bluuebunny/crossref_metadata_2025 huggingface dataset:
Parametric properties of the electron spin relaxation due to spin-orbit interaction in InAs quantum dots
Authors: Jiang Hong-Liang  , Zhang Rong-Jun  , Zhou Hong-Ming  , Yao Duan-Zheng  , Xiong Gui-Guang  ,   (1)Basic Department, The Jinling Institute of Technology, Nanjing 211169, China;Department of Physics, Wuhan University, Wuhan 430072, China; (2)Department of Physics, Wuhan University, Wuhan 430072, China
Published: December 2020

To deal with the Hamiltonian model in InAs QDs with a single electron, we’ve taken the SO interaction as a perturbation term, calculated the SO matrix elements under Fock-Darwin eigenfunction which are used for second order corrections on the energies and wave functions, and considered the influence of new energy levels on g factor and effective mass m*. The expression of phonon-assisted electron spin relaxation rate Γ in InAs QDs is deduced, which shows different dependences on confined potential frequency ω0, temperature T, vertical height z0 and magnetic field B. Among them, temperature for the electron spin relaxation plays a dominant role, followed by lateral confinement potential frequency, magnetic field and the vertical height, in order of importance. (1) Growth of ω0, which corresponds to the decrease of the effective transverse size d in InAs QDs, suppresses the increase of the rate Γ. (2) The temperature T affects the rate Γ evidently, which will reduce the inhibition of ω0 on Γ. With increase of the temperature from 1 K to 7 K, the spin inversion relaxation rate grows explosively from 103 s－1 to 108 s－1. (3) The rate Γ decreases with the growth of the vertical height z0 and have the order of magnitude 100－103 s-1 at T=1 K, whereas the influence of the temperature increase (at T=6 K) on the rate will gradually exceed that of the height growth. (4) At different frequencies ω0 all curves of the rate Γ versus magnetic field B have a peak that almost appears at the same field, which is attributed to the contribution of the Zeeman term H ^ Z exceeding that of H ^ SO since there is a considerable g factor in InAs material.
Study on the suppression mechanism of current collapse with field-plates in GaN high-electron mobility transistors
Authors: Zhang Jin-Cheng  , Mao Wei  , Liu Hong-Xia  , Wang Chong  , Zhang Jin-Feng  , Hao Yue  , Yang Lin-An  , Xu Sheng-Rui  , Bi Zhi-Wei  , Zhou Zhou  , Yang Ling  , Wang Hao  , Yang Cui  , Ma Xiao-Hua  ,   (1)School of Microelectronics, Xidian University, Key Lab of Ministry of Education for Wide Band-Gap Semiconductor Materials and Devices, Xi'an 710071, China; (2)School of Technical Physics, Xidian University, Xi'an 710071, China
Published: December 2020

The physical mechanisms underlying current collapse effects in the passivated GaN high-electron mobility transistors(HEMTs), the gate field-plated GaN HEMTs and the gate-source field-plated GaN HEMTs are investigated in experiments and numerical device simulations. And the intrinsic relationships of the current collapse with the carrier concentration, the probability of traps ionization, and the electric field within the cap layer are established. Results show that the direction of the longitudinal electric field, as well as the intensity distribution of both the transverse and longitudinal electric fields within the cap layer, can be modulated effectively by the field-plates. The electric field intensity near the gate is reduced and that beneath the field-plates increased. Due to the effects of the field-plates on electric field, the transverse movement of electrons near the gate is reduced, and the longitudinal electron movement beneath the field-plates is increased. These affects the electron concentration distribution and the ionization probability of the traps in the cap layer, which makes field-plates effective for the reduction in the current collapse.
Influence of curvature on transmission properties of finite curved slot arrays
Authors: Meng Zhi-Jun  , Wang Li-Feng  , Lü Ming-Yun  , Wu Zhe  ,   School of Aeronautic Science and Engineering, Beihang University, Beijing 100191, China
Published: December 2020

Transmission properties of finite curved slot arrays were investigated based on an extension of mutual admittance approach. One-dimensional curvature effects were analyzed, with the influence of column number and flare angle on magnetic current distribution, scattering patterns and frequency response curves. Results show that the curvature effect depends on the flare angle. When the flare angle is large (above 120°), strong curvature effect leads to violent fluctuation of magnetic current distribution, wide beamwidth and high side lobes, and considerable changes also occur in frequency-response characteristics, including resonant frequency, transmission bandwidth and transmission coefficient. When the flare angle is small enough, generally below 60°, only the magnetic current distributions of marginal elements would get influenced, consequently the scattering patterns and transmission characteristics are similar to those of finite planar arrays. The curvature effect may became very weak and be ignored on this condition.
Na effect on the electronic transport properties of C20H20 molecule
Authors: Cheng Xia  , Yang Chuan-Lu  , Tong Xiao-Fei  , Wang Mei-Shan  , Ma Xiao-Guang  ,   School of Physics, Ludong University, Yantai 264025 China
Published: December 2020

Using first-principles density functional theory and non-equilibrium Green’s function method, we investigate the electronic transport properties of Na@C20H20 molecule. The calculational results show that the I-V curve exhibits good linear characteristic in the range of bias V, and shows obvious negative differential resistance (NDR) characteristics. The equilibrium conductance of Na@C20H20 molecule is 0.0101 G0. Comparing the results with those of Li@C20H20 molecule, we find that doping Na can improve both the electronic transport capacity and the chemistry stability of C20H20 molecule, which makes it more suitable as candidate of molecular device.
Nonlinear magnetization dynamics excited by the spin-transfer torque effect
Authors: Jin Wei  , Wan Zhen-Mao  , Liu Yao-Wen  ,   (1)Department of Physics, Tongji University, Shanghai 200092, China; (2)Department of Physics, Tongji University, Shanghai 200092, China;College of Physics and Communication Electronics, Anhui Normal University, Wuhu 241000, China
Published: December 2020

The macrospin model based on Landau-Lifshitz-Gilbert equation is used to study the current-induced magnetization dynamics in magnetic spin valves. We find that the DC spin-polarized current could either switch the magnetization of free layer or excite the steady-state precessional motion via the so-called spin-transfer torque effect. The AC current could drive the chaotic oscillations. The route to chaotic oscillation depending on the strength of current is demonstrated through a series of period doubling bifurcations.
Mn-site Fe/Cr doping effects in charge-ordered antiferromagnetic manganite La0.4Ca0.6MnO3
Authors: Hu Ni  , Liu Yong  , Cheng Li  , Shi Jing  , Xiong Rui  ,   (1)Key Laboratory of Acoustic &Photonic Material and Device, Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072, China; (2)Key Laboratory of Acoustic &Photonic Material and Device, Ministry of Education, School of Physics and Technology, Wuhan University, Wuhan 430072, China;School of Science, Hubei University of Technology, Wuhan 430068, China
Published: December 2020

Impurity effects on the stability of a charge-ordered antiferromagnetic state in La0.4Ca0.6MnO3 are investigated by Fe3+/Cr3+ doping on Mn-site. All the samples with different doping concentrations possess the same orthorhombic crystalline structure,and no evident variation in the structure can be seen. Our results reveal that the Fe3+/Cr3+ doping effects on the transport behavior are rather different, although both impurities have the same valance and are commonly antiferromagnetically coupled with other transition metal ions. We assign this remarkable different doping effects to the different electronic structure of the doping cations.
Spin-polarized electron transport and magnetoresistance effect in symmetric parabolic-well magnetic tunneling junction
Authors: Jia Xiu-Min  , Liu De  , Zhang Hong-Mei  ,   (1)College of Physics and Information Engineering, Hebei Normal University, Shijiazhuang 050016,China;Hebei Advanced Thin Films Laboratory, Shijiazhuang 050016,China; (2)College of Sciences, Hebei University of Science and Technology, Shijiazhuang 050018,China
Published: December 2020

We investigated the spin-dependent transmission coefficient and tunneling magnetoresistance in symmetric parabolic-well with two ferromagnetic contacts (F/SPW/F). The quantum size effect and Rashba spin-orbit interaction are discussed simultaneously. The results indicate that the transmission coefficient and tunneling magnetoresistance are periodic function of the parabolic-well width. The oscillation frequencies of the transmission coefficient and tunneling magnetoresistance decrease with the increasing of the parabolic-well depth. The oscillation frequencies of the transmission coefficient and tunneling magnetoresistance increase with the increasing of the Rashba spin-orbit coupling strength. The amplitude and peak-to-valley ratio of the transmission coefficient and tunneling magnetoresistance are strongly dependent on the difference in orientations of the two magnetizations in the left and right ferromagnets.
Microwave absorbing properties of cobalt nanowires with transverse magnetocrystalline anisotropy
Authors: Chen Wen-Bing  , Han Man-Gui  , Deng Long-Jiang  ,   State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
Published: December 2020

Cobalt nanowires with c-axis perpendicular to the axial direction have been fabricated by the pulsed electrodeposition method. The hysterisis loops of the cobalt nanowire array show little anisotropy due to the competition between shape anisotropy and factors such as magnetocrystalline anisotropy and magnetostatic interaction. The permittivity and permeability dispersion spectra of the nanowire/paraffin composite were measured in the frequency range of 2—18 GHz. It was found that the imaginary part of the permittivity spectra shows a strong peak around 5 GHz and a weak peak around 10 GHz, which are contributed by the Debye relaxation and the conductivity of the nanowires. In the meantime, the imaginary part of the permeability spectra for the nanowire/paraffin composite samples exhibits a strong absorption peak at 6.1 GHz and two minor peaks above 10 GHz. The peak at 6.1 GHz is attributed to the natural resonance mechanism and the other two peaks are duc to eddy current effect. The permeability spectra attributed to natural resonance are fitted using the Landau–Lifshitz–Gilbert equation. Calculation based on the Kittel equation substantiates our fitting results. The electromagnetic wave reflection loss of the nanowire/paraffin composite sample is lower than -20 dB when the thickness of the nanowire/paraffin composite has been adjusted, suggesting that the cobalt nanowire composites can find application as a novel type of microwave absorbers.
Laser-induced ultrafast spin dynamics research on magnetic nanostructures
Authors: Li Chun  , Yang Fan  , Georgios Lefkidis  , Wolfgang Hübner  ,   (1)Department of Physics and Research Center OPTIMAS, Kaiserslautern University of Technology,67653 Kaiserslautern,Germany; (2)Northwestern Polytechnical University Press,Xi'an 710072,China; (3)School of Mechanics,Civil Engineering and Architecture,Northwestern Polytechnical University,Xi'an 710072,China
Published: December 2020

In this paper,taking one-magnetic-center NiO and two-magnetic-center nanostructures composed of Co and Ni as examples,we review our recent works in this field.To theoretically achieve ultrafast spin flip and transfer in magnetic nanostructures,an ultrafast spin dynamics mechanism,namely Λ process,was proposed.To properly simulate the laser-matter interaction,the accurate intragap d-states were predicted firstly through quantum chemistry calculations; then the spin localizations on magnetic atoms were analyzed considering external magnetic field and spin-orbit coupling; at last,laser pulse term was turned on to study the time history of the spin switching scenario via the Λ process.It was shown that spin flip and transfer can be achieved in a subpicosecond regime with linearly polarized light.In order to further realize checking and monitoring of the spin manipulations in magnetic molecules,a CO molecule was attached to one magnetic center to serve as an infrared marker.The calculated spin-state-dependent C-O stretching frequencies indicate that spin manipulations can be indirectly monitored through infrared spectrum experiments.
The modulation of a novel photonic crystalring resonator filter
Authors: Yang Chun-Yun  , Xu Xu-Ming  , Ye Tao  , Miao Lu-Ping  ,   Department of Physics, Nanchang University, Nanchang 330031, China
Published: December 2020

Adding two scattering dielectric cylinders in a photonic crystal ring resonator, a new type of ring resonator filter is achieved, the transmission of which attains 90% and the bandwidth are relatively small. By taking two different measures, the filter wavelength and bandwidth are modulated arbitrarily: (1) With the scattering dielectric cylinder radius decreasing, the bandwidth of output wavelength from the load waveguide gets larger, while the wavelength bandwidth of the bus waveguide decreases; and when the radius increases, they change adversely. (2) Changing the radius of dielectric cylinder in the coupling region, the wavelength in the filter will change accordingly, and the amount of change was proportional to the radius of dielectric cylinder, and the transmission changes significantly. This may serve as the foundation for applications in the preparation of integrated photonic device.
Time-resolved optical diagnosis of intense femtosecond laser ablation of silica glass
Authors: Guo Wen-Gang  , Hu Hao-Feng  , Wang Pan  , Wang Xiao-Lei  , Zhai Hong-Chen  ,   (1)Department of Basic Science, Institute of Military Traffic, Tianjin 300161, China; (2)Institute of Modern Optics, Nankai University, Key Laboratory of Optoelectronic Information Science & Technology,Ministry of Education, Tianjin 300071, China
Published: December 2020

The dynamic process of femtosecond laser pulse ablation of silica glass has been experimentally investigated by ultrafast time-resolved optical diagnosis. The digital holograms of material ejections outside the silica glass are recorded, and two-dimensional phase difference maps at different delay times are obtained, from which the composition and the structure of the ejected materials are deduced. Besides, the time-resolved shadowgraphs of the phenomena inside the silica glass are also recorded, and the evolution process of two stress waves inside the silica glass is observed in the shadowgraphs, which are believed to be related to two material ejections outside the target.
Degradation model of GaAs vacuum electron sources
Authors: Zou Ji-Jun  , Zhang Yi-Jun  , Yang Zhi  , Chang Ben-Kang  ,   (1)Institute of Electronic Engineering and Opto-electronic Technology,Nanjing University of Science and Technology,Nanjing 210094,China; (2)Institute of Electronic Engineering and Opto-electronic Technology,Nanjing University of Science and Technology,Nanjing 210094,China;Engineering Research Center of Nuclear Technology Application (East China Institute of Technology),
Published: December 2020

The degradation of activated GaAs vacuum electron source as a function of time has been investigated by using X-ray photoelectron spectroscopy (XPS).We found that the cathode surface element content changes with time and the significant decrease in sensitivity of electron source is mainly due to the change of dipole direction caused by the adsorption of harmful gases on the cathode surface.Based on the above results,we deduced the degradation model of GaAs electron source through analyzing the adsorption process of harmful gases on the surface in vacuum system.The model reveals the exponential degradation rule of GaAs electron sources and the inverse relationship between lifetime and pressure.The theoretical results are in full agreement with the experimental fact.
The extended inertia fluid model to interpret the size distribution of Si nanoparticles prepared by pulsed laser ablation
Authors: Fu Guang-Sheng  , Ding Xue-Cheng  , Guo Rui-Qiang  , Zhai Xiao-Lin  , Chu Li-Zhi  , Deng Ze-Chao  , Liang Wei-Hua  , Wang Ying-Long  ,   College of Physics Science and Technology, Hebei University, Baoding 071002, China
Published: December 2020

The inertia fluid model proposed by Yoshida et al. can only interpret the influence of ambient pressure on the average size of nanoparticles prepared by pulsed laser ablation. Basing on the model, the Maxwell velocity distribution of the initial ablated particles is considered, a new analytic expression of the size-distribution of nanoparticles is obtained. The simulation results are consistent with the statistic data from Yoshidas experiments under different He pressures. Additionally, the size-distribution of nanoparticles is simulated using the modified model under different ambient gases (He, Ne and Ar),the simulation results coincide with experimental data. The conclusions may serve as the basis for realizing the uniformity and controllability of Si nanoparticles.
rf excited optical emission spectrum of radicals generated during hot wire chemical vapour deposition for the preparation of microcrystalline silicon thin film
Authors: Li Tian-Wei  , Liu Feng-Zhen  , Zhu Mei-Fang  ,   College of Materials Science and Optoelectronics Technology, Graduate University of Chinese Academy of Sciences, Beijing 100049, China
Published: December 2020

To study the radicals behavior in the hot wire chemical vapour deposition (HWCVD) process for the preparation of microcrystalline Si (μc-Si: H) thin film, a weak radio frequency (rf) power was introduced to excite the radicals generated in HWCVD chamber. The spectrum of rf-excited HWCVD (rf-HWCVD) was obtained by subtracting the emission of hot wires from the spectrum measured by OES. The influence of the rf power on the rf-HWCVD spectrum can be neglected as the rf power density was less than 0.1 W/cm2. Under the same deposition parameters,the emission spectra for rf-HWCVD and plasma enhanced CVD (PECVD) processes are different. Under the low deposition pressure (7.5 Pa), the intensities of SiH* and Hα vary with the hot wire temperature reversely, which is characteristic of HWCVD with high gas dissociation rate and high concentration of atomic H. The ratio of intensity of Hα to SiH* in the emission spectrum of rf-HWCVD varying with deposition pressure is consistent with the crystalline fraction of μc-Si: H film. The results indicate that the optical emission spectroscopy measurement is a suitable method for the investigation of the HWCVD process excited by a weak rf-power.
Synthesis and thermoelectric properties of nonstoichiometric AgSbTe2+ x compounds
Authors: Tang Xin-Feng  , Du Bao-Li  , Xu Jing-Jing  , Yan Yong-Gao  ,   State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China
Published: December 2020

Nonstoichiometric AgSbTe2+x (x=0—0.05) compounds have been prepared by combining melting-quench and spark plasma sintering. The effects of excessive Te on thermoelectric properties were investigated at 300 K to 600 K. Results indicated that the concentration of Ag+ ion vacancy, hole concentration and electrical conductivity increase remarkably with the increasing amount of Te, while the Seebeck coefficient decreases. In addition, the total thermal conductivity of the samples increases slightly as Te content increases. The lattice thermal conductivities of nonstoichiometric samples range from 0.32 to 0.49 W/mK, which are less than the value of the stoichiometric sample, and close to the theoretical minimum thermal conductivity. For AgSbTe2.01 (x=0.01), a maximum figure of merit ZT=1.41 was obtained at 562K. This value is 15% higher than that of the stoichiometric sample.
Active disturbance rejection control of a chaotic system based on immune binary-state particle swarm optimization algorithm
Authors: Wu Jian-Hui  , Zhang Jing  , Zhang Ying-Jie  , Liu Zhao-Hua  ,   (1)College of Computer and Communication, Hunan University, Changsha 410082, China; (2)College of Electrical and Information Engineering, Hunan University, Changsha 410082, China; (3)College of Electrical and Information Engineering, Hunan University, Changsha 410082, China;College of Computer and Communication, Hunan University, Changsha 410082, China
Published: December 2020

The active disturbance rejection control (ADRC) has the property of requiring no knowledge about the precise mathematical model, but the parameters of controller is difficult to be tuned. An active disturbance rejection control based on immune binary-state particle swarm optimization algorithm (IBPSO-ADRC) is proposed, which takes advantage of the combination of the artificial immune systems (AIS) and particle swarm optimization (PSO). The proposed algorithm is applied to optimize the parameters of ADRC and then to control chaotic system. Furthermore, a new ADRC for the chaotic system is constructed. The simulation experiments indicate that the scheme requires no knowledge about the mathematical model with fast response speed, while restraining the parameter perturbation of chaotic system effectively and is robust to noise.
Detrended fluctuation analysis of time series in mixed traffic flow
Authors: Wu Jian-Jun  , Xu Shang-Yi  , Sun Hui-Jun  ,   (1)MOE Key Laboratory for Urban Transportation Complex Systems Theory and Technology, Beijing Jiaotong University, Beijing 100044, China; (2)State Key Laboratory of Rail Traffic Control and Safety, Beijing Jiaotong University, Beijing 100044, China
Published: December 2020

The detrended fluctuation analysis method is applied to analyse the complexity of traffic flow time series and the scale index is obtained, which is a parameter to depict the long term evolutionary behaviour of the mixed traffic flow time series. According to the changes of the scale index, it is shown that the traffic flow time series has long-range correlation characteristics or short-range correlation characteristics. It is found that the traffic flow series shows long-range correlation when the density ρ12; and when ρ1 or ρ>ρ2, the time series displays short-range correlation. That is to say, the vehicle density plays an important role in the changes of the scale index. Additionally, we also found that the ratio of slow vehicles have influence on the changes of the scale index.
The influence of different opening shapes of split-ring resonator on its transmittance in terahertz band
Authors: Li Lei  , Zhou Qing-Li  , Shi Yu-Lei  , Zhao Dong-Mei  , Zhang Cun-Lin  , Zhao Kun  , Tian Lu  , Zhao Hui  , Bao Ri-Ma  , Zhao Song-Qing  ,   (1)Beijing Key Laboratory for Terahertz Spectroscopy and Imaging, Key Laboratory of Terahertz Optoelectronics, Ministry of Education, Department of Physics, Capital Normal University, Beijing 100048, China; (2)College of Science, China University of Petroleum, Beijing 102249, China
Published: December 2020

Through the FDTD simulation of the transmittance in terahertz band of the split-ring resonator (SRR) with different opening shapes, we found a mean gap effect of SRR during the resonance and a particular conduction phenomenon in case of very sharp edge of the split.
Causal algebra and its applications to physics
Authors: Yang Shi-Lin  , Huang Yong-Chang  , Huang Chang-Yu  , Song Jia-Min  , He Bin  ,   (1)College of Physics, Peking University, Beijing 100871, China; (2)Institute of Applied Mathematics, Beijing University of Technology, Beijing 100124, China; (3)Institute of Theoretical Physics, Beijing University of Technology, Beijing 100124, China
Published: December 2020

A causal algebra and its application to high energy physics is proposed. Firstly on the basis of quantitative causal principle, we propose both a causal algebra and a causal decomposition algebra. Using the causal decomposition algebra, the associative law and the identity are deduced, and it is inferred that the causal decomposition algebra naturally contains the structures of group. Furthermore, the applications of the new algebraic systems are given in high energy physics. We find that the reactions of particles of high energy belonging neither to the group nor to the ring, and the causal algebra and the causal decomposition algebra are rigorous tools exactly describing real reactions of particle physics. A general unified expression (with multiplicative or additive property) of different quantities of interactions between different particles is obtained. Using the representation of the causal algebra and supersymmetric R number, the supersymmetric PR=(-1 )R invariance of multiplying property in the reactions of containing supersymmetric particles is obtained. Furthermore, a symmetric relation between any components of electronic spin is obtained, with the help of which one can simplify the calculation of interactions of many electrons. The reciprocal eliminable condition to define general inverse elements is used, which may renew the definition of the group and make the number of axioms of group reduced to three by eliminating a superabundant definition.
Adiabatic tunneling of Bose-Einstein condensatein double-well potential
Authors: Huang Fang  , Li Hai-Bin  ,   Department of Applied Physics, Zhejiang University of Technology, Hangzhou 310023, China
Published: December 2020

We studied the adiabatic tunneling of Bose-Einstein condensates (BEC) in double-well potential with circle adiabatic variation of energy level spacing. We found that the adiabatic theorem is violated during the evolution of BEC, when the initial state is chosen such that all condensate atoms are in the shallow well and the interaction between atoms is strong enough. Furthermore, we found that the condensates can return to the initial state or not, depending on the evolution periods. In addition, we also found the evolution is dependent on the choice of initial state, which indicates an asymmetric character. With the help of the graph of energy levels and the phase diagram, we explained the results obtained.
Influence of isotope substitution of sodium molecule on the integral cross sections of rotational excitation in low-temperature collisions of He-Na2
Authors:   (1)Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China; (2)Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065, China; School of Physics and Electronic Science, Guizhou Normal University, Guiyang 550001, China
Published: December 2020

Multiple ellipsoid model is applied to the 4He,10He-18Na2,23Na2, and 37Na2collision systems, and integral cross-sections for rotational excitation and the total collision cross-sections at the incident energy of 50,100 and 200 meV are calculated. By analyzing the differences of these integral cross-sections, the change rules of the integral cross sections with the increase of rotational angular quantum number of Na2 molecule, as well as with the change of the reduced mass of symmetric isotopic substituted system are obtained. Based on the calculation, influence on the cross-sections exerted by the variations in the reduced mass of systems and in the relative incoming energy of incident atom is discussed. Moreover, at the relative incident energy of 100 meV, the contributions of different regions of the potential to integral cross-sections of rotational excitation for10He-18Na2,23Na2 and 37Na2 collision systems are investigated.
The conversion between subluminal and superluminal lightpropagation phenomena in an inverted Y-typefour-level quantum system
Authors: Meng Dong-Dong  , Liu Xiao-Dong  , Zhang Sen-Lin  ,   (1)Department of Physics, College of Science, Tianjin Polytechnic University, Tianjin 300160, China; (2)Department of Physics, College of Science, Tianjin Polytechnic University, Tianjin 300160, China; Faculty of Science and Engineering, Saga University, Saga 840-8502, Japan
Published: December 2020

We have studied the light propagation properties in an inverted Y-type four-level quantum system coupled with probe, couple and driving fields. Using the numerical simulation method, we investigate the absorption properties of the probe light field when the Rabi frequency and detuning of the driving field are changed. From the three-dimensional graphics, we find the variations of the probe group velocity at the electromagnetically induced transparency windows. Farthermore, we theoretically obtain the conversion among subluminal, vacuum and superluminal light propagation by adjusting the Rabi frequency and detuning of the external driving field properly.
Interaction of force and coupled system and stochastic energetic resonance
Authors: Lin Min  , Zhang Mei-Li  ,   College of Metrology Technology and Engineering, China Jiliang University, Hangzhou 310018, China
Published: December 2020

The process of work done on the system by the external force is equivalent to the process of change in system state. The thermodynamic relations of coupled bistable system based on single stochastic trajectories are established by using microcosmic dynamics and macroscopic thermodynamic methods, according to the stochastic dynamics described by Langevin equation. The transmission and conversion relations of energy are quantitatively characterized via interaction of force and work of coupled system, which reveals the coupled system exhibiting stochastic energetic resonance phenomenon. Through analyzing relationship between work done and energy, the physical nature of produced stochastic resonance is further revealed.
Mechanism of high frequency resonance of parameter-adjusted bistable system
Authors: Leng Yong-Gang  ,   School of Mechanical Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

For clarifying the response of a bistable system to a high-frequency signal, the mechanism of high-frequency resonance with parameter-adjusted bistable system is investigated. It was shown that the method of twice sampling frequency transformation does not change the bistable system structure to realize resonance at the low frequency corresponding to the high frequency, and that the method of tuning bistable system parameters can directly realize resonance at the high frequency through adjusting the system parameters to change the system structure. The reason for the realization of high-frequency stochastic resonance of tuning system parameters is that adjusting the two parameters of the bistable system simultaneously leads to no limiting value for Kramers rate, and hence the limitation of stochastic resonance frequency within small frequency range is broken through.
Chaos for a class of complex epidemiological models
Authors: Di Gen-Hu  , Xu Yong  , Xu Wei  , Gu Ren-Cai  ,   Department of Applied Mathematics,Northwestern Polytechnical University,Xian 710129,China
Published: December 2020

We study the well-known SIR (susceptible, infected, recoverd) model with nonlinear complex incidence rates. Firstly,a series of coordinate transformations are carried out to change the equations as the amenable Hamiltonian systems. Secondly the Melnikov's method is used to establish the conditions of existence of chaotic motion and find the analytically critical values of homoclinic bifurcation. Good agreement can be found between numerical results and analytical results.
Complexity analysis of chaotic sequence based on the intensive statistical complexity algorithm
Authors: Sun Ke-Hui  , He Shao-Bo  , Sheng Li-Yuan  ,   School of Physics Science and Technology, Central South University, Changsha 410083,China
Published: December 2020

To analyze the complexity of the chaotic sequences, based on the intensive statistical complexity algorithm, the complexities of the discrete TD-ERCS and continuous simplified Lorenz chaotic systems were investigated respectively, and the complexities of the chaotic sequences with different system parameters were calculated. The complexities of pseudo-random sequences of the continuous chaotic systems disordered by m-series and chaotic pseudo-random sequences were analyzed. The results indicate that the intensive statistical complexity algorithm is an effective method for analyzing the complexity of the chaotic sequences, and the complexity of the discrete chaotic systems is larger than that of the continuous ones. However, after disordering by m-series or chaotic pseudo-random sequences, the complexities of the pseudo-random sequences can be increased significantly. This study provides a theoretical basis for the applications of chaotic sequences in the field of secure communication and information encryption.
Construction of grid multi-scroll chaotic attractors and its circuit implementation with polynomial and step function
Authors: Chen Shi-Bi  , Zeng Yi-Cheng  , Xu Mao-Lin  , Chen Jia-Sheng  ,   (1)Beijing Information Technology Institute, Beijing 100101, China; (2)School of Material Science and Photoelectronic Physics, Xiangtan University, Xiangtan 411105, China
Published: December 2020

A constructing approach to generating N×M-scroll attractors with polynomial and step function is reported. In Chuas circuit, only two or three scrolls can be generated by traditional polynomial function. On this basis, the multi-scroll of x direction in phase space is obtained by polynomial shift. And then the saddle-focus equilibrium points with index-2 in phase space are extended by combining both polynomial and step function, which makes it possible to extend the multi-scroll in y direction. Then the grid multi-scroll chaotic attractors are generated. The main feature of this constructing approach is generating grid multi-scroll chaotic attractors by combining both smooth curves and non-smooth curves for the first time. And the arbitrary planar grid multi-scroll chaotic attractors array can be generated by adjusting the values of natural numbers N and M. The effectiveness of this method has been verified by theoretical analysis, numerical simulation and circuit simulation.
Optimum parameters setting in symbolic dynamics of heart rate variability analysis
Authors: Song Ai-Ling  , Huang Xiao-Lin  , Si Jun-Feng  , Ning Xin-Bao  ,   Key Laboratory of Modern Acoustics of Ministry of Education, Institute of Biomedical Electronic Engineering,School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, China
Published: December 2020

The Shannon entropy Hk in symbolic dynamics analysis of time series has less data demand and can be complemented easily, and therefore is applied to heart rate variability (HRV) analysis. However, the criterion has not been established as to the parameter α, which is used during the transformation into symbols. Like all other physiological signals, great differences between individuals as well as nonstationarity are usual in HRV. Therefore, to achieve a robust and consistent analysis, the parameter α should be considered together with the mean and standard error of the series. In this paper, the integrative effects on Hk of the three parameters were studied firstly in simulation time series, and it was suggested that under certain conditions, the clusters of Hk approach a convergent upper boundary named Hk-up, which reflects the intrinsic dynamics of the time series. Then, in the heart beat interval series analysis of 15 subjects, the abilities of Hk-up to alleviate the impacts brought by both difference between individuals and nonstationarity were testified.
A novel unified equalization and demodulation of chaoticdirect sequence spread spectrum signal based on state estimation
Authors: Xu Xin-Zhi  , Guo Jing-Bo  ,   State Key Laboratory of Control and Simulation of Power System and Generation Equipments, Department of Electrical Engineering,Tsinghua University, Beijing 100084, China
Published: December 2020

A novel unified algorithm based on state estimation was proposed for equalization and demodulation of chaotic direct sequence spread spectrum (CD3S) signal through a non-ideal channel. The algorithm uses the state equations of the channel and the CD3S signal, as well as the reciprocal relationship between equalization and demodulation. Multiple extended kalman filters (EKF) were used for equalizing the channel while demodulating the binary message simultaneously by implementing them in reciprocal interaction. This algorithm could not only overcome the impact brought about by non-ideal channel, such as multipath interference and channel noise, but also demodulate the binary message from CD3S signal. This unified approach utilizes the information more adequately and has better real-time performance than independent approaches. Simulation results demonstrated that the proposed algorithm has a fast convergence rate, and is resistant to the multipath effect without knowledge of channel characteristic and the noise, so the efficient and reliable transmission of the CD3S signal through the non-idea channel is realized.
Synchronization of uncertain chaotic systems based on neural network and sliding mode control
Authors: Li Hua-Qing  , Liao Xiao-Feng  , Huang Hong-Yu  ,   College of Computer Science, Chongqing University, Chongqing 400044, China
Published: December 2020

The synchronization between two unknown chaotic systems is achieved by designing a controller based on the sliding mode control technique and radial basis function neural network. The controller design method is independent of the system mathematical model, but only depends on the output of the system state. Moreover, it is robust to parameter uncertainties and the outside interference. Finally, synchronization between unknown Lorenz systems and between unknown Lorenz system and Chen system are achieved using the proposed method. The response time is very short and the synchronization performance is good.
Approximate entropy based meso-spray transfer analysis of Al-alloy pulsed metal inert-gas welding under self-adapting control
Authors: Zhang Wei-Chao  , Yang Li-Jun  , Lü Xiao-Qing  ,   School of Material Science and Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

The meso-spray transfer of Al-alloys metal inert-gas (MIG) welding has the advantages of well-adjusting of the length of arc and beautiful appearance of weld due to the characters of droplet transfer. In this study, the self-adapting control which is brought to meet the arc of meso-spray transfer is accessed by analyzing the approximate entropy (ApEn) of the arc voltage on the aspect of non-linear dynamics. Under self-adapting control, the change of ApEn value with the varing metal transfer mode is discussed, which is due to the change of the parameter of process. Under spray transfer, two kinds of ApEn values of the self-adapting control and common pulsed control are compared, and we find that the self-adapting control is fit for meso-spray transfer. The results show that the smaller the value of approximate entropy is, the better the effect of the self-adapting control is.
Reliability of multi-state and multi-subsystem below stress-strength interference
Authors: Song Wei-Cai  , Zhang Yong-Jin  ,   (1)School of Computer, Jiangxi University of Traditional Chinese Medicine, Nanchang 330004, China; (2)School of Mathematics and Physics, Anhui University of Technology, Ma’anshan 243002, China
Published: December 2020

Based on multivariate random analysis and statistical physics, the reliability model of a system with stress-strength interference and initial failure is developed, the system has multi-state and dependent multi-subsystem. According to the definition of conditionally ordered order statistics, the probability density function of random strength vector is studied. Considering the coherence of subsystem items, the system reliability evaluation for different structures is given, and the reliability of any coherent structure is represented as a linear combination of the reliabilities of (n－i+1)-out-of-n system(1≤i≤n). Finally, an example is given to demonstrate the effectiveness of the model, where the stress-strength variable has a bivariate Pareto distribution.
Adaptive source biasing sampling for time-dependent radiation transport problems
Authors: Li Gang  , Deng Li  , Mo Ze-Yao  , Li Shu  ,   (1)Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing 100088, China; (2)Laboratory of Computational Physics, Institute of Applied Physics and Computational Mathematics, Beijing 100088, China;Graduate School of China Academy of Engineer Physics, Beijing 100088, China
Published: December 2020

Monte Carlo method is used to simulate the radiation transport problems which have characteristics of high temperature, high pressure, multi-media and large deformation of the grid. Due to the nonuniform particle distribution and great difference in the sizes of the grid, it makes the statistical errors of the grid fluxes fluctuate wildly. The error accumulation after many time steps may even influence the truth of the calculated results. So the global source biasing technique is developed. The importance function used here for source biasing sampling is based on the grid fluxes and errors of the previous time step. This is much faster than the traditional methods for solving the adjoint equation. The numerical tests showed that the neutron flux errors in the important grids are obviously reduced by using global source biasing which adaptively assigns the number of particles in each grid.
First principles study on the interaction of Aun(n=2, 3, 4) clusters with ethanol molecules
Authors: Yu Yong-Jiang  , Yang Chuan-Lu  , An Yi-Peng  , Wang Hua-Yang  ,   School of Physics, Ludong University,Yantai 264025,China
Published: December 2020

The mechanism of the adsorption between Au n (n=2,3,4) clusters and ethanol molecules is investigated with the density functional theory. It is found that Au n (n=2,3,4) clusters can adsorb several ethanol molecules to form the Aun-(C2H6O)1-ncompounds. There are many adsorbing conformations when the ethanol molecules are adsorbed by the Au4 cluster. The adsorbing sequence and the corresponding stable configurations are confirmed through the analysis of the adsorption energies and the Mulliken electrical displacement. When the last ethanol molecule is adsorbed,the bonding style changes from the Au—O bond to the Au—H bond. The constructions of the Aun clusters and the ethanol molecule are less changed in the adsorbing process. And the interaction between Aun clusters and ethanol molecules is weak interaction.
Full vibrational energy spectra and dissociation energies for some electronic states of diatomic alkali-metal molecules
Authors: Feng Hao  , Sun Wei-Guo  , Tian Yin  ,   (1)Research Center for Advanced Computation, School of Physics and Chemistry, Xihua University, Chengdu 610039, China; (2)School of Physical Science and Technology, Sichuan University, Chengdu 610064, China
Published: December 2020

It is difficult to obtain the accurate high-lying vibrational energies for most of the diatomic electronic states on modern experiments or theoretical computations based on quantum mechanics. Based on the new analytical formula for dissociation energy and algebraic method (AM) generated by Sun et al., the second order perturbation theory are used to study the full vibritional energies{EAMυ} and dissociation energies of the Li2－33Σ+g,Li2－13Δg,Li2－23Πg,Na2－B1Πu and K2－41Σ+g electronic states. The obtained results not only agree well with the experimental data for the low-lying vibrational energies, but also give all high-lying vibrational energies which are still difficult to obtain by experiment at present. These results supply necessary data for the studies which need high-lying vibrational energies and dissociation energies of diatomic alkali-metal molecule.
Probing the distorted wave effects in (e, 2e) reaction for the outer valence orbitals of ferrocene
Authors: Liu Kun  , Ning Chuan-Gang  , Shi Le-Lei  , Miao Yu-Run  , Deng Jing-Kang  ,   Key Laboratory of Atom and molecular Nanosciences of Ministry of Education, Department of Physics, Tsinghua University, Beijing 100084, China
Published: December 2020

The binding energy spectrum and electron momentum spectra of outer valence orbitals of ferrocene have been obtained by using our high efficiency electron momentum spectrometer at two different impact energies of 600 eV and 1500 eV. The theoretical momentum profiles of outer valence orbitals of ferrocene for the eclipsed and staggered conformations have been calculated by non-relativistic and scalar relativistic density functional methods. It was found that the outer valence orbitals in the eclipsed conformation are in one-to-one correspondence with the ones in the staggered conformation, and there is little difference between theoretical momentum profiles of them. In addition, it was found that relativistic effects have little influence on the momentum distributions of outer valence orbital of ferrocene. Strong distorted wave effect in the low momentum region related to the outer valence orbitals were observed, Which is due to that those orbitals are mainly composed of Fe 3d atomic orbital.
Effect of losses for squeezed surface plasmons
Authors: Li Wei  , Wang Yong-Gang  , Yang Bo-Jun  ,   School of Science,Beijing University of Posts and Telecommunications, Beijing 100876,China
Published: December 2020

The surface plasmon polaritons (SPPs) are electromagnetic excitation of electrons in metal surfaces, which propagates in wavelike fashion along the interface between a metal and a dielectric median.Recently Huck et al. reports on the efficient generation, propagation and reemission of squeezed surface plasmons.In this paper, the influence of waveguide loss was discussed for squeezed surface plasmons by means of the heat reservoir theory in quantum optics. Huck’s experimental result is explained theoretically.
Control of the evolution of an excited atom by using the dynamic Lorentzian reservior
Authors: Shi Yun-Long  , Yang Ya-Ping  , Liu Hai-Lian  , Huang Xian-Shan  ,   (1)Institute of Solid State Physics, Shanxi Datong University, Datong 037009, China; (2)Physics Department, Tongji University, Shanghai 200092, China; (3)School of Mathematics and Physics, Anhui University of Technology, Ma’anshan 243000, China; (4)School of Mathematics and Physics, Anhui University of Technology, Ma’anshan 243000, China;Institute of Solid State Physics, Shanxi Datong University, Datong 037009, China
Published: December 2020

We theoretically study the use of a dynamic Lorentzian reservoir environment to realize contro of the evolution of an excited two-level atom. It is found that the change of Lorentzian reservoir leads to the interaction between the electromagnetic modes in the cavity and those outside, resulting in the redistribution of the electromagnetic modes density. When the frequency of reservoir change is consistent with the process of exchange of energy between the atom and environment, a relatively stable coherent evolution can be obtained, and the decay is obviously inhibited.
Laser diode-pumped coaxial double crystals yellow laser
Authors: Li Bin  , Yao Jian-Quan  , Ding Xin  , Wang Peng  , Zhang Fan  ,   Key Laboratory of Optoelectric Information Science and Technology of Ministry of Education, Institute of Laser and Optoelectronics, College of Precision Instrument and Optoelectronics Engineering, Tianjin University, Tianjin 300072, China
Published: December 2020

A new configuration of 589 nm yellow laser with a single LD pump source and coaxial double crystal was proposed. When the incidence pump power was 1.5 W, 54 mW yellow laser at 589 nm was obtained, the optical to optical conversion efficiency was 3.6%, and the laser instability was about 5%. A conventional method for 589 nm laser was also tested under the same conditions, only 15 mW yellow laser was obtain. The configuration of single pump source and coaxial double crystals is compact and flexible, which can be used in many sum frequency lasers, such as the 491, 488, 593.5, 555 and 500.8 nm laser, and so on.