch function, and has low insertion loss, crosstalk, two states of the signal light on/off. Therefore the light switch is of high efficiency.
Effects of structure parameters on the dispersion properties of dispersion compensation photonic crystal fiber
Authors: Chen Xiang  , Zhang Xin-Ben  , Zhu Xian  , Cheng Lan  , Peng Jing-Gang  , Dai Neng-Li  , Li Hai-Qing  , Li Jin-Yan  ,   Wuhan National Laboratory of Optoelectronics, Huazhong University of Science and Technology, Wuhan 430074, China
Published: December 2020

Photonic crystal fiber has great potential applications such as dispersion compensation due to its adjustable and flexible dispersion characteristics. In this paper, we design a dispersion compensation photonic crystal fiber, simulate the dispersion characteristics by the finite-difference frequency-domain method, and analyse the effects of the structure parameters air hole spacing Λ and air-filling fraction d/Λ on the dispersion of photonic crystal fiber theoretically. And we also fabricate three photonic crystal fibers with different structural parameters. Through the comparison and analysis of their dispersion curves, we have the following conclusions: the dispersion coefficient increases with air hole spacing Λ and air-filling fraction d/Λ increasing when the air hole spacing of photonic crystal fiber is about 1 μm, but the dispersion is more sensitive to the change of air hole spacing Λ than to air-filling fraction d/Λ, and the effect of air hole spacing on the dispersion coefficient decreases with the increase of air hole spacing. One of the photonic crystal fibers realizes the designed structure: its dispersion coefficient is 241.5 ps·nm-1·km-1, relative dispersion slope is 0.0018 at 1550 nm, it has good ability in dispersion compensation.
Temperature sensitivity of microstructured optical fiber filled with ferrofluid
Authors: Miao Yin-Ping  , Yao Jian-Quan  ,   Tianjin Key Laboratory of Film Electronic and Communicate Devices, School of Electronics Information Engineering, Tianjin University of Technology, Tianjin 300384, China;,   College of Precision Instruments and Opto-Electronics Engineering, Institute of Laser and Otpoelectronics, Tianjin University, Tianjin 300072, China
Published: December 2020

In this paper ferrofluid is infiltrated in the index-guiding microstructured optical fiber (MOF) by the well-known capillary force and air pressure. The influences of the length and concentration of filled fiber on its guidance property are analyzed. Based on the response of fluid refractive index to temperature, the temperature sensitivities of filled MOF with different lengths are investigated without applying any external magnetic field. The results show that the short-wavelength edge of the absorption spectrum near 1460 nm remains unchanged, while the long-wavelength profile is sensitive to the temperature and the transmission power of the filled MOF decreases with the increase of temperature. There is a linear relationship between temperature and transmission power of the filled MOF. For the device with a length of 10 cm, its temperature sensitivity reaches 0.06 dB/℃. Combining the excellent thermo-optic effect of ferrofluid with MOF, the single edge of the device could be tuned by the temperature. It is potential to be used as a thermo-optic modulator, filter, and other adjustable photonics device. Considering a large number of magnetically tunable ferrofluids available and the high degree of freedom in MOF design, ferrofluid-filled MOF shows still a great promise and underexplored possibilities for both basic and applied research, opening new perspectives in optical telecommunication, all-optical switching and fiber-optic sensing applications, such as magnetic field sensors. The present study can offer an effective method for the novel technique and structure of all-in-fiber photonic devices.
Design and analysis of novel multi-core dual-mode large-mode-area optical fiber
Authors: Zheng Si-Wen  , Lin Zhen  , Ren Guo-Bin  , Jian Shui-Sheng  ,   Key Laboratory of All Optical Network and Advanced TelecommunicationNetwork of EMC, Beijing Jiaotong University, Beijing 100044, China;,   Institute of Lightwave Technology, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

A novel double air hole multi-core dual-mode large-mode-area optical fiber is proposed. The characteristics of mode field distribution, effective area of fundamental mode, and bending loss are analyzed. And the effects of all structure parameters on the effective refractive index and effective area are discussed. This structure makes TE01 and TM01 mode cut off, and it is of dual-mode transmission in the fiber. Besides, this structure can increase the effective area. The effective area of fundamental mode is approximately 1044 μm2. It is even able to achieve single-mode operation by adjusting the structure parameters. The fabrication of the structure is simple, and design is flexible. Therefore, it is suitable for the high-speed and large-capacity passive fibers as well as for active fibers. The effective area can reach or even exceed 3512 μm2 by adjusting the structure parameters, in order to satisfy the practical demands of large-capacity high-power fiber transmission in the optical communications.
A new method of soft X-ray transmission band-pass
Authors: Cao Zhu-Rong  , Dong Jian-Jun  , Yang Zheng-Hua  , Zhan Xia-Yu  , Yuan Zheng  , Zhang Hai-Ying  , Jiang Shao-En  , Ding Yong-Kun  ,   Research Center of Laser Fusion, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

Based on microchannel plate (MCP) X-ray optics, a transmission soft X-ray band-pass approach is presented. X-ray transmission band-pass characteristics are given through three structures of MCP channel. Calibration results from a square hole MCP and filter on Beijing Synchrotron Radiation Facility show that MCP transmission spectrum is of a wide range of band-pass options and high efficiency, and can achieve multi-point design of 100 eV bandwidth at lower than 1 keV with different filters.
First-principles study of high-pressure physical properties of α-Ti2Zr
Authors: Zhang Pin-Liang  , Gong Zi-Zheng  , Ji Guang-Fu  , Liu Song  ,   Key Laboratory of Advanced Technologies of Materials of Ministry of Education, School of Material Science and Engineering, Southwest Jiaotong University, Chengdu 610031, China;,   National Key Laboratory of Science and Technology on Reliabilityand Environment Engineering, Beijing Institute of Spacecraft Environment Engineering, Beijing 100094, China;,   Laboratory for Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China
Published: December 2020

The structure, elastic constant, Debey temperature and electron distribution of α-Ti2Zr under high pressure are presented by using first-principles pseudopotential method based on density functional theory in this paper. The calculated structural parameters at zero pressure are in agreement with experimental values. The elastic constants and their pressure dependence are calculated using the static finite strain technique. We obtain the bulk modulus, Young’s modulus and Poisson’s ratio for α-Ti2Zr. The G and B at zero pressure are 101.2 and 35.6 GPa, respectively. The G/B value is relatively small and decreases with pressure increasing, showing that the α-Ti2Zr is rather ductile. The Debye temperature Θ=321.7 K is obtained by the average sound velocity based on elastic constants. We investigate anisotropies of the compressional wave and two shear waves. The acoustic velocities are obtained from elastic constants by solving Christoffel equation. The results indicate the strong anisotropy for α-Ti2Zr. Moreover, the pressure dependence of s→d electron transfer indicates that β-Ti2Zr will occur under high pressure.
Temperature dependence of electrical resistivity for Sr-doped perovskite-type oxide Y1-xSrxCoO3 prepared by sol-gel process
Authors: Liu Yi  , Zhang Qing  , Li Hai-Jin  , Li Yong  , Liu Hou-Tong  ,   School of Mathematics and Physics, Anhui University of Technology, Maanshan 243032, China
Published: December 2020

The temperature dependences of electrical resistivity for Sr-substituted compounds Y1-xSrxCoO3 (x=0, 0.01, 0.05, 0.10, 0.15, 0.20), prepared successfully by sol-gel process, are investigated in a temperature range from 20 to 720 K. The results indicate that with the increase of doping content of Sr the resistivity of Y1-xSrxCoO3 decreases remarkably, which is found to be caused by the increase of carrier concentration. In a temperature range below 330 and 260 K for the sample x=0 and 0.01, the relationship of resistivity versus temperature processes exponential relationship lnρ∝1/T, with conduction activation energy 0.2950 and 0.1461 eV for the sample x=0 and 0.01 respectively. Moreover, experiments show that the relationship lnρ∝1/T exists only in high-temperature regime for the heavily doped samples; at low temperatures Mott’s law lnρ∝T-1/4 is observed, indicating that heavy doping produces strong potential, which leads to the formation of considerable localized state. By fitting the experimental data to Mott’s T-1/4 law, the density of localized states N(EF) at Fermi level is estimated, which is found to increase with doping content increasing.
The progress of flexible organic field-effect transistors
Authors: Dong Jing  , Chai Yu-Hua  , Zhao Yue-Zhi  , Shi Wei-Wei  , Guo Yu-Xiu  , Yi Ming-Dong  , Xie Ling-Hai  , Huang Wei  ,   School of Electrical and Information, Northeast AgriculturalUniversity, Haerbin 150030, China;,   Institute of Advanced Materials, Nanjing University of Posts and Telecommunacations, Nanjing 210046, China
Published: December 2020

Flexible organic field-effect transistors (OFETs) have revealed wide prospect in their applications to the flexible display, flexible sensor, flexible radio frequency tag and flexible integrated circuit due to their advantages such as foldability, light weight of device and low-cost fabrication process. On the basis of the introduction of advancement in the study of flexible OFETs in this paper, a broad overview about device structures of flexible OFETs, substrate materials, gate insulating layer materials, active layer materials and electrode materials used for flexible OFETs is given, the fabricating process of flexible OFETs is explained, and the effect of bending pattern on the performance of flexible OFETs is discussed. Finally, the application areas of flexible OFETs are summarized and prospected.