bluuebunny/crossref_metadata_2025 huggingface dataset:
Performance evaluation of the microPET system
Authors: Gao Fei  , Liu Hua-Feng  , Shi Peng-Cheng  ,   (1)南方医科大学医学图像处理重点实验室，广州 510515; (2)浙江大学现代光学仪器国家重点实验室，杭州 310027
Published: December 2020

The Concorde MicroPET Rodent R4 system designed by Concorde Microsystems Inc. is the dedicated positron emission tomography (ECT) for studies of rodents. The scanner has 32 detector rings and a 120mm animal aperture. The transversal field of view(FOV) is 100mm, and the axial FOV is 78mm. The spatial resolution at the center of FOV is smaller than 1.8mm. This paper designs a series of experiments to evaluate the performance parameters (spatial resolution, sensitivity, scatter ets.) of the scanner. In the center FOV the transversal spatial resolution is 1.9mm, the axial spatial resolution is 1.88mm. The absolute sensitivity of the system is 39.88 cps/kBq for an energy window of 250KeV-750KeV. For the same energy window the 2D-reconstructed scatter fractions is 50.6%, the 3D-reconstructed scatter fractions is 32.3%.
Size and morphology control of highly-ordered nano-silicon pillar fabricated by direct nanosphere lithography
Authors: Li Wei  , Xu Ling  , Sun Ping  , Zhao Wei-Ming  , Huang Xin-Fan  , Xu Jun  , Chen Kun-Ji  ,   南京大学物理系,固体微结构物理国家重点实验室,南京 210093
Published: December 2020

2D ordered, size-controlled nano-pillar was fabricated onto silicon substrate by direct nanosphere lithography with a mask of colloidal spheres. First, an ordered single layer of polystyrene (PS) nanosphere with a diameter of 200 nm was obtained by self-assembly on silicon surface. Then, the size of PS nanosphere on silicon substrate was reduced by reactive ion etching(RIE) with oxygen to form size-controllable PS nanosphere templates. Finally，these samples with nanosphere templates were etched by RIE with carbon fluoride to fabricate 2D ordered silicon pillar. The size of pillar is determined by the PS sphere diameter reducedby RIE and is controlled easily by choosing appropriate etching time. The period of silicon pillar arrays is determined by the initial diameter of PS spheres.
The distribution of solute elements in AZ61 magnesium alloy under electromagnetic field
Authors: Xu Guang-Ming  , Zheng Jia-Wei  , Liu Yong  , Cui Jian-Zhong  ,   东北大学材料电磁过程研究教育部重点实验室,沈阳 110004
Published: December 2020

Through studying the microstructure of AZ61 alloy solidified in different external fields, it is found that when solidified in single magnetostatic field , the grain boundaries were composed of matrix Mg and meshy Mg-Al-Zn compounds. When solidified in the field composed of magnetostatic field and alternating current , the grain boundaries were composed of matrix Mg and Mg-Al-Zn compounds which existed as isolated spots as well as a certain amount in the meshy state. But when solidified in the field composed of magnetostatic field and direct current, the mesh disappeared and together with matrix Mg a little Mg-Al-Zn compound appeared as discontinuous flakes. Compared with single magnetostatic field, solidification in magnetostatic field and currenmakes the solute content in grains to increase and the solute content in grain boundaries to decrease.
Electron transport in solid-state dye-sensitized solar cells based on polyaniline
Authors: Guo Li  , Liang Lin-Yun  , Chen Chong  , Wang Ming-Tai  , Kong Ming-Guang  , Wang Kong-Jia  ,   (1)中国科学院等离子体物理研究所，合肥 230031; (2)中国科学院等离子体物理研究所，合肥 230031;安徽建筑工业学院材料科学与工程系，合肥 230022; (3)中国科学院等离子体物理研究所，合肥 230031;中国人民解放军徐州空军学院，徐州 221000; (4)中国科学院固体物理研究所，合肥 230031
Published: December 2020

Solid-state dye-sensitized solar cells (DSCs) were prepared using polaniline (PANI) as hole- transport material. The charge transport and recombination in the cells were studied by means of intensity modulated photocurrent spectroscopy (IMPS) and intensity modulated photovoltage spectroscopy (IMVS). On the basis of lifetime (τn) and mean transit time (τd) of the electrons in nanoporous TiO2 film and fitting of the IMPS response, the effective diffusion coefficient (Dn) and the diffusion length (Ln) of electrons in the TiO2 film were acquired. The electron lifetime in the PANI-based DSCs was about 10 times lower than their liquid counterparts, indicating a much more serious recombination of photogenerated electrons in the TiO2 film, very likely mainly with holes of oxidized dye molecules. With increase in the thickness of TiO2 film, both τn and τd decreased, whereas Ln and Dn increased; and the better performance of the solid-state cells was available only in a suitable thickness range of TiO2 films.
Spectral shift and spectral transition of ultrashort pulsed Hermite-Gaussian beams in the turbulent atmosphere
Authors: Ji Xiao-Ling  , Tang Ming-Yue  , Zhang Tao  ,   四川师范大学物理学院，成都 610066
Published: December 2020

Based on the extended Huygens-Fresnel principle, the analytical expression for the spectrum of ultrashort pulsed Hermite-Gaussian (H-G) beams propagating through the turbulent atmosphere is derived. The spectral shift and spectral transition are studied, and reasonable physical explanations are given. It is shown that the spectrum depends on the structure constant of the refractive index, order of the Hermite polynomial, pulse duration and position of the observation point. The on-axis spectrum is blue-shifted, the off-axis spectrum becomes red-shifted with increasing transverse coordinate, and the position with null spectral shift is independent of pulse duration. Furthermore, there exists an off-axis spectral transition when the turbulence reaches a certain degree. The behavior of the off-axis spectral transition in turbulence is very different from that in free space, which is analyzed in detail.
Numerical simulation of the ionization effects of low-and high-altitude nuclear explosions
Authors: Zhao Zheng-Yu  , Wang Xiang  ,   武汉大学电子信息学院,武汉 430079
Published: December 2020

Low-altitude and high-altitude nuclear explosions are sources of intensive additional ionization in ionosphere. In this paper, in terms of the ionization equilibrium equation system and the equation of energy deposition of radiation in atmosphere, and considering the influence of atmosphere, the temporal and spacial distribution of ionization effects caused by atmospheric nuclear detonation are investigated. The calculated results show that the maximum of additional free electron density produced by low-altitude nuclear explosion is greater than that by the high-altitude nuclear burst. As to the influence of instant nuclear radiation, there is obvious difference between the low-altitude and the high-altitude explosions. The influence range and the continuance time caused by delayed nuclear radiation is less for the low-altitude nuclear detonation than that for the high-altitude one.
Synchronization of a class of time-varied nonlinear vibration system
Authors: Qin Wei-Yang  , Wang Hong-Jin  , Zhang Jin-Fu  ,   西北工业大学工程力学系，西安 710072
Published: December 2020

For a class of nonautonomous nonlinear vibration system，a corresponding derived system is constructed. A novel control method to realize the synchronization between the derived and the original system is presented. The method is proved by Lyapunov stability theory. The principle for choosing coupling parameters is given. For a Mathieu system excited by parameters and external force，the simulation is carried out. The result shows that the derived system can achieve fast synchronization with the original system under the action of chaos. The simulation for Duffing system excited by quasi-periodic force shows that the derived system can reach synchronization with the original system under the quasi-periodic motion.
Controlling optical spatiotemporal chaos of coupled phase-conjugate map system with nonlinear feedback
Authors: Yue Li-Juan  , Shen Ke  , Xu Ming-Qi  ,   (1)长春理工大学物理系，长春 130022; (2)东北师范大学物理学院，长春 130024
Published: December 2020

The optical phase-conjugate resonator consists of one normal mirror and one phase-conjugate mirror made of an instantaneous response lossless Kerr medium. Using the nonlinear feedback, we control the temporal chaos in the phase-conjugate resonator and spatiotemporal chaos in the coupled phase-conjugate map system. Stable control has been realized. The simulation shows that this controlling technique can be implemented easily in practical systems just by adjusting the feedback strength. The in-advance knowledge of the dynamic system is not required. The results are useful to theoretical analysis of chaos in phase-conjugate resonators.
A modified coupled map car-following model based on application of intelligent transportation system and control of traffic congestion
Authors: Han Xiang-Lin  , Jiang Chang-Yuan  , Ge Hong-Xia  , Dai Shi-Qiang  ,   (1)湖州师范学院理学院，湖州 313000; (2)湖州师范学院理学院，湖州 313000;上海大学上海市应用数学与力学研究所，上海 200072; (3)宁波大学理学院，宁波 315211; (4)上海大学上海市应用数学与力学研究所，上海 200072
Published: December 2020

A modified coupled map car-following model is proposed for a one-way with the application of intelligent transportation system to describe the dynamic characteristics of one-way traffic flow and the control of traffic congestion. Based on the present model and the theory of feedback control，the stability criteria are given for the change of speed of the lead vehicle. The theoretical analysis shows that the information on more leading vehicles of each vehicle could lead to a stabilization effect for the traffic flow，that is，the stability conditions could be considerably weakened. The corresponding numerical simulations confirm the correctness of the theoretical analysis. Through comparing the present results with those in previous works，it is concluded that the proposed control strategy is more effective in suppressing the formation of traffic congestion by applying and controlling the induction information provided by the intelligent transportation system.
Multi-reference configuration interaction study on analytical potential energy function and spectroscopic constants of XOn(X=S,Cl; n=0,±1)
Authors: Qian Qi  , Yang Chuan-Lu  , Gao Feng  , Zhang Xiao-Yan  ,   鲁东大学物理与电子工程学院，烟台 264025
Published: December 2020

The potential energy curves for the ground state of SO and ClO molecules as well as their corresponding molecular ions have been computed using the multi-reference configuration interaction (MRCI) method with aug-cc-PVXZ (X=D,T,Q) basis sets. The MRCI energies are extrapolated to the complete basis sets limit with Feller's method. The equilibrium geometries and disassociation energies also have been determined. The analytical potential energy functions of these states have been fitted using Murrell-Sorbie function and least square fitting method. Based on the analytical potential energy functions, the vibrational levels have been determined by solving Schrdinger equation of nuclear motion, and corresponding spectroscopic constants accurately calculated respectively. The present values for the spectroscopic constants of each state are compared with the other theoretical and the experimental values currently available.
Line intensities of 3000—0200 and 1001—0110 transition bands of 14N216O at high temperature
Authors: Song Xiao-Shu  , Cheng Xin-Lu  , Yang Xiang-Dong  , Linghu Rong-Feng  ,   (1)贵州师范大学理学院，贵阳 550001; (2)贵州师范大学理学院，贵阳 550001;四川大学原子与分子物理研究所,成都 610065; (3)四川大学原子与分子物理研究所,成都 610065
Published: December 2020

The total internal partition sums (TIPS) were calculated for nitrous oxide with the product approximation. For rotational partition sums Qrot, the centrifugal distortion corrections are under consideration. The calculation method for the vibrational partition sums Qvib used is the harmonic oscillator approximation. Using experimental transition moment squared and Herman-Waills factor coefficients and the calculated partition functions, we computed the line intensities of 3000—0200 and 1001—0110 transitions of nitrous oxide at several temperatures. The agreement between the calculated line intensities and experimental results and those extrapolated from HITRAN database is fairly good at temperatures up to 3000 K, which shows that the calculation of partition function and line intensity at high temperature is reliable. Furthermore, the line intensities and spectral simulations at the higher temperatures of 4000 and 5000 K are also presented.
Theoretical study of the potential energy surface and differential scattering cross sections of He-HI complex
Authors: Yu Chun-Ri  , Feng Er-Yin  , Cheng Xin-Lu  , Yang Xiang-Dong  ,   (1)安徽师范大学物理系,芜湖 241000; (2)安庆师范学院物理与电气工程学院,安庆 246011;安徽师范大学物理系,芜湖 241000;四川大学原子与分子物理研究所,成都 610065; (3)四川大学原子与分子物理研究所,成都 610065
Published: December 2020

The intermolecular potential energy surface for He-HI complex has been first calculated by employing supermolecule method and the single and double excitation coupled-cluster with a noniterative perturbation treatment of triple excitation CCSD(T) approach using a large basis set containing the bond function set 3s3p2d1f. The potential energy surface has two potential wells. The global minimum with a well depth of 4.473 meV has been found for the linear He-I-H configuration with R，the distance of the He atom and the center of mass of the HI molecule, of 0.363nm. In addition to the global minimum, there is a second minimum corresponding to the linear He-H-I configuration with a well depth of 2.996 meV and R of 0.442nm. Then the analytic expression of the interaction potential for the He-HI complex of the ground state has been obtained by utilizing the Barker potential-type analytic function to fit the calculated intermolecular energy data. On the basis of the above results, the differential scattering cross sections (DCS) at the energy of 100meV for collision between He atom and HI molecule have been calculated using the quantum close-coupling method. Finally, the validity of the potential energy surface of the He-HI system has been verified by comparing it with the CCSD(T) potential energy surface of the He-HX(X=F, Cl, Br) systems and by comparing their DCS at the same collision energy.
A ionization theory based on united and separated atom model
Authors: Li Ming-Sheng  , Cai Xiao-Hong  ,   (1)中国科学院近代物理研究所,兰州 730000; (2)中国科学院近代物理研究所,兰州 730000;中国科学院研究生院，北京 100049
Published: December 2020

The direct Coulomb ionization process can be generally well described by the ECPSSR theory, which bases on the perturbed-stationary-state(PSS) and accounts for the energy-loss, Coulomb-deflection, and relativistic effects. But the ECPSSR calculation has significant deviations for heavy projectile at low impinging energies. In this paper we propose a new modified ECPSSR theory, i.e. MECUSAR, in which PSS is replaced by an united and separated atom model, and molecule-orbit effect is considered. The MECUSAR calculations give better agreement with the experimental data at lower impinging energies, and agree with the ECPSSR calculations at high energies. By using OBKN (Oppenheimer-Brinkman-Kramers formulas of Nikolaev) theory to describe the contribution of the electron capture, we further modified the proposed MECUSAR theory, and calculated the target ionization cross sections for different charge states of the projectile.
Electron-vibration approximation method for hydrogen isotope compounds Al2O3X(X=H, D, T)
Authors: Chen Xiao-Hong  , Wang Ling  , Zhu Zheng-He  , Luo Shun-Zhong  ,   (1)四川大学原子与分子物理研究所，成都 610065; (2)西华大学理化学院，成都 610039; (3)西华大学理化学院，成都 610039;四川大学原子与分子物理研究所，成都 610065; (4)中国工程物理研究院核物理与化学研究所，绵阳 621900
Published: December 2020

The geometric configuration, vibration frequency and thermodynamic properties of Al2O3X(X=H, D, T) molecular clusters with lower energy were optimized using B3LYP/6-311++G(d,p) method. The changes of entropy, enthalpy and Gibbs free energy of the reactions between Al2O3 and hydrogen (deuterium or tritium) gas have been calculated under the solid electron-vibration approximation method using formulae in thermodynamics under temperatures of 298—1098 K. Then the equilibrium pressures of hydrogen (deuterium or tritium) gas in these reactions are obtained. The results show that, the gaseous Al2O3X may have two possible ground states Al2O3X(X=H,D,T)(2A′)Cs and Al2O3X (2B2) C2v. Tritium can be displaced by deuterium; deuterium can be displaced by hydrogen in the reactions between Al2O3 and X2 with the production of solid Al2O3X which relates to ground Al2O3X with C2v symmetry. This displacement sequence is the same as that in the reactions between titanium and X2. These displacement effects are very weak. But hydrogen can be displaced by deuterium; deuterium can be displaced by tritium in the reactions between Al2O3 and X2 with the production of solid Al2O3X which relates to ground gaseous Al2O3X with Cs symmetry. This displacement sequence is opposite to that in the reactions between titanium and X2. In all, these displacement effects are very weak, and they grow still weaker as the temperature increases.
Research of the effect of attenuator on high-frequency characteristics of helical slow-wave structure
Authors: Gong Yu-Bin  , Deng Ming-Jin  , Duan Zhao-Yun  , Lü Ming-Yi  , Wei Yan-Yu  , Wang Wen-Xiang  ,   电子科技大学物理电子学院，成都 610054
Published: December 2020

The sheath-helix model is used to analyze the helical slow-wave structure in which the helix turns are considered effectively shorted by the resistive coating on dielectric helix-support rods. Meanwhile, a gap is introduced to simulate the helix tape thickness, and the helix support rods are emulated by an effective dielectric tube and the difference of the radical propagation constant in different regions is taken into consideration. The dispersion equation and interaction impedance of arbitrary field modes are derived. On this basis, the effects of attenuation coating on the attenuation constant, phase constant and interaction impedance are discussed. The results presented here are useful for designing attenuator and improving the high-frequency characteristics of helical slow-wave structure as well as preventing the reflection oscillation and backward-wave oscillation of traveling-wave tubes.
Maximum a posteriori filtering for synthetic aperture radar images based on heavy-tailed Rayleigh distribution of speckle
Authors: Sun Zeng-Guo  , Han Chong-Zhao  ,   西安交通大学电子与信息工程学院，西安 710049
Published: December 2020

In order to reflect the statistics of high peak and heavy tail, speckle in synthetic aperture radar images is modeled as heavy-tailed Rayleigh distribution. First, based on Gamma prior distribution and heavy-tailed Rayleigh distribution of speckle, the maximum a posteriori filtering equation is proposed and its analytical form is provided in given characteristic parameter. Second, parameters of heavy-tailed Rayleigh distribution are estimated from the observed image using Mellin transformation. Last, maximum a posteriori de-speckling experiments and their quantitative measures are given. In order to eliminate the influence of window size and noise intensity on de-speckling results, dynamic relations of the de-speckling capability to noise variance and window size are suggested respectively. Results demonstrate that the heavy-tailed Rayleigh distribution accords with the real statistics of speckle, so the maximum a posteriori filter in heavy-tailed Rayleigh distribution of speckle has higher capability of noise reduction compared to the one in Rayleigh distribution of speckle and the Kuan filter.
Tunable all-optical wavelength conversion based on fiber ring lasers
Authors: Guo Yong-Juan  , Sun Jun-Qiang  , Wang Jian  , Li Jing  ,   华中科技大学光电子科学与工程学院，武汉 430074
Published: December 2020

Introducing a periodically poled LiNbO3 (PPLN) waveguide in fiber ring lasers, tunable wavelength conversion has been realized by the nonlinear interactions between the launched signals and the pump and control waves generated through the fiber ring lasers. The principle of all-optical wavelength conversion based on the cascaded sum-and difference_frequency generation in the quasi-phase-matched PPLN waveguide is introduced in the article. The evolution of the power of the pump, the signal, the control and the converted waves along the PPLN waveguide has been numerically simulated respcctively. The dependence of the conversion efficiency on the wavelength of the converted wave was calculated. Finally, the tunability of the wavelength conversion was experimentally verified.
The transmission properties of pairing structure of negative permittivity and negative permeability materials
Authors: Dong Li-Juan  , Jiang Hai-Tao  , Yang Cheng-Quan  , Shi Yun-Long  ,   (1)山西大同大学固体物理研究所,大同 037009; (2)山西大同大学固体物理研究所,大同 037009;同济大学波耳固体物理研究所,上海 200092; (3)同济大学波耳固体物理研究所,上海 200092;中国科学院上海微系统与信息技术研究所信息功能材料国家重点实验室,上海 200050
Published: December 2020

The transmission properties of pairing structure consisting of negative-permittivity and negative-permeability materials were studied using Maxwell equations. Most of energy of electromagnetic field is localized on the interface between the materials due to boundary conditions when electromagnetic wave is incident on the structure. Investigations show that the interface mode may evolve into resonance tunneling mode under specific incident angle, which leads to resonance transmission. The transmission properties can effect band-pass filtering.
Continuously adjusting the reflectivity of fiber loop mirror using a polarization controller
Authors: Feng Su-Juan  , Shang Liang  , Mao Qing-He  ,   中国科学院安徽光学精密机械研究所,合肥 230031
Published: December 2020

Reflection characteristics of a novel fiber loop mirror (FLM), which is formed by inserting a fiber polarization controller (PC) into the loop, are investigated. Based on the equivalent optical-path analysis, a theoretical model for the FLM is presented. The reflection characteristics of the FLM are then simulated in detail with the model. Our simulation results show that, by varying the PC working conditions, i.e. the fast axis orientation or the intensity of the birefringence induced by the PC, the refrectivity of the FLM may be continuously tuned between 0 and 1. The spectral characteristic of reflectivity of the FLM is wide and flattened, limited only by the operating bandwidth of the optical fiber coupler used. Moreover, the reflection characteristics of the FLM are further investigated experimentally. The experimental results also show that by varying the working conditions of the PC, the reflectivity of the FLM may actually be continuously adjusted between its maximum and minimum values,which were measured to be 93% and 2%, respectively. The experimentally determined dependence of the fast axis orientation and intensity of the birefringence induced by the PC on the inclination angle of the three rigid discs with respect to the level of the PC verified the results of theoretical simulations.
Effect of translation group symmetry on phononic band gaps studied by supercell calculation
Authors: Mu Zhong-Fei  , Wu Fu-Gen  , Zhang Xin  , Zhong Hui-Lin  ,   广东工业大学实验教学部,物理与光电工程学院,广州 510090
Published: December 2020

The band structure of two kinds of phononic crystals (the square lattice of mercury (water) rods in a water (mercury) host) has been calculated using the plane-wave expansion method based on super cell. The translation group symmetry of phononic crystal is changed by changing the size of adjacent rods. We found that by changing the lengths of sides of adjacent rods one can effectively adjust the phononic band gaps. The present work shows that the translation group symmetry of phononic crystal has an important influence on the formation of its band gaps, and the method based on super cell is an effective method of studying the influence of translation group symmetry of phononic crystal on the formation of phononic band gaps.
Impact of confined liquid thin film upon bioadhesive force between insect pads and smooth solid surface
Authors: Zhang Xiao-Hao  , Zhang Xiang-Jun  , Liu Yong-He  , Schaefer J. A.  , Wen Shi-Zhu  ,   (1)Department of Technical Physics,Centre for Micro and Nanotechnologies，Technical University of Ilmenau,Ilmenau 98693,Germany; (2)清华大学摩擦学国家重点实验室,北京 100084; (3)清华大学摩擦学国家重点实验室,北京 100084;Department of Technical Physics,Centre for Micro and Nanotechnologies，Technical University of Ilmenau,Ilmenau 98693,Germany
Published: December 2020

The outstanding climbing skills on smooth solid surface of some insects like beetle, bee and cockroach or some small reptiles like gecko have been under investigation for a long time. When some kinds of insects crawl on a smooth glass surface, the micro_pads leave traces of self-secreted organic liquid, which suggests that, the thin layer of confined liquid may contribute to the bioadhesive force between the micro_pad and the smooth surface. To investigate the properties of the confined liquid thin film, a series of experiments were carried out on a home-made microtribometer with a trace amount of ionic liquid (［emim］ ［Tf2N］) or PAO(poly_α_olefin) oil confined between a nano-scale smooth steel sphere and a glass plate. For a critical confined volume of pitoliters to nanoliters, and a critical clearance of tens to hundreds of nanometers, confinement-induced spontaneous spreading and abrupt shrinking were observed, accompanied by the presence of a stable interfacial adhesive force of remarkable magnitude. This spreading/shrinking-induced adhesive force was proved to be fundamentally different from the common meniscus capillary force and was considered to stem from confinement-induced solidification, according to our further investigations. The confinement-induced adhesive force of organic liquid may shed significant light on the physical principle “employed” by insects to crawl quickly on smooth vertical surfaces. By subtly adjusting the volume of confined liquid or the clearance between the pads and the surface, insects can control (i.e., switch on or off) the interfacial force at will. The interfacial bonding force of confined liquid thin film discovered in this paper may provide a basis for the principle of biomimetic attachment systems.
Traveling-wave convection with Eckhaus instability modulation in a binary fluid mixture
Authors: Li Guo-Dong  , Huang Yong-Nian  ,   (1)北京大学湍流与复杂系统研究国家重点实验室,北京 100871; (2)西安理工大学水利水电学院,西安 710048
Published: December 2020

For Rayleigh-Bénard convection in a binary fluid mixture, we obtained a traveling-wave state with periodic modulation of spatiotemporal dislocation defects in a rectangular cell by the numerical simulation of full hydrodynamic equations. The investigations show that the creation of pairs of convective rolls triggered by Eckhaus instability leading to this modulation. Because the generating frequencies of rolls at the left wall smaller than the annihilating frequencies of rolls at the right wall, the system soon move out of the stable region, in this way the system oscillates back and forth between the stable and unstable Echkaus wave number band. The properties of heat transfer and fluid mixing also studied too.
Current spin polarization in ferromagnetic/organic semiconductor/ferromagnetic system
Authors: Ren Jun-Feng  , Zhang Yu-Bin  , Xie Shi-Jie  ,   (1)山东大学物理与微电子学院，济南 250100; (2)山东师范大学物理与电子科学学院，济南 250014;山东大学物理与微电子学院，济南 250100
Published: December 2020

Based on the spin diffusion theory and the Ohm's law, we theoretically studied the spin polarized injection and transport through the ferromagnetic/organic semiconductor/ferromagnetic system and obtained the current spin polarization, which takes into account the special characteristics of organic semiconductors. Self-trapped states, such as spin polarons as well as spinless bipolarons are assumed to be the main carriers in organic semiconductors. From the calculation, it is found that polarons are the effective spin carriers in spin dependent injection and transport in organic semiconductors. The effect of the spin related interfacial resistances, conductivity match and organic semiconductor length on the current spin polarization are also discussed respectively.
First principles computational study on the stability of Li ion-vacancy two-dimensional ordered structures in intercalation compounds LixTiS2
Authors: Song Qing-Gong  , Jiang En-Yong  , Pei Hai-Lin  , Kang Jian-Hai  , Guo Ying  ,   (1)河北工业大学理学院，天津 300130; (2)天津大学理学院现代材料物理研究所，天津市低维功能材料物理与制备技术重点实验室，天津 300072; (3)天津大学理学院现代材料物理研究所，天津市低维功能材料物理与制备技术重点实验室，天津 300072;中国民航大学理学院，天津 300300; (4)中国民航大学理学院，天津 300300
Published: December 2020

Geometry optimization and total energy computation were carried out for TiS2, LiTiS2 and intercalation compound LixTiS2(x=1/4, 1/3, 1/2, 2/3, 3/4)ordered systems using first principles method based on local density approximation to density-functional theory. The computation results for these systems have been compared with other experimental and theoretical results available in the literature. The normalized increments of lattice parameters Δa0 and Δc0 increase monotonicly with the increasing concentration of Li ion. The curves show good agreement with lattice parameters obtained from experiment. The formation energies of ordered systems LixTiS2(x=1/4, 1/3, 1/2, 2/3, 3/4) are all negative, indicating their stability at low temperature. The formation energy of Li1/2TiS2 system with 3a0×a0 ordered structure is the lowest, implying the most stable structure. The results have shows that the local density approximation to density-functional theory can reasonably be applied to TiS2, LiTiS2 and intercalation compound LixTiS2(x=1/4, 1/3, 1/2, 2/3, 3/4)ordered systems.
Frequency matching method for stochastic resonance control
Authors: Lin Min  , Mao Qian-Min  , Zheng Yong-Jun  , Li Dong-Sheng  ,   中国计量学院计量技术工程学院，杭州 310018
Published: December 2020

A frequency matching method for stochastic resonance control is presented on the assumption that stochastic synchronization of stochastic resonance will be generated when the nonlinear bistable system is stimulated by noise and weak periodic signal. Theoretical analysis and numerical simulation show that stochastic resonance can be controlled. Not only the frequency range of stochastic resonance can be broadened, but also the intensity of stochastic resonance can be strengthened by controlling the frequency of the input signal and statistical characteristics of noise, resulting in more noise energy being converted into signal energy.
Form invariance and Hojman conserved quantity of Maggi equation
Authors: Hu Chu-Le  , Xie Jia-Fang  ,   (1)北京理工大学理学院力学系,北京 100081; (2)呼伦贝尔学院物理系,海拉尔 021008
Published: December 2020

This paper studies the form invariance of Maggi equation. Its definition and criterion are presented. A Hojman conserved quantity can be deduced using the form invariance. An example is given to illustrate the application of the result.
Modeling the excluded volume effect between the chains in linear polymers
Authors: Zhang Jin-Lu  , Jiang Jian-Guo  , Jiang Xin-Ge  , Huang Yi-Neng  ,   (1)南京大学物理系固体微结构实验室,南京 210093; (2)伊犁师范学院物理与电子信息学院凝聚态物理与材料设计研究所,伊宁 835000; (3)伊犁师范学院物理与电子信息学院凝聚态物理与材料设计研究所,伊宁 835000;南京大学物理系固体微结构实验室,南京 210093
Published: December 2020

A model of dodging (random) walk is proposed for the excluded volume effect between the chains in linear polymers, and computer simulations were performed for four model systems. The calculated results indicate that: (1) the relationship between the end-to-end distance of the coils 〈R2〉 and the walk steps N is still linear, same as that of the random coil; (2) but the coil size is suppressed compared with that of the random coils; and (3) the suppression of the coil size produced by dodging in the case of headon encounter is stronger than that in the case of walking abreast.
Chaos in fractional-order Liu system and a fractional-order unified system and the synchronization between them
Authors: Zhang Cheng-Fen  , Gao Jin-Feng  , Xu Lei  ,   郑州大学电气工程学院，郑州 450001
Published: December 2020

This paper studies the chaotic behaviors of the fractional-order Liu system and the fractional-order unified system which were presented several years ago. It is found that chaos exists in the both systems with order less than three and the lowest order to have chaos is 0.3. The calculation results of the maximum Lyapunov exponents when the system is chaotic illustrate the existence of chaos. Chaos synchronization between fractional-order Liu system, fractional-order Lorenz system and fractional-order Lü sytem is realized by employing active control technique. Theoretieal analysis and numerical simulations demonstrate the effectiveness of the proposed method.
Research on flow pattern classification method of two phase flow based on chaotic attractor morphological characteristic
Authors: Xiao Nan  , Jin Ning-De  ,   天津大学电气与自动化工程学院，天津 300072
Published: December 2020

Using the high sensitivity differential sensor,we collected 80 groups of fluctuating signals in vertical upward gas/liquid two phase flow. We established the general description method of chaotic attractor morphological characteristic using referenced sections, and then put forward a new flow pattern classification method of gas/liquid two phase flow by combining the chaotic attractor morphological feature parameters of different dimensions. The study shows that the proposed method can get a good clustering of gas/liquid two phase flow patterns, including the complex transitional flow pattern, and it implies that the method of chaotic attractor morphological characterization is an effective approach to study nonlinear time series in practice.
Network-based train-following model and study of train’s delay propagation
Authors: Xun Jing  , Ning Bin  , Li Ke-Ping  ,   北京交通大学轨道交通控制与安全国家重点实验室,北京 100044
Published: December 2020

Based on the cellular automaton concept, this paper presents a train-following model for the moving block system with different types of trains running. We apply the model to the rail network and simulate the running of trains. We also simulate the traffic phenomenon of delay propagation in moving block system. We investigate how the main factors including train deliver time interval and initial delay affect the delay propagation of trains. The simulation results are compared with the theoretical results to verity the reliabity and feasibility of the model.
Room-temperature optical properties of Al-doped ZnO nanowires array
Authors: Tang Bin  , Deng Hong  , Shui Zheng-Wei  , Wei Min  , Chen Jin-Ju  , Hao Xin  ,   (1)电子科技大学电子薄膜与集成器件国家重点实验室，成都 610054; (2)西南石油大学理学院，成都 610500; (3)西南石油大学理学院，成都 610500;电子科技大学电子薄膜与集成器件国家重点实验室，成都 610054
Published: December 2020

Al-doped ZnO nanowire arrays were synthesized with Au catalysis on Si(100) substrate using the chemical vapor deposition technique. Only (002) diffraction peaks of ZnO can be found in the XRD patterns of the samples, which shows that the as-grown nanowires are highly crystalline in nature and grow along the ［001］ direction. The SEM images show that the ZnO nanowires are perpendicular to the substrate surface. Room-temperature photoluminescence (PL) measurement shows 3 near band-edge emission peaks at 373, 375 and 389nm. Analysis shows that the band gap of Al-doped ZnO nanowaires is 3.343eV and the exciton binding energy is 0.156eV. Room-temperature PL spectrum of pure ZnO nanowaires shows 3 near band-edge emission peaks at 377, 379 and 389nm. The band gap of pure ZnO nanowaires is 3.301eV and the exciton binding energy is 0.113eV, which shows that the band gap increases due to Al doping.
Study on characteristics of a CO2-laser-induced ultra-long-period fiber grating
Authors: Zhu Tao  , Rao Yun-Jiang  , Mo Qiu-Ju  , Wang Jiu-Ling  ,   (1)成都电子科技大学通信与信息工程学院，成都 610054;重庆大学光电工程学院，重庆 400044; (2)重庆大学光电工程学院，重庆 400044; (3)重庆大学光电工程学院，重庆 400044;成都电子科技大学通信与信息工程学院，成都 610054
Published: December 2020

A novel ultra-long-period fiber grating with periods up to several millimeters induced by using CO2 laser pulses is reported and discussed based on the mode coupling theory. The refractive index change occurs mainly within the cladding area of the fiber and has an unsymmetrical distribution on the cross-section of the ULPFG. The characteristics of temperature, strain, torsion and the effect of the refractive index of environment were investigated in theory and by experiment. The experimental results showed that different resonant peaks of the ULPFG have different sensitivities in the characteristics above mentioned, which offers possible applications in optical communications and sensing.
Numerical simulation of plasma nonlinear phenomena excited by radio-frequency wave using FDTD method
Authors: Zhao Guo-Wei  , Wang Zhi-Jiang  , Xu Yue-Min  , Liang Zhi-Wei  , Xu Jie  ,   (1)中国科学院空间科学与应用研究中心,北京 100080; (2)中国科学院空间科学与应用研究中心,北京 100080;中国科学院研究生院，北京 100080
Published: December 2020

Radio-frequency excitation enables the plasma to contain two, three or more harmonic waves, and the modulating signal produced by signal source and excitation source under the plasma nonlinear influence should not be ignored. A new wave-plasma interaction model is set up considering the electron thermal motion, recombination and diffusion effect. It verifies the modulations of signal in different frequencies and explains the production of the second and high order harmonic waves in plasma excitation. The variation of the EM wave pedigree is analyzed taking into account the parameters such as input power, ionization field threshold and electron average energy. The result is of use in tuning the matching circuit or selecting the coupling element in plasma discharge, and it is helpful in electric magnetic interface design, plasma antenna transmission, etc.
First principle calculation of structural, elastic and electronic properties of XHfO3(X=Ba, Sr)
Authors: Yu Xiao  , Luo Xiao-Guang  , Chen Gui-Feng  , Shen Jun  , Li Yang-Xian  ,   (1)河北工业大学材料学院，天津 300130; (2)燕山大学材料科学与工程学院，秦皇岛 066004
Published: December 2020

Perovskite-type BaHfO3 and SrHfO3 are studied using the first principle density functional method. The lattice parameters, elastic constants, bulk and shear moduli, density of states, band structures and charge densities of BaHfO3 and SrHfO3 are calculated after structural relaxation. The calculation results show that both BaHfO3 and SrHfO3 are indirect semiconductors with relatively higher bulk moduli. In the unit cell, the ionic bond is formed between Sr (Ba) atom and HfO3, while the covalent bond is formed between Hf atom and O atom.
First principle study of the native defects in hexagonal aluminum nitride
Authors: Ye Hong-Gang  , Chen Guang-De  , Zhu You-Zhang  , Zhang Jun-Wu  ,   西安交通大学应用物理系，西安 710049
Published: December 2020

The change of atom configuration in hexagonal AlN, caused by native point defects (N and Al vacancies, N and Al antisites, N and Al interstitials), are calculated firstly by plan-wave pseudopotential method with the generalized gradient approximation in the frame of density functional theory, and the most stable structure are obtained. Then the formation energy of each kind of native point defect is calculated, by which the possibilities of the six kinds of native defects to be formed during crystal growth are analyzed. Finally, the defect energy levels responding to every kind of native point defect and their electron occupancy are analyzed from the aspect of density of states. The results show that all the native defects form very deep energy levels in the band gap except N vacancy, and foreign impurities are needed to realize n- or p-type AlN. The values of defect energy levels obtained will be helpful in ascertaining the luminescence mechanism of some AlN non-band-edge emissions.
Temperature dependence of the aggregation mechanism of silver atoms deposited on liquid substrates
Authors: Zhang Sheng-Lin  , Xie Jian-Ping  , Fang Yi-Jun  , Jin Jin-Sheng  , Ye Gao-Xiang  ,   (1)浙江大学物理系,杭州 310027; (2)浙江大学物理系,杭州 310027;绍兴文理学院物理系,绍兴 312000
Published: December 2020

Temperature dependence of the aggregation mechanism of silver atoms deposited on liquid substrates is reported. The experiment shows that the aggregation mechanism of the silver atoms conforms to the two-stage growth model approximately when the substrate temperature changes. The fringe effect of the substrates was visible in the experiment and the coverage ratio of the silver atom clusters in the central region of the sample was smaller than that on the edge of the sample. As the nominal film thickness increased, the coverage ratio went up rapidly first, then its growth speed slowed down and finally the coverage ratio approached a saturation value. The film thickness corresponding to the saturation coverage ratio decreased obviously with the increase of the substrate temperature. For a fixed nominal film thickness, as the oil temperature increased, the coverage ratio decreased. The evolvement behavior of the average length of the silver aggregate branches is similar to that of the coverage ratio in the central region of the sample. The diffusion mechanism of the silver atomic clusters towards the sample edge is also presented.
Structure of MnxGe1－x dilute magnetic semiconductor films
Authors: Sun Yu  , Sun Zhi-Hu  , Zhu San-Yuan  , Shi Tong-Fei  , Ye Jian  , Pan Zhi-Yun  , Liu Wen-Han  , Wei Shi-Qiang  ,   (1)中国科学技术大学国家同步辐射实验室，合肥 230029; (2)中国科学技术大学国家同步辐射实验室，合肥 230029;中国科学技术大学物理系，合肥 230026; (3)中国科学技术大学物理系，合肥 230026
Published: December 2020

The structure of MnxGe1-x dilute magnetic semiconductor thin films prepared by magnetron co-sputtering has been studied by X-ray diffraction (XRD) and X-ray absorption fine structure (XAFS) techniques. The XRD results show that in the MnxGe1-x thin film with low Mn doping concentration (x=0.070), only diffraction peaks attributed to crystalline Ge can be observed. In samples with high Mn doping concentrations (x=0.250, 0.360), the secondary phase Ge3Mn5 appears, and its content enhances with Mn doping concentration. The XAFS results indicate that for the Mn0.07Ge0.93 thin film, Mn atoms are mainly incorporated into the Ge lattice and located at the substitutional sites of Ge atoms with the ratio of 75%, while for the Mn0.25Ge0.75 and Mn0.36Ge0.64 samples, most of the Mn atoms are aggregated to form Ge3Mn5.
Influence of Nb doping on the dielectric properties of CaCu3Ti4O12 ceramics
Authors: Liu Peng  , He Ying  , Li Jun  , Zhu Gang-Qiang  , Bian Xiao-Bing  ,   陕西师范大学物理学与信息技术学院，西安 710062
Published: December 2020

The CaCu3Ti4-xNbxO12(x=0，0.01，0.04，0.08，0.2) ceramics have been prepared by solid-state reaction. The XRD of the sintered ceramics indicated that complete solutions are formed for all compositions x. Dielectric properties have been investigated in the frequency range from 40Hz to 110MHz. Compared with the un-doped CCTO sample，a Debye-type dielectric relaxation has been observed for the Nb-doping CCTO samples in the frequency range from 40Hz to 10kHz at room temperature，apart from the one already known in the frequency range higher than 10kHz. Moreover，the dielectric constant reaches 106 below the characteristic frequency of the lower frequency dielectric relaxation peak which shifts to higher-frequency with increasing Nb content. The experimental results are well explained in terms of the barrier layer capacitance model and an equivalent circuit containing three RC elements by showing three semicircles in the impedance spectroscopic plane.
Study of acoustical properties of supercritical carbon dioxide using liquid acoustical theory
Authors: Lu Yi-Gang  , Peng Jian-Xin  ,   华南理工大学物理科学与技术学院,广州  510640
Published: December 2020

Molar sound velocity, molar adiabatic compressibility and Van der Waals constant of gaseons, liquid and supercritical carbon dioxide at different temperature and pressure are calculated using liquid acoustical models and data of sound velocity, density, molar volume and adiabatic compressibility of carbon dioxide provided by National Institute of Standards and Technology, USA. The results show that the liquid acoustical models can be used in study acoustical property of supercritical carbon dioxide in wide ranges of temperature and pressure. The surface tension, conglutination and diffusivity at different temperatures and pressures are calculated. And the mutative rules of these physical quantities are analyzed. The data can provide reference for supercritical liquid technique.
Effect of rotation on photonic band gap of two-dimensional square lattice photonic crystal with hollow rod
Authors: Zhao Ming-Ming  , Lü Yan-Wu  , Yu Jia-Xin  , Pang Xu-Qian  ,   北京交通大学物理系,北京  100044
Published: December 2020

The plane-wave expansion method is used to calculate TE and TM mode band gaps for two-dimensional square lattice photonic crystal with hollow anisotropic tellurium (Te) rods under three different rotation operations. The effect of rotation on TE and TM mode band gaps and absolute band gap is investigated. The calculated results show that the high order band gaps of TM mode have a close relationship with structure rotation symmetry, and the rotation symmetry and the distribution of Te in x-y plane together influence TE mode band gaps.
First-principles study of electronic structure and transport properties of zigzag graphene nanoribbons
Authors: Ouyang Fang-Ping  , Xu Hui  , Wei Chen  ,   中南大学物理科学与技术学院，长沙  410083
Published: December 2020

By performing first-principles electronic structure and transport calculations, we have demonstrated the electronic structure and transport properties of single layer zigzag graphene nanoribbons with armchair edges and the effect of edge-vacancy defects. It is shown that perfect zigzag graphene nanoribbons are semiconductor with certain energy gaps which will become smaller due to the edge-vacancy defects combining with semiconductor-metal transition. This result may contribute to the electronic structure sewing of the graphene nanoribbons in the energy-band engineering.
Electronic structure in GaAs/AlxGa1-xAs spherical quantum dots
Authors: Wang Chuan-Dao  ,   中国科学院半导体研究所超晶格国家重点实验室,北京  100083
Published: December 2020

In this paper, how the dots’ radius, Al concentration and external electric field affect the single electron energy states in GaAs/AlxGa1-xAs spherical quantum dots are discussed in detail. Furthermore, the modification of the energy states is calculated when the difference in effective electron mass in GaAs and AlxGa1-xAs are considered. In addition, both the analytical method and the plane wave method are used in calculation and the results are compared, showing that they are in good agreement with each other. The results and methods can provide useful information for the future research and potential applications of quantum dots.
A new method to measure the electrical conductivity of metals in electric exploding
Authors: Jiang Ji-Hao  , Wang Gui-Ji  , Yang Yu  ,   中国工程物理研究院流体物理研究所,绵阳  621900
Published: December 2020

The electrical conductivity is an important transport coefficient for electric exploding. A new method to measure the electrical conductivity is designed using the experiment of electric gun. The electrical conductivity of copper is calculated using the data of electric gun. The electrical conductivity change exponentially with of the density.
Strain effect on microwave surface resistance of YBa2Cu3O7-δ/LaAlO3 and Tl2Ba2CaCu2O8/LaAlO3 high temperature superconducting thin films
Authors: Shi Li-Bin  , Zheng Yan  , Ren Jun-Yuan  , Li Ming-Biao  , Zhang Guo-Hua  ,   (1)北京科技大学应用科学学院物理系，北京  100083; (2)渤海大学物理系，锦州  121000
Published: December 2020

YBa2Cu3O7-δ (YBCO) thin films were prepared by thermal coevaporation on (LaAlO3) LAO substrates,and Tl2Ba2CaCu2O8 (TBCCO) thin films were synthesized by magnetron sputtering method on LAO substrates. We obtained the strain from the results of XRD of the films,which had the values of ΔCY=48483×10-3 and ΔCT=85272×10-5. We found that the strain in YBCO was larger than that in TBCCO. In addition, the curve of surface resistance of the films as a funttion of temperature was obtained by coplanar resonator technique, which showed the resistance of YBCO was larger than that of TBCCO at the same reduced temperature. In the paper, we also analyzed the strain effect on the surface resistance of the films.