bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation, microstructure of B film and its applications in MgB2 superconducting Josephson junction
Authors: Wang Song  , Wang Xing-Yun  , Zhou Zhang-Yu  , Yang Fa-Shun  , Yang Jian  , Fu Xing-Hua  ,   Department of Electronics, College of Big Data and Information Engineering, Guizhou University, Guiyang 550025, China;,   College of Science and Technical, Guizhou University, Guiyang 550025, China
Published: December 2020

Magnesium diboride is a binary compound with a simple AlB2 type crystal structure and a high-Tc (nearly 40 K) superconductor. The rather high Tc value and the specific properties make it a potential material for electronic applications. The key structure for the application is a Josephson junction. The growth of tri-layer structure consisting of MgB2 film and tunneling barrier layer is a key technology for a Josephson junction. Boron is a kind of good insulating medium. Preparation of MgB2/B/MgB2 tri-layer structures by chemical vapor deposition (CVD) method is investigated. The experimental results indicate that the depositing temperature will influence the microstructure of boron film significantly and different crystal structures of boron films are obtained at different temperatures.The boron film is an amorphous film while the deposition temperature is lower than 500 ℃, and the amorphous B film can be transformed into MgB2 superconducting film by annealing in Mg vapor. For precursor B films deposited at 470 ℃ and 500 ℃, the critical temperatures of the relevant MgB2 films are 39.8 K and 38.5 K, respectively. As the deposition temperature is higher than 550 ℃, the boron film becomes crystallized, and increasing deposition temperature will increase the crystallinity of the B film as can be seen from the samples deposited at 550 ℃, 600 ℃, 650 ℃ and 680 ℃. The boron film turns out to be of -phase crystalline texture, which is verified by X-ray diffraction and scanning electron microscope. What is more, the crystalline boron film is a kind of inert film, and it does not react with Mg in Mg vapor, thus it cannot be transformed into superconducting film in the subsequent annealing steps. By utilizing the property of the crystallized boron film, a square-shaped Josephson junction with a size 100 m100 m of MgB2/B/MgB2 structure is prepared. The thickness of boron dielectric layer is about 10 nm, and the DC Josephson effect is observed by the I-V measurement of the junction. Compared with other tri-layer structure based on MgB2 material, such as the MgB2/MgO/MgB2, the structure in which B film serves as a barrier layer eliminates the oxygen and can be fabricated in-situ easily by CVD method, and reliable Josephson junctions can be expected by such a technology.
Remote state preparation via photonic Faraday rotation in low-Q cavities
Authors: Yang Zhi-Gang  , Wu Ting-Ting  , Liu Jin-Ming  ,   State Key Laboratory of Precision Spectroscopy, East China Normal University, Shanghai 200062, China
Published: December 2020

Based on the input-output relation in low-Q cavities, we propose a feasible scheme to prepare remotely a single-atom state via photonic Faraday rotation, and then the scheme is generalized to the case of remote preparation of a two-atom entangled state. Our results show that when the coefficients of the initial atomic state to be prepared are real, both remote preparation of the single-atom state and that of the two-atom entangled state can be achieved deterministically by selecting appropriate parameters of the systems for the interactions among the atom, polarized single-photon pulse, and cavity field. Compared with the existing schemes for remote preparation of atomic states, in our scheme photons are used as flying qubits to transmit quantum information, which is suitable indeed to achieve a long-distance atomic state preparation in principle. Due to the fact that the information of atomic state is encoded in two degenerate ground-state levels of a -type three-level atom confined in a unilateral dissipative cavity, and that the atoms are only virtually excited, our schemes are insensitive to both cavity decay and atomic spontaneous emission. Besides, the two schemes we proposed do not need two- or multi-particle orthogonal measurements, only product-state measurements are involved, as well as they work in low-Q regime and do not require a strong coupling condition between the atoms and the optical cavities, which greatly reduce the experimental difficulty.
A novel arrangement scheme of laser quads for spherical hohlraum in laser indirect-driven facility
Authors: Hou Peng-Cheng  , Zhong Zhe-Qiang  , Wen Ping  , Zhang Bin  ,   College of Electronics and Information Engineering, Sichuan University, Chengdu 610064, China
Published: December 2020

In traditional laser quads arrangement schemes for spherical hohlraum in indirect-driven laser facilities, the laser quads to bring about the laser entrance hole (LEH) to close when they are incident at a large angle (55), while the complicated cross and overlap of laser quads inside the spherical hohlraum may be generated when they are incident at a small angle (35). To overcome these problems, a novel laser quads arrangement scheme for spherical hohlraum is proposed. The laser quads injected into the single LEH are divided into two cones (the incident angle of the inner cone is 35, and that of the outer cone is 55). Furthermore, the contrast and the fractional power above the intensity have been proposed to evaluate the irradiation uniformity of single laser quad, while the dispersion degree and the duty ratio are proposed to evaluate the distribution uniformity of all laser quads on the spherical hohlraum wall. Based on the beam smoothing scheme implemented by the combination of one-dimensional smoothing by spectral dispersion, the continuous phase plate and polarization control plate, the propagation model of laser quads in the spherical hohlraum has been built up, and further used to analyze the irradiation uniformity of single laser quad and all the laser quads on the spherical hohlraum wall. On this basis, the irradiation characteristics on the LEHs and the spherical hohlraum wall, and the propagation characteristic of laser quads in the novel and traditional laser quads arrangement schemes have been analyzed and compared. Results indicate that, compared with the traditional arrangement scheme of laser quads, the novel laser quads arrangement scheme has following advantages: The irradiation uniformity on the spherical hohlraum wall of single laser quad and all laser quads remains unchanged. Not only the LEH closure problem can be alleviated, but also the complicated cross and overlap of laser quads inside the spherical hohlraum in the traditional scheme could be avoided. The novel scheme may provide useful reference for the design of spherical hohlraum structure in laser indirect-driven facilities due to its obvious advantages over the traditional scheme.
Third-order nonlinear optical properties of an azobenzene derivate
Authors: Li Meng-Meng  , Zhu Bao-Hua  , Ran Xia  , Liu Bo  , Guo Li-Jun  ,   Institute of Photo-biophysics, School of Physics and Electronics, Henan University, Kaifeng 475004, China
Published: December 2020

In recent years, azobenzene derivates have received much attention for their potential application in optical data storage, biophotonics, holographic memories and waveguide switches optical sensors, and sensitive optical components from laser damage in both civilian and military applications. Experimental and theoretical studies demonstrate clearly the effect of the sonor-pi-acceptor (D- -A) conjugation on the steady-state and time-resolved PL spectra of azobenzene derivate films in multifarious situations, but comparatively little is concerned about the two-photon absorption and refraction involved in a single benzene ring. Furthermore, the excitation laser source on the azobenzene derivates in some investigations is continuum laser or nanosecond pulsed laser, where it is hard to avoid thermal effect on nonlinear optical (NLO) process produced by these lasers. To explore the origin of the azobenzene derivates' D- -A conjugation-dependent NLO process is a challenging task and has great signicance in describing the molecular structures of these azobenzene nanostructures as well as improving the performance of azobenzene derivates' devices. The D- -A conjugation of azobenzene functional material can be modified by mixing the azobenzene derivates with metal nanoparticles, so it is convenient to study how the D- -A conjugation affects the NLO properties by using the azobenzene derivate-metal composites. In this letter, the D- -A conjugation-dependent NLO absorption and refraction of the two kinds of azobenzene derivates 4-((4'-hydroxybenzene) azo) benzyl acid(BN) and N-(3, 4, 5-octanoxyphnyl)-N'-4-[(4-hydroxyphenyl) azophenyl]1, 3, 4-oxadiazole (AOB-t8) are investigated by Z-scan technology using 32 ps laser pulse width at 532 nm. The azobenzene derivates' surface is modified using the D- -A conjugation control and overcoating Au nanoparticles on the azobenzene derivates; and the Au/AOB-t8 composites, BN and AOB-t8 are characterized by Z-scans and absorption/fluorescence spectrum, and also calculated based on plasma resonance. The third-order NLO susceptibility of AOB-t8 is enhanced as compared with BN due to the growing conjugate chain and the increasingly extended bond. However, the third-order NLO susceptibility of AOB-t8 is decreased in the composite(Au/AOB-t8) for the cooperation of the local field effect induced by the gold nanoparticles and the extended bond of organic molecules. This work may be helpful to the understanding of the physical mechanism of the surface states and the surface-related optical nonlinearity of semiconductor QDs.
Study on elastic-wall fluid cavity resonant frequency of Helmholtz underwater acoustic transducer
Authors: Sang Yong-Jie  , Lan Yu  , Ding Yue-Wen  ,   Acoustic Science and Technology Laboratory, Harbin Engineering University, Harbin 150001, China;,   College of Underwater Acoustic Engineering, Harbin Engineering University, Harbin 150001, China
Published: December 2020

Helmholtz resonators are commonly used as underwater acoustic transducers to transmit low-frequency, great power acoustic waves at fluid cavity resonant frequency. Therefore, it is an important problem in the study of how to calculate accurately the fluid cavity resonant frequency of Helmholtz resonator, especially when the Helmholtz resonator is used in underwater acoustic environment where Helmholtz transducers cannot be designed using the classical air acoustic Helmholtz resonator theory. The elasticity of the cavity wall has to be considered because it has a strong influence on the fluid cavity resonant frequency at low frequency band. In this paper, the method of calculating accurately fluid cavity resonant frequency is researched for low-frequency Helmholtz underwater transducers. A Helmholtz resonator is a slender cylindrical shell, the boundary condition of its two ends is free: one side is a radiating port, and the other side is considered as a rigid baffle. Firstly, the fluid cavity resonant frequency of the rigid wall Helmholtz resonator is given, then the radial mechanical impedance of the slender cylindrical shell is derived based on the wave equations. Elasticity of the cavity wall is introduced into the acoustic impedance of fluid cavity in the form of additional impedance. Based on the low-frequency lumped parameter model of the slender cylindrical shell, additional acoustic impedance expression of elastic cavity wall is derived, complete equivalent circuit diagram of elastic Helmholtz underwater transducers is developed, taking into account the elasticity of the cavity wall. Based on the equivalent circuit, the accurate fluid cavity resonant frequency formula has been derived; the formula shows that both the structure size and material characteristics of the cavity wall have influence on the fluid cavity resonant frequency. The thinner the cavity wall, the lower the fluild cavity resonant frequency; and the smaller the Young's modulus of the material, the lower the fluild cavity resonant frequency. To verify the accuracy of the present theory, several slender cylindrical shell models with different wall thickness, materials, and wall length are investigated by both elastic theory method and finite element method (using ANSYS software). These results reveal that the elastic theory results are in excellent agreement with the finite element simulation results. That means, compared to traditional rigid wall theory results, the results from elastic theory in this paper is much closer to the real situation. This conclusion can provide a theoretical support for the accurate design of low-frequency elastic Helmholtz underwater acoustic transducers.
Study on the structure and properties of fullerene C20 tetramer
Authors: Zhang Zhong-Shuo  , Zhang Xiu-Rong  , Gu Jiang  , Ma Pan-Tao  ,   School of Mathematics and Physics, Jiangsu University of Science and Technology, Zhenjiang 212003, China
Published: December 2020

The possible geometrical and electronic structures of fullerene C20 tetramer are optimized by using the density functional theory (b3lyp) at the 6-31G level. For the ground state structures of C20 tetramer, the stability properties, natural bond orbits (NBO), the spectrum, the polarizability and the aromatic characteristics are analyzed. The calculated results show: C20 tetramer may be synthesized by [2+2] addition reaction of C20 carbon cages, which have good thermal stability. Carbon atoms in C20 tetramer are in sp2 hybridization and these atoms happen to have charge transfer. There are a lot of vibration peaks in IR and Raman spectra of C20 tetramer. The bonding interactions between atoms of C20 polymer increase with increasing number of the carbon cages. The C20 tetramer has aromaticity.
The change of microstructure in deuteron-implanted aluminum under electron irradiation
Authors: Li Jie  , Gao Jin  , Wan Fa-Rong  ,   Department of Material Physics and Chemistry, School of Materials Science and Engineering, University of Science and Technology Beijing, Beijing 100083, China
Published: December 2020

As known for a long time, bubbles in liquid would emit light under ultrasonic waves. This experiment, called sonoluminescence, has attracted many people to research on it, but its mechanism is not yet clear. It is reasonable to think that similar phenomenon involving bubbles may happen in solid materials, but its opacity prevents researchers to detect such a kind of phenomenon. This paper investigates the change of gas bubbles by transmission electron microscope (TEM), being able to overcome the difficulty of opacity of materials. Thin film samples of pure aluminum are prepared for TEM experiment by jet chemical polishing. The samples are implanted first by deuterium or hydrogen at room temperature using ion accelerator, followed by electron irradiation under 200 kV TEM. Gas bubbles will form in aluminum after ion implantation, and then grow into larger ones or be collapsed under electron irradiation. Electron diffraction rings of polycrystals appear together with the change of gas bubbles. This kind of diffraction rings of polycrystals could be observed both in deuterium-implanted and hydrogen-implanted aluminum, but would never be found in the case of electron irradiation on the aluminum without implantation of hydrogen or deuterium. The polycrystals of aluminum are not due to the heating effect of electron beam, even electron beam could make a hole in the film sample finally. For the sample of aluminum containing no hydrogen or deuterium, only dislocation loops can be observed during electron irradiation. It may be that a kind of heat emission occurs when the gas bubbles are irradiated by electron beams, but the heat emission would not be due to deuterium fusion reaction because the electron beam-induced polycrystals occur not only in deuterium case, but also in hydrogen case, indicating that the implanted deuterium is not the necessary condition for heat emission. In addition, the energy dispersive spectrometer in TEM is used to detect the possible unique X-ray signals, but none of any special peak below 40 keV in the X-ray spectrum can be found. The plasmatization of gas in the bubbles under electron beam irradiation is used to try to explain the mechanism of such heat emission.
The coupled electromagnetic field effects on quantum magnetic oscillations of graphene
Authors: Lu Ya-Xin  , Ma Ning  ,   College of Physics and Optoelectronics, Taiyuan University of Technology, Taiyuan 030024
Published: December 2020

We have investigated the quantum magnetic oscillations of graphene subjected to the spin-orbit interaction(SOI) in the presence of crossed uniform electric and magnetic fields and scattered from impurities at finite temperatures. Landau levels are shown to be modified in an unexpected fashion by the spin-orbit interaction, the electrostatic potential and magnetic confinement; this is strikingly different from the non-relativistic 2D electron gas. Furthermore, we derive the analytical expressions of the thermodynamic quantities subject to the SOI, such as density of states, thermodynamic potential, magnetization, and magnetic susceptibility etc. At finite temperatures, the magnetization and magnetic susceptibility can both be predicted to oscillate periodically as a function of reciprocal field 1/B and shown to be modulated through the SOI and the dimensionless parameter ( = E/ F B). As approaches unity, the values of magnetization and magnetic susceptibility finally move to infinity, indicating a transformation of closed orbits into open trajectories, thereby, leading to the vanishing of magnetic oscillations. And, the magnetic susceptibility depends largely on the external fields, suggesting that graphene should be a non-linear magnetic medium. Besides, the associative effect of impurity scattering and temperature may make the standard 2D electron gas be deemed as the consequence of the relativistic type spectrum of low energy electrons and holes in graphene. Also, we comment on a possibility of using magnetic oscillations for detecting a gap that may open in the spectrum of quasiparticle excitations due to the SOI.
A potential game based topology control algorithm for wireless sensor networks
Authors: Li Xiao-Long  , Feng Dong-Lei  , Peng Peng-Cheng  ,   School of Computer Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, China;,   School of Computer Science and Engineering, Guangxi Key laboratory of Trusted Software, Guilin 541004, China
Published: December 2020

In real-world applications, wireless sensor networks often consist of a large number of sensor nodes with constraint battery resources. How to reduce the power consumption of sensor nodes and maximize the network life, becomes the most important goal of topology control schemes in wireless sensor networks. During the operation of networks, sensor nodes may spend different levels of energy, and result in the uneven distribution of residual energy of sensor nodes. In order to extend the network life, it is essential to adjust the network burden of sensor nodes dynamically, so as to achieve energy balance among nodes under the consideration of different energy levels at nodes. In this paper, we introduce the game theory and the concept of game potential. By synthetically considering the factors of the residual energy and transmission power of nodes, a potential game based mathematical model of topology control is constructed. We prove the existence of Nash equilibrium. Through designing a payoff function, which takes into account both network connectivity and energy balance of nodes, the connectivity of sensor networks can be maintained while the power of sensor nodes is reduced. By increasing the average value of residual energy of neighbors, it enables to select nodes with more energy that reserves in neighborhood as neighbors, to improve the energy balance among nodes. Based on that, a distributed energy-balanced topology control algorithm (DEBA) is proposed. Theoretical analysis proves that the algorithm can maintain network connectivity. Compared with other existing game theory based algorithms DIA and MLPT, the topologies formed by the proposed algorithm have fewer bottleneck nodes which feature heavy traffic load and low residual energy, and smaller variance of node residual energy, thus achieving a longer life.
Global dynamics and stability of p53-Mdm2 oscillator mediated by Mdm2 production rate
Authors: Bi Yuan-Hong  , Yang Zhuo-Qin  , He Xiao-Yan  ,   School of Mathematics and Systems Science and LMIB, Beihang University, Beijing 100191, China;,   School of Statistics and Mathematics, Inner Mongolia University of Finance and Economics, Hohhot 010070, China
Published: December 2020

Studying global dynamics and stability of biological network is of importance in order to understand its function and behavior. In this paper, we consider the p53-Mdm2 oscillator module with PDCD5 as a core part of p53 signaling pathway after the DNA damage, and explore the dynamics and stability of the tumor suppressor p53. The dynamics of p53 may decide the cell fate after the DNA damage, while the oscillation of p53 may induce cell cycle arrest and so promote the repair of DNA, and the high levels of p53 can trigger apoptosis. However, p53 activity may be inhibited by its negative regulator Mdm2 in some cancer cells, as Mdm2 is of overexpression due to the increase in Mdm2 production rate. So we first investigate the effect of Mdm2 production rate on the kinetics of p53 through bifurcation analysis. after the DNA damage. With the increase in Mdm2 production rate, p53 can display a steady state, a stable-limit cycle and the coexistence of a stable-limit cycle and a stable steady state. Furthermore, the potential landscapes for oscillation show that the lower concentration of p53 means a stronger stability, whereas those for bistability of the higher steady state and the oscillatory state illustrate that stability of the higher steady state increases with the increasing Mdm2 production rate. In addition, noise strength can greatly affect the stability of p53 oscillations, so we explore the effect of noise strength on potential landscapes, barrier heights and periods. A smaller noise strength leads to a higher barrier height associated with more stable-limit cycle, and the harmonic oscillation with more uniform period and smaller variance is helpful to have more stable maintainance. Our results may be useful for understanding regulation of p53 signaling pathway after DNA damage.
A chaotic analyzing method based on the dependence of neighbor sub-sequences in the data series
Authors: Qiu Chen-Lin  , Cheng Li  ,   School of Aeronautics and Astronautics Engineering, Air Force Engineering University, Xi'an 710038, China;,   School of Jet Propulsion, Beijing University of Aeronautics and Astronautics, Beijing 100191, China
Published: December 2020

Ever since the special characteristics hidden in the chaos was discovered, the chaotic behavior has been extensively studied as a ubiquitous and complex nonlinear dynamic phenomenon, which is gradually extending to various disciplines of natural and social science, and the significant values in the theoretical and the practical application have attracted much attention from scholars of different fields in the recent decades. Conventional methods of analyzing chaotic dynamic systems, including the Lyapunov exponent, correlation dimension, Poincar map, unavoidably encounter some common problems, such as reconstruction of the phase space, determination of the linear area, etc. Besides, the current approaches each also possess a poor capability of balancing the direct observation and the quantitative calculation. Based on the fact that the neighbor data relate to each other to some degree, taking those shortages into consideration, aiming at depicting the chaotic features efficiently, a new method of analyzing the complicated chaotic motion is proposed. During the processing of that novel approach, the Euclidean distance is continuously computed to represent the dependence of the adjacent unit, after that, the original complicated array is converted into a simpler series composed of the distance of neighbor sub-sequences with more distinct characteristics. The mean value and the standard deviation of the newborn series are exacted to assist in describing the chaotic changing law. The method is adopted for studying the typical chaotic models, like Logistic model, Chebychev model, Duffing oscillator, Lorenz system, etc., which proves the good performances in explaining the chaotic variation rules in different systems. Based on the model verification, it could be seen that the method could detect the chaotic motion both qualitatively and quantitatively, and the ability for that method to resist the noise is improved up to some degree, what is more, the information about the real model is not required, thereby simplifying the analysis of the complicated chaotic behavior whose authentic model is unavailable. In addition, the method is applied to decomposing the vibration signal to monitor the working condition of the rotating rotor, and the results show that the conditional variation could be detected obviously. The analyses above show that the proposed method, on the basis of the dependence between nearby data, could perform well in observing the chaotic feature in an efficient way which simplifies the operation and clarifies the chaotic variation, moreover, the application potential of this method is worthy of great attention.
Theoretical study of the spectra and radiative transition properties of 6Li32S
Authors: Liu Hua-Bing  , Yuan Li  , Li Qiu-Mei  , Chen Xiao-Hong  , Du Quan  , Jin Rong  , Chen Xue-Lian  , Wang Lin  ,   College of Science, Xihua University, Chengdu 610039, China;,   Research Center for Advanced Computation, Xihua University, Chengdu 610039, China
Published: December 2020

Low-lying electronic states (X2, A2+, a4, B2, b4, C2, F2-, E2+ and D2) of the 6Li32S molecule are computed at the aug-cc-pV5Z/MRCI level. The potential energy curves are presented for these states; the corresponding spectroscopic constants are reported. Electronic transition moment, Einstein coefficients, Frank-Condon factors and radiative lifetimes for the A2+-X2, B2 -X2, C2 -X2 systems are calculated. The balanced distance between two nuclei, harmonic frequencies and inertia moment of ground state X2 are predicted in this paper, and they are in accordance with their corresponding experimental data. The balance distances between the two nuclei in the electronic states of b4, C2, D2 are all longer than 4 , so they are very unstable. The D2 electronic state will dissociate to Li+ ion and S- ion: they are far from each other. The electronic transition dipole moment, Einstein coefficient, Franck-Condon factor and radiative lifetime in transition from lowest excited A2+ state to ground state X2 are predicted in this paper. The electronic transition dipole moments from three low lying electronic state A2+, B2 and C2 to the ground state X2 are calculated at the aug-cc-pV5 Z/MRCI level. The results show that the electronic transition dipole moment of A2+X2 has a small positive value while the nucleus distance is short, and rapidly decreases down to a small negative value with the nucleus distance increasing to around balance distance. Then it is stable about zero value while the nucleus distance continually increases. The electronic transition dipole moment of B2 X2 has a small negative value (which is larger than that of A2+ X2) at a short nucleus distance, and rapid increases up to a small positive value with the nucleus distance increasing to about balance distance. Then it slows down to zero while the nucleus distance increases to about 4. Finally it turns stable about zero value while the nuclei distance continually increases. The electronic transition dipole moment of C2 X2 is more sophisticated, but it has a large value than other two transitions. So the low-lying electronic state A2+ is stabler than B2, and B2 is stabler than C2 . The results also show that the ground state X2 and the lowest excited state A2+ have similar IR frequencies, their difference is within 8 cm-1, so they cannot be distinguished by IR spectrum. The A2+ has a balanced distance about 0.076 shorter than ground X2, which implies that A2+ has stronger chemical bond than ground X2 .
Wavenumber calibration and phase measurement in swept source optical coherence tomography
Authors: Shangguan Zi-Wei  , Shen Yi  , Li Peng  , Ding Zhi-Hua  ,   State Key Laboratory of Modern Optical Instrumentation, College of Optical Science and Engineering, Institute of Laser Biomedicaine, Hangzhou 310027, China
Published: December 2020

Based on the phase information in time domain of a Mach-Zehnder interferometer (MZI), a method of calibrating the wavenumber of the source is proposed. Cross-correlation of wrapped phase in time-domain of the MZI is adopted to determine drifts among axial-lines. Owing to non-strictly periodic characteristics of wrapped phase in time-domain of the MZI, the determinable range of shift is unlimited. Synchronization of signals in time domain is then performed to correct their corresponding shifts. The obtained results demonstrate that it is feasible to realize phase measurement with high precision even under unstable swept source for the optical coherence tomography system.
Study on transmission characteristics of electromagnetic waves in inhomogeneously magnetized plasma sheath
Authors: Bo Yong  , Zhao Qing  , Luo Xian-Gang  , Liu Ying  , Chen Yu-Xu  , Liu Jian-Wei  ,   School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054, China;,   State Key Laboratory of Optical Technologies for Microfabrication, Institute of Optics and Electronics, Chinese Academy of Sciences, Chengdu 610209, China
Published: December 2020

We use simulation software to simulate the plasma sheath flow field of RAM-II at four different altitudes, and get the distribution information of electron density, temperature, and Mach number of plasma sheath at four typical flight altitudes. On this basis, the paper analyzes the cause of the distribution at each altitude. Secondly, Z transform FDTD formula is used to solve the electromagnetic problem in the dispersed medium. According to RAM-II aircraft plasma sheath data, we calculate the power transmission coefficient and power reflectance coefficient of L, S-band electromagnetic waves by Z transform FDTD method at each altitude. Because of the strength of magnetic field used in actual aircraft cannot be uniform, in this calculation the plasma sheath and the magnetic induction are both non-uniform. The transmission characteristics are also different between left-hand circularly polarized waves and right-hand circularly polarized wave in the magnetized plasma. Finally, the paper gives some theoretical design advise about communication antenna for supersonic speed aircraft.
Research on viscoelastic behavior and rheological constitutive parameters of metallic glasses based on fractional-differential rheological model
Authors: Xu Fu  , Li Ke-Feng  , Deng Xu-Hui  , Zhang Ping  , Long Zhi-Lin  ,   College of Civil Engineering and Mechanics, Xiangtan University, Xiangtan 411105, China
Published: December 2020

Metallic glasses offer novel physical, chemical and mechanical properties and have promising potential applications. Recently, exploring the structure and deformation mechanism of metallic glasses according to the rheological mechanical behavior in the nominal elastic region has been the object of intensive research. Physically the mechanical analogues of fractional elements can be represented by self-similarity spring-dashpot fractal networks. In light of the fractal distribution features of the structural heterogeneities, a fractional differential rheological model is introduced to explore the viscoelastic a behavior of metallic glasses in this paper. To investigate the viscoelastic deformation mechanism, carefully designed nanoindentation tests at ambient temperature are proposed in this study. Three kinds of metallic glasses with different Poisson's ratio and glass transition temperature, which have the chemical compositions of Pd40Cu30Ni10P20, Zr48Cu34Pd2Al8Ag8, and (Fe0.432Co0.288B0.192Si0.048Nb0.04) 96Cr4 are selected as the model materials. Experimental and theoretical results clearly indicate that in the nominal elastic region, these metallic glasses exhibit linear viscoelasticity, implying a loading rate-dependent character. Based on the fractional calculus and Riemann-Liouville definition, experimental results are analyzed by the fractional-differential and integer order rheology models respectively. According to the stability of the fitting parameters, here we show that the fractional-differential Kelvin model, which consists of a spring and a fractional dashpot element, can fit the experimental viscoelastic deformation data of the investigated metallic glasses better than that with integer order rheological model. The extracted elastic modulis E1 of the spring in the fractional-differential Kelvin model are comparable to those of samples measured by traditional methods. Such a similarity can be well explained by the mechanical analogue of fractal model proposed for describing the distribution features of the structural heterogeneities in metallic glasses. The rheological parameters obtained here including viscosity index A and fractional order are capable of reflecting the rheological features and the flowing tendency of the above-mentioned metallic glasses. It is found that there exists a clear relationship between the rheological parameters and the reduced glass transition temperature as well as Poisson's ratio, which is helpful for understanding the correlation between plasticity and Poisson's ratio from the micro-structural point of view. The current work provides a rheological model-structure-property relation that may be applicable to a wide range of glassy materials.
Thermal effect of translucent gold nanofilm based on transient reflection/transmission technique
Authors: Wu Wen-Zhi  , Gao Lai-Xu  , Kong De-Gui  , Gao Yang  , Ran Ling-Ling  , Chai Zhi-Jun  ,   School of Electronic Engineering, Heilongjiang University, Harbin 150080, China
Published: December 2020

In this work, the relaxation dynamics of optically excited electrons and lattice in translucent gold nanofilms is measured with femtosecond transient reflection and transmission technique. In order to investigate the mechanisms of heat transfer in metal nanofilm theoretically, the two-temperature model and the Crude-model approximation are used to estimate the profile of decays and the temperature of electrons and lattice. Ultrafast relaxation dynamics of gold nanofilm 60 nm in thickness is different obviously in transient reflection and transmission measurements. Electron-lattice coupling effect in the transmission method is stronger and more sensitive than that in the reflection method under the same experimental conditions. Gradient change of temperature along the direction of film thickness and interface thermal resistance due to the boundary scattering should be responsible for the difference between them. Experimental data suggest that both transient reflection and transient transmission of translucent films should be considered together in the investigation on the mechanism of heat transfer. With increasing energy of pump laser pulse, the rise time is about 1.0 ps, and the electron-lattice relaxation time becomes longer.
Vortex pattern in three-dimensional mesoscopic superconducting rings
Authors: Shi Liang-Ma  , Zhou Ming-Jian  , Zhang Qing-Qing  , Zhang Hong-Bin  ,   School of Mechanical and Electric Engineering, Chaohu College, Hefei 238000, China
Published: December 2020

Vortex structures in a mesoscopic a superconducting ring, which is in the magnetic field generated by a circular electric current, are investigated based on the phenomenological Ginzburg-Landau (G-L) theory. Due to the axial symmetry of the system, the three-dimensional problem is reduced to a two-dimensional problem. We can mesh a two-dimensional sample into grids, and discretize the first G-L equation by using the finite-difference method. Then the eigenvalues and eigenfunctions will be evaluated numerically by solving the discrete equations. With the eigenvalues and eigenfunctions we further obtain the minimum free energy of the system and the corresponding superconducting wave function. We discuss the influences of the ring size and magnetic field distribution on two kinds of the vortex structures: giant vortex state (GVS) and multivortex state (MVS). Calculations show: 1) the GVS with axial symmetric wave function exists only in a small size superconducting ring, as the GVS is a state of single vortex line that only goes through the hole at the center of the superconducting ring and carries several magnetic flux quanta with it; 2) with the increase of the ring size, the diamagnetism of superconducting ring becomes stronger, and the critical magnetic field value of a giant vortex state increases, and the maximal number of giant vortexes that the superconducting ring can accommodate is also growing; furthermore, the entrance of a flux line will cause fluctuations of critical field values; 3) when the superconducting ring size is large enough, a GVS splits into a number of MVS. The MVS is an excited state and the GVS is mostly a ground state; 4) the free energy of the system changes with the magnetic field distribution, the magnetic field provided by a central small current loop can pass through the superconducting ring easily, and produce multivortices whose formations are diverse; if the magnetic field runs parallel to the plane of the superconducting ring, it is difficult to pass through the superconducting ring and form multivortices; 5) the vortex lines are naturally bent with the magnetic field lines and can pass through the same horizontal plane twice, so that one of the two vortex states seems to be an antivortex state; generally, the magnetic field lines can go through the hole of a superconducting ring easily but can hardly penetrate through the body of a superconducting ring, the structure of multivortices is similar to that of the magnetic field distribution in a superconducting ring. We also obtain a vortex structure with coexistences of giant vortex and multivortices. This study is of significance for the application of superconducting nanomaterials.
Study on the electro-optic modulation properties of graphene-coated hollow optical fiber
Authors: Bi Wei-Hong  , Wang Yuan-Yuan  , Fu Guang-Wei  , Wang Xiao-Yu  , Li Cai-Li  ,   Key Laboratory for Special Fiber and Fiber Sensor of Hebei Province, School of Information Science and Engineering, Yanshan University, Qinhuangdao 066004, China
Published: December 2020

Active manipulation of light in optical fibers has been extensively studied with great interest because of the structure simplicity, small footprint, low insertion loss and the compatibility with diverse fiber-optic systems. While graphene can be seen to exhibit a strong electro-optic effect originating from its gapless Dirac-fermionic band structure, there is no report on the electro-absorption properties of all-fiber graphene devices. Here a novel tunable graphene-based hollow optical fiber structure is designed with graphene coated on the inner wall of the fiber central core. Evanescent field of the guided mode propagating in the hollow optical fiber interacts with a monolayer or stacked multilayer graphene, which could modulate the intensity of the propagating mode via altering the chemical potential of the graphene by an external electric field. A full vector finite element method is adopted to analyse the influences of the chemical potential, the air-hole's radius and layers of graphene on the electro-optic modulation properties of the structure. Numerical simulation results show that by adjusting the chemical potential of graphene, the phase and on-off features of the fiber can be tuned correspondingly, as well as the position, magnitude and width of the loss peak and the sub-peak. However, the air-hole's radius and layers of graphene will only affect the loss variation, the magnitude and width of the loss peak and the sub-peak, but have no influence on the on-off point and the position of the loss peak and the sub-peak. In addition, the loss variation caused by N-layer graphene is N times that of the monolayer graphene. Since it is the dielectric constant of graphene that determines the effective refractive index and the loss of the fiber, the dielectric constant is only related to its chemical potential while independent of the air-hole's radius and the layers of graphene. Finally, an optimal electro-absorptive modulator based on the penta-layer graphene-coated hollow optical fiber is proposed for its advantage of ultra-compact footprint (5 mm 125 m), ultrawide optical bandwidth (580 nm), high extinction ratio (16 dB), high modulation bandwidth (64 MHz) and low insertion loss (1.23 dB), as well as a broad operational spectrum that ranges from 1180 to 1760 nm. Our results can provide theoretical references for the design and application of graphene-based tunable photonic fiber devices.
Preparation and characterization of orthorhombic Fe2(MoO4)3 and first-principle study of its negative thermal expansion properties
Authors: Chai Feng-Tao  , Yue Ji-Li  , Qiu Wu-Jie  , Guo Hai-Bo  , Chen Li-Jiang  , Shi Si-Qi  ,   School of Sciences, Zhejiang Sci-Tech University, Hangzhou 310018, China;,   School of Materials Science and Engineering, Shanghai University, Shanghai 200444, China;,   Department of Chemistry & Laser Chemistry Institute, Fudan University, Shanghai 200433, China;,   Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China
Published: December 2020

Monoclinic Fe2(MoO4)3 sample is synthesized by the hydrothermal method, and characterized via high temperature X-ray diffraction and thermogravimetric-differential scanning calorimetry. It is observed that the reversible phase transition between the low-temperature monoclinic and high-temperature orthorhombic phases occurs at about 510 ℃. The cell parameters at different temperatures are calculated by the Rietveld refinement method. In a temperature range from 25 ℃ to 400 ℃, the a, b and c crystallographic axes with the monoclinic phase gradually expand. On the other hand, in a temperature range from 530 ℃ to 710 ℃, the orthorhombic phase exhibits a negative thermal expansion (NTE) behavior, in which the b and c axes gradually contract but the a axis first contracts and then expands a little. Atomic and electronic structures are investigated using first-principle calculation. Results indicate that the Mo-O bonds are much stronger than the Fe-O bonds in Fe2(MoO4)_{3} and the MoO4 tetrahedrons are more rigidly than FeO6 octahedrons. To reveal the relationship between NTE and polyhedral distortion, the phonon density of state of Fe2(MoO4)3 is calculated using the ab initio method. The experimental Raman spectrum positions can be identified in the calculated dispersion of the total phonon density of states (DOS). Meanwhile, by calculating the Grneisen parameters for phonon branches at point, the optical branch with the lowest vibration frequency is believed to have the largest negative Grneisen parameter. Furthermore, we analyze the vibrational behaviors of atoms, and find that oxygen atoms have different vibrational eigenvectors from Fe or Mo atoms. and more obvious amplitudes than Fe or Mo atoms. Therefore, it is concluded that the transverse vibration of the oxygen bridge atom between the MoO4 tetrahedron and FeO6 octahedron, the soft distortion of FeO6 octahedrons, and the rigid rotation of MoO4 tetrahedrons jointly lead to the negative thermal expansion of Fe2(MoO4)3,.
Numerical study of plasmonic filter based on metal-insulator-metal waveguide
Authors: Yang Yun-Ru  , Guan Jian-Fei  ,   College of Optoelectronic Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210023, China
Published: December 2020

A novel nanometeric plasmonic filter comprised of double-sided eight stub resonators side-coupled with a metal-isolator-metal waveguide is proposed and demonstrated numerically by the finite element method. The numerical results show that the four transmittance peaks in a transmission spectrum range from 400 nm to 2000 nm can be achieved due to the electromagnetically-induced-transparency-like spectral responses between every two adjacent stub resonators with detuned cavity length. Based on the magnetic field distributions from the two dimensional model, the physical origins of transmittance peaks and dips are clarified by phase analysis of Fabry-Perot resonance effect. In addition, the central wavelengths of transmittance peaks can be tuned by adjusting the cavity length of each stub resonator, which means the waveguide filter could be utilized to develop ultracompact and tunable narrowband photonic filters for high integration.
Potential energy curves and spectroscopic properties of GeS molecules: in ground states and low-lying excited states
Authors: Huang Duo-Hui  , Wan Ming-Jie  , Wang Fan-Hou  , Yang Jun-Sheng  , Cao Qi-Long  , Wang Jin-Hua  ,   Yibin University Key Laboratory of Computational Physics, Yibin University, Yibin 644000, China
Published: December 2020

The potential energy curves (PECs) for ground state (X1+) and five low-lying electronic states (11-, 11, A1, 15+, 25+) of the GeS molecule have been studied by multi-reference configuration interaction (MRCI) plus Davidson correction (+Q) with all-electron basis set aug-cc-pv5Z. Results show that the 25+ state is an unstable repulsive state, and the others are bound states, and the six electronic states are dissociated along the same channel, Ge(3P)+S(3P). The adiabatic transition energy Te equilibrium bond length Re, dissociation energy De, harmonic frequency e, anharmonic constant exe, and equilibrium dipole moments are obtained by fitting the PECs for the X1+, 11-, 11, A1 and 15+ states. While Re is 2.034 , De 5.728 eV, e 571.73 cm-1, exe 1.6816 cm-1, the equilibrium dipole moment is 1.9593 Debye for the ground state. The values of Te are 25904.81, 26209.22, 32601.19, 43770.26 cm-1 for 11, 11, A1 and 15+ states, respectively; the values of Re are 2.313, 2.322, 2.188, 2.8790 for 11, 11, A1 and 15+ states, respectively; the values of De are 2.524, 2.487, 1.694, 0.3036 eV for 11-, 11, A1 and 15+ states, respectively; the values of e are 358.90, 353.08, 376.32, 134.96 cm-1 for 11-, 11, A1 and 15+ states, respectively; the values of exe are 1.2421, 1.2151, 1.6608, 1.9095 cm-1 for 11, 11, A1 and 15+ states, respectively, and the values of equilibrium dipole moments are 1.3178, 1.4719, 1.5917, -1.9785 Debye for 11-, 11, A1 and 15+ states, respectively. By solving the radial Schrdinger equation of nuclear motion, the 30 vibration levels and 30 inertial rotation constants (J=0) for X1+, 11-, 11, A1 and 15+ states are also obtained, and all of are in good agreement with the available experimental and other theoretical values.